Abstract: The present application relates to an internal power supply apparatus for an auxiliary device supporting a PD protocol, including a battery interface, a USB-PD power interface, a forward power supply circuit, a reverse power supply circuit, a power bus, a control bus and a power supply control circuit; a first input end of the forward power supply circuit is connected with a battery; an input end of the power bus is connected with the forward power supply circuit, and the power bus is connected with an input end of the reverse power supply circuit, an input end of the power supply control circuit and an internal load of the auxiliary device; an output end of the reverse power supply circuit is connected with a photographic device through the USB-PD power interface; the power supply control circuit controls a voltage value output by the reverse power supply circuit.