Patent ID: 6943533

Claim:
A voltage conversion circuit, comprising: a switch circuit arranged so that a series circuit constituted of a P-type transistor and an N-type transistor is provided between a pair of power source lines in series; a smoothing circuit for smoothing an output voltage derived from a junction of the P-type transistor and the N-type transistor of the switch circuit; a pulse signal generating circuit for generating one or more pulse signals, each of which has a duty ratio for obtaining a desired output voltage, by using the output voltage smoothed by the smoothing circuit as a power source, so as to give the pulse signal to a control terminal of the P-type transistor and a control terminal of the N-type transistor; a start-up control signal for generating a control signal which forces the P-type transistor to turn ON and giving the control signal to the control terminal of the P-type transistor during a predetermined period on start-up.