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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Tue Apr 03, 2018 9:25 pm
by dtcicero
I'm interested in using the GP25A so great to see this info. I checked with Meanwell and the GP25A switching frequency is 65kHz. I also found the GP25A does not perform well unless the +15V output is loaded to at least 100mA. I think your tests showed a 50mA load on the +15V output?

Thanks,
Dave

Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Wed Apr 04, 2018 2:53 pm
by mediatechnology
dtcicero wrote: Tue Apr 03, 2018 9:25 pm I'm interested in using the GP25A so great to see this info. I checked with Meanwell and the GP25A switching frequency is 65kHz. I also found the GP25A does not perform well unless the +15V output is loaded to at least 100mA. I think your tests showed a 50mA load on the +15V output?

Thanks,
Dave
Thanks for posting Dave!

I just rechecked the GP25A under a heavier load and its bad regardless.

+15V @ 320 mA ripple is about 120 mV p-p and a combination of HF fast rise time spikes and LF ripple.
-15V was loaded in 160 mA, 5V loaded in 500 mA.
The -15V was relatively quiet but the 5V also had about 120 mV p-p ripple similar to the +15V.

(EDIT: Updated the measurements above to reflect that the 'scope probe was in X10 mode. I almost never use X10 but had been working on a power amp and had it switched on.)

I've been using the TDK open frame a lot lately and am very pleased with it. viewtopic.php?f=7&t=945

Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Wed Apr 04, 2018 4:52 pm
by mediatechnology
This is the GP25A +15V ripple loaded in about 320 mA. The peak-to-peak value is about 150 mV.
The 5V rail, loaded in 500 mA looks about as bad.
Loading or unloading the -15V and 5V rail doesn't affect the +15V ripple significantly.

Image
Meanwell GP25A14E-R1B Ripple

None of the other Meanwell bipolar supplies have this level of ripple.

Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Thu Apr 05, 2018 5:54 am
by dtcicero
Thanks for running the tests again! It's a shame the performance is not at least equal to what it's meant to replace. I really like the P25A/GP25A form factor, and no worries with UL or mains.

Dave

Meanwell RS-25-48 48V 0.57A Phantom Supply

Posted: Fri Apr 20, 2018 1:05 pm
by mediatechnology
The Meanwell RS-25-48 48V (adjustable) 0.57A switcher, when used with a simple RC post-filter, is suitable for phantom power.

Mouser Product Page: https://www.mouser.com/productdetail/me ... xiXg%3D%3D
Meanwell PS-25-48 Datasheet http://meanwellusa.com/productPdf.aspx?i=392#1

Image
Meanwell RS-25-48 48V 0,57A switching power supply.

When unloaded the output has a large sawtooth ripple around 1 kHz.
There is FM spread-spectrum EMI-reduction evident.
The next three frames show audio "in-band" ripple.

Image
Meanwell RS-25-48 48V supply unloaded ripple.
5 mV per vertical division, 1 ms horizontal.


When loaded in 24 mA the output is considerably quieter.

Image
Meanwell RS-25-48 48V supply ripple with 24 mA load.
5 mV per vertical division, 1 ms horizontal.


A simple 47Ω 22µF R-C post-filter lowers the in-band ripple significantly.

Image
Meanwell RS-25-48 48V supply ripple with with 47Ω/22µF post-filter and 24 mA load.
5 mV per vertical division, 1 ms horizontal.


With a faster 'scope sweep rate we can see out-of-band spikes at significantly higher amplitude near the 100 kHz switching frequency.

Image
Meanwell RS-25-48 48V supply ripple near the switching frequency with with 47Ω/22µF post-filter and 24 mA load.
20 mV per vertical division, 10 µs horizontal.


I haven't checked the ripple performance at higher currents.
My interest is primarily for builders making simple 1U and 3U rack projects and not powering entire consoles or big 500-series frames.

The lightly-loaded post-filtered in-band ripple of the RS-25-48 is low enough for phantom use and, in application, appears in common mode.

The out-of-band ripple might be improved with an inductive filter but the levels seen here are typical for any switcher.
When used in an actual preamp I doubt its high enough to be a problem.
emrr wrote: Thu Mar 29, 2018 5:47 pm I've used a bunch of the Meanwell RS-25-48 for phantom, with an RC filter after it. Not been a problem that I've detected. They are adjustable over a small range, so you can land voltage at a best spot for the range of load expected.
So there you have it folks.
The cigarette pack size Meanwell RS-25-48 seems to fit the bill for a $10 phantom supply.

Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Sat Apr 21, 2018 8:54 am
by JR.
Thinking some more about a simple MOSFET pass element configured as a ripple filter I wonder how the tradeoffs or pros and cons weigh out?

Pros
1- potentially very effective noise filter
2- relatively simple, depending on how fancy one gets
3-efficiency or loss, "could" be less than passive filter
4- low output impedance
con(s)
1- complexity... simple passive filter is "simple" (KISS)
2- will cost more than passive
3-slightly higher output impedance?
4-a dynamic ripple filter would take time to adapt to changing load, so could momentarily allow ripple after a load step.

An optimal design could be self regulating, sensing for ripple and minimizing that, instead of regulating to a hard specific voltage. Of course how clever this gets adds complexity and output voltage could shift with load, albeit slowly.

JR

Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Sat Apr 21, 2018 2:05 pm
by mediatechnology
I think TI makes one.

I also have design Idea Ripple Eater that was published recently.

Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Tue Apr 24, 2018 12:20 pm
by mediatechnology
The TI ripple eater regulators I was thinking about are the TPS7AXX-series:

TPS7A47 Positive: http://www.ti.com/product/TPS7A47
TPS7A33 Negative: http://www.ti.com/product/TPS7A33

Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Wed Apr 25, 2018 8:56 am
by JR.
Nice, I was thinking of automatically setting the voltage based on ripple, but if you have the budget a few hundred mV is no big deal.

JR

Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Wed Apr 25, 2018 11:43 am
by mediatechnology
wereoflu used the TPA7AXX-series in his minimixer which is where I found it: viewtopic.php?f=6&t=882#p10291

There's another ripple eater I recall from a Design Idea.
I'll dig, scan and post.

My goal is to have something that plugs in and works without any additional filtering.
Most of the Meanwell and TDK models I tested are great.
The simple RC required for the 24V and 48V supplies aren't a deal-breaker.
In the case of the 24V for powering relays external filtering may not be needed at all.
I haven't tried the 24V yet.