Embedded Current Sensing in Multichip Modules Without Loop Inductance
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Solution Overview
Problem
Current technologies for high-power applications with wide band-gap semiconductors face challenges in suppressing parasitic-induced ringing and achieving high-bandwidth current measurement without introducing geometric choke-points or degrading transient behavior.
Innovation Solution
A current transformer with a magnetic core, burden resistor, and a filter comprising capacitance, inductance, and resistance is used to provide effective current measurement and ringing suppression by selecting components to maintain a minimum insertion impedance across a known frequency range, allowing for galvanically isolated, high-bandwidth measurement while suppressing undesirable high-frequency spectral content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional current transformers are used to provide galvanic isolation, then current measurement is achieved, but loop inductance increases due to mechanical choke-point which degrades transient behavior
Solution Approach 1:
The patent extracts the current measurement function from the power bus by using a magnetic core current transformer that couples magnetically to the bus without making mechanical contact. This removes the choke-point structure while maintaining galvanic isolation through magnetic coupling alone, thereby reducing loop inductance while preserving measurement capability and isolation.
Solution Approach 2:
The patent introduces a magnetic core as an intermediary between the current bus and the measurement circuit. The magnetic core couples the primary current to the secondary measurement circuit through magnetic flux, providing galvanic isolation without requiring a mechanical choke-point. This intermediary enables isolation while minimizing inductance by avoiding direct mechanical connection.
2Power
If wide band-gap semiconductors are used to achieve high-power applications, then power capability is improved, but parasitic-induced ringing and overshoot increase due to very fast di/dt and dv/dt rising edges
Solution Approach 1:
The patent converts the harmful fast rising edges that cause ringing into a beneficial measurement opportunity. By using a magnetic core current transformer with optimized parasitic elements, the fast di/dt and dv/dt transitions are transformed into measurable signals while the magnetic coupling and filter design actually suppress the harmful ringing effects rather than merely tolerating them.
Solution Approach 2:
The patent changes the parasitic parameter values of the current transformer to beneficial ranges. Specifically, the parasitic inductance is minimized through optimized winding techniques and the parasitic capacitance is controlled through proper insulation and spacing. These parameter changes ensure that the fast switching edges of wide band-gap devices produce accurate measurements without excessive ringing.
3Speed
If resistive shunts are used for current measurement, then high bandwidth is achieved, but galvanic isolation is lost
Solution Approach 1:
The patent replaces the direct electrical connection (mechanical/electrical contact) of resistive shunts with magnetic coupling. The magnetic core current transformer uses electromagnetic induction to transfer the current signal across the isolation barrier, maintaining high bandwidth for measurement while providing galvanic isolation that protects against ground loops and voltage transients.
4Reliability
If hall-effect sensors are used for current measurement, then galvanic isolation is provided, but bandwidth is limited to modest frequencies (kHz)
Solution Approach 1:
The patent changes the frequency response parameters of the current measurement system by using a magnetic core transformer design optimized for high-frequency operation. The transformer's magnetic core material, winding configuration, and inter-winding capacitance are specifically designed to maintain low parasitic inductance and capacitance, enabling accurate measurement up to MHz frequencies rather than being limited to kHz ranges.
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 solution effectively measures current with high fidelity across a wide range of frequencies and suppresses parasitic-induced ringing, improving the transient response and dynamic performance of multi-chip power modules without increasing the device's dimensions or degrading converter behavior.
Implementation Method 1
a magnetic core current transformer having an insertion impedance Zin and turns ratio N
Implementation Method 2
a filter, the filter comprising a capacitance CP, an impedance LP and a resistance RP
Implementation Method 3
a filter, the filter comprising a capacitance CP, an impedance LP and a resistance RP
Data Source
AI summary
The current disclosure relates to the design of an apparatus for enhancing the operation and reliability of high-power multi-chip modules, which are used in the design and implementation of power electronics converters. This apparatus is especially useful for modules containing recently commercialized, high-performance wide band-gap semiconductors such as Silicon Carbide (SiC), which commonly emit undesirable high-frequency ringing and oscillation in the “Near-RF” spectral band between 1-30 MHz. The disclosed apparatus provides near-complete elimination of this high frequency spectral content, while leaving the desired frequency range (1-100 kHz) of the module unaffected. In addition to the suppression of this undesirable high-frequency content, the disclosed apparatus also provides for accurate, galvanically-isolated, high-bandwidth, real-time current measurement, which is essential for some types of power electronics converters. The apparatus disclosed here provides ringing suppression and current measurement in simple circuit topology that can be implemented compactly inside the geometry of a multi-chip power module.