Through the research on the light distribution and heat dissipation of 1000w LED light fixtures, this article understands the service life of 1000w LED light fixtures, the directionality of light output, the luminous efficiency of 1000w LED light beads, heat dissipation coefficient, and other related parameters. Improved the design of primary light distribution, secondary light distribution, and heat dissipation of 1000w LED light beads of the company’s existing 1000w LED light products. 1000w LED light chips have accelerated aging and shortened working life. Therefore, heat dissipation is a vital factor restricting its development.
This article introduces the currently widely used 1000w LED light heat dissipation design, heat dissipation technology, heat dissipation products, and thermal analysis tools. Using ANSYS software to conduct a thermal analysis on a 1000w LED light, the temperature field distribution of each part is obtained, which has exceeded the junction temperature. Maximum allowable value. Through thermal analysis, the LED lamp heat dissipation structure was improved, and the maximum temperature of the chip was reduced to 51.1226°C. The simulation analysis results showed that it was within the allowable range, which verified the feasibility of the improved design.
Background
In principle, the luminescence phenomenon of semiconductor devices can be roughly divided into three types: photoluminescence, electroluminescence, and cathodoluminescence. The first form of luminescence is when a certain amount of light is irradiated on the semiconductor, the semiconductor itself A phenomenon in which electrons and holes absorb the energy of light and emit light. The second form of luminescence is that when a forward voltage is applied to a semiconductor device, electrons and holes move due to energy, which in turn stimulates the luminescence phenomenon.
Cathodoluminescence is a phenomenon in which when certain rays are irradiated on the semiconductor, the carriers of the semiconductor absorb energy, and then produce composite luminescence.
The LED itself is also a semiconductor device, and the spontaneous light emission of the LED is caused by the recombination movement between electrons and holes. Its light-emitting principle is based on the light-emitting principle of electroluminescence and does not adopt the light-emitting principle similar to traditional light sources such as incandescent lamps and energy-saving lamps. The most important part of the LED is the P-N junction-which is composed of an N-type semiconductor and a P-type semiconductor, and a thin vacuum depletion layer is formed between the P-type semiconductor and the N-type semiconductor. The luminescence process of the P-N junction can be roughly divided into three processes: carrier injection under forwarding voltage, composite radiation, and light energy transmission. The very small semiconductor crystals are all packaging in clear epoxy resin. When the electrons in it pass through the wafer, the electrons dissociate to the hole area and recombine with them. At this time, the holes and electrons disappear at the same time and photons appear. . The energy of the photon produced by the recombination movement of electrons and holes is proportional to the electrons and holes themselves. However, the energy of the photon produced by the compound motion corresponds to the color of the light produced by the photon at the same time. Generally speaking, within the spectrum of visible light, the energy carried by the spectrum of different frequencies is different. Violet light and blue light have the most energy under normal circumstances, while red light and orange light tend to have the least energy. It is precise because of the difference in band gaps between different materials that different materials can emit different colors of light.
Imaging optics for 1000w LED light fixtures
As a new type of solid-state cold light source, LED has the advantages of small size, long life, high luminous efficiency, energy-saving, and environmental protection. The broad market prospects of 1000w LED light fixtures have triggered a climax of research on LED applications, especially in high-power lighting applications. However, because the light emitted by the LED chip is Lambertian distribution, such light field distribution is not subject to secondary optical design However, if it is directly applied to actual high-power lighting applications, it will cause serious light waste. The secondary optical design of LEDs has become the main problem that restricts the further promotion of LEDs in lighting applications. The traditional lighting design method cannot carry out the shortcoming of the wrong estimation. The method of combining non-imaging optics theory, lighting design software, and computer programming is used to carry out the secondary optical design of 1000w LED light fixtures. According to the classics of non-imaging optics Conservation of optical expansion and the principle of edge light, the curved surface equation of the lens is obtained, and then the discrete points of the free-form surface lens are calculated by Matlab programming, and the three-dimensional modeling is performed. The simulation is performed in Tracepro to verify the correctness of the design. The basic packaging structure of LED is to encapsulate a semiconductor module with an electroluminescent structure in epoxy resin, and use pins as positive and negative electrodes to support the structure. The LED structure is mainly composed of brackets, silver glue, wafers, and gold. Wire, epoxy resin is composed of five materials.
