A signal conversion circuit and an image acquisition system

Abstract

An embodiment of the present application provides a signal conversion circuit and an image acquisition system, including a signal conversion sub-circuit, a voltage sampling sub-circuit, and a control sub-circuit; the signal conversion sub-circuit is configured to receive a first voltage signal output by the control sub-circuit 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 following the change of the first voltage signal; the voltage sampling sub-circuit is configured to sample the bias voltage signal of the second input terminal of the signal conversion sub-circuit when the second input terminal of the signal conversion sub-circuit is connected to the output terminal, and transmit the sampled second voltage signal to the second input terminal of the control sub-circuit; the control sub-circuit is configured to compare the second voltage signal with the reference voltage signal of the reference voltage terminal, and adjust the first voltage signal until the voltage difference between the two is not greater than a preset threshold when the voltage difference between the two is greater than the preset threshold.

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] In current image acquisition systems, structures such as image sensors and charge-to-voltage circuits are usually included. As Figure 1 shown, the image sensor is used to convert optical signals into charge signals, and the charge-to-voltage circuit is used to convert the charge signals output by the image sensor into voltage signals and perform amplification processing.

[0003] In order to achieve the extreme performance of the image acquisition system, high-performance discrete devices are usually required to construct the amplifier in the charge-to-voltage circuit. However, due to the large discreteness of discrete devices, the offset voltages of the amplifiers are very discrete. According to the current circuit design, this will further cause the bias voltages of the image sensors to be very discrete, resulting in the working performance of the image acquisition system being lower than expected. Summary of the Invention

[0004] The purpose of the embodiments 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 solutions are as follows:

[0005] In a first aspect, the embodiments of the present application provide a signal conversion circuit, and the circuit includes:

[0006] A signal conversion sub-circuit, a voltage sampling sub-circuit, and a control sub-circuit;

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

[0008] The signal conversion sub-circuit is configured to, when its second input end is in communication with the output end, receive the first voltage signal output by the control sub-circuit through its first input end, and follow the change of the first voltage signal to change the bias voltage signal of its second input end; wherein, the bias voltage signal is the bias voltage signal of the signal source;

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

[0010] The control sub - circuit is used to compare the second voltage signal with the reference voltage signal at the reference voltage terminal. When the voltage difference between the second voltage signal and the reference voltage signal is greater than a preset threshold, it adjusts the first voltage signal at its output end until the voltage difference between the second voltage signal and the reference voltage signal is not greater than the preset threshold.

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

[0012] In a possible implementation manner, the control sub - circuit includes a comparison module and a voltage holding module;

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

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

[0015] The voltage holding module is used to hold the second voltage signal;

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

[0017] In a possible implementation manner, the voltage sampling sub - circuit includes a switch module and a voltage stabilizing 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. 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 holding module;

[0019] The switch module is used to collect the bias voltage signal by being in a conducting state when the second input end and the output end of the signal conversion sub-circuit 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 a conducting state.

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

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

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

[0024] In a possible implementation manner, the voltage holding 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 sub-circuit.

[0026] The second end 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 sub-circuit 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 sub-circuit. The output terminal of the second amplifier is respectively connected to the input terminal of the voltage sampling sub-circuit, 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 the signal conversion circuit according to any one of the first aspects above.

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

[0035] A signal conversion circuit and an image acquisition system provided by an embodiment of the present application. The signal conversion circuit includes a signal conversion sub-circuit, a voltage sampling sub-circuit, and a control sub-circuit. The input terminal of the voltage sampling sub-circuit is connected to the signal conversion sub-circuit. The output terminal of the voltage sampling sub-circuit is connected to the second input terminal of the control sub-circuit. The first input terminal of the control sub-circuit is connected to the reference voltage terminal. The output terminal of the control sub-circuit is connected to the first input terminal of the signal conversion sub-circuit. The second input terminal of the signal conversion sub-circuit is connected to the signal source. Wherein, the signal source is an image sensor. The signal conversion sub-circuit is configured to, when its second input terminal is communicated with the output terminal, receive the first voltage signal output by the control sub-circuit through its first input terminal, and follow the change of the first voltage signal to change the bias voltage signal of its second input terminal. Wherein, the bias voltage signal is the bias voltage signal of the signal source. The voltage sampling sub-circuit is configured to, when the second input terminal of the signal conversion sub-circuit is communicated with the output terminal, collect the bias voltage signal of the second input terminal of the signal conversion sub-circuit, and transmit the collected second voltage signal to the second input terminal of the control sub-circuit. Wherein, the second voltage signal is a voltage signal proportional to the bias voltage signal. The control sub-circuit is configured to compare the second voltage signal with the reference voltage signal of the reference voltage terminal. 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 of its 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 the voltage sampling sub-circuit and the control sub-circuit, the bias voltage signal of the image sensor is collected, and the collected second voltage signal 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 the 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 is kept stable, and the working performance of the image acquisition system is improved.

