Electrochemical sensor protection circuit

Abstract

According to the electrochemical sensor protection circuit provided by the invention, the output signal of the electrochemical sensor is amplified through the signal amplification module, and the reference voltage close to the maximum output voltage of the signal amplification module is generated through the reference voltage generation module; the voltage comparison module is used for comparing the real-time output voltage of the signal amplification module with the reference voltage generated by the reference voltage generation module, and when the real-time output voltage of the signal amplification module is larger than or equal to the reference voltage, the protection switch module is turned on to achieve short circuit of the positive electrode and the negative electrode of the electrochemical sensor. According to the electrochemical sensor protection circuit provided by the invention, when the output voltage of the operational amplifier is close to saturation or reaches saturation, an overload protection mechanism can be quickly triggered, and the electrochemical sensor is short-circuited, so that the operational amplifier is prevented from imbalance due to long-time saturation, and the positive and negative electrodes of the electrochemical sensor are prevented from accumulating voltage.

Description

Technical Field

[0001] This application relates to the field of electrochemical sensor detection technology, and in particular to an electrochemical sensor protection circuit. Background Technology

[0002] In the signal conditioning circuit of electrochemical sensors, operational amplifiers are commonly used to amplify the sensor's output signal. The operating principle of electrochemical sensors requires a very small voltage difference between the positive and negative electrodes to ensure the accuracy and stability of the measurement signal. However, in actual detection environments, the concentration of the analyte may far exceed the designed measurement range, leading to an extremely high current output from the sensor. Excessive current can cause the operational amplifier to saturate or even become unbalanced, resulting in voltage accumulation between the positive and negative electrodes, ultimately causing sensor malfunction or even damage.

[0003] Currently, one circuit design in electrochemical sensor signal conditioning circuits involves connecting a P-channel depletion-type metal-oxide-semiconductor field-effect transistor (MOSFET) between the positive and negative electrodes of the sensor. This design allows the PMOS transistor to conduct when the system loses power, short-circuiting the sensor's positive and negative electrodes and effectively preventing voltage accumulation between them, thus providing power-down protection. However, for situations where the concentration of the analyte far exceeds the design measurement range, leading to an extremely high sensor output current, this circuit design still cannot avoid the problem of voltage accumulation between the sensor's positive and negative electrodes after operational amplifier saturation offset. Summary of the Invention

[0004] This utility model provides an electrochemical sensor protection circuit to achieve overload protection for the electrochemical sensor.

[0005] This utility model embodiment provides an electrochemical sensor protection circuit, including:

[0006] The signal amplification module includes an operational amplifier connected to the positive electrode of the electrochemical sensor, used to amplify the output signal of the electrochemical sensor to obtain an output voltage;

[0007] A reference voltage generation module is used to generate a reference voltage based on the supply voltage of the system power supply and the maximum output voltage of the signal amplification module, wherein the reference voltage does not exceed the maximum output voltage;

[0008] A voltage comparison module, the input terminals of which are respectively connected to the output terminal of the signal amplification module and the reference voltage generation module, is used to compare the output voltage with the reference voltage in real time;

[0009] A protection switch module is connected in parallel between the positive and negative electrodes of the electrochemical sensor and connected to the output terminal of the voltage comparison module. It is used to turn on when the output voltage is greater than or equal to the reference voltage, so as to short-circuit the positive and negative electrodes of the electrochemical sensor.

[0010] Optionally, the operational amplifier is a rail-to-rail output operational amplifier, and the power supply of the operational amplifier is determined based on the system power supply.

[0011] Optionally, the reference voltage generation module includes a first resistor R1 and a second resistor R2, one end of which is connected to the system power supply, and the other end of which is grounded through the R2.

[0012] The resistance ratio of R1 and R2 ranges from 1:4 to 1:9.

[0013] Optionally, the voltage comparison module includes a push-pull output comparator, and the power supply for the comparator is the system power supply.

[0014] The non-inverting input of the comparator is connected to the voltage divider node of R1 and R2, the inverting input of the comparator is connected to the output of the signal amplification module, and the output of the comparator is connected to the protection switch module.

[0015] Optionally, the protection switch module includes a depletion-type PMOS transistor Q1;

[0016] The drain of Q1 is connected to the positive electrode of the electrochemical sensor, the source of Q1 is connected to the negative electrode of the electrochemical sensor, and the gate of Q1 is connected to the output terminal of the voltage comparison module.

[0017] Optionally, the negative electrode of the electrochemical sensor is connected to a reference potential Vref; the supply voltage of the system power supply is denoted as VCC, and the pinch-off voltage of Q1 is denoted as V0. OFF Then VCC, Vref and V OFF The following relationship exists between them:

[0018]

[0019] Optionally, the protection switch module includes an enhancement-mode PMOS transistor Q2; the source of Q2 is connected to the positive electrode of the electrochemical sensor, the drain of Q2 is connected to the negative electrode of the electrochemical sensor, and the gate of Q2 is connected to the output terminal of the voltage comparison module.

