Good low noise DIY linear 3A Power supply ?

[rafyc]

Hi,

I've ordered a new case 12u 114HP and looking for a good low noise power supply in DIY.
Regarding modular gird and the future modules that i want, full case will be 3A on +12 and 1,5A on -12.
Should i take 500mA of headroom to be sure ?

So i'm looking for linear toroidal power supply. Do you know any DIY brand ?
here is one but i'm afraid it's too shorthttp://www.metatronicmods.com/store/p9/ ... orack.html
In the title it says 3A 1,8A but in the description 2,5A and 1,5A
Do you think it will fit ?

If i only order the PCB would i be able with sourcing rights component to have 3,5A and 2A ?

Thanks

[MikeDB]

I trust you realise the power supply shown seems to have no power factor correction and hence probably doesn't meet IEC 61000-3-2 and is thus illegal to use in most countries ?

[rafyc]

Really !? in fact i'm based in France and i know EU standards are more strict over US

[MikeDB]

Oh definitely illegal in EU. Customs would just look for the EN number which has to be printed on the device together with a CE mark, and if not there probably just bin it.

[rafyc]

haha you make me save few bucks thanks ! do you think their bus bar will be fine ?
http://www.metatronicmods.com/store/p17 ... ack-B.html

[rafyc]

any idea for 3A linear PSU pcb ?

[ricko]

I trust you realise the power supply shown seems to have no power factor correction and hence probably doesn't meet IEC 61000-3-2 and is thus illegal to use in most countries ?

Are you sure? That standard does not seem to apply to "non-lightning equipment with rated power of 75W or less." (Nor to "professional equipment" which I suppose means installed in a studio by some qualified engineer, in this case.)

The PSU in question is rated n +12/-12/+5V @ 3A/1.8A/1A = 12 x 3 + 12 x 1.8 + 5 x 1 = 36 + 21.6 + 5 = 62.6W (P = I x V isn't it?)


Does anyone kniw of any little board with the inductor, cap or whatever for reducing reflected distortion on the AC lines?

[MikeDB]

Are you sure? That standard does not seem to apply to "non-lightning equipment with rated power of 75W or less." (Nor to "professional equipment" which I suppose means installed in a studio by some qualified engineer, in this case.)

The PSU in question is rated n +12/-12/+5V @ 3A/1.8A/1A = 12 x 3 + 12 x 1.8 + 5 x 1 = 36 + 21.6 + 5 = 62.6W (P = I x V isn't it?)

Does anyone kniw of any little board with the inductor, cap or whatever for reducing reflected distortion on the AC lines?

75W limit is for the input power, not the output. Given normal inefficiencies such as how hot toroids get, I think your example will be marginally over it.

The professional exemption doesn't apply to home studios, as it assumes you have mains cleaning equipment in place - usually a UPS. This case is actually covered under the AV clauses.

RS and Farnell have lots of filters - I expect one will do. My point was more that it wasn't installed in the first place on the PSU referred to so would be illegal to import to many places.

[MikeDB]

deleted

[acidbob]

I have used this brand in my workplace lab with great success

http://uk.rs-online.com/web/c/passive-c ... 4294965059

[ricko]

Are you sure? That standard does not seem to apply to "non-lightning equipment with rated power of 75W or less." (Nor to "professional equipment" which I suppose means installed in a studio by some qualified engineer, in this case.)

The PSU in question is rated n +12/-12/+5V @ 3A/1.8A/1A = 12 x 3 + 12 x 1.8 + 5 x 1 = 36 + 21.6 + 5 = 62.6W (P = I x V isn't it?)

75W limit is for the input power, not the output. Given normal inefficiencies such as how hot toroids get, I think your example will be marginally over it.

Yes. That toroid has 89% efficiency fullload but then there is any loss from the regulators too. They are LDOs, I think, (and may only regulate on over-voltages?) but still may have some loss: even if the 12V windings are being used: anyway, the 12V to 5V regulation would use something.

So does that mean that, a slightly lesser rated toroid would bring it into spec?
E.g. https://au.element14.com/vigortronix/vt ... dp/2817658 (60VA) for 2.5A?

