Embodiments of the present invention disclose a power supply method, including: rectifying a second alternating current, and converting the second alternating current into a second high voltage direct current; when the second high voltage direct current is abnormal, inputting a third high voltage direct current to a DC/DC module; when the second high voltage direct current is normal, inputting the second high voltage direct current to the DC/DC module; and converting, by the DC/DC module, the second high voltage direct current or the third high voltage direct current into a low voltage direct current for outputting.