Signal conversion circuit and image acquisition system

Abstract

The embodiment of the invention provides a signal conversion circuit and an image acquisition system. The signal conversion circuit comprises a signal conversion sub-circuit, a voltage sampling sub-circuit and a control sub-circuit, the signal conversion sub-circuit is used for receiving the first voltage signal output by the control sub-circuit through the first input end of the signal conversion sub-circuit under the condition that the second input end of the signal conversion sub-circuit is communicated with the output end, and changing a bias voltage signal of the second input end of the signal conversion sub-circuit along with the change of the first voltage signal; the voltage sampling sub-circuit is used for collecting a bias voltage signal of the second input end of the signal conversion sub-circuit under the condition that the second input end of the signal conversion sub-circuit is communicated with the output end, and transmitting the collected second voltage signal to the second input end of the control sub-circuit; and the control sub-circuit is used for comparing the second voltage signal with a reference voltage signal of a reference voltage end, and adjusting the first voltage signal until the voltage difference between the second voltage signal and the reference voltage signal is not greater than a preset threshold value under the condition that the voltage difference between the two is greater than the preset threshold value.

Description

Technical Field

[0001] The present application relates to the field of image sensing technology, and in particular to a signal conversion circuit and an image acquisition system. Background Art

[0002] The current image acquisition system usually includes image sensors, charge-to-voltage circuits and other structures, such as Figure 1 As shown, the image sensor is used to convert the light signal into a charge signal, and the charge-to-voltage circuit is used to convert the charge signal output by the image sensor into a voltage signal and perform amplification processing.

[0003] In order to achieve the ultimate performance of the image acquisition system, it is usually necessary to use high-performance discrete devices to build the amplifier in the charge-to-voltage circuit. However, since the discreteness of discrete devices is usually large, the offset voltage of the amplifier is very discrete. According to the current circuit design, this will further cause the bias voltage of the image sensor to be very discrete, resulting in the image acquisition system's operating performance being lower than expected. Summary of the invention

[0004] The purpose of the embodiment of the present application is to provide a signal conversion circuit and an image acquisition system to improve the working performance of the image acquisition system. The specific technical solution is as follows:

[0005] In a first aspect, an embodiment of the present application provides a signal conversion circuit, the circuit comprising:

[0006] Signal conversion subcircuit, voltage sampling subcircuit and control subcircuit;

[0007] The input end of the voltage sampling subcircuit is connected to the signal conversion subcircuit, the output end of the voltage sampling subcircuit is connected to the second input end of the control subcircuit, the first input end of the control subcircuit is connected to the reference voltage end, the output end of the control subcircuit is connected to the first input end of the signal conversion subcircuit, and the second input end of the signal conversion subcircuit is connected to a signal source; wherein the signal source is an image sensor;

[0008] The signal conversion subcircuit is used to receive the first voltage signal output by the control subcircuit through its first input terminal when its second input terminal is connected to the output terminal, and change the bias voltage signal of its second input terminal in accordance with the change of the first voltage signal; wherein the bias voltage signal is the bias voltage signal of the signal source;

[0009] The voltage sampling subcircuit is used to collect the bias voltage signal of the second input end of the signal conversion subcircuit when the second input end and the output end of the signal conversion subcircuit are connected, and transmit the collected second voltage signal to the second input end of the control subcircuit; wherein the second voltage signal is a voltage signal proportional to the bias voltage signal;

[0010] The control subcircuit is used to compare the second voltage signal with the reference voltage signal at the reference voltage end, and when the voltage difference between the second voltage signal and the reference voltage signal is greater than a preset threshold, adjust the first voltage signal at its own output end until the voltage difference between the second voltage signal and the reference voltage signal is no greater than the preset threshold.

[0011] In a possible implementation, the signal conversion sub-circuit is also used to receive the charge signal of the signal source through its own second input terminal when its own second input terminal is disconnected from the output terminal, convert the charge signal into a third voltage signal, and output the third voltage signal to the subsequent circuit through its own output terminal.

[0012] In a possible implementation, the control subcircuit includes a comparison module and a voltage holding module;

[0013] The second input terminal of the comparison module is connected to the output terminal of the voltage sampling subcircuit and the first terminal of the voltage holding module respectively, the first input terminal of the comparison module is connected to the reference voltage terminal, and the output terminal of the comparison module is connected to the first input terminal of the signal conversion subcircuit;

[0014] The second end of the voltage maintaining module is grounded;

[0015] The voltage maintaining module is used to maintain the second voltage signal;

[0016] The comparison module is used to accumulate charge in response to the voltage difference between the second voltage signal and the reference voltage signal, and output a current first voltage signal based on the current accumulated charge.

