Energy efficient voltage snubber circuit

Claim 2

A snubber circuit for use in a power converting circuit including an input for coupling to a source of power and an output for coupling to a load to which converted power is to be delivered, the power converting circuit further including at least one power semiconductor switching device coupled between the input and the output of the converting circuit, said switching device being turned on and off to selectively conduct current through the power converting circuit, said snubber circuit comprising: capacitance means, coupled across the switching device, for charging with current bypassing the switching device when the switching device is turned off; a voltage transformer having a primary winding and a secondary winding, said primary winding being coupled in series with said capacitance means to conduct a flow of current discharged by said capacitance means when the switching device is turned on; inductance means, coupled in series with said secondary winding of said transformer, for forming a resonant circuit with said capacitance means to regulate the flow of discharge current from said capacitance means; and circuit means, coupled to the power converting circuit input and said inductance means, for conducting the current flowing through said inductance means and said secondary winding of said snubber circuit, and returning energy stored in said capacitance means to the power source; so that energy stored in said capacitance means is transferred to the power source through said transformer and said inductance means at a rate determined by said resonant circuit when the switching device is turned on.

Claim 3

The snubber circuit of claim 1 further including first rectifying means, coupled across the primary winding of said transformer, for constraining to a single direction the flow of discharge current from said capacitance means through said primary winding.

Claim 4

The snubber circuit of claim 2 further including second rectifying means coupled in series with said inductance means and said secondary winding, for constraining to a single direction the flow of discharge current through said inductance means.

Claim 5

The snubber circuit of claim 3 wherein the power converting circuit includes third rectifying means, coupled across the switching device, for providing a path for load current to flow from the load to the source to bypass the switching device.

Claim 6

The snubber circuit of claim 1 further including rectifying means, coupled in series with said inductance means and said secondary winding, for constraining to a single direction the flow of discharge current through said inductance means.

Claim 7

The snubber circuit of claim 1 further including means, coupled in series with said primary winding, for increasing a rate of depleting energy stored in said primary winding after said capacitance means has been discharged.

Claim 8

The snubber circuit of claim 6 wherein said rate increasing means includes a capacitor.

Claim 9

The snubber circuit of claim 3 further including means, coupled in series with said primary winding, for increasing a rate of depleting energy stored in said primary winding after said capacitance means has been discharged.

Claim 10

The snubber circuit of claim 8 wherein said rate increasing means includes a capacitor.

Claim 11

A snubber circuit for use in a power converting circuit including an input for coupling to a source of power and an output for coupling to a load to which converted power is to be delivered, the power converting circuit further including at least one power semiconductor switching device having a first terminal coupled to the input of the converting circuit and a second terminal coupled to the output of the converting circuit, said switching device being turned on and off to selectively conduct current through the power converting circuit, said snubber circuit comprising: a capacitor for charging with current bypassing the switching device when the switching device is turned off; a voltage transformer having a primary winding and a secondary winding; said capacitor coupled in series combination with said transformer primary winding, said series combination being coupled across said first and second terminals of said switching device, so that said primary winding conducts a flow of current discharged from said capacitor when the switching device is turned on; an inductor, coupled in series with said secondary winding of said transformer, for forming a resonant circuit with said capacitor to regulate the flow of discharge current from said capacitor when the switching device is turned on; and circuit means, coupled to the power converting circuit input and said inductor, for conducting the current flowing through said inductor and said secondary winding of said snubber circuit, and returning energy stored in said capacitor to the power source; so that energy stored in said capacitor is transferred to the power source through said transformer and said inductor at a rate determined by said resonant circuit when the switching device is turned on.

Claim 12

A snubber circuit for use in a power converting circuit including an input for coupling to a source of power and an output for coupling to a load to which converted power is to be delivered, the power converting circuit further including at least one power semiconductor switching device having a first terminal coupled to the input of the converting circuit and a second terminal coupled to the output of the converting circuit, said switching device being turned on and off to selectively conduct current through the power converting circuit, said snubber circuit comprising: a capacitor for charging with current bypassing the switching device when the switching device is turned off; a voltage transformer having a primary winding and a secondary winding; said capacitor coupled in series combination with said transformer primary winding, said series combination being coupled across said first and second terminals of said switching device, so that said primary winding conducts a flow of current discharged from said capacitor when the switching device is turned on; an inductor, coupled in series with said secondary winding of said transformer, for forming a resonant circuit with said capacitor to regulate the flow of discharge current from said capacitor when the switching device is turned on; and circuit means, coupled to the power converting circuit input and said inductor, for conducting the current flowing through said inductor and said secondary winding of said snubber circuit, and returning energy stored in said capacitor to the power source; so that energy stored in said capacitor is transferred to the power source through said transformer and said inductor at a rate determined by said resonant circuit when the switching device is turned on.

