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UCC27714EVM-551: Power On/Off Procedure

Jose Maria Rey
Prodigy 60 points
Part Number: UCC27714EVM-551
Other Parts Discussed in Thread: UCC28950, UCC27714, UCC27524A

Hello,

The user's guide of the UCC27714EVM-551 says the following about the on procedure:

1. The EVM was not designed to startup from 0-V input voltage. Please make sure the input voltage is inbetween
370 V and 410 V before applying the bias voltages.

NOTE: It is important to follow the power up and power down procedure to ensure the EVM does
not get damaged.


This EVM was designed to show the performance of the UCC28950, UCC27714 and
UCC27524A in a phase-shifted, full-bridge and is not a standalone power supply. This EVM
does not included input under voltage lockout (UVLO) circuitry that would be present in a
standalone power supply.

Why isn't recommended to increase progressively the input voltage from 0V to 390V with the Vbias applied?

Is there any problem with the UCC28950 working at maximum duty cycle until the control loop starts regulating and the duty cycle decreases?

Thank you.

  • +1
    TI__Mastermind 21535 points

    Hello Jose,

    The start up sequence is set up so that the high voltage input is present and stable at the time that the controller starts the power up soft start sequence. If the biases are applied 1st the controller would have completed the soft start sequence and be at maximum duty cycle at the application of the VIN input.

    Regards,