U.S. patent application number 14/626692 was filed with the patent office on 2015-06-18 for dimming driver with stealer switch.
The applicant listed for this patent is Laurence P. Sadwick. Invention is credited to Laurence P. Sadwick.
Application Number | 20150173134 14/626692 |
Document ID | / |
Family ID | 48981757 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150173134 |
Kind Code |
A1 |
Sadwick; Laurence P. |
June 18, 2015 |
Dimming Driver With Stealer Switch
Abstract
An apparatus for supplying power includes a power input, a load
output and a switch connected in series to the power input, a pulse
generator comprising a pulse output connected to a control input of
the switch, and a stealer switch connected to the control input of
the switch. When the switch is closed, electrical current is able
to flow from the power input to the load output. When the pulse
output is in a low state, the stealer switch is closed.
Inventors: |
Sadwick; Laurence P.; (Salt
Lake City, UT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sadwick; Laurence P. |
Salt Lake City |
UT |
US |
|
|
Family ID: |
48981757 |
Appl. No.: |
14/626692 |
Filed: |
February 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13769378 |
Feb 17, 2013 |
8987997 |
|
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14626692 |
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Current U.S.
Class: |
315/291 |
Current CPC
Class: |
H05B 45/37 20200101;
Y02B 20/30 20130101; H05B 33/08 20130101 |
International
Class: |
H05B 33/08 20060101
H05B033/08 |
Claims
1. An apparatus for supplying power, comprising: a power input; a
load output and a switch connected in series to the power input,
wherein when the switch is closed, electrical current is able to
flow from the power input to the load output; a pulse generator
comprising a pulse output connected to a control input of the
switch; and a stealer switch connected to the control input of the
switch, wherein when the pulse output is in a low state, the
stealer switch is closed.
2. The apparatus of claim 1, wherein the stealer switch is
configured to pull the control input of the switch to a ground when
the stealer switch is closed.
3. The apparatus of claim 1, wherein the switch comprises a bipolar
junction transistor.
4. The apparatus of claim 3, further comprising a diode connected
between a base and an emitter of the bipolar junction transistor,
configured to assist the base of the bipolar junction transistor to
drain when the bipolar junction transistor is off.
5. The apparatus of claim 3, further comprising a diode connected
between a base and a collector of the bipolar junction transistor,
configured to prevent the bipolar junction transistor from entering
a deep saturation state.
6. The apparatus of claim 1, wherein the stealer switch comprises a
field effect transistor.
7. The apparatus of claim 1, further comprising an inductor
connected in series with the load output and the switch, and a
diode connected in parallel with the load output and the inductor,
wherein when the switch is open, electrical current circulates
through the inductor, the diode and the load output.
8. The apparatus of claim 1, further comprising an inverter having
an input connected to the pulse output and an output connected to a
control input of the stealer switch.
9. The apparatus of claim 1, further comprising a load current
sensor connected in series with the load output.
10. The apparatus of claim 9, further comprising a load current
detection circuit connected to the pulse generator, wherein the
pulse generator is configured to adjust a pulse width of pulses at
the pulse output based at least in part on a control signal from
the load current detection circuit.
11. The apparatus of claim 10, further comprising a reference
current source connected to the load current detection circuit,
wherein the load current detection circuit is configured to compare
a first signal from the reference current source with a second
signal from the load current sensor.
12. The apparatus of claim 10, further comprising a level shifter
connected between the load current detection circuit and the pulse
generator.
13. The apparatus of claim 10, further comprising a filter
connected between the load current sensor and the load current
detection circuit.
14. The apparatus of claim 13, wherein the filter is configured to
average the second signal from the load current sensor.
15. A method of supplying power, comprising: regulating current
from a power input to an output driver using an output driver
control switch; controlling the output driver control switch with a
pulse signal from a pulse generator; and connecting a control input
of the output driver control switch to ground when the pulse signal
is in a low state.
16. The method of claim 15, further comprising connecting the
control input of the output driver control switch to the ground
when an inverted version of the pulse signal is in a high
state.
17. The method of claim 15, further comprising powering the pulse
generator by drawing power from the output driver via inductive
coupling.
18. The method of claim 17, further comprising varying a current
through the output driver based on a dimming signal.
19. The method of claim 15, further comprising controlling the
pulse generator to vary a pulse width of the pulse signal to
regulate a current through the output driver.
20. The method of claim 19, wherein the pulse width is varied based
at least in part on a load current through the output driver.
