作者：Blade

The reason for damaged advanced led lights

High-power white LED as a new green lighting, it will own light conversion, high efficiency, low power consumption, long life, no maintenance, etc, and thus gradually being used in a variety of lighting in the area. The long life of the advanced led lights are based on a safe working environment. LED lighting is concerned. There are two threats affects their life. a electric shock over electric shock is applied to the LED on the current exceeds the maximum rated current of the LED technology in the data sheet, including over-voltage caused by over-current shock; another is overheating damage. Damage can be expressed as the immediate failure of the components that may also occur through electric shock after the incident for a long time before failure and to shorten the working life of LED.

The reason for damaged advanced led lights

The reason for advanced led lights 

The failure of LED lamps have two reasons. First, from the power supply and drive failure, the second is from the LED assembly failure. Normally, the failure from LED power supply and drive through electric shock (EOS) and the load side of  circuit failure. Input power over electric shock often cause damage to the driver chips in the driver circuit such as capacitors and other passive components breakdown damage; Load side short circuit failure may cause over-current drive of the drive circuit, drive circuit may short-circuit damage or short-circuit fault caused overheating damage.

The failure of LED components itself

Transient over-current events is to flow through the LED current to exceed the maximum rated current of the LED technology in the data sheet, which may be the direct result of the large current, and may be indirectly due to the high voltage generation, such as transient lightning switch over voltage event of power transient switching noise, power fluctuations caused by over-current. These events are transient, and shot duration, we usually referred as spikes, such as “current spikes, voltage spikes. The event caused by transient over current includes LED connected to the transient over-current power or hot plug.

For the LED lighting products in the car, ISO7637-2 transient load-dump surge impact is a major threat to their normal work.

The requirement for 12v LED lamps on the low-voltage driver chip

The requirement for 12v led lamps on the low-voltage driver led lights chip

1. The nominal input voltage range of driver chips should meet the DC 8 ~~ 40V, in order to cover a wider application needs. Pressure capacity should be greater than 45V. When input AC 12V led lamps or 24 V, a simple bridge rectifier output voltage with the grid voltage fluctuation, especially when the high voltage output DC voltage will be high.  If the driver IC does not have a wide input voltage range, often in the grid voltage is increased breakdown, and thus burn the LED light source.

The requirement for 12v LED lamps on the low-voltage driver chip

2. The nominal output current of the driver chip is greater than of 1.2 ~~ 1.5A.. As the lighting of the LED lighting source, 1W power LED lighting source, 1W power LED lighting source, the nominal operating current is 700mA. The need for greater current of the power LED street lights source, so the optional LED lighting driver IC must have enough current output driver IC design products at full load output of 70 to 90% of the best work area. Full load output current drive IC for lighting small spaces, poor heat dissipation, and easily lead to the lamps to the occurrence of fatigue and early failure.

3. The driver chip output current must be kept constant, so that the 12v led lamps can be solid light and does not blink. Driver chips in the same batch under the same conditions, the size of the output current should be as consistent as possible, so that in a high volume automated production line in order to ensure efficient and orderly. For certain discrete driver chips, the output current must be selected before the factory or put into production lines for the selection of sub-file, to adjust the current setting resistor size on the PCB,  so that the production of LED lighting keep the same with current driver board for similar LED products the light source luminance, in order to maintain the consistency of the final product.

 

 

How to select correct LED drivers IC

LED lighting will leap in the development in the near future. LED is widely recognized as a green clean light. The long life LED lights source, energy saving, easy application, the use of low-cost lighting in the home will be a flood of applications.

How to select correct LED drivers IC

In the field of LED lighting, the correct choice of the LED driver IC is essential. In order to reflect the characteristics of the LED lamp energy saving and long life. Good matching of the driver IC, the advantages of LED lighting can not be reflected. In the selection of LED drivers IC should be noted the performance indicators and how to use it?

The LED light source technology are getting mature. The per-watt light-emitting lumen rapid growth, and lead gradually decline to lower prices. 1W LED light source for example. The price in spring of 2008 is one-third of the price in spring of 2006, and it will dropped to fourth in year of 2009.

The high-energy, long life, and the environmental benefits of the superior performance of LED lamps are generally recognized.

1. High energy saving LED: DC drive, ultra-low power consumption(single tube 0.03-1W) electro-optical power conversion close to 100%, the same lighting effects than traditional energy sources more than 80%.

2. Long-life LED: LED light source is known as the longevity light. Solid cold light source, epoxy encapsulated, light body and no loose parts, it does not exist filament light easy to burn, heat deposition, the light fades and fast drawback life of up to  50000-100000 hours longer life than traditional light sources 10 times.

