Open-Loop Current Transducer Layout for High-Sensitivity Sensing
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Solution Overview
Problem
Conventional open-loop current transducers for surface mounting on circuit boards face challenges in achieving high measurement sensitivity while maintaining economical manufacturing and managing electrical creepage distances, particularly with flip-chip and wire bonded arrangements.
Innovation Solution
An open-loop current transducer design featuring a separately formed primary conductor plate overlying the IC chip's magnetic field sensing portion, interconnected by bond wires, with a grounded shielding conductor positioned below and overlapping the IC chip, and a lead frame arrangement with secondary conductors, all housed within an insulating overmold housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flip-chip connection is used to place the active sensing portion close to the primary conductor, then measurement sensitivity is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent divides the conductor structure into separate components: a primary conductor plate and a secondary conductor plate, connected by bond wires. This segmentation allows the active sensing surface to face the primary conductor for high sensitivity while using standard wire bonding techniques for manufacturing, avoiding the complexity of flip-chip connections.
Solution Approach 2:
Instead of flipping the IC chip to achieve close proximity sensing (flip-chip), the patent inverts the approach by positioning the active sensing surface to face the conductor and using wire bonds to connect the conductors. This achieves the same sensitivity benefit without the manufacturing complexity of flip-chip technology.
2Ease of manufacture
If wire bonding is used with active surface facing away from lead frame, then manufacturing is simplified, but measurement sensitivity decreases
Solution Approach 1:
The patent uses a vertically stacked configuration where the active sensing surface faces the primary conductor plate in the vertical dimension, while wire bonds connect the primary and secondary conductor plates. This three-dimensional arrangement maintains manufacturing simplicity while achieving high sensitivity through close proximity sensing.
3Object-affected harmful factors
If grounded shielding conductor is added for magnetic field shielding, then sensor protection is improved, but device complexity increases
Solution Approach 1:
The grounded shielding conductor is integrated with the secondary conductor plate, combining the shielding function with the existing conductor structure. This provides magnetic field shielding for the sensor without adding separate complex shielding components, maintaining manufacturing simplicity while protecting the sensor.
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 high measurement sensitivity, economical manufacturing, and effective electrical shielding, while maintaining a compact configuration.
Implementation Method 1
an integrated circuit chip having an active sensing layer thereon detecting the magnetic field induced by a current to be measured flowing in a primary conductor
Implementation Method 2
a plurality of bond wires interconnecting the secondary conductors to the connection terminals of the IC chip
Data Source
Figure 1~2
AI summary
An open-loop electrical current transducer (1) for surface mounting on an external circuit board, comprising - an integrated circuit (IC) chip (2) comprising an active first side (9a), a second side (9b), a magnetic field sensing portion on the active side, and connection terminals (11) on the active side, - a primary conductor (4) for carrying a current to be measured, - a lead frame arrangement (3) comprising a plurality of secondary conductors (5), - a plurality of secondary conductor bond wires (14) interconnecting two or more of the secondary conductors (5) to the connection terminals (11) of the IC chip, and - an insulating housing (7) overmolded over the IC chip, the secondary conductor bond wires, and a portion of the lead frame arrangement (3). The primary conductor (4) comprises - at least one pair of primary conductor terminals (13) which form part of the lead frame arrangement, the lead frame primary conductor terminals being separated from each other by an insulating gap, - a separately formed primary conductor plate (12) mounted on top of the active side (9a) of the IC chip (2), separated from the active side by an insulating sheet (22), the primary conductor plate overlying the magnetic field sensing portion, and - at least one primary bond wire (6) interconnecting each of the lead frame primary conductor terminals (13) to respective connection end portions (12a) of the primary conductor plate.