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Television apparatus having kinescope spot burn protection circuit with extended grid cut-off time constant

  • US 5,130,615 A
  • Filed: 07/01/1991
  • Issued: 07/14/1992
  • Est. Priority Date: 07/01/1991
  • Status: Expired due to Term
First Claim
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1. A grid bias control circuit for use with a kinescope, comprising:

  • an input terminal coupled to a source of switched supply voltage and coupled via a pulse forming capacitor to an output terminal for producing at said output terminal a given positive grid bias voltage for said kinescope when said supply voltage is present and for producing a negative grid cut-off bias pulse at said output terminal upon termination of said supply voltage for blanking said kinescope;

    a potential divider coupled between said input terminal and a source of ground potential and having an output for providing said given positive grid bias voltage when said supply voltage is present and a ground level voltage upon said termination of said supply voltage;

    a transistor having a conduction path coupled between said output of said potential divider and said output terminal of said grid bias control circuit, said transistor having a control electrode coupled to said source of ground potential; and

    whereinsaid grid bias control circuit having no discharge path, other than leakage paths, for said pulse forming capacitor.

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