Clipper circuit for power transistor circuit and inverter circuit utilizing the same

Claim 2

A clipper circuit for a power transistor circuit including a power transistor comprising: a first clipper circuit, adapted to absorb high dv/dt surge voltage, connected in parallel to a collector-emitter circuit of said power transistor and including a capacitor and a first diode; and a second clipper circuit, adapted to absorb surge energy generated by wiring inductance upon turning OFF of said power transistor, including a second diode connected to said capacitor in parallel to a discharge resistor wherein said second diode is connected to a junction between said capacitor and said first diode so that current flowing through said capacitor is shunted into a first shunted current flowing through said first diode and a second shunted current flowing through said second diode.

Claim 3

A clipper circuit as set forth in claim 1, wherein said second clipper circuit has greater inductance than said first clipper circuit.

Claim 4

A clipper circuit as set forth in claim 1, wherein said first and second clipper circuits are active for absorbing surges generated upon turning OFF of said power transistor and for reducing said first and second shunted currents flowing through said first and second diodes according to increasing voltage in said capacitor, and said first and second clipper circuits cause said first and second shunted currents to be decreased to zero at mutually different timings.

Claim 5

A clipper circuit as set forth in claim 3, wherein said second clipper circuit maintains said second shunted current after termination of said first shunted current flowing through said first diode.

Claim 6

A power transistor circuit comprising: a power transistor connected to a power source and switching between a first state for establishing a collector-emitter circuit and a second state for blocking said collector-emitter circuit for supplying drive power to a load connected thereto; and a clipper circuit for absorbing surge energy to be generated upon switching of said power transistor from said first state to said second state, said clipper circuit including a first clipper circuit connected in parallel to said collector-emitter circuit of said power transistor and including a capacitor and a first diode; and a second clipper circuit including a second diode connected to said capacitor in parallel to a discharge resistor; wherein said first clipper circuit is adapted to absorb high dv/dt surge voltage and said second clipper circuit is adapted to absorb surge energy generated by wiring inductance, upon switching of said power transistor from said first state to said second state and wherein said second diode of said second clipper circuit is connected to a junction between said capacitor and said first diode so that current flowing through said capacitor is shunted into a first shunted current flowing through said first diode and a second shunted current flowing through said second diode.

Claim 7

A power transistor circuit comprising: a power transistor connected to a power source and switching between a first state for establishing a collector-emitter circuit and a second state for blocking said collector-emitter circuit for supplying drive power to a load connected thereto; and a clipper circuit for absorbing surge energy to be generated upon switching of said power transistor from said first state to said second state, said clipper circuit including a first clipper circuit connected in parallel to said collector-emitter circuit of said power transistor and including a capacitor and a first diode; and a second clipper circuit including a second diode connected to said capacitor in parallel to a discharge resistor; wherein said first clipper circuit is adapted to absorb high dv/dt surge voltage and said second clipper circuit is adapted to absorb surge energy generated by wiring inductance, upon switching of said power transistor from said first state to said second state and wherein said second diode of said second clipper circuit is connected to a junction between said capacitor and said first diode so that current flowing through said capacitor is shunted into a first shunted current flowing through said first diode and a second shunted current flowing through said second diode.

Claim 8

A power transistor circuit as set forth in claim 5, wherein said second clipper circuit is provided greater inductance than said first clipper circuit.

Claim 9

A power transistor circuit as set forth in claim 5, wherein said first and second clipper circuits are active for absorbing surges generated upon switching of said power transistor from said first state to said second state and for reducing said first and second shunted currents through said first and second diodes according to the increase of charge voltage in said capacitor, and said first and second clipper circuits cause said first and second shunted currents to be decreased to zero at different times.

Claim 10

A power transistor circuit as set forth in claim 7, wherein said second clipper circuit maintains said second shunted current after termination of said first shunted current flowing through said first diode.

Claim 11

A power transistor circuit as set forth in claim 5, which further comprises an auxiliary capacitor connected in parallel to said first diode.

Claim 12

A power transistor circuit as set forth in claim 9, wherein said auxiliary capacitor has smaller capacity than said capacitor in said first clipper circuit.

Claim 13

An inverter circuit connected to a direct current source via a smoothing circuit including a smoothing capacitor; comprising: a plurality of power transistor circuits connected to a load for supplying an alternating current to the latter, each of said power transistor circuits including a power transistor switching between a first state for establishing a collector-emitter circuit and a second state for blocking said collector-emitter circuit; and a clipper circuit for absorbing surge energy generated upon switching of said power transistor from said first state to said second state, said clipper circuit including a first clipper circuit, adapted to absorb high dv/dt surge voltage, connected in parallel to said collector-emitter circuit of said power transistor and comprising a capacitor and a first diode, and a second clipper circuit adapted to absorb surge energy generated by wiring inductance, upon switching of said power transistor from said first state to said second state including a second diode connected to said capacitor in parallel to a discharge resistor wherein said second diode of said second clipper circuit is connected to a junction between said capacitor and said first diode so that current flowing through said capacitor is shunted into a first shunted current flowing through said first diode and a second shunted current flowing through said second diode.

