Bottom-Shielded Transformer Layout for EMI and Heat Reduction
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Solution Overview
Problem
Conventional isolation voltage converters using transformers face challenges with heat generation and electromagnetic interference (EMI), as the transformer is often the largest source of heat and can act as a dipole antenna generating EMI due to asymmetries and parasitic capacitance.
Innovation Solution
A four-layer or six-layer transformer structure is implemented on a substrate, with conductive layers forming windings and Faraday shields that also function as heat sinks, providing a path to ground for common mode currents and reducing EMI by offering a lower impedance path for common mode currents instead of allowing them to cross the barrier, thereby reducing heat and EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional transformer structure is used, then device complexity is reduced, but electromagnetic interference increases and heat generation increases
Solution Approach 1:
The transformer structure is segmented into multiple conductive layers (first through fourth conductive layers) with EMI shields positioned between the windings. This segmentation allows the transformer to be divided into functional zones: primary winding, EMI shield, secondary winding, and another EMI shield, enabling simultaneous achievement of electromagnetic shielding and heat management without requiring a completely separate shielding structure.
Solution Approach 2:
The EMI shields serve multiple functions simultaneously: they act as electromagnetic interference shields to reduce EMI, function as heat sinks to conduct heat away from the windings, and provide thermal pathways to ground. This multi-functionality resolves the contradiction by eliminating the need for separate EMI shielding components while still achieving the required electromagnetic protection.
2Loss of energy
If transformer is used for voltage conversion, then energy transfer is achieved, but heat generation increases
Solution Approach 1:
The EMI shields act as intermediary elements positioned between the primary and secondary windings. These shields serve as thermal mediators that conduct heat away from the high-power windings without interfering with the electromagnetic energy transfer function. The shields provide a dedicated thermal pathway that separates the heat management function from the power transfer function, allowing efficient energy transfer while reducing heat accumulation in the transformer core.
3Object-affected harmful factors
If asymmetries and parasitic capacitance are present in transformer, then winding configuration is simplified, but electromagnetic interference increases
Solution Approach 1:
The EMI shields are extracted as separate conductive layers positioned between the windings, rather than being integrated into the winding structure itself. This extraction approach allows the shields to be independently optimized for EMI reduction while the windings maintain their simplified configuration for ease of manufacture. The shields are taken out as distinct functional elements that address the EMI problem without complicating the winding process.
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 effectively reduces heat dissipation and electromagnetic interference by using Faraday shields as both EMI reduction and thermal load shedding elements, improving the efficiency and performance of the isolation voltage converter.
Implementation Method 1
The first conductive layer is on the substrate and includes a first electromagnetic interference (EMI) shield. The third conductive layer is over the second conductive layer opposite the first conductive layer and includes a second EMI shield.
Implementation Method 2
A four-layer or six-layer transformer structure is implemented on a substrate, with conductive layers forming windings and Faraday shields that also function as heat sinks, providing a path to ground for common mode currents and reducing EMI by offering a lower impedance path for common mode currents instead of allowing them to cross the barrier, thereby reducing heat and EMI.
Implementation Method 3
One die includes a circuit coupled to the primary winding of the transformer and includes a switching network to convert the DC input voltage to a switching waveform to transfer energy through from the primary winding to the secondary winding of the transformer.
Data Source
AI summary
An apparatus includes a substrate and first through fourth conductive layers. The first conductive layer is on the substrate and includes a first electromagnetic interference (EMI) shield. The second conductive layer is over the first conductive layer opposite the substrate and includes a first winding of a transformer. The third conductive layer is over the second conductive layer opposite the first conductive layer and includes a second EMI shield. The fourth conductive layer is over the third conductive layer opposite the second conductive layer and includes a second winding of the transformer.