PURPOSE: To get a high power factor converter, which is inexpensive and high in circuit design latitude, by modulating the pulse width of the converter input voltage wave, in place of a multiplier, by the carriers of triangular waves, and making this pulse train have the output of an error amplifier for output voltage control as amplitude, and removing the ingredients of carrier frequency by a low-pass filter.

CONSTITUTION: Converter input voltage Vi and the carriers Vc of triangular waves are compared by a comparator 11, and the pulse width of input voltage waves are modulated. On the other hand, it is made to have the output of an error amplifier 8 for voltage control, as the amplitude of a pulse train where the pulse width is modulated. And the ingredients of carrier frequency of a pulse train Vm are removed with a low-pass filter 12 so as to form a current reference Ir. Next, this current reference Ir and the voltage drop of a detecting resistor 4, which detects the input current of a converter, are input into a pulse width control circuit 10 so as to control the on/off of the switch element 3 of the converter. Hereby, the control circuit of a high power factor converter can be constituted with general purpose parts without using an expensive multiplier, and the latitude in circuit design becomes high.