• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 63 subscribers
  • Views 166 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC28070: Wide AC input range PFC.

Jacobo
Prodigy 215 points
Part Number: UCC28070
Other Parts Discussed in Thread: AMC1400,

Tool/software:

Hey team!

I recently got a client request for a system that needs a wide input AC voltage (220VACrms to 490ACVrms) for a 7kW setup. I’m using the UCC28070 device and following the guidance from the SLUA479 App note to make sure the power output is on point.

I’ve been digging around in the TI community and came across some interesting tips:

It looks like +5-10V mentioned that the output voltage levels need to be higher than the input peak voltage, which in my case is around 700Vdc. To reach that, I’ll need to play around with the sensing pins.

Right now, I’m using the SLUC114 - UCC28070 Excel App design tool. Is this spreadsheet reliable for the voltage range I’m working with? Can I trust the values it’s giving me for the sensing components?

I also calculated the current sense transformer, and it’s showing a turn ratio of about Ns/Np ~ 665. Would it be possible to use an isolated amplifier instead, say like AMC1400?

Is there anything else I should double-check while I'm at it?

Thanks for your support!

  • +1
    TI__Mastermind 38580 points

    Hello Jacobo,

    The guidance in the SLUA479 App-note is good for typical "universal line" input (85~265Vac) applications, but is not valid for high-voltage-only inputs.  The recommended inductor value result is too low.  This app-note supports the existing UCC28070 Excel calculator tool SLUA114A.

    There will be an upgraded version of this calculator tool released soon (next week maybe?) which recommends inductance following the method described in the UCC28070A datasheet  https://www.ti.com/lit/gpn/ucc28070a  section 7.2.2.3 page 35.  You can follow the datasheet calculation procedure until the new tool becomes available.

    For output voltage, I suggest to follow the same ratio currently used for "universal line" inputs, which is ~390Vdc / 375Vpk = 1.04 x (490Vac x 1.4142) = 720V. 
    For Nct turns-ratio, the choice is a matter of power loss (which is covered in the new tool), but I would think that a ratio closer to 200:1 should be good enough.
    An amplifier should not be necessary.

    The input voltages you quote (220Vac, 490Vac) seem to be close to nominal line values.  Please be sure to account for low-line and high-line conditions. 

    Regards,
    Ulrich

  • 0
    Prodigy 215 points

    Hi Urlich,

    Thank you for the guidance provided regarding the UCC28070A datasheet and the upcoming calculator tool. It’s really helpful to know that I can follow the datasheet calculations in the meantime for the inductors' value, and I appreciate the input on the output voltage and turns-ratio suggestions.

    I will follow your suggestions regarding the high-voltage inputs for both low-line and high-line conditions. I am looking forward to the new Excel calc. If you have any updates, please send me a message.

    Thank you once again for your support! I'll return to the design bench now~

    Best,
    Jacobo

  • +1 in reply to Jacobo
    TI__Mastermind 38580 points

    Hello Jacobo, 

    Fortunately, the new calculator was released a bit earlier than I expected and it is available now:
     https://dr-download.ti.com/design-tools-simulation/calculation-tool/MD-HcFEXblwq6/2.0/UCC28070_Design_Tool_2.0.xlsm  

    I hope it works well for you. 

    Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Prodigy 215 points

    Hi Urlich,

    Awesome, this is perfect timing! I'm going to double-check my design with it, and if anything comes up, I’ll definitely reach out.
    I’m pretty sure this will clear up a lot of stuff; I just need to redesign to be sure.

    Thanks a ton for the awesome support!

    Kudos!!

    Jacobo

  • 0 in reply to Ulrich Goerke
    Prodigy 215 points

    Hi Urlich,

    I hope you’re doing well. I have one more question, if that’s alright.
    I’ve been working on inputting all the data from the new Excel calculator into the TI TINA UCC28070 example.
    Also, I followed the recommendations on TINA for CSGAIN, CRESP and the rest on ther values for the boost macro, but unfortunately, my input current waveform isn’t what I expected.

    I noticed that reducing the voltage input to 600Vpk does seem to make it work as it should (I need to reach 680Vpk), on 605V input current gets totally deformed.
    Any insights you could share would be greatly appreciated!

    Thank you for your help.

    UCC28070_TRANS_6.6kW_v2.TSC

  • 0 in reply to Jacobo
    TI__Mastermind 38580 points

    Hello Jacobo, 

    I checked your TINA file and saw the current distortion at 605V peak input. 
    It resembles the current as if the output capacitor was peak-charging.  As if Vout was programmed to be 604V, for example. 

    That is not the only discrepancy that I found.  
    Your upper VSENSE resistor R23 = 12Meg, your lower R5 = 40kR.  This divider programs 900V output, but the simulation shows only ~735V average. 

    Since this device was designed for the usual "universal line" range of 85~265Vac, I suspect that the model may have some built-in limitations based on that assumption, which prevent it from operating correctly above ~600V peak (425Vrms). 

    The actual controller can work with higher inputs and outputs, but the model apparently cannot accommodate them.

    I'm sorry, I am not in a position to debug and correct this model.
    I don't expect behavior at 680V peak input to be much different than that at 600Vpk, so maybe you can still use the 600V results. 

    Regards,
    Ulrich 

  • 0 in reply to Ulrich Goerke
    Prodigy 215 points

    I truly appreciate your help and thank you for your fast respone Thumbsup

    Yes, for 600Vin all behaves well; the issue is beyond that point.


    I tried to correct it changing VSENSE, VINAC , and CSGAIN values without success and with the consequence that in many combinations the current waveform gets extremely distorted and voltage output goes to the roof.

    Anyhow, thank you again for your time and help, I'm in the process to fabricate the proof-of-concept and I will keep you posted.

    Have a great day!