U.S. patent application number 09/740110 was filed with the patent office on 2001-12-06 for dual input range power supply using two series or parallel connected converter sections with automatic power balancing.
This patent application is currently assigned to POWER-ONE, INC.. Invention is credited to Mallory, William D..
Application Number | 20010048606 09/740110 |
Document ID | / |
Family ID | 26884326 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010048606 |
Kind Code |
A1 |
Mallory, William D. |
December 6, 2001 |
Dual input range power supply using two series or parallel
connected converter sections with automatic power balancing
Abstract
A power supply comprises a first power converter having
respective input and output terminals, and a second power converter
having respective input and output terminals. The output terminals
of the first and second power converters are connected in series to
provide a combined output voltage. A switch is connected to the
input terminals of the first and second power converters. The
switch has a first state by which the input terminals of the first
and second power converters are connected in series, and a second
state by which the input terminals of the first and second power
converters are connected in parallel. A pulse width modulator (PWM)
unit provides a drive signal to regulate current provided to the
first and second power converters. A balance winding is coupled
between the first and second power converters in order to share
power between these two converters when their inputs are connected
in series.
Inventors: |
Mallory, William D.;
(Camarillo, CA) |
Correspondence
Address: |
Brian M. Berliner
O'MELVENY & MYERS LLP
400 South Hope Street
Los Angeles
CA
90071-2899
US
|
Assignee: |
POWER-ONE, INC.
|
Family ID: |
26884326 |
Appl. No.: |
09/740110 |
Filed: |
December 18, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60188640 |
Mar 10, 2000 |
|
|
|
Current U.S.
Class: |
363/65 |
Current CPC
Class: |
H02M 1/10 20130101; H02M
7/493 20130101; H02M 7/4807 20130101 |
Class at
Publication: |
363/65 |
International
Class: |
H02M 001/00 |
Claims
What is claimed is:
1. A power supply, comprising: a first power converter having
respective input and output terminals; a second power converter
having respective input and output terminals, said output terminals
of each of said first power converter and said second power
converter being connected in series to provide a combined output
voltage; a switch connected to said input terminals of said first
power converter and said second power converter, said switch having
a first state by which said input terminals of said first power
converter and said second power converter are connected in series,
and a second state by which said input terminals of said first
power converter and said second power converter are connected in
parallel; and a balance winding coupled between said first power
converter and said second power converter, said balance winding
sharing power between said first power converter and said second
power converter when said switch is in said second state.
2. The power supply of claim 1, wherein each of said first power
converter and said second power converter further comprises a
respective transformer having a primary side and a secondary
side.
3. The power supply of claim 2, wherein said balance winding is
further coupled between said primary sides of said respective
transformers of said first and second power converters.
4. The power supply of claim 2, wherein said balance winding
further comprises an additional transformer separated from said
respective transformers of said first and second power
converters.
5. The power supply of claim 2, wherein each of said first power
converter and said second power converter further comprises plural
respective field effect transistors (FETs) coupled to said primary
side of said respective transformers, said plural FETs adapted to
periodically apply at least a portion of an input voltage across
said primary side.
6. The power supply of claim 5, further comprising a pulse width
modulator (PWM) unit providing drive signals to said plural
respective FETs of said first power converter and said second power
converter.
7. The power supply of claim 1, wherein said switch further
comprises a double pole, double throw switch.
8. The power supply of claim 1, wherein said switch further
comprises a semiconductor device.
9. The power supply of claim 1, wherein said switch further
comprises a removable plug.
10. The power supply of claim 1, further comprising a pulse width
modulator (PWM) unit providing drive signals to said first power
converter and said second power converter.
11. A power supply, comprising: a first power converter having
respective input and output terminals; a second power converter
having respective input and output terminals, said output terminals
of each of said first power converter and said second power
converter being connected in series to provide a combined output
voltage; means for connecting said input terminals of each of said
first and second power connector to an input voltage source, said
connecting means having a first state by which said input terminals
of said first power converter and said second power converter are
connected in series, and a second state by which said input
terminals of said first power converter and said second power
converter are connected in parallel; and means for sharing power
between said first power converter and said second power converter
when said switch is in said second state.
12. The power supply of claim 11, wherein each of said first power
converter and said second power converter further comprises a
respective transformer having a primary side and a secondary
side.
13. The power supply of claim 12, wherein said power sharing means
further comprising a balance winding coupled between said primary
sides of said respective transformers of said first and second
power converters.
14. The power supply of claim 12, wherein said power sharing means
further comprises a balance winding further having an additional
transformer separated from said respective transformers of said
first and second power converters.
15. The power supply of claim 12, wherein each of said first power
converter and said second power converter further comprises plural
respective field effect transistors (FETs) coupled to said primary
side of said respective transformers, said plural FETs adapted to
periodically apply at least a portion of an input voltage across
said primary side.
