TW201802783A - Pixel sensing device and method for controlling the same - Google Patents

Abstract

A pixel sensing device includes a transistor, a capacitor, a photodiode, a first reset unit, a second reset unit, a transmitting unit, a control unit, and a reading unit. The transistor includes a first terminal, a control terminal, and a second terminal. The photodiode includes an anode and a cathode. The photodiode senses ambient light for outputting a signal voltage. The first reset unit resets the voltage of the cathode based on a first reset signal. The second reset unit outputs a reset voltage to the control terminal based on a second reset signal. The transmitting unit transmits the signal voltage of the cathode to the control terminal and couples the signal voltage to the second terminal based on a transmitting signal. The control unit provides a power supply voltage to the first terminal based on a control signal. The reading unit reads out the current based on a reading signal.

Description

Pixel sensing device and control method

The invention relates to a sensing device and a control method thereof, and more particularly to a pixel sensing device and a control method thereof.

Generally, the main video element sensor includes a plurality of transistors and capacitors to sense the light source and generate a current accordingly. However, due to the influence of the manufacturing process or after a long time operation, the threshold voltages (Vth) of the plurality of transistors in each main animation element sensor will be different. The same amount of light from the sensor, the current generated by each main animation sensor will still be different, resulting in an error in the read current.

It can be seen that the above existing methods obviously still have inconveniences and defects, and need to be improved. In order to solve the above-mentioned problems, the related fields have made every effort to find a solution, but a suitable solution has not been developed for a long time.

This summary is intended to provide a simplified summary of this disclosure so that readers may have a basic understanding of this disclosure. This summary is not a complete overview of this disclosure, and it is not intended to indicate the importance of the embodiments of the invention / Key elements or define the scope of the invention.

An object of the present invention is to provide a pixel sensing device and a control method thereof, so as to improve the problems of the prior art.

To achieve the above object, one aspect of the technical content of the present invention relates to a pixel sensing device. The pixel sensing device includes a first transistor, a first capacitor, a photodiode, a first reset unit, and a first pixel. Two reset units, a transfer unit, a control unit, a reading unit, a first capacitor, and a second capacitor. The first transistor includes a first terminal, a control terminal, and a second terminal. The first transistor is used to output a current. The first capacitor is coupled between the control terminal and the second terminal of the first transistor. The photodiode includes an anode terminal and a cathode terminal. The photodiode is used to sense a light source to output a signal voltage. The first reset unit is coupled to the cathode terminal of the photodiode, and is used to reset the voltage of the cathode terminal according to the first reset signal. The second reset unit is coupled to the control terminal of the first transistor, and is configured to output a reset voltage to the control terminal according to the second reset signal. The transmitting unit is coupled between the cathode terminal and the control terminal. The transmitting unit is used for transmitting the signal voltage of the cathode terminal to the control terminal according to the transmitted signal, and the signal voltage is coupled to the second terminal through the first capacitor. The control unit is coupled to the first terminal of the first transistor to provide a power supply voltage to the first terminal according to a control signal. The reading unit is coupled to the second terminal of the first transistor to read the current according to the reading signal. The second capacitor is coupled between the control unit and the reading unit.

To achieve the above object, another aspect of the present invention relates to a control method for controlling a pixel sensing device. The pixel sensing device includes a transistor, a capacitor, and a photodiode. The transistor includes a first terminal, a control terminal, and a second terminal. The photodiode includes an anode terminal and a cathode terminal. The capacitor is coupled to the control terminal and the second terminal. Between ends. This control method includes the following steps: During the compensation period During the compensation period, the voltage at the cathode terminal is reset according to the first reset signal; during the compensation period, the reset voltage is written to the control terminal according to the second reset signal; during a data writing period, the photodiode is transferred according to the transmitted signal. The signal voltage output from the cathode terminal of the body is transmitted to the control terminal, and the signal voltage is coupled to the second terminal through capacitance; during the reading period, the power supply voltage is provided to the first terminal according to the control signal, and the transistor is The voltage between the control terminal and the second terminal is used to output the current; and during the reading, the current is read according to the reading signal.

Therefore, according to the technical content of the present invention, the embodiments of the present invention provide a pixel sensing device and a control method to improve the pixel sensing device's readout caused by the threshold voltage (Vth) of the transistor in the pixel sensing device. There is an error in the current.

