Display Driver Circuit Luminance Compensation Flickering Reduction

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Solution Overview

Problem

LED displays experience luminance decay and screen flickering due to charge leakage in storage capacitors, which gamma correction and variable refresh rate cannot effectively compensate for, especially at lower grayscale values and frame rates.

Innovation Solution

A display driver circuit with an emission compensation circuit and an emission optimization circuit that generates a compensated emission signal by adjusting the duty cycles of emission pulses based on reference gray levels, initial emission duty cycles, and pulse counts to maintain consistent luminance and reduce flickering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If gamma correction and variable refresh rate are used to compensate for luminance decay, then luminance compensation is achieved at higher grayscale values and frame rates, but luminance compensation fails at lower grayscale values and frame rates, causing screen flickering

Engineering Contradiction:

Improveluminance compensationVSAvoidscreen flickering

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent changes the parameters of emission control by introducing emission duty cycle adjustment based on grayscale value and frame rate. The emission compensation circuit dynamically modifies the duty cycle of emission pulses according to the specific grayscale value and frame rate being used, enabling effective luminance compensation across the full range of operating conditions where traditional gamma correction fails.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamic emission control where the emission duty cycle is continuously adjusted based on real-time grayscale values and frame rates. The emission compensation circuit and optimization circuit work together to dynamically modify emission parameters, transitioning from static gamma correction to a dynamic system that adapts to varying display conditions, particularly at lower grayscale values and frame rates.

Inventive Principle:

Principle #15Dynamics

2Reliability

If variable refresh rate is used to relieve screen flickering, then flickering is reduced, but luminance decay occurs due to charge leakage in storage capacitors

Engineering Contradiction:

Improvescreen flickeringVSAvoidluminance decay

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The patent implements a feedback mechanism where the emission compensation circuit monitors the actual luminance output and adjusts the emission duty cycle accordingly. By using the grayscale value and frame rate as feedback parameters, the system continuously optimizes the emission signal to compensate for luminance decay caused by charge leakage, ensuring stable luminance output despite variable refresh rate operations.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies preliminary compensation by pre-calculating and applying emission duty cycle adjustments before the actual display refresh. The emission compensation circuit prepares compensated emission signals in advance based on the expected grayscale values and frame rates, proactively counteracting luminance decay before it manifests as visible flickering or luminance instability.

Inventive Principle:

Principle #10Preliminary action

3Illumination intensity

If emission duty cycle is increased to compensate for luminance decay, then luminance is maintained, but energy consumption increases

Engineering Contradiction:

Improveluminance maintenanceVSAvoidenergy consumption

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The patent applies local quality optimization by adjusting the emission duty cycle specifically for pixels or regions experiencing luminance decay, rather than uniformly increasing emission across the entire display. The emission optimization circuit selectively modifies emission parameters based on local grayscale values and frame rates, maintaining luminance where needed while minimizing unnecessary energy consumption in regions where compensation is not required.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent optimizes energy consumption by dynamically changing emission parameters (duty cycle) based on actual display conditions. Instead of maintaining a high fixed duty cycle, the system adjusts the emission duty cycle parameter in real-time according to grayscale values and frame rates, achieving luminance maintenance only when and where necessary, thereby reducing overall energy consumption compared to static high-duty-cycle operation.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11763738B1Display driver circuit for luminance compensation and flickering reduction and method of operating the same

Publication Date: 2023.09.19 NOVATEK MICROELECTRONICS CORP

AI summary

A display driver circuit of controlling a display panel includes an emission compensation circuit and an emission optimization circuit. The emission compensation circuit generates an emission compensation estimate according to at least a gray level, an initial emission duty cycle, and a pulse count of a number of emission pulses in a data frame of the display panel. The emission optimization circuit is coupled to the emission compensation circuit and generates a compensated emission signal according to the initial emission duty cycle and the emission compensation estimate, and drive the display panel according to the compensated emission signal.