A Novel Method of Direct Digital Integral-Cycle Power Control

A circuit, based on pulse-rate techniques, is described which provides direct digital integral half-cycle thyristor (or triac) control of ac power. It is shown, and proved experimentally, that the method provides the optimum time distribution of the conducting half-cycles. This results in minimal temperature ripple when, for example, the circuit is used to control heater power. The circuit is simple and inexpensive and uses only standard components.