Current Transducer Leadframe Layout for PCB-Insensitive Sensing
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Solution Overview
Problem
Existing compact open loop current transducers with integrated circuits are adversely affected by PCB conductor layout and thickness, leading to measurement signal inaccuracies and the need for costly calibration for each external PCB configuration.
Innovation Solution
A current transducer design with a magnetic field sensor, leadframe arrangement, and overmold housing, featuring a bridging branch with chamfered edges and indentations, which minimizes sensitivity to PCB conductor layout and thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact open loop current transducer with an integrated circuit and differential magnetic field measurement sensor is used, then the device achieves compact size and differential measurement capability, but the measurement signal becomes sensitive to PCB conductor layout and thickness variations
Solution Approach 1:
The patent applies local quality by creating an asymmetric current distribution in the leadframe conductor through the indent. The indent is positioned closer to one magnetic field sensor than the other, creating a non-uniform magnetic field distribution that compensates for PCB interference. This local modification of the current path geometry enables differential measurement while reducing sensitivity to PCB conductor variations.
Solution Approach 2:
The patent employs asymmetry through the indent in the leadframe conductor, which creates unequal current distribution between the two sides of the bridging branch. This asymmetric current distribution generates a differential magnetic field signal that enhances measurement capability while simultaneously reducing sensitivity to symmetric PCB conductor layout variations and thickness variations.
2Measurement precision
If calibration is performed for each external PCB configuration to maintain measurement accuracy, then measurement precision is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent implements self-service through the self-compensating differential measurement mechanism. The asymmetric indent creates a built-in reference that automatically compensates for PCB conductor variations without requiring external calibration. The differential measurement between the two magnetic field sensors inherently rejects common-mode interference from the PCB, enabling the device to self-calibrate across different PCB configurations.
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 design achieves accurate and economical measurement signals with reduced sensitivity to external PCB conductor layout and thickness, ensuring consistent performance across different PCB configurations.
Implementation Method 1
an integrated circuit (IC) chip with a magnetic field sensor detecting the magnetic field induced by a current to be measured flowing in the primary conductor
Implementation Method 2
Such current transducers typically have an integrated circuit (IC) chip with a differential magnetic field measurement sensor that measures a magnetic field gradient across a section of primary conductor
Data Source
Figure 1a~1b
Figure 2~3b
Figure 4a~4b
AI summary
A current transducer (1) comprising a magnetic field sensor (20), a leadframe arrangement (3) comprising secondary conductors (5) and a primary conductor (4), and an overmold insulating housing encapsulating the magnetic field sensor and portions of the primary conductor and secondary conductors, the primary conductor comprising a first connection end terminal (10a) and a second connection end terminal (10b) separate by a slot (6), and a bridging branch (13) interconnecting the first connection end terminal (10a) to the second connection end terminal, the first connection end terminal and a second connection end terminal having a thickness H1 and exposed pads for surface mount connection to conductive tracks on an external circuit board, the bridging branch having an indent (13) with a thickness H2 smaller than the connection end terminal thickness H1, the indent spanning across the bridging branch. The bridging branch comprises chamfer edges (17) formed in corners of the first and second connection terminals bounding the bridging branch, the chamfer edges extending from the slot and diverging outwardly from the slot at an angle (β) from a centreline (C).