Power Supply Design -an introduction Adapted from a Presentation By Doug Miller, SPU EE Alumnus

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

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