Power conversion apparatus includes a converter circuit, a control circuit, a simulation circuit and a sense circuit. The converter circuit includes a magnetic device for power conversion and a switching device, and is configured to convert power from a power supply into direct current power. The control circuit is configured to supply the converter circuit with a high frequency signal for turning the switching device on and off. The simulation circuit is configured to produce a simulation signal that simulates state or change of magnetic flux of the magnetic device. The sense circuit is configured to produce a signal which corresponds to at least one of the input and output of the converter circuit and is superposed on the simulation signal to form a superposed signal. The control circuit defines an on-period of the high frequency signal based on the superposed signal.