Backlight Driving Module Brightness Control Modes
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Solution Overview
Problem
Current backlight drivers for display devices face issues with low luminous efficiency in pulse width modulation and spectral variation in current control, leading to color shift problems.
Innovation Solution
A display device with a compound backlight driver that employs two driving modes: one adjusting brightness by duty ratio for lower ranges and another by current value for higher ranges, mitigating the limitations of existing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pulse width modulation control is used to drive the backlight, then the driving method is simple, but the luminous efficiency is low under high driving current
Solution Approach 1:
The patent dynamically switches between two driving modes based on the required brightness level. For low brightness ranges, pulse width modulation is used to maintain simple driving control. For high brightness ranges, current control is activated to improve luminous efficiency. This dynamic adaptation resolves the contradiction by selecting the appropriate driving method based on operational conditions.
Solution Approach 2:
The patent changes the driving parameter from duty ratio adjustment (PWM) to current value adjustment (current control) based on the brightness range. By transitioning between different control parameters depending on the operating point, the system achieves both simple driving control and high luminous efficiency where needed.
2Loss of energy
If current control is used to improve luminous efficiency, then the luminous efficiency is improved, but a digital-to-analog converter is required which increases circuit cost and causes spectral variation leading to color shift
Solution Approach 1:
The patent segments the brightness control range into two parts: low brightness range controlled by PWM and high brightness range controlled by current control. By dividing the operating range, the system applies current control only when necessary for efficiency, avoiding the need for continuous use of complex DAC circuits and minimizing spectral variation effects.
Solution Approach 2:
The patent dynamically selects the driving mode based on brightness requirements. Current control with DAC is activated only when high luminous efficiency is needed at high brightness levels, rather than being continuously applied. This dynamic selection reduces the impact of spectral variation and color shift by limiting current control to specific operating conditions.
Data Source
AI summary
A display device includes: a display panel having a light-tuning array; a backlight module providing a backlight to the light-tuning array; and a backlight driving module electrically connected with the backlight module. The backlight driving module has a first driving mode corresponding to a first range of brightness scale and a second driving mode corresponding to a second range of brightness scale. The first driving mode controls the brightness scale corresponding to the backlight by adjusting a duty ratio of a driving signal. The second driving mode controls the brightness scale corresponding to the backlight by adjusting a current value of the driving signal.