What aspects are tested for LED lamp performance testing?

by:ALLTOP      2020-02-18
Methods for measuring LED junction temperature and thermal resistance generally include infrared micrograph method, spectroscopy method, electrical parameter method, photothermal resistance scanning method, etc. Using infrared temperature microscope or micro thermocouple to measure the surface temperature of LED chip as the junction temperature of LED, the degree is not enough. The intensity of light is the intensity of light, which refers to the amount of light emitted at a certain angle. Because the light of LED is relatively concentrated, the inverse square law is not applicable in the case of short distance. The CIE127 standard provides A measurement condition for the measurement of light intensity (Far field conditions), Measurement condition B (Near field condition) Two conditions for measuring average normal light intensity, the detector area of both conditions is 1cm2. Normally, the luminous intensity is measured using standard condition B. Luminous flux and luminous efficiency detection luminous flux is the sum of the amount of light emitted by the light source, that is, the amount of light emitted. The detection methods mainly include the following two types :(1)Integral method. Ignite the standard lamp and the lamp to be tested in turn in the integrating sphere, and record their readings in the photoelectric converter as Es and ED respectively. If the luminous flux of the standard lamp is known as s, the luminous flux of the lamp to be measured is D = EDs/Es. The integration method uses the principle of point light source and is simple to operate, but the measurement error is large due to the influence of color temperature deviation between standard lamp and measured lamp. (2)Spectroscopic method. By Spectral energy P ()The distribution calculates the luminous flux. Using monochromator, 380nm ~ of standard lamp in integrating ball ~ 780nm spectrum is measured, and then the spectrum of the tested lamp is measured under the same conditions, and the luminous flux of the tested lamp is calculated by comparison. The luminous efficiency is the ratio of the luminous flux emitted by the light source to the power consumed. The luminous efficiency of the LED is usually measured by constant current. Spectral characteristic detection the spectral characteristic detection of LED includes spectral power distribution, color coordinates, color temperature, color rendering index, etc. The spectral power distribution indicates that the light of the light source is composed of color radiation of many different wavelengths, and the radiation power of each wavelength is also different, this difference is called the spectral power distribution of the light source in the order of wavelengths. Using a spectral Photometer (Monochromator)Compared with the standard lamp, the light source is obtained. The color coordinate is the amount of the luminous color of the light source on the coordinate map in a digital way. There are many coordinate systems for color coordinate diagrams, usually X and Y coordinate systems. The color temperature is the light source color table that the human eye sees (Appearance color performance)The amount. When the light emitted by the light source is the same color as the light emitted by blackbody at a certain temperature, the temperature is the color temperature. In the field of lighting, color temperature is an important parameter to describe the optical characteristics of light sources. The relevant theory of color temperature originates from blackbody radiation and can be obtained from the color coordinates containing blackbody trajectories through the color coordinates of the light source. The color rendering index indicates the amount of light emitted by the light source that correctly reflects the color of the illuminated object. It is usually expressed by the general color rendering index Ra, which is the arithmetic average value of the color rendering index of the light source for 8 color samples. Color rendering index is an important parameter of light source quality, which determines the application range of light source. Improving the color rendering index of white LED is one of the important tasks of LED research and development. Light intensity distribution test light intensity with spatial angle (Direction) The variable relation is called false light intensity distribution, and the closed curve connected by this kind of distribution is called light intensity distribution curve. Because there are many measuring points and each point is processed by data, automatic distribution photometer is usually used for measurement. The influence of temperature effect on the optical characteristics of LED, and temperature will affect the optical characteristics of LED. A large number of experiments can show that temperature affects LED emission spectrum and color coordinates. Surface brightness measurement: the brightness of the light source in a certain direction is the luminous intensity of the light source in the unit projection area of the direction. Generally, surface brightness meter and aiming brightness meter are used to measure surface brightness, there are two parts of aiming light path and measuring light path. The measurement of electrical parameters of LED lamps mainly includes forward, reverse voltage and reverse current, which is related to whether LED lamps can work normally and is one of the basis for judging the basic performance of LED lamps. There are two kinds of electrical parameters measurement of LED lamps: that is, under the condition of a certain current, test the voltage parameters; When the voltage is constant, test the current parameters. The specific methods are as follows :(1)Direct voltage. Apply forward current to the LED lamp to be detected, and voltage drop will be generated at both ends. Adjust the power supply determined by the current value and record the relevant readings on the DC voltmeter, which is the direct voltage of the LED lamp. According to relevant common sense, when the LED is being turned on, the resistance is small, and the ammeter external connection method is used for comparison. (2)Reverse current. Apply reverse voltage to the detected LED lamp and adjust the regulated power supply. The reading of ammeter is the reverse current of the tested LED lamp. Similar to measuring forward voltage, because the resistance of LED reverse wizard is large, ammeter internal connection method is adopted. The thermal characteristics of LED lamps test the thermal characteristics of LED, which have an important influence on the optical and electrical characteristics of LED. Thermal resistance and junction temperature are the main thermal characteristics of led2. Thermal resistance refers to the thermal resistance between the PN junction and the shell surface, I . e. the ratio of the temperature difference along the heat flow channel to the power dissipated on the channel. The junction temperature refers to the temperature of the PN junction of the LED. Methods for measuring LED junction temperature and thermal resistance generally include infrared micrograph method, spectroscopy method, electrical parameter method, photothermal resistance scanning method, etc. Using infrared temperature microscope or micro thermocouple to measure the surface temperature of LED chip as the junction temperature of LED, the degree is not enough. At present, the commonly used electrical parameter method uses the linear relationship between the forward voltage drop of LEDPN junction and the temperature of PN junction to obtain the junction temperature of LED by measuring the forward voltage drop difference at different temperatures.
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