EP1794874A1 - Bipolar power supply with lossless snubber - Google Patents

Bipolar power supply with lossless snubber

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Publication number
EP1794874A1
EP1794874A1 EP05793398A EP05793398A EP1794874A1 EP 1794874 A1 EP1794874 A1 EP 1794874A1 EP 05793398 A EP05793398 A EP 05793398A EP 05793398 A EP05793398 A EP 05793398A EP 1794874 A1 EP1794874 A1 EP 1794874A1
Authority
EP
European Patent Office
Prior art keywords
snubber
output terminal
rectifier
terminal
power
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05793398A
Other languages
German (de)
French (fr)
Other versions
EP1794874A4 (en
Inventor
Bryce L. Hesterman
Milan Ilic
Audrey B. Malinin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Advanced Energy Industries Inc
Original Assignee
Advanced Energy Industries Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Advanced Energy Industries Inc filed Critical Advanced Energy Industries Inc
Publication of EP1794874A1 publication Critical patent/EP1794874A1/en
Publication of EP1794874A4 publication Critical patent/EP1794874A4/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/34—Snubber circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Definitions

  • This invention relates generally to switch, mode power converters, and more particularly, to isolated dc power converters suitable for high power and high voltage applications such as plasma processing.
  • a common problem with isolated dc power converters in which the output of transformer windings is rectified and filtered with an inductor is that the rectifiers require some type of snubbing circuit to prevent energy that is built up in various circuit inductances during the reverse recovery of the rectifier diodes from causing the diodes to suffer reverse breakdown from voltage overshoots that occur in the transformer windings when the rectifier diodes turn off and the stored inductive energy is released.
  • This problem is typically handled by directing the stored energy away from the rectifiers with a snubber circuit.
  • Snubbers that are connected to transformer isolated output circuits are commonly called secondary snubbers. There are two main categories of snubber circuits, dissipative and lossless.
  • Dissipative snubbers direct the stored energy into resistors. Dissipative snubbers are often impractical in high power converters, and so a variety of lossless snubber circuits have been developed. Lossless snubbers direct the stored energy back to the converter input, the converter output, or a combination of the two. Lossless snubbers are constructed with components that are ideally lossless such as diodes, active switches, capacitors and inductors, in practice, however, so-called lossless snubbers do have some power losses, but they are much lower that the power losses of dissipative snubbers.
  • a prior-art secondary snubber that uses an active switch is described in: Jung-Goo Cho et al., "Zero-voltage and zero-current-switcbing full-bridge PWM converter using secondary active clamp," IEEE Transactions on Power Electronics, vol. 13, no.4, July 1988, pp. 601-607. Having active components in snubbing circuits adds cost and complexity to power converters, so it is often preferable to use passive snubbers.
  • a variety of passive secondary snubbers are described in: Jung G.
  • stacked output rectifier circuits power supplies with high output voltages.
  • the structure of stacked rectifiers may provide opportunities to employ snubber circuits that could not be implemented in power converters without stacked rectifiers.
  • An example of this is a particularly simple snubber circuit for a power converter with stacked output rectifiers is disclosed in Ashish Bendre, "New High Power DC-DC Converter with Loss Limited Switching and Lossless Secondary Clamp," Proceedings of the IEEE 2001 Power Electronics Specialists Conference (PESC), vol. 1, pp. 321-326. This prior art power converter circuit is illustrated in Figure 1.
  • a bipolar power supply BPS has a conventional phase shifted bridge inverter PSB that supplies ac power to bridge rectifiers RCTA and RCTB, Filter inductors LFA and LFB smooth the ripple in the currents supplied to filter capacitors CFA and CFB.
  • This type of converter usually operates in continuous conduction mode, which means the currents in the filter conductors flow continually instead of being interrupted during each switching cycle.
  • the diodes in the rectifiers operate in a freewheeling mode during the intervals of the switching cycle when the phase-shifted bridge PSB inverter is not supplying power.
