CN112926402B - Active pixel circuit, driving method and display panel - Google Patents
Active pixel circuit, driving method and display panel Download PDFInfo
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Abstract
The invention provides an active pixel circuit, a driving method and a display panel. The active pixel circuit provided by the invention does not need to transmit the first level for resetting to the circuit unit through the switch tube, but directly transmits the first level for resetting to the circuit unit through the reset pulse signal, so that the condition that the larger leakage current is avoided when the switch tube is turned off and the electric signal converted by the photosensitive sensing unit is influenced is avoided, the linear change of the electric signal converted by the photosensitive sensing unit is higher when the external illumination intensity is lower, and the higher sensitivity of the active pixel circuit is further ensured.
Description
Technical Field
The invention relates to the technical field of display, in particular to an active pixel circuit and a display panel.
Background
With the rapid development of science and technology, mobile products with a biological recognition function gradually enter life and work of people. The fingerprint identification technology is valued by people by virtue of the unique characteristic that the fingerprint identification technology can be distinguished from other people. Push-type and slide-type fingerprint recognition technologies based on silicon-based technology have been integrated into mobile products, and the core of interest in the future is the fingerprint recognition technology in the display area. The existing fingerprint identification device has the advantages and disadvantages of a capacitive type, an ultrasonic type and an optical type, but the common defects of the capacitive type and the ultrasonic type are that the sensing distance of a sensor is short, and the defects severely limit the structure and the performance of the fingerprint identification device and influence the wide application of the fingerprint identification device in mobile terminal products. Optical fingerprint recognition has the advantage of being sensitive over long distances due to the use of photosensitive elements. Therefore, an active pixel circuit suitable for a photosensitive element is one of the important research directions nowadays.
Disclosure of Invention
In view of the above, the present invention provides an active pixel circuit, a driving method and a display panel, wherein the active pixel circuit has a simple structure and a high sensitivity.
In order to achieve the above purpose, the technical scheme provided by the invention is as follows:
an active pixel circuit comprising: a photosensitive sensing unit and a reading unit;
the photosensitive sensing unit is electrically connected with a reset signal end, a reference voltage end and a reading node, the reset signal end outputs a reset pulse signal, the reset pulse signal comprises a first level and a second level which are alternate, and the photosensitive sensing unit is used for coupling the electric signal converted by the photosensitive sensing unit according to the optical signal to the reading node in response to the second level after resetting the reading node in response to the first level;
the reading unit is electrically connected with the reading node and the reading control signal end, and is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal end.
Correspondingly, the invention also provides a driving method for driving the active pixel circuit, which comprises a reset stage and a reading stage which pass through in sequence;
in the reset stage, the reset pulse signal outputs a first level, and the photosensitive sensing unit is used for resetting the reading node in response to the first level;
in the reading stage, the reset pulse signal outputs a second level, the photosensitive sensing unit is responsive to the second level to couple the electric signal converted by the photosensitive sensing unit according to the optical signal to the reading node, and the reading unit is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal terminal.
Correspondingly, the invention also provides a display panel which comprises the active pixel circuit.
Compared with the prior art, the technical scheme provided by the invention has at least the following advantages:
the invention provides an active pixel circuit, a driving method and a display panel, comprising the following steps: a photosensitive sensing unit and a reading unit; the photosensitive sensing unit is electrically connected with a reset signal end, a reference voltage end and a reading node, the reset signal end outputs a reset pulse signal, the reset pulse signal comprises a first level and a second level which are alternate, and the photosensitive sensing unit is used for coupling the electric signal converted by the photosensitive sensing unit according to the optical signal to the reading node in response to the second level after resetting the reading node in response to the first level; the reading unit is electrically connected with the reading node and the reading control signal end, and is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal end.
