LCD Column-Line DAC Integration Using Load Capacitance

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Solution Overview

Problem

Conventional liquid crystal display (LCD) systems require significant peripheral circuitry and electrical connections for digital-to-analog conversion, leading to high costs and complexity due to the need for separate data scanner and select scanner circuitry, which complicates synchronization and increases system costs.

Innovation Solution

Integration of a switch network using column load capacitances on adjacent pairs of column lines to convert digital data to analog data, eliminating the need for separate digital-to-analog conversion circuitry and associated amplifiers, with a row buffer and switch network comprising MOSFETs to distribute and convert digital data to analog signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If separate digital-to-analog conversion circuitry and peripheral ICs are used, then signal conversion capability is achieved, but system cost and device complexity increase significantly

Engineering Contradiction:

Improvesignal conversion capabilityVSAvoidsystem complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines the digital-to-analog conversion function with the existing column driver circuitry by utilizing the column load capacitances as DAC capacitors. This integration eliminates the need for separate DAC chips and reduces the number of peripheral ICs, directly addressing the contradiction by maintaining signal conversion capability while reducing system complexity and cost.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The column load capacitances, which originally served only as load elements for the column lines, are repurposed to function as DAC capacitors for digital-to-analog conversion. This multi-functional use of existing components enables signal conversion without adding dedicated conversion circuitry, thereby reducing device complexity while preserving adaptability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If separate digital-to-analog conversion circuitry is used, then signal conversion is achieved, but the number of electrical connections and mounting requirements increase

Engineering Contradiction:

Improvedigital-to-analog conversionVSAvoidmanufacturing complexity

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The conversion circuitry is merged with the substrate containing the pixel array, eliminating the need for separate DAC ICs and their associated mounting processes. This integration reduces the number of electrical connections required and simplifies manufacturing by consolidating multiple functions into a single substrate assembly.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of operation

If conventional separate scanner circuitry is used, then data and scan signal driving is achieved, but synchronization precision and reliability are compromised

Engineering Contradiction:

Improvesignal driving capabilityVSAvoidsynchronization reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The data scanner and select scanner circuitry are integrated on the same substrate, which improves synchronization reliability by reducing timing skew and signal propagation delays that occur with separate external ICs. The merged architecture ensures tighter synchronization between data and scan signals while maintaining full driving capability.

Inventive Principle:

Principle #5Merging (Combining)

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 approach reduces system costs and improves reliability by eliminating the need for peripheral ICs and connections, while maintaining precise timing and signal conversion necessary for LCD operation.

Implementation Method 1

A switch network can be coupled to the row buffer for converting the digital data received from the row buffer to analog data using column load capacitances on adjacent pairs of column lines of the LCD

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

Each switching device can include a logic circuit which can receive digital data from the row buffer and at least three MOSFETs which can convert the received digital data received from the logic circuit to analog data

Methodology Applied

Scientific EffectMOSFET switching:

Data Source

PatentUS7595782B2Liquid crystal display with integrated digital-analog-converters

Publication Date: 2009.09.29 KOPIN CORP

AI summary

An apparatus and method can convert digital data to analog data using column load capacitances on adjacent pairs of column lines of the LCD. The apparatus includes a data bus containing digital data. A row buffer is coupled to the data bus for receiving and distributing the digital data. A switch network is coupled to the row buffer for converting the digital data received from the row buffer to analog data using column load capacitances on adjacent pairs of column lines of the LCD.