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FORCED ZERO VOLTAGE SWITCHING FLYBACK CONVERTER

  • US 20180115252A1
  • Filed: 10/25/2016
  • Published: 04/26/2018
  • Est. Priority Date: 10/25/2016
  • Status: Active Grant
First Claim
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1. A method of operating a flyback converter, the flyback converter comprising a transformer having a primary winding receiving an input voltage and a secondary winding providing an output voltage, a primary switch coupled to the primary winding and a synchronous rectifier coupled to the secondary winding, the method comprising:

  • turning on the primary switch at a start of a switching cycle for a first time duration;

    in response to the primary switch being turned off, turning on the synchronous rectifier for a first on-duration;

    sensing a secondary current flowing in the secondary winding;

    in response to the secondary current reaching a zero current value, turning off the synchronous rectifier;

    monitoring the output voltage in a discontinuous conduction mode;

    in response to the output voltage being less than a reference voltage, turning on the synchronous rectifier for a second on-duration;

    sensing the secondary current flowing in the secondary winding during the second on-duration, the secondary current including a current ripple having a negative current excursion and a positive current excursion; and

    in response to the secondary current having a non-zero positive current value during the second on-duration, turning off the synchronous rectifier.

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