How to predict the life of LED?

How to predict the life of LED?

In general description, LED can be used for more than 50000 hours. Even some manufacturers promote their LED can operate 100000 hours or so. The main problem in this aspect is that the LED is not simply not working, and its rated service life can not be calculated by the measurement of the traditional lamp. In fact, when we test LED service life, nobody would be staying at the side of the lamp waiting it stop working. However, there are still other ways to measure the service life of LED. The reason why LED can work longer is because it won’t cause the problem of filament fuse. LED does not work directly, but it will gradually degenerate as time goes by. There are predictions show that the high quality LED can maintain the original lamp brightness of more than 60% after 50000 hours of continuous operation. Assuming that LED has reached its rated service life, actually it may still shine, just the light is very weak.

If we do not consider the power and drive failures, the service life of LED reflects as its decay, that is its brightness getting darker with the time, until finally extinguished. Usually defined the time decay to 30% as its life span.

So the life of LED can predict or not?

1.LED Light Decay

Most of the white LED is obtained by blue LED shining the yellow phosphor. The reasons lead to the LED light decay are mainly the following two, one is the blue LED itself light decay, blue LED decay even faster than red light, yellow light, and green light LED. Another reason is the fluorescent phosphor attenuation; fluorescent powder may decay seriously at high temperature.

Diagram1. LED Decay Curves

We may see from the diagram that LED light attenuation related with its junction temperature. So-called junction temperature is the junction temperature of the semiconductor pn. Decay may happen earlier when junction temperature gets higher, that is life gets shorter. We may see from the picture, if the junction temperature is 150 degrees, the service life is only 10 thousand huors when the brightness gets to 70%; if the temperature is 95 degree, then the life gets to 20 thousand hours; if the temperature decline to 75 degree, the life gets to 50 thousand hours; when the junction temperature decreases to 65 degrees, the life can be extended to 90 thousand hours. So the key to prolong the life is to reduce the junction temperature. However, these data are only suitable for LED of Cree, not for the LED from other companies. For example, the decay curves of LuxeonK2 as shown in diagram 2.

Diagram1. LED Decay Curves

When the junction temperature increases from 115°to 135°, the life span can be reduced from 50000 to 20000 hours.



2. How to extend the life of LED?

It is concluded that the key to extend its life span is to reduce its junction temperature. And the key to reduce the junction temperature is to have a good heat radiator. Be able to exhaust the heat generated by LED timely.

3. How to predict the life of lamp.

Predict the life from junction temperature seems to be very simple. As long as check the curves in the diagram 1, it may seems clear that the 20 thousand hours LED life corresponding the junction temperature of 95 degrees. However, this method may not very reliable when applied to the indoor LED lamps. If applied to outdoor LED lamps, especially high-power LED street lamps, where there are a lot of uncertain factors. The biggest problem is that the cooling efficiency of the radiator of LED street lamp decreases with time. This is due to the accumulation of dust, bird feces, so that the heat dissipation efficiency is reduced. Also because there is a very strong ultraviolet radiation outdoor can still reduce the life of LED. Ultraviolet radiation may has a great effect on the aging of the epoxy resin, if using silicone, this problem can be improved. The UV also has some bad effects on the aging of the phosphor, but it is not very serious.

LEDLM-80PL LED Lumen Maintenance and Aging Life Test System developed by LISUN is produced by the requirements of IES-LM-80, IES0LM-82, TM-21, GB2312-80 and CIE, IEC standards. It can record the change curve of luminous flux VS time and the color parameters VS time. Through test and record of the attenuation data records in a short period of time to calculate the life time of LED

Lisun Electronic (Shanghai) office is committed to the development and after-sales maintenance of lighting instrument, EMI / EMC Test System and safety testing instruments in the domestic and global market. The full range of products of Lisun are in strict accordance with the quality management and control of ISO9001:2008 requirements for R & D and production; Lisun is also the member unit of global lighting CIE association, all products are according to CIE requirements; in addition, all products of Lisun are certified by CE and get the qualification of the EU.

