Rohm Co., Ltd.

Akihiro Okui

Yoshihiro Ikefuji

Kimitake Utsunomiya

Hideki Nishiyama

Yoshiro Fujii

Takeshi Kuga

In a non-contact power feeding system which is formed with a power transmission device having a power transmission-side resonant circuit including a power transmission-side coil and a power reception device having a power reception-side resonant circuit including a power reception-side coil and which can transmit and receive power by a magnetic field resonance method, when the power is transmitted, the power transmission device monitors the amplitude of a current flowing through the power transmission-side coil. Then, when a current amplitude detection value (V) falls outside a predetermined normal range, it is determined that a foreign object is present, and thus the power transmission is stopped.

Power transmission device non-contact power feeding system with detection circuit to detect current amplitude in transmission-side coil

In this non-contact power feeding system that is capable of transmitting power from a power transmitting device () to a power receiving device () by a magnetic field resonance scheme, the power transmitting device () is provided with first to n-th resonant circuits (TT[]-TT[n]) which are provided with coils (T) that are different in size, respectively, and which have a resonant frequency set to a prescribed reference frequency. Prior to power transmission, test magnetic fields are generated in sequence in the first to n-th resonant circuits to detect the amplitude of current flowing through the coils of respective resonant circuits, and the presence/absence of a foreign object is determined on the basis of the obtained first to n-th amplitude detected values, to control execution of the power transmission.

Power transmitting device and non-contact power feeding system

An oscillator of the present invention includes a constant current circuit in which a constant current generated in the constant current circuit varies positively with an on threshold voltage of a transistor included in the constant circuit; and an oscillating circuit in which the oscillating frequency of a clock signal generated in the oscillating circuit varies positively with the constant current supplied from the constant current circuit, and the oscillating frequency of the clock signal generated in the oscillating circuit varies negatively with an on threshold voltage of a transistor included in the oscillating circuit.

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Kyoto, Japan

Akihiro Okui