PCB Planar Transformer Layout for Balanced MMF in Resonant Converters
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Solution Overview
Problem
Conventional resonant converters are bulky due to their transformer structure, leading to poor power density and inefficient heat dissipation, as the magnetomotive force is biased, increasing AC impedance and line losses.
Innovation Solution
A planar transformer with a specific stacked structure is implemented, where primary-side and secondary-side traces on a circuit board generate balanced magnetic fluxes using an iron core, maintaining magnetomotive force balance and reducing size and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional transformer structure with wound coils and iron cores is used, then magnetic circuit is closed, but the size becomes bulky and power density decreases
Solution Approach 1:
The patent replaces the traditional mechanical winding structure with planar printed circuit board traces to form the transformer coils. This substitution eliminates the need for manual wire winding and bulky three-dimensional coil structures, enabling a flat, integrated transformer design that significantly reduces size while maintaining electrical functionality.
Solution Approach 2:
The patent transitions from traditional three-dimensional wound coil structures to two-dimensional planar traces on a circuit board. This dimensional reduction allows the transformer to be integrated directly into the PCB layout, eliminating the need for separate bulky components and achieving compact form factor with high power density.
2Device complexity
If conventional transformer coil arrangement is used, then structure is simple, but magnetomotive force becomes biased causing increased AC impedance and line losses
Solution Approach 1:
The patent employs asymmetric stacking arrangements of primary and secondary trace layers, where odd-numbered layers contain primary traces and even-numbered layers contain secondary traces. This asymmetric configuration, combined with specific winding directions, creates balanced magnetomotive force that eliminates bias and reduces AC impedance and line losses.
Solution Approach 2:
The patent divides the transformer into multiple stacked layers with alternating primary and secondary traces. This segmentation allows independent optimization of each layer's trace pattern and winding direction, enabling precise control over magnetic flux distribution and magnetomotive force balance while maintaining structural organization.
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 planar transformer achieves reduced size, increased power density, and improved heat dissipation by balancing magnetomotive force, reducing AC eddy current losses and leakage inductance, thereby enhancing efficiency.
Implementation Method 1
the primary-side traces respectively generate a first direction magnetic flux
Implementation Method 2
the secondary-side traces respectively generate a second direction magnetic flux
Implementation Method 3
The primary-side traces and the secondary-side traces are configured in a specific stacked structure to maintain the first direction magnetic flux and the second direction magnetic flux within a specific range formed by a magnetic flux origin and a first predetermined offset and a second predetermined offset, so that a magnetomotive force of the planar transformer remains balanced
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A planar transformer (2A) is configured on a multi-layer circuit board (CB 1) of a resonant converter (100). The planar transformer (2A) includes multiple layers of primary-side traces (Tp1), multiple layers of secondary-side traces (Ts1), and an iron core (C1). The primary-side traces (Tp1) serve as a primary-side coil (22A) of the transformer to generate a first direction magnetic flux (F_D1) when the resonant converter (100) operates. The secondary-side traces (Ts1) serve as a secondary-side coil (24A) of the transformer to generate a second direction magnetic flux (F_D2) when the resonant converter (100) operates. The primary-side traces (Tp1) and the secondary-side traces (Ts1) surround a first core pillar (C12) and the second core pillar (C14), and the primary-side traces (Tp1) and the secondary-side traces (Ts1) are configured in a specific stacked structure on the multi-layer circuit board (CB1), so that a magnetomotive force (MMF) of the planar transformer (2A) can maintain balance during the operation of the resonant converter (100).