System and methods for aging compensation in AMOLED displays
Methods and systems to provide baseline measurements for aging compensation for a display device are disclosed. An example display system has a plurality of active pixels and a reference pixel. Common input signals are provided to the reference pixel and the plurality of active pixels. The outputs of the reference pixel is measured and compared to the output of the active pixels to determine aging effects. The display system may also be tested applying a first known reference current to a current comparator with a second variable reference current and the output of a device under test such as one of the pixels. The variable reference current is adjusted until the second current and the output of the device under test is equivalent of the first current. The resulting current of the device under test is stored in a look up table for a baseline for aging measurements during the display system operation. The display system may also be tested to determine production flaws by determining anomalies such as short circuits in pixel components such as OLEDs and drive transistors.
1. A display comprising:
an array of pixels arranged in rows and columns, the array of pixels comprising a pixel including:
a programming voltage input;
a light emitting device for emitting light;
a drive circuit for driving the light emitting device; and
a current output coupled to a monitor line for outputting an output current of a device under test within the pixel while a set programming voltage input is applied to the programming voltage input;
a first reference current source for generating a first reference current;
a second variable reference current source for generating a second variable reference current;
a comparator having a first current input, a second current input, and a signal output, the first current input coupled to the second variable reference current source and coupled to the current output of the pixel via the monitor line and for receiving a combination of the second variable reference current and the output current as a first input current, the second current input coupled to the first reference current source for receiving the first reference current as a second input current, the signal output for providing an output signal based on the first input current and the second input current;
a controller coupled to the second variable reference current source and the output of the comparator and for adjusting the second variable reference current source until a final second variable reference current is reached such that the output signal of the comparator indicates that the first input current and the second input current are the same, and for determining an output current value based on the magnitude of the final second variable reference current.
2. The display of claim 1 , wherein the controller is further for storing the determined output current value in a table associated with the device under test.
3. The display of claim 1 , wherein the device under test is the light emitting device.
4. The display of claim 1 , wherein the device under test is a drive transistor of the drive circuit.