Short Circuit Detector Using Gate Voltage Transition Monitoring
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Solution Overview
Problem
Conventional short circuit detection methods in semiconductor apparatuses often fail to detect short circuits early enough, particularly in wide bandgap semiconductor elements, leading to potential breakage due to delayed detection and increased risk of damage during the mirror period.
Innovation Solution
A short circuit detector system that includes a voltage detection circuit and a short circuit detection circuit, utilizing reference voltages to detect short circuits during transition and ON periods, with a timing specifying unit to define detection periods, and a cut-off circuit to prevent current flow upon detection, ensuring earlier detection and prevention of element breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional short circuit detection methods are used, then detection is performed after the mirror period, but semiconductor elements are broken due to delayed detection
Solution Approach 1:
The patent applies preliminary action by detecting short circuits during the transition period before the mirror period begins. The detection circuit monitors gate voltage in advance during the transition from off-state to on-state, enabling early detection of abnormal voltage increases that indicate short circuit conditions. This preliminary detection prevents delayed detection after the mirror period, thereby preventing semiconductor element breakage while reducing detection time loss.
2Loss of time
If detection is performed during the transition period, then earlier detection is achieved, but detection complexity increases
Solution Approach 1:
The patent uses an intermediary approach by introducing a detection circuit that monitors gate voltage through a voltage divider configuration. The circuit uses resistors (R1, R2) as intermediary elements to safely divide and scale down the gate voltage to a level suitable for comparison with reference voltage. This intermediary voltage division method enables transition period detection without requiring complex high-voltage measurement circuits, thus achieving early detection while controlling device complexity.
3Measurement precision
If reference voltage is set lower than mirror voltage, then transition period detection is enabled, but detection precision during ON period may be affected
Solution Approach 1:
The patent applies segmentation by dividing the detection process into two distinct time periods: transition period detection and ON period detection. During the transition period, the reference voltage is set lower than mirror voltage to detect abnormal voltage increases early. During the ON period, the reference voltage is adjusted to be higher (at or above mirror voltage) to maintain proper detection thresholds. This segmented approach allows the detection circuit to adapt to different operational phases, maintaining detection precision across both periods while accommodating the different voltage characteristics of each phase.
Data Source
AI summary
A first aspect of the present invention will provide a short circuit detector, including: a voltage detection circuit to detect gate voltage which is input from a gate driving circuit to the semiconductor element; and a short circuit detection circuit to detect a short circuit state of the semiconductor element, when gate voltage of the semiconductor element becomes higher than or equal to first reference voltage in a transition period from when a turn-on signal is input to the gate driving circuit until when a mirror period of the semiconductor element starts.