Power Supply Design

[slowaudio]

Are there any good resources for power supply design? I've found a few, but I don't think I'm doing something right. The TI Webbench application wasn't really getting the results I'd like.

What I need is a power supply that takes 120AC in and then a few output rails +/-15V, 5V, and 3V3. I'd like a linear regulator for the +/- 15 (low noise audio application) and I'm open to other suggestions for regulators for the other rails. They're going to power a micro and some digital peripherals, and to be honest I don't know what the best solution might be.

[madires]

How much current do you need for each rail?

[slowaudio]

Not much, I would say maximum 300mA/ rail, and that's being very conservative. The +/-15 rail will just be powering a handful of opamps, nothing exotic. 5V rail will just be power a supply and some LEDs. 3V3 rail will just be powering a STM32F3 micro, which has a max current rating of 100mA.

[Bored@Work]

I'm open to other suggestions for regulators for the other rails.

LM2596 based SMPS modules. Approx. $1.50 on eBay for one.

[mariush]

A transformer with center tap, preferrably larger than 24v ac , a bridge rectifier, a couple of capacitors, and LM317/LM337 to get stable +/-15v 

before the LM317, take the 15+v input and use a LM25** (cheap on ebay) regulator to get 5v  .. or get a MC34063 and the parts needed to make it yourself. 

Use a 1117-33 linear regulator to get 3.3v 100mA from 5v (1117 only needs about 1.1v above 3.3v to output stable 3.3v)

[slowaudio]

Is the noise not an issue??

[slowaudio]

A transformer with center tap, preferrably larger than 24v ac , a bridge rectifier, a couple of capacitors, and LM317/LM337 to get stable +/-15v 

before the LM317, take the 15+v input and use a LM25** (cheap on ebay) regulator to get 5v  .. or get a MC34063 and the parts needed to make it yourself. 

Use a 1117-33 linear regulator to get 3.3v 100mA from 5v (1117 only needs about 1.1v above 3.3v to output stable 3.3v)

So I'm familiar with the center tapped setup for the +/-15 rails and that seems really reasonable, and I've done a few power supplies before like that and I'm fairly comfortable with that.

I'm just unsure about the switch-mode regulators. Is there anything that I need to be concerned with?

[madires]

Not really. Maybe replacing cheap caps with branded ones when you buy SMPS modules from ebay. If you're doing the circuit and PCB youself follow the datasheet. On noise problems add an ripple filter. And power the SMPS directly, don't place it behind a linear regulator.