Pixel circuits for AMOLED displays
A method and system determine the characteristics of drive devices and load devices in selected pixels in an array of pixels in a display in which each pixel includes a drive device for supplying current to a load device. The method and system supply current to the load device via the drive device in a selected pixel, the current being a function of a current effective characteristic of at least one of the drive device and the load device; measure the current via a measurement line that is shared by adjacent pixels, and extract the value of a selected effective characteristic of one of the drive and load devices from the effect of the current on another of the drive and load devices. Current may be measured via a read transistor in each pixel.
1. A method of determining a value of a characteristic of a first pixel in an array of pixels in a display in which each pixel includes a drive transistor coupling a supply voltage to an OLED for controlling a supply of current to the OLED, said first pixel being one of a pair of pixels, said display system including a monitor line controllably coupled to said pair of pixels, and in which values of said characteristic of the pixels of the array of pixels are not identical, said method comprising:
forcing a second pixel of the pair of pixels into a known state including programming the drive transistor of the second pixel to a full ON state;
subsequent to forcing the second pixel into the known state, measuring at least one voltage or current over the monitor line generating one or more measurements; and
determining the value of the characteristic of the first pixel with use of at least one of the measurements including an effect of the second pixel on the at least one voltage or current, and with use of at least one of the measurements including an effect of the characteristic of the first pixel on the at least one voltage or current.
2. The method of claim 1 wherein determining the value of the characteristic of the first pixel comprises extracting from the one or more measurements, the effect of the second pixel on the at least one voltage or current.
3. The method of claim 1 further comprising:
during the measuring the at least one voltage or current, forcing the first pixel into one or more states,
wherein measuring the at least one voltage or current over the monitor line comprises:
for each of the one or more states, generating at least one measurement including the effect of the characteristic of the first pixel, and
wherein determining the value of the characteristic of the first pixel comprises extracting from the at least one measurement, the effect of the second pixel on the at least one voltage or current.
4. The method of claim 3 wherein forcing the first pixel into the one or more states comprises controlling a state of the OLED of the first pixel with use of the monitor line.
5. The method of claim 1 wherein forcing the second pixel of the pair of pixels into the known state comprises adjusting the supply voltage of the second pixel.
6. A method of determining a value of a characteristic of a first pixel in an array of pixels in a display in which each pixel includes a drive transistor coupling a supply voltage to an OLED for controlling a supply of current to the OLED, said first pixel being one of a pair of pixels, said display system including a monitor line controllably coupled to said pair of pixels, and in which values of said characteristic of the pixels of the array of pixels are not identical, said method comprising:
forcing the first pixel and a second pixel of the pair of pixels into known states;
subsequent to forcing the first pixel and the second pixel into known states, measuring at least one voltage or current over the monitor line generating one or more measurements, including:
measuring the at least one voltage or current while the first and second pixels are in the known states, generating a first measurement of the one or more measurements, and
measuring the at least one voltage or current after the first pixel has been controlled by the monitor line into a different state, generating a second measurement of the one or more measurements; and
determining the value of the characteristic of the first pixel with use of at least one of the measurements including an effect of the second pixel on the at least one voltage or current, and with use of at least one of the measurements including an effect of the characteristic of the first pixel on the at least one voltage or current,
wherein determining the value of the characteristic of the first pixel comprises extracting the characteristic of the first pixel from the second measurement by subtracting out the effect of the second pixel on the second measurement with use of the first measurement.
7. The method of claim 6 wherein determining the value of the characteristic of the first pixel comprises extracting from the one or more measurements, the effect of the second pixel on the at least one voltage or current.
8. The method of claim 6 wherein forcing the second pixel of the pair of pixels into a known state comprises programming the drive transistor of the second pixel to a full ON state.
9. The method of claim 8 wherein forcing the second pixel of the pair of pixels into the known state comprises adjusting the supply voltage of the second pixel.
10. A system for determining a value of a characteristic of a first pixel in an array of pixels in a display in which each pixel includes a drive transistor coupling a supply voltage to an OLED for controlling a supply of current to the OLED, said first pixel being one of a pair of pixels, said display system including a monitor line controllably coupled to said pair of pixels, and in which values of said characteristic of the pixels of the array of pixels are not identical, said system comprising a controller adapted to:
force a second pixel of the pair of pixels into a known state including programming the drive transistor of the second pixel to a full ON state;
subsequent to forcing the second pixel into the known state, measure at least one voltage or current over the monitor line generating one or more measurements; and
determine the value of the characteristic of the first pixel with use of at least one of the measurements including an effect of the second pixel on the at least one voltage or current, and with use of at least one of the measurements including an effect of the characteristic of the first pixel on the at least one voltage or current.
11. The system of claim 10 in which said controller is adapted to determine the value of the characteristic of the first pixel by extracting from the one or more measurements, the effect of the second pixel on the at least one voltage or current.
12. The system of claim 10 wherein the controller is further adapted to:
during measuring the at least one voltage or current, force the first pixel into one or more states,
wherein the controller is adapted to measure the at least one voltage or current over the monitor line including:
for each of the one or more states, generating at least one measurement including the effect of the characteristic of the first pixel, and
wherein the controller is adapted to determine the value of the characteristic of the first pixel by extracting from the at least one measurement, the effect of the second pixel on the at least one voltage or current.
13. The system of claim 12 wherein the controller is adapted to force the first pixel into the one or more states by controlling a state of the OLED of the first pixel with use of the monitor line.
14. The system of claim 10 wherein the controller is adapted to force the second pixel of the pair of pixels into the known state by adjusting the supply voltage of the second pixel.
15. A system for determining a value of a characteristic of a first pixel in an array of pixels in a display in which each pixel includes a drive transistor coupling a supply voltage to an OLED for controlling a supply of current to the OLED, said first pixel being one of a pair of pixels, said display system including a monitor line controllably coupled to said pair of pixels, and in which values of said characteristic of the pixels of the array of pixels are not identical, said system comprising a controller adapted to:
force the first pixel and a second pixel of the pair of pixels into known states;
subsequent to forcing the first pixel and the second pixel into the known states, measure at least one voltage or current over the monitor line generating one or more measurements, including:
measuring the at least one voltage or current while the first and second pixels are in the known states, generating a first measurement of the one or more measurements, and
measuring the at least one voltage or current after the first pixel has been controlled by the monitor line into a different state, generating a second measurement of the one or more measurements; and
determine the value of the characteristic of the first pixel with use of at least one of the measurements including an effect of the second pixel on the at least one voltage or current, and with use of at least one of the measurements including an effect of the characteristic of the first pixel on the at least one voltage or current,
wherein the controller is adapted to determine the value of the characteristic of the first pixel by extracting the characteristic of the first pixel from the second measurement by subtracting out the effect of the second pixel on the second measurement with use of the first measurement.
16. The system of claim 15 in which the controller's determining the value of the characteristic of the first pixel includes extracting from the one or more measurements, the effect of the second pixel on the at least one voltage or current.
17. The system of claim 15 wherein the controller's forcing the second pixel of the pair of pixels into the known state includes programming the drive transistor of the second pixel to a full ON state.
18. The system of claim 17 wherein the controller's forcing the second pixel of the pair of pixels into the known state includes adjusting the supply voltage of the second pixel.