Technical control: LED light bar bulb junction temperature measurement method

The blister bulb made of LED strips can realize 360 ​​degree full angle light source without adding a lens, which makes people feel the return to traditional incandescent lamps. LED light bar lights have many application advantages, and there is a big whirlwind in the market, which is quickly accepted by users. The LED light bar lamp combines the traditional tungsten filament bulb manufacturing technology with the emerging LED technology, and uses the glass bubble inflation technology to seal the LED light bar in the glass bulb and fill the mixed gas inside to make it dissipate heat. In order to reduce the LED junction temperature, reduce light decay, and extend the life.

The junction temperature of LED strips under working conditions is the main factor affecting various performance indicators, and is also a key factor that seriously affects LED light decay and service life. These parameters are extremely important lighting quality evaluation indicators for general lighting. A consensus has been reached in the lighting industry.

The LED light bar is sealed in the glass bulb filled with the mixed gas. Only the two guide wires of the positive and negative electrodes are connected to the driving power supply outside the sealed glass bulb. What method is used to test the junction temperature of the LED light bar lamp? Common measurements have pins thermometry, infrared imaging method, the voltage method and the like. Method apparently because they can not pin thermocouple adhered to the sealed glass bulb LED strip temperature not; IR imaging method can not be detected due to the strip surface temperature of the LED light through the glass shell can not be used; and the voltage The law can solve the problem of testing. Recently, the company's LEDT-300B whole lamp thermal management system using the voltage method as the test principle has measured and analyzed an LED light bar bulb manufactured by a certain company, and obtained a lot of interesting data to share with you. see picture 1:

Test principle: the voltage method, a sample to make LED light strip calibration line K, the temperature T acquired correspondence relationship between the Vf value of the lamp strip; then use its own drive for the lamp lighting test sample heating source, after the lamp is lit, real-time continuous measured junction temperature variation with respect to time, drawn with a continuous curve on the computer screen, at the same time drawing the adhesive bulb temperature of a thermocouple reference point and ambient temperature profile.

From the above figure, we can see that the LED junction temperature in the bulb gradually rises after the bulb is turned on (the first period), and the temperature reading is 122 °C when it reaches a steady state. Continue the test. At this time, artificially destroy the bubble-sealing port, let the mixed gas in the shell be released, and return the internal pressure to the atmospheric pressure. In the figure, the junction temperature curve starts to rise (the second time period) and gradually reaches the new stable platform. junction temperature reaches 160 ℃, the junction temperature is clearly too high. As can be seen from the above figure, the ambient temperature is basically above and below 26 °C throughout the experiment, while the reference point temperature of the glass bulb surface is maintained at about 40 °C under both test conditions.