AMOLED displays with multiple readout circuits
The OLED voltage of a selected pixel is extracted from the pixel produced when the pixel is programmed so that the pixel current is a function of the OLED voltage. One method for extracting the OLED voltage is to first program the pixel in a way that the current is not a function of OLED voltage, and then in a way that the current is a function of OLED voltage. During the latter stage, the programming voltage is changed so that the pixel current is the same as the pixel current when the pixel was programmed in a way that the current was not a function of OLED voltage. The difference in the two programming voltages is then used to extract the OLED voltage.
1. A system for determining a value of a pixel parameter of a pixel in an array of pixels in a display, the pixel including a storage capacitor coupled to a drive transistor for supplying current to a light-emitting device of the pixel as a function of a programming of the storage capacitor, the system comprising:
a controller adapted to:
while measuring a first output electrical signal from the pixel in response to a first input electrical signal provided to the pixel, vary the first input electrical signal until reaching a final first input electrical signal provided to the pixel when the first output electrical signal equals a predetermined electrical signal; and
extract the value of the pixel parameter with use of the final first input electrical signal,
wherein one of the first output electrical signal and the predetermined electrical signal is a function of the pixel parameter.
2. The system of claim 1 wherein the predetermined electrical signal is a predetermined known reference current and the first output electrical signal is a first output current which is a function of the pixel parameter.
3. The system of claim 1 wherein the predetermined electrical signal is a previously measured second output electrical signal, the second output electrical signal previously output from the pixel in response to a second input electrical signal provided to the pixel.
4. The system of claim 3 wherein the controller is adapted to extract the pixel parameter with use of the second input electrical signal provided to the pixel.
5. The system of claim 4 wherein the controller is adapted to extract the pixel parameter from a difference between the final first input electrical signal provided to the pixel and the second input electrical signal.
6. The system of claim 3 wherein the controller is further adapted to, prior to the measuring the first output electrical signal, setting the second input electrical signal provided to the pixel to generate the measured second output electrical signal, wherein only one of the first output electrical signal and the predetermined electrical signal is a function of the pixel parameter.
7. The system of claim 1 wherein the first output electrical signal is a function of the pixel parameter, and wherein the controller is further adapted to:
at an earlier time previous to the extracting of the pixel parameter, while measure a third output electrical signal from the pixel in response to a third input electrical signal provided to the pixel, vary the third input electrical signal until reaching a final third input electrical signal provided to the pixel when the third output electrical signal equals the predetermined electrical signal, wherein one of the predetermined electrical signal and the third output electrical signal is a function of the pixel parameter at the earlier time, and extract the value of the pixel parameter at the earlier time with use of the final third input electrical signal; and
extract the value of the pixel parameter with use of the final third input electrical signal provided to the pixel and the final first input electrical signal provided to the pixel and the value of the pixel parameter at the earlier time.
8. The system of claim 7 wherein only one of the predetermined electrical signal and the third output electrical signal is a function of the pixel parameter at the earlier time.
9. The system of claim 1 , wherein the pixel parameter is the operational voltage V OLED of the light-emitting device.
10. A method of determining a value of a pixel parameter of a pixel in an array of pixels in a display, the pixel including a storage capacitor coupled to a drive transistor for supplying current to a light-emitting device of the pixel as a function of a programming of the storage capacitor, the method comprising:
while measuring a first output electrical signal from the pixel in response to a first input electrical signal provided to the pixel, varying the first input electrical signal until reaching a final first input electrical signal provided to the pixel when the first output electrical signal equals a predetermined electrical signal; and
extracting the value of the pixel parameter with use of the final first input electrical signal provided to the pixel,
wherein one of the first output electrical signal and the predetermined electrical signal is a function of the pixel parameter.
11. The method of claim 10 wherein the predetermined electrical signal is a predetermined known reference current and the first output electrical signal is a first output current which is a function of the pixel parameter.
12. The method of claim 10 wherein the predetermined electrical signal is a previously measured second output electrical signal, the second output electrical signal previously output from the pixel in response to a second input electrical signal provided to the pixel.
13. The method of claim 12 wherein the extracting comprises extracting the pixel parameter with use of the second input electrical signal provided to the pixel.
14. The method of claim 13 wherein the extracting comprises extracting the pixel parameter from a difference between the final first input electrical signal provided to the pixel and the second input electrical signal provided to the pixel.
15. The method of claim 12 further comprising:
prior to the measuring the first output electrical signal from the pixel, setting the second input electrical signal provided to the pixel to generate the measured second output electrical signal, wherein only one of the first output electrical signal and the predetermined electrical signal is a function of the pixel parameter.
16. The method of claim 10 wherein the first output electrical signal is a function of the pixel parameter, the method further comprising:
at an earlier time previous to the extracting of the pixel parameter, while measuring a third output electrical signal from the pixel in response to a third input electrical signal provided to the pixel, varying the third input electrical signal until reaching a final third input electrical signal provided to the pixel when the third output electrical signal equals the predetermined electrical signal, wherein one of the predetermined electrical signal and the third output electrical signal is a function of the pixel parameter at the earlier time, and extracting the value of the pixel parameter at the earlier time with use of the final third input electrical signal provided to the pixel; and
extracting the value of the pixel parameter with use of the final third input electrical signal provided to the pixel and the final first input electrical signal provided to the pixel and the value of the pixel parameter at the earlier time.
17. The method of claim 16 wherein only one of the predetermined electrical signal and the third output electrical signal is a function of the pixel parameter at the earlier time.
18. The method of claim 10 , wherein the pixel parameter is the operational voltage V OLED of the light-emitting device.