LED lamps do not light up, LED power supply damage, LED damage and LED circuit damage account for a certain proportion; in the actual LED lighting application process, because LED is an electrically sensitive component, to prolong the life of LED, it is necessary to do a good job LED circuit protection measures, the analysis of LED circuit protection measures is as follows:
1. The fuse (tube) is used in the protection circuit
Because the fuse is one-time, and the response speed is slow, the effect is poor, and the use is troublesome, so the fuse is not suitable for use in finished LED lights, because LED lights are now mainly used in urban glory projects and lighting projects. It requires the LED protection circuit to be very strict: when the current exceeds the normal use current, the protection can be started immediately, so that the power supply path of the LED is disconnected, so that both the LED and the power supply can be protected, and the power supply can be automatically restored after the entire lamp is normal. Does not affect the LED work. The circuit should not be too complicated, the volume should not be too large, and the cost should be lower. Therefore, it is very difficult to use the fuse method.
2. Use Transient Voltage Suppression Diodes (TVS for short)
A TVS diode is a high-efficiency protection device in the form of a diode. When its two poles are impacted by reverse transient high energy, it can immediately reduce the high resistance between its two poles to low resistance at a speed of 10 to the minus 12 second power in a very short time, absorbing up to several kilowatts of surge power , the voltage between the two poles is clamped to a predetermined voltage value, which effectively protects the precision components in the electronic circuit. TVS diodes have the advantages of fast response time, large transient power, low leakage current, good consistency of breakdown voltage deviation, easier control of clamping voltage, no damage limit, and small size.
However, it is not easy to find TVS devices that meet the required voltage value in actual use. The damage of the LED light beads is mainly caused by the overheating of the inside of the chip due to excessive current. TVS can only detect overvoltage but not overcurrent. To choose the appropriate voltage protection point is difficult to grasp, this kind of device cannot be produced and it is difficult to use in practice.
3. Select the resettable fuse
The resettable fuse, also known as the polymer positive temperature thermistor PTC, is composed of polymer and conductive particles. After special processing, the conductive particles form chain-like conductive paths in the polymer. When the normal operating current passes (or the component is at normal ambient temperature), the PTC resettable fuse is in a low resistance state; when there is an abnormal overcurrent in the circuit (or the ambient temperature rises), the large current (or the ambient temperature rises) The generated heat causes the polymer to expand rapidly, which cuts off the conductive path formed by the conductive particles, and the PTC self-recovery fuse is in a high resistance state; when the overcurrent (overtemperature state) in the circuit disappears, the polymer cools and the volume recovers Normally, the conductive particles re-form the conductive path, and the PTC resettable fuse is in the initial low resistance state. In the normal working state, the heat generation of the self-recovery fuse is very small. In the abnormal working state, its heat generation is very high, and its resistance value is very large, which limits the current passing through it, thus playing a protective role. In a specific circuit, you can choose:
1. Shunt protection. Generally, LED lights are divided into many series branches. We can add a PTC component in front of each branch for protection. The advantage of this method is high accuracy and good reliability of protection.
2. Overall protection. Add a PTC component in front of all light beads to protect the whole lamp. The advantage of this method is that it is simple and does not take up volume. For civilian products, the results of this protection in practical use are still satisfactory
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