dual power supply

[paex30]

Hi everyone,

I wanted to design a simple dual power supply +-15V from a 24 V. Few months ago I found a video on EEVblog youtube channel where a dual power supply was designed simply using OPAMPs. Is there anyone who could remember what video it is or could have some suggestions to design the power supply?

Thanks

[+Mikie]

What you're asking should be easy to find on the net. But I would simply go for an IC voltage regulator, 7815/7915 for example if you only need fixed voltages. No need for mucking around with op amps. For adjustable there's that LM-something adjustable regulator name which I can't remember at the moment.

For schematics you can have a look at the manufacturers sites, look for "Application notes", but there should be basic schematics in the IC datasheets.

[paex30]

For this kind of IC you need generate a negative voltage but I have only positive 24 V and I want my design to have a low cost, so I think to use a flybuck converter with transformer or only OPAMPs.

[Zero999]

Hi everyone,

I wanted to design a simple dual power supply +-15V from a 24 V. Few months ago I found a video on EEVblog youtube channel where a dual power supply was designed simply using OPAMPs. Is there anyone who could remember what video it is or could have some suggestions to design the power supply?

Thanks

What is it powering?

It's possible the circuit can be modified to work with a single supply rail.

How much current is needed?

Can't you use a rail splitter to get +/-12V?

[paex30]

I need a +-15V with a maximum current of 170 mA per channel.

[schmitt trigger]

A 30 volt voltage span from a 24 volt input.

No. Definitively you are not going to get it with a purely linear regulator. You do require switchmode regulators.

There are some of options:
1- Two regulators, a buck and an inverting regulator fed each from +24 volt. No transformers, only two inductors.
2- A pushpull converter. This would be my preferred for higher power, but you require an output transformer with both primary and secondary center taps and two inductors.
3- Because the output power is low, a flyback converter would also work, but you still require a transformer with two secondaries. But no inductors.

[HB9EVI]

As we all see, there isn't yet much skill, already in the way the question is asked; I don't see much sense in proposing to build switching mode regulators; more meaningful would be to get small a center tapped 18V 10VA transformer and work with the 7815/7915 or LM317/337 if variable voltage is needed.

[Lee Leduc]

Unless you're set on designing and building your own, the easy solution is to buy a DC/DC converter. Take a look at a DC/DC converter like the Murata NDS6D2415C. 24VDC in, +/-15VDC at 200ma out.

Stock https://octopart.com/nds6d2415c-murata+power+solutions-49451068
Datasheet https://datasheet.octopart.com/NDS6D2415C-Murata-Power-Solutions-datasheet-8452589.pdf

About $20 USD. You'll have to check price and availability in your country.

[+Mikie]

A 30 volt voltage span from a 24 volt input.

No. Definitively you are not going to get it with a purely linear regulator. You do require switchmode regulators.

There is such a thing as capacitive voltage multiplier, invented long time before all this IC stuff. It would be quite feasible for such a low current.

However, save yourself a world of complications and start with a centre-tapped transformer of at least 18V per side. Again, at such a low current it will be small and cheap. Follow that with ANY linear regulator, IC or discrete and that's it.

[Zero999]

I need a +-15V with a maximum current of 170 mA per channel.

To power what?

It's quite likely you could re-configure the circuit to use a single 24V power supply, if you told us what the circuit is.