Dynamic LED Driver for LCD Backlight Brightness
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Solution Overview
Problem
The existing LED driver technology for liquid crystal displays (LCDs) using time-division drive results in a darker backlight due to the limited maximum duty ratio of PWM signals, as it requires fewer channels than the number of areas, leading to shorter illumination periods and reduced brightness.
Innovation Solution
A display device with light-emitting elements arranged in rows and columns, where the driver uses a dynamic driving method that alternates between driving rows and columns through different time slots, allowing for increased brightness by adjusting the duty ratio and current values, enabling brighter backlight illumination during time-division drive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If time-division drive is used to reduce the number of LED driver channels, then device complexity is reduced, but the maximum duty ratio of PWM signal decreases leading to darker backlight
Solution Approach 1:
The patent applies dynamics by making the time slot allocation flexible and adaptive rather than fixed. The driving method dynamically adjusts which rows are driven in each time slot based on predetermined conditions, allowing the system to optimize between channel reduction and brightness maintenance in real-time operation
Solution Approach 2:
The patent changes the driving parameters by varying the duty ratio and current values of PWM signals across different time slots. By adjusting these parameters, the system compensates for the reduced illumination time in time-division drive, maintaining adequate backlight brightness while using fewer driver channels
2Ease of manufacture
If LEDs are driven through division into n time slots with fewer driver channels, then ease of manufacture is improved, but the illumination time per LED decreases leading to reduced brightness
Solution Approach 1:
The patent compensates for reduced illumination time by changing PWM parameters - specifically increasing duty ratio and current values during the available illumination time slots. This parameter adjustment ensures that the total light output remains sufficient even though each LED is active for a shorter portion of the frame period
Solution Approach 2:
The patent uses periodic action by cycling through different row groups in sequential time slots within each frame period. This periodic driving pattern allows the same driver channel to serve multiple LED rows over time, simplifying manufacturing while maintaining continuous backlight illumination through the cycling pattern
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 approach enables the backlight to be lit up significantly brighter during time-division drive by optimizing the driving method based on predetermined conditions, such as screen brightness and power source status, effectively overcoming the limitations of traditional time-division LED drive systems.
Implementation Method 1
light-emitting elements disposed in a backlight divided into a plurality of areas
Data Source
AI summary
In a display device, a drive circuit drives LEDs arranged in n rows (n is an integer equal to or greater than two) so as to correspond to a plurality of areas of a backlight, row by row through division into n time slots or every k rows (k is an n's divisor equal to or greater than two and is smaller than n) through division into n/k time slots in accordance with the status of use of the display device.