CN111079719A - Ultrasonic circuit, fingerprint identification sensor and electronic equipment - Google Patents
Ultrasonic circuit, fingerprint identification sensor and electronic equipment Download PDFInfo
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- 229920002981 polyvinylidene fluoride Polymers 0.000 description 8
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- ZGEYCCHDTIDZAE-BYPYZUCNSA-N L-glutamic acid 5-methyl ester Chemical compound COC(=O)CC[C@H](N)C(O)=O ZGEYCCHDTIDZAE-BYPYZUCNSA-N 0.000 description 2
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- 239000004417 polycarbonate Substances 0.000 description 2
- 229920000515 polycarbonate Polymers 0.000 description 2
- 229920000915 polyvinyl chloride Polymers 0.000 description 2
- 239000004800 polyvinyl chloride Substances 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
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- MIZLGWKEZAPEFJ-UHFFFAOYSA-N 1,1,2-trifluoroethene Chemical group FC=C(F)F MIZLGWKEZAPEFJ-UHFFFAOYSA-N 0.000 description 1
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- 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
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Abstract
The invention relates to the technical field of ultrasonic waves, in particular to an ultrasonic circuit, a fingerprint identification sensor and electronic equipment, which comprise an ultrasonic transceiver, a driving circuit and a power supply circuit which are electrically connected in sequence, wherein the driving circuit comprises TFT transistors M2, M4 and M5, the TFT transistors comprise grid electrodes G, a first electrode and a second electrode, the first electrode of the M2 is electrically connected with the ultrasonic transceiver, the grid electrodes G of the M2 and the M4 are connected with an external circuit and are connected with a control signal, the second electrode of the M2 is electrically connected with the grid electrode G of the M5, the first electrode and the second electrode of the M5 are electrically connected with the grid electrode G of the M4, and the second electrode of the M4 outputs sampling current. The circuit can be ensured to be always in a charging state but not a saturation state in a signal sampling stage, and meanwhile, the effect of the isolating switch for transmitting and receiving ultrasonic waves is achieved, so that the acquired data are more accurate and reliable.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of ultrasonic waves, in particular to an ultrasonic circuit, a fingerprint identification sensor and electronic equipment.
[ background of the invention ]
The ultrasonic wave is widely applied to the fields of industrial nondestructive inspection, distance measurement and thickness measurement, agricultural ultrasonic breeding, ultrasonic seedling culture and ultrasonic induced spawning, biomedical diagnosis and operation, fingerprint identification in consumer electronics products and the like.
In the field of ultrasound applications, the ultrasound transmit circuitry is a critical component in the system. With the development of electronic technology and the increasing requirements of measuring devices and the like in terms of performance and precision, such as fingerprint identification modules, it has been developed towards high precision, high sensitivity and low power consumption. However, at present, there are many methods for designing ultrasonic circuits, but the circuits are always in a non-saturated state in the process of sampling ultrasonic signals, and there is no isolation effect between the received and transmitted ultrasonic signals, so that the acquired data have deviation.
[ summary of the invention ]
In order to overcome the problems in the prior art, the invention provides an ultrasonic circuit, a fingerprint identification sensor and electronic equipment.
The technical scheme for solving the technical problem is to provide an ultrasonic circuit: the ultrasonic wave transceiver, the driving circuit and the power circuit are electrically connected in sequence, wherein the driving circuit comprises a TFT transistor M2, a TFT transistor M4 and a TFT transistor M5, the TFT transistor M2, the TFT transistor M4 and the TFT transistor M5 respectively comprise a grid G, a first electrode and a second electrode, the first electrode of the TFT transistor M2 is electrically connected with the ultrasonic wave transceiver to form an electrical junction J, the grid G of the TFT transistor M2 and the grid G of the TFT transistor M4 are both connected with an external circuit and are connected with a control signal, the second electrode of the TFT transistor M2 and the grid G of the TFT transistor M5 are electrically connected to form an electrical junction pe, the first electrode and the second electrode of the TFT transistor M5 are electrically connected with the grid G of the TFT transistor M4, and the second electrode of the TFT transistor M4 outputs sampling current.
Preferably, the ultrasonic circuit further comprises a power supply circuit, the power supply circuit comprises a stabilized voltage power supply Vi, the driving circuit further comprises a TFT transistor M3, a first electrode of the TFT transistor M3 is electrically connected with the stabilized voltage power supply Vi, a second electrode of the TFT transistor M3 is electrically connected with a first electrode of the TFT transistor M4, and a gate G of the TFT transistor M3 is electrically connected with the electrical node pe.
Preferably, the power circuit further includes an adjustable voltage source Dv, the driving circuit further includes a TFT transistor M1, the second electrode of the TFT transistor M1 is electrically connected to the adjustable voltage source Dv, the first electrode of the TFT transistor M1 is electrically connected to the electrical node J, and the gate G of the TFT transistor M1 is connected to an external circuit for inputting a control signal.
