[writtenabode]

All Qi chargers already have a temperature sensor in them and any modern phone has many temperature sensors (MEMS sensors, SMPS, lipo battery charger). The Qi receiver already communicates back to the transmitter and can tell it to increase or decrease power. Having the Pixel 3 decrease charging rate if it noticed heating up would be trivial.

[vlovich123]

You're forgetting the problem of the charging stand being implemented incorrectly & catching fire. Phone sensors won't help you there & while you may think all Qi chargers would have a temperature sensor in them, the fact that something simpler like knock-off USB charging blocks cause fire hazards leads me to not be so bullish on the Qi front.

And hey, look.

https://www.youtube.com/watch?v=CEGlmQS692w https://www.youtube.com/watch?v=IxstYrJQkk8

I'm sure you can find more examples. Just because we'd like the world to work a certain way doesn't mean it actually does in practice & the job of engineers sometimes is to deal with the reality of the world.

[writtenabode]

The issues you raise aren't solved by limiting transmit power - they are only solved by actually using Qi standard chargers. If you are using a faulty transmitter it can catch fire at 5W or 10W.

The Qi standard as of 1.1 has the receiver communicate back to the transmitter the amount of power it has received. The transmitter then calculates transmit efficiency based on the amount of power it is outputting. If the efficiency is too low the transmitter will fault with the assumption that it could be heating up a foreign object.