Capacitive sensor PUF characteristic value generation method and PUF key generation method

Abstract

The present application provides a method for generating a PUF characteristic value of a capacitive sensor and a method for generating a PUF key, comprising: providing a capacitive sensor, turning on the power of the capacitive sensor, the capacitive sensor comprising a power module, a processor, a temperature adjustment module and a capacitive sensor structure; the processor is used to adjust the ambient temperature of the capacitive sensor structure by controlling the temperature adjustment module; the ambient temperature of the capacitive sensor structure is made to be a plurality of groups of test temperatures through the temperature adjustment module; the capacitance value of the capacitive sensor structure under each group of test temperatures is measured to obtain a plurality of groups of capacitance values; the plurality of groups of test temperatures are used as excitations, the capacitance values ​​under each group of test temperatures are used as responses, and a PUF characteristic value is generated, without increasing additional design and production costs, thereby reducing the PUF cost.

Description

Technical Field

[0001] The present application relates to the field of information security technology, and in particular to a method for generating a PUF characteristic value of a capacitive sensor and a method for generating a PUF key. Background Art

[0002] Physically Unclonable Function (PUF) has the characteristics of uniqueness and non-replicability, and has been successfully applied in the field of information security. It is a safe and effective encryption technology. The hardware identity is managed through the physical characteristics of the hardware PUF (Physical Unclonable Function), and the root key is generated based on this characteristic. The key generation technology based on PUF allows the key to be kept within the device, which is highly secure. In addition, the cost of using PUF hardware is low, and it is also suitable for low-cost terminal devices such as wireless sensor devices.

[0003] In the related art, PUF has been used in some large mobile terminal devices, such as using the data value after SRAM and DRAM initialization as PUF source data. However, this method is not suitable for small terminals, such as sensors. Therefore, an effective implementation method for PUF on sensors is needed. Summary of the invention

[0004] Based on this, it is necessary to provide a capacitive sensor PUF characteristic value generation method, a capacitive sensor PUF key generation method, a capacitive sensor security verification method, and a capacitive sensor security verification device that can solve the above-mentioned technical problems and effectively implement the PUF on the sensor.

[0005] In a first aspect, the present application provides a method for generating a PUF characteristic value of a capacitive sensor, comprising:

[0006] Providing a capacitive sensor, turning on the power of the capacitive sensor, the capacitive sensor comprising a power module, a processor, a temperature adjustment module and a capacitive sensor structure; the processor is used to adjust the ambient temperature of the capacitive sensor structure by controlling the temperature adjustment module;

[0007] The temperature adjustment module is used to adjust the ambient temperature of the capacitive sensor structure to a plurality of test temperatures.

[0008] Measuring and obtaining the capacitance value of the capacitive sensor structure at each set of test temperatures to obtain multiple sets of capacitance values;

[0009] The plurality of test temperatures are used as excitations, and the capacitance value at each test temperature is used as a response to generate a PUF characteristic value.

[0010] In one embodiment, the capacitance value of the capacitive sensor structure at each set of test temperatures is measured to obtain multiple sets of capacitance values, specifically:

[0011] Measure and obtain the output voltage value of the voltage output terminal of the capacitive sensor structure at each set of test temperatures to obtain multiple sets of output voltage values, wherein the output voltage value is equivalent to the capacitance value;

[0012] The generating of the PUF characteristic value specifically comprises taking the multiple groups of test temperatures as stimuli and taking the output voltage value corresponding to each group of test temperatures as a response to generate the PUF characteristic value.

[0013] In one embodiment, the capacitive sensor structure includes a central capacitor, a peripheral capacitor, and two fixed capacitors, and the central capacitor, the peripheral capacitor and the two fixed capacitors form a capacitive Wheatstone bridge.

[0014] In one embodiment, the power module includes a battery and a driving voltage adjustment module, and the method further includes:

[0015] Inputting a plurality of sets of driving voltages to the capacitive sensor structure via the driving voltage adjustment circuit;

[0016] Measuring and obtaining the capacitance value of the capacitive sensor structure under each set of driving voltages to obtain multiple sets of capacitance values;

[0017] The generating of the PUF characteristic value specifically comprises taking the multiple groups of the test temperatures and the multiple groups of driving voltages as stimuli, taking the output voltage values ​​corresponding to each group of test temperatures and the output voltage values ​​under each group of driving voltages as responses, and generating the PUF characteristic value.

