Hello!
I am currently working on building my own custom KVM and thought this might be the place to get some really good advice on it. I started this project due to the lack of good USB Hub switches with the specs I wanted and I was hoping to learn how to design PCBs and electronics. Now while I would have loved to buy a Level1Techs KVM, I am not quite ready to spend that money and I really want to build a custom one and open-source it.
I have started designing the KVM in kicad and have sourced almost all of the components needed for the USB hub switch but am struggling to find a good choice of power supply as I need ~200W of power. For more context, I am designing this KVM to be modular such that it will have two seperate components, the USB Hub switch/power conversion, and the displayport switch. These two boards will lay ontop of each other inside a case with one connector between them giving power and a āswitchā signal. This makes it much easier to design and splits up the testing and board complexity.
Now, 200W is a lot of power for a KVM but I wanted to do something I havenāt really seen before, I wanted to allow a 100W PD upstream (20V@5A). I have a framework 13 laptop and it can drain itās battery while charging at 60W so I thought it might be nice such that when I use it I can charge the device while doing demanding tasks. Additionally, the 5 downstream ports (3 USB-C 3.2 gen2, 2 USB-A 2.0) will collectively draw ~45W. That means around a total of 145W of power not including ICās for the USB hub or the display port switch.
I found some good MEAN WELL power supplies but they either have a R7B connector or a 6 pin Molex Mini Fit Jr. connector. I kind of donāt want to use the R7B connector as the right angle PCB header is harder to find and is less wear resistant(I believe) than the Molex option. Also current handling capability is a bit finicky on the R7B connector, especially if I want to use a 20V PSU so I donāt have to step down the voltage for my main upstream power rail.
Anyways, I was wondering if anyone has some good advice/suggestions on a power supply that can do ~200W? Also any suggestions on voltage input and connector types would be greatly appreciated!
Thank you!
are you asking about a PD PSU or a ābulkā PSU that you plan to adapt to a PD chipset?
Wow, crazy project. Best of luck 
at the office we just have up to 135w. If we had a 200w Iād offer to sell you one
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You could power the upstream and downstream device with separate power supplies, the more āstandardā the parts are the better for open source hardware projects. Turn your back for one minute and theyāll stop making that specialty part.
Iām looking for an external laptop like PSU that delivers something like a 24V-48V DC voltage. That way it makes it easier to fuse, hot-swap control and buck down to the PD(20V),regular USB (5V) and IC (3.3V) voltages.
If you have a different recommendation I am open to suggestions. I just thought that this would reduce the size on your desk and make the electronics easier.
Well Iām thinking that it wouldnāt be too difficult to swap out the PSU header on the PCB when that PSU gets discontinued, especially since I am planning on maintaining it. Especially since I do really want this project to be used by other friends and family, and any other people who want to learn a bit about electronics or just want to have the ability to swap out your KVM components as USB and Displayport/HDMI gets better.
I am also kind of waiting for USB-C PD 3.1 devices to become more widely available so that I can replace the connector with a 240W USB-C port for input power. I have only found one commercial device that supports 240W delivery on one port and itās about $500 CAD which is way too much for just your KVM.
There are a ton of ways to implement the PSU. What Iām use to for PD designs is that the PD chipset is integrated into a single power supply so that the existing secondary can provide the negotiated voltage; that way you donāt have to have a redundant secondary in the design.
Perhaps in your case this could complicate things since your going to be using this power for things besides an end deviceās USB PD.
Itād probably come down to your switching chipsetās power usage, if low enough you could just put in a medium voltage ldo and not have to worry about the input voltage wide range due to all the possible PD voltages being negotiated.
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Yeah, since I need two different 5V rails both which handle around 6A (up to 8A for safety) I donāt think a medium LDO is preferable for that and the 3.3V rail. I donāt know exactly the power draw yet of the 3.3V rail but I donāt think it is obscene, definitely less than 3.3W.
If a ready-made product is your budget-target, you are in for an ambitious project.
If you are okay with integrating the unit into the KVM, you get a lot more options.
AC is scary (as it should be), put a properly rated fuse in line and get a closed AC-DC-module from one of the usual supplies (MeanWell, FSP, TDK-Lambda, Delta, Traco, etc.) with screw-terminals or board-to-board connectors.
Have at it:
https://www.digikey.com/en/products/category/power-supplies-external-internal-off-board/8
Or a wide range DC-DC module, could reduce integration complexities a ton.
Haha, yes. I would like to design a ready-made product so that itās easy for anyone else to use it, not just people with a decent knowledge of electronics and PCB design.
I just looked into integrating the PSU into the unit, but I donāt think it is quite viable due to EMI and thermal management. I think that it may be a viable solution for later revisions as it makes it a whole lot cheaper, but a larger risk for signal integrity, testing and such.
For the DC-DC module you suggested, wouldnāt it be a better idea at such a point to keep a higher voltage main rail to reduce current, and then just place a bunch of buck converters close to the powered components to reduce heating and large copper pours carrying higher current? Also, for my PD design I have currently designed it with two possible voltage outputs for charging the upstream, 20V and 5V, obviously this doesnāt really stick with the traditional PD output of varying the voltage (5V, 9V, 12V, 15V, 20V), but my PD controller does correctly negotiate the voltages. Should this be changed? (I will comfirm the correct functionality of the IC later, I am pretty sure it can correctly show 5V and 20V capabilities)