In general, a PFC (Power Factor Correction) circuit is incorporated into a circuit which converts an alternating voltage to a direct voltage. The PFC circuit, which is a circuit for making an input current into a sine wave, can suppress harmonic of the input current.
The PFC circuit is composed of four members including an inductor, a switch element, a diode and a smoothing capacitor. In the PFC circuit, if the switch element is turned on, a current flows to the inductor and magnetic energy is stored in the inductor. Next, if the switch element is turned off, the magnetic energy stored in the inductor is converted to electrical energy. Then, through the electrical energy, an electric charge is stored in the smoothing capacitor, and a voltage of the smoothing capacitor rises due to an increase in the electric charge.
However, in the PFC circuit, when the switch element is switched from the off state to the on state, a reverse current instantly flows to the diode through a parasitic capacitance characteristic of the diode. Then, power loss occurs due to a product of the reverse current and a voltage generated at both ends of the switch element. Thus, if the PFC circuit is incorporated into the circuit which converts the alternating voltage to the direct voltage, there is a problem that power conversion efficiency deteriorates.
Thus, a power conversion apparatus which has the same phase factor improvement capacity as the PFC circuit and does not deteriorate the power conversion efficiency is required.