Publication Date: 2002-Feb-21
The IP.com Prior Art Database
ID607256 + ID607340
In colour P(O)LED displays and other classes of colour displays, such as
electroluminescent_displays the voltages and currents required to produce the same amount of
light from each pixel can vary. This is partially a function of the response of the eye (which
sees green better than red or blue) and also the fact that the different EL materials used for the
RGB pixels often have different efficiencies of light production.
In normal driving approaches, the driving electronics (either passive matrix or active
matrix) drives all types of pixels from a single driver. The power line voltage must therefore
be sufficient to drive the least efficient colour (e.g. red). Whilst this makes it possible to drive
the display from a single driver, it will result in the most efficient colour (green) being driven
from a driver (passive matrix) or power line (active matrix) operating at a far too high
voltage. As a result, this driver will dissipate far more power than required. In a typical
PLED, the power dissipated in the green pixel driver will be 4 times higher than necessary (as
the red pixel in this example operates at 4 times the voltage of the green pixel).
To reduce driver 1C area and cost the driver capability of the driver 1C for the higher
efficient colours can be reduced, so a smaller chip area is sufficient.
Alternatively it is possible to reduce the power dissipation by providing the colour EL
display with more than one power line. In this way, it will be possible to drive the different