With the continuous consumption of the earth's energy and the lack of resources, the harm of the greenhouse effect to human beings, the serious pollution of the atmosphere by the atmosphere, and the international demand for energy conservation and consumption reduction are getting higher and higher. Today's energy conservation ranks first, and road lighting accounts for about 30% of the total electricity consumption of lighting, which is closely related to people's production and life. Urban rural roads will be more and more open, wider and wider, and need a large number of various energy-saving lamps to match. With the acceleration of urbanization in China, green, high-efficiency, energy-saving, long-life LED street lights have gradually entered people's field of vision. At present, LED lighting technology is becoming more and more mature, and the efficacy of high-power LED light source has reached 80 lm/W, and energy-saving renovation of urban street lighting has become possible.
Unlike traditional lighting, LEDs have a point source, high brightness, and narrow beam output. Therefore, designers of new LED luminaires will put forward higher requirements. To do LED streetlights, first consider the use of limited luminous flux to the effective range of illumination. The street light requirement is the road lighting effect, and the open space beyond the road surface is not the way of street lighting. Therefore, the effective distribution of the light is controlled so that the light emitted by the light-emitting tube becomes a long strip of light spreading along the road surface, and at the same time, the glare is also taken into account. At the azimuth of the driver to view the light, the light is at 80°. The light intensity in the 90° height angle direction shall not exceed 30 cd/1000 lm and 10 cd/1000 lm, respectively, and the maximum light intensity in the 90° angular direction shall not exceed 1000 cd regardless of the light flux of the light source. Therefore, if the control angle is not strictly controlled, strong glare will occur, and some high-brightness LED products may even cause certain optical radiation damage to the human body.
Street lighting is a systematic project. To make semiconductor street lamps, we must first understand the standards and requirements of road lighting and the light distribution principle of conventional lighting fixtures. The difference between the spherical light reflector and the point light source is reasonable. Complementing each other, giving full play to the controllable advantages of the beam angle of the LED point source and the long life of the cold source.
Semiconductor LED light sources have their own characteristics in terms of optical structure and optical characteristics. Therefore, semiconductor street lamps should be designed according to these characteristics. Some manufacturers today use traditional lamp housings to replace semiconductor wicks, and heat conduction through transition conduction can not make good lamps. The problem is that the external shape of the lamp body should be combined with the heat dissipation of the light-emitting tube, and the heat dissipation depends on the area. The surface area of ​​the conventional conventional lighting fixture is far from enough. The "Joule heat law" is to have a good natural air convection environment. The operating temperature of LED products should be controlled below 65 °C (the international standard is 80 °C, when the working temperature of LED reaches 85 °C, the luminous flux will drop by half; the wavelength becomes longer, that is, red shift; if it exceeds 90 °C, there is danger of burning) . The installation of the luminous tube, the scientific and rational optical distribution, the sealing of the lamp body are very important. At the same time, the designed lamp body structure is also conducive to mass industrial production.
The heat dissipation of the LED is a problem that the semiconductor lamp should focus on. The light-emitting tube is a cold light source, which does not produce a hot high temperature like a gas discharge lamp. However, the limitation of the luminous efficacy of the LED light-emitting tube today also has its own thermal resistance, so the heat generated by the operation of the light-emitting tube must be effective. Dissipated into the air to ensure that the LED works at a safe temperature, so that the semiconductor lamp can truly reflect the advantages of long life.
It is very important to use LED tubes for LED street lamps. Some manufacturers today use integrated packages of 10W or more to make street lamps. There are defects such as difficulty in optical distribution, glare, and difficulty in overall heat dissipation. It also has 3W ~ 5W modules, its luminous tube meter has low light efficiency per watt, and there is also the overall heat dissipation problem. Compared with a single 1W, the price advantage is not obvious under the same luminous flux. Considering comprehensively, it is more reasonable to use a high-power 1W LED. From the current technical level of high-power LED, 1W light efficiency is relatively high, and it is obvious for lighting energy saving. At present, it is more reasonable to use 1W as street light source.
The choice of LED color is also an important factor to pay attention to. In the development of road lighting, there is a comparison of the use of yellow and white light. Huangguang is now the mainstream high-pressure sodium lamp. Because it is economical and energy-saving, it also has excellent fog-passing performance, so it has become the mainstream street lamp choice in China. Even so, Huang Guang has its inherent shortcomings: that is, the color reproduction ability is poor. People have the feeling that under sodium light, the color of any object is yellowish and distorted.
The goal of white light is natural sunlight. Because it has the best color performance, and the sun is a warm white light. Therefore, if you can achieve white light similar to daylight, and at the same time take into account the advantages of Huangguang's economical energy saving, it will be an ideal night lighting option. The early stage of white light is a metal halide lamp. Although it has a color performance that is several times higher than that of yellow light, it has not been widely applied due to some insurmountable technical problems such as poor fogging performance and low effective life. The LED light source can make up for this defect. It is more suitable to put about 3500K in the color temperature selection of the LED light source, and meet the lighting requirements in terms of clear vision and comfort. Moreover, it is feasible in the development of LED light efficiency and cost performance, and is suitable for large-scale promotion of LED street lamps.
There are different opinions on the use of white light above 6000K as a street light source, especially for high power of 160W or more. It is necessary to be cautious in the use of expressway. According to the national road lighting standards, the expressway and the main road must use light-cut or half-cut lamps.
Cut-off luminaire
The maximum light intensity direction of the luminaire and the downward vertical axis of the luminaire are between 0° and 65°, and the maximum allowable values ​​of light intensity at 90° and 80° are 10cd/1000lm and 30cd/1000lm respectively. Regardless of the light flux of the light source, the maximum light intensity in the 90° angular direction must not exceed 1000 cd.
Half cut light fixture
The maximum light intensity direction of the luminaire is between 0° and 75° with the downward vertical axis of the luminaire, and the maximum allowable values ​​of light intensity at 50° and 80° are 50cd/1000lm and 100cd/1000lm respectively. Regardless of the light flux of the light source, the maximum light intensity in the 90° angular direction must not exceed 1000 cd.
Because the expressway road is long, the road width is wide, the traffic volume is large, the vehicle speed is fast, and the visual sensitivity is high. Therefore, the illuminance, color temperature, brightness uniformity on the road, glare and other indicators are required. In order to compare with the 400W high-pressure sodium lamp, it is required to require high power and high brightness. Moreover, today's LEDs are difficult in terms of light efficiency and heat dissipation cost, and it is difficult to promote the price/performance ratio.
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