400 volts according to the on off of the switching transistor tr1 a rectifier 230 for rectifying the induced voltage from the booster transformer t1 and a voltage divider 240 for regulating the output voltage of the pfc circuit 200 in accordance with the fluctuation of the input voltage of the pfc controller 210 as well as load variation pwm control circuit 300 includes a pulse width modulation pwm controller 310 a switching transistor tr2 a resistance r4 for supplying a source voltage of for example about 12 volts to the pwm controller 310 while the pwm controller 310 is at a start mode thereof and a capacitor c3 the primary winding lp of the transformer 400 is connected between the pfc circuit 200 and the switching transistor tr2 and the windings ls1 u02dc ls4 thereof are connected to the rectifiers each which is composed of a resistor and a diode in the output circuit 500 the winding part ls1 at the secondary side of the transformer 400 has the number of turns enough to provide a first induced voltage v2 which is four times as high as a first source voltage applied to a microcomputer 710 and the winding part ls2 has the number of turns enough to provide a second induced voltage v3 which is four times.