Power transmission device

• US 8,258,652 B2
• Filed: 11/16/2009
• Issued: 09/04/2012
• Est. Priority Date: 12/02/2008
• Status: Active Grant

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Someya, Kaoru, Sekino, Shigeo
• Primary Examiner(s): Fureman, Jared
• Assistant Examiner(s): Borroto, Alfonso Perez
• Application Number:
  US12/618,888
• Publication Number:
  US 20100133917A1
• Time in Patent Office: 1,023 Days
• Field of Search: 307/104, 307149-151, 320/108, 363/21.02, 363/17
• US Class Current: 307/104
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge

Abstract

A power transmission device includes: a power transmission coil to transmit electric power to a power receiving coil by an electromagnetic induction method; a driving unit to supply a driving voltage to the power transmission coil; a detection unit to detect an electric current flowing in the power transmission coil based on the driving voltage; a control unit to change an amplitude of the driving voltage; a starting point detection unit to detect the amplitude of the driving voltage as a characteristic point at which an electric current starts to flow in the power receiving coil, on a characteristic line representing a relationship between the driving voltage supplied to the power transmission coil and the electric current detected by the detection unit; and a transmission stopping control unit to stop power transmission by the power transmission coil if the characteristic point is not detected by the starting point detection unit.

Claims

1. A power transmission device, comprising:

a power transmission coil which transmits electric power to a power receiving coil by an electromagnetic induction method;

a driving unit which supplies a driving voltage to the power transmission coil;

a detection unit which detects an amplitude of an electric current flowing in the power transmission coil based on the driving voltage supplied by the driving unit;

a control unit which changes an amplitude of the driving voltage supplied by the driving unit;

a characteristic determining unit which determines whether the amplitude of the electric current detected by the detection unit is increased at a constant rate when the control unit gradually increases the amplitude of the driving voltage supplied to the power transmission coil from a minimum value; and

a transmission stopping control unit which stops power transmission by the power transmission coil if the characteristic determining unit determines that the amplitude of the electric current is increased at a constant rate.