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Recently i bought a cooling pad for my laptop. Pretty good, works just fine and has a nice blue light when it is connected to the power source (connected to the laptop). It has two USB 2.0 ports. On the back of the fan it says it is supplied with 5V DC, 380mA.

I don't want it to be power supplied from the laptop itself, but I want it to be charged directly from AC. So, i got an USB AC to DC transformer (adapter), OUTPUT 5V DC, and 350mA.

When the Cooling pad is not connected to the laptop, but to AC via the adapter it is power supplied (The blue LED light is on) but the fans do not rotate at all. When I plug it into the laptop instead, fans work just fine.

Any ideas why this happens and how to resolve the problem? (And I don't think that 30mA difference is it)

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  • Does it have two USB plugs? Are you able to plug both plugs into the AC to USB DC adapter? – Run CMD Dec 28 '16 at 12:48
  • Yes (I wrote it in the cooler pad description). No I am not, and I don't think I should do that. One of the solutions would be that I plug one cooler USB port to AC and the other on to laptop, and then the cooler would have the power drawn from AC socket. But, I want to know why the fans don't rotate when the cooler is being supplied from the AC socket even dough it is switched ON and has the power supply (the blue LED light is working). – CptWhoWent Dec 28 '16 at 13:51
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I found the solution.

The problem was the value of current. The cooling pad fans just needed a bit more current from the AC socket than 350mA. So I was wrong. A friend of mine gave me a different adapter who's output current was 850mA DC, so now the fans do work.

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