[0036] Of course, it is not necessary for any product or method implementing the present application to achieve all of the above-described advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application, and those of ordinary skill in the art can also obtain other embodiments based on these drawings.

[0038] Figure 1 FIG. 9 is a schematic structural diagram of an image acquisition system in the related art;

[0039] Figure 2a FIG. 13 is a first schematic structural diagram of a signal conversion circuit provided by an embodiment of the present application;

[0040] Figure 2b FIG. 17 is a second schematic structural diagram of a signal conversion circuit provided by an embodiment of the present application;

[0041] Figure 3 FIG. 21 is a third schematic structural diagram of a signal conversion circuit provided by an embodiment of the present application;

[0042] Figure 4 FIG. 25 is a fourth schematic structural diagram of a signal conversion circuit provided by an embodiment of the present application;

[0043] Figure 5 FIG. 29 is a fifth schematic structural diagram of a signal conversion circuit provided by an embodiment of the present application;

[0044] Figure 6 FIG. 33 is a schematic structural diagram of an image acquisition system provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art based on the present application belong to the scope of protection of the present application.

[0046] In the current image acquisition system, it usually includes structures such as an image sensor and a charge-to-voltage circuit, as Figure 1As shown, the image sensor is used to convert optical signals into charge signals, 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 a reference voltage VREF1, and the output terminal OUT of the amplifier A is connected to the subsequent circuit) is used to convert the charge signals output by the image sensor into voltage signals and perform amplification processing.

[0047] In practical applications, a high-performance integrated amplifier can be used as the amplifier in the charge-to-voltage circuit. However, since a large number of devices are integrated in the integrated amplifier, there are more or less restrictions between its various parts. Therefore, the comprehensive performance of the integrated amplifier is lower than that of the amplifier composed of discrete devices. For application scenarios with high performance requirements, especially those requiring extremely low input noise, using an integrated amplifier often cannot achieve the ultimate performance of the image acquisition system.

[0048] To achieve the ultimate performance of the image acquisition system, it is usually necessary to use high-performance discrete devices to construct the amplifier in the charge-to-voltage circuit. However, due to the usually large discreteness of discrete devices, 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 performance such as the dynamic range and saturation charge amount of the image sensor being lower than expected, which affects the working performance of the image acquisition system.

[0049] To understand this solution more clearly, the concepts of the bias voltage of the image sensor and the offset voltage of the amplifier are explained below.

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

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

[0052] 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 by the embodiment of the present application will be described in detail. Refer to Figure 2a, which is the first structural schematic diagram of the signal conversion circuit 1 provided by the embodiment of the present application. The signal conversion circuit 1 includes:

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

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

[0056] The signal conversion sub-circuit 11 is configured to receive the first voltage signal Vc output by the control sub-circuit 13 through its first input end when its second input end is in communication with the output end, and change the bias voltage signal Vb at its second input end following 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 sub-circuit 12 is configured to collect the bias voltage signal Vb at the second input end of the signal conversion sub-circuit 11 when the second input end of the signal conversion sub-circuit 11 is in communication with the output end, and transmit the collected second voltage signal Va to the second input end of the control sub-circuit 13; wherein, the second voltage signal Va is a voltage signal proportional to the bias voltage signal Vb;

[0058] The control sub-circuit 13 is configured to compare the second voltage signal Va with the reference voltage signal VREF at the reference voltage terminal, and adjust the first voltage signal Vc at its output end until the voltage difference between the second voltage signal Va and the reference voltage signal VREF is not greater than a preset threshold when the voltage difference between the second voltage signal Va and the reference voltage signal VREF is greater than the preset threshold.

