Incandescent lamp life extension switch circuit (3)

It is an incandescent lamp with a two-wire connection method . Its warm-up time is relatively long, so
its service life is quite long.
    After closing switch S, only
negative 3F cycles of 220V AC power pass through VD1 and S to make bulb E energize and emit
light. At this time, it is in a half-voltage preheating state. The positive half cycle of alternating current
passes through VD2 and R. , R. divides the voltage to
charge the capacitor (-- until the voltage L at both ends of C rises to more than 3V
, breaks down the voltage regulator tube VS and turns on the thyristor
VT. At this time, the bulb E turns on and lights up.
The circuit half voltage The preheating time is mainly determined by the voltage stabilization value of vs and
the capacity of the capacitor C. The preheating time of the data shown in the figure is about 2s. VT can use micro-triggered unidirectional thyristors
with smaller triggering current , such as 2N6565, MC, R100 type 8 etc. vs is a 3V, 1/2W Zener diode. There are no special requirements for other components.