U.S. patent application number 13/524496 was filed with the patent office on 2012-11-15 for power supply.
This patent application is currently assigned to ACCESS BUSINESS GROUP INTERNATIONAL LLC. Invention is credited to David W. Baarman, Wesley J. Bachman, John James Lord, Joshua K. Schwannecke, Joshua B. Taylor.
Application Number | 20120286571 13/524496 |
Document ID | / |
Family ID | 39766760 |
Filed Date | 2012-11-15 |
United States Patent
Application |
20120286571 |
Kind Code |
A1 |
Baarman; David W. ; et
al. |
November 15, 2012 |
POWER SUPPLY
Abstract
A power supply to provide electrical power to one or more loads.
The power supply may include a resonant air core transformer to
provide an adjustable and adaptable source of power to electronic
devices. The power supply may include isolated primary-side
circuitry and secondary-side circuitry. The primary-side circuitry
may include control circuitry that, among other things, provides
drive waveforms for the primary-side switching circuitry. In
embodiments configured to produce AC output, the secondary-side
circuitry may also include switching circuitry. The primary-side
control circuitry may provide drive waveforms for the
secondary-side switching circuitry. The secondary-side circuitry
may include measurement circuitry that measures the current and/or
voltage of the output and provides those measurements to the
control circuitry through isolation circuitry. The control
circuitry may adjust the drive waveforms for the primary-side
and/or secondary-side switching circuitry as a function of the
measured values.
Inventors: |
Baarman; David W.;
(Fennville, MI) ; Schwannecke; Joshua K.; (Grand
Rapids, MI) ; Taylor; Joshua B.; (Rockford, MI)
; Lord; John James; (Springfield, IL) ; Bachman;
Wesley J.; (Auburn, IL) |
Assignee: |
ACCESS BUSINESS GROUP INTERNATIONAL
LLC
Ada
MI
|
Family ID: |
39766760 |
Appl. No.: |
13/524496 |
Filed: |
June 15, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12051939 |
Mar 20, 2008 |
8223508 |
|
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13524496 |
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60895968 |
Mar 20, 2007 |
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Current U.S.
Class: |
307/11 ;
323/318 |
Current CPC
Class: |
H01F 27/2804 20130101;
H02M 3/3376 20130101; H01F 38/14 20130101; H01F 30/08 20130101;
H01F 27/34 20130101; H02M 3/33523 20130101; Y02B 70/10 20130101;
H01F 27/2823 20130101; H01F 27/38 20130101 |
Class at
Publication: |
307/11 ;
323/318 |
International
Class: |
H02J 3/00 20060101
H02J003/00 |
Claims
1. A power supply system capable of supplying power to one or more
loads comprising: a power supply having control circuitry
configured to control operation of the power supply, said control
circuitry capable of selectively varying an operating parameter of
said power supply; a power supply line supplying power from said
power supply to the one or more loads disposed remotely from said
power supply; at least one remote monitor configured to measure a
characteristic of power at a location remote from said control
circuitry, said measured characteristic being indicative of a power
loss at said location; and wherein said control circuitry is
configured to adjust said operating parameter as a function of said
measured characteristic to adjust for said power loss.
2. The power supply system of claim 1 wherein said measured
characteristic is voltage.
3. The power supply system of claim 1 wherein said operating
parameter is a voltage set point.
4. The power supply system of claim 1 wherein said remote monitor
is incorporated into a load.
5. The power supply system of claim 1 wherein said remote monitor
includes a transmitter for transmitting said measured voltage.
6. The power supply system of claim 5 wherein each of said remote
monitors includes a unique address.
7. The power supply system of claim 1 further including a base for
receiving said measured characteristic and a computer for
determining an appropriate adjustment in said operating parameter
as a function of said measured characteristic.
8. A method for establishing an operating parameter of a power
supply applying power to a power supply line, comprising the steps
of: connecting one or more remote voltage monitors to the power
supply line; communicating a measured voltage from the one or more
remote voltage monitors to a base; analyzing the measured voltage
to determine power loss along the power supply line; and setting an
operating parameter of the power supply based on the measured
voltage to compensate for the power loss.
9. The method of claim 8 wherein said communicating step is further
defined as wirelessly communicating the measured voltage from the
one or more remote voltage monitors to the base.
10. The method of claim 9 further including the step of
incorporating the remote voltage monitor into a load, whereby the
remote voltage monitor remains coupled to the power supply line
along with the load.
11. The method of claim 10 further including the step of coupling
the base to a computer running software to interface the base and
the computer.
12. The method claim 8 wherein the power supply is further defined
as a power supply for landscape lighting and the power supply line
is further defined as the power supply line for a plurality of
landscape lamps; and wherein said connecting step is further
defined as connecting a remote voltage monitor to the power supply
line approximate a location of at least one landscaping lamp.
13. The method claim 8 wherein the power supply is further defined
as a power supply for landscape lighting and the power supply line
is further defined as the power supply line for a plurality of
landscape lamps; and wherein said connecting step is further
defined as connecting a remote voltage monitor to the power supply
line approximate a location of a landscaping lamp most remote from
the power supply.
14. A power supply tuning system for tuning a power supply for
supplying power to a plurality of loads via a supply line
comprising: one or more remote monitors disposed along the power
supply line remote from a power supply control circuit, each of
said remote monitors configured to measure a characteristic of
power at a location remote from the power supply control circuit to
determine a power loss at said location, each of said remote
monitors further including a transmitter to communicate said
measured characteristic; a receiver configured to receive said
measured characteristic from said one or more remote monitors; and
a computer capable of determining an operating parameter set point
for the control circuit as a function of said measured
characteristic of power received from said one or more remote
monitors, said computer configured to communicate said operating
parameter set point to the control circuit to allow the control
circuit to adjust for said power loss.
15. The power supply tuning system of claim 14 wherein said
measured characteristic is voltage.
16. The power supply tuning system of claim 15 wherein said
operating parameter is a voltage set point.
17. The power supply tuning system of claim 16 wherein each of said
remote monitors is incorporated into a corresponding one of the
loads.
18. The power supply tuning system of claim 14 wherein each of said
remote monitors includes a unique address.
19. The power supply tuning system of claim 14 in which said
receiver is further defined as a transceiver, said transceiver
being disposed within a base, said base configured to poll said one
or more remote monitors.
