I purchased an peltier cooler plate (90W maximum, but it could work at different power) like the model shown in this link http://pcbheaven.com/wikipages/The_Peltier_Thermo-Element/ . It has a wide working range on voltage and current. I use a AC-DC power supplier (12V, 0.5A), which was used to drive MP3 player, to drive the peltier. I also connected a fan (12V, 0.9W) in parallel to the peliter to the supplier. When I plug it to the home socket, it works for 10minutes, one side of the peliter is very cold and other side is so hot, and the fan is working (but spinning so slow). After 10 minutes, the power supplier becomes so hot. I thought the power of the fan is constant and the supplier provide 12V, so why the power supplier is getting that hot, it seems like it is drawing more and more current out of the wall.

  • \$\begingroup\$ You are saying your peltier can draw 90w, which at 12v is 90/12 = 7.5 Amps. Your power supply is ~15x under powered and will be working itself to death trying to supply as much power as it possibly can. \$\endgroup\$
    – John U
    Commented Aug 7, 2013 at 9:31
  • \$\begingroup\$ So it means even the power supplier states that the output is 12V and 0.5A, it does not really maintain the constant current? So is there any power supplier can fix the voltage and current output so the peltier can only consume certain power? \$\endgroup\$ Commented Aug 7, 2013 at 9:40
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    \$\begingroup\$ You need a larger power supply, capable of supplying at least 8A. \$\endgroup\$
    – pjc50
    Commented Aug 7, 2013 at 9:43
  • \$\begingroup\$ @user1285419 - It seems to me you need to work on your understanding of the basics of electricity, Ohm's law, etc. - The only reason your power supply has not exploded already is that it has some current limiting / protection built in. \$\endgroup\$
    – John U
    Commented Aug 7, 2013 at 12:14

1 Answer 1


A TEC may have a wide operating range, but it is still essentially a chunk of metal and consumes a lot of current. Your power supply is heating up simply because it is providing as much power as it can to the device and is not working at 100% efficiency (with the loss expressed as heat).

  • \$\begingroup\$ so will the power output of the supplier constant or not? \$\endgroup\$ Commented Aug 7, 2013 at 9:41
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    \$\begingroup\$ Read the TEC datasheet to find out. \$\endgroup\$ Commented Aug 7, 2013 at 9:59
  • \$\begingroup\$ @user1285419: As everyone is saying - A 0.5A supply CANNOT supply 7.5A. You shouldn't expect it to. Wall warts are not constant-power devices, they are not constant-current devices, they attempt to be near to constant voltage devices but only for a limited range of currents (e.g. perhaps 0.1 to 0.5A in your case). \$\endgroup\$ Commented Aug 7, 2013 at 10:12
  • \$\begingroup\$ Hi all, I just forgot to mention that as stated in the datasheet of the peltier plate, 90W is the maximum power, but it could work at different power. \$\endgroup\$ Commented Aug 7, 2013 at 17:40
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    \$\begingroup\$ Yes, but unless you limit the current the peltier draws, it will draw as much as it can from the supply, causing it to overheat. There seems to be thermal limiting in your AC/DC supply, but obviously not any current-limiting. \$\endgroup\$
    – dext0rb
    Commented Aug 7, 2013 at 18:30

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