3. The LED environmental benefits: LED is a green light, the environmental benefits of better. No ultraviolet and infrared spectra, low in calories and no flicker, no radiation, and waste recycling, no pollution, and no mercury element, cold light source. It is safe to touch and belongs to a typical green lighting.

The working character of LED lighting source

The VF voltage of the LED lighting is very low, under normal circumstances is 2.75 to 3.8V, the IF is generally is 15 to 1400mA. LED driver IC output voltage is VFxN, VFx1 IF constant current at 15 ~~ 1,400 mA, LED lamps use LED light source has low power (IF 15 to 20mA) and high power (IF greater than 200mA) two kinds.

The improvement measure for saving the failure of led light system

Second, the improvement measures

LED lights described above, the main failure mode analysis, from the informed to improve the LED in the actual life of the technology.

(1)cooling technology

Cooling technology has been an important part of the LED application, LED light system can not be heat will cause the junction temperature of the chip serious rise, then the luminous efficiency of a sharp decline in reliability(eg, life, color shift, etc.) will deteriorate; Meanwhile, the high temperature and high fever will make the LED package structure of the internal mechanical stress may further lead to a series of reliability issues. Therefore, in the manufacturing process, you can choose the good thermal conductivity of the base, and makes the LED heat dissipation area as large as possible, thereby increasing the thermal performance of the device.

The improvement measure for saving the failure of led light system

(2) anti-static technology

Using the GaN chip LED, a large electrostatic will effect. If you do not deal with this problem, it will seriously affect the life of the device. In LED light system design, we should give full consideration to the design of anti-static, and to avoid device failure phenomenon caused by the breakdown of the high electrostatic voltage.

(3) packaging technology

Epoxy material that used by the package, will change because of light and temperature rise. In the use of the original transparent epoxy material browning affect the device spectral power distribution. Therefore, during the time of LED package, we should strictly control the curing temperature. Avoid to result in the premature aging of the epoxy resin.

On the other hand, in order to prevent device corrosion phenomenon we need to pay attention to the injection molding process,  the row of clean material inside the bubble as far as possible to reduce the residual amount of water vapor, reducing devices of corrosion chance, while transparent good packaging materials.

(4) optimize the manufacturing process

LED manufacturing process requires an appropriate bonding conditions, if the bond is too large, it will be crushed chips, on the contrary, the device will result in insufficient bonding strength. The LED light system device is easy to take off the loose. Therefore, to ensure that the device bonding strength at the same time. We need to try the best to minimize the damage caused by the process of bonding the chip in order to achieve the purpose of optimization of the bonding process.

 

Analysis of LED light fittings failure

In terms of the package, there is an important factor to affect the LED life is corrosion. In the use of LED lights, the general corrosion caused mainly due to water vapor infiltrated within the packaging material, resulting in lead deterioration, PCB copper corrosion; sometimes movable ions introduced with the water vapor resides in the chip surface, resulting in leakage. In addition, the package poor quality of the devices, encapsulated within a large number of residual bubbles, these residual bubbles would also cause corrosion of the device.

Analysis of LED light fittings failure

(3) thermal stress failure of led light fittings

The temperature has been an important factor of the LED optical properties, LED failure modes of the research scholars to consider the working environment temperature accelerated stress to the LED accelerated life test. This is because the LED spot lights system thermal resistance of the same premise. The welding point of the package pin temperature, junction temperature will also increase, leading to early failure of LED.

Hsu test samples provided by different vendors LED, the LED samples in the experiment were placed 80、100、120℃, 3.2V voltage drive, and provisions when the optical power of the sample decreased to the stating value of 50%, which is determined to be invalid. High power led light fittings with the accelerated life test temperature and the accelerated and the acceleration time increases and decreases.  In the accelerated life test, the LED junction temperature rise will make the epoxy material mutation, thereby increasing the thermal resistance of the system between the chip and package thermal surface degradation, eventually leading to package failure.

(4) electrical overstress failure of led light fittings

If LED tunnel used under the current circumstances or electrostatic impact damage of the chip, the chip will result in open circuit, the formation of electrical overstress failures. For example, GaN is a wide band gap materials, high resistivity. If you use such chips, the induced charge due to static electricity generated in the production process which is not easy to disappear when its accumulated to considerable extent. It can produce very high electrostatic voltage, this voltage exceeds the bearing capacity of the material occurs of the material, it will occurs breakdown phenomena and discharge, and making the device failure.

