Sunday, March 4, 2012

Common Stoppage of LED Light

We must develop lighting appliance that tally to the stage of social development because the illumination is very important to our life, we might even say that we cannot live without lighting. Finally, LED light comes out, in the expecting of many people. Then what is LED light actually? The core of the light emitting diode is the chip which is composed of the psemiconductor and the n semiconductor, there is a transition layer between the p semiconductor and the n semiconductor, and it is called the p-n knot. Injected minority carrier and majority carriers compound in PN ties made of certain semiconducting material, will release the unnecessary energy by the light form when composited, and thus the electrical energy transforms directly into the light energy. Stoppage of LED lights mainly comes from LED drive power and LED components two aspects.

The most common reason for the fault is EOS and open circuit. EOS accessed in the current can lead to drive power impaired, lightning and short circuit can cause EOS accessed in current, that is also called Instantaneous ultra flow, also called "peak current", although it usually lasts for short duration but it can cause damage to the power circuit, including wire fusing, insulating material damage, components damage, and so on. Power supply circuit design needs to take the impact along with the fluctuation of lightning power grid into consideration, in order to ensure that the LED lights will not be damaged.

Consider to use PPTC to protect, PPTC refers to the high polymer thermistors, is composed by the polymer and conductive particles. PPTC is in low impedance condition during the normal work; when abnormal current through the circuit or environmental temperature rises, large current or environmental temperature rises, generated heat makes polymer rapid expansion, cut down conductive pathways that formed conductive particles, PPTC is in high impedance condition; when the current in the circuit (overtemperature condition) is removed, polymer cooling, the volume is back to normal, the conductive particles will reconstruct conductive pathways, PPTC will present the initial low resistance state. PPTC is small in size, low cost, can use repeatedly, and can therefore realize protection function of automatic startup and automatic recovery. LED power coil magnetic flux leakage also can produce additional current wave, generally it will not lead to serious consequences, but combined with other factors it can cause unpredictable risk, for example, if near a high frequency equipment directly connected to the electricity grid, and no buffer circuit to isolation may cause LED lights troubles.

Electro static discharge (ESD) is also a common cause of EOS, modern electronic components loses great for this, LED lamp manufacturers need to in accordance with the standard of " electrostatic discharge mode of the human body" 8 KV contact to discharge, or electrostatic release may cause permanent damage to LED PN junction. LED lights after-sales maintenance also need to be aware of the problem of electrostatic discharge, the best and the most simple solution to prevent ESD maintain grounding.

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