OLED Pixel Current Sensing via Time-Division Multiplexing
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Solution Overview
Problem
Existing OLED display devices face challenges in rapidly sensing pixel currents to compensate for luminance deviations and have difficulty in sensing and compensating for characteristic deviations due to driving TFT deterioration, especially after shipment, due to complex circuitry and high-speed sensing limitations.
Innovation Solution
The OLED display device employs a time-division sensing method where 2N pixels share a reference line, allowing for rapid sensing of pixel currents by dividing the sensing period into multiple time-division sensing periods, reducing the number of reference lines and data driver ICs, and enabling easy detection of initial and deterioration-related deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensing is performed by turning on all pixels simultaneously to measure current flowing to power lines, then current sensing can be performed, but sensing time increases due to parasitic capacitors making high-speed sensing difficult
Solution Approach 1:
The patent divides the pixel array into multiple groups (e.g., even and odd pixels) that share different reference lines. Each reference line is associated with a dedicated sensing circuit. This segmentation allows simultaneous sensing of multiple pixel currents through parallel processing, reducing total sensing time while maintaining accuracy by eliminating the need to charge large parasitic capacitors of the entire pixel array.
Solution Approach 2:
The patent implements periodic sensing cycles where different groups of pixels are sensed in alternating time slots. For example, even pixels are sensed during one time slot while odd pixels are sensed during the next time slot. This periodic approach enables high-speed sensing by continuously cycling through different pixel groups, effectively reducing the average sensing time while maintaining measurement precision for each group.
2Productivity
If multiple current sensing circuits are used to simultaneously sense currents of multiple pixels, then sensing speed increases, but circuit scale increases
Solution Approach 1:
The patent merges multiple pixel sensing functions into a reduced number of reference lines and sensing circuits. By organizing pixels into groups that share common reference lines (e.g., 2N pixels sharing N reference lines), the circuit scale is reduced while maintaining the ability to sense multiple pixels simultaneously. This merging approach achieves parallel sensing capability without proportionally increasing the number of sensing circuits.
Solution Approach 2:
Each reference line and its associated sensing circuit are designed to serve multiple pixel groups universally. The sensing circuits can be reconfigured or time-multiplexed to sense different pixel groups during different time slots, making the circuit multi-functional. This universality allows a smaller number of circuits to achieve the sensing capability that would otherwise require many more dedicated circuits.
3Measurement precision
If conventional current sensing methods are used, then initial characteristic deviation can be compensated, but deterioration-related characteristic deviation cannot be sensed and compensated after shipment
Solution Approach 1:
The patent implements a feedback mechanism where pixel currents are continuously or periodically sensed through the reference lines, and the sensed data is used to update compensation values stored in memory. This feedback loop enables the system to detect both initial characteristic deviations and subsequent deterioration-related deviations. The compensation values are dynamically adjusted based on sensed current variations, allowing the display device to maintain uniformity over time and adapt to aging effects after shipment.
Data Source
AI summary
The present invention relates to an organic light emitting diode display device capable of sensing driving current of each pixel with a simple configuration to compensate for a luminance deviation between pixels and a pixel current sensing method thereof. The organic light emitting diode display device includes a display panel including 2N (N being a natural number) pixels that share a reference line though which a reference signal is supplied and are respectively connected to 2N data lines through which data signals are applied, and a data driver for driving the 2N pixels sharing the reference line in a time division manner through the data lines, sensing currents of the time-division-driven 2N pixels as voltages through the shared reference line and outputting the sensed currents, in a sensing mode.