20. The power supply tuning system of claim 19 wherein said
transceiver communicates with said transmitter using wireless
communications.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to power supplies and more
particularly to a power supply having a transformer for converting
mains power into AC or DC power.
[0002] A typical power supply includes a transformer. A transformer
is an electrical device that transfers electrical energy from a
primary coil through a time varying magnetic field to a secondary
coil upon the addition of an electrical load to the secondary coil.
Transformers are used in a variety of applications, such as mains
power delivery for electronics and children's toys, and come in a
variety of sizes, from very large to miniature.
[0003] A conventional transformer consists of a core, which may be
made of iron or some other ferrous material, in the shape of a
loop. On one side of the core, wire is coiled around the core, and
primary or mains voltage is applied. This side of the core is
called the primary. Opposite the primary is a similar arrangement
called the secondary. By varying the number of turns of wire in the
coil more explicitly the turns ratio of the primary to secondary,
the voltage may be stepped up or down depending upon the required
usage, and the load applied to the secondary.
[0004] One disadvantage of transformers using an iron core is that
to achieve the necessary performance, the core had to be of a
substantial size and requisite weight. This results in transformers
that are bulky and difficult to package. In many cases these bulky
transformers consume precious space, such as those transformers
built directly into the mains plug, such that the transformer
blocks other outlets, as can be the case in power strips or wall
outlets. Due to the weight of traditional transformers, additional
effort must be expended to insure that that transformer casing is
suitably strong, to withstand a drop which may occur during normal
use. If the transformer is to be wall mounted, certain applications
may not be suitable due to the excess weight placed upon wall
mounts.
[0005] Also, the cost of the iron in traditional transformers is
also an undesirable factor. In addition to the direct material cost
of iron or other ferrous metals, the traditional transformer must
be made larger to accommodate the large coil, necessitating the use
of additional other materials, such as plastic, increasing cost.
Copper wire or other conductive material is used abundantly in
forming the primary and secondary coils, further adding to the cost
of traditional transformers.
[0006] Further, the iron core inherently retains a sizeable buffer
of energy, which is capable of being discharged through a short
circuit. Because energy is stored in the iron core, in the event of
a short circuit, it can take considerable time for the energy to
dissipate from the system, which could cause damage. Further, the
transformer may continue to provide power either until the mains
power breaker trips or the transformer itself fails, or the short
circuit is removed.
[0007] Traditional transformer power supplies are not dimmable, as
a result of their fixed turns of wire that only step up or step
down an input voltage for a set output voltage. As a result, if
dimming is required, a power supply with a transformer is not a
desirable selection as a power supply. For example, in the case of
lighting, there are many applications where full light intensity is
not desired at all times, as in the case of security lighting. A
security light could be set to run at less than full power for
normal operation, then switch to full power if a motion sensor
connected to the system detects motion, for example. This operation
would conserve energy yet also provide illumination for appearance
and security. Unfortunately, a power supply with a traditional
transformer is not usable in this application.
[0008] Voltage drop over a distance has plagued power supplies with
traditional transformers. Using the example of landscape lighting,
a transformer is located near a mains power source, and a power
supply line is connected to it. The line runs from the power supply
until it terminates some distance away, for example, 50 feet.
Lights are provided that clip into the supply line using connectors
that pierce the wire to make an electrical connection. In this way
the position of the lights can be varied according to the
particular landscape application. The power supply line, like any
wire, has some resistance. So the voltage measured at the end of
the supply line will be lower than at a point located near to the
transformer. With a power supply having a traditional transformer,
the instructions recommend placing the lights at somewhat equal
distances along the supply line in order to compensate for the
resistive effect of the wire. However, the particular landscape
application may call for most or all of the lights to be installed
toward the end of the supply line. A power supply with a
traditional transformer may have difficulty adequately powering the
lights, and the lights at the very end may be dim or fail to light
at all. This situation is undesirable and places unnecessary limits
on landscape lighting, or other applications.
[0009] Yet another disadvantage of an iron core transformer is the
inability to compensate for fluctuations in mains voltage. If there
is a power spike or sag, the iron core transformer is not equipped
to protect the devices it is powering, which could result in
permanent damage. No logic or circuitry is present in a power
supply with a traditional transformer, to detect power
fluctuations. Since many modern electronic devices are sensitive to
such power fluctuations, use of a traditional transformer with
these devices could result in damage or destruction of these
devices.
SUMMARY OF THE INVENTION
[0010] The present invention provides a power supply having a
resonant air core transformer, which overcomes a number of
disadvantages of traditional iron core transformers while providing
additional previously unavailable features. In one embodiment, the
transformer includes paired primary and secondary coils that are
coreless and separated by an air gap without any iron core.
[0011] In one embodiment, the power supply includes isolated
primary-side and secondary-side circuitry. The wireless transfer of
power is provided through the inductive coupling between the
primary coil and the secondary coil and wireless transfer of
control signals is provided through isolation circuitry. In one
embodiment, the isolation circuitry includes one or more
optocouplers or optoisolators.
[0012] In one embodiment, the secondary-side circuitry produces an
AC output. In this embodiment, the secondary-side circuitry may
include circuitry to rectify the transformer output and a switching
circuitry to generate an AC output at the desired frequency and
voltage. The secondary-side circuitry may include circuitry to
measure the output voltage of the secondary-side switching
circuitry and to adjust the duty-cycle of the secondary-side
switching circuitry to control the average voltage.
[0013] In one embodiment, the primary-side control circuitry may
adjust the duty cycle of the secondary-side switching circuitry
through the isolation circuitry. In this embodiment, the
secondary-side circuitry may include measurement circuitry that
measures the voltage and/or current of the secondary-side switching
circuitry output and sends a corresponding signal to the control
circuitry in the primary-side circuitry. This signal may be sent
through the isolation circuitry. The primary-side control circuitry
may control the duty cycle of the secondary-side switching
circuitry as a function of the measured voltage and/or current. The
control circuitry may also monitor the measured current received
from the measurement circuitry to look for the presence of
over-current situations. The control circuitry may reset, disable
or otherwise respond to the presence of an over-current
situation.
[0014] In one embodiment, the secondary-side circuitry produces a
DC output. In this embodiment, the secondary-side circuitry may
include a rectifier for rectifying the AC output of the secondary
coil. The output of the rectifier may be passed through filtering
circuitry and/or a voltage regulator.
