Parallel LED Branch Balancing via Severable PCB Resistor Bridges
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Solution Overview
Problem
The challenge in vehicle lighting devices is balancing branch currents in parallel-connected LEDs during manufacturing, which leads to thermal overloading and uneven light distribution due to manufacturing tolerances and different LED specifications, making it difficult to use cost-effective voltage converters.
Innovation Solution
The method involves connecting series resistors in parallel with a conductor track on the printed circuit board, allowing for bridging and severing of these resistors using a milling cutter to balance currents, ensuring all LED branches carry the same current, thereby maintaining uniform brightness and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LED branches are connected in parallel to reduce voltage and use cost-effective converters, then converter cost is reduced, but current asymmetry occurs leading to thermal overload and reduced LED lifespan
Solution Approach 1:
The patent changes the resistance parameter by providing multiple series resistors with different resistance values in each LED branch. This allows adjustment of branch currents to compensate for asymmetries, ensuring balanced current distribution while maintaining the cost-effective parallel connection architecture with buck converters.
Solution Approach 2:
The patent segments each LED branch into multiple series resistors that can be individually selected and combined. This segmentation enables flexible configuration of total resistance per branch, allowing precise current balancing across parallel connections without requiring expensive active balancing components.
2Adaptability or versatility
If LED branches are connected in parallel to standardize voltage, then converter topology is simplified, but current asymmetry impairs homogeneity of light distribution
Solution Approach 1:
The patent adjusts the resistance parameter in each LED branch by selecting from multiple series resistors with different values. This enables independent tuning of each branch's current, ensuring uniform light output across all LEDs while maintaining the simplified buck converter topology for standardized voltage operation.
Solution Approach 2:
The patent applies local quality by providing different series resistor configurations in different LED branches. Each branch can have customized total resistance based on its specific LED characteristics, achieving local current optimization that results in global light distribution homogeneity.
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 allows for simple and cost-effective balancing of LED currents during production, enabling the use of inexpensive voltage converters and maintaining consistent light distribution across all LEDs.
Implementation Method 1
severing of a conductor track (3) provided on a circuit board (10)
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a lighting device for vehicles, having at least two LED branches (ZW1, ZW2... ZWn) connected in parallel, each branch having at least one series resistor (R1... Rn) and at least one LED (D11... Dn2) in a series circuit. The at least one series resistor (R1... Rn) of each branch (ZW1... ZWn) is bridged by a conductor portion (LA1... LAn) provided on a conductor support, said conductor portion being accessible to a tool, by means of which the conductor portion can be severed. In order to symmetrize the branches, the current flowing through each branch and/or the brightness of at least one LED in each branch is measured, and in branches in which the measured current and/or the measured brightness exceeds a specifiable threshold, the bridging conductor portion of the at least one series resistor is severed by means of the tool.