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UCC27714: Driver is failing at start up of LLC converter

Part Number: UCC27714
Other Parts Discussed in Thread: ISO7220A,

UCC27714 driving half-bridge LLC converter mosfets.  ISO7220A giving pulses to UCC27714  to drive mosfets. initially controller senses input voltage of 400V gives PWM pulses of 250KHZ at dead band of 220ns each of 44 perent duty cycle. At the time of startup Driver is failing .

For your reference i am attaching some images of schematic

  • Hello Hema,

    There is likely a voltage transient or peak that is high enough amplitude to exceed the driver ratings during the startup. Have you confirmed the control signals are correct without the high voltage applied? Also, during your tests do you have a full load condition?

    For these conditions of troubleshooting I recommend operating the converter in a safer lower stress condition if possible to allow initial inspection of the waveforms. The might include lighter load, lower line voltage input (if possible). Or one good method is to slow down the power mosfet swtiching (for troubleshooting) byy increasing the gate resistance.

    We need to get some operating condition, to allow examination of the voltage signals so I can give good advice on resolving the issue.