PURPOSE: To reduce connection wires while improving the utilization rate of transformers by arranging a short stop section for the waveform of d.c. current fed to a digital timer with a pulse wave drawn from a part of a power half-wave.

CONSTITUTION: The voltage of a capacitor C2 is divided with resistances R2, R3 and R4 and connected to negative input terminals of comparators CP1 and CP2 while the secondary voltage of a transformer T is connected to a positive terminal through a diode D2. The output of the comparators CP2 and CP3 is connected and the positive input terminal of the comparator CP3 provides a voltage in a advanced phase. Therefore, following about 90° in the wave of a voltage Vb, a voltage Vc falls down to zero and the output of the comparator CP3 moves to a level L. The level H of the comparator CP2 is suppressed so much that pulses are cancelled appearing as the output of a window type comparator in a negative gradient area of the voltage Vb leaving only those in the positive gradient area. The output of a comparator CP4 is applied on the base of a transistor TrQ2 to invert the phase. Thus, an emitter voltage VOUT of a transistor TrQ1 is outputted.