Abstract: A power control circuit in which a direct current voltage (Vp) proportional to the a.c. power applied to a load (L) is derived from voltages (Vc and Vv) proportional to the a.c. current flowing in the load (L) and the a.c. voltage across the load, respectively, and compared with a voltage (Vnp) representing nominal power to the load to provide a d.c. signal (Vd) the amplitude of which is utilized in conjunction with a staircase or ramp generator (SG) to add or deduct cycles of the a.c. power to or from the load circuit according to a predetermined load power rating and in dependence upon variations in the a.c. supply voltage to the load and changes in resistance of the load.