UCC28070: UCC28070 spike current issue for every cycle

Hi Dexter,

What is happening at this time is a result of the current amplifier saturating.
(CA1 and CA2 in the block diagram of the data sheet)  

During normal operation of the pfc, the current signal is forced to equal the multiplier output signal.
Unfortunately at low line voltages the current transformer cannot sense an adequate line current because the current into the CT is is so small
and parasitics and ringing cause measurement errors.
Unequal input signal cause  CA1 and CA2 to saturate high.
When the line voltage is high enough you will see the large current spike because the multiplier output is fairly large and CA1,CA2 is also large.
It takes a finite time for CA1 and CA2 to come out of saturation and for the correct line current to be restored.

You can easily eliminate this current spike by placing a small DC offset voltage on the CSA/CSB inputs.
I suggest you add a 3k resistor from the 14V1_PFC node to CSA and also a 3k resistor from 14V1_PFC to CSB.
This will create a small dead zone around zero crossing in the line current.

The spike you see now will increase the current distortion and lower the power factor but you can easily eliminate it by adding the DC offset to CSA/CSB.

Regards

John