It does this by using a USB-powered programmable power supply (USB PD PPS)... Specifically, this phone can negotiate about 2.6 amps at 9.3 volts, providing a total of 25 watts of charging power. Advertising... The Galaxy S21 only uses the USB Power Delivery PSS plug to charge at 25W. ... USB PD (5V 3A, 9V 2A).