LED Backlight Driving Circuit with Dynamic Boost Control
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Solution Overview
Problem
The existing LED backlight driving circuits for large-size LCD TVs face inefficiencies in power transfer and heat loss, especially under light load conditions, as they require multiple boost circuits connected in parallel, leading to reduced transfer efficiency and increased energy loss.
Innovation Solution
The proposed LED backlight driving circuit employs N boost units connected in series and parallel, with a comparing unit that adjusts based on a PWM dimming signal, turning off boost units when the duty ratio is below a threshold, ensuring only necessary units operate, thereby optimizing power usage and reducing energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple boost circuits are used to drive LED light bars in parallel, then the output power is sufficient, but the transfer efficiency reduces and heat loss increases under light load conditions
Solution Approach 1:
The patent implements dynamic control of boost circuits by enabling or disabling specific circuits based on real-time detection of PWM dimming signal duty ratios. The control unit dynamically adjusts the number of active boost circuits to match the actual power requirements, transforming a static parallel configuration into a dynamic system that adapts to varying load conditions, thereby maintaining high transfer efficiency while providing sufficient output power when needed
Solution Approach 2:
The patent changes the operating parameters of the boost circuits by detecting the duty ratio of the PWM dimming signal and accordingly adjusting which boost circuits are activated. When the duty ratio exceeds the threshold, additional boost circuits are enabled to increase output power; when it is below the threshold, boost circuits are disabled to improve transfer efficiency and reduce energy loss, thus dynamically optimizing system performance based on parameter changes
2Power
If multiple boost circuits work simultaneously in parallel, then the power requirement is met, but the transfer efficiency is lower compared to a single boost circuit working in full load status
Solution Approach 1:
The system dynamically adjusts the number of active boost circuits based on the detected PWM duty ratio. When the duty ratio exceeds the preset threshold, the control unit enables additional boost circuits to meet the power requirement; when it is below the threshold, the control unit disables excess boost circuits, allowing the remaining active circuit(s) to operate in a more efficient full-load or near-full-load status, thereby optimizing transfer efficiency while meeting power requirements
3Illumination intensity
If PWM dimming signal duty ratio is low, then the backlight brightness is reduced, but the transfer efficiency of boost circuits reduces and heat loss increases
Solution Approach 1:
The control unit dynamically adjusts the configuration of boost circuits based on the detected PWM dimming signal duty ratio. When the duty ratio is below the preset threshold (indicating low brightness requirement), the control unit disables one or more boost circuits, allowing the remaining active circuit(s) to operate at higher load levels with improved transfer efficiency and reduced heat loss, while still meeting the reduced backlight brightness requirement
Solution Approach 2:
The system changes the operational parameters by detecting the PWM duty ratio and accordingly adjusting which boost circuits are active. When the duty ratio is low, the system reduces the number of active boost circuits, changing the system configuration to optimize for efficiency rather than maximum power output, thereby reducing heat loss while maintaining the required low brightness level
Data Source
AI summary
A light emitting diode (LED) backlight driving circuit includes a power supply, an LED light bar, and a constant current driving chip that adjusts brightness of the LED light bar. The constant current driving chip receives the PWM dimming signal. N boost units are connected in series between the power supply and the LED light bar, and the N boost units are connected in parallel with each other. Comparing units are correspondingly coupled to control ends of one or more of (N−1) boost units. When a duty ratio of the PWM dimming signal is less than a preset threshold, the comparing unit drives a corresponding boost unit to turn off. N is an integer greater than or equal to 2.