Power electronics deals with the application of electronic devices and associated components to the conversion, control, and conditioning of electric power. The primary characteristics of electric power, which are subject to control, include its basic form (ac or dc), its effective voltage or current (including the limiting cases of initiation and interruption of conduction), and its frequency and power factor (if ac). The control of electric power is a means for achieving control or regulation of one or more nonelectrical parameters, e.g., the speed of a motor, the temperature of an oven, the rate of an electrochemical process, or the intensity of lighting.

Aside from the obvious difference in function, power-electronics technology differs markedly from the technology of low-level electronics for information processing in that much greater emphasis is required on achieving high-power efficiency. Few low-level circuits exceed a power efficiency of 15 percent, but few power circuits can tolerate a power efficiency less than 85 percent. High efficiency is vital, first, because of the economic and environmental value of wasted power and, second, because of the cost of dissipating the heat it generates. This high efficiency cannot be achieved by simply scaling up low-level circuits; a different approach must be adopted.

This different approach is attained by using electronic devices as switches, e.g., approximating ideal closed (no voltage drop) or open (no current flow) switches. This differs from...