[0018] In one embodiment, the output voltage value V0=V+-V-, wherein V+ is the potential of the positive electrode of the voltage output end measured when the negative electrode of the voltage output end of the capacitive sensor is grounded, and V- is the potential of the negative electrode of the voltage output end measured when the positive electrode of the voltage output end of the capacitive sensor is grounded.

[0019] In one embodiment, the obtaining of multiple sets of capacitance values ​​is specifically as follows:

[0020] Measure the potential V+ of the positive electrode of the output voltage end of the capacitive sensor structure when the negative electrode of the output voltage end is grounded under multiple sets of driving voltages at each test temperature, and measure the potential V- of the negative electrode of the output voltage end when the positive electrode of the output voltage end of the capacitive sensor is grounded, to obtain multiple sets of (V+, V-) of multiple sets of driving voltages at each test temperature, wherein the (V+, V-) set under each set of driving voltages is equivalent to the capacitance value under the corresponding driving voltage at the corresponding test temperature;

[0021] Multiple groups of (V+, V-) at multiple groups of driving voltages at multiple groups of test temperatures are measured.

[0022] In one of the embodiments, the capacitive sensor is a MEMS sensor or an NMES sensor; the capacitive sensor is a capacitive pressure sensor, a capacitive force sensor, a capacitive displacement sensor, a capacitive mass sensor, a capacitive strain sensor, a capacitive flow sensor, a capacitive torque sensor, a capacitive vibration sensor, a capacitive liquid level sensor, a capacitive gyroscope, a capacitive gas sensor, a capacitive magnetic sensor, a capacitive biosensor, a capacitive humidity sensor, a capacitive temperature sensor, a capacitive chemical sensor, a capacitive acceleration sensor, or a capacitive inertial sensor.

[0023] The above-mentioned method for generating PUF characteristic values ​​of capacitive sensors uses multiple groups of test temperatures as excitations and the capacitance values ​​under each group of test temperatures as responses to generate PUF characteristic values. Based on the unique and stable characteristics of the capacitance values ​​under different test temperatures, the PUF characteristic values ​​of the sensor are generated in this way, and no additional design and production costs are required, thereby reducing the PUF cost.

[0024] In a second aspect, the present application provides a capacitive sensor PUF key generation method, comprising:

[0025] Combining the PUF characteristic values ​​obtained by the PUF characteristic value generation method described in the first aspect to obtain a plurality of CRP stimulus-response pairs;

[0026] Performing analog-to-digital conversion on the response in the CRP stimulus-response pair to obtain bit data;

[0027] The bit data is processed using a hash algorithm and combined with the stimulus data to generate a PUF key.

[0028] In one of the embodiments, the method further includes storing the PUF key in a security verification device of the capacitive sensor.

[0029] The above-mentioned capacitive sensor PUF key generation method can enhance the security and reliability of the PUF key by performing analog-to-digital conversion and hash algorithm processing on the CRP stimulus-response pair.

[0030] In a third aspect, the present application provides a security verification method for a capacitive sensor, comprising:

[0031] A capacitive sensor to be tested is provided, a security verification device is connected to the capacitive sensor to be tested, and a power supply of the capacitive sensor is turned on, wherein the security verification device stores a PUF key of the capacitive sensor to be tested generated by the PUF key generation method in the second aspect;

[0032] Under multiple test temperatures, the security verification device generates a first random number and sends it to the capacitive sensor to be tested, and the capacitive sensor to be tested takes the first random number as a challenge and generates a first response;

[0033] The capacitive sensor to be tested encrypts the first random number to obtain a second response, and sends the second response to the security verification device, where the encryption key of the first random number is the first response;

[0034] Decrypting the second response using the PUF key stored in the security verification device as a decryption key to obtain a second random number;

[0035] The second random number is compared with the first random number, and if the two are the same, it is determined that the capacitive sensor to be tested is a safety device.

