Power outage emergency lights (4)

The charging circuit is composed of transformer Tl, diodes VDI-VD4 and other components. The 220V AC power is stepped down by Tl,
rectified by VDI~VD4, and filtered by CI to become smooth direct current, which provides charging power for the battery G. S is the function selection switch , and the position shown in the picture
is the charging state. At this time, the DC voltage charges the battery G through the resistor Rl. The light-emitting tube LED is a charging indicator. When the battery
G is fully charged, the voltage drop on Rl also decreases due to the reduced charging current. If it is not enough to maintain the LED conduction, the LED will
automatically go out, indicating that G is fully charged.
    When the switch s is moved to position 3, it is the emergency lighting state. The transistor VT, the coils L1 and L2 of the boost transformer 1r2
and the capacitors C3~C5 form an inductive feedback oscillator. The oscillation voltage is boosted by the boost coil L3 and directly added to
both ends of the fluorescent tube H to excite the lamp H to emit light. When the switch is moved to position "2", it is in the off state.