dual power supply - Page 1
Forum section: electronics / beginners

author: paex30
author_rank: Newbie
timestamp: July 19, 2018, 08:02:35 am
content: 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

author: +Mikie
author_rank: Contributor
timestamp: July 19, 2018, 11:14:29 am
content: 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.

author: paex30
author_rank: Newbie
timestamp: July 19, 2018, 12:38:30 pm
content: 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.

author: Zero999
author_rank: Super Contributor
timestamp: July 19, 2018, 01:08:48 pm
content: Quote from: paex30 on July 19, 2018, 08:02:35 amWhat 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?

author: paex30
author_rank: Newbie
timestamp: July 19, 2018, 01:15:58 pm
content: I need a +-15V with a maximum current of 170 mA per channel.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 19, 2018, 01:55:18 pm
content: A30volt voltage span from a24volt 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.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 19, 2018, 02:01:11 pm
content: 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.

author: Lee Leduc
author_rank: Regular Contributor
timestamp: July 19, 2018, 03:21:01 pm
content: 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.Stockhttps://octopart.com/nds6d2415c-murata+power+solutions-49451068Datasheethttps://datasheet.octopart.com/NDS6D2415C-Murata-Power-Solutions-datasheet-8452589.pdfAbout $20 USD. You'll have to check price and availability in your country.

author: +Mikie
author_rank: Contributor
timestamp: July 20, 2018, 12:39:40 am
content: Quote from: schmitt trigger on July 19, 2018, 01:55:18 pmThere 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.

author: Zero999
author_rank: Super Contributor
timestamp: July 20, 2018, 02:11:44 pm
content: Quote from: paex30 on July 19, 2018, 01:15:58 pmTo 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.