Why some much circuitry in laptop charger

Discussion in 'General Electronics Chat' started by Scott216, Mar 30, 2012.

  1. Scott216

    Thread Starter New Member

    Jun 16, 2011
    The charger for my Alienware M17x died, so I decided to open it up and take a look. I was really surprised to see so much circuitry. It's looks like a mini computer inside. Why would a charger need to be so complex? See attached photos.
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    It's just very dense, but not complex. You need rectifiers, EMI-filters, primary and secondary capacitors, at least one transformer, a feedback loop and maybe some protection circuitry.
  3. BJT_user


    Oct 9, 2011
    What it is, is a transformerless switching power supply. It has to take 120 volts AC on its input and convert it to 17-19 volts regulated DC at its output. To do that, you need lots of capacitors and coils for filtering, diodes for rectifying, SCRs or high voltage transistors for switching and a regulator IC for controlling it all. Due to the high power output, the components are going to be fairly large and robust, as you can see by the large gauge wires in the filter coils and the large sizes of the storage capacitors. Also, since it has to be portable, as is the nature of a laptop, it must all be crammed into a very small plastic case and thus you see the huge amount of circuitry that is required for such a device, squeezed into a very small footprint. It's not terribly complex circuitry, but it is a fair amount that is required to do the job it has to do.
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    Looks like a typical offline switcher but it may have some "smarts" on board to be able to sense the battery type and know how to charge it (maybe not)
  5. kubeek


    Sep 20, 2005
    I don´t see anything complex, just a regular SMPS crammed into a very small package. Look at a PC PCU, you will see about the same amount of circuitry.
  6. Markd77

    Senior Member

    Sep 7, 2009
    There's a lot of chips on the back, <joke> maybe one is the warranty timer. </joke>
  7. Lundwall_Paul

    Active Member

    Oct 18, 2011
    They obviously don't want any of us working on it.