Cold Start Passes, Hot Restart Explodes? The Hidden Soft-Start Failure!
Cold start looks perfect.
Hot restart blows the input capacitor, MOSFET, and bridge rectifier.
The real issue may not be the MOSFET or PCB layout — it could be soft-start failure.
Residual voltage in the soft-start capacitor, compensation network, or LLC resonant tank can cause the controller to skip the startup ramp and hit the power stage with a high-duty-cycle surge.
Always test rapid power cycling and full-load hot restart before mass production.
Ask ICWantOpen for smarter hardware debugging.
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