New technology of road lighting: LED street lamp

At present, the main light source used in road lighting is high pressure sodium lamp, the initial light effect of the light source is above 100lm/W, while the high power LED device on the market has a light effect of 90-100lm/W, slightly lower than that of high pressure sodium lamp. But led has a high color rendering index, color temperature and other characteristics, can provide a higher quality of road lighting effect. LED light efficiency with the evolution of the technology has been increasing year by year, it can be seen that the replacement of high pressure sodium lamps become the main source of road lighting. In practical application, LED lamp design and development is the primary focus on the design of optical, heat, and power supply mechanism. This paper takes Wujiang City perch Township South of LED street lamp project as an example, to analyze the technology in energy saving and light effect on the characteristics of: it is understood that the Wujiang Lu Xiang Nan Lu configuration for single rod double, single rod installed 2 lamp 250 Watt sodium lamp. The use of sodium lamps in the installation of ballast, so the whole system power consumption of about 320 watts, single rod power consumption of 640 watts. The color index of sodium lamp is about 21 and the color temperature is 2100K. Facelift Delta LED configuration, using 200 Watt LED lamps in motorized vehicles, non motorized vehicles use 120 Watt LED lamps, the driving power in the lamp holder, there is no need to install driver or ballast, so the system power is only 200 watts and 120 watts of power, single pole 320W, color temperature 3500K display the color index is greater than 70.

The actual measuring values before and after the installation of ground illumination is shown in the table below, before and after the installation of motor vehicles (28.2-22.8) to enhance the average illumination /22.8=23.7%, non motorized road illumination to enhance (25.4-13) /13=95.4%, single pole power reduction (640-320) /640=50%. Not only has a significant increase in brightness, in order to replace 124 watts of sodium lamp calculation of 250, annual savings of more than 68 thousand yuan.

In addition to upgrading and energy saving effect of illumination, the advantages of using LED to replace the high-pressure sodium lamp also comprises a color index, the following chart as an example, the use of sodium lamp as light source, the color index is only 21, so the ball color can not be resolved clearly. The light source used for LED lamp, the color ball can be clearly identified.

Why there is such a good effect, but also from the LED street lamp design points to analyze:

Point one: Optical

At present, the domestic road lighting design according to the "CJJ45-2006 city road lighting design standards" requirements, and to long area in the actual road to meet the requirements of the illumination, must be through the design of two optical light type LED device floodlight, conversion of light distribution for bat wing. In order to achieve the optical distribution of the bat wing, the two optical design mainly includes a lens and a reflector. The two optical designs have their own advantages and disadvantages. The LED lamp light distribution application examples as the mirror type patent mechanism using high reflectance material for reflective surfaces, reduce light loss, surface use tempered glass, provide sufficient strength to prevent foreign body impact, and avoid the use of optical plastic lens aging problem.

In addition to the heat in the epitaxial layer node chip p-n, and an epitaxial layer using eutectic solder or flip chip packaging techniques such as package to increase the cooling efficiency of the substrate in the system design will be taken into consideration in selection and design of fin substrate, how to use the volume of fin to reach at least the best heat transfer design.

Point three: Power

In order to allow the LED to achieve the claimed longevity, and the use of constant current mode output LED driver power supply. Such as the use of constant voltage output of the LED power supply, will cause the various LED monomer through the current differential control difficulties, resulting in a large number of current and failure, which led to the failure of the entire LED lamps. Even if the same is a constant current power supply, there are also key technical indicators to determine the pros and cons:

1 power efficiency: the efficiency of conversion from AC to DC. Since the purpose of using LED in order to save energy, the efficiency of AC conversion DC naturally higher the better. Furthermore, the higher the efficiency of power supply, said the heat dissipated from the less, the heating effect of natural system is the least, indirectly also reduced LED decay.

2 power factor: high power factor driving power supply, can reduce the harmonic pollution, improve the stability of the grid and load.

3 driving current stability: LED emitting tube diode characteristics, is quite sensitive to the driving current, thus driving current instability will cause fluctuation of current received by LED, resulting in serious degradation and even failure.

Point four: mechanism design

LED now known as the light source of the new generation, which brought the change of road lighting is not only the change of the light source, the design should also bring the modernization of road landscape impression. At the same time, the appearance of the LED street lamp system to achieve the function of cooling, in order to maintain the normal operation of the LED for a long time. This case uses the LED street lamp using a modular design that can replace a single module to simplify the maintenance work. And its open architecture, in addition to improving the efficiency of natural convection heat dissipation, but also has a sense of the times the design elements.

Summary

Due to the limitations of physical properties, sodium lamp color temperature is limited to 2000K or so, there is no high efficiency and high color temperature sodium lamp to choose from. However, the human eye perception can be divided into two categories according to its shape, that is, the rod cells and cone cells, cones, the main visual perception, while the visual perception of the main stem cells. The rod cells are more sensitive to blue and green wavelengths of light (generally higher than the color temperature). At the same time, according to the study, under the same brightness, the use of high dark