Five kinds of LED Efficiency

Five kinds of LED Efficiency

Compare LED efficiency and life, the conception of efficiency is more complex. Firstly, there are three kinds of general efficiency。

Firstly, for lamp beads, there are two concepts of efficiency:

1. Lamp beads luminous efficiency, how much light can be issued every 1W input power. This efficiency is the indicator to measure the light efficiency of lamp beads, not the indicator to measure the light efficiency of total luminaries. Therefore, the light efficiency of single LED is the basic for the light efficiency of total luminaries; it is not equal to the light efficiency of the total luminaries.


2. Lamp beads conversion efficiency means that every 1W input power, how much power is used to emit light. Luminous efficiency is generally used. Conversion efficiency is often used to assess the development level of the chip.

Secondly, the efficiency of lamp beads in the application environment generally does not use. However, it is generally used to assess the quality of number of lamp beads, which is irrespective of the case without driver, the ratio of lamp beads direct consumed power in lamp board and the lamp board total luminous amount. The lumen amount calculated by this way can reflect the average luminous efficiency of a number of lamp beads, to determine the quality of number of lamp beads.

In addition, more people may be familiar with driver efficiency, it is the driver conversion efficiency that is the ratio of drive input power and drive output power.

Finally is the total luminaries luminous efficiency. This formula is simple; it is the ratio of luminaries luminous total amount and input total power. For the optical conversion efficiency generated by the lamp structure is a little special, lamp structure optical conversion efficiency=total luminaries total flux/lamp board total flux, which is defined as the ratio of the light emitted by lamp board of the light emitted by the total luminaries; this contains at least the optical attenuation because of expanding light board or translucent panel.

People usually confuse the total luminaries luminous efficiency and lamp beads luminous efficiency. We can roughly think the relationship between them: Total luminaries luminous efficiency=lamp beads luminous efficiency in the application environment-driver conversion efficiency –structure optical conversion efficiency.

In this relationship formula, we can see that total luminaries luminous efficiency should be less than lamp beads luminous efficiency, except the effect brought by the driver conversion efficiency mentioned above, there is also a problem often overlooked, that is the influence of lamp structure. Lamp structure influence is not only the influence of diffusion plate, especially for a side emitting type of lamp, its optical conversion efficiency is very low. It can be a bottleneck of side-emitting type of lamp. Therefore, if we say total luminaries luminous efficiency, you should deduct driver conversion efficiency and lamp structure conversion efficiency.

Efficiency is a relative complex concept in LED lighting. At the same time, we also need to point out that efficiency is not unchangeable; it can change with the work environment. For example, work temperature will make efficiency change. Therefore, when we talk about LED efficiency, not only we should point out which efficiency, but also efficiency in what temperature. Lisun LPCE-2(LMS-9000A) Spectroradiometer & Integrating Sphere system is for total luminaries luminous efficiency.

Lisun LPCE-2(LMS-9000A) Spectroradiometer & Integrating Sphere system is widely applied to Luminaries manufacturing enterprise and lab, such as Sharp Electronics in Memphis TN(USA), CS TECH MEXICO, S.A. DE C.V. (Mexico), DORADO Praha s.r.o. (Czech) etc. The reason why Lisun can win some many customers is because we always practice the motto of right products, right price and right service. Lisun will continue feedback good quality products and superior service in the feature.

 

LISUN Engineer goes to India customer to carry out LPCE-3 installation training.

Recently, LISUN engineers outside India, to do the installation training of LPCE-3 compact spectrum radiometer integrating sphere system for customers. The customer ordered the LPCE-3 compact spectrum radiometer integrating sphere system from LISUN this time.

LPCE-3 is a CCD Spectroradiometer Integrating Sphere Compact System for LED Testing. It is suitable for photometric and colorimetric measurement of luminaries such as LEDs, LED luminaires, Energy-saving lamps, Fluorescent lamps, HID lamps (high voltage sodium lamps and high voltage mercury lamps) and CCFL. The measured data meets the requirements of CIE, EN and LM-79 clause 9.1 for the measurement of photometry and colorimetry.



