The structure of LED street lights

The structure of LED street lights is not complicated, and after splitting it, there are several components as follows: LED light source (1W-200W), aluminum alloy heat dissipation aluminum sheet, LED constant current source (power supply), and lamp housing. In addition, street lights need to have sufficient height to illuminate a wider range, so necessary lamp posts are also necessary. Of course, in order to better shelter from wind and rain, lamp caps are also needed.

The commonly used LED lighting chips now include a single 1 W high-power white LED array and a high-power integrated packaged light source module Langzhong. The main parameters for measuring its advantages and disadvantages include: average road brightness, total illuminance uniformity, longitudinal illuminance uniformity, environmental ratio, glare control, etc.

The LED driver power supply is a key component of LED street lights and a bottleneck factor that affects the effectiveness and lifespan of LED street lights. Especially the issue of matching the lifespan of the driver power supply with the lifespan of the LED. At present, the light source of high-power LED street lights adopts low-voltage DC power supply, and a high-efficiency white light diode composed of GaN based power type blue light LED and yellow fluorescent powder. It has unique advantages such as high efficiency, safety, energy saving, environmental protection, long service life, fast response speed, and high color rendering index. The outer cover can be made of PC tubes, which can withstand high temperatures up to 135 degrees and low temperatures up to -45 degrees.

LED street light classification

LED street lights can be broadly divided into two types in terms of technology: vertical and integrated, depending on the arrangement of the lamp beads. Generally, using a single light source of over 10000 watts to manufacture street lights is classified. This is a type of LED street light that started to be used relatively early and now has relatively mature technology. Split type technology was used earlier and is now widely used by many enterprises.

The technology of using integrated chips as light sources to manufacture street lights is called integrated technology. Integrated technology is a relatively new technology for LED, which is currently flourishing because it has a larger luminous amount per unit area than discrete chips, and its market prospects are greater than discrete chips.

However, no matter what form it takes, it faces complex heat dissipation and lighting problems. It is necessary to scientifically solve these problems in order to improve light efficiency, achieve the advantages of energy conservation, environmental protection, and long lifespan of LED street lights, and truly establish the image of LED street lights as energy-saving, cost-effective, environmentally friendly, and high-end.

The advantages of LED street lights

1. LEDs do not contain harmful metal mercury, unlike high-pressure sodium lamps or metal halide lamps that pose a threat to the environment when discarded.

• Compared to traditional street lights, LED street lights have extremely low maintenance costs, and high-power LED street lights have significant energy-saving effects. Replacing high-pressure sodium lights can save more than 60% of electricity. Based on these characteristics, LED street lights are gradually coming into people's sight.
• In terms of light efficiency, high-pressure sodium lamps can reach up to 140 lm/W, which is higher than the current commercial high-power LED light efficiency of 100 lm/W. However, the color rendering index of LED is much higher than that of high-pressure sodium lamps. Moreover, under the same illumination, white LED is more helpful for drivers or pedestrians to recognize targets, and its road lighting effect and comfort are much higher than high-pressure sodium lamps.
• The unique secondary optical design illuminates the LED street lights to the desired lighting area, further improving lighting efficiency and achieving energy-saving goals.
• LED street lights have automatic control energy-saving devices, which can achieve maximum power reduction and save electricity while meeting lighting requirements at different time periods.
• Easy to install, without the need for buried cables or rectifiers, simply connect the street lamp holder to the lamp post or nest the light source into the original lamp housing.

Disadvantages of LED street lights

• The penetration ability is lacking, for example, on rainy or foggy days, the light of this type of lamp will be diluted, making it difficult to see clearly.
• The design of LED street lights determines that their illuminance will be insufficient. Existing technology is not easy to achieve both energy-saving effects and improved illuminance. Therefore, sometimes the former cannot be fully achieved, and only minor adjustments can be made to the latter.
• Excessive internal heat can easily cause damage. As it is used outdoors, sealing is chosen to protect the interior to prevent the influence of weather. As a result, the internal temperature will reach a high level after working for a period of time. If heat dissipation is not done well, it is easy to cause damage.
• This type of lamp is usually easy to attract mosquitoes and insects, so it can affect the environment on main roads, and it is not suitable to be too close to residents.
• Due to defects in the manufacturing process of white LED street lights and matching errors with reflective cups or lenses, it is easy to cause the problem of "yellow circles".