Description
BACKGROUND
[0001] Electricity is generated and distributed in alternating
current (AC) form, wherein the voltage varies sinusoidally between
a positive and a negative value. However, many electrical devices
require a direct current (DC) supply of electricity having a
constant voltage level, or at least a supply that remains positive
even if the level is allowed to vary to some extent. For example,
light emitting diodes (LEDs) and similar devices such as organic
light emitting diodes (OLEDs) are being increasingly considered for
use as light sources in residential, commercial and municipal
applications. However, in general, unlike incandescent light
sources, LEDs and OLEDs cannot be powered directly from an AC power
supply unless, for example, the LEDs are configured in some back to
back formation. Electrical current flows through an individual LED
easily in only one direction, and if a negative voltage which
exceeds the reverse breakdown voltage of the LED is applied, the
LED can be damaged or destroyed. Furthermore, the standard, nominal
residential voltage level is typically something like 120 V or 240
V AC, both of which are often higher than may be desired for a high
efficiency LED light. In addition, commercial and municipal voltage
levels can be significantly above 240 V AC and up to or above 480
VAC. Some conversion of the available power may therefore be
necessary or highly desired with loads such as an LED light.
[0002] In one type of commonly used power supply for loads such as
an LED, an incoming AC voltage is connected to the load and current
is drawn only during certain portions of the sinusoidal waveform.
For example, a fraction of each half cycle of the waveform may be
used by connecting the incoming AC voltage to the load each time
the incoming voltage rises to a predetermined level or reaches a
predetermined phase and by disconnecting the incoming AC voltage
from the load each time the incoming voltage again falls to zero or
capacitors that are used in the power supply circuit may charge
only near the peak of, for example, the rectified AC input voltage.
In this manner, a positive but reduced voltage may be provided to
the load. This type of conversion scheme is often controlled so
that a constant current is provided to the load even if the
incoming AC voltage varies. However, if this type of power supply,
and, often, other types of power supplies, with current control is
used in an LED light fixture or lamp, a conventional dimmer is
often ineffective. For many LED power supplies, the power supply
will attempt to maintain the constant current through the LED
despite a drop in the incoming voltage by increasing the on-time
during each cycle of the incoming AC wave.
SUMMARY
[0003] The driver disclosed herein provides power for lights such
as LEDs of any type and other loads, using pulse control of a
switch to adjust load current and/or voltage. A stealer switch is
provided to rapidly turn off the switch.
[0004] This summary provides only a general outline of some
particular embodiments. Many other objects, features, advantages
and other embodiments will become more fully apparent from the
following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] A further understanding of the various embodiments may be
realized by reference to the figures which are described in
remaining portions of the specification. In the figures, like
reference numerals may be used throughout several drawings to refer
to similar components.
[0006] FIG. 1 depicts a block diagram of a dimming driver with
stealer switch in accordance with some embodiments of the
invention;
[0007] FIG. 2 depicts a schematic of a dimming driver with stealer
switch in accordance with some embodiments of the invention;
[0008] FIG. 3 depicts a schematic of a dimming driver with stealer
switch wherein internal components derive power from a tag-along
inductor in accordance with some embodiments of the invention;
[0009] FIG. 4 depicts a portion of a dimming driver including an
inverter and stealer switch in accordance with some embodiments of
the invention;
[0010] FIG. 5 depicts an inverter and stealer switch in accordance
with some embodiments of the invention;
[0011] FIG. 6 depicts a block diagram of a dimming driver with
stealer switch in accordance with some embodiments of the
invention; and
[0012] FIG. 7 depicts a schematic diagram of a dimming driver with
stealer switch in accordance with some embodiments of the
invention.
DESCRIPTION
[0013] The lighting driver disclosed herein provides power for
lights such as LEDs of any type and other loads. The lighting
driver may be dimmed or otherwise controlled externally, for
example by controlling a line voltage supplying the lighting
driver, or internally, for example using a wireless controller to
command internal dimming circuits, etc. The current and/or voltage
to a load is adjusted using a switch to pass or block input
current, controlled by a variable pulse signal. A stealer switch is
provided to rapidly turn off the switch to block the input current,
with the stealer switch controlled in some embodiments by an
inverted version of the variable pulse signal.
[0014] The dimming driver with stealer switch may include driver
circuits and applications such as the various dimmable LED drivers
and their variations disclosed in U.S. patent application Ser. No.
12/422,258, filed Apr. 11, 2009 for a "Dimmable Power Supply", and
in U.S. patent application Ser. No. 12/776,409, filed May 9, 2010
for a "LED Lamp with Remote Control", which are incorporated herein
by reference for all purposes.
