Auxiliary active clamp circuit, a method of clamping a voltage of a rectifier switch and a power converter employing the circuit or method
First Claim
1. For use with a power converter having a main active clamp circuit associated with a main power switch coupled to a primary winding of a transformer and a rectifier switch coupled to a secondary winding of said transformer, said main power switch configured to conduct during a main conduction period of said power converter and said rectifier switch configured to conduct during an auxiliary conduction period of said power converter, an auxiliary active clamp circuit, comprising:
- an auxiliary clamp capacitor, coupled across said rectifier switch, configured to store a clamping voltage substantially equal to an off-state voltage of said rectifier switch; and
an auxiliary clamp switch, coupled in series with said auxiliary clamp capacitor, configured to receive a drive signal from another secondary winding and conduct during said main conduction period thereby clamping a voltage across said rectifier switch at about said clamping voltage.
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Accused Products
Abstract
The present invention is directed to an auxiliary active clamp circuit and a method of clamping a voltage of a rectifier switch associated with a power converter. The power converter includes a main active clamp circuit associated with a main power switch coupled to a primary winding of a transformer and a rectifier switch coupled to a secondary winding of the transformer. The main power switch conducts during a main conduction period of the power converter and the rectifier switch conducts during an auxiliary conduction period of the power converter. In one embodiment, the auxiliary active clamp circuit includes an auxiliary clamp capacitor, coupled across the rectifier switch, that stores a clamping voltage substantially equal to an off-state voltage of the rectifier switch. The auxiliary active clamp circuit also includes an auxiliary clamp switch, coupled in series with the auxiliary clamp capacitor, that receives a drive signal from a secondary winding and conducts during the main conduction period thereby clamping a voltage across the rectifier switch at about the clamping voltage.
78 Citations
20 Claims
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1. For use with a power converter having a main active clamp circuit associated with a main power switch coupled to a primary winding of a transformer and a rectifier switch coupled to a secondary winding of said transformer, said main power switch configured to conduct during a main conduction period of said power converter and said rectifier switch configured to conduct during an auxiliary conduction period of said power converter, an auxiliary active clamp circuit, comprising:
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an auxiliary clamp capacitor, coupled across said rectifier switch, configured to store a clamping voltage substantially equal to an off-state voltage of said rectifier switch; and
an auxiliary clamp switch, coupled in series with said auxiliary clamp capacitor, configured to receive a drive signal from another secondary winding and conduct during said main conduction period thereby clamping a voltage across said rectifier switch at about said clamping voltage. - View Dependent Claims (2, 3, 4, 5, 6)
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7. For use with a power converter having a main active clamp circuit associated with a main power switch coupled to a primary winding of a transformer and a rectifier switch coupled to a secondary winding of said transformer, said main power switch configured to conduct during a main conduction period of said power converter and said rectifier switch configured to conduct during an auxiliary conduction period of said power converter, a method of clamping a voltage of said rectifier switch, comprising:
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storing a clamping voltage substantially equal to an off-state voltage of said rectifier switch;
providing a drive signal from another secondary winding to an auxiliary clamp switch;
causing said auxiliary clamp switch to conduct during said main conduction period; and
clamping a voltage across said rectifier switch at about said clamping voltage. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A power converter, comprising:
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a main power switch coupled to an input of said power converter;
a main active clamp circuit associated with said main power switch that conducts during a main conduction period of said power converter;
a transformer having a primary winding coupled to said main power switch;
a rectifier coupled to a secondary winding of said transformer and including a rectifier switch that conducts during an auxiliary conduction period of said power converter; and
an auxiliary active clamp circuit, including;
an auxiliary clamp capacitor, coupled across said rectifier switch, that stores a clamping voltage substantially equal to an off-state voltage of said rectifier switch, and an auxiliary clamp switch, coupled in series with said auxiliary clamp capacitor, that receives a drive signal from another a secondary winding and conducts during said main conduction period thereby clamping a voltage across said rectifier switch at about said clamping voltage. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification