CN111027384A - Fingerprint identification detection circuit, detection method and display device - Google Patents
Fingerprint identification detection circuit, detection method and display device Download PDFInfo
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- CN111027384A CN111027384A CN201911080538.7A CN201911080538A CN111027384A CN 111027384 A CN111027384 A CN 111027384A CN 201911080538 A CN201911080538 A CN 201911080538A CN 111027384 A CN111027384 A CN 111027384A
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- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
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- G06V40/1318—Sensors therefor using electro-optical elements or layers, e.g. electroluminescent sensing
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- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
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Abstract
The invention discloses a fingerprint identification detection circuit, a detection method and a display device, wherein the fingerprint identification detection circuit comprises: the storage capacitor comprises a photodiode, a first transistor, a second transistor, a third transistor, a fourth transistor and a storage capacitor; the driving voltage of the second transistor is V1The driving voltage at the driving voltage signal terminal is V2The threshold voltage of the second transistor is V3Wherein V is1≥V2+V3(ii) a The driving voltage of the first transistor M1 is V4Wherein V is4≤V2(ii) a The value of the storage capacitor is C1The capacitance of the photodiode is C2，C1＜C2The invention realizes the amplification of output signals, improves the signal-to-noise ratio, enhances the anti-interference capability of the fingerprint identification circuit and then improves the fingerprint identification precision.
Description
Technical Field
The invention relates to the technical field of display, in particular to a fingerprint identification detection circuit, a fingerprint identification detection method and a display device.
Background
In recent years, with the hot sales of electronic products such as mobile phones with fingerprint identification unlocking function, fingerprint identification technology is promoted to a new application era. The fingerprint recognition process in electronic products is usually controlled by a fingerprint recognition driver. The fingerprint identification driver in the prior art generally comprises a switch transistor and a light sensing diode, the switch transistor is used for controlling the output of light current through a switch, the light sensing diode generates light currents with different sizes under the irradiation of different light intensities, when the switch transistor is switched on, a current signal is transmitted to a processing chip to be processed to obtain light intensity information, and whether fingerprint identification refers to ridges or valleys is judged.
Disclosure of Invention
In view of the above, the present invention provides a fingerprint identification detection circuit, a detection method and a display device, so as to improve the anti-interference capability of the fingerprint identification circuit.
In one aspect, the present invention provides a fingerprint identification detection circuit, including:
the photodiode is used for generating electric charges under the action of illumination and comprises a first pole and a second pole, wherein the first pole is connected with a reference voltage signal end, and the second pole is connected to a first node;
a first transistor for being turned on in response to a first control signal, and transferring the charge transferred to the first node to a second node;
a second transistor for turning on in response to a second control signal and transmitting a driving voltage signal of a driving voltage signal terminal to the second node;
a third transistor turned on in response to a voltage signal of a second node, transmitting a voltage of the second node to a third node;
a fourth transistor turned on in response to a third control signal, transmitting a voltage of the third node to the signal output terminal;
a storage capacitor coupled between the reference voltage signal terminal and the second node;
the driving voltage of the second transistor is V1The driving voltage of the driving voltage signal end is V2The threshold voltage of the second transistor is V3Wherein V is1≥V2+V3；
The driving voltage of the first transistor is V4Wherein V is4≤V2；
The value of the storage capacitor is C1The capacitance of the photodiode is C2Wherein, C1＜C2。
On the other hand, the invention also provides a detection method of the fingerprint identification detection circuit, which is applied to the fingerprint identification detection circuit, and the method comprises the following steps:
in the reset stage, the second transistor is controlled to be turned on by the second control signal, a driving voltage signal of a driving voltage signal end is transmitted to the second node, and the first transistor is controlled to be turned on by the first control signal;
the exposure stage is used for controlling the first transistor to be cut off through the first control signal, and the photodiode generates charges under the action of illumination and transmits the charges to a first node;
a charge transfer phase, wherein the first transistor is controlled to be turned on by the first control signal, and the second transistor is controlled to be turned off by the second control signal, so that the charge at the first node is transferred to a second node;
and in the signal output stage, the third transistor is controlled to be turned on by the voltage signal of the second node, the voltage of the second node is transmitted to the third node, the fourth transistor is controlled to be turned on by the third control signal, and the voltage of the third node is transmitted to a signal output end to be output.
Moreover, the invention also provides a display device which comprises the fingerprint identification driver.
