Desaturation Protection Circuit for Faster SiC MOSFET Fault Response
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Solution Overview
Problem
Conventional desaturation protection methods for SiC MOSFETs require a blanking time longer than the normal turn-on transient time, leading to slower fault response times and increased fault energy stress during short-circuit faults, while also compromising noise immunity.
Innovation Solution
A blanking-time-less desaturation protection method that utilizes both drain-source voltage and voltage rate of change (dv/dt) monitoring to achieve faster fault response times, employing a circuit with a desaturation protection circuit, a short-circuit monitoring circuit, and a totem-pole driver to actively clamp the short-circuit current and turn off the power device quickly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blanking time longer than turn-on transient time is used in conventional desaturation protection, then noise immunity is improved, but fault response time increases and fault energy stress on power devices increases
Solution Approach 1:
The protection method segments the monitoring approach by simultaneously implementing both desaturation protection (for noise immunity) and short-circuit monitoring (for fast response). The short-circuit monitoring circuit independently detects SC faults through alternative parameters, allowing immediate response without waiting for the desaturation protection's blanking period to expire.
Solution Approach 2:
The invention introduces a dedicated short-circuit monitoring circuit as an intermediary mechanism that works parallel to the conventional desaturation protection. This intermediary circuit provides a fast response pathway for SC faults while the desaturation protection continues to handle noise filtering and other fault conditions.
2Reliability
If a blanking time longer than turn-on transient time is used in conventional desaturation protection, then false triggering is reduced, but fault energy stress on power devices increases
Solution Approach 1:
The protection system is segmented into two independent monitoring pathways: desaturation protection for preventing false triggering through noise filtering, and short-circuit monitoring for immediate SC fault detection. This segmentation allows each pathway to optimize for its specific function without compromising the other.
Solution Approach 2:
The short-circuit monitoring circuit performs preliminary detection of SC faults during the blanking period before the desaturation protection would normally trigger. This preliminary action enables the system to respond to SC faults immediately upon detection, reducing the duration of fault energy stress on power devices.
3Speed
If short-circuit monitoring is implemented separately from desaturation protection, then fault response speed is improved, but device complexity increases
Solution Approach 1:
The invention merges the short-circuit monitoring circuit with the desaturation protection circuit into a unified protection system. Both monitoring functions share common components such as the microcontroller unit, signal processing infrastructure, and output control mechanisms, reducing overall device complexity while maintaining fast fault response capability.
Solution Approach 2:
The protection system is designed with multi-functionality where the same hardware infrastructure serves both desaturation protection and short-circuit monitoring functions. The microcontroller and associated circuits can process signals from both monitoring pathways, eliminating the need for completely separate dedicated circuits and reducing overall system complexity.
Data Source
AI summary
The disclosure relates to a devices, systems and methods implementing desaturation protection during faults (over-current or short-circuit faults) for a power device by monitoring drain source voltage and rate of change of the drain source voltage which provides a fault response time (t0 to t2) that is shorter than the blanking time (t0 to t5) required by conventional desaturation protection methods.