I need to build a power supply for an audio power amplifier that I'm designing. It needs to provide 35 V at at least 10 amps.

The particular amplifier I am building needs a regulated supply. I'm looking at using the LM5116 Buck Converter because of the 10 A current supply and the wide input range, which would make it easier to scrounge an appropriate transformer. Here's a link to the National page for the LM5116: http://www.national.com/pf/LM/LM5116.html

Is this the best way to approach this design? Does anyone have any comments or suggestions?

 

first thing i would be asking is if this supply needs to be electrically isolated.
is it going to be straight off the mains or off something else?

 

For a 35v supply at 10A using a conventional transformer, the transformer will have two dimensions: LARGE and HEAVY! You would need a transformer capable of perhaps 11-12A @ 40VAC output. At 50-60Hz, it would be perhaps 5" to 8" in H/W/D, and weigh in around 10lb to 15lb (this is a sort of wild guess, extrapolating from a 120/240 60Hz 36VCT @2.8A transformer I have sitting in front of me).
[eta]
Tripped across a possibly suitable transformer online:
5.3"x2.4" (135mmx61mm) 8.1lbs(3.7kg) 38vac@12.36A
http://www.toroid.com/standard_transformers/rectifier_transformers/solid_amps_pn2.htm#749.382
There's another:
4.9"x2.4" (114mmx61mm) 6.7lbs(3.0kg) 38vac@10.14A
http://www.toroid.com/standard_transformers/rectifier_transformers/solid_amps_pn2.htm#738.382

It might be difficult to scrounge such a transformer.

One of the techniques they're using nowadays is using high frequency drivers to switch current through a relatively small toroidal-wound bifilar (two windings) transformers. If you're switching current at 50kHz, the transformer can be quite a bit smaller and much lighter in weight.

However, I'm afraid I don't have a ready-made design for you. Something like this will take a good bit of research.

 

is it going to be straight off the mains or off something else?

I'll be using a transformer to step the mains voltage down. Or at least, that's the plan.

For a 35v supply at 10A using a conventional transformer, the transformer will have two dimensions: LARGE and HEAVY!

Heh, I figured as much. There are some transformers that fit that description lying around the lab at my university and I'm on good terms with the technicians so hopefully I can find something for the price of free. Thanks for the links to those two transformers, both of them look suitable.

One of the techniques they're using nowadays is using high frequency drivers to switch current through a relatively small toroidal-wound bifilar (two windings) transformers. If you're switching current at 50kHz, the transformer can be quite a bit smaller and much lighter in weight.

Do you have any links with more information (application notes, etc.)?

However, I'm afraid I don't have a ready-made design for you. Something like this will take a good bit of research.

I started designing from the speakers back, but about halfway through it struck me that designing the power supply for this monster was going to be as, or even more involved than designing the amplifier. Initially, I was planning on 200 W/channel but now I'd rather go with 150 W/channel just because of the transformer.

 

The June 2008 Elektor had has a go at designing a switched mode PSU especially for high power audio amps.

Interesting article.

 

The June 2008 Elektor had has a go at designing a switched mode PSU especially for high power audio amps.

Unfortunately, it costs money to download. Do you think it would be worth purchasing?

 

The easiest one to build will be a regulated PS, but will require a large transformer that you can find cheap at a scrap yard. If you want to be more efficient then you can build a Switch Mode PS which is very hard to build. For the regulated you can use an LM723 with external transistors for the voltage regulator in order to give you the 10A.

 

There are actually two article in this mag.
One is a general article on smps the other a dedicated 400w smps for audio amps.

Back issues are available cheaply from Elektor and possibly Jaycar in Oz,There is also a kit.

 

this forum is dedicated to Audio amp power supply design.

http://www.diyaudio.com/forums/forumdisplay.php?forumid=67