Claim 14

An inverter circuit connected to a direct current source via a smoothing circuit including a smoothing capacitor; comprising: a plurality of power transistor circuits connected to a load for supplying an alternating current to the latter, each of said power transistor circuits including a power transistor switching between a first state for establishing a collector-emitter circuit and a second state for blocking said collector-emitter circuit; and a clipper circuit for absorbing surge energy generated upon switching of said power transistor from said first state to said second state, said clipper circuit including a first clipper circuit, adapted to absorb high dv/dt surge voltage, connected in parallel to said collector-emitter circuit of said power transistor and comprising a capacitor and a first diode, and a second clipper circuit adapted to absorb surge energy generated by wiring inductance, upon switching of said power transistor from said first state to said second state including a second diode connected to said capacitor in parallel to a discharge resistor wherein said second diode of said second clipper circuit is connected to a junction between said capacitor and said first diode so that current flowing through said capacitor is shunted into a first shunted current flowing through said first diode and a second shunted current flowing through said second diode.

Claim 15

An inverter circuit as set forth in claim 11, wherein said second clipper circuit is provided greater inductance than said first clipper circuit.

Claim 16

An inverter circuit as set forth in claim 11, wherein said first and second clipper circuits are active for absorbing surges generated upon switching of said power transistor from said first state to said second state and for reducing said first and second shunted currents flowing through said first and second diodes according to increasing voltage in said capacitor, and said first and second clipper circuits said first and second shunted currents to be decreased to zero at mutually different timings.

Claim 17

An inverter circuit as set forth in claim 13, wherein second clipper circuit maintains said second shunted current after termination of said first shunted current flowing through said first diode.

Claim 18

A power transistor circuit comprising: a power transistor connected to a power source and switching between a first state for establishing a collector-emitter circuit and second state for blocking said collector-emitter circuit for supplying drive power to a load connected thereto; and a clipper circuit for absorbing surge energy to be generated upon switching of said power transistor from said first state to said second state, said clipper circuit including a first clipper circuit connected in parallel to said collector-emitter circuit of said power transistor and including a capacitor, and a first diode and an auxiliary capacitor connected in parallel to said first diode; and a second clipper circuit including a second diode connected to said capacitor in parallel to a discharge resistor and wherein said second diode of said second clipper circuit is connected to a junction between said capacitor and said first diode so that current flowing through said capacitor is shunted into a first shunted current flowing through said first diode and a second shunted current flowing through said second diode.

Claim 19

A power transistor circuit comprising: a power transistor connected to a power source and switching between a first state for establishing a collector-emitter circuit and second state for blocking said collector-emitter circuit for supplying drive power to a load connected thereto; and a clipper circuit for absorbing surge energy to be generated upon switching of said power transistor from said first state to said second state, said clipper circuit including a first clipper circuit connected in parallel to said collector-emitter circuit of said power transistor and including a capacitor, and a first diode and an auxiliary capacitor connected in parallel to said first diode; and a second clipper circuit including a second diode connected to said capacitor in parallel to a discharge resistor and wherein said second diode of said second clipper circuit is connected to a junction between said capacitor and said first diode so that current flowing through said capacitor is shunted into a first shunted current flowing through said first diode and a second shunted current flowing through said second diode.

Claim 20

A power transistor circuit comprising: a power transistor connected to a power source and switching between a first state for establishing a collector-emitter circuit and second state for blocking said collector-emitter circuit for supplying drive power to a load connected thereto; and a clipper circuit for absorbing surge energy to be generated upon switching of said power transistor from said first state to said second state, said clipper circuit including a first clipper circuit connected in parallel to said collector-emitter circuit of said power transistor and including a capacitor and a first diode; and a second clipper circuit including a second diode connected to said capacitor in parallel to a discharge resistor; wherein said first and second clipper circuits are mounted on a printed circuit board connected to collector and emitter electrode terminals of said power transistor formed on a substrate via connecting screws, and wherein said printed circuit board is placed in spaced apart relationship from said substrate.

Claim 21

A power transistor circuit comprising: a power transistor connected to a power source and switching between a first state for establishing a collector-emitter circuit and second state for blocking said collector-emitter circuit for supplying drive power to a load connected thereto; and a clipper circuit for absorbing surge energy to be generated upon switching of said power transistor from said first state to said second state, said clipper circuit including a first clipper circuit connected in parallel to said collector-emitter circuit of said power transistor and including a capacitor and a first diode; and a second clipper circuit including a second diode connected to said capacitor in parallel to a discharge resistor; wherein said first and second clipper circuits are mounted on a printed circuit board connected to collector and emitter electrode terminals of said power transistor formed on a substrate via connecting screws, and wherein said printed circuit board is placed in spaced apart relationship from said substrate.