Rick

(Btw "Professional Equipment" seems to mean equipment you need permission to install.)

[MikeDB]

So does that mean that, a slightly lesser rated toroid would bring it into spec?
E.g. https://au.element14.com/vigortronix/vt ... dp/2817658 (60VA) for 2.5A?

Probably yes.

But my main concern was having something ordered by the OP confiscated by customs and does he want to have that discussion with a customs official over the phone about the size of the toroid ? A switchmode power supply isn't so obvious, but a linear PSU with a heavy toroid is probably obvious to anybody that it's a PSU :-)

[rafyc]

Maybe if i only order the pbc it would be OK ?

[ricko]

Maybe if i only order the pbc it would be OK ?

I would email the company, and ask just for the built board without a toroid. Tell them why, too: see what their angle may be.

Rick

[MikeDB]

Maybe if i only order the pbc it would be OK ?

I would email the company, and ask just for the built board without a toroid. Tell them why, too: see what their angle may be.

Rick

Yes that will also save a fortune in carriage. And you can choose a slightly more powerful toroid possibly ?

[rafyc]

Maybe if i only order the pbc it would be OK ?

I would email the company, and ask just for the built board without a toroid. Tell them why, too: see what their angle may be.

Rick

Yes that will also save a fortune in carriage. And you can choose a slightly more powerful toroid possibly ?

1: Yep, but i'm new and working to improve my knowledge in electronic and wondering if i have to change other parts if i improve the transformer ?

2: Here it's given in the BOM 100VA transformer, 100VA = 8,3A x 12v but he says 2,5A on +12 and -12V at 1.5A. So i assume that there is 4,8A margin ?
I think i'm wrong.

How to calculate the size of the transformer according to the Amp combustion ? I think it's better to have oversized one and less head than push one to the limits.

3: Would the transfo must be outside the case due to the electromagnetic sensitivity ?

[MikeDB]

1: Yep, but i'm new and working to improve my knowledge in electronic and wondering if i have to change other parts if i improve the transformer ?

2: Here it's given in the BOM 100VA transformer, 100VA = 8,3A x 12v but he says 2,5A on +12 and -12V at 1.5A. So i assume that there is 4,8A margin ?
I think i'm wrong.

How to calculate the size of the transformer according to the Amp combustion ? I think it's better to have oversized one and less head than push one to the limits.

3: Would the transfo must be outside the case due to the electromagnetic sensitivity ?

2. It sounds like the toroid can deliver more power but not the regulators.

3. I actually always use switchmode PSUs because there is so much electromagnetic crap from toroids. Follow them with a good regulator and they are just as clean as linear PSUs.

[ricko]

Starting from the beginning.

* You want 3A on 12V and 1.5A on -12V

* The regulation requires power supplies over 75W have reflection-distortion correction (power factor correction). This is based on the input ratings of the device, not the actual power used.

* The toroid in the euro version of the product you are interested in has 8.34A output rating (Parallel) But a 100VA apparant power rating.

* Here is where I am unsure*. You want to provide 12.5V to the low dropout regulators. 75W / 12.5V = 6A. So you need to look for a toroid that is rated no more than 6A. (Assuming Customs or regulations are a problem you need to care about.)

* If you have a 6A max rated toroid with 83% efficiency = 5A output, that might provide your 3A for 12V, 1.5V for -12V with .5A left over (for 5V?) Which nominally meets your spec. Except experience suggests providing more juice than necessary, so the question is how much headroom is already built into your 3A figure? If it is generous, then maybe just going down to a 6A might be good enough. (Other people on this list are experts on this stuff: I hope they correct me on this, which is just back of envelope ballparking.)

But your best bet is to contact the vendor, tell them the issue, and see what they say.

Rick

* Is it /12V or /24V here? Or is it completely mistaken?

[Jarno]

I wonder how many of the commercially available equipment with toroids/linear supply have PFC. And how big a cosphi deviation actually would be from such a tiny thing. With all the fluorescent lighting being replaced with LED's, I think power companies are pretty happy already.
Obviously, it needs to be safe, that's without question.

