HEMT Bidirectional Switch With Unified Overvoltage Clamping
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Solution Overview
Problem
Bidirectional switches using high electron mobility transistors (HEMTs) made of wide-band-gap semiconductors like GaN and SiC are vulnerable to overvoltage in both directions, requiring complex overvoltage protection systems with multiple circuits.
Innovation Solution
A bidirectional switch with a simple circuit configuration utilizing a HEMT structure where one main electrode acts as a virtual source and the other as a virtual drain, coupled with an overvoltage protection circuit comprising a resistor and a constant voltage diode between the virtual drain and gate, effectively suppressing overvoltage in both directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a bidirectional switch uses HEMT structure with wide-band-gap semiconductor, then switching performance and voltage handling capability are improved, but vulnerability to overvoltage in both directions increases requiring complex protection circuits
Solution Approach 1:
The patent merges the overvoltage protection function into a single unified circuit configuration that operates bidirectionally. By connecting the series circuit of constant voltage diode and resistor between drain and gate, the same circuit structure protects against overvoltage from both positive and negative directions, eliminating the need for separate protection circuits for each direction.
Solution Approach 2:
The overvoltage protection circuit serves multiple functions simultaneously: it protects against overvoltage in both directions, limits gate-source voltage to prevent device breakdown, and provides clamping action during transient events. The constant voltage diode and resistor combination acts as a universal protection mechanism for the bidirectional HEMT switch.
2Reliability
If overvoltage protection circuits are added to protect against overvoltage, then device reliability is improved, but circuit complexity increases
Solution Approach 1:
The protection circuit elements (constant voltage diode and resistor) are merged into a single series connection between drain and gate, providing comprehensive overvoltage protection without requiring multiple separate circuits. This unified approach maintains reliability while minimizing circuit complexity.
Solution Approach 2:
The constant voltage diode automatically activates when overvoltage occurs, clamping the gate-source voltage to a safe level without requiring external control signals or additional active components. The circuit protects itself through the inherent characteristics of the constant voltage diode and resistor combination.
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 provides effective overvoltage protection in both directions using a single semiconductor element, reducing complexity and cost while maintaining reliability for applications like uninterrupted power sources and motor inverters.
Implementation Method 1
a constant voltage diode 15 whose breakdown voltage is lower than a withstand voltage of the FET Q1
Data Source
AI summary
A bidirectional switch includes a semiconductor switch Q3 having a gate and main electrodes serving as a drain and source. The semiconductor switch has a HEMT structure so that one of the main electrodes having a lower voltage than the other serves as a virtual source and the other main electrode as a virtual drain. The semiconductor switch receives a gate signal between the gate and the virtual source, to turn on/off a current in both directions. A gate signal generator 13 is connected between the gate and virtual source of the semiconductor switch, to apply the gate signal to the gate of the semiconductor switch. An overvoltage protection circuit is connected between the virtual drain and gate of the semiconductor switch. The overvoltage protection circuit has a resistor 16 and a constant voltage diode 15.