As can be seen from the above, the active pixel circuit provided by the invention has a simple structure. The active pixel circuit provided by the invention does not need to transmit the first level for resetting to the circuit unit through the switch tube, but directly transmits the first level for resetting to the circuit unit through the reset pulse signal, so that the condition that the larger leakage current is avoided when the switch tube is turned off and the electric signal converted by the photosensitive sensing unit is influenced is avoided, the linear change of the electric signal converted by the photosensitive sensing unit is higher when the external illumination intensity is lower, and the higher sensitivity of the active pixel circuit is further ensured.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of an active pixel circuit according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of another active pixel circuit according to an embodiment of the invention;
fig. 3 is a schematic structural diagram of another active pixel circuit according to an embodiment of the invention;
fig. 4 is a schematic structural diagram of another active pixel circuit according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of another active pixel circuit according to an embodiment of the invention;
fig. 6 is a schematic structural diagram of another active pixel circuit according to an embodiment of the invention;
fig. 7 is a schematic structural diagram of another active pixel circuit according to an embodiment of the invention;
fig. 8 is a schematic structural diagram of a display panel according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of another display panel according to an embodiment of the present invention;
FIG. 10 is a timing diagram according to an embodiment of the present invention;
FIG. 11 is a timing diagram illustrating another embodiment of the present invention;
FIG. 12 is a timing diagram of another embodiment of the present invention;
FIG. 13 is a timing diagram of another embodiment of the present invention;
fig. 14 is a schematic structural diagram of another display panel according to an embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As described in the background art, the existing fingerprint identification device has advantages and disadvantages of capacitance type, ultrasonic type and optical type, but the capacitance type and the ultrasonic type have a common defect that the sensing distance of the sensor is short, and the defect severely limits the structure and the performance of the fingerprint identification device, so that the wide application of the fingerprint identification device in mobile terminal products is affected. Optical fingerprint recognition has the advantage of being sensitive over long distances due to the use of photosensitive elements. Therefore, an active pixel circuit suitable for a photosensitive element is one of the important research directions nowadays.
Based on the above, the embodiment of the invention provides an active pixel circuit, a driving method and a display panel, wherein the active pixel circuit has a simple structure and high sensitivity.
In order to achieve the above objective, the technical solutions provided by the embodiments of the present invention are described in detail below, with reference to fig. 1 to 14.
Referring to fig. 1, a schematic structure diagram of an active pixel circuit according to an embodiment of the present invention is shown, where the active pixel circuit includes: a photosensitive sensing unit 100 and a reading unit 200.
The photosensitive sensing unit 100 is electrically connected with a reset signal terminal Vrst, a reference voltage terminal Vref and a reading node Q, the reset signal terminal Vrst outputs a reset pulse signal, the reset pulse signal includes a first level and a second level, the photosensitive sensing unit 100 is configured to respond to the first level to reset the reading node Q, and then respond to the second level to couple the photosensitive sensing unit 100 to the reading node Q according to an electrical signal converted by the optical signal.
The read unit 200 is electrically connected to the read node 100 and the read control signal terminal Vread, and the read unit 200 is configured to convert a signal of the read node Q into a detection signal and output the detection signal in response to control of the read control signal terminal Vread.
The active pixel circuit provided by the embodiment of the invention can be applied to optical fingerprint identification, the optical signal fed back by the finger is sensed by the photosensitive sensing unit in the fingerprint identification process, the optical signal is converted into an electric signal and coupled to the reading node, the reading unit converts the signal of the reading node into a detection signal, and the change of the optical signal detected by the photosensitive sensing unit is finally determined according to the difference of the detection signal in the reading process, so that the aim of fingerprint identification is finally achieved. The detection signal provided by the embodiment of the invention can be voltage, and the change of the optical signal detected by the photosensitive unit is determined by detecting the voltage difference in the reading process.
In order to improve the accuracy of the detection signal, the reading node is reset through the first level of the reset pulse signal, and the reading unit obtains the detection signal according to the signal conversion of the reading node, so that the accuracy of the detection signal can be improved. It can be understood that the reset pulse signal provided by the embodiment of the invention is a square wave signal formed by alternately forming a first level and a second level, wherein the first level can be a reset level of a low level, the second level is a high level, and the potential of the first level is lower than that of the second level. After the light-sensitive unit responds to the reset level of the low level to reset the reading node, the reset pulse signal is converted to output the high level, and at the moment, the light-sensitive unit converts the corresponding electric signal according to the optical signal and is coupled to the reading node. The reference voltage terminal provided by the embodiment of the invention is used for providing a fixed reference voltage for the photosensitive unit, and the voltage value of the reference voltage terminal is larger than or equal to the voltage value of the first level and smaller than the voltage value of the second level. The reading control signal end is used for providing a preset time sequence reading control signal for the reading unit so as to control the reading unit to start outputting or stop outputting the detection signal.