After referring to the following embodiments, those with ordinary knowledge in the technical field to which the present invention pertains can easily understand the basic spirit and other inventive objectives of the present invention, as well as the technical means and implementation aspects adopted by the present invention.

110‧‧‧First reset unit

120‧‧‧Second reset unit

130‧‧‧ Delivery Unit

140‧‧‧control unit

150‧‧‧reading unit

500‧‧‧point unit

900‧‧‧ Method

910 ~ 970‧‧‧step

C1 ~ C3‧‧‧Capacitor

D‧‧‧ the first end

EM‧‧‧Control signal

G‧‧‧Control terminal

I _OUT ‧‧‧ Current

N‧‧‧ cathode terminal

PD‧‧‧Photodiode

During P1 ~ P5‧‧‧‧

Reset1 ~ Reset2‧‧‧Reset signal

S‧‧‧ the second end

Select‧‧‧Read signal

SW‧‧‧Switch

T1 ~ T6‧‧‧Transistors

TX‧‧‧ pass signal

V _DD ‧‧‧ Power supply voltage

V _ref ‧‧‧ Reference voltage

V _rst ‧‧‧ reset voltage

V _sig ‧‧‧Signal voltage

V _ss ‧‧‧ Voltage

V _th ‧‧‧ critical voltage

In order to make the above and other objects, features, advantages, and embodiments of the present invention more comprehensible, the description of the drawings is as follows: FIG. 1 is a schematic diagram of a pixel sensing device according to an embodiment of the present invention .

FIG. 2 is a schematic diagram of a control waveform according to an embodiment of the present invention.

FIG. 3 is a detailed circuit diagram of the pixel sensing device according to the embodiment shown in FIG. 1 of the present invention.

FIG. 4 shows a pixel sensing device according to the embodiment shown in FIG. 3 of the present invention. Set operation diagram.

FIG. 5 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention.

FIG. 6 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention.

FIG. 7 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention.

FIG. 8 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention.

FIG. 9 is a flowchart illustrating a control method according to another embodiment of the present invention.

According to the usual operation method, various features and components in the figure are not drawn to scale. The drawing method is to present the specific features and components related to the present invention in an optimal way. In addition, between different drawings, the same or similar element symbols are used to refer to similar elements / components.

In order to make the description of this disclosure more detailed and complete, the following provides an illustrative description of the implementation mode and specific embodiments of the present invention; but this is not the only form of implementing or using the specific embodiments of the present invention. The embodiments include the features of a plurality of specific embodiments, as well as the method steps and their order for constructing and operating these specific embodiments. However, other specific embodiments can also be used to achieve the same or equal functions and sequence of steps.

Unless otherwise defined in this specification, science and technology used herein The meaning of the vocabulary is the same as that understood by those with ordinary knowledge in the technical field to which the present invention belongs. In addition, when not in conflict with the context, the singular noun used in this specification covers the plural form of the noun; and the plural noun used also covers the singular form of the noun.

In addition, as used in this document, "coupling" may mean that two or more elements make direct physical or electrical contact with each other, or indirectly make physical or electrical contact with each other, or that two or more elements operate mutually Or action.

FIG. 1 is a schematic diagram of a pixel sensing device according to an embodiment of the present invention. As shown in the figure, the pixel sensing device includes a first transistor T1, a first capacitor C1, a second capacitor C2, a photodiode PD, a first reset unit 110, a second reset unit 120, and a transfer unit 130. Control unit 140 and reading unit 150. The first transistor T1 includes a first terminal D, a control terminal G, and a second terminal S. The photodiode PD includes an anode terminal and a cathode terminal N.

In terms of connection, the first reset unit 110 is coupled to the cathode terminal N of the photodiode PD, and can receive the power supply voltage V _DD and the first reset signal Reset1. The transmission unit 130 is coupled between the cathode terminal N of the photodiode PD and the control terminal G of the first transistor T1, and can receive a transmission signal TX. The second reset unit 120 is coupled to the control terminal G of the first transistor T1 and can receive a reset voltage V _rst and a second reset signal Reset2. The first capacitor C1 is coupled between the control terminal G and the second terminal S of the first transistor T1. The control unit 140 is coupled to the first terminal D of the first transistor T1 and can receive a power supply voltage V _DD and a control signal EM. The reading unit 150 is coupled between the second terminal S of the first transistor T1 and the external integration unit 500 and can receive a reading signal Select. The second capacitor C2 is coupled between the control unit 140 and the reading unit 150.

