CN211239962U - Active pixel sensing circuit, image sensor and light detection display panel - Google Patents
Active pixel sensing circuit, image sensor and light detection display panel Download PDFInfo
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- CN211239962U CN211239962U CN201922314880.0U CN201922314880U CN211239962U CN 211239962 U CN211239962 U CN 211239962U CN 201922314880 U CN201922314880 U CN 201922314880U CN 211239962 U CN211239962 U CN 211239962U
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Abstract
Some embodiments of the present disclosure disclose an active pixel sensing circuit, an image sensor and a photo detection display panel, which relate to the field of display technologies and are used for improving the uniformity of an APS terminal output signal. The active pixel sensing circuit comprises a photosensitive device, a compensation following circuit and an output circuit. The compensation follower circuit includes a voltage follower transistor, a first compensation sub-circuit, and a second compensation sub-circuit. The first electrode of the photosensitive device is electrically connected with the first voltage end, and the second electrode of the photosensitive device is electrically connected with the first electrode of the voltage following transistor through the first compensation sub-circuit; the control electrode and the second electrode of the voltage following transistor are respectively and electrically connected with the second compensation sub-circuit; the first compensation sub-circuit is also electrically connected with the first scanning line; the second compensation sub-circuit is also electrically connected with the first scanning line and the second scanning line respectively; the output circuit is electrically connected to the read control line, the read signal line, and the first electrode of the voltage follower transistor, respectively.
Description
Technical Field
The present disclosure relates to the field of display technologies, and in particular, to an active pixel sensing circuit, an image sensor, and a photodetection display panel.
Background
The CMOS (Complementary Metal-Oxide Semiconductor) image Sensor mainly includes two types, namely, a Passive Pixel image Sensor (PPS) and an Active Pixel image Sensor (APS).
Referring to fig. 1, currently, a conventional APS includes a plurality of pixels, and an active pixel sensing circuit in each pixel includes a light sensing device D, a reset transistor Mrst, a source follower transistor M1, and an output control transistor M2; wherein, the output voltage of the light sensing device D can control the magnitude of the output current of the source follower transistor M1 after being transmitted to the gate of the source follower transistor M1. Therefore, the illumination intensity sensed by the light sensing device D can be correspondingly obtained by measuring the output current of the source follower transistor M1. Here, the output current of the source follower transistor M1 is related to its threshold voltage.
However, due to the difference in the manufacturing process, the threshold voltages of the source follower transistors M1 of different pixels are different, and the threshold voltage of each source follower transistor M1 is easily shifted by the influence of the temperature and the use time thereof. Therefore, even if the intensity of light irradiation sensed by the light sensing device D is the same, the output current of each source follower transistor M1 is likely to be different due to the difference of the corresponding threshold voltage, that is, the detection result of each pixel in the APS has an error and is difficult to be uniform.
SUMMERY OF THE UTILITY MODEL
It is an object of some embodiments of the present disclosure to provide an active pixel sensing circuit, an image sensor and a photo detection display panel, so as to improve uniformity, sensitivity and accuracy of the image sensor.
In order to achieve the above purpose, some embodiments of the present disclosure provide the following technical solutions:
in one aspect, an active pixel sensing circuit is provided. The active pixel sensing circuit includes: the circuit comprises a photosensitive device, a compensation following circuit and an output circuit. Wherein, the compensation follower circuit includes: a voltage follower transistor, a first compensation sub-circuit and a second compensation sub-circuit.
The first electrode of the photosensitive device is electrically connected with the first voltage end, and the second electrode of the photosensitive device is electrically connected with the first electrode of the voltage following transistor through the first compensation sub-circuit; and the control electrode and the second electrode of the voltage following transistor are respectively electrically connected with the second compensation sub-circuit.
The first compensation sub-circuit is also electrically connected to the first scan line and configured to output a voltage of the second pole of the light sensing device to the first pole of the voltage follower transistor in response to a first scan signal provided by the first scan line.
The second compensation sub-circuit is electrically connected with the first scanning line and the second scanning line respectively and is configured to respond to the first scanning signal and a second scanning signal provided by the second scanning line and store the compensation voltage. The compensation voltage is the sum of the photogenerated voltage of the photosensitive device and the threshold voltage of the voltage follower transistor.
