CN212302499U

CN212302499U - Control circuit for controlling optical fingerprint sensor

Info

Publication number: CN212302499U
Application number: CN202021483972.8U
Authority: CN
Inventors: 张岑玮; 夏志朋; 施伟伦; 陈泓竹; 连书纬; 萧圣文; 郑喨继
Original assignee: Novatek Microelectronics Corp
Current assignee: Novatek Microelectronics Corp
Priority date: 2019-07-24
Filing date: 2020-07-24
Publication date: 2021-01-05
Anticipated expiration: 2030-07-24
Also published as: TWM604434U; CN112287747A; TWI764210B; TW202105156A

Abstract

The utility model discloses a control circuit for controlling an optical fingerprint sensor, this optical fingerprint sensor include a plurality of pixels, and wherein each pixel has a first control signal line and a second control signal line, and each pixel still is coupled in a first voltage source line, a second voltage source line and a sensing line, and this control circuit and a touch control controller are integrated mutually and are carried out following operation: when the touch controller is in a touch operation period, at least one of the first control signal line, the second control signal line, the first voltage source line, the second voltage source line and the sensing line applies an anti-load driving signal.

Description

Control circuit for controlling optical fingerprint sensor

Technical Field

The utility model relates to a control circuit for optical fingerprint sensor especially relates to a control circuit that can be used to the optical fingerprint sensor who integrates with the touch-sensitive screen.

Background

Fingerprint identification technology has been widely used in various electronic products, such as mobile phones, notebook computers, tablet computers, Personal Digital Assistants (PDAs), and portable electronic devices, to realize identification. The user can be conveniently identified through fingerprint sensing, and the user can log in the electronic device only by placing a finger on a fingerprint sensing panel or an area without inputting a lengthy and tedious user name and password.

Among various types of fingerprint sensing technologies, an optical fingerprint sensing scheme is generally applied to electronic products having a display screen. Generally, the optical fingerprint sensing and the touch screen can be integrated with each other, so that the fingerprint sensing and the touch sensing can be simultaneously implemented in the electronic device. However, in order to capture a minute peak-to-valley difference of a fingerprint, an optical fingerprint sensing operation needs to be performed accurately, and the optical fingerprint sensing is easily interfered by a touch sensing operation. In view of this, there is a need for improvement in the art.

SUMMERY OF THE UTILITY MODEL

Therefore, the present invention is directed to a control circuit for an optical fingerprint sensor and an optical fingerprint sensor thereof, so as to eliminate or reduce interference between touch sensing operation and fingerprint sensing operation.

An embodiment of the utility model discloses a control circuit for controlling an optical fingerprint sensor. The optical fingerprint sensor comprises a plurality of pixels, wherein each pixel is provided with a first control signal line and a second control signal line, and is also coupled to a first voltage source line, a second voltage source line and a sensing line. The control circuit is integrated with a touch controller to perform the following operations: when the touch controller is in a touch operation period, at least one of the first control signal line, the second control signal line, the first voltage source line, the second voltage source line and the sensing line applies an anti-load driving signal.

Another embodiment of the present invention discloses a control circuit for controlling an optical fingerprint sensor. The optical fingerprint sensor comprises a plurality of pixels, wherein each pixel is provided with a first control signal line and a second control signal line, and is also coupled to a first voltage source line, a second voltage source line and a sensing line. The control circuit is integrated with a touch controller to perform the following operations: when the touch controller is in a touch operation period, the first control signal line, the second control signal line, the first voltage source line, the second voltage source line and the sensing line are all in a floating state.

Drawings

Fig. 1 is a schematic diagram of a display device according to an embodiment of the present invention.

Fig. 2 shows a 3-dimensional view of the display device of fig. 1.

Fig. 3 shows a detailed structure of a fingerprint sensing pixel included in the fingerprint sensing layer of fig. 1 and 2.

Fig. 4 is a schematic diagram of an arrangement of control signal lines, sense lines, and voltage source lines in a fingerprint sensing pixel array.

Fig. 5A is a schematic diagram of applying an anti-loading driving signal to a fingerprint sensing pixel.

FIG. 5B illustrates a detailed embodiment of applying an anti-load drive signal to control node floating.

Fig. 6 is a timing diagram illustrating the operation of the display device according to an embodiment of the present invention.

FIG. 7 shows a detailed implementation of the anti-load driving signal during a touch operation.

Fig. 8 is a schematic diagram of a display system according to an embodiment of the present invention.

Fig. 9 is a schematic diagram of another display system according to an embodiment of the present invention.

Fig. 10 is a schematic diagram of an anti-load driving circuit according to an embodiment of the present invention.

Fig. 11A and 11B are schematic diagrams illustrating a detailed embodiment of an anti-load driving generator.

Fig. 12 is a schematic diagram of another display system according to an embodiment of the present invention.

Fig. 13 is a flowchart of a process according to an embodiment of the present invention.

