How to tell if this is linear or switching?

Discussion in 'General Electronics Chat' started by poopscoop, Mar 6, 2013.

  1. poopscoop

    Thread Starter Member

    Dec 12, 2012
    I want to extend the battery life of my GTU 10 (A tracking unit I slap on my dog when I take him in the woods or to other people's homes). My plan is to take 3 or 4 NIMH cordless phone batteries (3.6v, 850mah, I have a cordless phone through which I can charge them) and wire them in series into this:

    It's an adapter, one end is the charging plug for the GTU 10, the other end is two bare wires. Device is rated to for an input of 8-48v DC and an output of 5v 500ma. (I doubt the device has a continuous draw of 500ma.)

    Is this a linear or SMPS? Is there any way to tell? If it's linear I may be wasting my time, as 10.8v at 850mah with a 20% first day self-discharge may not be worth the effort to charge the batteries individually.

    I've e-mailed Garmin, and while they are usually pretty good about technical e-mails, they claim the design of their adapter is proprietary and wont provide any information.
  2. crutschow


    Mar 14, 2008
    It is likely a switching supply. To check, apply a voltage of 8V or more to the input and a load to the output. Measure the input and output current. If they are they are nearly the same, the supply is linear. If the input current is less than the output current, the supply is switching.
    PackratKing likes this.
  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    It looks like a vehicle compatible regulated supply, and based on the input voltage range and it's tiny size and sealed construction (no air cooling) I think it is guaranteed to be a switching supply.
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    99.999% certain it's a switcher. A linear's power diss is proportional to input-output voltage differential so it would never tolerate such a high input voltage.
  5. poopscoop

    Thread Starter Member

    Dec 12, 2012
    Thanks a ton. Now that I think about it, that tiny plastic bead would be shedding 20 watts of heat if it were linear. ((48v-5v)*.5a = 21.5w)