Photoelectric conversion device, photoelectric conversion system, movable body, semiconductor substrate, and method for driving photoelectric conversion device

Abstract

To solve a problem in which: a power supply voltage varies when a gain of AD conversion is switched.SOLUTION: There is provided a photoelectric conversion device having a plurality of pixels arranged in array, and the photoelectric conversion device has a first pixel group arranged in a first direction among the plurality of pixels and a first output line to which the first pixel group is connected, and a second pixel group in which pixels not included in the first pixel group among the plurality of pixels are arranged in the first direction and a second output line to which the second pixel group is connected. The first output line is connected with a first current source. The second output line is connected with a second current source. The photoelectric conversion device has a control unit that, in accordance with control to reduce a current flowing in the first current source, performs control to increase a current flowing in the second current source.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photoelectric conversion device, a photoelectric conversion system including the photoelectric conversion device, a moving body, a semiconductor substrate, and a method for driving the photoelectric conversion device. [Background technology]

[0002] Patent Document 1 discloses a solid-state imaging device in which a current value of a comparator arranged for each pixel column is switched according to the AD conversion gain of the comparator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-187565 A Summary of the Invention [Problem to be solved by the invention]

[0004] The solid-state imaging device described in Patent Document 1 has a problem in that fluctuations in the power supply voltage cause a decrease in accuracy of the output signal of the solid-state imaging device.

[0005] The present invention has been made in consideration of the above-mentioned problems, and is directed to suppressing fluctuations in the power supply voltage of a photoelectric conversion device and improving the accuracy of an output signal from the photoelectric conversion device. [Means for solving the problem]

[0006] One aspect of the present disclosure is a photoelectric conversion device having a plurality of pixels arranged in an array, the photoelectric conversion device comprising: a first pixel group among the plurality of pixels arranged in a first direction; a first output line to which the first pixel group is connected; a second pixel group among the plurality of pixels, in which pixels not included in the first pixel group are arranged in the first direction; and a second output line to which the second pixel group is connected, the first output line being connected to a first current source and the second output line being connected to a second current source; and a control unit that performs control to increase a current flowing to the second current source in response to control to reduce a current flowing to the first current source.

[0007] Another aspect of the present disclosure is a photoelectric conversion device having a plurality of pixels arranged in an array, the photoelectric conversion device having a first pixel group among the plurality of pixels arranged in a first direction, a first output line to which the first pixel group is connected, a second pixel group among the plurality of pixels, in which pixels not included in the first pixel group are arranged in the first direction, and a second output line to which the second pixel group is connected, the first output line being connected to a first current source and the second output line being connected to a second current source, and characterized in that the photoelectric conversion device has a control unit that suppresses fluctuations in the total amount of current flowing by changing the current flowing to the second current source in response to changes in the current flowing to the first current source.

[0008] Yet another aspect of the present disclosure is a photoelectric conversion device having a plurality of output lines, a plurality of pixels each connected to one of the plurality of output lines, a plurality of current sources each connected to one of the plurality of output lines, and a plurality of comparators each connected to one of the plurality of output lines, wherein the plurality of current sources include a first current source and a second current source, the plurality of comparators include a first comparator and a second comparator, the second current source is disposed between the first current source and the first comparator, and the first comparator is disposed between the second current source and the second comparator.

[0009] Yet another aspect of the present disclosure is a semiconductor substrate for stacking on another semiconductor substrate, the semiconductor substrate comprising a first output line connected to a first current source, a second output line connected to a second current source, and a control unit that performs control to increase a current flowing through the second current source in response to control to decrease a current flowing through the first current source.

[0010] Yet another aspect of the present disclosure is a method for driving a photoelectric conversion device having a plurality of pixels arranged in an array, wherein a first pixel group among the plurality of pixels is arranged in a first direction, a first output line to which the first pixel group is connected, a second pixel group among the plurality of pixels, wherein pixels not included in the first pixel group are arranged in the first direction, and a second output line to which the second pixel group is connected, wherein the first output line is connected to a first current source and the second output line is connected to a second current source, the method being characterized in that the current flowing to the second current source is increased during a period in which a current flowing to the first current source is reduced. Effect of the Invention

[0011] According to the present disclosure, it is possible to improve the accuracy of an output signal from a photoelectric conversion device. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a photoelectric conversion device according to a first embodiment. [Diagram 2] 1 is a schematic diagram of a photoelectric conversion device according to a first embodiment. [Diagram 3] 1 is a schematic diagram of a photoelectric conversion device according to a first embodiment. [Figure 4] 3 is a timing chart according to the first embodiment. [Diagram 5] FIG. 11 is a schematic diagram of a photoelectric conversion device according to a second embodiment. [Figure 6] 10 is a timing chart according to a second embodiment. [Figure 7] FIG. 11 is a schematic diagram of a photoelectric conversion device according to a third embodiment. [Figure 8] 13 is a timing chart according to a third embodiment. [Figure 9] 13 is a timing chart according to a third embodiment. [Figure 10] FIG. 13 is a schematic diagram of a photoelectric conversion device according to a fourth embodiment. [Figure 11] FIG. 13 is a schematic diagram of a photoelectric conversion device according to a fourth embodiment. [Figure 12] 13 is a modification of the photoelectric conversion device according to the fourth embodiment. [Figure 13] FIG. 13 is a schematic diagram of a photoelectric conversion device according to a fifth embodiment. [Figure 14] FIG. 13 is a schematic diagram of a photoelectric conversion device according to a fifth embodiment. [Figure 15] 13 is a timing chart according to the fifth embodiment. [Figure 16] 13 is a timing chart according to the fifth embodiment. [Figure 17] FIG. 13 is a diagram illustrating a configuration of a photoelectric conversion system according to a sixth embodiment. [Figure 18] 13A to 13C are diagrams illustrating a configuration and an operation of a moving body according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Each embodiment will be described below with reference to the drawings.

