GaN HEMT Switch With Integrated Short-Circuit Detection
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Solution Overview
Problem
Existing GaN HEMTs face challenges in detecting short-circuit events quickly and effectively, with traditional methods requiring additional components and longer detection times, which are unsuitable for high-power applications due to their faster failure times.
Innovation Solution
A monolithically integrated short-circuit detection circuit for GaN HEMTs, comprising a power HEMT, a Miller clamp, an auxiliary GaN HEMT, and a short-circuit detection block, which uses minimal components to provide ultra-fast protection by turning off the power HEMT and reducing gate bias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional external desaturation circuits are used for short-circuit protection, then protection coverage is provided, but the delay time is too long (2-10 μs) for GaN HEMTs to survive
Solution Approach 1:
The patent merges the short-circuit detection circuit with the power HEMT into a single monolithic integrated circuit. The detection circuit shares common substrates, contact holes, and interconnect structures with the power device, eliminating the need for separate external protection circuits. This integration reduces the detection delay from 2-10 μs to a few hundred nanoseconds by removing interconnect parasitics and enabling direct sensing at the device level.
Solution Approach 2:
The patent segments the detection function into dedicated detection transistors (first and second detection transistors) that are separately integrated within the power device structure. These detection transistors have their own gate, source, and drain regions that are independently formed in the semiconductor substrate, allowing parallel operation with the power HEMT and enabling fast detection without interfering with the main power switching function.
2Productivity
If GaN HEMTs operate at high frequency to increase power density, then system efficiency improves, but short-circuit detection and protection becomes more challenging
Solution Approach 1:
The patent implements preliminary protection action by continuously monitoring the drain-source voltage through integrated detection transistors before a short-circuit condition can cause damage. The detection circuit is pre-configured with blanking circuits that can quickly identify abnormal voltage conditions and trigger protective shutdown. This preliminary detection mechanism operates at the same high frequency as the power device, enabling protection response times in the hundreds of nanoseconds range, which is sufficient for high-frequency GaN HEMT operation.
3Device complexity
If monolithic integration is used to reduce components, then device complexity decreases, but manufacturing precision requirements increase
Solution Approach 1:
The patent achieves universality by designing the detection transistors to share common structural elements with the power HEMT, including the same AlGaN/GaN heterostructure, common source and drain regions, and shared interconnect layers. This multi-functional design allows the same epitaxial growth process and fabrication steps to produce both power and detection devices with consistent electrical characteristics, reducing manufacturing complexity despite the integrated architecture.
Data Source
AI summary
A semiconductor switch may comprise a first main terminal, a second main terminal, and a control terminal. The semiconductor switch may further comprise a III-nitride high-electron-mobility transistor (HEMT), the III-nitride HEMT comprising a first source terminal, a first drain terminal, and a first gate terminal, the control terminal being operatively connected to the first gate terminal. The semiconductor switch may comprise a short-circuit detection circuit operatively connected to the first drain terminal and the first source terminal, the short-circuit detection circuit being configured to: scale down a voltage between the first drain terminal and the first source terminal (for example to generate a scaled down voltage), compare the scaled down voltage to a reference voltage, and when the scaled down voltage is higher than the reference voltage, output a short-circuit detection signal.