[0015] Turning to FIG. 1, a block diagram of a dimming driver with
stealer switch 10 is illustrated in accordance with various
embodiments of the invention. The dimming driver with stealer
switch 10 is powered in some embodiments by an AC input 12, for
example by a 50 or 60 Hz sinusoidal waveform of 120 V or 240 V RMS
or higher such as that supplied to commercial and residential
facilities by municipal electric power companies. It is important
to note, however, that the dimming driver with stealer switch 10 is
not limited to any particular power input. Furthermore, the voltage
applied to the AC input 12 may be externally controlled, such as in
an external dimmer (not shown) that reduces the voltage. The AC
input 12 is connected to a rectifier 14 to rectify and invert any
negative voltage component from the AC input 12. Although the
rectifier 14 may filter and smooth the power output 16 if desired
to produce a DC signal, this is not necessary and the power output
16 may be a series of rectified half sinusoidal waves at a
frequency double that at the AC input 12, for example 100 or 120
Hz. A variable pulse generator 20 is powered by the power output 16
from the AC input 12 and rectifier 14 to generate a train of pulses
at output 22. The pulse width of the pulses in output 22 is
controlled in the variable pulse generator 22 by load current
detector 24 based on load current levels. Various implementations
of pulse width control including pulse width modulation (PWM) by
frequency, analog and/or digital control may be used to realize the
pulse width control. Other features such as soft start, delayed
start, instant on operation, etc. may also be included if deemed
desirable, needed, and/or useful. Output driver 30 produces a
current through the load 26, with the current levels adjusted by
the pulse width at the output 22 variable pulse generator 22. The
load current is monitored by the load current detector 24 and may
also be monitored by a master load current detector sensor. Such a
sensor may be, but is not limited to, a sense resistor, a sense
transformer, a winding on a transformer or inductor, sensing via
passive and/or active components, etc.
[0016] A stealer circuit 40 is provided to increase the speed at
which the output driver 30 changes state or turns on and off,
passing current from power output 16 to the load 26.
[0017] Turning to FIG. 2, a schematic of an embodiment of a dimming
driver with stealer switch 100 is illustrated in accordance with
some embodiments of the invention. An AC input 112 is converted to
a DC supply 116 by rectifier 114. As noted above, the dimming
driver with stealer switch 100 is not limited to this particular
example power configuration. A switch 120 controls current from DC
supply 116 to a load 122. The load 122 is connected in parallel
with, for example, a capacitor 124 which is optional in some
embodiments of the present invention, with an optional load current
sense resistor 126 connected in series with the load 122. An
inductor 130 is connected in series with load 122 and capacitor 124
to store energy as current flows from DC supply 116 through the
load 122, when the switch 120 is on. A diode 132 is connected to
make a loop including load 122 and inductor 130, allowing energy
stored in inductor 130 to produce a current through load 122 when
switch 120 is off.
[0018] The switch 120 is controlled by pulses from a variable pulse
generator 134, for example with the on-time and/or off-time of the
pulses adjusted based on the current through the load 122 and/or
the current through switch 120 to provide the desired load current
and/or voltage. The output 136 of variable pulse generator 134 is
also provided to inverter 140 and stealer switch 142. The stealer
switch 142 pulls the control input of switch 120 down to ground 144
when the output 136 of variable pulse generator 134 is off, rapidly
turning off switch 120.
[0019] Turning to FIG. 3, power for internal components may be
drawn from a tag-along inductor 150 as described in U.S. Patent
Application 61/558,512, filed Nov. 11, 2011 for a "Dimmable LED
Driver with Multiple Power Sources", which is incorporated herein
by reference for all purposes. The first power source 102 draws
power from the DC rail 116, regulating or dividing or otherwise
setting the voltage level at an appropriate level, for example, for
the variable pulse generator 134. The second power source 104 draws
power from an inductor 150 adjacent the main inductor 130,
inductively coupling power flowing through the main inductor 130
into the power source 104.
[0020] Turning to FIG. 4, a portion of a dimming driver 400 with
inverter 402 and stealer switch 404 are depicted in accordance with
some embodiments of the invention. A variable pulse generator 406
produces a pulse signal 410 that drives the control input of main
switch 412. Main switch 412 may correspond to switch 120 in the
embodiments of FIGS. 2 and 3, and may comprise, for example, a
bipolar junction transistor (BJT), with the base as control input
connected to pulse signal 410. When the pulse signal 410 is on, the
main switch 412 is on, allowing current to flow from a power input
to a load. When the pulse signal 410 is off, the main switch 412 is
off, blocking current from the power input and allowing current to
circulate through the load in an internal loop in some embodiments,
as disclosed above. When pulse signal 410 is off, inverter 402
turns on stealer switch 404, pulling the base of BJT main switch
412 down and rapidly turning off BJT 412. A diode 414 is connected
between the base and emitter of main switch 412, allowing the base
of main switch 412 to discharge when it is off.
