Non-contact power transmission device

A non-contact power transmission device comprising:

• a power supply that supplies electric power;
• a power transmission coil unit that is connected to the power supply and transmits electric power in a non-contact manner;
• a power reception coil unit that is connected to a load that consumes electric power, receives the electric power transmitted from the power transmission coil unit in a non-contact manner, and supplies the received electric power to the load;
• and
• a controller configured to control the power transmission coil unit and the power reception coil unit, wherein
• at least one of the power transmission coil unit and the power reception coil unit includes an impedance variable circuit an impedance of which is variable,
• the impedance variable circuit includes at least one of a resonance coil capable of changing an inductance value of the impedance variable circuit and a resonance capacitor capable of changing a capacitance of the impedance variable circuit,
• the controller configured to change impedance of the impedance variable circuit, and match an output impedance on the power supply side with respect to the power transmission coil unit and an input impedance on the load side with respect to the power transmission coil unit,
• the impedance variable circuit includes a plurality of LC circuits including a pair of a resonance coil and a resonance capacitor,
• the controller configured to switch the LC circuits to be connected in series or in parallel to change the inductance value and the capacitance, and match the output impedance and the input impedance, and
• the resonance coils are sequentially connected in series, and a conductor cross-sectional area of the resonance coil at a later stage is smaller than a conductor cross-sectional area of the resonance coil at a former stage.

A non-contact power transmission device comprising:

• a power supply that supplies electric power;
• a power transmission coil unit that is connected to the power supply and transmits electric power in a non-contact manner;
• a power reception coil unit that is connected to a load that consumes electric power, receives the electric power transmitted from the power transmission coil unit in a non-contact manner, and supplies the received electric power to the load;
• and
• a controller configured to control the power transmission coil unit and the power reception coil unit, wherein
• at least one of the power transmission coil unit and the power reception coil unit includes an impedance variable circuit an impedance of which is variable,
• the impedance variable circuit includes at least one of a resonance coil capable of changing an inductance value of the impedance variable circuit and a resonance capacitor capable of changing a capacitance of the impedance variable circuit,
• the controller configured to change impedance of the impedance variable circuit, and match an output impedance on the power supply side with respect to the power transmission coil unit and an input impedance on the load side with respect to the power transmission coil unit,
• the load is operated with an operation switch that causes electric current to flow when being turned on and causes the electric current to be stopped when being turned off,
• the controller configured to change impedance of the impedance variable circuit based on an on or off operation of the operation switch, and
• the controller configured to further change the impedance of the impedance variable circuit based on time that has elapsed after the operation switch is turned on.