4 Technical Points of High -power LED Working Temperature Control

The application of high -power LED lighting equipment is becoming wider and wider, and the luminous brightness of high -power LED is actually proportional to its current, and the forward current of high -power LED will also change with the temperature changes. Today, I will take everyone to learn about the reason for LED knot temperature and LED semiconductor lighting source heat dissipation method. In recent decades of development, LED lighting efficiency has become higher and higher, the cost is getting less and less, and the colors have become richer and richer. This makes high -power LEDs as an efficient, energy -saving, environmentally friendly, and safe cleaning source in the near future. However, the heat dissipation problem of high -power LED lights is still a major development bottleneck in its application in the field of lighting. It is an important reason to restrict its new generation of lighting sources. Research data show that when the LED chip has a luminous light when the knot temperature of the LED chip is 25 C, then when the knot temperature rises to 60 C, its luminous amount will only be 90%; when the knot temperature reaches 100 C, it will drop to 80%. ; 140 C is only 70%. It can be seen that improving heat dissipation control knot temperature is very important for improving its luminous efficiency. If the heat dissipation problem of high -power LED lights is not resolved, the working temperature of LED lights will increase and the knot temperature will increase, which will cause the LED chroma to be offset, the color rendering index decreases, the color temperature increases, the light emitting efficiency decreases, and the service life will be shortened. The luminous brightness of high -power LED is actually proportional to its current. If the output optical flux of the high -power LED is controlled, it is equivalent to controlling its luminous brightness. The positive current of high -power LEDs will also change with the temperature. When the temperature of the environment exceeds a certain value (we call the safety temperature), the forward current of the LED will be reduced suddenly. At this time, if the current continues Increasing, it will cause LED life to reduce. Therefore, at this time, corresponding measures must be made. When the bubble lamp input current and the surrounding temperature are changed, the high -power LED positive current can be controlled in time. Use temperature compensation technology to dynamically adjust the output current according to the ambient temperature, and monitor the temperature of the LED in real time, so that the high -power LED at high temperature conditions will automatically reduce its current. 1. The current status of high-power LED lighting products "chip-aluminum substrate-the three-layer structure mode of the radiator" is used by most large-power LED lighting fixtures on the current market, that is, first packaging chip on aluminum substrates to form an LED light source module, and then Then install the light source module on the radiator so that you can make a high -power LED lighting fixture. At present, the early use of LEDs to display lights and indicators is used as a thermal management system for high -power LEDs. This thermal management mode is limited to small -power LED use. The high -power LED lighting prepared by the three -layer structure mode, there are still many unreasonable places in terms of system structure, such as high knot temperature, low heat dissipation efficiency, more contact thermal resistance between structures, lower heat dissipation efficiency, more contact thermal resistance As a result, the heat released by the chip cannot be effectively dispersed and exported, resulting in LED lighting fading, low light effect, and short life. Due to the limitations of many factors such as structure, cost, and power consumption, high -power LED lighting is difficult to adopt an active heat dissipation mechanism, and can only adopt a passive heat dissipation mechanism, but passive heat dissipation has great limitations; and the current energy conversion efficiency of LEDs is still effective Not high, about 70 % of the input power can be converted to heat, even if the light effect is increased by 40 %, the energy is converted into heat, that is, it is difficult to increase the degree of heat dissipation without considering heat dissipation. 2. The characteristics of LED lighting light sources are different from traditional fluorescent lamps, incandescent lamps, and halogen lamps. LED semiconductor lighting light sources are made of semiconductor material and consisting of PN. Electronics-grounded acupoints generate visible light through composite, PN positive guidance Tong, reverse cut off, of which N area corresponds to the negative electrode, and the P area corresponds to the positive pole. The LED semiconductor light sources have the advantages of high light emitting efficiency, short response time, small volume, energy saving and other advantages. In addition, it also has the characteristics of traditional lighting sources: 2.1 has the characteristics of similar PN semiconductor devices: 1) The positive current and forward voltage are negative temperature coefficients, which are reduced as the temperature increases; 2) Positive voltage voltage It must exceed a certain threshold to generate current; 3) When reverse, no current will not work. 2.2 There are many aspects to restrict its working temperature. The specifics are as follows: 1) The brightness of the LED and the positive current present a certain curve relationship. When the knot temperature exceeds a certain value, the brightness weakens with the decrease in the current to the current; 2 ) You must limit the knot temperature to below the rated value 95 C to 125 C; 3) If the surface contains plastic lenses, it will be limited by the melting point temperature of the lens material. 3. Introduction to LED knot temperature 3.1 The cause of the LED fever generated by the LED fever is because the energy added is not all transformed in the form of light energy, and some of them have been converted into thermal energy. At present, the light efficiency of the LED on the market is about 100 LM/W. In other words, about 70%of the electric energy is wasted in the form of thermal energy. Generally speaking, there are two factors that lead to the production of LED knot temperature. Specific as follows: 1) Internal quantum efficiency. When the acupuncture and electronic composite are compounded, they cannot all produce photons. This is usually called "current leakage", which is the reason why the compound rate of loading of the PN zone is reduced. The voltage of the leaked voltage and the current is the dispersion power of this part, that is, the transformation into thermal energy, but this part is not the main component, because the current technology can make the internal photon efficiency of LED close to 90%. 2) About 30%of external quantum efficiency. One of the main reasons is that the photons generated by the loadmons cannot be transformed into the outside of the chip but converted into heat. Although incandescent lamps are only about 15LM/W, but in the end, it radiates electrical energy in the form of light energy. Although most of the radiation energy is infrared and the light effect is very low, this is exempted from the problem of heat dissipation. The heat dissipation problem of LED has gradually become the focus of people's attention. This is because the life of LED or light decay is directly related to its knot temperature. If the heat dissipation problem is not handled well. 3.2 Methods to reduce LED knot temperature Control the rated input power; The design of the secondary heat dissipation structure; reduce the heat resistance between the secondary heat dissipation structure and the LED installation interface to the minimum; reduce the surrounding environment temperature; reduce LED's itself thermal resistance. 4. LED semiconductor lighting light source heat dissipation method In general, the radiator can be divided into passive heat dissipation and active heat dissipation according to the way to take away heat. The so -called passive heat dissipation refers to the heat generated by the heat source LED light source to the air through the heat sink. Its heat dissipation effect is proportional to the size of the heat dissipation tablet, but this heat dissipation effect is relatively unsatisfactory. In the device, or for the heat dissipation of low -power and low -heat, the vast majority of devices take active heat dissipation, active heat dissipation is to actively take the heat from the heat sink through some equipment. Higher heat dissipation efficiency is the main feature of active heat dissipation and it has a relatively small volume. Another way is to make LED components by adopting the "vertical" electrode. Because there are metal electrodes in the upper and lower ends of LED components, this can get greater help on the problem of heat dissipation. For example, the GAN substrate is used as the material. Because the GAN substrate is the conductive material, the electrode can be directly connected under the substrate to get the benefits of fast dispersion and light, but because of the high material cost, this approach will also It is much more expensive than the cost of traditional sapphire substrates, which will increase the production cost of components.