Power Transistor Protection Circuit for Short-Circuit Withstand Time
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Solution Overview
Problem
SiC transistors have a relatively shorter Short-Circuit Withstand Time (SCWT) compared to Si IGBTs due to increased power density, leading to potential device failure and system compromise in traction applications.
Innovation Solution
A circuit design incorporating a power transistor, a sense transistor, and a protection transistor, along with resistors and diodes, to quickly respond to over-current events and protect the gate dielectric, enhancing SCWT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If SiC material is used to fabricate transistors for higher voltage and current operation, then power density and operating capability are improved, but Short-Circuit Withstand Time decreases leading to device failure risk
Solution Approach 1:
The patent implements a protection circuit that proactively monitors drain-source voltage and drain-source current during operation. When a short-circuit condition is detected (VDS < threshold voltage and IDS > threshold current), the circuit immediately activates to limit current, preventing device failure before it occurs. This preliminary detection and response mechanism addresses the inherently short SCWT of SiC devices by providing real-time protection.
Solution Approach 2:
The protection circuit acts as an intermediary between the power transistor and the external circuit. It includes voltage detection circuitry, current detection circuitry, and control logic that mediates the operation by detecting abnormal conditions and adjusting the gate drive signal to limit current flow, thereby protecting the SiC device from exceeding its thermal and electrical limits during short-circuit events.
2Productivity
If higher current density is operated to improve power output, then device capability is enhanced, but thermal heating increases leading to potential device failure
Solution Approach 1:
The protection circuit implements a feedback mechanism by continuously monitoring the drain-source current and voltage. When the current exceeds a predetermined threshold during normal operation or short-circuit conditions, the circuit provides feedback to the gate drive to reduce the gate voltage, thereby limiting the current flow and preventing excessive thermal heating. This closed-loop control enables the device to operate at high current densities safely while automatically responding to thermal stress conditions.
Data Source
AI summary
A circuit and an electronic device can include a first transistor, a second transistor, a third transistor, and a resistor. Each of the first and the second transistors can be an IGFET. Drains of the first and second transistors can be electrically coupled to each other, gates of the first and second transistors can be electrically coupled to each other, sources of the first and third transistors, and a first terminal of the resistor can be electrically coupled to one another, a source of the second transistor, a gate of the third transistor, and a second terminal of the resistor can be electrically coupled to one another, and a source of the third transistor and the second terminal of the resistor can be electrically coupled to each other. The circuit and electronic device can react more quickly to a short-circuit event, thus, increasing short circuit withstand time.