Patent ID: 9741292
Date: 2017-08-22
CPC Classifications: G09G

Claim:
1. A method of programming a pixel circuit that drives a current-driven organic light emitting device independent of a threshold voltage of a drive transistor connected in series to the organic light emitting device, the pixel circuit further including a first switch transistor connected between the organic light emitting device and a node of the pixel circuit, the method comprising: adjusting during a programming cycle a controllable voltage supply to a compensation voltage; in a first operating cycle of the programming cycle, selecting a select line, to turn on a second switch transistor coupled to the drive transistor, for applying a reference voltage to the drive transistor through the second switch transistor, and to turn on the first switch transistor, and applying to a data line connected to the second switch transistor a voltage that exceeds a programming voltage to be applied to the drive transistor; responsive to the adjusting, allowing the node of the pixel circuit to charge or discharge through the drive transistor, via the first switch transistor, until the drive transistor turns off, thereby establishing the threshold voltage of the drive transistor across the drive transistor; in a further operating cycle of the programming cycle following the first operating cycle, selecting the select line to turn on the second switch transistor for applying a programming voltage from the data line to the drive transistor through the second switch transistor, thereby establishing a fixed voltage applied to the drive transistor according to both the threshold voltage and the applied programming voltage, wherein the programming voltage is lower than the reference voltage; responsive to the applying the programming voltage, selecting the select line with an intermediate selection voltage being sufficient to turn on the second switch transistor while turning off the first switch transistor; and applying a second reference voltage, via the data line, to allow the fixed voltage in the pixel circuit to be independent of the reference voltage.