LED Driver Circuit Topology for Uniform Brightness and Voltage Reduction
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Solution Overview
Problem
Existing systems for driving white light-emitting diodes (WLEDs) in portable equipment face challenges in maintaining uniform brightness due to varying current flow, which can exceed the voltage rating of available power supplies when WLEDs are connected in series, and require careful current regulation when driven in parallel.
Innovation Solution
A driver system with multiple branches of series-coupled LEDs, coupled in parallel, uses voltage-controlled current sources and control logic to regulate current based on feedback voltage measurements, ensuring consistent illumination across branches while reducing the required supply voltage and allowing for independent adjustment of current in each branch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If WLEDs are connected in series to ensure uniform current flow, then uniform brightness is improved, but the voltage required exceeds the power supply rating
Solution Approach 1:
The patent divides the WLED array into multiple parallel branches, with each branch containing series-coupled WLEDs. This segmentation allows the system to maintain uniform current flow within each branch while distributing the voltage requirement across multiple parallel paths, preventing any single branch from exceeding power supply ratings.
Solution Approach 2:
The patent applies different configuration strategies to different parts of the WLED array by creating multiple parallel branches with series-coupled WLEDs within each branch. This local differentiation allows uniform brightness to be achieved within each branch while the parallel structure overall manages voltage requirements.
2Power
If WLEDs are connected in parallel to reduce voltage requirements, then power supply voltage rating is reduced, but current regulation becomes more complex to maintain uniform brightness
Solution Approach 1:
The patent segments the WLED array into multiple parallel branches, where each branch contains series-coupled WLEDs. This segmentation simplifies current regulation because each branch can be independently controlled with simpler circuitry, avoiding the need for complex regulation across all parallel WLEDs simultaneously.
Solution Approach 2:
The patent regulates current at the branch level rather than at the individual WLED level within each branch. This partial regulation approach is sufficient to maintain uniform brightness while significantly reducing the complexity of current regulation circuitry compared to regulating each WLED individually.
3Stability of the object's composition
If multiple current sources are used to regulate current in each branch, then uniform current distribution is improved, but device complexity increases
Solution Approach 1:
The patent employs control logic that can selectively activate specific current sources based on which WLEDs require regulation. This multi-functional control logic serves multiple purposes: regulating current in different branches, selecting which WLEDs need adjustment, and coordinating multiple current sources, thereby managing complexity through universal control functionality.
Solution Approach 2:
The patent applies current regulation selectively to specific branches or WLEDs that exhibit non-uniform brightness characteristics. Rather than applying uniform regulation across all WLEDs, the system tailors current source activation and regulation strength to the local needs of each branch or WLED, improving current uniformity while avoiding unnecessary complexity.
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
The system maintains uniform brightness across WLEDs, reduces the need for high-voltage power supplies, and allows for efficient use of smaller power supplies, enabling consistent and predictable illumination in mobile electronic devices.
Implementation Method 1
The control logic is coupled to the current sources, and is configured to regulate current through each branch based at least in part on a feedback voltage measured at a node in one of the branches
Implementation Method 2
White light-emitting diodes (WLEDs) are increasingly being used as backlights in portable equipment
Implementation Method 3
the brightness of a WLED is proportional to the current flowing through the WLED
Data Source
AI summary
At least some embodiments include a LED driver system. The system includes multiple branches of series-coupled LEDs, multiple current sources, and control logic. Each of the current sources is coupled to a separate branch of series-coupled LEDs. The control logic is coupled to the current sources, and is configured to regulate current through each branch based at least in part on a feedback voltage measured at a node in one of the branches.