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ISO5452: Soft Turn-Off with Increased Drive Current

Ilya Mazurenko
Expert 1300 points
Part Number: ISO5452

Hello Team,

Please help with our customer's question about ISO5452:

In datasheet page 33 there are Figure 57(Current Buffer for Increased Drive Current):
Will Soft Turn-Off (STO) function work with it? 
How will it work with Increased Drive Current? When will it turn on?

Thank you in advance!

BR,
Ilya. 

  • 0
    TI__Intellectual 1665 points

    Hi Ilya,

    A capacitor can be added to the base terminal of the BJT buffer. The capacitance can be sized based on the soft turn-off timing. In case of the DESAT detection, the driver pull-down current is 130mA.

    With Regards,

    Xiong

  • 0 in reply to Xiong Li
    Expert 1300 points
    Hello Xiong,

    Thank you for the reply!

    If 10nF capacitance is added it provides huge increase in on/off delay during operation. (to 500-1000 ns).
    This leads to an increase of switching loss in IGBT.

    If they add capacitance lower than 10 nF, then it leads to the too much tempo of soft turn-off.
    Which leads to overvoltage on IGBT in case of short-circuit breaking current.

    Is there another way to apply soft turn-off in this scheme?

    Thank you in advance!

    BR,
    Ilya.
  • 0 in reply to Ilya Mazurenko
    TI__Intellectual 1665 points

    Hi Ilya,

    We can reduce the gate resistance value between driver output and base of BJT buffer to reduce the delay. 

    With Regards,

    Xiong