×

AC/DC flyback converter with improved power factor and reduced switching loss

  • US 5,991,172 A
  • Filed: 03/02/1998
  • Issued: 11/23/1999
  • Est. Priority Date: 06/21/1996
  • Status: Expired due to Term
First Claim
Patent Images

1. A single-stage single-switch flyback converter with input current shaping and output voltage regulation, comprising in combination:

  • rectified ac voltage means;

    an energy-storage inductor having a first terminal and a second terminal, said first terminal connected to said rectified ac voltage means;

    an energy-storage capacitor;

    a switch which is periodically closed and opened;

    an isolation transformer having a primary winding and a secondary winding, said primary winding connected in series with said switch across said energy-storage capacitor;

    a first rectifier means having a first terminal and a second terminal, said first terminal connected to said second terminal of said energy-storage inductor and said second terminal connected to the primary winding of said isolation transformer;

    an output-filter capacitor;

    a load connected across the output-filter capacitor;

    a second rectifier means connecting said secondary winding of said isolation transformer to said output-filter capacitor;

    control means for periodically closing said switch to couple said primary winding to said energy storage capacitor, wherein said control means includes a first sensing means to detect the onset of the discontinuous-current mode operation of said isolation transformer and a delay means for closing said switch at a predetermined instant after said first sensing means detects the onset of the discontinuous current mode operation of said isolation transformer in order to turn-on said switch when the voltage across said switch is substantially at a minimum value;

    said control means for periodically opening said switch to decouple said primary winding from said energy storage capacitor including a second sensing means to sense the current across said switch to turn off said switch when the current across said switch reaches a predetermined level.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×