A touch sensing circuit is provided. The circuit is configured to connect to a conducting wire in a touch area for measuring a signal variation. In a driving mode, the wire is coupled to AC voltage. If a first voltage variation which exceeds a first threshold is measured by the circuit, it is determined that something is approaching the touch area near the wire. In a passive mode, the wire is coupled to DC voltage. If a second voltage variation which exceeds a second threshold is measured by the circuit, it is determined that something is approaching the touch area near the wire. When measuring the second voltage variation, no AC voltage is coupled to the wire.