FIG. 14 is a flow chart of another process according to an embodiment of the present invention

Wherein the reference numerals are as follows:

10 display device

100. 804 display screen

102-line driving device

104-column sensing driving device

110 touch sensing layer

120 fingerprint sensing layer

112_1, 112_2 switch circuit

PD photoelectric component

SC storage capacitor

T1-T3 transistor

SVSS first voltage supply line

SVDD second Voltage Source line

R _ SW 1-R _ SW3 control signal line

C _ SEN sense line

N1, N2 node

CC1, CC2 and CC coupling capacitor

PSW 1-PSW 5 switching device

80. 90, 1200 display system

800 system processor

802 fingerprint touch display integrated circuit

820 fingerprint control circuit

822 touch control device

824 display driver

850. 950, 1000, 1250 anti-load driving circuit

902 touch display driving integrated circuit

903 fingerprint reading circuit

1002 voltage generator

1004 anti-load drive generator

ALDX original anti-load driving signal

VH, V1, V2 Voltage

1102. 1104 voltage stabilizer

1110 switch module

C1, C2 capacitor

1150D/A converter

DIG digital code

CTRL control signal

1300. 1400 flow chart

1302 to 1306, 1402 to 1406 steps

Detailed Description

Referring to fig. 1, fig. 1 is a schematic diagram of a display device 10 according to an embodiment of the present invention. As shown in FIG. 1, the display device 10 includes a display screen 100, a row driving device 102 and a column sensing driving device 104. In this case, the display screen 100 can be configured to have touch sensing and fingerprint sensing functions, and therefore, a touch sensing layer 110 having a touch sensor array and a fingerprint sensing layer 120 having a fingerprint sensing pixel array can be stacked and integrated in the display screen 100. The row driving device 102 and the column sensing driving device 104 may constitute a control circuit of the fingerprint sensing pixel array. The display apparatus 10 may further include switch circuits 112_1 and 112_2, wherein each switch circuit may be composed of a multiplexer and/or a switch for selectively transmitting a control signal to a target fingerprint sensing pixel in the fingerprint sensing layer 120 or transmitting a sensing signal from the fingerprint sensing pixel to a target receiver circuit in the column sensing driving device 104. The display device 10 may further include display and touch sensing control circuits, which are omitted from fig. 1 for simplicity.

Fig. 2 shows a 3-dimensional view of the display device 10. In detail, the touch sensing layer 110 includes a touch sensor array having a plurality of sensing pads (sensing pads) and a plurality of conductive lines. The touch controller can transmit a touch driving signal to the sensing pad and correspondingly receive a touch sensing signal to judge the touch behavior. The touch driving signal may be a periodic signal, which may have any type of pulse, such as a sine wave, a square wave, a triangular wave, or a trapezoidal wave. Therefore, the touch sensing signal can also be a corresponding periodic signal for carrying touch sensing information. The fingerprint sensing layer 120 includes an array of fingerprint sensing pixels, wherein each fingerprint sensing pixel may include a plurality of circuit elements connected to each other by conductive lines in a row direction and a column direction, respectively, the conductive lines in the row direction being connected to the row driving device 102 and the conductive lines in the column direction being connected to the column sensing driving device 104. The wires may include control signal lines for transmitting control signals, voltage source lines for transmitting power supply voltages, and sensing lines for transmitting fingerprint sensing signals.

As shown in fig. 2, the touch sensing layer 110 and the fingerprint sensing layer 120 are different but close to each other, so that a coupling capacitance that cannot be ignored exists between each conductive line connected to the touch sensing pad and each conductive line connected to the fingerprint sensing pixel. Therefore, when a touch driving signal is transmitted to the touch sensing pad, the coupling capacitor couples the touch driving signal or the corresponding sensing signal to interfere with the voltage on the control signal line, the voltage source line and/or the sensing line, thereby generating an insignificant capacitive load in the fingerprint sensing operation. From the perspective of the touch sensing operation, the coupling capacitance between the touch sensing layer 110 and the fingerprint sensing layer 120 also affects the sensing signal of the touch operation.

In this example, the touch sensing layer 110 is an upper layer stacked on the fingerprint sensing layer 120. However, in another embodiment, the fingerprint sensing layer may be disposed as an upper layer and the touch sensing layer may be disposed as a lower layer. Alternatively, the touch sensor and/or the fingerprint sensor may be provided as a multi-layer structure. The structure of the panels should not be used to limit the scope of the present invention.

Fig. 3 shows a detailed structure of a fingerprint sensing pixel included in the fingerprint sensing layer 120 of fig. 1 and 2. In this case, the fingerprint sensing pixel may be used to implement an optical fingerprint sensor, which includes a photo-electronic device PD, a storage capacitor SC and three transistors T1-T3. The fingerprint sensing pixel may operate by a first power voltage received through a first voltage supply line SVSS and a second power voltage received through a second voltage supply line SVDD. In an embodiment, the first power voltage may be a negative power voltage or a ground voltage or a positive power voltage, and the second power voltage may be a negative power voltage or a ground voltage or a positive power voltage, and the actual polarity arrangement of the voltage source line is determined by the circuit design of the sensing pixel, which is not limited herein. Three rows of control signals can be transmitted to the pixels through the control signal lines R _ SW 1-R _ SW3, respectively, so that the pixels can output a sensing signal through a sensing line C _ SEN. In another embodiment, the fingerprint sensing pixel may be used to realize an optical fingerprint sensor, which includes a photo-electric device PD, a storage capacitor SC and two transistors T1-T2, so that the circuit structure is more simplified.

