U.S. patent application number 14/710749 was filed with the patent office on 2015-09-17 for multi-path power factor correction.
This patent application is currently assigned to FINsix Corporation. The applicant listed for this patent is FINsix Corporation. Invention is credited to Justin Burkhart, Fred Chen, George Hwang, Anthony Sagneri.
Application Number | 20150263627 14/710749 |
Document ID | / |
Family ID | 45605681 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150263627 |
Kind Code |
A1 |
Sagneri; Anthony ; et
al. |
September 17, 2015 |
MULTI-PATH POWER FACTOR CORRECTION
Abstract
In an aspect, the present invention provides a high frequency
switching power converter. The high frequency switching power
converter may include a plurality of soft-switchable power cells
flexibly connected to receive an input signal in series and provide
an output. The high frequency switching power converter may further
include a controller for configuring the flexible connection and
for controlling the power cells to receive the input signal. In an
embodiment, each of the plurality of power cells may be separately
controllable by the controller. Further, a portion of the plurality
of power cells may be arranged with parallel outputs. Additionally,
at least one of the plurality of cells may include one or more
switched capacitors. In another embodiment, the at least one of the
plurality of cells may include at least one switched capacitor and
a DC/DC regulating converter.
Inventors: |
Sagneri; Anthony; (Boston,
MA) ; Hwang; George; (Cambridge, MA) ;
Burkhart; Justin; (Boston, MA) ; Chen; Fred;
(Boston, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FINsix Corporation |
Menlo Park |
CA |
US |
|
|
Assignee: |
FINsix Corporation
Menlo Park
CA
|
Family ID: |
45605681 |
Appl. No.: |
14/710749 |
Filed: |
May 13, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13213031 |
Aug 18, 2011 |
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14710749 |
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61392329 |
Oct 12, 2010 |
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61374993 |
Aug 18, 2010 |
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61374998 |
Aug 18, 2010 |
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Current U.S.
Class: |
363/21.02 |
Current CPC
Class: |
H02M 2001/0077 20130101;
H02M 3/33592 20130101; H02M 2001/0074 20130101; H02M 3/158
20130101; H02M 2001/0058 20130101; H02M 3/335 20130101; Y02B 70/10
20130101; H02M 1/42 20130101; H02M 3/07 20130101; H02M 1/4241
20130101; H02M 3/1584 20130101; H02M 3/285 20130101; H02M 2001/007
20130101 |
International
Class: |
H02M 3/335 20060101
H02M003/335; H02M 1/42 20060101 H02M001/42 |
Claims
1. A power converter, comprising: a plurality of power cells
configured to provide a plurality of energy transfer paths from a
voltage-varying input of the plurality of power cells to an output
of the plurality of power cells; and one or more energy storage
networks at an input of at least one of the plurality of power
cells, wherein the plurality of power cells is configured to
deliver a first fraction of available input energy to the one or
more energy storage networks, deliver a second fraction of
available input energy to the output of the plurality of power
cells, and adjust the first fraction and second fraction for
facilitating outputting a substantially constant output of the
plurality of power cells and for controlling the energy drawn from
the voltage-varying input of the plurality of power cells.
2. The power converter of claim 1, wherein the plurality of power
cells comprises a first power cell and a second power cell, wherein
an input of the first power cell is connected in series with an
input of the second power cell.
3. The power converter of claim 2, wherein the one or more energy
storage networks comprises a capacitor.
4. The power converter of claim 3, wherein the capacitor is
connected to a terminal between the input of the first power cell
and the input of the second power cell.
5. The power converter of claim 4, further comprising a switch
configured to bypass the capacitor when a voltage of the
voltage-varying input is less than a voltage across the
capacitor.
6. The power converter of claim 2, wherein an output of the first
power cell is connected in parallel with an output of the second
power cell.
7. The power converter of claim 2, wherein the first power cell is
configured to control the energy drawn from the voltage-varying
input.
8. The power converter of claim 7, wherein the second power cell is
configured to control the output of the plurality of power cells to
be substantially constant.
9. The power converter of claim 1, wherein the plurality of power
cells has a switching frequency higher than 1 MHz.
10. The power converter of claim 1, further comprising a rectifier
connected to an input of the plurality of power cells.
11. A power converter, comprising: a plurality of power cells
providing a plurality of energy transfer paths from a time-varying
input of the plurality of power cells to an output of the plurality
of power cells; at least one energy storage network coupled to an
input of at least one power cell of the plurality of power cells;
and a controller configured to control at least one first power
cell of the plurality of power cells to control power factor of the
power converter, and control at least one second power cell of the
plurality of power cells to regulate the output of the plurality of
power cells.
12. The power converter of claim 11, wherein the plurality of power
cells comprises a first power cell and a second power cell, wherein
an input of the first power cell is connected in series with an
input of the second power cell.
13. The power converter of claim 12, wherein the one or more energy
storage networks comprises a capacitor.
14. The power converter of claim 13, wherein the capacitor is
connected to a terminal between the input of the first power cell
and the input of the second power cell.
15. The power converter of claim 14, further comprising a switch
configured to bypass the capacitor when a voltage of the
time-varying input is less than a voltage across the capacitor.
16. The power converter of claim 12, wherein an output of the first
power cell is connected in parallel with an output of the second
power cell.
17. The power converter of claim 12, wherein the first power cell
is configured to control the power factor.
18. The power converter of claim 17, wherein the second power cell
is configured to regulate the output of the plurality of power
cells.
19. The power converter of claim 11, wherein the plurality of power
cells has a switching frequency higher than 1 MHz.
20. The power converter of claim 11, further comprising a rectifier
connected to an input of the plurality of power cells.
21. The power converter of claim 11, wherein the time-varying input
comprises an AC line voltage.
22. The power converter of claim 11, wherein the output of the
plurality of power converters comprises a DC voltage.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
13/213,031, filed Aug. 18, 2011, which claims the benefit of the
following provisional applications: U.S. Ser. No. 61/374,993 filed
Aug. 18, 2010; U.S. Ser. No. 61/374,998 filed Aug. 18, 2010; and
U.S. Ser. No. 61/392,329 filed Oct. 12, 2010. Each of the
above-identified applications is hereby incorporated by reference
in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field
[0003] The methods and systems described herein relate to very high
frequency power conversion technology, techniques, methods,
applications, and systems.
[0004] 2. Description of the Related Art
[0005] Increasing the switching frequency of a switched-mode power
supply (SMPS) is a goal that is widely sought after as a means to
increase power density and improve transient performance. However,
increasing switching frequency using conventional power converter
topologies (boost, buck, flyback, etc.) results with significantly
degraded efficiency. Additionally, as switching frequency is
increased, power density only increases until an optimal switching
frequency is reached, at which point power density begins to
decrease again. Therefore, conventional solutions appear to be
lacking to satisfy demand.
SUMMARY OF THE INVENTION
[0006] The methods and systems described herein may comprise a
next-generation very high frequency (VHF, 30-300 MHz) power supply
architecture using chip-scale components. Fundamental technology
and methods of VHF conversion and exemplary benefits for
solid-state lighting applications and the like are outlined herein
in light of several enhancements enabled by the methods and systems
described herein. Further applications of the core VHF converter
architecture, both AC-DC and DC-DC are enumerated in the figures
and associated descriptions. Together these elements provide both a
description of the basic innovations and methods and a range of
useful and beneficial applications for those innovations.
[0007] In the case of line-connected LED drivers, which are AC-DC
converters for general illumination applications, the benefits are
several including a greater than 10-fold reduction in volume, much
lower cost, higher reliability, a high degree of integration, high
efficiency and very fast transient response. Taken together these
characteristics form the basis for a useful array of LED driver
systems suitable for both retrofit lamps, such as A19, MR16, GU10,
and various PAR forms, as well as in solid-state luminaires.
However, applications of the inventive very high frequency
chip-scale power supply architecture are not limited to LED and/or
solid state drivers. This technology may be used in any application
that can benefit from the several benefits described herein.
[0008] The unique characteristics of the VHF power supply
architecture described herein enables power converters with very
high power density, high performance, and high transient response
while utilizing very few components. This enables applications in
many spaces, such as Solid State Lighting and portable mobile
devices, where size and cost are of key concern, and military and
industrial applications where the highest power densities and
improved reliability due to simpler and fewer components are of
interest. One exemplary application is radar, particularly
air-intercept radar on fighter jets, where size, weight, and
transient performance are key attributes. Present power converter
systems require large and heavy capacitor banks to sustain
transients demanded by the radar under transmit. By utilizing the
invention described herein, these capacitors no longer need to be
sized by transient considerations, rather ripple alone. This allows
a dramatic reduction in bulk energy storage in combination with the
reduction in the main power stage. This set of features will offer
a clear advantage in such high-performance military
applications.
[0009] In the retrofit lamp space the needs are several: foremost
is the requirement for low cost, nearly as important is small size,
while high-performance (efficiency), high-reliability, and a full
range of functionality are all of keen interest depending on the
particular lamp type and intended target market. In each case, the
existing power converter technology falls short of desired
characteristics necessary to propel SSL lamps to commercial
success. The inventive technology described herein in this area
addresses each of these shortfalls and offers a compelling package
to a lamp maker.
[0010] In an aspect, the present invention provides a high
frequency switching power converter. The high frequency switching
power converter may include a plurality of soft-switchable power
cells flexibly connected to receive an input signal in series and
provide an output. The high frequency switching power converter may
further include a controller for configuring the flexible
connection and for controlling the power cells to receive the input
signal. In an embodiment, each of the plurality of power cells may
be separately controllable by the controller. Further, a portion of
the plurality of power cells may be arranged with parallel outputs.
Additionally, at least one of the plurality of cells may include
one or more switched capacitors. In another embodiment, the at
least one of the plurality of cells may include at least one
switched capacitor and a DC/DC regulating converter.
[0011] The high frequency switching power converter may also
include an output stage for receiving outputs from the portion of
the plurality of power cells to provide a combined output and for
delivering the combined output to a load. The output stage may
include at least one transformer with multiple primary windings.
Further, each of the multiple primary windings may receive an
output from one of the plurality of power cells. The output stage
may further include a plurality of capacitors, an input of each of
which may be connected to an output from one of the plurality of
cells. Further, an output of each of the plurality of capacitors
may be connected in parallel for providing the combined output. In
an embodiment, the output stage may facilitate configuring a
parallel output combination of the plurality of power cells. The
DC/DC regulating converter may be disposed between the at least one
switched capacitor and the output stage.
[0012] In an embodiment, the high frequency switching power
converter may include a plurality of sets of stacked cells each set
providing at least one output. Further, a portion of the plurality
of sets of stacked cells may be configured to provide parallel
outputs. The high frequency switching power converter may further
include PCB etched inductors and/or transformers with or without
magnetic core material, varactor controlled network tuning,
resonant switching, and the like. In another embodiment, the high
frequency switching power converter may be adapted for use with a
laptop, may be integrated into a display screen module, may be
integrated into an AC line power cord assembly, may be adapted for
use with a mobile phone, may be integrated into a wireless base
station, may be integrated into an electrical vehicle, may be
adapted for use with airborne radar, and the like.
[0013] In another aspect, the present invention provides a stacked
cell switching power converter. The stacked cell switching power
converter may include a plurality of stacked power cells flexibly
connected to receive a DC input signal in series and may provide a
DC output. The stacked cell switching power converter may also
include a controller for configuring the flexible connection. The
controller may control the plurality of stacked power cells to
receive the DC input signal, and may facilitate resonant switching.
Further, the stacked cell switching power converter may include an
output stage for combining an output from each of a portion of the
plurality of stacked power cells to deliver a combined DC output to
a load.
[0014] In an embodiment, the stacked cell switching power converter
may include PCB etched inductors and/or transformers with or
without magnetic core material, varactor controlled network tuning,
resonant switching, and the like. In another embodiment, the
stacked cell switching power converter may be adapted for use with
a laptop, may be integrated into a display screen module, may be
integrated into an AC line power cord assembly, may be adapted for
use with a mobile phone, may be integrated into a wireless base
station, may be integrated into an electrical vehicle, may be
adapted for use with airborne radar, and the like.
[0015] In yet another aspect, the present invention provides a
stacked cell soft-switchable power converter. The stacked cell
soft-switchable power converter may include a plurality of stacked
power cells flexibly connected to receive an input signal and
provide an output. Further, the stacked cell soft-switchable power
converter may include a controller for configuring the flexible
connection. The controller may control the plurality of stacked
power cells to receive the input signal, and may facilitate power
cell soft switching. The stacked cell soft-switchable power
converter may also include an output stage for receiving an output
from each of a portion of the plurality of stacked power cells and
for delivering a combined output to a load.
[0016] In an embodiment, the stacked cell soft-switchable power
converter may include PCB etched inductors and/or transformers with
or without magnetic core material, varactor controlled network
tuning, resonant switching, and the like. In another embodiment,
the stacked cell soft-switchable power converter may be adapted for
use with a laptop, may be integrated into a display screen module,
may be integrated into an AC line power cord assembly, may be
adapted for use with a mobile phone, may be integrated into a
wireless base station, may be integrated into an electrical
vehicle, may be adapted for use with airborne radar, and the
like.
[0017] In still another aspect, the present invention provides a
silicon-based stacked-cell switching power converter. The
silicon-based stacked-cell switching power converter may include a
plurality of silicon power cells configured in a series stack to
receive an input signal with a peak amplitude greater than 50V and
to provide an output from each of the plurality of silicon power
cells. The silicon-based stacked-cell switching power converter may
further include a controller for controlling the plurality of
silicon power cells to receive the input signal. The controller may
facilitate switching the silicon-based stacked-cell switching power
converter at a frequency in excess of 5 MHz. In addition, the
silicon-based stacked-cell switching power converter may include an
output stage for receiving an output from a portion of the
plurality of silicon power cells and for delivering a combined
output to a load.
[0018] In an embodiment, the silicon-based stacked-cell switching
power converter may include PCB etched inductors and/or
transformers with or without magnetic core material, varactor
controlled network tuning, resonant switching, and the like. In
another embodiment, the silicon-based stacked-cell switching power
converter may be adapted for use with a laptop, may be integrated
into a display screen module, may be integrated into an AC line
power cord assembly, may be adapted for use with a mobile phone,
may be integrated into a wireless base station, may be integrated
into an electrical vehicle, may be adapted for use with airborne
radar, and the like.
[0019] In yet another aspect, the present invention provides a low
power density stacked-cell switching power converter. The low power
density stacked-cell switching power converter may include a
plurality of power cells configured to receive an input signal with
a peak amplitude greater than 50V in series and to provide an
output. Further, the low power density stacked-cell switching power
converter may include a controller for configuring the plurality of
power cells to receive the input signal. The controller may
facilitate switching the low power density stacked-cell switching
power converter at a frequency in excess of 5 MHz. The low power
density stacked-cell switching power converter may also include an
output stage for receiving an output from a portion of the
plurality of power cells and for delivering a combined output to a
load. In an embodiment, the low power density stacked-cell
switching power converter may provide power density that may be
lower than power density provided by a single cell power converter
providing a substantially identical function.
[0020] In an embodiment, the low power density stacked-cell
switching power converter may include PCB etched inductors and/or
transformers with or without magnetic core material, varactor
controlled network tuning, resonant switching, and the like. In
another embodiment, the low power density stacked-cell switching
power converter may be adapted for use with a laptop, may be
integrated into a display screen module, may be integrated into an
AC line power cord assembly, may be adapted for use with a mobile
phone, may be integrated into a wireless base station, may be
integrated into an electrical vehicle, may be adapted for use with
airborne radar, and the like.
[0021] In still another aspect, the present invention provides a
stacked-silicon cell switching power converter. The stacked-silicon
cell switching power converter may include a plurality of silicon
power converter cells configured in a series stack to receive an
input signal with a peak amplitude greater than 50V and to provide
a plurality of outputs. Further, the stacked-silicon cell switching
power converter may include a controller for controlling the
plurality of silicon power converter cells to ensure that no
silicon power converter cell receives an input signal in excess of
60V. The controller may facilitate switching the stacked-silicon
cell switching power converter at a frequency in excess of 5 MHz.
In addition, the stacked-silicon cell switching power converter may
include an output stage for combining an output from each of a
portion of the plurality of silicon power converter cells to
deliver a combined output to a load.
[0022] In an embodiment, the stacked-silicon cell switching power
converter may include PCB etched inductors and/or transformers with
or without magnetic core material, varactor controlled network
tuning, resonant switching, and the like. In another embodiment,
the stacked-silicon cell switching power converter may be adapted
for use with a laptop, may be integrated into a display screen
module, may be integrated into an AC line power cord assembly, may
be adapted for use with a mobile phone, may be integrated into a
wireless base station, may be integrated into an electrical
vehicle, may be adapted for use with airborne radar, and the
like.