As can be seen from the above, the active pixel circuit provided by the embodiment of the invention has a simple structure. In addition, the active pixel circuit provided by the embodiment of the invention does not need to transmit the first level for resetting to the circuit unit through the switch tube, but directly transmits the first level for resetting to the circuit unit through the reset pulse signal, so that the condition that the larger leakage current is avoided when the switch tube is turned off and the electric signal converted by the photosensitive sensing unit is influenced is avoided, the linear change of the electric signal converted by the photosensitive sensing unit is higher when the external illumination intensity is lower, and the higher sensitivity of the active pixel circuit is further ensured.
Specifically, the existing active pixel circuit sets a switching tube between a first level signal line for providing a first level and a reading node, and then couples the first level to the reading node through the switching tube so as to achieve the purpose of resetting the reading node, but the inherent performance of the switching tube has larger leakage current when the switching tube is turned off, and the larger leakage current inevitably affects the potential of the reading node, so that the photosensitive unit is affected to convert the electric signal transmitted to the reading node. Therefore, according to the technical scheme provided by the embodiment of the invention, the reset signal end is directly connected with the photosensitive unit, and the first level is directly transmitted to the photosensitive unit through the signal line during reset, so that the condition that the signal of the reading node is influenced due to the transmission of the switching tube is avoided.
Correspondingly, based on the active pixel circuit provided by the embodiment, the embodiment of the invention also provides a driving method for driving the active pixel circuit provided by the embodiment, wherein the driving method comprises a reset phase and a reading phase which sequentially pass through:
in the reset stage, the reset pulse signal outputs a first level, and the photosensitive sensing unit is used for resetting the reading node in response to the first level.
In the reading stage, the reset pulse signal outputs a second level, the photosensitive sensing unit is responsive to the second level to couple the electric signal converted by the photosensitive sensing unit according to the optical signal to the reading node, and the reading unit is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal terminal.
In an embodiment of the present invention, in the reset phase, the method further includes: the reading unit is used for converting a signal generated when the reading node is reset into a reset detection signal, and outputting the reset detection signal in response to the control of the reading control signal end, so that the reading unit is reset at the same time, and the detection accuracy of the active pixel circuit is guaranteed to be high.
In an embodiment of the present invention, the reading stage provided by the present invention includes a first sub-reading stage, a transition sub-stage, and a second sub-reading stage that sequentially pass through:
in the first sub-reading stage, the reading unit is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal terminal;
in the transition sub-stage, the reading unit stops outputting the detection signal in response to the control of the reading control signal terminal.
In the second sub-reading stage, the reading unit is configured to convert a signal of the reading node into a detection signal, and output the detection signal in response to control of the reading control signal terminal. Further, a change in the optical signal detected by the photosensitive sensor unit is determined based on a difference between the detection signal at the first sub-reading stage and the detection signal at the second reading stage.
In an embodiment of the present invention, the first sub-reading stage and the second sub-reading stage provided by the present invention have the same time, and since the voltage of the reading node is linearly changed according to a certain slope when the charge-discharge capacitor is charged, the first sub-reading stage and the second sub-reading stage are set to have the same time, and the duration is set to be far smaller than that of the whole reading stage (for example, the reading stage is in a millisecond level, and the first sub-reading stage and the second sub-reading stage are in a micrometer level), so that the first sub-reading stage and the second sub-reading stage are equivalent to sampling points for sampling the detection signal, and the detection signal acquired in the first sub-reading stage and the second sub-reading stage is determined as a mean value in the sub-reading stage.
Specific active pixel circuits and driving methods provided in the embodiments of the present invention are described in more detail below.
