A single LED luminous efficiency, luminous efficiency of lamps with LED 400W light sources have similarities and differences?
Plus provisions for a specific LED forward biased, for example, coupled with IF = 20mA forward current (corresponding to the VF ≈ 3.4V), the measured radiation luminous flux Φ = 1.2lm, this LED lumen efficiency is:
η = 1.2lm × 1000/3.4V × 20mA = 1200/68 ≈ 17.6lm / W
Obviously, for a single LED, such as applied electric power Pe = the VF × the IF, then the luminous flux of radiation measured power converted the lumens per watt is the single LED luminous efficiency.
However, as a lamp, LED strip lights PN junction on actual plus the power of the VF × IF is the number of lamps of electric power is always the lamp input port into the electric power, which includes the power supply part (such as the regulator, the steady flow source, AC rectifier into the power consumed by the DC power supply section, etc.). Lamps, the drive circuit of the existence of its luminous efficiency than testing a single LED luminous efficiency to decline. The larger the circuit losses, the lower luminous efficiency, therefore, looking for a high efficiency LED driver circuit becomes extremely important.
2, why a blue LED Floodlight 80W coated with a special white LED phosphor composition, the radiation luminous flux than the Blu-ray several times higher or more than 10 times?
We already know from the front white LED is created by the method used, one blue LED chip coated with YAG phosphor, part of the Blu-ray photon excitation YAG phosphor formed the photoelectric conversion fluorescence powder excitation Huang Guangguang child, blue light and yellow light mixed into white light, the white LEDs. This through a mixture of light? Convert light of different wavelengths of light, make it the spectral broadening, white LEDs generally have a much wider spectrum than the LED blue light spectrum. Compared with the monochromatic LED for blue chip and YAG phosphor made of white LED, the visual function of the human eye it should be the integral average of the various wavelength components of visual function, this value can be calculated approximately 296lm, this white LED when the emitted optical power 1W white, and its radiation luminous flux is about 296lm, 7.2 times this value increases the emission of radiation of the optical power 1W blue LED luminous flux 41.
3 What is the LED 200W junction temperature? How it is produced?
The basic structure of the LED is a semiconductor PN junction. The research indicates that when current flows through the LED devices, the PN junction temperature will rise in the strict sense, put the PN junction temperature is defined as the LED Blue 150W junction temperature. Usually due to the chip device with a small size, so we can also be the temperature of the LED chip regarded as the junction temperature.
Window layer of the substrate or the material of the junction area, as well as conductive silver glue, etc. There is a certain resistance value, the value of these resistors base plus each other, constitute the LED series resistance. When current flows through the PN junction, but also flow through these resistors, which will also produce Joule heat, causing the chip temperature or elevated junction temperature; LED chip material compared to the surrounding dielectric, with a much larger refractive index resulting chip internally generated most of the light can not be successfully overflow interface, total reflection in the chip and the media interface, return inside the chip and multiple internal reflection eventually chip material or substrate absorption, and lattice vibrations in the form of into heat, prompting the rise of junction temperature.