[0023] In yet another aspect, the present invention provides a
stacked-silicon cell switching power converter. The stacked-silicon
cell switching power converter may include a plurality of silicon
power converter cells configured in a series stack to receive an
input signal with a peak amplitude greater than 50V and to provide
a plurality of outputs. The stacked-silicon cell switching power
converter may further include a controller for controlling the
plurality of silicon power converter cells to ensure that no
silicon power converter cell receives an input signal less than 20V
nor in excess of 60V. The controller may facilitate switching the
stacked-silicon cell switching power converter at a frequency in
excess of 5 MHz. The stacked-silicon cell switching power converter
may also include an output stage for combining an output from each
of a portion of the plurality of silicon power converter cells to
deliver a combined output to a load.
[0024] In an embodiment, the stacked-silicon cell switching power
converter may include PCB etched inductors and/or transformers with
or without magnetic core material, varactor controlled network
tuning, resonant switching, and the like. In another embodiment,
the stacked-silicon cell switching power converter may be adapted
for use with a laptop, may be integrated into a display screen
module, may be integrated into an AC line power cord assembly, may
be adapted for use with a mobile phone, may be integrated into a
wireless base station, may be integrated into an electrical
vehicle, may be adapted for use with airborne radar, and the
like.
[0025] In still another aspect, the present invention provides a
VHF power converter. The VHF power converter may include a switched
capacitor stage. The switched capacitor stage may include a
plurality of switched capacitors for dividing the input voltage
among the plurality of capacitors. The VHF power converter may
further include a bypass switch. The bypass switch may select
between the input voltage and an output of the switched capacitor
stage. Further, a control of the bypass switch may be based on the
input voltage. The VHF power converter may also include a VHF
regulating stage for converting an input voltage to an output
voltage. The switched capacitor stage may be followed by the
by-pass switch that may be further connected to the VHF regulating
stage.
[0026] In an embodiment, the VHF power converter may include PCB
etched inductors and/or transformers with or without magnetic core
material, varactor controlled network tuning, resonant switching,
and the like. In another embodiment, the VHF power converter may be
adapted for use with a laptop, may be integrated into a display
screen module, may be integrated into an AC line power cord
assembly, may be adapted for use with a mobile phone, may be
integrated into a wireless base station, may be integrated into an
electrical vehicle, may be adapted for use with airborne radar, and
the like.
[0027] In another aspect, the present invention provides a method
of controlling average power delivered from a VHF power converter
to an auxiliary output. The method may include rectifying AC power
that may be generated from an inverter of the VHF power converter
and providing it to an auxiliary power port in a first phase. The
auxiliary power port may be used to supply the power required to
drive gates of one or more powered devices. In an embodiment, the
powered device may be an LED-based lighting unit. The auxiliary
power port may also be used to provide power to a portion of the
VHF power converter.
[0028] The method may further include generating AC power from the
auxiliary power port and providing it to the VHF power converter in
a second phase. Switching between generating auxiliary power in the
first phase to generating AC power in the second phase may be
controlled to facilitate controlling an average power delivered
from the VHF power converter. In an embodiment, the method may
further include controlling the auxiliary rectifier in an auxiliary
power control loop that may be independent of a control loop of the
VHF power converter for providing power to a load. In embodiments,
the auxiliary power control loop may be a feed forward control
loop.
[0029] In another aspect, the present invention provides a method.
The method may include receiving a varying input voltage signal to
be applied to a plurality of series stacked high frequency power
converter cells. The plurality of series stacked high frequency
power converter cells for producing an output from the varying
input voltage signal. In an embodiment, the varying input voltage
signal may be an AC line signal. Further, the output may be a DC
voltage, a fixed current, and the like. In an embodiment,
individual cells of the plurality of series stacked high frequency
power converter cells may be activated at different determined
amplitudes as the amplitude of the varying input voltage signal
varies. The individual cells of the plurality of series stacked
high frequency power converter cells may be deactivated at
different amplitudes as the determined amplitude of the varying
input voltage signal decreases. Further, the individual cells of
the plurality of series stacked high frequency power converter
cells may be bypassed at different determined amplitudes as the
determined amplitude of the varying input voltage signal
decreases.
[0030] In another embodiment, each of the plurality of series
stacked high frequency power converter cells may be separately
controllable. Also, a portion of the plurality of series stacked
high frequency power converter cells may be arranged with parallel
outputs. At least one of the plurality of series stacked high
frequency power converter cells may include one or more switched
capacitors. Further, at least one of the plurality of series
stacked high frequency power converter cells may include at least
one switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series with the at least
one switched capacitor.
[0031] The method may further include determining an amplitude of
the varying input voltage signal. The method may also include
controlling the series stacked high frequency power converter cells
to produce the output based on the amplitude of the varying input
voltage signal. The controlling may include soft switching of the
plurality of series stacked high frequency power converter cells.
Further, the controlling may be based on an instantaneous amplitude
of the varying input voltage signal, a local average of the varying
input voltage signal, and the like.
[0032] In an embodiment, the controlling may include operating at
least one high frequency power converter cell bypass function for
the plurality of series stacked high frequency power converter
cells. The controlling may further include maintaining efficiency
of the plurality of series stacked high frequency power converter
cells above a minimum efficiency threshold. In another embodiment,
the minimum efficiency threshold may be seventy percent,
seventy-five percent, eighty percent, and the like. In addition,
the controlling may include passive switched capacitor voltage
balancing. The method may further include an output stage that may
facilitate configuring a parallel output combination of the
plurality of series stacked high frequency power converter
cells.
[0033] In yet another aspect, the present invention provides a
method. The method may include receiving a varying input voltage
signal to be applied to a plurality of series stacked high
frequency power converter cells. The plurality of series stacked
high frequency power converter cells for producing an output from
the varying input voltage signal. In an embodiment, the varying
input voltage signal may be an AC line signal. Further, the output
may be a DC voltage, a fixed current, and the like. In an
embodiment, individual cells of the plurality of series stacked
high frequency power converter cells may be activated at different
determined amplitudes as the amplitude of the varying input voltage
signal varies. The individual cells of the plurality of series
stacked high frequency power converter cells may be deactivated at
different amplitudes as the determined amplitude of the varying
input voltage signal decreases. Further, the individual cells of
the plurality of series stacked high frequency power converter
cells may be bypassed at different determined amplitudes as the
determined amplitude of the varying input voltage signal
decreases.
[0034] In another embodiment, each of the plurality of series
stacked high frequency power converter cells may be separately
controllable. Also, a portion of the plurality of series stacked
high frequency power converter cells may be arranged with parallel
outputs. At least one of the plurality of series stacked high
frequency power converter cells may include one or more switched
capacitors. Further, at least one of the plurality of series
stacked high frequency power converter cells may include at least
one switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series with the at least
one switched capacitor.
[0035] The method may further include determining an amplitude of
the varying input voltage signal. The method may also include
controlling the series stacked high frequency power converter cells
to produce the output based on the amplitude of the varying input
voltage signal. The controlling may include soft switching of the
plurality of series stacked high frequency power converter cells.
Further, the controlling may be based on an instantaneous amplitude
of the varying input voltage signal, a local average of the varying
input voltage signal, and the like.
[0036] In an embodiment, the controlling may include operating at
least one high frequency power converter cell bypass function for
the plurality of series stacked high frequency power converter
cells. The controlling may further include maintaining efficiency
of the plurality of series stacked high frequency power converter
cells above a minimum efficiency threshold. In another embodiment,
the minimum efficiency threshold may be seventy percent,
seventy-five percent, eighty percent, and the like. In addition,
the controlling may include passive switched capacitor voltage
balancing. The method may further include an output stage that may
facilitate configuring a parallel output combination of the
plurality of series stacked high frequency power converter cells.
In an embodiment, the requirement of the output may be a current
requirement, a voltage requirement, a ripple requirement, a power
requirement, an isolation requirement, and the like.
[0037] In still another aspect, the present invention provides a
method. The method may include receiving a varying input voltage
signal to be applied to a plurality of series stacked high
frequency power converter cells. The plurality of series stacked
high frequency power converter cells for producing an output from
the varying input voltage signal. In an embodiment, the varying
input voltage signal may be an AC line signal. Further, the output
may be a DC voltage, a fixed current, and the like. In an
embodiment, individual cells of the plurality of series stacked
high frequency power converter cells may be activated at different
determined amplitudes as the amplitude of the varying input voltage
signal varies. The individual cells of the plurality of series
stacked high frequency power converter cells may be deactivated at
different amplitudes as the determined amplitude of the varying
input voltage signal decreases. Further, the individual cells of
the plurality of series stacked high frequency power converter
cells may be bypassed at different determined amplitudes as the
determined amplitude of the varying input voltage signal
decreases.
[0038] In another embodiment, each of the plurality of series
stacked high frequency power converter cells may be separately
controllable. Also, a portion of the plurality of series stacked
high frequency power converter cells may be arranged with parallel
outputs. At least one of the plurality of series stacked high
frequency power converter cells may include one or more switched
capacitors. Further, at least one of the plurality of series
stacked high frequency power converter cells may include at least
one switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series with the at least
one switched capacitor.
[0039] The method may further include determining an amplitude of
the varying input voltage signal. The method may also include
controlling the series stacked high frequency power converter cells
to produce the output based on the amplitude of the varying input
voltage signal. The controlling may include soft switching of the
plurality of series stacked high frequency power converter cells.
Further, the controlling may be based on an instantaneous amplitude
of the varying input voltage signal, a local average of the varying
input voltage signal, and the like.
[0040] In an embodiment, the controlling may include operating at
least one high frequency power converter cell bypass function for
the plurality of series stacked high frequency power converter
cells. The controlling may further include maintaining efficiency
of the plurality of series stacked high frequency power converter
cells above a minimum efficiency threshold. In another embodiment,
the minimum efficiency threshold may be seventy percent,
seventy-five percent, eighty percent, and the like. In addition,
the controlling may include passive switched capacitor voltage
balancing. The method may further include an output stage that may
facilitate configuring a parallel output combination of the
plurality of series stacked high frequency power converter cells.
Further, the feedback may be a measure of output current.
[0041] In yet another aspect, the present invention provides a
method. The method may include receiving a varying input voltage
signal to be applied to a plurality of series stacked high
frequency power converter cells. The plurality of series stacked
high frequency power converter cells for producing an output. The
input voltage may be greater than that which may be sustainable by
any one of the plurality of cells. In an embodiment, the varying
input voltage signal may be an AC line signal. Further, the output
may be a DC voltage, a fixed current, and the like. In an
embodiment, individual cells of the plurality of series stacked
high frequency power converter cells may be activated at different
determined amplitudes as the amplitude of the varying input voltage
signal varies. The individual cells of the plurality of series
stacked high frequency power converter cells may be deactivated at
different amplitudes as the determined amplitude of the varying
input voltage signal decreases. Further, the individual cells of
the plurality of series stacked high frequency power converter
cells may be bypassed at different determined amplitudes as the
determined amplitude of the varying input voltage signal
decreases.
[0042] In another embodiment, each of the plurality of series
stacked high frequency power converter cells may be separately
controllable. Also, a portion of the plurality of series stacked
high frequency power converter cells may be arranged with parallel
outputs. At least one of the plurality of series stacked high
frequency power converter cells may include one or more switched
capacitors. Further, at least one of the plurality of series
stacked high frequency power converter cells may include at least
one switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series with the at least
one switched capacitor.
[0043] The method may also include controlling the series stacked
high frequency power converter cells distribute the input voltage
among a portion of the plurality of power converter cells so that
no cell may receive a portion of the input that exceeds that which
may be sustainable by the cell. The controlling may include soft
switching of the plurality of series stacked high frequency power
converter cells. Further, the controlling may be based on an
instantaneous amplitude of the varying input voltage signal, a
local average of the varying input voltage signal, and the
like.
[0044] In an embodiment, the controlling may include operating at
least one high frequency power converter cell bypass function for
the plurality of series stacked high frequency power converter
cells. The controlling may further include maintaining efficiency
of the plurality of series stacked high frequency power converter
cells above a minimum efficiency threshold. In another embodiment,
the minimum efficiency threshold may be seventy percent,
seventy-five percent, eighty percent, and the like. In addition,
the controlling may include passive switched capacitor voltage
balancing. The method may further include an output stage that may
facilitate configuring a parallel output combination of the
plurality of series stacked high frequency power converter cells.
Further, each cell of the plurality of cells may be
silicon-based.
[0045] In another aspect, the present invention provides a method.
The method may include receiving a varying input voltage signal to
be applied to a plurality of series stacked high frequency power
converter cells. The plurality of series stacked high frequency
power converter cells for producing an output from the varying
input voltage signal. In an embodiment, the varying input voltage
signal may be an AC line signal. Further, the output may be a DC
voltage, a fixed current, and the like. In an embodiment,
individual cells of the plurality of series stacked high frequency
power converter cells may be activated at different determined
amplitudes as the amplitude of the varying input voltage signal
varies. The individual cells of the plurality of series stacked
high frequency power converter cells may be deactivated at
different amplitudes as the determined amplitude of the varying
input voltage signal decreases. Further, the individual cells of
the plurality of series stacked high frequency power converter
cells may be bypassed at different determined amplitudes as the
determined amplitude of the varying input voltage signal
decreases.
[0046] In another embodiment, each of the plurality of series
stacked high frequency power converter cells may be separately
controllable. Also, a portion of the plurality of series stacked
high frequency power converter cells may be arranged with parallel
outputs. At least one of the plurality of series stacked high
frequency power converter cells may include one or more switched
capacitors. Further, at least one of the plurality of series
stacked high frequency power converter cells may include at least
one switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series with the at least
one switched capacitor.
[0047] The method may further include determining an average of the
output voltage. The method may also include synchronously
controlling the series stacked high frequency power converter cells
to produce the output from the varying input voltage based on the
determined average. The controlling may include soft switching of
the plurality of series stacked high frequency power converter
cells. Further, the controlling may be based on an instantaneous
amplitude of the varying input voltage signal, a local average of
the varying input voltage signal, and the like.
[0048] In an embodiment, the controlling may include operating at
least one high frequency power converter cell bypass function for
the plurality of series stacked high frequency power converter
cells. The controlling may further include maintaining efficiency
of the plurality of series stacked high frequency power converter
cells above a minimum efficiency threshold. In another embodiment,
the minimum efficiency threshold may be seventy percent,
seventy-five percent, eighty percent, and the like. In addition,
the controlling may include passive switched capacitor voltage
balancing. The method may further include an output stage that may
facilitate configuring a parallel output combination of the
plurality of series stacked high frequency power converter
cells.
[0049] In another aspect, the present invention provides a method.
The method may include receiving a single input voltage signal into
a soft-switched high frequency power converter. The soft-switched
high frequency power converter may produce a plurality of output
values. The plurality of output values may be individually
controllable. Further, the plurality of output values may be
individually selected from a current output value and a voltage
output value. In an embodiment, the single input voltage signal may
be an AC input, a DC input, a fixed voltage, a varying voltage, and
the like. The method may further include controlling the
soft-switched high frequency power converter to produce a first
output during a first time interval for a first load and a second
output during a second time interval for a second load. The method
may also include providing at least one load isolation control
signal to facilitate bypassing the second load during the first
time interval and bypassing the first load during the second time
interval.
[0050] In an embodiment, the first output may be one of a current
and a voltage. Further, the first output may be regulated during
the first time interval. In another embodiment, the second output
may be one of a current and a voltage. Further, the second output
may be regulated during the second time interval. In embodiments,
the voltage output during at least one of the first and second time
intervals may be a substantially fixed voltage. Further, each
portion of the load may receive a different output voltage, a
substantially fixed current, a different current, and the like.
Power from the single input voltage signal may be
time-division-multiplexed among the outputs. In addition, at least
one of the first load and the second load may be a portion of a
string of LEDs. Also, the output provided during each time interval
may drive separate LEDs to facilitate achieving a substantially
constant color temperature light output.
[0051] In yet another aspect, the present invention provides a
method. The method may include receiving a single input voltage
signal into a soft-switched high frequency power converter
including a plurality of series stacked high frequency power
converter cells. The soft-switched high frequency power converter
may produce a plurality of output values. Each of the plurality of
series stacked high frequency power converter cells may be
separately controllable. Further, a portion of the plurality of
series stacked high frequency power converter cells may be arranged
with parallel outputs. In an embodiment, at least one of the
plurality of series stacked high frequency power converter cells
may include one or more switched capacitors. In another embodiment,
the at least one of the plurality of series stacked high frequency
power converter cells may include at least one switched capacitor
and a DC/DC regulating converter. The DC/DC regulating converter
may be disposed in series with the at least one switched
capacitor.