Our main products are Goniophotometer, Spectroradiometer, Integrating Sphere, LED Test Instruments, CFL Test Instruments, Photometer and Colorimeter, EMC & EMI Testing,Electronic Ballast Tester, Electrical Safety Testing, Environmental Test Chamber, Plug and Switch Testing, AC and DC Power Supply and etc.

Installation & Training in Bhutan

Recently,LISUN engineers went to Bhutan customer company for installation training.Customers bought the LPCE-2 high precision radiometer integrating sphere system and LSG-1200A compact distributed photometer from LISUN.

LPCE-2 is an Integrating Sphere Spectroradiometer LED Testing System for identifying the performance of single LEDs and LED lamps. LED’s quality should be tested by checking its photometric, colorimetric and electrical parameters. The customer is satisfied with our products and services. The speed of this installation training and the professional level of the engineer have been praised by the customers again, and we are looking forward to our future cooperation.

High Precision Spectroradiometer Integrating Sphere System

LSG-1200A Compact Goniophotometer

Our main products are Goniophotometer, Spectroradiometer, Integrating Sphere, LED Test Instruments, CFL Test Instruments, Photometer and Colorimeter, EMC & EMI Testing,Electronic Ballast Tester, Electrical Safety Testing, Environmental Test Chamber, Plug and Switch Testing, AC and DC Power Supply and etc.

How to predict the life of LED?

How to predict the life of LED?

In general, LED can be used for more than 50000 hours, and some manufacturers are promoting their LED to operate for about 100000 hours. The main problem in this area is that LED is not simply no longer operational. Its rated service life can not be calculated by traditional lamps and lanterns. In fact, when testing the life of LED, no one will be waiting for it to stop functioning. However, there are other ways to measure the life of LED. The reason why LED is durable is that it does not produce filament fuses. LED will not stop operation directly, but it will gradually deteriorate over time. It is predicted that high quality LED can maintain more than 60% of the initial lamp brightness after 50000 hours of continuous operation. Assuming that LED has reached its rated service life, it may still be luminous, but the light is very weak.

Without considering the power and driving failures, the life span of LED is characterized by its decay, that is, the longer the time is, the more darker the brightness will be, until finally extinguished. The time of decay of 30% is usually defined as its life.
So can the life of LED be predicted?

Light failure of 1.LED
Most white LED is obtained by irradiating yellow phosphor with blue LED. There are two main reasons for LED fading. One is the decay of Blu ray LED itself, and the blue light LED has far more light decay than red light, yellow light and green light LED. Another is the decay of phosphor, and the attenuation of phosphor at high temperature is very serious.

The decay of LED is related to its junction temperature. The so-called junction temperature is the temperature of the semiconductor pn junction. The higher the junction temperature is, the earlier the decay occurs, that is, the shorter the life. If the junction temperature is 105 degrees, the lifetime of the brightness to 70% is only more than 10000 hours, 95 degrees will be 20 thousand hours, and the junction temperature is reduced to 75 degrees, the life will be 50 thousand hours, and 65 degrees can be extended to 90 thousand hours. So the key to prolonging life is to reduce junction temperature. But these data are only suitable for Cree's LED. It's not suitable for other companies' LED. When the junction temperature is increased from 115 to 135, the life will be reduced from 50000 hours to 20000 hours.

2. how can we prolong the life of LED?
The key to prolonging its life is to reduce its junction temperature. The key to lowering the junction temperature is to have good radiator. It is able to send out the heat generated by LED in time.

3. how to predict the life of this lamp.

Judging from the junction temperature, life expectancy should be very simple. You can know that the life of LED can reach 20 thousand hours at the temperature of 95 knots. However, this method for indoor LED lamps and lanterns has certain credibility, if applied to outdoor LED lamps, especially high power LED street lamps, there are many uncertainties. The biggest problem is that the heat dissipation efficiency of the LED Street radiators decreases with time. This is due to the accumulation of dust and bird droppings, resulting in reduced heat dissipation efficiency. Also because there is a strong ultraviolet light outside, it will also reduce the life of LED. Ultraviolet radiation plays an important role in the aging of encapsulated epoxy resin. If silica gel is used, it can be improved. Ultraviolet radiation also has some bad effects on the aging of phosphors, but it is not very serious.

