Source Driver Interpolation for Flat Panel Display Gray Level Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional source drivers for flat panel displays face challenges in generating stable and uniformly distributed gray levels due to skewed interpolation of voltages, leading to instability in color reproducibility and increased circuit complexity.
Innovation Solution
A source driver design incorporating a gamma decoder and an amplifier with bias circuits and MOSFETs, which selects and interpolates analog gray voltages based on upper bits of image data to generate distributed analog signals, allowing for the creation of uniformly distributed gray levels through interpolation schemes like the half or quarter method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional amplifier interpolation schemes are used to reduce gamma decoder circuit area, then circuit complexity is reduced, but gray level distribution becomes skewed and unstable
Solution Approach 1:
The patent changes the operating parameters of the amplifier by introducing separate bias circuits for each MOSFET, allowing independent control of threshold voltages and bias currents. This enables the amplifier to generate uniformly distributed gray levels while maintaining reduced circuit complexity through the interpolation scheme.
Solution Approach 2:
The patent segments the biasing function by providing separate bias circuits for each MOSFET in the amplifier. This segmentation allows independent optimization of each transistor's operating point, ensuring uniform gray level distribution across all output levels while maintaining the compact interpolation architecture.
2Measurement precision
If more bits of image data are used to enhance color reproducibility, then color accuracy is improved, but gamma decoder circuit area increases proportionally
Solution Approach 1:
The patent segments the image data processing into two parts: upper bits processed by the gamma decoder to select representative gray voltages, and lower bits processed by the amplifier to generate intermediate interpolated voltages. This segmentation allows high-color-reproducibility performance with significantly reduced gamma decoder circuit area.
Solution Approach 2:
The amplifier acts as an intermediary between the gamma decoder and the display panel. It takes the representative gray voltages from the gamma decoder and generates additional intermediate voltages through interpolation, effectively increasing the resolution and color reproducibility without requiring the gamma decoder to handle all bits directly.
3Device complexity
If representative gray voltages are selected based on upper bits and intermediate values created from remaining lower bits, then circuit area is reduced, but interpolation uniformity deteriorates
Solution Approach 1:
The patent changes the biasing parameters of the amplifier by introducing separate bias circuits that provide optimized threshold voltages and currents for each MOSFET. This ensures that the interpolation process maintains uniformity and precision across all gray levels, even when using the reduced interpolation scheme.
Solution Approach 2:
The patent applies local quality optimization by providing each MOSFET in the amplifier with dedicated bias circuits tailored to its specific position and function in the interpolation process. This local optimization ensures uniform interpolation performance across all gray levels while maintaining overall circuit compactness.
Data Source
AI summary
A source driver that responds to image data by generating an output signal which can be used to drive a flat panel display. The source driver includes a gamma decoder and an amplifier. The gamma decoder selects a first voltage among first analog gray voltages based on some upper bits of the image data, selects a second voltage among second analog gray voltages based on other upper bits of the image data, and selectively outputs at least one of the first and second voltages as a plurality of distributed analog signals in response to lower bits of the image data. The amplifier interpolates between the distributed analog signals from the gamma decoder to generate the output signal of the source driver. The amplifier includes bias circuits that are each configured to generate a bias current, and a plurality of MOSFETs. Each of the MOSFETs includes a source, a drain, and a gate terminal. The gate terminal of each of the MOSFETS is separately connected to receive a different one of the distributed analog signals from the gamma decoder. One of the source/drain terminals of each of the MOSFETS is separately connected to a different one of the bias circuits to receive the bias current, and the other one of the source/drain terminals of each of the MOSFETS is connected together at an output node to generate an interpolated signal. The output signal is based on the interpolated signal.