[0052] The method may further include controlling the soft-switched
high frequency power converter cells to produce a first output
during a first time interval for a first load and a second output
during a second time interval for a second load. The method may
also include providing at least one load isolation control signal
to facilitate bypassing the second load during the first time
interval and bypassing the first load during the second time
interval. The controlling may include soft switching of the
plurality of series stacked high frequency power converter cells.
The controlling may also include operating at least one high
frequency power converter cell bypass function for the plurality of
series stacked high frequency power converter cells.
[0053] Further, the controlling may include maintaining efficiency
of the plurality of series stacked high frequency power converter
cells above a minimum efficiency threshold. In an embodiment, the
minimum efficiency threshold may be seventy percent, seventy-five
percent, eighty percent, and the like. The controlling may further
include passive switched capacitor voltage balancing. In an
embodiment, the method may include an output stage that may
facilitate configuring a parallel output combination of the
plurality of series stacked high frequency power converter
cells.
[0054] In an embodiment, the first output may be one of a current
and a voltage. The first output may be regulated during the first
time interval. In another embodiment, the second output may be one
of a current and a voltage. The second output may be regulated
during the second time interval. Further, the plurality of output
values may be individually controllable. The plurality of output
values may be individually selected from a current output value and
a voltage output value. In an embodiment, the single input voltage
signal may be an AC input, a DC input, a fixed voltage, a varying
voltage, and the like.
[0055] In another embodiment, the voltage output during at least
one of the first and second time intervals may be a substantially
fixed voltage. Further, each portion of the loads may receive a
different output voltage, a substantially fixed current, a
different current, and the like. At least one of the first load and
the second load may be a portion of a string of LEDs. The output
provided during each time interval may drive separate LEDs to
facilitate achieving a substantially constant color temperature
light output.
[0056] In still another aspect, the present invention provides a
method. The method may include receiving a single input voltage
signal into a soft-switched high frequency power converter for
producing a plurality of output values on an output port. The
method may further include controlling the soft-switched high
frequency power converter to produce a first output during a first
time interval and a second output during a second time interval.
The controlling may include maintaining efficiency of the
soft-switched high frequency power converter above a minimum
efficiency threshold. In an embodiment, the minimum efficiency
threshold may be seventy percent, seventy-five percent, eighty
percent, and the like. The controlling may further include passive
switched capacitor voltage balancing. In an embodiment, the first
output may be one of a current and a voltage. The first output may
be regulated during the first time interval. In another embodiment,
the second output may be one of a current and a voltage. The second
output may be regulated during the second time interval.
[0057] Further, the plurality of output values may be individually
controllable. The plurality of output values may be individually
selected from a current output value and a voltage output value.
The single input voltage signal may be an AC input, a DC input, a
fixed voltage, a varying voltage, and the like. The voltage output
during at least one of the first and second time intervals may be a
substantially fixed voltage. The method may also include connecting
a string of LEDs substantially in parallel to the output port. The
string of LEDs may be configured so that a first portion of the
LEDs may be controllable to form a circuit with the soft-switched
high frequency power converter during the first time interval and a
second portion of the LEDs may be controllable to form a circuit
with the soft-switched high frequency power converter during the
second time interval to facilitate achieving substantially constant
color temperature light.
[0058] Further, each LED in the string of LEDs may receive a
different output voltage, a substantially fixed current, a
different current, and the like. In addition, power from the single
input voltage signal may be time-division-multiplexed among the
outputs. The soft-switched high frequency power converter may
employ time-division-multiplexing of the output port.
[0059] In another aspect, the present invention provides a method.
The method may include receiving a single input voltage signal into
a soft-switched high frequency power converter for producing a
plurality of output values on an output port. The method may
further include controlling the soft-switched high frequency power
converter to output a first output during a first time interval for
a first motherboard circuit load and a second output during a
second time interval for a second motherboard circuit load. The
controlling may include maintaining efficiency of the plurality of
soft-switched high frequency power converter above a minimum
efficiency threshold. In an embodiment, the minimum efficiency
threshold may be seventy percent, seventy-five percent, eighty
percent, and the like.
[0060] The controlling may further include passive switched
capacitor voltage balancing. In an embodiment, the first output may
be one of a current and a voltage. The first output may be
regulated during the first time interval. In another embodiment,
the second output may be one of a current and a voltage. The second
output may be regulated during the second time interval. Further,
the plurality of output values may be individually controllable.
The plurality of output values may be individually selected from a
current output value and a voltage output value. In an embodiment,
the single input voltage signal may be an AC input, a DC input, a
fixed voltage, a varying voltage, and the like.
[0061] Further, the voltage output during at least one of the first
and second time intervals may be a substantially fixed voltage. The
method may also include providing at least one output to facilitate
disconnecting the second motherboard circuit load from the
converter during the first time interval and disconnecting the
first motherboard circuit load from the soft-switched high
frequency power converter during the second time interval. In an
embodiment, the first motherboard circuit load and the second
motherboard circuit load may receive a different output voltage, a
substantially fixed current, a different current, and the like. In
addition, power from the single input voltage signal may be
time-division-multiplexed among the outputs.
[0062] In yet another aspect, the present invention provides a
method. The method may include receiving a single input voltage
signal into a soft-switched high frequency power converter for
producing a plurality of voltages on an output. The method may
further include connecting at least one color changing LED to the
output. The method may also include controlling the soft-switched
high frequency power converter to produce a first color out of the
at least one color changing LED during a first time interval and a
second color during a second time interval. Further, the
controlling may include maintaining efficiency of the soft-switched
high frequency power converter above a minimum efficiency
threshold. In an embodiment, the minimum efficiency threshold may
be seventy percent, seventy-five percent, eighty percent, and the
like. The controlling may further include passive switched
capacitor voltage balancing.
[0063] In an embodiment, the first color may be regulated during
the first time interval. In another embodiment, the second color
may be regulated during the second time interval. The plurality of
voltages may be individually controllable. The plurality of
voltages may be individually selected from a current output value
and a voltage output value. In an embodiment, the single input
voltage signal may be an AC input, a DC input, a fixed voltage, a
varying voltage, and the like. Further, the voltage output during
at least one of the first and second time intervals may be a
substantially fixed voltage.
[0064] In embodiments, each LED in the at least one color changing
LED may receive a different output voltage, a substantially fixed
current, a different current, and the like. In addition, power from
the single input voltage signal may be time-division-multiplexed
among the outputs. Further, the soft-switched high frequency power
converter may employ time-division-multiplexing of the output
port.
[0065] In another aspect, the present invention provides a system.
The system may include a VHF power converter adapted for driving an
LED-based light. The VHF power converter may include at least one
soft-switched power converter cell and at least one inductor. Each
inductor may include an inductance value no greater than one micro
henry. In an embodiment, the at least one inductor may be a PCB
etch-based inductor. Further, the at least one soft-switched power
converter cell may be silicon-based. The at least one soft-switched
power converter cell may switch at greater than 5 MHz.
[0066] In yet another aspect, the present invention provides a
system. The system may include a VHF power converter adapted for
driving an LED-based light. The power converter may include at
least one soft-switched power converter cell and at least one
inductor. Each inductor may include an inductance value no greater
than five micro henries. In an embodiment, the at least one
inductor may be a PCB etch-based inductor. Further, the at least
one soft-switched power converter cell may be silicon-based. The at
least one soft-switched power converter cell may switch at greater
than 5 MHz.
[0067] In still another aspect, the present invention provides a
system. The system may include a high efficiency VHF power
converter adapted for driving an LED-based light. The power
converter may include at least one soft-switched power converter
cell and a plurality of electronic components. Further, none of the
plurality of electronic components may have an inductance value
greater than one micro henry. In an embodiment, the at least one
inductor may be a PCB etch-based inductor. Further, the at least
one soft-switched power converter cell may be silicon-based. The at
least one soft-switched power converter cell may switch at greater
than 5 MHz.
[0068] In another aspect, the present invention provides a system.
The system may include a stacked-cell, high efficiency,
soft-switched AC to DC power converter. The power converter may
include at least one soft-switched power converter cell and a
plurality of electronic components. Further, none of the plurality
of electronic components may have an inductance value greater than
one micro henry. Further, the at least one soft-switched power
converter cell may be silicon-based. The at least one soft-switched
power converter cell may switch at greater than 5 MHz.
[0069] In another aspect, the present invention provides a system.
The system may include a high efficiency, soft-switched power
converter for converting line AC to DC. The power converter may
include a plurality of electronic components. Further, none of the
plurality of electronic components may have an inductance value
greater than five micro henries. Further, the at least one
soft-switched power converter cell may be silicon-based. The at
least one soft-switched power converter cell may switch at greater
than 5 MHz.
[0070] In yet another aspect, the present invention provides a
stacked cell switching power converter. The stacked cell switching
power converter may include a plurality of stacked power cells
flexibly connected to receive an AC input signal in series and
provide a DC output. The stacked cell switching power converter may
further include a controller for configuring the plurality of
stacked power cells and the flexible connection to receive the DC
input signal and for facilitating fully resonant switching. The
stacked cell switching power converter may also include one or more
output synchronous rectifiers for receiving an output from each of
a portion of the plurality of stacked power cells in parallel and
for delivering a combined DC output to a load. Further, each of the
plurality of stacked power cells may be separately controllable. In
an embodiment, a portion of the plurality of stacked power cells
may be arranged with parallel outputs.
[0071] The stacked cell switching power converter may further
include an output stage that may facilitate configuring a parallel
output combination of the plurality of stacked power cells.
Further, at least one of the plurality of stacked power cells may
include one or more switched capacitors. At least one of the
plurality of stacked power cells may include at least one switched
capacitor and a DC/DC regulating converter. The DC/DC regulating
converter may be disposed in series with the at least one switched
capacitor.
[0072] In an embodiment, the controlling may include soft switching
of the plurality of stacked power cells. The controlling may
further include operating at least one power cell bypass function
for the plurality of stacked power cells. The controlling may also
include maintaining converter efficiency above a minimum efficiency
threshold. In another embodiment, the minimum efficiency threshold
may be seventy percent, seventy-five percent, eighty percent, and
the like. Further, the controlling may include passive switched
capacitor voltage balancing.
[0073] In still another aspect, the present invention provides a
method of converting AC to DC. The method may include disposing a
plurality of fully resonant switching VHF power converter cells
into a series stack to receive an AC input signal and output a DC
signal therefrom. Each of the plurality of fully resonant switching
VHF power converter cells may be separately controllable. Further,
a portion of the plurality of fully resonant switching VHF power
converter cells may be arranged with parallel outputs. The output
may facilitate powering an LED-based light with substantially no
visible light flicker. In an embodiment, the output may include
substantially no ripple voltage. Further, substantially no AC
frequency harmonics may be propagated to the output.
[0074] The method may further include connecting the DC signal
output from at least a portion of the plurality of fully resonant
switching VHF power converter cells in parallel to form a combined
output. The method may also include synchronously rectifying the
combined output. In addition, the method may include controlling
the plurality of fully resonant switching VHF power converter cells
for facilitating fully resonant switching and controlling the
output rectifier for synchronous rectification. In an embodiment,
the method may further include an output stage that may facilitate
configuring a parallel output combination of the plurality of fully
resonant switching VHF power converter cells. Further, at least one
of the plurality of fully resonant switching VHF power converter
cells may include one or more switched capacitors.
[0075] In another embodiment, at least one of the plurality of
fully resonant switching VHF power converter cells may include at
least one switched capacitor and a DC/DC regulating converter. The
DC/DC regulating converter may be disposed in series with the at
least one switched capacitor. The controlling may include soft
switching of the plurality of fully resonant switching VHF power
converter cells. Further, the controlling may include operating at
least one power cell bypass function for the plurality of fully
resonant switching VHF power converter cells. The controlling may
also include maintaining converter efficiency above a minimum
efficiency threshold.
[0076] In an embodiment, the minimum efficiency threshold may be
seventy percent, seventy-five percent, eighty percent, and the
like. The controlling may also include passive switched capacitor
voltage balancing. The output may facilitate powering an LED-based
light with substantially no visible light flicker. The output may
include substantially no ripple voltage. Further, substantially no
AC frequency harmonics may be propagated to the output.
[0077] In another aspect, the present invention provides a method
of converting DC to DC. The method may include disposing a
plurality of fully resonant switching VHF power converter cells
into a series stack to receive a DC input signal and output a DC
signal therefrom. Each of the plurality of fully resonant switching
VHF power converter cells may be separately controllable. Further,
a portion of the plurality of fully resonant switching VHF power
converter cells may be arranged with parallel outputs. The method
may further include connecting the DC signal output from at least a
portion of the plurality of fully resonant switching VHF power
converter cells in parallel to form a combined output. The method
may also include synchronously rectifying the combined output. In
addition, the method may include controlling the plurality of fully
resonant switching VHF power converter cells for facilitating
resonant switching. The method may further include controlling the
output rectifier for synchronous rectification.
[0078] In an embodiment, the method may include an output stage
that may facilitate configuring a parallel output combination of
the plurality of fully resonant switching VHF power converter
cells. Further, at least one of the plurality of fully resonant
switching VHF power converter cells may include one or more
switched capacitors. At least one of the plurality of fully
resonant switching VHF power converter cells may include at least
one switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series with the at least
one switched capacitor.
[0079] Further, controlling the plurality of fully resonant
switching VHF power converter cells may include soft switching of
the plurality of fully resonant switching VHF power converter
cells. The controlling the plurality of fully resonant switching
VHF power converter cells may include operating at least one power
cell bypass function for the plurality of fully resonant switching
VHF power converter cells. Furthermore, controlling the plurality
of fully resonant switching VHF power converter cells may include
maintaining converter efficiency above a minimum efficiency
threshold. In an embodiment, the minimum efficiency threshold may
be seventy percent, seventy-five percent, eighty percent, and the
like. The controlling the plurality of fully resonant switching VHF
power converter cells may also include passive switched capacitor
voltage balancing.
[0080] In yet another aspect, the present invention provides a
method of converting DC to DC. The method may include disposing a
plurality of fully resonant switching VHF power converter cells
into a serial stack to receive a DC input signal and output a DC
signal therefrom. The method may further include connecting the DC
signal output from at least a portion of the plurality of converter
cells in parallel to form a combined output. The method may also
include synchronously rectifying the combined output. Further, the
method may include controlling the power converter cells for
facilitating resonant switching. In addition, the method may
include controlling the power converter cells for facilitating
resonant switching. Each of the plurality of fully resonant
switching VHF power converter cells may be separately controllable.
Further, a portion of the plurality of fully resonant switching VHF
power converter cells may be arranged with parallel outputs.
[0081] In an embodiment, the method may further include an output
stage that may facilitate configuring a parallel output combination
of the plurality of fully resonant switching VHF power converter
cells. At least one of the plurality of fully resonant switching
VHF power converter cells may include one or more switched
capacitors. Further, at least one of the plurality of fully
resonant switching VHF power converter cells may include at least
one switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series with the at least
one switched capacitor.
[0082] In another embodiment, controlling the plurality of fully
resonant switching VHF power converter cells may include soft
switching of the plurality of fully resonant switching VHF power
converter cells. The controlling the plurality of fully resonant
switching VHF power converter cells may include operating at least
one power cell bypass function for the plurality of fully resonant
switching VHF power converter cells. Further, the controlling the
plurality of fully resonant switching VHF power converter cells may
include maintaining converter efficiency above a minimum efficiency
threshold. In an embodiment, the minimum efficiency threshold may
be seventy percent, seventy-five percent, eighty percent, and the
like. The controlling the plurality of fully resonant switching VHF
power converter cells may also include passive switched capacitor
voltage balancing. In addition, the output may facilitate powering
an LED-based light with substantially no visible light flicker. The
output may include substantially no ripple voltage.
[0083] In another aspect of the present invention, a method of
multi-path power factor correction is provided. The method may
include providing a plurality of energy transfer paths from an
voltage-varying input to an output. The method may also include
delivering a first fraction of available input energy to one or
more energy storage networks at the input of at least one of the
plurality of energy transfer paths. Further, the method may include
delivering a second fraction of available input energy to the
output. In addition, the method may include adjusting the first
fraction and second fraction for facilitating outputting a
substantially constant output and for controlling the energy drawn
from the input.
[0084] In an embodiment, the controlling may include controlling a
VHF power converter comprising the plurality of energy paths.
Further, a portion of the plurality of energy paths may include a
plurality of soft-switched power converter cells. The power factor
correcting may include switching at least one of the interleaved
power converter cells. The switching may produce unity power
factor. Further, a portion of the plurality of energy paths may
include a plurality of soft-switched stacked-cell power converters.
