MCU power supply + PC supply

[DzAnej]

Hi, I've got a quick and hopefully easy question.
I'm working a lot with microcontrollers (Arduino, ...) and quite often I am having pritty big loads. Project I am working on now I have a programmable LED strip that draws 7A at max, and the arduino needs to be connected to the computer. Then I have a power supply capable of those 7A to power the strip and the Arduino (5V pin of the arduino is connected to the 5V power supply). Now let's say that my power supply turns off for unknown reason and the only 5V supply comes from the computer. Then probably the load (LEDs) would try to pull that power from the computer and because it's not capable of that something would go wrong (either the fuse on the Arduino or the computer would turn off).
Is there any way/method to prevent that?
Oh, and the computer is not always connected to the arduino, so I can't power the arduino only from the PC...

[Psi]

Need a schematic of your system

[Asim]

Don't power your arduino from the same 7A power suuply. Use the USB port to power the arduino & the 7A supply to power the led strip seperetley. Note that you need a common ground, so connect a ground from your arduino board to the ground of the led strip.

[cowana]

I have a power supply capable of those 7A to power the strip and the Arduino (5V pin of the arduino is connected to the 5V power supply).

As Asim said, it's very bad practice to connect two power supplies directly together (which you have with your PC's 5v USB supply, and the external 7A supply).

Best solution is to only power the LED strip from the external supply, and not the arduino.