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Analysis of technical key points of LED street lights Related topics: LED Technology Time: 2009-12-03 09:49 Source: LED Global Online "Ten Cities and Ten Thousand Lights" is a demonstration project for my country's high-tech industry to promote development through application. Select a group of cities with good foundations, adopt a model of joint investment by the state, local governments, and enterprises, take the lead in carrying out LED municipal lighting application pilots, explore experience for the comprehensive promotion of semiconductor lighting in our country, and enhance the independent innovation level of the industry through application. Enhance international competitiveness and promote China's semiconductor lighting industry to become bigger and stronger.

This article selects three aspects of street lights, tunnel lights, which have many demonstration projects, and driving power supplies, which have a greater impact on products, to analyze their technological progress, and provide reference for the smooth implementation of "Ten Cities, Ten Thousand Lights".

At present, the traditional light source used for road lighting is mainly high-pressure sodium lamp, and LED street lamps are mainly used in pilot applications on some branch roads, but the two have shown obvious differences in their advantages and disadvantages.

In terms of light efficiency, high-pressure sodium lamps can reach up to 140lm/W, which is higher than the 100lm/W of current commercial high-power LEDs. However, the color rendering index of LEDs (about 80) is far higher than that of high-pressure sodium lamps (about 25), and

Under the same illumination, white LED is more helpful for drivers or pedestrians to identify targets, and its road lighting effect and comfort are much higher than that of high-pressure sodium lamps.

In terms of lamp efficiency, high-pressure sodium lamps adopt a spherical luminous design. Taking reflector efficiency into consideration, the lamp efficiency of high-pressure sodium lamps is generally only 70%. However, LED emits directional light. If an appropriate light distribution design is adopted, most of the light will be directly projected onto

On pavement, the efficiency of lamps can reach more than 85%.

Therefore, just from the perspective of light efficiency and lamp efficiency, we can see the huge potential of LED street lights to replace traditional street light sources.

To this end, this article will focus on the "Ten Cities Ten Thousand Lights" demonstration application project from the research results obtained by the Semiconductor Lighting System Research Center of Sun Yat-sen University on three key technologies such as light distribution, power supply and heat dissipation during the research and development process of LED lighting applications.

The technical route and technical support of the closely related "LED street lights".

Light distribution: Obtain bat-wing light intensity distribution through optical design. Currently, the light source part of LED street lights on the market is mainly divided into two methods: a single 1W high-power white LED array and a high-power integrated package light source module.

Although the national standard for LED street lights has not yet been released, the light distribution of LED street lights must achieve the following goals when referring to the requirements of traditional light source road lighting standards: appropriate average road brightness; high total illumination uniformity and longitudinal illumination uniformity; suitable

Environmental ratio; glare control, etc.

From the perspective of the light distribution curve, to achieve the above goals is mainly to obtain a bat-wing light intensity distribution through appropriate optical design, thereby obtaining a rectangular light spot distribution on the road surface.

However, the packaging lens (i.e. primary optical lens) of ordinary high-power white light LED is not suitable for direct application on LED street lights, so a secondary optical lens must be added to the primary optical lens of each high-power white light LED. Currently, it is "peanut rice".

Type of secondary optical lens can achieve better results.

The design idea developed by the Semiconductor Lighting System Research Center of Sun Yat-sen University is not to use a separate secondary optical lens, but to directly design a wave-shaped optical lens mask outside the luminous light source of the once-packaged LED, and use the lens mask to achieve the luminous light source of the entire LED street lamp.

The function of the secondary optical lens.

As the packaging industry moves closer to the needs of downstream application industries, the Semiconductor Lighting System Research Center of Sun Yat-sen University has also developed and designed a special-shaped primary optical lens, which is directly installed during LED chip packaging. It has the characteristics of small size and low cost, and is fully in line with LED street lights.

and road lighting requirements (Figure 1).

With the advancement of packaging technology, the packaging method of white LEDs has gradually shifted from a single 1W high-power LED device to a high-power integrated packaging light source module.

The power of current high-power integrated packaged light source modules can reach up to 100W or more. However, this type of light source brings difficulties to optical light distribution design due to its large light-emitting area.

The red light-enhanced high-power white LED intelligent control system technology developed by the Semiconductor Lighting System Research Center of Sun Yat-sen University can obtain a light source module with a color rendering index of more than 90 and an adjustable correlated color temperature of 2500~8000K (Figure 2).

This technology integrates a photoelectric conversion chip on the packaging substrate to monitor the white light chromaticity parameters of the light source module in real time. The photoelectric conversion chip feeds back the detected changes in the white light chromaticity parameters to the intelligent control system. After calculation, the system ensures that the lamps are

It can output white light with optimal colorimetric performance, which can ensure that the light source module output maintains the set correlated color temperature range and color rendering index; a temperature sensing chip is also integrated on the packaging substrate to detect the temperature of the packaging substrate in real time, realizing large-scale

Indirect monitoring of the junction temperature of the power LED chip. When the junction temperature exceeds the system's preset temperature, the system can automatically adjust the heat dissipation path of the cooling system or reduce the power of the LED.

The light source module can be composed of a single 1W high-power white LED array or a high-power integrated package light source module, and has been used in LED street lights.