Driving Transistor Threshold Voltage Shift Suppression in OLED Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The temporal shift in threshold voltage of driving transistors in organic electroluminescence (EL) displays due to voltage stress leads to variations in current supply, degrading display quality and causing errors in luminance control, as the actual threshold-voltage shift differs from the estimated shift during non-operation periods.
Innovation Solution
A display device and driving method that includes a control circuit to apply a certain voltage between the gate and source electrodes of the driving transistor during power supply cessation, suppressing the recovery of threshold voltage shift and offsetting the gate-source voltage based on the cumulative stress, thereby reducing errors between actual and estimated threshold-voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power supply is stopped to the signal line driving circuit, then energy consumption is reduced, but threshold voltage shift recovery occurs causing luminance control errors
Solution Approach 1:
The control circuit applies a balancing voltage between the gate and source electrodes of the driving transistor before stopping power supply to the signal line driving circuit. This preliminary action prevents threshold voltage shift recovery during the power-off period, ensuring that when power is restored, the transistor maintains its intended operating characteristics and luminance control accuracy is preserved.
2Ease of operation
If voltage stress is applied to the driving transistor during operation, then current control is achieved, but threshold voltage shifts causing display quality degradation
Solution Approach 1:
The control circuit dynamically adjusts the gate-source voltage by applying a balancing voltage that compensates for threshold voltage shifts. By changing the voltage parameter in response to detected threshold shifts, the system maintains stable current control and consistent display quality despite the inherent threshold voltage drift caused by operational voltage stress.
Solution Approach 2:
The system includes a threshold voltage detection mechanism that monitors the driving transistor's threshold voltage and feeds this information back to the control circuit. The control circuit then adjusts the balancing voltage accordingly, creating a feedback loop that continuously compensates for threshold voltage shifts and maintains display quality consistency throughout operation.
Data Source
AI summary
A display device includes a display unit including luminescence pixels each including a luminescence element and a driving transistor configured to supply a current to the luminescence element to cause the element to emit light, a signal line driving circuit configured to supply a voltage applied between a gate and a source of the driving transistor, and a control circuit configured to apply a certain voltage between the gate and the source of the driving transistor by controlling the signal line driving circuit and the display unit when a power supply to the signal line driving circuit is stopped. The control circuit applies the certain voltage between the gate and the source of the driving transistor so that a recovery of a shift amount of a threshold voltage of the driving transistor is suppressed, the recovery being made when the power supply to the signal line driving circuit is stopped.