Claim 13

The snubber circuit of claim 10 wherein a first terminal of said capacitor is coupled to said first terminal of the switching device and a second terminal of said capacitor is coupled to a first terminal of said primary winding of said transformer; said snubber circuit further including: a first diode having an anode coupled to the second terminal of said capacitor; and a second diode having an anode coupled to a cathode of said first diode and to the second terminal of the switching device, a cathode of said second diode being coupled to a second terminal of said primary winding of said transformer; so that said first and second diodes constrain to a single direction the flow of discharge current through said primary winding.

Claim 14

The snubber circuit of claim 11 further including a third diode, coupled in series with said inductor and said secondary winding, for constraining to a single direction the flow of discharge current through said inductor.

Claim 15

The snubber circuit of claim 12 wherein the power converting circuit includes a fourth diode, coupled across the switching device, for providing a path for load current to flow from the load to the source to bypass the switching device.

Claim 16

The snubber circuit of claim 10 further including a diode, coupled in series with said inductor and said secondary winding, for constraining to a single direction the flow of discharge current through said inductor.

Claim 17

The snubber circuit of claim 10 further including means, coupled in series with said primary winding, for increasing a rate of depleting energy stored in said primary winding after said capacitor has been discharged.

Claim 18

The snubber circuit of claim 15 wherein said capacitor is a first capacitor; and said rate increasing means includes a second capacitor.

Claim 19

The snubber circuit of claim 12 further including means, coupled in series with said primary winding, for increasing a rate of depleting energy stored in said primary winding after said capacitor has been discharged.

Claim 20

The snubber circuit of claim 17 wherein said capacitor is a first capacitor; and said rate increasing means includes a second capacitor.

Claim 21

The snubber circuit of claim 10 wherein a first terminal of said capacitor is coupled to the second terminal of the switching device; said snubber circuit further including: a first diode having a cathode coupled to a second terminal of said capacitor and an anode coupled to both the first terminal of the switching device and a first terminal of said primary winding; a second diode having an anode coupled to both said second terminal of said capacitor and said anode of said first diode, a cathode of said second diode being coupled to a second terminal of said primary winding; and so that said first and second diodes constrain to a single direction the flow of discharge current through said primary winding.

Claim 22

The snubber circuit of claim 19 further including a third diode, coupled in series with said inductor and said secondary winding, for constraining to a single direction the flow of discharge current through said inductor.

Claim 23

The snubber circuit of claim 20 wherein the power converting circuit includes a fourth diode, coupled across the switching device, for providing a path for load current to flow from the load to the source to bypass the switching device.

Claim 24

The snubber circuit of claim 20 further including means, coupled in series with said primary winding, for increasing a rate of depleting energy stored in said primary winding after said capacitor has been discharged.

Claim 25

The snubber circuit of claim 22 wherein said capacitor is a first capacitor; and said rate increasing means includes a second capacitor.

Claim 26

A power converting circuit, comprising: an input for coupling to a source of power; an output for coupling to a load to which converted power is to be delivered; at least one power semiconductor switching device coupled between said input and said output of said power converting circuit, said switching device being turned on and off to selectively conduct current through the power converting circuit; and snubber means, coupled to said switching device, for limiting a voltage change rate across said switching device when said switching device is turned off; said snubber means comprising: capacitance means, coupled across said switching device, for charging with current bypassing said switching device when said switching device is turned off; a voltage transformer having a primary winding and a secondary winding, said primary winding being coupled in series with said capacitance means to conduct a flow of current discharged by said capacitance means when said switching device is turned on; inductance means, coupled in series with said secondary winding of said transformer, for forming a resonant circuit with said capacitance means to regulate the flow of discharge current from said capacitance means; and circuit means, coupled to the power converting circuit input and said inductance means for conducting the current flowing through said inductance means and said secondary winding of said snubber circuit, and returning energy stored in said capacitance means to the power source.

Claim 27

A power converting circuit, comprising: an input for coupling to a source of power; an output for coupling to a load to which converted power is to be delivered; at least one power semiconductor switching device coupled between said input and said output of said power converting circuit, said switching device being turned on and off to selectively conduct current through the power converting circuit; and snubber means, coupled to said switching device, for limiting a voltage change rate across said switching device when said switching device is turned off; said snubber means comprising: capacitance means, coupled across said switching device, for charging with current bypassing said switching device when said switching device is turned off; a voltage transformer having a primary winding and a secondary winding, said primary winding being coupled in series with said capacitance means to conduct a flow of current discharged by said capacitance means when said switching device is turned on; inductance means, coupled in series with said secondary winding of said transformer, for forming a resonant circuit with said capacitance means to regulate the flow of discharge current from said capacitance means; and circuit means, coupled to the power converting circuit input and said inductance means for conducting the current flowing through said inductance means and said secondary winding of said snubber circuit, and returning energy stored in said capacitance means to the power source.

Claim 28

The power converting circuit of claim 24, said snubber means further including first rectifying means, coupled across said primary winding of said transformer, for constraining to a single direction the flow of discharge current from said capacitance means through said primary winding.

