0
\$\begingroup\$

I'd like to use this isolated DC-DC converter:

https://power.murata.com/datasheet?/data/power/ncl/kdc_nmg.pdf

to feed a 7915 linear regulator. I'm wondering if it is possible to use that DC-DC converter (the variant with +24V output) to feed the 7915 by reversing the polarity of the DC-DC output (so - goes to VIN on the 7915 and + goes to ground).

would that work correctly?

ps. I know it would be better to just get a single DC-DC converter to obtain -15V, but I really need to go into the 7915.

\$\endgroup\$
0
\$\begingroup\$

Since the converter is isolated you can used its positive output as ground. The circuit that you're envisioning will work, but note that the 9V drop will result in a lot of wasted power; you may need to use a TO-3 with a decent heatsink if you're pulling more than a few hundred mA.

\$\endgroup\$
  • \$\begingroup\$ actually this DC-DC converter can only provide 83mA max, so I guess heat on the 7915 is not a proble, right? \$\endgroup\$ – Dimitri Petrucci Nov 23 '17 at 1:23
  • \$\begingroup\$ That's still 0.75W, which means a 30-45K increase above ambient with no heatsink. So not dangerous, but you don't want to touch it. \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 23 '17 at 1:24
0
\$\begingroup\$

Yes. The linked datasheet specifically states that this is suitable for creating a negative rail in a system where only positive rails exist.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.