Overlapping Coil Transformer Layout for Low Leakage Inductance
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Solution Overview
Problem
Transformers with horizontally disposed primary and secondary coils face increased size and undesirable high leakage inductance, particularly in slim-type designs, and low leakage inductance is required for high-frequency operation.
Innovation Solution
The transformer design includes a core unit with an upper and lower core, a bobbin unit, and coils disposed in a specific overlapping configuration, where primary and secondary coils are positioned in intersecting directions, with guide recesses guiding coil ends to overlap vertically in non-core areas, reducing horizontal size and leakage inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the primary coil and secondary coil are disposed horizontally to secure leakage inductance, then the leakage inductance is maintained, but the overall area of the transformer increases
Solution Approach 1:
The patent transitions from horizontal coil arrangement to a vertical stacking arrangement where the primary coil and secondary coil are positioned in different vertical levels. The coils are disposed in a second direction (horizontal) within an accommodation space, but overlap each other in the first direction (vertical) outside the accommodation space, effectively utilizing the third dimension to reduce the transformer's footprint area while maintaining necessary leakage inductance characteristics
2Length of stationary object
If the primary coil and secondary coil are disposed horizontally in a slim-type transformer, then the leakage inductance is secured, but the overall area of the transformer increases
Solution Approach 1:
The patent employs vertical stacking of coils in the first direction to reduce the horizontal footprint. The core unit defines an accommodation space together with the bobbin unit, and the coils are disposed in the second direction within this space, allowing the transformer to achieve a slim profile in the first direction while minimizing the area in the second direction through the overlapping vertical arrangement
3Speed
If very low leakage inductance is required for high-frequency operation in an LLC circuit, then high-frequency operation is enabled, but the horizontal coil arrangement becomes problematic
Solution Approach 1:
The vertical overlapping arrangement of primary and secondary coils outside the accommodation space creates controlled magnetic coupling that achieves very low leakage inductance values suitable for high-frequency LLC resonant converters. This three-dimensional coil configuration allows the transformer to operate at high frequencies while maintaining a compact footprint area
Solution Approach 2:
The patent modifies the spatial parameters of coil arrangement by positioning coils in intersecting directions and allowing vertical overlap outside the core area. This parameter change in coil geometry and spatial distribution enables the transformation of leakage inductance characteristics to achieve very low values required for high-frequency operation
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 achieves reduced size and leakage inductance, improving coil imbalance and direct current resistance (DCR), while maintaining compactness and efficiency.
Implementation Method 1
a transformer may be used to perform a function of transferring energy from one circuit to another circuit
Implementation Method 2
because a transformer provides only inductive coupling between a primary winding and a secondary winding without directly forming a DC path, the transformer may also be used to block direct current while passing alternating current
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A transformer of an embodiment comprises: a core portion including an upper core and a lower core disposed in a first direction opposite to the upper core; a bobbin portion disposed at least partially within the core portion; and a coil portion including a primary coil and a secondary coil disposed at least partially on the bobbin portion, wherein the core portion forms a receiving space with the bobbin portion to receive the coil portion, and the primary coil and the secondary coil are disposed in a second direction intersecting the first direction in the receiving space and are disposed to overlap each other in the first direction on the outside of the receiving space.