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My laptop takes a 19V adapter but I accidentally plugged in a 12V adapter and the laptop started smoking. I unplugged it after about a second. I read that if the polarity is correct and the voltage is lower on the adapter than the requirement of the laptop that it's OK. Why did it start smoking? Did I irreparably damage the laptop?

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  • \$\begingroup\$ it is not possible to answer your questions without opening the laptop and checking to see what smoked ... any failure can be repaired \$\endgroup\$ – jsotola Jul 1 at 5:02
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    \$\begingroup\$ your question is not and eiectronics design question, so it does not belong here \$\endgroup\$ – jsotola Jul 1 at 5:04
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    \$\begingroup\$ That sounds very strange. What make an model? Are you 10 000 percent sure the polarity is correct? \$\endgroup\$ – winny Jul 1 at 6:37
  • \$\begingroup\$ If smoke came out of your laptop then the answer to the question is probably "yes" \$\endgroup\$ – user253751 Jul 1 at 10:30
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Probably. The 2/3 normal voltage might cause 100% duty cycle operation of the battery charger, meaning current SOARS far beyond tolerable operating currents.

Your switching FET may have smoked. Or the energy_transfer inductor may have gone into saturation, overheating either the inductor or the FET.

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    \$\begingroup\$ That's one crappy battery charger if it can't gracefully handle overcurrent though... \$\endgroup\$ – Lundin Jul 1 at 6:28
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    \$\begingroup\$ @Lundin Or undervoltage! How did it even handle startup and shutdown of the charger without UVLO? \$\endgroup\$ – winny Jul 1 at 6:38

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