A system for providing a power signal of a predetermined voltage to an input of a High Definition Multimedia Interface (HDMI) sink device is provided. The system includes an electronic device, generating HDMI signals transmitted on at least one differential signal line to another input of the HDMI sink device, and a startup circuit, providing the power signal of the predetermined voltage. The startup circuit includes a power harvesting circuit for obtaining an electrical power of a lower voltage, lower than the predetermined voltage, from at least one of the HDMI signals on the another input, and a voltage raiser circuit increasing the lower voltage to the predetermined voltage. A corresponding electronic cable containing the start-up circuit is also provided.