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Power supply circuit and power supply system

  • US 8,031,490 B2
  • Filed: 08/21/2007
  • Issued: 10/04/2011
  • Est. Priority Date: 08/25/2006
  • Status: Active Grant
First Claim
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1. A power supply circuit configured to self-oscillate by supply of power from a power supply section, the power supply circuit being comprising:

  • a resonance section including a resonance capacitor and a resonance coil, and adapted for supplying power to a load device;

    an oscillation section including a first switching element connected in series to said resonance section and a feedback coil magnetically coupled to said resonance coil, and adapted for turning on and off said first switching element to cause said resonance section to self-oscillate;

    a turn-off section including a second switching element and a turn-off capacitor connected between a control terminal of said second switching element and a negative electrode of the power supply section, wherein when an on-current which flows when said first switching element turns on reaches a predetermined level, said second switching element turns on to cause said first switching element to turn off; and

    a first charging section including a diode of which an anode is connected to said feedback coil side, and a zener diode of which a cathode is connected to a cathode of said diode and of which an anode is connected to said turn-off capacitor side,wherein said zener diode is operated when a voltage larger than a fixed value is outputted from the power supply section to charge said turn-off capacitor,wherein said first charging section is connected in parallel and in multiple numbers, andwherein each zener diode provided in each first charging section has a different breakdown voltage respectively.

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