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UCC28740: Flyback Controller Recommendation for Wide Input Range (80–1000 VDC) Auxiliary Power Supply

Manjesh Gowda Ramegowda
Prodigy 70 points
Part Number: UCC28740
Other Parts Discussed in Thread: UCC28C53, , UCC28700-Q1, UCC28730

Tool/software:

Hi Team,

We are developing an isolated flyback converter to be used as an auxiliary power supply in inverter and battery applications. The key design specifications are:

  • Input voltage: 80 VDC to 1000 VDC

  • Outputs: 18 VDC and 24 VDC

  • Output power: ~45 W

  • Isolation: Required

Based on functionality, BOM cost, and expected performance, we have shortlisted a few TI flyback controllers and reviewed available application notes and reference designs.

To finalize the selection, I would appreciate your input—particularly if you have experience or feedback from similar customer applications operating over such a wide input range. Any known challenges or design considerations would also be helpful.

The controllers we are currently considering are:

  1. UCC28C56HQDRQ1 / UCC28C53

  2. UCC28740

  3. UCC28700-Q1

We would greatly value your recommendation or insights that could help confirm the best fit for this use case.

Thank you in advance for your support!

  • 0
    TI__Guru 50090 points

    Hi Manjesh.

    Supporting such a wide input range is not easy, but we do have this lower power reference design using the UCC28730.

    This should help you get started.

  • 0 in reply to JCHK
    Prodigy 70 points

    Hi Jchk,

    Thank you for your response. However, the UCC28730 is typically recommended for output powers in the range of 5 W to 25 W. Since our application exceeds this range, we’re focusing on the alternative controllers listed above.

    Regards,
    Manjesh

  • 0 in reply to Manjesh Gowda Ramegowda
    TI__Guru 50090 points

    HI Manjesh,

    The UCC28730 is a controller and can support much higher power levels. PMP41063 is a 300V-1kV 48W reference design as an example.

    I hope this answers your question. 

    Regards,

    John

  • 0 in reply to JCHK
    Prodigy 70 points

    Hi John,

    Thank you for the information and the reference design. I hadn’t come across this reference design before. Based on the application note, I saw that the UCC28730 is typically recommended for output powers up to 25 W.

    I’m also interested in understanding whether the other three controllers I mentioned would be suitable for my application. This would help me narrow it down to two final options, as I’d prefer to keep some flexibility before making a final decision. I’ve found a reference design for the UCC28C56HQDRQ1 with similar parameters, but haven’t seen equivalent designs for the others yet.

    Regards
    Manjesh

  • 0 in reply to Manjesh Gowda Ramegowda
    TI__Guru 50090 points

    HI Manjesh,

    There is nothing limiting the UCC28730 to 25W, The power limitation is a function of the power stage, not the controller. Where are you finding the typical recommendation up to 25W?

    The key differences between the UCC28730 and the UCC28C56HQDRQ1 are:

    1. The UCC28730 is a dedicated valley switching flyback controller, the UCC28C56 is a general purpose PWM that does not valley switch. (Valley switching improves the efficiency over the full load range as is minimizes switching losses)

    2. The UCC28730 has high-voltage startup (but this works only up to 700V)

    3, The UCCC28730 varies its switching frequency as a function of the load, the UCC28C56 is a fixed frequency controlller

    4. The UCC28730 is optimized for light load efficiency and can acheive <5mW of standby power. 

    5. To save space and improve the power density of the design, the UCC28730 works with the UCC24650 wake-up IC. The wake-up IC can reduce the required output capacitance by ~1/7th. 

    In short, any of the controllers you are looking at can be made to work, the final choice will depend on your efficiency target. 

    I hope this helps to clarify.

    Regards,

    John

  • 0 in reply to JCHK
    Prodigy 70 points

    Hi John,

    yes, thanks for the information.

    I have read about recommendation upto 25W in the datasheet, page no 21 (Application information).
    UCC28730

    For our design, we’re targeting an efficiency around 85%, and overall BOM cost is a key consideration. Ease of use—such as availability of design tools, simulation models, and reference designs—is also important. Additionally, compatibility with SiC MOSFETs is a requirement.

    Given these priorities—efficiency, cost, and ease of implementation. Do you have a recommendation or preferences among the controllers?

    Regards,
    Manjesh

  • 0 in reply to Manjesh Gowda Ramegowda
    TI__Guru 50090 points

    HI Manjesh,

    I see. That recommendation is if you want the total standby power consumption to be under 5mW. As you go up in power, the other components leakages make 5mW difficult to achieve. The UCC28730 can easily support designs up to 100W beyond that we have more efficient controllers and topologies. 

    The key to driving SiC is making sure you have a headroom for the FET. The UCC28C56 and UCC28730 both have UVLO set to support SiC. The UCC28C56 has a stronger gate drive because it is hard switching.  The UCC28730 has a 14.5V clamp on the gate drive so may require an additional gate drive circuit to work properly. 

    So the UCC28C56 might be the best option here.