waveforms in Fig. 28-19. This ramp voltage, which has a constant peak-to-peak amplitude,
is compared with a control voltage. During alternate half-cycles when the ramp
voltage equals the control voltage, a pulse signal of controllable duration is generated as
is shown in Fig. 28-19. In this manner the delay angle can be varied over nearly the full
range between 0" and 180" and the delay angle is proportional to the control voltage.
Normally an integrated circuit such as one of the TCA780 family is used to implement this
control function. Such integrated circuits also incorporate additional features for start-up,
shut down, and so forth.