introduction
As the familiar backlight of the laptop is a combination of a large number of LED lights, the problem of chromatic aberration is becoming more and more obvious. If the LED lamp beads used are not in the same batch, it is easy to cause problems such as different wavelengths and chromatic aberrations. This problem is inevitable even if the same batch of LED lamp beads are used. For the testing of LED chips, the integrating sphere testing system is generally used.
Using the integrating sphere to measure parameters such as luminous flux, the measurement results can be more reliable. The integrating sphere reduces and removes errors caused by differences in light shape, divergence angle, and the like. Such high-precision and prudent measurement also drives LED integrating sphere manufacturers to increasingly choose higher performance power supplies in the system to power the LEDs to be tested.
LED integrating sphere test system
The LED integrating sphere is mainly used to measure the luminous efficiency, color rendering and chromatic aberration of the LED lamp, and the parameters that characterize the performance of the LED light source. In the large-volume test of the production line every day, there are two problems at present: one is how to improve the test efficiency and the other is how to better protect the LED to be tested in the measurement.
It is understood that in the current power industry, from the power supply to the LED lamp power supply to the software control system to collect back a stable voltage and current value, the total time is about 600ms, then on this basis, is there a possibility of breakthrough? The answer is yes. So what can be achieved? In fact, the power supply configured in the system to supply power to the LED to be tested plays a very important role.
LED integration ball test system schematic
one. Configure professional power supply to suppress overshoot and improve test efficiency
In the normal power supply, due to the loop response time, the power output does not reach the set output voltage value and stops outputting. Therefore, during this time, the voltage will overshoot. Excessive overshoot voltage can affect the life of the LED, and even severely break down the LED.
For low power LED lamps, the constant current operating current is typically between tens and hundreds of milliamps. When operating at a small current, the current and voltage climb speeds are reduced accordingly, sometimes the LED is lit for a period of time, even more than the time required to add the stable voltage and current values ​​from the normal supply of the LED lamp to the software control system. To be long.
In the face of the above two problems, in order to speed up the climb, improve the test efficiency, and improve the loop speed, it usually brings more serious overshoot. However, if the problem of overshoot is taken care of, the overall test efficiency will decrease. Such a problem can be achieved by configuring a professional test LED power supply, such as the Itech IT6874A power supply. The following two figures are waveform diagrams of the voltage rise phase when the IT6874A DC power supply is supplied to LEDs of 80V/20mA and 80V/400mA.
Figure 1: LED (80V/20mA) IT6874A climbing time: about 80ms 
Figure 2: LED (80V/400mA) IT6874A climbing time: about 50ms
As can be seen from the above figure, the ITECH IT6874A DC power supply can basically meet the high-speed and no-overshoot test requirements in 100ms, while the general power supply takes about 600ms. The IT6874A DC power supply has increased this number by nearly 6 times, which is of great significance for the improvement of test efficiency.
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