this stage the second transistor q 120 is turned off and the capacitor c 120 is not connected to the capacitor c 130 of the frequency oscillating section 180 in parallel subsequently the time constant representing the frequency oscillating section is varied and the pulse generating section 210 generates pulses having a frequency according to the varied time constant the frequency at this stage can be expressed by the following equation 3 the pulse generating section 210 supplies the pulses having the frequency f 2 in the equation 3 to the switching section 220 here the frequency f 1 applied to the pulse generating section 210 from the light load region is lower than the frequency f 2 by a predetermined level therefore consumption of electric power generated in accordance with operation of the switching section 220 can be reduced by reducing operation of the switching section 220 through reduction of the frequency generated from the pulse generating section 210 if the third diode d 130 of the output current detecting section 150 outputs the current in the heavy load region as shown in fig4 c the first transistor q 110 of the output current feedback section 160 is turned on by receiving the signal transmitted by the third diode d 130 at the base and.