Triac phase control with a line-frequency control signal
Joseph M. Diamond · Proceedings of the Institution of Electrical Engineers · 1971
A triac control circuit is presented which provides continuous (phase) control in response to the amplitude of a sine-wave signal of line frequency. Such signals might be obtained from a variety of a.c. transducers; e.g. from a resistance thermometer in a line-frequency bridge. A negative-resistance circuit is used which increases the control voltage exponentially to the trigger level for small signals. General curves are presented for conduction angle and power output as a function of signal amplitude.