Research and development progress of led street lamps

- May 22, 2019-

Shape structure

Appearance design, structure, full of modern flavor, conforms to the trend of The Times, in the aspect of heat we have creative adopted air convection cavity type aluminum radiator design scheme, the radiator fluctuation two radiating surface layer, middle connected by eight tud, connect fully, before and after air convection hole is left at the same time, strengthen the air circulation within the cavity, is advantageous to the heat discharge, effectively improve the heat transfer efficiency of LED light source. Above the unique design of heat dissipation to ensure the safety of the high power LED light source is under 45 ℃ temperature.

The LED light source

Self-developed and designed metal bolt type high-power LED light source. In order to improve the stability of the products we adopted American original installation import high quality LED chips, LED chips encapsulation directly on top of the metal bolt nut, product assembly will be LED metal bolt tightening on the aluminum radiator directly and effectively LED to radiator closely together, changed the traditional high power LED light source by means of thermal conductive silicone thermal conductivity of the status quo, greatly improved the leds and aluminum radiator efficiency, heat transfer between effective guarantee the service life of the LED light source is greater than 60000 hours. Meanwhile, high quality phosphor powder from Taiwan is adopted to make the brightness of a single LED reach over 80 lumens. And there are a variety of color temperature to choose, to meet the needs of different occasions for different color temperature.

Light distribution curve

Using unique secondary optical lens module and "strip spot" light design. The length of the light spot is determined by the LED light output Angle, so as to reasonably control the light distribution, avoid the light superposition waste, reduce the light loss, realize the connection between the strip light spots between the lamp poles, and make it reach the brightness index stipulated by the national standard. It eliminates LED glare and protects LED light source while ensuring ideal road illumination and uniformity.

Driver circuit

Dc 9V - 30V or ac 84V - 264V wide voltage input drive circuit design. Precise constant-current output enables each high-power LED light source to work at constant rated current, with small line loss and aging coefficient, and electric conversion efficiency 85%. Precise constant-current output ensures the service life of LED light source.

The light source module

The modular design scheme is adopted for the light source to achieve the best matching between the illumination and the power of the ground. The number of light sources is increased or decreased to meet the requirements of different road widths and illuminance, so as to meet the lighting requirements of the city without wasting electric energy.

To develop LED street lights, attention should be paid to the following aspects:

A. The improvement of optical pass also needs to be further improved from the basic level of epitaxial technology and chip technology of high-power LED. The method of making white LED at home and abroad is to place the LED chip on the encapsulated substrate, bond it with gold wire, and then coat the chip with YAG phosphor powder, and then encapsulate it with epoxy resin. The resin ACTS both as a protective chip and a condenser. The blue light emitted from the LED chip is reflected into the surrounding phosphor powder layer for several scattered reflections, absorption, and finally emitted externally. The spectral line of the LED(blue) peaks at 465nm with a half-width of 30nm. Part of the blue light emitted by the LED excites the yellow YAG phosphor powder layer and makes it emit yellow light (the peak value is 555nm). Part of the blue light is emitted directly or after reflection, and finally reaches the external light of blue and yellow, namely white light. FlipChip can get more efficient illumination than traditional LED chip packaging. But adding a reflective layer below the electrodes in the chip's light-emitting layer to reflect the wasted light energy would cause a loss of about 8%. So the reflector must be added to the base material. The light on the side of the chip must also be reflected by a heat-sink mirror to increase the output of the device. In addition, a layer of silica gel material should be added between Sapphire substrate and epoxy resin light guide bonding surface of flip chip to improve the refractive index of chip light. With the improvement of optical packaging technology, the output light rate (flux) of high-power LED devices can be greatly improved.

B. Optimize the design of LED lighting appliances to improve the quality of LED. Therefore, it is particularly urgent to study the secondary optical light distribution design of high-power LED light source to meet the light distribution requirements of large-area projection and floodlight lighting. By means of secondary optical design technology, additional reflector cup, multiple optical lens and aspheric surface can be designed to improve the efficiency of the device. Traditional illuminant direction of 360 °, lamps and lanterns is relying on the reflector will be most of the light reflection to a specific location, only about 40% of the light is directly through the glass to the road, the other is through the reflector lamps and lanterns to cast out the lamps and lanterns, the reflectors of lamps and lanterns of efficiency is only 50% ~ 60% commonly, so there are about 60% within the lamps and lanterns, light output is 30% ~ 40% in lost and then projected onto the pavement. A large part of the light output of the light source is limited in the lamp internal heat consumption. Most of the light of LED lamp is forward light, which can achieve the lighting effect of >95%. This is one of the important characteristics of LED that distinguishes it from other light sources. If this feature cannot be well used, the advantages of LED will be greatly reduced. More than most of the high power LED lights because it is the LED chip assembly, will be so much light source according to the different direction, we give full play to the whole chip encapsulation, the characteristics of settled with lens through the optical design, according to different needs, equipped with different convex curve, rely on the lens to the light distribution in different directions, of the light Angle can reach 120 ° ~ 160 °, small light can be gathered within 30 °, once the lens shape, in guarantee under the premise of production technology, the same light distribution characteristics of lamps and lanterns also reached consensus. The bat wing light type that can make LED street lamps meet the requirements of road lighting standards can be achieved through trial production and continuous summarization of experience. Tunnel lamps, street lamps and general lamps have reached the lighting requirements of their respective application sites.

C. Heat dissipation is a key problem to be solved for LED street lamps. As we all know, LED is a photoelectric device, only 15% ~ 25% of the electric energy in its working process is converted into light energy, the rest of the electric energy is almost converted into heat energy, making the temperature of LED rise. In high-power leds, heat dissipation is a big problem. A 10 w white LED, for example, if the photoelectric conversion efficiency is 20%, there were 8 w electrical energy into heat energy, if not add cooling measures, the high power LED is the core of the temperature will rise sharply, when its junction temperature (TJ) rise more than the maximum permissible temperature (typically 150 ℃), high power leds will be damaged due to overheating. Therefore, in the design of high-power LED lamps, the most important design work is heat dissipation design. Due to the high brightness requirements of LED street lamps and harsh operating environment, if the heat dissipation is not solved properly, LED aging will be rapidly caused and the stability will be reduced. A lamp using 250W high pressure sodium lamp, because the technology is mature, the heat dissipation control is very good, even if works 5000 hours, the light decline is still very small. Under the same conditions of high power LED street lamps, if the heat dissipation is not solved, the light will decline greatly. The main ways of heat dissipation of LED street lamps are: natural convection heat dissipation, forced heat dissipation by installed fans, heat pipe, loop heat pipe heat dissipation and heat dissipation by equal-temperature plate, etc. The installation of fan forced heat dissipation system is complicated and has low reliability.

D.LED street lamps will eventually choose modular installation and maintenance. At present the road surface USES the most high pressure sodium lamp, the internal ballast and other parts are not easy to damage, most of the reason is not bright light source damage, maintenance mode as long as the replacement of the light source. A skilled operator, can be fully personal operation platform. However, LED street lamps have many internal components. In addition to the light source (chip), other parts will be damaged and the chip will not be bright. Therefore, at the scene, can not immediately determine the cause of the LED street lamp damage. If the LED street lamp doesn't work, it needs to be removed and transported back to the factory for various tests. In this way, it is very tedious to replace LED street lamps. The final version of the development of LED street lights is to develop into modular. The light source, electrical and so on are all replaced in accordance with the plug, so that a skilled worker, also completely independent to judge the cause of damage and on-site maintenanc