[0017] In a possible implementation, the voltage sampling subcircuit includes a switch module and a voltage stabilization module;

[0018] The first end of the switch module is connected to the output end of the signal conversion sub-circuit, the second end of the switch module is connected to the first end of the voltage stabilizing module, and the second end of the voltage stabilizing module is respectively connected to the second input end of the comparison module and the first end of the voltage maintaining module;

[0019] The switch module is used for collecting the bias voltage signal by being in a conducting state when the second input terminal and the output terminal of the signal conversion subcircuit are connected;

[0020] The voltage stabilizing module is used to stabilize the voltage signal at the second end of the switch module when the switch module is in the on state.

[0021] In a possible implementation, the comparison module includes a first amplifier, a first capacitor, and a first resistor;

[0022] The inverting input terminal of the first amplifier is respectively connected to the first end of the first resistor and the second end of the first capacitor, the non-inverting input terminal of the first amplifier is connected to the reference voltage terminal, and the output terminal of the first amplifier is respectively connected to the first end of the first capacitor and the first input terminal of the signal conversion sub-circuit;

[0023] The second end of the first resistor is connected to the output end of the voltage sampling subcircuit and the first end of the voltage holding module respectively.

[0024] In a possible implementation, the voltage maintaining module includes a second capacitor;

[0025] The first end of the second capacitor is respectively connected to the second input end of the comparison module and the output end of the voltage sampling subcircuit;

[0026] The second terminal of the second capacitor is grounded.

[0027] In a possible implementation manner, the switch module includes a first switch;

[0028] The first end of the first switch is connected to the output end of the signal conversion sub-circuit, and the second end of the first switch is connected to the first end of the voltage stabilizing module.

[0029] In a possible implementation manner, the voltage stabilizing module includes a second resistor;

[0030] The first end of the second resistor is connected to the second end of the switch module, and the second end of the second resistor is respectively connected to the second input end of the comparison module and the first end of the voltage holding module.

[0031] In a possible implementation manner, the signal conversion subcircuit includes a second amplifier, a second switch, and a third capacitor;

[0032] The inverting input terminal of the second amplifier is respectively connected to the signal source, the first terminal of the second switch, and the first terminal of the third capacitor, the non-inverting input terminal of the second amplifier is connected to the output terminal of the control subcircuit, and the output terminal of the second amplifier is respectively connected to the input terminal of the voltage sampling subcircuit, the second terminal of the second switch, and the second terminal of the third capacitor.

[0033] In a second aspect, an embodiment of the present application provides an image acquisition system, which includes an image sensor and a signal conversion circuit as described in any one of the first aspects above.

[0034] Beneficial effects of the embodiments of the present application:

[0035] The embodiment of the present application provides a signal conversion circuit and an image acquisition system, wherein the signal conversion circuit includes a signal conversion subcircuit, a voltage sampling subcircuit and a control subcircuit; the input end of the voltage sampling subcircuit is connected to the signal conversion subcircuit, the output end of the voltage sampling subcircuit is connected to the second input end of the control subcircuit, the first input end of the control subcircuit is connected to the reference voltage end, the output end of the control subcircuit is connected to the first input end of the signal conversion subcircuit, and the second input end of the signal conversion subcircuit is connected to a signal source; wherein the signal source is an image sensor; the signal conversion subcircuit is used to receive a first voltage signal output by the control subcircuit through its first input end when its second input end is connected to its output end, and to change its a bias voltage signal at the second input terminal of the control subcircuit; wherein the bias voltage signal is a bias voltage signal of the signal source; a voltage sampling subcircuit, used for collecting the bias voltage signal at the second input terminal of the signal conversion subcircuit when the second input terminal of the signal conversion subcircuit is connected to the output terminal, and transmitting the collected second voltage signal to the second input terminal of the control subcircuit; wherein the second voltage signal is a voltage signal proportional to the bias voltage signal; a control subcircuit, used for comparing the second voltage signal with the reference voltage signal at the reference voltage terminal, and when the voltage difference between the second voltage signal and the reference voltage signal is greater than a preset threshold, adjusting the first voltage signal at its own output terminal until the voltage difference between the second voltage signal and the reference voltage signal is not greater than the preset threshold. By setting a voltage sampling subcircuit and a control subcircuit, the bias voltage signal of the image sensor is collected, and the collected second voltage signal which is proportional to the bias voltage signal is compared with the reference voltage signal. When the voltage difference between the second voltage signal and the reference voltage signal is greater than a preset threshold, the output first voltage signal is adjusted until the voltage difference between the second voltage signal and the reference voltage signal is not greater than the preset threshold, and the output first voltage signal remains unchanged, so that the bias voltage signal remains stable, thereby improving the working performance of the image acquisition system.

