Patent ID: 9214107
Filing Date: 2015-12-15
Classification: G09G

Abstract:
1. An active matrix display device comprising: an array of display pixels, respective pixels of the array comprising: a current-driven light emitting display element; a drive transistor communicating with the display element and configured for driving a first current through the display element to emit light from the display element; a storage capacitor communicating with a gate of the drive transistor and communicating with the display element, the storage capacitor configured to store a pixel drive voltage to control the drive transistor to drive and stop driving the first current, to control the drive transistor to drive and stop driving the first current through the display element, the storage capacitor is discharged at a first rate to compensate for ageing of the display element; a light-dependent device configured for detecting the brightness of the display element, and providing an output on which the first rate depends; a measuring circuit configured to measure the output of the light-dependent device and based on the measured output, to determine an input voltage of a ramp corresponding to a predetermined brightness; a compensation circuit configured for combining a compensation voltage including a measured threshold voltage of the drive transistor, with the pixel drive voltage, to compensate for variations in the threshold voltage of the drive transistor; a discharge transistor for discharging the storage capacitor thereby to switch off the drive transistor, wherein the storage capacitor communicates between the source and drain of the discharge transistor, wherein a diode-connected timing switch is connected to the gate of the discharge transistor between the gate of the discharge transistor and the light-dependent device.