Pulse Width Modulation, or PWM, is a control method that turns a signal on and off very quickly. By changing how long the signal stays on during each cycle, a circuit can control average power.
Where PWM is used
PWM is used for LED brightness, motor speed, audio signals, power regulation, fans, servos, and many embedded projects. A microcontroller can often generate PWM signals.
Duty cycle
The duty cycle is the percentage of time the signal is on. A 25 percent duty cycle is on for one quarter of the cycle, while a 75 percent duty cycle is on for three quarters.
PWM is useful because a digital on/off output can create smooth-looking control in the real world.