  • the rectifier diodes When the inverter begins to supply power to the rectifiers, the rectifier diodes turn off and snubber diodes DSA and DSB clamp the rectifier bridge voltages to the total output voltage between positive output terminal PT and negative output terminal NT.
  • this snubbing scheme is simple and effective, it has the disadvantage of limiting the allowable operating range of the inverter duty cycle to values somewhat greater than 0.5 in order to prevent the snubber diodes DSA and DSB from delivering large current pulses to the output filter capacitors CFA and CFB. This effect limits the available range of voltage conversion ratios obtainable with this power converter circuit. It would be desirable if there were provided an isolated wide-range power converter suitable for high power and high voltage applications in which stacked rectifiers are snubbed with lossless snubbers circuits that do not restrict the voltage conversion range.
  • the power supply has a positive output terminal, a negative output terminal, and a common output terminal.
  • a first rectifier circuit receives ac power from an inverter and delivers dc power between a first positive rectifier terminal and a first negative rectifier terminal
  • a second rectifier circuit receives ac power from the inverter and delivers dc power between a second positive rectifier terminal and a second negative rectifier terminal.
  • the first positive rectifier terminal is connected to the positive output terminal
  • the second negative rectifier terminal is connected to the negative output terminal.
  • a first filter inductor is connected between the first negative rectifier terminal and the common output terminal, and a second filter inductor is connected between the second positive rectifier terminal and the common output terminal.
  • a first filter capacitor is connected between the positive output terminal and the common output terminal, and a second filter capacitor is connected between the negative output terminal and the common output terminal.
  • a first snubber inductor is connected between the positive output terminal and a first snubber junction, and a second snubber inductor is connected between the negative output terminal and a second snubber junction.
  • a first snubber capacitor is connected between the first snubber junction and an output terminal, and a second snubber capacitor is connected between the second snubber junction and an output terminal.
  • a first snubber diode is connected between the second positive rectifier terminal and the first snubber junction, and a second snubber diode is connected between the second snubber junction and the first negative rectifier terminal.
  • the snubber diodes are oriented such that when they conduct current in the forward direction, a first diode current flows through the first snubber diode into the first snubber junction, and a second diode current flows out of the second snubber junction into the second snubber diode.
  • Figure 1 illustrates a prior art bipolar power supply with a simple lossless snubber circuit that limits the available voltage conversion range.
  • Figure 2 illustrates a bipolar power supply with lossless smibbers that permit a wide voltage conversion range.
  • Figure 3 illustrates waveforms of the power supply of Figure 2 when the inverter has a duty cycle of 0.7.
  • Figure 4 illustrates waveforms of the power supply of Figure 2 when the inverter has a duty cycle of 0.4.
  • FIG. 2 there is shown a wide range bipolar power supply WRBPS that has an inverter INV that receives dc power from input terminals PIT and NIT.
  • the inverter has switches SW1-SW4 that drive a transformer Tl.
  • the switches may be operated by a control circuit (not shown) so that the inverter functions as a phase shifted bridge or as a pulse width modulated H bridge.
  • Inverter INV may also be implemented with any known inverter circuit that delivers current pulses into a transformer.
  • Transformer Tl has secondary windings TlA and TlB that supply ac power to bridge rectifiers RCTl and RCT2. Alternatively, Tl could be replaced with two transformers that serve the same function as Tl .
  • Rectifier RCTl delivers dc power between a positive output terminal PRTl and a negative output terminal NRTl .
  • Rectifier RCT2 delivers dc power between a positive output terminal PRT2 and a negative output terminal NRT2.
  • Rectifiers RCTl and RCT2 may be implemented with other known rectifier circuits, for example, center- tapped full-wave rectifiers, and half-wave rectifiers such as those used in forward converters and flyback converters.
  • Power supply WRBPS has a positive output terminal POT, a negative output terminal NOT, and a common output terminal COT.
