Voltage/Current Driven OLED Pixel Circuit for Grayscale Control
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Solution Overview
Problem
Conventional active matrix organic electroluminescent (EL) display devices face challenges in uniformly driving voltage and current due to non-uniformity in thin film transistors (TFTs), leading to deteriorated picture quality and complexity in grayscale control, with voltage-driven circuits having a simple structure but poor grayscale control and current-driven circuits having a complex structure requiring specific driving ICs.
Innovation Solution
A voltage/current driven active matrix organic EL pixel circuit is developed, utilizing a single pixel circuit with five transistors and a storage capacitor, allowing for both voltage and current programming, and an organic EL display device that includes a gate driver and source driver for selective signal output, enabling flexible data mode control between voltage and current modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a voltage driven pixel circuit is used, then the circuit structure is simple, but picture quality deteriorates due to non-uniformity in TFTs and grayscale control becomes difficult
Solution Approach 1:
The pixel circuit is designed to perform both voltage programming and current programming functions using the same circuit structure. The circuit can operate in voltage mode where the storage capacitor stores voltage data, or in current mode where it stores current data, making the circuit universal for both driving methods without requiring separate dedicated circuits for each mode.
Solution Approach 2:
The pixel circuit incorporates dynamic switching capability through control signals that can change the operating mode between voltage-driven and current-driven operations. The circuit can dynamically adjust its function based on external control, allowing it to switch between storing voltage data and storing current data in the storage capacitor, thereby adapting to different driving requirements.
2Manufacturing precision
If a current driven pixel circuit is used, then grayscale control is improved and picture quality is compensated, but the circuit structure becomes complicated and requires specific driving ICs
Solution Approach 1:
The pixel circuit integrates both voltage programming and current programming capabilities within a single unified structure. By using the same storage capacitor and transistor arrangement for both modes, the circuit eliminates the need for separate dedicated circuits and reduces dependency on specific driving IC configurations, thereby simplifying the overall system while maintaining current-driven precision.
Solution Approach 2:
The invention merges the voltage-driven and current-driven circuit architectures into a single hybrid pixel circuit. The control logic and switching mechanisms are combined to allow the same physical circuit to perform both functions, reducing the total component count and simplifying the driving interface while preserving the grayscale control benefits of current-driven operation.
3Adaptability or versatility
If voltage data is programmed in the storage capacitor, then the circuit operates in voltage mode, but grayscale control deteriorates for current driven OLED
Solution Approach 1:
The pixel circuit incorporates dynamic switching capability through control signals that can change the operating mode between voltage-driven and current-driven operations. The circuit can dynamically adjust its function based on external control, allowing it to switch between storing voltage data and storing current data in the storage capacitor, thereby adapting to different driving requirements.
Solution Approach 2:
The circuit changes its operational parameters based on the programming mode. When programmed with voltage data, it operates in voltage mode with the storage capacitor holding voltage; when programmed with current data, it switches to current mode where the storage capacitor holds current. This parameter change allows the same hardware to optimize for grayscale control in current-driven OLED operation.
Data Source
AI summary
Provided is a voltage/current driven active matrix organic electroluminescent (EL) pixel circuit. In particular, a voltage/current driven active matrix organic EL pixel circuit capable of driving organic ELs by a voltage programming method and a current programming method using one pixel circuit and an organic EL display device that uses such a pixel circuit are provided. The voltage/current driven active matrix organic EL pixel circuit can be used for a voltage driven active matrix organic EL and a current driven active matrix organic EL by programming such that the flexibility and applicability of the pixel circuit and the driving circuit are excellent.