Compared with the prior art, the fingerprint identification detection circuit, the fingerprint identification detection method and the fingerprint identification display device provided by the invention at least realize the following beneficial effects:
the fingerprint identification detection circuit of the present invention includes: the photodiode is used for generating electric charges under the action of illumination and comprises a first pole and a second pole, wherein the first pole is connected with a reference voltage signal end, and the second pole is connected to a first node; the first transistor is adapted to be turned on in response to a first control signal,transferring the charge transferred to the first node to a second node; the second transistor is used for responding to a second control signal and conducting, and transmitting a driving voltage signal of the driving voltage signal end to a second node; the third transistor is used for responding to the voltage signal of the second node and conducting, and transmitting the voltage of the second node to the third node; a fourth transistor turned on in response to a third control signal, transmitting a voltage of the third node to the signal output terminal; the storage capacitor is coupled between the reference voltage signal end and the second node; the driving voltage of the second transistor is V1The driving voltage at the driving voltage signal terminal is V2The threshold voltage of the second transistor is V3Wherein V is1≥V2+V3(ii) a The driving voltage of the first transistor M1 is V4Wherein V is4≤V2(ii) a The value of the storage capacitor is C1The capacitance of the photodiode is C2，C1＜C2According to the invention, the voltage high-low well is constructed between the first node and the second node, when the charge at the first node is transferred to the second node, the voltage difference variation delta V2 of the second node is larger than the voltage difference variation delta V1 of the first node N1, and then the output signal of the transmission signal output end is amplified after passing through the third transistor and the fourth transistor, so that the signal-to-noise ratio is improved, the anti-interference capability of the fingerprint identification circuit is enhanced, and the fingerprint identification precision is improved.
Of course, it is not necessary for any product in which the present invention is practiced to achieve all of the above-described technical effects simultaneously.
Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.
FIG. 1 is a prior art fingerprint recognition drive;
FIG. 2 is a graph of fingerprint identification drive output noise of FIG. 1;
FIG. 3 is a schematic diagram of a fingerprint identification detection circuit according to the present invention;
FIG. 4 is a schematic diagram of the fingerprint identification driving reset phase for constructing a high-low well;
FIG. 5 is a schematic diagram of the fingerprint recognition driven exposure phase;
FIG. 6 is a schematic diagram of the fingerprint identification drive charge transfer phase;
FIG. 7 is a schematic diagram of the fingerprint identification driving signal output phase;
FIG. 8 is a schematic diagram of another fingerprint identification detection circuit provided in the present invention;
FIG. 9 is a schematic diagram of another fingerprint identification detection circuit provided in the present invention;
FIG. 10 is a flow chart of a detection method of the fingerprint identification detection circuit provided by the invention;
FIG. 11 is a control timing diagram of the fingerprint identification circuit driver;
fig. 12 is a schematic structural diagram of a display device according to an embodiment of the present invention.
Detailed Description
Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
The fingerprint identification driver in the prior art has the problems of poor anti-jamming capability and high noise, and in order to solve the problems, the inventor researches the following:
referring to fig. 1 and 2, fig. 1 is a fingerprint identification driver provided in the prior art, and fig. 2 is a schematic diagram of output noise of the fingerprint identification driver in fig. 1. The fingerprint recognition drive of fig. 1 comprises a switching transistor T0And a photodiode S0Of course, the storage capacitor Cst, the driving voltage signal line 01 and the signal line 02, and the photo diode S0The reference voltage Vbias is connected, the fingerprint identification drive is called a passive detection circuit, a light-sensitive diode S0For detecting intensity of light, switching transistor T0The light-sensitive diodes are used as switch to control the light current output, the light currents generated by the light-sensitive diodes under the irradiation of different light intensities are different, and the switching transistor T is arranged on the switch0When the switch is switched on, the current signal is transmitted to a processing chip for processing and is converted into a voltage signal inside the processing chip. In particular, the fingerprint recognition drive comprises a switching transistor T electrically connected0Photodiode S0Switching transistor T0Comprises a gate electrically connected with a drive voltage signal line 01, a source connected with a photodiode S0Is electrically connected to the negative electrode, the drain electrode is electrically connected to the signal line 02, and the photodiode S0Is connected with a reference voltage Vbias. Drive voltage signal line 01 and switching transistor T0Is electrically connected to the gate of the switching transistor T, and is activated by supplying an electric signal to the driving voltage signal line 010When the photodiode S0When illuminated, the photodiode S0The voltage corresponding to the negative electrode of the light source changes, namely when a finger touches the screen, the light source is reflected when irradiating the valley line and the ridge line of the finger fingerprint, and because the reflection angle of the valley line and the ridge line and the reflected illumination intensity are different, the light is projected to the photodiode S0Above, cause the photodiode S0Changes the resistance value of and thus the current through the switching transistor T in the on-state changes0And is transmitted to the signal line 02 so that the processing chip connected to the signal line 02 recognizes the valleys and ridges of the fingerprint. With reference to fig. 2, the passive detection circuit has a simple structure, but has poor Noise immunity, and especially after being integrated in a display panel, due to the problems of crosstalk between long traces and data lines in the display panel, the Noise (e.g., Noise in fig. 2) finally output to a processing chip is very large, and the current signal and the Noise are amplified together in an amplifying circuit inside the processing chip, which affects the accuracy of fingerprint identification.
