Power outage emergency light circuit

281 is a simple power outage emergency circuit . When the 220V AC power grid suddenly loses power, the small lamp
will automatically light up. When the power grid is supplying power normally, the alternating current is reduced by jK, VIJ [~~7] through the transformer T. The 4-bridge
rectifier and (filter) output a DC voltage of about 7V. At this time, the PNP tube VT1 is turned on, and the upper end of R
is high . level, the pNp tubes VT2 and VT3 are both cut off, and the small light E does not light up. At the same time, the 7V current i voltage decelerates to
VD5 and R; it charges the battery G. If the power grid suddenly loses power, VTI loses its electrode bias current and cut off,
VT2 can obtain the base bias current through R and be turned on, VT3 is turned on one after another, and the small lamp E is energized and emits light for emergency lighting
. At this time, VI)5 is reverse biased, preventing the battery (; from discharging to VT1.
    T The temple adopts 220V, /5v, SVA high-
quality power transformer, which is required to be powered on for a long time
without generating heat. The amplification factors of VTl---VT3
are required to be 100. G uses 4 sections of 12V
nickel-cadmium or nickel-neon voltage transformer. Series connection. F can use
small light bulbs of 38~4.8V, 03A.