I'm not sure if this topic fits in this subforum, but I couldn't find a better fit.
I'm using a Raspberry Pi 3 Model B+ with a LCD touch monitor, which is connected over HDMI. I'm powering the LCD touch monitor over the USB ports of the Raspberry Pi.
I've tried this setup in the following 3 situations:
1. Power the Raspberry Pi with a power adapter of 1.8A at 5V. I get a notification of undervoltage (yellow blitz) at the monitor.
2. Power the Raspberry Pi with a PoE switch and a PoE HAT. The monitor goes on and off all the time. The Raspberry Pi works fine with no undervoltage. I suspect the provided current is not enough, but at the specifications of this HAT is stated that it can deliver 2.5A (more than the power adapter).
3. Power the Raspberry Pi with a PoE switch and a Adafruit PoE splitter (https://www.adafruit.com/product/3785). The Raspberry and monitor work fine. There are no problems in this situation.
This raises a few questions:
1. Why do I get a undervoltage notification in situation 1, but not in situation 2 and 3?
2. Why does it look like the provided current is not enough in situation 2, but is enough in situation 1 and 3?
Could someone help me here?
Thanks in advance,