Discussion on light and light effect of LED street lamp

Many domestic manufacturers in the technical parameters of LED street lamp, in order to claim high efficiency products, often the initial flux divided by the chip light source power consumption that ratio as high efficiency data. In fact, this is to confuse the concept of. In order to let you know, I explain these two concepts:

1 initial luminous flux (Initial luminous flux) is the amount of energy per unit of time to arrive, leave, or pass through the surface, unit: lumen (LM). Luminous flux is usually represented by.

2 the actual flux (Actual luminous flux) refers to open lighting equipment, light emitted from the light source, through the lighting equipment (such as lamp lens or other), until it reaches the work plane until it needs light quantity. We say that the luminous flux at the working plane is the actual luminous flux.

Through the introduction of the above two points, we can know that the actual luminous flux value is less than the initial luminous flux. See figure.

By the definition of the light, we immediately come up with another important concept: light effect.

The light efficiency (Efficacy) is the ratio of the total luminous flux emitted by the light source to the electric power consumed by the light source.

Because there are two kinds of data, the initial luminous flux and the actual luminous flux, so the light effect has the initial light effect and the actual light effect of the two different data.

We know that the Ten City million project is the reason to promote LED street lamp, is the need for energy saving and carbon reduction. The initial luminous flux of the chip passes through the lens lampshade and reaches the road surface, which can be used for the lighting of the pedestrian vehicle. What we need is a high efficiency brought by the actual flux, does not need high efficiency brought by the initial flux.

Now the LED lamp industry blindly promote initial flux of high luminous efficiency, many manufacturers in the inside also played a role. Some businessmen played a high luminous efficiency LED street lamp 120 lm/w, the world's first light LED lights and other slogans. The reasons for this situation, it is precisely because the national or industry standards are not developed, the relevant test standards are not implemented. In addition, although the introduction of local standards in some places, such as Guangdong's DB44 standard, Shenzhen LED norms, etc., but the standard is not uniform. Take the DB44, suitable for LED lamps in high speed regulation on the main road, in the 4000K~6500K color temperature condition, I standard is not less than 78 lm/w; the Shenzhen specification defines the initial light effect maximum shall not be less than 60 lm/w, but the Shenzhen standard additional energy efficiency standards of rating is mentioned: the minimum I level of energy efficiency is not less than 80 lm/w. DB44 and Shenzhen norms have been released according to the actual situation of the place, you can see that the difference is still relatively large. Therefore, the state should formulate a unified industry standard as soon as possible, the harmonization of norms, so that each region will follow.

Although domestic for the harmonization of standards is still in the discussion, but abroad in December 3, 2009, after the release of the three draft, the U.S. Department of energy DOE issued a final version of the LED Standard Energy Star requirements, came into effect on August 31, 2010.

To this end, we read a lot of information to study. U.S. Department of energy DOE released in July 1, 2009 on the three SSL lamps performance standards of the second draft draft, noting that other indicators can not fully measure the energy efficiency of lamps. Therefore, this paper proposes a new metric -- FTE (Fitted Target Efficacy) for specific target performance. The minimum light output of outdoor road lighting is required to reach 1000 LM (initial luminous flux).

FTE as the object of study, "illuminated area". Therefore, FTE has two key assumptions:

1 rectangular distribution can cover the largest area, more effective than the circular distribution. See figure.

The 2 circle is a white light source, the green part is the target area is effective lighting illuminate the area in red is a target lighting area is not effectively illuminate the area black area in the target region is illuminated, falls on the flux of the black area should be abandoned. See figure.

The FTE formula is as follows:

FTE= (green area luminous flux * green area area percentage of total area of green and red)

It can be seen that the U.S. Department of energy issued to FTE as the future development of LED energy efficiency is very reasonable.

We are opposed to blindly promote high efficiency initial luminous flux. In road lighting, only need a reasonable illumination, the so-called "more bright and better, light effect is good, is not suitable for the current energy saving carbon forms, but also does not conform to the human visual real pursuit of health. We should rationally treat the prospects of LED street lights, not blindly follow. Only with a correct, objective, mature attitude, with a rational, solid analysis, with a basic, practical research, in order to enable the rapid and stable development of the LED industry.