Claim 29

The power converting circuit of claim 25, said snubber means further including second rectifying means, coupled in series with said inductance means and said secondary winding, for constraining to a single direction the flow of discharge current through said inductance means.

Claim 30

The power converting circuit of claim 26 further including third rectifying means, coupled across said switching device, for providing a path for load current to flow from the load to the source to bypass said switching device.

Claim 31

The power converting circuit of claim 24, said snubber means further including rectifying means, coupled in series with said inductance means and said secondary winding, for constraining to a single direction the flow of discharge current through said inductance means.

Claim 32

The power converting circuit of claim 24, said snubber means further including means, coupled in series with said primary winding, for increasing a rate of depleting energy stored in said primary winding after said capacitance means has been discharged.

Claim 33

The power converting circuit of claim 29 wherein said rate increasing means includes a capacitor.

Claim 34

The power converting circuit of claim 26, said snubber means further including means, coupled in series with said primary winding, for increasing a rate of depleting energy stored in said primary winding after said capacitance means has been discharged.

Claim 35

The power converting circuit of claim 31 wherein said rate increasing means includes a capacitor.

Claim 36

A three-phase AC-to-AC power converting circuit, comprising: rectifier circuit means, having an input for coupling to a three-phase AC voltage source, for rectifying the three-phase voltage of the AC source and providing a DC output voltage; filter circuit means, coupled to receive the DC output voltage of said rectifier circuit means, for filtering the DC output voltage and providing on a filter output a filtered DC output voltage, said filter circuit means including at least one filter capacitor; three-phase inverter circuit means, coupled to receive the filtered DC output voltage, for providing a three-phase AC output voltage on a three-phase AC output; said inverter circuit means including three inverter pole circuits having respective inverter pole outputs that together form the three-phase AC output; each said inverter pole circuit including at least one power semiconductor switching device coupled between the filter output and the inverter pole output, said switching devices of said respective inverter pole circuits being selectively turned on and off to convert the filtered DC output voltage to said three-phase Ac output, and snubber means, coupled to said switching device, for limiting a voltage change rate across said switching device when said switching device is turned off; said snubber means comprising capacitance means, coupled across said switching device, for charging with current bypassing said switching device when said switching device is turned off; a voltage transformer having a primary winding and a secondary winding, said primary winding being coupled in series with said capacitance means to conduct a flow of current discharged by said capacitance means when said switching device is turned on; inductance means, coupled in series with said secondary winding of said transformer, for forming a resonant circuit with said capacitance means to regulate the flow of discharge current from said capacitance means; and circuit means for conducting current flowing through said inductance means and said secondary winding of said snubber means to said filter capacitor; so that energy stored in said capacitance means is transferred to said filter capacitor through said transformer and said inductance means at a rate determined by said resonant circuit when said switching device is turned on.

Claim 37

A three-phase AC-to-AC power converting circuit, comprising: rectifier circuit means, having an input for coupling to a three-phase AC voltage source, for rectifying the three-phase voltage of the AC source and providing a DC output voltage; filter circuit means, coupled to receive the DC output voltage of said rectifier circuit means, for filtering the DC output voltage and providing on a filter output a filtered DC output voltage, said filter circuit means including at least one filter capacitor; three-phase inverter circuit means, coupled to receive the filtered DC output voltage, for providing a three-phase AC output voltage on a three-phase AC output; said inverter circuit means including three inverter pole circuits having respective inverter pole outputs that together form the three-phase AC output; each said inverter pole circuit including at least one power semiconductor switching device coupled between the filter output and the inverter pole output, said switching devices of said respective inverter pole circuits being selectively turned on and off to convert the filtered DC output voltage to said three-phase Ac output, and snubber means, coupled to said switching device, for limiting a voltage change rate across said switching device when said switching device is turned off; said snubber means comprising capacitance means, coupled across said switching device, for charging with current bypassing said switching device when said switching device is turned off; a voltage transformer having a primary winding and a secondary winding, said primary winding being coupled in series with said capacitance means to conduct a flow of current discharged by said capacitance means when said switching device is turned on; inductance means, coupled in series with said secondary winding of said transformer, for forming a resonant circuit with said capacitance means to regulate the flow of discharge current from said capacitance means; and circuit means for conducting current flowing through said inductance means and said secondary winding of said snubber means to said filter capacitor; so that energy stored in said capacitance means is transferred to said filter capacitor through said transformer and said inductance means at a rate determined by said resonant circuit when said switching device is turned on.

Claim 38

The power converting circuit of claim 33 further including first rectifying means, coupled across said switching device, for providing a path for load current to flow from the load to the source to bypass said switching device; said snubber means further including: second rectifying means, coupled across said primary winding of said transformer, for constraining to a single direction the flow of discharge current from said capacitance means through said primary winding; and third rectifying means, coupled in series with said inductance means and said secondary winding, for constraining to a single direction the flow of discharge current through said inductance means.