Preferably, when the input of the control signal causes the TFT transistor M1, the TFT transistor M2 and the TFT transistor M4 to be all in conduction, the ultrasonic circuit is in a reset/initialization state;
when the input control signal causes the TFT transistor M1 to be turned on, the TFT transistor M2 and the TFT transistor M4 are both turned off, the current of the adjustable voltage source Dv flows through the TFT transistor M1 to the electrical junction J and not to the ultrasonic transceiver, and the ultrasonic circuit is in the ultrasonic pre-transmitting state;
when the ultrasonic circuit is in an ultrasonic wave pre-transmitting state, the current of the adjustable voltage source Dv reaches the ultrasonic transceiver, and the ultrasonic circuit is in an ultrasonic wave transmitting state.
Preferably, when the input control signal causes the TFT transistor M1 to be in the non-saturation charging mode, the TFT transistor M2 is turned on, the TFT transistor M4 is turned off, the current of the adjustable voltage source Dv flows through the TFT transistor M1, the current passes through the TFT transistor M2 and does not reach the electrical node pe, and the ultrasonic circuit is in the ultrasonic pre-receiving state;
when the ultrasonic circuit is in an ultrasonic wave pre-receiving state, the voltage value of the adjustable voltage source Dv is adjusted and increased, the current of the adjustable voltage source Dv reaches an electrical node pe to charge the TFT transistor M5, and at the moment, the voltage value of the electrical node pe is gradually increased, and the ultrasonic circuit is in an ultrasonic wave receiving state.
Preferably, after the TFT transistor M5 is charged for a preset time, the TFT transistor M2 and the TFT transistor M1 are sequentially turned off, the Dv voltage value is adjusted to be reduced to 0V, and the ultrasonic circuit is in an ultrasonic pre-reading state;
when the ultrasonic circuit is in an ultrasonic pre-reading state, when a control signal is input to enable the TFT transistor M4 to be conducted, the TFT transistor M4 outputs sampling current, and the ultrasonic circuit is in an ultrasonic reading state;
after the reflected ultrasonic signals are collected and read, the TFT transistors M1, M2, M3, M4 and M5 all restore the initial setting state, so that the ultrasonic circuit enters the next working cycle of the cycle, and the ultrasonic circuit is in the ending state at the moment.
Preferably, the charging time of the TFT transistor M5 is less than 50 ns.
Preferably, the parasitic capacitance of the TFT transistor M5 has a capacitance of 0.1Pf to 0.5 Pf.
Preferably, a fingerprint identification sensor includes ultrasonic circuit, signal generator and signal acquisition circuit, signal generator with drive circuit connects and provides input control signal for it, drive circuit with ultrasonic transceiver signal acquisition circuit electric connection, signal acquisition circuit is used for gathering the ultrasonic emission signal of feeding back to calculate according to the sampling current and obtain fingerprint information.
Preferably, an electronic device includes the fingerprint identification sensor and a touch interface, wherein the fingerprint identification sensor is electrically connected to the touch interface.
Compared with the prior art, the ultrasonic circuit has the following beneficial effects:
1. an ultrasonic circuit comprises an ultrasonic transceiver, a driving circuit and a power circuit which are electrically connected in sequence, wherein the driving circuit comprises three TFT transistors M2, a TFT transistor M4 and a TFT transistor M5, all the TFT transistors comprise a grid G, a first electrode and a second electrode, the first electrode of the TFT transistor M2 is electrically connected with the ultrasonic transceiver to form an electrical junction J, the grid G of the TFT transistor M2 and the grid G of the TFT transistor M4 are connected with an input control signal, the second electrode of the TFT transistor M2 is electrically connected with the grid G of the TFT transistor M5 to form an electrical junction pe, the first electrode and the second electrode of the TFT transistor M5 are electrically connected with the grid G of the TFT transistor M4, and the second electrode of the TFT transistor M4 outputs sampling current. The circuit can be ensured to be always in a charging state but not a saturation state in a signal sampling stage, and meanwhile, the effect of the isolating switch for transmitting and receiving ultrasonic waves is achieved, so that the acquired data are more accurate and reliable.
2. The first electrode of the TFT transistor M3 in the ultrasonic circuit is electrically connected with a stabilized voltage power supply Vi, and the second electrode of the TFT transistor M4 is electrically connected with the first electrode of the TFT transistor M3, so that the static working points of the TFT transistors M4 and M3 are adjusted, and current is output to the TFT transistors M3 and M4.
3. The TFT transistor M1 is adopted in the ultrasonic circuit, and mainly when the charging time of the TFT transistor M5 is less than 50ns, the narrow pulse width signal can be generated more easily by adopting the time difference between the mutual conduction and the mutual closing of the TFT transistors M2 and M1.