[MikeDB]

I wonder how many of the commercially available equipment with toroids/linear supply have PFC. And how big a cosphi deviation actually would be from such a tiny thing. With all the fluorescent lighting being replaced with LED's, I think power companies are pretty happy already.
Obviously, it needs to be safe, that's without question.

Most power distribution companies, at least in Europe, would happily support an outright and retrospective ban on all linear supplies. It's not that any one item makes a huge deviation, but they all add up. The same with all these cheap Chinese switchmode phone chargers which have no PFC either. They're a few Watts each but there's millions of them on at any one time. Remember it's not the transformer that is the problem, it's the rectifiers charging the capacitors.

As for LEDs, the cheaper Chinese ones are even worse than flourescents. There are two types. One uses a capacitor phase shift dropper, whilst the other switches the supply on at one voltage then off again at a higher voltage so as not to overvoltage the LEDs. The effect on the mains of the first is bad, the latter horrendous.

The newer smart meters do send info on your phase distortion and so once they are legally allowed to do so, the power distribution companies will be able to send users letters telling them to fix the problem.

[rafyc]

Starting from the beginning.

* You want 3A on 12V and 1.5A on -12V

* The regulation requires power supplies over 75W have reflection-distortion correction (power factor correction). This is based on the input ratings of the device, not the actual power used.

* The toroid in the euro version of the product you are interested in has 8.34A output rating (Parallel) But a 100VA apparant power rating.

* Here is where I am unsure*. You want to provide 12.5V to the low dropout regulators. 75W / 12.5V = 6A. So you need to look for a toroid that is rated no more than 6A. (Assuming Customs or regulations are a problem you need to care about.)

* If you have a 6A max rated toroid with 83% efficiency = 5A output, that might provide your 3A for 12V, 1.5V for -12V with .5A left over (for 5V?) Which nominally meets your spec. Except experience suggests providing more juice than necessary, so the question is how much headroom is already built into your 3A figure? If it is generous, then maybe just going down to a 6A might be good enough. (Other people on this list are experts on this stuff: I hope they correct me on this, which is just back of envelope ballparking.)

But your best bet is to contact the vendor, tell them the issue, and see what they say.

Rick

* Is it /12V or /24V here? Or is it completely mistaken?

Honestly i'm totally lost. I did not tought power supply was so complex. (rectifier, parallel / series...)
Cant find a documentation especially for modular and toroid, lot of spare things and exemple but never with my specs.

I also niticed than peoples used 2 transformers. What is the adventage ?

I'm looking for a good quality low noise DIY linear regulated PSU for a 12U 115hp given for 2735 mA +12V | 1462 mA -12V on modular gird.

I dont know enough to choose components by myself. It's because i'm looking for an already made PCB and BOM.

[artparks]

Oh definitely illegal in EU. Customs would just look for the EN number which has to be printed on the device together with a CE mark, and if not there probably just bin it.

I've bought and built several of these PSUs and they got through customs fine, before (spit) Brexit. They've also not, yet, killed me!

[MikeDB]

Oh definitely illegal in EU. Customs would just look for the EN number which has to be printed on the device together with a CE mark, and if not there probably just bin it.

I've bought and built several of these PSUs and they got through customs fine, before (spit) Brexit. They've also not, yet, killed me!

Nobody said they'd kill you. But they are probably messing up your mains supply.

[artparks]

Nobody said they'd kill you. But they are probably messing up your mains supply.

I was being facetious about it killing me! Are these problems just inherent to all linear power supplies? Would the kinds of filters linked to here solve issues it would potentially cause to my mains?

[MikeDB]

Nobody said they'd kill you. But they are probably messing up your mains supply.

I was being facetious about it killing me! Are these problems just inherent to all linear power supplies? Would the kinds of filters linked to here solve issues it would potentially cause to my mains?

There is an argument, which I don't want to get into but you can google for the main protagonists, that all linear power supplies should be illegal in the EU as they are in many cases in for example Australia.

Passive filters reduce the issue a little but really it needs an active power factor correction circuit which costs peanuts but people don't design them in.

Not sure if your Brexit comment was fateous, but the EN standards are from the EU and were one of the things they were insisting the UK didn't relax once we'd left.