The design of high power LED light

The design of high power LED light

Discovery
In recent years, the fast development of high power LED in structure and performance, there are great improvement, production rose, falling prices; Developed a single power for 100 W white LED the super power. A few years ago, the luminous efficiency compared in have great progress. For example, Edison company in the first few years of the 20 W white LED, the flux for 700 lm, luminous efficiency of 35 lm/W. 2007 years of development 100 W white LED, the flux for 6000 lm, luminous efficiency for 60 lm/W. And for example, recently developed K2 Lumiled company white LED, with its ¢ñ, ¢ó series product is the same as is shown in table 1. From the table can see: K2 in flux, the biggest white LED junction temperature, thermal resistance and outside profile on size has more improvement. Cree company the launch of new XLamp XR ~ E cold white LED to its highest brightness in 350 when mA block QS flux can reach 107 ~ 114 lm. These the good performance of high power LED to the development of white LED lighting lamps and lanterns created the conditions.


Before a few years, all kinds of white LED lighting lamps and lanterns is mainly used in the power ¦µ 5 white LED to do. Such as 1 ~ 5 W bulb, 15 ~ 20 W GuanDeng and 40 to 60 W street lamp, and shooting, shoot the light, etc. These lamps and lanterns USES dozens to hundreds of ¦µ 5 white LED, production process complex, poor reliability, high failure, the size, and powerful enough. To improve the above shortcomings, these a few years the white LED gradually high power to replace ¦µ 5 white LED to design new lamps and lanterns. For example, with 18 2 W white LED street light, if you use made of ¦µ 5 white LED is to several hundred. Additional, with a 1.25 W series of K2 white LED, but make it flux for 65 lm's strong light flashlight, illuminate distances of up to a dozen meters. If you use ¦µ 5 white LED to do is not possible.


Figure 1 "TJ temperature and the relative out light rate relationship chart

High power LED with the lamps and lanterns incandescent lamp, fluorescent lamp, its price is energy-saving lamps to much higher, but it effect of energy saving and a shorter life expectancy than other lamps and lanterns is much higher. If in the street lamp system and the lobby, large department stores or supermarket, senior hotel lobby large public places such as electricity all using LED lamps and lanterns, its one-time investment is higher, but the long-term effect of power saving and economy is to look forward to.

Adopts mainly 1 ~ 3 W high power white LED lights, because of its high luminous efficiency, low price and flexible application. The high power LED heat LED a photoelectric device, the course of their work only 15% to 25% of the electrical energy into light energy conversion, the rest of the electrical energy converted into heat energy, almost all that LED the temperature rise. In high power LED, heat is a big problem. For example, a 10 W white LED if the photoelectric conversion efficiency is 20%, there are 8 W electrical energy converted into heat energy, if be not added measures, the heat of the high power LED the core temperature will be shot up, when the junction temperature (TJ) rise above the maximum allowable temperature (150 ¡æ is generally), high power LED will be in overheating and damage. So in high power LED lamps and lanterns design, the main design work is cooling design.


In addition, general power devices (such as power supply IC) in the calculation of heat, as long as the junction temperature is smaller than the maximum allowed temperature and temperature (125 ¡æ is generally). But in high power LED in the design of the heat, and TJ than 125 ¡æ temperature requirements low much. The reason for this is the light of LED a TJ rate and life has a great influence on TJ: the higher the LED light will make the rate is lower, life is short.

Figure 1 is K2 series of white LED junction temperature and relative TJ relation curves of the light rate. TJ = 25 ¡æ in relatively light out for 1; rate TJ = 70 ¡æ relatively light rate drop out when 0.9; TJ = 115 ¡æ is down to 0.8. Table 2 is Edison high power companies are white LED the junction temperature TJ in brightness with the life of the relationship between attenuation 70% (LED the life of different manufacturers are not identical, make reference only).

In table 2 of that: 50 ¡æ TJ =, life for 90000 hours; TJ = 80 ¡æ, the life to 34000 hours; TJ = 115 ¡æ, its life is only 13300 hours. TJ on cooling design should put forward in the maximum allowable junction temperature

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