Logarithmic-Linear Converting Circuit for LCD Backlight Control
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Solution Overview
Problem
Existing liquid crystal display devices face challenges in maintaining visibility under varying illuminance conditions, as they either suffer from negation by intense external light or insufficient light under low illuminance, and existing backlight control methods are not adaptable to different types of external light sensors with unique input-output characteristics.
Innovation Solution
A logarithmic-linear converting circuit is introduced to convert illuminance signals from both linear and logarithmic output sensors into linear signals, allowing for uniform backlight control, and the circuit's settings can be adjusted to accommodate sensors with different characteristics, ensuring consistent backlight management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear output illuminance sensor is used, then the output signal has a linear relationship with incident light, but it cannot detect illuminance difference finely in low illuminance range
Solution Approach 1:
The patent introduces a logarithmic-linear converting circuit as an intermediary component between the logarithmic output illuminance sensor and the backlight control circuit. This converter mediates the signal transformation, converting logarithmic sensor output to linear signal format, thereby enabling fine illuminance difference detection in low illuminance ranges while maintaining compatibility with existing linear control systems.
Solution Approach 2:
The patent applies parameter changes by transforming the output signal characteristic from logarithmic to linear through the converting circuit. This parameter transformation allows the system to utilize the advantages of logarithmic sensors (fine detection in low illuminance) while presenting a linear signal that is compatible with standard backlight control algorithms.
2Measurement precision
If a logarithmic output illuminance sensor is used, then illuminance difference can be detected finely in low illuminance range, but the input-output characteristics differ among manufacturers or products
Solution Approach 1:
The patent designs the backlight control circuit with a universal logarithmic-linear converting circuit that can handle logarithmic output signals from different illuminance sensor manufacturers. The converter is configured to universally transform various logarithmic sensor outputs into standardized linear signals, enabling the system to work with multiple sensor types and manufacturers without requiring manufacturer-specific customization.
3Illumination intensity
If backlight amount is increased under intense illuminance, then visibility of display image is improved, but power consumption increases
Solution Approach 1:
The patent implements a feedback control mechanism where the backlight control circuit continuously receives illuminance information from the illuminance sensor, processes it through the logarithmic-linear converting circuit, and adjusts the backlight amount accordingly. This closed-loop feedback system automatically increases backlight under intense external light for improved visibility and reduces backlight under low illuminance conditions to minimize power consumption.
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 solution enables improved visibility and reduced power consumption in liquid crystal display devices by uniformly controlling backlight across various external light sensors, regardless of their type or characteristics, effectively addressing the limitations of previous methods.
Implementation Method 1
a logarithmic-linear converting circuit for converting an illuminance signal having a logarithmic relationship with incident light into a linear signal is provided so as to equally treat a linear signal of a linear output illuminance sensor and a logarithmic signal of a logarithmic output illuminance sensor
Data Source
AI summary
A display brightness control circuit of a liquid crystal display device includes a logarithmic-linear converting circuit for converting an illuminance signal having a logarithmic relationship with incident light into a linear signal. When an output of an external light sensor is a logarithmic signal, the logarithmic signal is converted into a linear signal through the logarithmic-linear converting circuit, and when an output of the external light sensor is a linear signal, the logarithmic-linear converting circuit is not involved. The logarithmic-linear converting circuit corresponds to an exponential circuit which is an inverse function of a logarithm log. Further, when even the same logarithmic output illuminance sensor is different in input-output characteristics, setting of the abovementioned exponential circuit can be changed.