The LEDLM-80PL LED luminous flux maintenance rate and aging life testing system, launched by Shanghai power Shantou, are designed and manufactured according to the CIE and IEC standards such as IES-LM-80, IES0LM-82, TM-21, GB2312-80 and so on. It can record the curve of luminous flux with time and the curve of color parameter changing with time. The life time of LED is calculated by testing the data of light decay for a short time.

Shanghai Li Shan is committed to lighting test instruments, EMI/EMC testing systems and safety testing instruments in the domestic market development and after-sales maintenance. All Lisun products are developed and produced in strict accordance with ISO9001:2008's quality control and control requirements; Lisun is also a member of the global lighting CIE Association. All products comply with the requirements of CIE; in addition, Lisun products are certified by CE and are eligible for export to the EU.

Installation and training of LPCE-3 CCD Spectroradiometer Integrating Sphere Compact System（India）

Installation and training of LPCE-3 CCD Spectroradiometer Integrating Sphere Compact System（India）

A company in India recently purchased a set of LPCE-3 CCD Spectroradiometer Integrating Sphere Compact System. Shanghai Li Shan engineer went to customer company to carry out equipment installation training.

[caption id="attachment_10361" align="alignnone" width="800"] a-photo-of-with-our-engineer-and-customer-after-the-training[/caption]

The integrating sphere spectrometer testing system is the most basic luminaire testing equipment, and is first considered by the manufacturers and laboratories of lamps and lanterns. This set of equipment is also one of our hot selling products. We will connect the internal connections in front of the factory. After the customers receive the equipment, they only need to connect the power supply and electrical parameter meter to the inside of the cabinet according to the instructions. Our equipment and services have been recognized by this customer, and we hope that we can cooperate for a long time.

Since the establishment of Lisun Li Shan brand testing instrument in 2003, our products have been exported to over 150 countries and regions all over the world. The main products of Shanghai power Shantou include Goniophotometer,Spectroradiometer,Integrating Sphere, Photometer and Colorimeter, LED test instrument, EMI/EMC test system, Environmental Test Chamber, Electrical Safety Tester, Electronic Ballast Tester and AC and DC power supply. Since the founding of Lisun force Shantou brand testing instrument in 2003, we have been adhering to the idea of providing customers with appropriate products, reasonable prices and providing timely after-sales service. More details of the product see:

http://www.inventfine.com/products/

The following is a photo taken by our engineers after the installation and training.

Two Directions on LED Intelligentized: Intelligent Agriculture and Lifi

Two Directions on LED Intelligentized: Intelligent Agriculture and Lifi

With 4.0 concepts emerged on the industry, the traditional mind of manufacturing is experiencing unprecedented impact, integration and upgrade of industrialization and information will be the main theme of the transformation for production structure in the future. LED industry as a huge lighting market, in the new historical situation, only LED intelligent road can go farther. For now, the direction of the LED intelligent is divided into two aspects: agricultural intelligence and optical communication.

For the Internet concept is still in the mainstream of the world, the German academic and industry in 2013 in Hannover industrial exposition on the first proposed "industrial 4.0 research project", the core of this concept is the Systems Cyber-Physical (CPS), the integration of a variety of digital information, resources, products and persom, thus building an efficient and fast and flexible information, digital products and services production pattern. This concept was quickly spread to Europe from Germany and began to affect the world.

Connotation of intelligent LED lighting

The traditional LED had already appeared in 1962, and a LED product can only emit a low luminosity, and now the light has been spread all over the visible, infrared and ultraviolet light. Recent years, with the emergence of new technologies such as Internet, cloud computing, people are not satisfied with the basic functions of high brightness, low energy consumption, long life and low power, but more to LED and advanced things and cloud computing technology, from human psychology, physiology and sociology, considering the individual comfort, light biological safety and other conditions to improve learning, working and living conditions of the social benefits of reducing air pollution protection environment, that is LED intelligent.

And on the background of industry 4.0, combined with the traditional LED homogenization of the past ten years of serious overcapacity problems. The development and requirement of LED products are not only on their own lighting performance, but efforts to combine with other industrial technology, in order to obtain a composite function of LED smart light, thus the LED industry capacity to carry out the diversion. So far, there are two main diversion direction. The first is to break through in the field of agricultural lighting, and the second is to develop the field of optical communication.

