Soft switched three phase inverter with staggered resonant recovery system

• US 5,576,943 A
• Filed: 05/22/1995
• Issued: 11/19/1996
• Est. Priority Date: 05/22/1995
• Status: Expired due to Term

• Current Assignee: DRS Power Technology, Inc. (Leonardo S.p.A.), Northrop Grumman Corporation
• Original Assignee: Kaman Electromagnetics Corp. (Kaman Corporation), Newport News Shipbuilding And Dry Dock Company
• Inventors: Keir, Alexander S.
• Primary Examiner(s): Hecker, Stuart N.
• Application Number:
  US08/445,690
• Time in Patent Office: 547 Days
• Field of Search: 363/56, 363/132
• US Class Current: 363/56.05
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: H02M 7/538 in a push-pull configuration H02M7/5375 takes precedence ; with oscillating arrangements H02M7/53832, H02M7/53846
• CPC Class Codes: H03K 17/163 Soft switching
• CPC Class Codes: H03K 17/168 in composite switches
• CPC Class Codes: Y02B 70/10 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

Abstract

A resonant recovery circuit operates to discharge switching energy losses stored in a snubber capacitor associated with each pole of an inverter to return the discharged current to the DC supply by means of an inductor coupled to the resonant recovery switch. In a multiple pole inverter, the snubber capacitors associated with each of the pole'"'"'s switching devices is sequentially discharged during the clock cycle of the switching frequency. A plurality of recovery circuits may be used in a multi-phase inverter.

Claims

1. A resonant recovery circuit for returning semiconductor switching device loss energy from a snubber circuit of a DC to AC inverter to a DC voltage supply potential powering the semiconductor switching device, said recovery circuit comprising:

a recovery circuit per phase signal output of a DC to AC inverter including;

a first controllable semiconductor recovery switch means having a conductive state and non-conductive state;

a second controllable semiconductor recovery switch means having a conductive state and non-conductive state;

a split DC voltage supply means for supplying a positive DC voltage bus and a negative DC voltage bus relative to the positive DC voltage bus;

said first and second recovery switch means being connected in a series circuit arrangement between said positive and negative DC voltage buses, respectively and defining a junction at the connection between said first and second recovery switches;

a capacitor divider circuit means connected between said positive and negative DC voltage buses, respectively, said capacitor divider circuit means further comprising a first and second capacitor in a series circuit arrangement and defining a junction at the connection between said first and second capacitor;

a recovery inductor connected between said recovery switches junction and said capacitors junction;

first and second sets of diode means where each set of diode means is configured to return energy to the DC bus line from a power pole of a DC to AC inverter, the actuation of the power poles being staggered from one another to efficiently recover energy generated by switching losses within each power pole;

each set of diode means per power pole comprising a first recovery diode means coupled between a first snubber capacitor of a first snubber circuit associated with a first semiconductor power pole switching device and said first recovery switch means for discharging said first snubber capacitor through said recovery inductor when said first recovery switch means is made conductive by switch control circuitry which is timed so that a first pulse of current is delivered to the junction of said first and second switching capacitors to be returned to the DC voltage buses during a positive half cycle of the AC output of the inverter;

a second recovery diode means coupled between a second snubber capacitor of a second snubber circuit associated with a second semiconductor power pole switching device and said second recovery switch means for discharging said second snubber capacitor through said recovery inductor when said second recovery switch means is made conductive by switch control circuitry which is timed so that a second pulse of current is delivered to the junction of said first and second capacitors to be returned to the DC voltage buses during a negative half cycle of the AC output of the inverter, said first recovery switch means being conductive when said secondary recovery switch means is non-conductive and said first recovery switch means being non-conductive when said second recovery switch means is conductive.

2. A resonant recovery circuit as defined in claim 1 wherein said first and second switching devices form one pole of an H-shaped bridge and have controllable conduction periods to generate a desired output voltage at a predetermined frequency.

