Coupling means mutual interference between LED driver output channels for LEDs on the same lines and within the same sub-block. This is primarily attributed to the parasitic capacitors on channels and scan lines, as well as parasitic capacitors across LEDs. This issue is even more pronounced in high contrast ratio image. In other words, high-brightness areas of the image are near the low brightness areas of the image. Such as bright object in dark background, and object shadows in a bright environment.

There are 2 common kinds of coupling, brighter coupling and darker coupling, as the demos shown in Figure 3-14 and Figure 3-15. Brighter Coupling means high brightness area makes low brightness area brighter and the opposite for darker coupling. We can see that area A and B are supposed to behave like D area. However, area A and B are affected by C area.

In Figure 3-14, high-brightness area makes low-brightness area brighter. The bright horizontal guidelines in area C couple the corresponding lines in areas A and B to be brighter than the other lines, such as those in area D.

In Figure 3-15, low-brightness area makes high-brightness area darker. The dark area C couples areas A and B to be darker than the other lines, such as those in area D.

Figure 3-14 Brighter Coupling

Figure 3-15 Darker Coupling