What is Pulse Width Modulation (PWM) and why is it used?

PWM is a technique where the switch duty cycle is varied to control average output voltage or current. In a constant-frequency PWM, the ratio of on-time to period (duty cycle D) determines output: Vout = D x Vin for a buck converter. PWM enables efficient voltage control with minimal power loss (switches are either fully on or off), variable-frequency AC generation in inverters, and linear control using digital signals. Typical switching frequencies range from 1kHz to several hundred kHz.