[0020] Optionally, the negative electrode of the electrochemical sensor is connected to a reference potential Vref; the supply voltage of the system power supply is denoted as VCC, and the threshold voltage of Q2 is denoted as V0.th The constant potential difference between the positive and negative electrodes of the sensor is ΔV. Then VCC, Vref, ΔV, and V... th The following relationship exists between them:

[0021]

[0022] Furthermore, a dynamic control module is provided between the output terminal of the voltage comparison module and the protection switch module, which is used to control the protection switch module to conduct when the output voltage of the signal amplification module is greater than or equal to the reference voltage, or when the system power supply fails, so as to short-circuit the positive and negative electrodes of the electrochemical sensor.

[0023] Optionally, the dynamic control module includes a third resistor R3 and a fourth resistor R4. One end of R3 is connected to the system power supply, and the other end of R3 is connected to the output terminal of the voltage comparison module through R4.

[0024] The electrochemical sensor protection circuit provided in this embodiment amplifies the output signal of the electrochemical sensor through a signal amplification module, generates a reference voltage close to the maximum output voltage of the signal amplification module through a reference voltage generation module, and compares the real-time output voltage of the signal amplification module with the reference voltage generated by the reference voltage generation module through a voltage comparison module. When the real-time output voltage of the signal amplification module is greater than or equal to the reference voltage, the positive and negative electrodes of the electrochemical sensor are short-circuited through a conduction protection switch module. This electrochemical sensor protection circuit provides real-time monitoring of the operational amplifier output voltage. When the operational amplifier output voltage approaches or has reached saturation, an overload protection mechanism is quickly triggered to short-circuit the electrochemical sensor, thereby preventing the operational amplifier from becoming unbalanced due to prolonged saturation. Furthermore, the overload protection mechanism effectively prevents voltage accumulation at the positive and negative electrodes of the electrochemical sensor, thus preventing damage to the electrochemical sensor due to overload and extending its service life. Attached Figure Description

[0025] Figure 1 A schematic diagram of the structure of an electrochemical sensor protection circuit provided in an embodiment of this utility model;

[0026] Figure 1a A structural example diagram of an electrochemical sensor protection circuit provided in this embodiment of the present invention;

[0027] Figure 1b A structural example diagram of another electrochemical sensor protection circuit provided in this embodiment of the present invention;

[0028] Figure 2A schematic diagram of the structure of an electrochemical sensor protection circuit provided in an embodiment of this utility model;

[0029] Figure 2a A structural example diagram of an electrochemical sensor protection circuit provided in this embodiment of the present invention;

[0030] Figure 2b This is a structural example diagram of another electrochemical sensor protection circuit provided in an embodiment of the present invention. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, the embodiments and features described herein can be combined with each other unless otherwise specified. It should also be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings, not the entire structure.

[0032] Understandably, based on the operating characteristics of electrochemical sensors, these sensors generate current signals through oxidation / reduction reactions on the electrode surfaces. During normal operation, the potential difference between the working electrode (positive electrode) and the reference electrode (negative electrode) is maintained by a constant potential circuit, forming a stable electrochemical reaction environment. Furthermore, the potential difference between the positive and negative electrodes must be very small; otherwise, it will lead to inaccurate and unstable measurement signals. However, in actual detection environments, the concentration of the analyte may far exceed the designed measurement range, causing the sensor to output an extremely large current. Excessive current can saturate or even de-adjust the operational amplifier, leading to voltage accumulation between the positive and negative electrodes of the sensor.

[0033] Voltage accumulation is essentially a coupling effect of circuit linearity disruption and electrochemical dynamic equilibrium imbalance. When the op-amp fails due to overload, it cannot maintain the potential balance between the electrodes through feedback. At the same time, the electrochemical reaction rate inside the sensor is mismatched with the response speed of the external circuit, ultimately leading to charge accumulation and voltage shift between the sensor electrodes.

[0034] The accumulated voltage continuously applied to the electrodes may trigger unexpected electrolytic reactions (such as electrolyte decomposition or electrode material oxidation / reduction), leading to decreased sensor sensitivity or shortened lifespan. Furthermore, residual charge in the high-impedance electrolyte layer of the sensor is difficult to release spontaneously, potentially causing electric field distortion and interfering with the accuracy of subsequent measurements. In addition, prolonged residual voltage may alter the catalytic activity or electrolyte ion distribution on the electrode surface, causing baseline current shifts or nonlinear responses.

[0035] In existing technologies, to address the problem of voltage accumulation at sensor electrodes during system power-down, a solution has been proposed that involves connecting a depletion-type PMOS transistor between the positive and negative electrodes. By turning on the PMOS transistor after system power-down, the impedance between the positive and negative electrodes drops to the level of the PMOS transistor's on-resistance (typically in the milliohm range), allowing residual charge to be rapidly released through a low-resistance path, thereby eliminating residual voltage. Furthermore, short-circuiting reduces the potential difference between the positive and negative electrodes to zero, preventing continued electrolysis or side reactions of the electrolyte and thus suppressing polarization reactions. In addition, short-circuiting also prevents damage to the sensitive electrodes from reverse currents caused by external interference (such as electrostatic discharge).

