Failure Analysis of LED lamps and circuit protection measures

The reason for the damage of LED lamps in 'China Building Materials Network' is that the failure of LED lamps comes from the failure of power supply and drive, and the failure of LED devices themselves. Generally, the damage of LED power supply and drive comes from the over-power impact of input power supply (EOS)And the fault of the load end. The over-power impact of the input power supply often causes damage to the drive chip in the drive circuit and breakdown damage to passive components such as capacitors. The short circuit fault at the load end may cause the over-current drive of the drive circuit, and the drive circuit may have short circuit damage or overheating damage caused by short circuit fault. The failure of LED device itself mainly includes the following situations. Transient overcurrent event means that the current flowing through the LED exceeds the large rated current in the LED Technical Data Manual, which may be caused directly by large current or indirectly by high voltage, overcurrent caused by overvoltage events such as transient lightning strike, transient switching noise of switching power supply, grid fluctuation, etc. These events are transient and have a very short duration. We usually call them spikes, such as current spikes and voltage spikes. The situation that causes transient overcurrent events also includes the transient overcurrent when the LED is turned on or when the LED is plugged in and out with electricity. For LED lighting in automobiles, ISO7637- 2 transient throwing load surge impact is an important threat to its normal operation. The failure mode after LED suffers from electric shock is not fixed, but it usually causes welding line damage, as shown in Fig. 1. This kind of damage is usually caused by a very large transient overcurrent. In addition to causing the welding line to burn out, it may also cause damage to other parts near the welding line, such as sealing materials.