System and methods for aging compensation in AMOLED displays
A voltage-programmed display system allows measurement of effects on pixels in a panel that includes both active pixels and reference pixels coupled to a supply line and a programming line. The reference pixels are controlled so that they are not subject to substantial changes due to aging and operating conditions over time. A readout circuit is coupled to the active pixels and the reference pixels for reading at least one of current, voltage or charge from the pixels when they are supplied with known input signals. The readout circuit is subject to changes due to aging and operating conditions over time, but the readout values from the reference pixels are used to adjust the readout values from the active pixels to compensate for the unwanted effects.
1. A voltage-programmed display panel having a display area containing multiple pixels and allowing measurement of effects on pixels in the panel, comprising:
a plurality of normal pixels to display an image under an operating condition, the normal pixels each being coupled to a supply line and a programming line for displaying images under said operating condition;
a plurality of reference pixels included in the display area and coupled to said supply line and said programming line, the reference pixels being coupled to said supply line and said programming line in a manner that said reference pixels are controlled so that they are subject only to global effects on said display panel over time;
a readout circuit coupled to said normal pixels and said reference pixels for reading at least one of current, voltage and charge from said normal and reference pixels when said normal and reference pixels are supplied with known input signals; and
a controller coupled to each of said plurality of reference pixels and configured to
measure data from said normal pixels and said reference pixels,
correct the measured data from the reference pixels by subtracting the effect of global effects from the data measured from the reference pixels,
trim the data measured from the normal pixels with the corrected data read from the reference pixels, and
compensate the signals supplied to said normal pixels on said programming line, based on said trimmed data.
2. The system of claim 1 , wherein said global effects include temperature.
3. The system of claim 1 , wherein said effects affect both said active normal pixels and said reference pixels.
4. The voltage-programmed display panel of claim 1 in which said effect of global effects is determined by averaging the values of at least a selected group of said reference pixels.