Abstract: A circuit for providing firing signals for SCRs, particularly suitable for use where the power waveform is distorted. The firing signals are based on fixed angles of the power signal rather than on a time basis. Ramp signals from a ramp generator are compared with a loop error voltage or reference voltage for providing the SCR firing signals. A voltage controlled oscillator in a phase locked loop generates an undistorted signal used to start the ramp generator. The output of a lowpass filter in the phase locked loop provides a frequency compensating signal for controlling the slope of the ramp signals.