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Power electronics

Switching Regulators

How a switching regulator actually moves energy, how its parts are chosen, and why the layout is part of the circuit rather than a drawing of it.

  • Intermediate
  • 10 lessons

About this course

A switching regulator is one of the few circuits where the schematic tells you remarkably little. Two boards with identical schematics can differ by twenty degrees of temperature rise and a long way in radiated emissions, and the difference is in where the parts were placed and which numbers were chosen rather than copied.

This course works from the current. Where it flows in each switching state, which loop it closes through, what that loop does to the board, and which component parameter actually limits the design. The arithmetic is worked rather than quoted: every number here is derived in front of you, with its assumptions, so you can redo it for a different rail.

Scope is deliberately low voltage. Everything here is DC-DC conversion on a board, not mains input, isolation, or anything that touches a safety standard.

Course contents

In order. Each lesson assumes the one before it.

  1. How a Buck Converter Actually Works

    Two switch states, one inductor, and where the current goes in each.

  2. How a Boost Converter Works, and What It Costs

    Output voltage goes up. Input current goes up more.

  3. Buck-Boost: Three Different Circuits With One Name

    The requirement decides the topology, and they are not interchangeable.

  4. Switching Frequency: What Actually Changes

    Doubling the frequency halves the inductor and doubles a loss you were ignoring.

  5. How to Choose the Inductor for a Buck Converter

    Worked from a blank sheet: ripple, peak, RMS, saturation and heat.

  6. The Input Capacitor and the Hot Loop

    The one loop on the board that carries a square wave of current.

  7. Choosing the Output Capacitor

    Ripple is the easy part. Transient response and stability are not.

  8. The Feedback Node: Quiet, High Impedance, Easy to Ruin

    A few megohms of divider, a few millivolts of reference, and a switching node nearby.

  9. Switch Node Layout: Small, But Not At Any Price

    The node with the fastest voltage edges on the board, and a thermal job to do.

  10. Why a Switching Regulator Oscillates

    Phase margin explained without a control theory course.

Other courses

  • Power electronics

    Power Integrity & Decoupling

    Why a capacitor on the schematic is not a capacitor on the board, and how to decide placement, value and count with reasoning instead of folklore.

  • PCB design

    PCB Grounding & Return Paths

    Grounding explained as a current path rather than a set of rules: where return current actually flows, what changes with frequency, and how to review a finished board.

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