Introduced the use of high-power blue LED chips as the light source, with the conversion method and the red LED phosphor prepared by the low compensation and high color temperature white LED color rendering method, and from high-power device performance and application point of view of two advantages and disadvantages.
GaN-based blue, green and ultraviolet light-emitting diode (LED), opened up new markets for LED, high power LED lighting. High-power LED lighting power is the core of white LED.
Method of producing white power LED in red, green, and blue color LED synthesis, blue LED + yellow phosphor, UV LED + phosphor, and multilayer three electroluminescent (OLED), etc.. Taking into account the technical and cost advantages, and blue LED chip + phosphor white high power LED technology into the mainstream.
Through the phosphor conversion white LED technology, due to the lack of phosphor emission spectrum of the red component, is difficult to simultaneously achieve low color temperature and high color rendering. But people in their daily life have been accustomed to a low color temperature (3000K or so) of the light source, and high color rendering light source in the museum, surgery and other special lighting of premises with its potential applications. Therefore the development of high-color low color temperature white LED power has important significance.
Using high-power blue LED chips as the excitation source, respectively, and red LED phosphor conversion method of compensation prepared by the low color temperature and high color rendering white LED,
Using high-power blue LED chips with a number of experiments:
(1) high-power blue LED chips with yellow phosphors excited at the same time and red phosphors, by adjusting the ratio of phosphor in Pink, you can get different color temperature and color rendering index of white high power LED. Help with high-power LED work light-emitting and red phosphor content of the current varies.
(2) excitation with high-power blue LED plus yellow phosphor, and compensate with a red LED, power LED chips and phosphor to adjust the luminous intensity, resulting in a low color temperature and high color rendering white LED. If a higher level of LED chip, experimental results will be better.
The red phosphor white LED emission spectra of the main spectral peak wavelength of 610nm, color coordinates x0.4093, y0.3678. The color temperature and color rendering index for the 3200K and 83.2. Adjust the ratio of two phosphors, get a different color temperature white LED. With increasing the content of phosphor in Pink, more high-power LED chips red phosphor absorption occurs after Blu-ray radiation generated by transitions and a red light, resulting in a relative spectral red shift, while decreasing power of the color temperature , while the LED color rendering index higher. However, as the red phosphors used in low quantum efficiency, to produce more red light must absorb more blue light, which causes the device in the spectrum of blue and Huang Guangcheng one decreases, the device reduced the overall light Shu Chu.
High-power blue LED chips with yellow phosphor excitation, while low power high brightness red LED can also be prepared to compensate white LED. To make more compact, can be low-power red LED chip bonding in high-power LED chip, according to the actual situation, the two can share the P electrode and N electrode. CCP experiment used a high-power blue LED chips and five low-power red LED chips, high-power blue LED chips coated with phosphor, the phosphor should be covered to avoid red LED chip, avoid the scattering and absorption reduce phosphor red LED's light output.
High-power blue LED with 350mA DC drives, electric power consumption of 1.15W, 5 支 are red LED's operating current 20mA, consumption of electric power and for 0.22W. The color temperature and color rendering index of 93.9 for the 3450K and the color coordinates x = 0.3630, y = 0.3721. Luminous flux and luminous efficiency of the device were 26.6lm and 19.42lm / W, much higher than while using blue LED excitation of two yellow and red phosphors of the device level.
(1) blue LED with yellow and red stimulated phosphor, by increasing the content of the red phosphor can be obtained with low color temperature and high color rendering white LED. This approach has the advantage of two kinds of phosphor mixed, making the blue LED devices generate, yellow and red light evenly throughout the space easier mixing, can expect the device color space is better uniformity. The disadvantage is that, at present, the lower quantum efficiency of red phosphors, causing the device luminous efficiency is not high, adding the red phosphor, the luminous efficiency of the device is almost halved.
(2) blue LED with yellow phosphor excited at the same time to compensate with a red LED, also available with low color temperature and high color rendering white LED. This approach has the advantage of avoiding the inefficient use of the red phosphors, so the overall high-power LED light more efficient. Driving circuit is relatively complex, but technically easy to implement. As the blue LED, phosphor, and red LED is composed of relatively independent of light, on a single device color space for the possible uneven, but the array can be arranged through the appropriate way to solve this problem.
Low color temperature, high power LED color rendering white LED excitation mainly blue with yellow phosphor and the red LED to compensate, with the red phosphor quantum efficiency and stability of continuous improvement, blue LED with yellow and red stimulated phosphor, or phosphor can also stimulate a variety of excellent properties of white LED, drive circuit is simple.