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Need help selecting parts for a 300W DC/DC Boost application

Ryan McDaniel
Prodigy 55 points
Other Parts Discussed in Thread: LM5156, LM5122

Hello,

I'm having trouble finding parts for a power supply design and could use some help to point me in the right direction.

I have a 24V DC input (18V/28V min/max) and would like to create a ~300W output from it with a variable voltage range from as close to 28V/10A as possible (for efficiency) up to 60V/5A.  The output voltage I plan to adjust via a DAC & resistor combo in the feedback path.

I was looking at the LM5156 and can use Power Designer to get a circuit that outputs 60V/5A (and even a 60V/10A with ideal FETs) but power designer won't generate a config for 30V/10A with this part.  I'm not sure what parameter doesn't work.

I see people have made modules that can do this: DC-DC Boost Converter 600W Adjustable 10A Step Up Constant Current (directvoltage.com).  I'm guessing that is a flyback topology?  Any thoughts on how I can create something similar is appreciated!

  • 0
    TI__Guru 67865 points

    Hello Ryan,

    Have a look at this reference design: https://www.ti.com/tool/PMP7979

    The problem you will face in reality with LM5156 is that the external diode will have difficulties to handle the power, so it is recommended to go with a synchronous boost converter in this case.

    It might be possible to use a single phase converter, but you will have lower efficiency then.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 55 points

    Hello Brigitte,

    Thank you for the feedback.  I'm digging into the LM5122 further.  Can web bench create multi-phase designs or should I just put in a single phase at 1/2 my output current to create a design?  Along the same lines, assuming I am doing a two phase design but putting 1/2 the current requirements into web bench, to get a design that can support 30V@5A and 60V@2.5A should I put requirements into web bench for 60V@5A to ensure the inductor and FETs are sized appropriately for both 60V and 5A and then manually modify the FB resistors to lower the output voltage down to 30V for simulations?

    Regards,

    Ryan

  • +1 in reply to Ryan McDaniel
    TI__Mastermind 31315 points

    Hi Ryan, 

    I don't think Webench creates multi-phase design. I think in your case, it would be best to put in a single phase at 1/2 the output current. If you are getting a design that can support both 30V @ 5A and 60V @ 2.5A, I'm afraid that you may not have an optimal design for either scenario. That being said, if that is ok with you, your approach is correct. 

    Thanks,

    Richard

  • 0 in reply to Richard Fu22
    Prodigy 55 points

    Thank you for the feedback Richard.