LED flashlights can be used at home and out at night. This flashlight has a rechargeable battery as a power source, and some can be recharged more than 2000 times. It can be used for several days after a single charge. The LED flashlight has high brightness and the irradiation distance can reach 100 meters to 1000 meters. , And consume less power at the same time. When the LED flashlight does not light up, we need to find the point of failure and then deal with it accordingly. The following is the working principle of the circuit and maintenance methods of the LED hand power supply.

The working principle of the circuit

Although the LED flashlight circuit is relatively simple, it is necessary to know its circuit wiring and working process when repairing it. This kind of LED flashlight charging is generally made by AC 220V city power 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 capacitance of the capacitor is between 1 microfarad and 0.68 micros. Between methods, the withstand voltage can be 400V to 450V. Then four IN4007 rectifier diodes form a rectifier circuit, and the DC power obtained after rectification charges the battery.

 Generally, it takes about 7 to 8 hours to fully charge the battery. This is mainly related to the resistance-capacitance step-down link. When using LED flashlights, you will find that some have two dimming functions, which are usually 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 is adjustable to a strong light state by connecting a smaller resistor in series.

Repair method

1. Inspection of the switch and LED lamp failure

Combining with the circuit diagram of the LED light, we can analyze that when the flashlight is not on, it is mainly because those links have failed. According to the principle of "from simple to easy" in maintenance, we first connect the flashlight with a 220 volt AC charging voltage to see if the LED light is bright. If it is not good, we use a multimeter resistance file (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 poorly contacted or damaged and cannot be turned on. 

If the switch is turned on well and the LED light still does not light, it means that the LED light is damaged (because the LED lights are connected in parallel, it may be that one light does not turn on or several lights do not turn on), then it is enough to replace the same type of LED light. Pay attention to the polarity not to be reversed.

In addition, if the LED battery is damaged, it can show that it cannot be charged. It can only light up when it is plugged into the mains socket. This is to replace the battery of the same specification.

2. Repair methods for faults in the resistance-capacitance step-down link and the charging link

If it appears that it cannot be charged, we must detect the damage of the high-voltage resistance and capacitance link, first cut off the power and use a multimeter to test whether the resistance is open, and then measure the high-voltage capacitor to see if it fails. 

This high-voltage capacitor generally has a withstand voltage between 250V and 400V, if it is a capacitor If it breaks down, you need to replace a capacitor with the same capacity and a larger withstand voltage, for example, it can be increased to 450V. After replacement, the rectifier circuit should be tested to see if there is a breakdown or short-circuit failure. According to experience, if the capacitor is broken down, the failure rate of the rectifier diode will greatly increase, so the rectifier must be tested.

If it is the quality of the LED flashlight itself, we can contact the repair shop of the merchant for repair or replacement. If you want to learn more about LED flashlights after reading the above content, you can contact us to get a more comprehensive solution.

As a professional manufacturer of LED light products, we have accumulated rich manufacturing experience. We have a professional production team and strict quality management system, which can conduct a full range of inspections on the quality of our products. We can also provide thoughtful one-stop service according to customer needs. If you are interested in our LED flashlights, please contact us immediately!