PMP20122: Design calculation

Anand Meharwade

Part Number: PMP20122
Other Parts Discussed in Thread: UCC28710, PMP10834

Hello,

Can I get the design calculation details for PMP20122 to modify it to my requirement. I have DC input range 110V - 200V and I wanted to have 12V/ 200mA output design.

I tried applying conventional buck principle but not able to correlate with the design. Appreciate your support.

Anand M

over 4 years ago

+1 Sheng-yang Yu1 over 4 years ago

TI__Expert 4840 points

Hi Anand,

PMP9087 design meets your specification.

I also upload my design flow and calculation of designing a buck converter using PSR Flyback (UCC2871x).

https://txn.box.com/shared/static/sn68x542yo824ucutr5tpbb6awgydkc7.pdf

The link will be available before March 4, 2022.

Regards,

Sheng-Yang Yu

0 Anand Meharwade over 4 years ago in reply to Sheng-yang Yu1

Expert 1090 points

Dear Sheng-Yang Yu,

Thanks and appreciate for the quick response. The world is very small.

BTW, I see that its designed for AC input. Does it requires any kind of modifications? Whether same calculation apply for DC input?

Regards,

Anand M

0 Sheng-yang Yu1 over 4 years ago in reply to Anand Meharwade

TI__Expert 4840 points

Yes, you can short the rectifier stage if your input is DC. The calculation is the same. For AC input, we need to calculate input capacitor capacitance so we maintain input voltage valley is still higher than the desired minimum DC voltage level for the converter.

0 Anand Meharwade over 4 years ago in reply to Sheng-yang Yu1

Expert 1090 points

Dear Sheng-Yang Yu,

Thanks for the clarifications.

I could able see your hand written procedure, will get back to you if there are any clarifications.

Regards,

Anand M

0 Anand Meharwade over 4 years ago in reply to Anand Meharwade

Expert 1090 points

Dear Sheng-Yang Yu,

May I know how do you arrive at Ton and Toff in DCM. And my case the input voltage is 110V to 200Vdc range, what vin I need to consider Vin, min or Vin, max? What is the use of D1, D2 and R2.

Could pls help me in calculating L, Output ripple voltage, power diss of the UCC28710. it would be helpful if you can share the calculations of the design to arrive at the values and part selection.

Regards,

Anand M

0 Anand Meharwade over 4 years ago in reply to Sheng-yang Yu1

Expert 1090 points

Hi Sheng-Yang Yu,

Could you please re-share the calculation method for the UCC2871x in buck mode. I am planning to modify this for DC input 200V to Output voltage 5V.

Thanks for the support.

Regards,

Anand M

+1 Sheng-yang Yu1 over 4 years ago

TI__Expert 4840 points

Anand,

Updated link below:

https://txn.box.com/shared/static/pdfn4e14n8ibg0u95lrpwwlgvhik1727.pdf

You will have issue to use UCC2871x in buck mode based on PMP9087 structure as 5V output is lower than UCC2871x VDD UVLO point. The controller won't even startup.

I believe you will need to use a coupled-inductor to do a Flybuck like PMP10834 design, but 500mA is also considered high for a high voltage buck. So you will likely need to customize the coupled-inductor. But then Flyback will be much efficient than HV Flybuck. That is, it is better to use PSR Flyback instead of HV Buck or Flybuck for 5V out in my opinion.

https://www.ti.com/tool/PMP10834

Regards,

Sheng-Yang Yu

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PMP20122: Design calculation