LLC Resonant Converter Electromagnetic Assembly for Common Mode Current Reduction
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Solution Overview
Problem
LLC-type resonant converters in electric or hybrid vehicle chargers experience common mode current emissions that exceed authorized thresholds, posing challenges for electromagnetic compatibility, particularly in high power converters, where existing solutions are either expensive or not compact.
Innovation Solution
An electromagnetic assembly for LLC-type resonant converters is introduced, featuring a ferrite structure with a single-phase transformer and series inductance windings arranged symmetrically around magnetic cores, along with symmetrical capacitors to eliminate common mode currents, ensuring compactness and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional LLC resonant converter structure is used, then power conversion is achieved, but common mode current emissions exceed authorized thresholds
Solution Approach 1:
The patent applies asymmetry by intentionally creating magnetic asymmetry through the asymmetrical arrangement of magnetic paths. The first magnetic path includes a ferrite plate while the second magnetic path uses an air gap, creating deliberate asymmetry that balances the common mode currents generated by the half-bridge circuit, thereby reducing electromagnetic interference and achieving compliance with electromagnetic compatibility standards.
2Ease of manufacture
If leakage inductance of transformer is used as series inductance, then cost is reduced, but this solution is only valid for low power converters
Solution Approach 1:
The patent segments the series inductance function from the transformer by providing a separate series inductance component with its own magnetic core and winding. This segmentation allows the series inductance to be independently optimized for high power applications while keeping the transformer focused on voltage transformation, enabling cost-effective manufacturing for both low and high power converters without relying on transformer leakage inductance.
3Object-affected harmful factors
If series inductance is integrated in magnetically and geometrically symmetrical manner, then common mode currents are reduced, but the solution becomes expensive and cumbersome
Solution Approach 1:
The patent applies local quality by providing asymmetry only in the specific region where it is needed for common mode current cancellation (the magnetic paths of the series inductance), while the rest of the converter structure remains simple and conventional. This localized asymmetrical design achieves electromagnetic compatibility compliance without requiring complete structural asymmetry throughout the entire device, thereby avoiding excessive complexity and cost.
4Volume of moving object
If compact design is achieved, then space is saved, but existing solutions are not compact for high power converters
Solution Approach 1:
The patent merges the series inductance and transformer into a single integrated electromagnetic assembly where the series inductance winding is coupled to the primary winding of the transformer. This merging allows the two components to share magnetic flux and physical space, achieving a compact design that can handle high power applications without requiring separate, bulky components for each function.
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 solution effectively eliminates common mode currents while maintaining a compact and inexpensive design, suitable for high power converters, thereby meeting electromagnetic compatibility standards.
Implementation Method 1
the series inductance comprising a winding wound around a second magnetic core
Implementation Method 2
said ferrite structure comprising: a first compartment housing a single-phase transformer, said single-phase transformer comprising a secondary winding wound around a first magnetic core and a primary winding wound around said secondary winding
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to an electromagnetic assembly for an LLC-type resonant converter, comprising: a first compartment housing a single-phase transformer, the secondary winding of which is wound around a first magnetic core (N1) and the primary winding of which is wound around the secondary winding, a second compartment housing the series inductor of the converter, the series inductor being wound around a second magnetic core (N2), the winding of the series inductor having a first winding wound around the second magnetic core and electrically connected to a terminal of the primary winding, the other terminal of the primary winding being electrically connected to a second winding of the series inductor, the second winding being wound around the first winding.