[0021] Turning to FIG. 5, an inverter and stealer switch are
depicted in accordance with some embodiments of the invention. The
inverter comprises a pull-up resistor 500 and pull-down BJT 502
connected in series and controlled by the pulse control signal 504
through resistor 506, although the inverter can be made from any
type of circuit, topology, approach, etc. including but not limited
to field effect transistors (FETs) including but not limited to
MOSFETs, JFETs, NMOS, PMOS, CMOS, BiCMOS, DMOS, EMOS, BCD, etc.
made from or based on any appropriate material including silicon
(Si), silicon carbide (SiC), silicon germanium (SiGe), silicon on
insulator (SOI), gallium arsenide (GaAs), indium phosphide (InP),
gallium nitride (GaN), combinations of these, etc. along with any
type and number of passive components, if needed. When pulse
control signal 504 is on, pull-down BJT 502 is on, pulling the gate
510 (or, for example, base if a BJT is used) of stealer switch 404
down and turning it off. When pulse control signal 504 is off,
pull-down BJT 502 is off, pulling the gate 510 of stealer switch
404 up through pull-up resistor 500 and turning stealer switch 404
on. A diode 414 is connected between the base and emitter of main
switch 412, allowing and assisting the base of main switch 412 to
discharge when it is off. A diode 512 is connected between the base
and collector of main switch 412 as part of a Baker circuit or
desaturation circuit and/or related circuits, keeping the main
switch 412 out of deep saturation and V.sub.BE>V.sub.CE. Other
elements of a Baker circuit can also be used and incorporated into
the present invention. In addition, other Baker elements or
desaturation circuits including additional diodes, capacitors,
resistors, inductors, etc. can be used and incorporated into the
present invention as well as protection circuits such as, for
example, snubber, clamps, peak detectors, limiters, rate limiters,
including current and voltage rate limiters, etc.
[0022] The inverter and stealer switch enable the use of a BJT 412
as the main switch in a dimming driver, greatly improving the
reverse recovery time and efficiency and reducing switching
loss.
[0023] Turning to FIG. 6, a block diagram of a dimming driver with
stealer switch 600 is depicted in accordance with some embodiments
of the invention. In the diagram of FIG. 6, the load 602 is shown
inside the output driver 604 for convenience in setting forth the
connections in the diagram. The dimming driver with stealer switch
600 is powered from an AC input 606 through a fuse 610 and an
electromagnetic interference (EMI) filter 612. A DC input may also
be used. The fuse 610 may be any device suitable to protect the
dimming driver with stealer switch 600 from overvoltage or
overcurrent conditions, such as a traditional meltable fuse or
other device (e.g., a small low power surface mount resistor), a
breaker, etc. The EMI filter 612 may be any device suitable to
prevent EMI from passing into or out of the dimming driver with
stealer switch 600, such as a coil, inductor, capacitor and/or any
combination of these, or, also in general, a filter, etc. The AC
input 606 is rectified in a rectifier 614. In this embodiment, the
dimming driver with stealer switch 600 may generally be divided
into a high side portion including a load current detector 616 and
a low side portion including a variable pulse generator 620, with
the output driver 604 spanning or including the high and low side.
In this case, a level shifter 620 may be employed between the load
current detector 616 in the high side and the variable pulse
generator 620 in the low side to communicate the control signal 622
to the variable pulse generator 620. The variable pulse generator
620 and load current detector 616 are both powered by the supply
voltage 608 from the rectifier 614, for example through resistors
624 and 626, respectively, although they may alternatively be
powered from a tag-along inductor as disclosed above or in any
other manner. The high side, including the load current detector
616, floats at a high potential under the supply voltage 608 and
above the circuit ground 630. A local ground 632 is thus
established and used as a reference voltage by the load current
detector 616.
