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UCC256303: Fullbridge LLC pri. wire low side 2xMOSFETs drive <transformer>

Hiroshi Doi35
Expert 2845 points
Part Number: UCC256303
Other Parts Discussed in Thread: UCC27712, UCC25600, UCC28950, UCC27714

Hi all,

I want to configure the Full Bridge LLC by using one UCC256303.

How to connect to drive pri.wire low side 2x MOSFETs?

In case of using drive transformer, how about below.

For high side mosfet drive trans connection :   HO-HS(pri.) - Gate-Source.

For low side mosfet drive trans connection :   LO-GND(pri.) - Gate-Source.

Is this OK ?  Any additional caution point?

  • 0
    TI__Guru* 85616 points
    Hello Hiroshi,
    I am not sure if this is possible with the UCC256303 since the device has high side and low side gate drivers built in. This may be possible with the UCC25600 that was designed to work with 1 to 2 gate drive transformers. You could just use two 1 to 2 gate drive transformers having the phase of the transformers at 180 degrees. I am not sure at how well this would share current or if you might so this may not be a good idea. You could use two isolated drivers like the UCC27712 with the UCC25600 but this would require adding delay circuit to ensure that there are no shoot through issues.
    I have designed half bridge LLC converters and phase shifted full bridge (PSFB) converters. Both of these topologies provide ZVS. The phase shifted full bridge however is easier to design compared to an phase shifted full bridge LLC and can attain ZVS over a wider input range. We have a UCC28950 phase shifted full bridge controller designed for this application that would be easier to design with in the application.
    www.ti.com/.../ucc28950.pdf

    We have an application note that goes through the step by step design process, as well as, an excel design tool and MathCad tool that goes through the step by step design process.

    Application Note with a step by step design process:
    www.ti.com/.../slua560

    Excel
    www.ti.com/.../sluc222
    www.ti.com/.../sluc210

    Regards,

    Mike
  • 0 in reply to Mike O'
    Expert 2845 points

    We can not win in such a costly way.
    Please only answer my question about UCC 256303.

  • 0 in reply to Hiroshi Doi35
    TI__Mastermind 27095 points
    Hi Doi-san,

    I would not recommend using gate a drive transformer on the low side with UCC25630x. This is because the inital low side pulse is intentionally long (~150us) in order to charge the boot capacitor. The longer on time could potentially saturate a gate drive transformer. You could use a gate drive transformer to translate the floating high side gate to a ground referenced signal and feed this signal to a half bridge driver such as UCC27714 (for full bridge you would need 2x UCC27714 drivers).

    Best Regards,
    Ben Lough