Hello to all!
I need help to develop a power supply that is capable of receiving the input 12Vdc or 9VAC rms and delivered to the output +12 Vdc and -12Vdc with capacity of up to 8W of power.
Attached is the circuit I'm trying to use and need to determine the values of the components.
If anyone has a better suggestion for a circuit that does not need transformer to generate the positive voltage and negative and use in place of the transformer capacitors shall be very grateful to anyone who can day provide.
Thanks to everyone who can help me.

Best regards
Paulo

 

What is the background for your specifications, and how did you end up with that circuit

 

http://www.oneal.com.br/#produtos?id=171

 

So you want make a power supply for that mixer unit you posted a link to? what is probably something we can help you with. But I would say you are on the wrong track with your schematic. Let us first start with your AC voltage what is the source of this. Is it a transformer? Then designing a power supply it kind of important to get the specs on the transformer correct. So let us start in that end.

 

I found the wiring diagram on the Internet that mixer and tried to assemble.
The oscillator did not work with the transistors shown in the diagram. It worked when I rode using BC546.
The negative voltage of-12Vdc only reaches -4Vdc.
Attached is the schematic.
I was looking for an idea for a power supply that could work with 120Vac and 12Vdc generating output +12 Vdc and-12Vdc but did not use transformer to produce the positive and negative voltages, I found this project and tried to build, but did not work as is in the scheme.

 

There is a connection error. The gate on Q4 needs to be connected to R4, not R3.

 

You can use something as simple as a 555 timer to create a negative voltage if your input voltage is low. I seem to recall using one to create a dual rail supply for an op-amp comparator in the past.