The main reasons for LED damage are:
(1) The power supply voltage suddenly rises;
(2) A certain component or printed line or other wire in the circuit is short-circuited to form a short-circuit of the local LED power supply circuit, which increases the voltage of the part;
(3) One LED is short-circuited due to its own quality damage, and its original voltage drop is transferred to other LEDs;
(4) The temperature inside the lamp is too high, resulting in deterioration of LED characteristics;
(5) The lamp is filled with water and conducts electricity;
(6) The anti-static work was not done well during assembly, so that the inside of the LED has been damaged by static electricity.
Although normal voltage and current values are used, it is also easy to cause damage to the LED.
Can the selection of suitable circuit protection components for LED be used for LED circuit protection? Here are some suggestions;
1. A fuse (tube) is used in the protection circuit
Because the fuse is disposable, and the response speed is slow, the effect is poor, and it is troublesome to use, so the fuse is not suitable for the finished product of LED lamps, because LED lamps are now mainly used in urban lighting projects and lighting projects. It needs to lead the protection circuit to be very harsh: if the current exceeds the normal use, the protection can be started immediately, so the lead power supply path is disconnected, so the lead and power can be protected, and the whole lamp is normal, and the power supply can be automatically restored without affecting the work. The circuit cannot be too complicated or too large, and the cost should be low. So it's hard to use a fuse.
2. Use a transient voltage suppressor diode (referred to as TVS)
A transient voltage suppressor diode is a high-performance diode protection device. When its two poles are hit by revers transient high-energy, it can immediately reduce the high resistance between the two poles to low resistance at a speed of 10-12 seconds, absorb up to several kilowatts of surge power, and make the voltage between the two poles The clamp is within the predetermined voltage value, effectively protecting the precision components in the electronic circuit. Transient voltage suppression diodes have the advantages of fast response time, high transient power, small leakage current, good breakdown voltage deviation-consistency, convenient breakdown voltage control, no damage limit, and small size.
However, in actual use, it is not easy to find a TVS device that meets the required voltage value. The damage of the LED lamp is mainly caused by the overheating inside the current ambassador chip. TVS can only detect overvoltage, not overcurrent. It is difficult to choose a suitable voltage protection point, so the device cannot be manufactured and is difficult to use in practice.
3. Choose resettable fuse
Self-resetting fuses, also known as polymer positive temperature thermistors PTC, are composed of polymers and conductive particles. After special treatment, the conductive particles form a chain of conductive paths in the polymer. When passing normal operating current (or the element is at normal ambient temperature), the PTC resettable fuse has low resistance.
When an abnormal overcurrent (or ambient temperature rise) occurs through the circuit, the heat generated by the large current (or ambient temperature rise) causes the polymer to expand rapidly, and at the same time cuts off the conductive path formed by the conductive particles, and the PTC resettable fuse is in high resistance. state; when the overcurrent (overtemperature state) in the circuit disappears, the polymer cools down, the volume returns to normal, the conductive particles reconstitute the conductive path, and the PTC self-resetting fuse returns to the initial low resistance state.