  • Positive rectifier terminal PRTl is connected to the positive output terminal POT 5 and negative rectifier terminal NRT2 is connected to negative output terminal NRT2.
  • a filter inductor LFl is connected between negative rectifier terminal NRTl and the common output terminal COT.
  • a second filter inductor LF2 is connected between positive rectifier terminal PRT2 and the common output terminal.
  • An output filter capacitor CFl is connected between the positive output terminal and the common output terminal, and an output second filter capacitor CF2 is connected between the negative output terminal and the common output terminal.
  • Filter inductors LFl and LF2 smooth the ripple in the currents supplied to filter capacitors CFl and CF2.
  • a snubber inductor LSI is connected between the positive output terminal and a snubber junction SJl, and a second snubber inductor LS2 is connected between the negative output terminal and a second snubber junction SJ2.
  • a snubber capacitor CSl is connected between the snubber junction SJl and the negative output terminal, and a second snubber capacitor CS2 is connected between the second snubber junction and the positive output terminal.
  • the snubber capacitor connections shown in Figure 2 generally produce the least ripple current in the output filter capacitors, but the snubber capacitors could also be connected to any of the output terminals, preferably in a symmetrical manner.
  • CSl could have one end connected to the positive output terminal
  • CS2 could have one end connected to the negative output terminal
  • both CSl and CS2 could each have one end connected to the common output terminal.
  • a snubber diode DSl is connected between positive rectifier terminal PRT2 and the snubber junction SJl
  • a second snubber diode DS2 is connected between snubber junction SJ2 and negative rectifier terminal NRTl.
  • the snubber diodes are oriented such that when they conduct current in the forward direction, the current in DS 1 flows into snubber junction SJl, and the current in DS2 flows out of junction SJ2.
  • Secondary windings TlA and TlB are preferably wound in a way that they produce essentially equal voltages and identical waveforms between the rectifier output terminals of rectifiers RCTl and RCT2. If these rectifiers are implemented using full- wave rectifier circuits, then the polarities of the secondary windings are not important. If, however, rectifiers RCTl and RCT2 are implemented using half- wave rectifier circuits, then the secondary winding polarities should be as indicated in Figure 2. If the secondary windings are implemented so that the output voltages of rectifiers RCTl and RCT2 are nearly equal, then the two snubber inductors LSI and LS2, and the two filter inductors LFl and LF2 may be coupled as shown in Figure 2.
  • the snubber capacitors CSl and CS2 should preferably have equal capacitances, and it is also preferable that filter capacitors CFl and CF2 have equal capacitances.
  • Figures 3 and 4 illustrate waveforms of power supply WKBPS when the inverter is operating with a duty cycles of 0.7 and 0.4, respectively.
  • the waveforms were produced by computer simulations with the component values and parameters specified in Table 1.
  • Table 2 lists operating performance parameters.
  • V O UT is the output voltage between the positive and negative output terminals
  • V BRIDGE is the voltage between each set of positive and negative rectifier terminals
  • V S NUB is the voltage across the snubber capacitors.
  • IL F is the current flowing out of the dotted ends of filter inductors LFl and LF2
  • I LS is the current flowing out of the dotted ends of snubber inductors LS 1 and LS2.
  • ISEC is the current flowing out of the dotted ends of secondary windings TlA and TlB.
  • Figure 3 illustrates waveforms of power supply WRBPS in Figure 2 when inverter INV is operating with a duty cycle of 0.7.
  • the snubber diodes will conduct very little current when the peak-to-average ratio of the voltages between the output terminals of rectifiers RCTl and RCT2 is less than two, and the snubber voltage V SN U B will be approximately equal to the peak value of the bridge voltage. This condition will be met when the duty cycle of a square- wave inverter such DSfV is somewhat greater than 0.5.
  • the duty cycle of the rectifier output voltages will be smaller than the duty cycle of the inverter due to transformer leakage inductance.
  • the prior art power supply BPS in Figure 1 operates in a similar manner when the inverter duty cycle is high.
  • Figure 4 illustrates waveforms of power supply WRBPS in Figure 2 when inverter
  • INV is operating with a duty cycle of 0.4.
  • the snubber diodes may conduct substantial current when the peak-to-average ratio of the voltages between the output terminals of rectifiers RCTl and RCT2 is greater than two. This condition will be met when the duty cycle of a square-wave inverter such ESfV is less than about 0.5. This is also true for the prior art power supply BPS in Figure 1.
  • the peak values of the currents flowing through snubber diodes DSl and DS2 are limited by snubber inductors LSI and LS2, as shown by waveform I LF -
  • the bottom plot of Figure 4 shows that the currents through the snubber inductors are the greater than currents through the filter inductors, but the ripple in the output voltage is still relatively low.
  • the peak value of the snubber capacitor voltage V S NU B is about the same in
  • the optimal values of the snubber capacitors depend on the application.
  • the capacitor values listed in Table 2 are suitable for a power supply that is used to deliver power to a plasma load, and could be utilized to implement the dc power supply in the co-pending patent application: Apparatus and Method For Fast Arc Extinction With Early Shunting of Arc Current in Plasma, serial number 10/884,119 filed July 2, 2004.
  • the high output voltage capability, wide output voltage range, and low output capacitance of this power supply makes it well suited for such an application, hi this application, the common output terminal is not used.
  • the WRBPS power supply circuit could also be used in applications where the bipolar output voltage capability is used.
  • An example of this would be to use it as a pre- regulator power supply for creating a stable isolated dc bus voltage from a rectified three- phase voltage.
  • the pre-regulator would supply power to a stacked power converter that has three corresponding input terminals such as the soft switching stacked buck power converter described in co-pending patent application "Soft Switching Interleaved Power Converter," filed August 24, 2004.
  • DC inverter input terminals PIT and NIT would receive power from the output voltage of a three-phase bridge rectifier. In this application, the wide voltage conversion range would be used to accommodate changes in the ac input voltage.
  • the output capacitors would preferably be much larger, on the order of a few hundred microfarads, to provide bulk energy storage that would enhance the ability to ride thought power line transients.
  • the control circuitry for the inverter should be designed to draw a relatively constant current from the bridge rectifier while maintaining a relatively stable output voltage.
  • Such a control circuit would have an inner input-current control loop with a bandwidth of a few kHz, and an outer control loop that would have a bandwidth substantially less than the ac power line frequency to regulate the isolated dc bus output voltage.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

There is provided by this invention an isolated power converter suitable for high power and high voltage applications that has stacked rectifiers that are snubbed with lossless snubber circuits which do not restrict the voltage conversion range.

Description

BIPOLAR POWER SUPPLY WITH LOSSLESS SNUBBER
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates generally to switch, mode power converters, and more particularly, to isolated dc power converters suitable for high power and high voltage applications such as plasma processing.
Brief Description of the Prior Art
A common problem with isolated dc power converters in which the output of transformer windings is rectified and filtered with an inductor is that the rectifiers require some type of snubbing circuit to prevent energy that is built up in various circuit inductances during the reverse recovery of the rectifier diodes from causing the diodes to suffer reverse breakdown from voltage overshoots that occur in the transformer windings when the rectifier diodes turn off and the stored inductive energy is released. This problem is typically handled by directing the stored energy away from the rectifiers with a snubber circuit. Snubbers that are connected to transformer isolated output circuits are commonly called secondary snubbers. There are two main categories of snubber circuits, dissipative and lossless.
Dissipative snubbers direct the stored energy into resistors. Dissipative snubbers are often impractical in high power converters, and so a variety of lossless snubber circuits have been developed. Lossless snubbers direct the stored energy back to the converter input, the converter output, or a combination of the two. Lossless snubbers are constructed with components that are ideally lossless such as diodes, active switches, capacitors and inductors, in practice, however, so-called lossless snubbers do have some power losses, but they are much lower that the power losses of dissipative snubbers.
