Introduction to the causes of damage to LED lamp beads and protection methods
White LED lamp beads are voltage-sensitive devices. In actual work, the current is 20mA as the upper limit. However, the current will often increase due to various reasons in use. If no protective measures are taken, this increase The LED lamp beads will be damaged after the current exceeds a certain time and amplitude.
The main reasons for the damage of LED lamp beads are:
① The short circuit of a certain component or printed line or other wires in the circuit forms a local short circuit of the power supply path of the LED lamp beads, which increases the voltage in this place.
② Sudden increase in power supply voltage.
③The temperature inside the lamp is too high, which makes the characteristics of the LED lamp bead deteriorate.
④ A certain LED lamp bead is short-circuited due to its own quality damage, and its original voltage drop is transferred to other LED lamp beads.
⑤When assembling, the anti-static work was not done well, so that the inside of the LED lamp bead has been damaged by static electricity. Although the normal voltage and current values are applied, it is very easy to cause damage to the LED lamp beads.
⑥Water enters the lamp, and the water is conductive.
So, should we protect the LED lamp beads?
1. Use transient voltage suppression diode
Transient voltage suppression diode is a high-efficiency protection component in the form of a diode. 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 speed of 10 minus 12 seconds in a very short time, and absorb 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. Transient voltage suppression diodes have the advantages of fast response time, large transient power, low leakage current, good uniformity of breakdown voltage deviation, easier control of the 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 bead is mainly caused by the overheating inside the chip due to excessive current. TVS can only detect overvoltage but not overcurrent. It is difficult to select a suitable voltage protection point, and this kind of device cannot be produced and it is difficult to use in practice.
2. Fuse is used in the protection circuit
Because the fuse is disposable, the reaction speed is slow, the effect is poor, and the use is troublesome, so the fuse is not suitable for use in the finished LED lamp, because the LED lamp is now mainly used in the city's glorious project and lighting project. It requires the LED lamp bead protection circuit to be very harsh: the protection can be activated immediately when the normal use current is exceeded, so that the power supply path of the LED is disconnected, so that the LED and the power supply can be protected, and it can automatically restore after the entire lamp is normal. Power supply does not affect the operation of the LED. The circuit cannot be too complicated, not too big, and the cost is low. Therefore, it is very difficult to implement using a fuse.
3. Select the self-recovery fuse
Self-recovery fuse, also known as polymer positive temperature thermistor PTC, is composed of polymer and conductive particles. After special processing, the conductive particles form a chain-like conductive path in the polymer. When the normal working 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, the heat generated by the large current causes the polymer to expand rapidly, and it is cut off. The conductive path formed by conductive particles, the PTC resettable fuse is in a high resistance state; when the overcurrent in the circuit disappears, the polymer cools and the volume returns to normal, and the conductive particles re-constitute the conductive path, and the PTC resettable fuse assumes the original state. Low resistance state.
The above is the protection method of LED lamp beads, I hope it will be helpful to everyone.
