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UCC21710QDWEVM-025: Half bridge drive with two Evalboards

Part Number: UCC21710QDWEVM-025

Hello,

we bought two EVM´s to get a half bridge setting of two SIC-Fet. The halfbridge has actually no load and the switches are G2 Generation in  TO-247 from CREE.

The switching time is 35ns dv/dt and the problems are:

If we getting higher with the voltage of about 350V-400V there are no stable work

 -> first the UVLO/OVLO of the Chip signalize that the Voltage VDD-COM is getting low, this was because the TPS3700QDDCRQ1 pull down the enable signal and shut down the SN6505BDBVR.

-> also we have a problem with the Vsat measurement first we try to make the blanking time very long to get the circuit running, but the noise seems to be so high that we cant work with that also when we short the circuit from pin 2-3 the OC protection signalize on 350V-400V a fault.

We did not realy no whats getting wrong could you please help us or give us some advise.

  • Hello Philipp,

    Thanks for reaching out.

    Are there modifications made to the EVM's from out of the box?

    I believe this is with no load and both EVMs configured in a half-bridge, You mentioned that at >350V, "there are no stable work", what do you mean? What do the waveforms look like? Does this mean that for <350V bus voltage the bridge works normally? Can you please share waveforms of the signals in questions with the power train off (Vbus=0V) or at low voltage? 

    WHat is your targeted blanking time? The noise you describe seems to indicate long connections from high-side transistor to low-side FET. You want to minimize your switch node loop and Bus+ connections.

    Regards,

    -Mamadou

  • Hello Mamadou,

    we solve the Problem with a small capacitor over the half bridge to stable Vzwk-Com.

    Regards

    Philipp