* Question
What is the principle of PWM?
* Answer
Principle of Pulse Width Modulation (PWM)
1. What is PWM?
Pulse Width Modulation (PWM) is a technique for controlling the amount of power delivered to an electrical device by adjusting the width of the ON pulse in a periodic digital signal. It is widely used in electronics for tasks such as motor speed control, LED dimming, and power regulation.
2. How PWM Works
PWM generates a square wave signal at a constant frequency, but with a variable duty cycle—the percentage of time the signal is in the HIGH (ON) state during one cycle.
Duty Cycle (%)=(ON Time/Total Period)×100
By increasing or decreasing the duty cycle, the average voltage or power delivered to the load is modified:
100% duty cycle → fully ON → maximum power
50% duty cycle → ON half the time → half power
0% duty cycle → always OFF → no power
Though the signal is digital (ON/OFF), the result is an analog-like effect due to time averaging.
3. Key Parameters
Frequency: The number of PWM cycles per second, typically in hertz (Hz).
Duty Cycle: The proportion of the cycle that the signal remains ON.
Period: The total duration of one PWM cycle, equal to 1 / frequency.
4. Applications
Application | Description |
Motor Control | Adjusts speed by controlling average voltage |
LED Brightness | Modifies perceived brightness through ON-time modulation |
Power Supply Design | Used in switch-mode power supplies to regulate output |
Signal Generation | Converts digital signals into analog-like outputs via filters |
5. Advantages of PWM
High efficiency due to minimal power loss in switching states.
Digital compatibility, allowing easy implementation with microcontrollers.
Precise control over power without requiring digital-to-analog conversion.
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