hello,
i have a transformer which gives 27v 4A as it's output.
I want to reduce the output to 12v without the loss of amperes .
I want to use it as a power supply for an audio amplifier project which use two la4440 ic . So how can i build a circuit to serve my need ,using commonly available parts ?
Hope you guys can help me with this.

 

It'd be a lot easier to start with the right transformer.

It's easy to regulate the voltage at 12V using, for instance, a 7812 voltage regulator, but this would be very inefficient. You would also need a few in parallel, or a high current alternative, to get to 4A.

 

You wouldn't get a loss on current, you would get a gain in current if you used a second transformer surely?

 

It'd be a lot easier to start with the right transformer.

It's easy to regulate the voltage at 12V using, for instance, a 7812 voltage regulator, but this would be very inefficient. You would also need a few in parallel, or a high current alternative, to get to 4A.

can you plz suggest a high current alternative ?
Or if i use 7812 regulators, how many of them will be needed in parellel to get the desired result ?
Sorry for being a noob in this.

 

You wouldn't get a loss on current, you would get a gain in current if you used a second transformer surely?

edward i have a step down transformer (27v,4A output). Just want to regulate the output to 12v 4A ,to use with an audio amp project.

 

Does your transformer have a center-tap connection?
Then you can use a full wave 2-rectifier configuration.

For an audio amp you do not need regulation.

 

For an audio amp you do not need regulation.

yes it has centre tap. And you mean i can directly apply the rectified output from a 27v transformer ,to the supply pin of LA4440 IC ???

 

Usually a transformer is rated for voltage across the secondary winding.
If it is 27VAC then it is likely to be 13.5V from the center tap.
This will give about 18VDC after rectification.
The LA4440 is rated to 18VDC max.

 

But unfortunately it is a 27-0-27 transformer.

 

Can you get a 12-0-12 transformer instead?

 

Can you get a 12-0-12 transformer instead?

well that's not the aim of this thread.
But since experienced guys like you are asking like this, now i think it is better to get a 12v one.

 

You can get a DC to DC converter for about $20 and cut out the design process.

http://www.ebay.com/itm/waterproof-...17?pt=US_Power_Inverters_&hash=item460e282ca9

 

Can you lay your hands on a surplus PC power supply?

Ramesh