[0014] In the following embodiments, an image pickup device will be mainly described as an example of a photoelectric conversion device. However, each embodiment is not limited to an image pickup device, and can be applied to other examples of photoelectric conversion devices. For example, a distance measuring device (a device for measuring distance using focus detection or TOF (Time Of Flight)) or a photometric device (a device for measuring the amount of incident light) may be used.

[0015] First Embodiment 1 to 3 are schematic diagrams of a photoelectric conversion device according to this embodiment.

[0016] 1 includes a pixel array 110, vertical output lines 130 and 131, current source transistors 140 and 141, switches 150 and 151, a GND pad 160, and a power supply pad 161. It further includes control signal lines PWR1 and PWR2, and a bias line BS, and resistors 170 and 171 are parasitic resistors.

[0017] The pixel array 110 has a plurality of pixels 100 arranged in an array across a plurality of rows and a plurality of columns.

[0018] Vertical output lines 130, 131 are arranged in each column of the pixel array 110, extending in the column direction (the vertical direction in FIG. 1). The vertical output lines are respectively connected to the pixels 100 arranged in the column direction, and serve as signal lines common to these pixels 100.

[0019] There is no particular limitation on the number of pixels 100 constituting the pixel array 110. For example, the pixel array 110 may be constituted of several thousand rows and several thousand columns of pixels 100 as in a general digital camera, or the pixel array 110 may be constituted of a plurality of pixels 100 arranged in a single row.

[0020] The pixel signals read out from the pixels 100 are input to a column signal processing circuit (not shown) via vertical output lines. The column signal processing circuit may include a memory or the like that holds the pixel signals read out from the pixels 100. The pixel signals output from the column signal processing circuit are output sequentially for each column via the signal processing circuit.

[0021] A power supply voltage is supplied to the pixel array 110 via the power supply pad 161 and the resistor 171 .

[0022] The GND pad 160 is connected to the ground, which is a ground potential. Hereinafter, the ground will also be referred to as GND.

[0023] A GND potential serving as a reference potential is supplied to the current source transistors 140 and 141 via a GND pad 160 and a resistor 170, and a bias voltage is input from a bias line BS to the gates of the current source transistors 140 and 141. The bias source that supplies the bias voltage to the bias line BS includes, for example, a current source and a variable transistor as shown in Fig. 2. A bias voltage according to the size of the variable transistor is output to the bias line BS.

[0024] A current is supplied to the vertical output line 130 in response to the on / off state of a switch 150 connected to a control signal line PWR1. Similarly, a current is supplied to the vertical output line 131 in response to the on / off state of a switch 151 connected to a control signal line PWR2.

[0025] The timing generator 190, which is a control unit, controls the signals to be output to the control signal lines PWR1 and PWR2. In this way, the timing generator 190 controls the operations of the switches 150 and 151. The timing generator 190 also controls the readout operation of signals from the pixels of the pixel array 110 and the driving of the signal processing operation of the column signal processing circuit and the signal processing circuit.

[0026] (Pixel configuration) The configuration of the pixel 100 according to this embodiment will be described.

[0027] 3 shows an equivalent circuit diagram of a pixel circuit. Take as an example one of the pixels connected to the vertical output line 130. Each pixel 100 has a photodiode 400, a transfer transistor 410, a floating diffusion 420, a source follower transistor 430, a selection transistor 440, a GND node 450, a reset transistor 455, and a power supply node 460.

[0028] The photodiode 400 is grounded at a GND node 450. The photodiode 400 is connected to a transfer transistor 410. A control signal TX is input to the gate of the transfer transistor 410. The transfer transistor 410 has a common node with the reset transistor 455 and the source follower transistor 430, and the common node becomes a floating diffusion 420. The reset transistor 455 and the source follower transistor 430 are both connected to a power supply node 460. A reset signal RES is input to the gate of the reset transistor 455. The source follower transistor 430 is connected to a selection transistor 440, and a selection signal is input to the gate of the selection transistor 440 from a selection signal line SEL. The selection transistor 440 is connected to the vertical output line 130.

[0029] (Functions of each element of a pixel) The function of each element of the pixel 100 will now be described.

[0030] The photodiode 400 converts incident light into an electric charge and generates an electric charge.

[0031] The charge photoelectrically converted by the photodiode 400 is transferred to the floating diffusion 420 via the transfer transistor 410 and converted into a signal voltage by the parasitic capacitance associated with the floating diffusion 420. The signal voltage is input to the gate of the source follower transistor 430 and output to the vertical output line 130 via the selection transistor 440. The source follower transistor 430 forms a source follower together with the current source transistor 140 in FIG. 1, and the signal voltage on the floating diffusion 420 is output to the vertical output line 130 via the source follower.

[0032] (Driving the photoelectric conversion device) In the photoelectric conversion device according to this embodiment, a full pixel readout mode with high resolution and normal S / N ratio and a column thinning mode with low resolution and high S / N ratio are switched between for use. By making the current consumption in both modes roughly equivalent, it is possible to suppress fluctuations in the power supply and GND, which is the reference voltage source, and improve the accuracy of the output signal.

