Method for measuring white light LED
Date: 2015-11-10 08:20:11 Hits: 509

From the current mechanism and structure of white LED products, the characteristic parameters used to measure the quality of white light LED are generally below 9.

1, white LED current / voltage parameters (positive and negative)

white LED has the typical I-V characteristics of PN junction, the current through the direct effect of white LED brightness and PN series parallel combination, characteristics of the white LED related must match, in the exchange state must also consider the reverse power characteristic. Therefore, it is necessary to test their forward and forward voltage drops at the operating point, as well as reverse leakage current and reverse breakdown voltage. The total electromagnetic energy flux and radiation flux

white LED

2, white LED in unit time emission is called radiant flux, or optical power (W). The white light LED light source for illumination is more concerned with the visual effects of illumination, i.e., the amount of radiation that can be emitted by the light source, which is known as luminous flux. The ratio of the radiation flux to the electrical power of the device represents the radiation efficiency of the white LED.

3, white LED luminous intensity distribution curve

intensity distribution curve is used to express the LED light distribution in all directions of space. In lighting applications, illuminance distribution is the most basic data for calculating illuminance uniformity and spatial arrangement of LED. For space beam as a rotationally symmetric distribution of LED, with a beam axis plane curve of beam can be said; elliptic distribution LED, with two vertical plane beam axis and the short axis of the oval curve to represent; for complex graphics asymmetric, commonly used planar curve beam more than 6 shaft section to express. The spectral power spectral power distribution

white LED distribution

4, white LED said the radiation power function with the change of wavelength, it can determine the color of light, it also determined the luminous flux and color index. In general, the relative spectral power distribution is expressed in S (&lambda). When the spectral power decreases to 50% of the value along the two sides of the peak, the difference between the two corresponding wavelengths (Δ λ =λ 2-λ) is the spectral band.

5, white LED chromaticity coordinates for

RGB red (R), green (G) and blue (B), x=R/ (R+G+B), y=G/ (R+G+B), z= (R+G+B). Because of x+y+z=1, you can uniquely determine a color by simply giving the value of X and y, which is commonly referred to as the chromaticity diagram. If the X and y are used as plane coordinate systems, the X and Y values of various colors in nature can be measured by the colorimetric experimental method, and the chromaticity diagram can be obtained by plotting them in the coordinate plane. Any point of the chromaticity diagram on the edge of the tongue shaped curve represents a particular wavelength of light colors, while the curve indicated at any point within the one eye to see the mixed light color. The color temperature values of the color coordinate values of the characteristic points A., B, C, D and E in the white light region are shown in the following table.

6, white LED color temperature and color rendering index

for white LED light color is white light source, can accurately express the concept of color of the light source table with chromaticity coordinates, but the specific numerical hard habits and color feel together. People often put the color orange partial called “ warm ”, more blazing white or slightly blue called “ cool ”, therefore, the use of color to light color temperature that will be more intuitive. With the LED luminous efficiency and the thermal performance of power


7, white LED increase is one of the key problems in the development of LED industry. At the same time, LED PN junction temperature and shell heat dissipation problem is particularly important, generally with thermal resistance, shell temperature, junction temperature and other parameters. Radiation safety

8 white LED, at present, the International Electrotechnical Commission (IEC) will be LED products equivalent to the requirements of the semiconductor laser radiation safety test and demonstration. Because LED is a narrow beam, high brightness light emitting device, taking into account the radiation may harm to the retina, for different applications of LED, the international standard specifies requirements and test methods for the value of effective radiation limit. Currently, in the European Union and the United States, radiation safety of lighting LED products is implemented as a mandatory safety requirement.

9, white LED reliability and life

reliability index for measure of LED in various environments, work, life quality evaluation index is available LED product cycle, usually represented by effective life or the end of life. In lighting applications, the effective life is the duration of the LED in the rated power conditions, the luminous flux attenuation to the initial value of the percentage (specified value).

(1): the average life expectancy of a batch of LED lit up at the same time, when after a period of time, with the bright LED ratio reached 50% of the time.

(2) economic life: taking into account the LED damage and light output decay conditions, the comprehensive output reduction to a certain proportion of the time, this ratio for outdoor light is 70%, for indoor light is 80%.

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