Signcomplex Limited.
Signcomplex Limited.

Analysis of the Working Principle of Emergency Lights

Mar, 22, 2022

1. Introduction of emergency light

Evacuation emergency lights and sign lights, collectively referred to as fire emergency lighting lamps, are an important product required in fire safety measures. Usually it should provide lighting like ordinary lamps. When there is an emergency, such as an earthquake, fire or circuit failure, the power supply is suddenly interrupted, and all light sources have stopped working. At this time, the emergency lamp must provide reliable lighting immediately and indicate the evacuation of people. The direction of the emergency exit and the location of the emergency exit to ensure the smooth evacuation of people stranded in the dark. So what is the working principle of emergency lights?


2. The working principle of emergency lights

The emergency lighting system is mainly of the independent control type with its own power supply. The normal power supply is connected to the general lighting power supply circuit, and the emergency light battery is usually charged. When the normal power supply is cut off, the backup power supply (battery) automatically supplies power. Each lamp of this form of emergency lamp has a large number of electronic components such as voltage transformation, voltage stabilization, charging, inverter, storage battery, etc. The battery needs to be charged and discharged when the emergency light is used, repaired, or malfunctions.

The other is the centralized power supply centralized control type. There is no independent power supply in the emergency lamps. When the normal lighting power supply fails, the centralized power supply system will supply power. In this form of emergency lighting system, all the complicated electronic circuits inside the emergency lamps are omitted. The emergency lamps are no different from ordinary lamps, and the centralized power supply system is set in a dedicated room. When the power supply is normal, J2 (condenser) is energized and closed, its moving contact is connected with "N/O (normally open)", and the positive terminal of the backup battery is connected to the reverse terminal of IC1. IC1 (LM308) and D5, D6 form a voltage comparator, and the reference voltage is determined by D5 and D6. The charging current can be adjusted by changing the resistance of R2. As the charging time increases, the voltage of IC1's pin 2 gradually increases. When the voltage is greater than the reference voltage of 6.9V, IC1's pin 6 outputs a low level, T1 is cut off, and J1 (Polymer) loses power, disconnects the charging circuit and realizes automatic charge protection function.

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