A prior-art secondary snubber that uses an active switch is described in: Jung-Goo Cho et al., "Zero-voltage and zero-current-switcbing full-bridge PWM converter using secondary active clamp," IEEE Transactions on Power Electronics, vol. 13, no.4, July 1988, pp. 601-607. Having active components in snubbing circuits adds cost and complexity to power converters, so it is often preferable to use passive snubbers. A variety of passive secondary snubbers are described in: Jung G. Cho et al., "Novel zero- voltage and zero-eurrent-switching (ZVZCS) full-bridge PWM converter using a simple auxiliary circuit," Proceedings of the IEEE 1998 Applied Power Electronics Conference and Exposition (APEC), vol.2, pp. 834-839.
It is often desirable to use stacked output rectifier circuits power supplies with high output voltages. The structure of stacked rectifiers may provide opportunities to employ snubber circuits that could not be implemented in power converters without stacked rectifiers. An example of this is a particularly simple snubber circuit for a power converter with stacked output rectifiers is disclosed in Ashish Bendre, "New High Power DC-DC Converter with Loss Limited Switching and Lossless Secondary Clamp," Proceedings of the IEEE 2001 Power Electronics Specialists Conference (PESC), vol. 1, pp. 321-326. This prior art power converter circuit is illustrated in Figure 1.
In Figure 1, a bipolar power supply BPS has a conventional phase shifted bridge inverter PSB that supplies ac power to bridge rectifiers RCTA and RCTB, Filter inductors LFA and LFB smooth the ripple in the currents supplied to filter capacitors CFA and CFB. This type of converter usually operates in continuous conduction mode, which means the currents in the filter conductors flow continually instead of being interrupted during each switching cycle. The diodes in the rectifiers operate in a freewheeling mode during the intervals of the switching cycle when the phase-shifted bridge PSB inverter is not supplying power. When the inverter begins to supply power to the rectifiers, the rectifier diodes turn off and snubber diodes DSA and DSB clamp the rectifier bridge voltages to the total output voltage between positive output terminal PT and negative output terminal NT. Although this snubbing scheme is simple and effective, it has the disadvantage of limiting the allowable operating range of the inverter duty cycle to values somewhat greater than 0.5 in order to prevent the snubber diodes DSA and DSB from delivering large current pulses to the output filter capacitors CFA and CFB. This effect limits the available range of voltage conversion ratios obtainable with this power converter circuit. It would be desirable if there were provided an isolated wide-range power converter suitable for high power and high voltage applications in which stacked rectifiers are snubbed with lossless snubbers circuits that do not restrict the voltage conversion range.
SUMMARY OF THE INVENTION There is provided by this invention an isolated power converter suitable for high power and high voltage applications that has stacked rectifiers that are snubbed with lossless snubber circuits which do not restrict the voltage conversion range. The power supply has a positive output terminal, a negative output terminal, and a common output terminal. A first rectifier circuit receives ac power from an inverter and delivers dc power between a first positive rectifier terminal and a first negative rectifier terminal, and a second rectifier circuit receives ac power from the inverter and delivers dc power between a second positive rectifier terminal and a second negative rectifier terminal. The first positive rectifier terminal is connected to the positive output terminal, and the second negative rectifier terminal is connected to the negative output terminal. A first filter inductor is connected between the first negative rectifier terminal and the common output terminal, and a second filter inductor is connected between the second positive rectifier terminal and the common output terminal. A first filter capacitor is connected between the positive output terminal and the common output terminal, and a second filter capacitor is connected between the negative output terminal and the common output terminal. A first snubber inductor is connected between the positive output terminal and a first snubber junction, and a second snubber inductor is connected between the negative output terminal and a second snubber junction. A first snubber capacitor is connected between the first snubber junction and an output terminal, and a second snubber capacitor is connected between the second snubber junction and an output terminal. A first snubber diode is connected between the second positive rectifier terminal and the first snubber junction, and a second snubber diode is connected between the second snubber junction and the first negative rectifier terminal. The snubber diodes are oriented such that when they conduct current in the forward direction, a first diode current flows through the first snubber diode into the first snubber junction, and a second diode current flows out of the second snubber junction into the second snubber diode. BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a prior art bipolar power supply with a simple lossless snubber circuit that limits the available voltage conversion range.