[0024] A reference current source 634 supplies a reference current
signal 636 to the load current detector 616, and a current sensor
such as a resistor 640 provides a load current signal 642 to the
load current detector 616. The reference current source 634 may use
the circuit ground 630 as illustrated in FIG. 6, or the local
ground 632, or both, or some other reference voltage level as
desired. The load current detector 616 compares the reference
current signal 636 with the load current signal 642 using a time
constant to effectively average out and disregard current
fluctuations due to any waveform at the input voltage 608 and
pulses from the variable pulse generator 620, and generates the
control signal 622 to the variable pulse generator 620. The
variable pulse generator 620 adjusts the pulse width of a train of
pulses at the pulse output 644 of the variable pulse generator 620
based on the level shifted control signal 646 from the load current
detector 616. The level shifter 620 shifts the control signal 622
from the load current detector 616 which is referenced to the local
ground 632 in the load current detector 616 to a level shifted
control signal 646 that is referenced to the circuit ground 630 for
use in the variable pulse generator 620. The level shifter 620 may
comprise any suitable device for shifting the voltage of the
control signal 622, such as an opto-isolator or opto-coupler,
resistor, transformer, etc.
[0025] The pulse output 644 from the variable pulse generator 620
drives a switch 650 such as a BJT in the output driver 604. When a
pulse from the variable pulse generator 620 is active, the switch
650 is turned on, drawing current from the input voltage 608,
through the load path 652 (and an optional capacitor 654 connected
in parallel with the load 602), through the load current sense
resistor 640, an inductor 656 in the output driver 604, the switch
650, and a current sense resistor 660 to the circuit ground 630.
When the pulse from the variable pulse generator 620 is off, the
switch 650 is turned off, blocking the current from the input
voltage 608 to the circuit ground 630. The inductor 656 resists the
current change and recirculates current through a diode 662 in the
output driver 604, through the load path 652 and load current sense
resistor 640 and back to the inductor 656. The load path 652 is
thus supplied with current alternately through the switch 650 when
the pulse from the variable pulse generator 620 is on and with
current driven by the inductor 656 when the pulse is off.
[0026] The pulses from the variable pulse generator 620 have a
relatively much higher frequency than variations in the input
voltage 608. Note that any suitable frequency for the pulses from
the variable pulse generator 620 may be selected as desired, with
the time constant in the load current detector 616 being selected
accordingly to disregard load current changes due to the pulses
from the variable pulse generator 620 while tracking changes on the
input voltage 608 that are slower than or on the order of the
waveform on the input voltage 608. Changes in the current through
the load 602 due to the pulses from the variable pulse generator
620 may be smoothed in the optional capacitor 654, or may be
ignored if the load is such that high frequency changes are
acceptable. For example, if the load 602 is an LED or array of
LEDs, any flicker that may occur due to pulses at many thousands of
cycles per second will not be visible to the eye. In the embodiment
of FIG. 6, a current overload protection 664 is included in the
variable pulse generator 620 and is based on a current measurement
signal 670 by the current sense resistor 660 connected in series
with the switch 650. If the current through the switch 650 and the
current sense resistor 660 exceeds a threshold value set in the
current overload protection 664, the pulse width at the pulse
output 644 of the variable pulse generator 620 will be reduced or
eliminated. The present invention is shown implemented in the
discontinuous mode; however with appropriate modifications
operation under continuous or critical conduction modes or any
other modes including resonant circuit modes can also be
realized.
[0027] Efficiency is improved in the dimming driver 600 when switch
650 is a BJT by including inverter 672 and stealer switch 674 to
rapidly discharge the base of the BJT used as switch 650 when the
pulse signal from variable pulse generator 620 is off, as disclosed
above.
[0028] Turning to FIG. 7, a schematic diagram of a dimming driver
with stealer switch 700 is depicted in accordance with some
embodiments of the invention. Notably, a number of optional
elements are included in the example dimming driver with stealer
switch 700 that may be omitted without departing from the inventive
concepts disclosed herein. The dimming driver with stealer switch
700 is powered from an AC input 702 through a resistor 704 used as
a fuse, and a diode bridge as a rectifier 706. As disclosed above,
other power sources may be used in other embodiments. Some
smoothing of the voltage on the supply rail 710 may be provided by
a capacitor 712, although it is not necessary as described above.
Capacitor 712 is optional and may be eliminated or reduced to a
small value and, as mentioned above, is included as desired and or
needed, etc.
[0029] A variable pulse generator 716 generates pulses at the pulse
output 722, with the pulse width varied by one or more feedback
signals as disclosed below or in other manners. The pulses from
variable pulse generator 716 may have any suitable shape, such as
substantially square pulses, semi-sinusoidal, triangular, etc.
although square or rectangular are perhaps most common in driving
field effect transistors. The frequency of the pulses may also be
set at any desired rate by a clock or multi-phase clock 714, such
as, for example, 30 kHz or 100 kHz.
[0030] The width of the pulses may be controlled by load current
detector 724, although a maximum width may be established if
desired. The load current detector 724 includes an operational
amplifier (op-amp) 726 acting as an error amplifier to compare a
reference current 730 and a load current 732. The op-amp 726 may be
embodied by any device suitable for comparing the reference current
726 and load current 732, including active devices and passive
devices.
