ABSTRACT
Switch-mode power supplies (SMPSs) have almost completely overtaken linear power supply technology. Some arc lamp fixtures even use a SMPS that is matched to the lamp. Some SMPSs compensate for distortion power factor by adding power factor correction circuitry. There are several different SMPS designs, all of which are fairly complex but basically similar in operation. Regardless of the design, there are at least four stages that they have in common: rectification and filtering, pulse-width modulation, voltage transformation, and feedback and control. The output of the transformer is a high-frequency square wave, but if the goal of the SMPS is to supply direct current (DC) then it will have an additional stage to filter out the high frequency and convert it to steady-state DC. Transformers can have one or more taps for the purpose of supplying a variety of voltages in a single package.
