LED flashlights are widely used in some rural areas, for example, they can be used at home and at night. This flashlight has a rechargeable battery as a power source, and some can be recharged more than 2,000 times, and can be used for several days after a single charge. Moreover, this LED flashlight has high brightness, and the irradiation distance can range from 100 meters to 1,000 meters. , while consuming less power. It is widely used by our broad masses. Next, I will tell you how to repair the LED flashlight.

Although the LED flashlight circuit is relatively simple, it is necessary to know its circuit wiring and working process during maintenance. Let me tell you about its working process first. This kind of LED flashlight is generally charged by AC 220V mains through a resistance-capacitance step-down circuit composed of a resistor and a capacitor. The resistance of the resistor is generally between 330KΩ and 390KΩ, and the capacity of the capacitor is between 1 microfarad and 0.68 microfarad. Between the law, the withstand voltage value can be taken from 400V to 450V. Then, four IN4007 rectifier diodes form a rectification circuit, and the rectified direct current is used to charge the battery. Generally, it takes about 7 to 8 hours to fully charge, which is mainly related to the RC step-down link. When using LED flashlights, you will find that some have two dimming functions, which are generally realized by switching SW. As shown in the circuit diagram below, one group can be adjusted to a weak light state by connecting a larger resistor in series; the other group can be adjusted to a strong light state by connecting a smaller resistor in series.

Maintenance method of LED flashlight circuit

1. Inspection of switch and LED lamp failure

Combining with the circuit diagram of the LED light, we can analyze that when the flashlight does not light up, it is mainly because of the faults in those links. According to the principle of "from simple to easy" maintenance, we first connect the flashlight to the charging voltage of 220 volts AC to see if the LED light is correct. Bright. If it is bad, we use the multimeter resistance gear (power-off test) to measure whether the switch SW is in good contact. If the resistance is large or infinite, it means that the toggle switch is in poor contact or damaged and cannot be turned on. If the switch is turned on well and the LED light is still off, it means that the LED light is damaged (because the LED lights are connected in parallel, it may be that one light or several lights are off), then replace the same type of LED light. Note that the polarity cannot be reversed; in addition, if the LED battery is damaged, it may appear that it cannot be charged, and it can only light up when it is plugged into the socket of the mains. This requires replacing the battery with the same specification.

2. The maintenance method for faults in the resistance-capacitance step-down link and the charging link

If it shows that it cannot be charged, we need to detect the damage of the high-voltage resistance-capacitance link. First cut off the power and use a multimeter to measure whether the resistance is open, and then measure the high-voltage capacitor to see if it fails. This kind of high-voltage capacitor generally has a withstand voltage between 250V and 400V. If it breaks down, you need to replace it with a capacitor with the same capacity and a higher withstand voltage, for example, it can be increased to 450V. After the replacement, it is necessary to test the rectifier circuit to see if there is a breakdown or short circuit fault. According to experience, if the capacitor breaks down, the failure rate of the rectifier diode will increase greatly, so the rectifier must be tested.