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Method to control a minimum pulsewidth in a switch mode power supply

  • US 9,318,965 B2
  • Filed: 03/05/2013
  • Issued: 04/19/2016
  • Est. Priority Date: 10/10/2012
  • Status: Active Grant
First Claim
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1. A method of controlling a switching mode power converter, the method comprising:

  • configuring a switching mode power converter comprising a transformer having a primary winding coupled to an input supply voltage and a secondary winding, a switch coupled in series to the primary winding, a controller coupled to the switch, and a primary side auxiliary winding electrically coupled to the controller and magnetically coupled to the secondary winding;

    determining a minimum voltage across the secondary winding to enable energy transfer from a primary side of the transformer to a secondary side;

    turning ON the switch;

    comparing a voltage across the auxiliary winding to a threshold voltage while the switch is ON, wherein the threshold voltage is proportional to the minimum voltage; and

    turning OFF the switch once the voltage across the auxiliary winding reaches the threshold voltage, wherein a time period between turning ON the switch and turning OFF the switch is a minimum pulse width of the switch corresponding to a minimum energy necessary to enable the energy transfer from the primary side to the secondary side.

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