[0036] In the above-mentioned security verification method of the capacitive sensor, by using the PUF key and the challenge-response mechanism, the security verification of the capacitive sensor is achieved, the authenticity of the sensor and the security of the data are ensured, thereby enhancing the security and anti-attack capabilities.

[0037] In a fourth aspect, the present application provides a safety verification device for a capacitive sensor, wherein the safety verification device can use the safety verification method described in the third aspect to perform safety verification on the capacitive sensor, and the safety verification device includes:

[0038] A memory, used to store PUF keys of multiple capacitive sensors generated by the method according to the second aspect;

[0039] A random number generation module, used to generate a first random number;

[0040] A decryption module, configured to decrypt a second response returned by the capacitive sensor using the PUF key to obtain a second random number;

[0041] A comparison module, used for comparing the second random number with the first random number to obtain a comparison result;

[0042] A display module is used to display the comparison result and / or display the first random number and the second random number.

[0043] In the above-mentioned security verification device of the capacitive sensor, by integrating the memory, random number generation module, decryption module, comparison module and display module, efficient and accurate identity authentication and response checking of the capacitive sensor are realized, thereby enhancing the security and reliability of the sensor data, ensuring the safety performance of the sensor in various applications, and effectively preventing unauthorized access and data tampering.

[0044] In a fifth aspect, the present application provides a capacitive sensor, which can be applied to the PUF characteristic value generation method described in the first aspect, and the capacitive sensor includes: a power module, a processor, a storage module, an interface module, a temperature adjustment module, and a capacitive sensor structure; the power module is used to provide power to the processor, the storage module, the interface module, the temperature adjustment module, and the capacitive sensor structure, and the temperature adjustment module includes a temperature detection module and a heating resistor arranged in the capacitive sensor structure area; the processor is electrically connected to the capacitive sensor structure, and is used to calculate the capacitance value of the capacitive sensor structure, and is used to control the working state of the power module, and the processor is also used to respond to a first test signal of an external test device, and adjust the ambient temperature of the capacitive sensor structure by controlling the temperature of the heating resistor;

[0045] Wherein, when the capacitive sensor is in a testing state, the battery supplies power to the heating resistor, and when the capacitive sensor is in a working state, the battery stops supplying power to the heating resistor.

[0046] In one embodiment, a battery, a first switch module and a voltage adjustment module, wherein the first switch module controls the voltage adjustment module to output a corresponding driving voltage in response to a second test signal sent by the processor.

[0047] In one embodiment, the voltage adjustment module includes k voltage output nodes, and resistors R1, R2...Rk connected in series in sequence, k is a positive integer, and a voltage output node is arranged between two adjacent resistors. The first switch module selects to connect the corresponding voltage output node in response to the second test signal sent by the processor to control the voltage adjustment module to output the corresponding driving voltage.

[0048] In one embodiment, the power supply module also includes a second switch module and a third switch module, the first end of the second switch module is connected to the positive electrode V+ of the output voltage of the capacitive sensor structure, and the second end is grounded; the first end of the third switch module is connected to the negative electrode V- of the output voltage of the capacitive sensor structure, and the second end is grounded; the second switch module is closed in response to the output voltage test signal of V-, and is opened in response to the output voltage test signal of V+; the third switch module is closed in response to the output voltage test signal of V+, and is opened in response to the output voltage test signal of V-.

[0049] In the above-mentioned capacitive sensor, the processor, storage module, interface module, and capacitive sensor structure are powered by the power module, and the processor is used to switch between the test state and the working state. In the working state, the processor controls the battery to directly power the capacitive sensor structure so that the capacitive sensor works normally. In the test state, the processor controls the battery to power the heating resistor, and the processor also responds to the first test signal of the external testing equipment, and adjusts the ambient temperature of the capacitive sensor structure by controlling the temperature of the heating resistor. The processor measures the capacitance value of the capacitive sensor structure at each set of test temperatures to obtain multiple sets of capacitance values, and uses the multiple sets of test temperatures as excitation, and uses the capacitance value at each set of test temperatures as a response to generate a PUF characteristic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 A schematic diagram of a capacitive sensor structure in one embodiment of the present application;