LED agricultural intelligence

In agriculture, we know that light is one of the most important environmental factors for plant growth and development, and it has a direct regulatory effect on the growth and development of plants. As we known that the environmental factors, such as relative humidity, temperature, light intensity and light quality, are closely related to the growth and development of plants. In these factors, the quality of light directly affects the growth of plant stem, lateral branching, leaf growth and pigment deposition, and other major growth indicators. And the integration of these optical quality, mainly through the continuous intensity of red light, blue light, and the path of the hormone signal on the plant has a profound impact on the physiological response and thus the plant's growth and development plays a important role.

Using LED as the advantages of artificial light source for plant growth is that it has high energy conversion efficiency, DC power supply, small volume of products, is the use of, long service life, determine the wavelength and light intensity / mass ratio to reconcile low heat output. Some of the crops has been LED light culture, such as pepper, spinach, wheat dwelling, etc.. The research shows that the red light has an important effect on the development of the organs of photosynthesis in plants, and it can also increase the amount of starch in plants. It is also reported that the use of far infrared radiation can improve the antioxidant properties of rice husk. This indicates that the specific light radiation can increase the nutritional composition of food.

Overall, in the long run, there is a trend to replace the traditional lighting source with LED. Intelligent lighting system based on LED can be widely used in biological research of plants or animals; and this kind of intelligent system can also be used to determine the intensity and quality of light intensity for specific plant growth. It can be predicted that the agricultural intelligent system based on LED will be the important embodiment of the application of "industry 4" in agriculture.

LED optical communication (lifi)

Lifi is considered as a new type of optical equipment in twenty-first Century. The basic idea of designing this device is to transmit data through the LED light. But the amount of data transmitted by LED is relatively small. At present, Lifi is known as an optimized version of Wi-Fi, which has the advantage can reduce the cost of a large amount of wireless communication.



Hass Harald (Haas Harald), a professor at University of Edinburgh in the UK, is known as "the father of Li-Fi", which is the core of the Lifi technology, the intensity and the potential of the light emitting diode. He also believes that this technology can change our Internet, video, send and receive messages, etc.. Since the development of social development of data transmission is a wide range of needs, so the application of lifi technology can be extended to the areas of Wifi technology, such as medical technology, engine and other industries. Since lifi is considered to be the most fast Internet access service, this technology is likely to replace the current research institute and the company's wide application of WiFi, while people can use lifi technology to expand more special areas.

Under the influence of the 4.0 concepts of industry, the traditional industry of LED is bound to change the trend of the intelligent, and its development direction is also the high degree of industrialization and informationization. The 21st century is often referred to as "the century of light", and plant photosynthesis and is all of life, by virtue of the LED artificial lighting system with high efficiency and low energy consumption, taking into account the advantages of information control, LED intelligent agriculture will promote agriculture and biotechnology industries rapid development.

On the other hand, in the optical communications industry, the concept of Lifi has gradually been concerned, this is not only because it is more efficient than the radio electromagnetic wave, more widely used. When more and more people and devices are connected to the wireless network, the electromagnetic waves in the air will become increasingly blocked, which makes it difficult to obtain a sustained high speed signal. Therefore, the emergence of lifi based on LED technology can overcome many limitations in wireless network, and providing a safe, efficient and high-speed optical communication environment

If you test high power small size HID lamp, how do you choose Integrating Sphere?

If you test high power small size HID lamp, how do you choose Integrating Sphere?

HID lamp refers to the general term for High Intensity Discharge lamp. High pressure sodium lamp, high pressure mercury lamp, xenon lamp, metal halide lamp belong to HID lamp.

We generally use Integrating Sphere Spectroradiometer Test System to test the photometric, colorimetric and electrometric parameters. Generally we suggest the diameter size of Integrating Sphere according to the size of lamp under test. If you test single LED or LED chips, we recommend small integrating sphere such as IS-0.3M or IS-0.5M. 1.2m luminaries should at least use D=1.5M integrating sphere to measure.

