Planar Current Sense Transformer for SiC and GaN Switching
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Solution Overview
Problem
Existing current sensing technologies in power electronics circuits are costly, inaccurate, and impact circuit layout and inductance, particularly in applications with wide band gap devices like SiC and GaN switches, where fast switching and precise timing control are critical to prevent shoot-through currents, EMI, and switching losses.
Innovation Solution
A current sense transformer with planar conductive traces and conductive connectors on a PCB, positioned between solid-state devices, provides accurate current sensing and modulates gate voltages to control switching, minimizing shoot-through currents and EMI, while maintaining a small footprint and low inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional current sensing circuits (Hall sensors, current sense transformers) are used, then current sensing capability is provided, but cost increases, accuracy decreases, and circuit layout is impacted
Solution Approach 1:
The patent combines the current sensing function with the existing PCB trace structure by forming a planar current sense transformer using conductive traces and connectors that are integrated into the circuit board layout. This merging eliminates the need for separate, bulky current sense transformers while maintaining accurate current sensing capability through the inherent inductance of the PCB trace structure.
Solution Approach 2:
The patent replaces traditional electromagnetic current sense transformers with planar PCB-based structures using controlled impedance traces and conductive connectors. This substitution eliminates mechanical windings and ferrite cores, reducing device complexity and layout requirements while maintaining the electromagnetic sensing function through planar geometry.
2Measurement precision
If current sense transformers with wire windings and magnetic cores are used, then current sensing is achieved, but the size increases and miniaturization is inhibited
Solution Approach 1:
The patent replaces traditional three-dimensional magnetic core structures with two-dimensional planar PCB traces and conductive connectors. This substitution eliminates the need for wire windings and ferrite cores, reducing the transformer volume to a thin planar structure that can be integrated directly into the PCB layout without adding significant height or footprint.
Solution Approach 2:
The patent transitions from three-dimensional wire-wound transformer structures to two-dimensional planar PCB trace structures. By utilizing the PCB plane for current sensing, the transformer function is achieved in a flattened geometry that minimizes volume while maintaining the necessary electromagnetic characteristics for accurate current sensing.
3Speed
If wide band gap devices (SiC, GaN) are used for fast switching, then switching speed improves, but transition times are extremely short (nanoseconds) requiring ultra-fast sensing and control
Solution Approach 1:
The patent replaces traditional electromagnetic current sense transformers with planar PCB-based structures that have significantly lower inductance and parasitic elements. This substitution reduces the sensing circuit's own inductance, enabling faster current detection and control response that can keep up with the nanosecond-scale switching transitions of wide band gap devices.
Solution Approach 2:
The patent changes the physical and electrical parameters of the current sensing structure by using planar PCB traces with controlled impedance and minimal loop area. This reduces the sensing circuit's inductance and parasitic capacitance, enabling the sensing bandwidth to extend into the gigahertz range and match the ultra-fast switching speeds of SiC and GaN devices.
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 enables precise control of switching times, reducing shoot-through currents, turn-on losses, and EMI, while allowing for compact and efficient power electronics circuit designs, especially in applications like electric vehicles with tight layouts.
Implementation Method 1
a current sense transformer positioned between the first and second solid-state devices and configured to sense a current flowing on a conductive trace connecting the first and second solid-state devices
Data Source
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AI summary
A power electronics circuit is disclosed that includes a switching circuit comprising a first solid-state device coupled in series with a second solid-state device, with at least the first sohd-state device comprising a solid-state switch having a gate terminal. The power electronics circuit also includes a cuirent sense transformer positioned between the first and second solid-state devices and configured to sense a current flowing on a conductive trace connecting the first and second solid-state devices, and a controller coupled to the switching circuit and the current sense transformer so as to be in operable communication tiierewith. The controller is programmed to receive a current sense signal from the current sense transformer indicative of the current flowing on the conductive trace and modulate a gate voltage to the gate terminal of the first solid-state device based on the received current sense signal, so as to control switching thereof.