Display Driving Method for High-Speed Threshold Voltage Compensation
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Solution Overview
Problem
The existing active-matrix organic EL display apparatus faces challenges in achieving high-speed writing operations and large-sized or high-definition displays due to the limitations imposed by threshold voltage compensation methods, which require a long time for the terminal-to-terminal voltage of the capacitor to fall to the threshold voltage of the driving transistor, thereby restricting the time available for writing operations.
Innovation Solution
The proposed driving method divides the frame period into initializing, threshold detection, writing, and luminescence periods, utilizing a specific configuration of capacitors and switches to apply differential voltages and image signal voltages efficiently, allowing for high-speed writing and independent compensation of the threshold voltage of the driving transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threshold voltage compensation is performed using a data line for supplying image signal, then the threshold voltage can be compensated, but the time available for writing operation is limited and it becomes difficult to achieve large-sized or high definition display apparatus
Solution Approach 1:
The patent divides the frame period into multiple sub-periods: initialization period, threshold detection period, writing period, and luminescence period. This temporal segmentation allows threshold voltage compensation to be performed independently from the image signal writing operation, eliminating the time conflict between the two functions and enabling both high-speed writing and accurate compensation.
Solution Approach 2:
The patent extracts the threshold voltage detection function from the data line that normally supplies image signals. By using a dedicated detection period with specific switch configurations (setting second switch OFF and first, third, fourth switches ON), the threshold voltage compensation is separated from the image signal writing path, allowing the data line to be fully available for high-speed image signal writing without compensation time constraints.
2Speed
If the terminal to terminal voltage of the capacitor is much higher than the threshold voltage, then the capacitor is discharged rapidly, but as the voltage decreases toward the threshold voltage, the discharging speed becomes slow and a long time is required
Solution Approach 1:
The patent applies preliminary action by setting the second switch OFF and the first, third, and fourth switches ON during the initialization period to apply a differential voltage to the second capacitor. This pre-charging of the capacitor to a known voltage state before the threshold detection period ensures that when the detection begins, the capacitor voltage is already in a controlled state, enabling rapid and predictable discharge to the threshold voltage without long waiting times.
Data Source
AI summary
A method for driving a display apparatus including a current light emitting device which allows a threshold voltage of a driving transistor to be detected independently of an image signal voltage Vsg (j), such that a writing period of the display apparatus can be shortened. The writing period T3 of the display apparatus is larger than a sum of a time needed for determining image signal voltage Vsg (j) and a time needed for charging a first capacitor which is coupled to a gate of the driving transistor.