OLED Driving Transistor Threshold Voltage Compensation Circuit
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Solution Overview
Problem
Organic light emitting display devices face non-uniformity issues due to variations in threshold voltage of driving transistors, which are exacerbated at low brightness levels where compensation is inadequate, leading to mura (unevenness or nonuniformity) in display images.
Innovation Solution
An organic light emitting display device and driving method that includes a gray level determining unit and an initialization power generator to control the voltage level of the initialization power, adjusting it based on gray level values to stabilize the threshold voltage of driving transistors, with a configuration that decreases voltage difference as brightness increases, ensuring adequate compensation across varying brightness levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compensation circuit is added to compensate for threshold voltage variation, then display uniformity is improved, but device complexity increases
Solution Approach 1:
The patent combines the initialization function and compensation function into a single initialization circuit that uses the data signal itself to initialize the driving transistor gate. This merging eliminates the need for separate compensation circuits while achieving both uniformity improvement and threshold voltage compensation through the same circuit structure.
Solution Approach 2:
The initialization circuit is designed to serve multiple functions: it initializes the driving transistor gate voltage, compensates for threshold voltage variations, and adapts to different brightness levels. By making the circuit multi-functional, the patent avoids adding extra complexity while achieving display uniformity improvement.
2Measurement precision
If the panel is driven at high resolution and high driving frequency, then image quality is improved, but threshold voltage compensation becomes inadequate, generating low brightness mura
Solution Approach 1:
The patent implements a dynamic initialization voltage adjustment mechanism where the initialization voltage is not fixed but is dynamically adjusted based on the data signal level and gray level. This dynamic adjustment ensures adequate compensation across different brightness levels and driving conditions, preventing low brightness mura while maintaining high image quality.
Solution Approach 2:
The patent changes the initialization voltage parameter according to the data signal characteristics and display requirements. By adjusting the initialization voltage level dynamically, the system maintains effective threshold voltage compensation even at high resolution and high driving frequencies where static compensation would fail.
3Device complexity
If a fixed initialization voltage is used, then circuit simplicity is maintained, but threshold voltage compensation is inadequate at low brightness levels
Solution Approach 1:
The patent changes the initialization voltage parameter from a fixed value to a dynamically adjusted value based on the data signal and gray level. This parameter change allows the circuit to maintain simplicity in structure while achieving adaptive compensation that works effectively across all brightness levels, including low brightness where fixed voltage fails.
Data Source
AI summary
An organic light emitting display device capable of stably compensating for a threshold voltage of a driving transistor is provided. The organic light emitting display device includes pixels each having a driving transistor and being configured to initialize a voltage of the driving transistor by an initialization power, a gray level determining unit for generating a gray level value using externally supplied data, and an initialization power generator for controlling a voltage level of the initialization power to correspond to the gray level value.