[0036] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0038] Figure 1 A structural schematic diagram of an image acquisition system in the related art;

[0039] Figure 2a A first structural schematic diagram of a signal conversion circuit provided in an embodiment of the present application;

[0040] Figure 2b A second structural schematic diagram of the signal conversion circuit provided in an embodiment of the present application;

[0041] Figure 3 A third structural schematic diagram of the signal conversion circuit provided in an embodiment of the present application;

[0042] Figure 4 A fourth structural schematic diagram of the signal conversion circuit provided in an embodiment of the present application;

[0043] Figure 5 A fifth structural schematic diagram of the signal conversion circuit provided in an embodiment of the present application;

[0044] Figure 6 A schematic diagram of the structure of an image acquisition system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field based on the present application belong to the scope of protection of the present application.

[0046] The current image acquisition system usually includes image sensors, charge-to-voltage circuits and other structures, such as Figure 1As shown, the image sensor is used to convert the light signal into a charge signal, and the charge-to-voltage circuit (including a reset switch K, a feedback capacitor C and an amplifier A, the image sensor is connected to the inverting input terminal - of the amplifier A, the non-inverting input terminal + of the amplifier A is connected to the reference voltage VREF1, and the output terminal OUT of the amplifier A is connected to the subsequent circuit) is used to convert the charge signal output by the image sensor into a voltage signal and amplify it.

[0047] In practical applications, high-performance integrated amplifiers can be used as amplifiers in charge-to-voltage circuits. However, since integrated amplifiers integrate a large number of devices into one, there are more or less constraints between their various parts. Therefore, the overall performance of integrated amplifiers is lower than that of amplifiers composed of discrete devices. For application scenarios with higher performance requirements, especially those requiring extremely low input noise, the use of integrated amplifiers often cannot achieve the ultimate performance of the image acquisition system.

[0048] In order to achieve the ultimate performance of the image acquisition system, it is usually necessary to use high-performance discrete devices to build the amplifier in the charge-to-voltage circuit. However, since the discreteness of discrete devices is usually large, the offset voltage of the amplifier is very discrete. According to the current circuit design, this will further cause the bias voltage of the image sensor to be very discrete, resulting in the dynamic range, saturation charge and other performance of the image sensor being lower than expected, affecting the working performance of the image acquisition system.

[0049] In order to more clearly understand the present solution, the concepts of the bias voltage of the image sensor and the offset voltage of the amplifier are explained below.

[0050] Bias voltage of image sensor: Bias voltage is a constant DC voltage applied to electronic devices to set their working state. In image sensors, bias voltage is used to control the working point of core components such as photodiodes to make them in the best detection or signal conversion state.

[0051] Amplifier offset voltage: The amplifier offset voltage refers to the non-zero voltage at the output of the amplifier when the input voltage is zero (the two input terminals are short-circuited) in an actual amplifier. For an ideal amplifier, when the input voltage is zero, the output voltage should also be zero, but due to the limitations of manufacturing processes and device characteristics, when the input of an actual amplifier is zero, the output may have a small voltage offset, which is the offset voltage.

[0052] In order to improve the above problems, an embodiment of the present application provides a signal conversion circuit and an image acquisition system.