[0015] In DC-output embodiments, the secondary-side circuitry may
include measurement circuitry that measures the voltage and/or
current of the secondary-side output and sends a corresponding
signal to the control circuitry in the primary-side circuitry
through the isolation circuitry. The primary-side control circuitry
may control the primary-side switching circuitry (e.g. frequency or
duty cycle) as a function of the measured voltage and/or current.
The control circuitry may also monitor the measured current
received from the measurement circuitry to look for over-current
situations. The control circuitry may reset, disable or otherwise
respond to the presence of an over-current situation.
[0016] In both AC- and DC-output embodiments, the control circuitry
may be programmed to maintain the secondary-side output at a
specific voltage set point. In one embodiment, the present
invention may include a power supply tuning system that has one or
more remote voltage monitors that permit the voltage set point to
be adjusted to compensate for variations in the resistance of the
power supply lines running from the secondary-side output to the
load(s). These adjustments may be made during installation or at
other times. The remote voltage monitors may be wireless and
provide wireless signals to a base that collects the signals and
provides them to control software on a computer. The software may
provide information indicative of the power-loss resulting from the
power supply lines to permit the voltage set point to be adjusted
to compensate for the loss. For example, in landscape lighting
application where a plurality of lamps are installed along a power
supply line, one or more remote voltage monitors may be used to
measure voltage at each lamp. In situations where a significant
power loss is found, the voltage set point of the power supply can
be increased as a function of the measured power loss to provide a
voltage that yields the desired balance between the plurality of
lamps.
[0017] The air core transformer does not store energy in the same
manner as a cored-transformer, so in the event of a short circuit,
the primary side of the inductive coil may react much faster than
an iron core transformer and the energy remaining in the secondary
side of the inductive coil of the air core transformer is quickly
dissipated. This fault detection ability and quick recovery is not
present in traditional iron core transformers. As a result, if a
short circuit occurs, the traditional transformer may continue to
provide power until a line circuit breaker trips, or the cause of
the short circuit is removed. This situation is undesirable and is
potentially hazardous as well. In many applications, traditional
transformers are used in applications where the likelihood of a
short circuit is greater. For example, in outdoor lighting
applications, wired lamps are powered by a transformer. The power
supply wire is buried within landscaping, but is exposed to water
and the elements. Due to the lamps' location in landscaping areas,
the power supply wire is more likely to be in jeopardy from sharp
tools are used to tend to the neighboring flora. It is conceivable
that a sharp tool could cut or damage the power supply wire,
resulting in a short circuit situation. Due to the rapid response
of the air-core transformer as disclosed herein, if such an event
were to occur, the voltage in the line would be halted relatively
quickly.
[0018] Another feature of the resonant air core transformer is the
ability of the power supply to compensate for lead-in wire voltage
drop. Using the circuitry integrated into the air core transformer,
the voltage drop is compensated for, allowing placement of loads
and distance from the power supply. The circuitry determines the
best frequency by sensing the load(s) placed on it, including
factoring in the resistance of the power supply line. Thus, the
power supply can provide the same power to loads clustered near the
transformer as to those clustered far away from the transformer on
the power supply line.
[0019] Another advantage of the resonant air core transformer is
its ability to quickly adjust and compensate for fluctuations in
mains voltage. In the event of a power spike or sag, the power
supply easily detects and regulates the secondary side voltage to
prevent under- or over-voltage conditions. The logic or circuitry
of the power supply senses changes in the mains voltage and adjusts
appropriately in an effort to preserve any attached devices drawing
a load. Thus, the resonant air core transformer helps to protect
devices from damage due to mains power abnormalities.
[0020] Another feature of the power supply is its ability to be
soft-started using control circuitry to reduce startup stress on
electronic devices. Soft-starting is the ability to ramp up or
slowly increase power supplied to a device(s) so as to avoid
damaging it. Many sensitive modern devices require or benefit from
a soft-start and can be damaged if a soft-start is not used.
Additionally, soft-starting may extend the life of many devices by
placing less stress on energized components.
[0021] Another feature of the power supply is its dimming
capabilities. Because of the control circuitry, the output voltage
is regulatable even though the wire turns ratio is fixed. As a
result, in a lighting application for example, the lights connected
to the air core transformer are dimmable from full intensity to
completely unlit.
[0022] The air core transformer may also operate at a higher
ambient temperature than traditional transformers. Traditional iron
core transformers cannot operate at temperatures dramatically above
ambient room temperature. Because of the self-heating efficiency of
the air core transformer, its lack of a large conductive iron core,
the operating temperatures are dramatically reduced when compared
to a traditional transformer, to near ambient temperature in some
embodiments. This temperature reduction is beneficial because the
extra heat of the traditional transformer is wasted energy, and can
have a detrimental effect on electronic devices or other items
located nearby when exposed to the high operating temperatures of a
traditional transformer. Further, the iron core transformer must be
designed to accommodate the accompanying heat of its operation,
which increases cost.
[0023] The power supply may also include over-current protection
circuitry, which helps to protect both itself and any devices
drawing power. In the event of an over-current situation, such as
adding too many landscape lamps to the power supply line, when
pulse width modulation duty cycle reaches a predetermined level,
the transformer may shut down momentarily after which a soft start
commences. The lamps, in this example, will blink at a reduced
power output until the over current condition is resolved. In other
cases, other signaling means could be employed, such as an audible
tone or other indicators as the application requires.
[0024] For a better understanding of the present invention,
together with other and further features and advantages thereof,
reference is made to the following description, taken in
conjunction with the accompanying drawings, and the scope of the
disclosure will be laid out in the claims.
[0025] It will be readily understood that the components of the
present disclosure, as generally described and illustrated in the
figures herein, may be arranged and designed in a wide variety of
different configurations. Thus, the following more detailed
description of the embodiments of the apparatus, system, and method
of the present disclosure, as represented in the accompanying
figures, is not intended to limit the scope of the disclosure, as
claimed, but is merely representative of selected embodiments of
the disclosure.
[0026] Reference throughout this specification to "one embodiment"
or "an embodiment" (or similar) means that a particular feature,
structure, or characteristic described in connection with the
embodiment is included in at least one embodiment of the present
disclosure. Thus, appearances of the phrases "in one embodiment" or
"in an embodiment" in various places throughout this specification
are not necessarily all referring to the same embodiment.
