About the current gain

Usually, the LED driving current value is achieved by setting the resistor of the Rext terminal of the driving IC, so that the display can meet the required brightness within a safe range, such as 6000cd/m2. But after years of using, the efficiency of the LED will degrade, which will cause the brightness decrease at the initial current value. If we want the brightness to be 6000cd/m2, the current gain is needed.

By adjusting the current gain value of the RGB on the Uni-Master software, the instructions are sent to the driving IC through the serial port. The brightness of the LED is adjusted by changing the drive IC output current value, thereby changing the Rext terminal voltage value of driving IC, which can increase the current value of 200%.

Take the Artemis XT 16mm with NICHIA 346KS as an example, the brightness gain can make the LED screen still meet the normal demand after 10 years of use.

The data came from the 10-year monitoring on a LED screen with an over 500 square meters in Xi'an.

If we use Artemis XT 16mm with 346KS on a American Standard billboard Bulletin size (14 'x48'), the brightness and power consumption are shown in the following diagram:

We set the initial current value to set the brightness to 7500 cd/m2. When the brightness of LED attenuates, the driving current of LED can be increased by the current gain function of UNI-MASTER, so that the attenuated LED reaches the expected brightness value. In the first five years, the brightness remains 7500 cd/m2 unchanged, and 5500 cd/m2 brightness after ten years are still available.

In this way the initial current can be set to 75% of the maximum current at the very beginning, and the brightness is increased by the current gain in the later period. In this condition, the LED is not always driven by the maximum current. The drive current reduces, the heat reduces as well, so the decay rate of LED will be reduced (shown below by the Nichia test). This means that LED can work for a longer time with a certain brightness, and its power consumption will be relatively lower.