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Coil unit and noncontact power transmission apparatus

  • US 9,524,823 B2
  • Filed: 02/28/2014
  • Issued: 12/20/2016
  • Est. Priority Date: 11/04/2011
  • Status: Active Grant
First Claim
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1. A coil unit configured to transmit or receive electric power by electromagnetic induction in a noncontact manner, comprising:

  • a coil into or from both terminals of which a high-frequency voltage is input or output;

    a metal conductor placed near the coil; and

    a first capacitor and a second capacitor respectively connected to the terminals of the coil, whereinthe ratio of the capacitance between the first capacitor and the second capacitor is set to a value at which a current induced into the metal conductor due to capacitance coupling when a high-frequency voltage is input into or output from the coil is reduced, andthe ratio between capacitances C1 and C2 (C1/C2) where C1 is the capacitance of the first capacitor and C2 is the capacitance of the second capacitor is set to satisfy conditions (1) and (2) below when a high-frequency voltage is input into or output from the coil;

    (1) a combined capacitance [C1×

    C2/(C1+C2)] of the first capacitor and the second capacitor serially connected to the coil is constant; and

    (2) the current induced into the metal conductor due to capacitance coupling is smaller than that observed when C1=C2.

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