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Variable frequency, zero voltage switching, quasi-resonant converters with resonant bridge switch

  • US 5,532,919 A
  • Filed: 03/30/1993
  • Issued: 07/02/1996
  • Est. Priority Date: 03/30/1993
  • Status: Expired due to Term
First Claim
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1. A variable frequency controlled, zero-voltage switched, quasi-resonant converter for receiving power from a DC power source and providing power to a DC load, said converter comprising:

  • switching bridge means for connecting and disconnecting said power from said DC power source to and from said DC load, said switching bridge comprising;

    (a) a resonant inductor having a first end operatively connected to a first node and a second end operatively connected to a second node;

    (b) a first diode having an anode operatively connected to said first node and a cathode operatively connected to a third node;

    (c) a second diode having an anode operatively connected to said second node and a cathode operatively connected to said third node;

    (d) a third diode having an anode operatively connected to a fourth node and a cathode operatively connected to said second node;

    (e) a fourth diode having an anode operatively connected to said fourth node and a cathode operatively connected to said first node;

    (f) first and second active switch means for connecting and disconnecting said DC power source to and from said DC load, said first active switch means operatively connected across said third diode, said second switch means operatively connected across said fourth diode;

    (g) a first resonant capacitor;

    (h) a second resonant capacitor;

    wherein said first resonant capacitor is operatively connected to said first node such that any voltage change across said first resonant capacitor necessitates a substantially equal voltage change across said fourth diode as represented by ##EQU6## and wherein said second capacitor is operatively connected to said second node such that any voltage change across said second resonant capacitor necessitates a substantially equal voltage change across said third diode as represented by ##EQU7## such that any voltage change across said fourth diode necessitates a substantially equal and opposite voltage change across said first diode;

    at least one filtering inductor having first and second ends, said first end operatively connected to said first node, said second end operatively connected to said DC power source;

    at least one filtering capacitor operatively connected in parallel with said switching bridge;

    a timing means for controlling the turning on and turning off of said first active switch means and said second active switch means such that the turn-on and turn-off of said first active switch means is delayed by an amount equal to the switching period Ts relative to the turn-on and turn-off of said second active switch means, and such that said first active switch means and said second active switch means and said first diode and said second diode turn on and turn off with substantially zero volts across them.

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