Contactless power transmission circuit

A contactless power transmission circuit for transmitting a power via a magnetic field from a power transmitting coil to a power receiving coil,

• comprising:
• a driving circuit for supplying an alternating voltage to the power transmitting coil,
• a rectifier circuit for rectifying a voltage generated in the power receiving coil with a magnetic field generated by the power transmitting coil,
• a transmission current detecting circuit for detecting a transmission current flowing through the power transmitting coil,
• an output voltage detecting circuit for detecting an output voltage of the rectifier circuit, and
• a control circuit for controlling a period of the alternating voltage output from the driving circuit,
• wherein the control circuit comprises
• a target voltage setter for outputting a target value of the output voltage,
• a target current setter for outputting a target value of the transmission current,
• a first subtracter for subtracting an output of the output voltage detecting circuit from an output of the target voltage setter,
• a second subtracter for subtracting an output of the transmission current detecting circuit from an output of the target current setter,
• a first PFM controller which is connected to an output of the first subtracter and outputs a first command value which is a command value for the period of the alternating voltage,
• a second PFM controller which is connected to an output of the second subtracter and outputs a second command value which is a command value for the period of the alternating voltage,
• a comparator which connects an output of the first PFM controller to an inverted input and connects an output of the second PFM controller to a non-inverted input,
• a multiplexer which connects the output of the first PFM controller and the output of the second PFM controller to an input and connects an output of the comparator to a selection control input,
• wherein the multiplexer is set to select the output of the first PFM controller when the output of the comparator is a high level, and to select the output of the second PFM controller when the output of the comparator is a low level.