In order to solve the above problems, the present invention provides a fingerprint identification detection circuit, a detection method and a display device, and specific embodiments are described in detail below.
Referring to fig. 3, fig. 3 is a schematic structural diagram of a fingerprint identification detection circuit provided in the present invention; the fingerprint identification detection circuit 00 in fig. 3 includes: a photodiode 100 for generating charge under illumination, the photodiode 100 comprising a first pole 101 and a second pole 102, the first pole 101 being connected to the reference voltage signal terminal 200, the second pole 102 being connected to the first node N1; a first transistor M1 for turning on in response to a first control signal to transfer the charge transferred to the first node N1 to the second node N2; a second transistor M2, which is turned on in response to the second control signal, for transmitting the driving voltage signal of the driving voltage signal terminal 300 to the second node N2; a third transistor M3 turned on in response to the voltage signal of the second node N2, transmitting the voltage of the second node N2 to the third node N3; a fourth transistor M4 for turning on in response to the third control signal, transmitting the voltage of the third node N3 to the signal output terminal 400; a storage capacitor 500 coupled between the reference voltage signal terminal 200 and a second node N2; the driving voltage of the second transistor M2 is V1The driving voltage of the driving voltage signal terminal 300 is V2The threshold voltage of the second transistor M2 is V3Wherein V is1≥V2+V3(ii) a The driving voltage of the first transistor M1 is V4Wherein V is4≤V2(ii) a The value of the storage capacitor 500 is C1The capacitance of the photodiode 100 is C2Wherein, C1＜C2。
It is understood that, as shown in fig. 3, the fingerprint identification detecting circuit 00 further includes a driving voltage signal line 91 for providing a driving voltage signal to the driving voltage signal terminal 300, and an output signal line 92 for transmitting the voltage signal of the signal output terminal 400 to a processing chip (not shown). A in FIG. 3 is a first control signal terminal for providing a first control signal; b is a second control signal end for providing a second control signal; and C is a third control signal terminal for providing a third control signal.
With reference to fig. 4-7, fig. 4 is a schematic diagram of the fingerprint identification driving reset phase for constructing high and low wells; FIG. 5 is a schematic diagram of the fingerprint recognition driven exposure phase; FIG. 6 is a schematic diagram of the fingerprint identification drive charge transfer phase; fig. 7 is a schematic diagram of the output phase of the fingerprint identification driving signal, and the signal amplification principle of the fingerprint identification driving is specifically explained with reference to fig. 4 to 7, where the fingerprint identification driving includes four phases, which are respectively a reset phase, an exposure phase, a charge transfer phase, and a signal output phase:
referring to fig. 3 and 4, in the reset phase, the first transistor M1 is turned on in response to the first control signal; the second transistor M2 is turned on in response to the second control signal, and transmits the driving voltage signal of the driving voltage signal terminal 300 to the second node N2. The driving voltage of the second transistor M2 is V1The driving voltage of the driving voltage signal terminal 300 is V2The threshold voltage of the second transistor M2 is V3，V1≥V2+V3Therefore, when the second transistor M2 is turned on, it can be ensured that the voltage at the second node N2 is equal to the driving voltage V of the driving voltage signal terminal 3002Let the voltage at the second node N2 be VN2Then V at this timeN2＝V2(ii) a In addition, the driving voltage V of the first transistor M1 in the invention4V is less than or equal to2Therefore, after the first transistor M1 is turned on, the voltage at the first node N1 gradually increases, and when the threshold voltage of the first transistor M1 is V5Then the first node N1 can reach V at the highest2-V5That is, let the voltage at the first node N1 be VN1Therefore V isN1＝V2-V5At this time, the voltage difference between the second node N2 and the first node N1 is VN2-VN1＝V5The voltage difference high-low well in fig. 4 is constructed, that is, the voltage difference between the first node N1 and the second node N2 is formed.
Referring to fig. 3 and 5, in the exposure phase, the first transistor M1 is turned off, the photodiode 100 generates charges under illumination, that is, the finger touches the screen, the light source reflects when illuminating the valley line and the ridge line of the finger fingerprint, and due to the difference between the reflection angle of the valley line and the ridge line and the intensity of the reflected light, the light is projected onto the photodiode 100, so that the resistance of the photodiode 100 changes, and charges are generated, at this time, the voltage changes due to the charge at the first node N1, and at this time, compared with the absence of illumination, the voltage difference before and after illumination at the first node N1 is Δ V1.
In conjunction with fig. 3 and 6, during the charge transfer phase, when the first transistor M1 is turned on, the second transistor M2 is turned off, and the charge at the first node N1 is transferred to the second node N2.
