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Dual/multiple voltage level input switching power supply

  • US 5,751,564 A
  • Filed: 08/10/1994
  • Issued: 05/12/1998
  • Est. Priority Date: 08/10/1994
  • Status: Expired due to Fees
First Claim
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1. A switching power supply system comprising:

  • a rectifier circuit which rectifies a primary AC power source into a DC voltage;

    said rectifier circuit being connected to a transformer circuit;

    a secondary power source;

    the transformer circuit has a first and a second power source input, the first power source input is connected to the primary power source through the rectifier circuit and the second power source input is connected to the secondary power source;

    a first and second control input is connected to a first and second switching circuit, respectively, which control switching currents from the primary and secondary power sources to the transformer circuit;

    an output of the transformer circuit is connected to a load and to a first and second pulse width modulator circuit as feedback control;

    the first pulse width modulator circuit is connected to the transformer circuit and a first output of the first pulse width modulator circuit is connected to the first control input of the first switching circuit and a second output is connected to a monitor circuit, the output from the transformer circuit is used as a feedback control signal and an output pulse from the first output of the first pulse width modulator circuit controls the first switching circuit'"'"'s ON-OFF operation;

    the second output of the first pulse width modulator circuit provides the monitor circuit a monitoring signal of the operation condition of the first switching circuit sourced by the primary power source;

    the second pulse width modulator circuit is connected to the transformer circuit and the monitor circuit and an output of the second pulse width modulator circuit is connected to the second control input of the second switching circuit, the output voltage from the transformer circuit is used as a feedback control signal and an output pulse from the second pulse width modulator circuit controls the second switching circuit'"'"'s ON-OFF operation;

    an output from the monitor circuit controls the second pulse width modulator circuit according to the supply condition of the primary power source;

    the first switching circuit is connected to the first pulse width modulator circuit mentioned above and the transformer circuit;

    the first switching circuit'"'"'s ON-OFF operation is controlled by the first pulse width modulator circuit and will control the switching current in the transformer circuit sourced by the primary power source;

    the second switching circuit is connected to the second pulse width modulator circuit mentioned above and the transformer circuit;

    the second switching circuit'"'"'s ON-OFF operation is controlled by the second pulse width modulator circuit and will control the switching current in the transformer circuit sourced by the secondary power source;

    the monitor circuit is connected to the rectifier circuit and the first pulse width modulator circuit, and the output from the monitor circuit is connected to the second pulse width modulator circuit;

    voltages from the rectifier circuit and the first pulse width modulator circuit will be monitored in the monitor circuit and if a power failure is detected, the monitor circuit will enable the second switching circuit to bring the second power source on line.

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