Planar Transformer Coil Stacking for Lower Parasitic Capacitance
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Solution Overview
Problem
Planar transformers in low-voltage DC to DC converters for eco-friendly vehicles face issues with increased common noise and reduced efficiency due to high coupling coefficients and parasitic capacitance, which affect power density and size requirements.
Innovation Solution
A planar transformer design with optimized winding structure, including primary and secondary coil elements on a flat plate with varying insulating sheet thicknesses and core configurations, reduces parasitic capacitance and enhances efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If primary and secondary windings are replaced with PCB pattern to reduce transformer size, then the transformer volume is reduced, but the coupling coefficient between primary and secondary windings increases
Solution Approach 1:
The secondary winding is divided into multiple secondary coil elements that are spatially separated and arranged in different layers. This segmentation reduces the parasitic capacitance between primary and secondary windings by increasing the distance and adding insulation layers, thereby reducing common noise while maintaining the compact PCB-based structure.
Solution Approach 2:
The patent transitions from a planar two-dimensional PCB pattern to a three-dimensional multi-layer structure with insulating sheets between layers. By utilizing the vertical dimension with stacked primary and secondary coil elements separated by insulation, the design reduces parasitic capacitance while maintaining compact volume.
2Volume of moving object
If PCB pattern is used for windings to reduce size, then transformer dimensions are reduced, but current-conducting area decreases and efficiency is reduced
Solution Approach 1:
The patent implements a nested multi-layer structure where primary and secondary coil elements are stacked in different layers with insulating sheets between them. This nesting approach maximizes the current-conducting area within a compact volume by utilizing vertical space, thereby improving efficiency while maintaining reduced dimensions.
Solution Approach 2:
The patent uses composite construction combining PCB traces with additional copper plating or thicker copper layers on specific layers to increase current-conducting area. This composite approach allows the transformer to maintain compact size while providing sufficient current-carrying capacity for high efficiency.
3Volume of moving object
If coupling coefficient between primary and secondary windings is increased, then transformer size is reduced, but resonant waveform magnitude of leakage inductance and parasitic capacitance increases
Solution Approach 1:
By segmenting the secondary winding into multiple coil elements arranged in different layers and separated by insulating sheets, the patent reduces the overall parasitic capacitance between primary and secondary windings. This segmentation allows for a compact design while controlling the resonant waveform magnitude by reducing the total parasitic capacitance.
4Reliability
If insulating sheet thickness between primary and secondary coil elements is increased, then electrical insulation is improved, but transformer volume increases
Solution Approach 1:
The patent applies different insulating sheet thicknesses at different locations based on local requirements. Thicker insulation is used where voltage stress is highest (between primary and secondary), while thinner insulation is used where less insulation is needed, optimizing the balance between electrical insulation and compact volume.
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 optimized design reduces common noise and improves efficiency, leading to enhanced power density and reduced size, while maintaining electrical insulation and electromagnetic performance.
Implementation Method 1
a plurality of secondary coil elements included on the flat plate and having an induced current generated by the primary coil elements
Data Source
AI summary
Provided is a planar transformer, and more particularly, a planar transformer including: a plurality of primary coil elements included on a flat plate and laminated together; and a plurality of secondary coil elements included on the flat plate and having an induced current generated by the primary coil elements, wherein the plurality of secondary coil elements are respectively disposed above and below the primary coil element.