There is provided a power supply apparatus for supplying power to an external electrical load, including a power transmission line or cable through which an alternating or direct current may flow, a power supply module, a control unit, an output terminal for connection to the external electrical load, and a converter. The power supply module includes an input terminal connected to the power transmission line or cable, and includes switching elements and energy storage device(s). The control unit controls the switching elements to selectively switch each energy storage device into circuit to direct a current flowing in the power transmission line or cable to flow through each energy storage device so as to store energy to form a power source. The converter draws power from the power source and supplies the drawn power to the output terminal.