Reducing voltage drop with split load and powering in series?

Discussion in 'Power Electronics' started by T3STY, Aug 22, 2018.

  1. T3STY

    Thread Starter New Member

    Oct 4, 2016
    25
    0
    Hi,

    I want to build a handheld device that uses 4x 18650 battery cells in series, and I want to integrate battery charger circuits based on the TP4056 chip (4x ICs will be used, 1A max charging rate).
    The TP4056 needs a 5V nominal power supply, while I am planning on using a 19V one (like the ones used for laptops). While charging the batteries, the power supply will also provide power to the device itself (batteries will be disconnected from the load during this time).

    Problem is that the voltage drop on a 5V regulator is a lot to power it directly from the 19V. Moreover, 5V @ 4A regulators use quite large components, and I need to maintain a low profile (10mm height is desired) on all components. Heat is also a concern since it's a handheld device.

    To solve these issues I was thinking about doing the following:
    1) use 2x LM2673-5.0 based voltage regulators (5V@3A) to split the load. Each regulator circuit will power 2x TP4056 battery chargers
    2) one thing that I'm not sure it can be done (or if it's safe to do it this way): connect the voltage regulator circuits in series to the 19V power supply in order to lower the voltage drop on the regulators. I would like to avoid using large voltage divider resistors to split the power to minimize heat. An additional series resistor could be added to take in part of the voltage difference.

    See below a picture of this idea:
    VREG_series_PSU_idea.png

    Do you think it's worth pursuing this idea? Or can you suggest better solutions?
     
  2. T3STY

    Thread Starter New Member

    Oct 4, 2016
    25
    0
    Hi again,

    Maybe it is too much to read, but could someone please try to tell me if I'm wrong at any point? This way at least I know for sure that I have to find a different solution...

    Thank you very much in advance!
     
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