RF Power Transformer Using Multilayer PCB and Ferromagnetic Core
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Solution Overview
Problem
Existing high-frequency power transformers are costly to manufacture and suffer from non-optimal magnetic coupling and energy losses due to complex thermally conductive substrates, making them inefficient for integration in electronic circuits.
Innovation Solution
A high-frequency power transformer is designed using a low-cost multilayer printed circuit board with stacked conductive and dielectric layers, featuring a magnetic core and capacitive coupling between windings to minimize losses and optimize impedance matching, with ferrite ferromagnetic blocks and compensation capacitors for improved impedance control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermally conductive substrate is used to dissipate heat, then thermal management is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The standard FR4 substrate serves its traditional insulation function while the separate ferromagnetic block handles thermal management, allowing each component to perform its designated function without requiring the substrate to be specially modified for thermal conduction
Solution Approach 2:
The transformer is divided into distinct functional components: the printed circuit board handling electrical insulation and signal routing, and a separate ferromagnetic block handling magnetic flux and thermal dissipation, which can be manufactured independently and assembled together
2Loss of energy
If wire windings on ferromagnetic cores are used, then magnetic coupling is improved, but manufacturing cost increases
Solution Approach 1:
The manual wire winding process is replaced with automated printed circuit board fabrication techniques, where copper traces are deposited and etched onto the substrate, eliminating labor-intensive winding operations while maintaining consistent magnetic coupling through standardized trace geometries
Solution Approach 2:
The winding geometry is defined by controllable PCB parameters such as trace width, trace spacing, and copper thickness, which can be precisely adjusted through standard PCB manufacturing processes to optimize magnetic coupling without requiring manual intervention
3Ease of manufacture
If printed coils are used, then manufacturing is simplified, but magnetic coupling and energy losses deteriorate
Solution Approach 1:
The transformer combines printed circuit board traces with a ferromagnetic block, creating a composite structure that leverages the manufacturing simplicity of PCBs while using the ferromagnetic material to concentrate and guide magnetic flux, thereby improving coupling efficiency despite the printed nature of the coils
4Ease of manufacture
If standard ferromagnetic blocks are used, then manufacturing cost is reduced, but magnetic field concentration deteriorates
Solution Approach 1:
The ferromagnetic block is positioned specifically at the center of the PCB traces where magnetic flux density is highest, providing localized magnetic field concentration exactly where needed to improve coupling between primary and secondary windings, rather than using ferromagnetic material throughout the entire structure
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 solution results in a cost-effective, high-performance transformer with reduced magnetic coupling losses and improved impedance matching, capable of operating efficiently in the 1 MHz to 50 MHz frequency range with powers up to several watts, while simplifying integration into electronic circuits.
Implementation Method 1
the widths of the turns of s windings being chosen according to the thicknesses of the dielectric substrate layers, the instantaneous frequency band and the power of the high-frequency signal passing through the transformer in order to minimize losses and promote impedance matching in the RF band considered. Thus, the primary winding is clamped by the secondary winding, the choice of the width of the lines and of the thickness of the layers of substrate making it possible to optimize the capacitive coupling between the windings.
Implementation Method 2
the ferromagnetic block comprising two parts assembled to form a binocular block, each part of said block occupying one side of the printed card, the first part of said block being formed of an extruded E, the central branch of the E being inserted into the hole formed in the center of the printed circuit board, thus forming a magnetic core in the center of the windings, the second part of said block being formed of a substantially flat plate. The presence of a magnetic core makes it possible in particular to obtain a better concentration of the magnetic field.
Implementation Method 3
Power transformers are generally made by wire windings on cores of ferromagnetic materials. A high-frequency power transformer comprises a primary winding and a secondary winding
Data Source
Figure 1
Figure 2~4
Figure 3a~3b
AI summary
The present invention relates to a power transformer for radiofrequency signals. The transformer is made in a low-cost multilayer printed circuit card (201) comprising at least successively the following stacked layers: a first conducting layer, a first dielectric substrate layer, a second conducting layer, a second dielectric substrate layer, and a third conducting layer, the primary winding being formed by a turn printed in the second conducting layer, the secondary winding (103) being formed by a first turn printed in the first conducting layer, this first turn being linked to a second turn printed in the third conducting layer, the turns of the secondary winding being placed opposite the turn of the primary, the card being clamped above and below by two plates of ferromagnetic material. Capacitive components connected between winding(s) and an exposed conductive part can improve the performance of the proposed transformer.