[0033] A specific drive will be described below.

[0034] 1, by increasing the bias voltage supplied from the bias line BS to the current source transistor 140 and the current source transistor 141, the current supplied to each of the vertical output lines 130 and 131 increases. This makes it possible to reduce the 1 / f noise generated in the source follower transistor 430 in the pixel 100 and improve the S / N ratio.

[0035] At this time, either the switch 150 or the switch 151 can be turned off by setting either the control line PWR1 that controls the switch 150 or the control signal line PWR2 that controls the switch 151 to a low level. An example will be described in which the switch 151 is turned off while the switch 150 is turned on. At this time, no current is supplied to the vertical output line 131 (power saving state), and a column thinning readout mode is entered in which signals from a pixel group made up of the pixels 100 connected to the vertical output line 131 are not read out. In such a column thinning mode, the resolution of an image based on the output signal decreases, but the amount of data output from the pixel array 110 decreases, thereby reducing the load on the data processing in the subsequent stages and reducing power consumption.

[0036] When changing the readout mode in this way, the current consumption of each pixel column fluctuates, causing fluctuations in the power supply voltage. If a signal is read out while such fluctuations are occurring, the fluctuations are superimposed on the signal as noise, reducing the signal-to-noise ratio of the output signal.

[0037] Therefore, in this embodiment, the current supplied from the current source transistor 140 to the vertical output line 130 is increased in the column thinning mode. Specifically, the control unit changes the transistor size of the variable transistor connected to the bias source in response to switching of the signal level of the control signal line PWR, which determines the amount of current supplied to the vertical output line by the control unit, and changes the bias voltage supplied to the current source transistor. By suppressing the fluctuation in the total amount of current and suppressing the voltage fluctuation of the power supply and GND when changing the readout mode, it is possible to suppress deterioration of image quality.

[0038] The driving of the photoelectric conversion device will be described below with reference to the timing chart shown in FIG.

[0039] First, at time t0, the control signals PWR1 and PWR2 are at high level. A bias voltage is supplied from a common bias line BS to the gates of the current source transistors 140 and 141. The current flowing through the current source transistors 140 and 141 is approximately equal.

[0040] Between times t0 and t1, signals from the pixels 100 in the pixel array 110 are read out sequentially, row by row.

[0041] After reading out the signals for all the rows, at time t1, the control signal PWR2 is set to low level, the switch 151 is turned off, and the mode is switched to column thinning mode. At the same time, the bias voltage supplied from the bias line BS to the gates of the current source transistors 140 and 141 is increased. This makes it possible to suppress fluctuations in the total amount of current and fluctuations in the power supply voltage when switching to the column thinning mode.

[0042] That is, the fluctuation of the current flowing through the path of the power supply pad 161, the resistor 171, the pixel array 110, the vertical output line 130, the current source transistor 140, the resistor 170, and the GND pad 160 is suppressed.

[0043] This suppression of current fluctuations makes it possible to suppress fluctuations in the power supply voltage of the power supply node 460 of the pixel 100 and fluctuations in the source node potentials of the current source transistor 140 and the current source transistor 141. It is possible to suppress deterioration in image quality caused by interference of fluctuations in the potential of the power supply node 460 with the floating diffusion 420 via the drain-gate capacitance of the source follower transistor 430. At this time, in order to prevent fluctuations in the total amount of current, it is desirable for the increase in the current flowing through the current source transistor 140 and the decrease in the current flowing through the current source transistor 141 to be as close as possible to each other, but the balance between the current increase and decrease can be determined according to the allowable image quality.

[0044] Moreover, by suppressing fluctuations in the potential of the source nodes of the current source transistors 140 and 141, it is possible to suppress fluctuations in the currents of the current source transistors 140 and 141 and deterioration of the signals of the vertical output lines 130 and 131. Moreover, since the current source transistors 140 and 141 are identical circuit elements arranged adjacent to each other and the impedances from the respective source nodes to the GND pad 160 are almost the same and common, it is possible to enhance the effect of suppressing fluctuations in the source nodes by suppressing current fluctuations.

[0045] In this way, in the photoelectric conversion device according to the present embodiment, it is possible to suppress fluctuations in the power supply when switching modes. Furthermore, by suppressing fluctuations in the power supply voltage, the signal-to-noise ratio is improved, and deterioration of image quality can be suppressed.

[0046] 1, an example has been described in which the bias line of the gates of the current source transistors 140 and 141 is common, and the control lines of the switches 150 and 151 are separate, so that one of them is put into the power saving state, but the configuration is not limited to this. The bias lines of the gates of the current source transistors 140 and 141 may be separate, so that one of them is put into the power saving state. In this case, the power saving state may be a state in which a weak current of, for example, about 0.1 μA is allowed to flow without cutting off the current. By allowing a weak current to flow even in the power saving state, the time required for recovery can be shortened.

[0047] In this embodiment, the timing generator 190 included in the photoelectric conversion device controls the current amounts of the current source transistors 140 and 141. As another example, a control unit provided outside the photoelectric conversion device may control the current source transistors 140 and 141. For example, the current source transistors 140 and 141 may be controlled by an overall control / calculation unit 1009 included in the photoelectric conversion system in FIG. 17 described in a sixth embodiment to be described later. Also, the current source transistors 140 and 141 may be controlled from outside the photoelectric conversion system in FIG. 17.

