Display systems with compensation for line propagation delay
A method for characterizing and eliminating the effect of propagation delay on data and monitor lines of AMOLED panels is introduced. A similar technique may be utilized to cancel the effect of incomplete settling of select lines that control the write and read switches of pixels on a row.
1. A method of extracting a propagation delay effect in a display system having a pixel circuit to allow the pixel circuit sufficient time during a programming budget to settle, the pixel circuit having a light emitting device driven by a driving transistor, the pixel circuit connected to a signal line for providing programming information to the pixel circuit for influencing the current through the driving transistor and a monitor line for measuring current levels through at least the driving transistor, the method comprising:
first programming the pixel circuit with a first time duration sufficient to avoid settling effects on the signal line;
responsive to the first programming, measuring, from the monitor line, a current from the pixel circuit to produce a first measurement;
second programming the pixel circuit with a second time duration different from the first time duration;
responsive to the second programming, measuring, from the monitor line, a current from the pixel circuit to produce a second measurement;
comparing the first measurement and the second measurement to extract a propagation delay effect on the signal line; and
storing a representation of the extracted propagation delay effect in a memory device.
2. The method of claim 1 , further comprising using the propagation delay as a feedback for compensating for aging of the pixel circuit and hysteresis.
3. The method of claim 1 , wherein the extracting the propagation delay effect on the signal line is carried out during an initial factory calibration and used in future operation of the display system.
4. The method of claim 1 , further comprising calibrating the measured current using the extracted propagation delay effect.
5. The method of claim 1 , further comprising calibrating the programming information for the pixel circuit to account for at least the extracted propagation delay effect.
6. The method of claim 5 , wherein the calibration accounts for at least the extracted propagation delay effect and at least one of pixel non-uniformity or hysteresis.
7. The method of claim 5 , wherein the first time duration or the second time duration varies as a function of a physical distance of the pixel circuit from a readout circuit that carries out the measuring.
8. The method of claim 5 , wherein the first time duration or the second time duration is a function of a row position of the pixel circuit in the display system.
9. The method of claim 5 , further comprising determining a pixel non-uniformity effect using the extracted propagation delay effect.
10. The method of claim 5 , further comprising extracting aging information associated with the pixel circuit during non-active frame times.
11. The method of claim 10 , wherein the non-active frame times include a reset frame, a blanking frame, or during a display standby time.