Pulse width modulation (PWM) is an analog control mode, which modulates the bias of the transistor base or MOS gate according to the change of the corresponding load to change the turn-on time of the transistor or MOS transistor, thus realizing the change of the output of the switching power supply. This method can keep the output voltage of the power supply constant when the working conditions change. it is a very effective technology to control the analog circuit by using the digital signal of the microprocessor.
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