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

4.1 Short-Circuit Current-Based Protection Implementation

There are two implementation options for current detection approach:

  • Shunt resistor based approach
  • R-sense resistor based approach

Option1: Shunt resistor-based approach

UCC21750Q1 Shunt Resistor Implementation Circuit Figure 4-2 Shunt Resistor Implementation Circuit

In Figure 4-2, the current detection implementation approach is shown with an Rshunt resistor. The Rshunt is added in the high current path, the voltage across the resistor is measured using the RC filter by the OC detection pin. When the voltage across the resistor is higher than the OC detection threshold, the gate driver triggers a fault event and turns off the gate driver output to protect the system.

This implementation approach is very simple and fast. However, as the resistor is in the high current path, this method causes high-power loss. Due to that, this approach is not recommended for systems with high operating current, to minimize the power loss.

Option2: Rsense resistor-based approach:

UCC21750Q1 Rsense Resistor Implementation Circuit Figure 4-3 Rsense Resistor Implementation Circuit

This approach is similar to the Rshunt-based approach. However, in the case of the Rsense-based approach, the sense resistor is added in the sense path, not on the high current path. Some power modules have a separate terminal that has around 5000x lower current sense path apart from the high current path. The sense resistor is added in the lower current sense path and hence the power loss is minimal. This approach is faster and has lower power loss as well. However, it can be implemented only with the power modules with the sense option.