SLUAB45 October   2026 UCD3138

 

  1.   1
  2.   Abstract
  3. 1Issue Description: Abnormal SR Voltage Stress Under Output Short-Circuit
    1. 1.1 Abnormal Phenomenon: SR Voltage Stress Exceeds the Limit in Short-Circuit Testing
    2. 1.2 Root Cause Analysis: Timing Mechanism of Turn-Off Stress Caused by Negative Current
  4. 2Solution: SR Stress Optimization Based on the UCD3138 Automatic Mode Switching Capability
    1. 2.1 Key Technology: Principle of the UCD3138 Automatic Mode Switching Capability
    2. 2.2 Solution Implementation: Dynamically Adjusting the Control Timing of the SR On-Time With Mode Switching
  5. 3Experimental Verification: Effectiveness Testing of the Optimization Solution
    1. 3.1 Result Comparison: SR Stress Reduced From 69V to 29.6V
    2. 3.2 Waveform Analysis: Dynamic Switching of the SR On-Time and Early Turn-Off
  6. 4Conclusion
  7. 5References
Application Note

SR Stress Suppression in LLC Converters Under Output Short-Circuit Using UCD3138 Automatic Mode Switching Capability