An alternating current (AC) to direct current (DC) power converter may have a connector with a pair of power supply contacts and a pair of data contacts. An electronic device may be connected to the connector of the power converter. The power converter may supply DC power to the electronic device using the power supply contacts. The power converter may include control circuitry that has a resistor coupled across the data contacts. When the electronic device and the power converter are connected to each other, each may advertise to the other that capabilities are present that exceed industry standards. At the same time, standard-compliant discovery operations may be performed to probe the value of the resistance of the resistor that is coupled across the data contacts. When extended capabilities are discovered, extended functions may be performed including accelerated charging functions and data communications functions.