Referring to fig. 3 and 7, in the voltage output stage, after the charge at the first node N1 can be transferred to the second node N2, the charge amount before and after the charge transfer is the same, as can be seen from the formula Q ═ cxv, Q is the charge amount, C is the capacitor, V is the voltage, and the voltage difference before and after the transfer at the second node N2 is Δ V2, since C is C21＜C2Therefore, Δ V2>Δ V1, when the third transistor M3 is turned on in response to the voltage signal of the second node N2 to transmit the voltage of the second node N2 to the third node N3, and then the fourth transistor M4 is turned on in response to the third control signal to transmit the voltage of the third node N3 to the signal output terminal 400, since the voltage of the second node is amplified, the output signal of the transmission signal output terminal, which is then passed through the third transistor and the fourth transistor, is also amplified, thereby realizing the amplification of the output signal.
It should be noted that the third transistor M3 is turned on in response to the voltage signal of the second node N2, and the degree of opening and closing of the third transistor M3 is related to the voltage signal of the second node N2, so that the degree of opening of the third transistor M3 is greater when the voltage signal of the second node N2 is greater, and conversely, the degree of opening of the third transistor M3 is smaller when the voltage signal of the second node N2 is smaller.
It should be noted that the output signal is a voltage signal in the application, and because a high-low well is constructed, charge transfer can be performed, so that the voltage difference variation is improved, a voltage amplification function is provided in the fingerprint identification detection circuit, the signal-to-noise ratio is improved, the anti-interference capability is enhanced, and the fingerprint identification precision is improved.
Compared with the prior art, the fingerprint identification driver of the invention at least has the following beneficial effects:
the fingerprint identification detection circuit 00 of the present invention includes: a photodiode 100 for generating charge under illumination, the photodiode 100 comprising a first pole 101 and a second pole 102, the first pole 101 being connected to the reference voltage signal terminal 200, the second pole 102 being connected to the first node N1; a first transistor M1 for turning on in response to a first control signal to transfer the charge transferred to the first node N1 to the second node N2; a second transistor M2, which is turned on in response to the second control signal, for transmitting the driving voltage signal of the driving voltage signal terminal 300 to the second node N2; a third transistor M3 turned on in response to the voltage signal of the second node N2, transmitting the voltage of the second node N2 to the third node N3; a fourth transistor M4 for turning on in response to the third control signal, transmitting the voltage of the third node N3 to the signal output terminal 400; a storage capacitor 500 coupled between the reference voltage signal terminal 200 and a second node N2; the driving voltage of the second transistor M2 is V1The driving voltage of the driving voltage signal terminal 300 is V2The threshold voltage of the second transistor M2 is V3Wherein V is1≥V2+V3(ii) a The driving voltage of the first transistor M1 is V4Wherein V is4≤V2(ii) a The value of the storage capacitor 500 is C1The capacitance of the photodiode 100 is C2Wherein, C1＜C2The invention constructs a high-low voltage well between a first node N1 and a second node N2After the charge at the first node N1 is transferred to the second node N2, the voltage difference variation Δ V2 of the second node N2 is greater than the voltage difference variation Δ V1 of the first node N1, and then the output signal of the transmission signal output end is amplified after passing through the third transistor and the fourth transistor, so that the signal-to-noise ratio is improved, the anti-interference capability of the fingerprint identification circuit is enhanced, and the accuracy of fingerprint identification is improved.
In some alternative embodiments, C1≤1/2C2. With continued reference to fig. 3 to 7, according to the above output signal amplification principle, no further description is provided herein, when C1≤1/2C2In time, according to Q ═ cxv, Δ V2 is greater than or equal to 2 Δ V1, that is, the voltage difference is amplified by at least two times, and at this time, the output signal is obviously amplified, so that the signal-to-noise ratio is improved, the anti-interference capability of the fingerprint identification circuit is enhanced, and the accuracy of fingerprint identification is improved.
Referring to fig. 8, fig. 8 is a schematic structural diagram of another fingerprint identification detection circuit provided by the present invention, in which the first transistor M1, the second transistor M2, the third transistor M3 and the fourth transistor M4 in fig. 8 all have a control terminal, a first terminal and a second terminal.
A control terminal of the first transistor M1 is connected to the first control signal terminal a, a first terminal of the first transistor M1 is connected to the first node N1, and a second terminal of the first transistor M1 is connected to the second node N2;
a control terminal of the second transistor M2 is connected to the second control signal terminal B, a first terminal of the second transistor M2 is connected to the driving voltage signal terminal 300, and a second terminal of the second transistor M2 is connected to the second node N2;
a control terminal of the third transistor M3 is connected to the second node N2, a first terminal of the third transistor M3 is connected to the driving voltage signal terminal 300, and a second terminal of the third transistor M3 is connected to a first terminal of the fourth transistor M4;
a control terminal of the fourth transistor M4 is connected to the third control signal terminal C, a first terminal of the fourth transistor M4 is connected to the second terminal of the third transistor M3, and a second terminal of the fourth transistor M4 is connected to the signal output terminal 400.
