OLED Pixel Circuit Transistor Sharing for Area Reduction
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Solution Overview
Problem
Conventional OLED display devices with internal compensation pixel circuits have complex structures due to multiple transistors, limiting the number of pixels per inch and making it difficult to achieve high-resolution displays.
Innovation Solution
The OLED display device simplifies the pixel circuit structure by sharing a transistor for initializing a storage capacitor and gate electrode between adjacent pixel circuits, omitting the need for an additional transistor in each circuit and reducing the circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an internal compensation pixel circuit with multiple transistors is used to compensate for threshold voltage variations, then display quality is improved, but pixel circuit area increases and device complexity increases
Solution Approach 1:
The patent merges the initialization function with the data writing function by using the same transistor (first transistor) to initialize both the storage capacitor and the gate electrode of the driving transistor. This combining of functions reduces the number of transistors from seven to six per pixel circuit, thereby reducing device complexity while maintaining the internal compensation capability that ensures display quality.
Solution Approach 2:
The first transistor is designed to perform multiple functions: it acts as a switch for initializing the storage capacitor during the initialization phase, and also serves as a switch for writing data to the gate electrode during the data writing phase. This multi-functionality reduces the total transistor count and simplifies the pixel circuit structure while preserving the threshold voltage compensation function.
2Reliability
If a 7T1C pixel circuit structure is used for internal compensation, then threshold voltage compensation is achieved, but the number of pixels per inch decreases
Solution Approach 1:
By merging the initialization switch function and data writing switch function into a single first transistor, the patent reduces the transistor count from seven to six. This area reduction enables higher pixel density while maintaining the threshold voltage compensation capability through the internal compensation circuit architecture.
3Adaptability or versatility
If multiple transistors are used in each pixel circuit for initialization and data writing, then circuit functionality is improved, but parasitic effects increase
Solution Approach 1:
The patent reduces the number of transistor instances from seven to six by having the first transistor perform dual functions. Fewer transistors mean fewer parasitic capacitances and resistances, which reduces parasitic effects while maintaining all necessary circuit functionalities including initialization, data writing, and threshold voltage compensation.
Data Source
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AI summary
An organic light emitting diode (OLED) display device for simplifying a structure of an internal compensation pixel circuit is disclosed. The OLED display device is configured in such a way that an Nth pixel circuit shares a transistor for initializing a storage capacitor and a gate electrode of a driving transistor that belong to an (N+1)th pixel circuit to initialize an OLED element. Accordingly, a transistor for initializing an OLED element is omitted from each pixel circuit, thereby simplifying a circuit structure and reducing a circuit area.