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Switching power supply with automatic power factor correction

  • US 4,683,529 A
  • Filed: 11/12/1986
  • Issued: 07/28/1987
  • Est. Priority Date: 11/12/1986
  • Status: Expired due to Fees
First Claim
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1. An off-line switching power supply with automatic power factor correction, comprising:

  • input connection means for connecting to a power source and for receiving input current;

    first rectifier means connected to said input connection means for rectifying said input current and for producing rectified input current;

    inductor means for charging and discharging said rectified input current;

    switching means connected to said inductor means and to said first rectifier means for placing said inductor means in a first position so that said rectified input current from said first rectifer means is charged in said inductor means and for placing said inductor means in a second position so that said charged rectified input current is discharged from said inductor means;

    second rectifier means connected to said inductor means for receiving said discharged rectified input current and for producing rectified inductor current when said inductor means is placed in said second position by said switching means;

    capacitor means connected to said second rectifier means for receiving said rectified inductor current, for charging the voltage produced when said inductor means is placed in said second position by said switching means and for discharging regulated direct current and voltage;

    output connection means connected to said capacitor means for driving a load with said discharged regulated direct current and voltage;

    control means connected to said switching means for alternately placing said inductor means in said first and said second positions, which comprises;

    on-time amplifier means connected to said capacitor means for generating an on-time error signal in response to said voltage across said voltage capacitor;

    off-time amplifier means connected to said voltage storage means for generating an off-time error signal in response to said voltage across said voltage storage means;

    reset detect means connected to said second rectifier means for generating a reset signal when said rectified inductor current through said second rectifier means is approximately zero;

    clock circuit means for producing a high frequency clock signal to control said switching means having an on-time interval corresponding to the amount of time said switching means places said inductor means in said first position and having an offtime interval corresponding to the amount of time said switching means places said inductor means in said second position;

    the length of said on-time interval controlled by the magnitude of said on-time error signal; and

    the length of said off-time interval controlled by said reset signal and said off-time signal so that said reset signal operates to terminate said off-time interval and said off-time error signal operates to extend the off-time interval beyond the termination point set by said reset signal.

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