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Soft switching DC-to-DC converter with coupled inductors

  • US 5,781,419 A
  • Filed: 04/12/1996
  • Issued: 07/14/1998
  • Est. Priority Date: 04/12/1996
  • Status: Expired due to Term
First Claim
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1. A DC-to-DC converter, comprising:

  • (a) a first input side converter bridge circuit including first DC bus lines adapted to be connected to a DC voltage source, a first switching device and a first diode connected together in series at a first pole of the first input side circuit and between the first DC bus lines, and a second switching device and second diode connected together in series at a second pole of the first input side circuit and between the first DC bus lines such that when the first and second switching devices are turned on a DC voltage applied on the first DC bus lines is applied between the first and second poles of the first input side circuit;

    (b) a second input side converter bridge circuit including second DC bus lines adapted to be connected to a DC voltage source, a third switching device and a third diode connected together in series at a first pole of the second input side circuit and between the second DC bus lines, and a fourth switching device and fourth diode connected together in series at a second pole of the second input side circuit and between the second DC bus lines such that when the third and fourth switching devices are turned on a DC voltage applied on the second DC bus lines is applied between the first and second poles of the second input side circuit;

    (c) a first coupled inductor coupling the first pole of the first input side circuit to the second pole of the second input side circuit;

    (d) a second coupled inductor coupling the second pole of the first input side circuit to the first pole of the second input side circuit;

    (e) a transformer having a secondary winding and a first primary winding connected between the first and second poles of the first input side circuit and a second primary winding connected in opposite polarity to the first primary winding between the first and second poles of the second input side circuit;

    (f) an output side converter circuit having output terminals and connected to the secondary of the transformer and including means for converting an AC signal on the secondary of the transformer to a DC output signal on the output terminals; and

    (g) a converter controller including switching device control means for turning on and off the first, second, third, and fourth switching devices in a sequence to alternately connect the first DC bus lines to the first primary winding of the transformer and the second DC bus lines to the second primary winding of the transformer to generate an AC signal on the secondary winding of the transformer, the switching device control means including means for delaying the turn on of a switching device in a one of the input side circuits following the turn off of a switching device in the other of the input side circuits until a voltage across the switching device being turned on is reduced to zero by energy stored in a one of the coupled inductors such that the switching device is turned on under zero voltage switching conditions.

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