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Power supply system and image forming apparatus having the same

  • US 9,537,419 B2
  • Filed: 09/26/2013
  • Issued: 01/03/2017
  • Est. Priority Date: 12/28/2012
  • Status: Active Grant
First Claim
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1. A power supply system comprising:

  • a switching power supply configured to rectify and smooth an AC voltage of an AC power supply to generate a predetermined DC voltage;

    a low-capacity power supply circuit that includes;

    a first capacitor including a first electrode connected to one end of the AC power supply, and a second electrode;

    a second capacitor that has a first electrode connected to the other end of the AC power supply, and a second electrode;

    a rectifier circuit that is electrically connected between the second electrode of the first capacitor and the second electrode of the second capacitor, and is configured to rectify an AC voltage applied between the first and second capacitors;

    a smoothing capacitor that is connected at a subsequent stage of the rectifier circuit and is configured to smooth the AC voltage; and

    a signal generating circuit configured to generate a zero-cross detection signal corresponding to zero-cross points of the AC power supply based on a rectified current flowing in the smoothing capacitor, the signal generating circuit comprising;

    a transistor connected between the smoothing capacitor and the reference potential line; and

    a resistor connected between a collector of the transistor and the rectifier circuit,wherein the signal generating circuit converts a rectified current flowing from the rectifier circuit to the reference potential line through the smoothing capacitor, a base of the transistor and an emitter of the transistor into a pulse signal as the zero-cross detection signal; and

    a controller configured to receive the zero-cross detection signal from the signal generating circuit and perform a determining process of determining whether a voltage value of the received zero-cross detection signal is equal to or higher than a predetermined value for at least a first period, andwherein if the control unit determines in the determining process that the voltage of the received zero-cross detection signal is not equal to or higher than the predetermined value for at least the first period, the control unit performs a zero-cross point detecting process of detecting the zero-cross points based on the zero-cross detection signal.

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