LED energy-saving lamp

LED I have done more than a year, driving in difficult, on-line information is also a lot of, you can look at. I think LED itself is more important to understand, only to find out its temper, in order to design a good drive to. Some time ago to go to Shanghai to participate in the international LED Technology Show, rewarding to the latest information on LED principle of the discussion follows, but it is not affixed on the map, you want to help:

1, LED light-emitting mechanism: PN junction barrier voltage to a certain extent, when the Canadian base forward bias voltage drop times, P area and N area the majority of the proliferation of carriers to each other. As the electron mobility is much greater than the hole mobility, it will be a large number of e-zones spread to the P constitutes the P District minority carrier injection. These electronic belt hole recombination with the price of the composite when the energy to get the release out in the form of light. This is the PN junction light-emitting principle.

2, LED luminous efficiency: commonly known as the components of the external quantum efficiency as a component of their internal quantum efficiency and removal efficiency of the product components. The so-called components of the internal quantum efficiency, in fact, their electro-optical conversion efficiency of components, the main features and components themselves (such as component materials, energy band, defects, impurities), a component of the composition and crystal structure of barrier-related. The removal efficiency of the component refers to the components of internally generated photons, after component itself, absorption, refraction, reflection in a practical component to the external measurable number of photons. Thus, with regard to the efficiency of removal of factors, including the absorption of the component material itself, a component of the geometric structure, components and packaging materials and components of the refractive index of the structure of differential scattering characteristics, etc.. The components of the internal quantum efficiency and removal efficiency of the product components, that is, the luminous effect of the entire component, that is, the external quantum efficiency of the component. Early components of development was focused on improving its internal quantum efficiency, mainly by the quality of crystal by increasing the base and change the structure of crystal bases, so easy to convert electrical energy into heat energy, and thus indirectly enhance the LED luminous efficiency, and thus get about 70% of the Theory of internal quantum efficiency, but that the internal quantum efficiency is almost close to the theoretical limit. In such a situation, to improve the component alone is not possible to improve the internal quantum efficiency of the total amount of light components, and therefore improve the efficiency of the component out will become an important research topic. The current approach is mainly: grain shape change - TIP structure, surface roughening techniques.

3, LED Electrical Characteristics: Current-controlled device, the load characteristics similar to the PN junction of the UI curve of forward voltage for a very small change will cause great changes in forward current (index level), the reverse leakage current is small, there is reverse breakdown voltage. In actual use, should be selected. LED forward voltage with temperature and become smaller, with a negative temperature coefficient. LED power consumption, partly converted into light energy, which is what we need. The rest is converted into heat, so that the junction temperature rise. The heat (power) can be expressed as.

4, LED optical properties: LED provides is a great half-width of the monochromatic light, due to the semiconductor energy gap decreases with temperature rise, so it has a peak emission wavelength with temperature rise and growth, that is, spectrum red-shifted, the temperature coefficient of +2 ~ 3A /. Brightness LED forward current approximation of L and is proportional to:, K the proportional coefficient. Current increased brightness is also similar increases. Also brightness and the ambient temperature is also related to the ambient temperature is high, the compound reduced efficiency, reduced emission intensity.

5, LED thermal characteristics: low current, LED temperature is not obvious. If the ambient temperature is high, LED will be red-shift of the dominant wavelength, brightness will decline, light uniformity, consistency variation. In particular, dot matrix, large LED display temperature rise of the reliability, stability, influence is even more significant. Therefore, thermal design is critical.

6, LED life: LED's long decline caused by aging work will be light, especially for high-power LED, the light bad problem even worse. In measuring LED life, the only damage to the lamp end of life as the LED is not enough, and should be based on the percentage of LED light attenuation of the provisions of LED life, such as 35%, so that more meaningful.

7, high-power LED packages: the main consideration heat and Idemitsu. Cooling, the hot-lining with copper and then connected to the aluminum radiator, the grain and the thermal contrast between the piece of tin solder as the connection method of this cooling effect is better, a higher price. Idemitsu, the use of flip chip technology, and an increase in the bottom and side reflective surface reflecting light energy waste, so that there are consumers get more out of light.

8, white-light LED: class of natural spectrum white LED are mainly three types: the first is a relatively mature and has been the commercialization of blue-chip + yellow phosphor to obtain white, this white the lowest cost, but the blue light-emitting wavelength of the grain offset, intensity changes and the thickness of phosphor coating change will affect the uniformity of white light, and the spectrum was narrow band, color incomplete, color temperature high and low color rendering, lighting, gentle on the eye is not inconsistent . Through the evolution of the human eye is best adapted to sunlight, incandescent continuous spectrum is the best color temperature of 2500K, color rendering index is 100.

Therefore, this white light still needs to be improved, such as gado luminescence process to improve the spectrum, so that continuous and wide enough. The second is the ultra-violet or purple chip + red, blue, green, three-color phosphors to obtain white light similar to fluorescent light-emitting principle, the method has better color, and UV-LED does not participate in the color white, so UV -LED wavelength and intensity fluctuations for the distribution will not be out of white light in terms of particular sensitivity, and can be colored phosphors by the selection and matching, modulation an acceptable color temperature and color rendering of white light. But equally there is the effective conversion efficiency of phosphors used in low, in particular, the efficiency of red phosphors require substantial increase in problems. Poor stability of such light-emitting phosphor, light a larger decline, with the choice of phosphor wavelength UV, UV-LED production of packaging material difficulty and the development of anti-UV is also necessary to overcome the difficulties. The third principle is to use three primary colors RGB three kinds of ultra-high-brightness LED will be combined to form white light, the method has the advantage of the conversion without having phosphor directly with a white light, in addition to avoid phosphor conversion losses are better luminous efficiency, but also separately control the red, green and blue LED's luminous intensity, and reached full-color of the color effect (variable color temperature), and may by the LED wavelength and intensity of the choices are better color rendering. But the problem is that this approach green conversion efficiency is low, mixed light difficult, driving circuit design complexity. In addition, because these three light colors are heat, heat dissipation issues that other packages of three times, has increased the use difficulties. Polarization and the three-wavelength LED-based white LED full-color will be the future direction of development.