Reference-Voltage Output Circuit for Compact Multi-Level LCD DACs
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Solution Overview
Problem
Differential amplifiers used in liquid crystal display devices face challenges in outputting multi-valued voltage levels over a wide range, leading to increased chip area and cost in data drivers, and are limited in their ability to handle high precision voltage requirements for advanced image data.
Innovation Solution
An output circuit with a selection circuit and amplifier that extrapolates reference voltages to output a maximum of multi-valued voltage levels, reducing the number of input voltages and transistors, and a digital-to-analog converter that selects reference voltages based on digital data signals to achieve high precision voltage output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional differential amplifiers are used to output multi-valued voltage levels, then voltage output capability is maintained, but chip area and cost increase
Solution Approach 1:
The patent combines multiple reference voltage inputs into a single differential amplifier structure. The selection circuit merges multiple reference voltages (Vref1, Vref2, Vref3, Vref4) into two differential inputs, allowing the amplifier to generate multiple output voltage levels (Vout1-Vout16) without requiring separate amplifiers for each level, thus reducing chip area while maintaining multi-valued output capability
Solution Approach 2:
The differential amplifier is designed with universal functionality to handle multiple reference voltage inputs and generate multiple output voltage levels through a single device. The amplifier can output up to 16 different voltage levels (2^4) by receiving 4-bit digital data, making one amplifier perform the work of multiple amplifiers and reducing overall chip area
2Measurement precision
If more reference voltages are used to increase output precision, then voltage precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces a selection circuit as an intermediary between the multiple reference voltages and the differential amplifier. This selection circuit, controlled by 4-bit digital data, selectively connects appropriate reference voltages to the amplifier inputs, enabling high-precision voltage output without requiring direct complex connections between all reference voltages and the amplifier, thus managing device complexity
Solution Approach 2:
The patent transitions from a spatial arrangement of multiple amplifiers to a temporal/digital control dimension. Instead of having separate amplifiers for each voltage level, the system uses 4-bit digital data to control which reference voltages are connected, enabling 16 different output levels through a single amplifier. This dimensional shift from physical multiplication to digital control reduces circuit complexity while maintaining precision
Data Source
AI summary
A selection circuit receives a plural number (m) of respective different values of voltages as reference voltages to select and output two voltages. An amplifier receives at two input terminals the two reference voltages output from the selection circuit to output an output voltage extrapolated.