Control circuits operating with pulse-width modulated signals

摘要

A control circuit operating with a pulse-width modulated signal which is operative to control a driving circuit portion provided therein for driving a unit to be driven so as to operate in accordance with a pulse-width modulated control signal and in which an analog control signal is provided with a first DC voltage level at a biasing circuit portion (15), a triangular or saw-toothed waveform voltage signal which is obtained from a reference voltage producing circuit portion (17) with an amplitude varying in response to variations in a power supply voltage is superposed on both a second DC voltage level higher than the first DC voltage level and a third DC voltage level lower than the first DC voltage level, and a driving circuit portion (32) provide for driving a unit to be driven (43) is controlled with first and second pulse-width modulated control signals obtained from a level comparing circuit portion (30, 31) in which the level of the analog control signal provided with the first DC voltage level is compared respectively with the voltage level of the triangular or saw-toothed waveform voltage signal superposed on the second DC voltage level and with the voltage level of the triangular or saw-toothed waveform voltage signal superposed on the third DC voltage level. As a result of such arrangements, the control for the driving circuit portion (32) is stably carried out without requiring a specific power source stabilized particularly, and furthermore the power consumption caused by the unit to be driven (43) is effectively reduced.