UCC28070: UCC28070 ITH problem

Mahendar Reddy

Part Number: UCC28070

I am doing 2 KW PFC with UCC28070 Fsw is 150Kz . I am getting V THD <5%, But I THD is coming 40% at Low load 8.5% at max load at 170 V AC Input. Where as at 275 V Ac at low load 80% at full load 35%. Can anyone can suggest How to reduce I THD to <5%.

Regards,

B Mahendar Reddy

over 7 years ago

0 Colin Gillmor over 7 years ago

TI__Mastermind 25570 points

Hi Mahendar

Please post some input current waveforms - these usually give some clues. Can you also post your schematic.

Regards
Colin

0 Mahendar Reddy over 7 years ago in reply to Colin Gillmor

Prodigy 70 points

0 Mahendar Reddy over 7 years ago in reply to Mahendar Reddy

Prodigy 70 points

Yellow is Vin Ac and Blue is current

0 John Griffin1 over 7 years ago in reply to Mahendar Reddy

TI__Mastermind 34465 points

Something is really wrong with your design.
Really there should be no distortion on the voltage signal and you should expect to get 5% THD at low line full load.
THD will increase as the load decreases and as the input voltage increases.
The first thing you should do is use the calculator tool for the UCC28070 and compare your circuit values with the values predicted by the calculator.
Check your inductor design.
Also check your current transformer. Is it accurately detecting the MOSFET drain current ?

Regards
John

0 Mahendar Reddy over 7 years ago in reply to John Griffin1

Prodigy 70 points

Hi John,
Actually my Voltage THD is <5%. I have measured THD with HIOKI Power meter.

Regards,
Mahendar Reddy

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UCC28070: UCC28070 ITH problem