SLUAAY2 December   2024 ISO5451 , ISO5451-Q1 , ISO5452 , ISO5452-Q1 , ISO5851 , ISO5851-Q1 , ISO5852S , ISO5852S-EP , ISO5852S-Q1 , UCC21710 , UCC21710-Q1 , UCC21717-Q1 , UCC21732 , UCC21732-Q1 , UCC21736-Q1 , UCC21737-Q1 , UCC21738-Q1 , UCC21739-Q1 , UCC21750 , UCC21750-Q1 , UCC21755-Q1 , UCC21756-Q1 , UCC21759-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 SiC and IGBT Characteristics
  6. 3 Failure Modes
  7. 4 Short-Circuit Protection Approaches
    1. 4.1 Short-Circuit Current-Based Protection Implementation
    2. 4.2 Short Circuit Voltage-Based Protection Implementation
  8. 5 DESAT Circuitry Design
    1. 5.1 DESAT Circuit Component Selection
    2. 5.2 Effect of Parasitic Elements
    3. 5.3 Effect of Rlim on DESAT Noise
  9. 6 Safe Shutdown
    1. 6.1 Safe Shutdown Mechanisms
    2. 6.2 Safe Shutdown Considerations
  10. 7 Short-Circuit Test Setup and Data
    1. 7.1 Short-Circuit Bench Measurement Setup
    2. 7.2 SC Board Setup for Data Collection
    3. 7.3 Different Circuit Configurations for SC Testing
    4. 7.4 Bench Measurement Results
    5. 7.5 Overall Summary of SiC vs IGBT Power Module SC Observation
  11. 8 Key Consideration in Designing SC Protection Circuit
  12. 9 Summary
  13. 10References

4 Short-Circuit Protection Approaches

There are two major protection approaches applicable in terms of detecting short-circuit (SC) and over-current (OC) events.

  1. Current threshold (ISC)-based protection
  2. Voltage threshold (VSC)-based protection
  • Current threshold (ISC)-based protection
    • During both SC and OC events, the current is increased at least 10x or more, so detecting the increased ICE/ID accurately is one of the approaches to detect the OC/SC event. The detection logic needs to be defined so that the detection current threshold is at least 1.5 to 2 times higher than the maximum operating current. Providing enough margin helps to avoid false detection during the maximum operating current.
  • Voltage threshold (VSC)-based protection
    • Based on IGBT and SiC power module IV characteristics, another approach to detect the OC/SC event is by measuring the voltage across the power module effectively to detect the faulty condition. During the OC/SC event, the voltage across the power module (both VCE and VDS) increases to a much higher value than the normal operating condition. The current saturation characteristic in an IGBT gives us a very clear VCE voltage at which point you can decisively say the IGBT is leaving the saturation region, or “De-saturating". In case of SiC, it is recommended to define 2x the normal operating voltage to detect the OC/SC threshold.
UCC21750Q1 VSC and ISC Thresholds on IGBT and SiC IV Curves Figure 4-1 VSC and ISC Thresholds on IGBT and SiC IV Curves