3. A resonant recovery circuit for use in a multi-phase DC-to-AC high power inverter of the type having "M" phase inverters wherein each of said "M" phase inverters has "N" poles each of which poles include at least one controllable power semiconductor switching device and an associated snubber circuit for storing switching loss energy of the semiconductor switching device, said recovery circuit comprising:

a first controllable semiconductor recovery switch means having a conductive state and non-conductive state;

a second controllable semiconductor recovery switch means having a conductive state and non-conductive state;

diode means connected one-for-one with a respective snubber circuit associated with said controllable semiconductor switching device of each of the "N" poles of one phase inverter of the "M" phase inverters, said diode means being connected to said first and second recovery switch means such that a snubber capacitor discharges through its associated diode when one of said first and second recovery switch means is made conductive at the same time that a controllable semiconductor switching device of the corresponding pole of said "N" poles is made conductive, said first recovery switch means being operable to discharge a snubber capacitor of a snubber circuit corresponding to the controllable semiconductor switching device conducting a positive polarity voltage to the output of the inverter and the second recovery switch means being operable to discharge a snubber capacitor of a snubber circuit corresponding to the controllable semiconductor switching device conducting a negative polarity voltage to the inverter output;

a split DC voltage supply means for supplying a DC voltage potential to a positive DC voltage bus and a negative DC voltage bus, respectively;

a capacitor divide circuit means connected between said positive and negative DC voltage buses, respectively, said capacitor divider circuit means further comprising a first and second capacitor in a series circuit arrangement and defining a junction at the connection between said first and second capacitor;

a first inductor coupled to said first and second recovery switches and to said capacitor divider circuit for delivering a pulse of current to said capacitor divider circuit each time one of said snubber capacitors is discharged.

4. A resonant recovery circuit as defined in claim 3 wherein said controllable semiconductor switching devices associated with each of said "N" poles is made conductive sequentially during a conduction period of said first and second recovery switch means.

5. A three phase DC-to-AC power inverter having a resonant recovery circuit comprising:

three DC-to-AC power inverters each producing an output AC voltage phase shifted equally from one another, each of said inverters comprising;

a split DC voltage supply means for supplying a positive DC voltage bus and a negative DC voltage bus;

"N" inverter poles comprising a first and second controllable semiconductor switching devices connected in series between said positive and negative DC voltage buses, said first and second controllable semiconductor switching devices having a common output connection defining a voltage output;

snubber circuit means associated one-for-one with each of said first and second controllable semiconductor switching devices of said "N" poles for storing semiconductor switching loss energy;

a first controllable semiconductor recovery switch means having a conductive state and non-conductive state;

a second controllable semiconductor recovery switch means having a conductive state and non-conductive state;

diode means connected one-for-one with a respective snubber circuit associated with said controllable semiconductor switching device of each of the "N" poles of the inverter, said diode means being connected to said first and second recovery switch means such that a snubber capacitor discharges through its associated diode when one of said first and second recovery switch means is made conductive at the same time that a controllable semiconductor switching device of the corresponding pole of said "N" poles is made conductive, said first recovery switch means being operable to discharge a snubber capacitor of a snubber circuit corresponding to the controllable semiconductor switching device conducting a positive polarity voltage to the output of the inverter and the second recovery switch means being operable to;

discharge a snubber capacitor of a snubber circuit corresponding to the controllable semiconductor switching device conducting a negative polarity voltage to the inverter output, said controllable semiconductor switching devices associated with each of said "N" poles becoming conductive sequentially at predetermined timed intervals during a conduction period of said first and second recovery switch means;

an inductor having one end coupled to said first and second recovery switches;

a capacitor divider circuit means connected between said positive and negative DC voltage buses, respectively, said capacitor divider circuit means further comprising a first and second capacitor in a series circuit arrangement and defining a junction at the connection between said first and second capacitors wherein the opposite end of each of said inverter inductors is connected to said capacitor junction to deliver in a staggered time sequence a pulse of current to said capacitor divider circuit each time one of said snubber capacitors is discharged.