In the fingerprint sensing pixel, the photo device PD may be a photodiode (photodiode) for sensing light and converting the intensity of the sensed light into an electrical signal (e.g. a voltage signal or a current signal), which is called "exposure". During the exposure period, the electrical signal flows to the storage capacitor SC and is stored in the storage capacitor SC. The transistor T1 serves as a reset transistor for resetting the voltage at the node N2 (i.e., resetting the charge stored in the storage capacitor SC) prior to the exposure operation. The transistor T2 is used as a source follower (source follower) to transmit the electrical signal sensed by the photo device PD and stored in the storage capacitor SC to the sensing line C _ SEN after the exposure operation is completed. The transistor T3 is used as a selection transistor and can be turned on by a corresponding control signal when its corresponding pixel is selected.

As shown in fig. 3, the transistor T1 has a gate terminal coupled to the control signal line R _ SW1 for receiving a control signal (e.g., a reset signal), a first terminal coupled to the first voltage source line SVSS, and a second terminal coupled to the photo device PD and the storage capacitor SC. It is noted that the first terminal of the transistor T1 may be one of a drain terminal and a source terminal, and the second terminal of the transistor T1 is the other terminal, which may depend on the current direction of the transistor T1. The photo device PD and the storage capacitor SC each have a first terminal coupled to the control signal line R _ SW2 for receiving a control signal (e.g., a bias voltage), and a second terminal coupled to the second terminal of the transistor T1. The transistor T2 has a gate terminal coupled to the second terminal of the transistor T1, the second terminal of the photo device PD, and the second terminal of the storage capacitor SC, a first terminal coupled to the second voltage source line SVDD, and a second terminal coupled to the transistor T3. It is noted that the first terminal of the transistor T2 may be one of a drain terminal and a source terminal, and the second terminal of the transistor T2 is the other terminal, which may depend on the current direction of the transistor T2. The transistor T3 has a gate terminal coupled to the control signal line R _ SW3 for receiving a control signal (e.g., a selection signal), a first terminal coupled to the second terminal of the transistor T2, and a second terminal coupled to the sensing line C _ SEN. It is noted that the first terminal of the transistor T3 may be one of a drain terminal and a source terminal, and the second terminal of the transistor T3 is the other terminal, which may depend on the current direction of the transistor T3.

Referring to fig. 4, fig. 4 is a schematic diagram illustrating the arrangement of the control signal lines R _ SW 1-R _ SW3, the sensing line C _ SEN, and the voltage source lines SVSS and SVDD in the fingerprint sensing pixel array. Referring to fig. 4 in conjunction with fig. 1, each of the control signal lines R _ SW 1-R _ SW3 is coupled to a row of pixels, each of the sensing lines C _ SEN is coupled to a column of pixels, and each of the voltage source lines SVSS or SVDD is coupled to the pixels through a column-wise connection line. Therefore, the control signal lines R _ SW 1-R _ SW3 can be coupled to the column driving devices 102 for sending corresponding control signals. The sensing line C _ SEN may be coupled to the column sensing driving device 104, which is used for receiving a fingerprint sensing signal. Since the control signal lines R _ SW1 to R _ SW3, the sensing line C _ SEN, and the voltage source lines SVSS and SVDD are distributed in the fingerprint sensing layer 120, the above conductive lines are interfered by the touch driving/sensing signal applied to the touch sensing layer 110.

According to the optical fingerprint sensing operation, the electrical signal generated by the photo-electronic device PD is stored in the storage capacitor SC, so that the capacitive load on the two terminals (i.e., nodes N1 and N2) of the storage capacitor SC, which may be caused by the touch driving or sensing signal on the touch sensing pad, should be avoided or reduced. For example, if there is a coupling capacitance between the node N1 of the fingerprint sensing pixel and the touch sensing pad of the touch sensing layer 110, the touch driving or sensing signal applied to the touch sensing pad will interfere with the electronic signal stored in the storage capacitor SC, resulting in an error in the output fingerprint sensing signal. To eliminate or reduce the capacitive load, Anti-load Driving (ALD) signals may be applied to the conductive lines of the fingerprint sensing layer 120 or floating (floating) when the touch Driving signals are transmitted to the touch sensing layer 110. When the touch controller is in a touch operation period, at least one of the control signal lines R _ SW 1-R _ SW3, the voltage source lines SVSS and SVDD, and the sensing line C _ SEN may be applied with an anti-load driving signal, and the other lines may be in a floating state without being applied with the anti-load driving signal. In another embodiment, each of the control signal lines R _ SW 1-R _ SW3, the voltage source lines SVSS and SVDD, and the sensing line C _ SEN may be all in a floating state when the touch controller is in a touch operation. The switch disconnection with signal source can make this wire be in the floating state, or make its output be the high impedance, the utility model discloses do not limit here. In summary, the coupling interference of signals between the touch controller and the fingerprint sensor can be minimized by applying the anti-load driving signal or the conducting wire in the floating state, or by using various permutation and combination of the two technologies.

Referring to fig. 5A, fig. 5A is a schematic diagram illustrating applying an anti-loading driving signal to a fingerprint sensing pixel. In detail, a first anti-load driving signal may be applied to the control signal line R _ SW 2. Since the control signal line R _ SW2 is directly coupled to the node N1, the first anti-load driving signal can be transmitted to the node N1 to eliminate or reduce the capacitive load on the first end of the storage capacitor SC. To eliminate or reduce the capacitive loading on the second terminal of the storage capacitor SC, a second anti-loading driving signal may be transmitted to the node N2. Since the node N2 is coupled to the transistors T1 and T2, the second anti-load driving signal can be applied to any one or more wires connected to the transistors T1 and/or T2. These wires include, but are not limited to, a control signal line R _ SW1, a first voltage source line SVSS, a second voltage source line SVDD, and a sensing line C _ SEN. If the second anti-load driving signal is applied to the control signal line R _ SW1 and/or the first voltage source line SVSS, the second anti-load driving signal may be coupled to the node N2 through the parasitic capacitance of the transistor T1. If the second anti-load driving signal is applied to the second voltage source line SVDD and/or the sensing line C _ SEN, the second anti-load driving signal may be coupled to the node N2 through the parasitic capacitance of the transistor T2.

