AC-DC Full-bridge boost PFC 5kW

[ricp]

Hi,

I´m developing a AC[220Vrms,50Hz] - DC [400V] full-bridge boost PFC for 5kW output, but i can´t understand some things:

- first, how I can get a current with frequency of source AC and a constant output DC at the same time?
- In this moment, I control the four switches only by Vout, by: duty-cycle = 1-Vac/400, but I don´t have any results.

Can you help me?

Thanks!

 

[Skogsgurra]

Are you doing this from scratch? Or do you use a PFC control IC?
The manufacturer's application notes are very detailed and you should not have a problem making it work - or understand how it works.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ricp]

Hi,

I´m construct the PFC by zero. 4mosfets, a inductor, a capacitor and a load...

 

[Skogsgurra]

Then you may need to study how it is done. Have a look at this AN:

http://www.fairchildsemi.com/an/AN/AN-6026.pdf

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ricp]

Thank you for your answer. I will read the document, but the full-bridge can´t compare with the simple boost in each half-cycle? In other words, and sorry for my bad english, for example in half-cycle positive: I have two switches that commutes and has a same behavior that a boost DC-DC. In half-cycle negative the behaviour is the same, but with other two switches.

Or not?

Thanks!

 

[Skogsgurra]

True, I think. But PFC principles are the same and you can learn a lot from the appnote referenced. You can perhaps do some googling on your own to find the missing information?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ricp]

Yes, I have acess to IEEEXplore that contain many information about the theme (but not information as "low-level"

 

[DHambley]

rcip,
Can you send a sketch of what your circuit looks like with the full bridge please? I have designed many PFC circuits using single-switch boost, transformer coupled, 2-switches and full bridge. I may be familiar with what you are trying to do. skogsgura's recommendation for app notes is very good. This one from TI is pretty good also. <

http://www.ti.com/lit/an/slua144/slua144.pdf>

google TI UC2854 and the website points to other good reading.

 

[ricp]

First, thanks for your answer.

My circuit, is attached. In short, is 4mosfets, a source AC, a auxiliar inductance input and capacitor output; the resistor in load simulate the load for 5kW..

Can you send me some information about yours PFC circuits full-bridge, please?

Thank you!

 

[electricuwe]

Beside the control issues discussed in the previous replies, I'd recommend to reconsider the choice of power devices. With a Mosfet, even with one where the intrinsic diode is labelled as a "fast recovery diode" you will have much poorer recovery performance than with individual silicon-diode or even a silicon-carbide diode as it is used in many PFC-applications today.

What is your switching frequency ? What is your target for efficiency ?

 

[ricp]

Hi,

Thank you for your opinion. In this momment, the goal is do convert works after, I will study the methods (control and design) for improve the efficiency. But, in your opinion, you think that I have substitute the mosfets diode´s for diodes?

Thanks!

 

[DHambley]

ricp,
The circuit you showed is a typical "bridgeless PFC". If you changed the transistors to IGBT's with parallel ultrafast rectifiers you will solve you slow diode problem.