Common causes of LED lamp damage and protection solutions

As a new green lighting technology, high-power white LED has the advantages of high light conversion efficiency, low energy consumption, long life, and no maintenance, and is gradually being used in various lighting fields. The long life of LED is based on its safe working environment. For LED lighting, there are two main threats that affect its life: one is overcurrent shock, that is, the current applied to the LED exceeds the maximum rated current in the LED technical data sheet, including overcurrent shock caused by overvoltage; the other is overheating damage. These damages can be manifested as immediate failure of the device, or they may fail long after the overcurrent shock event, shortening the working life of the LED.

Causes of LED lamp damage

LED lamp failure comes from the failure of power supply and driver, and the failure of LED device itself. Usually, the damage of LED power supply and driver comes from overcurrent shock (EOS) of input power supply and short circuit failure of load end. Overcurrent shock of input power supply often causes damage to driver chip in driver circuit, and breakdown damage of passive components such as capacitor. Short circuit failure of load end may cause overcurrent drive of driver circuit, and driver circuit may be damaged by short circuit or overheating caused by short circuit. The failure of LED device itself mainly includes the following situations.

1. Transient overcurrent events

A transient overcurrent event is when the current flowing through an LED exceeds the maximum rated current in the LED technical data sheet. This may be caused directly by a large current or indirectly by a high voltage, such as transient lightning strikes, transient switching noise from a switching power supply, grid fluctuations, and other overvoltage events. These events are transient and last for a very short time. We usually call them spikes, such as "current spikes" and "voltage spikes." Other situations that cause transient overcurrent events include transient overcurrent when the LED is powered on or when it is plugged in or unplugged while powered on.

For LED lighting in automobiles, the transient load dump surge shock of ISO7637-2 is a major threat to its normal operation.

The failure mode of LED after overcurrent shock is not fixed, but it usually causes damage to the welding wire, as shown in Figure 1. This damage is usually caused by extremely large transient overcurrent. In addition to causing the welding wire to burn out, it may also cause damage to other parts close to the welding wire, such as sealing materials.

2. Electrostatic discharge incident

Electrostatic discharge (ESD) damage is the most common transient overvoltage hazard in the manufacturing, transportation and application of highly integrated semiconductor devices. LED lighting systems must meet the 8kV contact discharge of the "human body electrostatic discharge model" of the IEC61000-4-2 standard to prevent the system from failing due to overcurrent shock caused by electrostatic discharge.

The performance of the LED PN junction array will be reduced or damaged, as shown in Figure 2. The internal failure of the LED chip caused by the discharge path of the ESD event may only cause local functional damage, but in severe cases it may also cause permanent damage to the LED.