The output circuit is electrically connected with the read control line, the read signal line and the first pole of the voltage follower transistor respectively, and is configured to respond to a read control signal provided by the read control line and transmit the output current of the voltage follower transistor compensated by the compensation voltage to the read signal line.
In some embodiments of the present disclosure, the first compensation sub-circuit is capable of transmitting an output voltage of the light sensing device to the first pole of the voltage follower transistor in response to the first scan signal. The second compensation sub-circuit is capable of storing a compensation voltage, i.e., a sum of a photo-generated voltage of the photo-sensing device and a threshold voltage of the voltage follower transistor, in response to the first scan signal and the second scan signal. In this way, after receiving the read control signal, the second compensation sub-circuit transmits the stored compensation voltage to the control electrode of the voltage follower transistor, so that the output current of the voltage follower transistor can be correspondingly controlled, and the output circuit transmits the output current to the read signal line in response to the read control signal.
Therefore, the active pixel sensing circuit provided by some embodiments of the present disclosure uses the compensation voltage as the control terminal voltage of the voltage follower transistor, so as to offset the threshold voltage required when the voltage follower transistor is turned on, and completely convert the photo-generated voltage of the light sensing device into the output current of the voltage follower transistor for transmission. Thus, even under the condition that the light-generated voltage of the photosensitive device is small, the current signal read by the reading signal line can be ensured not to be interfered by the threshold voltage of the voltage following transistor. Therefore, the uniformity, the sensitivity and the accuracy of the image sensor are effectively improved.
In some embodiments, the first compensation sub-circuit comprises: a first transistor. The control electrode of the first transistor is electrically connected with the first scanning line, the first electrode of the first transistor is electrically connected with the second electrode of the photosensitive device, and the second electrode of the first transistor is electrically connected with the first electrode of the voltage following transistor.
The second compensation sub-circuit comprises: a second transistor, a third transistor, and a storage capacitor. The first electrode of the storage capacitor is electrically connected with the second voltage end, and the second electrode of the storage capacitor is electrically connected with the control electrode of the voltage following transistor; a control electrode of the second transistor is electrically connected with the first scanning line, a first electrode of the second transistor is electrically connected with a second electrode of the storage capacitor, and a second electrode of the second transistor is electrically connected with a second electrode of the voltage following transistor; the control electrode of the third transistor is electrically connected with the second scanning line, the first electrode of the third transistor is electrically connected with the second voltage end, and the second electrode of the third transistor is electrically connected with the second electrode of the voltage following transistor.
In some embodiments, the active pixel sensing circuit further comprises a reset circuit.
The reset circuit is electrically connected with the reset control line and the second pole of the photosensitive device respectively and is configured to respond to a reset signal provided by the reset control line to reset the voltage of the second pole of the photosensitive device.
In some embodiments, the reset circuit includes a fourth transistor.
And a control electrode of the fourth transistor is electrically connected with the reset control line, a first electrode of the fourth transistor is electrically connected with the second voltage end, and a second electrode of the fourth transistor is electrically connected with the second electrode of the photosensitive device.
In some embodiments, the output circuit includes a fifth transistor.
A control electrode of the fifth transistor is electrically connected to the read control line, a first electrode of the fifth transistor is electrically connected to a first electrode of the voltage follower transistor, and a second electrode of the fifth transistor is electrically connected to the read signal line.
In some embodiments, the voltage follower transistor, the first transistor, the second transistor, the third transistor, the fourth transistor, and the fifth transistor are all N-type transistors.
The voltage provided by the second voltage terminal is higher than the voltage provided by the first voltage terminal.
In some embodiments, the light sensing device comprises a photodiode.
In another aspect, an image sensor is provided. The image sensor includes: a plurality of pixels arranged in an array. An active pixel sensing circuit as described in any of the above embodiments is provided in each of the plurality of pixels.
The beneficial effects that can be achieved by the image sensor provided in some embodiments of the present disclosure are the same as those that can be achieved by the active pixel sensing circuit provided in some embodiments, and are not described herein again.
