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Switching power supply device

  • US 9,397,575 B2
  • Filed: 02/10/2014
  • Issued: 07/19/2016
  • Est. Priority Date: 08/11/2011
  • Status: Active Grant
First Claim
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1. A switching power supply device, comprising:

  • a power supply voltage input unit configured to accept input of an input power supply voltage;

    a direct current voltage output unit configured to receive output of a direct current voltage;

    a transformer including a primary winding and a secondary winding;

    a low side switching element connected in series to the primary winding and configured to apply a voltage at the power supply voltage input unit to the primary winding upon being turned on;

    a switching control circuit configured to control the low side switching element; and

    a rectifying smoothing circuit configured to rectify and smooth a voltage output from the secondary winding and output an output voltage to the direct current voltage output unit;

    whereinthe switching control circuit includes;

    a current-mode-controlling switching control IC that includes;

    a current detection terminal, to which a current that is supposed to flow through a power conversion circuit during an on time of a switching element in the power conversion circuit is detected as a voltage signal and is input;

    a feedback terminal;

    a zero voltage timing detection terminal; and

    a switching element control signal output terminal;

    whereinthe current-mode-controlling switching control IC is configured to output a drive signal that causes the low side switching element to turn off from the switching element control signal output terminal in response to a voltage applied to the current detection terminal reaching a voltage applied to the feedback terminal;

    a feedback voltage signal generating circuit configured to generate a feedback voltage signal based on the output voltage and apply the generated feedback voltage signal to the feedback terminal;

    a drive voltage signal output unit configured to receive a signal input to the zero voltage timing detection terminal and output, upon detecting an inversion of a voltage polarity in the transformer, a drive voltage signal that causes the low side switching element to turn on; and

    a reference voltage generating circuit configured to generate a reference voltage of which a voltage increases monotonously along with a time that has elapsed since the drive voltage signal has been output and function as a voltage-time conversion circuit by inputting the generated reference voltage to the current detection terminal; and

    in a power conversion operation in which a current flowing through the low side switching element during an on time of the low side switching element does not increase monotonously along with the time that has elapsed, the current-mode-controlling switching control IC is used.

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