POWER TRANSMISSION DEVICE

• US 20100133917A1
• Filed: 11/16/2009
• Published: 06/03/2010
• Est. Priority Date: 12/02/2008
• Status: Active Grant

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Sekino, Shigeo, Someya, Kaoru
• Granted Patent: US 8,258,652 B2
• Time in Patent Office: Days
• 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; 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 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 supplied by the driving unit;

a control unit to change an amplitude of the driving voltage supplied by the driving unit;

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.

2. The power transmission device according to claim 1, wherein the starting point detection unit determines whether or not a gradient of the characteristic line or an absolute value of the electric current detected by the detection unit is within a predetermined range if the characteristic point is detected, and repeats an operation for detecting a characteristic point representing that an electric current starts to flow in the power receiving coil if the gradient of the characteristic line or the absolute value of the electric current detected by the detection unit is not within the predetermined range.

3. The power transmission device according to claim 1, wherein

the driving unit supplies the driving voltage whose voltage value changes periodically to the power transmission coil, and

the control unit increases the amplitude of the driving voltage whose voltage value changes periodically.

4. The power transmission device according to claim 1, wherein the characteristic point corresponds to a bending point on the characteristic line.

5. The power transmission device according to claim 1, wherein the starting point detection unit detects the amplitude of the driving voltage as the characteristic point at which the electric current starts to flow in a rectifier circuit connected to the power receiving coil.