A power-saving circuit is provided for saving electrical power by detecting a presence or absence of an object in a localized area. The power-saving circuit includes a sensor module, and a switch module connected to the sensor module. The detector is adapted for outputting a control signal at a first state when an object is detected in the localized area, and outputting a control signal at a second state when an object is detected not in the localized area. The switch module provides a stable DC voltage according to the control signal at the first state, and not provides the stable DC voltage according to the control signal at the second state.