In order to make the operation method of the pixel sensing device of the embodiment of the present invention easy to understand, please refer to FIG. 2 together, which is a schematic diagram of a control waveform according to the embodiment of the present invention. As shown in FIG. 1 and FIG. 2, the photodiode PD is used to sense a light source to output a signal voltage. The first reset unit 110 is configured to reset the voltage of the cathode terminal N according to the first reset signal Reset1 during the compensation period P2. The second reset unit 120 is configured to write a reset voltage V _rst to the control terminal G according to the second reset signal Reset2 during the compensation period P2, so that the second terminal S gradually approaches the reset voltage V _{rst to} buckle the transistor. T1 threshold voltage. The integration period P3 is the integration time of the photodiode PD exposure.

In addition, the transmitting unit 130 is configured to transmit the signal voltage of the cathode terminal N to the control terminal G according to the transmission signal TX during the data writing period P4, and couple the signal voltage to the second terminal S through the first capacitor C1. During the reading period P5, the control unit 140 is configured to provide a power supply voltage V _DD to the first terminal D according to the control signal EM, and the first transistor T1 outputs a current according to the voltage between the control terminal G and the second terminal S. The reading unit 150 is configured to read the current according to the reading signal Select.

In this way, the pixel sensing device of the present case resets and compensates the first transistor T1 during the above period, so that the current output by the first transistor T1 is independent of its own threshold voltage, so it can be effectively improved. The pixel sensing device has a problem that an error occurs in a read current due to a difference in a threshold voltage (V _th ) of a transistor therein.

Please refer to FIG. 1 and FIG. 2 together. For example, the first reset unit 110 resets the voltage of the cathode terminal N according to the high-level first reset signal Reset1 during the compensation period P2. Subsequently, during the compensation period P2, the second reset unit 120 writes a reset voltage V _rst to the control terminal G according to the second reset signal Reset2 at a high level, so as to form a first voltage difference (V _rst- V _th ).

Then, photodiode PD sensing light source at its cathode terminal N to generate a signal voltage V _sig, 130 P4 transfer unit to transfer the cathode terminal N of the signal voltage V _sig to a high level according to a transfer signal TX data during the writing The control terminal G couples the signal voltage V _sig to the second terminal S through the first capacitor C1 to form a first voltage difference (V _rst -V _th ) and a second voltage difference (V _sig -V _rst ) at the second terminal s. ) * a voltage sum ((V _rst- V _th ) + (V _sig -V _rst ) * a). Then, during the reading period P5, the control unit 140 is configured to provide the power supply voltage V _DD to the first terminal D according to the high-level control signal EM. At this time, the first transistor T1 may be based on the voltage and ((V _rst- V _th ) + (V _sig -V _rst ) * a) to output current I _OUT , the above parameter a is the ratio of the capacitance value of the first capacitor C1 to the sum of the capacitance values of the first capacitor C1 and the second capacitor C2, The relationship is as follows:

The current I _OUT generated according to the above operation will have nothing to do with the threshold voltage V _th , which will be described later.

First, the current formula of the transistor is as follows:

During the reading period P5, the voltage V _GS between the control terminal G and the second terminal S of the first transistor T1 is V _sig -((V _rst -V _th ) + (V _sig -V _rst ) * a), Bringing the above voltage V _GS into Equation 1, the current I _{OUT of the} first transistor T1 is as follows:

After finishing the above formula 2, the following formula is obtained:

It can be known from Equation 3 that even if the transistor used in the main video sensor is affected by the process or after a long time operation, the threshold voltage V _{th is} different. The current output by the reading unit 150 of the pixel sensing device of the present case I _OUT is indeed not related to the threshold voltage V _{th of the} first transistor T 1. Therefore, the problem of the error in the read current due to different threshold voltage V _th in the prior art can be effectively improved.