The fingerprint identification detection circuit 00 of the present embodiment includes a photodiode 100 for illuminatingThe photodiode 100 includes a first pole 101, a second pole 102, the first pole 101 is connected to the reference voltage signal terminal 200, the second pole 102 is connected to the first node N1; a control terminal of the first transistor M1 is connected to the first control signal terminal a, a first terminal of the first transistor M1 is connected to the first node N1, and a second terminal of the first transistor M1 is connected to the second node N2, and is turned on in response to the first control signal to transfer the charge transferred to the first node N1 to the second node N2; second transistor M2 the control terminal of the second transistor M2 is connected to the second control signal terminal B, the first terminal of the second transistor M2 is connected to the driving voltage signal terminal 300, the second terminal of the second transistor M2 is connected to the second node N2, and is turned on in response to the second control signal, so as to transmit the driving voltage signal of the driving voltage signal terminal 300 to the second node N2; a control terminal of the third transistor M3 is coupled to the second node N2, a first terminal of the third transistor M3 is coupled to the driving voltage signal terminal 300, a second terminal of the third transistor M3 is coupled to a first terminal of the fourth transistor M4, and the third transistor M3 is turned on in response to the voltage signal of the second node N2 to transmit the voltage of the second node N2 to the third node N3; a control terminal of the fourth transistor M4 is connected to the third control signal terminal C, a first terminal of the fourth transistor M4 is connected to the second terminal of the third transistor M3, and a second terminal of the fourth transistor M4 is connected to the signal output terminal 400, and is configured to be turned on in response to the third control signal, so as to transmit the voltage of the third node N3 to the signal output terminal 400; a storage capacitor 500 coupled between the reference voltage signal terminal 200 and a second node N2; the driving voltage of the second transistor M2 is V1The driving voltage of the driving voltage signal terminal 300 is V2The threshold voltage of the second transistor M2 is V3Wherein V is1≥V2+V3(ii) a The driving voltage of the first transistor M1 is V4Wherein V is4≤V2(ii) a The value of the storage capacitor 500 is C1The capacitance of the photodiode 100 is C2Wherein, C1＜C2In this embodiment, a voltage high-low well is formed between the first node N1 and the second node N2, after the charge at the first node N1 is transferred to the second node N2, the voltage difference variation av 2 of the second node N2 is greater than the voltage difference variation av 1 of the first node N1,and then the output signal of the transmission signal output end is amplified after passing through the third transistor and the fourth transistor, so that the signal to noise ratio is improved, the anti-interference capability of the fingerprint identification circuit is enhanced, and the fingerprint identification precision is improved.
With continued reference to fig. 3, the first transistor M1, the second transistor M2, the third transistor M3, and the fourth transistor M4 are all N-type transistors (as shown in fig. 8), or the first transistor, the second transistor, the third transistor, and the fourth transistor are all P-type transistors (not shown).
In the above-described exemplary embodiments, all the transistors are N-type transistors; it will be readily apparent to those skilled in the art that the fingerprinting drive provided by the present disclosure may be readily adapted to a P-type transistor fingerprinting drive. It should be noted that when the first transistor M1, the second transistor M2, the third transistor M3 and the fourth transistor M4 are all P-type transistors, unlike the driving voltage signals provided when the first transistor M1, the second transistor M2, the third transistor M3 and the fourth transistor M4 are all N-type transistors, when the first transistor M1, the second transistor M2, the third transistor M3 and the fourth transistor M4 are all P-type transistors, the driving signal provided by the driving voltage signal terminal is low, for example, when the first transistor M1, the second transistor M2, the third transistor M3 and the fourth transistor M4 are all N-type transistors, the driving signal provided by the driving voltage signal terminal is 5V, the reference voltage of the reference voltage signal terminal 200 is 0V, and when the first transistor M1, the second transistor M2, the third transistor M3 and the fourth transistor M352 are all P-type transistors 4, the driving signal provided by the driving voltage signal terminal is-5V, and the reference voltage of the reference voltage signal terminal 200 is-10V, although the voltage values herein are merely illustrative and not specifically limited.