[0036] However, existing technical solutions cannot solve the problem of voltage accumulation between the positive and negative electrodes of the sensor caused by the concentration of the analyte far exceeding the design measurement range, which leads to the sensor outputting a very large current and then causing the operational amplifier to saturate and become misaligned.

[0037] The purpose of this application is to improve the existing technical solution so that when the output voltage of the signal amplification module is close to its maximum output voltage, the positive and negative electrodes of the sensor can be short-circuited, thereby achieving overload protection for the sensor.

[0038] Figure 1 This is a schematic diagram of an electrochemical sensor protection circuit provided in an embodiment of the present invention. This protection circuit is suitable for situations where, under overload conditions, the positive and negative electrodes are short-circuited to prevent voltage accumulation between them. Figure 1 As shown, the protection circuit for this electrochemical sensor includes:

[0039] The signal amplification module 101 includes an operational amplifier connected to the positive electrode of the electrochemical sensor, used to amplify the output signal of the electrochemical sensor to obtain an output voltage;

[0040] The reference voltage generation module 102 is used to generate a reference voltage based on the power supply voltage of the system power supply and the maximum output voltage of the signal amplification module 101, wherein the reference voltage does not exceed the maximum output voltage;

[0041] The voltage comparison module 103 has its input terminals connected to the output terminal of the signal amplification module 101 and the reference voltage generation module 102, respectively, and is used to compare the output voltage with the reference voltage in real time.

[0042] A protection switch module 104 is connected in parallel between the positive and negative electrodes of the electrochemical sensor and connected to the output terminal of the voltage comparison module 103. It is used to turn on when the output voltage is greater than or equal to the reference voltage to short-circuit the positive and negative electrodes of the electrochemical sensor.

[0043] It should be noted that electrochemical sensors are generally classified into two types: current-type and potential-type. Current-type sensors generate a current signal proportional to the concentration of the target substance through an electrochemical reaction, while potential-type sensors measure the potential difference between electrodes. The technical solution of this application mainly applies to current-type electrochemical sensors. Therefore, the signal amplification module 101 amplifies the output signal of the electrochemical sensor, that is, it amplifies the current signal output by the electrochemical sensor.

[0044] In addition, it should be noted that the output signal of the signal amplification module 101 is a voltage signal, indicating that the signal amplification module 101 realizes the conversion of current signal to voltage signal. Therefore, the signal amplification function of the signal amplification module 101 in this application is not narrowly defined as amplifying a small current signal into a large current signal, but can also be the conversion of a weak (small) current signal into a measurable (large) voltage signal.

[0045] It can be understood that operational amplifiers are typically used in sensor signal conditioning circuits to amplify signals. An operational amplifier capable of converting a weak (small) current signal into a measurable (large) voltage signal can be a transimpedance amplifier. If further amplification of the voltage signal output by the transimpedance amplifier is required, a voltage amplifier, such as an inverting voltage amplifier, can be cascaded after the transimpedance amplifier, thus achieving two stages of signal conditioning: current → voltage → voltage amplification.

[0046] However, if an inverting voltage amplifier is to be used alone, an input resistor needs to be added, so that the conversion of current signal to voltage signal can also be achieved.

[0047] Optionally, the signal amplification module 101 can be a transimpedance amplifier, an inverting voltage amplifier with an input resistor, or a combination of both.

[0048] It is understandable that regardless of the operational amplifier used in the signal amplification module 101, saturation or even offset phenomena may occur when the electrochemical sensor outputs a very large current. Therefore, the technical solution of this application provides a solution to monitor the output voltage of the signal amplification module 101 in real time, and to turn on the protection switch module 104 when its output voltage approaches its maximum output voltage (i.e., saturation voltage), thereby short-circuiting the positive and negative electrodes of the electrochemical sensor and thus achieving overload protection for the sensor.

[0049] In one embodiment, the operational amplifier used in the signal amplification module 101 is a rail-to-rail output operational amplifier, and its power supply can be determined according to the system power supply.

[0050] In a circuit system, depending on the power supply requirements of different devices, there can be only one system power supply, or there can be multiple system power supplies, or there can be a reference system power supply, and then multiple different power supplies can be derived from the reference system power supply.

[0051] Optionally, the operational amplifier used in the signal amplification module 101 can be powered by a single power supply or by a dual power supply.

[0052] Understandably, when using a rail-to-rail output operational amplifier, its output voltage can be close to the upper and lower limits of the op-amp's power supply.

[0053] It should be noted that if the signal amplification module 101 uses a multi-stage operational amplifier cascade, the output voltage of each operational amplifier stage needs to be monitored in real time. Since the monitoring method for each operational amplifier stage can refer to the method for monitoring a single operational amplifier stage, this application focuses on the case where the signal amplification module 101 uses a single operational amplifier stage.

