Application Technology of LED Lighting

At present, the world’s energy shortage, to find and solve the future world’s energy problems has become a top priority. After the advent of brightness white light LED, it has been paid attention to in the lighting application because of its high luminous efficiency, good power saving effect, low energy consumption, safety, low heat, no pollution, long life and excellent economy. With it to replace the traditional lighting research and development work continues, and achieved some results. The service life of LED lamp is about 80000-100000 hours. Under the same brightness, the power consumption of LED lamp is 1 / 8 of incandescent lamp and 1 / 3 of fluorescent tube lamp. Therefore, it can be predicted that: LED will get worldwide attention and application.

LED performance characteristics

LED (light emitting diode) is a kind of semiconductor device which can directly convert electricity into light.

Light is generated by the recombination of positive and negative charges in the material. The intrinsic characteristics of LED determine that it is the most ideal alternative to the traditional light source and has a wide range of uses.

1. Energy saving and safety

LED uses low-voltage power supply. Generally, the working voltage of LED is 2-3.6v, the working current is 0.02-0.03a, and the power consumption is low, no more than 0.1W. It is a kind of electrical appliance which is safer than using high voltage power supply. At present, it is widely used in various indicating appliances in public places.

2 high brightness and low heat

It can reach the brightness of traditional bulb, and its power consumption is about 30% of that of ordinary bulb, even less thermal radiation than HID or incandescent lamp.

3. Strong applicability and small volume

LED is basically a very small chip encapsulated in epoxy resin, so it’s very small. Suitable for all kinds of environme

4. Long service life

Under the appropriate current and voltage, the service life of LED can reach 100000 hours.

5. Stable performance

It can work normally for 80000-100000 hours.

6. short response time

The response time of ordinary lamp is millisecond, while that of LED lamp is nanosecond.

7. environmental protection

LED is made of non-toxic materials, which has little heat radiation and can be recycled.

8. strong and durable, good shock resistance

Compared with the traditional lamp, it has stronger anti-seismic performance and can meet the installation requirements of various occasions. LED is completely sealed and installed in the epoxy resin, there is no loose part in the lamp body, which makes the LED not easy to damage.

9. beam concentration
10. Heat generated is bery low
11. strong controllability

Can achieve a variety of color changes.

Classification of LED chips

Classified By brightness

1. General brightness: R? PH? PG? Py? PE, etc
2. High brightness: VG? PVY? PSR, etc
3. Ultra high brightness: UG? Puy? Pur? Puys? PURF? Pue, etc
4. Invisible light (infrared): R? PSIR? Pvir? Phir
5. Infrared receiver: Pt
6. Photocell: PD

By special category

1. Infrared lamp (invisible light)
2. Infrared receiver
3. Phototube

Problems needing attention in production and application of LED chip

The power of LED ranges from 0.005w to 1W, even from 3W to 4.5w. Therefore, LED work needs to meet two conditions:

3. Forward voltage V1 ≤ 3.4V.
4. Forward current I ≥ 20mA. Generally 20mA to 1a.

In the production or use of LED, we should pay attention to the protection of static electricity.

The Applications of LED

1. The white LED is used as the backlight of small LCD color screen to replace the cold cathode fluorescent lamp (CCFT). Because the driving white LED has the characteristics of simple circuit, no positive and negative power supply, high efficiency and small size, it is widely used in portable electronic devices.

The product has been widely used in many fields. The application of white LED as backlight is not only used in small color screen electronic products such as mobile phone, game console, PDA, MP4 and digital camera, but also used in DVD, GPS and 15 inch notebook computers with larger screen size. It has become one of the largest users of LED, accounting for about 30% of the annual output of LED.

2. White LED is used as the flash of small digital camera to replace the traditional xenon lamp.

The circuit of driving LED flash does not need high voltage power supply, nor does it have the disadvantage of charging for a long time, so it can get more capture opportunity and make the battery last longer.

3. a real green lighting system composed of solar cells, batteries and white LEDs.

The production capacity of solar cells around the globe is very large, reaching 1110 mW in 2006, and the production capacity of solar modules is more than 2000mW~3000MW. This creates a very good condition for using solar energy to light up white LED lamp. At present, China has been able to produce a complete set of white LED lighting system suitable for people in pastoral areas. In some cities, solar cells, batteries and light control circuits are used to form LED street lamps, which can automatically turn on at dark and turn off at dawn. Using solar energy to replace thermal power generation is the most ideal, but large-scale application of solar energy is a big system engineering. Although China has been able to produce a large number of solar cells, out of which 95% of them are used for export and only 5% of them are used in China. At present, using solar energy to light LED lamps is still in its infancy.

4. Replace incandescent lamp with white LED lamp

The research and development of using white led to replace incandescent lamp started not late, and many Units adopted it after 2004 Φ 5 high brightness white LED has developed low-power LED bulbs (15W), 15 ~ 20W tube lamps and 40 ~ 60W street lamps, projection lamps and other products, but not mass production.

