As a new green technology illumination High power white Led tube have some advantages such as : Long life , low power , non-maintenance etc .So it will replace the old fluorescent in future in many illumination areas .The long life of the led tube based on the safe working enviroment , As a led illumination ,the main threats of affecting their life is from 2 method .
First ,it through the electricity to hurt the Led tube it means, the current on the Led tube is over the Led tube datasheet maximum rated current and including over pression .
The second one is too hot and it also can be hurt the Led tube .All of these hurt should be displayed the material are broken immediately or broken in a long time after it happened .These will reduce the life of the Led tube .
What make the Led tube broken?
There are some reasons as below that can make the led tube broken :
1.The power supply of the Led tube is broken will make the Led tube stop working .
2.The material of Led tube is broken also will make the Led tube stop working .
Usually The broken of Led power supply (another word is Led driver ) is from the input curent,if the current is over than the maximum allowed current .It is going to stop working of the led chips that in the led tube power supply And capacitors and other passive components breakdown damage occurred. Load short-circuit failure may cause over-current drive circuit, driving circuit may be a short circuit or short circuit damage caused by overheating damage. LED tube device failure itself mainly following situations.
A. Transient over-current events
Transient over-current event is the current flowing through LED over the data sheet the maximum rated current, which may be due to high current directly from the high voltage may also be indirect, such as transient lightning, switching power supply of the instantaneous state switching noise, power fluctuations caused by over-voltage over-current events. These events are transient, lasting a very short time, usually we call it peak, such as "current spikes", "voltage spike." Events caused by transient over-current situation also includes LED power on, or plug in the transient charged over current.
LED lighting for automobiles, ISO7637-2 surge impact load transient throw their normal work is a major threat.
LED subjected to electric shocks after the failure mode is not fixed, but often result in damaged welding wire. This damage is usually transient over-current caused great. In addition to lead solder wire burns out, but also near the welding line may cause damage to other parts, such as sealing materials.
B. Electrostatic Discharge Event
Electrostatic Discharge (ESD) damage is highly integrated semiconductor device manufacturing, transport and application of the most common type of transient overvoltage damage, while the LED lighting systems are required to meet the IEC61000-4-2 standard "human body model electrostatic discharge" 8kV contact discharge, in order to prevent electrostatic discharge when the system may lead to failure over electric shock.
LED PN junction array performance will occur or reduce the damage. ESD event the LED chip discharge channel leading to an internal failure, this failure may be only a partial functional damage, serious, permanent damage can lead to LED.
For close to 80% are converted into heat energy LED tube lighting design, the thermal management and thermal protection is their fault a challenge. Theory and practice have proved that, LED tube performance and life with LED's PN junction operating temperature is closely related. When the LED tube chip junction temperature rise 10 ?? flux will decay 1%, LED's life will be reduced by 50%.
Power supply and drive circuit protection
LED tube power supply and drive circuit as easily have suffered electrical shock and short circuit damage, so the design of the drive circuit fault state to fully consider all the protection measures to enhance the reliability of the circuit, thus reducing failure rates. LongTech Technology LVR series of PTC can be achieved AC over-current and short circuit protection, ROV used for surge protection through electric shock and. POLYZEN series is used for DC power input port, an integrated over-voltage over-current protection devices, LED light string in the surface mount series is a load or circuit overcurrent fault protection.
PPTC in LED tube lighting in the over-current and overheat protection
Although many high-end LED driver device gradually integrated over-current, overheating and other protection, but in many occasions, especially in overheating protection, discrete components still need to protect the program as a collaborative program to make lamps with higher reliability and a longer life.
PPTC is the polymer positive temperature thermistor, is a polymer with conductive particles, etc., and after special processing, the conductive particles form chains in the polymer conductive pathway. When the normal operating current through (or components in a normal ambient temperature) when, PPTC was low resistance state. When the circuit by an abnormal over-current (or temperature rise), the high current (or temperature rise) the heat generated by the rapid expansion of the polymer, cut off the conductive particles form conductive network, PPTC showed a high resistance state. When the circuit over-current (over temperature state) ruled out, the polymer cooling, the volume back to normal, in which conductive particles constitute a conductive path again, PPTC it was the initial low resistance state. PPTC's small size, low cost, can be used repeatedly to achieve the automatic start circuit protection and automatic recovery.
In the LED tube , according to the different lighting applications have different thermal protection mode, usually divided into two types. One way to immediately start the required temperature shutdown protection, such protection is usually applied to road traffic lights. Another way is to start the protection of certain temperature, for reducing current drive, such protection usually used in interior lighting and road lighting.
Pingwei Technology Application for LED tube lighting developed a PolySwitch products. The product temperature of 65 ??in the environment can guarantee that under normal 350mA current passed by the environmental temperature exceeds 85 ?? protection, through rational design, configure, can be adjusted separately in order to shutdown or dark way to protect LED lamps.
Series-parallel combination of a giant array of lighting or landscape lights over-current and over temperature protection and conservation programs in the cost of the mutual balance, there are generally two kinds of protection schemes can be used. The first splitter protection: multi-string LED system that can every branch on the road in series a PPTC were to protect. This approach is that we can achieve accurate protection, not because a slip of the fault caused the lights do not work to protect the reliability. Second, the trunk road protection: This protection is the main loop in the lamp in series a PPTC, to protect the entire lamp. This approach has the advantage of low cost, small footprint.
Furthermore, PPTC can be used as temperature sensors and LED drivers used in conjunction to achieve LED array illumination of thermal protection, in a large array of lighting, because the LED tube light series of large and structure is more complicated, in practical applications prone to overheating fault location, often not fixed in a particular location, so single overheating detection device is difficult to provide complete thermal protection. PPTC in low resistance under normal and positive temperature coefficient characteristics, can easily be several pieces PPTC series on the thermal protection detection circuit, multi-point thermal control. Multiple PPTC series, and installed in the possible overheating of parts. As the PPTC low resistance, THRM-pin level is 0, the power circuitry. When the lamp somewhere or multiple occurrence of over-temperature failure, THRM Loop 1 or How many pieces PPTC heat, resistance rapidly increased, THRM pin level becomes high, and thus start the LED driver design of the thermal protection program achieve thermal shutdown or reduction drive overheating. The solution to the overheating protection LED surface light source in terms of cost-effective. LongTech Electronics can provide customers with services related to design and verification.
The Summary of this articl
PPTC Because of its many features and is suitable for LED tube lighting system, over-current and over temperature protection, PTC in the design can be installed in the metal core circuit board or LED cooling plate in order to achieve the best heat conduction, so that more timely PPTC protection and effective. Furthermore, PPTC product packaging forms, customized packages according to customer requirements, flexibility, strong. However, there is no standard thermal protection solutions specifically designed to be combined with practical lamps, and fully verified. LongTech Electronics engineers willing to join with the industry, according to the actual situation on a solution, LED tube lighting system reduces the failure rate and maintenance costs.