[0053] Next, the signal conversion circuit provided in the embodiment of the present application is described in detail. Figure 2a, is a first structural diagram of a signal conversion circuit 1 provided in an embodiment of the present application, the signal conversion circuit 1 comprises:

[0054] A signal conversion subcircuit 11, a voltage sampling subcircuit 12 and a control subcircuit 13;

[0055] The input end of the voltage sampling subcircuit 12 is connected to the signal conversion subcircuit 11, the output end of the voltage sampling subcircuit 12 is connected to the second input end of the control subcircuit 13, the first input end of the control subcircuit 13 is connected to the reference voltage end, the output end of the control subcircuit 13 is connected to the first input end of the signal conversion subcircuit 11, and the second input end of the signal conversion subcircuit 11 is connected to a signal source; wherein the signal source is an image sensor;

[0056] The signal conversion subcircuit 11 is used to receive the first voltage signal Vc output by the control subcircuit 13 through its first input terminal when its second input terminal is connected to the output terminal, and change the bias voltage signal Vb of its second input terminal in accordance with the change of the first voltage signal Vc; wherein the bias voltage signal Vb is the bias voltage signal of the signal source;

[0057] The voltage sampling subcircuit 12 is used to collect the bias voltage signal Vb of the second input end of the signal conversion subcircuit 11 when the second input end and the output end of the signal conversion subcircuit 11 are connected, and transmit the collected second voltage signal Va to the second input end of the control subcircuit 13; wherein the second voltage signal Va is a voltage signal proportional to the bias voltage signal Vb;

[0058] The control subcircuit 13 is used to compare the second voltage signal Va with the reference voltage signal VREF at the reference voltage end, and when the voltage difference between the second voltage signal Va and the reference voltage signal VREF is greater than a preset threshold, adjust the first voltage signal Vc at its own output end until the voltage difference between the second voltage signal Va and the reference voltage signal VREF is no greater than the preset threshold.

[0059] In the image acquisition system, the signal conversion subcircuit 11 (charge-to-voltage circuit) is used to convert the charge signal into a voltage signal. Before each reading of the charge signal, a reset operation can be performed by connecting the second input terminal of the signal conversion subcircuit 11 to the output terminal (directly or indirectly through a series resistor or other device with a certain conductivity). At this time, the voltage signal at the output terminal of the signal conversion subcircuit 11 is approximately equal to the voltage value of the bias voltage signal at the second input terminal. Through the reset operation, it is ensured that the signal conversion subcircuit 11 starts working from a known initial state.

[0060] The voltage sampling subcircuit 12 can indirectly collect the bias voltage signal by collecting the voltage signal at the output end of the signal conversion subcircuit 11 (the second input end of the signal conversion subcircuit 11 is connected to the output end, and the voltage signal at the output end of the signal conversion subcircuit 11 is approximately equal to the voltage value of the bias voltage signal at the second input end). Figure 2a The voltage sampling subcircuit 12 can also directly collect the bias voltage signal of the second input terminal of the signal conversion subcircuit 11, which can be seen in Figure 2b , this application does not make any specific limitation on this.

[0061] The second voltage signal Va is a voltage signal in proportional relationship with the bias voltage signal Vb. The proportional relationship may be 1:1 or other proportional relationships, depending on the actual design of the circuit.

[0062] The preset threshold and the reference voltage signal VREF can be set according to the actual situation of the circuit. In one example, the preset threshold can be 0.1V, and the voltage value of the reference voltage signal VREF can be 5V. When the voltage value of the second voltage signal Va collected by the voltage sampling subcircuit 12 is 4.5V, the control subcircuit 13 compares the second voltage signal Va with the reference voltage signal VREF, and obtains that the voltage difference between the two is 0.5V. 0.5V is greater than the preset threshold value 0.1V, and the control subcircuit 13 will adjust the first voltage signal Vc at its output end to increase, and the bias voltage signal Vb of the image sensor increases with the increase of the first voltage signal Vc, until the voltage difference between the second voltage signal Va and the reference voltage signal VREF is not greater than the preset threshold value 0.1V, ensuring that the image sensor operates at the target operating point (depending on the actual characteristic requirements of the circuit).

[0063] In one example, the preset threshold value may be 0.1V, and the voltage value of the reference voltage signal VREF may be 5V. When the voltage value of the second voltage signal Va collected by the voltage sampling subcircuit 12 is 5.5V, the control subcircuit 13 compares the second voltage signal Va with the reference voltage signal VREF, and obtains a voltage difference of 0.5V between the two. 0.5V is greater than the preset threshold value of 0.1V, and the control subcircuit 13 adjusts the first voltage signal Vc at its output end to decrease, and the bias voltage signal Vb of the image sensor decreases with the decrease of the first voltage signal Vc, until the voltage difference between the second voltage signal Va and the reference voltage signal VREF is not greater than the preset threshold value of 0.1V, ensuring that the image sensor operates at the target operating point.

