Switch-Mode Power Supplies

EE October 1987 SWITCH-MODE POWER SUPPLIES Recent advances in power semiconductor technology and inductive components have boosted the use of compact, high efficiency power supplies of the switch-mode type. Now SMPSs of various power ratings are becoming widely available at reasonable prices, it seems timely to focus on their design principles and practical aspects. Most electronic circuits can not work without a power supply of some kind. The basic mains supply consists of a trans- former, a rectifier, a filter (smoothing/reservoir capaci- tor), and a linear control circuit (regulator) for adjusting the out- put voltage to the desired value. It may be argued that the basic power supply has a number of important disadvantages. For relatively high powers, the mains transformer is often bulky and expensive, and the same goes for the smoothing capacitor(s). Moreover, the product of the voltage drop across the regulator and the current consumption of the load forms dissipated, and the...