PWM Explained
Pulse-width modulation: how a digital square wave controls an analogue value.
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What you will learn
- Define duty cycle and frequency
- Explain average voltage
- Relate PWM to actuator control
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Pulse-width modulation keeps the output fully on or fully off but varies how long it stays on. The ratio of on-time to total period is the duty cycle. A 50% duty cycle at 12 V gives an average of about 6 V, which is why PWM can dim a lamp, set a solenoid position or run a motor at a chosen speed.
Because the switch losses are low, PWM is efficient. Frequency is chosen so the load does not vibrate or buzz audibly — and some actuators behave badly when the frequency or duty is wrong.
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Key points
- Duty cycle sets the average value.
- PWM is efficient because the switch is either off or on.
- Always confirm the load responds, not just the signal.
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Key points
- PWM switches fully on and off
- Duty cycle sets the average
- Frequency matters for some loads
All values shown are training examples. Real thresholds depend on the manufacturer, engine, temperature and system — always confirm with the vehicle service documentation.
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