See Figure 2. The compensation period P2 and the integration period P3 partially overlap. Therefore, the pixel sensing device in this case can perform compensation and integration operations simultaneously during the above-mentioned overlapping period, so as to improve the execution efficiency of the pixel sensing device.

Please refer to FIG. 1 and FIG. 2 together. In the initial period P1, the control unit 140 writes the power supply voltage V _DD to the first terminal D according to the control signal EM, and the reading unit 150 selects the read signal Select in the initial period P1. A reference voltage V _{ref is} written to the second terminal S. In one embodiment, the initial period P1 partially overlaps the read period P5. In another embodiment, please refer to FIG. 2, the initial period P1 and the reading period P5 may be the same period, that is, the pixel sensing device in this case can perform initialization and reading current operations at the same time to improve the pixel feeling Measure the implementation efficiency of the device.

FIG. 3 is a detailed circuit diagram of the pixel sensing device according to the embodiment shown in FIG. 1 of the present invention. As shown in the figure, the first reset unit 110 includes a second transistor T2. The second transistor T2 includes a first terminal, a control terminal, and a second terminal. The first terminal of the second transistor T2 is used to receive power supply. At the voltage V _DD , the control terminal of the second transistor T2 is used to receive the first reset signal Reset1, and the second terminal of the second transistor T2 is coupled to the cathode terminal N of the photodiode PD. In addition, the second reset unit 120 includes a third transistor T3. The third transistor T3 includes a first terminal, a control terminal, and a second terminal. The first terminal of the third transistor T3 is used to receive the reset voltage V _rst. The control terminal of the third transistor T3 is used to receive the second reset signal Reset2, and the second terminal of the third transistor T3 is coupled to the control terminal G of the first transistor T1. Furthermore, the transmission unit 130 includes a fourth transistor T4. The fourth transistor T4 includes a first terminal, a control terminal, and a second terminal. The first terminal of the fourth transistor T4 is coupled to the cathode of the photodiode PD. Extreme N, the control terminal of the fourth transistor T4 is used to receive the transmission signal TX, and the second terminal of the fourth transistor T4 is coupled to the control terminal G of the first transistor T1.

In addition, the control unit 140 includes a fifth transistor T5. The fifth transistor T5 includes a first terminal, a control terminal, and a second terminal. The first terminal of the fifth transistor T5 is used to receive the power supply voltage V _DD . The control terminal of the transistor T5 is used to receive the control signal EM. The second terminal of the fifth transistor T5 is coupled to the first terminal D of the first transistor T1. On the other hand, the reading unit 150 includes a sixth transistor T6. The sixth transistor T6 includes a first terminal, a control terminal, and a second terminal. The first terminal of the sixth transistor T6 is coupled to the first transistor T1. The second terminal S, the control terminal of the sixth transistor T6 is used to receive the read signal Select, and the second terminal of the sixth transistor T6 is coupled to the inverting input terminal of the external integration unit 500. In addition, the second capacitor C2 is coupled between the first terminal of the fifth transistor T5 and the second terminal S of the first transistor T1, and is coupled to the first terminal of the sixth transistor T6. In addition, the integrating unit 500 includes an amplifier, a third capacitor C3, and a switch SW. The third capacitor C3 is coupled between the inverting input terminal and the output terminal of the amplifier. The switch SW is also coupled between the inverting input terminal and the output terminal of the amplifier. The inverting input terminal of the amplifier is coupled to the second terminal of the sixth transistor T6. The non-inverting input terminal of the amplifier is used to receive the reference voltage V _ref .

FIG. 4 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention. Please refer to FIG. 2 and FIG. 4 together. In the initial period P1, the read signal Select is a high-level signal, the sixth transistor T6 is turned on according to the read signal Select, and at the same time, the amplifier of the integration unit 500 is inverted. The input terminal is at the same potential as the non-inverting input terminal and is the reference voltage _Vref . Therefore, the sixth transistor T6 writes the reference voltage V _{ref of the} inverting input terminal to the second terminal S of the first transistor T1. In addition, the control signal EM is a high-level signal, and the fifth transistor T5 is turned on according to the control signal EM to provide a power supply voltage V _DD to the first terminal D. Furthermore, the remaining signals are all low-level signals. Therefore, the second transistor T2, the third transistor T3, and the fourth transistor T4 are not turned on. During this period, the photodiode PD can be used to sense the light source and generate a signal voltage at its cathode terminal N. However, since the second transistor T2 and the fourth transistor T4 are not turned on, the photodiode PD The cathode terminal N will discharge to the ground terminal V _SS , and the photodiode PD will not transmit a signal voltage to the control terminal G of the first transistor T1. Furthermore, the third transistor T3 is not turned on. Therefore, the reset voltage V _{rst is} not transmitted to the control terminal G of the first transistor T1. According to this, the first transistor T1 is based on the control terminal G and the second terminal S. Voltage difference without conducting.

