Application Of Led Lights
In recent years, with the rapid development of LED technology and the incomparable advantages of LED lamp, LED lamp as the fourth generation lamps after incandescent lamp, fluorescent lamp, high intensity gas discharge lamp (HID) has been widely used in the field of lighting, small to table lamp, flashlight, various electrical indicators, signal lights, etc.
As large as indoor and outdoor lighting, solar street lights, decorative lights, dock lights, construction lights, studio lights, car lamps, LCD backlight module, etc. By early 2011, the global value of high-brightness leds had reached $10.6 billion.
(I)How do led lights work
LED chip is use of semiconductor PN junction illuminated, p-n junction is composed of p-type and n-type semiconductor semiconductor, deep formation of PN junction on both sides of their interface, p-n junction with unidirectional conductivity, when add forward voltage to PN junction, the majority carrier of P and N area spread to the other party, due to the electron mobility is much bigger than the hole mobility.
You have a lot of electrons diffusing into the P region, and you have an injection of a few electrons into the P region. These electrons combine with holes in the valence band, and when they do, they emit photons that emit light, which is how a PN junction, or LED, emits light.
(2)The characteristics of LED lights
- LED lamp is driven by DC power supply, low driving voltage, small power, less power consumption, energy saving.
As the light-emitting part of LED is a semiconductor PN junction chip, which has the characteristics of single guide pass and reverse intercept, the LED lamp can only be powered by DC power supply, and the driving voltage is very low. The driving voltage of single bead is 3.2V-3.4V, and the power is very small. The current should not exceed 20m A.
High-power leds are now commonly used with 1W and 3W, and the heat dissipation problem needs to be solved for high-power leds, which can be obtained by integrating multiple chips. The commonly used method to obtain higher power LED working light is to connect multi-bead LED in series or hybrid, so that you can obtain arbitrary power LED work light.
Because of these features, LED lamps consume very little power. Taking the power consumption of a street lamp as an example, the high pressure sodium lamp, LED street lamp and solar LED street lamp are compared.
If the daily power supply is 10 hours, among which the solar street lamp is 2 hours plus 8 hours of solar energy, the annual power consumption of the three lamps is 54750KW/h, 21900KW/h and 4380KW/h, respectively. The annual electricity consumption of LED is only about 40% of that of high-pressure sodium lamp, and the annual electricity consumption of solar LED street lamp is only about 8% of that of high-pressure sodium lamp.
In contrast, using the latter as street lights will greatly save power and save electricity bills. Now the high-power large-scale LED street lamp and solar LED street lamp system have been put into use in our country.
- Single bead LED has small size, long service life, and can realize intelligent lighting.
LED size is small, packaging resin rather than glass, not easy to damage, flexible and convenient to use, LED lamp laboratory life up to 100000h, normal use up to 5000000h above, and as long as in the rated current range, frequent switching power supply or through the control system to adjust the current, no impact on LED life.
Because the LED light source working current can be controlled, so through the circuit design, the brightness of the lamps made can also be controlled, can realize the intelligent lighting control, according to the above characteristics can be made into a variety of LED decorative lights, dynamic patterns, etc. For LED dock lights, according to the different brightness required at different times under the working state, can be set to adjust the brightness at different times, which can not only save energy better, but also do not affect its life.
Compared with other working lights, greatly reduce the replacement rate, reduce the maintenance cost and easy installation and maintenance.
- No flicker, no ultraviolet light, very low heat radiation, no harm to human eyes.
The LED lamp is used for indoor lighting and work and study places, which can protect eyes. LED light monochrome, strong directivity, fast response, especially suitable for working light, car lamps, dock lights, stage lamps and so on.
(3)The application of LED lights
Due to the incomparable advantages of LED lamps, LED work light are developing at a very fast speed and gradually replacing other working light.
Now LED working light have been widely used in various working lighting fields. Due to its small size and flexible application, LED can be arranged into various shapes and controlled by computer programs, so it can display static and dynamic patterns such as text, image, animation, film and television.
In 2008 Beijing Olympic Games opening ceremony, LED lights showed its endless charm and advantages. LED is widely used in public displays, such as a variety of signal lights, landscape lighting, square street beautification, public entertainment beautification, stage effect lighting, building lighting, etc.
In liquid crystal displays, leds are used as backlight for display screens such as computers, televisions and mobile phones. On the traffic road, LED has been used for controllable energy-saving street lighting, tunnel lighting, overpass lighting, traffic signal lights and so on.
In the aspect of automobile lamps, now many cars brake lights, position lights, turn signal lights, rear fog lights, reverse lights and other lamps have begun to use LED light source.
As the construction lights, With the continuous improvement of LED technology, technical problems continue to be solved, and the continuous emergence of high-power LED lamps, LED in indoor lighting, automotive lamps, studios, viewing lights and other fields of application will be more popular.
(4) Some technical problems faced by LED lights
- High-power LED technology.
LED has the performance bottleneck and heat dissipation problems such as electrostatic release damage and thermal expansion coefficient, so that its power can not be very large and its brightness is low.
At present, the commonly used high-power LED chips with relatively stable performance are 1W and 3W. LED power can be improved by integrated chip, but the current technology is not mature, mainly need to solve the heat dissipation problem, can also achieve high-power LED lamps through multi-bead LED series, parallel or hybrid.
The latter two are less efficient and less used. Multi-bead LED series is the mainstream application of LED lamps in the field of lighting.
But single-bead series has an Achilles heel. If one bead is damaged, the whole route is blocked. This is a major bottleneck restricting the application of high-power LED lamps in the field of lighting.
To improve the power of LED lamps, one is to improve the power from the chip, the other is to optimize the circuit design to improve the power.
- Heat dissipation technology
Temperature is an important factor affecting LED, the increase of temperature will speed up the light attenuation of LED, and the temperature at the chip node directly affects the life of LED, so LED and heat dissipation capacity is limited by the strength of LED power.
The heat inside the LED is generated when the LED chip and printed circuit board work. For low-power LED, the heat can be dissipated by natural conduction and convection, but for high-power LED, it is necessary to consider various heat dissipation.
In the heat dissipation design, the heat dissipation of LED package, circuit board and adding heat dissipation components are usually considered. With good thermal conductivity silicone encapsulation, printed circuit board with thermal insulation layer, metal base, etc. For high-power LED dock lights, to solve the heat dissipation problem, in addition to the good heat dissipation structure of the LED itself, the shell of the dock lights should be used as the heat dissipation channel.
The shell is designed as a heat dissipation surface above the side and a heat dissipation fin to facilitate air convection, or the shell is designed as an air hole type convection heat dissipation, fan assisted air cooling and capillary water cooling and other ways are still in the test stage, the car’s LED front fog lamp, headlamp and other lamps in the design of aluminum circuit board, bracket, etc., to speed up heat dissipation.
In the structural design of LED lamps, some people put forward the heat pipe radiator heat dissipation in lamps. In order to improve the heat dissipation effect, many factors need to be considered in the design of lamps, such as the arrangement and arrangement of the radiator of the lamp body to consider the spacing, direction, surface treatment, etc., on the metal shell of lamps and lanterns, heat dissipation coating.
At present, the development of LED industry focuses on high power, high brightness, small size products, using ceramic heat dissipation fetters as the way of LED grain heat dissipation.