Flat Panel Display Data Driver Chopping Controllers
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Solution Overview
Problem
Active matrix type flat panel displays, particularly organic light emitting displays, suffer from image quality deterioration due to random DC offsets in amplifiers, causing brightness variations and vertical stripes across the screen.
Innovation Solution
The implementation of chopping controllers in the data driver, which periodically change the signals applied to the amplifiers' input terminals using control signals, effectively averaging the offsets and reducing or eliminating the vertical stripes by alternating the input signals between positive and negative terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple amplifiers are used in the data driver for multiple channels, then the data signals can be supplied to multiple data lines simultaneously, but random DC offsets in the amplifiers cause output variations between channels resulting in vertical stripes and image quality deterioration
Solution Approach 1:
The patent applies periodic switching of input terminals in amplifiers through chopping controllers. The input terminals are periodically switched between different signal sources (e.g., between the actual data signal and a reference signal) at a frequency higher than the human visual perception threshold. This periodic action causes the DC offset variations to be averaged out over time, eliminating the vertical stripe artifacts while maintaining the ability to drive multiple channels simultaneously.
Solution Approach 2:
The patent introduces chopping controllers as intermediary devices between the data driver and the amplifiers. These chopping controllers periodically switch the input signals to the amplifiers, acting as mediators that transform the raw data signals into chopped signals. The chopping controllers enable the system to compensate for amplifier DC offsets without requiring precise matching of amplifier characteristics, thus resolving the output consistency issue while maintaining multi-channel capability.
2Adaptability or versatility
If amplifiers with random DC offsets are used to drive data lines, then the data driver can handle multiple channels, but the output variations appear as brightness differences and vertical stripes on the screen
Solution Approach 1:
The chopping controllers periodically switch the amplifier inputs at a frequency above human visual perception. This causes the brightness variations caused by DC offsets to be temporally averaged, making them imperceptible to the human eye. The periodic switching effectively converts static brightness differences into temporal variations that are averaged out, maintaining screen uniformity across all channels while preserving multi-channel adaptability.
Solution Approach 2:
The patent converts the harmful effect of DC offsets into a beneficial averaging effect through periodic chopping. By intentionally introducing high-frequency switching, the static DC offset errors are transformed into dynamic variations that average to zero over time. This converts the harmful brightness differences into a neutral effect, eliminating vertical stripes while maintaining the ability to drive multiple channels with different amplifier characteristics.
Data Source
AI summary
The data driver of a flat panel display includes: an output driver configured to output a plurality of amplified data signals for a plurality of channels corresponding to a plurality of data lines, the plurality of channels including: a plurality of amplifiers configured to amplify a plurality of input data signals and to supply the amplified data signals to the data lines; and a plurality of chopping controllers, each of the chopping controllers being coupled connected to a plurality of input terminals of a corresponding amplifier of the amplifiers and configured to receive a first control signal or a second control signal to periodically change signals applied to positive and negative input terminals from among the input terminals of the amplifiers.