IC Controlled Emergency Light with Charger Circuit Design

Circuit diagram:

Description

Here is the circuit diagram of IC Controlled Emergency Light With Charger or simply 12V to 220V AC inverter circuit. The circuit presented here is that of the IC controlled emergency light. Its key characteristics encompass automatic switching-on of the light during mains outages and a battery charger incorporating over-charge protection features. When the mains power is unavailable, relay RL2 remains in an inactive state, feeding the battery power to the inverter section via its normally closed contacts and switch S1.

The inverter section is based on IC2 (NE555), utilized in a stable mode to generate sharp pulses at a frequency of 50 Hz for driving the MOSFETs. The output from IC2 is directly applied to the gate of MOSFET (Q4) while it’s also fed to the gate of MOSFET (Q3) after inversion by transistor Q2. Consequently, the power amplifier constructed around MOSFETs Q3 and Q4 operates in a push-pull configuration. The output across the secondary of transformer T2 can easily power a 230-volt, 20-watt fluorescent tube. To deactivate the light during power failure, simply switch S1 to the off position. The battery overcharge prevention circuit is built around IC1 (LM308).

Its non-inverting pin is maintained at a reference voltage of approximately 6.9 volts, obtained using diode D5 (1N4148) and a 6.2-volt zener D6. The inverting pin of IC1 is connected to the positive terminal of the battery. Therefore, when the mains supply is active, IC1 comparator output is high, unless the battery voltage exceeds 6.9 volts. Consequently, transistor Q1 is normally forward-biased, which energizes relay RL1. Within this state, the battery remains on charge via the normally open contacts of relay RL1 and a current-limiting resistor R2. If the battery voltage surpasses 6.9 volts (an overcharged condition), IC1’s output goes low and relay RL1 becomes inactive, thus halting further charging of the battery. MOSFETs Q3 and Q4 may be mounted on appropriate heat sinks.

Parts: