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I have a UMPC (ultra mobile PC) GPD Win 3 as Pictured below. My goal is to use this with a USB-c enabled monitor and get more than 2 hours out of it (I can only do this while using the battery's power). I want to provide power to the device while using the monitor at the same time. I believe a need a special docking device? I cannot find something that does this. I hope you'll excuse my use of images to explain the problem:

enter image description here Normally while "on the go" I can bring a Bluetooth keyboard and power the device. I could also use a generic USB-c to USB device to plug in multiple USB things.


enter image description here Using the dock I could use an HDMI conneciton and power the device at the same time. The problem here is that I'm using the wrong monitor.


enter image description here Connecting up the monitor and everything I want works except that the device is not powered. The power does not go through the monitor into the PC


There are devices (USB-c splitters) that look like this which only work for headphones and typically say that they are not for use with monitors: enter image description here


My question is what sort of device can I purchase to send power in to the PC while allowing a monitor connection to be made.

Graphically it would look like this: enter image description here

2 Answers 2

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use a USB-c enabled monitor and provide power to the device

This has been an almost unattainable goal for a long time. Chaining Thunderbolt docks had downstream USB C ports which were capable of DP alt mode, however most of these were big desktop docks with separate heavy AC/DC bricks supplying more than 100W. A notable exception was the JEYI Thunderdock mini which used a USB PD power input. However, it didn't work correctly with a <100W adapter and so JEYI changed it to contain a small 100W GaN power supply. This and the StarTech DKM31C3HVCPD were the only solutions I am aware of. Both were very expensive, though. Nowadays with USB4 there are more such adapters built around the Intel JHL8140 USB4 endpoint chipset. Examples are the Sparkle Travel Dock and the j5create JCD401.

Another solution is to combine two adapters:

  1. Convert the USB C signal to DisplayPort using an adapter which is capable of passing power. A very cheap such solution is https://www.amazon.com/dp/B0915ZR21Y this noname adapter is widely available. It has a USB C port on the side which is capable USB data only and USB 2.0 speeds at that but that's still useful for a keyboard and a mouse. This adapter is part of a family characterized by the PD input on the back, data only port on the side and something useful at the end: DP, mini DP, HDMI, Ethernet, VGA. I have been using it for some time and it does the job. No wonder, it's not a particularly complex device: it doesn't renegotiate PD and doesn't contain any data converters.
  2. reconstruct a DP signal with a bidirectional cable or appropriate "reverse" cable. Dan S. Charlton's blog contains many useful lists, in this case Bi-directional DisplayPort->USB-C, HDMI->USB-C, and HDMI->DP cables. One example would be the Amazon Basics Bi-Directional USB-C to DisplayPort Cable note this link goes to Amazon UK, Amazon US doesn't have it at this time. There are some which also injects power like the fairikabe DisplayPort to USB C same availability caveat. Dan's list has many, many more. This is typical: availability of these very special cables is spotty.

The disadvantage of doing this is you need a PD source with two ports.

However, these days there are adapters/cables which can take a USB C signal from the phone/laptop containing a DisplayPort signal, another from a PD source and has a third USB C port which contains the same DP signal and power from said source. Often only part of it: the adapter will send some to the host as well. Compared to the solution above, these solutions only use one power port from a PD source. Once again his blog contains a list of USB-C -> DP alt mode + power delivery “splitter” (or merger depending on your perspective) devices, this list is much, much shorter, at the time of this writing only contains four devices.

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Use a USB-C hub like this: https://www.amazon.com/dp/B0B49QYYCX that is specified for USB-PD pass through. You will plug this dock directly into your PC and then plug display, keyboard, and power into the dock. The USB splitter you showed is not in spec for USB and will work with very few devices.

enter image description here

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  • These things do not allow connecting a USB C monitor. Such hubs with DP alt mode capable downstream USB C are extremely rare.
    – chx
    Commented Jan 7 at 8:58

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