Figure 2 illustrates a bipolar power supply with lossless smibbers that permit a wide voltage conversion range.
Figure 3 illustrates waveforms of the power supply of Figure 2 when the inverter has a duty cycle of 0.7.
Figure 4 illustrates waveforms of the power supply of Figure 2 when the inverter has a duty cycle of 0.4.
DETAILED DESCRIPTION OF THE INVENTION
In Figure 2 there is shown a wide range bipolar power supply WRBPS that has an inverter INV that receives dc power from input terminals PIT and NIT. The inverter has switches SW1-SW4 that drive a transformer Tl. The switches may be operated by a control circuit (not shown) so that the inverter functions as a phase shifted bridge or as a pulse width modulated H bridge. Inverter INV may also be implemented with any known inverter circuit that delivers current pulses into a transformer. Transformer Tl has secondary windings TlA and TlB that supply ac power to bridge rectifiers RCTl and RCT2. Alternatively, Tl could be replaced with two transformers that serve the same function as Tl . Rectifier RCTl delivers dc power between a positive output terminal PRTl and a negative output terminal NRTl . Rectifier RCT2 delivers dc power between a positive output terminal PRT2 and a negative output terminal NRT2. Rectifiers RCTl and RCT2 may be implemented with other known rectifier circuits, for example, center- tapped full-wave rectifiers, and half-wave rectifiers such as those used in forward converters and flyback converters.
Power supply WRBPS has a positive output terminal POT, a negative output terminal NOT, and a common output terminal COT. Positive rectifier terminal PRTl is connected to the positive output terminal POT5 and negative rectifier terminal NRT2 is connected to negative output terminal NRT2. A filter inductor LFl is connected between negative rectifier terminal NRTl and the common output terminal COT. A second filter inductor LF2 is connected between positive rectifier terminal PRT2 and the common output terminal. An output filter capacitor CFl is connected between the positive output terminal and the common output terminal, and an output second filter capacitor CF2 is connected between the negative output terminal and the common output terminal. Filter inductors LFl and LF2 smooth the ripple in the currents supplied to filter capacitors CFl and CF2.
A snubber inductor LSI is connected between the positive output terminal and a snubber junction SJl, and a second snubber inductor LS2 is connected between the negative output terminal and a second snubber junction SJ2. A snubber capacitor CSl is connected between the snubber junction SJl and the negative output terminal, and a second snubber capacitor CS2 is connected between the second snubber junction and the positive output terminal. The snubber capacitor connections shown in Figure 2 generally produce the least ripple current in the output filter capacitors, but the snubber capacitors could also be connected to any of the output terminals, preferably in a symmetrical manner. For example, CSl could have one end connected to the positive output terminal, and CS2 could have one end connected to the negative output terminal. Alternatively, both CSl and CS2 could each have one end connected to the common output terminal. A snubber diode DSl is connected between positive rectifier terminal PRT2 and the snubber junction SJl, and a second snubber diode DS2 is connected between snubber junction SJ2 and negative rectifier terminal NRTl. The snubber diodes are oriented such that when they conduct current in the forward direction, the current in DS 1 flows into snubber junction SJl, and the current in DS2 flows out of junction SJ2.
