Stacked PCB Rogowski Coil Layout for Low-Current Noise Rejection
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Solution Overview
Problem
Current sensors, particularly Rogowski coils, are susceptible to electrostatic and magnetic interference, and their sensitivity is limited by the constraints of printed circuit board (PCB) thickness, making it difficult to increase loop area and signal amplitude, especially in low-current applications.
Innovation Solution
A current sensor assembly comprising a stacked plurality of substrates, each with identical current measurement coils, is designed such that adjacent coils have inverted polarities to cancel interference and increase signal output, allowing for greater sensitivity without altering individual coil designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the loop area of a Rogowski coil is increased to improve signal amplitude and sensitivity, then the smallest measurable current is improved, but the device complexity and PCB thickness constraints worsen
Solution Approach 1:
The patent transitions from a single-plane PCB layout to a three-dimensional stacked configuration with multiple PCB layers. Measurement coils are distributed across multiple layers (e.g., layers 1, 3, 5, 7) with alternating current paths, creating a volumetric loop structure that increases effective loop area without increasing single-layer complexity or PCB thickness
Solution Approach 2:
The measurement coil is divided into multiple segments distributed across different PCB layers. Each layer contains a portion of the coil (e.g., 4 coils per layer), and these segments are electrically connected through vias to form a complete multi-turn coil, allowing the system to achieve high sensitivity while maintaining manageable complexity at each layer
2Reliability
If Rogowski coils are used to avoid physical connection to the current carrying conductor, then isolation is improved, but susceptibility to electrostatic and magnetic interference worsens
Solution Approach 1:
Multiple measurement coils from different PCB layers are electrically merged in series to form a single equivalent coil with increased turns ratio. The alternating current paths through the stacked layers create a unified magnetic coupling with the conductor while maintaining electrical isolation, and the combined signal provides better noise immunity through constructive interference
Solution Approach 2:
The patent uses the alternating current path configuration across stacked layers to convert potential interference into a benefit. By arranging coils with alternating polarity orientations, the system creates differential signaling that naturally rejects common-mode noise and electrostatic coupling, transforming the vulnerability to interference into enhanced noise rejection capability
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 stacked coil configuration enhances sensitivity by constructively adding signals while canceling noise, improving measurement accuracy and immunity to external interference, particularly in low-current scenarios.
Implementation Method 1
Another type of current sensor uses an electromagnetic transducer to detect changes in a magnetic field generated by the current carrying conductor
Implementation Method 2
A major challenge with Rogowski coils is this sensitivity to electrostatic or capacitive coupling from nearby AC conductors
Data Source
AI summary
A current sensor is provided, the current sensor comprising a plurality of substrates that are stacked such that each substrate is rotated with respect to an adjacent substrate of the plurality of substrates. Each substrate comprises a path for a conductor for carrying current to be measured by the current sensor. Each substrate comprises a plurality of measurement coils that progress around the path for the conductor.