Assessment of Lighting Situation
High pressure sodium lamps are currently the predominant type of conventional lighting used for road illumination. The majority of branch roads have seen testing of LED street lighting. However, the two have clearly demonstrated their benefits and drawbacks.
High-pressure sodium lamps have a luminous efficiency of up to 140 lm/W, which is greater than the 120 lm/W of contemporary high-power commercial LEDs. However, compared to high-pressure sodium lights, which have a colour rendering index of roughly 25, LEDs have one that is significantly greater (about 80). Additionally, under the same lighting conditions, white LEDs are more useful for assisting drivers or pedestrians in identifying objectives, and they have far greater road lighting effects and comfort than high-pressure sodium lamps.
The high-pressure sodium lamp has a spherical luminous design to maximise lamp efficiency. High-pressure sodium lamps often only have a 70% lamp efficiency when taking the reflector efficiency into full consideration. However, because LED is directional, if the lamp's designer uses the right light distribution strategy, the majority of the light will be directed directly towards the road, increasing the lamp's efficiency to more than 90%.
Therefore, it is clear that LED street lights have a significant potential to replace conventional street light sources just from the standpoint of light efficiency and lamp efficiency. In order to do this, the study findings on the three crucial technologies of light distribution, power supply, and heat dissipation during the research and development process of LED lighting applications will be the main topic of this article, which will concentrate on the technical route and technical support of LED street lamps.
Distribution of Light
Using optical design, obtaining bat-wing light intensity distribution
The two major types of light sources used in LED street lighting nowadays are a single 1W high-power white LED array and a high-power integrated packaged light source module.
When compared to the criteria of traditional light source road lighting standards, LED street lamps should accomplish the following objectives even if the worldwide standard for LED street lamps has not yet been established:
average road brightness that is appropriate,
a high degree of longitudinal and total illuminance uniformity
an appropriate setting,
glare management.
Design of the light intensity distribution
From the light distribution curve, the rectangular light spot distribution on the road surface is obtained by obtaining a bat-wing light intensity distribution by proper optical design. The primary optical lens, or package lens, of common high-power white LEDs is not suited for direct application to LED street lighting. As a result, each high-power white LED should have a secondary optical lens in addition to its primary optical lens. Currently, a secondary optical lens of the "peanut" kind produces superior performance.
A novel design concept is to directly construct a wave-shaped optical lens mask outside the once-packaged LED's luminous light source in order to achieve the secondary optical lens's function across the full LED street light luminous light source.
The white LED packaging technique has steadily changed from a single 1W high-power LED device to a high-power integrated packaged light source module as packaging technology has advanced. The present high-power integrated packaged light source modules have a maximum power of more than 100W, however because of their excessively huge light-emitting surface, these light sources make it difficult to develop optical light distribution systems.
