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UCC28710 Input Range and Current without Transformator

Gokhan Sahin
Prodigy 210 points
Other Parts Discussed in Thread: UCC28720, UCC28710

Hi everyone,

We are working on a project and using your reference design one which is PMP9649. Input voltge range is from 85V to 265V  and output current is 400mA in the reference design. However, we want the input voltage range to be around from 50V to 150V and its output voltage also should be 48V/1A or 12V/4A. Is it posibble for me to use the input voltage range or the output voltage / current at level which I have mentioned you ? Or is it better for me to use your another option which you can suggest ?

P.S: We don't want to use a transformator in our design. Because it is custom and too expensive.

Best Regards.

  • 0
    TI__Guru* 86266 points
    Hello Sahin,

    Is your input AC or DC?

    Regards,

    Mike
  • 0 in reply to Mike O'
    Prodigy 210 points
    It is DC voltage and supplies from battery.
  • 0 in reply to Gokhan Sahin
    TI__Guru* 86266 points
    Hello Gokhan,

    The UCC28710 is similar to the UCC28720/2 and should work in a high side buck application.
    The 50 V to 150 V DC is a 3 to 1 input range will work as well. If the input range was over 5 to 1 it could cause issues.

    I did notice that your power level was around 48W. I believe this device is recommended for 25 to 30W.
    However, it should be able to control a 48W design. One issue that you may run into is the controller is not able to achieve complete valley switching.

    The UCC28710 to operate correctly needs a (1-Dmax) < or = 42.5%. This means the maximum duty cycle needs to be less than 57.5% so 48V is not possible with this device. With a 12V output with a 50V input the duty to achieve regulation would be 24% and with a 150V input the duty cycle would be 8%. This could be possible but consideration needs to be taken not to run into a minimum on time limitation. The minimum on time is based on a current sense leading edge blanking of roughly 235 ns (TCSLEB).

    This device has a 4 to 1 input range so to avoid the control law having issues requires selecting and inductor/max frequency based on the following equation. (Dmin @ Full Load) < or = 4*(TCSLEB) fmax. Dmin @ Full Load = 8%. In this example based on your input the maximum frequency for selecting the buck inductor would be 85 kHz.

    I believe this device could regulate a buck converter for your application, it just would not have optimum valley switching. Since this controller was design for near critical conduction DCM applications it will have slightly higher Coss losses.

    Regards,

    Mike
  • 0 in reply to Mike O'
    TI__Guru* 86266 points
    Hello Gokhan,

    I found this off line buck reference design using the UCC28710. www.ti.com/.../PMP10319
    I did not know if you had seen it but this may help you in your design process.

    Regards,

    Mike