Secondary windings TlA and TlB are preferably wound in a way that they produce essentially equal voltages and identical waveforms between the rectifier output terminals of rectifiers RCTl and RCT2. If these rectifiers are implemented using full- wave rectifier circuits, then the polarities of the secondary windings are not important. If, however, rectifiers RCTl and RCT2 are implemented using half- wave rectifier circuits, then the secondary winding polarities should be as indicated in Figure 2. If the secondary windings are implemented so that the output voltages of rectifiers RCTl and RCT2 are nearly equal, then the two snubber inductors LSI and LS2, and the two filter inductors LFl and LF2 may be coupled as shown in Figure 2. The snubber capacitors CSl and CS2 should preferably have equal capacitances, and it is also preferable that filter capacitors CFl and CF2 have equal capacitances.
Figures 3 and 4 illustrate waveforms of power supply WKBPS when the inverter is operating with a duty cycles of 0.7 and 0.4, respectively. The waveforms were produced by computer simulations with the component values and parameters specified in Table 1. Table 2 lists operating performance parameters.
In Figures 3 and 4, VOUT is the output voltage between the positive and negative output terminals, VBRIDGE is the voltage between each set of positive and negative rectifier terminals, and VSNUB is the voltage across the snubber capacitors. ILF is the current flowing out of the dotted ends of filter inductors LFl and LF2, and ILS is the current flowing out of the dotted ends of snubber inductors LS 1 and LS2. ISEC is the current flowing out of the dotted ends of secondary windings TlA and TlB.
Table 1. Component values and parameters for Figure 2.
Figure 3 illustrates waveforms of power supply WRBPS in Figure 2 when inverter INV is operating with a duty cycle of 0.7. The snubber diodes will conduct very little current when the peak-to-average ratio of the voltages between the output terminals of rectifiers RCTl and RCT2 is less than two, and the snubber voltage VSNUB will be approximately equal to the peak value of the bridge voltage. This condition will be met when the duty cycle of a square- wave inverter such DSfV is somewhat greater than 0.5. The duty cycle of the rectifier output voltages will be smaller than the duty cycle of the inverter due to transformer leakage inductance. The prior art power supply BPS in Figure 1 operates in a similar manner when the inverter duty cycle is high. Figure 4 illustrates waveforms of power supply WRBPS in Figure 2 when inverter
INV is operating with a duty cycle of 0.4. The snubber diodes may conduct substantial current when the peak-to-average ratio of the voltages between the output terminals of rectifiers RCTl and RCT2 is greater than two. This condition will be met when the duty cycle of a square-wave inverter such ESfV is less than about 0.5. This is also true for the prior art power supply BPS in Figure 1. The peak values of the currents flowing through snubber diodes DSl and DS2 are limited by snubber inductors LSI and LS2, as shown by waveform ILF- The bottom plot of Figure 4 shows that the currents through the snubber inductors are the greater than currents through the filter inductors, but the ripple in the output voltage is still relatively low. The peak value of the snubber capacitor voltage VSNUB is about the same in
Figures 3 and 4, but the ripple voltage is much greater in Figure 4. Even so, the volt- ampere product of the snubber capacitor ac voltages and currents is only about 2.5 kVA, which is still small in comparison to the 15 kW output power.
The optimal values of the snubber capacitors depend on the application. The capacitor values listed in Table 2 are suitable for a power supply that is used to deliver power to a plasma load, and could be utilized to implement the dc power supply in the co-pending patent application: Apparatus and Method For Fast Arc Extinction With Early Shunting of Arc Current in Plasma, serial number 10/884,119 filed July 2, 2004. The high output voltage capability, wide output voltage range, and low output capacitance of this power supply makes it well suited for such an application, hi this application, the common output terminal is not used. The WRBPS power supply circuit could also be used in applications where the bipolar output voltage capability is used. An example of this would be to use it as a pre- regulator power supply for creating a stable isolated dc bus voltage from a rectified three- phase voltage. The pre-regulator would supply power to a stacked power converter that has three corresponding input terminals such as the soft switching stacked buck power converter described in co-pending patent application "Soft Switching Interleaved Power Converter," filed August 24, 2004. DC inverter input terminals PIT and NIT would receive power from the output voltage of a three-phase bridge rectifier. In this application, the wide voltage conversion range would be used to accommodate changes in the ac input voltage. The output capacitors would preferably be much larger, on the order of a few hundred microfarads, to provide bulk energy storage that would enhance the ability to ride thought power line transients. The control circuitry for the inverter (not shown) should be designed to draw a relatively constant current from the bridge rectifier while maintaining a relatively stable output voltage. Such a control circuit would have an inner input-current control loop with a bandwidth of a few kHz, and an outer control loop that would have a bandwidth substantially less than the ac power line frequency to regulate the isolated dc bus output voltage.
