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Power supply system for an electronic apparatus having memory

  • US 4,677,311 A
  • Filed: 12/24/1985
  • Issued: 06/30/1987
  • Est. Priority Date: 12/29/1984
  • Status: Expired due to Term
First Claim
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1. A power supply circuit for supplying electrical power to an electronic apparatus having a memory device comprising:

  • p1 (a) a main power unit connected to an external power source and said apparatus for supplying necessary power to said apparatus in response to the operation of a switching means;

    (b) an auxiliary power unit connected to said external power source and said apparatus for supplying power necessary for said memory device to retain stored information at least during an off-state of said main power unit;

    (c) a battery serving as a back-up of said auxiliary power unit and main power unit for supplying power to said memory device for retaining stored information;

    (d) detection means for detecting the output voltage of said auxiliary power unit; and

    (e) power shut-off means which cuts off the power supply from said auxiliary power unit to said memory device upon expiration of a predetermined time after said detection means has detected a falling voltage.

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