Hardware soft protection circuit with IGBT function multiplexing function

Abstract

The invention discloses a hardware soft protection circuit with an IGBT function multiplexing function. The circuit comprises: an IGBT soft turn-off unit, wherein when a fault occurs, a fault signal passes through a latch and a digital isolation chip to control a secondary side MOS tube to forcibly charge a DESAT pin of a driving chip, the DESAT protection is triggered when a threshold value is reached, and the driving chip achieves soft turn-off protection; a secondary side PWM waveform detection unit used for transmitting a secondary side IGBT gate-level PWM signal back to a primary side through a digital isolation chip, wherein the DSP is used for monitoring whether the duty ratio and the period of the transmitted PWM signal are consistent with those of the PWM signal sent by the DSP ornot; and a DESAT function detection unit used for transmitting a DSP given control signal to a secondary side control MOS tube by adopting a digital isolation chip for conduction, triggering the DESAT soft turn-off protection of the driving chip, and determining whether the DESAT function is normal or not by detecting the high-low attribute of the PWM signal level fed back by an IGBT. The hardware soft protection circuit performs soft turn-off protection on the IGBT in the full range, reduces the stress of the device, avoids hard turn-off of the IGBT during the desaturation current period, and can detect the secondary side PWM waveform and the functional integrity of the driving chip DESAT at the same time.

Description

technical field [0001] The invention relates to the field of IGBT protection, in particular to a hardware and software protection circuit for IGBT function multiplexing. Background technique [0002] When a series of faults such as overvoltage, overcurrent, and overtemperature occur in the existing IGBT, the hardware is generally protected by forcibly shutting down the PWM. This method can effectively protect the safety of the system when the current is small, but when the current is large , Forced hard shutdown will greatly increase the stress on the device and reduce the service life of the device. Especially during the period from the IGBT rated current to the desaturation current, there is currently no protection strategy for this stage. Hard shutdown at this stage may cause damage to the IGBT due to instantaneous overvoltage. At the same time, considering the functional safety requirements, the real-time monitoring of the gate-level PWM signal of the IGBT has also beco...

AI Technical Summary

Problems solved by technology

[0008] The purpose of the present invention is: the present invention proposes a hardware soft protection circuit for IGBT function multiplexing, which can effectively implement soft turn-off protection to IGBT in the whole range, reduce device stress, and effectively solve the problem of IGBT in existing solutions. The risk of hard shutdown during the period from the rated current to the desaturation current. At the same time, it can detect the secondary IGBT gate-level PWM waveform, power-on detection and drive chip DESAT function, improve the safety of the device, and circuit reuse to further reduce the circuit cost.

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