Am I getting 18A from this PSU? - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 02:58:54 pm
content: Ok, so this is the original thread regarding a PSU drawing X amount of current on each rail:https://www.eevblog.com/forum/beginners/1-0-mm-diameter-copper-%28awg-18-%29/Here's the deal, the speck on this PSU states: 4x 12V rails, max 18A (I guess arbitrarily any rail), but not all of them at the same time.I've since opened the PSU and have taken pictures of the inside. On the board, I only see "2 rails" or 2 connections.Is it possible that there are only indeed 2 rails? Or am I mistaken? Can it still have 4 rails? And, how do I tell which wires are from which rail?What I need is 5 circuits drawing 1.6A @ 39V (or 62.4W). This is 5.2A @ 12V, assuming 90% efficiency, 5.8A. I also have 1 circuit which needs 0.9A @ 36V (or 32.4W). This is 3A @ 12V using same efficiency factor.So I need a total of 32 Amps @ 12V. Obviously 1 rail cannot do that. So I want to split it between 4 rails, 8A each, or say, 12A 1 rail, 12A second rail, and 9A third rail, leaving one open.But, this has failed miserably. I've had 2 circuits connected to the 6+2 molex connector (I believe the graphics card wire) which flashed the LEDs for a split second and shut off (I guess overcurrent protection kicking in). This was only drawing 2x 1.6A 39V, or 125W (140W with 90% efficiency), or 11.7A @ 12V.I then connected 1 1.6A 39V circuit + 1 0.9A 36V circuit, which although they turned on, they were pulsing like crazy (like a strobe). The 0.9A circuit was drawing a somewhat "stable" 0.85A - 1A but the 1.6A circuit was only pulling in the 1.3A range. When I dropped the current draw on the 1.6 to 1A, there was stability. But why??? Is this really overdrawing that rail.I thought that graphics card rail was supposed to pull a whole bunch!!! It's also the only wire assembly in the whole psu which uses 18AWG (1mm) diameter wire. The rest uses 20AWG (or .8mm wire).How can I solve my problem?

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 02:59:17 pm
content: Here is a picture of the overall PSU:

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 03:00:35 pm
content: What if I connect ALL 12V+ together and ALL ground wires together, would this perhaps give me the necessary effect I want? Drawing 32A @ 12V? Or will this kick in overcurrent protection?What if I connect ALL 12V+ wires from 1 Rail together, and all 12V+ wires from 2nd Rail together, might this work?Thank you all!!!!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 16, 2014, 04:01:09 pm
content: That's 18A max per set of connections, 550W (46A) total through all in parallel.You wouldn't want to do 46A through a single wire, or even a single set, since they only use cheapass 18AWG wire or whatever.But really, I'd be impressed if you got more than 300W combined (maybe 100W at 5V, 200W at 12V), either before shutdown or magic smoke (which may occur in minutes to months, but will happen sooner or later).Tim

author: madires
author_rank: Super Contributor
timestamp: February 16, 2014, 04:03:41 pm
content: I think the four 12V rails are just virtual, i.e. to spread the load current across the wires. And based on the pictures I doubt that the PSU is able to provide 650W. Even 32A * 12V = 384W might be too much for that PSU.

author: mariush
author_rank: Super Contributor
timestamp: February 16, 2014, 04:04:13 pm
content: Ah, a Deer or Solytech made power supply..You can see on the pcb by the yellow wires saying 12V1 and 12V2 - do you see anywhere 12v3 and 12v4?So in theory, the power supply from the start only has2 rails. In practice, I'm not sure they're even separate because the protection chip (that small 8pin chip on the left of the yellow wires) doesn't have 2 separate overcurrent protections so it wouldn't know if you're loading a rail more than the limit. I also doubt there's 2 12v rectifiers on that secondary heatsink.The primary capacitor is 120uF 450v, which is very small. 500w power supplies usually need at least 220uF. Main transformer is also a bit on the small side but it depends on power supply design.For comparison here are two Sirtec ( High Power) power supplies that were tested and proved to work at 400w and 500w:400w :http://www.mygarage.ro/teste-si-review-uri/119199-review-sirtec-high-power-element-plus-hpc-400-g12s.html500w:http://www.mygarage.ro/teste-si-review-uri/118490-review-sirtec-high-power-element-bronze-500w-hpc-500-g12s-br-ep-500-br.htmlScroll down on those pages and see the pictures with the power supply. In fact I'm going to attach the pictures 2 below:Notice the similarities between these designs and yours, it almost looks like the designers of your psu flipped a large part of the sirtec design vertically... they either copied this design or that design is an older designed licensed (or cloned/copied) from Sirtec.The Sirtec 400w model uses a 150uF main capacitor and a slightly smaller transformer, the 500w model uses a 220uF main capacitor and a bit larger transformer. Yours uses 120uF and a small transformer.To know more precisely how much current it can output, you'd have to look at what it says on the chips on that second heatsink, the one closer to the cables. I realize it may be very hard to read what says on those components due to those large inductors, so if you can't don't bother.My estimations based on what I see in the pictures is this power supply should be labeled (at best) as a 400w-420w power supply, with 300w on 12v. Realistically, for continuous use, I wouldn't recommend you to load it with more than 250 watts on 12v.