A portion of the stacked-cell power converters may be connected to
a common node. In an embodiment, the power converter may operate
above 5 MHz.
[0085] In yet another aspect of the present invention, a VHF
switching power converter is provided. The VHF switching power
converter may include at least one power cell configured to receive
an AC line input signal to provide an output suitable for powering
an LED. Each of the at least one power cell may be separately
controllable. Further, a portion of the at least one power cell may
be arranged with parallel outputs. The VHF switching power
converter may also include a controller for configuring the at
least one power cell to receive the input signal and for
facilitating switching the power converter at a frequency in excess
of 5 MHz. In addition, the VHF switching power converter may
include an output stage for receiving an output from the at least
one power cell and for delivering a combined output to an LED.
[0086] In an embodiment, the VHF switching power converter may
further include an output stage that may facilitate configuring a
parallel output combination of the at least one power cell. The at
least one power cell may include one or more switched capacitors.
Further, the at least one power cell may include at least one
switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series with the at least
one switched capacitor. The controller soft switching of the at
least one power cell. In an embodiment, the minimum efficiency
threshold may be seventy percent, seventy-five percent, eighty
percent, and the like. Further, the controlling the at least one
power cell may include passive switched capacitor voltage
balancing. The VHF switching power converter may operate above 5
MHz. In addition, powering the LED-based light may not require use
of electrolytic capacitors.
[0087] In another aspect of the present invention, a method of
powering an LED is provided. The method may include receiving an AC
line input signal with at least one VHF switching power cell. The
method may further include operating the power cell at a frequency
in excess of 5 MHz for providing a DC output suitable for powering
an LED. The method may also include receiving an output from the at
least one VHF switching power cell to provide a combined output. In
addition, the method may include delivering the combined output to
an LED. Each of the at least one power cell may be separately
controllable. A portion of the at least one VHF switching power
cell may be arranged with parallel outputs.
[0088] In an embodiment, the method may further include an output
stage that may facilitate configuring a parallel output combination
of the at least one VHF switching power cell. The at least one VHF
switching power cell may include one or more switched capacitors.
The at least one VHF switching power cell may include at least one
switched capacitor and a DC/DC regulating converter. The DC/DC
regulating converter may be disposed in series the at least one
switched capacitor.
[0089] In yet another aspect of the present invention, a stacked
cell soft-switchable power converter is provided. The stacked cell
soft-switchable power converter may include a plurality of stacked
power cells flexibly connected to receive an AC input signal and
provide an output suitable for powering an LED. The stacked cell
soft-switchable power converter may also include a controller for
configuring the power cells and the flexible connection to receive
the input sign. Further, the stacked cell soft-switchable power
converter may include an output stage for receiving an output from
each of a portion of the plurality of stacked power cells and for
delivering a combined DC output to an LED.
[0090] In an embodiment, each of the plurality of stacked power
cells may be separately controllable. Further, a portion of the
plurality of stacked power cells may be arranged with parallel
outputs. The stacked cell soft-switchable power converter may
further include an output stage that may facilitate configuring a
parallel output combination of the plurality of stacked power
cells. The plurality of stacked power cells may include one or more
switched capacitors. Further, the plurality of stacked power cells
may include at least one switched capacitor and a DC/DC regulating
converter. The DC/DC regulating converter may be disposed in series
the at least one switched capacitor.
[0091] In another embodiment, the controller operating at least one
power cell may bypass function for at least one power cell.
Further, the controller may maintain converter efficiency above a
minimum efficiency threshold. The minimum efficiency threshold may
be seventy percent, seventy-five percent, eighty percent, and the
like. The controller may be configured for passive switched
capacitor voltage balancing. Further, powering the LED-based light
may include controlling the operation of at least one cell in the
stacked power cell. The powering may include pulse-width-modulating
at least one cell in the stacked power cell. Further, the powering
may include power factor correcting.
[0092] In an aspect, the present invention provides a method. The
method may include receiving an input voltage signal to be applied
to a plurality of series stacked very high frequency power
converter cells. The plurality of series stacked very high
frequency power converter cells for producing an output voltage or
current. The method may also include determining an output current.
The method may further include controlling a portion of the
plurality of series stacked high frequency power converter cells
through pulse-width modulation to control the output current. Each
of the plurality of series stacked very high frequency power
converter cells may be separately controllable. A portion of the
plurality of series stacked very high frequency power converter
cells may be arranged with parallel outputs.
[0093] In an embodiment, the method may include an output stage
that may facilitate configuring a parallel output combination of
the plurality of series stacked very high frequency power converter
cells. Further, at least one of the plurality of series stacked
very high frequency power converter cells may include one or more
switched capacitors. At least one of the plurality of series
stacked very high frequency power converter cells may include at
least one switched capacitor and a DC/DC regulating converter. The
DC/DC regulating converter may be disposed in series the at least
one switched capacitor. The controlling the plurality of series
stacked very high frequency power converter cells may include soft
switching of the plurality of series stacked very high frequency
power converter cells.
[0094] Further, the controlling the plurality of series stacked
very high frequency power converter cells may include operating at
least one power cell bypass function for the plurality of series
stacked very high frequency power converter cells. The controlling
the plurality of series stacked very high frequency power converter
cells may include maintaining converter efficiency above a minimum
efficiency threshold. The minimum efficiency threshold may be
seventy percent, seventy-five percent, eighty percent, and the
like. Further, the controlling the plurality of series stacked very
high frequency power converter cells may include passive switched
capacitor voltage balancing.
[0095] In another aspect of the present invention, a system for
providing high isolation AC to DC power conversion within a
bounding box no larger than five US quarter dollar coins is
provided. The system may include a power cell disposed to receive
an AC input signal and provide a DC output. The system may also
include a controller for configuring the power cell to receive the
input signal. Further, the system may include an output stage for
receiving an output from the power cell and for delivering an
isolated output to a load. In an embodiment, the controller may
soft switch the power cell. Further, the controller may operate the
power cell bypass function for the power cell. The controller may
maintain converter efficiency above a minimum efficiency threshold.
The minimum efficiency threshold may be seventy percent,
seventy-five percent, eighty percent, and the like. In an
embodiment, the controller may be configured for passive switched
capacitor voltage balancing. The bounding box no larger than five
US quarter dollar coins may include a cubic volume of less than
4050 cubic millimeters.
[0096] In yet another aspect, the present invention may include a
system for providing high isolation AC to DC power conversion
within a bounding box no larger than five US quarter dollar coins.
The system may include a soft-switchable power cell disposed to
receive an AC input signal and provide a DC output. The system may
further include a VHF speed controller for configuring the
soft-switchable power cell to receive the input signal. Also, the
system may include a transformer stage for receiving an output from
the soft-switchable power cell and for delivering an isolated
output to a load. The VHF speed controller may soft switch the
soft-switchable power cell. Further, the VHF speed controller may
operate the soft-switchable power cell bypass function for the
power cell. The VHF speed controller may maintain converter
efficiency above a minimum efficiency threshold. In an embodiment,
the minimum efficiency threshold may be seventy percent,
seventy-five percent, eighty percent, and the like. In addition,
the VHF speed controller may be configured for passive switched
capacitor voltage balancing.
[0097] In still another aspect, the present invention provides a
system for providing high isolation AC to DC power conversion
within a bounding box no larger than five US quarter dollar coins.
The system may include a plurality of soft-switchable power cells
flexibly connected to receive an input signal in series and provide
an output. The system may also include a controller for configuring
the plurality of soft-switchable power cells and the flexible
connection to receive the input signal. Further, the system may
include a transformer stage for receiving outputs from a portion of
the plurality of soft-switchable power cells and for delivering a
combined isolated output to a load. Each of the plurality of
soft-switchable power cells may be separately controllable.
Further, a portion of the plurality of soft-switchable power cells
may be arranged with parallel outputs.
[0098] In an embodiment, the system may further include an output
stage that may facilitate configuring a parallel output combination
of the plurality of soft-switchable power cells. The plurality of
soft-switchable power cells may include one or more switched
capacitors. The plurality of soft-switchable power cells may
include at least one switched capacitor and a DC/DC regulating
converter. The DC/DC regulating converter may be disposed in series
the at least one switched capacitor. Further, the controller may
soft switch the soft-switchable power cell. The controller may
operate the soft-switchable power cell bypass function for the
power cell. The controller may also maintain converter efficiency
above a minimum efficiency threshold. In an embodiment, the minimum
efficiency threshold may be seventy percent, seventy-five percent,
eighty percent, and the like. The controller may be configured for
passive switched capacitor voltage balancing. Further, a bounding
box no larger than five US quarter dollar coins may include a cubic
volume of less than 4050 cubic millimeters.
[0099] In another aspect, the present invention provides a power
converter for providing a DC output comprising arbitrarily small
ripple from an AC source within a bounding box no larger than five
US quarter dollar coins. The power converter may include a power
cell disposed to receive an input signal and provide an output. The
power converter may also include a controller for controlling the
power cell to convert the input signal to an output comprising
arbitrarily small ripple. Further, the power converter may include
a feedback path for providing a representation of the output to the
controller to facilitate providing the arbitrarily small ripple.
The controller may soft switch the power cell. The controller may
operate the power cell bypass function for the power cell. The
controller may maintain converter efficiency above a minimum
efficiency threshold.
[0100] In an embodiment, the minimum efficiency threshold may be
seventy percent, seventy-five percent, eighty percent, and the
like. The controller may also be configured for passive switched
capacitor voltage balancing. Further, a bounding box no larger than
five US quarter dollar coins may include a cubic volume of less
than 4050 cubic millimeters.
[0101] The present invention further provides a VHF power converter
for providing a DC output comprising arbitrarily small ripple from
an AC source within a bounding box no larger than five US quarter
dollar coins. The VHF power converter may include a soft-switchable
power cell disposed to receive an input signal and provide an
output. The VHF power converter may further include a VHF frequency
controller for controlling the power cell to convert the input
signal to an output comprising arbitrarily small ripple. In
addition, the VHF power converter may include a feedback path for
providing a representation of the output to the controller to
facilitate providing the arbitrarily small ripple. The controller
may soft switch the power cell. The controller may operate the
power cell bypass function for the power cell.
[0102] In an embodiment, the controller may maintain converter
efficiency above a minimum efficiency threshold. The minimum
efficiency threshold may be seventy percent, seventy-five percent,
eighty percent, and the like. Further, the controller may be
configured for passive switched capacitor voltage balancing. In
another embodiment, the bounding box no larger than five US quarter
dollar coins may include a cubic volume of less than 4050 cubic
millimeters.
[0103] In still another aspect of the present invention, a high
efficiency VHF power converter for providing at least two watts of
DC output power from an AC source within a bounding box no larger
than five US quarter dollar coins is provided. The high efficiency
VHF power converter may include a soft-switchable power cell
disposed in the converter to receive an input signal and provide an
output. The high efficiency VHF power converter may further include
a VHF frequency controller for controlling the power cell to
produce at least two watts of power from the input signal with at
least seventy percent conversion efficiency. The controller may
soft switch the power cell. In addition, the controller may operate
the power cell bypass function for the power cell.
[0104] In an embodiment, the controller may maintain converter
efficiency above a minimum efficiency threshold. The minimum
efficiency threshold may be seventy percent, seventy-five percent,
eighty percent, and the like. The controller may be configured for
passive switched capacitor voltage balancing. In an embodiment, a
bounding box no larger than five US quarter dollar coins may
include a cubic volume of less than 4050 cubic millimeters.
[0105] In another aspect, the present invention provides a high
efficiency VHF power converter for providing at least two watts of
DC output power from an AC source within a bounding box no larger
than five US quarter dollar coin. The high efficiency VHF power
converter may include a soft-switchable power cell disposed in the
converter to receive an input signal and provide an output.
Further, the high efficiency VHF power converter may include a VHF
frequency controller for controlling the power cell to produce at
least two watts of power from the input signal with at least
seventy-five percent conversion efficiency. The controller may soft
switch the power cell.
[0106] In an embodiment, the controller may operate the power cell
bypass function for the power cell. The controller may maintain
converter efficiency above a minimum efficiency threshold. The
minimum efficiency threshold may be seventy percent, seventy-five
percent, eighty percent, and the like. The controller may be
configured for passive switched capacitor voltage balancing. In an
embodiment, a bounding box no larger than five US quarter dollar
coins may include a cubic volume of less than 4050 cubic
millimeters.
[0107] In still another aspect of the present invention, a high
efficiency VHF power converter for providing at least fifty watts
of DC output power within a bounding box no larger than three US
quarter dollar coins is provided. The high efficiency VHF power
converter may include a plurality of series-stacked soft-switchable
power cells disposed in the converter to receive an input signal
and provide at least fifty watts of power to an output. The high
efficiency VHF power converter may also include a VHF frequency
controller for controlling the plurality of power cells to produce
the at least fifty watts of power from the input signal. In an
embodiment, the bounding box no larger than three US quarter dollar
coins may include a cubic volume of less than 2430 cubic
millimeters.
[0108] In yet another aspect of the present invention, a high
efficiency VHF power converter for providing at least fifteen watts
of output power within a bounding box no larger than one US quarter
dollar coin is provided. The high efficiency VHF power converter
may include a plurality of series-stacked soft-switchable power
cells disposed in the converter to receive an input signal and
provide at least fifteen watts of power to an output. Further, the
high efficiency VHF power converter may include a VHF frequency
controller for controlling the plurality of power cells to produce
the at least fifteen watts of power from the input signal. In an
embodiment, the bounding box no larger than one US quarter dollar
coin may include a cubic volume of less than 810 cubic
millimeters.
[0109] In an aspect of the methods and systems described herein, a
method of control may include receiving a varying input voltage
signal to be applied to a plurality of series stacked high
frequency power converter cells, the power converter cells for
producing an output from the varying input; determining an average
of the input voltage; and synchronously controlling the series
stacked high frequency power converter cells to produce the output
from the varying input voltage based on the determined average.
[0110] In an aspect of the methods and systems described herein, a
method of control may include receiving a varying input voltage
signal to be applied to a plurality of series stacked high
frequency power converter cells, the power converter cells for
producing an output from the varying input; determining an average
of the input current; and synchronously controlling the series
stacked high frequency power converter cells to produce the output
from the varying input voltage based on the determined average.
[0111] In an aspect of the methods and systems described herein, a
method of control may include receiving a varying input voltage
signal to be applied to a plurality of series stacked high
frequency power converter cells, the power converter cells for
producing an output from the varying input; determining an average
of the output current; and synchronously controlling the series
stacked high frequency power converter cells to produce the output
from the varying input voltage based on the determined average.
[0112] In an aspect of the methods and systems described herein, a
method of controlling a stacked-cell VHF power converter may
include sensing a voltage input to the converter; adjusting a
by-pass function for at least one stacked-cell based on the sensed
input voltage; sensing the input current; sensing the output
current; and adjusting operation of at least one stacked-cell to
control the input current and the output current based at least in
part on one of the sensed input current and the sensed output
current.
[0113] In an aspect of the methods and systems described herein, a
method of controlling a stacked-cell VHF power converter may
include sensing a voltage input to the converter; adjusting a
by-pass function for at least one stacked-cell based on the sensed
input voltage; sensing the input current; sensing at least one of
the output voltage and the output current; and adjusting operation
of at least one stacked-cell to control the input voltage to at
least one other stacked-cell based at least in part on one of the
sensed input voltage, the sensed input current, the output voltage,
and the sensed output current.
[0114] These and other systems, methods, objects, features, and
advantages of the present invention will be apparent to those
skilled in the art from the following detailed description of the
preferred embodiment and the drawings. All documents mentioned
herein are hereby incorporated in their entirety by reference.
