Designing a DC Power supply

[vick5821]

Hey friends, I plan to build a DC power supply for my future usage of electricity to replace battery.

I plan to use the adapter(Approximate 16 -18V) as input and I plan to use voltage regulators too -- 7805, 7806, 7809, and 7812( Common source of voltage)

My concept is like this :

I plan to have a DC power supply and a switch so that I can adjust to the voltage output that I need. For eg, I want 9V, so I make the 9V available by adjusting the switch. What most important is, I plan to have only ONE output terminal and not 4 output terminal(As it will be messy) So it means when I want 6V , I adjust it to be 6V at the output. And when I want 9V, I adjust it to be 9V that will be appearing at the output terminal

This is my initial sketch of my circuit :

In this sketch, I will add diode 4007 before the Vin of the regulator and PLAN TO ADD 4007 diode too at the Vout of regulator. But placing diode in the Vout of regulator cause me one problem - Diode has voltage drop of apporximate 0.7V. This means when the Vout is 5V, the exact voltage at the output terminal will be only around 4.3V.

Any ideas on how to overcome this and any more suggestion on implementing this DC power supply circuit ?

Thank you

 

[godfreyl]

It would be better to use an adjustable regulator like LM317. Then you only need one regulator, and you can change the voltage by switching the resistors. Here's a datasheet to show how it works: **broken link removed**

 

[papunblg]

It appears that you are getting power from adapter(Approximate 16 -18V). In that case the adapter output is 16-18V DC. Check the adapter. So no need to "add diode 4007 before the Vin of the regulator". You jast need a voltage regulator IC. If you want you can use 78xx series fixed voltage regulator or 317 variable regulator.
Remember:-
You did not mention your power requirement and also we dont know the rating of your adapter.
Check the datasheet of a regulator IC before using it.