[0054] The function of the reference voltage generation module 102 is to provide a reference voltage that is close to the maximum output voltage of the signal amplification module 101, so as to serve as a comparison reference value for monitoring whether the output voltage of the signal amplification module 101 is close to saturation.

[0055] There are various ways to generate a reference voltage, including but not limited to the following: 1) Voltage divider network method: extracting an intermediate voltage from the power supply voltage as a reference through resistor voltage division; 2) Zener diode method: generating a stable voltage using the reverse breakdown characteristics of a Zener diode; 3) Bandgap reference circuit method: combining the temperature characteristics of bipolar transistors to achieve a high-precision voltage reference; 4) Operational amplifier feedback method: constructing a feedback loop through an operational amplifier to improve the stability and driving capability of the reference voltage; 5) Application-specific integrated circuit (ASIC) reference source method: an integrated high-precision reference source that provides a standardized voltage output.

[0056] It is understandable that the system power supply serves as the power source for the entire circuit system and also as the power supply for the reference voltage generation module 102. That is, the reference voltage generation module 102 processes the supply voltage from the system power supply and converts it into a voltage close to the maximum output voltage of the signal amplification module 101, i.e., the reference voltage. The maximum output voltage of the signal amplification module 101 depends on the selection of the operational amplifier; once the selection is determined, its corresponding maximum output voltage is a definite parameter.

[0057] Optionally, the reference voltage can be set to 80%-95% of the maximum output voltage.

[0058] In one embodiment, the reference voltage generation module includes a first resistor R1 and a second resistor R2. One end of R1 is connected to the system power supply, and the other end of R1 is grounded through R2. The resistance ratio of R1 and R2 ranges from 1:4 to 1:9.

[0059] The function of the voltage comparison module 103 is to acquire the output voltage of the signal amplification module 101 in real time, compare it with the reference voltage provided by the reference voltage generation module 102, and finally output an output signal indicating the comparison result.

[0060] There are several ways to compare two voltages and obtain the comparison result, including but not limited to the following: 1) Voltage comparator method: A voltage comparator is a core circuit element specifically used to compare two voltages. Its output is a high level or a low level, indicating the comparison result; 2) Analog circuit comparison method: For example, using analog circuits such as difference comparison, proportional comparison, and bridge comparison to achieve voltage comparison; 3) Digital processing comparison method: For example, using a combination of analog-to-digital converter and microcontroller to achieve voltage comparison, or using a digital comparator chip to achieve voltage comparison.

[0061] In one embodiment, the voltage comparison module 103 uses a comparator to perform voltage comparison, including but not limited to using a basic voltage comparator, a hysteresis comparator, and a window comparator.

[0062] In one embodiment, the voltage comparison module 103 adopts a push-pull output comparator, and the power supply of the comparator is determined based on the system power supply; the non-inverting input terminal of the comparator is connected to the voltage divider node of R1 and R2 in the reference voltage generation module 102, the inverting input terminal of the comparator is connected to the output terminal of the signal amplification module 101, and the output terminal of the comparator is connected to the protection switch module 104.

[0063] Optionally, the comparator used in the voltage comparison module 103 can be powered by a single power supply or by a dual power supply.

[0064] Understandably, push-pull output comparators can actively output high and low levels without the need for external pull-up resistors.

[0065] The protection switch module 104 functions as a low-resistance short-circuit switch, connected in parallel between the positive and negative electrodes of the electrochemical sensor. It switches on and off based on the comparison result output by the voltage comparison module 103. When the output voltage of the signal amplification module 101 is greater than or equal to the reference voltage, it indicates that the output voltage of the signal amplification module 101 is approaching its maximum output voltage (i.e., saturation voltage), and may continue to increase beyond its maximum output voltage, potentially causing operational amplifier saturation or even misalignment. At this point, the protection switch module 104 turns on, creating a low-resistance path that short-circuits the positive and negative electrodes of the electrochemical sensor. This prevents voltage accumulation between the positive and negative electrodes of the electrochemical sensor after potential operational amplifier saturation or misalignment, thus providing overload protection for the electrochemical sensor.

[0066] Switching devices with low-resistance short-circuit characteristics can be selected from a variety of options, including but not limited to the following types: MOSFET drive network, junction field-effect transistor (JFET) drive network, and insulated-gate bipolar transistor (IGBT) drive network.

[0067] In one embodiment, the protection switch module 104 includes a depletion-type PMOS transistor Q1, the drain of Q1 is connected to the positive electrode of the electrochemical sensor, the source of Q1 is connected to the negative electrode of the electrochemical sensor, and the gate of Q1 is connected to the output terminal of the voltage comparison module 103.

[0068] In one embodiment, the protection switch module 104 includes an enhancement-mode PMOS transistor Q2, the source of which is connected to the positive electrode of the electrochemical sensor, the drain of which is connected to the negative electrode of the electrochemical sensor, and the gate of which is connected to the output of the voltage comparison module 103.

