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how does a mobile phone charger work? Answered

 i just want to know how does a cell phone charger works.
i know that it uses a transformer and diodes for rectification.
my actual doubt is that i have read in a news paper that there would be 30% losses when the charger is given supply and no mobile is connected.
am surprised how there can be so much loss


Trouble is - most transformers are the old style, which are essentially a short circuit over a coil to make a magnetic field and convert the power down to a usable voltage.  When nothing is connected these transoformers just choke on their own eddy currents in the transformer...and burn power.

Newer cel phone chargers dont use the old wall-wart brick type transformer; rather they have an efficient switch mode power supply that runs at very high efficiency (excluding power factor); and these newer models dont use much if any power with nothing connected.  Smarter ones even shut themselves completely off when nothing is connected - sadly these are rare.

This site by the Lawrence Berkeley National Laboratory has some interesting data.

They measured the power consumption of 32 chargers alone and 24 chargers with fully charged phone. Newspapers write what sells, this site appears to be more reliable and scientific than a newspaper :p

Seconded - fantastic information!

I'd read the newspaper figures with a big pinch of salt. Percentage of WHAT ? The 5W that the charger uses to charge your phone, 30% of THAT is 1.5Watts. 600 Hours to waste one unit of electricity.