[0031] The reference current 726, for example, may be supplied by a
transistor such as bipolar junction transistor (BJT) 734 connected
in series with resistor 736 to the supply rail 710. Resistors 740
and 742 are connected in series between the supply rail 710 and the
circuit ground 744, forming a voltage divider with a central node
746 connected to the base 750 of the BJT 734. The BJT 734 and
resistor 736 act as a constant current source that is varied by the
voltage on the central node 746 of the voltage divider 740 and 742,
which is in turn dependent on the input voltage at supply rail 710.
A capacitor 752 may be connected between the supply rail 710 and
the central node 746 to form a time constant for voltage changes at
the central node 746. The dimming driver with stealer switch 700
thus responds to the average voltage of supply rail 710 rather than
the instantaneous voltage although the lighting driver can be
designed to respond to the instantaneous voltage and/or both the
instantaneous and average voltage or any combination, etc. Other
embodiments can employ voltage dividers including simple resistive
network voltage dividers, capacitive dividers and other active and
passive networks, approaches, topologies, transistor types,
circuits, electronics, etc.
[0032] In one particular embodiment, the local ground 754 floats at
about 10 V below the supply rail 710 at a level established by the
load 756. A capacitor 760 may be connected between the supply rail
710 and the local ground 754 to smooth the voltage powering the
load current detector 724 if desired. A Zener diode 762 may also be
connected between the supply rail 710 and the central node 746 to
set a maximum load current 732 by clamping the reference current
730 that BJT 734 can provide to resistor 764. In other embodiments,
the load current detector 724 may have its current reference
derived by a simple resistive voltage divider, with suitable AC
input voltage sensing, level shifting, and maximum clamp, rather
than BJT 734.
[0033] The load current 732 (meaning, in this embodiment, the
current through the load 756 and through the capacitor 766
connected in parallel with the load 756) is measured using the load
current sense resistor 770 although any current sensing element,
including but not limited to a transformer or winding on a
transformer or inductor, may be used in place of or in addition to
sense resistor 770. The current measurement 772 is provided to an
input of the error amplifier 726, in this case, to the
non-inverting input 774. A time constant is applied to the current
measurement 772 using any suitable device, such as the RC lowpass
filter made up of the series resistor 776 and the shunt capacitor
780 to the local ground 754 connected at the non-inverting input
774 of the error amplifier 726.
[0034] As discussed above, any suitable device for establishing the
desired time constant may be used such that the load current
detector 724 disregards rapid variations in the load current 732
due to the pulses from the variable pulse generator 716 and any
regular waveform on the supply rail 710. The load current detector
724 thus substantially filters out changes in the load current 732
due to the pulses, averaging the load current 732 such that the
load current detector output 784 is substantially unchanged by
individual pulses at the variable pulse generator output 716.
[0035] The reference current 730 is measured using a sense resistor
764 connected between the BJT 734 and the local ground 754, and is
provided to the inverting input 782 of the error amplifier 726. The
error amplifier 726 is connected as a difference amplifier with
negative feedback, amplifying the difference between the load
current 732 and the reference current 730. An input resistor 786 is
connected in series with the inverting input 782. A feedback
resistor 790 is connected between the output 784 of the error
amplifier 724 and the inverting input 782. A capacitor 792 is
connected in series with the feedback resistor 790 between the
output 784 of the error amplifier 724 and the inverting input 782.
An output resistor 794 is connected in series with the output 784
of the error amplifier 724 to further establish a time constant in
the load current detector 724. Again, the load current detector 724
may be implemented in any suitable manner to measure the difference
of the load current 732 and reference current 730.
[0036] A level shifter 796, in this case, an opto-isolator, is
connected to the output resistor 794 of the load current detector
724 to reference the output signal to the circuit ground 744 rather
than the local ground 754. In other embodiments a level shifter
and/or opto-isolator is not required. In other embodiments, a PNP
transistor may be used.
[0037] A Zener diode 800 and series resistor 802 may be connected
between the supply rail 710 and the output of output resistor 794
for overvoltage protection. Again, the above are merely example
embodiments for illustrative purposes and not meant to be limiting
in any way or form.
