PWM Overview & History

PWM (Pulse Width Modulation) is a technique used by microcontrollers to simulate analog output using digital signals. It has been widely adopted since the 1980s for motor control, LED dimming, power regulation, and audio signal generation.

• Digital Signal: A square wave with variable duty cycle
• Duty Cycle: Percentage of time the signal is high within a single period
• Applications: Motors, LEDs, heaters, communication interfaces
• Efficiency: PWM allows precise control with minimal energy loss

PWM Technical Function

Microcontrollers generate PWM by rapidly switching a digital output on and off:

1. The timer module or counter generates a repetitive period signal.
2. The duty cycle is set by comparing the timer value with a threshold.
3. When the timer is below the threshold, the output is high; otherwise, it is low.
4. Changing the threshold adjusts the width of the high pulse, effectively controlling average voltage.
5. For motors or LEDs, this controls speed or brightness smoothly despite digital switching.

PWM Diagram