[0064] In an example, the preset threshold value can be 0V. When the preset threshold value is 0V, the control subcircuit 13 is used to compare the second voltage signal Va with the reference voltage signal VREF. When the voltage value of the second voltage signal Va is not equal to the voltage value of the reference voltage signal VREF, the control subcircuit 13 is used to adjust the first voltage signal Vc at its output end until the voltage value of the second voltage signal Va is equal to the voltage value of the reference voltage signal VREF. Specifically, when the second voltage signal Va is greater than the reference voltage signal VREF, the control subcircuit 13 will adjust the first voltage signal Vc at its output end to decrease, and the bias voltage signal Vb of the image sensor will decrease along with the decrease of the first voltage signal Vc, until the voltage value of the second voltage signal Va is equal to the voltage value of the reference voltage signal VREF, thereby ensuring that the image sensor operates at the target operating point; when the second voltage signal Va is less than the reference voltage signal VREF, the control subcircuit 13 will adjust the first voltage signal Vc at its output end to increase, and the bias voltage signal Vb of the image sensor will increase along with the increase of the first voltage signal Vc, until the voltage value of the second voltage signal Va is equal to the voltage value of the reference voltage signal VREF, thereby ensuring that the image sensor operates at the target operating point; when the second voltage signal Va is equal to the reference voltage signal VREF, the first voltage signal Vc remains constant.

[0065] In the embodiment of the present application, the closed-loop control of the bias voltage signal Vb is realized by setting the voltage sampling subcircuit 12 and the control subcircuit 13. Specifically, the bias voltage signal Vb of the image sensor is collected, and the collected second voltage signal Va which is proportional to the bias voltage signal Vb is compared with the reference voltage signal VREF. When the voltage difference between the second voltage signal Va and the reference voltage signal VREF is greater than the preset threshold, the output first voltage signal Vc is adjusted until the voltage difference between the second voltage signal Va and the reference voltage signal VREF is not greater than the preset threshold, and the output first voltage signal Vc remains unchanged, so that the bias voltage signal Vb is stabilized at the target working point, thereby improving the working performance of the image sensor and the working performance of the image acquisition system.

[0066] In one possible implementation, see Figure 3 The signal conversion subcircuit 11 is also used to receive the charge signal of the signal source through its own second input end when its own second input end is disconnected from the output end, convert the charge signal into a third voltage signal, and output the third voltage signal to the subsequent circuit through its own output end.

[0067] When the second input terminal of the signal conversion sub-circuit 11 is disconnected from the output terminal (at this time, the voltage sampling sub-circuit 12 is also turned off), the signal conversion sub-circuit 11 enters a normal working state (charge signal reading stage), receives the charge signal through its own second input terminal, and generates a corresponding output voltage according to the size of the input charge signal.

[0068] In the embodiment of the present application, the second input terminal of the signal conversion subcircuit 11 is disconnected from the output terminal, so that the signal conversion subcircuit 11 enters a normal working state (charge signal reading stage), converts the charge signal into an analog voltage signal, and outputs it to the subsequent circuit.

[0069] In one possible implementation, see Figure 4 , the control subcircuit 13 includes a comparison module 131 and a voltage holding module 132;

[0070] The second input terminal of the comparison module 131 is respectively connected to the output terminal of the voltage sampling subcircuit 12 and the first terminal of the voltage holding module 132, the first input terminal of the comparison module 131 is connected to the reference voltage terminal, and the output terminal of the comparison module 131 is connected to the first input terminal of the signal conversion subcircuit 11;

[0071] A second terminal of the voltage maintaining module 132 is grounded to GND;

[0072] The voltage maintaining module 132 is used to maintain the second voltage signal Va;

[0073] The comparison module 131 is used for accumulating charges in response to the voltage difference between the second voltage signal Va and the reference voltage signal VREF, and outputting a current first voltage signal Vc based on the current accumulated charges.

[0074] The voltage holding module 132 may be a capacitor module, which holds the second voltage signal Va collected by the voltage sampling sub-circuit 12 through a capacitor.

[0075] The comparison module 131 may include an input resistor, a feedback capacitor and an amplifier. The specific implementation method and working process are described in detail below.