FIG. 5 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention. Please refer to FIG. 2 and FIG. 5 together. During the compensation period P2, the first reset signal Reset1 is a high-level signal, and the second transistor T2 is turned on according to the first reset signal Reset1 to turn the power supply voltage V _{DD is} written into the cathode terminal N of the photodiode PD. In addition, the control signal EM is still a high-level signal, and the fifth transistor T5 is turned on according to the control signal EM to provide a power supply voltage V _DD to the first terminal D. Furthermore, the remaining signals are all low-level signals. Therefore, the third transistor T3, the fourth transistor T4, and the sixth transistor T6 are not turned on. During this period, since the fourth transistor T4 is not turned on, the photodiode PD does not transmit a signal voltage to the control terminal G of the first transistor T1. Furthermore, the third transistor T3 is not turned on. Therefore, the reset voltage V _{rst is} not transmitted to the control terminal G of the first transistor T1. According to this, the first transistor T1 is based on the control terminal G and the second terminal S. Voltage difference without conducting. In addition, the sixth transistor T6 is not turned on. Therefore, the inverting terminal of the integration unit 500 will not receive a voltage, and its switch SW is short-circuited. Accordingly, the integration unit 500 will not perform integration to read any signal.

FIG. 6 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention. Please refer to FIG. 2 and FIG. 6 together. During the compensation period P2, the second reset signal Reset2 is a high-level signal, and the third transistor T3 is turned on according to the second reset signal Reset2, so that the first transistor is turned on. The control terminal G of T1 writes a reset voltage V _rst to form a first voltage difference (V _rst -V _th ) at the second terminal S. In addition, the control signal EM is still a high-level signal, and the fifth transistor T5 is turned on according to the control signal EM to provide a power supply voltage V _DD to the first terminal D. Furthermore, the remaining signals are all low-level signals. Therefore, the second transistor T2, the fourth transistor T4, and the sixth transistor T6 are not turned on. During this period, the photodiode PD can be used to sense the light source and generate a signal voltage at its cathode terminal N. However, since the second transistor T2 and the fourth transistor T4 are not turned on, the photodiode PD The cathode terminal N is discharged to the ground terminal V _SS . In addition, the sixth transistor T6 is not turned on. Therefore, the inverting terminal of the integration unit 500 will not receive a voltage, and its switch SW is short-circuited. Accordingly, the integration unit 500 will not perform integration to read any signal.

FIG. 7 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention. Please refer to FIG. 2 and FIG. 7 together. During the data writing period P4, the photodiode PD senses the light source to generate a signal voltage V _sig at its cathode terminal N, and the transmission signal TX is a high level signal. The crystal T4 is turned on according to the transmission signal TX, so as to transmit the signal voltage V _sig of the cathode terminal N of the photodiode PD to the control terminal G of the first transistor T1, and couple the signal voltage V _sig to the first through the first capacitor C1. The two terminals S form a voltage sum of the first voltage difference (V _rst -V _th ) and the second voltage difference (V _sig -V _rst ) * a at the second terminal S of the first transistor T1 ((V _rst- V _th ) + (V _sig -V _rst ) * a). Furthermore, the remaining signals are all low-level signals. Therefore, the second transistor T2, the third transistor T3, the fifth transistor T5, and the sixth transistor T6 are not turned on. In addition, the sixth transistor T6 is not turned on. Therefore, the inverting terminal of the integration unit 500 will not receive a voltage, and its switch SW is short-circuited. Accordingly, the integration unit 500 will not perform integration to read any signal.

