Hybrid Dimming Control Circuit for Display Backlight Flicker Reduction
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Solution Overview
Problem
High-resolution display devices face image quality degradation and longer response times due to flicker phenomena in LED backlight units and increased dimming data complexity, particularly in high-resolution displays like 4K or 8K resolutions, which require more channels for local dimming control.
Innovation Solution
A hybrid dimming control device and method that includes an analysis circuit to determine dimming data types, using PWM dimming control for low-grayscale data and active dimming control for high-grayscale data, reducing channel count and latency by connecting multiple dimming control devices in a daisy-chain manner to a microcontroller unit, allowing each device to process and transmit data efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM signal is used to control LED backlight unit, then local dimming is achieved, but flicker phenomenon occurs causing image quality degradation
Solution Approach 1:
The patent changes the control parameter from PWM duty cycle to analog voltage level. Instead of using pulse width modulation which causes flicker, the system uses direct analog voltage control where the voltage level directly corresponds to the desired brightness level, eliminating the flicker phenomenon while maintaining local dimming capability
Solution Approach 2:
The patent replaces the PWM control mechanism with an analog voltage control mechanism. By substituting the temporal modulation approach (PWM) with a direct voltage level approach, the system achieves smooth brightness transitions without the flicker artifacts associated with PWM switching
2Illumination intensity
If multiple channels are used for high-resolution display local dimming, then detailed local dimming control is achieved, but response time increases beyond one frame period
Solution Approach 1:
The patent implements preliminary action by having the dimming control device determine the dimming data type and prepare the appropriate processing method in advance, before the actual dimming control is executed. This allows the system to process multiple channels simultaneously without sequential delays, maintaining response time within one frame period
Solution Approach 2:
The patent segments the dimming data into different types (first type and second type) with different processing requirements. By categorizing data in advance, the system can apply optimized processing paths for each type, improving overall processing efficiency and reducing response time for high-resolution displays with multiple channels
3Productivity
If dimming data type determination is implemented, then processing efficiency is improved, but device complexity increases
Solution Approach 1:
The patent uses parameter changes by examining specific bit patterns (MSB and LSB values) in the dimming data to determine the data type. This approach requires only simple bitwise comparisons rather than complex analysis, achieving efficient data type determination with minimal additional circuit complexity
Solution Approach 2:
The patent applies local quality by implementing the type determination logic only where needed in the data path, specifically at the dimming control device that receives the dimming data. Rather than adding complexity throughout the entire system, the solution localizes the processing logic to the specific component that benefits from it
Data Source
AI summary
A hybrid dimming control device, which prevents image quality degradation during local dimming of a backlight unit, includes an analysis circuit configured to determine a type of dimming data for controlling the local dimming of a light source included in a backlight unit by analyzing the dimming data, a pulse width modulation (PWM) dimming control circuit configured to control the local dimming of the light source by a PWM method when the type of the dimming data is a first type, and an active dimming control circuit configured to convert some bits of the dimming data into an analog signal and control the local dimming of the light source using the analog signal when the type of the dimming data is a second type.