Forward TOPGX, Universal input,PFC

Posted by: marcin on 04/26/2009

Hi,

I've been doing 5V,12V forward supply based on TOP-GX 247Y. Everything looks fine except I have to add PFC (Boost) to have Universal input 85-265VAC for this project. My PFC is based on ONSEMI NCP1606 which works fine to me. However when I tried to combine these two projects into ONE it appeared that NCP produces output voltage for DC BUS on average level 400V which is TOO HIGH for GX.

Maybe there is PFC solution from PI to fit GX expectations for DC BUS?

Any suggestions are really welcome ;)

Thanks,
Marcin

Comments

Hello Marcin
400V DC it is not to high voltage for TOP GX.
You can simply try to put DC Power supply in value 400V to PI EXPERT.
Maximum value of recommended DC voltage is 425V DC.
Please note, that reflected output voltage, is added to primary input voltage, and, can not exceed 700V (max drain- source voltage)

Hi,

Let's give it a goal:
1) I've changed: VDSOP from 580 to 610. Max level is 700 (breakdown), is 610 fine or should I consider StackFET for this?
2) Next changed value was: VACmax to 141 - to simulate Vmax=400V and VOR to 410 as it must be higher then Vmax.
3) I also had to change NP to 42 (originally it was 45) as BP was too high. RC,RD,CVS were changed automatically. And that's all.

Is this OK? I still have some feelings that "constructing forward converter based on GX is like balancing on the edge" ;) ... however DAK-12 works GREAT!

BTW to PI team: Do you have any DAK-12 kit still available?

There are no more DAK-12 units available. The design, however is a good reference. Please use the zener primary clamp circuit shown in DAK-12. When you use clamp circuit which is referenced to circuit return the issue becomes max allowable duty factor, not peak VDS on TOPSwitch. Since DAK-12 was not intended for PFC boost input you are right that this could be marginal -- especially if peak boost output voltage surges above 420 volts. I would not increase zener clamp voltage to increase transformer reset range. I really question whether design will have enough margin....