FIG. 8 is a schematic diagram illustrating the operation of the pixel sensing device according to the embodiment shown in FIG. 3 of the present invention. Please refer to FIG. 2 and FIG. 8 together. During the reading period P5, the control signal EM is a high level signal, and the fifth transistor T5 is turned on according to the control signal EM to provide the power supply voltage V _DD to the first transistor. The first terminal D of T1, at this time, the first transistor T1 can be based on the sum of the voltage V _{sig of the} control terminal G and the voltage of the second terminal S ((V _rst- V _th ) + (V _sig -V _rst ) * a) With the output current I _OUT , the current I _OUT generated according to the above operation will be independent of the threshold voltage V _th . Furthermore, the read signal Select is a high-level signal, and the sixth transistor T6 is turned on according to the read signal Select to read the current I _OUT . The parameter a of the voltage sum of the second terminal S of the first transistor T1 is the ratio of the capacitance value of the first capacitor C1 to the sum of the capacitance values of the first capacitor C1 and the second capacitor C2, and the relationship is as follows:

The current I _OUT generated according to the above operation will have nothing to do with the threshold voltage V _th , which will be described later.

First, the current formula of the transistor is as follows:

During the reading period P5, the voltage V _GS between the control terminal G and the second terminal S of the first transistor T1 is V _sig -((V _rst -V _th ) + (V _sig -V _rst ) * a), Bringing the above voltage V _GS into Equation 1, the current I _{OUT of the} first transistor T1 is as follows:

After finishing the above formula 2, the following formula is obtained:

It can be known from Formula 3 that even if the transistor used in the main pixel sensor is affected by the process or after a long time operation, the threshold voltage V _{th is} different. The sixth transistor T6 of the pixel sensor in this case outputs The current I _OUT is indeed independent of the threshold voltage V _{th of the} first transistor T1, and therefore, the problem of errors in the read current due to different threshold voltage V _th in the prior art can be effectively improved. In addition, the remaining signals are all low-level signals. Therefore, the second transistor T2, the third transistor T3, and the fourth transistor T4 are not turned on. In the meantime, the integrating unit 500 the switch SW open circuit, and received by the sixth transistor T6 to the current I _OUT and subjected to integral operation, corresponding to the photodiode PD measured current sensing light intensity I _OUT Read to external circuit. In addition, the photodiode PD can still be used to sense the light source and generate a signal voltage at its cathode terminal N. However, since the second transistor T2 and the fourth transistor T4 are not turned on, the photodiode The cathode terminal N of the bulk PD is discharged to the ground terminal V _SS .

FIG. 9 shows a control device according to another embodiment of the present invention. Process flow chart. As shown in the figure, the control method 900 can be used to control the pixel sensing device as shown in FIG. 1 and includes the following steps: Step 910: During the initial period, write a reference voltage to the second terminal according to the read signal Step 920: During the initial period, write the power supply voltage to the first terminal according to the control signal; Step 930: During the compensation period, reset the cathode terminal voltage according to the first reset signal; Step 940: According to the compensation period The second reset signal is used to write a reset voltage to the control terminal; step 950: during the integration period, the photodiode is exposed to generate a signal voltage at the cathode terminal of the photodiode; step 960: during the data writing, according to The signal is transmitted to transmit the signal voltage output from the cathode terminal of the photodiode to the control terminal, and the signal voltage is coupled to the second terminal through capacitance; step 970: during the reading period, a power supply voltage is provided to the first according to the control signal Terminal, wherein the transistor outputs current according to the voltage between its control terminal and the second terminal during the reading period; and step 980: during the reading period, the current is read according to the reading signal.

In order to make the control method 900 of the embodiment of the present invention easy to understand, please refer to FIG. 1, FIG. 2, and FIG. 9 together. In step 910, in the initial period P1, the reading unit 150 writes the reference voltage _{Vref to} the second terminal S of the transistor T1 according to the reading signal Select. In step 920, during the initial period P1, the control unit 140 writes the power supply voltage V _{DD to} the first terminal D of the transistor T1 according to the control signal EM. In step 930, during the compensation period P2, the first reset unit 110 resets the voltage of the cathode terminal N of the photodiode PD according to the first reset signal Reset1. In step 940, during the compensation period P2, the second reset unit 120 writes a reset voltage V _rst to the control terminal G of the transistor T1 according to the second reset signal Reset2 to make the second of the transistor T1 The terminal S gradually approaches the first voltage difference (V _rst -V _th ). In step 950, during the integration period P3, the photodiode PD exposes the integration and generates a signal voltage at the cathode terminal N. In an embodiment, referring to FIG. 2, the compensation period P2 and the integration period P3 partially overlap.