LED lamp design failure analysis

At present, although the theoretical life of the LED can be achieved 50kh, however, in actual use, due to various factors, LED lights often amounted to less than such a theory of life, premature failure phenomenon, which greatly hindered the LED as a new energy-saving the pace of the products. LED lamp design failure carry out systematic analysis, and proposed some improvement measures, and to expect to be able to improve the actual service life of the LED.

LED lamp design failure analysis

一、LED spot failure modes

LED failure modes: chip failure, the package fails, the thermal stress failure, electrical overstress failures and assembly failure, especially in chip failure and package failure is most common. The text will analyze these types of failure modes.

一、LED grow lights chip failure modes

Chip failure refers to the chip itself get failure or other causes chip failure. The reason of this failure are many: the die crack is due to improper bonding process condition, resulting in a larger stress, with the accumulation of heat generated by the thermo-mechanical stress, with the accumulation of heat generated by the term-mechanical stress also will strengthen, causing the chip to produce micro-cracks, work when injected into the current will be further exacerbated by the micro crack expanding until the device fails completely. Second, if the chip active are injured, it will lead to gradual degradation during power-up failure, the same can also cause the lamps in the use of a coherent state of serious decline until it does not shine. Furthermore, if the chip bonding technology is bad, chip bonding layer is completely out of the bonding surface and the sample will open to lapse. The same will cause the LED lamp design in the course of “dead light” phenomenon occurs. The bad chip bonding process may be due to the use of silver paste expired or the exposure time is too long, silver paste is too small, the curing time is too long, solid crystal base surface contaminated.

(2) package failure

Package failure is improper package design or production processes lead to device failure. Epoxy materials, packaging occur in the course of the degradation problem, resulting in reduced life of the LED.

small led grow light and reducing cost

LED lights display used in many ways, the emerging field of LED display industry, the technical aspects of development tend to have many deficiencies. This article will discuss the key technical issues need to be resolved, attributed to “three high and one low”, ie, high light efficiency, high color rendering, high reliability and low cost technology to achieve low cost and its essence is also a technical problem.

small led grow light and reducing cost

Of course, to solve these technical problems also need a series of measures displayed in the LED industry chain. Such as the use of new technologies, new structure, new processes, new materials. In this paper, stresses v. to take the technical route and its direction, and hope that through this article is described in the product innovation of the LED industry entrepreneurs.

The following from the “three high and one low” high light efficiency, high color rendering, high reliability and low cost:

High light efficiency

The luminous efficiency for the LED display can be said to be an important indicator of the energy saving effect, and effect of the luminous efficiency there to be strengthened in order to really to do to solve technical problems related to all aspects of the high light efficiency, from the industrial chain, and then how to achieve high light effect it? This article will specifically compete to explore the epitaxy, packaging, lighting, etc. to solve technical problems.

A. Improve the internal quantum efficiency and external quantum efficiency.

Two. To improve encapsulation efficiency of the light and reduce the junction temperature.

3. Improve the lighting of the light extraction efficiency.

High color rendering

LED display the quality of light and color, including color temperature, color, light and color fidelity, light color natural tones to identify the degree of visual comfort. Here we only discuss and resolve the problem of the color temperature and color. Production of high-color LED display light, will lose more light efficiency, and to take care of these two factors in the design. Of course, to improve the high color rendering must also consider the combination of the three primary colors RGB. Here I have three ways to:

A. Multi-primary color phosphors.

Two. RGB multi-chip combination.

3. Fluorescent powder and chips.

High reliability

Including the failure rate, life expectancy and other indicators. But in the application but there is a different understanding and elaboration. High reliability refers to the ability of the product under specified conditions and provisions within the time to complete the required function. LED fails categories have a serious failure to failure and parameters. Life is the value of the product reliability characterization. : Generally refers to the statistical average of a large number of components in terms of the life of the LED devices is the meaning of this description. But affect the LED street lights chip manufacturing, packaging, thermal resistance, heat and other factors curtain product reliability. Speaking of LED display products based on the implementation of comprehensive quality control for the 2:00:

A. Reduce the loss of efficiency.

Two. Extend the depletion time to failure.

Reduce product cost

Many consumers in the purchase of LED display at all times feel that price is too high, so the contention that this many LED spot display entrepreneurs have taken the appropriate measures to reduce costs in addition to mass production, mainly from the technical to take measures to reduce costs approach, ways. In epitaxial silicon, package, driver, heat, reduce costs, a fundamental solution to the cost of LED display products. Specific talk about the following four aspects:

A. Epitaxial silicon link to ways to reduce costs.

Two. The package links lower costs.