6. A resonant recovery circuit for returning semiconductor switching device loss energy from a snubber circuit to a DC voltage supply potential powering the semiconductor switching device, said recovery circuit comprising:

a split DC voltage supply means for supplying a positive DC voltage bus and a negative DC voltage bus;

a first controllable semiconductor recovery switch means including a first terminal connected to the positive DC voltage bus, and including a second terminal, the first recovery switch having a conductive state and non-conductive state;

a second controllable semiconductor recovery switch means including a first terminal connected to the negative DC voltage bus, and including a second terminal, the second recovery switch having a conductive state and non-conductive state;

a first recovery diode having a cathode connected to the second terminal of the first recovery switch, and having an anode connected to the negative DC voltage bus;

a second recovery diode having an anode connected to the second terminal of the second recovery switch, and having a cathode connected to the positive DC bus;

a first snubber capacitor having first and second terminals, the first terminal connected to the positive DC voltage bus;

a first snubber diode including an anode connected to the second terminal of the first snubber capacitor at a first junction, the first terminal of the first snubber capacitor and the cathode of the first snubber diode to be respectively connected to terminals of a first controllable switching device;

a second snubber capacitor having first and second terminals, the first terminal connected to the negative DC voltage bus;

a first snubber diode including an cathode connected to the second terminal of the second snubber capacitor at a second junction, the first terminal of the second snubber capacitor and the anode of the second snubber diode to be respectively connected to terminals of a second controllable switching device;

the cathode of the first recovery diode connected to the anode of the second recovery diode at an output junction;

a first recovery inductor connected between the first junction and the second terminal of the first recovery switch; and

a second recovery inductor connected between the second junction and the second terminal of the second recovery switch;

during a negative half cycle at the output junction, when the second switching device is turned off by control circuitry, the second snubber capacitor charging through the second snubber diode to the positive DC voltage to maintain a low voltage across the second switching device which is maintained until the next on pulse when the second switching device and the second recovery switch are turned on by control circuitry, the energy stored in the capacitor then being transferred to the second inductor such that when the energy stored in the second snubber capacitor is about equal to the energy transferred to the second inductor, the second recovery switch being turned off to allow the energy originally stored in the second snubber capacitor to be transferred to the DC supply; and

during a positive half cycle at the output junction when the first switching device is turned off by control circuitry, the first snubber capacitor charging through the first snubber diode to the positive DC voltage to maintain a low voltage across the first switching device which is maintained until the next on pulse when the first switching device and the first recovery switch are turned on by control circuitry, the energy stored in the capacitor then being transferred to the first inductor such that when the energy stored in the first snubber capacitor is about equal to the energy transferred to the first inductor, the first recovery switch being turned off to allow the energy originally stored in the first snubber capacitor to be transferred to the DC supply.

7. A staggered resonant recovery circuit for returning semiconductor switching device loss energy from a snubber circuit of an AC to DC inverter to a DC voltage supply potential powering the semiconductor switching device, said circuit comprising:

a DC voltage supply means for supplying a positive DC voltage bus and a negative DC voltage bus relative to the positive DC voltage bus;

a first controllable semiconductor recovery switch means having first and second conductor terminals, the first recovery switch having a conductive state and non-conductive state;

a second controllable semiconductor recovery switch having first and second conductor terminals, the second recovery switch having a conductive state and non-conductive state;

a first recovery diode having a cathode connected to the first terminal of the first recovery switch, and having an anode connected to the negative DC voltage bus;

a second recovery diode having an anode connected to the first terminal of the second recovery switch, and having a cathode connected to the positive DC bus;

a first recovery inductor having a first end connected to the positive DC bus, and having a second end connected to the first terminal of the first recovery switch;

a second recovery inductor having a first end connected to the negative DC bus, and having a second end connected to the first terminal of the second recovery switch;

the first recovery switch, the first recovery diode and the first recovery inductor cooperating to form as first recovery circuit to return energy to the DC bus line during a positive half cycle of the AC output of an AC to DC inverter, the second recovery switch, the second recovery diode and the second recovery inductor cooperating to form a second recovery circuit to return energy to the DC bus line during a negative half cycle of the AC output of an AC to DC inverter;

an inverter phase circuit to communicate with an inverter power pole, the phase circuit including;

a first snubber capacitor having first and second terminals, the first terminal connected to the positive DC voltage bus;

