Data Line Driving Circuit for LCD Power Reduction

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Solution Overview

Problem

The existing data line driving circuits for liquid crystal displays consume high power due to the large voltage range required for AC pixel driving, especially in column inversion systems, where the prior art's charge recovery method is not effective in reducing power consumption during column inversion driving.

Innovation Solution

A data line driving circuit that includes comparison units and switches to control the connection or interruption of data lines based on reference voltage levels, allowing for efficient charge recovery and reducing power consumption by setting the charge recovery level to a reference voltage, thereby optimizing the voltage range and power usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a fixed voltage is continued to be applied to the liquid crystal capacitances, then the liquid crystal display can operate with a simple driving system, but polarization is generated in the liquid crystals and physical property degradation occurs

Engineering Contradiction:

Improvedriving system complexityVSAvoidliquid crystal physical property

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements periodic polarity inversion of the voltage applied to liquid crystal capacitances. The data line driving circuit alternates between positive and negative voltage polarity in a periodic manner, preventing polarization accumulation and physical property degradation of the liquid crystal material while maintaining reliable display operation.

Inventive Principle:

Principle #19Periodic action

2Reliability

If polarity inversion is implemented to prevent liquid crystal degradation, then liquid crystal physical property is maintained, but the voltage range to drive becomes larger and power consumption increases

Engineering Contradiction:

Improveliquid crystal physical propertyVSAvoiddata line driving circuit power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent connects all data lines to a common node and uses an external storage capacitor to average the potentials at respective data lines to an intermediate level. This equipotential approach allows polarity inversion to be achieved while reducing the voltage swing range, thereby lowering power consumption of the data line driving circuit.

Inventive Principle:

Principle #12Equipotentiality

Solution Approach 2:

The patent changes the reference voltage parameter from which polarity inversion is performed. By inverting polarity relative to an intermediate voltage level rather than ground, the voltage swing range is reduced, resulting in lower power consumption while maintaining the necessary AC driving function for liquid crystal reliability.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If all data lines are short circuited to a common node with an external storage capacitor for charge recovery, then power consumption is reduced, but the charge recovery level is limited to ½ VDD and the voltage difference remains large

Engineering Contradiction:

Improvedata line driving circuit power consumptionVSAvoidvoltage range optimization

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The patent changes the reference voltage parameter for charge recovery from ½ VDD to a programmable reference voltage level. This allows optimization of the charge recovery level to achieve a smaller voltage swing range, further reducing power consumption while providing flexibility to adapt to different operating conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a programmable reference voltage that can be dynamically adjusted. This dynamic parameter allows the charge recovery level to be optimized based on operating conditions, enabling better power consumption management and voltage range control compared to fixed charge recovery schemes.

Inventive Principle:

Principle #15Dynamics

4Use of energy by moving object

If column inversion driving is used, then power consumption is reduced compared to other inversion systems, but the voltage range is still larger than necessary and power consumption can be further reduced

Engineering Contradiction:

Improvepower consumptionVSAvoidvoltage efficiency

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent optimizes the charge recovery voltage parameter in column inversion driving by using a programmable reference voltage instead of a fixed level. This parameter optimization reduces the voltage swing range during column inversion, achieving lower power consumption and higher voltage efficiency while maintaining the benefits of column inversion driving.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8319768B2Data line driving circuit for liquid crystal display device and method for controlling the same

Publication Date: 2012.11.27 RENESAS ELECTRONICS CORP

AI summary

A data line driving circuit for a liquid crystal display device comprising: a plurality of first data lines applied with a positive potential, a plurality of second data lines applied with a negative potential, comparison units that compare with a reference voltage at least one of a potential at a first common line connected to the plurality of first data lines and a potential at a second common line connected to the plurality of second data lines, and switches that are controlled so that the first data lines and the second data lines are set to a connection state or an interruption state according to a comparison result by the comparison units.