In some embodiments, the image sensor further comprises: and a reading circuit electrically connected to the reading signal lines of the plurality of active pixel sensing circuits, respectively.
In yet another aspect, a light detecting display panel is provided. The light detection display panel includes: such as the image sensor described in some of the embodiments above.
The beneficial effects that can be achieved by the photodetection display panel provided in some embodiments of the present disclosure are the same as those that can be achieved by the image sensor provided in some embodiments described above, and are not described herein again.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the disclosure and are incorporated in and constitute a part of this disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and not to limit the disclosure. In the drawings:
fig. 1 is a block diagram of an active pixel sensing circuit in the related art;
FIG. 2 is a block diagram of an active pixel sensing circuit according to some embodiments of the present disclosure;
FIG. 3 is a block diagram of another active pixel sensing circuit provided by some embodiments of the present disclosure;
FIG. 4 is a block diagram of yet another active pixel sensing circuit provided by some embodiments of the present disclosure;
FIG. 5 is a timing diagram of an active pixel sensing circuit according to some embodiments of the present disclosure;
FIG. 6 is a plot of the current-voltage characteristics of the voltage follower transistors in the active pixel sensing circuit of FIG. 4;
FIG. 7 is a simulated simulation of the active pixel sensing circuit of FIG. 1 in a first state;
FIG. 8 is a simulated simulation of the active pixel sensing circuit of FIG. 4 in a first state;
FIG. 9 is a simulated simulation of the active pixel sensing circuit of FIG. 1 in a second state;
FIG. 10 is a simulated simulation of the active pixel sensing circuit of FIG. 4 in a second state;
fig. 11 is a block diagram of an image sensor according to some embodiments of the present disclosure.
Detailed Description
For the convenience of understanding, the technical solutions provided by some embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It is obvious that the described embodiments are only some, not all embodiments of the proposed solution. All other embodiments that can be derived by one skilled in the art from some of the embodiments of the disclosure are intended to be within the scope of the disclosure.
Unless otherwise defined, technical or scientific terms used in the embodiments of the present application should have the ordinary meaning as understood by those having ordinary skill in the art to which the present disclosure belongs. The use of "first," "second," and similar terms in the embodiments of the disclosure is not intended to indicate any order, quantity, or importance, but rather to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items.
In the field of X-ray detection, APS may be an integral part of a planar X-ray detector. Illustratively, the X-ray detector includes an X-ray emitter and an APS. A plurality of pixels arranged in an array are arranged in the APS, and each pixel corresponds to one active pixel sensing circuit. The working principle of the X-ray detector is as follows: the X-ray emitted by the X-ray emitter passes through the object to be detected (e.g. patient) and then irradiates each pixel of the APS, and the magnitude of the output voltage of the photosensitive device D in each pixel after receiving the X-ray irradiation is related to the radiation intensity of the X-ray received by the corresponding photosensitive device D. Therefore, the image of the internal structure of the detected object can be effectively acquired according to the magnitude of each output voltage.
Due to the health of the patient, the adoption of low-dose illumination is one of the core requirements of the X-ray detector, and particularly during dynamic image acquisition, the requirement of low dose is more strict when the patient continuously irradiates X-rays. In the related art, APS is used as a component of an X-ray detector, and can detect a weak X-ray signal. However, in the case where the active pixel sensing circuit of the APS is as shown in fig. 1, the APS is liable to have a problem that the detection result has an error, that is, it is difficult to be uniform, due to a difference or a drift of the threshold voltage of the source follower transistor M1 in each pixel.