If you test high power small size HID lamp, how do we choose Integrating Sphere? If the power of HID lamp is over 200W, we generally recommend use D=2.0m integrating sphere, we will not suggest small integrating sphere because of small size. Because if integrating sphere is too small, cooling is not good, the temperature of integrating sphere will affect the test result.

As the leading manufacturer of lamp test instrument, we can provide all kinds of integrating sphere, from D=0.3m to D=3.0m, constant temperature and electric integrating sphere.

The Methods and Principles of Applying Interference for LED Lighting Burst Test

The Methods and Principles of Applying Interference for LED Lighting Burst Test

When doing EFT test, there have L1, L2, L3, N and PE interface. PE and earth are two different concepts. Electrical fast pulse interference is common mode, in the experimental setup figure of the standard, we can see the signal cable which is from the test generator can connect with corresponding power lines (L1, L2, L3 , N and PE) through the selectable coupling capacitor, and the signal cable shield connects with the chassis of coupling/decoupling network, and the chassis is connected to the reference ground terminal.
This indicates that burst interference is actually applied between the power line and the reference earth, so the interference which is added on the power line is common mode interference, and for the experimental method of using coupled folder, the electrical fast pulse will be added into the tested cable through the distributed capacitance which is between coupling plate and the tested cable. But the pulse which tested cable received is still relatively to the reference ground plane.
Thus, the interference applied on the tested cable by coupling clamp is still common mode. After confirming the nature of the interference, we can take the appropriate measures to make the equipment passed the test. So we can see, the X capacitor (differential mode capacitor) which used in power filters cannot inhibit EFT interference.
If the device included metal shell, the Y capacitors (common mode capacitance) will work. We can bypass the high frequency EFT to the shell, and then back to the signal source via the distributed capacitance which between the device shell and the reference ground, so as not to enter the circuit.
The mechanism of electrical fast pulse interference causes equipment failed, according to foreign scholars’ research, the single pulse energy is small, it will not cause malfunction of the equipment. However, the interference signal of burst charges apparatus line junction capacitance, when the above energy accumulated to a certain extent, it is possible to cause malfunction of the power line (as well as the system).
Therefore, there will be a time process for the line error, and there will be some chance (cannot guarantee the time interval of the error, especially when the tested voltage reaches the critical point). And it is difficult to judge whether the device is more likely to fail for separately applying a single pulse or applying pulse group together. And it is hard to say whether the device is more sensitive for positive pulses or negative pulses.
Practice shows that one device is usually particularly sensitive to a polarity of a power cable under a certain kind of tested voltage. Experiments show that the signal line is much more sensitive than the power line for the electrical fast pulse interference.
Effective measures for equipment passing the electrical fast pulse test. First we analyze the methods of interference injection: EFT interference signal is coupling to the main power lines by coupling the 33nF capacitance of decoupling network (and the signal or control cables applies interference through capacitive coupling clamp, the equivalent capacitance is 100pF). For 33nF capacitance, it’s cutoff frequency is 100K, which means

the interference signal which is more than 100KHZ can be passed; but for 100pF capacitance, the cut-off frequency is 30M, only allows interference whose frequency is more than 30MHz passed. The interference waveform of the electrical fast pulse is 5ns / 50ns, repetition frequency is 5K, pulse duration is 15ms, burst repetition period is 300ms. According to the Fourier transform, its spectrum is from 5K to 100M discrete spectral lines, and the distance between each spectral line is the pulse repetition frequency.
After the above, we can know that the coupling capacitance which applies the interference plays a role of a high-pass filter, because the impedance of the capacitance decreases as the frequency increases, the low-frequency in the interference will not be coupled to the EUT, only the interference signal with higher frequencies will enter the EUT. When we add the common mode inductance into the EUT circuit (with particular attention to that, the common mode inductance must be added to the main power line and its return line or it will reach saturation and thus cannot reach the purpose of attenuating interference), it will attenuate some of the high frequency interference, because the impedance of the capacitance increases as frequency increases. Therefore, the interference signal which actually applied to EUT only left the intermediate frequency.