PWM (Pulse Width Modulation) working, applications and benefits used in Microcontroller
Introduction : Pulse Width Modulation (PWM) is a fundamental technique used in microcontrollers to control the power delivered to various devices. By modulating the width of pulses, PWM enables efficient management of energy for components like motors, LEDs and audio signals. This versatile method plays a crucial role in numerous applications, offering precise control with minimal energy loss. In this guide, we’ll explore how PWM works, its key benefits and its wide ranging applications in embedded systems.
What is PWM?
PWM stands for Pulse Width Modulation. It refers to variation in the pulse width. Now-a-days microcontrollers support PWM outputs. The digital pulses are available as output at these pins. The different pulse width will provide different DC voltages(average). Most of the microcontrollers will have built in timers which helps in generation of PWM signal with various widths. The low pass filters (usually RC type) are used to convert the PWM output to DC voltage. Following equation mentions relationship between average output voltage and duty cycle. The term duty cycle refers to ratio of amount of ON time and period of the pulse train. It is specified in percentage. Hence 10% refers to 10/100 and 90% refers to 90/100 in decimal format.
Average DC voltage output = Voltage to represent High State x Duty Cycle

Fig:1 PWM signal with different DC outputs
The figure depicts two different PWM waveforms with duty cycle of 10% and 90%. This will generate different DC output voltages. This is used in brightness control applications in any technology. It is also used in speed control of motors.
Example:
For 3.28V and 10% duty cycle, Output = 0.328
For 3.28V and 90% duty cycle, output = 2.952
Working of PWM
Pulse Width Modulation (PWM) works by switching a digital signal between high (on) and low (off) states at a high frequency,
creating a square wave. The duration for which the signal remains in the "on" state within each cycle,
known as the duty cycle, determines the average power delivered to the load. By varying the duty cycle,
PWM can precisely control the output voltage or current without wasting energy.
➨For example, a 50% duty cycle delivers half the maximum power, while a 75% duty cycle delivers three quarters.
This efficient technique is widely used in microcontrollers for tasks like dimming LEDs, regulating motor speeds,
and generating audio signals.
PWM Applications
Following are some of the applications of PWM.
• Brightness control in smart lighting systems by controlling voltage to LED driver connected with LED bulbs.
• Speed control of motors by varying voltage supply to it.
• It is also used as modulation scheme to encode message into pulsing signal for transmission.
➨Refer PWM vs PAM vs PPM>>.
Advantages of PWM
Following are some of the benefits of PWM (Pulse Width Modulation). By leveraging these benefits, PWM is widely adopted in microcontroller-based designs across various industries.
1. Energy Efficiency :
PWM ensures minimal power loss by switching devices between fully on and fully off states, making it highly energy efficient.
2. Precise Control :
It offers precise control over output voltage and current, ideal for applications like motor speed regulation and LED brightness adjustment.
3. Heat Reduction :
By efficiently managing power, PWM minimizes heat generation in electronic circuits, reducing the need for extensive cooling solutions.
4. Versatility :
PWM is compatible with a wide range of applications, including motor control, audio signal generation, and power regulation.
5. Signal Integrity :
It enables high resolution control without distortion, ensuring reliable operation in sensitive devices.
6. Compact and Cost Effective :
PWM circuits are compact and can be implemented without complex hardware, reducing overall system cost.
7. High Speed and Accuracy :
PWM works at high frequencies, making it suitable for rapid and accurate modulation in dynamic systems.
Conclusion
PWM or Pulse Width Modulation, is an indispensable tool in the world of microcontrollers, enabling precise and energy efficient control of devices. Whether you're dimming LEDs, controlling motor speeds or generating audio signals, PWM provides the flexibility and simplicity needed for modern electronic applications. By mastering PWM, engineers and enthusiasts can unlock the full potential of microcontroller based systems.
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