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Inverter type switching power supply with transformer and short circuit arrangement therefor

  • US 4,737,974 A
  • Filed: 01/14/1985
  • Issued: 04/12/1988
  • Est. Priority Date: 01/17/1984
  • Status: Expired due to Fees
First Claim
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1. A method of controlling a full-bridge type inverter used in an inverter type switching power supply circuit including:

  • a transformer having at least a primary winding and a secondary winding;

    a full-bridge type inverter for converting a DC power source to an AC voltage to be supplied to said primary winding, said inverter including a series circuit of a first switching element connected to a first polarity terminal of said DC power source and a second switching element connected to a second polarity terminal of said DC power source, first and second diodes connected in anti-parallel with said first and second switching elements of said series circuit, respectively, another series circuit of a third switching element connected to said first polarity terminal of said DC power source and a fourth switching element connected to said second polarity terminal of said DC power source, and third and fourth diodes connected in anti-parallel with said third and fourth switching elements of said another series circuit, respectively, and wherein one end of said primary winding is connected to the connecting point of said first and second switching elements and another end of said primary winding is connected to the connecting point of said third and fourth switching elements;

    rectrifier means connected to said secondary winding for rectifying the output of said transformer; and

    smoothing capacitor means for smoothing the output of said rectifier means and supplying the smoothed output to a load;

    the method comprising;

    a first step of turning on said first switching element and simultaneously turning off said second switching element, while said fourth switching element is maintained on and said third switching element is maintained off to provide an on-period;

    a second step of, upon elapse of the on-period after initiation of said first step, turning off said first switching element and simultaneously turning on said second switching element, while maintaining said third and fourth switching elements in the off and on states, respectively, to provide an off-period;

    a third step of, upon elapse of the off-period since initiation of said second step, turing off said fourth switching element and simultaneously turning on said third switching element, while maintaining said first and second switching element in the off and on states, respectively, to provide another on-period;

    a fourth step of, upon elapse of the another on-period since initiation of said third step, turning on said fourth switching element and simultaneously turning off said third switching element, while maintaining said first and second elements in off and on states, respectively, to provide another off-period; and

    a fifth step of returning to said first step upon elapse of the another off-period since initiation of said fourth step and wherein the step of short-circuiting said transformer during the off-periods includes establishing two paths forming a bidirectional low-impedance path, one of said two paths being constituted by said primary winding, said second switching element and said fourth diode and the other of said two paths being constituted by said primary winding, said fourth switching element and said second diode, and maintaining on said second and fourth switching elements during the off-periods

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