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System and method providing over current protection based on duty cycle information for power converter

  • US 10,615,684 B2
  • Filed: 06/14/2018
  • Issued: 04/07/2020
  • Est. Priority Date: 12/08/2010
  • Status: Active Grant
First Claim
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1. A system for protecting a power converter, the system comprising:

  • a threshold signal generator configured to generate a threshold signal; and

    a drive signal generator coupled to the threshold signal generator and configured to receive at least a comparison signal, generate a drive signal based at least in part on the comparison signal, and output the drive signal to a switch in order to affect a primary current flowing through a primary winding of the power converter, the comparison signal being associated with the threshold signal, the drive signal being associated with one or more first switching periods and a second switching period following the one or more first switching periods, the one or more first switching periods corresponding to one or more first duty cycles, the second switching period including an on-time period and an off-time period;

    wherein the threshold signal generator is further configured to, for the second switching period,determine a first threshold signal value based at least in part on the one or more first duty cycles;

    set a time to zero at a beginning of the on-time period;

    if the time satisfies one or more first predetermined conditions, generate the threshold signal equal to the determined first threshold signal value so that the threshold signal is constant in magnitude as a function of the time; and

    if the time satisfies one or more second predetermined conditions, generate the threshold signal so that the threshold signal decreases with the increasing time in magnitude.

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