[0052] Figure 2 This is a schematic diagram of the structure of a power module in one embodiment of the present application;

[0053] Figure 3 A circuit diagram of a capacitive sensor structure capacitor in one embodiment of the present application;

[0054] Figure 4 A circuit diagram of a capacitor of a capacitive sensor structure in another embodiment of the present application;

[0055] Figure 5 A schematic diagram of a flow chart of a method for generating a PUF characteristic value in one embodiment of the present application;

[0056] Figure 6 A graph showing the relationship between ambient temperature and capacitance value in one embodiment of the present application;

[0057] Figure 7 A schematic flow chart of a method for generating a PUF characteristic value in another embodiment of the present application;

[0058] Figure 8 A schematic diagram of a PUF key generation method in one embodiment of the present application;

[0059] Fig. 9 A schematic diagram of a flow chart of a safety verification method for a capacitive sensor in one embodiment of the present application;

[0060] Fig.10 It is a schematic diagram of the structure of a safety verification device for a capacitive sensor in one embodiment of the present application. DETAILED DESCRIPTION

[0061] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0062] It is understandable that Physical Unclonable Functions (PUF) is an important type of hardware security technology. It uses the inherent properties of silicon-based semiconductors to randomly extract unclonable physical features, similar to biological fingerprints, which are unique identifiers for each chip. It uses the inevitable small differences in semiconductor devices during the manufacturing process (such as transistor threshold voltage, interconnect length, capacitance, etc.) to generate unique and unpredictable outputs. These differences make the response of each device unique and cannot be completely replicated even using the same manufacturing process. Therefore, PUF can be used as a "fingerprint" of the device for security applications such as identity authentication, key generation, and data encryption.

[0063] In the related art, PUFs based on other hardware features include static RAM static random access memory (SRAM), ring oscillator (RO), arbitration PUFs (arbiterPUFs), and dynamic random access memory (coating PUFs and dynamic RAM dynamic random access memory, DRAM). However, the limitation of sensor hardware resources makes it impossible to effectively use PUFs based on SRAM and DRAM. Secondly, RO PUF technology that increases additional design and production costs is not suitable. Therefore, in order to solve the technical problem of the lack of effective implementation methods for PUF on sensors in the related art, a method for generating PUF characteristic values ​​for capacitive sensors is proposed, which can solve the effective implementation of PUF applications on sensors while realizing the application of PUF key technology on capacitive sensors at a low cost.

[0064] In order to solve the above technical problems, the technical solution of the present application redesigns the existing capacitive sensor. In an exemplary embodiment, Figure 1 As shown, a capacitive sensor applicable to the PUF characteristic value generation method described in the first aspect is provided, and the capacitive sensor includes: a power module 10, a processor 20, a storage module 30, an interface module 40, a temperature adjustment module 50, and a capacitive sensor structure 60. The power module 10 is used to provide power to the processor 20, the storage module 30, the interface module 40, the temperature adjustment module 50, and the capacitive sensor structure 60, and the temperature adjustment module 50 includes a temperature detection module and a heating resistor arranged in the region of the capacitive sensor structure 60; the processor 20 is electrically connected to the capacitive sensor structure 60, and is used to calculate the capacitance value of the capacitive sensor structure 60, and is used to control the working state of the power module 10, and the processor 20 is also used to respond to a first test signal of an external test device, by controlling the temperature of the heating resistor, to adjust the ambient temperature of the capacitive sensor structure; wherein, when the capacitive sensor is in the test state, the battery supplies power to the heating resistor, and when the capacitive sensor is in the working state, the battery stops supplying power to the heating resistor.

[0065] It can be understood that changes in the ambient temperature of the capacitive sensor structure 60 will cause changes in the capacitance value to which it responds. In this example embodiment, a heating resistor is provided in the capacitive sensor, and different current values ​​are output to the heating resistor through the temperature adjustment module 50, causing its temperature to change, thereby causing the capacitance value of the capacitive sensor structure 60 to change.