In step 960, during the data writing period P4, the transmission unit 130 transmits the signal voltage V _sig output from the cathode terminal N of the photodiode PD to the control terminal G according to the transmission signal TX, and couples the signal through the capacitor C1. Voltage V _sig to the second terminal S, so that the voltage sum of the first voltage difference (V _rst -V _th ) and the second voltage difference (V _sig -V _rst ) * a ((V _rst- V _th ) + (V _sig -V _rst ) * a). In step 970, during the reading period P5, the control unit 140 provides a power supply voltage V _DD to the first terminal D according to the control signal EM. In addition, during the reading period P5, the transistor T1 is based on the voltage of the control terminal G. V _sig and the voltage sum ((V _rst -V _th ) + (V _sig -V _rst ) * a) of the second terminal S are used to output current. The current generated according to the above operation will have nothing to do with the threshold voltage V _th . In step 980, during the reading period P5, the reading unit 150 reads the current according to the reading signal Select. The parameter a of the voltage sum of the second terminal S of the first transistor T1 is the ratio of the capacitance value of the first capacitor C1 to the sum of the capacitance values of the first capacitor C1 and the second capacitor C2, and the relationship is as follows:

The current I _OUT generated according to the above operation will have nothing to do with the threshold voltage V _th , which will be described later.

First, the current formula of the transistor is as follows:

During the reading period P5, the voltage V _GS between the control terminal G and the second terminal S of the first transistor T1 is V _sig -((V _rst -V _th ) + (V _sig -V _rst ) * a), Bringing the above voltage V _GS into Equation 1, the current I _{OUT of the} first transistor T1 is as follows:

After finishing the above formula 2, the following formula is obtained:

It can be known from Equation 3 that even if the transistor used in the pixel sensing device controlled by the control method 900 is based on the influence of the manufacturing process or after a long-term operation, the threshold voltage V _{th is} different, and the pixel sensing is performed by the control method 900 of the present case. the control means, such that the output of the sixth transistor T6 pixel sensing device current I _OUT is indeed independent of the threshold voltage V _th of the first transistor T1 is, therefore, to improve on the prior art varies the threshold voltage V _th Causes the problem that the read current has an error.

Those with ordinary knowledge in the technical field should understand that the steps in the control method 900 are named according to the functions performed by them, only to make the technology in this case more obvious and understandable, and not to limit these steps. Integrating each step into the same step or splitting it into multiple steps, or changing any step to another step for execution, still belongs to the embodiments of the present disclosure.

It can be known from the foregoing embodiments of the present invention that the application of the present invention has the following advantages. Embodiments of the present invention provide a pixel sensing device and a control method. This method can improve the pixel sensing device's error caused by the difference in the threshold voltage of the transistor.

Although the above embodiments disclose specific examples of the present invention, they are not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains should not deviate from the principles and spirit of the present invention. Various changes and modifications can be made to it, so the scope of protection of the present invention shall be defined by the scope of the accompanying patent application.

110‧‧‧First reset unit

120‧‧‧Second reset unit

130‧‧‧ Delivery Unit

140‧‧‧control unit

150‧‧‧reading unit

500‧‧‧point unit

C1 ~ C3‧‧‧Capacitor

D‧‧‧ the first end

EM‧‧‧Control signal

G‧‧‧Control terminal

PD‧‧‧Photodiode

Reset1 ~ Reset2‧‧‧Reset signal

S‧‧‧ the second end

Select‧‧‧Read signal

SW‧‧‧Switch

T1‧‧‧Transistor

TX‧‧‧ pass signal

V _DD ‧‧‧ Power supply voltage

V _ref ‧‧‧ Reference voltage

V _rst ‧‧‧ reset voltage

N‧‧‧ cathode terminal

V _ss ‧‧‧ Voltage

I _OUT ‧‧‧ Current

Claims (13)

