Display Driving Transistor Threshold Voltage Compensation
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Solution Overview
Problem
In flat panel displays, variations in threshold voltages of driving transistors lead to inconsistent brightness across pixels, and integrating compensation units reduces the aperture ratio, which is problematic as display sizes increase.
Innovation Solution
A driving device comprising PMOS or NMOS transistors and capacitors is designed to compensate for threshold voltage shifts, allowing for consistent image signal delivery to light-emitting elements while maintaining a high aperture ratio by using specific transistor configurations and control signal logic levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each pixel is integrated with a compensation unit, then the threshold voltage effects are compensated, but the aperture ratio of the display is reduced
Solution Approach 1:
The patent extracts the compensation function from the pixel-level integration and implements it at the transistor level within the existing pixel structure. By using the gate terminal of the driving transistor as the compensation node and utilizing the inherent capacitance of the transistor gate, the compensation unit is effectively removed from the pixel area, thus maintaining high aperture ratio while achieving threshold voltage compensation.
Solution Approach 2:
The driving transistor's gate terminal serves multiple functions: it controls the driving current and simultaneously acts as the compensation node for threshold voltage compensation. The gate capacitance of the driving transistor is utilized as the compensation capacitor, eliminating the need for separate compensation components and enabling the pixel structure to perform both driving and compensation functions.
2Reliability
If a conventional compensation unit is used, then the threshold voltage variation is compensated, but the pixel area is increased
Solution Approach 1:
The patent merges the compensation function with the driving transistor structure. The compensation node is formed by the gate terminal of the driving transistor itself, and the compensation capacitor is implemented using the gate capacitance of the transistor. This merging eliminates separate compensation components and integrates the compensation function into the existing pixel area without increasing it.
Solution Approach 2:
The driving transistor provides its own compensation capability through its inherent gate capacitance and gate terminal. The transistor's own physical structure (gate, source, drain) is utilized to implement the compensation function, eliminating the need for external or additional compensation components that would increase pixel area.
Data Source
AI summary
A driving device includes a pixel array, a controller and a driver. The driver has a plurality of driving devices. Each of the driving devices includes a plurality of transistors and at least one capacitor to drive a light emitting device. By controlling the timing scheme of control signals applied to the driving device, the voltage for driving the light emitting device would not be affected by threshold voltages of the transistors.