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3 phase High voltage ac to low power 5V dc out

Genius 3300 points
Other Parts Discussed in Thread: PMP11302, PMP, UCC28881

1. Have 3 phase ac input with neutral, where each phase voltage goes from, 85V-600Vacrms
2. Need output at 5V/500mA

3. training.ti.com/.../Very_high_Voltage_bias_BK_13-Sept_complete.pdf
page 22 shows external fet operation, but again limited to 1200V, very close, so cant use

4. Anyone have experience in this low power application where size/size constraints? Any reference design?
Transformelss is preferred (sealed application), size and sace constraint.

  • Can this be extended to 3 phase also?  www.ti.com/.../slua721

  • Hello VT,

    I suggest that the PMP11302 concept shown in the trainging pdf can be extended to your 600Vac input. 
    Single phase or three phase rectified voltage ends up with the same peak value with respect to Neutral.  Higher if phase-to-phase rectified.

    For the highest peak rectified voltage, why not use a higher-rated cascode MOSFET such as 800V or 900V instead of 650V as in the PMP design.
    The concept is the same, to use a cascaded MOSFET to bear the difference in input voltage over what the UCC28881 can withstand.
    An additional stacked bulk can also be added to accommodate a higher peak. 

    I suggest that PMP11302 can be modified and adapted to meet your requirements.

    Regards,
    Ulrich

     .  

  • 1. Yes easy to use by single phase and neutral.

    2. But if I use like this? The output dc will go to max 850Vdc? 
    Advantage is here, if one phase get missing/broken, system keeps on running. What do you think for this?  It will max dc output to 848Vdc ? i.e 600*1.414

  • Hello VT,

    Your concept is correct, but the maximum bulk voltage may be higher, depending on the tolerance of the 600Vac source and any swells.

    For example, the normal AC line of 240Vac usually has a +/-10% tolerance, so peak voltage = 240V*1.1*1.414 = 373Vpk. 
    But sometimes a +30% swell (for 1s duration) is considered, so peak may be 240V*1.3*1.414 = 441Vpk.

    Similarly, your 600Vac source may have a peak of 933Vpk, or 1103Vpk if a 30% swell is anticipated. 

    Your design and component selections should account for the highest probable peak voltage on the input line, including the clamp level of the varistors when line surges come in.

    Regards,
    Ulrich

     

  • Hi Ulrich,

    is the selection of varistor ok?  600Vac is absolute max in system.

    www.digikey.com/.../651267

  • Hello VT,

    Reading the specs of the varistor shows that it is designed for 385Vrms maximum.  620V is a dc rating and 600Vac will blow it up.

    If that distinction is not clear to you, I think this project may be beyond your current capabilities.  I suggest that you find a local expert to guide you.

    Regards,

    Ulrich

  • Hi Ulrich,

    This is copy paste error actually.

    I am selecting 900V varistor for this application

  • Hello VT,

    I can't address the suitability of any of the components you choose for your application.  Earlier, I made mention of some, though not all, of the considerations involving high input voltage and these still apply.

    Here is a link to a small collection of reference designs that TI has involving wide AC-input, low DC-output designs.  

    https://www.ti.com/reference-designs/index.html#search?applid=120&vinmax=379.68,903.66&vinmin=71.87,104.86

    None of them are exactly what you are looking for, but certain elements of each design may inform your own application. I suggest that you peruse them to help give you a better idea of the issues involved.

    Regards,
    Ulrich