System and methods for extraction of threshold and mobility parameters in AMOLED displays
A system extracts effective parameters from a pixel circuit that includes a light emitting device, a drive device to provide a programmable drive current to the light emitting device, a programming input, and a storage device to store a programming signal. The system measures the value of at least one operating parameter of the pixel circuit at a plurality of levels, and then extracts the value of at least one related parameter of the pixel circuit, based on the measured values of the at least one operating parameter. The measured values of the operating parameter are translated to effective values for driving the pixel circuit, based on the extracted value. Then effective parameters for driving effective devices in the pixel circuit are extracted, based on the translated values, and stored for use in compensating input signals to the pixel circuit.
1. A method of translating parameters extracted from a pixel circuit to parameters for compensating said pixel circuit, said pixel circuit including a light emitting device, a drive device to provide a programmable drive current to the light emitting device, a programming input, a storage device to store a programming signal, the method comprising:
extracting a given set of parameters for a pixel model based on measurement cycle conditions from a set of measurements,
calculating outputs of the pixel circuit for a set of given inputs based on a pixel model for a driving (emission) cycle using the extracted parameters,
using said calculated outputs and a model to extract a new set of parameters, and
using the new set of parameters to compensate the pixel circuit during a driving (emission) cycle.
2. The method of claim 1 in which said outputs of the pixel circuit include current driving said light emitting device during a driving (emission) cycle.
3. The method of claim 1 in which said parameters include at least one of mobility of the drive transistor and a threshold voltage in a current-voltage relationship of the pixel circuit.
4. The method of claim 1 in which said pixel model for a driving (emission) cycle includes the effect of parasitic components and changes in the voltage levels.
5. The method of claim 1 in which said model used to extract a new set of parameters is the same model used to extract said given set of parameters.
6. The method of claim 5 in which said model is a function of the mobility and threshold voltage of said drive transistor.
7. A method of extracting parameters of a pixel circuit that includes a light emitting diode, a drive transistor to provide a programmable drive current to the light emitting device, a programming input for receiving programming signals, and a storage device to store a programming signal, said method comprising
measuring data of the pixel circuit under measurement conditions,
using a model to modify the said measured data based on driving (emission) cycle conditions,
using the modified measured data to extract parameters of the pixel circuit, and
using the extracted parameters to compensate the pixel circuit during a driving (emission) cycle.
8. The method of claim 7 in which said data is a calibration voltage for a said pixel circuit to provide a predefined output.
9. The method of claim 8 in which the said predefined output is current, voltage or charge.
10. The method of claim 7 in which said model includes the effect of parasitic capacitance.
11. The method of claim 7 in which said model is measured or calculated.