Display Controller Common Voltage Adjustment for Flicker Reduction

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Solution Overview

Problem

Thin film transistor (TFT)-liquid crystal display (LCD) systems experience flickering due to pixel voltage unbalance between positive and negative polarities when switching to lower frame rates, which existing methods attempt to mitigate by reducing leakage current, increasing development and manufacturing costs.

Innovation Solution

Adjusting the common voltage (Vcom) to balance pixel voltages across different frame rates, such as from 60 Hz to 40 Hz, without reducing leakage current, by determining optimal Vcom values for each frame rate and storing them for recall when switching, thus reducing flicker and power consumption without the need for complex oxide TFT backplanes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the frame rate is reduced to save power, then power consumption decreases, but display artifacts like flickering occur due to pixel voltage unbalance

Engineering Contradiction:

Improvepower consumptionVSAvoiddisplay artifacts (flickering)

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent changes the common voltage parameter dynamically based on the frame rate. When switching from 60Hz to 40Hz, the common voltage is adjusted from a first value to a second value to compensate for increased leakage current effects at lower refresh rates, thereby maintaining pixel voltage balance and eliminating flicker while preserving power savings

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system dynamically adjusts the common voltage in response to frame rate changes. The display controller monitors the current frame rate and automatically selects the appropriate common voltage value, making the system adaptive to different operating conditions without manual intervention

Inventive Principle:

Principle #15Dynamics

2Reliability

If oxide TFT backplanes are used to reduce leakage current, then pixel voltage unbalance decreases, but development and manufacturing costs increase

Engineering Contradiction:

Improvepixel voltage balanceVSAvoiddevelopment and manufacturing costs

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of changing the physical structure of the TFT backplane, the patent changes the electrical parameter (common voltage) to achieve the same effect of reducing pixel voltage unbalance. This software-based solution avoids the high costs associated with oxide TFT backplane manufacturing while achieving comparable performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the physical/material solution (oxide TFT backplane) with an electrical control solution (dynamic common voltage adjustment). This substitution achieves the same functional outcome of reducing leakage current effects without the complexity and cost of specialized materials and manufacturing processes

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If the common voltage is adjusted to balance pixel voltages at lower frame rates, then flicker is reduced, but the system complexity increases due to multiple voltage values

Engineering Contradiction:

ImproveflickerVSAvoidmultiple common voltage values

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent pre-determines and stores the optimal common voltage values for different frame rates before operation. The display controller has a lookup table or memory containing the first common voltage value for 60Hz and the second common voltage value for 40Hz, eliminating the need for real-time calculation or complex control logic during operation

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11335291B2Display controller with multiple common voltages corresponding to multiple refresh rates

Publication Date: 2022.05.17 INTEL CORP

AI summary

A display controller for a display may include a frame rate circuit to change a frame rate of the display from a first frame rate to a second frame rate, and a reference voltage circuit to adjust a reference voltage of the display from a first reference voltage corresponding to the first frame rate to a second reference voltage corresponding to the second frame rate. The display may be a thin film transistor liquid crystal display. The reference voltage may correspond to a common voltage (Vcom) for the display.