BRIEF DESCRIPTION OF THE FIGURES
[0115] The invention and the following detailed description of
certain embodiments thereof may be understood by reference to the
following figures:
[0116] FIG. 1 depicts a basic structure of a switching DC/DC
converter;
[0117] FIG. 2 depicts a Class-E inverter joined with a series
loaded resonant rectifier;
[0118] FIG. 3 depicts current and voltage waveforms of an AC/DC
converter;
[0119] FIG. 4 depicts waveforms representing loss of ZVS as load is
decreased;
[0120] FIG. 5 depicts resistance compression networks;
[0121] FIG. 6 depicts topology of a .PHI..sub.2 inverter;
[0122] FIG. 7 depicts a voltage waveform across a switch of the
circuit of FIG. 6;
[0123] FIG. 8 depicts an on-off modulation converter schematic;
[0124] FIG. 9 shows inverter and rectifier voltages for a plurality
of input voltages;
[0125] FIG. 10 depicts a Class-E inverter connected to a rectifier
dual circuit;
[0126] FIG. 11 depicts a .PHI..sub.2 inverter connected to a
rectifier dual circuit;
[0127] FIG. 12 depicts various configurations of series stacked
cell embodiments;
[0128] FIG. 13 depicts two embodiments of a VHF converter
system;
[0129] FIG. 14 depicts a switched cell based on a switched
capacitor stage followed by a VHF stage;
[0130] FIG. 15 depicts a serial stacked cell VHF converter;
[0131] FIG. 16 depicts a timeline view of one rectified cycle of an
137.5 VAC input;
[0132] FIG. 17 depicts an input current control loop and an output
current control loop;
[0133] FIG. 18 depicts an exemplary VHF converter architecture
block diagram;
[0134] FIG. 19 depicts an embodiment of a VHF converter that maybe
suitable for use with MR16 lighting applications;
[0135] FIG. 20 depicts a bi-phase auxiliary power circuit;
[0136] FIG. 21 depicts a waveform of a rectified AC voltage with a
current waveform that achieves unity power-factor;
[0137] FIG. 22 depicts a block diagram that illustrates one
implementation of power factor correction;
[0138] FIG. 23 depicts simulated waveforms over a single AC line
cycle for the power factor correction embodiment of FIG. 22;
[0139] FIG. 24 depicts a switch network embodiment of a power
factor correction circuit;
[0140] FIG. 25 depicts sample waveforms over a complete AC cycle
for the embodiment of FIG. 24;
[0141] FIG. 26 depicts an example current waveform is presented
that contains odd harmonics in addition to the fundamental;
[0142] FIG. 27 depicts a multi-channel embodiment of a VHF
converter; and
[0143] FIG. 28 depicts an application of a VHF converter for
replacing an incandescent bulb with a multiple LED light.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0144] Increasing the switching frequency of a switched-mode power
supply (SMPS) is a goal that is widely sought after as a means to
increase power density and improve transient performance. However,
increasing switching frequency using conventional power converter
topologies (boost, buck, flyback, etc.) results with significantly
degraded efficiency. Additionally, as switching frequency is
increased, power density only increases until an optimal switching
frequency is reached, at which point power density begins to
decrease again. A new power converter architecture is described
herein that breaks the bounds of conventional techniques, enabling
efficient high frequency operation while delivering increased power
per converter volume.
[0145] Soft-switched resonant inverters have been developed for
high efficiency radio-frequency (RF) transmitter applications.
These techniques have been adapted to form efficient DC/DC
converters at switching frequencies greater than 100 MHz. The basic
structure of this type of converter is shown in FIG. 1. The
inverter stage takes DC power from the input and delivers RF AC
power to the transformation network. The transformation network
scales the AC signal to the appropriate level using either passive
components and/or a transformer. The rectifier takes AC power from
the transformation network and converters it back to DC.
[0146] Inverters that are suitable for efficient operation at VHF
use resonance and characteristics of the load to achieve
zero-voltage switching. Resonant rectifier topologies are often
used and can be modeled as an impedance in a describing function
sense. The transformation stage serves to form an impedance match
between the inverter and the rectifier impedance, providing the
appropriate voltage and current level shifting and isolation if
required. The transformation stage can be realized from passive
transformation networks, conventional transformers, wide-band or
transmission-line transformers, or similar means. An example of
this type of converter is formed by joining a Class-E inverter with
a series loaded resonant rectifier, shown in FIG. 2. For this
converter to operate with high efficiency at VHF three primary loss
mechanisms that grow with frequency must be overcome: switching
loss due to the overlap of voltage and current at the switching
instance and due to capacitive discharge, gating loss due to
charging and discharging the gate capacitor once per cycle, and
losses in magnetic materials. Switching losses are overcome by
operating with zero-voltage switching (ZVS). As shown in the
waveforms of FIG. 3, the resonant components in the circuit are
tuned specifically such that when the switch S.sub.1 is opened, the
voltage across the switch (V.sub.D(t)) will naturally ring up and
then back to zero at a known time period later, offering an
opportunity to turn the switch back on with no penalty. With
switching losses overcome, gating losses that arise from charging
and discharging the gate capacitor once per cycle are mitigated by
either using a resonant gate drive scheme to recover a portion of
the energy stored in the gate, rather than discharging it to
ground, or by optimizing the size of the transistor such that
gating loss is a small portion of the overall converter loss.
Finally, with switching and gating losses minimized, losses in
magnetic materials are avoided by operating the converter at a high
enough frequency such that high permeability core material can be
eliminated and air-core magnetics or low-permeability RF magnetic
materials are used.
[0147] While the circuit of FIG. 2 overcomes all of the major
frequency dependent loss mechanisms that prohibit conventional
power converter circuits from operation at VHF, it has a number of
drawbacks. First, the switch S.sub.1 must survive a peak voltage
stress of about 3.6 times the input voltage. It is well known that
increasing the breakdown voltage of a transistor results in
increased on-state resistance and increased parasitic capacitance.
The performance of converters of this type has been shown to be
directly related to the product of the on-state resistance and
device output capacitance squared. Thus, a topology with lower peak
voltage stress will typically suffer less device loss. Second, the
minimum output power is limited by the parasitic drain-to-source
capacitance of the switch S.sub.1. Additionally, the circuit can
only operate with ZVS over a very narrow load range. Since the
quality factor (Q) of the resonant components is set by the load
resistance, ZVS can only be obtained for a single load. As the load
changes the circuit becomes de-tuned, and ZVS is lost. This effect
is demonstrated in FIG. 4, where the loss of ZVS is observed as the
load is decreased. Resistance compression networks, shown in FIG.
5, are a matching/transformation passive network that can be
employed to reduce the sensitivity of the tuned inverter circuit to
variations in the load. These drawbacks have led to the development
of numerous other topologies that utilize higher-order resonant
networks to reduce the peak voltage stress and break the tight
coupling of output power and device capacitance. An example of such
a topology is the .PHI..sub.2 converter, shown in FIG. 6
[0148] The .PHI..sub.2 uses a multi-resonant network to shape the
voltage waveform across the switch to approximate a square-wave
with a peak value of approximately 2 times the input voltage, as
shown in FIG. 7. This allows a lower voltage transistor to be used,
reducing device loss. Additional resonant components are required,
however, increasing the complexity (and potentially size) of the
converter. In addition to the .PHI..sub.2 there are numerous other
converter topologies employing the similar strategy of increasing
the circuit complexity to gain additional control over the shape of
the converter waveforms. The .PHI..sub.2, however, is considered to
be the preferred embodiment as it strikes a good balance between
additional complexity and performance. While a resistance
compression network allows the converter to operate over a wide
load range without loss of ZVS, it does not provide a means of
regulation. Pulse-Width Modulation (PWM) is a commonly used
technique for controlling power converter circuits. However, PWM
control at VHF is not practical since the converters are designed
to achieve ZVS at a particular duty cycle. Frequency modulation
provides a method of control, however, it is a challenge to
maintain high efficiency over a wide load range as losses from
gating and losses from providing the resonant currents required to
achieve ZVS do not scale back with power.
[0149] A method that achieves high efficiency over a wide load
range is on/off modulation, shown in FIG. 8. This technique
separates the functions of energy conversion and regulation by
designing the converter to operate at full power, and then
regulating average delivered power by modulating the converter on
and off at a frequency less than the switching frequency of the
converter. With this technique the resonant components of the
converter are sized relative to the switching frequency and the
input and output filter components are sized relative to the
modulation frequency. Inclusion of a resistance compression network
with a converter that is controlled through on/off modulation
increases the input and output voltage range of the converter.
[0150] While the rectifier stage of FIG. 1 is classically realized
using diodes, transistors can also be used to build a synchronous
rectifier. Replacing an uncontrolled switch with a controlled
switch adds the requirement of knowing the correct times to turn
the switch on and off within a cycle. This is demonstrated in FIG.
9 by varying the input voltage of the converter of FIG. 2 and
observing that the rectifier's duty cycle and phase vary relative
to the inverter. All of the soft-switched resonant inverter
topologies previously introduced have a dual circuit that operates
as a rectifier. FIGS. 10 and 11 show schematics of both the Class-E
and .PHI..sub.2 inverters connected to their respective rectifier
dual circuit. In these examples the transformation network is only
a simple impedance, but just as with converters built with diode
rectifiers, more complex passive transformation networks,
conventional transformers, wide-band or transmission-line
transformers, or similar means can also be used.
[0151] When designing a synchronous rectifier in a converter that
is controlled through on/off modulation, the primary task is to
control the duty cycle of the rectifier and inverter switches as
well as the phase shift between the inverter and rectifier to
achieve the desired switching waveform. This may be accomplished
through the following method:
[0152] 1. Determine the duty cycle for the inverter and rectifier
switches as well as the phase shift between the inverter and
rectifier as a function of input and output voltage that results
with the desired switching waveforms. Since ZVS is not necessarily
obtainable for all combinations of input and output voltage, the
desired waveforms are chosen to minimize converter loss and/or
damage to the converter for the cases when ZVS cannot be obtained.
Depending on the converter topology used this can be done using
different methods. Converters for which closed for solutions
describe their operation the duty cycles and phase shift can be
determined from analysis of the equations. If no such set of
equations exist for the topology simulation sweeps across
parameters or through a numerical converter solution.
[0153] 2. With the desired duty cycles and phase shift known as a
function of input and output voltage, the remaining task is to
realize a practical system that implements the desired transfer
functions. One method to accomplish this is to read the input and
output voltage at a bandwidth less than the switching frequency.
This ensures that the duty cycles and phase are being adjusted with
the DC input and output voltages, where the term DC loosely is
meant to mean slowly varying local average relative to a switching
cycle.
[0154] 3. Using the measured local average input and output
voltages, the duty cycle of the inverter and rectifier circuits are
set as well as the phase shift between the inverter and rectifier.
Synchronous rectifiers can also be used to implement a phase-shift
control system in which in addition to ensuring the converter
operates with the desired switching waveforms, regulation is also
controlled through adjustment of the phase shift between the
inverter and rectifier.
[0155] Building VHF power converters where the main switching
devices are fabricated in an integrated power process typically
limits the selection of suitable devices to those having a
breakdown voltage of 80-100 Volts at most. Since the best designed
resonant converters of this type have a peak voltage stress of 2
times the input voltage in the inverter and 2 times the output
voltage in the rectifier, the input and output voltages are both
constrained to being less than 50 Volts at most. Many applications
exist that require higher input or output voltage, however. For
example, a system that is powered directly from the AC line must
handle a peak input voltage of about 190 Volts and a peak device
stress of 380 Volts, forcing the converter to be built from either
poorly integrated devices or external devices. Here we describe a
method and system of extending the peak input and/or output voltage
of a VHF resonant DC/DC converter without requiring devices with a
higher breakdown voltage. Rather than using a single converter
cell, the converter can be built from multiple converter cells, and
peak voltage is extended by connecting the converters in series. It
is not necessary that both the converter's input and output both be
series connected, but rather as shown in FIG. 12 the cells' inputs
can be connect in series and their output is parallel, such as to
extend peak input voltage. Similarly, to increase the peak output
voltage of the converter only, the cells' outputs can be connected
in series and the inputs in parallel. Additionally, some
combination of series and parallel can be utilized at the input
and/or output to achieve a particular peak voltage and power. It is
further envisioned that sets of series stacked inverters may be
configured in parallel (e.g. parallel outputs) for providing
greater power than could be provided by a single series stack. A
determination of which type of configuration may be based on a
requirement to deliver a required amount of output power.
Configuring series stacked inverters in parallel may be an
arrangement that satisfies the output power delivery
requirement.
[0156] The cells used to form the multi-cell converter will be
described herein and may vary depending on a variety of factors
including size, cost, performance objectives, input voltage range
limit, and the like. In addition to increasing the converter's peak
input and/or output voltage for a particular device breakdown
voltage, the range at which the converter can operate over can also
be increased. This may be accomplished by selectively using only a
subset of the cells that make up the multi-cell converter. For
example, if a multi-cell converter is formed from 5 converter cells
that can each operate over an input voltage range of 20-30 Volts,
with all cells in use, the multi-cell converter can operate over a
voltage range of 100 Volts-150 Volts. However, by selectively using
a subset of the cells in the series stack, the multi-cell converter
can operate over an input voltage range of 20-150 Volts. A
multi-cell converter may additionally include control functionality
for each cell so that active cells remain within their input and
output voltage range.
[0157] In the present disclosure some embodiments of a VHF
converter are described as including VHF soft-switching resonant
DC/DC converter stages that are cascaded with an AC bridge to form
an AC/DC converter that can operate efficiently with a VHF
switching frequency. This AC/DC converter may be used to drive
light emitting diodes as well as space constrained consumer
devices, such as an AC/DC converter used to power a laptop
computer, and the like.
[0158] A block diagram of two similar embodiments of such a VHF
converter system is presented in FIG. 13. Embodiment VHF1302
includes energy storage, whereas embodiment VHF1304 does not. The
DC/DC converter stages VHF1308 may be operated with a switching
frequency that is much greater than the line frequency so that the
line voltages appears to the DC/DC converter VHF1308 to be a widely
but slowly varying DC voltage. The stages VHF1308 may be formed
from any of the previously described VHF resonant DC/DC converter
cells and/or multi-cell configurations, including combinations
thereof.
[0159] The input voltage range of the stage may determine which
portion of the line cycle that the stage is able to operate over.
For a portion of the line cycle where the line voltage is below the
minimum input operation voltage of the stage, energy storage may be
required to maintain the output voltage or output current to within
any ripple limits specified by a particular application system.
Additionally, in many applications, the method in which power is
drawn from the AC line is constrained by government standards. This
may further reduce the ability of the stage to regulate the output
voltage or current to within the specified ripple limits. Although
one option to maintain output ripple to within its limits is to
increase the energy storage buffer at the output, this may reduce
the flexibility and increase the complexity.
[0160] An alternative solution is to cascade a second DC/DC
converter stage with energy storage to perform load regulation and
ripple reduction. This allows the amount of energy stored to ripple
widely within a line cycle, thereby reducing the total amount of
energy storage required which may reduce complexity, overall size,
and cost.
[0161] A very high frequency power converter suitable for
implementation in a semiconductor process that overcomes size,
efficiency, and cost limitations of larger discrete component
embodiments is described herein. The VHF power converter may be
configured to deliver substantial benefits of high frequency
operation while providing power output that is far greater than may
have economically been provided by VHF converter technology
heretofore. The VHF power converter may take advantage of a
switched stacked cell architecture that enables the converter to
accept an input voltage far greater than could be tolerated by any
single cell while achieving performance, cost, size, and efficiency
levels afforded by the current VHF power converter as described
herein.
[0162] A VHF power converter may include a core cell architecture
that may include a switched capacitor stage followed by a switched
VHF converter stage. A switched capacitor stage may facilitate each
cell accepting a wider range of input voltage by providing a
controllable voltage halving function. By employing one or more
switched capacitors, each capacitor can be charged up to one-half
of the input voltage by alternating capacitor charging with
capacitor discharging. Therefore, an input voltage to a cell of 60V
may be divided in half to 30 V through the switched capacitor
stage. The number of switched capacitors may be dependent on a
variety of factors such as reduced input current, and the like. The
output of the switched capacitor stage may be provided to a VHF
power converter stage so that the VHF converter stage receives no
more than 30V. This concept may be further enhanced by providing a
switched direct path from the input to the VHF converter to support
input voltages that do not exceed 30V and therefore do not
necessarily benefit from being divided in half by the switched
capacitor stage. In an example, a switched capacitor-based VHF
converter cell may accept an input voltage from 15V to 60V while
never presenting more than 30V to the VHF stage.
[0163] When a VHF converter is configured with a plurality of
switched cells, such as the capacitor stage plus VHF stage cells
describe above are configured in series across an input, an input
voltage to the converter may range from as little as a minimum
required for VHF conversion in a single cell to a maximum
determined by the number of cells. In an example, a VHF converter
using four of the switched capacitor stage plus VHF stage described
above may support an input range of 15V minimum to as much as 240V
maximum peak.
[0164] An exemplary embodiment of a switched cell based on a
switched capacitor stage followed by a VHF stage is depicted in
FIG. 14. This exemplary cell architecture may comprise a pair of
switched capacitor charging circuits 1402 and 1404 wherein energy
in each capacitor may be provided to a VHF stage 110 via a VHF
stage input switch 1408. Each capacitor circuit, such as 1402 may
comprise four series switching transistors and a capacitor
connected between a junction of the top two series switches and the
bottom two series switches. The capacitor may be alternatively
charged and discharged by operating the switches in two phases. In
the first phase the top switch and the switch just below the
midpoint are closed and the remaining two switches are open. In
this phase, energy drawn by the VHF stage 1410 through input switch
1408 charges the capacitor. In the second phase, the state of each
switch is reversed, and the energy drawn by the VHF stage 1410
through input switch 1408 discharges the capacitor. With the VHF
stage 1410 drawing substantially the same energy in both phases,
the switched capacitor circuit presents a voltage half of the cell
input voltage 1412 to the VHF stage 1410 through input switch 1408.