In some alternative embodiments, with continued reference to fig. 3, the drive voltage V of the second transistor M21Is a high level voltage; drive voltage V of first transistor M14Is a high level voltage. It can be understood that the driving voltage V of the second transistor M21Is a high level voltage, the driving voltage V of the first transistor M14At a high level voltage, V1≥V2+V3It can be ensured that the voltage at the second node N2 is equal to the driving voltage V of the driving voltage signal terminal 300 after the second transistor M2 is turned on2。
Referring to fig. 9, fig. 9 is a schematic structural diagram of another fingerprint identification detection circuit provided by the present invention, in fig. 9, a fingerprint identification detection circuit 00 includes a photodiode 100 for generating electric charge under illumination, the photodiode 100 includes a first pole 101 and a second pole 102, the first pole 101 is connected to a reference voltage signal terminal 200, and the second pole 102 is connected to a first node N1; a control terminal of the first transistor M1 is connected to the first control signal terminal a, a first terminal of the first transistor M1 is connected to the first node N1, and a second terminal of the first transistor M1 is connected to the second node N2, and is turned on in response to the first control signal to transfer the charge transferred to the first node N1 to the second node N2; second transistor M2 the control terminal of the second transistor M2 is connected to the second control signal terminal B, the first terminal of the second transistor M2 is connected to the driving voltage signal terminal 300, the second terminal of the second transistor M2 is connected to the second node N2, and is turned on in response to the second control signal, so as to transmit the driving voltage signal of the driving voltage signal terminal 300 to the second node N2; a control terminal of the third transistor M3 is coupled to the second node N2, a first terminal of the third transistor M3 is coupled to the driving voltage signal terminal 300, a second terminal of the third transistor M3 is coupled to a first terminal of the fourth transistor M4, and the third transistor M3 is turned on in response to the voltage signal of the second node N2 to transmit the voltage of the second node N2 to the third node N3; a control terminal of the fourth transistor M4 is connected to the third control signal terminal C, a first terminal of the fourth transistor M4 is connected to the second terminal of the third transistor M3, and a second terminal of the fourth transistor M4 is connected to the signal output terminal 400, and is configured to be turned on in response to the third control signal, so as to transmit the voltage of the third node N3 to the signal output terminal 400; a storage capacitor 500 coupled between the reference voltage signal terminal 200 and the second node N2, the fingerprint identification driver further includes a driving voltage signal line 91, a first control signal line 93, a second control signal line 94, a third control signal line 95 and an output signal line 92, a control terminal of the first transistor M1 is connected to the first control signal line 93; a control terminal of the second transistor M2 is connected to the second control signal line 94, and a first terminal of the second transistor M2 is connected to the driving voltage signal line 91; a first end of the third transistor M3 is connected to the driving voltage signal line 91; a control terminal of the fourth transistor M4 is connected to the third control signal line 95, and a second terminal of the fourth transistor M4 is connected to the signal output line 92.
With continued reference to fig. 9, fig. 9 only shows the case where the driving voltage signal line 91, the first control signal line 93 and the third control signal line 95 are arranged along the first direction X and extend along the second direction Y, the second control signal line 94 and the signal output line 92 are arranged along the second direction Y and extend along the first direction X, and the driving voltage signal line 91 and the second control signal line 94 intersect, which may be arranged in other forms, and is not limited herein.
The wiring mode is easy to realize, the spatial arrangement is reasonable, the wiring is short, and the noise generated by overlong wiring is reduced.
Based on the same idea, the present invention further provides a detection method of a fingerprint identification detection circuit, which is applied to the fingerprint identification detection circuit described in any one of the above embodiments, with reference to fig. 10 and 11, fig. 10 is a flowchart of a detection method of a fingerprint identification detection circuit provided by the present invention, fig. 11 is a control timing diagram of driving of the fingerprint identification circuit, fig. 11 shows a timing diagram of a second control signal Rst, a first control signal Tx, a third control signal Sel, an output Noise signal Noise, and an output fingerprint identification signal Sig, and the detection method of the fingerprint identification detection circuit in fig. 10 includes the following steps:
referring to fig. 3, 10 and 11 in combination, corresponding to the reset phase T1 in fig. 11, the first control signal Tx and the second control signal Rst are both high-level voltages, and the first transistor M1 is turned on in response to the first control signal Tx; the second transistor M2 is turned on in response to the second control signal Rst to transmit the driving voltage signal of the driving voltage signal terminal 300 to the second node N2, forming a voltage difference between the first node N1 and the second node N2.
102, in an exposure stage, a first transistor is controlled to be turned off through a first control signal, and a photodiode generates charges under the illumination effect and transmits the charges to a first node;
referring to fig. 3, 10 and 11, corresponding to the exposure period T2 in fig. 11, the second control signal Rst is at a high level voltage, the first control signal Tx is at a low level voltage, the first transistor M1 is turned off, the photodiode 100 generates charges under illumination, it is understood that the first pole 101 of the photodiode 100 is connected to the reference voltage signal terminal 200, and when the photodiode 100 is illuminated, i.e., the finger touches the screen, the light source is reflected when it impinges on the valleys and ridges of the finger fingerprint, because the reflection angles of the valley line and the ridge line and the intensity of the reflected light are different, the light is projected onto the photodiode 100, so that the resistance value of the photodiode 100 changes, and charges are generated, at this time, the voltage at the first node N1 changes due to the charges, and at this time, compared with the case of no light, the voltage difference before and after the light at the first node N1 is Δ V1.