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

[0060] The voltage sampling sub - circuit 12 can indirectly sample the bias voltage signal by sampling the voltage signal at the output end of the signal conversion sub - circuit 11 (the second input end of the signal conversion sub - circuit 11 is connected to the output end, and the voltage value of the voltage signal at the output end of the signal conversion sub - circuit 11 is approximately equal to the voltage value of the bias voltage signal at the second input end). Refer to Figure 2a ; the voltage sampling sub - circuit 12 can also directly sample the bias voltage signal at the second input end of the signal conversion sub - circuit 11. Refer to Figure 2b ; this application does not make specific limitations on this.

[0061] The second voltage signal Va is a voltage signal proportional to the bias voltage signal Vb. The proportional relationship can be 1:1 or other proportional relationships, specifically 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 sampled by the voltage sampling sub - circuit 12 is 4.5V, the control sub - circuit 13 compares the second voltage signal Va with the reference voltage signal VREF, and the voltage difference between the two is 0.5V. Since 0.5V is greater than the preset threshold 0.1V, the control sub - circuit 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 following 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 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 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 sampled by the voltage sampling sub - circuit 12 is 5.5V, the control sub - circuit 13 compares the second voltage signal Va with the reference voltage signal VREF, and the voltage difference between the two is 0.5V. Since 0.5V is greater than the preset threshold 0.1V, the control sub - circuit 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 following 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 0.1V, ensuring that the image sensor operates at the target operating point.

[0064] In one example, the preset threshold value can be 0V. When the preset threshold value is 0V, the control sub-circuit 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 first voltage signal Vc at its output terminal is adjusted 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 sub-circuit 13 will adjust the first voltage signal Vc at its output terminal to decrease, and the bias voltage signal Vb of the image sensor will decrease following 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, 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 sub-circuit 13 will adjust the first voltage signal Vc at its output terminal to increase, and the bias voltage signal Vb of the image sensor will increase following 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, 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 unchanged at a certain value.

[0065] In the embodiment of the present application, by setting the voltage sampling sub-circuit 12 and the control sub-circuit 13, the closed-loop control of the bias voltage signal Vb is achieved. Specifically, the bias voltage signal Vb of the image sensor is collected, and the second voltage signal Va collected and 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 value, 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 value, and the output first voltage signal Vc remains unchanged, so that the bias voltage signal Vb is stabilized at the target operating point, improving the operating performance of the image sensor and the operating performance of the image acquisition system.

[0066] In a possible implementation manner, referring to Figure 3 , when the second input terminal and the output terminal of the signal conversion sub-circuit 11 are disconnected, the signal conversion sub-circuit 11 is further configured to receive the charge signal of the signal source through its second input terminal, convert the charge signal into a third voltage signal, and output the third voltage signal to the subsequent circuit through its output terminal.

[0067] When the second input terminal and the output terminal of the signal conversion sub-circuit 11 are disconnected (at this time, the voltage sampling sub-circuit 12 is also turned off), the signal conversion sub-circuit 11 enters the 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 magnitude of the input charge signal.

[0068] In the embodiment of the present application, by disconnecting the second input terminal and the output terminal of the signal conversion sub-circuit 11, the signal conversion sub-circuit 11 enters the 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 a possible implementation manner, refer to Figure 4 , the control sub-circuit 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 sub-circuit 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 sub-circuit 11;

[0071] The second terminal of the voltage holding module 132 is grounded to GND;

[0072] The voltage holding module 132 is used to hold the second voltage signal Va;

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

[0074] The voltage holding module 132 can be a capacitor module, and the second voltage signal Va collected by the voltage sampling sub-circuit 12 is held by the capacitor.

[0075] The comparison module 131 can include an input resistor, a feedback capacitor and an amplifier. The specific implementation manner and working process will be described in detail later.

[0076] In the embodiment of the present application, the voltage holding module 132 holds the second voltage signal Va collected by the voltage sampling sub-circuit 12; the comparison module 131 responds to the voltage difference between the second voltage signal Va and the reference voltage signal VREF to accumulate charges, and outputs the current first voltage signal Vc based on the currently accumulated charges. 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 a preset threshold, and the output first voltage signal Vc remains unchanged, so that the bias voltage signal Vb is stabilized at the target operating point, improving the operating performance of the image sensor and the operating performance of the image acquisition system.

