SMPS Switching Mode Power Supply for symmetrical PSU ?

[thomasdf]

Hello

I have used a few Meanwell SMPS now, and I've been super happy with the results. I am wondering if someone here has pointer for such a device with a symmetrical output ? Looking for +/-12VDC and +/-15VDC
So far I have used a pair of single output SMPS but I would be surprised if such unit didn't exist ? My google searches weren't very successful so far.

Bo Deadly shared an interesting design in this post, but maybe there's an even simpler solution ? I'm lazy, I know...

SMPS, stack them like this:

remove the diodes and reduce the filter caps to whatever the SMPS can handle.

Thanks in advance

Thomas

 

[chilidawg]

MeanWell PD-2512 and PD-2515. Downside is, only 25W.

 

[chilidawg]

I have used the PD-2515 for a couple of custom order audio stuff in the past, and they're pretty quiet.

 

[Bo Deadly]

Note that drawing is from my pre-capacitance multiplier period. Now I strongly advocate using CMs instead of chokes.

SMPS are one of several great new(er) electrical components that new designs should definitely use. However, they require a lot of planning. It's not hard, but you need to use the right parts to get truly good results. If you want help with that, post your specific requirements. The most important being what is the load?

 

[thomasdf]

Thanks for your answers !

What's a pre capacitance multiplier ? In most case I don't need much more than 1A per rail...! Not much !

 

[Bo Deadly]

Just meant "before" I decided CMs would be best, I used to advocate using chokes and before that common mode chokes.

You should really provide much more detail about the actual load. For example, if your load is going to sometimes be less than 1A, that might not work out.

 

[Newmarket]

I have used the PD-2515 for a couple of custom order audio stuff in the past, and they're pretty quiet.

Had a brief look at those today. Look useful but lack of stock/lead times and shipping costs seems problematic atm.
Wrt UK at least.

 

[charlesaudio]

I have built some big console psu's made with Meanwell and added filtering. Works find and stay cool.

 

[thomasdf]

Just meant "before" I decided CMs would be best, I used to advocate using chokes and before that common mode chokes.

You should really provide much more detail about the actual load. For example, if your load is going to sometimes be less than 1A, that might not work out.

I am inquiring because I need a +/-12VDC PSU for a DBX118 with a pair of THAT opamps added on the input & output, and also a +/-15VDC for 3 or 4 2520 opamps providing makeup gain for passive EQs.

 

[charlesaudio]

I am inquiring because I need a +/-12VDC PSU for a DBX118 with a pair of THAT opamps added on the input & output, and also a +/-15VDC for 3 or 4 2520 opamps providing makeup gain for passive EQs.

I would use one of those and not mess with the 120VAC :

https://www.digikey.ca/en/products/...BVrikNGmCaNM4tsZWUACYoAAQcJONj4ygkwgBuxQUlLUA

 

[chilidawg]

Had a brief look at those today. Look useful but lack of stock/lead times and shipping costs seems problematic atm.
Wrt UK at least.

Sorry, I didn't know that. I knew they were manufactured in limited quantity, even at 8 years ago, which is the last time I bought one from Mouser.

 

[abbey road d enfer]

Hello

I have used a few Meanwell SMPS now, and I've been super happy with the results. I am wondering if someone here has pointer for such a device with a symmetrical output ?

Symmetrical rail smps are not as common as single rail.You're replacing a problem (minor complexity) with another (purchaseability).

Bo Deadly shared an interesting design in this post, but maybe there's an even simpler solution ?

Only way to make it simpler is to remove the chokes. It may or may not result in acceptable performance. I wouldn't take the risk.

 

[thomasdf]

By simpler, I meant "straight out of the box supplied by the factory" haha
It's a super simple design, and I know PSU are a thing that needs to be approached seriously and without cutting corners.

BTW, your PCB design is super nice Abbey, it just has a footprint that's too big for my needs with the +/-12VDC project.

I know I can still use two 12VDC SMPS and then a 7812 and a 7912 for each rail, that will suit my needs just fine. I was just wondering if something able to deliver more power and being already designed / assembled / regulated / protected existed Not sure if I'm being clear... it's still sunday morning haha

 

[Newmarket]

Sorry, I didn't know that. I knew they were manufactured in limited quantity, even at 8 years ago, which is the last time I bought one from Mouser.

No apologies needed. Just putting the availability issue up here for info. And supply chain issues are all over the place atm.

 

[abbey road d enfer]

I know I can still use two 12VDC SMPS and then a 7812 and a 7912 for each rail, that will suit my needs just fine.

If you do that, you need to use 15V smps that you can adjust to about 16-17V, in order to leave enough differential between input and output.
78/79 series require min. 3V differential. Or you could choose a LDO regulator such as LM1085; which requires only about 1.5V differential. I'm not sure there is a negative counterpart, though.

 

[thomasdf]

That's great to know, thanks

 

[Tubetec]

I got a couple of very good quality multirail switcher psu's from old digidesign 003 units I scrapped ,
I think it has 5v,12v +/-18v and a 48v phantom power rail .

 

[thomasdf]

If you do that, you need to use 15V smps that you can adjust to about 16-17V, in order to leave enough differential between input and output.
78/79 series require min. 3V differential. Or you could choose a LDO regulator such as LM1085; which requires only about 1.5V differential. I'm not sure there is a negative counterpart, though.

If I use LM78XX and 79XX for each rail do I still need to use a choke, resistor or some sort of load between the output of the SMPS and the regulator ?
Thanks

 

[abbey road d enfer]

If I use LM78XX and 79XX for each rail do I still need to use a choke, resistor or some sort of load between the output of the SMPS and the regulator ?

It's a wise precaution, because at the switching frequency, the 78xx and 79xx have very poor rejection.

 

[thomasdf]

Is a 1000uF 35V enough of a load ? I was planing on using one of these to a 100uH choke, to the regulator.