DC/DC converter

Some time ago there was some discussion about running mic pres on battery supplies. I have just built a small DC/DC converter that should make that possible...

You can see a photo here: http://stiftsbogtrykkeriet.dk/~mcs/DC-DC_con.jpg
It's the small vertical PCB (size 27*27mm).

The schematic is here: http://stiftsbogtrykkeriet.dk/~mcs/DC-DC_con.gif - straight from the data sheet...

With 11.8V in I get +21.4V and -20V out. There is some noise in the output - about 30mVpp at 33kHz. But I use a standard LM317/337 supply after the DC/DC converter, and in the +/-14V output I see no noise at all.

I have also tried running the converter with 8V in. At that voltage I get +14V and -13V out.

I don't know how much current the converter can supply. In my circuit it supplies the LM317/337 regulators and two OPA604 op. amps. The converter chip does get hot, so a small heatsink is probably a good idea.

Best regards,

Mikkel C. Simonsen

[quote author="mcs"]I don't know how much current the converter can supply. [/quote]
Taken from the datasheet, you won't be able to get more than 300mA.
Maybe enough for phantom powering , it will depend on the mike you'll be using

http://www.linear.com/prod/datasheet.html?datasheet=185

[quote author="daArry"]http://www.linear.com/prod/datasheet.html?datasheet=185[/quote]
No, in this case it's http://focus.ti.com/docs/prod/folders/print/lt1054.html actually :wink:

But the LT datasheet does include a coloured version of the schematic I posted...

Best regards,

Mikkel C. Simonsen

Phantom power max. is something around 14mA per channel - when shorted. In real-life mostly some 2-6mA.

So there should be plenty of power here - even for a whole stack of mics.

Jakob E.

Has someone ever diyed a switched power supply?

Michael Krusch > it will depend on what your planning to do. Switching Power Supply (SPU) are used in your computer e.g. From those SPU, you can get 20A from +5V. These SPU are really useful for laboratory experiments. The major problem with those SPU is that you can't adjust output voltage. Usually, you get +12V / +5V / +3.3 / -5V / -12V.

[quote author="Michael Krusch"]Has someone ever diyed a switched power supply?[/quote]

Sure, I've made a switching PS based around this circuit: http://www.shlrc.mq.edu.au/~robinson/Information/Inverter_4W.html
...based on an IC commonly pulled from computer power supplies. It's easy to change the voltage by altering the feedback.