[0077] In a possible implementation manner, refer to Figure 4 , the voltage sampling sub-circuit 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 holding module 132;

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

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

[0081] The switch module 121 may include one switch or multiple switches, and the present application does not specifically limit this.

[0082] The voltage stabilizing module 122 may be a resistor module or other types of buffering or damping devices, and the present application does not specifically limit this.

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

[0084] In a possible implementation manner, refer to 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 terminal of the first resistor R1 and the second terminal of the first capacitor C1. The non-inverting input terminal + of the first amplifier A1 is connected to the reference voltage terminal. The output terminal OUT1 of the first amplifier A1 is respectively connected to the first terminal of the first capacitor C1 and the first input terminal of the signal conversion sub-circuit 11;

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

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

[0088] In a possible implementation manner, refer to Figure 5 , the voltage holding module 132 includes a second capacitor C2;

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

[0090] The second terminal of the second capacitor C2 is grounded to GND.

[0091] In a possible implementation manner, refer to Figure 5 , the switch module 121 includes a first switch K1;

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

[0093] The first switch K1 can be a MOS (a type of field effect transistor) switch tube, or a power load switch, or other types of analog switches, etc. The present application does not specifically limit this.

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

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

[0096] The second resistor R2 is a buffer resistor, and an ordinary resistor is sufficient.

[0097] In a possible implementation manner, refer to 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 terminal of the second switch K2, and the first terminal of the third capacitor C3. The non - inverting input terminal + of the second amplifier A2 is connected to the output terminal of the control sub - circuit 13. The output terminal OUT2 of the second amplifier A2 is respectively connected to the input terminal of the voltage sampling sub - circuit 12, the second terminal of the second switch K2, and the second terminal 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, in combination with Figure 5 The working process of the signal conversion circuit 1 provided in this application will be described in detail:

[0101] In an image acquisition system, the signal conversion sub - circuit 11 (charge - to - voltage circuit) is used to convert a charge signal into a voltage signal. Before each charge signal is read, a reset operation can be performed by briefly closing the second switch K2. At this time, the inverting input terminal - and the output terminal OUT2 of the second amplifier A2 are connected, the feedback path of the second amplifier A2 is connected, and the voltage at the output terminal OUT2 is forced to be approximately equal to the voltage at the inverting input terminal -. The reset operation clears the charge on the third capacitor C3, ensuring that the signal conversion sub - circuit 11 starts working from a known initial state.

[0102] During the closing of the second switch K2, 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 certain period of time during this period to collect the bias voltage signal Vb. Among them, the main function of the second resistor R2 is to buffer and damp the current impact when the first switch K1 is closed, so as to stabilize the voltage signal at the second terminal of the first switch K1 and improve the problem of instantaneous voltage drop.

[0103] In the control sub - circuit 13, the second capacitor C2 is used to hold the collected second voltage signal Va. The first amplifier A1, the first capacitor C1, and the first resistor R1 implement a comparison circuit, which is used to accumulate charges in response to the voltage difference between the second voltage signal Va and the reference voltage signal VREF, and output the current first voltage signal Vc corresponding to the currently accumulated charges. 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 a preset threshold.

[0104] In the comparison module 131 of the control sub-circuit 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 at the output terminal OUT1 and the voltage at the inverting input terminal - of the first amplifier A1. Combining 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 as follows:

[0105]

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

[0108] When the second switch K2 is open, the first switch K1 is also open, and the signal conversion sub-circuit 11 enters the 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 embodiment of the present application also provides an image acquisition system 2. Refer to 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 text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0111] Each embodiment in this specification is described in a related manner. For the same and similar parts among the embodiments, reference can be made to each other, and the differences between each embodiment and other embodiments are emphasized. In particular, for system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and reference can be made to the relevant parts of the method embodiments for the relevant content.

[0112] The above are only the preferred embodiments of the present application and are not intended to limit the protection scope of the present application. Any modifications, equivalent replacements, improvements, 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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