As new green lighting technology, high-power white LED has high optical conversion efficiency, low energy consumption, long service life, less maintenance etc. It is gradually applied to all kinds of lighting area.
LED long life is based on the safety of working environment, for LED lighting, there are two main threat to affect their life: one is the over-electricity shock: working current exceeds the maximum rated current in LED technology data sheet, including the shock by overvoltage cause and damage by overheat. These can cause the device immediately failed, or failed after long time, shorten the working life of the LED.
The reasons of LED lamp failure
one is derived from the power supply failure, the other is to coming from LED the failure of the device itself. Usually the LED power supply and driver’s damage is from the input power of the CLP (EOS) and load side open circuit failure. Input power to shock often causes the damage of drive circuit of driver chip, as well as passive components such as capacitor damage occurrence breakdown. Load the fault may cause power circuit of the over current drive, drive circuit might be short-circuit damage or a short circuit fault damage caused by overheating. LED the failure of the device itself has the following several ways.
1. The transient flow of events
Transient flow events is more than the current through the LED LED maximum rated current in the technical data sheet, this may be due to high current directly can also be produced by high voltage indirectly, such as transient lightning and transient of the switch switch power supply noise, power grid volatility overvoltage event caused by the flow. These events are transient, short duration, usually we call it rush, such as “current peak”, the “voltage peak”. Cause the transient flow events also including LED, power supply is connected or charged plug of the transient current.
For LED lighting in the car, ISO7637-2 cast transient impact load surge is its normal work is an important threat.
LED by CLP shock after the failure mode is not fixed, but usually cause damage of welding line, as shown in figure 1. This kind of damage is often caused by great instantaneous over current. Besides lead to burn out welding line, can also lead to close to other parts of the welding wire is damaged, such as sealing material.
2. The electrostatic discharge
Electrostatic discharge (ESD) damage is a high level of integration of semiconductor device manufacturing, transport, and application of one of the most common transient overvoltage hazard, and the LED lighting system must satisfy IEC61000-4-2 standard “human body electrostatic discharge model” 8 kv contact discharge, in order to prevent the system maximum impact in electrostatic discharge that may lead to failure.
LED the p-n junction array performance will be reduced or damaged. Discharge the ESD event access internal failure caused by LED chips, this failure may be only partial function damage, serious word will result in permanent damage to the LED.