Experience summary of 3 protection methods for LED circuits

Although LED technology is the mainstream in today's market, there are still many unsolved problems in LED technology, and the lifespan, energy saving and price of LED have always been hotly discussed topics. In this process, the protection circuit of LED circuit is very important. Without saying anything else, let's first discuss the experience summary of 3 protection methods of LED circuit:

1. Use fuses (tubes) to protect LED circuits

Since fuses are disposable, slow to react, poor in effect, and inconvenient to use, fuses are not suitable for LED lamps . LED lamps are now mainly used in urban lighting projects. It requires the LED protection circuit to be very demanding: when the normal current is exceeded, the protection can be activated immediately, so that 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, without affecting the operation of the LED. The circuit cannot be too complicated, the volume cannot be too large, and the cost must be low. Therefore, it is difficult to implement using fuses.

2. Use transient voltage suppression diodes (TVS for short )

Transient voltage suppression diodes are a type of high-efficiency protection device in the form of diodes. When its two poles are subjected to a reverse transient high-energy impact, it can immediately reduce the high resistance between its two poles to a low resistance at a very short speed of 10 to the negative 12th power of seconds, absorb up to several kilowatts of surge power , clamp the voltage between the two poles at a predetermined voltage value, and effectively protect 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, easier control of clamping voltage, no damage limit, and small size.
However, in actual use, it is found that it is not easy to find TVS devices that meet the required voltage value. The damage of LED light sources is mainly caused by excessive current causing overheating inside the chip. TVS can only detect overvoltage but not overcurrent. It is difficult to select the appropriate voltage protection point, so this device cannot be produced and is difficult to use in practice.

3. Choose a resettable fuse

The resettable fuse is also called a polymer positive temperature thermistor (PTC), which is composed of polymers and conductive particles. After special processing, the conductive particles form a chain-like conductive path in the polymer. When the normal working current passes through (or the component is at normal ambient temperature), the PTC resettable fuse is in a low resistance state; when an abnormal overcurrent passes through the circuit (or the ambient temperature rises), the heat generated by the large current (or the ambient temperature rises) causes the polymer to expand rapidly, thus cutting off the conductive path formed by the conductive particles, and the PTC resettable fuse is in a high resistance state; when the overcurrent (overtemperature state) in the circuit disappears, the polymer cools down and the volume returns to normal, in which the conductive particles re-constitute the conductive path, and the PTC resettable fuse is in the initial low resistance state. In the normal working state, the resettable fuse generates very little heat, and in the abnormal working state, it generates very high heat and has a large resistance, which limits the current passing through it, thereby playing a protective role. In a specific circuit, you can choose:

①Branch 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 protection reliability.

② Overall protection. Add a PTC element in front of all light beads to protect the entire lamp. The advantage of this method is that it is simple and does not take up space. For civilian products, the results of this protection in actual use are satisfactory.