Switched capacitor charging circuit 1404 operates similarly to
switched capacitor charging circuit 1402. Switched capacitor
charging circuits 1402 and 1404 may be operated cooperatively with
opposite phase to reduce the RMS current stress of the converter.
The example of FIG. 14 includes two switched capacitor charging
circuits; however any practical number of capacitor charging
circuits or switch configurations may be used, such as to
facilitate different cell input voltages 1412, make system
efficiency tradeoffs, and the like.
[0165] VHF stage input switch 1408 may comprise a pair of switches
connected in series between the cell input voltage 1412 and the
center point of each switch capacitor charging circuit 1402 and
1404. The joining point of the two switches may be an input point
to a VHF stage 1410. VHF stage input switch 1408 may facilitate
selecting either cell input 1412 or voltage from switched capacitor
converter as an input to the VHF stage 1410. If both switches in
VHF stage input switch 1408 are off/open, no power will be input to
the VHF stage 1410. Control of the two switched capacitor circuits
1402 and 1404 along with the VHF stage input switch 1408 may be
coordinated to ensure that VHF stage 1410 receives a voltage that
is sufficient for operation but does not exceed a safe operating
voltage by controlling the charging of capacitors 1402 and 1404 and
selecting between the power sources provided to VHF stage input
switch 1408. In an example of steady state operation of the cell
depicted in FIG. 14 with an AC cell input voltage 1412, VHF stage
input switch 1408 may connect the VHF stage 1410 to the cell input
voltage 1412 while the cell input voltage 1412 is within the input
input voltage range of the VHF stage 1410. Furthermore, stage input
switch 1408 may connect the switched capacitor circuits as a source
of power to the VHF stage 1410 while the switched capacitor output
voltage in within the input voltage range of the VHF stage 1410 One
example of selecting the cell input voltage to directly energize
the VHF stage 1410 may include a configuration in which the cell
input voltage is a DC voltage within the safe operating input range
of the VHF stage 1410.
[0166] An exemplary embodiment of a serial stacked cell VHF
converter is depicted in FIG. 15. The embodiment of FIG. 15
includes four switched VHF cells that are arranged in pairs to
drive a load through transformer isolation. The four switched VHF
cells work cooperatively to handle a rectified AC line voltage up
to 120 VAC. Each of the cells has at least one specific function
that is activated based on the input voltage. Cells 1 and 2 provide
an output power regulation throughout the full line cycle. Cell 3
is bypassed until the input reaches approximately 125V above which
it provides input voltage regulation across cells 3 and 4. Cell 4
is off until the input reaches approximately 80V above which it
provides input current regulation for the entire stack.
[0167] FIG. 16 provides a timeline view of one rectified cycle of
an 137.5 VAC input that helps one visualize the portions of the
cycle for which each of the four cells performs its at least one
specific function. In FIG. 16, the cycle is divided into five
voltage zones rising 0-80V, rising 80-125V, rising and falling
above 125V, falling 125-80V, and falling 80-0V. As noted above
cells 1 and 2 provide an output power regulation function
throughout the cycle. During the rising 0-80V zone and during the
falling 80-0V zone cell 3 is bypassed and cell 4 is off. During
rising 80-125V and falling 125-80V zones, cell 3 is bypassed and
cell 4 regulates input current. During the rising and falling above
125V zone cell 3 is activated to regulate input voltage across
cells 3 and 4, cell 4 continues to regulate input current, and
cells 1 and 2 continue to regulate output power. Also depicted in
the timeline of FIG. 16 are the typical voltages present on each
cell represented by V1 for cell 1, V2 for cell 2, V3 for cell 3,
and V4 for cell 4. The cells are controlled (switched) so that at
no time is a voltage across any one cell greater than 60V.
[0168] Referring back to FIG. 15, in addition to the four switched
cells that are arranged in pairs, each pair drives the load through
multiple primary windings of a transformer. Because the embodiment
of FIG. 15 includes four cells arranged in two groups, two
transformers are depicted. Although the embodiment of FIG. 15
depicts pairs of cells connected through a single transformer with
multiple primary windings, an alternate embodiment could include
other arrangements, such as a separate transformer for each cell.
Although other types of isolation are possible (e.g. capacitive),
transformer isolation also may provide benefits, such as
facilitating storage of converter energy. Therefore, as depicted in
FIG. 15, a VHF switched power converter may be configured to
deliver power through a transformer connected to outputs of
multiple switched cells through multiple primary transformer
windings. Also, a plurality of such configured multiple switched
cell to transformer circuits may be configured substantially in
parallel to drive a load, such as an LED-based light. The
embodiment of FIG. 15 further depicts controlling each switched
cell separately while coordinating control of each cell within a
designated pair to facilitate achieving various functional and/or
performance objectives and/or coordinating control of each of the
pairs of cells to achieve various functional and/or performance
objectives as described herein and otherwise understood by one
knowledgeable in the state of the art.
[0169] The embodiment depicted in FIG. 15 also facilitates power
factor correction through at least the use of capacitor designated
as CPFC and at least through the control of cell 3. Power factor
may be corrected by controlling cell 3 in FIG. 15 so that capacitor
CPFC charges and discharges throughout the power AC line cycle. In
the AC line cycle portion depicted in FIG. 16, capacitor CPFC
discharges during rising 0-80V and during falling 80-0V portions.
Capacitor CPFC charges during rising and falling above 80V portions
of the cycle.
[0170] Selected thresholds shown in FIG. 16 are representative only
and may be adjusted based on the fabrication technology chosen for
the cells, the number of cells, the frequency of switching, the
output power, the capacitance value of CPFC, and various other
design choices that may impact such thresholds.
[0171] Each cell in the stacked-cell configuration of FIG. 15 may
require control bandwidth that facilitates proper control of each
cell throughout an AC cycle. In an example wherein harmonics within
the system are generally 1 kHz, cell 1 may be controlled at a 1 MHz
rate, cells 2 and 3 at a 100 kHz rate, and cell 4 at a 10 kHz rate.
This difference in control frequency may enable control for high
efficiency, accurate cell voltage balancing, and the like.
[0172] The embodiment of FIG. 15 further includes an overvoltage
protection circuit 1504 to facilitate protecting the VHF converter
circuits from voltage spikes, overvoltage conditions, and the like.
The protection circuit 1504 may be controlled so that input
voltages to the converter and/or to any element or group of
elements of the converter that exceed a maximum safe operating
threshold may be limited by the protection circuit 1504 to avoid
damage or overstress thereto.
[0173] In applications of the VHF power converter of FIG. 15 for
driving a light, such as an LED-based light, dimming, such as by a
phase-cutting line input switch (e.g. Triac for conventional
incandescent bulb dimming), may be accommodated by the VHF power
converter. For reliable phase-cut dimming, a minimum load may be
required to be presented to the phase-cut dimmer throughout the
phase-cut dimming function. This may be accomplished by controlling
the VHF converter to present a low impedance when the phase-cut
dimmeris blocking the AC line voltage through switch 1502
controlled by cell 3 in FIG. 15 and controlling the VHF converter
to maintain a minimum holding current when the phase-cut dimmer
passing the AC line voltage during the dimming function.
[0174] One approach to operate the VHF converter with a phase-cut
dimmer for light dimming is for the VHF converter to detect the AC
line conduction angle and adjust capacitor charging and output
current accordingly. In LED-based lighting applications, the
minimum holding current required by the phase-cut dimmer may be
greater than the current required to power the LED. In this
scenario, cells 1 and 2 in FIG. 15 may be controlled to regulate
the output, cells 3 and 4 in FIG. 15 may be controlled to draw the
required holding current and deliver no output power, and switch
1502 in FIG. 15 may be controlled to charge CPFC to the desired
value to maintain the output power while the phase-cut dimmer is
blocking the AC line voltage. By adjusting the control scheme based
on conduction angle, dimming with a VHF power converter can be
accomplished without adding components that are dedicated to the
dimming function. This reduces footprint and costs of such a VHF
solution over other multi-component dimming solutions.
[0175] VHF converters, and in particular multiple cell VHF
converters may benefit from precise clock synchronization among the
cells. When multiple cells share an output rectifier (as depicted
in FIG. 15 for cells 1/3 and 2/4), clocks of the rectifier-paired
cells may be synchronized. Generally cell to cell clock skew of 500
ps or greater may result in reduction in efficiency due to energy
losses when operating at VHF frequencies. Although cells may be
implemented within a single integrated circuit, some applications
may demand separation of cells to distinct integrated circuits that
are connected by printed circuit board traces and/or through
additional components which may introduce additional skew. To
accommodate precise synchronization of cell clocking, a reference
clock may be provided throughout the VHF circuit topology that can
be used to adjust for circuit related frequency skew. In addition,
clock phase skew may be detected from analyzing flux generated by
cell switching and transformer coupling with peak and hill climbing
algorithms because phase skewed clocks may produce flux peaks that
could be determined from such analysis. Clocks to the cells can be
adjusted based on the detected peak analysis with the objective of
improving cell to cell clock synchronization which may be
determined by detecting a single flux peak. In embodiments in which
cells do not share a rectifier stage, demand for cell-to-cell clock
synchronization may be reduced.
[0176] Clock frequency accuracy (e.g. repeatability) that may also
be important for highly efficient VHF conversion may be
accomplished by use of Zero Voltage Sensing (ZVS) sensors that may
facilitate accurate clocks without the use of a crystal oscillator,
a complex calibration architecture, and the like. By taking a
snapshot of an amplitude (voltage) of an input of one or more of
the switched circuits an instant before the circuit is switched one
can determine if the switch clock is occurring precisely as desired
(e.g. when the input voltage is zero). The snapshot voltage may be
used to control a phase-lock loop or the like to adjust the clock
frequency as desired. In an application in which an AC line signal
is used as an input to the VHF converter, the clock may initially
be synchronized to the AC line input. This may facilitate effective
use of a phase-lock loop by configuring the phase-lock loop to
track the zero voltage crossing of the AC line input that is
generally controlled to within approximately 10 percent. Once the
clock frequency is locked to the a multiple of the AC line
frequency, the converter can begin to run, and the ZVS sensors may
be used to further set the clock frequency. The techniques for
clock period adjustment and/or clock synchronization as described
herein may further be used to overcome variations in manufacturing
process and temperature-based drift that may impact clock related
issues without requiring extensive production or test time
calibration.
[0177] In VHF converter configurations that include a synchronous
rectifier stage, maintaining a particular phase angle for the
synchronous rectification may provide benefits including efficient
and accurate operation of the conversion function. Detection and
control of the phase angle of a synchronous rectifier may be
implemented in a VHF converter through phase angle sensing and
processing techniques, such as through the use of a delay locked
loop, and the like. Phase angle control of synchronous
rectification may include average feed forward sensing, zero
voltage detection feedback, average sensing, duty ratio/clock
frequency/phase angle adjustment based on sensed voltage changes,
and the like.
[0178] A multi-cell VHF converter, such as based on the switched
stacked cell converter architecture depicted in FIG. 15 may include
control to facilitate cooperative operation of the cells and
related components to achieve various functional and performance
objectives, such as clock synchronization and others. Control may
further be based on any of a variety of parameters including
feedback associated with converting an input to an output voltage,
predetermined parameters, learned parameters, user provided
parameters, and the like. Control may be provided by a controller,
such as logic, state machines, microcontrollers, and the like. FIG.
18 depicts a block diagram of a VHF power converter that includes
control. A controller may facilitate control of the VHF converter
to achieve a degree of constant input current, constant output
current, and cell control based on aspect of an input voltage such
as an AC line voltage.
[0179] Control may be based on a plurality of control loops a
portion of which may be nested. In one embodiment of the VHF
converter for powering an LED-based light, control may include at
least two control loops--an outer loop and an inner loop that
operates at a faster cycle time than an outer loop and that may
implement proportional feedback to directly control each aspect of
the VHF converter (e.g. cell clocks, feedback sampler, and the
like). The outer slower loop may facilitate providing input to the
inner loop when the inner loop is controlling the VHF converter to
maintain a constant input current. The outer loop may facilitate
detection and feedback of an average of the output current to
ensure that an average of the output current is also controlled.
The outer loop may first integrate the difference between an
instantaneous output current and an output current reference (e.g.
an average of the output current from a previous AC line cycle).
This integral is then processed to generate a reference value for
the inner loop.
[0180] Any number of control loops that may be required may be
implemented in a controller, such as depicted in FIG. 17. Generally
a VHF converter is controlled to maintain at least one of a desired
input current and a desired output current. However, control of
both input and output currents may be required to ensure high
efficiency VHF conversion, to manage thermal impact, to perform
power-factor correction, and the like. In another embodiment, a
controller may include control for dimming, line voltage variation
(normal cycle and exceptional variation), VHF converter start-up
mode, steady state mode, line transient, and the like. Startup mode
may be controlled to facilitate avoiding damage to the cells as
power to the VHF converter turns on. Steady state mode may be
controlled to facilitate efficient, high quality power conversion;
Line transient or over-voltage may be controlled to facilitate
protection of the converter cells and other devices, such as with
the protection circuit 1704 described herein. Dimming may require
control for operation of a phase-cut dimer, and the like as
described herein.
[0181] Referring to FIG. 17, an input current control loop and an
output current control loop are depicted. As noted in the
description of FIG. 15, cells 1 and 2 primarily control output
current and cells 3 and 4 primarily control input current. The flow
diagram of FIG. 17 provides a visualization of control flow with
respect to both input and output current. Input current (A) and
output current (B) may be combined to provide feedback for power
balance 1702 which may impact an input current reference 1704.
[0182] An input current control loop may include input current
reference 1704 and filtered input current 1708 may be combined and
processed, such as through compensator 1710, to impact control of
cells 3 and 4 1712.
[0183] An output current control loop may include an output
reference 1714 and filtered output current 1718 that may be
combined and processed, such as through compensator 1720 to impact
control of cells 1 and 2 1722. Output current control may further
include combining sensed portions of input current (E) and sensed
portions of cells 1 and 2 1722.
[0184] The cells of the converter are modulated on and off as a
primary means for providing control of the input current, output
current and voltage, and the like. In FIG. 18, a PWM block provides
pulse width modulation control of the various cells, the power
core, and the like. The PWM block may also provide overall PWM
control of the converter output to enable pulse-width modulation of
the output voltage or current presented to a load, such as to an
LED-based light. This may be helpful in applications in which PWM
operation of an LED-based light may facilitate adjusting color of
an LED string, brightness of the LED, and the like. PWM control of
the output may facilitate dimming an LED-based light in response to
the converter input being controlled by a conventional phase-cut
dimmer.
[0185] As described herein, control of a VHF converter, such as an
AC to DC converter, a VHF stacked cell, soft switched converter,
and the like may be based on input voltage requirements, output
voltage requirements, instantaneous input voltage, average output
voltage, and the like. In an AC-DC VHF converter, stack control
varies throughout the AC cycle as described above in regards to
FIG. 15 and FIG. 16. As noted above a control loop, such as may be
executed by a controller, may be responsible for adjusting the
number of active cells because the number may vary with the
amplitude of the input voltage and/or the direction of the
amplitude (rising or falling). Generally control may attempt to
ensure that the active number of cells is proportional to a measure
of input voltage. Activating (adding/turning on) a cell may be
appropriate as input voltage rises. Deactivating (turning
off/bypassing/removing) a cell may be appropriate as voltage
decreases. Control may include a cell bypass function that may
switch in/out cells from the active stack of cells to achieve
certain objectives. In an example, opening a cell bypass switch as
the input voltage increases may enable support for greater input
voltages. In another example, closing a cell bypass switch as the
input voltage decreases may maintain efficiency and facilitate
staying within an operating range of the stacked cells.
[0186] Control of the various functions, cells, switches, and the
like of the VHF converter may be provided by a communications
channel among the elements. The communication channel may be an
asynchronous bus that may be implemented as any type of physical
bus. The communication channel may be an isolated. Examples include
a level shifting bus, a digital bus, capacitive coupling, magnetic
coupling, optical coupling, and the like. The communication channel
infrastructure may include individually addressable cells and
subsystems on and among circuits in the converter. Messaging over
the communication channel may include high/low priority messages,
broadcast messages, single listener messages, and the like.
