Current detection method based on parasitic inductance and application of current detection method

Abstract

The invention provides a current detection method based on parasitic inductance and application of the current detection method. Voltage signals on two ends of the parasitic inductance at a connecting line between a source pin of a switch tube and a power ground are detected to judge whether overcurrent occurs, an overcurrent turn-off instruction is sent through a logic control circuit, and the grid-source voltage of the switch tube is limited to protect the switch tube through a grid voltage clamp circuit when the overcurrent condition occurs. According to the method and the application thereof, a soft turn-off function is integrated, the speed for overcurrent turn-off is slowed down, the voltage spike at the turn-off moment is reduced, and the rapidity of short circuit protection of a SiC device is realized while an EMI (Electro-Magnetic Interference) problem is reduced.

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...

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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

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