Compared with traditional incandescent lamp, compact fluorescent lamps, light source, light emitting diode (LED) has high luminous efficiency, long service life, high directivity many advantages, is being industry favour and is used for General Lighting (General lighting) market. flexible led strip applications to accelerate popularization, the short term still has come from cost, and technology, standard and other aspects of the problems must be overcome, technology, including color temperature, color rendering and improve efficiency, still needs to be further improved. And LED in general lighting the application of the market is related to many requirements, must be from the point of view of the system to consider, such as LED light source, power conversion, motion control, heat and optical etc.
Film chip technology swell Sunday
At present, LED chip technology is key to the development of crystal growth technology substrate round. Base material in addition to the traditional sapphire materials, silicon (Si), silicon carbide (SiC) beyond, zinc oxide (ZnO) and gallium nitride (GaN) is also the focus of current research. Whether focus lighting and integral illume of the high power chips, or used for decorative lighting and some simple auxiliary lighting of small power chips, and the key technologies to promote are focusing on how to develop higher efficiency and more stable chip. Thus, improving the efficiency of the LED chips becomes ascension LED lighting whole technical indexes of the key. In a few short years, with the aid of the chip structure, surface coarsening, quantum well structures, a series of technical improvement in the design, the luminous efficiency in LED a significant breakthrough, led the development of the chip structure as showed in figure 1 below. To believe that with the technology continues to mature, LED quantum efficiency will be further improved and LED chips will then climb the luminous efficiency.
Figure 1 LED chip structure of the development process
Film chip technology (Thinfilm) is the production of ultra bright LED chips key technology, can reduce the lateral out light loss, through the bottom reflective surface can make more than 97% of the light from the output (figure 2), not only greatly improve LED efficiency, also simple lens design.
Figure 2 common LED and BoJi technology of the positive rate of light LED comparison
Three big packaging technology is introduced
High power LED packaging technology for single chip can distinguish, integration and chip board chip packages three categories, the following will show.
The luminous efficiency, heat dissipation, reliability for single chip packages advantage
Single chip packages are packaging technology application in most, its main technical bottleneck in chip yield, the color temperature control and phosphor coating technology, and Osram onto semiconductors of Golden DRAGON Plus LED, by silica packaging, packaging appearance and internal briefly the structure as showed in figure 3 below. This LED the beam of light has 170 degree angle, can cooperate with ideal second optical lens or reflective glass. The silicon lens has high temperature resistant and low attenuation characteristics. The unique packaging design further enhances the heat dissipating performance of LED, make the product of the thermal resistance control in each tile 6.5 or so, help to lower the heat resistance. In addition, the specific configuration makes phosphor LED colour temperature cover cold white, neutral white gentle white range. Single chip packages's advantage lies in the high efficiency, easy heat dissipation, easy to light distribution and reliability.
Figure 3 osram onto semiconductors Golden DRAGON Plus LED the encapsulation of the exterior and interior structure
More in small packages chip integration volume of specular highlights flux
Many chip is the integration of components high density led strip components of the most common another encapsulation, a distinction for small power and high power chip integrated components two kinds, the first with six low power chip integrated 1 w high power LED the most typical components, such components's advantage lies in the low cost, is the main component of many high power making way. High power chip combined with OSTAR SMT series for representing, the packaging appearance as showed in figure 4 shows, through the optimization design, can make the end product of thermal resistance control in each tile 3.1, and at the same time can drive as high as 15 watts of high power. The package's advantage is in a small space reach high flux.
Figure 4 osram onto semiconductors OSTAR SMT LED the encapsulation of the appearance
COB improve heat dissipation defects
COB Technology adheres to the traditional semiconductor technology, namely direct will LED chips fixed in a printed circuit board (PCB). Using this technology, at present had only 0.3mm thickness of the following LED. Because LED chips directly and PCB contact, increase the heat conduction area. Heat dissipation problems can be improved. This package in the form small power chips gives priority to.
Heat lamps, optical drive IC design, the balance
Increase the cooling effectiveness prolong service life lamps
The life of the lamps is what we are concern has been one of the major problems. Construct the lamps and lanterns of good cooling systems, only depending on the choice of low thermal resistance and not enough LED components, must reduce meet face to the environment of PN thermal resistance, in order to reduce the surface temperature PN LED by, improve the life and the actual LED lamps and flux. And the traditional light source is different, that is the power supply PCB LED carrier, is also heat carrier, therefore, PCB and radiator cooling design is also particularly important. In addition, the thickness of the material, cooling material, size and heat processing, connection way interface is lamps manufacturers factors to consider.