[0048] Second Embodiment A schematic diagram of a photoelectric conversion device according to the second embodiment is shown in Fig. 5. Explanations that overlap with the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

[0049] The photoelectric conversion device according to this embodiment is used by switching between a high-speed mode with a normal S / N ratio and a high S / N mode with a low speed but high S / N ratio.

[0050] The vertical output line 130 of the photoelectric conversion device according to this embodiment has a switch 180, and the vertical output line 131 has a switch 181. The vertical output line 130 is connected to a group of pixels arranged in even columns of the pixel array 110, and the vertical output line 131 is connected to a group of pixels arranged in odd columns of the pixel array 110. The switch 180 is controlled by a signal input from a control signal line VLON1, and the switch 180 is controlled by a signal input from a control signal line VLON2.

[0051] The driving of the photoelectric conversion device will be described below with reference to the timing chart of FIG.

[0052] The operation from time t0 to t1 is the same as in FIG. 4. At time t0, the control signal VLON1 is at a high level, and the switch 180 is in an on state, and the control signal VLON2 is at a low level, and the switch 181 is in an off state. In addition, the control signals PWR1 and PWR2 are at a high level, and the switches 150 and 151 are in an on state. The currents of the current source transistors 140 and 141 flow to the GND pad 160 via the vertical output lines 130 and 131, respectively, in a substantially equal state. In this state, signals of the pixels 100 in the pixel array 110 are read out row by row in sequence.

[0053] At time t1, the control signal PWR2 is set to low level to turn off the switch 151 and switch the read mode from the high speed mode to the high SN mode. At the same time, the bias voltage supplied to the gate of each current source transistor from the bias line BS is increased. This suppresses the fluctuation of the total amount of current when the read mode is switched, and suppresses the fluctuation of the power supply voltage.

[0054] From time t1 to t2, the control signal VLON1 is at high level and the switch 180 is in an on state, and the control signal VLON2 is at low level and the switch 181 is in an off state, so that the current of the current source transistor 140 flows through the vertical output line 130. In this state, the signals of the pixels 100 in the even columns of the pixel array 110 are read out via the vertical output line 130.

[0055] At time t2, the control signal VLON1 goes to a low level, turning off the switch 180. The control signal VLON2 goes to a high level, turning on the switch 181. The current of the current source transistor 141 flows through the vertical output line 131. In this state, the signals of the pixels 100 in the odd-numbered columns of the pixel array 110 are read out through the vertical output line 131.

[0056] In this way, in the high SN mode, signals from the pixels 100 in one row are read out twice between times t1 and t3: signals from the pixels 100 in odd-numbered columns and signals from the pixels 100 in even-numbered columns.

[0057] At times t3 to t5, signals from the pixels 100 in the next row are read out by a similar operation. By driving in this manner, in this embodiment, it is possible to read out signals without reducing the resolution in the high SN mode. Also, it is possible to suppress the power supply voltage fluctuation when the readout mode is shifted from the high speed mode to the high SN mode, and to suppress the deterioration of image quality due to the power supply voltage fluctuation.

[0058] Third embodiment FIG. 7 is a schematic diagram showing a photoelectric conversion device according to the third embodiment.

[0059] In the photoelectric conversion device according to this embodiment, as in the second embodiment, a high-speed mode with a normal S / N ratio and a high S / N mode with a low speed but high S / N ratio are used by switching between them. The following mainly describes the differences from the second embodiment.

[0060] 7 has a comparator 200 as a signal processing circuit following the vertical output line 130, and a comparator 201 as a signal processing circuit following the vertical output line 131. Also shown is a GND pad 210 and a resistor 220 connected to the comparator 200, and a GND pad 211 and a resistor 221 connected to the comparator 201. Furthermore, the photoelectric conversion device has a ramp signal line RAMP, a bias signal line CBS, a control line CPWR1, and a control line CPWR2.

[0061] In the photoelectric conversion device shown in Fig. 7, in addition to the power supply voltage fluctuation of the wiring, the power supply voltage fluctuation and GND fluctuation of the comparator can also be suppressed. The bias current values ​​of the comparators 200 and 201 are driven by a bias voltage supplied from a bias line CBS. A ramp signal supplied from a ramp signal line RAMP is input to the input terminal as a reference signal. In addition, the current flowing through each of the vertical output lines is controlled by a control line PWR1 and a control line PWR2.

[0062] As an example of the operation, a timing chart is shown in Fig. 8. The timing chart shown in Fig. 8 is the same as the timing chart shown in Fig. 6, except that the control lines CPWR1, CPWR2, and bias line CBS are controlled in the same manner as the control lines PWR1, PWR2, and bias line BS, respectively.

[0063] Between times t0 and t1, the control lines CPWR1 and CPWR2 are both at a high level, and the comparators 200 and 201 process the signals output via the vertical output lines 130 and 131, respectively.

[0064] At time t1, when the read mode is shifted from the high speed mode to the high SN mode and the bias voltage CBS is increased, the control line CPWR2 is set to low level to stop the supply of current to the comparator 201. This suppresses the fluctuation of the total amount of current of the comparators 200 and 201, and suppresses the power supply voltage fluctuation and GND fluctuation. Each of the comparators 200 and 201 has a differential stage and an amplifier stage, and each of the differential stage and the amplifier stage has a current source, but when the mode is shifted, the current supply to either the differential stage or the amplifier stage may be changed.

