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Low-noise switching power supply having variable reluctance transformer

  • US 4,876,638 A
  • Filed: 02/10/1988
  • Issued: 10/24/1989
  • Est. Priority Date: 02/10/1988
  • Status: Expired due to Fees
First Claim
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1. A low-noise switching power supply for producing a regulated output voltage from an unregulated supply including a non-saturating main transformer having a core with a variable reluctance path, a load winding associated with said core for producing said output voltage, means for producing from said unregulated supply an alternating magnetic flux in said core so as to produce said output voltage from said load winding, and means for varying the reluctance of at least a portion of said transformer core so as to maintain said output voltage at a substantially constant predetermined value, said transformer having a high leakage reactance whereby noise, pulses and voltage spikes are effectively isolated from said means for producing alternating magnetic flux and said load winding, said transformer further comprising first, second, and third legs, said third leg including an air gap therein, wherein the reluctance of a path through said second and third legs is greater than the reluctance of a path through said first and second legs, said load winding being associated with said third leg, said means for producing an alternating magnetic flux comprising a primary winding associated with said second leg and switching means responsive to the unregulated supply for providing an oscillating voltage of substantially constant frequency to said primary winding, whereby a voltage is induced in said primary winding and magnetic flux is produced by alternating voltage acting upon said primary coil.

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