As shown in fig. 2, a schematic structural diagram of another active pixel circuit according to an embodiment of the present invention is provided, where the photosensitive sensing unit 100 provided in the embodiment of the present invention includes: a photosensitive element 110 and a charge-discharge capacitance 120.
A first end of the photosensitive element 110 is electrically connected with a reset signal end Vrst, and a second end of the photosensitive element 110 is electrically connected with a reading node Q; a first plate of the charge-discharge capacitor 120 is electrically connected to the reference voltage terminal Vref, and a second plate of the charge-discharge capacitor 120 is electrically connected to the read node Q. Optionally, as shown in fig. 3, a schematic structural diagram of another active pixel circuit according to an embodiment of the present invention is provided, where the capacitance value of the charge-discharge capacitor 120 provided in the embodiment of the present invention is greater than the capacitance value of the parasitic capacitor Cp of the photosensitive element 110.
In an embodiment of the present invention, the photosensitive element 110 is a photodiode, a first end of the photosensitive element 110 is a cathode, and a second end of the photosensitive element 110 is an anode, so that the reading node Q can be quickly led out to the reset signal terminal Vrst through the photodiode during reset, and the reset effect of the reading node Q is improved.
As shown in fig. 2, the reading unit 200 provided by the embodiment of the present invention includes a source follower 210 and a reading module 220, an input end of the source follower 210 is electrically connected to the reading node Q, an output end of the source follower 210 is electrically connected to an input end of the reading module 220, and the source follower 210 is configured to convert a signal of the reading node Q into a detection signal; the control terminal of the read module 220 is connected to the read control signal terminal Vread, and the read module 220 is configured to output the detection signal in response to the control of the read control signal terminal Vread. Referring to fig. 4, a schematic structural diagram of another active pixel circuit according to an embodiment of the present invention is shown, in which the source follower 210 provided by the embodiment of the present invention includes a first transistor M1, the reading module 220 includes a second transistor M2, the gate of the first transistor M1 is electrically connected to the reading node Q, the first end of the first transistor M1 is connected to the power supply voltage VDD, the second end of the first transistor M1 is electrically connected to the first end of the second transistor M2, and the gate of the second transistor M2 is electrically connected to the read control signal Vread. Alternatively, the first transistor M1 and the second transistor M2 provided in the embodiment of the present invention may be N-type transistors.
The driving method according to the embodiment of the present invention will be described in detail with reference to fig. 4 and 10. Fig. 10 is a timing chart provided by an embodiment of the present invention, and the driving method includes a reset phase (time t1 to time t 2) and a read phase (time t2 to time t 5) sequentially passed, wherein the read phase includes a first sub-read phase t2 to time t3, a transition sub-phase t3 to time t4, and a second sub-read phase t4 to time t 5. Specific:
in the reset phase, the reset pulse signal terminal Vrst outputs a first level of low level, and at this time, the charge-discharge capacitor 120 discharges through the photosensitive element 110, and the read node Q discharges to the low level output by the reset pulse signal terminal Vrst and the forward voltage drop of the photosensitive element 110, so that the read node Q completes the reset. Meanwhile, the signal of the read node Q of the first transistor M1 is converted into a reset detection signal, and the second transistor M2 is turned on in response to the control of the read control signal terminal Vread, and outputs the reset detection signal (OUT in fig. 7 is the output terminal of the second transistor M2).
In the first sub-reading stage, the reset pulse signal terminal Vrst outputs a second level of high level, and charges the charge-discharge capacitor 120 through the photocurrent of the photosensitive element 110. Meanwhile, the signal of the read node Q of the first transistor M1 is converted into an initial detection signal, and the second transistor M2 is turned on in response to the control of the read control signal terminal Vread to output the voltage V1 of the initial detection signal.
In the transition sub-stage, the second transistor M2 is turned off in response to the control of the read control signal terminal Vread, so that the second transistor M2 output OUT is floated; meanwhile, the charge-discharge capacitance 120 maintains a charged state.
