Multiple-Legged Transformer Current Balancing for CCFLs
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Solution Overview
Problem
Current balancing in Cold Cathode Fluorescent Lamps (CCFLs) is challenging, especially under open lamp conditions, as existing techniques are either complex and expensive or fail to provide balanced current sharing effectively.
Innovation Solution
A single multiple-legged transformer with multiple windings is employed to achieve balanced currents across lamps, using configurations like zig-zag and star-delta connections, reducing the number of magnetic cores and manufacturing costs while enabling current balancing under open lamp conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If independently controlled inverters are used for each lamp, then current sharing accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple current balancing functions into a single shared transformer with multiple windings, where each winding corresponds to one lamp. This merging approach achieves accurate current sharing for multiple lamps without requiring separate inverters for each lamp, thereby reducing device complexity while maintaining measurement precision.
2Device complexity
If a single inverter drives all lamps, then device complexity is reduced, but current balancing capability deteriorates
Solution Approach 1:
The patent segments the single inverter output into multiple independent current paths through a transformer with multiple windings. Each winding provides isolated current control for individual lamps, enabling precise current balancing while maintaining the simplicity of a single inverter architecture.
3Ease of manufacture
If conventional current balancing transformers are used, then manufacturing cost is reduced, but reliability under open lamp conditions deteriorates
Solution Approach 1:
The patent designs the transformer with a specific winding configuration where the magnetic circuit is structured to tolerate open lamp conditions. The multi-winding transformer maintains magnetic balance and current distribution even when one or more lamps are open, providing beforehand cushioning against failure modes without increasing manufacturing 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
This approach provides accurate current balancing, reduces manufacturing costs, and allows for compact designs that maintain balanced current sharing even when some lamps are not operational, enhancing the reliability and efficiency of CCFL systems.
Implementation Method 1
A single multiple-legged transformer with multiple windings is employed to achieve balanced currents across lamps
Implementation Method 2
A single multiple-legged transformer with multiple windings is employed to achieve balanced currents across lamps, using configurations like zig-zag and star-delta connections
Data Source
AI summary
Methods and apparatus are disclosed for balancing currents passing through multiple parallel circuit branches and in some cases through parallel fluorescent lamps. Single transformers with multiple-leg magnetic cores are wound in specific manners that simplify current balancing. Conventional three-legged EE-type magnetic cores, with disclosed windings are used to balance current in circuits with three or more parallel branches, such as parallel connected Cold Cathode Fluorescent Lamps (CCFLs).