OLED Driving Transistor Threshold Voltage Compensation
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Solution Overview
Problem
Organic light emitting display devices face non-uniform display luminance due to variability in threshold voltages of driving transistors, which becomes exacerbated at high driving frequencies like 120 Hz, making it difficult to compensate for threshold voltage variations in time.
Innovation Solution
The solution involves an organic light emitting display device with a control line driver that supplies non-concurrent control signals to control lines and a scan driver that sequentially supplies scan signals during a compensation period, allowing for sufficient voltage compensation of the driving transistor, enabling high-speed driving and uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed driving at 120 Hz or more is implemented, then motion blur phenomenon is removed, but charging duration of threshold voltage is shortened making compensation impossible
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation during a dedicated compensation period before the emission period. The control line driver supplies control signals to charge the capacitor with the threshold voltage during the compensation period, ensuring compensation is completed before high-speed emission begins. This allows the system to maintain sufficient charging duration for compensation while achieving high-speed driving at 120 Hz or more.
2Manufacturing precision
If compensation circuit is added to compensate for threshold voltage variability, then display luminance uniformity is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the control line driver to perform multiple functions: it controls both the compensation operation during the compensation period and the emission operation during the emission period. The same driver circuit supplies different control signals at different times, eliminating the need for separate dedicated compensation control circuits. This reduces device complexity while maintaining the ability to compensate for threshold voltage variability and achieve uniform display luminance.
3Manufacturing precision
If threshold voltage compensation is performed, then display luminance uniformity is improved, but driving frequency is limited
Solution Approach 1:
The patent applies periodic action by dividing each frame period into distinct periods: a compensation period for threshold voltage compensation and an emission period for displaying images. This periodic structure allows the system to perform compensation regularly at the start of each frame while maintaining high-speed driving capability. By alternating between compensation and emission periods, the system achieves both uniform display luminance through compensation and high driving frequency of 120 Hz or more.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively compensates for threshold voltage variations, allowing for high-speed driving and maintaining uniform luminance even at high frequencies, while simplifying the device structure and reducing manufacturing costs by enabling simultaneous emission and non-emission schemes.
Implementation Method 1
An organic light emitting display device displays images by using organic light emitting diodes that emit light by recombination of electrons and holes
Data Source
AI summary
An organic light emitting display device includes: a plurality of pixels at crossing regions of a plurality of scan lines and data lines; a first control line and a second control line commonly connected with the plurality of pixels; a control line driver configured to supply a first control signal to the first control line and a second control signal to the second control line, where the second control signal is not concurrent with the first control signal; and a first power supply that supplies a first power to each of the plurality of pixels, where a voltage level of the first power is configured to change at least once during a frame period for each of the pixels.