Planar Transformer Winding Layout for Lower AC Resistance
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Solution Overview
Problem
Existing planar transformers for DC/DC converters face challenges in high frequency operations due to the proximity effect between conducting copper layers, which increases AC resistance and induces thermal stress, and parasitic capacitances between winding layers, forming a trade-off that current technologies fail to adequately address.
Innovation Solution
The planar transformer design comprises a stacked structure with electrically isolated layers on separate PCBs, utilizing transposed layers and interleaved pairs to reduce AC resistance and parasitic capacitance, and employs Litz-type transpositions to ensure equal current sharing, all while maintaining manufacturing simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple conducting copper layers are stacked closely together in planar transformer windings, then the transformer achieves compact size and high power density, but the proximity effect increases AC resistance and induces thermal stress
Solution Approach 1:
The patent divides the conductor into multiple transposed segments within each layer. Instead of using a single solid copper layer, the winding is segmented into multiple conductors that are transposed relative to each other, reducing the proximity effect while maintaining the compact stacked structure.
Solution Approach 2:
The patent introduces transposition of conductor segments along the length of the winding. The conductors dynamically change positions relative to each other through transposition, ensuring that no single conductor is consistently adjacent to high-current conductors throughout the entire winding length, thereby reducing AC resistance.
2Volume of moving object
If multiple conducting copper layers are stacked closely together in planar transformer windings, then the transformer achieves compact size and high power density, but thermal stress increases due to proximity effect
Solution Approach 1:
The conductor is segmented into multiple transposed segments that distribute current more evenly. This segmentation prevents localized overheating and reduces thermal stress by ensuring that no single conductor bears the full brunt of proximity effect heating throughout its entire length.
Solution Approach 2:
The transposition of conductor segments creates a dynamic arrangement where thermal loading is distributed more uniformly across all conductor segments. This dynamic repositioning prevents persistent hot spots and reduces cumulative thermal stress on any single conductor.
3Reliability
If inter-winding capacitances between layer turns of different windings are reduced, then high frequency performance improves, but manufacturing complexity increases
Solution Approach 1:
The patent segments the windings into distinct layers with controlled positioning. By dividing the winding structure into discrete, manufacturable layers on PCB substrates, the design controls parasitic capacitances while maintaining manufacturing feasibility through standard PCB fabrication techniques.
Solution Approach 2:
The patent uses PCB substrates as intermediaries between conductor layers. The PCB material acts as a controlled dielectric medium that manages inter-winding capacitances, providing both electrical isolation and mechanical support, thereby controlling parasitics without requiring complex assembly processes.
4Loss of energy
If transposed layers with multiple conductor segments are used, then AC resistance and parasitic capacitance are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent merges the transposition function with the PCB manufacturing process. Instead of requiring separate transposition operations, the conductor segments are integrated into the PCB layer structure during standard PCB fabrication, combining multiple functions into a single manufacturing step.
Solution Approach 2:
The PCB structure itself provides the transposition arrangement through its layered construction. The manufacturing process creates the transposed configuration automatically as part of the PCB fabrication, rather than requiring additional post-processing operations to achieve the transposed arrangement.
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 design effectively reduces AC resistance and parasitic capacitance, enabling high-frequency and high-current operation with improved thermal performance and manufacturing efficiency, suitable for applications like electric vehicle battery packs and wireless power transfer systems.
Implementation Method 1
DC/DC converters typically include electrical transformers to match voltage levels and ensure galvanic isolation
Implementation Method 2
the first portion and the second portion are arranged such that a layer of the first set of layers of the first portion faces a layer of the first set of layers of the second portion across an air gap
Data Source
AI summary
A planar electrical transformer for a DC/DC converter comprises first and second stacked structures. Each stacked structure comprises a set of primary winding layers comprising first and second pairs of layers, and a set of secondary winding layers comprising first and second pairs of layers. The set of secondary winding layers is arranged between the first pair of layers of the set of primary winding layers and the second pair of layers of the set of primary winding layers. The first stacked structure and the second stacked structure are arranged such that a layer of the set of primary winding layers of the first structure faces a layer of the set of primary winding layers of the second structure across an air gap.