Notably, the purpose of the anti-loading drive signal is to eliminate or reduce capacitive loading in the fingerprint sensing pixel. Preferably, the anti-load driving signal can be designed to be identical to the touch driving signal transmitted to the touch sensing pad, as shown in fig. 5A. Through the coupling operation of the coupling capacitors CC1 and CC2, the fingerprint sensing pixels are interfered by the touch driving signals. Without the anti-load driving signal, when the touch driving signal is switched up and down, the voltage variation of the touch driving signal charges and discharges the coupling capacitors CC1 and CC2, resulting in unexpected voltage variation at the nodes N1 and/or N2. When the touch driving signal is switched up and down, if the anti-load driving signals applied to the nodes N1 and N2 are completely the same as the touch driving signal, the voltages across the coupling capacitors CC1 and CC2 are kept constant, i.e., the coupling capacitors CC1 and CC2 are not charged or discharged, so that the electronic signals stored in the storage capacitor SC are not affected.

As described above, the touch driving signal may be a periodic signal having a plurality of pulses. Therefore, the anti-load driving signal may also be a modulation signal having a plurality of pulses, and the frequency, phase and amplitude of the pulses are substantially the same as those of the pulses of the touch driving signal, respectively. Since the touch driving signal may include any type of pulse, such as a sine wave, a square wave, a triangular wave, or a trapezoidal wave, the anti-load driving signal may be modified to include the same or similar type of pulse.

It is noted that the anti-load driving signal may or may not be identical to the touch signal (e.g., the touch driving signal or the touch sensing signal). For example, in one embodiment, the amplitude of the anti-load driving signal may be slightly smaller than the amplitude of the touch driving signal, and the frequency and phase thereof are substantially the same. Alternatively or additionally, the phase of the anti-load driving signal may be slightly shifted with respect to the phase of the touch driving signal, and the frequencies thereof are substantially the same. If the similarity between the anti-load driving signal and the touch signal is high, the efficiency of controlling the reduction of the capacitive load of the fingerprint sensing pixel can be improved.

The anti-load drive signal may be applied to the conductors of the fingerprint sensing pixel by any means. In one embodiment, the anti-load driving signal is applied to a target line by driving the target line with the anti-load driving signal, wherein the anti-load driving signal is substantially the same as the touch signal (has the same frequency, phase and/or amplitude). Alternatively or additionally, the anti-load driving signal may be applied to a switch of a target conductor to control the corresponding node to be in a floating state, in which case the anti-load driving signal may have any possible type. The anti-load drive signal may be, for example, a periodic signal with pulses of any of the types described above, or may be a signal at an appropriate voltage level that is capable of turning off the corresponding switch. The anti-load driving operation is possible as long as the switch can be turned off by the anti-load driving signal so that the target node is in a floating state for a period of time. The floating state allows the voltage of the target node to shift up or down with the pulse of the touch signal under the operation of the coupling capacitor CC1 or CC 2. The node is in a floating state, which means that each end of the node is connected to a high impedance terminal only, or any external connection of the node is disconnected, that is, all switches connected to the node are closed. To save power, or when the target conductor cannot be driven by a signal, a floating operation may be used. The target conductor receiving the anti-load driving signal may be the control signal line R _ SW2 coupled to the node N1 and/or any other conductor coupled to the pixel, such as the control signal lines R _ SW1 and R _ SW3, the first voltage source line SVSS, the second voltage source line SVDD, the sensing line C _ SEN, etc.

FIG. 5B illustrates a detailed embodiment of applying an anti-load drive signal to control node floating. The pixel structure shown in fig. 5B is similar to the pixel structure shown in fig. 5A, and therefore signals or components with similar functions are denoted by the same symbols. The structure of fig. 5B further includes switches PSW 1-PSW 5 coupled to the control signal line R _ SW2, the control signal line R _ SW1, the first voltage source line SVSS, the second voltage source line SVDD, and the sensing line C _ SEN, respectively. Note that each of the switches PSW1 to PSW5 may be a switch dedicated to a target pixel or a switch for connecting a target wire of one row or one column of pixels. In another embodiment, the switch disconnection of source of signal can make this signal line, voltage source line or sensing line be in floating state, or make its output be high impedance, also can connect above-mentioned all wires together and control by a master switch, the utility model discloses not limit here.

In detail, in order to apply the anti-load driving signal to the fingerprint sensing pixel, a first anti-load driving signal may be applied to the switch PSW 1. In this case, the switch PSW1 coupled between the node N1 and the control signal line R _ SW2 may be turned off, thereby controlling the node N1 to float. In addition, to control the node N2 to float, a second anti-load driving signal may be applied to any one or more of the switch PSW2 coupled to the control signal line R _ SW1, the switch PSW3 coupled to the first voltage source line SVSS, the switch PSW4 coupled to the second voltage source line SVDD, and the switch PSW5 coupled to the sensing line C _ SEN. In this case, any node of the pixel coupled to the control signal line R _ SW1, the first voltage source line SVSS, the second voltage source line SVDD, and the sensing line C _ SEN can be in a floating state, and thus the node N2 is also in a floating state.