Based on this, some embodiments of the present disclosure provide an active pixel sensing circuit. Referring to fig. 2, the active pixel sensor circuit includes: a light sensing device 1, a compensation following circuit 2 and an output circuit 3. Wherein, the compensation follower circuit 2 includes: a voltage follower transistor Tvf, a first compensation sub-circuit 21 and a second compensation sub-circuit 22. A first pole of the light sensing device 1 is electrically connected with the first voltage terminal V1, and a second pole of the light sensing device 1 is electrically connected with the first pole of the voltage following transistor Tvf through the first compensation sub-circuit 21; the control and second poles of the voltage follower transistor Tvf are each electrically connected to the second compensation sub-circuit 22. The first compensation sub-circuit 21 is also electrically connected to the first scan line Gate1, and is configured to transmit the voltage of the second pole of the light sensing device 1 to the first pole of the voltage follower transistor Tvf in response to a first scan signal supplied from the first scan line Gate 1. The second compensation sub-circuit 22 is also electrically connected to the first scan line Gate1 and the second scan line Gate2, respectively, and is configured to store a compensation voltage in response to the first scan signal and a second scan signal supplied from the second scan line Gate 2. The compensation voltage is the sum of the photo-generated voltage of the photo-sensing device 1 and the threshold voltage of the voltage follower transistor Tvf. The output circuit 3 is electrically connected to the read control line Emn, the read signal line Readline, and the first pole of the voltage follower transistor Tvf, respectively, and is configured to transmit the output current of the voltage follower transistor Tvf compensated by the compensation voltage to the read signal line Readline in response to the read control signal provided by the read control line Emn.
The light-sensing device 1 may be an electronic device having a function of converting an optical signal into an electrical signal after receiving light irradiation. For example, referring to fig. 4, the light sensing device 1 includes a photodiode PD.
The first compensation sub-circuit 21 and the second compensation sub-circuit 22 function as described above, and the structure thereof can be selected according to actual requirements. For example, referring to fig. 4, the first compensation sub-circuit 21 includes: the first transistor T1. A control electrode of the first transistor T1 is electrically connected to the first scan line Gate1, a first electrode of the first transistor T1 is electrically connected to a second electrode of the light sensing device 1, and a second electrode of the first transistor T1 is electrically connected to a first electrode of the voltage follower transistor Tvf. Thus, in a state where the first transistor T1 is turned on, the voltage of the second pole of the light sensing device 1, that is, the output voltage thereof may be transmitted to the first pole of the voltage follower transistor Tvf through the first transistor T1. The second compensation sub-circuit 22 comprises: a second transistor T2, a third transistor T3, and a storage capacitor C. The first electrode of the storage capacitor C is electrically connected to the second voltage terminal VDD, and the second electrode of the storage capacitor C is electrically connected to the control electrode of the voltage follower transistor Tvf. A control electrode of the second transistor T2 is electrically connected to the first scan line Gate1, a first electrode of the second transistor T2 is electrically connected to a second electrode of the storage capacitor C, and a second electrode of the second transistor T2 is electrically connected to a second electrode of the voltage follower transistor Tvf. A control electrode of the third transistor T3 is electrically connected to the second scan line Gate2, a first electrode of the third transistor T3 is electrically connected to the second voltage terminal VDD, and a second electrode of the third transistor T3 is electrically connected to the second electrode of the voltage follower transistor Tvf.
The output circuit 3 functions as described above, and its structure can be selected according to actual requirements. For example, with continued reference to fig. 4, the output circuit 3 includes a fifth transistor T5. A control electrode of the fifth transistor T5 is electrically connected to the read control line Emn, a first electrode of the fifth transistor T5 is electrically connected to a first electrode of the voltage follower transistor Tvf, and a second electrode of the fifth transistor T5 is electrically connected to the read signal line Readline. That is, the fifth transistor T5 is provided between the voltage follower transistor Tvf and the read signal line Readline, and the fifth transistor T5 can be used as an output control switch of the voltage of the first pole of the voltage follower transistor Tvf. In this manner, in a state where the fifth transistor T5 is turned on, the output current of the voltage follower transistor Tvf compensated by the compensation voltage is transmitted to the read signal line Readline.
In the active pixel sensing circuit provided by some embodiments of the present disclosure, the first compensation sub-circuit 21 is capable of transmitting the output voltage of the light sensing device 1 to the first pole of the voltage follower transistor Tvf in response to the first scan signal. The second compensation sub-circuit 22 is capable of storing a compensation voltage, that is, the sum of the photo-generated voltage of the light sensing device 1 and the threshold voltage of the voltage follower transistor Tvf, in response to the first scan signal and the second scan signal. Thus, after receiving the read control signal, the second compensation sub-circuit 22 transmits the stored compensation voltage to the gate of the voltage follower transistor Tvf, so as to correspondingly control the output current of the voltage follower transistor Tvf, so that the output circuit 3 transmits the output current to the read signal line Readline in response to the read control signal.
