Pulse Transformer Inductance Control via Core Gap Grinding
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Solution Overview
Problem
Surface-mount pulse transformers with smaller sizes, such as 3.3 mm×3.3 mm×2.7 mm, struggle to achieve the required inductance of 350 μH under high bias currents due to magnetic saturation, as existing techniques that enhance contact between the drum and plate cores lead to increased magnetic resistance and reduced inductance.
Innovation Solution
Intentionally creating a minute magnetic gap by roughly grinding the contact surfaces of the drum and plate cores to suppress magnetic saturation, allowing for an average gap length of 0.60 μm to 0.75 μm, and arranging an adhesive between the plate core and wound wires to increase the inductance initial value without the need for an adhesive filling groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mirror finishing is performed on the contact surfaces of the drum core and plate core to reduce magnetic resistance, then the inductance increases, but the device size cannot be reduced further while maintaining the required inductance
Solution Approach 1:
The invention changes the surface finish parameter from mirror finishing (smooth) to rough grinding, creating intentional gaps between the drum core and plate core. This parameter change in surface roughness and gap formation resolves the contradiction by maintaining high inductance through controlled magnetic path characteristics while enabling smaller device dimensions.
2Manufacturing precision
If the drum core and plate core are brought into close contact to increase inductance, then the magnetic resistance decreases, but magnetic saturation occurs under high bias current
Solution Approach 1:
The invention applies local quality by creating non-uniform surface characteristics through rough grinding, producing specific gap distributions at contact points. This local gap formation prevents magnetic saturation in high-field regions while maintaining adequate magnetic coupling overall, thus resolving the contradiction between high inductance and saturation resistance.
Solution Approach 2:
The rough grinding process beforehand creates intentional gaps that act as cushioning against magnetic saturation. These pre-formed gaps provide magnetic flux leakage paths that prevent saturation before it occurs under high bias current, resolving the contradiction between close contact for high inductance and saturation prevention.
3Strength
If adhesive is applied to the entire contact surfaces to fix the plate core, then the mechanical strength increases, but the gap between cores is enlarged reducing inductance
Solution Approach 1:
The invention changes the adhesive application parameter from full surface coverage to selective area application. By applying adhesive only to specific regions rather than the entire contact surface, the patent achieves adequate mechanical bonding while preserving the intentional gaps created by rough grinding, thus maintaining high inductance values.
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 configuration enables the pulse transformer to maintain an inductance of 350 μH or higher under bias currents from 0 mA to 8 mA, even in smaller sizes, by controlling magnetic saturation and enhancing the inductance initial value.
Implementation Method 1
Intentionally creating a minute magnetic gap by roughly grinding the contact surfaces of the drum and plate cores to suppress magnetic saturation
Implementation Method 2
The plate core and the drum core constitute a closed magnetic path therebetween
Implementation Method 3
Four wires that constitute a coil are wound around the winding core portion
Data Source
AI summary
Disclosed herein is a pulse transformer that includes a drum core having a winding core portion and first and second flange portions, a plate core connected to the first and second flange portions, and a plurality of wires that are wound around the winding core portion. The first and second flange portions and the plate core are ground such that an inductance of the pulse transformer is 350 μH or more when a bias current of 8 mA is applied to the wires.