Comments on: Power adapters http://adammonsen.com/post/487 blog and sundries of Adam Monsen Wed, 14 Jul 2010 19:18:21 +0000 hourly 1 http://wordpress.org/?v=3.0 By: Graeme http://adammonsen.com/post/487/comment-page-1#comment-12058 Graeme Wed, 20 Jan 2010 07:32:43 +0000 http://adammonsen.com/post/487#comment-12058 Most modern PSUs (notebook bricks, cellphone chargers and desktop internal supplies) are switched mode, so don't have any transformers. Normally the only coils are in the output regulator. http://en.wikipedia.org/wiki/Switched-mode_power_supply Strictly speaking the supply doesn't push current, but the load draws it. This means that you're safe if the load draws less current than the PSU's rated maximum, but it may blow it if you try to draw more. This can be spectacular and very smelly. Don't ask how I know. Loosely speaking, watts = volts x amps. Also, if the output voltage of your little white cube (5 V, say) is less than the voltage required by the notebook's charging circuitry (around 15 V for my Toshiba) nothing will happen or, at worst, the battery (rated at 10.8 V for the Toshiba) will try to discharge through the charger unless there is something (e.g., a diode) to prevent this. Most modern PSUs (notebook bricks, cellphone chargers and desktop internal supplies) are switched mode, so don’t have any transformers. Normally the only coils are in the output regulator.

http://en.wikipedia.org/wiki/Switched-mode_power_supply

Strictly speaking the supply doesn’t push current, but the load draws it.

This means that you’re safe if the load draws less current than the PSU’s rated maximum, but it may blow it if you try to draw more. This can be spectacular and very smelly. Don’t ask how I know.

Loosely speaking, watts = volts x amps.

Also, if the output voltage of your little white cube (5 V, say) is less than the voltage required by the notebook’s charging circuitry (around 15 V for my Toshiba) nothing will happen or, at worst, the battery (rated at 10.8 V for the Toshiba) will try to discharge through the charger unless there is something (e.g., a diode) to prevent this.

]]> By: adam http://adammonsen.com/post/487/comment-page-1#comment-12028 adam Fri, 01 Jan 2010 02:49:18 +0000 http://adammonsen.com/post/487#comment-12028 From Steven on Facebook: <blockquote>It's not the volts, it's the wattage. Voltage stepdown is easy, adding the "push" or the current is the difficult part and usually requires a larger coil to translate the voltage into the current required for larger items. That's soon to change with some very interesting I.C.'s from TI... Looks for wallet-sized laptop power supplies in the near future...</blockquote> From Steven on Facebook:

It’s not the volts, it’s the wattage. Voltage stepdown is easy, adding the “push” or the current is the difficult part and usually requires a larger coil to translate the voltage into the current required for larger items. That’s soon to change with some very interesting I.C.’s from TI… Looks for wallet-sized laptop power supplies in the near future…

]]> By: Andrew Forman http://adammonsen.com/post/487/comment-page-1#comment-12027 Andrew Forman Thu, 31 Dec 2009 19:54:43 +0000 http://adammonsen.com/post/487#comment-12027 USB provides 5v and 500mA, where your typical laptop brick is around 12-20v and 15A. While I'm sure you could wire it up, charging your laptop via USB would likely be an all-day event. USB provides 5v and 500mA, where your typical laptop brick is around 12-20v and 15A.
While I’m sure you could wire it up, charging your laptop via USB would likely be an all-day event.

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