Low-power PWM circuit is simple, inexpensive

摘要

A common technique for imple-menting PWM involves comparing a triangular waveform of fixed am-plitude and frequency with a variable dc voltage level. Although this approach results in a PWM signal of precise frequency and with duty cycle variable from 0 to 100%, the need for a reference triangle waveform and a suitable fast comparator can be prohibitively expensive in low-cost applications. Furthermore, if an application requires a high-frequency PWM signal, the power consumption may be unacceptable in power-sensitive applications, such as high-efficiency, low-power switch-mode regulators.