[0027] Furthermore, the described features, structures, or
characteristics may be combined in any suitable manner in one or
more embodiments. In the following description, numerous specific
details are provided, such as examples, to provide a thorough
understanding of embodiments of the present disclosure. One skilled
in the art will recognize, however, that the disclosure can be
practiced without one or more of the specific details, or with
other methods, components, materials, etc. In other instances,
well-known structures, materials, or operations are not shown or
described in detail to avoid obscuring aspects of the
disclosure.
[0028] The illustrated embodiments of the disclosure will be best
understood by reference to the drawings, wherein like parts are
designated by like numerals or other labels throughout. The
following description is intended only by way of example, and
simply illustrates certain selected embodiments of devices,
systems, and processes that are consistent with the disclosure as
claimed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a block diagram of a power supply in accordance
with an embodiment of the present invention.
[0030] FIG. 2 is an exploded perspective view of an air core
transformer.
[0031] FIG. 3 is a cross-sectional view of the air core
transformer.
[0032] FIG. 4 is a block diagram of an alternative power supply
adapted to provide DC power output.
[0033] FIG. 5 is a representation of the main dialog screen for the
power supply software.
[0034] FIG. 6 is a representation of the EEPOM configuration dialog
screen for the power supply software.
[0035] FIG. 7 is a block diagram of an alternative embodiment
having remote voltage monitors.
[0036] FIGS. 8A-C are collectively a circuit diagram of a power
supply in accordance with an embodiment of the present
invention.
DETAILED DESCRIPTION OF CURRENT EMBODIMENTS
[0037] Referring now to FIG. 1, a diagram of a power supply 10
having an air core transformer 20 in accordance with an embodiment
of the present invention is shown. The power supply 10 generally
includes a primary-side circuit 12 and a secondary-side circuit 14.
As perhaps best shown in FIG. 2, the primary-side circuit 12
includes a primary coil 16 and the secondary-side circuit 14
includes a secondary coil 18. The primary coil 16 and secondary
coil 18 cooperate to form a transformer 20. The transformer 20 may
be coreless. The primary-side circuit 12 also generally includes a
controller 22, a switch driver 24 and switching circuitry 26. The
control circuitry 22 controls operation of the switch driver 24,
which in turn controls the application of power to the primary coil
16. The secondary-side circuit 14 generally includes a rectifier
28, switching circuitry 30, measurement circuitry 32, isolation
circuitry 34 and a switch driver 36. The output of the
secondary-side circuit 14 may be applied to a load L. The output of
the secondary-side circuit 14 is controlled by the control
circuitry 22. The measurement circuitry 32 provides information
regarding the output to the secondary-side circuit 14 to the
control circuitry 22 through the isolation circuitry 34. The
control circuitry 22 analyzes the information provided by the
measurement circuitry 32 and controls operation of the switch
driver 36 through the isolation circuitry 34.
[0038] The embodiment of FIG. 1 will now be described in more
detail in connection with an operational overview of the power
supply 10. Line mains voltage, in a common range, such as 80-270
VAC, is supplied to the line filter and AC mains rectifier 37. For
purposes of disclosure, the present invention is described in
connection with a power supply operating on line mains voltage of
80-270 VAC. The present invention may be readily adapted to provide
AC or DC power from a wide variety of alternative AC and DC power
sources. The line filter removes any unwanted electrical noise that
may be present on the mains voltage, and helps prevent electrical
noise from being radiated from the transformer, and the rectifier
converts the VAC to VDC. A wide variety of filtering and rectifying
circuits are known to those skilled in the art, and therefore the
specific line filter/AC mains rectifier circuitry will not be
described in detail. Suffice it to say that the line filter/AC
mains rectifier 37 of the illustrated embodiment may be essentially
any line filtering and rectifying circuitry capable of providing
the desired filtering and rectifying of the incoming line mains
power.
[0039] In the illustrated embodiment, DC voltage leaves the line
filter/AC mains rectifier 37 at approximately 113-382 VDC for two
components--the switching power supply 38 and the half bridge
switching circuitry 26. The switching power supply 38 receives the
113-382 VDC and processes it to a desired level, for example, 13
VDC. A wide variety of switching power supplies are known to those
skilled in the art, and therefore the switching power supply of the
illustrated embodiment will not be described in detail. The
switching power supply 38 may be essentially any switching power
supply or other circuit components capable of producing DC power
for the switch driver 24 and the control circuitry 22 from the
output of the line filter/AC mains rectifier 37.
[0040] The control circuitry 22 is powered by the VDC generated
from the switching power supply 38 and produces drive waveforms,
which are sent to the switch driver 24 and to the isolation
circuitry 34. In one embodiment, the control circuitry 22 includes
a microcontroller 35 (See FIGS. 8A-C) capable of generating the
primary-side and secondary-side drive waveforms. In the illustrated
embodiment, the microcontroller 35 is programmed to carry out
various features and functions as described herein. If desired,
specific features and functions of the microcontroller 35 may be
alternatively implemented in analog circuit components. The switch
driver 24 then amplifies the drive waveforms sent from the control
circuitry 22 and sends these newly amplified waveforms to the
half-bridge switching circuitry 26. In the illustrated embodiment,
the switch driver 24 may be a microprocessor specifically designed
to function as a driver. The switch driver 24 may alternatively be
essentially any circuitry capable of sufficiently amplifying the
drive waveforms and applying them to the primary-side switching
circuitry 26.
[0041] The primary-side switching circuitry 26 may include
half-bridge switching circuitry having a first FET with its drain
connected to the high voltage rail and its source connected to the
tank circuit 21, and a second FET with its drain connected to the
tank circuit 21 and its source connected to ground. The switch
driver 24 is connected to the gates of the two FETs to selectively
connect the tank circuit to the high voltage rail and ground in
accordance with the drive waveforms.
[0042] The tank circuit 21 of the illustrated embodiment is a
series resonant tank circuit that generally includes the primary
coil 16 and a capacitor 17. The primary coil 16 and the capacitor
17 may be selected so that the tank circuit 21 is substantially at
resonance when operating within an anticipated range of
frequencies. If desired, the capacitor 17 may be a variable
capacitor and/or the primary coil 16 may be a variable inductor to
provide the tank circuit 21 with an adjustable resonant frequency.
