Level Voltage Circuit Layout for Uniform Data Driver Output
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Solution Overview
Problem
In active matrix drive display apparatuses, variations in output voltages among data driver ICs cause display unevenness due to inaccuracies in the level voltage generation circuit, leading to issues with multi-gradation, higher definition, and image quality.
Innovation Solution
A level voltage generation circuit that uses N differential amplifiers and a resistor ladder with N voltage supply points and M voltage output points, where at least one differential amplifier has an input pair connected to a voltage supply point, and the voltage supply and output points are positioned differently on the resistor ladder, connected to capacitive loads to reduce voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional level voltage generation circuit is used, then the circuit structure is simple, but the output voltage precision deteriorates due to contact resistance variations
Solution Approach 1:
The patent divides the resistor ladder into multiple segments with different numbers of resistors (first resistor ladder with more resistors, second resistor ladder with fewer resistors). This segmentation allows different portions of the voltage range to be generated with different precision requirements, improving overall output voltage precision while managing circuit complexity.
Solution Approach 2:
The patent applies different circuit configurations to different parts of the voltage generation system. The first resistor ladder uses more resistors for higher precision in certain voltage ranges, while the second resistor ladder uses fewer resistors for other ranges. This local differentiation optimizes precision where needed without unnecessarily increasing complexity throughout the entire circuit.
2Manufacturing precision
If the number of resistors in the resistor ladder is increased to improve precision, then the output voltage precision improves, but the manufacturing complexity and area increase
Solution Approach 1:
Instead of using one large resistor ladder with many resistors, the patent segments the voltage generation into two separate resistor ladders with different numbers of resistors. This segmentation achieves the required precision for different voltage ranges without requiring a single excessively complex resistor ladder, thereby improving ease of manufacture.
Solution Approach 2:
The patent changes the parameter of resistor count differently across two separate ladders rather than uniformly increasing resistors throughout. The first resistor ladder has a different number of resistors than the second, allowing optimization of precision versus manufacturability by adjusting resistor counts locally rather than globally.
3Reliability
If a single resistor ladder is used, then the device area is small, but the output voltage variation among data driver ICs increases
Solution Approach 1:
The patent uses two separate resistor ladders instead of one, which segments the voltage generation function. This segmentation improves reliability by reducing output voltage variation among data driver ICs, as each ladder can be optimized for specific voltage ranges and can compensate for process variations better than a single large ladder.
Solution Approach 2:
The patent combines two resistor ladders with different numbers of resistors to achieve the overall voltage generation function. This merging of multiple simpler structures achieves better reliability and uniformity than a single complex structure, while the total area remains manageable due to the modular nature of the combined approach.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively suppresses variations in output voltages among data driver ICs, ensuring uniform display quality by precisely generating level voltages that are not affected by contact resistance variations, thereby improving display uniformity and image quality.
Implementation Method 1
N differential amplifiers having output ends, which receive the N input voltages respectively, amplify the N input voltages respectively and output amplified N input voltages
Implementation Method 2
a resistor ladder having N voltage supply points respectively connected to the output ends of the N differential amplifiers and M voltage output points for outputting the M level voltages
Implementation Method 3
the M voltage output points are connected to capacitive loads on input sides of the load amplifiers
Data Source
AI summary
The display apparatus includes: N differential amplifiers having output ends, amplifying N input voltages and outputting amplified voltages, and a resistor ladder having N voltage supply points connected to the output ends of the N differential amplifiers and M voltage output points outputting M level voltages. The M voltage output points are connected to capacitive loads on input sides of the amplifiers, and at least one N differential amplifier has an input pair and an output end connected to one of the N voltage supply point. One of the N input voltages is received by one of the input pair, the other one of the input pair is connected to one of the M voltage output points outputting a level voltage closest to a voltage at the one voltage supply point. The one voltage supply point and the one voltage output point are at different positions on the resistor ladder.