Semiconductor Device Overcurrent Protection Circuit
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Solution Overview
Problem
Existing semiconductor devices with power switching elements face issues with overcurrent protection, particularly the risk of burning resistors and damaging gate drivers due to reverse currents flowing through parasitic diodes when a negative drive voltage is applied.
Innovation Solution
The semiconductor device incorporates a first and second n-channel power switching element, a diode, and a charge discharge circuit, where the charge discharge circuit acts as a path to reduce the control voltage of the first power switching element during overcurrents and suppresses reverse currents by providing a discharge path for excess charge, thereby minimizing the impact of negative drive voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is performed using current sensors to suppress gate voltage during overcurrent, then current limiting function is achieved, but reverse current flows through parasitic diode causing resistor burning and gate driver damage
Solution Approach 1:
The harmful reverse current path is extracted and isolated from the main circuit by introducing a dedicated charge discharge circuit. This separate path allows excess charge to be discharged safely without flowing through the parasitic diode, thereby preventing damage to resistors and gate drivers while maintaining the current limiting function.
Solution Approach 2:
A charge discharge circuit is introduced as an intermediary component between the power switching element and the external circuit. This mediator provides a controlled path for charge discharge, preventing direct reverse current flow through the parasitic diode and protecting other circuit components from damage.
2Device complexity
If monolithic protection circuit is constructed, then integration is achieved, but reverse current path cannot be eliminated
Solution Approach 1:
The protection function is segmented into distinct operational paths: the main current limiting path and the separate charge discharge path. By dividing the protection mechanism into these independent segments, the circuit can maintain integration benefits while eliminating the harmful reverse current path that exists in monolithic designs.
3Ease of operation
If negative drive voltage is applied to gate, then switching control is achieved, but reverse current flows through parasitic diode
Solution Approach 1:
The parasitic diode, which normally causes harmful reverse current, is effectively neutralized by providing an alternative discharge path. The charge discharge circuit converts the potentially harmful reverse current flow into a beneficial controlled discharge process, where excess charge is safely removed from the gate without damaging other components.
Data Source
AI summary
A semiconductor device includes a main IGBT, a sense, a resistor, a MOSFET and a diode, as main components. The sense IGBT and the main IGBT are connected in parallel with each other. The drain of MOSFET is connected to the gate of the sense IGBT, the source thereof is connected to the gate of the main IGBT, and the gate thereof is connected to the emitter of the sense IGBT and the cathode of diode. One end of the resistor is connected to the gate of the main IGBT and the source of the MOSFET, and the other end of the resistor is connected to the emitter of the main IGBT and the anode of the diode.