Although herein there is illustrated and described specific structure and details of operation of the invention, it is clearly understood that the same were merely for purposes of illustration and that changes and modifications may be readily made therein by those skilled in the art without departing from the spirit and the scope of this invention.

Claims

WE CLAIM
1. A bipolar power converter for delivering power to at least one load comprising: a) a positive output terminal, a negative output terminal, and a common output terminal; b) a first rectifier circuit that receives ac power from an inverter and delivers dc power between a first positive rectifier terminal and a first negative rectifier terminal, and a second rectifier circuit that receives ac power from the inverter and delivers dc power between a second positive rectifier terminal a second negative rectifier terminal; c) the first positive rectifier terminal connected to the positive output terminal, and the second negative rectifier terminal connected to the negative output terminal; d) a first filter inductor connected between the first negative rectifier terminal and the common output terminal, and a second filter inductor connected between the second positive rectifier terminal and the common output terminal; e) a first filter capacitor connected between the positive output terminal and the common output terminal, and a second filter capacitor connected between the negative output terminal and the common output terminal; f) a first snubber inductor connected between the positive output terminal and a first snubber junction, and a second snubber inductor connected between the negative output terminal and a second snubber junction; g) a first snubber capacitor connected between the first snubber junction and an output terminal, and a second snubber capacitor connected between the second snubber junction and an output terminal; h) a first snubber diode connected between the second positive rectifier terminal and the first snubber junction, and a second snubber diode connected between the second snubber junction and the first negative rectifier terminal, the snubber diodes oriented such that when they conduct current in the forward direction, a first diode current flows through the first snubber diode into the first smibber junction, and a second diode current flows out of the second snubber junction into the second snubber diode.
EP05793398A 2004-08-30 2005-08-29 Bipolar power supply with lossless snubber Withdrawn EP1794874A4 (en)

Applications Claiming Priority (2)

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US93017204A 2004-08-30 2004-08-30
PCT/US2005/030695 WO2006031427A1 (en) 2004-08-30 2005-08-29 Bipolar power supply with lossless snubber

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EP1794874A1 true EP1794874A1 (en) 2007-06-13
EP1794874A4 EP1794874A4 (en) 2008-08-20

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US9685872B2 (en) 2012-12-21 2017-06-20 Weilun Chen Single-pole switch power source
CN103543775B (en) * 2013-09-30 2015-09-30 西北核技术研究所 A kind of Low-noise precision bipolar direct current voltage source and production method thereof
CN104410290A (en) * 2014-12-08 2015-03-11 重庆瑜欣平瑞电子有限公司 Frequency converter for digital power generator
JP6439602B6 (en) * 2015-06-12 2019-01-30 Tdk株式会社 Switching power supply
CN112219346A (en) * 2018-04-11 2021-01-12 航天喷气发动机洛克达因股份有限公司 Power converter including a recirculation buffer
TWI659597B (en) * 2018-06-01 2019-05-11 I-Shou University Power supply apparatus
US10608527B2 (en) 2018-06-01 2020-03-31 I-Shou University Power supply apparatus
CN111884518B (en) * 2020-07-31 2021-08-13 广东电网有限责任公司电力科学研究院 DAB control method, device, equipment and storage medium based on capacitance current ripple
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TW200623597A (en) 2006-07-01
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JP2008512082A (en) 2008-04-17
EP1794874A4 (en) 2008-08-20
CN101048931A (en) 2007-10-03

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