Pulse-Width Modulation
Lesson notes
Overview
Switching a signal fully on and off quickly and varying the duty cycle controls average power. This topic is rated advanced and is number 36 of 93 in Engineering. Deeper models, formal results and harder reasoning.
What you are seeing
The panel above shows a graph of the function. Each slider changes one parameter, so you can see exactly how the curve bends, shifts or stretches. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.
In depth
Pulse-width modulation controls average power by switching a signal fully on and off very rapidly and varying the fraction of time it is on, the duty cycle D: V_avg = D·V. Switching wastes little energy compared with a resistor, so it is efficient. It is used to dim LEDs, control the speed of motors, regulate power supplies and produce audio in class-D amplifiers. The switching frequency is made high enough that the load smooths it.
Reading the relationship
The expression "V_avg = D·V" is a compact summary of the idea. It uses the symbols D, V; name what each one stands for before you start. Then use the sliders to see how changing one quantity changes the others.
A guided exploration
1. Set every slider to its middle value and note the shape of the curve. 2. Move one slider at a time and describe whether the curve shifts, stretches or turns. 3. Find the value where the behaviour changes sharply, then connect it to the formula.
Try this
Try to explain why the pattern holds, not just what it is. Look for limiting cases and what happens at the edges.
Common pitfalls
Always ask what the safety margin is and which assumption would break the design first. Idealised models hide losses, noise and limits.
How it connects
It builds on “RC Filter Frequency Response”, the topic before it in Engineering. Once you are comfortable, continue with “Shannon Channel Capacity”.
Why it matters
Engineers use this idea to design structures, machines and systems that are safe, efficient and reliable.
Where you might use it
- Revising “Pulse-Width Modulation” before a class, exam or certification
- Designing safe structures, machines and control systems that must work reliably
- Diagnosing faults in electrical, mechanical or signal-processing equipment
- Checking that a design meets safety margins before it is built or deployed
Frequently asked questions
What is Pulse-Width Modulation?
Switching a signal fully on and off quickly and varying the duty cycle controls average power. It is an advanced topic in Engineering.
How do I use the Pulse-Width Modulation simulation?
The panel at the top shows a graph of the function. Each slider changes one parameter, so you can see exactly how the curve bends, shifts or stretches. Move the sliders one at a time, then press Space to pause the animation and look closer.
What does the formula mean?
The expression V_avg = D·V packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.
Who is this topic for?
Deeper models, formal results and harder reasoning. If the quiz feels hard, reread the lesson notes and try the previous topic first.
What should I learn before this?
Start with “RC Filter Frequency Response”, the previous topic in Engineering. Each topic in a subject builds on the ones before it.
How do I track my progress?
Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.
Quick quiz
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