[M17x R2] - Dual PSU (2 x 240W)

[Guest]

A warning to those who consider combining two PSUs without the use of a diode.

Our PSUs are Switched-mode Power Supply Units (SMPS) and unless you have two of them with the exact same voltage output, then you gonna end up messing with the duty cycle of the PSU with the lower voltage output and eventually burn it.

Please proceed with caution and at your own risk.

More info about SMPS here:

https://en.wikipedia.org/wiki/Switched-mode_power_supply

[Guest]

Sorry Mr. Fox. I just tried to draw the circuit and it won't work with the bridge rectifier, my mistake. You can only use half of the bridge in this configuration so you would need two bridge rectifiers to go parallel. Just check the rectifier you have to make sure it can take the current, each diode has to handle about 22A of continuous current at max load.

@imsolidstate - I am not an electrical engineer so you are talking Greek to me. StamatisX might understand, being from Athens. So, I may easily misunderstand or be left like a deer in the headlights if you are too brief. Sorry for being a noob when it comes to your specialty.

I have a 4-post 25A bridge rectifier that looks like the one in the opening post photos. I have a 40A version on order. I have one AC adapter connected to a terminal labeled AC. I have the other AC adapter connected to a second terminal labeled AC. I have the power out to the laptop connected to the terminal labeled "+" (positive) and I am not using the terminal labeled "-" (negative) and everything seems to be working fine. I will be doing more testing after work.

Question: If I add another bridge rectifier for a total of two as you suggest, how should I connect the wiring? Should they be made differently than the 4-lug rectifier I am using? (I believe a bridge rectifier is the same thing as a diode bridge, just a different nomenclature - if not, please correct me, as I cannot find any diode bridges for sale.)

Or, am I misunderstanding and the 4-lug is actually a two-in-one dual-rectifier (diode) bridge which negates the need for a second one? Meaning I am already good to go as long as it will handle the load?

[StamatisX]

Thanks for the warning, bro. Did you have this happen with the diode bridge, or only warning those that want to skip using a rectifier/diode bridge?

It didn't happen to me due to the use of diodes that prevent the current from going to the wrong direction. The warning goes only to those who combine two PSUs without two diodes (that's all you need).

[vulcan78]

I figured it out. It has to be wired in parallel, not series. Wiring it in parallel maintains the same voltage as one AC adapter while (hopefully) delivering higher power output. I need to test the power output to see what it's actually doing, but the dual 330W mod functions with no errors in detection, charging, etc. Basically followed the wiring diagram of what StamatisX did with the dual 240W units, except that I did not purchase meters and I have the AC adapter signal wire from both adapters connected. My heat sink is mounted to the exterior of the box with a metal cover plate sandwiched between the rectifier and heat sink. After I confirm the power output, I'll post a thread with photos in the M18x sub-forum. A teaser photo is provided below. It looks promising, as I am able to run 3DMark11 with the CPU and GPU heavily overclocked without manipulating CPU clock speeds using TactX profiles with ThrottleStop. I ran all the way through the benchmark at 4.6GHz on CPU and GPU core OC above 1.1GHz across all 3DMark11 tests without a shutdown. That wasn't possible before.

@DigitalFubar - if you need any assistance let me know.

You never cease to amaze Mr. Fox! Now that I am not as mobile I might look into this, especially if 780M SLI is in my future. Keep up the good work.

[Guest]

Sorry Mr. Fox. I just tried to draw the circuit and it won't work with the bridge rectifier, my mistake. You can only use half of the bridge in this configuration so you would need two bridge rectifiers to go parallel. Just check the rectifier you have to make sure it can take the current, each diode has to handle about 22A of continuous current at max load.

@imsolidstate - I am not an electrical engineer so you are talking Greek to me. StamatisX might understand, being from Athens. So, I may easily misunderstand or be left like a deer in the headlights if you are too brief. Sorry for being a noob when it comes to your specialty.

I have a 4-post 25A bridge rectifier that looks like the one in the opening post photos. I have a 40A version on order. I have one AC adapter connected to a terminal labeled AC. I have the other AC adapter connected to a second terminal labeled AC. I have the power out to the laptop connected to the terminal labeled "+" (positive) and I am not using the terminal labeled "-" (negative) and everything seems to be working fine. I will be doing more testing after work.

Question: If I add another bridge rectifier for a total of two as you suggest, how should I connect the wiring? Should they be made differently than the 4-lug rectifier I am using? (I believe a bridge rectifier is the same thing as a diode bridge, just a different nomenclature - if not, please correct me, as I cannot find any diode bridges for sale.)

Or, am I misunderstanding and the 4-lug is actually a two-in-one dual-rectifier (diode) bridge which negates the need for a second one? Meaning I am already good to go as long as it will handle the load?

It didn't happen to me due to the use of diodes that prevent the current from going to the wrong direction. The warning goes only to those who combine two PSUs without two diodes (that's all you need).

@StamatisX and @imsolidstate... thanks to both of you for the assistance. To clarify my prior post...