Therefore, the active pixel sensing circuit provided by some embodiments of the present disclosure uses the compensation voltage as the control terminal voltage of the voltage follower transistor Tvf, so as to cancel the threshold voltage required when the voltage follower transistor Tvf is turned on, and completely convert the output voltage of the light sensing device 1 into the output current of the voltage follower transistor Tvf for transmission. In this way, even in the case where the output voltage of the light sensing device 1 is small, it can be ensured that the current signal read by the read signal line Readline is not disturbed by the threshold voltage of the voltage follower transistor Tvf. Therefore, the uniformity, the sensitivity and the accuracy of the image sensor are effectively improved.
In some embodiments, referring to fig. 3, the active pixel sensing circuit further includes a reset circuit 4. The reset circuit 4 is electrically connected to the reset control line Emn +1 and the second pole of the photo sensing device 1, respectively, and is configured to reset the voltage of the second pole of the photo sensing device 1 in response to a reset signal provided by the reset control line Emn + 1.
The structure of the reset circuit 4 can be selected according to actual requirements. For example, referring to fig. 4, the reset circuit 4 includes a fourth transistor T4. A control electrode of the fourth transistor T4 is electrically connected to the reset control line Emn + 1, a first electrode of the fourth transistor T4 is electrically connected to the second voltage terminal VDD, and a second electrode of the fourth transistor T4 is electrically connected to the second electrode of the photo sensing device 1. That is, the fourth transistor T4 is provided between the second voltage terminal VDD and the photo sensing device 1, and the fourth transistor T4 may be used as a reset control switch for the voltage of the second pole of the photo sensing device 1. Thus, in a state where the fourth transistor T4 is turned on, the voltage of the second pole of the photo sensing device 1 is reset to the voltage of the second voltage terminal VDD.
It should be noted that, in some embodiments, the voltage follower transistor Tvf, the first transistor T1, the second transistor T2, the third transistor T3, the fourth transistor T4 and the fifth transistor T5 are all N-type transistors. The voltage provided by the second voltage terminal VDD is higher than the voltage provided by the first voltage terminal V1.
It is to be understood that the transistor may be an enhancement transistor or a depletion transistor. The first pole of the transistor may be a source and the second pole may be a drain, or the first pole of the transistor may be a drain and the second pole may be a source, which is not limited in some embodiments of the present disclosure.
In the embodiments of the present disclosure, the turning on and off processes of each transistor are described by taking all transistors as N-type transistors as an example. Of course, each transistor in the embodiments of the present disclosure may also be of a P-type, and when all the transistors are of a P-type, the corresponding control signal may be provided for each transistor.
In order to more clearly illustrate the active pixel sensing circuit and the method for using the same provided in the above embodiments, the following embodiments take the active pixel sensing circuit shown in fig. 4 as an example to be described in detail.
Referring to fig. 4 and 5, the light sensing device 1 is a photodiode PD, and the first electrode is a positive electrode and the second electrode is a negative electrode. The anode of the photodiode PD is electrically connected with a first voltage terminal V1The cathode of the diode PD is electrically connected to the first node Q1. The first node Q1 is electrically connected to the second voltage terminal VDD through the reset circuit 4, i.e., the fourth transistor T4. The first voltage terminal V1 provides a low level and the second voltage terminal VDD provides a high level. After the reset circuit 4 resets the voltage of the cathode of the photodiode PD, the initial voltage of the first node Q1 is high level. The photodiode PD is reverse biased. The active pixel sensing circuit has a use phase in one cycle including a signal acquisition phase t1Pre-reading stage t2Reading stage t3And a reset phase t4。
In the signal acquisition phase t1When the photodiode PD receives light, the output voltage of the photodiode PD is represented as the voltage of the first node Q1.