[0065] Between times t1 and t2, the signal output from the vertical output line 130 is compared with a ramp signal by the comparator 200, thereby performing AD conversion.

[0066] Between times t2 and t3, the signal output from the vertical output line 131 is compared with a ramp signal by the comparator 201, thereby performing AD conversion.

[0067] Here, the operation when AD converting the signal of the vertical output line will be described using the vertical output line 130 and the comparator 200 as an example, with reference to the timing chart of Fig. 9. Note that the symbols t0 to t5 in Fig. 8 are unrelated to the symbols t0 to t8 in Fig. 9.

[0068] 3 goes high to turn on the reset transistor 455, thereby resetting the floating diffusion 420. In response to this, the potential of the vertical output line 130 goes to the reset level.

[0069] At time t2, a slope operation is started to change the potential of the ramp signal over time. Although a case where the potential drops uniformly is illustrated, the ramp signal may be a signal whose potential increases continuously over time, or a signal whose potential changes in a sawtooth pattern.

[0070] At time t3, the magnitude relationship between the ramp signal input to the comparator 200 and the output signal of the vertical output line 130 is inverted, and the output of the comparator 200 is inverted. The time until this inversion of the comparator output is measured by a counter (not shown), and AD conversion of the reset level is performed.

[0071] At time t4, the ramp signal is reset.

[0072] 3 goes high and the transfer transistor 410 turns on, transferring photocharges from the photodiode 400 to the floating diffusion 420. The potential of the floating diffusion 420 drops according to the amount of charge, and the potential of the vertical output line 130 accordingly goes to the signal level.

[0073] From time t7, the slope operation of the ramp signal starts again.

[0074] At time t8, the magnitude relationship between the ramp signal input to the comparator 200 and the output of the vertical output line 130 is inverted again, and the output of the comparator changes. The time until the comparator output changes is measured by a counter (not shown), and AD conversion of the signal level is performed. Then, in a downstream processing circuit, so-called CDS processing is performed by taking the difference between the reset level and the AD conversion result of the signal level.

[0075] The above operation is performed between times t1 and t2 in Fig. 8 to perform AD conversion of the signal on the vertical output line 130. Similarly, AD conversion is performed on the signal on the vertical output line 131 between times t2 and t3 in Fig. 8. This process is repeated thereafter.

[0076] As described above, in this embodiment, it is possible to suppress the power supply voltage fluctuation and GND fluctuation of the comparator caused by mode switching.

[0077] In order to prevent fluctuations in the total amount of current, it is desirable that the amount of increase in current flowing through the current source transistor 140 and the amount of decrease in current flowing through the current source transistor 141 are as close as possible, but the balance between the amount of increase and decrease in current can be determined according to the allowable image quality. For example, a photoelectric conversion device having a mode in which current flows through all comparators and a mode in which current is reduced or not flowed through 1 / 3 of all comparators and current flowing through the remaining 2 / 3 of comparators can be increased. In other words, a balance between the amount of increase and decrease in current may be maintained between the current source group including the current source transistor 140 and the current source group including the current source transistor 141.

[0078] In addition, in Fig. 9, it is possible to switch the AD conversion gain (V / LSB) by changing the slope of the ramp signal. When transitioning to the high SN mode at time t1 in Fig. 8, the AD conversion gain may be switched at the same time, or AD conversion may be performed without switching the AD conversion gain.

[0079] 7, an example has been described in which the bias line of the gates of the current source transistors 140 and 141 is common, and the control lines of the switches 150 and 151 are separate, so that one of them is put into the power saving state, but the configuration is not limited to this. The bias lines of the gates of the current source transistors 140 and 141 may be provided separately, so that one of the current source transistors may be put into the power saving state. In this case, the power saving state may be a state in which a weak current of, for example, about 0.1 μA is allowed to flow without cutting off the current. By allowing a weak current to flow even in the power saving state, the time required for recovery can be shortened.

[0080] (Fourth embodiment) 10 and 11 are schematic diagrams showing a photoelectric conversion device according to the fourth embodiment. The following mainly describes the differences from the third embodiment.

[0081] Fig. 10 is a block diagram of a photoelectric conversion device according to a fourth embodiment, which includes a circuit 700 including a first current source, a circuit 701 including a second current source, a circuit 710 including a first comparator, and a circuit 711 including a second comparator. Fig. 11 shows a specific example of the circuit of the photoelectric conversion device shown in Fig. 10. In the photoelectric conversion device shown in Fig. 11, the vertical output lines 130 and 131 are capable of reading out signals of different pixel rows in the same pixel column in parallel. In other words, high-speed (simultaneous reading of multiple rows) is possible.

[0082] In the third embodiment, as shown in the timing chart of FIG. 8, pixel signals are read out one row at a time from time t0 to t1, and in the high SN mode after time t1, pixel signals corresponding to odd columns and even columns are read out alternately.

[0083] In the photoelectric conversion device shown in Fig. 11, pixel signals are read out in parallel two rows at a time from time t0 to t1, and in the high SN mode after time t1, pixel signals are read out one row at a time, according to a timing chart similar to that of Fig. 8. In this case as well, it is possible to suppress the power supply voltage fluctuation when the readout mode is changed at time t1.

[0084] As shown in FIG. 10, a circuit 700 including a first current source and a circuit 701 including a second current source are arranged adjacent to each other, and a circuit 710 including a first comparator and a circuit 711 including a second comparator are also arranged adjacent to each other.