Although described in connection with a series resonant tank
circuit, the power supply 10 may include alternative tank circuits,
such as a parallel resonant tank circuit.
[0043] In operation, the switch driver 24 alternately closes and
opens the first and second FETs of the half-bridge switching
circuitry 26 to alternately connect the series resonant primary
coil 16 and capacitor (the "primary" half of the inductively
coupled coil) between the high voltage DC (113-382 VDC) rail and
the ground. The resulting alternating current (AC) flows into the
primary portion of the inductive coil. Using the circuitry
component of the half-bridge 26, the drive waveforms sent to the
primary coil 16 can be adjusted using frequency or duty cycle
modulation.
[0044] The second half of the inductive coil, in this embodiment a
secondary center-tapped coil 18, is placed within the magnetic
field created by the primary coil 16. Once the secondary coil 18 is
within range (but not in direct electrical contact), the inductive
coupling is achieved and power is transferred from the primary coil
16 to the secondary coil 18, no core or direct electrical
connection between the coils exists therefore electrical isolation
from the mains provided.
[0045] The AC current received from the primary coil 16 is passed
from the secondary coil 18 to a full wave rectifier 28. While a
half-wave rectifier could be used, a full wave rectifier is more
efficient in that both components of the AC waveform are converted
to DC. However, the converted DC voltage is not constant and
requires further treatment in order to be a constant DC voltage.
Using a linear regulator 40, the converted DC voltage leaving the
rectifier 28 is stabilized to a constant 12 VDC. Linear regulators
are well known to those skilled in the art and therefore will not
be described in detail. Suffice it to say that the linear regulator
40 may be selected from essentially any linear regulator circuitry
or other circuitry capable of providing the desired level of
regulation.
[0046] This constant 12 VDC from the linear regulator 40 is used to
power the isolation circuitry 34, the measurement circuitry 32, and
the switch driver 36 on the secondary side of the transformer. The
control circuitry 22, which is powered by 13 VDC from the switching
power supply 38 and provides drive waveforms to the switch driver
24, also provides drive waveforms to the isolation circuitry 34.
The isolation circuitry 34 then passes these isolated drive
waveforms to the switch driver 36, where they are amplified. The
isolation circuitry 34 may be essentially any circuitry or circuit
component(s) capable of passing signals from the secondary-side
circuitry 14 to the primary-side circuitry 12 without a direct
electrical connection. In the illustrated embodiment, the isolation
circuitry 34 includes two optocouplers (or optoisolators), one
passing signals from the measurement circuitry 32 to the control
circuitry 22 and one passing drive waveforms from the control
circuitry 22 to the secondary-side switch driver 36.
[0047] The now-amplified drive waveforms cause the switch driver 36
to alternately connect a full H-bridge switching circuit 30 that
modulates the unregulated (not constant) DC voltage supplied from
the full wave rectifier 28 back to a low voltage AC regulated
waveform. The measurement circuitry 32 monitors and reports the low
voltage AC output from the full H-bridge switching circuitry 30.
The measurement circuitry 32 may include a voltage sensor (not
shown) and a current sensor (not shown). The output of the voltage
sensor of the measurement circuitry 32 is processed by the control
circuitry 22 and used to determine the drive waveforms to be sent
to the full H-bridge switching circuit 30. In the illustrated
embodiment, the control circuitry 22 is programmed to attempt to
maintain the output of the power supply 10 at a fixed voltage. This
voltage is stored in memory as the voltage set point. If the
voltage measured by the measurement circuitry 32 is higher than the
voltage set point, the control circuitry 22 will reduce the duty
cycle of the drive waveforms applied to the secondary-side switch
driver 36. The reduction in duty cycle will in turn reduce the
output voltage. Similarly, if the voltage measured by the
measurement circuitry 32 is below the voltage set point, the
control circuitry 22 will increase the duty cycle of the drive
waveforms applied to the secondary-side switch driver 36. The
output of the current sensor of the measurement circuitry 32 is
processed by the control circuitry 22 to determine whether the
secondary-side output is in an overcurrent or undercurrent state.
If so, the control circuitry 22 may take appropriate action, such
as to shut-off or reset the power supply. The control circuitry 22
may also or alternatively activate an overcurrent or undercurrent
signal, such as a warning light (LED) or audible warning
signal.
[0048] The control circuitry 22 may be programmed to provide
additional functionality, as desired. For example, the control
circuitry 22 may be programmed to selectively scale-up or
scale-down the voltage or power of the output of the power supply
10. To achieve this functionality, the control circuitry 22 may
adjust the drive waveforms applied to one or both of the
primary-side and secondary-side switching circuitry, such as by
varying the frequency and/or duty cycle of either or both drive
waveforms. In the context of landscape lighting applications, this
functionality permits landscape lamps to be selectively dimmed.
This functionality may permit alternative control operations in
other applications. For example, this functionality may be used to
control motor speed in application in which the load includes a
motor. Further, this functionality may permit the power supply to
have a "soft start" in which the power to the load L is slowly
ramped up.
[0049] The design and configuration of the transformer 20 may vary
from application to application. However, in the illustrated
embodiment, the transformer 20 is an air core transformer having a
primary coil 16 that sandwiched between a split secondary coil 18.
FIG. 2 is an exploded view of the transformer 20 of this embodiment
showing the secondary coil 18 with first coil section 18a and
second coil section 18b disposed on opposite sides of the primary
coil 16. The first coil section 18a may be electrically connected
to second coil section 18b as represented by the broken line
connecting point A to point A'. Referring now to FIG. 3, a
cross-section of the inductive coils of one embodiment is shown. As
can be seen, the illustrated inductive coils are constructed in
layers, and are largely coextensive with one another having similar
inner and outer diameters. The primary coil 16 is spiral wound of,
in this embodiment, 260.times.38 Litz wire, and sandwiched between
split secondary spiral coil sections 18a and 18b made of #20 AWG
magnet wire, in this embodiment. Although the illustrated
embodiment includes a primary coil 16 sandwiched between the split
secondary coil sections 18a and 8b, the primary coil 16 may
alternatively be split. For example, the secondary coil 18 may
include a single coil that is sandwiched between split coil
sections of a primary coil. However, it is not necessary for either
the primary coil 16 or the secondary coil 18 to be split.