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 05:36:59 pm
content: ##$%$#LKTJQGFA DSJKVK DLS!!!!!!So much for a German brand!!!! Made in wherever the hell!!!

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 05:45:47 pm
content: I've seen some other posts / videos where people are placing dummy loads across the 12V in order to get the PSU to work "properly".I will attempt to place a 22Ohm load on the 12V and report back whether any more stability was achieved using this method.@Mariush I will try to get a picture / details on the components connected to the heatsink.

author: mrflibble
author_rank: Super Contributor
timestamp: February 16, 2014, 05:47:05 pm
content: Well it does say "hergestellt fuer: ...", which just means "made by whoever in whereever (China), to be resold by Netzteil Wuerstchen GmbH".

author: madires
author_rank: Super Contributor
timestamp: February 16, 2014, 06:22:11 pm
content: That company seems to be reselling Chinese stuff. If you bought that PSU in the EU you may return it because it doesn't deliver what the vendor promises. A quick search tells me that the non-Coba PSUs are mostly junk. BTW, the CP-650W is about 31 Euros.

author: mariush
author_rank: Super Contributor
timestamp: February 16, 2014, 06:33:55 pm
content: Well, pretty much the only benefit of being a German seller is that it has decent input filtering (chokes, x capacitors, y capacitors etc). But you guys in Germany are more anal about noise and good fans as far as I'm aware.trs80 so like I said, I would be comfortable saying it can do 250w on 12v for long periods of time. You can probably also safely pull about 10 amps on 5v (50w) and maybe 10a on 3.3 (30w).As for your comment about resistor on 12v, that's related to how some power supply designs stabilize the output voltages ... if there's nothing on 12v, the 5v output may not be 5v but 4.6v or 5.3v. For those designs, there has to be something using power on 12v for the power supply in order to get proper 5v and 3.3v. For your application (powering leds), you wouldn't care much about it because your led drivers won't care about the exact voltage

author: madires
author_rank: Super Contributor
timestamp: February 16, 2014, 06:58:06 pm
content: Quote from: mariush on February 16, 2014, 06:33:55 pmI think your observation is correctOther important things are reliability, power output and price.

author: Bored@Work
author_rank: Super Contributor
timestamp: February 16, 2014, 06:58:46 pm
content: It says gaming power supply ...

author: madires
author_rank: Super Contributor
timestamp: February 16, 2014, 07:00:35 pm
content: Quote from: Bored@Work on February 16, 2014, 06:58:46 pmRoll a dice to determine the power output

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 07:02:20 pm
content: Obviously I was not expecting it to be Made In Germany, otherwise it would probably cost around 100-200 Euros.But I was not ready for them to not "tell the truth".As for taking it back, its been taken apart, the connectors cut, can't exactly say that the Warranty is still Valid!!!

