Question: I have a car cigarette extension cord with a USB out on it as well. The USB out though will not charge my phone, which is a bit annoying. I had a look at the circuit inside in the device and it looked something like this:

![Power supply circuit](https://i.imgur.com/faPZh30.png)

I'm guessing the reason the phone won't charge is the 78L05 chip is only rated for 100mA. Therefore I was thinking of changing it to a 7805 chip, which is rated for 1A. Would this idea stand up to my reasoning? Or am I likely to damage any equipment I connect if I go down this root?

Also, if I go about this, will I also need to do something with the capacitor and the resistor on the board?

Edit:

Thanks for all the answers.  

I didn't think of the heating problems I might have in my scenario above.  

Its looking like the best solution for the device is the one Nick Alexeev gave below if I'm going to stick with the device I have.

I have also changed the diagram above as the resistor is actually 360 ohm.

Also, I am including a image of the device itself below as requested to show exactly what I was talking about.

![Extension Cord Device](https://i.imgur.com/BkWeRoW.jpg)

Answer: 
The basic concept is sound, although a bit profligate. You want to worry a little bit about heat-sinking the 7805, since for every 5 mW out, you're burning 7 mW in the regulator heat sink (because current out essentially = current in, and you're dropping 7V across the regulator). You'd do a lot better with a 12V-to-5V stepdown switcher.

The capacitor is there to smooth out ripple and noise on the input to the regulator. I would add a 1 uf TANTALUM (!) across the 7805 output, to suppress spurious oscillation of the regulator IC. I've seen that happen on a friend's homemade linear supply; adding the capacitor fixed it. (Supposedly, current-gen 78xx regulators don't need it, but it is CHEAP insurance.)

What color LED is it, and how much current does it require? That's what sizes the resistor.
A better alternative is by using SMR88xx ([eBay link](http://www.ebay.com/itm/DC-DC-converter-mini-SMR88xx-high-current-replacement-7805-7809-1-Lot-10pcs-/181181177608)), it's has higher power, less dissipation heat.