[0050] The primary and secondary coils 16 and 18, respectively, may
be arranged adjacent to each other, or they may be interwoven but
separated by small gaps and held in an epoxy-based adhesive, or
printed into a circuit board. While the spaces or air gaps between
the coils may be very small, there is still sufficient space to
allow isolation protection as disclosed herein, as opposed to a
traditional iron or metal core transformer. If desired, the coils
may be disposed directly against one another relying on the
insulation to provide the gap necessary for the desired electrical
isolation.
[0051] FIGS. 8A-C are collectively a circuit diagram of a power
supply in accordance with an embodiment of the present invention.
Various subcircuits are grouped together in and labeled with
reference numerals corresponding to the description of the
embodiment of FIG. 1. As shown, the circuit diagram includes line
filter/AC mains rectifier 37, switch driver 24, primary-side
switching circuitry 26, tank circuit 21 with primary coil 16 and
parallel capacitors 17, secondary coil 16, rectifier 28, switching
circuitry 30, measurement circuitry 32, isolation circuitry 34a and
34b, secondary-side switch driver 36 and linear regulator 40. The
embodiment of FIGS. 8A-C differs, however, in that the measurement
circuitry 32 is not connected to the control circuitry 22 via the
isolation circuitry 32. Rather, the measurement circuitry 32 is
directly connected to the control circuitry 22. This alternative is
represented in FIG. 1 by a phantom line D. The measurement
circuitry 32 could be isolated from the control circuitry 22 by
adding an isolator, such as an optocoupler or optoisolator, between
the measurement circuitry 32 and the control circuitry 22. Further,
elements 34a and 34b of FIGS. 8A-C may function as level
shifters.
[0052] Referring now to FIG. 4, a diagram of an alternative
embodiment of the air core transformer is shown. In this
embodiment, AC mains voltage is transformed to regulated DC voltage
by the power supply 10'. DC voltage as an output is desirable for
certain applications, such as use with solar cells and their
storage batteries, batteries of any kind, automotive applications,
telephone and other communication means, fuel cells, and
transportation systems such as subway or other electromotive
transportation systems. Many of the components of this embodiment
are similar to those of the embodiment of FIG. 1. Accordingly, like
components will be identified with like reference numerals and only
those components that are not similar will be described in
detail.
[0053] For solar cell applications, the transformer can be
integrated into a system which supplements the solar cell storage
batteries. Batteries used in solar systems are generally DC, but if
an AC storage system is used, the AC resonant air core transformer
as disclosed herein may be substituted. Power demands vary over
periods of time, which mean that the cost of electric power also
varies. As such, the resonant air core transformer can be used to
replenish the solar system batteries at off-peak and/or off-demand
periods, such as the early morning hours. Other replenish periods
could be determined based upon cost, or electrical grid capacity.
As such, the resonant air core transformer in DC or AC form could
augment a solar cell system.
[0054] For transportation systems, many of which operate on DC
power, but some AC as well, the resonant air core transformer is
also well-suited to provide electrical power to the motive portions
and onboard storage batteries and systems of these transportation
systems. Scaling up an air core transformer, and including a
plurality strategically placed about a subway or light rail system,
for example, power can be provided to the transport vehicles
electric motors, lights, climate control and other systems with the
attributes as disclosed above. As such, the compactness of the
resonant air core transformer, for example, is one such advantage
that allows for a smaller transportation support footprint. In
urban areas, space is at a premium, and setting aside large spaces
for transformers (and their required safety zone) is avoided with
the resonant air core transformer.
[0055] The embodiment of FIG. 4 will now be described in connection
with an operational overview of the power supply 10'. Line mains
voltage, in a common range, such as 80-270 VAC, is supplied to the
line filter and AC mains rectifier 37'. The line filter removes and
unwanted electrical noise that may be present on the mains voltage,
and helps prevent electrical noise from being radiated from the
transformer, and the rectifier converts the VAC to VDC.
[0056] DC voltage leaves the line filter/AC mains rectifier 37' at
approximately 113-382 VDC for two components--the switching power
supply 38' and the half bridge switching circuitry 26'. The
switching power supply 38' receives the 113-382 VDC and processes
it to a desired level, for example, 13 VDC.
[0057] The control circuitry 22' is powered by the VDC generated
from the switching power supply 38' and produces drive waveforms,
which are sent to the switch driver 24'. The switch driver 24' then
amplifies the drive waveforms using power from the switching power
supply 38' and sends these newly amplified waveforms to the
half-bridge switching circuitry 26'.
[0058] The switching circuitry of the half-bridge alternately
connect the tank circuit 21' (e.g. series resonant primary coil and
capacitor) between the high voltage DC (113-382 VDC) rail and the
ground. The resulting alternating current (AC) flows into the
primary portion of the inductive coil. Using the circuitry
component of the half-bridge, the drive waveforms sent to the
primary coil 16' can be adjusted using frequency or duty cycle
modulation.
[0059] The second half of the inductive coil, in this embodiment a
secondary center-tapped coil 18', is placed within the magnetic
field created by the primary coil 16'. Once the secondary coil 18'
is within range (but not in direct contact), the inductive coupling
is achieved and power is transferred from the primary coil 16' to
the secondary coil 18', leaving an "air core" in between in the
illustrated embodiment.
[0060] The AC current received from the primary coil 16' is passed
from the secondary coil 18' to a full wave rectifier 28'. While a
half-wave rectifier could be used, a full wave rectifier is more
efficient in that both components of the AC waveform are converted
to DC. However, the converted DC voltage is not constant and may
benefit from further treatment in order to be a constant DC
voltage. The secondary-side circuitry 14' may include a linear
regulator 40' to stabilize the converted DC voltage and provide a
constant 12 VDC. This constant 12 VDC from the linear regulator 40'
is used to power the isolation circuitry 34' and the measurement
circuitry 32' on the secondary side of the transformer 20'.