4. In the ultrasonic circuit of the present invention, the TFT transistor M5 is regarded as a capacitor in the application process, and its parasitic capacitance has a large capacitance value to ensure that it is in an unsaturated charging state in the reading stage of the ultrasonic circuit, and can keep the charged voltage until the next data update, so that it needs to use the parasitic capacitance of the TFT transistor M5 as a storage capacitor to store more electric quantity for keeping.
5. The ultrasonic circuit is applied to the field of fingerprint identification of a fingerprint identification sensor and electronic equipment, and has application value.
[ description of the drawings ]
FIG. 1 is a block diagram of an ultrasonic circuit according to a first embodiment of the present invention;
FIG. 2 is a schematic diagram of a specific circuit structure of an ultrasonic circuit according to a second embodiment of the present invention based on the first embodiment;
FIG. 3 is a schematic diagram of an actual TFT transistor analysis of the ultrasonic circuit of the present invention;
FIG. 4 is a schematic diagram of an equivalent analysis circuit of an ultrasonic circuit according to a third embodiment of the present invention based on the second embodiment;
FIG. 5 is a waveform diagram showing the circuit simulation effect of the ultrasonic circuit according to the third embodiment of the present invention based on the second embodiment;
FIG. 6 is a block diagram of a fingerprint sensor according to a fourth embodiment of the present invention;
fig. 7 is a schematic diagram of an electronic device according to a fifth embodiment of the invention.
Description of reference numerals:
10. an ultrasonic circuit; 11. a power supply circuit; 12. a drive circuit; 12. an ultrasonic transceiver; 131. a piezoelectric film; 132. an Ag film; 133. an ITO film.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, a first embodiment of the present invention provides an ultrasonic circuit 10, which includes an ultrasonic transceiver 13, a driving circuit 12 and a power circuit 11 electrically connected in sequence. The ultrasonic transceiver 13 has a piezoelectric effect and is configured to transmit an ultrasonic signal and receive the ultrasonic signal reflected back after transmission, the driving circuit 12 is configured to amplify an input control signal to be provided to the ultrasonic transceiver 13 as a driving source, the power circuit 11 provides power for the driving circuit 12, and may also provide a certain current driving capability to drive a circuit at a later stage to operate.
The ultrasonic circuit 10 provided by the invention is mainly used for generating and transmitting ultrasonic signals and receiving reflected ultrasonic signals, and converting the ultrasonic signals into electric signals to acquire, output and analyze the acquired fingerprint information, and is widely applied to the field of fingerprint identification of electronic equipment.
Referring to fig. 2, as an embodiment, the ultrasonic transceiver 13 includes a piezoelectric film 131. The piezoelectric film is an in-situ polarized piezoelectric film, namely the piezoelectric film is formed by polarization in an in-situ polarization mode. Specifically, the piezoelectric film is formed in situ on one surface of a substrate, and comprises a first surface and a second surface which are opposite to each other, so that the potential of the first surface of the piezoelectric film is zero; providing a first electric field and a second electric field at the side of the second surface of the piezoelectric film, wherein the potential of the first electric field is higher than that of the second electric field; and ionizing the ambient gas on the side where the second surface of the piezoelectric film is located under the action of the first electric field, wherein the ambient gas passes through the second electric field and is gathered on the second surface of the piezoelectric film, so that an intra-film electric field in the film thickness direction is formed in the piezoelectric film, and the piezoelectric film is polarized to form the piezoelectric film.
In actual production, the piezoelectric film may be formed on the substrate by chemical vapor deposition, physical vapor deposition, plasma sputtering, or the like. In the prior art, the piezoelectric film is usually polarized by purchasing an existing finished product and adhering the finished product on a substrate through an adhesive layer, and the thickness of the piezoelectric film formed by the method is usually more than 30 μm, which is not suitable for the development trend of lightness and thinness of the existing electronic device. The piezoelectric film provided by the invention is formed on the substrate in situ, so that the thickness is very thin, and the forming process is simple, thereby reducing the transmission loss of signals. In addition, compared with the method of directly arranging the electrodes on the upper surface and the lower surface of the film, the method of the invention can not make the piezoelectric film directly bear the applied high-voltage electric field and can prevent the film from being broken down. The piezoelectric film can be formed by adopting a plasma polarization (see the Chinese patent application with the application number of 201710108374.9 specifically) or an X-ray polarization (see the Chinese patent application with the application number of 201611222575.3 specifically), the formed piezoelectric film can be very thin, the piezoelectric effect is good, the service life is long, and the range of the piezoelectric effect of the piezoelectric film subjected to in-situ polarization is 20-35 pC/N.
The piezoelectric film is made of a piezoelectric material, and can be selected from but not limited to: polyvinylidene fluoride, polyvinyl chloride, poly-gamma-methyl-L-glutamate, polycarbonate and polyvinylidene fluoride copolymer or a combination of a plurality of the polyvinylidene fluoride, the polyvinyl chloride, the poly-gamma-methyl-L-glutamate, the polycarbonate and the polyvinylidene fluoride copolymer.
