Wireless power feeding system

A wireless power feeding system comprising

• a power transmission unit including a power transmission coil and a power receiving unit including a power receiving coil, and feeds electric power to the power receiving unit from the power transmission unit, wherein
• the power transmission unit includes a power transmission-side resonant capacitor configuring a power transmission-side resonance mechanism together with the power transmission coil, a first power transmission-side alternating-current (AC) current generation circuit which is electrically connected to one side of the power transmission-side resonance mechanism, a second power transmission-side AC current generation circuit which is electrically connected to the other side of the power transmission resonance mechanism, and a switching control circuit,
• the first power transmission-side AC current generation circuit includes a first switch circuit which is equivalently configured by a parallel connection circuit of a switching element, a diode, and a capacitor, and a first inductor having an inductance which generates, from an input DC voltage, a first current source capable of being regarded as a DC current relatively to an AC current flowing through the power transmission-side resonance mechanism,
• the second power transmission-side AC current generation circuit includes a second switch circuit which is equivalently configured by a parallel connection circuit of a switching element, a diode, and a capacitor, and a second inductor having an inductance which generates, from the input DC voltage, a second current source capable of being regarded as a DC current relatively to an AC current flowing through the power transmission-side resonance mechanism,
• the switching control circuit generates the AC current in the power transmission coil from the first power transmission-side AC voltage generation circuit and the second power transmission-side AC voltage generation circuit by alternately turning ON and OFF the switching element of the first switch circuit and the switching element of the second switch circuit,
• the power receiving unit includes a power receiving-side resonant capacitor configuring a power receiving-side resonance mechanism together with the power receiving coil, and a power receiving-side rectifying circuit which is electrically connected to the power receiving coil and rectifies an AC current generated in the power receiving coil,
• a first resonant frequency which is determined by the power transmission-side resonance mechanism is lower than a switching frequency of the first switch circuit and the second switch circuit,
• a second resonant frequency which is determined by the power transmission-side resonance mechanism and the capacitor of the first switch circuit or the second switch circuit is higher than or equal to the switching frequency,
• the switching control circuit switches the switching elements of the first switch circuit and the second switch circuit at a switching frequency at which a first impedance when a load side is observed from both ends of one switch circuit of the first switch circuit and the second switch circuit with the power transmission-side resonance mechanism interposed therebetween in a state in which the other switch circuit is short-circuited without involving a capacitance of the one switch circuit is an inductive impedance and switches the switching elements of the first switch circuit and the second switch circuit at a switching frequency at which a second impedance when the load side is observed from both ends of one switch circuit of the first switch circuit and the second switch circuit with the power transmission-side resonance mechanism interposed therebetween in a state in which the other switch circuit is short-circuited while involving the capacitance of the one switch circuit is an inductive impedance to make each of both-end voltages of the first switch circuit and the second switch circuit have a half sine wave-like waveform for each half period, and
• an equivalent electromagnetic field resonance coupling circuit is configured by a mutual inductance or a mutual capacitance which is equivalently formed between the power transmission coil and the power receiving coil to cause the power transmission-side resonance mechanism and the power receiving-side resonance mechanism to resonate.