LED Backlight Brightness Adjustment via Dynamic Current and PWM Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LED backlight brightness adjustment methods, such as PWM dimming, result in lower luminous efficiency, increased backlight loss, and noise generation in LED drive circuits due to fixed current levels and frequency ranges within human hearing frequencies.
Innovation Solution
The method involves adjusting LED backlight brightness by maintaining a maximum PWM duty ratio when brightness is above a preset value and adjusting the conduction current, and using constant conduction current with varying PWM duty ratio when brightness is below the preset value, thereby optimizing luminous efficiency and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM dimming is used to adjust LED backlight brightness, then brightness adjustment is achieved, but LED luminous efficiency decreases and backlight loss increases
Solution Approach 1:
The patent dynamically switches between two dimming modes (PWM dimming and conduction current dimming) based on the required brightness level. At high brightness levels, conduction current dimming is used to maintain high luminous efficiency, while at low brightness levels, PWM dimming is used to achieve precise brightness control. This dynamic adaptation resolves the contradiction by selecting the optimal control method for each operating condition.
Solution Approach 2:
The patent changes the operating parameters of the LED drive circuit by adjusting either the conduction current or the PWM duty ratio based on the required brightness level. By changing which parameter is adjusted (current vs. duty ratio), the system optimizes luminous efficiency at high brightness and achieves precise control at low brightness, resolving the energy loss contradiction.
2Illumination intensity
If fixed current is used for PWM dimming, then brightness adjustment is achieved, but noise is generated in the LED drive circuit
Solution Approach 1:
The patent dynamically selects between conduction current dimming and PWM dimming based on the brightness level. At high brightness levels where PWM would generate audible noise, the system uses conduction current dimming instead. This dynamic switching avoids the noise problem while maintaining brightness adjustment capability.
Solution Approach 2:
The patent converts the potential harm of PWM noise into a benefit by using conduction current dimming at high brightness levels where PWM would be problematic. The system exploits the advantage of conduction current dimming (no noise) in the brightness range where PWM would cause harm, while using PWM where it is beneficial for precise control.
Data Source
AI summary
An adjustment method for LED backlight brightness, comprising the following steps of: if the current LED backlight brightness is greater than a preset value, maintaining the PWM duty ratio as the maximum value, and adjusting the LED backlight brightness by adjusting an LED conduction current (S10); and if the current LED backlight brightness is not greater than the pre-set value, maintaining the LED conduction current to be constant, and adjusting the LED backlight brightness by adjusting the change of the PWM duty ratio between the maximum value and the minimum value (S20). This method can improve the light-emitting efficiency of LEDs, reduce backlight loss, and reduce the noise generated by an LED drive circuit.