Emergency lights are mainly used to provide emergency lighting after the normal lighting power is cut off or the power grid loses power. They are often used in factories, mines, institutions, schools, buildings and tunnels. The emergency lighting system used in China 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