PWM Signal Generating Circuit

Published:2011/8/17 10:00:00 Author: | Keyword: PWM, Signal, Generating | From:SeekIC

The switching power separate excitation control method has pulse width modulation (PWM) and pulse frequency modulation (PFM). And the most cases use the PWM method. So here it would introduce the PWM control principle. The picture shows the PWM signal generating circuit diagram and working waveform. Its working process is following. By detecting the controlled voltage Uo it could get the feedback voltage Ur and then add it to the in-phase port of the amplifier A1. The fixed referenced voltage Uo is added to the out-phase port of A1. After the amplification of A1, the DC error voltage Ue is added to the out-phase port of amplifier A2. And the sawtooth signal Usa, which is generated from the fixed frequency oscillator, is added to the in-phase port of A2.



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