boost full bridge converter

Hi Cristian,

UC3825 is not good choice to drive full bridge. Full bridge Controller is UCC28950.

Maybe you have to think about burst or flyback  topology. Ratio Uout/Uin is high  ,so  to make 400V you have to use (for low power) burst converter followed    by  voltage multiplier or (for higher power) flyback . If you still wont to stay with full bridge UCC28950 is good and complete solution.

Dragan

Hi Svalina ,

Thank You for reply !

Why UCC28950  and not  UC3875  , the prices are similar and the functions too .

From datasheet and AN I understand that UC3875 can drive directly  two gtd .

The datasheet  and AN of UCC28950  consider  other drivers to control gtd ( UCC27324).

I don' t  understand if phase shift controller is used only in resonant converter or no.

The power is no so hi (300W)  I take from an FV panel (25-40V ) and convert it to 400V(0.75A)

with un 1:20 ratio . Also I want  to use full bridge to increase efficiency ( more then 95% ).

May you give me more information , about  similar applications  ?

You think is good idea to use  1:10 transformer ratio and after to use an duplicator .

Thank You V.M.

Cristian

Hi Cristian,

"Phase  shift " is not preserved for "resonant" converter." Resonant" in same time means "soft switch"  . Phase Shift Full  Bridge topology can bee realize like Hard Switch  (no resonant tanks). With good choice of component "Hard Switch" can achieve over 90% efficiency .

If your target  efficiency is over 95% in solar power application you have chance to reduce ratio  Uout/Uin by choosing solar panel with Vpp  over 100V@ 300W and you can use boost controller to make 400V very easy. My suggestion will bee UCC28220 ( or UCC28221) interleaved controller. 

If you interested in boos interleaved solution I can help you with some  practical advices.

Dragan 

Hi Dragan ,

I can't change Vin because a lot of panels have the voltage range (35-40V).

But if  I use  1:10 transformer ratio and after  a doubler voltage rectifier ?

Cristian

In that case, Cristian go with voltage  doubler  and transformer 1:10

Dragan

hi Cristian,

I have to correct my self. With transformer 1:10 and input voltage 35V and duty cycle 0.85 after voltage doubler ,output voltage will be about 300V.

So, you have to make transformer ratioo about 1:14 to make 400V from 35V input voltage and  duty cycle 0.8-0.9.

Dragan

Hi Dragan / all,

PV input range : 25V to 55VDC

i want to boost it to 380V / 400VDC. Can i go with interleaved flyback or interleaved boost controller ic for dc to dc conversion.

Can i use UCC28220 interleaved flyback IC. anyone suggest me hw much the transformer ratio will be suitable for this.

Yes,  Suresh

If you use UCC28220 in flyback topology (insulated ) transformer ratio should be 1:6.5  for Max.duty cycle 0.6, Vin=25V and Vout=400V. For non- insulated version and auto-transformer (central tap connected to drain) ratio can be 1:5.4 for same input voltage , output voltage and Max. duty cycle. Now you have boost topology. Input riple current is less and efficiency  is better. Overshoot voltage on mosfet drain is drastically reduced (lower snubber  loss, if any ). For rectifier (output diode) is good to use one of SiC Shotky  diodes to reduce switching loos in mosfet .

Dragan

hi dragon,

thanks for the reply. am planning to implement s/w freq of 170 to 200KHz and the output power is 190W (400VDC / 0.475A)

i can go with  either of this ic UCC28220 / UCC28221.

Suresh

Hi Suresh ,

You want to implement sw freq. 170-200kHz , but I read in datasheet ..  min freq 450 typ 500kHz ?

Have you an idea about efficiency of this converter ?

Thanks ,

Cristian

Hi Cristian,

Efficiency >85% because it is interleaved flyback topology.

thanks

Suresh

Hi Suresh

UCC28220 works from 12V power  supply and UCC28221 can work from110V. Everythingelse is identical.

Dragan

Hi Dragon,

thats correct. Actually my PV input is 25VDC to 55VDC range. So out of this which will be suitable & best for interleaved flyback.

Hi Suresh,

UCC28221 is good choice .

Dragan

Hi Dragan,

Thanks for the suggestion. Let me proceed with UCC28221.

Suresh

Hi Dragan,

Can you provide me some application notes for this particular. like design calculation for Interleaved flyback of this UCC28221.

Because in TI, the application note is for Forward Converter.

Thanks

Suresh

Sorry Suresh,

I don't have nothing  like that in my "Kook Book". Maybe  somebody  from TI member can help you. To encourage you Flyback is very similar to Boost converter and good applcation notes for interleaved boost is LM5032. (App.Notes 1820).only  you have to respect major difference  between this two topologies. 

Dragan