SIGNAL CONVERSION CIRCUIT AND FINGERPRINT IDENTIFICATION SYSTEM
The present disclosure provides a signal conversion circuit and fingerprint identification system. The signal conversion circuit is configured to generate a first digital signal according to a first analog signal, and includes a comparator and counter. The comparator includes a first input terminal configured to receive the first analog signal, a second input terminal connected to a reference voltage generator and configured to receive a reference voltage, and an output terminal configured to output a second digital signal. The counter is connected to the output terminal, and is configured to generate a first digital signal. The signal conversion circuit according to the present disclosure has the advantages of simple circuit structure, small circuit area, low cost and low power consumption.
1 . A signal conversion circuit, comprising:
a comparator, comprising:
a first input terminal, configured to receive a first analog signal;
a second input terminal connected to a reference voltage generator, and configured to receive a reference voltage; and
an output terminal, configured to output a second digital signal; and
a counter connected to the output terminal, and configured to generate a first digital signal.
2 . The signal conversion circuit according to claim 1 , wherein when the first analog signal is greater than the reference voltage, the second digital signal has a first potential, or when the first analog signal is less than the reference voltage, the second digital signal has a second potential.
3 . The signal conversion circuit according to claim 1 , wherein the signal conversion circuit is used in a fingerprint identification system, wherein the fingerprint identification system comprises a pixel array circuit, and the first input terminal is connected to the pixel array circuit.
4 . The signal conversion circuit according to claim 3 , wherein the pixel array circuit is configured to receive a contact of a finger, and convert a capacitance formed between the pixel array circuit and the finger into a pixel output signal, wherein the pixel output signal is correlated to the first analog signal.
5 . The signal conversion circuit according to claim 4 , wherein the fingerprint identification system further comprises an amplifier, wherein the amplifier is connected between the pixel array circuit and the first input terminal, and configured to enhance a signal strength of the pixel output signal to form the first analog signal.
6 . The signal conversion circuit according to claim 1 , wherein a signal-to-noise ratio of the first analog signal is less than 3.
7 . The signal conversion circuit according to claim 1 , wherein the reference voltage generator comprises a control circuit, wherein the control circuit generates a definite voltage.
8 . The signal conversion circuit according to claim 7 , wherein the reference voltage generator further comprises a digital-to-analog converter, wherein the digital-to-analog converter is connected to the control circuit, and is configured to convert the definite voltage into the reference voltage.
9 . A fingerprint identification system, comprising:
a pixel array circuit, configured to receive a contact of a finger, and convert a capacitance formed between the pixel array circuit and the finger into a pixel output signal;
a signal conversion circuit, connected to the pixel array circuit, and configured to generate a first digital signal according to a first analog signal, wherein the signal conversion circuit comprises:
a comparator, comprising:
a first input terminal, configured to receive the first analog signal;
a second input terminal connected to a reference voltage generator, and configured to receive a reference voltage;
an output terminal, configured to output a second digital signal;
a counter connected to the output terminal, and configured to generate a first digital signal; and
a fingerprint judging module, connected to the signal conversion circuit, and configured to judge, according to the first digital signal, whether the pixel output signal corresponds to a finger ridge or a finger valley.
10 . The fingerprint identification system according to claim 9 , wherein when the first analog signal is greater than the reference voltage, the second digital signal has a first potential, or when the first analog signal is less than the reference voltage, the second digital signal has a second potential.
11 . The fingerprint identification system according to claim 9 , further comprising:
an amplifier, connected between the pixel array circuit and the first input terminal, and configured to enhance a signal strength of the pixel output signal to form the first analog signal.
12 . The fingerprint identification system according to claim 9 , wherein a signal-to-noise ratio of the first analog signal is less than 3 .
13 . The fingerprint identification system according to claim 9 , wherein the reference voltage generator comprises a control circuit, wherein the control circuit generates a definite voltage.
14 . The fingerprint identification system according to claim 13 , wherein the reference voltage generator further comprises a digital-to-analog converter, wherein the digital-to-analog converter is connected to the control circuit, and is configured to convert the definite voltage into the reference voltage.