High-power white LED as a new type of green lighting technology, light conversion efficiency, low energy consumption, long life, no maintenance and other advantages, and gradually be applied to a variety of lighting areas. Led the long life is based on its safe working environment, for LED lighting is concerned, there are two main threats affect its life: First, over-shock, that is, the LED applied to the current exceeds the LED technical data in the maximum rated current , Including overpressure caused by over-voltage shock; the other is overheating damage. These damage can be expressed as immediate failure of the device, it may occur in the over-current shock event after a long time to fail, shorten the LED working life.
LED lighting damage causes
LED lamp failure is derived from the power supply and drive failure, the second is derived from the LED device itself failure. Often the damage to the LED power supply and drive comes from the over-current shock (EOS) of the input power supply and the fault at the load side. The input power of the over-voltage shock will often cause the drive circuit to drive the chip damage, as well as capacitive passive components such as breakdown damage. Short-circuit fault at the load side may cause the overcurrent drive of the drive circuit, which may cause short-circuit damage or over-temperature damage caused by short-circuit faults. LED device itself, the main failure of the following circumstances.
Transient transient event
Transient overcurrent events refer to the current flowing through the LED that exceeds the maximum rated current in the LED data sheet, which may be due to direct or high voltage generation, such as transient lightning, switching power State switch noise, power grid fluctuations and other overvoltage events caused by overcurrent. These events are transient, very short duration, usually we call it a spike, such as "current spikes", "voltage spikes." The case of transient overcurrent events also includes the LED power supply, or the transient overcurrent at the time of plugging.
For automotive LED lighting, ISO7637-2 transient load shedding surge impact is an important threat to its normal work.
The failure mode of the LED after an electric shock is not fixed, but it usually causes the welding line to be damaged, as shown in Fig. This damage is usually caused by a great transient overcurrent. In addition to causing the weld line to burn, it may cause damage to other parts of the weld line, such as sealing material.
2. Electrostatic discharge event
Electrostatic discharge (ESD) damage is the most common transient over voltage hazard in the manufacture, transportation and application of highly integrated semiconductor devices. LED lighting systems are required to meet the IEC 61000-4-2 standard "Electrostatic discharge mode" 8kV contact discharge to prevent the system in the electrostatic discharge may lead to over-electric shock failure.
LED PN junction array performance will be reduced or damaged, as shown in Figure 2. ESD event discharge path caused by the internal failure of the LED chip, this failure may only be local functional damage, serious cases will lead to permanent damage to the LED.