For an array of fingerprint sensing pixels on the fingerprint sensing layer 120, the anti-loading drive signal on each pixel can be implemented elastically by driving and/or controlling the node floating with the anti-loading drive signal. For example, the conductive lines of a first pixel may be driven by an anti-load driving signal, while the conductive lines of a second pixel may be controlled by an anti-load driving signal such that the corresponding nodes are floated. The anti-loading drive signals for a fingerprint sensing pixel array having 2 columns (column 1 and column 2) and 2 rows (row 1 and row 2) can be implemented in various ways of table 1, as follows:

TABLE 1

According to table 1, the anti-loading driving signal for the pixel array includes at least 16 different embodiments, and the anti-loading driving signal can be applied when the touch driving signal is transmitted to the touch device. It is noted that a typical fingerprint sensing pixel array may include more than 2 rows and 2 columns of pixels, and thus, there are more possible combinations of drive and float operations. In one embodiment, the anti-loading driving signal can be implemented differently for different connecting wires for the same row of pixels and/or different connecting wires for the same column of pixels, so as to achieve flexibility of the anti-loading driving operation.

Referring to fig. 6, fig. 6 is a timing diagram illustrating operations of a display device according to an embodiment of the present invention. To reduce interference between display, touch sensing, and fingerprint sensing operations, these operations may be performed in a time-sharing manner. As shown in fig. 6, the touch operation period (TP) and the Display Period (DP) are alternately set in the display time of each frame (frame), and the fingerprint sensing period (FP) can be set to the blank time (blank time) between two consecutive display frames. Referring to FIG. 6 in conjunction with FIG. 3, the operation of the optical fingerprint sensor requires that node N2 be reset to a predetermined voltage level, then exposure is initiated, and then the electrical signals generated during the exposure process are read out at the end of the exposure period. Generally, the exposure period may last for one frame of display period, which includes multiple display periods and a touch operation period, as shown in fig. 6. In another embodiment, the exposure period may also span several display frames in order to generate a sufficient amount of sensing signal.

During the exposure period, the electro-optical device PD can continuously generate an electrical signal and accumulate the electrical signal in the storage capacitor SC, so that the voltage at the node N2 is changed accordingly. Therefore, the anti-load driving signal is applied during the exposure period to prevent the charges stored in the storage capacitor SC (i.e. the voltage across the storage capacitor SC) from being interfered by the touch signal before the fingerprint sensing signal is read out.

More specifically, the touch operation can be performed during the touch operation period, i.e., the touch driving signal is usually switched up and down during the touch operation period. Therefore, the anti-load driving signal can be applied during the touch operation. FIG. 7 shows a detailed implementation of the anti-load driving signal during a touch operation. As shown in fig. 7, during a touch operation, the touch sensing line can receive a touch signal from a sensing pad, wherein the touch signal has a square wave pulse with an amplitude equal to Δ V. Accordingly, an anti-load driving operation may be applied on the fingerprint sensing pixel during a touch operation.

In this case, the first voltage source line SVSS and the second voltage source line SVDD may transmit a power voltage during the fingerprint sensing period and the display period, and transmit the anti-load driving signal during the touch operation period, wherein the anti-load driving signal may include a plurality of pulses, which may be generated by modulating on the power voltage and have substantially the same frequency, phase and amplitude as the touch signal applied to the touch sensing line. The control signal lines R _ SW 1-R _ SW3 can transmit corresponding control signals during the fingerprint sensing period and the display period, and transmit an anti-loading driving signal during the touch operation period, wherein the anti-loading driving signal can include a plurality of pulses, which can be generated by modulating the control signal and have substantially the same frequency, phase and amplitude as the touch signal applied to the touch sensing line. The sensing line C _ SEN may transmit a sensing signal during a fingerprint sensing period and transmit an anti-load driving signal during a touch operation, wherein the anti-load driving signal may include a plurality of pulses, which may be generated by modulating on the sensing signal and have substantially the same frequency, phase and amplitude as a touch signal applied on the touch sensing line.

Referring to fig. 8, fig. 8 is a schematic diagram of a display system 80 according to an embodiment of the present invention. As shown in fig. 8, the Display system 80 includes a system processor 800, a Fingerprint Touch Display Integration (FTDI) circuit 802, and a Display screen 804, wherein the Touch Display Integration circuit 802 may be a single chip integrating Display, Touch and Fingerprint processing circuits. In detail, the system processor 800 may be a core processor of the display system 80, such as a Central Processing Unit (CPU), a Micro Controller Unit (MCU), or a microprocessor. For a smart phone, the system processor 800 may be a single chip for controlling various applications and operations of the smart phone. It should be noted that the algorithm for fingerprint identification is usually quite complex, and therefore, the fingerprint matching and determination should be executed on the system processor 800 with huge computing resources, which is difficult to be implemented in the fingerprint touch display integration circuit 802. The fingerprint touch display integration circuit 802 is responsible for capturing or retrieving fingerprint images from the display screen 804 and processing the received fingerprint sensing signals to amplify and retrieve the required peak and valley information.