Optical design should be properly play LED standards
12v led light bars the directional and point light source is different from the traditional source of one of the most typical characteristics, how to use the LED to the two characteristics of optical design key for lamps. Through the LED second optical design, the LED lighting can achieve an ideal light distribution curve, as in the whole of the indoor lighting for the brightness of lamps is high, can use through the higher rate of chimney in order to improve the efficiency of the light; There are also add guide lamps setting technology, make LED point light source area light become, and improve the evenness and prevent glare occurred; In addition to assist illume, key part lighting is need certain contracts to effect to highlight just content, can choose match a few focusing lens or reflective cup to achieve optical requirements.
Drive design shall ensure that constant current output
LED driver circuit requirements to ensure that constant current output, LED by positive work, LED the forward voltage change relatively small area, to ensure that LED drive current constant also led the output power is to ensure that the constant. In addition, it is also the design that moves light driving circuit is one of the mainstream of the design, the application of lighting in some situations more, according to different environment to allocate different brightness, fully meet energy effect. At present the main drive design direction around improve power factor, reduce power consumption, increase control precision and speed up the response speed mainly. In addition to drive the design of the power supply outside, PCB wiring and series-parallel model are design consideration.
Standards in place
LED lighting as a new field, need to product standards and measurement standards, control and interface standards, the formulation, on the market and the LED lighting products or other, many products are not enough information is complete, easy to mislead consumers, and from including organic light emitting diode (OLED) and other high efficiency light source and traditional low-cost light sources of a competition, the LED lighting industry need a set of perfect standard system to safeguard and promote the health of the industry sustainable development. The current us department of energy (DOE) is actively promoted about the relative standard semiconductor lighting, mainland China, Taiwan, South Korea, Japan and so on also actively spread LED standards work.
High power LED lighting technology challenges of crossing
Although the focus of the indoor lighting in LED lighting and decorative lighting gets play spaces, but from the real LED general lighting or environment lighting has many challenges, such as initial cost, low colour temperature of the luminous efficiency, show color index and the system reliability, etc.
Through the whole system optimization initial cost reduced
Indoor lighting is concerned, especially family lighting to cost is relatively sensitive, although LED lamp design continues to increase, more and more is also high luminous efficiency, but the price expensive problems remain. This needs to be further reduction in price LED light source, and needs the whole system level to optimize the design, lower total cost. From compact fluorescent lamps came into the market in the early days of around $15 reduced to the current of the below $1.5, predictably, along with the market development, in the near future, the price of LED lights is also enhancing public acceptance.
Get rid of phosphor low color temperature limit the luminous efficiency
Indoor lighting will often tend to a family under a low of 4000 K color temperature. Warm white light let the whole environment has become relatively sweet and relax; and cold white light to clean, efficient and lively feeling, suitable for the office lighting and outdoor lighting. By the influence of phosphor, LED low colour temperature of when the luminous efficiency often than high efficiency low when the color temperature is about 30%.
Both the efficacy and mixed red LED show color index
LED the higher efficiency, the show color index often some low, and indoor illumination requirement can be objective shows shades and colour sex object, get the human eye directly observed the scenery outside the reality effect, so usually require a higher show color index. This LED to the luminous efficiency at the same time in ascension, and further improve the show color index, but also by the mixed in with some level of the light red LED to get more than 90 results show index.
Improve large current drivers efficiency LED cost reduction
At present, 1 watt LED drive current can reach 350-1000 ma, but usually in the large current drivers conditions, although flux improve, but the overall efficiency of the decline is quite obvious, so the overall cost and system must seek balance between efficiency and to be able to improve the large current drivers in LED the luminous efficiency, it can ensure the high luminous efficiency premise in system, large reduction LED a number needed, thus obviously reduce the cost.
Reduce the encapsulation of the LED to increase the size design flexibility
The development of indoor lamps LED in energy conservation and environmental protection health, under the premise of also go artistry, mini, and personalized the direction of development, thus narrowing the encapsulation of the size can increase LED in a light design of flexibility and innovation space. some shall be used to improve the mix light color rendering occasions. Smaller size package will help to mix with mixing and light lens design of light effect.
Key components improve system reliability life, be short of one cannot
For general lighting in LED, the application shall be from the point of view of the system to improve the overall efficiency, service life and reliability. Traditional lighting products components of the system are relatively simple, and LED lighting system involving multiple components.