In some embodiments of the present invention, the piezoelectric film is made of polyvinylidene fluoride copolymer, which is polyvinylidene fluoride-trifluoroethylene copolymer, and in order to obtain a piezoelectric film with a better piezoelectric effect, the mass ratio of polyvinylidene fluoride to trifluoroethylene is in the range of (60-95): (5-30), preferably, the mass ratio thereof is in the range of (75-86): (15-25), further preferably, the mass ratio is 80: 20, compared with the polyvinylidene fluoride selected independently, the polyvinylidene fluoride and trifluoroethylene copolymer can reduce the cost and has better piezoelectric effect.
The thickness of the piezoelectric thin film is less than 30 μm, and the thickness may be further less than 9 μm, and further the thickness may be 1.5 to 7.4 μm, 1.9 to 7.2 μm, 2.2 to 8.6 μm, 2.8 to 8.4 μm, or 3.6 to 6.6 μm, and further, may be specifically 1.8 μm, 2.4 μm, 2.6 μm, 3.7 μm, 3.9 μm, 4.2 μm, 4.6 μm, 5.6 μm, 5.8 μm, 6.7 μm, 8.6 μm, 8.7 μm.
The ultrasonic transceiver 13 further comprises an Ag film 132 sprayed on the upper surface of the piezoelectric film 131 facing the air, and the Ag film 132 has low surface resistance, so that when the Ag film 132 is in contact with a fingerprint, the electrode of the Ag film has better charge conduction performance and is applied; the lower surface of the piezoelectric film 131 facing the circuit to be electrically connected to the driving circuit 12 is coated with an ITO film 133, which is widely used because of its high electrical conductivity, high visible light transmittance, high mechanical hardness, and good chemical stability.
With reference to fig. 1 and fig. 2, a second embodiment of the present invention provides an ultrasonic circuit 10, which can be understood as a specific circuit configuration scheme of the first embodiment. The power circuit 11 comprises a stabilized voltage power supply Vi and an adjustable voltage source Dv, and the stabilized voltage power supply Vi and the adjustable voltage source Dv both have a positive pole and a negative pole. The driving circuit 12 includes five TFT transistors, which are a TFT transistor M1, a TFT transistor M2, a TFT transistor M3, a TFT transistor M4, and a TFT transistor M5, wherein each of the five TFT transistors includes a gate G and a first electrode and a second electrode. A gate G, TFT of the TFT transistor M1, a gate G of the transistor M2 and a gate G of the TFT transistor M4 are both connected to an input control signal, a first electrode of the TFT transistor M1 is electrically connected to a first electrode of the TFT transistor M2 and the ITO thin film 133 of the ultrasonic transceiver 13 to form an electrical junction J, a second electrode of the TFT transistor M1 is electrically connected to the adjustable voltage source Dv, the adjustable voltage source Dv can adjust a voltage value input to the second electrode of the TFT transistor M1, a second electrode of the TFT transistor M2 is electrically connected to the gate G of the TFT transistor M3 and the gate G of the TFT transistor M5 to form an electrical junction pe, a first electrode and a second electrode of the TFT transistor M5 are electrically connected to the gate G of the TFT transistor M4, a first electrode of the TFT transistor M3 is electrically connected to a regulated voltage source Vi to provide a power source for the driving circuit 12, and a second electrode of the TFT transistor M3 is electrically connected to the first electrode of the TFT transistor M4, finally, the second electrode of the TFT transistor M4 outputs the sampling current Io, so that the external information to be measured can be analyzed and identified.
In another embodiment of this embodiment, the driving circuit 12 may further include three TFT transistors, which are the TFT transistor M2, the TFT transistor M4, and the TFT transistor M5, wherein the first electrode of the TFT transistor M2 is electrically connected to the ultrasonic transceiver to form an electrical node J, the gates G of the TFT transistor M2 and the TFT transistor M4 are both connected to an external circuit and are connected to a control signal, the second electrode of the TFT transistor M2 and the gate G of the TFT transistor M5 are electrically connected to form an electrical node pe, the first electrode and the second electrode of the TFT transistor M5 are electrically connected to the gate G of the TFT transistor M4, and the second electrode of the TFT transistor M4 outputs a sampling current. The external information to be measured can be analyzed and identified.
Referring to fig. 3, in order to better understand the operation principle and the technical effect of the ultrasonic circuit 10 according to the second embodiment of the present invention, it is necessary to analyze the TFT transistors as follows:
it is understood that the first electrode of the TFT transistor referred to in the present invention may be either the drain electrode D or the source electrode S of the TFT transistor, and the second electrode is opposite to the first electrode, that is, if the first electrode is the drain electrode D of the TFT transistor, the second electrode is the source electrode S of the TFT transistor; if the first electrode is the source S of the TFT transistor, the second electrode is the drain D of the TFT transistor.
