UCC28070: PF reduce when UCC28070 works in city electricity comparing with AC source

user4681182

Intellectual 370 points

Part Number: UCC28070

UCC28070 Implement Bridgeless PFC Pre-Regulator in the circuit.

Cpmparing with AC source, the PF decrease obviously when the input is city electricity.

Can you figure out the reason about this issue?

And how can we optimize the shcematic?

TKS~

over 5 years ago

0 Steven Mappus1 over 5 years ago

TI__Mastermind 33115 points

Hi,

What are the test conditions shown for the waveforms you inserted? Can you share the schematic?

Regards,

Steve

0 user4681182 over 5 years ago in reply to Steven Mappus1

Intellectual 370 points

The input is 220VAC/50Hz and the output is 360V.

the schematic is almost as same as below circuit.

RA=1428K, RB=12K(2.2nF capacitor in parallel)

0 user4681182 over 5 years ago in reply to Steven Mappus1

Intellectual 370 points

Hi Steve

woudl you mind repling me today?

THX~

0 John Griffin1 over 5 years ago in reply to user4681182

TI__Mastermind 34465 points

Hello user4681182,

The pfc schematic you attached is a simplified application and it lacks capacitance across the input which will absorb ripple due to the pfc switching frequency.
With a laboratory grade AC source you will have enough capacitance on the output to act as a reservoir for the high frequency switching
but with a utility source there is a significant line inductance and this will cause a line current corruption

An interleaved application will have a capacitor on the DC side of the bridge rectifier and this will absorb the switching pulses
With the semi bridgeless application there is no capacitance whatsoever and that is why your results are degraded.
You can improve the current waveform by adding an EMI filter on the AC line.

Regards

John

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UCC28070: PF reduce when UCC28070 works in city electricity comparing with AC source