[0061] The unregulated DC voltage may be connected to an optional
voltage regulator 31', which regulates the input DC voltage to a
desired DC output voltage. A variety of voltage regulators are well
known to those skilled in the field. The voltage regulator 31' may
be essentially any voltage regulator suitable for operation with
the expected input and output power characteristics. If desired,
the secondary-side circuitry 14' may include additional filtering
and conditioning circuitry (not shown) to produce power for the
load L. For example, conventional filtering and conditioning
circuitry may be included between the rectifier 28' and the
secondary-side output. In some applications, the DC power produced
by the rectifier 28' is adequate to power the load L without
further conditioning, filtering or other treatment. In such
applications, the optional voltage regulator 31' may be
eliminated.
[0062] The measurement circuitry 32' analyzes the DC output voltage
and provides that data to the isolation circuitry 34' as voltage
and current feedback signals. These signals are passed to the
control circuitry 22' through the isolation circuitry 34' for
analysis and as a continuous (or, alternatively, periodic) control
on the current supplied on the primary coil side. In one
embodiment, the control circuitry 22' monitors for overcurrent and
undercurrent conditions. In this embodiment, the measurement
circuitry 32' may include current sensor circuitry that measures or
otherwise determines the current of the secondary-side output. If
an overcurrent or undercurrent condition arises, the control
circuitry 22' may take appropriate action as described above in
connection with the embodiment of FIG. 1. In another embodiment,
the control circuitry 22' may alternatively or in addition monitor
the voltage of the secondary-side output. If the voltage is too
high or too low, the control circuitry 22' may take remedial
action. For example, if the voltage is too low, the control
circuitry 22' may vary the drive waveforms applied to the primary
coil 16. This may include varying the duty cycle or frequency of
the drive waveforms. More specifically, if the measured voltage is
too low, the control circuitry 22' may increase the duty cycle
and/or the frequency of the drive waveforms applied to the primary
coil 16 and, if the measured voltage is too high, the control
circuitry 22' may decrease the duty cycle and/or the frequency of
the drive waveforms applied to the primary coil 16.
[0063] The power supply 10 and 10' may include a simple integrated
user interface that permits a user to program the power supply 10
and 10' without the assistance of any additional components.
Although the user interface may vary from application to
application, in one embodiment, the user interface includes a push
button and a light emitting diode (LED). The push button and LED
are used to set a variety of operational parameters. Using the
landscaping lighting example as before, when the user has connected
a number of lights to the air core transformer via its power supply
cable, and has connected the transformer to mains power, the user
interface may be used as follows.
[0064] The power supply is optionally equipped with a photocell or
other light-measurement device, which is used (in this example) to
control when the lights should be powered on and off, to conserve
electricity. The user energizes the power supply, either by
engaging the push button or by connecting the power supply to mains
power. The photocell or similar devices begins measuring ambient
light levels, and turns off the lights (ceases supplying power) if
the calibrated photocell reaches a sufficient level of ambient
light.
[0065] If the user desires to setup the power supply and its
connected lights, the user engages the push button on the power
supply, which results in the power supply entering a configuration
mode. In this example, four settings are possible--high (light
brightness), medium, low and off. Each depression of the push
button will cause the power supply to operate at the next setting.
A fifth depression of the push button will result in the return to
the first, thereby creating a loop. Thus, if the button is pushed
three times, the current setting will be low (light brightness). If
the setting is made during daylight, the selected setting (if one
of lamps being on at some intensity), the lamps will remain lit for
that daylight period, through the following night, and the lamps
will be extinguished at sufficient ambient light the next day.
[0066] In order to permanently set the power supply in the
illustrated embodiment, a setup mode is entered by pushing the
button and holding for five or more seconds, in this example. The
LED will blink slowly at 50% duty cycle to indicate that the setup
mode has been entered. Once the LED has begun blinking, the user
releases the button. At this point, the button operates as above,
only in this setup mode, the selection is stored in the power
supply's electrically erasable programmable read-only memory
(EEPROM). If the user does not select an operating mode within 5
seconds, the power supply will default to a predetermined mode
(such as high). If the user has selected an operating mode within
the 5-second window, however, that mode is stored in memory and
will be followed for every subsequent activation of the power
supply (every night).
[0067] In the event that the power supply detects an excessive
amount of current (short circuit) passing through the power supply
line while in automatic (programmed) mode, the power supply will
automatically deactivate the lamps and indicate an error using the
LED. This indication is made using a series of LED blinks, in this
example, such as frequent flashing followed by a pause and another
group of frequent LED flashes.
[0068] In the event the power supply detects an open circuit
(undercurrent condition), again the power supply will deactivate
and display, using the LED, that such a condition exists. In the
case of an undercurrent condition, a single LED flash followed by a
long pause, repeating, could be displayed, for example.
[0069] In normal operation, the LED remains lit to indicate to the
user that the power supply is operating as programmed and there are
no operational faults present.
[0070] Computer software with a graphical user interface (See FIGS.
5 and 6) may additionally or alternatively be used to program the
power supply 10 or 10' or to perform diagnostics. The power supply
10 or 10' may include a wired or wireless programming port 50 or
50'. The power supply is optionally equipped with a communications
link 50, either wired or wireless, that enables communication, such
as with a laptop computer or other similar device. This software
allows high-level maintenance, repair, or installation of the air
core transformer, and provides much more detailed information and
parameters pertaining to the transformer's performance and
operating condition.
[0071] On the laptop computer, once a connection has been
established, a main display window of the computer software
appears. The main display window 100 of one embodiment of the
computer software is shown in FIG. 5. A user may obtain information
about the power supply and control its operating parameters by
interacting with the main display window as summarized below:
[0072] Serial Port 102--Allows the user to select the port for
communication--in this case, using a serial computer port.
[0073] Status Poll Interval 104--a display of the interval in
milliseconds between polls of the transformer for status
information. The smaller the number, the faster the display window
will update.
[0074] Connect to Device/Disconnect from Device button 106--this
button allows the user to connect or disconnect from the
transformer by toggling a display window button.
[0075] Output Frequency 108--shows the present output frequency of
the transformer.
[0076] New Frequency 110--editable field that allows the user to
manually enter a new frequency for the transformer.
[0077] Unconverted ISEC A/D 112--field that shows the raw A/D
return for the secondary coil current sense peak detector, useful
for calibration purposes.
[0078] Secondary Current 114--field that shows the result of
converting the raw A/D value into Amps.
[0079] Photocell Voltage 116--gives an indication of the ambient
light level as detected by the CdS cell. Usually low voltages
indicate more light and high voltages indicate low light.
