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I recently bought a cheap USB-C power delivery charger and 2m USB-C cable for my Surface Go. When I connect it, everything seems to work fine, it charges at full speed, etc, but there's one weird thing: The touchpad starts acting weirdly, as if it received random signals. Touchscreen seems to work fine though.

My question is, what could have caused this? I'm not looking for a solution, because that would obviously be to buy better charger, rather for explanation what exactly might be happening.

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    \$\begingroup\$ I recently bought a cheap USB-C power delivery charger Do the problems occur only with such a cheap charger? Is there a problem when you use the charger that came with the Surface Go? If so then obviously it's the charger. It might have more capacitive coupling to the mains than it should have. That can disturb the touchpad. \$\endgroup\$ – Bimpelrekkie Jan 30 '20 at 15:45
  • \$\begingroup\$ It's also worth considering how good your USB cable is. If it's not USB-IF compliant you could have other problems with it. \$\endgroup\$ – VBwhatnow Jan 31 '20 at 8:49
  • \$\begingroup\$ @Bimpelrekkie Yes, the same cable with an Anker USB-C PD charger does not give me such problems. Works fine with the charger that came in the box too. \$\endgroup\$ – user3518753 Jan 31 '20 at 11:55
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Not working is different from acting weird.

If your touch pad stops working then it could be the voltage doesn't reach or over certain point like the original charger / supply.

If acting weird the voltage could be too high or too low or high EMI emitted from the charger because bad design or improper use of component.

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    \$\begingroup\$ Cheap USB chargers often have pretty high EMI lygte-info.dk/info/usbPowerSupplyTest%20UK.html \$\endgroup\$ – Bruce Abbott Jan 31 '20 at 8:57
  • \$\begingroup\$ that's true, because it's cheaper so they will remove safety factor or proper use component, example they will use higher rate ic regulator because they have overstock and it will be costly to buy another regulator. so yeah no safety \$\endgroup\$ – Cubic273.15 Jan 31 '20 at 9:00
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I had a similar incidence a few years ago and the solution was, as you said, buy a better charger. The issue, as Bruce Abbott already pointed out, is lots of EMI being radiated from cheapo chargers. The charger cord is probably acting as an antenna and radiating that EMI. If you open the charger, you may even find the cable shield is not grounded/connected. Something about .001 ufd should kill all of that noise, in any case.

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