[0085] In FIG. 11, which shows the circuit arrangement of FIG. 10 in a circuit diagram, the current source transistors 140 and 141 are arranged adjacent to each other, and the comparators 200 and 201 are arranged adjacent to each other. In other words, the circuit 701 is arranged between the circuit 700 and the circuit 710, and the circuit 710 is arranged between the circuit 701 and the circuit 711. The order of the current source transistor 140, the comparator 200, the current source transistor 141, and the comparator 201 from the pixel side to the power supply pad side may be used, but it is preferable to arrange the same circuit elements adjacent to each other as shown in FIG. 11. With this arrangement, the common impedance from the comparators 200 and 201 to the GND pad 210 and the power supply pad 211 is made almost equal, thereby making it possible to enhance the effect of suppressing power supply and GND fluctuations.

[0086] The photoelectric conversion device in each embodiment may have a stacked structure as shown in FIG.

[0087] 12 includes a pixel substrate 800 and a circuit substrate 810. A case in which the current source transistor 140, the current source transistor 141, the comparator 200, and the comparator 201 are arranged on the circuit substrate 810 will be considered.

[0088] When the unit current of the current source transistor 140, the current source transistor 141, the comparator 200, and the comparator 201 is increased upon transition to the read mode, the number of operating circuits is reduced, thereby making it possible to suppress current fluctuations and suppress increases in the amount of heat generated and its unevenness. This makes it possible to suppress image quality degradation due to an increase in dark current of the photodiode 400 and unevenness in the dark current in the pixel 100 in the pixel substrate 800. Furthermore, by suppressing current fluctuations between adjacent circuits, it is possible to enhance the effect of suppressing unevenness in the amount of heat generation.

[0089] For example, the mode in which the comparator current is lower may be the moving image mode, and the mode in which the comparator current is higher may be the still image mode.

[0090] Fifth embodiment 13 and 14 are schematic diagrams showing a photoelectric conversion device and a comparator according to the fifth embodiment.

[0091] In the photoelectric conversion device according to this embodiment, a global shutter mode in which a signal is read out by a global shutter and a rolling shutter mode in which a signal is read out by a rolling shutter are switched between for use.

[0092] 13 and 14, a unit 500 (hereinafter also referred to as a pixel AD) is a pixel and a comparator, and each pixel has one comparator. 505 is a control circuit.

[0093] 14 includes a photodiode 510, an overflow transistor 520, a transfer transistor 530, a reset transistor 540, and a floating diffusion 550. Transistors 560 and 570 form a differential pair. Transistor 580 operates as a current source. Transistors 590 and 600 form a current mirror. 610 is a switch.

[0094] The global shutter operation will be described with reference to FIG.

[0095] 15, OFG1 is OFG corresponding to the pixel AD500 arranged in the first row of Fig. 13, and OFG2, OFG3, and OFD4 correspond to the second, third, and fourth rows, respectively. Similarly, RES1 is RES corresponding to the pixel AD500 arranged in the first row of Fig. 13, TX1 is TX corresponding to the pixel AD500 arranged in the first row of Fig. 13, and PWR1 is PWR corresponding to the pixel AD500 arranged in the first row of Fig. 13.

[0096] At times t1 to t2, the control signals OFG1 to OFG4 are set to high level, thereby turning on the overflow transistors 520 in all the pixels AD500 in FIG. 13, and resetting the charge of the photodiodes 510.

[0097] At times t3 to t4, the control signals RES1 to RES4 are set to high level to turn on the reset transistors 540 of all the pixels AD500, and the floating diffusions 550 are reset.

[0098] The reset level of the floating diffusion 550 is AD converted by performing a slope operation of the ramp signal from time t5 to time t6.

[0099] At times t7 to t8, the control signals TX1 to TX4 are set to high level, thereby transferring photocharges from the photodiode 510 to the floating diffusion 550. The charge accumulation time is the same for all rows of pixels, from times t2 to t8. The potential of the floating diffusion 550 drops to the signal level according to the amount of photocharges.

[0100] From time t9 to t10, the ramp signal is again subjected to a slope operation, thereby performing AD conversion on the signal level of the floating diffusion 550.

[0101] In addition, from time t0 to t11, the control signals PWR1 to 4 are all at a high level, and all the pixel ADs 500 are in an operating state. The control signals PWR1 to 4 are at a high level from time t0, which is before time t3 when the read operation starts, in order to allow a certain amount of time for the power supply voltage fluctuation caused by the current fluctuation to subside.

[0102] Next, the rolling shutter operation will be described with reference to FIG.

[0103] As in Fig. 15, OFG1 is OFG corresponding to the pixel AD500 arranged in the first row of Fig. 13, and OFG2, OFG3, and OFD4 correspond to the second, third, and fourth rows, respectively. Similarly, RES1 is RES corresponding to the pixel AD500 arranged in the first row of Fig. 13, TX1 is TX corresponding to the pixel AD500 arranged in the first row of Fig. 13, and PWR1 is PWR corresponding to the pixel AD500 arranged in the first row of Fig. 13.

[0104] In this manner, in FIG. 15, the pixels AD perform charge accumulation at the same timing for all rows, a so-called global shutter operation.

[0105] At time t0 to t1, the control signal OFG1 is set to high level, thereby turning on the overflow transistor 520 in the pixel AD500 in the first row of FIG. 13, and resetting the charge of the photodiode 510.

