Electrical – Why are there two different output voltage ratings on some power supplies? and How it works?

chargerpower supplyratings

some power supplies (ex. chargers) have two different output voltage ratings like:

5V 2A OR 9V 2A

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-why is that?

-How the charger knows that my load needs 5V or 9V? and not damaging the load

-How the switching work?

thanks,

Best Answer

This adapter clearly states "Quick Charge".

To read more about QC, read here.

In short: this adapter supports a protocol called "Quick Charge" which uses communication over the USB datalines to detect if a QC compatible product is connected.

If a non-QC compatible product is connected, the adapter will output 5 V

If a QC compatible product is connected, the adapter will output 5 V until the product requests 9 V from the adapter. Only then will the adapter output 9V.