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

7.4 Bench Measurement Results

There are four different SC tests conducted with different detection approaches. 9V DESAT threshold gate driver UCC21750-Q1 is used to capture SC data for both without external charge current and with external charge current. Also, 0.7V OC threshold gate drivers UCC21710-Q1 and UCC21732-Q1 are used to capture SC data for STO and 2LTO, different turn-off approaches.

  • Case1: 9V DESAT without external charge current, with STO
  • Case2: 9V DESAT with external charge current, with STO
  • Case3: 0.7V OC threshold, with STO
  • case4: 0.7V OC threshold, with 2LTO
UCC21750Q1 Case1 and Case2 SiC SC Event Screen Captures Figure 7-7 Case1 and Case2 SiC SC Event Screen Captures

As shown in Figure 7-7, with a default charge current of 0.5mA, the detection time, peak SC current, shutdown energy, and shutdown time are all high compared to external charge circuitry to enable faster detection.

UCC21750Q1 Case3 and Case4 SiC SC Event Screen Captures Figure 7-8 Case3 and Case4 SiC SC Event Screen Captures

As shown in Figure 7-8, the “OC as DESAT” peak current and detection time (Case3 and 4) are comparable to the “DESAT” detection time with external charge current (Case2).

In case of shutdown energy, 400mA STO performance Case3 matched Case2, however, 2LTO performance of Case4 showed higher shutdown energy and shutdown time as the Gate was held approximately 9V for approximately 1μsec and the peak current did not reduce and kept It the same. This is because the gate holding voltage of 9V threshold is keeping the SiC module conducting and the peak current was not reduced. If the power module “turn on threshold” is just below 9V, then it would reduce the SC current and the 2LTO would be effective in such case only.

The four cases shown above are repeated for IGBT power module as well.

UCC21750Q1 Case1 and Case2 IGBT SC Event Screen Captures Figure 7-9 Case1 and Case2 IGBT SC Event Screen Captures
UCC21750Q1 Case3 and Case4 IGBT SC Event Screen Captures Figure 7-10 Case3 and Case4 IGBT SC Event Screen Captures

The performance of the IGBT was comparable to SiC power module in terms of how DESAT/OC circuit behavior.

However, as the overall peak current observed in the IGBT module was much lower compared to SiC. Because of this, the shutdown energy and shutdown time are all much lower for IGBT module.