UCC28251 current sharing

Alen,

Thank you for your inquiry. I'll look into this and get back to you today.

-John

Alen,

While the UCC28251(and UCC28250) can be configured in peak current-mode control, it has a synchronization capability through the RT pin that could be used to interleave, and it has an ENable pin (all of which are beneficial for interleaving mulitple controllers+powerstages with outputs tied together), the synchrounous rectifier control scheme makes this controller not really ideal for multiple converters in parallel for current sharing with tied outputs.

The synch fet outputs of this controller are always on; their is no DCM or light-load management that shuts off the synch fet outputs at low load. This means that at light loads or if the inductor ripple current is significantly large, there is a risk of the current going negative and feeding back into the supply which could result in damage. Though it can start up with its pre-bias startup circuity without negative current, at steady-state the risk of negative current is still a danger.

ORing controllers with reverse current blocking capabliity would be a needed additional feature if they are to interleave 2x UCC28250s.

What are the input voltage, output voltage, and output power requirements for the customer? How far along in the design process are they?

The UCC28950 Analog Phase-Shifted Full-Bridge controller is a great candidate for interleaving because it has a DCM mode where the synch FET outputs are shutoff at light load, it can operate in peak current mode control, it has a SYNC and EN. Also, depending on the power level, a single UCC28950 full-bridge or other controller could be more ideal.

-John

Thank you for the prompt and thorough response.

The input voltage is 270VAC, output power is 150W (various voltage options will be made available).

The UCC28950 is also being looked at.

Alen,

That is a borderline power level to use PSFB with UCC28950. They could also consider doing resonant half-bridge using UCC25600 since they are doing offline with a high-input voltage. This will give them the efficiency savings needed with the high input voltage but will keep component count below that of a full bridge.

 If PFC is needed they may consider using a UCC28051 Transition-Mode boost converter as stage one from 270VAC followed by the DC/DC UCC25600.

Hello

I am going to use both UCC28251 and UCC27210 in a full-bridge converter circuit.

the designed circuit is given in following. I test it but I didnt get result. Could you please look at this

and if there is any problem about connection or design please let me know.

thank you

Hi all , iam looking for a good application note on designing current mode control for ucc28251 , can any one help me in doing it . Thanks in advance.