GaN Cascode Semiconductor Device with Kelvin Source Isolation

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Solution Overview

Problem

GaN-based semiconductor devices face challenges in achieving normally-off operation and suffer from delays and ringing due to shared source inductance in power semiconductor circuits, which is problematic for high-voltage applications requiring safe and efficient power handling.

Innovation Solution

A semiconductor device configuration that includes a normally-off transistor, a normally-on transistor, capacitors, diodes, and a gate drive circuit with a Kelvin connection, utilizing a second capacitor to isolate the main circuit current from the gate drive current, thereby suppressing delay and ringing by ensuring the normally-off transistor turns on before the normally-on transistor and allowing controlled turn-off timing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a cascode connection between normally-on GaN transistor and normally-off Si transistor is used to achieve normally-off operation, then safety and normally-off operation are improved, but device complexity increases

Engineering Contradiction:

Improvenormally-off operation safetyVSAvoidcircuit configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the normally-on GaN transistor and normally-off Si transistor into a single integrated device structure, combining the advantages of both transistor types while eliminating the need for separate external connections and reducing overall circuit complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated device structure performs multiple functions simultaneously - achieving normally-off operation, high-voltage handling, and high-frequency performance within a single device, eliminating the need for separate components

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Device complexity

If main circuit current and gate driving current share source inductance, then device complexity is reduced, but switching delay and ringing increase

Engineering Contradiction:

Improvecircuit configuration simplicityVSAvoidswitching delay

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent segments the current paths by providing separate source connections for the main circuit current and gate driving current, isolating the gate drive loop from the power loop to eliminate mutual interference and reduce switching delays

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces separate source terminals and internal connection structures that act as intermediaries to isolate the gate drive circuit from the main power circuit, preventing electromagnetic interference and reducing switching ringing

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If main circuit current and gate driving current share source inductance, then device complexity is reduced, but switching ringing increases

Engineering Contradiction:

Improvecircuit configuration simplicityVSAvoidswitching ringing

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

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

The configuration effectively achieves cascode-connected operation with reduced delay and ringing, improving the switching efficiency and reliability of the semiconductor device, as demonstrated by reduced switching loss and energy loss in the circuit.

Implementation Method 1

a second capacitor having a third end and a fourth end, the third end electrically connected to the reference potential wiring and the fourth end electrically connected to the second source

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a first diode having a first anode electrically connected between the second end and the second gate, and a first cathode

Methodology Applied

Scientific EffectDiode rectification: Diode

Data Source

PatentUS10658356B2Semiconductor device and semiconductor package

Publication Date: 2020.05.19 KK TOSHIBA

AI summary

A semiconductor device according to an embodiment is a semiconductor device including: a normally-off transistor having a first source, a first drain, and a first gate; a normally-on transistor having a second source electrically connected to the first drain, a second drain, and a second gate; a first capacitor having a first end and a second end, the second end electrically connected to the second gate; a first diode having a first anode electrically connected between the second end and the second gate, and a first cathode; a first resistor electrically connected between the first end and the first gate; a second diode having a second anode electrically connected to the first end, and a second cathode electrically connected to the first gate, the second diode provided in parallel to the first resistor; a gate drive circuit electrically connected to the first resistor and the second anode, a reference potential wiring being connected to the gate drive circuit and the first source; and a second capacitor having a third end and a fourth end, the third end electrically connected to the reference potential wiring and the fourth end electrically connected to the second source.