16. The power supply of claim 15, further comprising a pulse width
modulator (PWM) unit providing drive signals to said plural
respective FETs of each said first power converter and said second
power converter.
17. The power supply of claim 11, wherein said connecting means
further comprises a double pole, double throw switch.
18. The power supply of claim 11, wherein said connecting means
further comprises a semiconductor device.
19. The power supply of claim 11, wherein said connecting means
further comprises a removable plug.
20. The power supply of claim 11, further comprising a pulse width
modulator (PWM) unit providing drive signals to said first power
converter and said second power converter.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit pursuant to 35 U.S.C.
.sctn. 119(e) of U.S. Provisional Application No. 60/188,640, filed
Mar. 10, 2000, which application is specifically incorporated
herein, in its entirety, by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a direct current (DC)
output power supply which implements an automatic power-balancing
scheme enabling it to operate from two input voltage ranges. In
particular, this invention achieves this duality by connecting the
inputs of two power converters in either series or parallel,
according to voltage supply level, and providing a balance winding
unit to compensate for any power imbalance generated during
operation.
[0004] 2. Description of Related Art
[0005] With the increasing popularity of computers and other
electronic devices over the past few years, the demand for power
conversion power supplies that convert alternating current (AC)
into DC has also increased. Although conventional power conversion
supplies are limited to operating within one particular input
voltage level, the voltage available to operate these power
supplies often comes in two distinct ranges. In order for
conventional power supplies to continuously operate over two input
voltages, power semiconductors must be selected according to their
functionality at both voltage levels. In particular, these
semiconductors must simultaneously meet the voltage rating
requirements of operating at the higher input voltage and the
current rating requirements of operating at the lower input
voltage. Semiconductors with such characteristics are very
expensive though, making this design undesirable. Also, in order to
meet requirements of several safety agencies, such as Underwriters
Laboratories (UL), the Canadian Standards Association (CSA), and
Technischer Uberwachungs-Verein (TUV), the physical spacing between
primary windings and safety extra low voltage (SELV) windings
inside the transformers must be designed for voltages associated
with the higher input voltage range.
[0006] The most commonly used method for achieving the
aforementioned duality is to switch the power supply from operating
as a full-wave rectifier to a voltage doubler. In particular, these
circuits provide for the automatic configuration of a power supply
by switching between these two modes of operation in response to
either a low AC input voltage level V.sub.IN or a high AC input
voltage level 2 V.sub.IN. More specifically, these circuits operate
as voltage doublers when the AC input signal is V.sub.IN, and as
full-wave rectifiers when the AC input signal is 2 V.sub.IN. When
operating as a full-wave rectifier, these circuits simply create a
DC equivalent to the AC input signal and pass it through the
remainder of the circuit. When operating as a voltage doubler,
these circuits create a rectified signal that is two times larger
than the AC input signal. Limitations to this design include its
need for separate circuits to accommodate this bimodal operation.
These circuits are, however, somewhat complicated and often require
excessive hardware.
[0007] Accordingly, it would be very desirable to provide a
simplified power supply, which implements an automatic
power-balancing scheme, to operate from two input voltage
ranges.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to a simplified dual input
power supply that avoids the complexities of prior art power
supplies through the implementation of an automatic power-balancing
scheme.
[0009] In an embodiment of the invention, a power supply comprises
a first power converter having respective input and output
terminals, and a second power converter having respective input and
output terminals. The output terminals of the first and second
power converters are connected in series to provide a combined
output voltage. A switch is connected to the input terminals of the
first and second power converters. The switch has a first state by
which the input terminals of the first and second power converters
are connected in series, and a second state by which the input
terminals of the first and second power converters are connected in
parallel. A pulse width modulator (PWM) unit provides a drive
signal to regulate current provided to the first and second power
converters. The automatic power-balancing scheme is provided by a
balance winding coupled between the first and second power
converters in order to share power between these two converters
when their inputs are connected in series.
[0010] A more complete understanding of the dual input power range
power supply will be afforded to those skilled in the art, as well
as a realization of additional advantages and objects thereof, by a
consideration of the following detailed description of the
preferred embodiment. Reference will be made to the appended sheets
of drawings, which will first be described briefly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a block diagram showing a switching mechanism used
to connect two power converters in either series or parallel, in
accordance with the present invention;
[0012] FIG. 2 is an electrical schematic diagram of a power supply
switched to internally connect the inputs of two converters in
parallel;
[0013] FIG. 3 is a block diagram showing the control inputs and
outputs for the power supplies of FIGS. 2, 5, and 6;
[0014] FIG. 4 is a timing diagram of the control inputs and outputs
of FIG. 3;
[0015] FIG. 5 is an electrical schematic diagram of the power
supply switched to internally connect the inputs of two converters
in series; and
[0016] FIG. 6 is an electrical schematic diagram of an alternative
method to implementing the series connection described in FIG.
