Current detection method based on parasitic inductance and its application

Abstract

The present invention proposes a current detection method based on parasitic inductance and its application. It determines whether there is overcurrent by detecting the voltage signal at both ends of the parasitic inductance connected between the source pin of the switch tube and the power ground, and sends an overcurrent shutdown through the logic control circuit. command, when an overcurrent condition occurs, the gate-source voltage of the switch tube is limited through the gate voltage clamp circuit to protect the switch tube. At the same time, it integrates a soft turn-off function to slow down the speed of over-current turn-off and reduce the turn-off instant. voltage spikes, while achieving fast short-circuit protection of SiC devices and reducing EMI problems.

Description

technical field [0001] The invention proposes a novel overcurrent protection circuit suitable for SiC devices, relates to a fast detection and protection circuit based on parasitic inductance current detection and integrated overcurrent soft shutdown function, and belongs to the technology in the field of power electronic equipment. Background technique [0002] In recent years, SiC devices have become ideal devices for improving the efficiency and power density of power converters due to their advantages such as low on-resistance, fast switching speed, and high temperature and high pressure resistance. However, there is a lack of fast and reliable overcurrent protection circuits in practical applications. [0003] Compared with Si devices, SiC devices have smaller chip area, higher current density, and lower short-circuit withstand capability. For SiC MOSFETs packaged in TO-247, when the bus voltage is 700V and the driving positive voltage is +18V, the short-circuit withst...

AI Technical Summary

Problems solved by technology

The overcurrent phenomenon is detected by using the principle that the voltage on the FET increases significantly during overload, but this method limits the response speed of the overcurrent protection due to the internal logic delay of the chip at the moment of short circuit.

Another known overcurrent protection circuit for SiC devices is the undersaturation detection circuit, which triggers the overcurrent protection circuit by utilizing the characteristics of the SiC device exiting the saturation region during overcurrent, but this method is not suitable for SiC where the saturation region is not obvious MOSFET, and this method has poor noise immunity at high switching frequencies and is prone to false triggering

Images