LED lamps and common cause damage analysed

22 May

High power LED as new green white lighting technology, there is light conversion efficiency, low energy consumption, long service life, no maintenance etc, and gradually be applied in all kinds of lighting area. The LED long life is based on its safe work environment, to the flexible led strip lighting speaking, there are two major kinds of threat affect its life: one is the CLP impact, is on the current applied LED more than this LED technology in a manual maximum rated current data, including pressure caused by impact b; The other is overheating damage. The damage can be represented as a device failure immediately, can also occur in a current shock after the event for a long time to failure, shorten LED the service life.

LED lighting the cause of damage

LED lamps and a power supply failure is from the failure and the driver, 2 it is derived from the device itself LED the failure. Usually the power source and the drive of the damaged LED from the input power of the CLP impact (EOS) and the open circuit fault load. Vani: input voltage to the impact often causes driving circuit drive chip in the damage, and capacitance and passive components breakdown damage occurred. The load short-circuit fault may cause the current drivers drive circuit, drive circuit is possible damage or have a short circuit fault of damage to overheating. The failure of the device itself LED basically has the following kinds of situation.

1. The transient flow events

Transient flow incident is more than the current flows through a LED technology data handbook maximum rated current, this may be due to the large current directly produce may also is made from high voltage indirectly from, such as transient by lightning, switch power supply noise, transient switch power grid fluctuation etc, over voltage of the event that caused the flow. These events are transient, last time is very short, usually we refer to this as the peak, such as “current peak”, “voltage peak”. Cause transient flow of events including LED switch on the power, or a charged when inserted the transient over electric current.

For the car of high watt led lights, ISO7637-2 of transient cast load surge is the impact of the regular work a significant threat.

Vani: after the impact of LED from failure mode is not fixed, but usually cause the welding line damage, as shown in figure 1 below. This damage normally by great transient currents cause. In addition to causing welding line burned off outside, still can lead to other parts of the welding line near the damage, such as sealing material.

Figure 1: LED the welding and broken damage.

2. The electrostatic discharge events

Electrostatic discharge (ESD) damage is the high level of integration of semiconductor devices, transportation and manufacturing application of the most common a transient overvoltage harm, and LED lighting system is required to meet IEC61000-4-2 standard of “the human body of electrostatic discharge mode” 8 kV contact discharge, in order to prevent the system in electrostatic discharge is likely to result in a CLP impact failure.

LED PN junction array performance will appear to reduce or damage, as shown in figure 2 shows. ESD events to discharge path LED chips internal failure, the failure may be just local functionality failure, serious word can also lead to permanent damage LED.

Figure 2: LED part PN junction damage.

For close to 80% of the energy is transformed into the heat of mini led light bars design character, thermal management and fault overheating protection is the face of a challenge. Theory and practice have proved that the performance and life is LED and LED the PN junction temperature is closely related to the work. When LED chips and 10 ℃ high temperature within, flux will attenuation 1%, LED the life will be reduced by 50%.


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