[Resolved] Status, specialty and defects of LED road lighting fixtures

Present situation of light distribution of road lamps using LED light sources

At present, the most common form of LED used in road lamps and lanterns is mainly two types, one is to use the traditional road lamp shell, only in the lamp, in a nearly flat mounting surface (also reflective surface), mounted on the matrix LED, this design method is not possible to get a good lamp distribution. The other type is to integrate multiple LEDs in a circular area (approximately 30 mm to 40 mm in diameter) so that the light output density of this small area is close to that of a high-intensity discharge lamp, and then the lamp reflector is used for light distribution. However, the luminosity distribution of this kind of design will not be better than that of traditional road lamps, and due to the integration of high-density LEDs in a small area, the heat dissipation of the LED will be significantly worse, not only affecting the light emission of the LED. Efficiency, but also often affect the life of the LED.

The status and defects of ordinary road lighting

Currently, the commonly used light source in road lamps and lanterns is a high-pressure sodium lamp or a metal-toothed lamp. The most prominent feature of these two kinds of light sources is that the arc tube of light emission is small in size, and a very large light output is generated from a small-sized arc tube, and the light source is very large. High light efficiency, the former including matching electrical appliances, up to 110 lm / w, the latter including supporting appliances up to 80 lm / w. However, when this type of light source used in road lighting, only about 40% of the light is directly through When the glass cover reaches the road surface, the other light is projected out of the light fixture through the reflector of the lamp. At present, there are basically two deficiencies in traditional lamps that commonly use such light sources.

One is that the illuminance is very high in the direction of the direct illumination of the lamps, which can reach more than 50 lx on the secondary road. This area is obviously over-illuminated, and the illuminance at the intersection of the two lamps is only 40% of the illuminance under the lamp. 20%.

The second is that the efficiency of reflectors of such lamps and lanterns is generally only 50% ~ 60%, so there is about 60% of the light output in the lamp, after the loss of 40% ~ 30% and then cast onto the road. The overall efficiency of such lamps is generally around 70% (the efficiency of such road lamps of famous international brands can reach 80%), and the excessive illumination in the above-mentioned over-illuminated areas is also a waste.

A comprehensive analysis of the above-mentioned traditional road lighting has only 50% of its integrated effective lighting efficiency (excluding excessive lighting). Because of the above reasons, the lighting effects of China's secondary arterial roads (the uniformity of the road illumination and the illuminance) can hardly meet the requirements of CJJ45-2006 and CIE31 and CIE115 standards.

LED lighting features and applications

The most prominent feature of current lighting LEDs is their ability to emit light directionally, as current power LEDs are almost always equipped with reflectors, and the efficiency of such reflectors is significantly higher than that of lamps. In addition, the efficiency of the LED has already included the efficiency of its own reflector. LED road lighting should use the characteristics of LED's directional light emission as much as possible, so that each LED in the road lamp directly shoots light to each area of ​​the illuminated road, and then use the auxiliary light distribution of the lamp reflector to achieve Very reasonable road lighting integrated light distribution.

It should be said that the road lamps and lanterns should truly meet the requirements of CJJ45-2006 and CIE31 and CIE115 standards for illuminance and illuminance uniformity, and the lamps should contain three times of light distribution functions to be able to achieve better. The LED with a reflector and a reasonable beam output angle has a good primary light distribution function. In the luminaire, a good secondary light distribution function can be achieved by designing the position of each LED and the direction of the emitted light according to the height of the luminaire and the width of the road. Reflectors in such lamps are used only as an auxiliary three-time light distribution method to ensure better uniformity of road illumination.