[0080] Activate/Deactivate Output button 118--allows the user to
toggle the output status of the transformer.
[0081] Commit Frequency button 120--sends the value of the New
Frequency field to the transformer and assigns it as the active
frequency. The Output Frequency field then updates to display the
new value.
[0082] EEPROM Configure button 122--launches the EEPROM
configuration dialog.
[0083] Referring now to FIG. 6, the EEPROM configuration dialog 200
allows the user to set various parameters that govern the operation
of the transformer. Some of the parameters are listed below:
[0084] Current Conversion Factor 202--a value used in the
conversion between raw A/D values and the estimated secondary
current in Amps.
[0085] Current Offset 204--a value used in the conversion between
raw A/D values and the estimated secondary current in Amps.
[0086] Maximum Secondary Current 206--the maximum current in Amps
that the transformer will provide to the secondary coil before
deactivating and indicating a short circuit condition.
[0087] Minimum Secondary Current 208--the minimum current in Amps
that the transformer will provide before deactivating and
indicating an open circuit condition.
[0088] Photocell Voltage for Auto-Activate 210--if the photocell
voltage remains above this value for the Minimum Photocell Level
Sustain Time, the transformer will activate and power the
lamps.
[0089] Photocell Voltage for Auto-Shutoff 212--the inverse of the
above. By separating the On and Off light voltage levels into two
values, a useful hysteresis can be developed with respect to the
light levels, providing the desired light operation.
[0090] Min. Photocell Level Sustain Time 214--the amount of time
that the photocell voltage must be above the auto activation
threshold or below the auto shutoff threshold before the
transformer changes operational state. This allows for momentary
changes in ambient light without interfering with the standard
operation of the transformer. For example, if light from a passing
car causes a momentary increase in ambient light, the transformer
will continue to power the lights.
[0091] Frequency Upper Bound 216--the maximum frequency at which
the transformer will power the lights, even under manual control
(using the push button). Set at safe operational levels.
[0092] Frequency Lower Bound 218--same as above, but for the lower
bound.
[0093] Frequency for HIGH setting 220--the frequency at which the
transformer is programmed to the HIGH level output.
[0094] Frequency for MEDIUM setting 222--the frequency for medium
transformer output.
[0095] Frequency for LOW setting 224--the frequency for low
transformer output.
[0096] Active Setting 226--shows the current operational setting of
the transformer.
[0097] In an alternative embodiment, the present invention may
include a power supply tuning system 300 that is useful in
adjusting the voltage set point or other operating characteristics
of the power supply 10 or 10' to compensate for power loss along a
power supply line being powered by the power supply 10 or 10'. The
tuning system 300 generally includes a base 302, one or more remote
voltage monitors 304 and a computer 306 or other similar device. In
the illustrated embodiment, the base 302 is configured to receive
voltage measurements from the remote voltage monitors 304. The
remote voltage monitors 304 may be used to measure voltage at
various locations along the power supply line and to communicate
the measured line voltages to the base 302. The base 302 is
connected to a computer 306, such as a laptop computer, for
example, by a USB connection. The computer 306 runs software
configured to interface with the base 302 and provide output
indicative of the voltage measurements received from the remote
voltage monitors 304. The software may show voltage or voltage loss
at each of the remote voltage monitors 304. By reviewing the output
of the software, the installer can determine voltage loss along the
power supply line and vary the voltage set point to provide optimal
voltage to the load(s). If desired, the software may be programmed
to evaluate the voltage loss and provide an optimal voltage set
point. The remote voltage monitors 304 may be used to measure power
loss during installation or at other times. The remote voltage
monitors 304 may be removable or they may be integrated into the
loads.
[0098] In one embodiment, the base 302 is capable of programming
the power supply 10 or 10', for example, to assign the voltage set
point. In this embodiment, the system 300 includes a programmer
module 308 that is configured to interface with the power supply
control circuitry 22 or 22', and to communicate with the base 302.
The programmer module 308 may include a transceiver that permits
the programmer module 308 to communicate wirelessly with the base
302. In an alternative embodiment, the programmer module 308 may be
coupled to the base 302 or the computer 306 by a wired connection.
In either event, the software operating on the computer 306 may
include functionality that permits the computer 306, either
directly or through the base 302, to set the voltage set point of
the power supply 10 or 10'. Although described in connection with
adjustments to the voltage set point of the power supply, the
system 300 may be used to vary other operating parameters of the
power supply 10 or 10', if desired.
[0099] In the illustrated embodiment, the remote voltage monitors
304 each include a true RMS voltmeter to measure line voltage and
are capable of reporting measured voltage back to the base 302 when
polled. For example, the remote voltage monitors 304 and base 302
may each include an RF transceiver. In applications that include
multiple remote voltage monitors 304, each voltage monitor 304 may
be tagged with a unique address to avoid collisions on the RF link
with the base 302. In the illustrated embodiment, each remote
voltage monitor 304 has its address set by a series of dip switches
on the circuit board. In operation, the base 302 may poll each
remote voltage monitor 304 to determine the line voltage at the
monitor 304. Although the remote voltage monitors 304 of the
illustrated embodiment include a wireless communication system,
they may alternatively utilize a wired connection.
[0100] In landscape lighting applications where a plurality of
lamps are installed along a power supply line, one or more remote
voltage monitors 304 may be used to measure voltage at each lamp L.
In situations where a significant power loss is found along the
power supply line, the voltage set point of the power supply can be
increased as a function of the measured voltages to provide a
voltage set point that yields the most appropriate balance between
the plurality of lamps L.
[0101] If not otherwise stated herein, it is to be assumed that all
patents, patent applications, patent publications, and other
publications (including web-based publications) mentioned and cited
herein are hereby fully incorporated by reference herein as if set
forth in their entirety herein.
[0102] Although illustrative embodiments of the present disclosure
have been described herein with reference to the accompanying
drawings, it is to be understood that the disclosure is not limited
to those precise embodiments, and that various other changes and
modifications may be affected therein by one skilled in the art
without departing from the scope or spirit of the disclosure as
defined in the claims, which are to be interpreted in accordance
with the principles of patent law including the doctrine of
equivalents. Any reference to claim elements in the singular, for
example, using the articles "a," "an," "the" or "said," is not to
be construed as limiting the element to the singular.
* * * * *