In a pre-read phase t2The first scan signal supplied from the first scan line Gate1 is at a high level. The first transistor T1 in the first compensation sub-circuit 21 is turned on under the control of the high level, and the voltage of the first node Q1 can be transmitted to the first pole of the voltage follower transistor Tvf, i.e., the second node Q2. The second transistor T2 in the second compensation sub-circuit 22 is turned on under the control of the high level. Meanwhile, in the first period of the pre-read period t2, the second scan signal supplied from the second scan line Gate2 is at a high level. The first pole of the storage capacitor C is electrically connected to the second voltage terminal VDD. The third transistor T3 of the second compensation sub-circuit 22 is turned on under the control of the high level, and the voltage of the second voltage terminal VDD may be transferred to the second pole of the storage capacitor C through the second transistor T2.
Then, in a pre-read phase t2The second scan signal supplied from the second scan line Gate2 is at a low level. The third transistor T3 in the second compensation sub-circuit 22 is turned off under the control of the low level. The first transistor T1 and the second transistor T2 maintain a conductive state. In this way, the storage capacitor C is charged, and the compensation voltage, that is, the sum of the photogenerated voltage of the light-sensing device 1 and the threshold voltage of the voltage follower transistor Tvf can be stored.
In a reading phase t3The first scan signal provided by the first scan line Gate1 is lowAnd (7) flattening. The first transistor T1 in the first compensation sub-circuit 21 is turned off under the control of the low level, and the second transistor T2 in the second compensation sub-circuit 22 is turned off under the control of the low level. The second scan signal provided by the second scan line Gate2 is at a high level, and the third transistor T3 in the second compensation sub-circuit 22 is turned on under the control of the high level. Thus, the storage capacitor C is discharged, the voltage follower transistor Tvf is controlled to be turned on, and the threshold voltage of the voltage follower transistor Tvf can be compensated by the compensation voltage stored therein, so that the output current of the voltage follower transistor Tvf can accurately represent the photo-generated voltage of the photodiode PD.
At the same time, the read control signal provided by the read control line Emn is high. The fifth transistor T5 in the output circuit 3 is turned on under the control of the high level, and may transmit the output current of the voltage follower transistor Tvf to the read signal line Readline. Therefore, the illumination intensity sensed by the photodiode PD can be effectively acquired according to the current signal read by the read signal line Readline.
In a reset phase t3The reset control signal supplied from the reset control line Emn + 1 is at a high level. The fourth transistor T4 in the reset circuit 4 is turned on under the control of the high level, and can transmit the voltage provided by the second voltage terminal VDD to the first node Q1, i.e., the second pole of the photodiode PD, and reset the voltage of the second pole of the photodiode PD, so as to be in the signal acquisition phase T of the next cycle1Ready for use.
It is added that, in some embodiments, the current I of the voltage follower transistor Tvf in the linear region of the current-voltage characteristic curve thereofdSatisfies the formula:
the control electrode of the voltage follower transistor Tvf is a gate, the second electrode is a source, and the first electrode is a drain. I isdIs the drain current (output current) of the voltage follower transistor Tvf, μ is the carrier mobility, CoxIs the capacitance of the unit gate, and is,
for voltage to follow the width-to-length ratio, V, of the conducting channel in transistor TvfgsIn order to voltage follow the voltage between the gate and source of transistor Tvf, VthTo voltage follow the threshold voltage, V, of transistor TvfdsIs the voltage between the drain and source of the voltage follower transistor Tvf.
According to the above formula to VdsBy performing a differential calculation, the current of the voltage follower transistor Tvf in the saturation region of its current-voltage characteristic curve satisfies the following formula:
this can result in: vds＝Vgs-VthNamely: vgs＝Vds+Vth。
And because of Vds＝VpinWherein V ispinIs the photo-generated voltage of the photo-sensing device 1 (i.e. the electromotive force generated by the photo-sensing device 1 due to illumination),
thus, Vgs＝Vpin+Vth。
As such, with the first and second compensation sub-circuits 21 and 22, the compensation voltage, i.e., the sum of the photo-generation voltage of the light sensing device 1 and the threshold voltage of the voltage follower transistor Tvf, can be effectively stored in the second period of the pre-read phase t 2.
In order to more clearly illustrate the function of the active pixel sensing circuit in some embodiments described above, the inventors of the present application performed relevant circuit simulations, such as those shown in fig. 6 to 10.
Fig. 6 is a region of a current-voltage characteristic curve of a control electrode (i.e., a gate) of the voltage follower transistor Tvf, which includes a linear region and a saturation region.