[0076] In the embodiment of the present application, the second voltage signal Va collected by the voltage sampling subcircuit 12 is maintained through the voltage holding module 132; the voltage difference between the second voltage signal Va and the reference voltage signal VREF is responded to through the comparison module 131 to realize charge accumulation, and the current first voltage signal Vc is outputted based on the current accumulated charge. The bias voltage signal Vb of the image sensor changes with the change of the first voltage signal Vc until the voltage difference between the second voltage signal Va and the reference voltage signal VREF is not greater than the preset threshold value, and the output first voltage signal Vc remains unchanged, so that the bias voltage signal Vb is stabilized at the target operating point, thereby improving the working performance of the image sensor and the working performance of the image acquisition system.

[0077] In one possible implementation, see Figure 4 , the voltage sampling subcircuit 12 includes a switch module 121 and a voltage stabilizing module 122;

[0078] The first end of the switch module 121 is connected to the output end of the signal conversion sub-circuit 11, the second end of the switch module 121 is connected to the first end of the voltage stabilizing module 122, and the second end of the voltage stabilizing module 122 is respectively connected to the second input end of the comparison module 131 and the first end of the voltage maintaining module 132;

[0079] The switch module 121 is used for collecting the bias voltage signal Vb by being in a conducting state when the second input terminal and the output terminal of the signal conversion sub-circuit 11 are connected;

[0080] The voltage stabilizing module 122 is used to stabilize the voltage signal at the second end of the switch module 121 when the switch module 121 is in the on state.

[0081] The switch module 121 may include one switch or multiple switches, which is not specifically limited in the present application.

[0082] The voltage stabilizing module 122 may be a resistor module or other types of buffer or damping devices, which is not specifically limited in the present application.

[0083] In the embodiment of the present application, the bias voltage signal Vb is collected by the conduction state of the switch module 121; by setting the voltage stabilizing module 122, the current impact when the switch module 121 is turned on is buffered and damped to stabilize the voltage signal at the second end of the switch module 121.

[0084] In one possible implementation, see Figure 5 , the comparison module 131 includes a first amplifier A1, a first capacitor C1, and a first resistor R1;

[0085] The inverting input terminal - of the first amplifier A1 is respectively connected to the first end of the first resistor R1 and the second end of the first capacitor C1, the non-inverting input terminal + of the first amplifier A1 is connected to the reference voltage terminal, and the output terminal OUT1 of the first amplifier A1 is respectively connected to the first end of the first capacitor C1 and the first input terminal of the signal conversion sub-circuit 11;

[0086] The second end of the first resistor R1 is connected to the output end of the voltage sampling sub-circuit 12 and the first end of the voltage holding module 132 respectively.

[0087] The first capacitor C1 is a feedback capacitor, and the first resistor R1 is an input resistor.

[0088] In one possible implementation, see Figure 5 , the voltage maintaining module 132 includes a second capacitor C2;

[0089] The first end of the second capacitor C2 is respectively connected to the second input end of the comparison module 131 and the output end of the voltage sampling sub-circuit 12;

[0090] A second end of the second capacitor C2 is connected to the ground GND.

[0091] In one possible implementation, see Figure 5 , the switch module 121 includes a first switch K1;

[0092] A first end of the first switch K1 is connected to the output end of the signal conversion sub-circuit 11 , and a second end of the first switch K1 is connected to a first end of the voltage stabilizing module 122 .

[0093] The first switch K1 may be a MOS (a field effect transistor) switch tube, a power load switch, or other types of analog switches, etc., which is not specifically limited in the present application.

[0094] In one possible implementation, see Figure 5 , the voltage stabilizing module 122 includes a second resistor R2;

[0095] The first end of the second resistor R2 is connected to the second end of the switch module 121 , and the second end of the second resistor R2 is connected to the second input end of the comparison module 131 and the first end of the voltage holding module 132 , respectively.

[0096] The second resistor R2 is a buffer resistor, and can be a common resistor.

[0097] In one possible implementation, see Figure 5, the signal conversion sub-circuit 11 includes a second amplifier A2, a second switch K2, and a third capacitor C3;

[0098] The inverting input terminal - of the second amplifier A2 is respectively connected to the signal source, the first end of the second switch K2, and the first end of the third capacitor C3, the non-inverting input terminal + of the second amplifier A2 is connected to the output end of the control subcircuit 13, and the output terminal OUT2 of the second amplifier A2 is respectively connected to the input end of the voltage sampling subcircuit 12, the second end of the second switch K2, and the second end of the third capacitor C3.

