PCB Rogowski Coil Layout for Accurate Current Sensing
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Solution Overview
Problem
Integration of planar Rogowski coils into printed circuit boards (PCBs) for power conversion applications is challenging due to issues such as increased current commutation loop stray inductance and inaccurate current measurement in cases of non-uniform current distribution, especially in high-density applications.
Innovation Solution
A PCB with integrated current sense that includes a planar Rogowski coil positioned between DC traces, extending beyond their edges, allowing for accurate current measurement even in non-uniform current distribution scenarios, while minimizing the impact on current commutation loop stray inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If planar Rogowski coils are integrated into PCBs for compact size, then the device footprint is reduced, but integration difficulty increases and measurement accuracy deteriorates in non-uniform current distribution
Solution Approach 1:
The patent transitions from traditional planar 2D Rogowski coil windings to a 3D vertically-stacked configuration where multiple winding layers are positioned at different heights above and below the current-carrying trace. This dimensional extension allows the sensor to capture magnetic flux more effectively while maintaining compact PCB integration, resolving the contradiction between compact footprint and measurement accuracy.
Solution Approach 2:
The patent implements nested winding layers where inner windings are positioned closer to the current-carrying trace and outer windings surround them at greater distances. This nested configuration optimizes the magnetic coupling between the trace and sensor windings, improving measurement accuracy while maintaining a compact integrated PCB structure.
2Ease of manufacture
If planar Rogowski coils are placed between DC traces, then integration is achieved, but current commutation loop stray inductance increases
Solution Approach 1:
The patent positions the Rogowski coil windings asymmetrically with respect to the DC traces, placing more winding turns on one side of the trace than the other. This asymmetric local configuration creates magnetic flux cancellation that reduces the net stray inductance in the current commutation loop, enabling PCB integration without significant performance degradation.
3Measurement precision
If traditional Rogowski coils are used, then current measurement is achieved, but device size and complexity increase
Solution Approach 1:
The patent combines multiple functional elements into a single integrated PCB structure: the current-carrying DC traces, the Rogowski coil sensing windings, and the substrate form one unified device. This merging eliminates the need for separate discrete components and complex assembly, reducing overall device complexity while maintaining measurement capability.
Solution Approach 2:
The patent replaces traditional mechanical wire-winding processes with PCB fabrication techniques for creating the Rogowski coil windings. Conductive traces are patterned directly onto PCB layers using standard printing and etching processes, eliminating complex manual or automated wire winding operations and significantly reducing manufacturing complexity.
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
Enables compact, accurate, and high-bandwidth current measurement during high-speed switching, with reduced parasitic elements and improved sensor placement flexibility.
Implementation Method 1
Rogowski coils operate based on Faraday's law of electromagnetic induction. For example, when an AC current flows through a conductor, a magnetic field may be generated around the conductor. A Rogowski coil can measure the change in magnetic flux density around the conductor, and the changing magnetic flux density can induce a voltage in the Rogowski coil proportional to the rate of change of the current flowing through the conductor.
Data Source
AI summary
An example printed circuit board (PCB) with integrated current sense includes a direct current (DC) bus including a first DC trace and a second DC trace. The PCB with integrated current sense further includes a planar Rogowski coil positioned between the first DC trace and the second DC trace and electrically separated from the first DC trace and the second DC trace. The planar Rogowski coil can extend beyond an edge-to-edge distance between a first side edge and a second side edge of the first DC trace in a first direction. The planar Rogowski coil can further extend beyond an edge-to-edge distance between a first edge and a second edge of the second DC trace in the first direction.