The display screen 804 may be the display screen 100 shown in fig. 1, which includes the touch sensing layer 110 and the fingerprint sensing layer 120 for implementing three-in-one operation of display, touch sensing and fingerprint sensing. The fingerprint touch display integration circuit 802 may be used as a control circuit for controlling the display, touch and fingerprint sensing operations of the display screen 804. In one embodiment, the display screen 804 may be an in-cell (in-cell) touch and fingerprint panel, in which a touch sensor and a fingerprint sensor and their associated connection lines are disposed. Therefore, the distance between the touch sensing layer 110 and the fingerprint sensing layer 120 is very close, and thus the coupling capacitance between the touch sensing layer 110 and the fingerprint sensing layer 120 may generate a large amount of load on the fingerprint sensing operation.

As shown in fig. 8, the fingerprint touch display integration circuit 802 integrates a fingerprint control circuit 820, a touch control device 822 and a display driver 824, wherein each module can communicate with the system processor 800 through a specific interface. The fingerprint touch display integration circuit 802 may further include an anti-loading driving circuit 850, which may be selectively disposed in the touch control device 822 or the fingerprint control circuit 820 (in the embodiment of fig. 8, the anti-loading driving circuit 850 is disposed in the fingerprint control circuit 820). The fingerprint control circuit 820 may include, for example, the row driving device (and/or sensing device) and the column driving device (and/or sensing device) shown in FIG. 1, which can send control signals to control the fingerprint sensing pixels on the display 804 such that the pixels output the fingerprint sensing signals in a specific sequence. The fingerprint control circuit 820 may also include a readout circuit for receiving a sensing signal from each fingerprint sensing pixel. The touch control device 822 can be used for sending a touch driving signal to a touch sensing pad on a touch sensing layer of the display screen 804 and correspondingly receiving a touch sensing signal. The display driver 824 may be used to perform display control of the display screen 804. More specifically, the display driver 824 receives image data from the system processor 800 and generates and outputs image signals to the display screen 804 accordingly.

To implement the anti-loading driving operation, the anti-loading driving circuit 850 in the fingerprint touch display integration circuit 802 may further drive the wires connected to the fingerprint sensing pixels by the anti-loading driving signal or control the corresponding nodes in the fingerprint sensing pixels to float during the touch operation and/or during the exposure. In one embodiment, the anti-load driving circuit 850 disposed in the fingerprint control circuit 820 may apply the anti-load driving signal according to the notification received from the touch control device 822, such that the anti-load driving signal is synchronized with the touch signal, and the anti-load driving signal and the touch signal may be set to have the same frequency and phase, and/or the same amplitude. The notification from the touch control device 822 can be in any form, such as a flag, a voltage level, or a signal switch generated on a connection line between the fingerprint control circuit 820 and the touch control device 822.

During touch operation, in addition to the fingerprint control circuit 820, the display driver 824 may also apply an anti-loading driving signal to the display circuits of the display screen 804, so as to avoid or reduce capacitive loading on the display circuits caused by the coupling capacitance between the display pixels and the touch sensing layer.

It is noted that the implementation of the fingerprint touch display integration circuit 802 in fig. 8 is only one of many embodiments of the present invention. In another embodiment, the circuit for controlling the display screen can also be implemented by using a dual-chip scheme. Referring to fig. 9, fig. 9 is a schematic view of another display system 90 according to an embodiment of the present invention. The circuit structure of the display system 90 is similar to that of the display system 80, and therefore, signals or components with similar functions are denoted by the same symbols. As shown in fig. 9, the Display system 90 is different from the Display system 80 in that the Display system 90 includes a Touch and Display Driving Integration (TDDI) Circuit 902 and a Fingerprint reading Integrated Circuit (FPR ROIC)903, which can be used to replace the function of the Fingerprint Touch Display Integration Circuit 802 in the Display system 80. The fingerprint readout circuit 903 may have a load-resistant driving circuit 950. The fingerprint readout circuit 903 may be used to read out a fingerprint sensing signal from the fingerprint sensing pixel and may apply an anti-loading driving signal to the conductive line of the fingerprint sensing pixel through the anti-loading driving circuit 950. The touch display driver integration circuit 902 and the fingerprint readout circuit 903 may be integrated circuits implemented in a chip, and the two chips may operate together to control the display, touch sensing, and fingerprint sensing operations of the display screen 804. An interface is provided between the touch display driver integration circuit 902 and the fingerprint readout circuit 903 for transmitting necessary information, such as a notification of applying an anti-load driving signal and information for synchronizing the display driving, touch sensing and fingerprint sensing operations. The detailed operation of the display system 90 is similar to that of the display system 80, and is omitted for simplicity.

The anti-load driving circuit in the fingerprint touch display integration circuit 802 or the fingerprint readout circuit 903 can be implemented in various ways. Referring to fig. 10, fig. 10 is a schematic diagram of an anti-load driving circuit 1000 according to an embodiment of the present invention. As shown in fig. 10, the anti-load driving circuit 1000 includes a voltage generator 1002, an anti-load driving generator 1004 and a coupling capacitor CC. The voltage generator 1002 is used to generate a voltage VH, which may be any possible voltage, such as a control voltage supplied to a control signal line or a power supply voltage supplied to a voltage supply line. The anti-load driving generator 1004 may be utilized to generate a raw anti-load driving signal ALDX. The primary anti-load drive signal ALDX can be a periodic signal having any type of pulse, such as a sine wave, a square wave, a triangular wave, or a trapezoidal wave. The original anti-load driving signal ALDX is coupled to the output terminal of the anti-load driving circuit 1000 through the coupling capacitor CC, and carried at the level of the voltage VH to be output by the anti-load driving circuit 1000, as shown in fig. 10.

