TPS7A4700

[lew247]

I want to build power supplies for 5V and 12V to replace all the "plug in" cheap switched mode power supplies for things like telephone, broadband router, external HDD, and many other items around the house.
What I'd like to know is could I use one of the boards of fleabay that use the TPS7A4700 chip and then use tip35's or 2n3055 etc to get greater current from the circuit?
something like the attached circuit.
BUT instead of using a 7815, use one of the TPS7A4700 modules
I know I'd have to bypass the diodes on the TPS7A4700 board as I'd be supplying it with dc not ac.
I'd make 2, one for 5V and one for 12V
I obviously wouldn't need 20A I reckon 5A would be enough.

I want pure clean psu's for the equipment because I do a lot of listening on SDR radio's of extremely weak signals and at the moment the noise from the smps's are ruining it.

If not has anyone got any examples of circuits that would be just as clean and simple/easy to build?

 

[Nigel Goodwin]

You 'could', however the regulation will be poor, as with the 78xx example you posted - although you 'may' be able to connect the sense pin to the output of the external transistor.

Why not just use multiple TPS7A4700's, and separate supplies - it doesn't seem a good idea to try and feed everything off the same supply anyway.

These units are also presumably switch-mode, so will likely also produce 'some' degree of RFI.

 

[lew247]

How could I get better regulation if I was to use say a 7805 and/or a 7812?

 

[Nigel Goodwin]

Using a PNP transistor across the regulator - as shown in the datasheets - however this messes up the current protection.