OLED Pixel Circuit Reset Sub-Circuit for Afterimage Elimination

The patent applies preliminary action by setting the drive transistor to an on-bias state during the reset period before the actual display operation. This preliminary on-bias state ensures that holes are detrapped consistently across all sub-pixels, preventing the short-term afterimage phenomenon that would otherwise occur during grayscale transitions. The reset sub-circuit writes an initial voltage to the gate electrode of the drive transistor, establishing this preparatory state that eliminates display defects before the display operation begins.

The patent changes the operational parameter of the drive transistor from a conventional off-state or linear state during reset to a specifically controlled on-bias state. By adjusting the gate voltage to maintain the transistor in a controlled on-state with specific current characteristics, the patent achieves uniform hole detrapping across all sub-pixels. This parameter change transforms the reset operation from a simple voltage write to a controlled biasing operation that actively prevents afterimage effects.

The reset sub-circuit is designed with multi-functionality to reduce overall device complexity. The same reset sub-circuit and reset signal mechanism serve multiple purposes: they initialize the gate voltage of the drive transistor, maintains the on-bias state during the reset period, and work in coordination with the compensation sub-circuit to ensure threshold voltage compensation. By making the reset sub-circuit multi-functional, the patent avoids adding separate dedicated circuits for each function, thereby mitigating the increase in device complexity.

The patent merges the reset function with the compensation function in the pixel circuit. The reset sub-circuit works in conjunction with the compensation sub-circuit, where both operate during the reset period to simultaneously initialize voltages and compensate for threshold variations. This merging of functions allows the circuit to achieve brightness consistency and eliminate afterimage effects without requiring completely separate dedicated circuits for each function, thus controlling the increase in device complexity.

The patent applies preliminary action by establishing a specific on-bias state in the drive transistor during the reset period before the display operation begins. This preliminary action ensures that all sub-pixels undergo consistent hole detrapping in advance, eliminating the afterimage problem. The reset control signal is timed to occur before the display refresh, preparing the transistors in a uniform state that ensures consistent behavior during subsequent operation.

The reset operation is implemented as a periodic action that occurs at the beginning of each display frame or refresh cycle. By periodically resetting all drive transistors to the on-bias state with consistent gate voltages, the patent ensures that hole detrapping is uniformly performed across all sub-pixels at regular intervals. This periodic reset mechanism maintains display quality throughout operation without requiring continuous control signals.