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Electronic products with improved surge protecting circuit

  • US 5,892,669 A
  • Filed: 11/26/1997
  • Issued: 04/06/1999
  • Est. Priority Date: 11/29/1996
  • Status: Expired due to Fees
First Claim
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1. An improved surge protection circuit for an electronic product, the circuit comprising:

  • an alternating current (AC) input circuit responsive to an AC power source, having an AC ground pattern associated therewith, the AC input circuit including;

    (a) a rectifying circuit connected to said AC power source for rectifying AC power from said AC power source, said rectifying circuit being connected to said AC ground pattern;

    (b) a switch regulating circuit responsive to said rectified AC power, said switch regulating circuit being connected to said AC ground pattern;

    (c) a transformer having a primary winding and a secondary winding, said primary winding being connected to said regulating circuit for receiving said rectified power, said primary winding being connected to said AC ground pattern;

    (d) a surge absorption pattern having a pair of terminals, said terminals of said surge absorption pattern being separated by an arc discharge gap which is smaller than a safety distance, one of said terminals of said surge absorption pattern being connected to an AC input terminal of said AC input circuit; and

    (e) a varistor, said varistor being connected in series between one of said terminals of said surge absorption pattern and said AC ground pattern for isolating noise generated by said AC power source; and

    a direct current (DC) operating circuit being electromagnetically coupled to said AC input circuit through said transformer and having a DC ground pattern associated therewith which is separated from said AC ground pattern by said safety distance or more, the DC operating circuit including;

    (a) a DC circuit, said DC circuit receiving power from said secondary winding of said transformer, said DC circuit and said secondary winding being connected to said DC ground pattern; and

    (b) a terminal to which external surges are transmitted, said terminal being connected to said DC circuit, whereby external surges received by said terminal of said DC circuit are transmitted through said DC operating circuit to said AC input circuit through said transformer to said AC ground pattern wherein the external surge is then absorbed by an arc discharge in said arc discharge gap of said surge absorption patterns.

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