Power conversion circuitry

The present invention provides an electric power conversion circuit system having a primary side electric power conversion circuit, a secondary side electric power conversion circuit, and a control circuit. The control circuit sets at least one of a half-bridge phase difference between a lower-left-arm transistor and a lower-right-arm transistor of the primary side electric power conversion circuit and a half-bridge phase difference of the secondary side electric power conversion circuit based on OFF periods of the primary side and secondary side electric power conversion circuits, dead-times of the primary side and secondary side electric power conversion circuits, and an amount of change of a power supply voltage so that a current in a non-transmission period of electric power is zero between the primary side and secondary side electric power conversion circuits.