UCC256404: Resonant current is high during start up

Vinayak Mavarkar

Part Number: UCC256404
Other Parts Discussed in Thread: UCC28180, , UCC24624

We are currently working on 750W desing in which we have use UCC28180+UCC256404+UCC24624 IC combination.

In which at initial start up there is a current spike in resonant as you can se in below image. Which is around 22A peak to peak. Sometimes it also goes in OCP, and unit is start after two to three hiccups..

Pink is resonant current

Green is Boost voltage

Yellow is RVCC

Could you please suggest us in which section we need to work or do modification to reduce this spike.

over 1 year ago

0 Manikanta Pallantla over 1 year ago

TI__Genius 16155 points

Hi Vinayak,

Could you share the schematic and the design calculator with the power stage values?

Regards

Manikanta P

0 Vinayak Mavarkar over 1 year ago in reply to Manikanta Pallantla

Prodigy 10 points

7242.UCC25640x Design Calculator Rev4.0.xlsx CEL-22-LF00000016867X2_SCH_VALUE.pdf

0 Manikanta Pallantla over 1 year ago in reply to Vinayak Mavarkar

TI__Genius 16155 points

Hi Vinayak,

Thanks for sharing the files. Could you increase the LL/SS cap value to increase the start up switching frequency. Also, the VCR caps also determines the startup frequency. You can try tuning those values to reduce the startup current. And, you can try BW option 5 to disable the VSSINIT voltage to increase the startup frequency.

Regards

Manikanta P

Power management

Power management forum

UCC256404: Resonant current is high during start up