Chapter 1 of 5 · Chapter Overview

Buck Converter: Understanding Switch-Mode Power from Scratch

Build and simulate a Buck converter through 5 progressive circuits.

Starting from the basic need for voltage step-down, we answer step by step: Why not use a resistor divider? Can a switch reduce voltage? How do capacitors and inductors help? And how do they combine into an efficient DC-DC converter.

Start Lesson 1 Open complete Buck example

What you will learn in this chapter

Understand why Buck converters exist: efficient voltage step-down
Learn how switch + PWM produces an adjustable average voltage
See intuitively how capacitors and inductors each smooth the output
Understand why the LC filter combination is the core of a Buck converter

How to use this chapter

Each section has an interactive simulation. Run it, observe the waveforms, and try changing parameters (duty cycle, capacitance, etc.) to deepen your understanding.

Why Not Use a Resistor Divider?

The most intuitive way to reduce voltage is a resistor divider, but it has a fatal flaw: too much power loss.

The Simplest Switching Circuit: Square Wave Output

With switch + PWM control, the load sees a square wave. Average value Vout = D × VIN.

Adding a Capacitor: Some Smoothing, but Not Enough

A capacitor resists sudden voltage changes, smoothing the output through charge/discharge cycles. But a capacitor alone is not enough.

Adding Inductor and Diode: Limiting Current Slew Rate

The inductor resists sudden current changes; the diode provides a freewheeling path. Current is smoothed, but output voltage ripple remains large.

Inductor + Capacitor = The Complete Buck!

Inductor smooths current, capacitor smooths voltage. Together, the output is clean DC. This is the Buck converter.