Patent ID: 8319376
Filing Date: 2012-11-27
Classification: H02J,H02M,Y02B

Abstract:
1. A contactless power transmission circuit for transmitting power in a contactless state to a power receiving device placed on a placing portion, comprising: a resonant circuit including a power transmission coil for transmitting power to the power receiving device and a resonant capacitor which resonates with the power transmission coil; a switching element for resonating the resonant circuit by being repeatedly turned on and off; and a driving circuit for detecting whether or not the power receiving device is placed on the placing portion using a property that a voltage of the power transmission coil is lower when the power receiving device is placed on the placing portion than when the power receiving device is not placed on the placing portion, and driving the switching element such that an ON-period of the switching element is shorter when the power receiving device is detected not to be placed on the placing portion than when the power receiving device is placed on the placing portion, wherein the driving circuit includes wherein the self-oscillating circuit causes the self-oscillation of the resonant circuit for a period during which the intermittent driving circuit keeps the switching element on, and does not cause the self-oscillation of the resonant circuit for a period during which the intermittent driving circuit keeps the switching element off.