It is understood that the TFT transistor may be any one of an N-type field effect transistor or a P-type field effect transistor.
In the actual production manufacturing process of the TFT transistor, since metal layer leads are employed as electrodes on the gate G, the drain D, and the source S of the TFT transistor, the actual TFT transistor includes an ideal transistor and mutual parasitic capacitances of the three electrodes to the ground GND, respectively, and mutual parasitic capacitances between the three electrodes. That is, the gate G and the drain D of the ideal transistor form a parasitic capacitance Cgd, the gate G and the source S form a parasitic capacitance Cgs, the drain D and the source S form a parasitic capacitance Cds, the gate G and the ground GND form a parasitic capacitance Cgd, the source S and the ground GND form a parasitic capacitance Csd, and the drain D and the ground GND form a parasitic capacitance Cdd.
To better explain the ultrasonic circuit 10 provided in the second embodiment, the TFT transistor M5 may be further equivalent to three capacitors by analyzing the TFT transistor in fig. 3 and using an equivalent circuit analysis method in the circuit analysis method, and please refer to fig. 4, in which the equivalent partial circuits are connected as follows: the first electrode of the capacitor C1 and the first electrode of the capacitor C2 are electrically connected to the electrical node pe, the second electrode of the capacitor C2 and the first electrode of the capacitor C3 are electrically connected to the gate G of the TFT transistor M4, and the second electrode of the capacitor C1 and the second electrode of the capacitor C3 are both connected to the ground GND. The equivalent capacitance value of the capacitor C1 is equal to 2Cgd, that is, C1 is equal to 2Cgd, the equivalent capacitance value of the capacitor C2 is equal to Cgs and Cds, that is, C2 is equal to Cgs + Cds, and the equivalent capacitance value of the capacitor C3 is equal to Cdd and Csd, that is, C2 is equal to Cdd + Csd. The TFT transistor M5 is a TFT transistor with a large capacitance value of parasitic capacitance, for example, the capacitance value of the parasitic capacitance is 0.1Pf to 0.5Pf, so as to ensure a non-saturated charging state during the ultrasonic reading stage.
With continuing reference to fig. 4 and 5, the working principle of the specific actual circuit of the ultrasonic circuit 10 of the second embodiment can be better understood by analyzing the working principle of the equivalent circuit of the ultrasonic circuit 10, which includes 8 working modes or working states and flows, as follows:
state S1: when the input control signals En1, En2, and En3 are respectively input to the gate G, TFT of the TFT transistor M1, the gate 2 of the transistor M2, and the gate G of the TFT transistor M4, the TFT transistor M1, the TFT transistor M2, and the TFT transistor M4 are all made conductive. The current of the adjustable voltage source Dv flows through the TFT transistor M1, through the TFT transistor M2, the capacitor C2 and the capacitor C3 to the ground GND, while the second electrode of the TFT transistor M4 outputs the sampling current Io equal to 0. At this time, the ultrasonic circuit 10 is in a reset/initialization state (abbreviated as RST), and the voltage value of the electrical node pe, the voltage value of the Ag film 132 on the ultrasonic transceiver 13, and the voltage value of the ITO film 133 on the ultrasonic transceiver 13 are all 0V, so that the charge amounts on the capacitor C1, the capacitor C2, and the capacitor C3 are all 0.
State S2: when the input control signals En1, En2, and En3 are respectively input to the gate G, TFT of the TFT transistor M1, the gate 2 of the transistor M2, and the gate G of the TFT transistor M4, respectively, the TFT transistor M1 is caused to be turned on, and both the TFT transistor M2 and the TFT transistor M4 are turned off. The current of the adjustable voltage source Dv flows through the TFT transistor M1 to the electrical junction J and has not yet reached the ITO film 133 of the ultrasonic transceiver 13, while the second electrode of the TFT transistor M4 outputs a sampling current Io equal to 0. At this time, the ultrasonic circuit 10 is in the ultrasonic Pre-transmitting state (Pre Tx for short), and the voltage value of the electrical node pe, the voltage value of the Ag film on the ultrasonic transceiver, and the voltage value of the ITO film on the ultrasonic transceiver are all 0V, so that the charge amounts on the capacitor C1, the capacitor C2, and the capacitor C3 are all 0.
State S3: when the ultrasonic circuit 10 is in an ultrasonic Pre-transmitting state (Pre Tx for short), the current of the adjustable voltage source Dv reaches the ITO film 133 of the ultrasonic transceiver 13, and the second electrode of the TFT transistor M4 outputs a sampling current Io equal to 0. At this time, the ultrasonic circuit 10 is in an ultrasonic wave emitting state (Tx for short), the voltage value of the electrical node pe is measured to be 0V, the ITO film 133 on the ultrasonic transceiver 13 generates a high voltage signal, and the Ag film 132 on the ultrasonic transceiver 13 couples the high voltage signal from the ITO film 133, so that the charge amounts on the capacitor C1, the capacitor C2 and the capacitor C3 are all 0.