[0099] The second switch K2 is a reset switch, and the third capacitor C3 is a feedback capacitor.

[0100] Next, combine Figure 5 The working process of the signal conversion circuit 1 provided in this application is described in detail:

[0101] In the image acquisition system, the signal conversion subcircuit 11 (charge-to-voltage circuit) is used to convert the charge signal into a voltage signal. Before each reading of the charge signal, the second switch K2 can be briefly closed to perform a reset operation. At this time, the inverting input terminal - of the second amplifier A2 is connected to the output terminal OUT2, the feedback path of the second amplifier A2 is connected, and the voltage of the output terminal OUT2 is forced to be approximately equal to the voltage of the inverting input terminal -. The reset operation will clear the charge on the third capacitor C3 to ensure that the signal conversion subcircuit 11 starts working from a known initial state.

[0102] During the period when the second switch K2 is closed, the first switch K1 can be controlled to be closed during this period, or the first switch K1 can be controlled to be closed only for a period of time during this period to collect the bias voltage signal Vb. The second resistor R2 mainly functions to buffer and damp the current impact when the first switch K1 is closed, so as to stabilize the voltage signal at the second end of the first switch K1 and improve the problem of instantaneous voltage drop.

[0103] In the control subcircuit 13, the collected second voltage signal Va is maintained by the second capacitor C2, and the first amplifier A1, the first capacitor C1 and the first resistor R1 implement a comparison circuit for accumulating charges in response to the voltage difference between the second voltage signal Va and the reference voltage signal VREF, and outputting the current first voltage signal Vc based on the current accumulated charge. The bias voltage signal Vb of the image sensor changes with the change of the first voltage signal Vc until the voltage difference between the second voltage signal Va and the reference voltage signal VREF is no greater than a preset threshold.

[0104] In the comparison module 131 of the control subcircuit 13, the input second voltage signal Va generates an input current through the first resistor R1, and the input current charges the first capacitor C1. The voltage of the first capacitor C1 is the difference between the voltage of the output terminal OUT1 of the first amplifier A1 and the voltage of the inverting input terminal -. Combined with the "virtual short" characteristic of the first amplifier A1, the relationship between the first voltage signal Vc, the reference voltage signal VREF and the second voltage signal Va is obtained as follows:

[0105]

[0106] Wherein, R1 represents a first resistor, C1 represents a first capacitor, t represents time, Vc represents a first voltage signal, VREF represents a reference voltage signal, and Va represents a second voltage signal.

[0107] The comparison module 131 is used to compare the second voltage signal Va with the reference voltage signal VREF, and adjust the output according to the difference. When the second voltage signal Va is greater than the reference voltage signal VREF, the first voltage signal Vc output by the comparison module 131 decreases linearly with time, and the bias voltage signal Vb decreases along with the decrease of the first voltage signal Vc until the second voltage signal Va approaches the reference voltage signal VREF; when the second voltage signal Va is less than the reference voltage signal VREF, the first voltage signal Vc output by the comparison module 131 increases linearly with time, and the bias voltage signal Vb increases along with the increase of the first voltage signal Vc until the second voltage signal Va approaches the reference voltage signal VREF; when the second voltage signal Va approaches the reference voltage signal VREF, the first voltage signal Vc remains unchanged at a certain value.

[0108] When the second switch K2 is disconnected, the first switch K1 is also disconnected, and the signal conversion subcircuit 11 enters a normal working state (charge signal reading stage), receives the charge signal output by the image sensor, converts the charge signal into an analog voltage signal, and outputs the analog voltage signal to the subsequent circuit.

[0109] The present application also provides an image acquisition system 2, see Figure 6 The image acquisition system 2 includes an image sensor 21 and the signal conversion circuit 1 described in any one of the above embodiments.