In the second sub-read phase, the second transistor M2 is turned on in response to the control of the read control signal terminal Vread, and outputs the voltage V2 of the final detection signal. Since the voltage of the reading node Q linearly changes according to a certain slope when the charge-discharge capacitor 120 is charged, the voltage of the initial detection signal and the voltage of the final detection signal also linearly change according to a slope K1 (specifically, the detection signal output by OUT in the timing chart shown in fig. 11); the duration of the first sub-reading stage and the second sub-reading stage provided by the invention are the same, the first sub-reading stage and the second sub-reading stage are equivalent to sampling points for sampling the detection signals, and the detection signals (namely, the voltage V1 and the voltage V2) acquired in the first sub-reading stage and the second sub-reading stage are respectively determined to be the average value in the corresponding sub-reading stage. Further, by determining the difference between the voltage V1 and the voltage V2, the change of the optical signal detected by the photosensitive element 110 can be obtained; alternatively, the change of the optical signal detected by the photosensitive element 110 is obtained by calculating the formula Δv=iop (t 4-t 2)/C, where Iop is the photocurrent of the photosensitive element 110 and C is the capacitance of the charge-discharge capacitor 120.
As shown in fig. 5, a schematic structural diagram of another active pixel circuit according to an embodiment of the present invention is provided, where a photosensitive sensing unit 100 according to an embodiment of the present invention includes: a photosensitive element 130 and a charge-discharge capacitance 140.
A first polar plate of the charge-discharge capacitor 140 is electrically connected with the reset signal end Vrst, and a second polar plate of the charge-discharge capacitor 140 is electrically connected with the reading node Q; a first terminal of the photosensor 130 is electrically connected to the read node Q, and a second terminal of the photosensor 130 is electrically connected to the reference voltage terminal Vref. Optionally, as shown in fig. 6, a schematic structural diagram of another active pixel circuit according to an embodiment of the present invention is provided, where the capacitance value of the charge-discharge capacitor 140 provided in the embodiment of the present invention is greater than the capacitance value of the parasitic capacitor Cp of the photosensitive element 130.
In an embodiment of the present invention, the photosensitive element 130 is a photodiode, the first end of the photosensitive element 130 is a cathode, and the second end of the photosensitive element 130 is an anode, so that the output voltage of the reference voltage end can be ensured to be a lower fixed voltage, and in particular, the output voltage can be lower than the voltage of the second level of the reset pulse signal, thereby ensuring that the overall power consumption of the active pixel circuit is lower.
As shown in fig. 4, the reading unit 200 provided in the embodiment of the present invention includes a source follower 230 and a reading module 240, an input end of the source follower 230 is electrically connected to the reading node Q, an output end of the source follower 230 is electrically connected to an input end of the reading module 240, and the source follower 230 is configured to convert a signal of the reading node Q into a detection signal; the control terminal of the read module 240 is electrically connected to the read control signal terminal Vread, and the read module 240 is configured to output the detection signal in response to the control of the read control signal terminal Vread. Referring to fig. 7, a schematic structural diagram of another active pixel circuit according to an embodiment of the invention is shown, wherein the source follower 230 includes a first transistor M10, the read module 240 includes a second transistor M20, a gate of the first transistor M10 is electrically connected to the read node Q, a first end of the first transistor M10 is connected to the power voltage VDD, a second end of the first transistor M10 is electrically connected to a first end of the second transistor M20, and a gate of the second transistor M20 is electrically connected to the read control signal Vread. Alternatively, the first transistor M10 and the second transistor M20 provided in the embodiment of the present invention may be N-type transistors.
The driving method provided by the embodiment of the present invention is described in detail below with reference to fig. 7 and 12. Fig. 12 is a timing chart of still another embodiment of the present invention, where the driving method includes a reset phase (from time t1 to time t 2) and a read phase (from time t2 to time t 5) sequentially passed, and the read phase includes a first sub-read phase from time t2 to time t3, a transition sub-phase from time t3 to time t4, and a second sub-read phase from time t4 to time t 5. Specific:
in the reset phase, the reset pulse signal terminal Vrst outputs a first level of low level, and the charge-discharge capacitor 140 corresponds to the reset capacitor, so that the read node Q resets at low level. Meanwhile, the signal of the read node Q of the first transistor M10 is converted into a reset detection signal, and the second transistor M20 is turned on in response to the control of the read control signal terminal Vread, and outputs the reset detection signal (OUT in fig. 8 is the output terminal of the second transistor M2).
