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UCC28950 :Configuration of circuit

KIM Andy
Expert 2530 points
Part Number: UCC28950
Other Parts Discussed in Thread: UCC28951,

Hi

Currently my customers are developing 600W class solar converters using SM72445 and UCC28950.

The configuration is as follows.

The company is trying to apply ucc28950 as a boost circuit.

Input: 48V, Output: 400V, Input maximum: 600W

Could you please review the circuit diagram below?

PSFB_Controller_schematic.pdfPSFB_Power_schematic.pdf
I am currently in the process of reviewing the circuit schematic. I am busy, but can you help me?
I did not see the use to Boost Output, including me.

If it is 600W class, can it be configured as LLC IC?
At the customer company, it is said that the efficiency is not good when the input voltage moves when constructing the LLC. Is it true? I also heard that resonance is difficult to apply.
I think UCC25630X is also applicable if LLC is applicable.

  • 0
    TI__Mastermind 25570 points
    Hello Andy

    I would suggest that they use the UCC28951 instead of the UCC28950. The UCC28951 is a 100% drop in replacement for the UCC28950.
    They might want to add a small signal MOSFET to the SS/EN pin so that they can turn the PSFB on and off directly.
    They are using diode rectification with a full bridge output - this is a good arrangement at 400Vdc out. The SR outputs from the UCC28951 can be left open circuit. It is also possible to tie the DCM pin to VREF so that the OUTE and OUTF signals are not active. I see they have provided for this possibility through R21. (set R21 and R24 to zero Ohms and set R25 to No Pop).

    The UCC28951 and UCC28950 cannot be used to drive a LLC.

    The customer is correct that it is difficult to design a LLC circuit when the input/output voltage ratio changes over a wide range - you didn't say what the input voltage range is but a 48V battery could be as low as 40V or as high as 60V and an LLC operating over this range would be difficult to design. The problem is that the LLC would have to operate away from its resonant frequency over most of the input voltage range and it will be less efficient as a result. A PSFB would be much easier.

    The UCC25630x is a good choice for an LLC - the question is whether the LLC is the correct topology.

    Regards
    Colin
  • 0
    Prodigy 70 points
    Hello Andy,
    Maybe you can look the current-fed full-bridge boost converter with active clamp. This is a very good option working with low input voltages and when the ratio input to output is high. In addition, the battery will be very happy because the input current ripple will be very low.