[0110] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0111] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0112] The above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A signal conversion circuit, characterized in that: The circuit comprises: Signal conversion subcircuit, voltage sampling subcircuit and control subcircuit; The input end of the voltage sampling subcircuit is connected to the signal conversion subcircuit, the output end of the voltage sampling subcircuit is connected to the second input end of the control subcircuit, the first input end of the control subcircuit is connected to the reference voltage end, the output end of the control subcircuit is connected to the first input end of the signal conversion subcircuit, and the second input end of the signal conversion subcircuit is connected to a signal source; wherein the signal source is an image sensor; The signal conversion subcircuit is used to receive the first voltage signal output by the control subcircuit through its first input terminal when its second input terminal is connected to the output terminal, and change the bias voltage signal of its second input terminal in accordance with the change of the first voltage signal; wherein the bias voltage signal is the bias voltage signal of the signal source; The voltage sampling subcircuit is used to collect the bias voltage signal of the second input end of the signal conversion subcircuit when the second input end and the output end of the signal conversion subcircuit are connected, and transmit the collected second voltage signal to the second input end of the control subcircuit; wherein the second voltage signal is a voltage signal proportional to the bias voltage signal; The control subcircuit is used to compare the second voltage signal with the reference voltage signal at the reference voltage end, and when the voltage difference between the second voltage signal and the reference voltage signal is greater than a preset threshold, adjust the first voltage signal at its own output end until the voltage difference between the second voltage signal and the reference voltage signal is no greater than the preset threshold.

2. The circuit according to claim 1, characterized in that The signal conversion sub-circuit is also used to receive the charge signal of the signal source through its own second input end when its own second input end is disconnected from the output end, convert the charge signal into a third voltage signal, and output the third voltage signal to the subsequent circuit through its own output end.

3. The circuit according to claim 1, characterized in that The control subcircuit includes a comparison module and a voltage holding module; The second input terminal of the comparison module is connected to the output terminal of the voltage sampling subcircuit and the first terminal of the voltage holding module respectively, the first input terminal of the comparison module is connected to the reference voltage terminal, and the output terminal of the comparison module is connected to the first input terminal of the signal conversion subcircuit; The second end of the voltage maintaining module is grounded; The voltage maintaining module is used to maintain the second voltage signal; The comparison module is used to accumulate charge in response to the voltage difference between the second voltage signal and the reference voltage signal, and output a current first voltage signal based on the current accumulated charge.

4. The circuit according to claim 3, characterized in that The voltage sampling subcircuit includes a switch module and a voltage stabilization module; The first end of the switch module is connected to the output end of the signal conversion sub-circuit, the second end of the switch module is connected to the first end of the voltage stabilizing module, and the second end of the voltage stabilizing module is respectively connected to the second input end of the comparison module and the first end of the voltage maintaining module; The switch module is used for collecting the bias voltage signal by being in a conducting state when the second input terminal and the output terminal of the signal conversion subcircuit are connected; The voltage stabilizing module is used to stabilize the voltage signal at the second end of the switch module when the switch module is in the on state.

5. The circuit according to claim 3, characterized in that The comparison module includes a first amplifier, a first capacitor, and a first resistor; The inverting input terminal of the first amplifier is respectively connected to the first end of the first resistor and the second end of the first capacitor, the non-inverting input terminal of the first amplifier is connected to the reference voltage terminal, and the output terminal of the first amplifier is respectively connected to the first end of the first capacitor and the first input terminal of the signal conversion sub-circuit; The second end of the first resistor is connected to the output end of the voltage sampling subcircuit and the first end of the voltage holding module respectively.

6. The circuit according to claim 3, characterized in that The voltage maintaining module includes a second capacitor; The first end of the second capacitor is respectively connected to the second input end of the comparison module and the output end of the voltage sampling subcircuit; The second terminal of the second capacitor is grounded.

7. The circuit according to claim 4, characterized in that The switch module includes a first switch; The first end of the first switch is connected to the output end of the signal conversion sub-circuit, and the second end of the first switch is connected to the first end of the voltage stabilizing module.

8. The circuit according to claim 4, characterized in that The voltage stabilizing module includes a second resistor; The first end of the second resistor is connected to the second end of the switch module, and the second end of the second resistor is respectively connected to the second input end of the comparison module and the first end of the voltage holding module.

9. The circuit according to claim 1, characterized in that The signal conversion subcircuit includes a second amplifier, a second switch, and a third capacitor; The inverting input terminal of the second amplifier is respectively connected to the signal source, the first terminal of the second switch, and the first terminal of the third capacitor, the non-inverting input terminal of the second amplifier is connected to the output terminal of the control subcircuit, and the output terminal of the second amplifier is respectively connected to the input terminal of the voltage sampling subcircuit, the second terminal of the second switch, and the second terminal of the third capacitor.

10. An image acquisition system, characterized in that: The image acquisition system comprises an image sensor and a signal conversion circuit as described in any one of claims 1 to 9.

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