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PSU that comes with any electronics device usually has a single output voltage rating. This is because they are intended for use with a single device.

These Samsung phone chargers have multiple output ratings!

enter image description here

  1. Why is this necessary?
  2. How is the output switched to different output voltages? There is no switch to do this so I assume the device being charged tells what voltage it needs.
quantum231
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1 Answers1

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The one on the right is an older Samsung Adaptive Fast Charger. It communicates on the data pins to allow for the faster 9V charging voltage. Its a proprietary Samsung protocol.

The one on the left is a newer USB C with Power Delivery standard (PD) 3.0 (or newer) with PD 2.0 PDO charging (fixed profiles) and PD 3.0 PPS charging (arbitrary voltages in a range). Communication for selecting the higher voltages are done on the USB C CC lines.

Both require active communication to enable and keep enabled the higher voltages. They default to 5V. The purpose is to allow higher power and more efficient charging by reducing the current over the wire which causes voltage drop and heat. Essentially because backwards compatibility is important for usb.

Passerby
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