# Can a power supply be too powerful for a device assuming that the power supply is at operating voltage of the device? [duplicate]

Let’s say a device’s operating voltage is 5V and maximum current that it can draw is 5A.

Is it possible for a 5V power supply to have very low internal resistance such that a device that operates at 5V turns down its resistance in attempt to draw 5A from the power supply , but instead accidentally draws greater than > 5A due to the power supply having very low internal resistance or being “too powerful” ?

Of course this is assuming that the way a basic electronic device draws current is first, it assumes that it is being supplied the correct voltage, and 2nd, it lowers down its resistance at some constant number base on the current it needs to draw

Is this how regular devices such as servo motors draw current? Or can they actually monitor how much current a power supply can give and lowers its resistance base on that?

I know that it is possible to be at operating voltage and still not supply enough current, but could it be possible to be at operating voltage, and supply too much current for a load?

Wait Unless of course, as long as the voltage across the load is less than or equal to the operating voltage, it can never accidentally draw too much current. ( I think I answered my own question, not sure if this is right )

## marked as duplicate by Ignacio Vazquez-Abrams, winny, JRE, Leon Heller, Dmitry GrigoryevJul 14 '18 at 10:35

• A power supply with stable 5V output effectively has 0 resistance already. – Dmitry Grigoryev Jul 14 '18 at 10:35
• There are power supplies requiring a minimum load current. – Uwe Jul 14 '18 at 15:12

My two cents here

Is it possible for a 5V power supply to have very low internal resistance such that a device that operates at 5V turns down its resistance in attempt to draw 5A from the power supply , but instead accidentally draws greater than > 5A due to the power supply having very low internal resistance or being “too powerful” ?

Assuming power supply can provide voltage of 5V (10A)... If the current drawn by load (6A, accidentally) is less than the current supported by the power supply, power supply will be just fine. If the current drawn accidentally is more than 10A (max. Supported by the power supply) Power supply will either detect that and trips, or drops the output voltage to zero or may get damaged.

Power supply's current output is completely dictated by the load as long as load is drawing the current which is with in the power supply limits.

So if the load's operating voltage and current are within the specs of power supply it will be a safe working setup.

Can a power supply be too powerful for a device

Yes. For an example.. If power supply can supply up to 30 A and we are using a small Motor and an arduino.. Due to some accident if we do short then it can fry the parts..too powerful

PTCs are some examples which can be used to limit the current inrush, in case if it helps.

A power supply that is capable of delivering more current at its rated voltage will not harm a load that draws less current. Generally the load will draw what it will and as long as that current is within the capability of the power supply things are going to be just fine.

If you did have a load that varied its current draw requirements in a dynamic manner then the power supply has to be rated to supply the worst case current requirement. Although it is possible to deal with short term impulse loads by adding capacitors on the power supply output to supply the current of the short term demand. An example of a load like that would be a motor that draws the stall current amount as it first starts up but reduces to its running current when it gets up to speed.