Fig. 7 is a simulation diagram of the three active pixel sensing circuits shown in fig. 1 in the first state in the conventional APS. Fig. 8 is a simulation diagram of the three active pixel sensing circuits shown in fig. 4 in a first state. Here, the first state is a state in which the light intensity is small, that is, the photo-generated voltage of the light sensing device 1 is small. In the first state, simulation curves corresponding to three active pixel sensing circuits of the conventional APS are respectively shown as simulation curve a, simulation curve b and simulation curve c. The simulation curves corresponding to the three active pixel sensing circuits of the present application are substantially coincident.
Fig. 9 is a simulation diagram of the three active pixel sensing circuits shown in fig. 1 in the second state in the conventional APS. Fig. 10 is a simulation diagram of the three active pixel sensing circuits shown in fig. 4 in a second state. Here, the second state is a state in which the light intensity is large, that is, the photo-generated voltage of the light sensing device 1 is large. In the second state, simulation curves corresponding to three active pixel sensing circuits of the conventional APS are respectively shown as a simulation curve a ', a simulation curve b ' and a simulation curve c '. The simulation curves corresponding to the three active pixel sensing circuits of the present application are substantially coincident.
Therefore, compared with an active pixel sensing circuit in a conventional APS, the output current signal of the active pixel sensing circuit provided by the embodiment of the present disclosure is significantly less affected by the fluctuation of the threshold voltage of the voltage follower transistor Tvf, and the stability of signal detection can be effectively improved to ensure the uniformity, sensitivity and accuracy of the corresponding image sensor.
In another aspect, some embodiments of the present disclosure provide an image sensor. Referring to fig. 11, the image sensor includes a plurality of pixels PX arranged in an array, and the active pixel sensing circuit according to some embodiments is disposed in each pixel PX.
The beneficial effects that can be achieved by the image sensor provided in some embodiments of the present disclosure are the same as those that can be achieved by the active pixel sensing circuit provided in some embodiments, and are not described herein again.
In some embodiments, the image sensor further comprises: and the reading circuits are respectively and electrically connected with the reading signal lines Readline in the plurality of active pixel sensing circuits.
For example, referring to fig. 11, the reading circuit includes an analog signal processing module MdAnd analog-to-digital conversionModule Madc. Analog signal processing module MdIs configured to perform denoising processing on the current signal transmitted to Readline by each pixel PX so as to facilitate the subsequent analog-to-digital conversion module MadcThe conversion process of (1). Optionally, an analog signal processing module MdThe method comprises the following steps: amplifier OP, capacitor CfbResistance RsampAnd a capacitor CsampWherein, the capacitor CfbIn parallel with the amplifier OP, the resistor RsampThrough a capacitor CsampAnd (4) grounding.
Analog-to-digital conversion module MadcAnd the noise-removed current signal is converted into a digital signal. Optionally, an analog-to-digital conversion module MadcIncluding an analog to digital converter.
In yet another aspect, some embodiments of the present disclosure provide a light detecting display panel. The photo detection display panel comprises an image sensor as described in some embodiments above.
Optionally, the light detection display panel further includes a display signal processing circuit. The input end of the display signal processing circuit is connected with the output end of the reading circuit in the image sensor and is configured to convert the electric signal transmitted by the output end of the reading circuit in the image sensor into a display signal.
The beneficial effects that can be achieved by the photodetection display panel provided in some embodiments of the present disclosure are the same as those that can be achieved by the image sensor provided in some embodiments described above, and are not described herein again.
In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only for the specific embodiments of the present disclosure, but the scope of the present disclosure is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present disclosure, and all the changes or substitutions should be covered within the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.