[0069] It is important to note that when using a MOSFET as the core component of the protection switch module 104, a MOSFET with extremely low reverse leakage current should be selected. Reverse leakage current refers to the small current that still exists between the drain and source of the MOSFET when it is in the off state. Essentially, it is the leakage current generated by the reverse-biased drain-substrate PN junction (or source-substrate PN junction), plus additional current caused by other physical effects. If the selected MOSFET has a large reverse leakage current, current will still flow between the drain and source even when the MOSFET is in the off state. This will cause partial shunting of the output current of the electrochemical sensor, thus affecting the accuracy of the measurement results. Selecting a MOSFET with extremely low reverse leakage current ensures that almost no current flows between the drain and source when the MOSFET is in the off state, thereby avoiding interference with the output current of the electrochemical sensor.

[0070] The electrochemical sensor protection circuit provided in this embodiment amplifies the output signal of the electrochemical sensor through a signal amplification module, generates a reference voltage close to the maximum output voltage of the signal amplification module 101 through a reference voltage generation module, and compares the real-time output voltage of the signal amplification module with the reference voltage generated by the reference voltage generation module through a voltage comparison module. When the real-time output voltage of the signal amplification module is greater than or equal to the reference voltage, the positive and negative electrodes of the electrochemical sensor are short-circuited through a conduction protection switch module. This electrochemical sensor protection circuit provides real-time monitoring of the operational amplifier output voltage. When the operational amplifier output voltage approaches or has reached saturation, an overload protection mechanism is quickly triggered to short-circuit the electrochemical sensor, thereby preventing the operational amplifier from becoming unbalanced due to prolonged saturation. Furthermore, the overload protection mechanism effectively prevents voltage accumulation at the positive and negative electrodes of the electrochemical sensor, thus preventing damage to the electrochemical sensor due to overload and extending its service life.

[0071] For example, Figure 1a A structural example diagram of an electrochemical sensor protection circuit according to an embodiment of this utility model is provided. Figure 1a As shown, the protection circuit includes: a transimpedance amplifier U1, a first resistor R1, a second resistor R2, a comparator U2, and a depletion-type PMOS transistor Q1.

[0072] The inverting input of U1 is connected to the positive electrode (pin 2) of the electrochemical sensor SENSOR, and the non-inverting input of U1 is connected to the negative electrode (pin 1) of the SENSOR and the reference potential Vref. The output SIN of U1 is connected to the feedback resistor R. f Connect the inverting input of U1 to the inverting input terminal. Connect the power supply terminal of U1 to the system power supply VCC and the reference ground GND. Connect one end of R1 to VCC and the other end of R1 to GND via R2. Connect the non-inverting input of U2 to the voltage divider node of R1 and R2. Connect the inverting input of U2 to the output terminal SIN of U1. Connect the power supply terminal of U2 to the system power supply VCC and the reference ground GND. Connect the drain of Q1 to the positive electrode of the sensor (pin 2), the source of Q1 to the negative electrode of the sensor (pin 1), and the gate of Q1 to the output terminal of U2.

[0073] The resistor network composed of R1 and R2 generates a reference voltage that does not exceed the maximum output voltage of U1 through voltage division. When the output voltage of U1 is less than the reference voltage, U2 outputs a high level, Q1 is cut off, and the electrochemical sensor works normally; when the output voltage of U1 is greater than the reference voltage, U2 outputs a low level, and Q1 is turned on.

[0074] It should be noted that for the depletion-type PMOS transistor Q1, the pinch-off voltage of Q1 is denoted as V. OFFThen VCC, Vref and V OFF The following relationship exists between them: (1)

[0075] Understandably, for a depletion-type PMOS transistor, its pinch-off voltage V OFF It is a positive value. When Q1 is off, its gate-source voltage is... Should meet ,Right now When Q1 is turned on, its gate-source voltage Should meet ,Right now .

[0076] For example, Figure 1b A structural example diagram of another electrochemical sensor protection circuit according to an embodiment of this utility model is provided. Figure 1b As shown, the protection circuit includes: a transimpedance amplifier U1, a first resistor R1, a second resistor R2, a comparator U2, and an enhancement-type PMOS transistor Q2.

[0077] The inverting input of U1 is connected to the positive electrode (pin 2) of the electrochemical sensor SENSOR, and the non-inverting input of U1 is connected to the negative electrode (pin 1) of the SENSOR and the reference potential Vref. The output SIN of U1 is connected to the feedback resistor R. f Connect the inverting input of U1 to the inverting input terminal. Connect the power supply terminals of U1 to the system power supply VCC and the reference ground GND. Connect one end of R1 to VCC and the other end of R1 to GND via R2. Connect the non-inverting input of U2 to the voltage divider node of R1 and R2. Connect the inverting input of U2 to the output terminal SIN of U1. Connect the power supply terminals of U2 to the system power supply VCC and the reference ground GND. Connect the source of Q2 to the positive electrode of the sensor (pin 2), the drain of Q2 to the negative electrode of the sensor (pin 1), and the gate of Q2 to the output terminal of U2.

