Power Supply Design

-an introduction

Adapted from a Presentation By Doug Miller, SPU EE Alumnus

Power Supplies Overview • Linear Regulators • Switching “DC-to-DC Converter” Regulators

Linear Regulators + Simple, inexpensive + Electrically “quiet” pure DC output - Vout < Vin - Poor Efficiency e.g., if Vin = 6V, Vout = 3V, Efficiency near 50% - Can be physically large

Switching Regulators • Also known as “DC-DC Converters” or “Switchmode Regulators” + Wide range of input voltages + Multiple output voltages possible + High Efficiency (often > 90% ) + Compact - Complex, more expensive - Electrically “noisy” (not pure DC)

Switching Regulators A few types… • Buck (step-down) • Boost (step-up) • Flyback (supports multiple outputs; transformer needed) • Buck-boost (step-up or –down) • Charge Pump (no inductor)

Switching Regulators Buck Converter – V Down only

Switching Regulators Boost Converter – V up only

Switching Regulators Buck-Boost – V Up or Down • What the source power fluctuates up/down past the desired output voltage?

• A Buck-Boost regulator can go either way as needed • More complicated, but often worth it

Design Considerations • Use linear regulators only if: – Energy conservation is not a concern – Wasted power is insignificant (less than 1 Watt) – Low noise is critical • Switching regulators are finicky – Use only the specified parts (by brand if possible) – Read and follow app note precisely • Make regulators “isolatable” with jumpers and/or fuses that can be removed