[0187] Referring to FIG. 19, an embodiment of the inventive VHF
power converter system described herein that may be suitable for
use in MR16 type lighting power applications, some additional
control-related techniques are depicted. In addition to PWM,
control, input and output sensing, and the like, characteristics of
any of the inverters and/or of the synchronous rectifier may be
sensed and used in control, such as to control clock phase, skew,
zero voltage switching, and the like. In the embodiment of FIG. 19,
waveform characteristics for an inverter denoted as DI and/or
waveform characteristics of a synchronous rectifier denoted as DR
may be sensed, compared to a threshold, and provided to clock
control logic for use in controlling clocks to individual cells, to
gate drivers, and the like. Sensing DI and/or DR may enable dynamic
control of clock related aspects to facilitate compensating for
manufacturing variations, temperature drift, and the like. FIG. 19
also depicts various other control inputs including sampling the
VHF converter input voltage that may be optionally divided by
divider 1902 to support full AC line voltages, input current
sensing 1904, output current sensing 1908, controller state/input
sensing 1910, and the like.
[0188] Powering switch drive gates in a VHF power converter may
require a substantial amount of drive energy (e.g. hundreds of
milliwatts). In a semiconductor process, a switch drive gate may
need to be driven in the range of 0-3 volts, yet a typical VHF
power converter may receive as much as 120 VAC input. Therefore,
converting a rectified AC line to the 3 volts required for driving
a switch drive gate can be costly in real estate, heat, efficiency,
or the like. In addition to requiring a power source for the switch
drive gates, digital logic for a VHF power converter also needs a
continuous source of power to keep the digital logic functioning
properly to control the VHF power converter for example. To provide
the continuous power for digital logic and/or for switch drive gate
operation, an auxiliary source of power may be provided. This
auxiliary power may be provided by a dedicated VHF converter
circuit that converts a main power close to the required
voltage.
[0189] An embodiment of a dedicated VHF converter for auxiliary
power may be designed to overcome many of the drawbacks noted above
while providing a continuous source of power. Such an embodiment
may function in two controlled power phases (i) using the main VHF
power input for charging an auxiliary power capacitor that provides
energy storage to drive auxiliary power loads (sending energy to
the auxiliary power subsystem), and (ii) discharging the auxiliary
power capacitor to generate power that can be provided back to the
main VHF converter that provides power to the main load (sending
electrical energy from the auxiliary power subsystem to the main
power converter system). A ratio of time driving power to the
auxiliary power subsystem versus time driving power from the
auxiliary power system to the primary VHF converter system may
determine the average auxiliary power provided. Switching between
driving power into the auxiliary power system and driving power out
of the auxiliary power system may be adjusted (phase, duty cycle,
and the like) to manage average auxiliary power consumption. A
dedicated VHF converter configured as described herein for
providing auxiliary power may be much more efficient than a linear
regulator and much smaller than a Buck-type converter.
[0190] Operation of a dedicated Auxiliary power converter may
include alternating between a first phase that rectifies AC power
generated from a portion of a main VHF converter stage (e.g. an
inverter) and provides the rectified power to an auxiliary output
for use and storage thereby and a second phase that generates AC
power from the stored auxiliary power and provides the generated AC
power to the main VHF converter.
[0191] Such a bi-phase auxiliary power circuit is depicted in FIG.
20. First to facilitate proper operation during initial power-up
(e.g. before the auxiliary power VHF rectifier is a reliable power
source), a linear regulator circuit 2002 may be included to power
circuits during power-up. Once the converter control logic and
power circuits are stable, the linear regulator may be disabled via
linear regulator monitor 2004 to reduce overall power
consumption.
[0192] Energy transfer direction may be controlled by selecting a
clock source 2008 for the auxiliary power dedicated converter.
CLKFWD and CLKREV may clock the auxiliary VHF converter at
different phases of the AC cycle to result in energy being
transferred to auxiliary power capacitor 2010 when clocked by
CLKFWD. When clocked by CLKREV, energy may be reversed from
capacitor 2010. Auxiliary power VDD may be maintained during CLREV
operation by the energy stored in capacitor 2010.
[0193] Power-Factor Correction (PFC) is a power conversion
technique that limits the amount of reactive power drawn from a
source. High power factor, which is defined as the ratio of real to
apparent power, is achieved by controlling the current that is
drawn from a source such that the load appears to be substantially
resistive. PFC is often employed in devices that are connected to
the AC main as reactive power unnecessarily loads the AC grid. FIG.
21 shows the waveform of a rectified AC voltage with a current
waveform that achieves unity power-factor. From this figure it is
readily observed that a key limitation and challenge faced by AC/DC
PFC converters is the necessity to buffer energy at twice the AC
line frequency as the power drawn from the AC source reduces to
zero twice per cycle.
[0194] An energy buffer may be required to maintain the DC output
power while the input power drops to zero. This energy buffer is
often realized as a capacitor. A simple method of implementing the
buffer is to include a capacitor at the output of single-stage PFC
converter. An arbitrarily small output ripple can be obtained by
increasing the size of this capacitor. However, in many
space-constrained applications this can be prohibitive as the
volume occupied by the capacitor can be quite large.
[0195] For a given output power, the size of the energy buffer
capacitor may be reduced if its voltage is allowed to ripple as a
function of the line power. However, this method is incompatible
with the simple single-stage PFC solution described previously. In
that solution the capacitor is connected directly across the output
and the load ripple voltage and capacitor ripple voltage are
identical. Since most loads require a stable DC output with very
small ripple, a second converter may be cascaded in series with the
first to remove the ripple from the output as was shown in FIG. 13.
In such a configuration, the output port of the first converter is
attached to the input port of the second converter and this common
port is also shared by the capacitor. This allows a pure DC output
to be obtained while the capacitor voltage is rippling, but
efficiency suffers owing to the system efficiency being the product
of the efficiencies of each stage.
[0196] Yet another approach to reduce the capacitor size involves a
single stage AC/DC converter with the energy storage capacitor
located at the input. This allows a much smaller total capacitance
because the energy is buffered at line voltage and the total energy
stored in a capacitor is proportional to its terminal voltage
squared. This solves the problem of poor efficiency experienced
with two-stage converters while also allowing for a small
capacitance. However, existing examples of this approach have poor
power factor (typically 0.5 or less) because the capacitor
contributes a current component that is orthogonal to the rectified
line voltage.
[0197] Herein we describe an AC/DC PFC converter architecture that
achieves a fully-regulated DC output with arbitrarily small ripple,
high efficiency, and high power factor with use of a small energy
storage capacitor. The architecture uses a plurality of converter
cells connected to provide multiple single-converter-cell paths
from the source to the load. This allows for high efficiency while
providing control over the current drawn by an energy storage
capacitor connected to the input side of the converter cells such
that the system has high power factor. This capacitor can store
energy at a relatively high voltage and with substantial ripple
enabling it to be very small. The resulting converter, fully
described below, is a significant advance over state-of-the-art PFC
converter technology.
[0198] FIG. 22 presents a block diagram that illustrates one
implementation of the power factor correction methods and systems
of this disclosure. This implementation operates with two paths for
energy transfer to the load that are series connected across the
rectified AC source and parallel connected across the load. This
implementation also includes a capacitive energy storage network in
parallel with the input to one of the energy transfer paths. The
energy transfer paths are controlled such that a fraction of the
energy drawn from the AC source is delivered to the load, and the
remaining fraction of the energy is delivered to the capacitor. As
shown in FIG. 22, the input voltage of energy transfer path 1 (V1)
is equal to the rectified AC voltage (VLINE) minus the capacitor
voltage (VC). Since Path 1 is in series with the rectifier, the
power that is drawn by this path sets the current that is drawn
from the AC source (ILINE). The capacitor current (IC) is set by
the difference between the ILINE current and the current drawn by
energy transfer path 2 (12). This allows the ratio of power
delivered to the load and power delivered to the capacitor to be
controlled.
[0199] One method to perform AC/DC PFC with this architecture is to
control Path 1 to draw the desired PFC current waveform from the AC
source. Since the voltage V1 is set by the difference between VLINE
and VC, Path 1 is unable to perform PFC by controlling the input
current and simultaneously regulate the output. However, if over
the entire line cycle the instantaneous power drawn by Path 1 is no
more than the DC output power delivered to the load, Path 2 can be
used to regulate the power delivered to the load by supplying the
difference between the DC output power and the power delivered by
Path 1. The difference in energy (e.g. an instantaneous difference)
between what is drawn from the AC line and what is delivered to the
load is naturally sourced or sunk by the capacitor.
[0200] FIG. 23 presents simulated waveforms over a single AC line
cycle for the PFC implementation of FIG. 22. Energy transfer path 1
begins conducting when VLINE rises above VC. A pure DC output can
be obtained if the sum of P1 and P2 is equal to average power drawn
from the AC source. This condition is met if
V C .gtoreq. V LINE - P AVG I LINE ##EQU00001##
while Path 1 is conducting. The capacitance must be chosen such
that the capacitor voltage does not violate this relationship. Path
1 ceases conduction when VLINE drops below VC. Path 2 then
discharges the capacitor to maintain the DC output power until
VLINE rises above VC in the next half line cycle, at which point
the cycle repeats.
[0201] With this configuration, unity power factor might not be
obtained since current might not be drawn from the AC source
throughout the entire line cycle (i.e. the portion where VC is
greater than VLINE). While unity power factor might not be
obtained, the waveforms of FIG. 23 achieve a power factor greater
than 0.95 which is sufficient for many applications.
[0202] One method to implement each energy transfer path is through
the use of a high frequency switched-mode power supply (SMPS) (e.g.
with a switching frequency that is greater than 1 MHz, for
example). On/off control can be used to obtain the desired average
output of each SMPS to supply the load.
[0203] A second implementation of power factor correction includes
a switch network in addition to the previously described
implementation such that unity power factor may be obtained. FIG.
24 presents a block diagram of the implementation. The switch
network, labeled S1 in FIG. 24, is utilized to enable energy
transfer path 1 to conduct current (e.g. control ILINE) throughout
the entire AC cycle. In the portion of the AC cycle for which VC is
greater than VLINE, the switch S1 is used to bypass the capacitor
and energy transfer path 2, such that the voltage across the input
of Path 1 is not driven negative. This enables Path 1 to conduct
current throughout the entire line cycle and unity power factor may
be achieved. FIG. 25 presents sample waveforms over a complete AC
cycle for this implementation. Since Path 1 is enabled to control
ILINE throughout the entire line cycle, unity power factor is
achievable. Furthermore, this implementation has an advantage when
used in applications in which the frequency components of ILINE are
constrained since ILINE is controlled throughout the entire AC
cycle.
[0204] It will be appreciated that there are a range of variants to
the PFC architecture discussed herein that fall within the scope of
this disclosure. For example, it is not necessary that the current
drawn from the AC source be substantially sinusoidal. In many
applications it is acceptable to draw current from the AC source
that contains frequency components in addition to the fundamental.
In FIG. 26 an example current waveform is presented that contains
odd harmonics in addition to the fundamental. The current waveform
has a shape that may not peak at the same time as the AC voltage
within an AC cycle. As a result, the peak minimum capacitor voltage
for maintaining a pure DC output may be reduced. With this reduced
peak, a smaller capacitance can be used because VC may ripple over
a wider range without violating the minimum.
[0205] Furthermore, while the exemplary embodiments have described
a pure DC output, a time varying output (e.g. AC) can be utilized
without departing from the scope of the disclosure. For example,
allowing the output to ripple with a fundamental frequency equal to
that of the AC source reduces the size of the capacitor required.
Additionally, in many applications it is desirable to control the
output to an average value, such as through on/off modulation. One
such application is driving one or more LEDs for illumination or
other applications where it is desirable to achieve a consistent
set of light emission characteristics as the power delivered to the
LEDs is varied. This may be accomplished by driving the LEDs at a
particular instantaneous power level, and then controlling average
power through on/off modulation of the LEDs (e.g. such as with high
frequency switched-mode power supplies as described herein).
Implementing this with multiple paths for energy transfer to the
output may be accomplished by the energy transfer paths being
controlled such that when any subset of paths is conducting the
load is delivered a constant output power. One way this can be
accomplished is to interleave the on-time of each subset of the
energy transfer paths. As a result, each subset may deliver the
desired instantaneous output power, and only a single subset may be
delivering power at a particular instant of time.
[0206] The previously described implementations include the use of
two energy transfer paths and a capacitive energy storage network.
The scope hereof includes the generalization of this technique to a
plurality of paths for energy transfer to the output, where the
energy transfer paths are controlled to deliver a fraction of the
energy to a capacitive energy storage network, and a fraction of
the energy to the load.
[0207] Many electronic systems require multiple regulated output
voltages or currents derived from a single input source. For
instance, in a cellular telephone there are typically multiple buss
voltages--a logic core voltage, an intermediate voltage for
interface, and a third that is used for the RF power amplifier.
Some phones may require a high voltage or power output for driving
LED camera flashes or displays, as well. Many complex systems have
similar requirements. Often these are met by using a multitude of
independent regulators, whether linear or switch-mode, where each
produces one of the desired outputs.
[0208] Another common realization of multiple outputs is a single
converter, such as a switch-mode power supply (SMPS), with multiple
taps on a transformer or inductor winding. Each point on the
winding can be used to provide a desired output voltage relative to
a single regulated voltage. This has the benefit of reducing the
overall complexity (and typically, size) of the system, but only
permits the regulation of one output voltage. The others are
subject to variations introduced by AC-side reactance, such as
transformer leakage inductances that make the output voltage a
function of the load current.
[0209] Regulation of each tap in a multiple-output converter as
described above may be accomplished (where required) by means of
linear post regulation stages. A low-dropout, linear regulator
(LDO) is inserted between a tap and provides compensation for the
droop that normally occurs. This is effective, but requires the
addition of an LDO for each desired output (excepting the one that
is already regulated), adding cost and complexity to the system. It
also reduces efficiency, as some minimum dropout voltage is
required for the LDO to function properly.
[0210] Herein we describe a high-efficiency converter system that
is capable of producing multiple independently regulated output
voltages and/or currents using a single converter without the
addition of a tapped magnetic structure, or LDO post-regulation
stages. In the proposed converter system, multiple outputs may be
obtained when the single converter core is employed on a time-share
basis. This allows a single power stage to alternately connect to
any one of the loads to affect regulation as needed. In most cases,
this may require a very high bandwidth power stage, precluding the
approach for SMPS systems operating at typical switching
frequencies (1 MHz and below). VHF power converters, such as those
described herein may have the necessary bandwidth allowing many
outputs to be serviced with high bandwidth.
[0211] FIG. 27 shows a VHF power converter implementation with
multiple time-shared outputs implemented as described herein. The
converter may be a high-bandwidth converter that alternately
supplies energy to a plurality of loads according to a schedule
imposed by a control system. The converter system may be capable of
supplying the total average power delivered to each load as well as
the peak power required of any given load over the course of a
modulation cycle. It may also operate over the output voltage range
set by the difference between the minimum and maximum output
voltages.
[0212] In one method of control, a controller may simultaneously
monitors each load (V1, V2, V3 . . . ) as depicted in FIG. 27. The
converter is then connected through switches S1, S2, S3 . . . to
each load over an even fraction of the total modulation period TM
equal to TM/N, where N is the number of loads. When any individual
load is connected to the converter cell (a period henceforth
referred to as a load window), the converter may operate such that
the average output voltage or current over TM is maintained at the
desired value according to a reference value that may be accessible
to the controller. This may be achieved by varying the on-off
modulation duty ratio of the converter cell during the load window.
As the load demands more power, the duty ratio may be increased and
vice versa. The controller cycles through all the load windows in
the period TM, therefore no load remains unregulated for a period
longer than TM-TM/N. Since TM can be short with a high performance
power stage, the effective regulation bandwidth can be very
high.
[0213] This method of regulation may be achieved when the power
stage is capable of a peak output equal to N times the highest
average load power. This derives because the converter cell may
only deliver power to a load for 1/N of the modulation period, TM.
When a constant output is desired, the load capacitors shown in
parallel with the load V1, V2 are preferably sized to sustain the
output during at least the period (N-1)TM/N.
[0214] Another method of control relaxes the requirements on the
converter and filters. In this method, the load window periods may
be dynamically scaled according to the average output power of each
load. This may permit the converter to spend more time supplying
power to larger loads while reducing the peak power required of the
converter for a given average load power. One such method is to
scale the load window period in direct proportion to the average
power demanded from the load. This will give longer windows to
higher loads. In steady stage this may correspond to requiring
minimum peak converter power. The load window scaling period may be
adjusted at a frequency well below the cutoff of a control loop
frequency of the converter. However, in certain cases it will be
advantageous to make the load window period nearly equal to or
equal to the duty ratio of the converter with respect to the
load.
[0215] For the converter depicted in FIG. 27, the operation when
supplying three loads with different output voltages is described
subsequently. Each output is assumed to be a unique value for the
purpose of illustration, though all could be identical in
practice.