State S4: an appropriate input control signal En1 is input to the gate G of TFT transistor M1, e.g., 5V, in accordance with the transfer current profile of TFT transistor M1 in order to adjust the state of the charge mode when TFT transistor M1 is in non-saturation, while input control signals En2 and En3 are input to the gate G of TFT transistor M2 and the gate G of TFT transistor M4, respectively, to cause the TFT transistor M2 to be on and the TFT transistor M4 to be off. The current Ids of the adjustable voltage source Dv flows through the TFT transistor M1, passes through the TFT transistor M2 and has not yet reached the electrical node pe, while the second electrode of the TFT transistor M4 outputs the sampling current Io equal to 0. At this time, the ultrasonic circuit 10 is in the ultrasonic Pre-receiving state (Pre Rx), and the voltage value of the electrical node pe, the voltage value of the Ag film 132 on the ultrasonic transceiver 13, and the voltage value of the ITO film 133 on the ultrasonic transceiver 13 are all 0V, so that the charge amount of the capacitor C1, the capacitor C2, and the capacitor C3 are all 0.
State S5: when the ultrasonic circuit is in an ultrasonic wave pre-receiving state, the voltage value of the adjustable voltage source Dv is adjusted and increased according to the time for receiving the reflected ultrasonic wave and the transfer current curve of the TFT transistor M1. The current Ids of the adjustable voltage source Dv reaches the electrical node pe to charge the equivalent capacitor C1 and the equivalent capacitor C2 of the TFT transistor M5, and the voltage value of the electrical node pe gradually increases, and at this time, the ultrasonic circuit 10 is in an ultrasonic receiving state (abbreviated as Rx).
State S6: after the equivalent capacitors C1 and C2 of the TFT transistor M5 are charged for a preset time, the input control signal En2 is input to the TFT transistor M2 to turn off the TFT transistor M2, the input control signal En1 is input to the TFT transistor M1 to turn off the TFT transistor M1, and finally the voltage value of the adjustable voltage source Dv is adjusted to be reduced to 0V. At this time, the ultrasonic circuit 10 is in an ultrasonic Pre-read state (Pre Readout). It can be appreciated that when the charging time is <50ns, it is difficult to generate a narrow pulse width signal with a single TFT transistor, so it is easy to generate the same narrow pulse width signal with the time difference between the TFT transistors M2 and M1 turning on and off.
State S7: when the ultrasonic circuit is in the ultrasonic pre-reading state, because the capacitance value of the charged capacitor C2 is greater than that of the capacitor C1, the input control signal En3 applied to the gate G of the TFT transistor M4 causes the TFT transistor M4 to be turned on, and the second electrode of the TFT transistor M4 outputs the sampling current Io. At this time, the ultrasonic circuit 10 is in an ultrasonic reading state (Readout).
State S8: after the reflected ultrasonic signals are collected and read, when control signals En1, En2 and En3 are respectively input to the gate G, TFT of the TFT transistor M1, the gate G of the transistor M2 and the gate G of the TFT transistor M4 to restore the settings of various signals generated during the operation of the ultrasonic circuit, that is, the TFT transistors M1, M2, M3, M4 and M5 are all restored to the initial setting state, so that the ultrasonic circuit 10 enters the next cycle of operation. At this time, the ultrasonic circuit 10 is in an End state (End for short).
In summary, the analysis operation of the ultrasonic circuit 10 for fingerprint recognition is as follows:
step P1: when the ultrasonic circuit 10 is in an ultrasonic receiving state (Rx for short), the ultrasonic signal can be obtained by transmitting the ultrasonic signal to receiving the reflected ultrasonic signal;
that is, it can be understood that, in the above step P1, the voltage V at the gate G of the TFT transistor M1En1And a voltage V of the first electrode of the TFT transistor M1ITOBetween which a voltage difference av is generatedg1(ii) a A current variation amount Δ Ids is generated in the TFT transistor M1, which causes a variation in the amount of charge Δ Q;
step P2: when the ultrasonic circuit 10 is in an ultrasonic Pre-reading state (Pre Readout for short), the voltage value of the electrical node pe can be measured, and the corresponding calculation formula is shown in formula (1):
wherein,
the average value of the current in the charging time t of the capacitor C1 and the capacitor C2 after the TFT transistor M5 is equalized for Δ Ids, and the corresponding calculation formula is shown in formula (2):
wherein, the charging time t of the capacitor C1 and the capacitor C2 after the TFT transistor M5 is equivalent is equal to the closing time t of the TFT transistor M2M2Minus the rise time t of the adjustable voltage source DvDvThe corresponding calculation formula is shown in formula (3):
t＝tM2-tDv； (3)
step P3: when the ultrasonic circuit 10 is in an ultrasonic reading state (Readout for short), the voltage value of the electrical node pe at that time can be measured, and the corresponding calculation formula is shown in formula (4):
Vpe2＝Vpe1+VgM4*C2/(C1+C2)； (4)
VgM4, a voltage value of a control signal En3 is loaded on the grid G of the TFT transistor M4 for the time;
step P4: in conjunction with the above equations (1) to (3), the relationship between the amount of change Δ Ids in the current generated in the TFT transistor M1 and the time t corresponding to the change Δ Q in the amount of charge according to the law of conservation of charge can be expressed by the following equation (5):
ΔQ＝ΔIds*t； (5)
thus, the variation Δ I of the second electrode output sampling current Io of the TFT transistor M4 can be analyzed by calculation in combination with the above equations (1) to (5)OTherefore, the external information to be measured can be analyzed and identified.
