Pulse Width Modulation (PWM) is a method of digitally encoding the level of an analog signal. Through the use of high-resolution counters, the duty cycle of the square wave is modulated to encode the level of a specific analog signal. The PWM signal is still digital because at any given moment, full-scale DC power is either completely on (ON) or not at all (OFF). A voltage or current source is applied to an analog load in a repetitive pulse sequence of ON or OFF. When it is on, it is when the DC power supply is added to the load, and when it is off, it is when the power supply is disconnected. Any analog value can be encoded using PWM as long as the bandwidth is sufficient. Most loads (whether inductive or capacitive) require a modulation frequency higher than 10Hz, usually between 1kHz and 200kHz. Many microcontrollers contain a PWM controller internally.

PWM is called a pulse width modulation signal, which uses the width of the pulse to adjust the brightness, and can also be used to control a DC motor. The basic frequency of the PWM pulse width modulation signal is at least about 400HZ-10KHZ. When adjusting the brightness or darkness of the LED, this basic frequency cannot be changed, but the width of the wave above this frequency is changed. The wider the width, the brighter and the wider the width. Narrower is darker.