In the first sub-reading stage, the reset pulse signal terminal Vrst outputs the second level of the high level, and the voltage of the two plates of the charge-discharge capacitor 140 cannot be suddenly changed, so that the read node Q is pulled to the high level. The charge-discharge capacitance 120 is then charged by the photocurrent of the photosensor 130, which manifests itself as a voltage drop at the read node Q. Meanwhile, the signal of the read node Q of the first transistor M1 is converted into an initial detection signal, and the second transistor M20 is turned on in response to the control of the read control signal terminal Vread to output the voltage V10 of the initial detection signal.
In the transition sub-stage, the second transistor M20 is turned off in response to the control of the read control signal terminal Vread, so that the second transistor M20 output OUT is floated; meanwhile, the charge-discharge capacitance 140 maintains a charged state.
In the second sub-read stage, the second transistor M20 is turned on in response to the control of the read control signal terminal Vread, and outputs the voltage V20 of the final detection signal. Since the voltage of the reading node Q linearly changes according to a certain slope when the charge-discharge capacitor 140 is charged, the voltage of the initial detection signal and the voltage of the final detection signal also linearly change according to a slope K2 (specifically, the detection signal output by OUT in the timing chart shown in fig. 13); the duration of the first sub-reading stage and the second sub-reading stage provided by the invention are the same, the first sub-reading stage and the second sub-reading stage are equivalent to sampling points for sampling the detection signals, and the detection signals (namely, the voltage V10 and the voltage V20) acquired in the first sub-reading stage and the second sub-reading stage are respectively determined to be the average value in the corresponding sub-reading stage. Further, by determining the difference between the voltage V10 and the voltage V20, the change of the optical signal detected by the photosensitive element 130 can be obtained; alternatively, the change of the optical signal detected by the photosensitive element 130 is obtained by calculating the formula Δv=iop (t 4-t 2)/C, where Iop is the photocurrent of the photosensitive element 130 and C is the capacitance of the charge-discharge capacitor 140.
In any of the above embodiments, at least one of the first transistor and the second transistor provided by the present invention is an IGZO transistor, so that leakage currents of the first transistor and the second transistor can be reduced, and performance of the active pixel circuit can be improved. Alternatively, a polar plate of the charge-discharge capacitor provided by the embodiment of the invention can be the same layer as the active layer of the IGZO transistor. Namely, the photosensitive sensing unit provided by the embodiment of the invention comprises: a photosensitive element and a charge-discharge capacitance; the charge-discharge capacitor comprises a first polar plate and a second polar plate which are oppositely arranged, the IGZO transistor comprises an active layer, a grid electrode layer and a source-drain electrode layer, wherein one of the first polar plate and the second polar plate is arranged on the same layer as the active layer, the situation that the conducting layer of the polar plate forming the capacitor is independently manufactured is avoided, the manufacturing cost is reduced, and the manufacturing process is simplified.
Fig. 9 is a schematic structural diagram of a display panel according to an embodiment of the present invention, where the display panel includes:
a substrate base 10.
The ingan-zn oxide layer on the substrate 10 includes an active layer 21 for forming an IGZO transistor, and a plate 22 for forming a charge-discharge capacitor after conducting a part of the ingan-zn oxide layer (for example, fluorine ions enter the IGZO layer or ions such as boron ions and phosphorus ions are implanted into the IGZO layer when patterning the film layer).
A first insulating layer 30 on the side of the indium gallium zinc oxide layer facing away from the substrate 10.
A first metal layer on the side of the first insulating layer 30 facing away from the substrate 10, the first metal layer comprising a gate 41 forming an IGZO transistor, wherein the other plate 42 of the capacitor may be located on the first metal layer.
A second insulating layer 50 on the side of the first metal layer facing away from the substrate 10.
The second metal layer on the side of the second insulating layer 50 facing away from the substrate 10 includes a source electrode 61 and a drain electrode 62 forming an IGZO transistor, the source electrode 61 and the drain electrode 62 being connected to the active layer 21 through a via hole.
