Precharge Circuit for OLED Sub-pixel Brightness Uniformity
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Solution Overview
Problem
Existing organic electroluminescent devices suffer from a cross-talk phenomenon where sub-pixels intended to emit the same gray scale level exhibit different brightness due to uneven charge stabilization, leading to inconsistent light emission.
Innovation Solution
A light-emitting device with a precharge controlling circuit that calculates and applies a precharge current based on the cathode voltage and scan line resistance, ensuring equal charge stabilization across sub-pixels, and a data driving circuit that applies data current corresponding to the calculated cathode voltage to prevent cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed precharge voltage is applied to all sub-pixels, then the circuit design is simple, but sub-pixels exhibit different brightness due to varying cathode voltages caused by scan line resistance
Solution Approach 1:
The patent applies different precharge voltages to different sub-pixels based on their specific cathode voltage requirements. The precharge controlling circuit calculates and applies customized precharge voltages to each sub-pixel group, making each part receive tailored treatment rather than uniform treatment, thereby resolving the brightness inconsistency caused by scan line resistance variations.
Solution Approach 2:
The patent dynamically adjusts the precharge voltage parameter based on the cathode voltage of each sub-pixel. By changing the precharge voltage parameter according to the specific requirements of each sub-pixel (calculated from scan line resistance and data current), the system achieves consistent brightness across all sub-pixels while maintaining circuit simplicity.
2Manufacturing precision
If different precharge voltages are applied to each sub-pixel to compensate for scan line resistance, then brightness consistency is improved, but circuit complexity increases
Solution Approach 1:
The precharge controlling circuit automatically calculates the cathode voltage for each sub-pixel based on the data current and scan line resistance, then determines and applies the appropriate precharge voltage without external intervention. This self-service mechanism achieves precise brightness control while minimizing the need for additional complex external circuitry.
Solution Approach 2:
The precharge controlling circuit performs multiple functions: it calculates cathode voltage, determines required precharge voltage, and controls the precharge operation. By integrating these functions into a single multi-functional circuit, the patent achieves precise brightness control without proportionally increasing overall circuit complexity.
3Ease of operation
If precharge current is applied without considering scan line resistance, then the operation is simple, but cross-talk phenomenon occurs between adjacent sub-pixels
Solution Approach 1:
The patent applies precharge current to each sub-pixel before the actual display operation. By performing this preliminary charging action with calculated voltage compensation, the system prevents cross-talk and brightness inconsistency from occurring during normal operation, maintaining both simplicity and reliability.
Solution Approach 2:
The precharge operation counteracts the potential cross-talk effect before it can manifest during display operation. By applying compensatory voltage in advance, the system prevents the harmful cross-talk phenomenon while maintaining operational simplicity.
Data Source
AI summary
A light-emitting device avoids a cross-talk phenomenon. The device includes a precharge controlling circuit and a precharge circuit. The precharge controlling circuit provides a precharge controlling signal in accordance with display data input from an external source. The precharge circuit applies a precharge current corresponding to display data and a scan line resistance to the data lines in accordance with the precharge controlling signal transmitted from the precharge controlling circuit. As a result, precharge current is applied to data lines according to a pixel cathode voltage, and thus cross-talk occurs is eliminated or at least substantially reduced in the device.