Power Supplies

Publisher Summary The power supply is a vital part of any electronic product. It is the interface between the noisy, variable, and ill-defined power source from the outside world, and the hopefully clear-cut requirements of the internal circuitry. A conceptual block diagram for the two common types of power supply is linear supply mode and switch mode. The component blocks of a linear supply are common to all variants, and are described as input circuit and transformers that isolate the output circuitry from the AC input, and step down (or up) the voltage to the required operating level. The advantage of the direct-off-line switch-mode supply is that it eliminates the 50-Hz mains transformer and replaces it with one operating at a much higher frequency, typically 30_300 kHz. This greatly reduces its weight and volume. The technical and commercial considerations that apply to a power supply can add up to a formidable list including input parameters, efficiency, output parameters, abnormal conditions, and cost and availability requirements.