Claims (10)
1. An active pixel sensing circuit, comprising: the circuit comprises a photosensitive device, a compensation following circuit and an output circuit; the compensation follower circuit includes: a voltage follower transistor, a first compensation sub-circuit and a second compensation sub-circuit; wherein the content of the first and second substances,
the first electrode of the photosensitive device is electrically connected with the first voltage end, and the second electrode of the photosensitive device is electrically connected with the first electrode of the voltage following transistor through the first compensation sub-circuit; the control electrode and the second electrode of the voltage following transistor are respectively and electrically connected with the second compensation sub-circuit;
the first compensation sub-circuit is also electrically connected with a first scanning line and is configured to respond to a first scanning signal provided by the first scanning line and output the voltage of the second pole of the photosensitive device to the first pole of the voltage following transistor;
the second compensation sub-circuit is electrically connected with the first scanning line and the second scanning line respectively and is configured to respond to the first scanning signal and a second scanning signal provided by the second scanning line and store compensation voltage; the compensation voltage is the sum of the photogenerated voltage of the photosensitive device and the threshold voltage of the voltage following transistor;
the output circuit is electrically connected to a read control line, a read signal line, and the first pole of the voltage follower transistor, respectively, and is configured to transmit an output current of the voltage follower transistor compensated by the compensation voltage to the read signal line in response to a read control signal provided by the read control line.
2. The active pixel sensing circuit of claim 1,
the first compensation sub-circuit comprises: a first transistor; a control electrode of the first transistor is electrically connected with the first scanning line, a first electrode of the first transistor is electrically connected with a second electrode of the photosensitive device, and the second electrode of the first transistor is electrically connected with a first electrode of the voltage following transistor;
the second compensation sub-circuit comprises: a second transistor, a third transistor, and a storage capacitor; wherein the content of the first and second substances,
the first electrode of the storage capacitor is electrically connected with the second voltage end, and the second electrode of the storage capacitor is electrically connected with the control electrode of the voltage following transistor;
a control electrode of the second transistor is electrically connected with the first scanning line, a first electrode of the second transistor is electrically connected with a second electrode of the storage capacitor, and a second electrode of the second transistor is electrically connected with a second electrode of the voltage following transistor;
a control electrode of the third transistor is electrically connected to the second scan line, a first electrode of the third transistor is electrically connected to the second voltage terminal, and a second electrode of the third transistor is electrically connected to a second electrode of the voltage follower transistor.
3. The active pixel sensing circuit of claim 2, further comprising a reset circuit;
the reset circuit is electrically connected with the reset control line and the second pole of the photosensitive device respectively and is configured to reset the voltage of the second pole of the photosensitive device in response to a reset signal provided by the reset control line.
4. The active pixel sensing circuit of claim 3, wherein the reset circuit comprises a fourth transistor;
and the control electrode of the fourth transistor is electrically connected with the reset control line, the first electrode of the fourth transistor is electrically connected with the second voltage end, and the second electrode of the fourth transistor is electrically connected with the second electrode of the photosensitive device.
5. The active pixel sensing circuit of claim 2 or 4, wherein the output circuit comprises a fifth transistor;
a control electrode of the fifth transistor is electrically connected to the read control line, a first electrode of the fifth transistor is electrically connected to a first electrode of the voltage follower transistor, and a second electrode of the fifth transistor is electrically connected to the read signal line.
6. The active pixel sensing circuit of claim 5, wherein the voltage follower transistor, the first transistor, the second transistor, the third transistor, and the fifth transistor are all N-type transistors;
in the case where the active pixel sensing circuit includes a reset circuit including a fourth transistor, the fourth transistor is an N-type transistor;
the voltage provided by the second voltage terminal is higher than the voltage provided by the first voltage terminal.
7. The active pixel sensing circuit of claim 1, wherein the light sensing device comprises a photodiode.
8. An image sensor, comprising: a plurality of pixels arranged in an array;
an active pixel sensing circuit according to any one of claims 1 to 7 is provided in each of the plurality of pixels.
9. The image sensor of claim 8, further comprising: and a reading circuit electrically connected to a reading signal line of each of the plurality of active pixel sensing circuits.
10. A light detecting display panel, comprising: the image sensor of claim 8 or 9.
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| CN201922314880.0U CN211239962U (en) | 2019-12-20 | 2019-12-20 | Active pixel sensing circuit, image sensor and light detection display panel |
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| CN201922314880.0U CN211239962U (en) | 2019-12-20 | 2019-12-20 | Active pixel sensing circuit, image sensor and light detection display panel |
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| CN211239962U true CN211239962U (en) | 2020-08-11 |
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