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isolated dc/dc boost converter + controller

Gemini1000
Intellectual 500 points
Other Parts Discussed in Thread: UCC28951, PMP20657, PMP6712, LM5122, LM5045, UCD3138

Hello,

We need to choose a right topology and appropriate controller for one of our projects with the following specs: Does anyone have any suggestion/recommendation on the topology and the controller ?

Input= 24V , output= 70-90VDC, 500W, isolated, EFFICIENCY > 90 %

Have the following questions:

- What topology do you suggest ?

- What controller does TI offer for this solution ? digital or analog ? what part numbers ?

Appreciate the urgent response.

Thanks

  • 0
    TI__Intellectual 2770 points

    Hello Sir,

    for 500W would recommend full bridge topology;
    for best effcy would recommend phase shifted full bridge;
    for up to 7A output current would also recommend synchronous rectification.

    So we end up at UCC28951 - PMP20657 shows a 400W full bridge in your power range;
    PMP6712 shows synchronous rectification for bigger output voltage.

    Beside analog control a digital control w/ C2000 is possible, but this needs additional C++ software efforts.
    You will meet efficiency 90%+, expect 93% to 95%, w/ UCC28951.

    Attached a short analysis for your power stage.

    Best regards, Bernd

    PSFB_Gemini1000.pdf

  • 0 in reply to Bernd Geck
    Intellectual 500 points

    Thank you Bernd! The project is very cost sensitive. That being said, have the following questions :

    - Won't a half bridge or push pull solution be less expensive ?

    - Does TI offer any eval board for a  BOOST isolated DC/DC converter? Seems like most of isolated eval boards are designed for buck solutions.

    - Do you suggest a current fed or voltage fed solution ? 

  • 0 in reply to Gemini1000
    TI__Intellectual 2770 points

    well, the topology could be Push Pull, Weinberg, Half Bridge and Full Bridge;
    for best efficiency I would go for phase shifted full bridge - here our controller supports synchronous rectification;

    for lowest cost and simplicity you could analyze push pull topology;
    fine for low voltage input and both FETs are low side driven, just transformer needs center tap.
    Transformer is slightly bigger, only half of the winding is used.

    Expect efficiency slightly below 90%, attached a power stage analysis, best regards, Bernd

    PP_Gemini1000.pdf

  • 0 in reply to Bernd Geck
    TI__Intellectual 2770 points

    above I could read BOOST, up to now I thought isolation is a topic;
    if there is no need for isolation I would go for a multiphase boost converter using LM5122;
    controller handles Vout up to 100V and has multiphase feature.
    would start my evaluation w/ a two phase solution for lowest cost.

    Duty cycle is around 70% - using a three phase solution will provide ripple cancelation.

    Best regards, Bernd

  • 0 in reply to Bernd Geck
    Prodigy 50 points

    Hello,

      Glad to find this thread!

    I'm looking to design a "smart", isolated, 24V (nominal) to 48V, 500W DCDC converter. I'm interested in hearing more about the C2000 w/ UCC28951 solution mentioned above with such high efficiencies. I've never used C2000 devices before and have looked for some reference designs but hadn't found anything until I came across this thread.

    Thanks,

    Kurt

  • 0 in reply to Kurtis Unger1
    TI__Intellectual 2770 points

    Hello Kurt,

    typically for a 500W full bridge I would go for UCC28951;
    at 24V input only a hard switched full bridge using LM5045 will work fine, too.
    Benefit of UCC28951 is easy control of synchronous rectifiers.

    If digital control is a topic we got either C2000 or UCD3138;
    for C2000 you work on a signal processor using C++;
    for UCD3138 you work on ARM7 using firmware programming.

    For information in general check the past Power Supply Design Seminars,
    you'll find a bunch of white papers regarding DIGITAL CONTROL.
    In 2007 myself presented a Telecom Rectifier at PSDS across Europe.
    The past decade we added much more topics on this:

    www.ti.com/.../login.shtml SUPPLY DESIGN SEMINARS

    please select TOPIC "Digital Controls"

    Best regards, Bernd