Power outage emergency light circuit (2)

Figure 282 shows another simple power outage
emergency light circuit . When the power grid stops supplying normal power, the mains
power is stepped down by T, rectified by VD1~VD4, filtered by C- and passed through R. and VD5 to charge the battery (;. At this time,
VT1 is closed and R. is forward-biased and conducts, and its collector is at low potential, so V, r2 is cut off, and the small light F does not light up. When the city
lu suddenly loses power, due to the isolation of VD5 , G
will not pass through R. Supply power to the base of VT1, VT]
is cut off due to a power outage, thereby releasing
the blockade of VT2, VT2 is turned on because the base passes through the ruler. It obtains bias current from the battery G
, and the emergency light E is powered on The requirements for light emission
,
    voltage regulator T, battery (G) and small lamp E are
the same as those in the seven examples. The parameters of other components are shown in the figure. There are no
special requirements.