[0038] Pulses from the variable pulse generator 716 turn on a
switch 804, in this case a BJT via a resistor 806 to the base of
the switch 804. This allows current 732 to flow through the load
756 and capacitor 766, through the load current sense resistor 770,
inductor 810, the switch 804 and a current sense resistor 812 to
circuit ground 744. In between pulses, the switch 804 is turned
off, and the energy stored in the inductor 810 (or, in other
embodiments, a transformer) when the switch 804 was on is released
to resist the change in current. The current from the inductor 810
then flows through diode 814 and back through the load 756 and load
current sense resistor 770 to the inductor 810. Because of the time
constant in the load current detector 724, the load current 732
monitored by the load current detector 724 is an average of the
current through the switch 804 during pulses and the current
through the diode 814 between pulses. Additional elements, for
example, capacitors, base coil and/or inductor, additional
resistors, etc. can be added in conjunction with resistor 806, for
example in parallel or series with resistor 806; an example of
which would be a capacitor in parallel with resistor 806.
[0039] The current through the channel 720 of the dimming driver
with stealer switch 700 is monitored by the current sense resistor
812, with a current feedback signal 816 returning to the variable
pulse generator 716. If the current exceeds a threshold value, the
pulse width is reduced or the pulses are turned off in the variable
pulse generator 716.
[0040] An inverter comprising a pull-up resistor 820 and pull-down
BJT 822 connected in series is connected to the pulse output 722
through resistor 824. When pulse output 722 is on, pull-down BJT
822 is on, pulling the gate 826 (or base if, for example, a BJT is
used) of stealer switch 830 down and turning it off. When pulse
output 722 is off, pull-down BJT 822 is off, pulling the gate 826
of stealer switch 830 up through pull-up resistor 820 and turning
stealer switch 830 on, rapidly discharging the base of switch 804.
A diode 832 is connected between the base and emitter of BJT 804,
allowing the base of BJT 804 to discharge when it is off. A diode
834 is connected between the base and collector of BJT 804 as part
of a Baker circuit or desaturation circuit, keeping the BJT 804 out
of deep saturation and V.sub.BE>V.sub.CE. Other types of
inverters may be used including, but not limited to, CMOS, NPN-PNP
inverters, BCD, BiCMOS, etc.
[0041] The inverter and stealer switch enable the use of a BJT 804
as the main switch in the dimming driver 700, greatly improving the
reverse recovery time and efficiency and reducing switching
loss.
[0042] The present invention can be used in high power factor (PF)
circuits with or without dimming including triac, forward and
reverse dimmers, 0 to 10 V dimming, powerline dimming, wireless and
other wired dimming, DALI dimming, PWM dimming, DMX, etc., as well
as any other dimming and control protocol, interface, standard,
circuit, arrangement, hardware, etc.
[0043] The example embodiments disclosed herein illustrate certain
features of the present invention and not limiting in any way, form
or function of present invention. Note that linear or switching
voltage or current regulators or any combination can be used in the
present invention and other elements/components can be used in
place of the diodes, etc. The present invention can also include
passive and active components and circuits that assist, support,
facilitate, etc. the operation and function of the present
invention. Such components can include passive components such as
resistors, capacitors, inductors, filters, transformers, diodes,
other magnetics, combinations of these, etc. and active components
such as switches, transistors, integrated circuits, including
ASICs, microcontrollers, microprocessors, FPGAs, CLDs, programmable
logic, digital and or analog circuits, and combinations of these,
etc. and as also discussed below.
[0044] The present invention can be used in power supplies,
drivers, ballasts, etc. with or needing high power factor (PF)
and/or lower THD circuits with or without dimming including triac,
forward and reverse dimmers, 0 to 10 V dimming, powerline dimming,
wireless and other wired dimming, DALI dimming, PWM dimming, DMX,
etc., as well as any other dimming and control protocol, interface,
standard, circuit, arrangement, hardware, etc.
