Why is a 20 volt ac adapter so much bigger than a 9 volt?

Discussion in 'General Electronics Chat' started by YallbinZAAAPPED, Feb 6, 2014.

  1. YallbinZAAAPPED

    Thread Starter New Member

    Feb 6, 2014

    Just had a few questions regarding consumer electronics ac adapters. Hopefully someone can answer these.

    1) What are the additional components that a 20 volt laptop ac adapter has in addition to the components of a 9 volt cellphone adapter?

    2) Why do consumer electronics tend to get smaller but ac adapters have only reduced in size marginally?

  2. Brownout

    Well-Known Member

    Jan 10, 2012
    You cell phone is much smaller than your laptop. Your cellphone adapter is much smaller than your laptop adapter. See the pattern?
  3. Art

    Distinguished Member

    Sep 10, 2007
    AC adapters have reduced significantly since switchmode power supplies became commonplace.

    You need to be looking at wattage rather than voltage to compare them.
    Your laptop's power consumption will be written on a sticker underneath.
  4. Dave_UYZ

    New Member

    Jan 16, 2014
    1] It's implicit that the gadget requiring a 20v suppply requires a fair bit of Power (W=V*I), so whatever does the conversion from the Mains will be larger.

    2] Conversion Processes (AC-DC) take a bit longer to develop.
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
    Lets compare apples to apples. I have a new notebook, and the new adapter (rated for the same power) is about 1/3 the volume of a ten year old adapter, and it doesn't get even warm, while the old one was a good space heater. I say there is still some development going on.
    PackratKing likes this.
  6. MaxHeadRoom


    Jul 18, 2013
    The DC output adapters are now much smaller and are regulated due to SMPS.
    The AC output type still rely on the simple iron transformer and are converted and regulated in the device.
  7. ian field

    AAC Fanatic!

    Oct 27, 2012
    Generally its the total power (VA rating) that actually determines the size - modern switch-mode types are generally a fair bit smaller than equivalently rated iron cored transformer types.
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Your laptop power supply is generally 20 volts x 2.5 amps (50 'watts'). For comparison, your cell phone is 5 volts and 0.5 amps (2.5 'watts'). Now, instead of asking why laptop adapters are so big, why not ask why cell phone chargers are so big?

    Note: watts, in this case are better described as volt*amps.