Power Module EMI Reduction via Magnetic Bus Coatings
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Solution Overview
Problem
Power modules generate high frequency harmonics that result in electromagnetic interference (EMI), affecting both the module's operation and surrounding electrical devices due to parasitic capacitive coupling and common mode currents.
Innovation Solution
The implementation of high permeability magnetic coatings on bus terminals, internal capacitors (X and Y capacitors) within the power module packaging, and the use of magnetic cores and conductive materials like metal flashing to redirect and filter EMI currents, reducing loop inductance and enhancing filtering efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high frequency harmonics are generated by switching devices, then power conversion efficiency is improved, but electromagnetic interference increases
Solution Approach 1:
A common mode choke is introduced as an intermediary component between the switching device and the power buses. This choke acts as a mediator that allows the high frequency switching signals to pass through for efficient power conversion while simultaneously blocking and filtering the resulting electromagnetic interference and common mode currents, thus resolving the contradiction between productivity and harmful emissions
Solution Approach 2:
The patent converts the harmful high frequency harmonics and common mode currents into a beneficial filtering action. The common mode choke utilizes the harmful electromagnetic signals to induce currents that are then dissipated through the housing and grounding paths, effectively transforming the EMI problem into a self-filtering mechanism that protects against electromagnetic interference
2Reliability
If common mode currents are generated through parasitic capacitive coupling, then power conversion function is maintained, but electromagnetic interference affecting surrounding devices increases
Solution Approach 1:
The patent extracts and isolates the common mode currents generated by parasitic capacitive coupling from the main power conversion path. The common mode choke separates these harmful currents and directs them through dedicated filtering paths (housing and grounding) away from the power buses and surrounding devices, maintaining power conversion reliability while eliminating EMI effects on external equipment
3Object-generated harmful factors
If external filters are used to reduce electromagnetic interference, then electromagnetic interference is reduced, but device complexity and component size increase
Solution Approach 1:
The patent merges the EMI filtering function with the existing power module housing and structural components. The housing is designed to serve dual purposes: mechanical protection and electromagnetic shielding/filtering. By integrating the common mode choke and filtering paths into the housing structure itself, the patent eliminates the need for separate external filters, reducing overall device complexity and component size while maintaining effective EMI reduction
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
This approach effectively dampens EMI close to its source, reducing the need for external filters and allowing the use of lower-rated, smaller components, thereby minimizing operational disruptions and component costs.
Implementation Method 1
The input bus includes a first coating of a high permeability magnetic conductive material... The output bus includes a second coating of the high permeability magnetic conductive material
Implementation Method 2
A metal flashing is disposed between the switching device and the housing to enable the metal flashing to capture electric fields generated during operation of the power model and to direct the induced current to the positive input bus, the negative input bus, or both
Implementation Method 3
The switching device is electrically coupled to the first input bus, and is configured to selectively connect and disconnect to facilitate converting the input DC electrical power into output alternating current (AC) electrical power
Data Source
AI summary
A power module includes an input bus, a switching device, and an output bus. The input bus includes a first coating of a high permeability magnetic conductive material and is configured to receive input direct current (DC) electrical power from an electrical power source. The switching device is electrically coupled to the first input bus, and is configured to selectively connect and disconnect to facilitate converting the input DC electrical power into output alternating current (AC) electrical power. The output bus includes a second coating of the high permeability magnetic conductive material, and is electrically coupled to the first switching device. The output bus is configured to supply the output AC electrical power to an electrical load.