Analysis on the improvement of LED lamp cooling level

Introduction: LED lighting reliability (life) to a large extent depends on the level of heat dissipation, so improve the level of heat dissipation is one of the key technologies. It is mainly to solve the problem of excess heat generated by the chip through the heat sink, heat transfer, which is a very complex technical problems.

LED lamp power, which LED need to consider the issue of heat dissipation, power LED need heat. Power LED refers to the working current of more than 100mA light emitting diode. China is the standard reference to the United States ASSIST alliance defines, according to the existing two kinds of typical forward voltage value of LED 2.1V and 3.3V, that the input power at 210MW and 330MW above LED are power LED, need to consider the device heat dissipation problem, some people may have different views, but the practice has proved that in order to improve the reliability of power LED (life), it is necessary to consider the problem of heat dissipation of power LED.

The main parameters related to the heat dissipation of the LED are thermal resistance, junction temperature rise and so on.

Thermal resistance refers to the difference between the effective temperature of the device and the external reference point temperature divided by the steady-state power dissipation in the device. It is the most important parameter that indicates the degree of heat dissipation. At present, better cooling thermal resistance of power LED is not higher than 10 DEG /W, the thermal resistance is less than or equal to the best reported domestic /W 5 degrees, up to foreign resistance is not higher than 3 DEG /W, as do this level can ensure the power of LED life.

Junction temperature refers to the temperature of the semiconductor junction in the LED device. It is the embodiment of LED devices in working conditions, can withstand the temperature value. To this end, the United States SSL plans to develop a goal to improve heat resistance. The heat resistance of the chip and the phosphor is very high, the chip junction temperature has been reached at 150 DEG C, and the fluorescent powder has no influence on the life of the device at the temperature of 130 DEG C. This shows that the higher the heat resistance of the chip, the lower the requirement of heat dissipation.

There are several kinds of temperature rise in temperature rise. What we are talking about here is that the shell temperature rise. It refers to the LED device shell (LED lamps can be measured to the hottest point) temperature and the environment (in the light emitting plane, 0.5 meters away from the lamp) temperature difference. It is a direct measurement of the temperature value, and can directly reflect the LED device peripheral cooling, practice has proved that when the environment temperature is 30 DEG C, if the measured LED shell is 60 DEG C, the temperature should be 30 degrees, this basically ensures that the lifetime of LED devices, such as the high temperature, the retention rate of LED light source will be greatly reduced.