How to get good isolated / idiot proof 9VDC supply from +/-15VDC rails?

So I have a modular synthesizer with a +/-15VDC power supply and I'd like to power something (guitar effects pedal) that requires 9VDC.

I was initially planning to just use a 7809 off the +15 rail to get my 9V power supply, but realized that several of my pedals actually ground the positive rail to get a -9V internal supply. My thoughts was to run the 7809 through a 1:1 transformer, but I've never specced out a transformer before for isolating a DC supply and have no idea where to start.

I'd be looking at supplying about 250mA max.

I'd also like this supply to be idiot proof.. so if I short something out, or draw more than 250mA - I don't want to damage anything, or take down my +/-15VDC supply.

Maybe there's even IC's designed to deliver a 9VDC isolated supply, etc... I'm totally OK with the supply being switchmode too.

Hi,

There are ready to buy isolated DCDC converters for almost any input and any output voltage.
Many manufacturers, different features. Many if them have built in current limitation.
If not use an external polyfuse.

Just do an internet search and compare some datasheets.

Klaus

Yes what Klauss says is correct. Recom, and Murata are 2 big manufacturers. Or search Digi-Key for “isolated dc-dc converter”.

Well you can use 30V to 9 voltage isolated dc to dc converter, you can take 30V form +/- 15VDC
Hope output power is about 3W (9x 0.25A)

Simple one is available
https://www.mouser.in/ProductDetail...GsmoEFRKS8Koqt8Pjkl39eJ/pVuAatgt7lOZcp4AVTg==


Hope it will really help to you

- - - Updated - - -

Well you can use 30V to 9 voltage isolated dc to dc converter, you can take 30V form +/- 15VDC
Hope output power is about 3W (9x 0.25A)

Simple one is available
https://www.mouser.in/ProductDetail...GsmoEFRKS8Koqt8Pjkl39eJ/pVuAatgt7lOZcp4AVTg==


Hope it will really help to you