Series Power Module Isolation Using AlN Thermal Substrates

Solution Overview

Problem

Existing high voltage modules face limitations in voltage capability due to parallel connection of semiconductor chips, which leads to heating issues complicating electrical isolation and increased manufacturing costs.

Innovation Solution

The use of an electrically isolating, thermally conductive substrate, such as aluminum nitride (AlN) sheets or plates, to connect switching devices in series with rubber buffers for insulation and thermal management, allowing controlled deadtime gating and passive clamping circuits to manage current/voltage sharing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If multiple semiconductor chips are connected in parallel to increase current capability, then current capability is improved, but voltage capability is limited and heating issues complicate electrical isolation

Engineering Contradiction:

Improvecurrent capabilityVSAvoidelectrical isolation

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

Instead of connecting chips in parallel to increase current capability, the patent inverts the approach by connecting switching devices in series to achieve high voltage capability (up to 50 kV). This inversion resolves the contradiction by prioritizing voltage capability while using alternative methods (multiple devices in series with controlled deadtime gating) to maintain current capability.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces thermal interfaces (electrically isolating, thermally conductive substrates) as intermediaries between switching devices and cooling surfaces. These intermediaries provide both thermal conduction and electrical isolation, resolving the contradiction between heat dissipation requirements and electrical isolation needs in high voltage series-connected configurations.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If switching devices are connected in series to increase voltage capability, then voltage capability is improved, but thermal management becomes more challenging

Engineering Contradiction:

Improvevoltage capabilityVSAvoidthermal management

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

The patent introduces thermal interfaces (electrically isolating, thermally conductive substrates) as intermediaries between switching devices and cooling surfaces. These intermediaries provide both thermal conduction and electrical isolation, resolving the contradiction between heat dissipation requirements and electrical isolation needs in high voltage series-connected configurations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the thermal management system by providing individual cooling surfaces and thermal interfaces for each switching device in the series string. This segmentation allows independent thermal management of each device, addressing the thermal challenges of series-connected high voltage switches.

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If discrete non-isolated devices are used to reduce cost, then manufacturing cost is improved, but electrical isolation becomes more difficult

Engineering Contradiction:

Improvemanufacturing costVSAvoidelectrical isolation

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces thermal interfaces (electrically isolating, thermally conductive substrates) as intermediaries between switching devices and cooling surfaces. These intermediaries provide both thermal conduction and electrical isolation, resolving the contradiction between heat dissipation requirements and electrical isolation needs in high voltage series-connected configurations.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 approach enhances voltage capability up to 50 kV with reduced thermal resistance and cost, providing efficient heat dissipation and electrical insulation while minimizing module size and cost.

Implementation Method 1

thermal interfaces disposed between switching devices of the switching device pairs and cooling surfaces of the module, the thermal interfaces electrically isolating the switching devices from the cooling surface

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

The AlN sheet or plate can be disposed between two or more switching devices and the adjacent cooling surface

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Implementation Method 3

one or more rubber buffer disposed between switching device pairs of the plurality of switching devices

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS12597786B2High voltage isolation using discrete non-isolated devices and electrically isolating, thermally conductive substrate

Publication Date: 2026.04.07 NORTH CAROLINA STATE UNIV

AI summary

Various examples are provided for high voltage isolation. The isolation can be provided for discrete non-isolated devices using an electrically isolating substrate that is thermally conductive. In one example, a module includes a plurality of switching devices connected in series; one or more rubber buffer disposed between switching device pairs of the plurality of switching devices; and thermal interfaces disposed between switching devices of the switching device pairs and cooling surfaces of the module, the thermal interfaces electrically isolating the switching devices from the cooling surface. In another example, an extreme fast charger (EFC) station includes an active front end (AFE) module that includes at least one module, where the module is a half-bridge power module. The EFC station can include a dual-active-bridge (DAB) high voltage (HV) module that includes at least one module, where the module is a half-bridge power module.