SLVAFE4 june   2023 TLC6983

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Common issues in NPP Matrix LED Panel
    1. 2.1 Ghosting
    2. 2.2 Non-Uniformity in Low Gray Scale
    3. 2.3 Coupling
    4. 2.4 Caterpillar
    5. 2.5 Color Shift in Low Gray Scale
    6. 2.6 Gray Scale Gradient Discontinuity Issue
    7. 2.7 First Scan Line Dim
  6. 3Summary
  7. 4References

2.4 Caterpillar

Figure 2-11 shows the LOD caterpillar issue, suppose the LED11 is an opened LED, when scans to the line0 and the OUT1 is turned on, the OUT1 voltage is forced to approach to VLED because of the broken path of the current source. However, if the difference between VOUT1 and Vline is larger than the LED forward voltage, it will cause all LEDs connecting to the channel OUT1 light unwanted.


GUID-20220725-SS0I-TKCH-VFBS-HTMB94NNXLHR-low.gif

Figure 2-11 LOD Caterpillar Issue

Figure 2-12 shows the LSD caterpillar issue, suppose the LED11 is an short LED, when scans to the line2 and the OUT1 is turned off, the OUT1 voltage is the same with scan line0 voltage because of the short path of the LED01, at this time, there is a current path from the line1 to the GND through the LED11 and SW2, which causes LED21 light unwanted.


GUID-20220628-SS0I-6PXB-TCGD-MM0H7ZNNWV4W-low.gif

Figure 2-12 LSD Caterpillar Issue