Referring to fig. 6, the ultrasonic driving circuit of the present invention is applied to a fingerprint sensor 20, and is mainly used for fingerprint identification, and includes a power circuit 11, a driving circuit 12, an ultrasonic transceiver 13, a signal generator 21 and a signal acquisition circuit 22, where the power circuit 11 provides power for the whole circuit system of the fingerprint sensor 20, the signal generator 21 is electrically connected to the driving circuit 12 and provides an input control signal for the driving circuit, the driving circuit 12 is electrically connected to the ultrasonic transceiver 13 and the signal acquisition circuit 22, and the signal acquisition circuit 22 is used to acquire an ultrasonic emission signal fed back and calculate fingerprint information according to a sampling current.
Referring to fig. 7, the ultrasonic circuit of the present invention is applied to an electronic device 30, which includes a touch interface 301 for fingerprint recognition, and the fingerprint recognition sensor 20 is electrically connected to the touch interface. The electronic device 30 may be a mobile phone, a computer, an intelligent wearable device, an intelligent home device, or the like.
Compared with the prior art, the ultrasonic circuit has the following beneficial effects:
1. an ultrasonic circuit comprises an ultrasonic transceiver, a driving circuit and a power circuit which are electrically connected in sequence, wherein the driving circuit comprises three TFT transistors M2, a TFT transistor M4 and a TFT transistor M5, all the TFT transistors comprise a grid G, a first electrode and a second electrode, the first electrode of the TFT transistor M2 is electrically connected with the ultrasonic transceiver to form an electrical junction J, the grid G of the TFT transistor M2 and the grid G of the TFT transistor M4 are connected with an input control signal, the second electrode of the TFT transistor M2 is electrically connected with the grid G of the TFT transistor M5 to form an electrical junction pe, the first electrode and the second electrode of the TFT transistor M5 are electrically connected with the grid G of the TFT transistor M4, and the second electrode of the TFT transistor M4 outputs sampling current. Due to the arrangement of the TFT transistor M5, the ultrasonic sensing circuit can be ensured to be in a charging state instead of a saturation state all the time in a signal sampling stage, and meanwhile, the effect of a disconnecting switch can be achieved in the ultrasonic transmitting and receiving of the whole ultrasonic sensing circuit, so that the acquired data are more accurate and reliable.
2. The first electrode of the TFT transistor M3 in the ultrasonic circuit is electrically connected with a stabilized voltage power supply Vi, and the second electrode of the TFT transistor M4 is electrically connected with the first electrode of the TFT transistor M3, so that the static working points of the TFT transistors M4 and M3 are adjusted, and current is output to the TFT transistors M3 and M4.
3. The TFT transistor M1 is adopted in the ultrasonic circuit, and mainly when the charging time of the TFT transistor M5 is less than 50ns, the narrow pulse width signal can be generated more easily by adopting the time difference between the mutual conduction and the mutual closing of the TFT transistors M2 and M1.
4. In the ultrasonic circuit of the present invention, the TFT transistor M5 is regarded as a capacitor in the application process, and its parasitic capacitance has a large capacitance value to ensure that it is in an unsaturated charging state in the reading stage of the ultrasonic circuit, and can keep the charged voltage to the next data updating, so that it needs to use the parasitic capacitance of the TFT transistor M5 as a storage capacitor to store more electric quantity for keeping.
5. The ultrasonic circuit is applied to the field of fingerprint identification of a fingerprint identification sensor and electronic equipment, and has application value.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. An ultrasonic circuit, characterized by: the ultrasonic sampling circuit comprises an ultrasonic transceiver, a driving circuit and a power circuit which are electrically connected in sequence, wherein the driving circuit comprises a TFT transistor M2, a TFT transistor M4 and a TFT transistor M5, the TFT transistor M2, the TFT transistor M4 and the TFT transistor M5 respectively comprise a grid G, a first electrode and a second electrode, the first electrode of the TFT transistor M2 is electrically connected with the ultrasonic transceiver to form an electrical node J, the grid G of the TFT transistor M2 and the grid G of the TFT transistor M4 are both connected with an external circuit and are connected with a control signal, the second electrode of the TFT transistor M2 and the grid G of the TFT transistor M5 are electrically connected to form an electrical node pe, the first electrode and the second electrode of the TFT transistor M5 are both electrically connected with the grid G of the TFT transistor M4, and the second electrode of the TFT transistor M4 outputs sampling current.
