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TIDA-010933: Q3, Q4 failure

DKelektronik
Prodigy 60 points

Part Number: TIDA-010933

Tool/software:

Dear TI Designe Team,

Currently, we are designing the DC/AC part as a Voltage Source Inverter, not as the Grid-Connected Inverter that you originally designed.

We have finished designing the AC voltage output, but sometimes both low switching MOSFETs Q3 and Q4 break and explode; sometimes U24 also breaks.

We are currently investigating the cause.

Have you encountered this phenomenon during your design process? Do you know the cause?

Here is a case where the error occurs:

C1: 75V bus voltage

C2: 400V bus voltage

C3: AC output voltage

C4: AC output current

When we suddenly cut off the input power, the waveform appears abnormal.

  • 0
    TI__Expert 3290 points

    Hi, 

    the implemented gate resistors are too small. I suggest you to place 20 Ohm. This will decrease significantly the switching speed of the low frequency FETs. This should not impact your efficiency. 

    Thanks

    BR 

    Riccardo

  • 0 in reply to Riccardo Ruffo
    Prodigy 60 points

    Hi Riccardo,

    Thanks for your reply!

    I'm trying it by changing Ron = 10Ω, Roff = 3.3Ω, and R104=91kΩ, C146=220pF to fit in recommendations from the U24 datasheet.

    At the same time, turn OFF both Q3, Q4 at the AC output zero crossing when any protections appear.

    Until now, they haven't blown again.