[0078] The resistor network composed of R1 and R2 generates a reference voltage that does not exceed the maximum output voltage of U1 through voltage division. When the output voltage of U1 is less than the reference voltage, U2 outputs a high level, Q2 is cut off, and the electrochemical sensor works normally; when the output voltage of U1 is greater than the reference voltage, U2 outputs a low level, and Q2 is turned on.

[0079] It should be noted that for the enhancement-mode PMOS transistor Q2, the threshold voltage of Q2 is denoted as V. th If the constant potential difference between the positive and negative electrodes of the sensor is ΔV, then VCC, Vref, ΔV, and V th The following relationship exists between them:

[0080] (2)

[0081] It is understandable that for an enhancement-mode PMOS transistor, its threshold voltage V th It is a negative value. When Q2 is off, its gate-source voltage is negative. Should meet ,Right now When Q2 is turned on, its gate-source voltage Should meet ,Right now .

[0082] Figure 2 This utility model provides an electrochemical sensor protection circuit that is suitable for situations where the electrochemical sensor, under overload or power failure conditions, prevents voltage accumulation between the positive and negative electrodes by short-circuiting them. This protection circuit... Figure 1 Based on the protection circuit shown, a dynamic control module is added between the output terminal of the voltage comparison module and the protection switch module. This module is used to control the protection switch module to conduct when the output voltage of the signal amplification module is greater than or equal to the reference voltage, or when the system power supply fails, so as to short-circuit the positive and negative electrodes of the electrochemical sensor.

[0083] like Figure 2 As shown, the protection circuit includes: a signal amplification module 201, a reference voltage generation module 202, a voltage comparison module 203, a dynamic control module 204, and a protection switch module 205.

[0084] Understandable, Figure 1 In the protection circuit shown, the output of the voltage comparator module is directly connected to the protection switch module, so that... Figure 1a and Figure 1b Taking the circuit shown as an example, when the system power is off, the output of comparator U2 is in a high-impedance state. Its voltage is determined by parasitic capacitance or leakage current from external circuits, and may leave an uncertain level. Therefore, Q1 may not be able to conduct reliably due to its gate being floating. Figure 1 The proposed solution cannot guarantee that the protection switch module can reliably conduct in the event of a system power failure, thus failing to guarantee power failure protection for the electrochemical sensor.

[0085] To achieve power-down protection for the electrochemical sensor, the protection switch module 205 needs to be able to conduct in the event of a system power failure, thus short-circuiting the positive and negative electrodes of the electrochemical sensor. Therefore, a system power failure can be considered a sufficient condition for the protection switch module 205 to conduct. Furthermore, the purpose of this embodiment is to achieve protection for the electrochemical sensor under both overload and system power failure conditions, building upon the aforementioned embodiments. Therefore, while adding the dynamic control module 204 to achieve power-down protection, it is also necessary to ensure that the overload protection effect is not compromised.

[0086] In one embodiment, the dynamic control module 204 includes a third resistor R3 and a fourth resistor R4. One end of R3 is connected to the system power supply, and the other end of R3 is connected to the output terminal of the voltage comparison module 203 through R4. The common node of R3 and R4 is connected to the protection switch module 205.

[0087] Optionally, R3 and R4 have the same resistance value, ranging from 1kΩ to 10kΩ.

[0088] The electrochemical sensor protection circuit provided in this embodiment amplifies the output signal of the electrochemical sensor through a signal amplification module, generates a reference voltage close to the maximum output voltage of the signal amplification module through a reference voltage generation module, and compares the real-time output voltage of the signal amplification module with the reference voltage generated by the reference voltage generation module through a voltage comparison module. When the real-time output voltage of the signal amplification module is greater than or equal to the reference voltage, or when the system power fails, the dynamic control module controls the protection switch module to conduct, thereby short-circuiting the positive and negative electrodes of the electrochemical sensor. This electrochemical sensor protection circuit provides real-time monitoring of the operational amplifier output voltage. When the operational amplifier output voltage approaches or reaches saturation, an overload protection mechanism is quickly triggered to short-circuit the electrochemical sensor, thus preventing the operational amplifier from becoming unbalanced due to prolonged saturation. Furthermore, the overload protection mechanism effectively prevents voltage accumulation at the positive and negative electrodes of the electrochemical sensor, thus preventing damage to the electrochemical sensor due to overload and extending its service life. In addition, when the system loses power, a power-down protection mechanism is triggered to short-circuit the electrochemical sensor, ensuring that no voltage accumulates at the positive and negative electrodes of the electrochemical sensor. Therefore, this embodiment of the invention can protect the electrochemical sensor under both overload and power failure conditions by short-circuiting the positive and negative electrodes.

[0089] For example, Figure 2a A structural example diagram of an electrochemical sensor protection circuit according to an embodiment of this utility model is provided. Figure 2a As shown, the protection circuit includes: a transimpedance amplifier U1, a first resistor R1, a second resistor R2, a comparator U2, a depletion-type PMOS transistor Q1, a third resistor R3, and a fourth resistor R4.