5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] The present invention satisfies the need for a power supply
that operates over two distinct input voltage ranges. In the
detailed description that follows, like element numerals are used
to describe like elements illustrated in one or more of the
figures.
[0018] Referring first to FIG. 1, a block diagram is shown of a
switching mechanism used to connect the inputs of two identical
power converters, 12 and 14 in either series or parallel, in
accordance with the present invention. Each of the power converters
12 and 14 are adapted to convert an input voltage to an output
voltage, and have respective input and output terminals. In
particular, a connector module 10 is connected to the inputs of
both converter 12 and converter 14. The outputs of converters 12
and 14, meanwhile, are always connected in series. This causes the
output voltages to add and the output current of each converter to
be equal since the same current flows through both output
terminals.
[0019] An input voltage is applied between a positive input
terminal 16 and a negative input terminal 18. The positive input
terminal 16 is connected to the positive terminal of converter 12,
while the negative input terminal 18 is connected to the negative
terminal of converter 14. In order to connect converters 12 and 14
in parallel, the connector module 10 is in a first state in which
the negative terminal of converter 12 is connected to the negative
input terminal 18 of the supply voltage and the positive terminal
of converter 14 is connected to the positive input terminal 16 of
the supply voltage. For a series connection, the connector module
is in a second state in which the negative terminal of converter 12
is connected to the positive terminal of converter 14. The
connector module 10 may be provided by a double pole, double throw
switch used to connect the converter inputs in either series or
parallel. Alternatively, the connector module 10 may be provided in
the form of a removable plug having jumpers electrically configured
to connect the respective converter inputs in series or parallel.
There may further be a first plug adapted to provide a series
connection, and a second plug adapted to provide a parallel
connection. It should be noted that other types of switching
devices could also be used to implement the connector module 10,
such as semiconductor switches.
[0020] The input voltage range of this power supply is either
V.sub.IN or 2 V.sub.IN. When operating in the low input voltage
range V.sub.IN, the inputs to the two power converters are
connected in parallel making the input voltage to each converter
simply V.sub.IN. Meanwhile, operation in the high input voltage
range 2 V.sub.IN would require a series connection between the two
converters causing the supply voltage to theoretically divide
equally into each converter. As a result, the input voltage of each
converter should be V.sub.IN. In reality though, the impedances of
the converters 12 and 14 are never identical causing the input
supply voltage to be unevenly distributed to each converter. To
circumvent this problem, a balance winding technique is used to
force converters 12 and 14 to share this voltage equally, as will
be described in greater detail below.
[0021] FIG. 2 shows conventional full bridge converters 12 and 14
connected in parallel to an input voltage V.sub.IN. The internal
circuitry of these converters 12 and 14 includes a primary side,
secondary side, and transformer. The primary side of converter 12
is comprised of a capacitor 20, transistors 22, 24, 26, and 28, a
primary winding 42, and a balance winding 44. Likewise, the primary
side of converter 14 is comprised of a capacitor 30, transistors
32, 34, 36, and 38, a primary winding 52, and a balance winding 54.
Capacitors 20 and 30 are respectively connected in parallel to the
sources of transistors 22 and 24, and transistors 32 and 34. The
drains of transistors 22 and 24, are respectively connected to the
sources of transistors 26 and 28. Likewise, the drains of
transistors 32 and 34 are respectively connected to the sources of
transistors 36 and 38. The positive terminal of primary winding 42
is connected to the drain of transistor 22 and the source of
transistor 26, while the negative terminal of primary winding 42 is
connected to the drain of transistor 24 and the source of
transistor 28. Primary winding 52 makes a similar connection with
its positive terminal to the respective drain and source of
transistors 32 and 36, and its negative terminal to the respective
drain and source of transistors 34 and 38. The negative terminals
of balance windings 44 and 54 are connected together, while their
positive terminals are connected together via a current limiting
resistor 60.
[0022] Power transformers 40 and 50 respectively separate the
primary and secondary sides of converters 12 and 14. The secondary
sides of converters 12 and 14 respectively include secondary
windings 46 and 56 that are tied together at both terminals. The
output signals from secondary windings 46 and 56 are fed through a
rectifying unit 70 and then through a filter 80. It should be noted
that current divides equally between converters 12 and 14 because
the output of each is connected in series. Therefore, no special
circuitry is needed to cause the total throughput power to divide
equally between converters 12 and 14.
