Pixel Circuit Driving Method for Current Uniformity
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Solution Overview
Problem
Existing methods for preventing non-uniform output current in pixel circuits, such as those used in large screen display devices, still suffer from significant current non-uniformity issues due to manufacturing variations, leading to display quality deterioration and spot generation.
Innovation Solution
A method involving a pixel circuit with a driving element, capacitor, and electro-optical element that alternates between two driving modes with opposite error polarities for the driving current, reducing current errors by offsetting them, thereby improving display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional current mirror circuits are used to control output current, then the circuit structure is simple, but significant current non-uniformity occurs due to manufacturing variations
Solution Approach 1:
The pixel circuit is divided into two distinct driving modes (first driving mode and second driving mode) with different connection states. By segmenting the driving process into alternating phases, the patent achieves current uniformity improvement without complicating the overall circuit structure. Each mode uses the same physical components but in different configurations, resolving the contradiction between simplicity and precision.
Solution Approach 2:
The patent implements periodic switching between the first and second driving modes in a predetermined sequence. This periodic action allows the system to average out manufacturing variations over time, achieving current uniformity without requiring more complex circuitry. The alternating modes compensate for each other's deviations, maintaining simplicity while improving precision.
2Manufacturing precision
If periodic conversion of current controlling elements is used to average non-uniformity, then current uniformity is improved, but block-shaped spots are generated on the display
Solution Approach 1:
The patent dynamically switches the connection state of the pixel circuit between two modes, rather than using static periodic conversion of physical elements. This dynamic approach within each pixel avoids the block-shaped spots that occur when groups of pixels are periodically converted, as the switching happens at the pixel level with opposite error polarities that cancel out visually.
Solution Approach 2:
The second driving mode is designed with connection states that are essentially inverted compared to the first mode. By inverting the connection configuration and using opposite error polarities, the patent cancels out the non-uniformity effects that would otherwise manifest as display spots, while maintaining current uniformity improvement.
3Manufacturing precision
If alternating driving modes with opposite error polarities are implemented, then current errors are reduced and display quality is improved, but the control complexity increases
Solution Approach 1:
The same physical components (transistors, capacitors, electro-optical elements) serve multiple functions by being configured differently in the two driving modes. The transistors act as switching elements in one mode and current controlling elements in another, reducing the need for additional components while achieving error reduction. This multi-functionality manages control complexity by reusing existing elements.
Solution Approach 2:
The patent changes the connection state parameters and error polarity parameters between the two driving modes rather than changing the physical structure. By altering electrical connection configurations and operating parameters of existing components, the system achieves current uniformity improvement without adding significant control complexity, as the same hardware is reconfigured rather than expanded.
Data Source
AI summary
To effectively reduce or prevent the deterioration of display quality caused by the errors included in the current supplied to an electro-optical element a pixel circuit includes a capacitor C1, transistors T1 and T2 that constitute a current mirror, and an organic EL element OLED. When a first driving mode is set, the transistor T1 functions as a programming element that writes data in the capacitor C1 in accordance with data current Idata and the second transistor T2 functions as a driving element that generates driving current Ioled in accordance with data stored in the capacitor C1. When the second driving mode that is alternately switched to the first driving mode in a predetermined period is set, the transistor T2 functions as the programming element and the transistor T1 functions as the driving element.