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Switching power-supply unit

  • US 20010010638A1
  • Filed: 01/31/2001
  • Published: 08/02/2001
  • Est. Priority Date: 01/31/2000
  • Status: Active Grant
First Claim
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1. A switching power-supply unit having a rectifier circuit for converting an alternating current from an alternating power supply to a direct current, a switching element for switching a current rectified by this rectifier circuit, and a primary coil for supplying a current to be switched by this switching element, comprising:

  • a transformer having a secondary coil for inducing power corresponding to current supplied to this primary coil;

    DC output means for rectifying and smoothing a power induced at this transformer'"'"'s secondary coil to output a secondary direct current power;

    switching control means for controlling a switching operation of said switching element so as to output a specified voltage from this DC output means; and

    control means for controlling operations of said switching control means, wherein said control means, in the normal operation mode, continuously operates said switching control means so as to operate said switching element at a basic oscillation frequency, wherein said control means, in the standby mode, intermittently operates said switching control means so as to turn on said switching element at a given repetition interval and for a given time period, wherein that repetition interval is shorter than a time for decreasing an output voltage from said DC output means down to a guaranteed load operating voltage due to power consumption of the load and said DC output means in the standby mode and is longer than a time for entering a sonic frequency band, and wherein that time period is longer than a time for stabilizing an output from said DC output means and is longer than a time for entering a sonic frequency band.

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