[0090] The inverting input of U1 is connected to the positive electrode (pin 2) of the electrochemical sensor SENSOR, and the non-inverting input of U1 is connected to the negative electrode (pin 1) of the SENSOR and the reference potential Vref. The output SIN of U1 is connected to the feedback resistor R. f Connect the inverting input of U1 to the inverting input terminal. Connect the power supply terminal of U1 to the system power supply VCC and the reference ground GND. Connect one end of R1 to VCC and the other end of R1 to GND via R2. Connect the non-inverting input of U2 to the voltage divider node of R1 and R2. Connect the inverting input of U2 to the output terminal SIN of U1. Connect the power supply terminal of U2 to the system power supply VCC and the reference ground GND. Connect one end of R3 to VCC and the other end of R3 to the output terminal of U2 via R4. Connect the drain of Q1 to the positive electrode of the sensor (pin 2), the source of Q1 to the negative electrode of the sensor (pin 1), and the gate of Q1 to the common node of R3 and R4.

[0091] The resistor network composed of R1 and R2 generates a reference voltage that does not exceed the maximum output voltage of U1 through voltage division. When the output voltage of U1 is less than the reference voltage, U2 outputs a high level, Q1 is cut off, and the electrochemical sensor works normally; when the output voltage of U1 is greater than the reference voltage, U2 outputs a low level, and Q1 is turned on; when the system power supply is lost, the end of R3 connected to VCC is equivalently grounded, and Q1 is turned on.

[0092] It should be noted that for the depletion-type PMOS transistor Q1, the pinch-off voltage of Q1 is denoted as V. OFF Then VCC, Vref and V OFF The following relationship exists between them:

[0093] (3)

[0094] Understandably, during normal measurement by the electrochemical sensor, comparator U2 outputs a high level, which is transmitted to the gate of Q1 through R4. Simultaneously, R3 acts as a pull-up resistor, raising the gate voltage of Q1 to the system power supply voltage VCC. Together, they ensure that the gate voltage of Q1 remains high. When the current output by the electrochemical sensor is too large, causing the output voltage of operational amplifier U1 to approach saturation, comparator U2 outputs a low level. At this time, R3 and R4 form a voltage divider, and the gate voltage of Q1 becomes... In addition, R3 also protects Q1 by preventing its gate from being floating and avoiding instability caused by external interference. When the system power fails, the end of R3 connected to VCC is effectively grounded, the output of U2 is in a high-impedance state, and R5 has no effective current path. At this time, R3 provides a low-impedance path to ground for the gate of Q1, and R3 is equivalent to a pull-down resistor, pulling the gate voltage of Q1 down to 0V.

[0095] For a depletion-type PMOS transistor, its pinch-off voltage V OFF It is a positive value. When Q1 is off, its gate-source voltage is... Should meet ,Right now When Q1 is turned on during power-off, its gate-source voltage is... Should meet ,Right now When Q1 is turned on under overload conditions, its gate-source voltage... Should meet ,Right now .

[0096] When R3 = R4 and the resistance range is 1kΩ to 10kΩ, it can balance system power consumption and response speed. At this time, equation (3) becomes:

[0097] (4)

[0098] For example, Figure 2b A structural example diagram of an electrochemical sensor protection circuit according to an embodiment of this utility model is provided. Figure 2b As shown, the protection circuit includes: a transimpedance amplifier U1, a first resistor R1, a second resistor R2, a comparator U2, an enhancement-type PMOS transistor Q2, a third resistor R3, and a fourth resistor R4.

[0099] The inverting input of U1 is connected to the positive electrode (pin 2) of the electrochemical sensor SENSOR, and the non-inverting input of U1 is connected to the negative electrode (pin 1) of the SENSOR and the reference potential Vref. The output SIN of U1 is connected to the feedback resistor R. f Connect the inverting input of U1 to the inverting input. Connect the power supply of U1 to the system power supply VCC and the reference ground GND. Connect one end of R1 to VCC and the other end to GND via R2. Connect the non-inverting input of U2 to the voltage divider node of R1 and R2. Connect the inverting input of U2 to the output SIN of U1. Connect the power supply of U2 to the system power supply VCC and the reference ground GND. Connect one end of R3 to VCC and the other end to the output of U2 via R4. Connect the source of Q2 to the positive electrode of the sensor (pin 2), the drain of Q2 to the negative electrode of the sensor (pin 1), and the gate of Q2 to the common node of R3 and R4. The resistor network consisting of R1 and R2 generates a reference voltage that does not exceed the maximum output voltage of U1 through voltage division. When the output voltage of U1 is less than the reference voltage, U2 outputs a high level, Q2 is cut off, and the electrochemical sensor works normally; when the output voltage of U1 is greater than the reference voltage, U2 outputs a low level, and Q2 is turned on; when the system power is off, the end of R3 connected to VCC is equivalently grounded, and Q2 is turned on.