[0106] At times t2 to t3, the control signal OFG2 is set to high level, thereby turning on the overflow transistor 520 in the pixel AD500 in the second row of FIG. 13, and resetting the charge of the photodiode 510.

[0107] At times t4 to t5, the control signal OFG3 is set to high level, thereby turning on the overflow transistor 520 in the pixel AD500 in the third row of FIG. 13, and resetting the charge of the photodiode 510.

[0108] Between times t7 and t8, the control signal OFG4 is set to high level, thereby turning on the overflow transistor 520 in the pixel AD500 in the fourth row of FIG. 13, and resetting the charge of the photodiode 510.

[0109] By setting the control signal RES1 to a high level from time t9 to t10, the reset transistor 540 is turned on in the pixel AD500 on the first row in FIG.

[0110] At times t11 to t12, the ramp signal is caused to perform a slope operation, thereby AD converting the reset level of the floating diffusion 550. At this time, the control signal PWR1 is at a high level, and PWR2 to 4 are at a low level, and the switch 610 is turned on only in the pixel AD500 in the first row of Fig. 13, causing a current to flow and enabling AD conversion. The control signal PWR1 is at a high level from time t6, which is before time t9 when the read operation starts, because it takes a certain amount of time for the power supply voltage fluctuation caused by the current fluctuation to subside.

[0111] By setting the control signal TX1 to a high level from time t13 to t14, photocharges are transferred from the photodiode 510 to the floating diffusion 550. At this time, the accumulation time of the pixel AD in the first row of FIG. 13 is from time t1 to t14.

[0112] The signal level of the floating diffusion 550 is AD converted by performing a slope operation of the ramp signal from time t15 to t16.

[0113] Similarly, from time t17 to time t19, AD conversion of the reset level and the signal level is performed in the pixel AD500 in the second row of Fig. 13. The charge accumulation time is from time t3 to time t18.

[0114] Similarly, in the pixel AD500 in the third row of FIG. 13, the accumulation time is from time t5 to time t20, and in the pixel AD500 in the fourth row of FIG. 13, the accumulation time is from time t8 to time t22.

[0115] In this manner, in FIG. 16, the pixels AD perform accumulation at different timings for each row, which is a so-called rolling shutter operation.

[0116] At time t17 in the rolling shutter mode, the control signal PWR1 goes to low level and the control signal PWR2 goes to high level, thereby maintaining the current consumption and suppressing fluctuations in the power supply voltage. Similar operations are performed at times t19 and t21.

[0117] Here, a case will be considered in which the readout mode is shifted from the rolling shutter mode in which the rolling shutter operation of FIG. 16 is performed to the global shutter mode in which the global shutter operation of FIG. 15 is performed.

[0118] At time t23 in Fig. 16, only the control signal PWR4 is at a high level, and the control signals PWR1 to 3 are at a low level. On the other hand, at time t0 in Fig. 15, the control signals PWR1 to 4 are all at a high level. By lowering the bias voltage supplied to the transistor 580 from the bias line BS at the timing when the read mode transitions and reducing the current consumption per pixel AD500, the total amount of current can be kept approximately constant, and fluctuations in the power supply voltage during the transition can be suppressed.

[0119] In this embodiment, the case where the readout mode is changed from the rolling shutter mode in which row-sequential readout is performed to the global shutter mode has been described as an example, but the readout operation is not limited to this. For example, the readout mode may be changed from column-sequential readout to the global shutter operation. Also, the readout mode may be changed from the global shutter operation in which the number of operating pixels AD500 is thinned out to the global shutter operation in which the number of operating pixels AD500 is not thinned out.

[0120] Also, the embodiment has been described with reference to the pixel AD in which a comparator is provided for each pixel, but the embodiment may be applied to a block AD in which a comparator is provided for a plurality of pixels (pixel block) in a matrix.

[0121] (Sixth embodiment) The photoelectric conversion system according to this embodiment will be described with reference to Fig. 17. Fig. 17 is a block diagram showing a schematic configuration of the photoelectric conversion system according to this embodiment.

[0122] The photoelectric conversion devices described in the first to fifth embodiments are applicable to various photoelectric conversion systems. Examples of the applicable photoelectric conversion systems include digital still cameras, digital camcorders, security cameras, copiers, fax machines, mobile phones, car-mounted cameras, and observation satellites. Camera modules equipped with an optical system such as a lens and an imaging device are also included in the photoelectric conversion systems. FIG. 15 illustrates a block diagram of a digital still camera as an example of these.

[0123] 17 includes an image pickup device 1004, which is an example of a photoelectric conversion device, and a lens 1002 that forms an optical image of a subject on the image pickup device 1004. The system further includes an aperture 1003 that varies the amount of light passing through the lens 1002, and a barrier 1001 that protects the lens 1002. The lens 1002 and the aperture 1003 form an optical system that focuses light on the image pickup device 1004. The image pickup device 1004 is a photoelectric conversion device according to any one of the above embodiments, and converts the optical image formed by the lens 1002 into an electrical signal.

[0124] The photoelectric conversion system also has a signal processing unit 1007 which is an image generating unit that generates an image by processing an output signal output from the imaging device 1004. The signal processing unit 1007 performs various corrections and compression as necessary to output image data. The signal processing unit 1007 may be formed on the semiconductor substrate on which the imaging device 1004 is provided, or may be formed on a semiconductor substrate separate from the imaging device 1004.