Fig. 11A shows a detailed embodiment of the anti-load drive generator 1004. As shown in fig. 11A, the anti-load driving generator 1004 includes

voltage regulators

1102 and 1104, capacitors C1 and C2, and a switch module 1110. Voltage regulator 1102 is configured to generate and output a voltage V1, and voltage regulator 1104 is configured to generate and output a voltage V2, wherein the voltage V1 is higher than the voltage V2 by a suitable difference. Capacitors C1 and C2 are coupled to the output terminals of

regulators

1102 and 1104, respectively, to improve the stability of voltages V1 and V2. The switch module 1110 receives the voltages V1 and V2 and alternately outputs the voltages V1 and V2 under the control of the switch to generate the original anti-load driving signal ALDX. In this example, the original anti-load drive signal ALDX can be a square wave signal that switches between the levels of voltages V1 and V2.

Fig. 11B shows another embodiment of the anti-load drive generator 1004. As shown in fig. 11B, the anti-load driving generator 1004 includes a Digital-to-Analog Converter (DAC) 1150. The digital-to-analog converter 1150 receives a digital code DIG sequence and converts the digital code DIG sequence into an analog voltage to correspondingly generate and output the original anti-load driving signal ALDX. In this case, the original anti-load driving signal ALDX may have any feasible waveform according to the received digital code DIG.

As described above, the anti-load driving circuit may be included in the fingerprint touch display integration circuit 802 shown in fig. 8, for example, or included in the fingerprint readout circuit 903 shown in fig. 9, for example. In another embodiment, an anti-load driving circuit may also be implemented in the fingerprint sensor of the display screen. Referring to fig. 12, fig. 12 is a schematic view of another display system 1200 according to an embodiment of the present invention. The circuit structure of the display system 1200 is similar to that of the display system 80, and therefore, signals or components with similar functions are denoted by the same symbols. As shown in fig. 12, the display system 1200 differs from the display system 80 in that in the display system 1200, the anti-load driving circuit 1250 is implemented in a fingerprint sensor on the display screen 804. The anti-loading driving circuit 1250 is coupled to the fingerprint sensing pixel array and operates according to a control signal CTRL received from the fingerprint touch display integration circuit 802. For example, the anti-load driving circuit 1250 may have a structure similar to that of the anti-load driving circuit 1000 of fig. 10, wherein when the anti-load driving generator 1004 receives the control signal CTRL to enable or trigger, the original anti-load driving signal ALDX is outputted. Alternatively, the control signal CTRL may be the original anti-load driving signal ALDX, which may be used to drive the anti-load driving circuit 1250 to output the anti-load driving signal at a predetermined voltage level.

In another embodiment, the configuration of including the anti-load driving circuit in the fingerprint sensor may also be combined with a dual-chip structure having a fingerprint reading circuit and a touch display driving integration circuit as shown in fig. 9, and the operation manner thereof is similar to the description in the foregoing paragraphs and is not repeated herein.

It should be further noted that an embodiment of the present invention is directed to a control method for an optical fingerprint sensor, and a related control circuit and an optical fingerprint sensor. Those skilled in the art can make modifications or changes thereto without being limited thereto. It will be appreciated by those skilled in the art that there may be various types of pixel structures on the fingerprint sensing layer of the display screen, and the pixel structure described in this specification is only one of various embodiments of the fingerprint sensing pixel. For example, an additional switch may be disposed between the optoelectronic device and the storage capacitor to adjust the exposure time by controlling the operation of the switch. In this case, the anti-load drive signal should be applied according to the structure of the fingerprint sensing pixel.

In addition, the arrangement of the row (horizontal) control signal lines, the column (vertical) sensing lines, and the column (vertical) voltage source lines shown in fig. 4 is only one of the embodiments of the present invention. In another embodiment, the sensing lines and the voltage source lines may be disposed along a horizontal direction, and the control signal lines may be disposed along a vertical direction; alternatively, some of the control signal lines may be disposed in the horizontal direction and the other control signal lines may be disposed in the vertical direction. The row/column control circuit for the fingerprint sensing pixels can be configured accordingly, for example, if the sensing lines are row sensing lines arranged along a horizontal direction, the row control circuit can include a sensor module for receiving the sensing signals. The arrangement of these wires and control circuits should not be construed as limiting the scope of the present invention.

Furthermore, the method of applying the anti-loading driving signal to the fingerprint sensing pixel can also be applied to various types of Display screens integrating touch and fingerprint sensing functions, such as a Liquid Crystal Display (LCD) Panel, an Organic Light-Emitting Diode (oled) Panel, or a Plasma Display Panel (PDP). For the liquid crystal display, the anti-load driving operation may be applied to an in-cell (in-cell) or an out-cell (out-cell) liquid crystal display. It should be noted that the anti-loading driving signal is more suitable for an in-cell touch screen with a fingerprint sensing function, because the touch sensing layer and the fingerprint sensing layer are closer in an in-cell structure, but the implementation manner should not be limited thereto.