a first snubber diode including an anode connected to the second terminal of the first snubber capacitor at a first power pole junction, the first terminal of the first snubber capacitor and the cathode of the first snubber diode to be respectively connected to terminals of a first controllable power pole switching device;

a second snubber capacitor having first and second terminals, the first terminal connected to the negative DC voltage bus;

a second snubber diode including a anode connected to the second terminal of the second snubber capacitor at a second power pole junction, the first terminal of the second snubber capacitor and the cathode of the second snubber diode to be respectively connected to terminals of a second controllable power pole switching device;

a first connecting diode having a cathode connected to the second terminal of the first recovery switch, and having an anode to be connected to the first power pole junction;

a second connecting diode having an anode connected to the second terminal of the second recovery switch, and having a cathode to be connected to the second power pole junction;

during a negative half cycle at the output junction, when the second switching device is turned off by the control circuitry with the second snubber capacitor charged, the second snubber diode becoming reverse biased and the second connecting diode to become forward biased such that the voltage potential at the second power pole junction falls to minus Vdc relative to the negative DC bus and becomes the input to the recovery circuit, the second recovery switch being turned on by the control circuitry to build up a current in the second recovery inductor flowing from the negative DC bus through the second power pole switch, through the second snubber capacitor, through the second connecting diode, through the second recovery switch and the second recovery inductor to return to the negative DC bus; and

during a positive half cycle at the output junction, the current returning to the positive DC bus in substantially the same way as that during the negative cycle by corresponding components associated with the first power pole.

8. A system including a staggered resonant recovery circuit for returning semiconductor switching device loss energy from a snubber circuit of an AC to DC inverter to a DC voltage supply potential powering the semiconductor switching device, said system comprising:

a DC voltage supply means for supplying a positive DC voltage bus and a negative DC voltage bus relative to the positive DC voltage bus;

a clock and control circuit for controlling the actuation and timing of the resonant recovery circuit and switching devices of the inverter;

a first controllable semiconductor recovery switch means having first and second conductor terminals, the first recovery switch having a conductive state and non-conductive state;

a second controllable semiconductor recovery switch having first and second conductor terminals, the second recovery switch having a conductive state and non-conductive state;

a first recovery diode having a cathode connected to the first terminal of the first recovery switch, and having an anode connected to the negative DC voltage bus;

a second recovery diode having an anode connected to the first terminal of the second recovery switch, and having a cathode connected to the positive DC bus;

a first recovery inductor having a first end connected to the positive DC bus, and having a second end connected to the first terminal of the first recovery switch;

a second recovery inductor having a first end connected to the negative DC bus, and having a second end connected to the first terminal of the second recovery switch;

the first recovery switch, the first recovery diode and the first recovery inductor cooperating to form a first recovery circuit to return energy to the DC bus line during a positive half cycle of the AC output of an AC to DC inverter, the second recovery switch, the second recovery diode and the second recovery inductor cooperating to form a second recovery circuit to return energy to the DC bus line during a negative half cycle of the AC output of an AC to DC inverter;

an inverter phase circuit comprising an inverter power pole, each set of power poles including;

a first snubber capacitor having first and second terminals, the first terminal connected to the positive DC voltage bus;

a first snubber diode including an anode connected to the second terminal of the first snubber capacitor at a first power pole junction, the first terminal of the first snubber capacitor and the cathode of the first snubber diode to be respectively connected to terminals of a first controllable power pole switching device;

a second snubber capacitor having first and second terminals, the first terminal connected to the negative DC voltage bus;

a second snubber diode including a anode connected to the second terminal of the second snubber capacitor at a second power pole junction, the first terminal of the second snubber capacitor and the cathode of the second snubber diode to be respectively connected to terminals of a second controllable power pole switching device;

a first connecting diode having a cathode connected to the second terminal of the first recovery switch, and having an anode to be connected to the first power pole junction;

a second connecting diode having an anode connected to the second terminal of the second recovery switch, and having a cathode to be connected to the second power pole junction;

