Advice for 120vAC to 3.7V DC circuit

[joshzstuff]

My project is to build a power supply that will allow devices powered by battery to run on continuous power (mains).

Objectives:
-120AC to 3.7v DC
- smallest package possible
- small power requirements (<150ma output)

One Idea I'm researching now is to use a USB wall adapter.
**broken link removed**

Should I tweak this device, or add a few components to drop the voltage from 5 to 3.7? (i.e. diodes, regulator)

I'm just getting started in learning electronics, so any recommendations on research that will help me understand the principles will be appreciated.

Go easy on me, I'm just learning
Thanks in advance.

 

[hameeds01]

just add two Diodes in series on the output of 5v USB charger u will get the desired voltage

 

[Tahmid]

Hi,
You can use the adapter, but be careful, as the output of these devices is not tightly regulated to 5v. If you carefully measure and observe the output, you can see it going to 6v or more. So, I think you could use a zener-transistor circuit like this for your purpose.

Hope this helps.
Tahmid.