JPS6447121A - Pulse width modulation signal generating circuit - Google Patents

Abstract

PURPOSE:To obtain a digitized pulse width modulation (PWM) signal with comparatively lower carrier resolution by latching a reference waveform in a carrier maximum or minimum timing and revising the processing logic of a comparator depending on the decreasing state or increasing state of the carrier. CONSTITUTION:A triangle wave carrier generating circuit 20 generate a triangle wave carrier while comprising with a counter or the like driven by a clock CK having the same or more excellent resolution as that of an output of a digital reference waveform generating circuit 10 having a prescribed resolution. A latch circuit 40 receives a timing signal SP representing the maximum or minimum value of the carrier waveform of the circuit 20 to latch the output of the circuit 10. Then a comparator 30 compares the signals with a different logic in response to on U/D signal representing whether the output of the circuit 20 is increasing or decreasing and uses a clock, inverse of CK to latch a latch circuit 50. Thus, only when the resolution of the carrier is equal to or more than the resolution of a reference waveform, a prescribed PWM signal is obtained without causing hazard.