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Power supply device including induction voltage detection coil for charging portable electronic devices

  • US 5,122,729 A
  • Filed: 01/02/1991
  • Issued: 06/16/1992
  • Est. Priority Date: 01/08/1990
  • Status: Expired due to Term
First Claim
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1. A power supply device which applies power from an oscillation circuit to a primary coil and supplies power by means of non-contact electromagnetic induction to a secondary coil juxtaposed to the primary coil, said device further comprising:

  • a detection coil which is inductively connected to the primary coil and responsive to a variation in magnetic flux of an alternating signal applied to said primary coil, for detecting a load fluctuation resulting from and varying in accordance with a said secondary coil, and for outputting a voltage signal representing the load fluctuation as a change in an induction voltage induced in said detection coil, anda control means which controls, based on the change in the induction voltage output by the detection coil, an output of said oscillation circuit so that the power supplied to the secondary coil remains constant.

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