[0216] The modulation period is divided into three distinct periods
defined by which load is connected to the converter's output. Each
of these periods is a load window, occurring when the respective
load switch (S1-3) is closed and the others remain open. For this
particular example, the load windows are of constant length and
active sequentially.
[0217] During operation, a master controller continually monitors
the output voltage of each load. When a load window becomes active,
the converter output voltage may quickly rise (or fall) to close to
the load voltage required. The converter may then be operated for a
fraction of the load window period, such that the output voltage is
maintained within pre-specified limits over the entire modulation
period. The fraction of the load window period may range from 0 to
1 and may be determined in an average sense by the controller. In
one example control scheme, each load is controlled by an
independent window loop where the fraction of the window would
correspond to a duty ratio similar to a standard PWM control
scheme. A primary difference being that the fraction relates to the
actual converter on-time, such as by a scale factor of TW/TM.
[0218] When the master controller asserts the "next" window,
control of the converter is based on a "next" window loop. The
converter output may immediately slew to the "next" output voltage.
The converter may then be operated with the appropriate duty ratio
as described above. This cycle may repeat continuously as the
master control loop sequentially shifts the active window.
[0219] Owing to the very small energy storage inherent in a VHF
power stage, the output voltage slew time at the start of each new
load window may be very short. As a result, it has substantially no
effect on the control system in an average sense. Instead, control
may be dominated by the load-output capacitor time constant, and
the window-window modulation delay. This may allow standard PWM
schemes to be directly compatible. Many other control schemes are
possible where the converter output is time-shared across multiple
loads. These include hysteretic, average current mode control, and
PWM with hysteretic override.
[0220] A primary benefit of this scheme is the ability to simplify
the overall converter architecture while achieving multiple
fully-regulated outputs. This derives from the time-sharing aspect
of this technique as enabled by a high-bandwidth VHF converter as
described herein.
[0221] One application of particular interest is for control of
multiple LED strings to affect color shifting and modulation of
overall brightness. In this case, the converter may operate as a
current regulator. Each string may be one load. As the converter
cycles through each load window, the output current may be
regulated to the desired value and the power stage may naturally
obtain the desired string voltage very rapidly. Since the current
to each stage can be independently regulated using this scheme,
color shifting may be readily achieved. A master control loop may
set the current for each string such that the color temperature and
brightness may be simultaneously satisfied.
[0222] Since the AC/DC VHF converter stages described herein may
also have very high control bandwidth, a VHF AC/DC converter may be
readily controlled in this manner. The result is a converter system
that achieves independent regulation of multiple output strings in
a single stage. This compares favorably with existing technology
that requires a separate AC/DC stage to provide a regulated DC rail
followed by a dedicated set of controllers that are DC/DC
converters to match the voltages required by each string. For the
LED case, in particular, it may not be necessary to use hold-up
capacitors at the output because the modulation frequency can be
maintained very far above the persistence of vision limits of the
human eye.
[0223] Another application of particular interest is in portable
electronics that require multiple output voltages, for example, the
cell phone. In this case, each output is buffered by a capacitor
that is sized to sustain the output during the interval when the
converter is servicing other loads. Allowing for dynamic windowing
in this case can minimize the load capacitor sizes. The total
system size may be reduced regardless, because multiple power
stages may be replaced by a single controllable stage that may have
equivalent or greater power density.
[0224] A VHF power converter architecture as described herein may
operate with very high efficiency. Efficiencies of 70% or greater
can be delivered by a VHF soft-switched power converter through
modest control optimization. Although higher efficiencies may be
desirable in limited applications, the VHF power converter
architecture described herein may operate at efficiencies of 90% or
greater with control optimized for efficiency.
[0225] Very high efficiency may also ameliorate a demand that is
often an important consideration in switch mode power supply
integration--heat build up from efficiency loss. The result may be
a very highly efficient converter that produces less heat energy
per unit volume (power density) than conventional converters for a
given output power requirement. At 50% efficiency, a SMPS must
dissipate half of the energy that it consumes from an input as
heat. Whereas an 80% efficient VHF power converter based on the
soft-switched cell technology and the like described herein need
only be concerned with dissipating twenty percent of power consumed
as heat.
[0226] VHF power converter size may be influenced by the component
technology required; therefore faster switching rates generally
enable smaller devices. Key component size considerations include
inductors and capacitors. By reducing the amount and quality of
stored energy, the high efficiency, soft-switching VHF converters
described herein may be successfully and economically implemented
with small value (and therefore small size) inductors and
capacitors. While these two components are not the only
beneficiaries of the architecture and switch control techniques
described herein, they are generally significant size factors. By
enabling use of air-core printed circuit board etch-based inductors
and/or transformers with or without magnetic core material,
physical device size is essentially moot. The stacked cell high
efficiency, soft-switched VHF power converter architectures
described herein may be applied in an LED driver application
without requiring inductors greater than one micro-henry. Likewise
a switching AC to DC power converter based on the cell-based
architectures described herein may be implemented with no inductors
larger than five micro-henry.
[0227] Such a small form factor device may be implemented as a
stacked cell serial input, parallel out high efficiency fully
resonant switching VHF AC to DC power converter further including
synchronous rectification at the output. Other features and/or
benefits from using a VHF converter in such a small form factor
device may include built in FCC emissions filtering, lightning
strike protection, a diode-based input rectifier, no need for
electrolytic capacitors, VHF operation frequency, little or no DC
energy storage while providing substantially pure DC output from an
AC source, capable of driving an LED with no visible light flicker,
substantially no output ripple, substantially no 2F line frequency
being propagated to the output, and the like. A small form factor
VHF converter may further include generating an output voltage that
is independent of instantaneous input voltage to allow for
delivering substantially constant output power throughout an AC
line cycle.
[0228] By enabling the use of ceramic surface mount capacitors and
printed circuit board etched inductors (rather than discrete
inductors and/or large capacitors) a VHF power converter shape may
result in a substantially planar form. Such a form can readily be
integrated into small spaces such as laptop display screens, mobile
phones, and the like.
[0229] The size benefits of a VHF cell-based power converter as
described herein may facilitate providing an AC to DC high
isolation converter in a volume less than five US quarter dollar
coins (approx. 4,050 cubic millimeters). Other features that may be
provided in this small volume may include providing substantially
ripple free (arbitrarily small ripple) output, ultra-high
efficiency (e.g. greater than 75%), and the like. In a volume of
approximately three US quarter dollar coins (approx. 2,430 cubic
millimeters), the VHF conversion techniques and architecture
described herein may provide a very high power 50 W capable VHF
power converter (e.g. for a laptop computer). Alternatively an
ultra-small 15 W capable VHF power converter (e.g. for driving an
LED) may be provided in a volume smaller than one US quarter dollar
coin (approx. 800 cubic millimeters).
[0230] LED lighting may be controlled/powered by the inventive VHF
converter cell-based architecture described herein. Referring to
FIG. 28, a circuit for replacing an incandescent bulb with a
multiple LED light 2802 is compared to an LED driver 2804 based on
the VHF converter techniques and architecture described herein. Not
only is size of the converter substantially reduced, but the space
that was previously occupied by the LED driver 2802 can be used for
heat sinking/cooling the LEDs thereby enabling much higher
potential light output from the same size package (e.g. an A19
style bulb).
[0231] LED lighting controllers that may be possible with the VHF
cell-based power converter methods and systems described herein may
include: an AC to DC VHF converter to pulse-width-modulate an LED;
a VHF converter to pulse-width-modulate an LED; a stacked VHF
converter to pulse-width-modulate an LED; an AC to DC VHF switching
converter to power an LED; a VHF switching power converter to power
an LED; a stacked cell VHF converter to power an LED; a power
converter operating at greater than 5 MHZ to drive an LED without
use of an electrolytic capacitor; cycling on/off a power conversion
stage of the VHF converter to control an LED; using a conversion
stage of the VHF converter as a pulse-width-modulation mechanism; a
stacked-cell series input, parallel output high efficiency
soft-switching/fully resonant switching VHF LED power supply
including PWM control of the LED with optional power factor
correction.
[0232] The VHF power converter of the present invention may be used
in laptop power supplies, mobile phones, sports equipment,
household appliances, LED-based lights, wireless base stations,
electric vehicles, radar systems, soldier-carried military field
equipment and the like. The VHF power converter described herein
may be used with any application where a higher voltage, such as
12V may need to be converted to a lower voltage, such as 3V to
power digital electronics and the like. The inventive VHF power
converter may have fast transient response and may be configured to
accept a very wide range of inputs such as from 12V Direct Current
(DC) to 240 V Alternating Current (AC). Note that the voltage
references here are merely exemplary and different voltages and
current types (e.g. 15 VAC input, 12V output) may be used and/or
provided by the VHF converter. Further, the methods and systems of
a VHF power converter described herein may provide significant size
benefits to product designers by enabling configuration of a very
small sized power source for use with electronic devices.
[0233] Examples of an electronic device that may receive DC power
from the inventive VHF power converter or other power circuit may
include a handheld computer, a miniature or wearable device, a
portable computer, a desktop computer, a router, an access point, a
backup storage device with wireless communications capabilities, a
mobile telephone, a music player, a remote control, a global
positioning system device, a device that combines the functions of
one or more of these devices, and the like.
[0234] A laptop may present several opportunities for use of the
VHF converter including converting may DC motherboard power to
provide various DC voltages as is sometimes needed for operating a
processor, bus logic, peripherals, display backlight and the like.
Not only are these supplemental power needs met by the inventive
VHF converter, but the main power converter from AC line (e.g. to
charge the laptop battery) may be provided. The small size of the
power converter may require less space than other contemporary
solutions. For example, the main AC to DC power supply, that is
typically found in-line with the line cord may be made
substantially smaller or even eliminated because the VHF power
converter may be put inside the laptop or battery enclosure.
[0235] Another laptop application is to use the inventive VHF power
converter as a source of power for the display (e.g. for a display
backlight). This may benefit the quality of the display because the
fast transient response offered by the VHF power converter may
provide improved display quality, brightness, sharpness, and the
like. In addition, the VHF power converter small size requirement
may allow it to be built into the display housing (e.g. the laptop
fold-up top cover) thereby reducing assembly complexity of the
laptop system.
[0236] As mentioned herein, the power converter may receive a wide
range of inputs for powering low voltage systems mentioned herein
and further including devices such as portable radios, two-way
radios, televisions, audio equipment, wearable microphones,
headsets, virtual reality eyewear, augmented reality headgear, and
the like. In addition to these mostly portable devices, other small
devices that may be powered from the AC line such as a mobile phone
charger, a battery charger, and the like may benefit from
application of the inventive VHF converter described herein. Other
AC line applications include, without limitation charging a
palmtop, a smart phone, a Global Positioning System (GPS) system,
electric razor, and the like. In embodiments, the power converter
of the present invention may be used for powering devices that
range in power from a high-power laptop to a low-power cell
phone.
[0237] Further, the power converter may be used in wireless
security monitoring system, energy saving lamps and other household
appliances. The power converter may convert standard AC voltage
supply in houses to DC voltages required in wireless security
monitoring system, energy saving lamps and other household
appliances. The inventive VHF power converter may accept a very
wide range of inputs, and hence, it can be employed in different
household appliances requiring different voltages. Further, the
small size requirement of the VHF power converter may allow it to
be built into any household appliance.
[0238] The VHF power converter may be used for sports equipment,
such as a helmet camera. A helmet camera may also require a variety
of voltages, for powering the memory, image sensor, lighting,
radio, and the like. An embodiment of the VHF power converter may
convert a DC voltage that may be supplied from a battery (e.g. 18V)
various DC voltages required in the operation of the helmet camera.
By applying the multi-channel capabilities described herein, each
load (lighting, sensor, radio, etc.) that requires a different
voltage or current for proper operation can be serviced by a single
multi-channel converter described herein. Further, because of its
small size, the VHF power converter may fit easily into the helmet
camera housing and may be readily integrated into a printed circuit
board that may include the logic and functional elements powered by
the converter.
[0239] The inventive VHF power converter may be integrated into a
display screen module to provide power for backlighting the display
of a laptop or the like. This may benefit the quality of the
display because the fast transient response offered by the VHF
power converter may provide improved display quality, brightness,
sharpness, and the like. In addition, the small size requirement of
the VHF power converter may allow it to be built into the display
screen module housing, thereby reducing assembly complexity of the
display screen module.
[0240] The inventive VHF power converter may be integrated into an
AC power cord. As mentioned earlier, the inventive VHF power
converter may receive a wide range of power inputs. Hence, the AC
power cord having the inventive VHF power converter may be
connected to nearly any type of power source (e.g. AC line cord,
12V car charger, and the like). In a typical application, line AC
power may be converted to low voltages that meet low-voltage safety
requirements (e.g. less than 30V). The small size of the power
converter may require less space than other contemporary solutions
so that a typical 50 W line cord power converter may be disposed in
an enclosure no larger than five U.S. quarter dollar coins (approx.
4050 cubic mm).
[0241] Mobile phone applications of the VHF power converter include
providing the main electronics power from a battery, dedicated
power for the phone's display including a backlit display, keypad
back lighting, camera flash lamp, and the like. The high degree of
integration afforded by the inventive VHF power converter described
herein and the simplified PCB-based embedded inductor functionality
with which the VHF power converter is compatible may afford direct
integration on the main electronics printed circuit board.
[0242] The inventive VHF power converter may also be used in
LED-based lighting. LED lighting products that are compatible with
existing incandescent fixtures need to operate from standard AC
line voltage. LED light bulbs include multiple diodes, which use
direct current (DC). The inventive VHF power converter may convert
standard AC voltage to DC voltage required by diodes in LED light
bulbs. In addition, the small size requirement of the VHF power
converter may allow it to be built into the base of an LED-based
replacement light bulb, thereby reducing assembly complexity of the
LED light bulbs and providing a substantial amount of the interior
of the bulb for heat sinking the LEDs.
[0243] A multi-channel embodiment of the inventive VHF power
converter may be used to power LED strings so that each light or
group of lights can be individually controlled for brightness,
color, on/off (blink), and the like by employing a separate output
value (current or voltage) for each light/group of lights. In
addition, the inventive VHF power converter may improve design and
packaging of the LED strings owing to its small size.
[0244] The inventive VHF power converter may also be used in color
changing LEDs. The inventive VHF power converter may provide color
light intensity control. The inventive VHF power converter may
further provide color point maintenance against LED junction
temperature change, and limiting LED device temperature to prolong
LED lifetime.
[0245] The inventive VHF power converter may also be used in a
wireless base station. The inventive VHF power converter may
convert an input voltage to an output voltage or current required
by the wireless base station transceiver. The inventive VHF power
converter may benefit low power RF applications through its fast
transient response time, RF envelope tracking output, and small
size.
[0246] The VHF converter may find varied applications in
vehicle-based electronics. In an embodiment, the power converter
may be used for powering vehicle accessories such as cell phone
chargers, GPS Systems, mp3 players, stereo system, and the like
that may plug into a 12 VDC vehicle power port. The inventive VHF
power converter may provide power to display units of GPS systems.
This may result in improved display quality, brightness, sharpness,
and the like because of the fast transient response offered by the
VHF power converter. In addition, the small size requirement of the
VHF power converter may allow it to be built into the display unit,
thereby reducing assembly complexity of the GPS system. Owing to
the small size, the inventive VHF power converter may be integrated
into the cell phone chargers, GPS Systems, mp3 players, and stereo
systems in vehicles.
[0247] The inventive VHF power converter may also be used in
airborne radar. Airborne radar presents unique design challenges,
mainly in the installation constraints on the size of the airborne
radar. The inventive VHF power converter small size requirement may
allow it to be built into the airborne radar, thereby solving
installation constraints of the airborne radar. Radar systems may
further benefit from the fast transient response ability of the VHF
power converter and wide range of output voltage capability,
extremely low ripple, high isolation, and the like.
[0248] The inventive VHF power converter may also be used in
Soldier-carried military field equipment. The inventive VHF power
converter may convert an input signal to an output signal (e.g.
voltage), as per requirement of a military field equipment, and aid
in efficient power management. The military field equipment may
include night-vision goggles, laptops, and communication devices
such as GPS, sensors, and the like. The small size requirement of
the VHF power converter may allow it to be built into the military
field equipment, thereby making the military field equipment
lightweight, reliable, and portable. In addition, the inventive VHF
power converter may provide military equipment designers with a
single power converter design that is able to adapt to the power
needs of all sorts of military field equipment.
[0249] The inventive VHF converter methods and systems described
herein may be combined with varactor-based network tuning to
support a very large load range. Such a combination may take
advantage of varactor control of resonance and VHF on/off switching
to facilitate compensation for impedance changes as a function of
load.
* * * * *