Two USB-C power sources simultaneously

[Luka_sk]

Hi,

I need to connect my notebook to the monitor via USB-C cable.  My monitor is able to deliver 90W using USB-C, but my notebook requires 100W power source. Just to be sure, I would like to use original 100W USB-C power adapter and keep using USB-C connection to the monitor. The question is what happen if I connect my notebook to the USB-C 100W power adapter and to the monitor with USB-C PD 90W simultaneously.  Is it ok, or can something go wrong or can be someting damaged?

Thank you.

[Sneha_01 · Accepted solution]

Hi @Luka_sk 

Welcome to HP Support Community.

Thank you for posting your query, I will be glad to help you.

Hi! That's a good question, and it's great that you're being cautious about connecting multiple power sources to your notebook. Let’s break it down to give you a clear answer.

What Happens When You Connect Two USB-C Power Sources?

When you connect both a USB-C power adapter (providing 100W) and a monitor (providing 90W via USB-C Power Delivery), here's what typically happens:

USB-C Power Delivery (PD) Protocol: USB-C with Power Delivery (PD) is designed to negotiate power between devices. When you connect your notebook to both the power adapter and the monitor, the devices involved will communicate using the USB-C PD protocol to decide how much power to provide and to whom.

Power Source Priority: In most cases, the notebook will prefer the higher wattage power source (in this case, the 100W adapter). The system will first try to draw power from the source that can supply the higher wattage, which would be the 100W power adapter. If the notebook needs more than 90W, it will simply pull the remaining power from the 100W adapter, without overloading either source.

Simultaneous Charging: USB-C PD typically supports the idea that both power sources can be connected at the same time, but the notebook will only draw power from one (the higher wattage one). If the power sources are designed well (as most modern devices are), they won't send power to each other or cause a conflict. The monitor will only provide as much power as the notebook needs (up to 90W), and the remaining power needed (the additional 10W) will be drawn from the 100W adapter.

Power Management: Most modern laptops and devices have built-in power management circuits that ensure they only draw the necessary power from each source. So, in your case, your notebook will safely draw 90W from the monitor and the additional 10W from the 100W adapter, as needed.

While this setup is generally safe and should work without any problems, here are a couple of things to consider:

Power Flow Regulation: In some rare cases, if there’s a mismatch in power flow regulation between the monitor’s USB-C PD port and the laptop, it could result in minor power instability (like charging not happening properly), but this is not common with well-designed systems.

Monitor's Power Limitations: The 90W power limit from the monitor means that if your notebook is running heavy workloads (like gaming or rendering), it might draw more than the 90W provided by the monitor, and the laptop will need to draw the remaining power from the 100W adapter. If the monitor cannot supply enough power consistently, the laptop might slowly deplete its battery, even if it's plugged in (though this is unlikely unless the power draw consistently exceeds the 90W).

I hope this helps.

Take care and have a good day.

Please mark this post as “Accepted Solution” if the issue is resolved and if you feel this reply was helpful click “Yes”.

Rachel571

HP Support

[Luka_sk]

Hi @Rachel571

Thanks a lot for the detailed answer! That is exactly what I was looking for 🙂