PCB Ground Plane Segmentation for Coreless Current Sensors
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Solution Overview
Problem
Conventional coreless current sensors face challenges in accurately measuring primary current due to parasitic magnetic fields induced by eddy currents in the printed circuit board (PCB) ground plane, which introduce errors and delays in current measurement.
Innovation Solution
The implementation of a coreless current sensor system with a printed circuit board ground plane featuring designs such as holes or elongated cuts that reduce or eliminate eddy currents, improving the accuracy and response time of current sensing by disrupting eddy current paths and aligning the ground plane with magnetic field sensing elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ground plane is used in the PCB to reduce return current impedance and protect against electromagnetic interference, then electromagnetic shielding and reference potential stability are improved, but eddy currents are induced in the ground plane by current flow in the conductor, generating parasitic magnetic fields that introduce error and delay in current measurement
Solution Approach 1:
The ground plane is segmented by introducing cuts or slots that divide the continuous conductive layer into isolated sections. This segmentation interrupts the eddy current paths while preserving the ground plane's electromagnetic shielding capability, as the cuts are positioned to block parasitic current loops without compromising the overall ground reference structure.
Solution Approach 2:
The ground plane structure is modified locally in the region surrounding the magnetic field sensing element. Cuts or slots are introduced specifically in areas where eddy currents would generate parasitic magnetic fields that interfere with sensing, while other regions of the ground plane maintain continuous conductivity for effective shielding and reference potential.
2Reliability
If a ground plane is used in the PCB to reduce return current impedance and protect against electromagnetic interference, then electromagnetic shielding and reference potential stability are improved, but response time is delayed due to eddy current generation
Solution Approach 1:
The ground plane is segmented by introducing cuts or slots that divide the continuous conductive layer into isolated sections. This segmentation interrupts the eddy current paths while preserving the ground plane's electromagnetic shielding capability, as the cuts are positioned to block parasitic current loops without compromising the overall ground reference structure.
3Device complexity
If no core is used in the current sensor, then the sensor is referred to as a coreless current sensor, but accurately measuring the intended primary current through the conductor becomes challenging due to parasitic magnetic fields from eddy currents in the ground plane
Solution Approach 1:
The ground plane is segmented by introducing cuts or slots that divide the continuous conductive layer into isolated sections. This segmentation interrupts the eddy current paths while preserving the ground plane's electromagnetic shielding capability, as the cuts are positioned to block parasitic current loops without compromising the overall ground reference structure.
Solution Approach 2:
The ground plane structure is modified locally in the region surrounding the magnetic field sensing element. Cuts or slots are introduced specifically in areas where eddy currents would generate parasitic magnetic fields that interfere with sensing, while other regions of the ground plane maintain continuous conductivity for effective shielding and reference potential.
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 described designs effectively reduce or eliminate eddy currents, enhancing the accuracy and response time of current sensing in coreless current sensor systems, particularly at higher frequencies and during current surges.
Implementation Method 1
at least one magnetic field sensing element supported by the semiconductor die and configured to sense a current in a proximate primary conductor
Implementation Method 2
eddy currents can be induced in the PCB ground plane by the current flow in the conductor. Such eddy currents can generate a parasitic magnetic field that can be sensed by the current sensor
Data Source
AI summary
A current sensor system includes a current sensor integrated circuit (IC) and a printed circuit board (PCB) having a ground plane with a feature configured to reduce an eddy current. The current sensor IC includes a lead frame comprising a die attach pad and at least one lead, a semiconductor die having a first surface attached to the die attach pad and a second, opposing surface, at least one magnetic field sensing element supported by the semiconductor die and configured to sense a current in a proximate primary conductor, and a non-conductive mold material enclosing the semiconductor die and a portion of the at least one lead. The PCB ground plane feature can take various forms such as a hole of a dimension larger than the current sensor IC, elongated cuts, or x-shaped cuts.