Interleaved Current Probe Layout for Low-Inductance GHz Measurement
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Solution Overview
Problem
Existing current measurement systems struggle with high switching frequencies due to limitations in bandwidth, signal distortion, insertion inductance, and device footprint, particularly in wide-bandgap device testing, which leads to inaccurate measurements and potential device damage.
Innovation Solution
An ultra-fast current probe utilizing a stack of dielectric layers with interleaved conductive paths and resistive elements to achieve mutual inductance cancellation, reducing total inductance and increasing bandwidth to radio and microwave frequencies, facilitating accurate measurements of high switching rates and short switching transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Rogowski coils are used for magnetic measurement, then simultaneous measurements on high and low sides are enabled, but DC current measurement capability is lost and high frequency performance is limited by integrator performance and turn-to-turn capacitance
Solution Approach 1:
The measurement system is segmented into separate measurement paths: a low-inductance shunt resistor path for DC and low-frequency measurements, and a Rogowski coil path for high-frequency AC measurements. This segmentation allows each component to optimize for its specific frequency range, with the shunt providing accurate DC measurement capability while the Rogowski coil handles high-frequency measurements.
2Speed
If coaxial current shunts are used to measure voltage drop, then band-pass bandwidth in GHz range is achieved, but large insertion inductances generate voltages that may damage semiconductor devices and introduce inductive zeros that reduce measurement accuracy
Solution Approach 1:
The design fundamentally changes the inductance parameter by using a planar meander configuration with interleaved current paths that achieve mutual inductance cancellation. This reduces the insertion inductance from typical values of several nanohenries to less than 1 nH, eliminating the harmful voltage spikes while maintaining GHz-range bandwidth capability.
3Productivity
If fast switching times are implemented, then switching losses are reduced and switching frequencies are increased, but parasitic inductance causes over-voltage damage and measurement accuracy deteriorates
Solution Approach 1:
The probe design changes the inductance parameter to extremely low values through mutual inductance cancellation in the meander configuration. This allows fast switching operations to proceed without generating dangerous over-voltages, enabling high switching frequencies while maintaining device reliability and measurement accuracy.
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 current probe provides low inductance and high bandwidth, enabling accurate measurements with reduced distortion and lower electrical loading, protecting devices from voltage spikes and improving measurement accuracy at high frequencies.
Implementation Method 1
The plurality of conductive paths are arranged or interleaved such that the first and second sets of conductive paths alternate in the stack of layers
Data Source
AI summary
A radio/microwave frequency current probe comprising one or more resistive elements electrically connected between a current input region and a current output region, and a stack of layers each comprising a dielectric material. For each of the resistive elements, the current probe further comprises a plurality of conductive paths each separated by one or more of the layers. A first set of the conductive paths are configured to provide a current path between the current input region and the resistive element, while a second set of conductive paths are configured to provide a current path between the resistive element and the current output region. The plurality of conductive paths are arranged such that the first and second sets of conductive paths alternate in the stack of layers. The current probe may also be integrated into current measurement systems.