The operation of the optical fingerprint sensor and the fingerprint control circuit can be summarized as a process 1300, as shown in FIG. 13. The process 1300 can be implemented in a fingerprint control circuit or an anti-load driving circuit, which is applied to an optical fingerprint sensor integrated with a touch controller and having a plurality of fingerprint sensing pixels, wherein each pixel may include a first control signal line and a second control signal line, and is coupled to a first voltage source line, a second voltage source line and a sensing line, such as the pixel structure shown in fig. 3. As shown in fig. 13, the process 1300 includes the following steps:

step 1302: and starting.

Step 1304: when the touch controller is in a touch operation period, at least one of the first control signal line, the second control signal line, the first voltage source line, the second voltage source line and the sensing line applies an anti-load driving signal.

Step 1306: and (6) ending.

It should be noted that one of the first control signal line, the second control signal line, the first voltage source line, the second voltage source line, and the sensing line, to which the anti-load driving signal is not applied, can control the floating state. Further, the fingerprint control circuit may also adopt a floating or floating-based control manner, as shown in the process 1400 of fig. 14, wherein the process 1400 includes the following steps:

step 1402: and starting.

Step 1404: when the touch controller is in a touch operation period, the first control signal line, the second control signal line, the first voltage source line, the second voltage source line and the sensing line are all in a floating state.

Step 1406: and (6) ending.

For details of the implementation and variations of the

processes

1300 and 1400, reference is made to the description in the previous paragraphs, which are not repeated herein.

To sum up, the embodiment of the present invention provides a control method and a control circuit for an optical fingerprint sensor, and an optical fingerprint sensor. The optical fingerprint sensor can be integrated into a touch screen, wherein one of the touch sensing layer and the fingerprint sensing layer can be overlapped on the other layer, and the two layers are close to each other, so that the coupling capacitance between the touch sensing layer and the fingerprint sensing layer causes huge capacitive load. During a touch operation, the touch signal may form a capacitive load on the conductive lines of the fingerprint sensing pixels. To eliminate or reduce capacitive loading, an anti-loading drive signal may be applied to the conductors of the fingerprint sensing pixels. The anti-load driving signal can be used to drive the conductive line, wherein the frequency, phase and/or amplitude of the anti-load driving signal are substantially the same as the frequency, phase and/or amplitude of the touch signal, respectively. Alternatively or additionally, the anti-load driving operation may also be achieved by controlling the target node of the fingerprint sensing pixel into a floating state. The anti-load driving operation may be performed during a touch operation of the touch controller and/or during an exposure period of the optical fingerprint sensor. The conductive lines in the fingerprint sensing pixels for receiving the anti-loading driving signals may include a conductive line directly coupled to the storage capacitor in the pixel and a conductive line coupled to the storage capacitor through a transistor. Under the anti-load driving operation, the voltage across the storage capacitor is prevented from being interfered by the touch signal, so that the correctness of the fingerprint sensing signal is maintained.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A control circuit for controlling an optical fingerprint sensor, the optical fingerprint sensor comprising a plurality of pixels, wherein each pixel has a first control signal line and a second control signal line, and each pixel is further coupled to a first voltage source line, a second voltage source line and a sensing line, the control circuit and a touch controller are integrated to perform the following operations:

when the touch controller is in a touch operation period, at least one of the first control signal line, the second control signal line, the first voltage source line, the second voltage source line and the sensing line applies an anti-load driving signal.

2. The control circuit of claim 1, wherein the control circuit is configured to apply the anti-loading driving signal during an exposure period of the optical fingerprint sensor.

3. The control circuit of claim 1, wherein none of the first control signal line, the second control signal line, the first voltage source line, the second voltage source line, and the sense line to which the anti-load driving signal is applied is maintained in a floating state.

4. The control circuit of claim 1, wherein the second control signal line is coupled to a first terminal of a storage capacitor of a corresponding pixel of the plurality of pixels.

5. The control circuit of claim 4, wherein a second terminal of the storage capacitor is coupled to a first transistor and a second transistor of the corresponding pixel.

6. The control circuit of claim 5, wherein the first transistor is further coupled to the first control signal line and the first voltage source line.

7. The control circuit of claim 5, wherein the second transistor is further coupled to the second voltage source line.

8. The control circuit of claim 5, wherein the second transistor is further coupled to the sense line through a third transistor.

9. The control circuit of claim 1, wherein the optical fingerprint sensor is in an exposure period.

10. The control circuit of claim 4, wherein the storage capacitor is coupled to an electro-optical device.

11. The control circuit of claim 1, wherein the control circuit, the touch controller and a display driving device are integrated, and the anti-load driving signal comprises a pulse having a frequency and a phase substantially identical to a frequency and a phase of a touch signal of the touch controller, respectively.

12. The control circuit of claim 11, wherein the anti-load driving signal has an amplitude substantially the same as an amplitude of the touch signal.

13. The control circuit of claim 1, wherein the control circuit applies the anti-load driving signal according to a notification received from the touch controller.

14. A control circuit for controlling an optical fingerprint sensor, the optical fingerprint sensor comprising a plurality of pixels, wherein each pixel has a first control signal line and a second control signal line, and each pixel is further coupled to a first voltage source line, a second voltage source line and a sensing line, the control circuit and a touch controller are integrated to perform the following operations:

when the touch controller is in a touch operation period, the first control signal line, the second control signal line, the first voltage source line, the second voltage source line and the sensing line are all in a floating state.