Sensing method of fingerprint sensor and related sensing circuit

A sensing circuit for sensing a capacitance between an electrode plate to be measured of a fingerprint sensor and a finger, the sensing circuit comprising:

• a first switch unit, comprising a first node and a second node, the first node being connected to the electrode plate to be measured, wherein in a first phase, the first node is coupled to a first voltage, the second node is coupled to a second voltage different from the first voltage, and the first node is disconnected from the second node;
• and in a second phase, the first node is disconnected from to the first voltage, the second node is uncoupled to the second voltage, and the first node is connected to the second node;
• a second switch unit, wherein in the first phase, the second switch unit couples a third voltage to a conductor adjacent to the electrode plate to be measured;
• and in the second phase, the second switch unit couples a fourth voltage different from the third voltage to the conductor;
• a third switch unit, wherein in the first phase, the third switch unit couples a first finger drive voltage to a finger drive electrode;
• in the second phase, the third switch unit couples a second finger drive voltage different from the first finger drive voltage to the finger drive electrode, wherein the finger drive electrode is arranged for coupling the finger;
• a readout circuit, coupled to the second node of the first switch unit, the readout circuit arranged for reading out a measurement result of the electrode plate to be measured according to a signal on the second node;
• and
• a control unit, arranged for controlling operations of the first switch unit, the second switch unit and the third switch unit in the first phase and the second phase;
• wherein the first voltage is greater than the second voltage, the third voltage is greater than the fourth voltage, and the first finger drive voltage is less than the second finger drive voltage;
• or the first voltage is less than the second voltage, the third voltage is less than the fourth voltage, and the first finger drive voltage is greater than the second finger drive voltage.