wkrinsky
2 Bronze

XPS 15 9500 and U4320Q monitor - USB C Power Delivery

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Hi,

I think I might know the answer to this question, but I would like to confirm. 

I'm set to purchase the U4320Q monitor that includes USB C input; however, part of my intention is to use a single USB C cable to deliver video and receive power to the laptop. I read in the tech specs that the monitor only delivers 90 watts of power and ofcourse the full power of the XPS requires 130 watts. 

Will the laptop be able to run with full performance in this configuration (and maintain enough power to make it through a day of work?)

Is an alternative available outside of using the power adapter that came with the laptop?

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jphughan
7 Gold

Re: XPS 15 9500 and U4320Q monitor - USB C Power Delivery

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@wkrinsky  XPS 15 9500 systems that do NOT have an NVIDIA GPU are only designed for 90W, so if you have an Intel-only configuration, you would be fine.  But otherwise, if your system is designed for 130W, then no you're not going to be able to run it at full performance from a 90W source -- otherwise Dell wouldn't have needed to design the system for 130W.  The symptoms you're most likely to encounter are slower battery charging and throttled CPU and GPU.  The system would be unlikely to drain its battery while connected to that source, because most systems will throttle performance in that situation in order to operate "sustainably" rather than operate in a way that would cause them to potentially die even while connected to power.  That said, there are some other systems -- like the XPS 17 9700 and certain gaming systems -- that use "Dell Hybrid Power", where the system actually IS designed to potentially drain the battery even while on AC power during heavy load periods.  I think that's a lame design and that Dell should have simply shipped the system with the power source it requires rather than using an undersized power source and using the battery to pick up the slack when needed.  That imposes needless wear on the battery, and if you have a long-running intensive task, then your system will eventually throttle if you drain your battery low enough, AND you might end up with practically no remaining battery life whenever you do finally disconnect from the power source.

Anyway, in terms of a solution, the only options are either Dell's 130W power source or one of Dell's docks that are rated for providing 130W over USB-C/TB3.  Since you're dealing with an XPS 15 9500 and also a 4K 60 Hz display, the only dock that would provide 130W and allow 4K 60 Hz output from that system is the Dell WD19TB.  The regular WD19 can also provide 130W if you order the version that comes with a 180W power source (rather than the 130W version that only passes through 90W), but it can only support a single 4K 60 Hz display when connected to a system that supports DisplayPort 1.4/HBR3 over USB-C, and the XPS 15 9500 only supports DP 1.2/HBR2.  (The specs page that as of this writing claims DP 1.4 support is available from the non-Thunderbolt port on the right of the system is incorrect.)  By comparison, since the WD19TB uses Thunderbolt 3 rather than USB-C, it would allow you to run dual 4K 60 Hz displays if you wanted.  But as of this writing, Dell doesn't have any USB-C displays that provide up to 130W.  And since 130W is above the 100W max of the official USB Power Delivery spec, you're not likely to find 130W support on any non-Dell products at all.  Dell did something proprietary on some of their systems, docks, and power adapters to support 130W over USB-C/TB3.

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jphughan
7 Gold

Re: XPS 15 9500 and U4320Q monitor - USB C Power Delivery

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@wkrinsky  XPS 15 9500 systems that do NOT have an NVIDIA GPU are only designed for 90W, so if you have an Intel-only configuration, you would be fine.  But otherwise, if your system is designed for 130W, then no you're not going to be able to run it at full performance from a 90W source -- otherwise Dell wouldn't have needed to design the system for 130W.  The symptoms you're most likely to encounter are slower battery charging and throttled CPU and GPU.  The system would be unlikely to drain its battery while connected to that source, because most systems will throttle performance in that situation in order to operate "sustainably" rather than operate in a way that would cause them to potentially die even while connected to power.  That said, there are some other systems -- like the XPS 17 9700 and certain gaming systems -- that use "Dell Hybrid Power", where the system actually IS designed to potentially drain the battery even while on AC power during heavy load periods.  I think that's a lame design and that Dell should have simply shipped the system with the power source it requires rather than using an undersized power source and using the battery to pick up the slack when needed.  That imposes needless wear on the battery, and if you have a long-running intensive task, then your system will eventually throttle if you drain your battery low enough, AND you might end up with practically no remaining battery life whenever you do finally disconnect from the power source.

Anyway, in terms of a solution, the only options are either Dell's 130W power source or one of Dell's docks that are rated for providing 130W over USB-C/TB3.  Since you're dealing with an XPS 15 9500 and also a 4K 60 Hz display, the only dock that would provide 130W and allow 4K 60 Hz output from that system is the Dell WD19TB.  The regular WD19 can also provide 130W if you order the version that comes with a 180W power source (rather than the 130W version that only passes through 90W), but it can only support a single 4K 60 Hz display when connected to a system that supports DisplayPort 1.4/HBR3 over USB-C, and the XPS 15 9500 only supports DP 1.2/HBR2.  (The specs page that as of this writing claims DP 1.4 support is available from the non-Thunderbolt port on the right of the system is incorrect.)  By comparison, since the WD19TB uses Thunderbolt 3 rather than USB-C, it would allow you to run dual 4K 60 Hz displays if you wanted.  But as of this writing, Dell doesn't have any USB-C displays that provide up to 130W.  And since 130W is above the 100W max of the official USB Power Delivery spec, you're not likely to find 130W support on any non-Dell products at all.  Dell did something proprietary on some of their systems, docks, and power adapters to support 130W over USB-C/TB3.

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fatslice
1 Copper

Re: XPS 15 9500 and U4320Q monitor - USB C Power Delivery

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I just got an XPS 15 9500 (i7-10875H, GTX 1650 Ti) and a U2421E monitor and was similarly concerned about the charging functionality. My laptop came with a 130W power adapter and the monitor is rated for 90W power output via usb-c, but so far so good. I tested the charging rate of the monitor vs the laptop power adapter and they were the same in a certain context. My battery happened to be at 43%, I had minimal apps open, and I plugged in the power adapter and hovered over the battery icon; it read "1hr 16min to full charge". I unplugged the power adapter and connected the laptop to the monitor (usb-c) and after a minute it also said " 1hr 16min to full charge", despite a consistent yellow warning symbol on the battery icon that said "slow charger". So perhaps under light use the monitor will be sufficient to charge the laptop at the same rate as the power adapter can.

When connected via usb-c to the monitor, if you click on the battery icon it will show you a "power mode" slider, with one end being best performance, and the other being best battery life. I had it on "best performance" and didn't notice a difference under light use. that may all change with heavy use (photo/video editing, rendering, gaming, etc.) btw the video, ethernet and any usb peripheral worked great over usb-c. i tried daisy chaining the u2421e to a P2417H monitor but it didn't work, not sure if the p24 supports daisy chaining though.

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jphughan
7 Gold

Re: XPS 15 9500 and U4320Q monitor - USB C Power Delivery

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@fatslice  90W may be fine for workloads that don't involve the NVIDIA GPU, in fact the XPS 15 9500 configurations that don't include an NVIDIA GPU come with 90W power supplies.  But if you start using that GPU, especially if you're also trying to charge the battery at the same time, you might run into the limitations of that 30% power shortfall.  In terms of daisy chaining, I would expect the P2417H to work just fine at the end of a daisy chain since the display at the end of the daisy chain doesn't have to support daisy chaining at all.  It only needs to support DisplayPort 1.1a, and even DisplayPort 1.2 was well established long before 2017, which is the "model year" of the P2417H.  Did you enable MST on the U2421E?  And are you using a regular DisplayPort cable to connect the two displays rather than something like DisplayPort to HDMI?

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