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UC3827-1 - Required to keep SRC isolated from GND/PGND?

Shawn Standfast
Prodigy 170 points
Other Parts Discussed in Thread: UC3827-1

Hello All,

 

I am looking to build a ~1KW offline buck- current fed full-bridge converter using the UC3827-1 controller.  The issue is that my input voltage is going to be about 340 Vdc using 120-240 Vac input.  Since the UC3827-1 can only sustain up to a maximum of 90Vdc for the floating buck driver, the chip cannot be used at this voltage level.  I have found different FET drivers capable of up to 600Vdc floating operation which I plan to use between the Buck output and the actual FET.  However, my question is, does the floating driver of this chip have to remain isolated from GND/PGND supply reference?  I would like to use the same VCC for both the PWM controller and the FET driver if at all possible.

 

Thanks,

 

Shawn

  • 0
    Prodigy 170 points

    In other words, does the high-side driver have to float with respect to the chip's ground reference?  Will it cause problems to reference the floating driver with the same ground as the PUSH/PULL and controller ground?  Mainly, are there any pitfalls I should look out for when doing this?

     

    Thanks,

     

    Shawn

  • 0
    Prodigy 170 points

    Any thoughts on this?  Anybody?

  • 0 in reply to Shawn Standfast
    TI__Mastermind 25130 points

    Shawn,

    I know of no reason why using a separate driver to provide the drive to the Buck output would cause a problem. I would connect the SRC to PGND and V+ to VCC.

    I would expect the converter to work fine especially as the noise from the BUCK switch waveform will not be directly connect to the control IC.

    Only point I would suggest is that there will be leakage inductance in the transformer primary and you will be feeding that with an inductor where the current is different than in the primary. This can lead to some high voltage spikes which in turn can lead to problems.

    I personnally prefer the Voltage fed version of this circuit.

    Regards,

    John