Balanced CLLC Solid-State Transformer for Common-Mode EMI Reduction
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Solution Overview
Problem
Bi-directional DC/DC converters, particularly those using switched-mode technology, generate significant common mode electromagnetic interference (EMI) due to fast switching times, which can disrupt electrical circuits and systems.
Innovation Solution
A balanced bi-directional CLLC solid-state transformer (SST) is designed with distributed capacitance and inductance across the transformer's primary and secondary windings to mitigate common mode EMI by incorporating resonant circuits that filter and reduce this interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast switching times are used in power semiconductor devices, then voltage and current signal rise and fall times are faster, but electromagnetic interference (EMI) increases
Solution Approach 1:
The patent divides the resonant circuit into multiple segments (primary resonant circuit with L1 and C1, secondary resonant circuit with L2 and C2) distributed across the transformer windings. This segmentation allows each segment to independently contribute to EMI filtering while maintaining overall circuit functionality, thereby reducing common mode EMI without sacrificing switching speed.
Solution Approach 2:
The resonant circuits act as intermediary elements between the power semiconductor devices and the transformer. These intermediary LC circuits filter out high-frequency EMI signals generated by fast switching devices before they propagate through the transformer, thus mediating between the need for fast switching and the need to reduce EMI.
2Object-generated harmful factors
If distributed capacitance and inductance are incorporated into resonant circuits, then common mode EMI is reduced, but circuit complexity increases
Solution Approach 1:
The patent merges the EMI filtering function with the existing transformer structure by distributing resonant circuits across the primary and secondary windings. This integration allows the resonant circuits to serve dual purposes: maintaining voltage transformation functionality and filtering common mode EMI, thereby reducing overall circuit complexity compared to adding separate filtering stages.
Solution Approach 2:
The resonant circuits incorporated into the transformer structure serve multiple functions simultaneously: they provide voltage transformation through the transformer windings, filter common mode EMI through their LC resonance, and maintain bidirectional power flow capability. This multi-functionality reduces the need for additional dedicated EMI filtering components, thus managing circuit complexity.
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 balanced bi-directional CLLC SST effectively reduces common mode EMI by up to 20 dB at frequencies above 1 MHz, improving operational efficiency and minimizing interference within and outside the circuit.
Implementation Method 1
a first resonant circuit comprising a first resonant inductor and a first resonant capacitor... a second resonant circuit comprising a second resonant inductor and a second resonant capacitor
Implementation Method 2
a transformer comprising a primary winding and a secondary winding
Data Source
AI summary
A balanced bi-directional CLLC transformer circuit comprising: a first converter comprising a first set of switches; a second converter comprising a second set of switches; a transformer; a primary resonant circuit; and a secondary resonant circuit; wherein the first converter and the primary resonant circuit are electrically coupled to a primary winding of the transformer; wherein the second converter and the secondary resonant circuit are electrically coupled to a secondary winding of the transformer; wherein the primary resonant circuit is balanced across the primary winding of the transformer; and wherein the secondary resonant circuit is balanced across the secondary winding of the transformer.