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 07:47:43 pm
content: OK, so more testing. I've tried with the 20 Ohm over 12V, no difference as Marush stated.And I've started connecting some load to Rail 1 and some to Rail 2. I think I've found my problem (or the cause of the instability).What happens, when more than one load is placed, voltage starts to drop!!! When I had 2 loads on the first rail (1.6A/39V) or 5.8A @ 12, and another 2x 12V@1A, for another 2A @ 12V, for a total of 7.8A @ 12V, I noticed that my input voltage (coming from the PSU) had dropped to around 11.7V. Ok, no big deal, my drivers can handle it.However, when I placed another load on the second rail, this time 36V @ 1A (or 3A @ 12V), for a total of 7.8A on "Rail 1" and 3A on "Rail 2", the voltage dropped to a staggering 9.6V or thereabouts. And the shit started going downhill. The LED drivers started to pulse (they are rated 10-32V IN), and the whole system started to loose stability. (Excellent strobe though)!!!So, it seems, for the moment, my problem is not necessarily one of Over Current, but of Under Voltage!!!I'm completely lost now. I don't know whether it is something that I did or something that I've omitted, but I'm having no luck with this PSU!!!If anyone has any idea why the voltage drop, whether it is some kind of "Protection" kicking in to save the PSU, I have no idea. I mean, it can't even handle 11AOr, inversely, 130W

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 16, 2014, 07:52:07 pm
content: Did you ever load 5V as well?Normally 5 and 12V are regulated jointly. If the loads differ by more than, say, 20%, expect awful results.Tim

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 08:14:34 pm
content: @Tim,so you're saying that if I don't place a dummy load on the 5V, I will get this fluctuation on the 12V line?I will try this as well and report on it tomorrow, for now I'm taking a step back from this project.

author: megajocke
author_rank: Regular Contributor
timestamp: February 16, 2014, 08:29:09 pm
content: That is very likely.You could try something like a 10% load on 5 V (2-3 A or so). Just a little might be enough, preventing peak-rectification of spikes and such, even though the output voltage balance will be best when the load is balanced.Not as common I guess, but I have come across PC power supplies that needed a little load on 3.3 V too or otherwise they would go overvoltage and shut down when the other rails were loaded.

author: made2hack
author_rank: Frequent Contributor
timestamp: February 18, 2014, 12:32:52 pm
content: So, results are in.Placed 10 Ohm 10W resistor over the 5V. This stabilized the PSU some. Still some voltage drop, to around 10.8V when all units plugged in. It started to destabilize somewhere around the 360W draw.Had to reduce amps going in to one of the circuits.This PSU just won't cut it. Dedicated 400W LED supply going in tomorrow.@All thank you for all your help.

author: mrflibble
author_rank: Super Contributor
timestamp: February 18, 2014, 12:57:43 pm
content: Quote from: trs80 on February 18, 2014, 12:32:52 pmGiven that you mainly load the 12V, not bad for a "650W gaming power supply".

author: made2hack
author_rank: Frequent Contributor
timestamp: February 18, 2014, 02:00:19 pm
content: Game PSU manufacturers should just take into considerations our needs and give us 10000W PSU's with proper rails!!! For 29.95$$

author: lapm
author_rank: Frequent Contributor
timestamp: February 18, 2014, 02:49:43 pm
content: I am honestly surprised you got even that good results out of it considering the loading.

author: mrflibble
author_rank: Super Contributor
timestamp: February 18, 2014, 02:55:54 pm
content: Quote from: lapm on February 18, 2014, 02:49:43 pmAs am I.I usually derate this type of el cheapo random OEM supply to about 50%, so not bad at all.Oh, just for the fun of it ... could you measure the supply ripple before it starts to go unstable? That might be interesting. Not too much of an issue for led lighting, but might be relevant for someone who would actually use it in their gaming rig (yeah right).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 18, 2014, 03:32:27 pm
content: A half an amp, well it's a start. If you have 1 ohm 50W laying around, you might even get half way to rated load.

author: Fabiusp98
author_rank: Contributor
timestamp: February 19, 2014, 09:34:16 am
content: It's not very on topic but can I suggest to solder an atx connector(https://www.sparkfun.com/products/9497) to a board an try the resistors and the other things on that board?So if you destroy your power supply you don't have to restart from the beginning.

author: made2hack
author_rank: Frequent Contributor
timestamp: February 19, 2014, 11:50:26 am
content: TO measure ripple, do I need an oscilloscope or spec analyzer? All I have is a multimeter!!!

author: andtfoot
author_rank: Unknown
timestamp: February 19, 2014, 11:53:33 am
content: Quote from: trs80 on February 19, 2014, 11:50:26 amFor lower frequency stuff maybe you could use the AC Voltage mode on the multimeter.