[0023] The pulse width modulator (PWM) unit illustrated in FIG. 3
governs the control of this power supply. This PWM unit includes a
PWM controller 90, an internal RC oscillator 92, and two gate drive
transformers 94 and 96. Scaled current signals (e.g., 300:1)
produced by current sense transformers (not shown) coupled to
primary windings 42 and 52, as well as feedback from the power
supply's output voltage, are connected as input signals to a PWM
controller 90. These inputs, in conjunction with an internal RC
oscillator 92, produce output signals A and B that are respectively
connected as inputs to gate drive transformers 94 and 96. Gate
drive transformer 94 is connected to the gates of transistors 22,
28, 32, and 38, while gate drive transformer 96 is connected to the
gates of transistors 24, 26, 34, and 36. After passing through gate
transformers 34 and 36, signals A and B are used to sequentially
drive transistors 22, 24, 26, 28, 32, 34, 36, and 38 as described
in FIG. 2. Waveforms of signals A and B are shown in FIG. 3.
[0024] Converter 12 operates by having transistors 22, 24, 26, and
28 switch on and off, in the proper sequence, to generate an
alternating voltage on primary winding 42 of transformer 50.
Transistors 32, 34, 36, and 38 perform the same operation on
primary winding 52 of transformer 50 in converter 14. A single PWM
circuit that simultaneously drives both converters 12 and 14
produces control signals A and B. In particular, transistors 22,
28, 32, and 38 all turn ON and OFF at the same time from the A
phase gate drive signal, while transistors 24, 26, 34, and 36 all
turn ON and OFF at the same time from the B phase. Next, the
secondary winding of transformers 40 and 50, 46 and 56
respectively, feed a conventional rectifying unit 70. Taking this
rectified signal and passing it through a filter 80 then produce
the output voltage of the power supply.
[0025] Although balance windings 44 and 54 are shown in FIG. 2,
their inclusion does not alter operation when the power supply is
operating in its parallel configuration. These balance windings 44
and 54 are only necessary for proper power sharing between
converters 12 and 14 when their inputs are connected in series.
FIG. 5 shows a detailed circuit schematic of the power supply with
inputs to converters 12 and 14 now connected in series and with an
input supply voltage raised to 2 V.sub.IN. It should be noted that,
other than these two exceptions, FIG. 5 is identical to FIG. 2.
[0026] Unlike operation in the parallel configuration, operation in
the series configuration results in the negative input of converter
12 and the positive input of converter 14 having no direct
connection to either input terminal 16 or 18. Because a single PWM
controller 90 is used, the two converters 12 and 14 have an input
characteristic that look like a constant current sink. However, due
to differences in propagation delays in the MOSFET gate drive,
differences in transformer magnetizing and leakage inductance and
other differences between the two converters 12 and 14, the current
sink characteristics are unequal. Trying to connect two devices in
series, where each one requires a different amount of current
flowing through it, leads to instability. This causes the
connection between the negative input of converter 12 and the
positive input of converter 14 to not be equal to half the input
voltage as would be desired. This inequality creates an excessive
voltage at the input of one converter and excessive voltage stress
levels in its semiconductors and transformer. The circuit is not
inherently able to correct an input voltage imbalance between the
two converters once it occurs.
[0027] The solution to this problem is to add the balance winding
44 to transformer 40 and the balance winding 54 to transformer 50.
By ensuring that transformers 40 and 50 respectively use identical
turns ratios between primary windings 42 and 52, secondary windings
46 and 56, and balance windings 44 and 54, current will
automatically transfer from one converter to the other whenever the
switching transistors are on. Additional current will be drawn by
the converter that has a higher input voltage, causing the input
voltage to decrease. This current flows through the primary winding
42 of transformer 40, through the balance winding 44 of transformer
40, into the balance winding 54 of transformer 50 and then into the
primary winding 52 of transformer 50. Transistors 32, 34, 36, and
38 rectify this current. This current will flow into the input to
the converter that has a lower input voltage causing it to increase
in voltage. The circuit allows current to flow in either direction
until the voltage at the inputs of each converter is equal. It does
not matter which converter has a higher input, the circuit will
always correct the imbalance and it does so with very little power
loss.
[0028] FIG. 6 illustrates an alternative embodiment to the circuit
described in FIG. 5. By including a third transformer 64 and
slightly modifying the terminal connections of balance windings 44
and 54, this circuit achieves the same automatic balancing scheme
previously described. Transformer 64 has two identical, isolated
windings that connect across primary windings 52 and 62, of
transformers 50 and 60 respectively. The two terminals of balance
winding 44 are now connected to the two terminals of primary
winding 42, with one of those connections made via a current
limiting resistor 60. A similar connection is made with balance
winding 54, where both terminals are connected to primary winding
52, with one connection made via a current limiting resistor
62.
[0029] Having thus described a preferred embodiment of a dual range
power supply, it should be apparent to those skilled in the art
that certain advantages of the within system have been achieved. It
should also be appreciated that various modifications, adaptations,
and alternative embodiments thereof may be made within the scope
and spirit of the present invention. The invention is further
defined by the following claims.
* * * * *