Pixel sensing circuit for fingerprint identification, fingerprint identification system and electronic device thereof

A fingerprint identification system comprising a plurality of pixel sensing circuits, the pixel sensing circuit comprising:

• a capacitance sensing layer;
• a plurality of shielding layers, comprising a first-type shielding layer and a second-type shielding layer, the second shielding layer being coupled to a ground terminal;
• and
• a charging circuit, coupled to the capacitance sensing layer and the first-type shielding layer, and comprising a positive voltage generator configured to providing a positive voltage;
• wherein when the pixel sensing circuit is in a fingerprint identification mode, the charging circuit periodically provides the positive voltage for the capacitance sensing layer and the first-type shielding layer;
• and
• when the pixel sensing circuit is in the noise detection mode, the charging circuit cuts off connections between the positive voltage generator and the capacitance sensing layer and the first-type shielding layer, and the charging circuit periodically outputs a voltage of the capacitance sensing layer to a first output terminal,
• wherein the pixel sensing circuit is switched between a positive mode and a negative mode, when the pixel sensing circuit is in the fingerprint identification mode and in the positive mode, the charging circuit provides the positive voltage for the capacitance sensing layer and the first-type shielding layer in a first duration within a period, and conducts the connection between the ground terminal and the first-type shielding layer in a second duration within the period;
• and
• when the pixel sensing circuit is in the fingerprint identification mode and in the negative mode, the charging circuit conducts a connection between the ground terminal and the capacitance sensing layer and the first-type shielding layer,
• wherein the plurality of pixel sensing circuits is arranged in an array.

An electronic device comprising a fingerprint identification system, wherein the fingerprint identification system comprising a plurality of pixel sensing circuits, wherein the pixel sensing circuit comprising:

• a capacitance sensing layer;
• a plurality of shielding layers, comprising a first-type shielding layer and a second-type shielding layer, the second shielding layer being coupled to a ground terminal;
• and
• a charging circuit, coupled to the capacitance sensing layer and the first-type shielding layer, and comprising a positive voltage generator configured to providing a positive voltage;
• wherein when the pixel sensing circuit is in a fingerprint identification mode, the charging circuit periodically provides the positive voltage for the capacitance sensing layer and the first-type shielding layer;
• and
• when the pixel sensing circuit is in the noise detection mode, the charging circuit cuts off connections between the positive voltage generator and the capacitance sensing layer and the first-type shielding layer, and the charging circuit periodically outputs a voltage of the capacitance sensing layer to a first output terminal,
• wherein the pixel sensing circuit is switched between a positive mode and a negative mode, when the pixel sensing circuit is in the fingerprint identification mode and in the positive mode, the charging circuit provides the positive voltage for the capacitance sensing layer and the first-type shielding layer in a first duration within a period, and conducts the connection between the ground terminal and the first-type shielding layer in a second duration within the period;
• and
• when the pixel sensing circuit is in the fingerprint identification mode and in the negative mode, the charging circuit conducts a connection between the ground terminal and the capacitance sensing layer and the first-type shielding layer,
• wherein the plurality of pixel sensing circuits is arranged in an array.