Although LED technology is the mainstream in today's market, there are still many unsolved problems in LED technology, and LED lifespan, energy saving, and price issues have always been the topics of enthusiastic discussion. In this process, the LED circuit protection circuit is very important. Let me talk about nothing, let's discuss the three protection methods of the LED circuit:
1. A fuse (tube) is used to protect the LED circuit
Because the fuse is disposable, and the reaction speed is slow, the effect is poor, and the use is troublesome, the fuse is not suitable for use in the finished LED lamp, because the LED lamp is now mainly in the city's glorious project and lighting project. It requires the LED protection circuit to be very harsh: protection can be started immediately when the normal use current is exceeded, the power supply path of the LED is disconnected, so that 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 low. Therefore, it is very difficult to realize by fuse.
2. Select self-recovery fuse
Self-recovery fuse, also known as polymer polymer positive temperature thermistor PTC, is composed of polymer and conductive particles. After special processing, the conductive particles form a chain-shaped conductive path 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-impedance state; when an abnormal overcurrent passes (or the ambient temperature increases) in the circuit, the large current (or ambient temperature increases) The generated heat causes the polymer to expand rapidly, which cuts off the conductive path formed by conductive particles. The PTC self-recovery fuse is in a high-resistance state; when the overcurrent (overtemperature) in the circuit disappears, the polymer cools and the volume recovers Normally, the conductive particles reconstruct the conductive path, and the PTC resettable fuse assumes the initial low resistance state. In normal working state, the self-recovery fuse has very little heat. In abnormal working state, its heat is very high and its resistance value is very large, which also limits the current passing through it and thus plays a protective role. In the specific circuit, you can choose:
â‘ Shunt protection. Generally, LED lights are divided into many serial branches. We can add a PTC element in front of each branch to protect separately. The advantages of this method are high accuracy and good reliability of protection.
â‘¡Overall protection. Add a PTC element in front of all the light beads to protect the whole lamp. The advantage of this method is that it is simple and does not occupy volume. For civilian products, the results of this protection in actual use are satisfactory.
3. Use transient voltage suppression diode (referred to as TVS)
Transient voltage suppression 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 reduce the high resistance between its two poles to low resistance at a very short time of 10 negative 12th power seconds, absorbing surge power of up to several kilowatts. , The voltage clamping element between the two poles is at a predetermined voltage value, which effectively protects the precision components in the electronic circuit. Transient voltage suppression diodes have the advantages of fast response time, large transient power, low leakage current, good consistency of breakdown voltage deviation, easy control of clamp voltage, no damage limit, and small size.
But in actual use, it is not easy to find TVS devices that meet the required voltage value. The damage of the LED bead is mainly caused by the overheating inside the chip due to the current passing through the ambassador. TVS can only detect overvoltage but not overcurrent. It is difficult to choose the appropriate voltage protection point, this device cannot be produced and is difficult to use in practice.
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