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TPS23753A: Regarding the FET circuit on the secondary side

Kaji@PAN
Mastermind 7260 points
Part Number: TPS23753A
Other Parts Discussed in Thread: PMP9175, TPS23755, TPS23734

Hi,

I would like to ask you about the TPS23753A device.
I'm looking at the PMP9175 schematic in a reference design.
I want to use the secondary FET circuit (Q7) used in this circuit diagram to reduce loss.
However, the secondary side output voltage of this circuit is 5V, but my specifications assume a 24V output voltage.
Is it possible to use the secondary side FET circuit even with 24V output?
Also, for 24V output, are there any parts that require constant changes in the peripheral circuits that drive this FET?

Best regards,

  • 0
    TI__Mastermind 40640 points

    Hi Kaji-san,

    The self driven flyback is not recommended for 24V outputs as you will find that it is difficult to minimize shoot through losses for high output voltages. This means the efficiency will NOT be any higher than a diode rectified flyack. Since we have studied this in the past, we do not have a recommended TI design that supports this.

    For a 24V output, we recommend a diode flyback using the TPS23755. You can use the EVM to put the parallel secondary windings (12V) and modify them in series to get 24V output.

    Or we recommend a driven flyback, if efficiency is absolutely  necessary. This does mean you will need an external gate drive transformer driven by a second gate drive. For example, you can use the TPS23734 which has a secondary gate drive pin to drive the gate drive transformer.

    Please let us know if this helps. Thanks!