UCC28070A: Power limitation at high line

Hi, poster

The replier of this post is out of office, please expect a response by this Friday.

Yunsheng

Hi Poster,

C14/C16 is just used as a filter on the CT second winding. the Resistor in series with C14/C16 was set to be avoid CT saturation. C14 and C16 can be removed in some real case.

The yellow scope looks normal with mosfet ID current sampling.

so what is your concern?

Hi David,

My problem is a power limitation in high line (230Vac). Do you think C14/16 can make this problem ? or another parameter ?

Regards,

Could you check my parameters ?

First problem : power limitation, I don't manage to reach 600W (at 400W, Vout goes down. Less than 390V). 

Second problem :the boost doesn't start à 230Vac sometimes. Still OK at 220Vac. VINAC value and filtering seems to be OK.

As mentionned in my first message, Irmo has still the same value @110Vac or @230Vac, looking strange...

Thanks,

Hi Poster,

I am sorry the schematic you attached is not clear enough to review.

one suggestion is VINAC resistor divider should be the same as Vsense resistor divider.

For power limited issue, please check CSA/CSB and see whether it triggers PKLMT function.

also you should check whether resistor on Imo pin with a  correct value.

C14/C16 should not influence the high line power limited.(if you have a filter on CSA/CSB pin that can filter the noise.)

Hi David,

Sorry for my schematics...

Divider resistors are the same between VINAC et VSENSE.

I will check CSx and PKLMT, can I disable PKLMT by removing R9/R10?

I would try to change the R12/R22 saturation resistors with diode+zener. Which values can you advise ?

Thanks

Hi Alboussiere,

you can try R9/R10 to set a high level power limit threshold.

for the diode+zener, I suggest you follow the schematic with PMP4311.(diode: BAS16, Zenor:33V)

www.ti.com/.../slur515.pdf

Hi David,

No more power by changing the reset resistor with diode+zener.

Power limitation is not made by PKLMT.

Could you take time to check my parameters in my Design Tools file ?

Thanks,

Hi Alboussiere,

It looks to me that the design tool parameter is ok.

have you tried the Rimo resistor?

I would suggest you can order an UCC28070evm as reference to see whether anything missing.

Hi David,

It seems to work better by changing current loop values.

Vsense capacitor value is also critical.

I see PFC has less power at 185Vac, I don't know why but I will investigate !

Regrads,

Hi Alboussiere,

Do you have any progress?

so this time is low line power limitation issue? and high line power limitation issue already closes?

lower line power limit may be influece by PKLMT pin threshold, please double confirm.

Hi David,

I still have less power between 150-185Vac (50W minus) and sometimes no PFC start at 230Vac.

Regards,