3. Lighting aspects of cost reduction methods.

4. Other ancillary cost reduction

These are mainly from the high light efficiency, high color rendering, high reliability and low cost of the four technology to solve the LED display technology and take corresponding measures, total Overall, through the adoption of new technologies, new processes, new structure, new materials and other measures to achieve a high luminous efficiency of LED display, high color rendering, high reliability and low-cost outside the deeper point of view, should be to improve the quality of energy efficiency and light color as the LED display higher, so the real people provide products on demand!

 

Factors affecting the life of LED driving lights

Using long-life capacitor does not necessarily ensure the power supply life-span. In order to improve the life of power led lights, you need to improve in many ways: the use of the higher life of the capacitor, and to improve power efficiency, good thermal design of power supply life, optimizing the thermal design of the lamp. Many lighting companies in order to reduce weight, small volume and install in a confined space, in order to consider the lighting design of compact thermal conditions of its power limited. High efficiency, small size and better thermal design challenges faced by the led driving lights.

Factors affecting the life of LED driving lights

In traditional lighting, except some part of power conversion convert into lighting, most of the power radiation infrared radiation energy to the lighting of external space. While different from LED lamps, the LED is a semiconductor light-emitting. In addition to the part of the power converted to light, the vast majority of power is converted to heat, this heat can only use the chip in close connection with the lamp body heat.

In order to have the beautiful structure of the whole lighting products, businesses always tend to put LED power supply and LED lamp structure together, so that the power and the LED light source in a poor working environment. When work environment temperature exceeds a certain temperature, theled driving lights and LED life is greatly reduced. Power supply internal temperature protection is set to repeatedly switch lights phenomenon, temperature protection would lead to high temperature and damage the power devices and accelerate the LED light failure if it does not set switch light.

led driving lights is a switching power supply, switching power supply quality and reliability depends on its circuit design, production process and the quality of the device.  The electrolytic capacitor is an essential component of high-power switching power supply.

While the normal working life of the switching power supply depends on the power supply electrolytic capacitors used in the life of electrolytic capacitors in turn depends on the capacitor itself, the life and operating temperature.

The working life of Electrolytic capacitors in the different temperature are very different.

 

small led grow lights and print method

Lighting applications or backlighting applications, the light guide plate and the LED lights source with the best in the compatibility of the product quality and poor quality of the light guide plate for the entire LED products have an important impact, the most important performance in the brightness and uniformity. The same module, the light guide plate will have different effects, high-quality light guide plate transmittance significantly than low-quality high, but also to prevent the bright spot, dark areas appear.

small led grow lights and print method

The production of light guide material is plexiglass or PC material, but the market is more and are based on acrylic sheet, because it is the most excellent quality so far synthetic transparent material, with unparalleled high brightness, can improve the light use efficiency. Acrylic and then through a series of processing before they can be called the light guide plate, the processing of the main methods of network production.

Speaking of network production, familiar screen printing LGP, a large number of customers because of its low cost and used as a backlight. In fact, countries develop energy-saving environmental protection engineering, screen printing light guide plate manufacturers should follow the development trend of environmental protection, aligned with the environmental protection industry. Below the shortcomings of the production of silk screen light guide plate.

As we all know, the silk screen of the production of the light guide plate can not be separated from the ink, which is produced materials. But the ink is the biggest source of pollution of the printing industry, has reached hundreds of thousands of tons of emissions annually by the ink-induced global volatile organic compounds (VOC) contamination, these volatile organic compounds, the formation of a more serious greenhouse effect than carbon dioxide, and sunlight irradiation, the formation of oxides and photochemical smog, seriously pollutes the atmospheric environment, affect people’s health.

LED products, not only energy saving, long life advantages. Long life is an important feature of the LED products, determine the LED light source, light guide plate is almost decided the life of the entire LED products. LED lighting process inevitably produces heat, heat ink for screen printing light guide plate will have been affected. A test of the industry experts in the use of screen printing LGP LED panel lights, lights for three months, resulting in a nearly one-third of the degree of light failure. This situation resulted mainly due to the lighting process, the heat generated by the LED so that the light guide plate of the ink volatile, deterioration of the stability of the light guide, so contrary to the view of the LED products durable.

In the screen printing process, you must also pay attention to the production environment. Strictly speaking, must be in a clean room for production, clean room is defined as having the air filter, allocation, optimization, structural materials and equipment room, is the basis of pollution control, clean room, the light guide plate of pollution-sensitive ink screen printing can not mass production. Production is completed, the application need to pay attention to the application environment humidity, UV screen printing outlets, rainy and sunny weather will speed up the phenomenon of light failure.