103, in the charge transfer stage, the first transistor is controlled to be turned on by the first control signal, and the second transistor is controlled to be turned off by the second control signal, so that the charge at the first node is transferred to the second node;
referring to fig. 3, 10 and 11, in the charge transfer phase T3, the second control signal Rst is at a low level, the first control signal Tx is at a high level, and the third control signal Sel is at a high level, at which time the first transistor M1 is turned on, the second transistor M2 is turned off, and the charge at the first node N1 is transferred to the second node N2.
And 104, in the signal output stage, the third transistor is controlled to be turned on through the voltage signal of the second node, the voltage of the second node is transmitted to the third node, the fourth transistor is controlled to be turned on through the third control signal, and the voltage of the third node is transmitted to the signal output end to be output.
Referring to fig. 3, 10 and 11, corresponding to the signal level sensing T5 in fig. 11, the second control signal Rst is at a low level, the first control signal Tx is at a low level, and the third control signal Tx is at a low levelSel is a high level voltage. When the voltage at the first node N1 can be transferred to the second node N2, the amount of charge before and after the charge transfer is the same, while C in the present invention1＜C2Since the formula Q is the charge amount, C is the capacitance, and V is the voltage, the voltage difference Δ V2 before and after the transition of the second node N2 after the transition is obtained as shown in C × V>Δ V1, when the third transistor M3 is turned on in response to the voltage signal of the second node N2 to transmit the voltage of the second node N2 to the third node N3, and then the fourth transistor M4 is turned on in response to the third control signal to transmit the voltage of the third node N3 to the signal output terminal 400, the voltage difference change amounts are Δ V2, Δ V2>And delta V1, realizing output signal amplification. It is understood that the present invention further includes a reset level readout stage T4, and the reset level readout stage T4 reads out a reference signal of the fingerprint identification detection circuit, which includes a noise reference signal.
According to the invention, the voltage high-low well is constructed between the first node N1 and the second node N2, when the charge at the first node N1 is transferred to the second node N2, the voltage difference variation delta V2 of the second node N2 is larger than the voltage difference variation delta V1 of the first node N1, and then the output signals of the output ends are amplified after passing through the third transistor and the fourth transistor, so that the signal-to-noise ratio is improved, the anti-interference capability of the fingerprint identification circuit is enhanced, and the precision of fingerprint identification is improved.
In some alternative embodiments, when C1≤1/2CpdAnd when the voltage difference value of the output end of the signal is more than or equal to two times of the voltage difference value at the first node. When C is present1≤1/2C2In time, according to Q ═ cxv, Δ V2 is greater than or equal to 2 Δ V1, that is, the voltage difference is amplified by at least two times, and at this time, the output signal is obviously amplified, so that the signal-to-noise ratio is improved, the anti-interference capability of the fingerprint identification circuit is enhanced, and the accuracy of fingerprint identification is improved.
In some optional embodiments, please refer to fig. 12, where fig. 12 is a schematic structural diagram of a display device according to an embodiment of the present invention, and the display device 111 according to this embodiment includes the fingerprint identification detection circuit 00 according to the above embodiment. The embodiment of fig. 12 is only an example of a mobile phone, and the display device 111 is described, it is understood that the display device 111 provided in the embodiment of the present invention may be another display device 111 having a display function, such as a computer, a television, an electronic paper, and a vehicle-mounted display device, and the present invention is not limited thereto. The display device 111 provided in the embodiment of the present invention has the beneficial effects of the fingerprint identification detection circuit 00 provided in the embodiment of the present invention, and specific descriptions of the fingerprint identification detection circuit 00 in the above embodiments may be specifically referred to, and this embodiment is not described herein again.
By the above embodiments, the fingerprint identification detection circuit, the fingerprint identification detection method and the fingerprint identification display device provided by the invention at least achieve the following beneficial effects:
the fingerprint identification detection circuit of the present invention includes: the photodiode is used for generating electric charges under the action of illumination and comprises a first pole and a second pole, wherein the first pole is connected with a reference voltage signal end, and the second pole is connected to a first node; the first transistor is used for responding to a first control signal and conducting, and transmitting the charges transmitted to the first node to the second node; the second transistor is used for responding to a second control signal and conducting, and transmitting a driving voltage signal of the driving voltage signal end to a second node; the third transistor is used for responding to the voltage signal of the second node and conducting, and transmitting the voltage of the second node to the third node; a fourth transistor turned on in response to a third control signal, transmitting a voltage of the third node to the signal output terminal; the storage capacitor is coupled between the reference voltage signal end and the second node; the driving voltage of the second transistor is V1The driving voltage at the driving voltage signal terminal is V2The threshold voltage of the second transistor is V3Wherein V is1≥V2+V3(ii) a The driving voltage of the first transistor M1 is V4Wherein V is4≤V2(ii) a The value of the storage capacitor is C1The capacitance of the photodiode is C2，C1＜C2The invention constructs a voltage high-low well between the first node and the second node, after the charge at the first node is transferred to the second node, the voltage difference change quantity delta V2 of the second node is larger than the voltage difference change quantity delta V1 of the first node N1, and then the third node is passed throughThe output signal of the transmission signal output end behind the transistor and the fourth transistor is amplified, the signal to noise ratio is improved, the anti-interference capability of the fingerprint identification circuit is enhanced, and then the accuracy of fingerprint identification is improved.
Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.
Claims (10)
1. A fingerprint identification detection circuit, comprising:
the photodiode is used for generating electric charges under the action of illumination and comprises a first pole and a second pole, wherein the first pole is connected with a reference voltage signal end, and the second pole is connected to a first node;
a first transistor for being turned on in response to a first control signal, and transferring the charge transferred to the first node to a second node;
a second transistor for turning on in response to a second control signal and transmitting a driving voltage signal of a driving voltage signal terminal to the second node;
a third transistor turned on in response to a voltage signal of a second node, transmitting a voltage of the second node to a third node;
a fourth transistor turned on in response to a third control signal, transmitting a voltage of the third node to the signal output terminal;
a storage capacitor coupled between the reference voltage signal terminal and the second node;
the driving voltage of the second transistor is V1The driving voltage of the driving voltage signal end is V2The threshold voltage of the second transistor is V3Wherein V is1≥V2+V3；
The driving voltage of the first transistor is V4Wherein V is4≤V2；
The value of the storage capacitor is C1The capacitance of the photodiode is C2Wherein, C1＜C2。
2. The fingerprint identification detection circuit of claim 1, wherein C is1≤1/2C2。
3. The fingerprint recognition detection circuit of claim 1, wherein the first transistor, the second transistor, the third transistor, and the fourth transistor each have a control terminal, a first terminal, and a second terminal, wherein,
the control end of the first transistor is connected with a first control signal end, the first end of the first transistor is connected with the first node, and the second end of the first transistor is connected with the second node;
the control end of the second transistor is connected with a second control signal end, the first end of the second transistor is connected with a driving voltage signal end, and the second end of the second transistor is connected with the second node;
a control end of the third transistor is connected with the second node, a first end of the third transistor is connected with the driving voltage signal end, and a second end of the third transistor is connected with a first end of a fourth transistor;
the control end of the fourth transistor is connected with a third control signal end, the first end of the fourth transistor is connected with the second end of the third transistor, and the second end of the fourth transistor is connected with a signal output end.
4. The fingerprint identification detection circuit according to any one of claims 1 to 3, wherein the first transistor, the second transistor, the third transistor and the fourth transistor are all N-type transistors, or the first transistor, the second transistor, the third transistor and the fourth transistor are all P-type transistors.
5. The fingerprint identification detection circuit of claim 1, wherein the drive voltage V of the second transistor is V1Is a high level voltage; a drive voltage V of the first transistor4Is a high level voltage.
6. The fingerprint identification detection circuit of claim 3, further comprising a drive voltage signal line, a first control signal line, a second control signal line, a third control signal line, and an output signal line, wherein,
the control end of the first transistor is connected with the first control signal line;
the control end of the second transistor is connected with the second control signal line, and the first end of the second transistor is connected with the driving voltage signal line;
a first end of the third transistor is connected to the driving voltage signal line;
a control terminal of the fourth transistor is connected to the third control signal line, and a second terminal of the fourth transistor is connected to the signal output line.
7. The fingerprint identification detection circuit of claim 6, wherein the driving voltage signal line, the first control signal line and the third control signal line are arranged along a first direction and extend along a second direction, the second control signal line and the signal output line are arranged along the second direction and extend along the first direction, and the driving voltage signal line and the second control signal line intersect.
8. A method for detecting a fingerprint identification detection circuit, applied to the fingerprint identification detection circuit of any one of claims 1 to 7, the method comprising:
in the reset stage, the second transistor is controlled to be turned on by the second control signal, a driving voltage signal of a driving voltage signal end is transmitted to the second node, and the first transistor is controlled to be turned on by the first control signal;
the exposure stage is used for controlling the first transistor to be cut off through the first control signal, and the photodiode generates charges under the action of illumination and transmits the charges to a first node;
a charge transfer phase, wherein the first transistor is controlled to be turned on by the first control signal, and the second transistor is controlled to be turned off by the second control signal, so that the charge at the first node is transferred to a second node;
and in the signal output stage, the third transistor is controlled to be turned on by the voltage signal of the second node, the voltage of the second node is transmitted to the third node, the fourth transistor is controlled to be turned on by the third control signal, and the voltage of the third node is transmitted to a signal output end to be output.
9. The method as claimed in claim 8, wherein the time C is1≤1/2CpdAnd when the voltage difference value of the output end of the signal is more than or equal to two times of the voltage difference value at the first node.
10. A display device comprising a fingerprint recognition drive according to any one of claims 1 to 7.
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