A pixel sensing device includes: a first transistor including a first terminal, a control terminal, and a second terminal for outputting a current; a first capacitor coupled to the first transistor Between the control terminal and the second terminal; a photodiode including an anode terminal and a cathode terminal for sensing a light source to output a signal voltage; a first reset unit coupled to the photoelectric diode The cathode terminal of the electrode body is used to reset the voltage of the cathode terminal according to a first reset signal; a second reset unit is coupled to the control terminal of the first transistor, and is used according to a first Two reset signals to output a reset voltage to the control terminal; a transmission unit coupled between the cathode terminal and the control terminal, and configured to transmit the signal voltage of the cathode terminal to the cathode terminal according to a transmission signal; A control terminal, and coupling the signal voltage to the second terminal through the first capacitor; a control unit coupled to the first terminal of the first transistor to provide a power supply voltage to the control circuit according to a control signal; The first terminal; a reading unit, coupled to the first transistor A second terminal for reading, a current in accordance with a read signal; and a second capacitor coupled between the control unit and the reading unit. The pixel sensing device according to claim 1, wherein the control unit writes the power supply voltage to the first terminal according to the control signal, and the reading unit writes to the second terminal according to the read signal. Enter a reference voltage. The pixel sensing device according to claim 1, wherein the first reset unit includes: a second transistor including: a first terminal for receiving the power supply voltage; a control terminal for receiving The first reset signal; and a second terminal coupled to the cathode terminal. The pixel sensing device according to claim 1, wherein the second reset unit includes: a third transistor including: a first terminal for receiving the reset voltage; a control terminal for receiving The second reset signal; and a second terminal coupled to the control terminal of the first transistor. The pixel sensing device according to claim 1, wherein the transmission unit includes: a fourth transistor including: a first terminal coupled to the cathode terminal; a control terminal for receiving the transmission signal; And a second terminal, which is coupled to the control terminal of the first transistor. The pixel sensing device according to claim 1, wherein the control unit includes: A fifth transistor includes: a first terminal for receiving the power supply voltage; a control terminal for receiving the control signal; and a second terminal coupled to the first transistor of the first transistor end. The pixel sensing device according to claim 1, wherein the reading unit includes: a sixth transistor including: a first terminal coupled to the second terminal of the first transistor; a control terminal For receiving the read signal; and a second terminal. A control method for controlling a pixel sensing device, wherein the pixel sensing device includes a transistor, a capacitor, and a photodiode, and the transistor includes a first terminal, a control terminal, and a first terminal. Two terminals, the photoelectric diode includes an anode terminal and a cathode terminal, wherein the capacitor is coupled between the control terminal and the second terminal, wherein the control method includes: during a compensation period, according to a first reset Signal to reset the voltage at the cathode terminal; to write a reset voltage to the control terminal according to a second reset signal during the compensation period; during a data write period, to transfer the photodiode according to a signal A signal voltage output from the cathode terminal of the body is transmitted to the control terminal, and the signal voltage is coupled to the second terminal through the capacitor; Providing a power supply voltage to the first terminal according to a control signal during a reading period, wherein the transistor outputs a current according to a voltage between the control terminal and the second terminal during the reading period; and During the read period, the current is read according to a read signal. The control method according to claim 8, further comprising: writing the power supply voltage to the first terminal according to the control signal in an initial period before the compensation period. The control method according to claim 8, further comprising: during the initial period, writing a reference voltage to the second terminal according to the read signal. The control method according to claim 8, wherein the step of writing the reset voltage to the control terminal according to the second reset signal during the compensation period includes: providing the reset voltage to the control during the compensation period Terminal, so that a first voltage difference is formed at the second terminal, wherein the first voltage difference is a voltage difference between the reset voltage and a threshold voltage. The control method according to claim 11, wherein during the data writing period, the signal voltage output from the cathode terminal of the photodiode is transmitted to the control terminal according to the transmission signal, and the capacitor is coupled through the capacitor. The step of signal voltage to the second terminal includes: During the data writing period, the signal voltage is coupled to the second terminal through the first capacitor to form a voltage sum of the first voltage difference and a second voltage difference at the second terminal. The second voltage difference is The voltage difference between the signal voltage and the reset voltage. The control method according to claim 12, wherein the step of outputting the current according to the voltage between the control terminal and the second terminal during the reading period comprises: the first transistor in the reading period The period is based on the voltage sum to output the current.