[0045] The present invention is, likewise, not limited in materials
choices including semiconductor materials such as, but not limited
to, silicon (Si), silicon carbide (SiC), silicon on insulator
(SOI), other silicon combination and alloys such as silicon
germanium (SiGe), etc., diamond, graphene, gallium nitride (GaN)
and GaN-based materials, gallium arsenide (GaAs) and GaAs-based
materials, etc. The present invention can include any type of
switching elements including, but not limited to, field effect
transistors (FETs) such as metal oxide semiconductor field effect
transistors (MOSFETs) including either p-channel or n-channel
MOSFETs, junction field effect transistors (JFETs), metal emitter
semiconductor field effect transistors, etc. again, either
p-channel or n-channel or both, bipolar junction transistors
(BJTs), heterojunction bipolar transistors (HBTs), high electron
mobility transistors (HEMTs), unijunction transistors, modulation
doped field effect transistors (MODFETs), etc., again, in general,
n-channel or p-channel or both, vacuum tubes including diodes,
triodes, tetrodes, pentodes, etc. and any other type of switch,
etc. The present invention can, for example, be used with
continuous conduction mode (CCM), critical conduction mode (CRM),
discontinuous conduction mode (DCM), etc., of operation with any
type of circuit topology including but not limited to buck, boost,
buck-boost, boost-buck, cuk, etc., SEPIC, flyback, etc. In
addition, the present invention does not require any additional
special isolation or the use of an isolated power supply, etc. The
present invention applies to all types of power supplies and
sources and the respective power supply(ies) can be of a constant
frequency, variable frequency, constant on time, constant off time,
variable on time, variable off time, etc. Other forms of sources of
power including thermal, optical, solar, radiated, mechanical
energy, vibrational energy, thermionic, etc. are also included
under the present invention. The present invention may be
implemented in various and numerous forms and types including those
involving integrated circuits (ICs) and discrete components and/or
both. The present invention may be incorporated, in part or whole,
into an IC, etc. The present invention itself may also be
non-isolated or isolated, for example using a tag-along inductor or
transformer winding or other isolating techniques, including, but
not limited to, transformers including signal, gate, isolation,
etc. transformers, optoisolators, optocouplers, etc.
[0046] The present invention includes other implementations that
contain various other control circuits including, but not limited
to, linear, square, square-root, power-law, sine, cosine, other
trigonometric functions, logarithmic, exponential, cubic, cube
root, hyperbolic, etc. in addition to error, difference, summing,
integrating, differentiators, etc. type of op amps. In addition,
logic, including digital and Boolean logic such as AND, NOT
(inverter), OR, Exclusive OR gates, etc., complex logic devices
(CLDs), field programmable gate arrays (FPGAs), microcontrollers,
microprocessors, application specific integrated circuits (ASICs),
etc. can also be used either alone or in combinations including
analog and digital combinations for the present invention. The
present invention can be incorporated into an integrated circuit,
be an integrated circuit, etc.
[0047] The present invention can also incorporate at an appropriate
location or locations one or more thermistors (i.e., either of a
negative temperature coefficient [NTC] or a positive temperature
coefficient [PTC]) to provide temperature-based load current
limiting. The present invention may provide thermal control or
other types of control to, for example, a dimming LED driver. For
example, the circuit of FIGS. 1 and 2 or variations thereof may
also be adapted to provide overvoltage or overcurrent protection,
short circuit protection for, for example, a dimming LED driver, or
to override and cut the phase and power to the dimming LED
driver(s) based on any arbitrary external signal(s) and/or
stimulus. The present invention can also include circuit breakers
including solid state circuit breakers and other devices, circuits,
systems, etc. That limit or trip in the event of an overload
condition/situation. The present invention can also include, for
example analog or digital controls including but not limited to
wired (i.e., 0 to 10 V, RS 232, RS485, IEEE standards, SPI, I2C,
other serial and parallel standards and interfaces, etc.),
wireless, powerline, etc. and can be implemented in any part of the
circuit for the present invention. The present invention can be
used with a buck, a buck-boost, a boost-buck and/or a boost,
flyback, or forward-converter design etc., topology,
implementation, etc.
[0048] Other embodiments can use comparators, other op amp
configurations and circuits, including but not limited to error
amplifiers, summing amplifiers, log amplifiers, integrating
amplifiers, averaging amplifiers, differentiators and
differentiating amplifiers, etc. and/or other digital and analog
circuits, microcontrollers, microprocessors, complex logic devices,
field programmable gate arrays, etc.
[0049] The present invention includes implementations that may
contain various other control circuits including, but not limited
to, linear, square, square-root, power-law, sine, cosine, other
trigonometric functions, logarithmic, exponential, cubic, cube
root, hyperbolic, etc. in addition to error, difference, summing,
integrating, differentiators, etc. type of op amps. In addition,
logic, including digital and Boolean logic such as AND, NOT
(inverter), OR, Exclusive OR gates, etc., complex logic devices
(CLDs), field programmable gate arrays (FPGAs), microcontrollers,
microprocessors, application specific integrated circuits (ASICs),
etc. can also be used either alone or in combinations including
analog and digital combinations for the present invention. The
present invention can be incorporated into an integrated circuit,
be an integrated circuit, etc.
[0050] While detailed descriptions of one or more embodiments of
the invention have been given above, various alternatives,
modifications, and equivalents will be apparent to those skilled in
the art without varying from the spirit of the invention.
Therefore, the above description should not be taken as limiting
the scope of the invention, which is defined by the appended
claims.
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