Pixel Sensing Circuit Integrator Comparator Counter OLED Brightness
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Solution Overview
Problem
Existing organic light-emitting display devices face challenges in maintaining uniform brightness across pixels due to variations in driving characteristics, leading to brightness deviations, which existing compensation technologies struggle to fully address due to limitations in sensing reliability and chip size constraints.
Innovation Solution
A pixel sensing device incorporating an integrator circuit, comparator, and counter to sense pixel currents, allowing for compensation of display voltage by determining the time for the integrator output to reach a reference voltage, thereby simplifying the sensing process and improving reliability without the need for sample and hold circuits or analog-to-digital converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensing means including sample and hold circuit and scaler circuit are used, then pixel current can be sensed, but the chip area of driver IC increases significantly
Solution Approach 1:
The patent extracts and removes the sample and hold circuit and scaler circuit from the traditional sensing architecture. By eliminating these redundant components and keeping only the essential integrator circuit, the chip area is significantly reduced while maintaining the core sensing functionality through direct integration of pixel current.
Solution Approach 2:
The integrator circuit is designed to perform multiple functions: it integrates the pixel current directly, generates the sensing output voltage, and provides the basis for compensation calculations. This multi-functional design eliminates the need for separate sample and hold circuits and scaler circuits, reducing overall chip area while maintaining sensing precision.
2Measurement precision
If ADC with pre-determined sensing range is used, then voltage conversion is possible, but the actually sensible range is narrower than specified range due to low reliability at boundary parts
Solution Approach 1:
Instead of using an ADC that converts voltage to digital signal with fixed sensing ranges, the patent inverts the approach by using a counter that measures the time duration of voltage change. This time-based measurement method eliminates the boundary reliability issues inherent in voltage-threshold-based ADC sensing, as time measurements can be extended indefinitely without losing precision at boundaries.
Solution Approach 2:
The patent changes the measurement parameter from voltage magnitude (ADC approach) to time duration (counter approach). By measuring how long it takes for the integrator output voltage to reach a reference level, the system achieves extended sensing range with maintained reliability, as time-based measurements do not suffer from the boundary reliability problems of voltage-based measurements.
3Measurement precision
If sample and hold circuit and scaler circuit are connected to each sensing channel, then sensing output voltage can be generated, but the chip size increases
Solution Approach 1:
The patent extracts and removes the sample and hold circuit and scaler circuit from each sensing channel. By eliminating these components and using direct integration of pixel current through the integrator circuit, the sensing output voltage is generated more simply, reducing both chip size and circuit complexity while maintaining the essential sensing function.
4Reliability
If traditional compensation technology is used, then brightness deviation can be compensated, but the chip size of driver IC and fabrication cost increase
Solution Approach 1:
The patent extracts and removes redundant sensing components (sample and hold circuit, scaler circuit) from the driver IC architecture. By using a simplified integrator circuit with counter-based measurement, the chip area is reduced while maintaining the compensation capability needed for brightness uniformity across the display.
Solution Approach 2:
The patent changes from voltage-based ADC measurement to time-based counter measurement. This parameter change simplifies the sensing circuit architecture, reducing chip area and fabrication cost while preserving the ability to accurately measure pixel characteristics for brightness compensation.
Data Source
AI summary
A display device includes a display panel, a sensing circuit, and a compensation circuit. The sensing circuit senses a current generated by a pixel of the display panel. The sensing circuit includes an integrator circuit, a comparator, and a counter. The integrator circuit is initialized to have a first reference voltage as an output. The output of the integrator circuit changes with a rate according to the sensed current. The comparator compares the output of the integrator circuit to a second reference voltage. The counter determines a time for the output of the integrator circuit to reach the second reference voltage from the first reference voltage. The compensation circuit receives the determined time and determines a compensation amount from the received time. The compensating circuit further compensates a display voltage for the pixel by the determined compensation amount in a subsequent display frame of the display device.