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DCDC converter circuit recommendation

Ernest Yong
Expert 4315 points
Other Parts Discussed in Thread: LM5122

Hi Team,

My customer is looking for a budgetary estimate for a DC to DC converter circuit for their printer system.

The input will be LiON batteries.

The output needs to support 24 volts.

The highest option would be 20A out.

They can also look at the cost savings for 15A out.

 

The input needs to be 480W / efficiency / 50W per cell.

What that means is that if they need 480W and the circuit is 90% and each cell can deliver 50W,

they would need at least 10.6 cells.

The max pack voltage can be selected by them.

6S-2P would be a battery with a max voltage of 25.2 volts and it could deliver 30 Amps.

I'm not sure if that is a low cost configuration.

Maybe 5S-2P would be a lower cost circuit.

With a low voltage cutoff of 3.5V per cell, the input range would be 17.5 to 21V

and the cells can support 15A x 2 = 30A.

So on the low end 17.5V * 30A * 90% eff = 472W 

Could you please kindly provide guidance base on the specs above?

  • 0
    TI__Guru 59445 points

    Hello Ernest,

    If they need the maximum power for a long period of time, the converter needs to be thermally designed to be able to deliver it, if the peak power is there fore very short times, the thermal design might not be needed for the full power. This influences heavily the design cost. For example if the 500W are needed for the whole time, I would recommend using 2 phases, if we speak about a few ms, I would recommend 1 phase.

    For a 1-phase design, LM5123 would be a good choice, for 2 phases, have a look at LM5122.

    The whole cost is really difficult to get as we do not know how much a customer is paying for the external components. A good starting point might be Webench configured for low cost designs. Have a look to the 2 product folders (links below) and check out the different choices. Be aware that Webench is giving a rough budget, but Webench does not include all components a customer is able to use, so it might be necessary that the customer himself adds components to Webench for a more accurate calculation for his specific case and cost structure.

    LM5123-Q1 data sheet, product information and support | TI.com

    LM5122 data sheet, product information and support | TI.com

    Best regards,
    Brigitte