Incandescent lamp life extension switch circuit (1)

The thermal resistance of the incandescent lamp filament is relatively small and the cold resistance is very small. Therefore, at the moment when the lamp is turned on, the impact current flowing through the filament
is very large, which can easily cause the filament to be burned and damaged. The use of a life extension switch with a circle of 1l/ji can solve this problem and
extend the service life of the bulb .
    When the switch S is turned on,
the voltage at the capacitor terminal cannot change suddenly, so the voltage at the terminal (1A) is zero, and the thyristor
VT has no trigger voltage and is cut off. At this time,
the current flowing through the bulb K is rectified by VD2 Half-wave current, the bulb
is preheated and glows dimly, and the impact current is very small. At this time, the capacitor f
is charged by VD1 and R. After a delay of about 0.6 s, the voltage
at both ends of rises and reaches the opening level of the thyristor VT. ,
VT is turned on, and the bulb E is lit normally.
There is a buffer delay time of 0.6s between the cold state and normal lighting of the bulb E, so the service life of the bulb is extended.