LED Lighting Performance Must Be Tested(Part 2)

4. Light intensity distribution test

The relationship between the light intensity and the spatial angle (direction) and the pseudo light intensity distribution is called the light intensity distribution curve by the closed curve of the distribution. Since there are many measurement points and the data processing of each point is very complicated, an automatic photometer is usually used for measurement.

5. The influence of temperature on the optical characteristics of LED

The temperature will affect the optical characteristics of the LED. A large number of experiments can explain the temperature and color coordinates of the LED emission spectrum.

6. Surface brightness measurement

The brightness of a light source in one direction is the luminous intensity of the light source in the projection area of the direction. Generally, a surface luminance meter and an aiming luminance meter are used to measure the surface luminance. The aiming light path and the measuring light path are two parts.

7. Measurement of electrical parameters of LED lights

Electrical parameters include forward, reverse voltage and reverse current, which are related to the normal operation of the LED light and are one of the advantages and disadvantages that determine the basic performance of the LED light. There are two measurement methods for the electrical parameters of LED lights: current and test voltage parameters under certain conditions; voltage and test current parameters under certain conditions. The specific method is as follows:

(1) Forward voltage. A positive current is applied to the LED light under test and a voltage drop is applied to it. Adjust the current value to determine the power supply, and record the relevant readings on the DC voltmeter, that is, the forward voltage of the LED light. According to common sense, the LED is positively conductive, and the smaller the resistance, the more accurate it is to use the ammeter external method.

(2) Reverse current. The reverse voltage of the tested LED light, adjust the power supply, and the ammeter reading is to measure the reverse current of the LED light. When measuring the forward voltage in the same way, because the reverse conduction resistance of the LED is relatively large, an ammeter connection is adopted.

8. LED light thermal characteristics test

The thermal characteristics of the LED have a significant impact on the optical and electrical properties of the LED. Thermal resistance and junction temperature, LED2 is the main thermal characteristic. Thermal resistance refers to the thermal resistance between the PN junction and the shell surface, that is, the ratio of the temperature difference along the heat flow path to the power dissipated in the channel. The junction temperature is the temperature of the PN junction of the light-emitting diode.

The methods for measuring the junction temperature and thermal resistance of LEDs generally include infrared microscopy, spectroscopy, electrical parameters, and thermal resistance scanning. Using an infrared temperature measuring microscope or a miniature thermocouple to measure the surface temperature of the LED chip as the LED junction temperature is not accurate enough.

The commonly used method for calculating electrical parameters is to use the linear relationship between the LEDPN junction forward voltage drop and the PN junction temperature and obtain the junction temperature by measuring the LED junction forward voltage drop.

The information is provided by flashlight LED chip supplier.