Optionally, the other electrode plate of the charge-discharge capacitor may be further located on the second metal layer, or the first metal layer and the second metal layer together form the other electrode plate of the capacitor, which is not specifically limited in the present invention, and needs to be specifically designed according to practical applications. Fig. 10 is a schematic structural diagram of another display panel according to an embodiment of the present invention, where the display panel includes:
a substrate base 10.
The ingazinc oxide layer on the substrate 10 includes an active layer 21 for forming an IGZO transistor, and a plate 22 for forming a charge-discharge capacitor after conducting a portion of the ingazinc oxide layer (e.g., doping metal particles).
A first insulating layer 30 on the side of the indium gallium zinc oxide layer facing away from the substrate 10.
A first metal layer on the side of the first insulating layer 30 facing away from the substrate 10, the first metal layer comprising a gate 41 forming an IGZO transistor.
A second insulating layer 50 on the side of the first metal layer facing away from the substrate 10.
The second metal layer is located on one side of the second insulating layer 50 away from the substrate 10, the second metal layer comprises a source electrode 61 and a drain electrode 62 which form an IGZO transistor, the source electrode 61 and the drain electrode 62 are connected with the active layer 21 through a via hole, wherein the other polar plate 72 of the capacitor can be formed by the first metal layer and the second metal layer together, compared with the prior art, the storage capacity of the capacitor is improved, the charge and discharge performance of the capacitor is improved, and fingerprint identification precision is improved.
Correspondingly, the embodiment of the invention also provides a display panel, which comprises the active pixel circuit provided by any one of the embodiments.
Referring to fig. 14, a schematic structural diagram of another display panel provided in an embodiment of the present invention is shown, where a display panel 1000 provided in an embodiment of the present invention may be a mobile terminal device.
Optionally, the display panel provided by the invention can also be electronic display devices such as a computer and a wearable display device, and the invention is not particularly limited.
The embodiment of the invention provides an active pixel circuit, a driving method and a display panel, comprising the following steps: a photosensitive sensing unit and a reading unit; the photosensitive sensing unit is electrically connected with a reset signal end, a reference voltage end and a reading node, the reset signal end outputs a reset pulse signal, the reset pulse signal comprises a first level and a second level which are alternate, and the photosensitive sensing unit is used for coupling the electric signal converted by the photosensitive sensing unit according to the optical signal to the reading node in response to the second level after resetting the reading node in response to the first level; the reading unit is electrically connected with the reading node and the reading control signal end, and is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal end.
As can be seen from the above, the active pixel circuit provided by the embodiment of the invention has a simple structure. In addition, the active pixel circuit provided by the embodiment of the invention does not need to transmit the first level for resetting to the circuit unit through the switch tube, but directly transmits the first level for resetting to the circuit unit through the reset pulse signal, so that the condition that the larger leakage current is avoided when the switch tube is turned off and the electric signal converted by the photosensitive sensing unit is influenced is avoided, the linear change of the electric signal converted by the photosensitive sensing unit is higher when the external illumination intensity is lower, and the higher sensitivity of the active pixel circuit is further ensured.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (13)
1. An active pixel circuit, comprising: a photosensitive sensing unit and a reading unit;
the photosensitive sensing unit is electrically connected with a reset signal end, a reference voltage end and a reading node, the reset signal end outputs a reset pulse signal, the reset pulse signal comprises a first level and a second level which are alternate, and the photosensitive sensing unit is used for coupling the electric signal converted by the photosensitive sensing unit according to the optical signal to the reading node in response to the second level after resetting the reading node in response to the first level; the reference voltage end is used for providing a fixed reference voltage for the photosensitive unit, and the voltage value of the fixed reference voltage is larger than or equal to the voltage value of the first level and smaller than the voltage value of the second level;
the reading unit is electrically connected with the reading node and the reading control signal end, and is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal end.