In the south of China, some factories produce all kinds of 1 ~ 5W LED bulbs and some white LED lamps, but most of them are exported. At present, batch production of alternative incandescent lamps are: miner’s lamp, all kinds of flashlights, emergency lamp, small wattage reading lamp and lamp, etc. In addition, some cities use LED street lamps for pilot work, but it has not yet been popularized.

It is very important to replace incandescent lamp with white LED lamp to reduce the emission of carbon dioxide and sulfur dioxide and save electricity significantly. Professor Zhang Guoyi of Beijing University wide band gap semiconductor research center, said: “if 50% of the electric lights used by residents in China can be switched to LED lights, the annual electricity saving is the sum of the power generation of a Three Gorges power station.” From the current point of view, it is just the beginning to replace incandescent lamps with white LED lamps, which accounts for a small proportion of LED users, less than 3% of the annual output of LED.

With the progress of semiconductor optoelectronic materials and process technology, and the improvement of high-power white LED packaging structure, these problems become more and more serious. In the past few year, the luminous efficiency of white LED has made great progress.

The luminous efficiency of 1 ~ 5W white LED has been increased from 30 ~ 40lm / w to 50 ~ 60lm / W, and recently to 80lm / W. Some of the top luminescent efficiency can reach more than 100 LM / W. For example, a 4W cold white LED made by Cree company, its light flux is divided, and its maximum range is 107-114lm (its power is 0.35A) at 350mA current × 3 V = 1.15 W, the luminous efficiency is 93 ~ 99 LM / W), the typical luminous efficiency is 80 LM / W, and the development goal is 200 LM / W.

In terms of luminous efficiency, white led not only far exceeds incandescent lamps, but also exceeds ordinary fluorescent lamps and compact fluorescent lamps (energy-saving fluorescent lamps), which means that white LED lamps are brighter and more energy-saving than them. And it’s far ahead in terms of longevity.

The improvement of luminous efficiency of high-power white LED creates conditions for the design of white LED lamps. At present, 1 ~ 3W high power LED lamps are gradually used.

Low power LED replaced by white LED Φ 5 white LED design led lamp. One to several (or more than a dozen) LEDs replace dozens to hundreds of small power LEDs Φ 5 white LED, not only increase the brightness, reduce the volume, but also improve the reliability, simplify the process.

For example, a small street lamp with 18 pcs 1W white LEDs can emit a luminous flux of 1440 LM. If incandescent lamps are used, it needs to be at least 100W. In addition, a strong light flashlight made of a 65lm 1W white LED can shine tens of meters away, If adopted Φ5 It’s impossible to do it with LED.

Problems of LED

The above has introduced the characteristics of white LED and the improvement of its performance, and developed white LED lamps used in various occasions, but LED lights are hard to get into people’s homes.

The main reason is that the luminous efficiency of white LED lighting is not too high, and the price is too expensive. Compared with the price of incandescent lamp, energy-saving fluorescent lamp and white LED lamp with the same brightness, the unit price of 1W white LED is $1.20 ~1.50, and that of 3W is $ 3.00 – 3.90 (related to the quality and brand of LED), in addition to the drive circuit and structural parts.

Considering the profit and commercial profit of the manufacturer, the unit price may be more than $19.00. The luminous efficiency of 9W energy-saving fluorescent lamp is similar to that of LED, but the unit price is more than ten times lower than that of white LED lamp with the same power. Energy saving fluorescent lamps have been on the market for nearly 20 years (this has the process of quality improvement and price decline).

The popularity of white LED lamps may be faster than that of energy saving fluorescent lamps（ Φ The unit price of high brightness white LED was more than $1.50 when it came into the market, and now the unit price of batch LED has been reduced to $0.125-0.15).

The promotion and popularization of white LED lighting is of great significance, but there is still a lot of work to be done in our country

To do so, we need to make a major breakthrough in technology (the luminous efficiency reaches 120-150lm / W) and price (8-10 times lower than the current price). The promotion and popularization of white LED lighting is a system engineering and major project, which needs the planning, guidance and support of the state, as well as policy and economic support.

1. Street lighting system (including solar street lighting system) of urban streets,
2. Tunnels and underground car parks (including underground shopping malls),
3. Lighting of vehicles (interior and part of exterior lighting of automobiles, trams, ships, airplanes, etc.),
4. LED lighting system in large public places, such as railway station, subway station, airport, supermarket and department store

Departments, buildings and hospitals, etc.

1. LED lighting project in no electricity area.

As the LED lighting generally uses low-voltage DC (constant current) power supply. If AC 220 V power supply is used, special transformer is needed.

The electric device outputs low-voltage DC (such as 12V, 24V, etc.) and the LED driver drives the LED lamp. Therefore, it is better to consider the use of LED lights when building these new buildings, and it is much more economical to design them in the architectural design.

However, if the original fluorescent lighting system of the building is to be transformed into LED lighting, it will cost a lot of money and take a long time (such as the transformation of the lighting system of a subway station or a waiting hall), and it is difficult to succeed without policy support and economic support.