Why did the power supply fry itself

power supply

I am in Europe. There was a switch on my PSU that could switch the voltage between 230v and 130v (not 100% sure). In Europe we use 230. I switched the PSU to 110 and turned it on. Several sparks and a power failure resulted, the PSU was fried.

Can someone explain why this happened. I was assuming that because the system was using 230 and the PSU only draws 130 it would be safe cause it's less. I guess I was wrong.

Can someone explain me the physics behind this.

Best Answer

Here is a simplified explanation of what's going on in the power supply. The power supply divides the input voltage (230V in your case) by a fixed amount to give the voltages needed by the motherboard and other components. There are various outputs, but one of them is 5V. To get this you have to divide 230 by 46, or divide 110 by 22.

Power supplies can work on 230V (most of the world) or 110V (North America). The switch selects which divisor is used inside the power supply. In your case you set the switch to 110. This selected the 22 divisor. However, you applied 230V to the input. This resulted in a voltage of about 10.5V on the 5V circuits. This voltage was too high and something blew. It may not have been on the 5V circuit, but the story is still the same. You applied too high a voltage for the setting of the divisor. If you are lucky only the power supply was damaged and all the other components are still OK.

If that didn't make sense, then consider this. Suppose your car is stuck in the snow (I'm from Canada; somebody's car is always stuck in the snow). If you push the car out by hand you won't damage it. If you push the car out with a tractor you will probably dent the metal. The tractor pushes too hard. The voltage is like that push. Voltage pushes electrons around. When you applied 230 volts to a circuit designed for 110 volts, you pushed too hard.

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