Principle and Improvement Principle: The 220V AC power supply is subjected to C1 voltage reduction (R1 is the discharge resistance), VD1-VD4 rectification, and C2 filtering to provide a DC current of about 100mA to the electromagnetic relay J with conversion contacts to make it close, J-1 conduction, and the charging circuit is isolated by VD5 to charge the battery GB. LED1 and LED2 light up, indicating that charging is in progress. When there is a power outage, J loses power and J-1 returns to the lighting circuit, disconnecting the charging circuit. At this point, S1 and S2 can be turned on respectively to light up the emergency lighting of incandescent beads EL1 and EL2. [1] The faults in repairing this lamp often occur on the voltage reducing capacitor C1 and the battery GB. When C1 fails, there are cracks or burn marks on the shell, internal open circuit, and the fault phenomenon is that there is no output voltage at points A and B. Selectable voltage withstand 400V, 1.0-2.2 μ Replacement of F's polyester capacitor (the capacity of the step-down capacitor is proportional to the output current, when the AC input voltage is 220V: O.1 μ F is 70mA; one point two μ F is 82mA; one point five μ F is 105mA; two point two μ F is 157mA). The highest failure rate of this lamp is the 6V2Ah sealed battery GB, which mostly fails due to dry electrolyte. It can be repaired according to the six methods introduced in the 21st edition of the article in the 34th issue of Electronic News in 2007, with ideal results. Improvement 1. Lighting: Change 6V0.5A incandescent bead EL to φ 5mm white high brightness LED, the two EL's in the original circuit can work continuously for 2 hours with sufficient power in GB. When replacing one EL with two LEDs in series, the power consumption is 20 μ A-30 μ Between A, the lighting time can be significantly extended. 2. Voltage stabilization and current limitation: The no-load voltage of point AB is 30V without connecting to the charging circuit, and regardless of whether the GB is fully charged or not, its charging current is around 100mA, which affects the lifespan of the GB
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