2. The ultrasonic circuit of claim 1, wherein: the ultrasonic wave circuit still includes power supply circuit, power supply circuit includes constant voltage power supply Vi, drive circuit still includes TFT transistor M3, and TFT transistor M3's first electrode carries out electric connection with constant voltage power supply Vi, TFT transistor M3's second electrode with TFT transistor M4's first electrode electric connection, TFT transistor M3's grid G with electrical node pe electric connection.
3. The ultrasonic circuit of claim 2, wherein: the power circuit further comprises an adjustable voltage source Dv, the driving circuit further comprises a TFT transistor M1, a second electrode of the TFT transistor M1 is electrically connected to the adjustable voltage source Dv, a first electrode of the TFT transistor M1 is electrically connected to the electrical junction J, and a gate G of the TFT transistor M1 is connected to an external circuit for inputting a control signal.
4. An ultrasound circuit as claimed in claim 3, wherein: when the input of the control signal causes the TFT transistor M1, the TFT transistor M2, and the TFT transistor M4 to be all in conduction, the ultrasonic circuit is in a reset/initialization state;
when the input control signal causes the TFT transistor M1 to be turned on, the TFT transistor M2 and the TFT transistor M4 are both turned off, the current of the adjustable voltage source Dv flows through the TFT transistor M1 to the electrical junction J and not to the ultrasonic transceiver, and the ultrasonic circuit is in the ultrasonic pre-transmitting state;
when the ultrasonic circuit is in an ultrasonic wave pre-transmitting state, the current of the adjustable voltage source Dv reaches the ultrasonic transceiver, and the ultrasonic circuit is in an ultrasonic wave transmitting state.
5. The ultrasonic circuit of claim 4, wherein: when a control signal is input to enable the TFT transistor M1 to be in a non-saturated charging mode, the TFT transistor M2 is turned on, the TFT transistor M4 is turned off, the current of the adjustable voltage source Dv flows through the TFT transistor M1 and does not reach an electrical node pe through the TFT transistor M2, and the ultrasonic circuit is in an ultrasonic pre-receiving state;
when the ultrasonic circuit is in an ultrasonic wave pre-receiving state, the voltage value of the adjustable voltage source Dv is adjusted and increased, the current of the adjustable voltage source Dv reaches an electrical node pe to charge the TFT transistor M5, and at the moment, the voltage value of the electrical node pe is gradually increased, and the ultrasonic circuit is in an ultrasonic wave receiving state.
6. The ultrasonic circuit of claim 5, wherein: after the TFT transistor M5 is charged for a preset time, the TFT transistor M2 and the TFT transistor M1 are sequentially turned off, the Dv voltage value is adjusted to be reduced to 0V, and the ultrasonic circuit is in an ultrasonic wave pre-reading state;
when the ultrasonic circuit is in an ultrasonic pre-reading state, when a control signal is input to enable the TFT transistor M4 to be conducted, the TFT transistor M4 outputs sampling current, and the ultrasonic circuit is in an ultrasonic reading state;
after the reflected ultrasonic wave signals are collected and read, the TFT transistors M1, M2, M3, M4 and M5 all restore the initial setting state, and the ultrasonic wave circuit is in the ending state.
7. The ultrasonic circuit of claim 5, wherein: the charging time of the TFT transistor M5 is less than 50 ns.
8. The ultrasonic circuit of claim 1, wherein: the parasitic capacitance of the TFT transistor M5 has a capacitance of 0.1Pf to 0.5 Pf.
9. The utility model provides a fingerprint identification sensor, mainly used carries out fingerprint identification, its characterized in that: the fingerprint identification sensor comprises the ultrasonic circuit, a signal generator and a signal acquisition circuit, wherein the ultrasonic circuit, the signal generator and the signal acquisition circuit are in any one of claims 1 to 8, the signal generator is connected with the driving circuit and provides input control signals for the driving circuit, the driving circuit is respectively and electrically connected with the ultrasonic transceiver and the signal acquisition circuit, and the signal acquisition circuit is used for acquiring ultrasonic emission signals fed back and calculating fingerprint information according to sampling current.
10. An electronic device, characterized in that: comprising the fingerprint sensor according to claim 9 and a touch interface, wherein the fingerprint sensor is electrically connected to the touch interface.
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| CN202010058058.7A CN111079719B (en) | 2020-01-19 | Ultrasonic circuit, fingerprint identification sensor and electronic equipment |
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