A switching circuit includes a live wire power obtaining circuit, a control circuit, and a tunable capacitor array. The live wire power obtaining circuit is coupled to a live wire to receive an alternating current (AC) voltage. The control circuit is configured to perform a zero-crossing detection to the alternating current voltage. The tunable capacitor array is coupled to the live wire power obtaining circuit and the control circuit. The control circuit is configured to control the live wire power obtaining circuit to supply power to the control circuit or the tunable capacitor array to discharge to supply power to the control circuit based on a state of a first switch and a zero-crossing detection result.