What I have (25A from RadioShack) looks like this... (basically the same as what StamatisX is using, except 25A versus 20A)

What I have ordered to replace the above component (it was not available locally) is... http://www.mouser.com/Search/ProductDetail.aspx?R=GBPC4002virtualkey53310000virtualkey821-GBPC4002

I don't know the proper scheme for including two of these in the wiring layout and only saw one in the example provided by StamatisX. Where I might be confused by the recommendation is knowing if this part is the equivalent of using two bridge rectifiers, or you are recommending a different arrangement than what I am already using.

[imsolidstate]

Mr. Fox, your 40A regulator should be perfect. The 25A may not stand up for the long haul as it is probably rated for 25A of rectified AC current which is a much different thing than 25A of DC. You don't need to parallel anything with the 40A, that is the way to go.

Forget about what I said about paralleling diodes, I said that because you are only using two of the four diodes in the bridge, but they are connected together so you can't do what I mentioned. That 40A rectifier should be fine as long as you don't overheat it. It could potentially be operating at 15 watts.

[Khenglish]

Mr. Fox, your 40A regulator should be perfect. The 25A may not stand up for the long haul as it is probably rated for 25A of rectified AC current which is a much different thing than 25A of DC. You don't need to parallel anything with the 40A, that is the way to go.

Forget about what I said about paralleling diodes, I said that because you are only using two of the four diodes in the bridge, but they are connected together so you can't do what I mentioned. That 40A rectifier should be fine as long as you don't overheat it. It could potentially be operating at 15 watts.

Isn't it more than that? The item descriptions says forward voltage drop is 1.1V, not the regular .7V. So say 1.1V * 25A = 27.5W

[Guest]

Mr. Fox, your 40A regulator should be perfect. The 25A may not stand up for the long haul as it is probably rated for 25A of rectified AC current which is a much different thing than 25A of DC. You don't need to parallel anything with the 40A, that is the way to go.

Forget about what I said about paralleling diodes, I said that because you are only using two of the four diodes in the bridge, but they are connected together so you can't do what I mentioned. That 40A rectifier should be fine as long as you don't overheat it. It could potentially be operating at 15 watts.

Thanks for the most helpful reply, my friend. I tried to give you rep, but it won't let me do it right now. Will have to add some later.

If the heat sink and paste are doing an effective job and they are reflective of what the rectifier is doing in the way of heat, it's not overheating right now. I haven't pushed it for an extended period of time with sustained and repetitive extreme CPU and GPU overclocking. That huge CPU heat sink may be more than enough, and that's why I am using it instead of a smaller one. I will do some short burst benchmark testing of power output until the 40A arrives, then I will crack the box open to install that 40A rectifier once I receive it. I will also do a few more tweaks to the box to help keep the wiring secure. (I have ordered strain-relief grommets and have some cable clamps that I will use to fasten the cables internally so that nothing gets pulled loose.)

It doesn't really need to deliver 2x the power output as long as it delivers more than adequate power, and based on my brief preliminary testing it appears to be "mission accomplished" since it does not shut down any more when the CPU and GPUs are maxed out.

Isn't it more than that? The item descriptions says forward voltage drop is 1.1V, not the regular .7V. So say 1.1V * 25A = 27.5W

Unless I missed one, I did not find a comparable unit with the .5v or .7v forward voltage drop I was searching for. Almost all of them are 1.1v or greater.

[imsolidstate]

Good catch @Khenglish. I was figuring ~22A since that was the max I pulled from my 330W supply before shutdown when I load tested it. So 22A * 1.1V = ~24W.

[MENTION=119]Mr. Fox[/MENTION] sounds like you've got it sorted. Good work.

[johnksss]

So I have mine up and running as well. So far the 680M SLI with a mild over clock will run around 510W.... thus far.

780M running a tad bit higher.

[Brian]

So I have mine up and running as well. So far the 680M SLI with a mild over clock will run around 510W.... thus far.

780M running a tad bit higher.

20k gpu?

Sent from my GT-I9100

[johnksss]

Nope. not yet.

[Guest]

Well, I finally broke 18K on GPU with the dual AC adapter mod. Here's a couple of things to look at. Still waiting for the 40A bridge, so this is with the 25A. I had to change my ThrottleStop profile because I had the power limits set to 500W for both power limits and that was shutting down, but lowering it to 350W per power limit stopped that for now. It's still doing great. Was able to run 4.7GHz on across all tests without shutdown, but that was with a bit of a throttle due to the lower power limits in ThrottleStop. I think it's going to be perfect with the 40A bridge.

Running a ThrottleStop 32M test on the 3920XM at 4.7GHz, CPU alone is pulling 250W.

NVIDIA GeForce GTX 680M video card benchmark result - Intel Core i7-3920XM Processor Extreme Edition,Alienware M18xR2

You can see when each test begins and ends by watching the watts draw on the meter rise and fall.

[sangemaru]

Mr. Fox, the level of performance you've managed to pull from a non-desktop machine is downright scary.