[0100] It should be noted that for the enhancement-mode PMOS transistor Q2, the threshold voltage of Q2 is denoted as V. th If the constant potential difference between the positive and negative electrodes of the sensor is ΔV, then VCC, Vref, ΔV, and V th The following relationship exists between them:

[0101] (5)

[0102] It is understandable that for an enhancement-mode PMOS transistor, its threshold voltage V th It is a negative value. When Q2 is off, its gate-source voltage is negative. Should meet ,Right now When Q2 is turned on during power-off, its gate-source voltage is... Should meet ,Right now When Q1 is turned on under overload conditions, its gate-source voltage... Should meet ,Right now .

[0103] When R3 = R4 and the resistance range is 1kΩ to 10kΩ, it can balance system power consumption and response speed. At this time, equation (5) becomes:

[0104] (6)

[0105] It is worth noting that in the above embodiments of the electrochemical sensor protection circuit, the modules included are divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of each functional unit are only for easy differentiation and are not used to limit the protection scope of this utility model.

[0106] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. An electrochemical sensor protection circuit, characterized by, The application relates to an electrochemical sensor protection circuit, which comprises the following modules: a signal amplification module, which comprises an operational amplifier and is connected with a positive electrode of an electrochemical sensor and used for amplifying an output signal of the electrochemical sensor to obtain an output voltage; a reference voltage generation module, which is used for generating a reference voltage according to a power supply voltage of a system power supply and a maximum output voltage of the signal amplification module, and the reference voltage does not exceed the maximum output voltage; a voltage comparison module, which is connected with an output end of the signal amplification module and the reference voltage generation module and used for comparing the output voltage with the reference voltage in real time; and a protection switch module, which is connected in parallel between positive and negative electrodes of the electrochemical sensor, connected with an output end of the voltage comparison module and used for being turned on to short the positive and negative electrodes of the electrochemical sensor when the output voltage is greater than or equal to the reference voltage. The operational amplifier is a rail-to-rail output type operational amplifier, and a power supply of the operational amplifier is determined based on the system power supply. The reference voltage generation module comprises a first resistor R1 and a second resistor R2, one end of the R1 is connected with the system power supply, and the other end of the R1 is connected with the ground through the R2. The resistance ratio of the R1 and the R2 ranges from 1:4 to 1:

9. The voltage comparison module comprises a push-pull output type comparator, and a power supply of the comparator is determined based on the system power supply.

2. The electrochemical sensor protection circuit of claim 1, wherein, The non-inverting input end of the comparator is connected with a voltage division node of the R1 and the R2, the inverting input end of the comparator is connected with the output end of the signal amplification module, and the output end of the comparator is connected with the protection switch module.

3. The electrochemical sensor protection circuit according to claim 1 or 2, characterized in that The protection switch module comprises a depletion mode PMOS tube Q1. The drain of the Q1 is connected with the positive electrode of the electrochemical sensor, the source of the Q1 is connected with the negative electrode of the electrochemical sensor, and the gate of the Q1 is connected with the output end of the voltage comparison module.

4. The electrochemical sensor protection circuit of claim 3, wherein, The negative electrode of the electrochemical sensor is connected with a reference potential Vref.

7. The electrochemical sensor protection circuit according to claim 6, wherein 5. The electrochemical sensor protection circuit according to any one of claims 1, 2, 4, wherein, The protection switch module comprises an enhancement mode PMOS tube Q2. The source of the Q2 is connected with the positive electrode of the electrochemical sensor, the drain of the Q2 is connected with the negative electrode of the electrochemical sensor, and the gate of the Q2 is connected with the output end of the voltage comparison module.

6. The electrochemical sensor protection circuit of claim 5, wherein, The negative electrode of the electrochemical sensor is connected with a reference potential Vref. The power supply voltage of the system power supply is denoted as VCC, the pinch-off voltage of the Q1 is denoted as V OFF , and the following relationship is satisfied among VCC, Vref, and V OFF ​ 。 The output end of the voltage comparison module and the protection switch module are further provided with a dynamic control module, which is used for controlling the protection switch module to be turned on to short the positive and negative electrodes of the electrochemical sensor when the output voltage of the signal amplification module is greater than or equal to the reference voltage or when the system power supply is powered off. The dynamic control module comprises a third resistor R3 and a fourth resistor R4, one end of the R3 is connected with the system power supply, the other end of the R3 is connected with the output end of the voltage comparison module through the R4, and a common node of the R3 and the R4 is connected with the protection switch module. ​ 8. The electrochemical sensor protection circuit of claim 7, wherein, ​ The power supply voltage of the system is VCC, the threshold voltage of Q2 is V th , and the constant potential difference between the positive and negative electrodes of the sensor is ΔV. The following relationship is satisfied between VCC, Vref, ΔV, and V th ​ 。 9. The electrochemical sensor protection circuit according to any one of claims 1, 2, 4, 6-8, wherein, ​ 10. The electrochemical sensor protection circuit of claim 9, wherein, ​

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