Non-Circular EMI Choke Layout for Higher Inductance
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Solution Overview
Problem
Conventional EMI filters with circular magnetic cores face limitations in increasing inductance and safety distance, leading to design challenges and large device volumes due to fixed inner diameters and diagonal winding arrangements, which restrict the number of turns and layout flexibility on circuit boards.
Innovation Solution
An EMI filter system utilizing a non-circular magnetic core, such as an oval ring-shape or wave ring-shape core, allows for increased inner diameter, sufficient winding distance, and flexible capacitor placement, enabling more windings and capacitors to be arranged in series or parallel, thereby enhancing inductance and space utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of turns of the coils is increased to increase inductance, then the inductance is improved, but the inner diameter of the circle-shape magnetic core limits the maximum number of turns and coils that can be wound
Solution Approach 1:
The patent changes the circular magnetic core to an oval-shaped magnetic core. This asymmetric shape provides a larger inner diameter in certain directions, allowing more coils to be wound around the magnetic core without increasing the overall footprint of the component. The oval shape specifically enables increased coil quantity while maintaining compact dimensions.
2Reliability
If a larger-sized circle-shape magnetic core is adopted to increase inductance and meet safety distance requirements, then the inductance and safety distance are improved, but the device volume increases
Solution Approach 1:
The oval-shaped magnetic core provides asymmetric dimension distribution that optimizes space utilization. The longer axis of the oval provides sufficient safety distances in critical directions while the shorter axis minimizes the overall device volume. This allows meeting safety requirements without proportionally increasing all dimensions of the device.
Solution Approach 2:
The patent transitions from a circular cross-section to an oval cross-section, effectively utilizing a different geometric dimensioning approach. This dimensional change allows the magnetic core to provide adequate safety distances in specific directions (along the major axis) while maintaining a compact overall footprint, rather than uniformly increasing size in all directions.
3Quantity of substance
If three coils are wound on the circle-shape magnetic core in a diagonal manner, then the inductance is achieved, but the outlet positions of the pins are deflected at oblique angles making circuit board layout difficult
Solution Approach 1:
The oval-shaped magnetic core changes the geometric symmetry from circular to elliptical, which naturally aligns the coil winding axes with the principal axes of the oval. This results in pin outlet positions that are oriented at convenient angles (typically 0°, 90°, or other standard angles) relative to the oval's axes, making circuit board layout and component placement significantly easier compared to the diagonal orientations produced by circular cores.
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 non-circular magnetic core design increases inductance, reduces device volume, and improves space utilization on circuit boards, allowing for efficient current shunting and reduced losses while effectively suppressing electromagnetic interference.
Implementation Method 1
The choke is an inducting element for inhibiting noise generation. Moreover, the choke includes at least one winding coil, a magnetic core assembly
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
An EMI filter system (4) includes a circuit board (3) and a choke (2). The circuit board (3) includes at least three capacitors (31). The choke (2) mounts on the circuit board (3) and includes a non-circular magnetic core (21) and at least three windings (22). The at least three windings (22) are wound on the non-circular magnetic core (21). The at least three capacitors (31) are disposed adjacent to the choke (2), and first outlet ends (22a) of the at least three windings (22) are respectively connected to the corresponding at least three capacitors (31).