Power supply control system and method

The invention discloses a power supply control system, which comprises power supply equipment, a transmission device and power receiving equipment, wherein the power supply equipment comprises a transmission interface and a processor; the processor is used for converting voltage output by a power supply into a first type of voltage, and the first type of voltage is output to the power receiving equipment through a first transmission line of the transmission device; when the first type of voltage is received, the power receiving equipment outputs a mode signal to the power supply equipment through a second transmission line of the transmission device; and the power supply equipment outputs a second type of voltage to the power receiving equipment through a first pin to cause the power receiving equipment to enter a second work mode. The invention also provides a power supply control method. The power supply control system and method changes the output voltage of an interface to guarantee that the power receiving equipment normally works, and therefore, the damage of the interface due to the increase of current flowing through the interface can be avoided.