Power Module Gate Coils Shielded from Eddy Currents
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Solution Overview
Problem
In inverter drive systems for electrified vehicles, the presence of eddy currents in heat conductive plates and cold plates reduces the effectiveness of enhanced common source inductance due to opposing magnetic flux, hindering the enhancement of switching performance and energy efficiency.
Innovation Solution
Incorporating a magnetic shielding sheet or creating an electrically non-conductive region at the heat conductive plate to prevent eddy currents from interfering with inductive coils, thereby maintaining effective magnetic coupling between the gate and power loops for enhanced common source inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat conductive plates and cold plates are used to remove heat from transistor dies, then heat dissipation performance is improved, but eddy currents are generated that produce opposing magnetic fields reducing common source inductance effectiveness
Solution Approach 1:
A magnetic shielding layer is introduced as an intermediary between the heat conductive plate and the inductive coils. This shielding layer blocks the magnetic field interaction between the eddy currents in the heat plate and the gate signal in the inductive coils, preventing the opposing magnetic field that reduces common source inductance effectiveness. The shielding layer acts as a mediator that allows heat dissipation to continue while preventing the harmful magnetic interaction.
Solution Approach 2:
The magnetic shielding layer is applied locally at specific positions where the heat conductive plate is in close proximity to the inductive coils, rather than uniformly across the entire heat plate. This localized approach targets the specific region where eddy currents would most strongly interfere with the common source inductance, while maintaining heat dissipation effectiveness in other areas.
2Productivity
If inductive coils are added to enhance common source inductance, then switching performance is improved, but eddy currents in heat conductive plates generate opposing magnetic flux that reduces the enhancement
Solution Approach 1:
The magnetic shielding layer serves as an intermediary that protects the inductive coils from the harmful opposing magnetic flux generated by eddy currents in the heat conductive plate. This allows the inductive coils to maintain their enhanced common source inductance function without being counteracted by the eddy current magnetic fields.
Solution Approach 2:
The invention acknowledges the presence of eddy currents as an unavoidable byproduct of using heat conductive plates, but converts this harmful effect into a manageable situation by introducing magnetic shielding. The shielding layer essentially neutralizes the harmful opposing magnetic flux, allowing the system to benefit from both heat dissipation and enhanced common source inductance simultaneously.
3Temperature
If electrically conductive heat conductive plates are used, then thermal conduction is improved, but eddy currents are induced that interfere with magnetic coupling between gate and power loops
Solution Approach 1:
The magnetic shielding layer is positioned between the electrically conductive heat conductive plate and the inductive coils to prevent direct magnetic interaction. This intermediary layer allows the heat plate to maintain its electrical conductivity for thermal conduction purposes while blocking the induction of eddy currents that would interfere with the magnetic coupling between gate and power loops.
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
This solution effectively prevents eddy currents from reducing the magnetic coupling between the gate and power loops, allowing for improved switching performance and energy efficiency by maintaining the enhanced common source inductance, thus enhancing the power conversion efficiency in inverter drive systems.
Implementation Method 1
A gate signal is applied to a control electrode having an inductive coil magnetically coupling with the power loop
Implementation Method 2
A heat conductive plate underlies the dies
Implementation Method 3
Eddy currents generated in these surfaces can produce magnetic fields that can hinder the attempt to enhance the common source inductance
Data Source
AI summary
An inverter for an electric vehicle drive has a bridge configuration using power transistors packaged in actively cooled power modules. Control electrodes in the power modules carrying gate signals to drive the transistors contain inductive coils to increase a common source inductance in order to reduce power losses. Each inverter power module comprises a pair of transistor dies with output electrodes defining a power loop. The control electrodes with inductive coils carrying respective gate signals are arranged to be magnetically coupled with the power loop. For active cooling, a heat conductive plate underlies the dies. A magnetic interrupter is disposed at the heat conductive plate. A localized eddy current preventer is interposed at the heat conductive plate in alignment with the inductive coils to avoid eddy currents that could otherwise reduce the coupling of the inductive coils with the power loop.