Sensing method and circuit of fingerprint sensor
A sensing method and sensing circuit technology, applied in the directions of measuring electrical variables, acquiring/arranging fingerprints/palmprints, measuring resistance/reactance/impedance, etc., can solve problems affecting measurement results, etc.
Active Publication Date: 2016-06-22
ELAN MICROELECTRONICS CORPORATION
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Problems solved by technology
However, the measurement of the capacitance between the electrode plate 51 and the finger 60 will be affected by other factors. For example, when measuring the electrode plate PlateA, the electrode plate PlateA and its surrounding electrode plates PlateB~PlateD form capacitance, and the capacitance C formed between the electrode plate PlateA and the protective electrode 52 (such as the electrostatic protection electrode) FAS , will affect the measurement results
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[0046] Figure 1A and image 3 The first embodiment of the sensing circuit 10 of the present invention will be described. The sensing circuit 10 includes a plurality of measurement units 11 and a control unit 12, and the plurality of measurement units 11 are respectively connected to the electrode plates PlateA-PlateD.
[0047]The following description will take the electrode plate PlateA as an electrode plate to be measured as an example. The measurement unit 11 connected to the electrode plate PlateA to be measured includes a first switching unit 111 and a readout circuit 13 , and the measurement units 11 connected to the other electrode plates PlateB to PlateD respectively include a second switch unit 112a and a readout circuit 13 . circuit 13. The guard electrode 52 is connected to a second switching unit 112b.
[0048] like image 3 As shown, the first switching unit 111 includes a first terminal N 1a Connected to the electrode plate to be measured PlateA, and a seco...
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A sensing method and a circuit of a fingerprint sensor are disclosed. In a first phase, the sensing method supplies a first to third voltages to an electrode plate to be measured, a read-out circuit of the electrode plate to be measured and a conductor adjacent to the electrode plate to be measured, respectively. In a second phase, the sensing method stops supplying the first to third voltages and supplies voltage to the conductor and connects the electrode plate to be measured to the read-out circuit so the read-out circuit reads out a measurement result of the electrode plate to be measured. According to the sensing method and circuit, the measurement result of the electrode plate to be measured is not affect by capacitors between the electrode plate to be measured and the conductor.
Description
technical field [0001] The present invention relates to a fingerprint sensor, in particular to a sensing method and circuit of the fingerprint sensor. Background technique [0002] see Figure 12 and Figure 13 As shown, a schematic diagram of a projected capacitive fingerprint sensor 50 includes a plurality of electrode plates 51 arranged in a matrix, a guard electrode 52 , and a sensing circuit 53 connected to the plurality of electrode plates 51 . The sensing circuit 53 is used to detect the capacitance between each electrode plate 51 and the finger 60 , for example, the capacitance C between the electrode plate PlateA and the finger 60 SA , the fingerprint image of the finger 60 can be obtained according to the capacitance between each electrode plate 51 and the finger 60 . However, the measurement of the capacitance between the electrode plate 51 and the finger 60 will be affected by other factors. For example, when the electrode plate PlateA is measured, the electrod...
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IPC IPC(8): G06K9/00
CPCG06V40/1306G01D5/24G01R27/26G01R27/2605H03K17/955G06V40/12
Inventor 杨昭锜
Owner ELAN MICROELECTRONICS CORPORATION