Voltage conversion circuit and semiconductor integrated circuit device provided therewith

A voltage conversion circuit comprising:

• an output pulse generator for generating an output pulse signal having a fixed pulse width at variable pulse periods;
• a switch circuit composed of a PMOS transistor receiving a first supply voltage at a source thereof and an NMOS transistor receiving a second supply voltage at a source thereof, the switch circuit outputting a voltage at a node at which drains of the PMOS and NMOS transistor are connected together;
• a filter circuit for smoothing the voltage output from the switch circuit to produce an output voltage;
• and
• a switch timing controller for producing from the output pulse signal generated by the output pulse generator, first and second control signals with which to control on/off states of the PMOS and NMOS transistors,
• wherein the output voltage is determined according to a ratio of the pulse width to the pulse period of the output pulse signal.