AC active clamp for isolated power factor corrector and method of operating the same
First Claim
1. For use with a power factor corrector having a primary switching circuit coupled to a primary winding of an isolation transformer and a rectifier coupled to a secondary winding of said isolation transformer, said primary switching circuit having first and second power switches configured to receive unrectified AC power, an AC active clamp, comprising:
- a switching circuit having first and second clamping switches series coupled in opposition; and
a capacitor coupled to said switching circuit, said switching circuit and said capacitor coupled across at least a portion of said primary winding and configured to mitigate adverse effects of a reverse recovery phenomenon associated with said rectifier and to effect substantially zero voltage switching of said first and second power switches of said primary switching circuit.
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Accused Products
Abstract
An AC active clamp, a method of operating the same and a power factor corrector employing the AC active clamp or the method. The power factor corrector has a primary switching circuit coupled to a primary winding of an isolation transformer and a rectifier coupled to a secondary winding of the isolation transformer. The primary switching circuit has first and second power switches configured to receive unrectified AC power. In one embodiment, the AC active clamp includes a switching circuit having first and second clamping switches series coupled in opposition and a capacitor coupled to the switching circuit. The switching circuit and the capacitor are coupled across at least a portion of the primary winding and are configured to mitigate adverse effects of a reverse recovery phenomenon associated with the rectifier and to effect substantially zero voltage switching of the first and second power switches of the primary switching circuit.
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Citations
21 Claims
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1. For use with a power factor corrector having a primary switching circuit coupled to a primary winding of an isolation transformer and a rectifier coupled to a secondary winding of said isolation transformer, said primary switching circuit having first and second power switches configured to receive unrectified AC power, an AC active clamp, comprising:
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a switching circuit having first and second clamping switches series coupled in opposition; and
a capacitor coupled to said switching circuit, said switching circuit and said capacitor coupled across at least a portion of said primary winding and configured to mitigate adverse effects of a reverse recovery phenomenon associated with said rectifier and to effect substantially zero voltage switching of said first and second power switches of said primary switching circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7)
a first auxiliary diode coupled across said capacitor; and
a second auxiliary diode coupled across said second capacitor.
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5. The AC active clamp as recited in claim 1 wherein said switching circuit further includes third and fourth clamping switches series coupled in opposition, said AC active clamp further comprising a second capacitor coupled to said series-coupled third and fourth clamping switches.
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6. The AC active clamp as recited in claim 1 wherein said power factor corrector employs a magnetically coupled filter.
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7. The AC active clamp as recited in claim 1 wherein said power factor corrector employs topologies selected from the group consisting of:
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boost topologies;
topologies having capacitive coupling between an input and an output of said power factor corrector;
SEPIC topologies;
flyback topologies; and
Zeta topologies.
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8. For use with a power factor corrector having a primary switching circuit coupled to a primary winding of an isolation transformer and a rectifier coupled to a secondary winding of said isolation transformer, said primary switching circuit having first and second power switches configured to receive unrectified AC power, a method of actively clamping energy of said power factor corrector, comprising:
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mitigating adverse effects of a reverse recovery phenomenon associated with said rectifier with an AC active clamp having;
a switching circuit including first and second clamping switches series coupled in opposition, and a capacitor coupled to said switching circuit, said switching circuit and said capacitor coupled across at least a portion of said primary winding; and
effecting, with said AC active clamp, substantially zero voltage switching of said first and second power switches of said primary switching circuit. - View Dependent Claims (9, 10, 11, 12, 13, 14)
boost topologies;
topologies having capacitive coupling between an input and an output of said power factor corrector;
SEPIC topologies;
flyback topologies; and
Zeta topologies.
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15. An isolated power factor corrector having an input and adapted to provide a DC output voltage at an output thereof, comprising:
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an isolation transformer having a primary winding and a secondary winding;
a primary switching circuit, interposed between said input and said primary winding, including first and second power switches configured to receive unrectified AC power;
a rectifier, interposed between said secondary winding and said output, configured to rectify a waveform from said isolation transformer to develop said DC output voltage; and
an AC active clamp, coupled to said primary switching circuit, comprising;
a switching circuit having first and second clamping switches series coupled in opposition; and
a capacitor coupled to said switching circuit, said switching circuit and said capacitor coupled across at least a portion of said primary winding and configured to mitigate adverse effects of a reverse recovery phenomenon associated with said rectifier and to effect substantially zero voltage switching of said first and second power switches of said primary switching circuit. - View Dependent Claims (16, 17, 18, 19, 20, 21)
boost topologies;
topologies having capacitive coupling between said input and said output;
SEPIC topologies;
flyback topologies; and
Zeta topologies.
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Specification