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Isolated DC/DC flyback - primary side controller

Parameshwara Bhat
Intellectual 290 points
Other Parts Discussed in Thread: UC3842A, UCC2800

Hello All,

I would like to use a controller for DC input of 12V-30V and output of 16 VDC, 2A.

I prefer to use primary side regulated flyback for it's simplicity, but not averse to using any other isolated topology.

I checked on UCC2863x family,UCC287xx family. When I enter the input and output values on their design calculators, many values in the calculated outputs turn to negative values or RED. I guess they can work with only AC line range.

I also checked on UC3842a. It's description seems to match with my requirement,but 'WEBWNCH' returns 'Vin out of range' when I insert my input range.

Can anybody clarify if above controllers can be used with Vin range of 12V-30V DC ( OR corresponding Vac-rms ?

If they cannot be used, which are better suited to my requirement ?

Thanks in advance,

Param.

  • 0
    TI__Mastermind 31580 points
    Hi Parameshwara,

    I suspect your main issue is the minimum value of the 12V input and the required start-up value of the Vcc rail for many of the controllers will be higher than 12V.

    Take a look at the UCC2800 datasheet it two of the devices turn on below 10V which make them suitable for low input voltage designs.

    Regards

    Peter
  • 0
    TI__Expert 3200 points
    Param,

    The start-threshold for the UC3842A is 17.5 V max so your low Vin range of 12 V will not work. Same for UCC2863x as the start threshold is 16.5 V max. Same for UCC2871x, 23 V max turn-on threshold.

    I will have an AE look into a recommendation for your DC input of 12V-30V and output of 16 VDC, 2A.
  • 0 in reply to Peter Meaney
    Intellectual 290 points
    Hi Peter,

    Vin(max) is only 13.5 V, I have not gone into the datasheet yet. But designs seem to be using higher Vin.There must be a way.

    Thanks.

    Param.
  • 0 in reply to Brian Johnson96
    Intellectual 290 points
    Hi Brian,

    In the parametric selection, for all these controllers, Vin-min, Vin-max is not used, but UVLO threshold parameter is used which is in the range I am looking for. This is a little misleading.

    I will wait for your list. Peter has suggested UCC2800. But, if in TI's vast available choices, there is a higher efficiency or primary side controlled controller,I will go with that.

    Thanks,

    Param.
  • 0 in reply to Parameshwara Bhat
    TI__Expert 3200 points
    Hi Param,

    It can be difficult to just use the UVLO parametric data because there are also absolute maximum ratings which is 12 V on the VCC input for the UCC2800. I did send your E2E request to the AE Team that is in a better position to support you then I am.