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UCC287XX-Power-Supply-Recommendations

Parameshwara Bhat
Intellectual 290 points
Other Parts Discussed in Thread: UCC28720, UCC28700, UCC28722, UCC28630

Hello All,

In all the datasheets of UCC287XX, following text appears,

Controllers, UCC2871x, UCC28720 have HV pins which directly connect to Vac Line or Vbulk Line. So, the above statement is convinving.

But, UCC28700,UCC2970X,UCC28722 have no HV PIN. They have only Vdd PIN with a Vmax rating of 35 V. So, the statement  about  Vac min of 85 V  is not conving for these controllers.

I would like to see internal variable list for above controllers like the example list below for UCC28630

                                                           (UCC28630-Page-50, Device Internal Parameters)

OR at least what is the Min Vbulk,Max Vbulk  for UCC2870X Family, UCC2871x family, UCC2872O,UCC28722  ?

Thanks in advance,

Param

  • 0
    TI__Expert 4015 points
    Hi Param. The HV pin only affects the ability of the IC to start up without resistors connected from Vbulk to the Vcc cap. Having HV startup helps reduce standby power. However even the devices without HV startup are still targeted at 85Vac to 265Vac applications. The startup behaviour does not impact the performance of the power train after startup.
    That is not to say that these are the max an min values. It is possible to get the IC to run at higher or lower voltages by correctly selecting the values of the resistors connected to the Vs pin. The min to max Vbulk ratio is about 4.5 and this should be maintained.
    The key internal variable are listed in the electrical specification table of the datasheet.

    Thanks
    Billy
  • 0 in reply to Billy Long
    Intellectual 290 points
    Hi Billy,

    Targetting devices at a segment is a commercial decision, not technical.

    Continuing with the example of UCC28630, it's VDD range is 16/8. so without the internal parameter restriction on HV pin of Vac-on, Vac-min (80/60) , it could theoretically work with a supply of say,>18 V. I guess, though not mentioned in the datasheets, UCC2871X,UCC28720 also have the same restriction on their HV pin of Vac-on, Vac-min (80/60).

    I am wondering if UCC2870x, UCC28722 can be powered by a solar panel of Vopen = 22 V. [ Now, please do not suggest solar chargers, read it as a test case ] That can give an efficient,low-cost isolated output.

    UCC2870x,UCC28722 have no HV pin. It has a UVLOstart-UVLOrun range of 21/8 and VDD max = 38 V. only. So, I do not expect any restrictive Vac-on, Vac-min as in UCC28630 With an appropriate Nbias, can I make it worrk with a Solar panel as above ?

    The datasheets do not expose all internal parameters. UCC28630 has exposed all. But other datasheets,not. If all device internal parameters were listed, I could answer above question myself. Now can you answer for me ?

    Regards,Param.
  • 0 in reply to Parameshwara Bhat
    TI__Expert 4015 points

    Param, the device does not start switching until the current until the current out of the Vs pin exceeds the Ivsl(run) threshold. This is listed and explained in the datasheet. This depends on the input voltage level, the transformer turns ratio and the values of the resistors connected between the bias winding and the Vs pin.