2. The active pixel circuit of claim 1, wherein the photosensitive sensing unit comprises: a photosensitive element and a charge-discharge capacitance;
the first end of the photosensitive element is electrically connected with the reset signal end, and the second end of the photosensitive element is electrically connected with the reading node; the first polar plate of the charge-discharge capacitor is electrically connected with the reference voltage end, and the second polar plate of the charge-discharge capacitor is electrically connected with the reading node.
3. The active pixel circuit of claim 1, wherein the photosensitive sensing unit comprises: a photosensitive element and a charge-discharge capacitance;
the first polar plate of the charge-discharge capacitor is electrically connected with the reset signal end, and the second polar plate of the charge-discharge capacitor is electrically connected with the reading node; the first end of the photosensitive element is electrically connected with the reading node, and the second end of the photosensitive element is electrically connected with the reference voltage end.
4. An active pixel circuit as claimed in claim 2 or 3, wherein the photosensitive element is a photodiode, the first end of the photosensitive element is a cathode, and the second end of the photosensitive element is an anode.
5. The active pixel circuit of claim 1, wherein the read unit comprises a source follower and a read module, an input of the source follower is electrically connected to the read node, an output of the source follower is electrically connected to the input of the read module, and the source follower is configured to convert a signal of the read node into the detection signal;
the control end of the reading module is electrically connected with the reading control signal end, and the reading module is used for responding to the control of the reading control signal end and outputting the detection signal.
6. The active pixel circuit of claim 5, wherein the source follower comprises a first transistor, the read block comprises a second transistor,
the gate of the first transistor is electrically connected with the reading node, the first end of the first transistor is connected with a power supply voltage, the second end of the first transistor is electrically connected with the first end of the second transistor, and the gate of the second transistor is electrically connected with the reading control signal end.
7. The active pixel circuit of claim 6, wherein at least one of the first transistor and the second transistor is an IGZO transistor.
8. The active pixel circuit of claim 7, wherein the photosensitive sensing unit comprises: a photosensitive element and a charge-discharge capacitance;
the charge-discharge capacitor comprises a first polar plate and a second polar plate which are oppositely arranged, the IGZO transistor comprises an active layer, a grid electrode layer and a source-drain electrode layer, and one of the first polar plate and the second polar plate is arranged on the same layer as the active layer.
9. A driving method for driving the active pixel circuit according to any one of claims 1 to 8, the driving method comprising a reset phase and a read phase which pass in sequence;
in the reset stage, the reset pulse signal outputs a first level, and the photosensitive sensing unit is used for resetting the reading node in response to the first level;
in the reading stage, the reset pulse signal outputs a second level, the photosensitive sensing unit is responsive to the second level to couple the electric signal converted by the photosensitive sensing unit according to the optical signal to the reading node, and the reading unit is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal terminal.
10. The driving method according to claim 9, characterized in that in the reset phase, further comprising: the reading unit is used for converting a signal when the reading node is reset into a reset detection signal and outputting the reset detection signal in response to the control of the reading control signal terminal.
11. The driving method according to claim 9, wherein the reading phase includes a first sub-reading phase, a transition sub-phase, and a second sub-reading phase that pass sequentially;
in the first sub-reading stage, the reading unit is used for converting the signal of the reading node into a detection signal and outputting the detection signal in response to the control of the reading control signal terminal;
in the transition sub-stage, the reading unit responds to the control of the reading control signal terminal to stop outputting the detection signal;
in the second sub-reading stage, the reading unit is configured to convert a signal of the reading node into a detection signal, and output the detection signal in response to control of the reading control signal terminal.
12. The driving method according to claim 11, wherein the first sub-reading stage and the second sub-reading stage are identical in time.
13. A display panel comprising the active pixel circuit of any one of claims 1-8.
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| WO2009025223A1 (en) * | 2007-08-21 | 2009-02-26 | Sharp Kabushiki Kaisha | Display device |
| CN103000133B (en) * | 2012-12-19 | 2015-05-20 | 四川虹视显示技术有限公司 | Pixel driving circuit for display screen of active matrix organic light emitting diode |
| CN106409224A (en) * | 2016-10-28 | 2017-02-15 | 京东方科技集团股份有限公司 | Pixel driving circuit, driving circuit, display substrate and display device |
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