Key points for selecting LED street lights

• Luminescence efficiency
• Light attenuation
• Structure
• Heat dissipation
• Color rendering index

Nowadays, LED lighting products are changing rapidly, among which high-power LED light sources (usually one watt per unit) have the most mature technology, and the bead light flux of conventional LED lights has exceeded 130LM/W. Next is to choose COB integrated LED light sources, whose luminous flux is steadily increasing with the advancement of technology. Generally, the higher the luminous flux, the higher the luminous efficiency and energy-saving effect, which is the most important indicator when purchasing LED street lights.

Some unscrupulous merchants, in order to reduce costs, choose some LED beads with poor quality and severe light attenuation. Their lifespan of light attenuation to 80% is only 1000 hours, and they cannot be used as LED street lights that require long-term lighting.

LED street lights, due to their outdoor suspension, can withstand wind, frost, rain, and snow for a long time. The structure of the LED lamp head and its ability to withstand wind and rain as well as heat dissipation must be high.

The key component of LED street lights is the LED chip. As a semiconductor component, temperature has a significant impact. If the temperature is too high, it will seriously affect the service life of LED street lights. Some unreasonable heat dissipation designs can reduce the service life of street lights by half or even more.

The color rendering index should generally be above 65 to ensure good color rendering and a more realistic presentation of the actual color.

Precautions for using LED street lights

• The power supply must have a constant current
• Constant current accuracy of power supply
• The working voltage of the power supply
• The working current of the power supply
• Series parallel connection and wide voltage of power boards
• Isolation/Non Isolation
• Power efficiency

The lighting material characteristics of LED street lights determine their environmental impact, such as an increase in temperature and voltage, which will cause the current of the LED to increase accordingly. If operated for a long time beyond the rated current, it will greatly shorten the service life of LED beads.

The constant current accuracy of some power sources in the market is poor, and the error may reach ± 8%. The constant current error is too large. A general requirement of ± 3% is sufficient. According to a 3% design plan. The production power supply needs to be fine tuned to achieve a ± 3% error.

The recommended working voltage for general LEDs is 3.0-3.5V. After testing, most LEDs operate at 3.2V, so the calculation formula for 3.2V is more reasonable. The total voltage of N lamp beads in series=3.2 * N

For example, the rated working current of LED is 350 milliampere. Some factories have used it all at the beginning and designed it to be 350 milliampere. However, in reality, the heat generated during operation at this current is very serious. After multiple comparative experiments, the design of 320 milliamperes is relatively ideal. Try to minimize heat generation and convert more electrical energy into visible light energy.

To ensure that the LED street light power supply operates within a wide input voltage range of AC85-265V, the LED series parallel connection method of the light board is important. Try not to use wide voltage and classify AC220V and AC110V as much as possible to ensure power supply reliability.

In addition, the number of series connections shall not exceed 45. Do not have too many parallel connections, otherwise the working current will be too high and the power supply will heat up severely.

Generally, if a 15W isolated power supply is made and placed inside the LED street light power supply tube, its transformer volume is large and difficult to fit inside. It mainly depends on the specific situation of the spatial structure, and the isolation can generally only reach 15W, with very few exceeding 15W, and the price is very expensive. So, the cost-effectiveness of isolation is not high. In fact, if non isolated safety measures are in place, there is no problem.

The parameter of subtracting the output power from the input power is particularly important. The larger the value, the lower the efficiency, which means that a large part of the input power is converted into heat and dissipated; If installed inside the lamp, it will generate a very high temperature, combined with the heat emitted by our LED's light efficiency ratio, it will superimpose to produce a higher temperature. 9. Heat dissipation

The main factor in the heat dissipation scheme is that LED street lamp beads can greatly extend their lifespan when used under non overheated conditions, and aluminum alloy is generally used for easier heat dissipation. That is to say, the LED street light power supply beads are attached to the aluminum substrate, and the external heat dissipation area is maximized as much as possible.