[0125] The photoelectric conversion system further includes a memory unit 1010 for temporarily storing image data, and an external interface unit (external I / F unit) 1013 for communicating with an external computer or the like. The photoelectric conversion system further includes a recording medium 1012 such as a semiconductor memory for recording or reading out imaging data, and a recording medium control interface unit (recording medium control I / F unit) 1011 for recording or reading out data on the recording medium 1012. The recording medium 1012 may be built into the photoelectric conversion system, or may be removable.

[0126] The photoelectric conversion system further includes an overall control / calculation unit 1009 that performs various calculations and controls the entire digital still camera, and a timing generation unit 1008 that outputs various timing signals to the image capture device 1004 and the signal processing unit 1007. Here, the timing signals and the like may be input from outside, and the photoelectric conversion system only needs to include at least the image capture device 1004 and the signal processing unit 1007 that processes the output signal output from the image capture device 1004.

[0127] The imaging device 1004 outputs an imaging signal to a signal processing unit 1007. The signal processing unit 1007 performs predetermined signal processing on the imaging signal output from the imaging device 1004, and outputs image data. The photoelectric conversion system uses this image data to generate an image.

[0128] In this way, according to this embodiment, it is possible to realize a photoelectric conversion system to which the photoelectric conversion device (imaging device) according to any one of the above embodiments is applied.

[0129] Seventh embodiment The photoelectric conversion system and the moving object of this embodiment will be described with reference to Fig. 18. Fig. 18 is a diagram showing the configuration of the photoelectric conversion system and the moving object of this embodiment.

[0130] FIG. 18(a) shows an example of a photoelectric conversion system related to an in-vehicle camera. The photoelectric conversion system 300 has an imaging device 310. The imaging device 310 is the photoelectric conversion device (imaging device) described in any of the above embodiments. The photoelectric conversion system 300 has an image processing unit 312 that performs image processing on a plurality of image data acquired by the imaging device 310, and a parallax acquisition unit 314 that calculates parallax (phase difference of parallax images) from the plurality of image data acquired by the photoelectric conversion system 300. The photoelectric conversion system 300 also has a distance acquisition unit 316 that calculates a distance to an object based on the calculated parallax, and a collision determination unit 318 that determines whether or not there is a possibility of collision based on the calculated distance. Here, the parallax acquisition unit 314 and the distance acquisition unit 316 are examples of distance information acquisition means that acquire distance information to the object. That is, the distance information is information related to the parallax, the defocus amount, the distance to the object, and the like. The collision determination unit 318 may determine the possibility of collision using any of these distance information. The distance information acquisition means may be realized by dedicated hardware, a software module, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a combination of these.

[0131] The photoelectric conversion system 300 is connected to a vehicle information acquisition device 320, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The photoelectric conversion system 300 is also connected to a control ECU 330, which is a control unit that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 318. The photoelectric conversion system 300 is also connected to an alarm device 340 that issues an alarm to the driver based on the judgment result of the collision judgment unit 318. For example, when the judgment result of the collision judgment unit 318 indicates that there is a high possibility of a collision, the control ECU 330 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 340 warns the user by sounding an alarm, displaying alarm information on the screen of a car navigation system, etc., or vibrating the seat belt or steering wheel.

[0132] In this embodiment, the surroundings of the vehicle, for example, the front or rear, are imaged by the photoelectric conversion system 300. Fig. 18(b) shows the photoelectric conversion system when imaging the area in front of the vehicle (imaging range 350). The vehicle information acquisition device 320 sends instructions to the photoelectric conversion system 300 or the imaging device 310. This configuration can further improve the accuracy of distance measurement.

[0133] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from lanes, etc. Furthermore, the photoelectric conversion system is not limited to vehicles such as the vehicle itself, but can be applied to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the present invention can be applied not only to moving bodies, but also to a wide range of devices that use object recognition, such as intelligent transport systems (ITS).

[0134] [Modified embodiment] The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0135] For example, an example in which part of the configuration of any one of the embodiments is added to another embodiment, or an example in which part of the configuration of another embodiment is substituted therefor, is also included in the embodiments of the present invention.

[0136] Furthermore, the photoelectric conversion systems shown in the sixth and seventh embodiments are examples of photoelectric conversion systems to which a photoelectric conversion device can be applied, and photoelectric conversion systems to which the photoelectric conversion device of the present invention can be applied are not limited to the configurations shown in Figures 15 and 16.

[0137] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0138] 100 pixels 130 Vertical Output Line 131 Vertical output line 140 Current source 141 Current source

Claims

1. A plurality of output lines; A plurality of pixels each connected to one of the plurality of output lines; A plurality of current sources, each of which is connected to one of the plurality of output lines; A photoelectric conversion device having a plurality of comparators, each of which is connected to any one of the plurality of output lines. the plurality of current sources includes a first current source and a second current source; the plurality of comparators includes a first comparator and a second comparator; the second current source is disposed between the first current source and the first comparator; a first comparator disposed between the second current source and the second comparator;

2. The plurality of pixels are formed on a first semiconductor substrate; the first and second current sources are formed in a second semiconductor substrate; 2. The photoelectric conversion device according to claim 1, which is configured by stacking a plurality of semiconductor substrates including the first and second semiconductor substrates.

3. The photoelectric conversion device according to claim 1 or 2, a signal processing unit that generates an image using a signal output from the photoelectric conversion device.

4. A moving object comprising the photoelectric conversion device according to any one of claims 1 to 3, A moving body comprising: a control unit that controls the movement of the moving body using a signal output from the photoelectric conversion device.

Images