2017-09-20 Use LM7805 To Charge Phone?

I posted this comment to FB Arduino group 2017-09-22.

“Can I use a 7805 (regulator IC) to charge my cell phone?”

The output is 5 volts, which is what the phone needs to charge.  But the average smart phone will take more than 1 amp, up to 2 amps to charge quickly.  The 7805 can’t put out that much current.  So your phone will take a lot longer to charge.

The 7805 is a huge power waster.  It works by wasting the excess voltage as heat.  You will have to use a large heatsink, because the 7805 will have to dissipate a lot of heat and it will get very hot.  If it gets too hot, the thermal protection that’s built in will shut it down and that will slow the charging down.

It’s better to use a DC-DC buck converter, which takes 12V at 1 amp and converts it into 5 volts at 2 amps, so your phone will charge much faster.  And there will be very little power wasted, it will not get so hot.  They are cheap, only a few dollars (US).  To find one, search for DC-DC buck converter USB.

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