Admittedly, the design of the screen printing network technology is very mature, and the effect on the brightness and uniformity welcomed by many customers, but in view of the complexity of production processes and the requirements on the flatness of the acrylic sheet is very high (screen printing requirements of the acrylic sheet surface very flat, or can not be printed, so they use the extruded sheet, in order to ensure flatness) a lot of companies are beginning to transition to the direction of the laser scribing or laser dot design, this also causes the laser light guide plate products in the market and screen printing light guide plate to compete for market share reasons.

small led lamps and fire proof

With the rapid development of modern technology, LED lights display screen industry sustained rapid speed of growth, expanding industry, technology innovation, market share since 1993, continued to grow by an annual average growth rate of 40%, however, in 2012 Hong Kong Harbour Grand caught fire incident on April 2, knocked to the entire LED industry a wake-up call: the rapid growth of this industry, LED display screen safe application of technology to the remaining short board, LED products standardization and Standardization was again put on the agenda. In particular, LED display screen fire safety application techniques is the focus of today I would take you to see what factors will affect the display of fire safety issues.

small led lamps and fire proof

Display fire prevention technology is good or bad is closely associated with display fire raw materials, cabinet craft.

The fire main raw materials, including the display of these four aspects of the use of the screen inside the wire, power supply, external protection, structural fire protection materials and plastic kit:

The first point: in most display applications, the unit area of ​​the screen shows the greater the greater the power consumption, higher requirements on the power stability of the wire. Many wire products, in line with GB requirements of the wire to be able to guarantee its security and stability, requires three things: wire core copper conductive carrier, wire core cross-sectional area of ​​tolerance in the value of the standard range, wrapped wire core rubber insulation up to standard and flame retardant, compared to the copper clad aluminum wire core wire core cross-sectional area is small enough level of insulation rubber wire, power performance is more stable, less prone to short-circuit condition;

Second point: UL approved power products also chose the best choice when similar products, the effective conversion rate power load to ensure security and stability in the external ambient temperature of the hot case, can also work;

The third point: display external protective structure material on the market, higher fire rating display products are mostly fire-resistant aluminum composite panel, its fire resistance and excellent fire retardant is also strong, the core material Special Material oxygen aging properties is also very strong, melting temperature 135 ° C, decomposition temperature ≥ 300 ° C, the environmental performance of halogen, in line with SGS, flame retardant B-S1, d0, t0, reference standard the UL94 GB/8624-2006. General outdoor display screen products of the aluminum plate with high temperature, rain and hot and cold impact aging rapidly, season segment in a more humid climate, make it rain easily penetrate inside the screen body leading to electronic components caused by short fire;

The fourth point: the curtain fire raw materials, there is an important part of that is plastic kit, plastic kit modules available for the use of the mask bottom shell materials, the main use of raw materials with a flame retardant PC + fiberglass materials, not only has the resistance burning function better at high temperature and long-term use, no distortion, does not become brittle and crack, combined with the tightness of good glue to use, can effectively block the external environment of the rain in through causing a short circuit within the fire .

In addition to the internal raw materials will affect the fire effect, external configuration and design also very important, but the external configuration is mainly involved to fire prevention, heat in the display screen work at the same time, configure the row of fans and air conditioners cooling the inside of the screen body cooling, recommended every 8-10 square assembly 1P air conditioning to ensure that screen the body temperature is kept constant temperature is not configured in place of air conditioning or exhaust fans can cause uneven heat treatment, easily lead to elevated temperature caused by the screen within the security risks. A lot of LED down lights companies during the cabinet level of protection test simply to simulate the spray water testing in the external environment, pending research on the persistence and strength of the waterproofing effect, with the result in the display products used for some time after there seepage occurred, this is the outdoor display is easy to fire or short service life of the important reasons. In response to a lightning storm, the Screen device arrester is to avoid the lightning assault and burned an essential tool of the screen within the device, the lightning to ground impact without Screen.

Above belong to the display of internal reasons, of course we can not ignore the later maintenance process caused by human factors, in the follow-up maintenance work, for example, the operator did not follow a strict process flow operation (module screws did not matter, wire reverse polarity, conductive objects left over after the operation, etc.), and easily lead to the house on fire.

The exact cause of the fire events of the Hong Kong hotel display there is to be investigated, but not incident on Hong Kong’s LED display product application to hold a negative attitude, while the entire industry standards has not been established, but the industry is doing better LED business or, for example, Chau Ming, Shenzhen City, display products have been the England Test Center BS476 building materials fire retardant test, display products to meet international certification standards within the LED industry leader, we should in line to lead exemplary corporate, high quality, strict specifications required, and guide the healthy development of the industry, thereby enhancing the competitiveness of the industry as a whole in the international arena and globalize.