The imaging optics of 1000w LED light fixtures. In the imaging optics design, the optical system is the main imaging tool. The law of light propagation is mainly studied through the concept of geometric light. There is a lack of corresponding research on the changes in energy transfer in light propagation. However, non-imaging optics is different from imaging optics. From the perspective of physics, it is believed that light carries corresponding radiant energy in the process of propagation, and the direction of light propagation is the corresponding radiant energy propagation direction. Therefore, when starting from the perspective of studying energy changes, the optical system itself is also a medium that transmits the corresponding radiant energy. The propagation process of light itself is the corresponding energy transfer process. Non-imaging optics theory mainly follows the law of this energy propagation. The angle of the whole optical system is studied. The main purpose of the application of non-imaging optics theory is to study the entire illumination system, but the illumination system itself plays a control role in the transmission of light energy in the process of light propagation, rather than playing an imaging role similar to the imaging optics theory, But imaging problems cannot be excluded from non-imaging design. Non-imaging optics theory is mainly produced to solve two major types of problems. One is how to maximize the energy transferred, and the other is how to The illuminance distribution that meets the lighting requirements is obtained on the target plane. These two problems are usually called light collection and illumination in the field of general lighting. Concentrators can usually be divided into two categories, one is called three-dimensional concentrators, the other is two-dimensional concentrators, two-dimensional concentrators can also be called linear concentrators, the convergence ratio of linear concentrators is usually expressed by the ratio of the input and output dimensions on the cross-section. For the two-dimensional condenser and the three-dimensional condenser (with axisymmetric characteristics), the maximum value of c can be obtained. Assuming that the input and output media have the same refractive index when the circular light source is at infinity, the value of iθ The divergence angle emits light. When passing through the optical system, the maximum concentration ratio max reaches 21/siniθ. When the angle of the exiting light and the exiting surface converge to form a secondary light distribution. The optical expansion has a certain physical meaning: the optical expansion can be used to evaluate the influence of the optical element on the energy utilization rate of the entire optical system, and it can also be used to describe the characteristics of the light beam itself. For specific optical elements, the optical expansion represents the ability of the optical element to converge the beam. Using the concept of optical expansion, the degree of matching between the illumination system and the imaging system can be judged.
Lens model of 1000w LED light fixtures
For an ideal optical system, when reflection, refraction, scattering, and other losses are not considered, the optical extension of the light beam is conserved after passing through the optical system. In non-imaging optical design, this is required in the design process A very important factor to consider is from two aspects. For the light source, the smaller the optical expansion, the better. However, for the optical element, the situation is just the opposite. The optical expansion should be the opposite for the optical element. The larger is the better. Of course, the greater the optical expansion is not the better, because the increase in the optical expansion does not necessarily bring the same degree of energy efficiency improvement to the entire optical system, but will cause the optical system design to be complicated. Therefore, when designing non-imaging optical systems, the concept of optical expansion should be reasonably used to control the trend of light and realize the conservation of optical expansion in order to obtain the ideal light energy utilization rate. And to meet the requirements of the illumination uniformity index, the solid model of the lens can be obtained by rotating the curve once, and the outer surface of the lens model of the 1000w LED light fixture is the desired free-form surface.
Design of 1000w LED light heat sink
The heat transfer of 1000w LED light fixtures is the heat transfer process of matter under the action of temperature difference. No matter inside an object or between some objects, as long as there is a temperature difference, the heat will be spontaneously generated in one or several ways. The ground spreads from high temperature to low temperature. There are three basic ways of heat transfer: heat conduction (heat conduction), heat convection, and heat radiation. Compared with traditional light sources, LEDs are distinguished by their small size, compact structure, and easy insertion into various lamps. As the carrier of the light source, the heat dissipation design of the lamp is very important for the LED to play its advantages. If the heat dissipation efficiency of the lamp is designed to be high, not only can the service life of the LED be prolonged, but also the weight of the lamp can be reduced, and its application range can be expanded. On the contrary, it will affect the use of LED advantages, and even become a bottleneck in its application.
Therefore, this chapter focuses on the design of the radiator. We know that there are usually two heat dissipation methods: the first is active heat dissipation, that is, heat dissipation is performed by forced cooling methods such as external fans, water cooling or heat pipe loops, microchannel refrigeration, semiconductor refrigeration, etc., which is characterized by heat dissipation High efficiency, small radiator, and compact structure. The disadvantage is that it will increase the additional power consumption, and considering the requirements of the protection level of the lamp, it will also increase the difficulty of the lamp design; the second is passive heat dissipation, which mainly relies on the natural convection of the air, and the heat generated by the heat source is naturally transferred through the heat sink. Dissipated into the air, the heat dissipation effect is related to the size of the heat sink. This method has a simple structure, but the heat dissipation efficiency is relatively low. For the lighting system, because the heat dissipation method is easy to combine with the structure of the lamp, the structure is relatively simple, and no additional power consumption is required. At the same time, for the comprehensive consideration of processing, material cost, maintenance factor, etc., passive heat dissipation is used The overall cost is relatively low. At present, the mainstream direction is to adopt the second method, which can meet the heat dissipation requirements of the lighting system to the greatest extent by rationally designing the radiator, and at the same time save the cost to the greatest extent. A high-power LED street light radiator sold by our company is specifically optimized. The radiator is composed of two identical modules.
Summary
1000w LED light is one of the hotspots of research and application in recent years, especially after the emergence of high-power LED chips, the application of 1000w LED light in the field of lighting has a trend to replace traditional lighting. Currently, LEDs are still facing problems in driving power supply design, light distribution design, and heat dissipation design. In this paper, the secondary optical design of the Lambertian high-power white light LED is carried out, and the free-form lens that realizes the uniform round spot and the uniform rectangular spot is designed respectively. At the same time, this article also studies the heat dissipation of high-power LEDs, expounds the optimization process of high-power LED flat heat sinks using ANSYS optimization function to write programs, and gives a specific product design process.