during a negative half cycle at the output junction, when the second switching device is turned off by the control circuitry with the second snubber capacitor charged, the second snubber diode becoming reverse biased and the second connecting diode to become forward biased such that the voltage potential at the second power pole junction fails to minus Vdc relative to the negative DC bus and becomes the input to the recovery circuit, the second recovery switch being turned on by the control circuitry to build up a current in the second recovery inductor flowing from the negative DC bus through the second power pole switch, through the second snubber capacitor, through the second connecting diode, through the second recovery switch and the second recovery inductor to return to the negative DC bus; and

during a positive half cycle at the output junction, the current returning to the positive DC bus in substantially the same way as that during the negative cycle by corresponding components associated with the first power pole.

9. A system as defined in claim 8, wherein the inverter further comprises:

a second power pole;

a second inverter phase circuit including;

a third snubber capacitor having first and second terminals, the first terminal connected to the positive DC voltage bus;

a third snubber diode including an anode connected to the second terminal of the third snubber capacitor at a third power pole junction, the first terminal of the third snubber capacitor and the cathode of the third snubber diode to be respectively connected to terminals of a third controllable power pole switching device;

a fourth snubber capacitor having first and second terminals, the first terminal connected to the negative DC voltage bus;

a fourth snubber diode including an anode connected to the second terminal of the fourth snubber capacitor at a fourth power pole junction, the first terminal of the fourth snubber capacitor and the cathode of the fourth snubber diode to be respectively connected to terminals of a fourth controllable power pole switching device;

a third connecting diode having a cathode connected to the second terminal of the first recovery switch, and having an anode to be connected to the third power pole junction;

a fourth connecting diode having an anode connected to the second terminal of the second recovery switch, and having a cathode to be connected to the fourth power pole junction, the first and second power poles to be actuated in a staggered sequence relative to one another by the control circuitry.

10. A system as defined in claim 8, wherein the inverter is three-phase, the system further comprising:

a second power pole including third and fourth power pole switching devices for generating the second phase of the inverter;

a second inverter phase circuit associated with the second power pole, comprising;

a third snubber capacitor having first and second terminals, the first terminal connected to the positive DC voltage bus;

a third snubber diode including an anode connected to the second terminal of the third snubber capacitor at a third power pole junction, the first terminal of the third snubber capacitor and the cathode of the third snubber diode to be respectively connected to terminals of the third controllable power poles switching device;

a fourth snubber capacitor having first and second terminals, the first terminal connected to the negative DC voltage bus;

a fourth snubber diode including an anode connected to the second terminal of the fourth snubber capacitor at a fourth power pole junction, the first terminal of the fourth snubber capacitor and the cathode of the fourth snubber diode to be respectively connected to terminals of the fourth controllable power pole switching device;

a third connecting diode having a cathode connected to the second terminal of the first recovery switch, and having an anode to be connected to the third power pole junction;

a fourth connecting diode having an anode connected to the second terminal of the second recovery switch, and having a cathode to be connected to the fourth power pole junction;

a third power pole including fifth and sixth power pole switching devices for generating the third phase of the inverter;

a third inverter phase circuit associated with the third power pole, comprising;

a fifth snubber capacitor having first and second terminals, the first terminal connected to the positive DC voltage bus;

a fifth snubber diode including an anode connected to the second terminal of the fifth snubber capacitor at a fifth power pole junction, the first terminal of the fifth snubber capacitor and the cathode of the fifth snubber diode to be respectively connected to terminals of the fifth controllable power pole switching device;

a sixth snubber capacitor having first and second terminals, the first terminal connected to the negative DC voltage bus;

a sixth snubber diode including an anode connected to the second terminal of the sixth snubber capacitor at a sixth power pole junction, the first terminal of the sixth snubber capacitor and the cathode of the sixth snubber diode to be respectively connected to terminals of the sixth controllable power pole switching device;

a fifth connecting diode having a cathode connected to the second terminal of the first recovery switch, and having an anode to be connected to the fifth power pole junction; and

a sixth connecting diode having an anode connected to the second terminal of the second recovery switch, and having a cathode to be connected to the sixth power pole junction.