Dell XPS 14 coil whine was much worse with USB-C monitor power - changing the power source helped

Posting my observations in case someone else is troubleshooting something similar.

My laptop is a Dell XPS 14 DA14260 with Intel Arc integrated graphics. I noticed an annoying high-pitched sound coming from inside the laptop when rotating a 3D model in Autodesk Fusion or when GPU usage go high. My external monitor is an MSI MPG 491C OLED, connected through USB-C, which also supplied power.

Initially, I thought it was simply GPU load. Here’s what I tested:

• Fusion capped at 60 FPS: the pitch changed, but the noise remained.
• 30 FPS: less annoying, but still audible.
• Different laptop power profiles: no substantial improvement.
• Monitor disconnected, running on battery: almost silent; I could only hear a faint sound with my ear very close.
• Monitor connected, Windows set to “PC screen only”: still noisy, despite the external display being disabled.
• Original Dell charger instead of monitor power: noticeably quieter.
• Original Dell charger and USB-C monitor both connected: quieter than using monitor power alone.
• Monitor’s “Type C PD Charge” setting turned off, external display still working, laptop on battery: no noticeable whine.
• Same setup with the original Dell charger connected: some whine returned, although much less than with monitor power.
• A different, lower-powered charger/hub: no noticeable whine during my testing, and my normal work felt fine and can't hear coil whine at all.

One relevant detail: the battery wasn’t actively charging during the later comparisons. I use a 50–80% charging range, and it was around 60%, below the upper limit but above the threshold for restarting charging. I observed roughly 20–30 W consumption during light use; that isn’t a measurement of peak demand.

My takeaway is that the power source made a much bigger difference than the performance profiles or FPS cap. The sound was coming from the laptop, but changing what powered it changed the noise dramatically.

I haven’t measured the electrical cause or benchmarked performance across chargers. This doesn’t prove that higher-wattage chargers cause whine, that the monitor is faulty, or that a lower-powered charger is suitable for every workload. It could be a power-supply interaction or a change in the laptop’s operating behavior.

For now, disabling the monitor’s USB-C power delivery and using a separate supply has helped a lot.

Has anyone else reproduced this? In particular, has anyone found a full-power 100 W USB-C PD charger that keeps their XPS quiet without performance loss?