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Is it better to step up or down the voltage?

Discussion in 'Power Electronics' started by JRMoore, Feb 7, 2021.

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  1. JRMoore


    Feb 7, 2021
    Hi, I'll try to give some context to the question as it's too broad.

    Currently I have two routers, two Raspberry Pi model Bs and a laptop each with its own power supply. The routers require 12v ~1.5A each, 5v 2A for the Pis and 3.4A at 19v for the laptop (either through a USB PD type C connector or a barrel jack) and I'd like to simplify the setup using a single power supply also adding one of those variable voltage modules for a bench power supply. Maybe even something to log the power those things consume, but that's secondary.

    These are the options I have thought of:
    - Getting a 24v or 27v power supply, like those 12v ones for LEDs, and stepping down the voltage for the different things.
    - Getting a computer power supply which has 12v and 5v rails already and boosting it to 19v for the laptop. It also has 3.3v which could be useful for microcontrollers.
    - Designing and building a custom solution, tricky because I have little virtually no experience on the matter (e.g. I have never wound a transformer), but I'm open to it too.

    I think PSUs are less efficient at low loads and while the laptop is not going to be on 24/7 like the other things, it's safe to assume it will be on for most part of the day, so I wouldn't get a 500w power supply for example, it would probably be in the 150-250w.

    At those power ratings power factor correction is probably not in the mix, but I think the adapters I use currently don't have it either, except for the laptop maybe.

    In any case, would it be preferable to step the voltage down from 24v to 19v, 12v and 5v or step it up from 12v to 19v for the laptop?

    - James.
  2. Martaine2005


    May 12, 2015
    I personally wouldn’t go with that.
    I would go with a computer PSU (ATX) type for the 12V, 5V and 3.3V but keep the laptop PSU (19V) separate.
    No real reason other than gut feeling.

  3. davenn

    davenn Moderator

    Sep 5, 2009

    Use the computer PSU, that way no need to and you should never think about winding transformers anyway
    Plus you dont use transformers on DC voltages
    You could easily boost the PSU 12V rail to 19V with switching boost DC-DC converter ... dirt cheap on ebay

    eg. this one ..... DC-DC Boost Converter Adjustable Step Up Voltage Charger Module 10-32V to 12-35V | eBay
  4. JRMoore


    Feb 7, 2021
    Thanks for the answers! I will go with the computer power supply then and step its voltage up for the laptop.

    It seems to be easier to find quality computer PSUs than the other ones too, it may end up being a more powerful unit, but it'll also give me some headroom if I add a variable voltage part.
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