Power-receiving device and power transmission system

A power transmission system comprising:

• a power-sending device;
• and
• a power-receiving device for receiving first alternating current power from the power-sending device in a contactless manner, wherein
• the power-sending device has a primary-side coil to which the first alternating current power is input, and
• the power-receiving device includes:
• a secondary-side coil capable of receiving the first alternating current power from the power-sending device in the contactless manner;
• a connecting portion to which a cable used to transmit second alternating current power is connected;
• a load;
• a first power transmission path that connects the secondary-side coil and the load to each other;
• a second power transmission path that connects the connecting portion and the load to each other;
• a common path provided in common in the first and second power transmission paths;
• and
• a voltage regulator arranged on the common path, wherein the voltage regulator rectifies the first alternating current power received by the secondary-side coil or the second alternating current power provided from the connecting portion, and wherein the voltage regulator converts the rectified power into a predetermined specific voltage value and outputs the power, wherein
• the voltage regulator includes a switching element, the voltage regulator rectifies the first alternating current power or the second alternating current power into the predetermined specific voltage value and outputs the power due to that the switching element switches periodically,
• the power-receiving device includes a control section that controls the switching element alternating current power, and
• the control section controls the switching element such that the switching frequency of the switching element in a state in which the voltage regulator is receiving the second alternating current power is lower than the switching frequency of the switching element in a state in which the voltage regulator is receiving the first alternating current power.