A power conversion apparatus, comprising: a converter circuit comprising a transformer for power conversion, a switching device, a diode and a capacitor, the transformer having a primary winding and a secondary winding, the secondary winding having first and second ends, the capacitor having first and second ends, the first end of the secondary winding being connected with a cathode of the diode, wherein the first and second ends of the capacitor are connected with an anode of the diode and the second end of the secondary winding, respectively, or the anode and the cathode of the diode are connected with the first end of the primary winding and the first end of the capacitor, and wherein the converter circuit is configured to supply the transformer with an electric current from a power supply to store energy in the transformer when the switching device is turned on in accordance with a high frequency signal; configured to discharge the energy stored in the transformer when the switching device is turned off in accordance with the high frequency signal; and configured to thereby convert power from the power supply into direct current power; and a control circuit configured to supply the high frequency signal to the converter circuit; characterised in that the power conversion apparatus further comprises a simulation circuit configured to produce a simulation signal which simulates a state or a change of magnetic flux of the transformer, and output the simulation signal; and a sense circuit (4, 5) configured to produce a signal (S4, S5) which corresponds to an input current, an input power, an output current, an output voltage or an output power of the converter circuit, the produced signal (S4, S5) being superposed on the simulation signal to form a superposed signal, wherein the control circuit defines an on-period of the high frequency signal based on the superposed signal. a converter circuit comprising a transformer for power conversion, a switching device, a diode and a capacitor, the transformer having a primary winding and a secondary winding, the secondary winding having first and second ends, the capacitor having first and second ends, the first end of the secondary winding being connected with a cathode of the diode, wherein the first and second ends of the capacitor are connected with an anode of the diode and the second end of the secondary winding, respectively, or the anode and the cathode of the diode are connected with the first end of the primary winding and the first end of the capacitor, and wherein the converter circuit is configured to supply the transformer with an electric current from a power supply to store energy in the transformer when the switching device is turned on in accordance with a high frequency signal; configured to discharge the energy stored in the transformer when the switching device is turned off in accordance with the high frequency signal; and configured to thereby convert power from the power supply into direct current power; and a control circuit configured to supply the high frequency signal to the converter circuit; characterised in that the power conversion apparatus further comprises a simulation circuit configured to produce a simulation signal which simulates a state or a change of magnetic flux of the transformer, and output the simulation signal; and a sense circuit (4, 5) configured to produce a signal (S4, S5) which corresponds to an input current, an input power, an output current, an output voltage or an output power of the converter circuit, the produced signal (S4, S5) being superposed on the simulation signal to form a superposed signal, wherein the control circuit defines an on-period of the high frequency signal based on the superposed signal.