Abstract: Provide are a power reception device, a wearable device, and a non-contact power feeding system that can improve the transmission efficiency while suppressing upsizing of the circuit thereof. A power reception device (3) includes a variable capacitance circuit (100) and a power reception coil (41) constituting a resonance circuit together with the variable capacitance circuit (100), in which the variable capacitance circuit (100) includes a first capacitor (C1) and a second capacitor (C2) connected in parallel to each other, a first switch (Tr1) connected in series to one end side of the first capacitor (C1), and a switch control circuit (110) that controls turning on and off of the first switch (Tr1) and includes a first comparator (OP1) that supplies a first control voltage to the first switch (Tr1) according to a comparison result between a reference voltage and an AC voltage applied to the second capacitor (C2).

Abstract: Provide are a power reception device, a wearable device, and a non-contact power feeding system that can improve the transmission efficiency while suppressing upsizing of the circuit thereof. A power reception device (3) includes a variable capacitance circuit (100) and a power reception coil (41) constituting a resonance circuit together with the variable capacitance circuit (100), in which the variable capacitance circuit (100) includes a first capacitor (C1) and a second capacitor (C2) connected in parallel to each other, a first switch (Tr1) connected in series to one end side of the first capacitor (C1), and a switch control circuit (110) that controls turning on and off of the first switch (Tr1) and includes a first comparator (OP1) that supplies a first control voltage to the first switch (Tr1) according to a comparison result between a reference voltage and an AC voltage applied to the second capacitor (C2).

Abstract: A wireless power transmission system includes a transmitting antenna, a power supply for supplying power of a resonance frequency f0 to the transmitting antenna, a first capacitor connected in series to the transmitting antenna, a receiving antenna magnetically coupled to the transmitting antenna, a load connected to the receiving antenna, and a second capacitor connected in series to the receiving antenna. Supposing that the coupling factor between the transmitting antenna and the receiving antenna is represented by k, the internal resistance of the power supply by Rs and the resistance of the load by RL, then the self-inductance LS of the transmitting antenna and the self-inductance LL of the receiving antenna are determined to satisfy an equation: LS×LL=RS×R1/(2?f0k)2. Further, the capacitance CS of the first capacitor and the capacitance CL of the second capacitor are determined to satisfy equations: CS=1/(2?f0)2LS and CL=1/(2?f0)2LL.

Abstract: A wireless power transmission system includes a transmitting antenna, a power supply for supplying power of a resonance frequency f0 to the transmitting antenna, a first capacitor connected in series to the transmitting antenna, a receiving antenna magnetically coupled to the transmitting antenna, a load connected to the receiving antenna, and a second capacitor connected in series to the receiving antenna. Supposing that the coupling factor between the transmitting antenna and the receiving antenna is represented by k, the internal resistance of the power supply by Rs and the resistance of the load by RL, then the self-inductance LS of the transmitting antenna and the self-inductance LL of the receiving antenna are determined to satisfy an equation: LS×LL=RS×R1/(2?f0k)2. Further, the capacitance CS of the first capacitor and the capacitance CL of the second capacitor are determined to satisfy equations: CS=1/(2?f0)2LS and CL=1/(2?f0)2LL.

Abstract: There is provided a high frequency power supply device. The power control unit comprises an impedance adjuster that includes a variable reactance element and adjusts a load side impedance by changing a reactance value of the variable reactance element, and an impedance control unit that controls the variable reactance element of the impedance adjuster in response to a power value detected by a power detection unit so as to perform control of approximating the power value of the high frequency power, which is fed from the high frequency power generation unit to the load, to the setting value or control of maintaining the power value within the set allowable range by changing a resistance of the load side impedance in response to the power value detected by the power detection unit.

Abstract: There is provided a high frequency power supply device. The power control unit comprises an impedance adjuster that includes a variable reactance element and adjusts a load side impedance by changing a reactance value of the variable reactance element, and an impedance control unit that controls the variable reactance element of the impedance adjuster in response to a power value detected by a power detection unit so as to perform control of approximating the power value of the high frequency power, which is fed from the high frequency power generation unit to the load, to the setting value or control of maintaining the power value within the set allowable range by changing a resistance of the load side impedance in response to the power value detected by the power detection unit.