[0066] The processor 20 measures the capacitance value of the capacitive sensor structure 60 at each set of test temperatures to obtain multiple sets of capacitance values, uses the multiple sets of test temperatures as excitations, and uses the capacitance values ​​at each set of test temperatures as responses to generate corresponding PUF characteristic values.

[0067] In some other embodiments, the capacitive sensor structure 60 may be placed in a temperature-adjustable device to change the temperature of the environment in which the capacitive sensor structure is located. In comparison, by changing the temperature of the environment in which the capacitive sensor structure is located through a heating resistor, the influence of temperature on other circuits of the capacitive sensor during the test process can be avoided, thereby affecting the test results.

[0068] It should be noted that the present application is not limited to the above-mentioned methods of changing the ambient temperature, and other methods in the technical field are not described in detail.

[0069] In addition to the influence of temperature on the capacitance value of the capacitive sensor structure 60 , the voltage applied to the capacitive sensor structure 60 also affects its capacitance value.

[0070] In another example embodiment, Figure 2 As shown, the power module 10 includes: a battery U1, a first switch module S1 and a voltage adjustment module 110. The first switch module S1 controls the voltage adjustment module 110 to output a corresponding driving voltage in response to a second test signal sent by the processor 20.

[0071] In this example embodiment, a heating resistor and / or a voltage adjustment module may be used to change the response of the capacitive sensor structure 60 to produce more different capacitance values.

[0072] Specifically, the voltage adjustment module 110 includes k voltage output nodes, and resistors R1, R2...Rk connected in series in sequence, where k is a positive integer, and a voltage output node is arranged between two adjacent resistors. The first switch module S1 responds to the second test signal sent by the processor 20, and selects to connect the corresponding voltage output node to control the voltage adjustment module 110 to output the corresponding driving voltage.

[0073] When it is necessary to apply different driving voltages to the capacitive sensor structure 60, the voltage division principle can be used to connect different numbers of resistors according to different needs, so that the voltages on different numbers of resistors are applied to the capacitive sensor structure 60, thereby meeting the need to apply different voltages to the capacitive sensor structure 60.

[0074] In other embodiments of the present application, the voltage adjustment module is a sliding rheostat. Based on the voltage division principle, the resistance value can be changed by the position of the sliding contact of the sliding rheostat on the resistance wire to meet the need of connecting different resistance values ​​in the circuit, so as to apply voltages at different resistance values ​​to the capacitive sensor structure 60, thereby meeting the need of applying different voltages to the capacitive sensor structure 60, and then obtaining the excitation-response pair required by the PUF technology.

[0075] In other embodiments of the present application, the power module 10 further includes an inverter disposed between the voltage adjustment module and the capacitive sensor structure 60, for converting the direct current output by the voltage adjustment module into alternating current.

[0076] It should be noted that the inverter can convert direct current into alternating current, that is, convert the direct current from the battery, solar panel or other direct current power source into standard alternating current, so that the electronic devices that require alternating current can work normally, that is, the capacitive sensor provided in this application. The inverter can not only realize the conversion of the form of electric energy, but also control the output voltage and frequency to ensure the quality and stability of the output electric energy to meet the needs of different loads. In addition, the inverter also has a protection function to prevent faults such as overload, short circuit and voltage fluctuation, ensuring the safe and reliable operation of the system.

[0077] In other embodiments of the present application, the capacitive sensor structure 60 is a parallel plate capacitor structure, a variable area capacitor structure, a comb-shaped capacitor structure, or a differential capacitor structure. Parallel plate capacitors can be used in static environments that require high-precision output and are also under high voltage conditions; variable area capacitors are suitable for tuning circuits or environments that require dynamic displacement measurement; comb-shaped capacitors are suitable for environments that require high sensitivity and have nano-level measurement and integrated application requirements; differential capacitors are suitable for environments that have high-precision measurement, noise suppression requirements, and a wide dynamic range. Capacitive sensor structures 60 that are more suitable for different environments can be selected according to the requirements of different environments.

[0078] In other embodiments of the present application, the support structure of the capacitive sensor structure 60 is a cantilever beam structure, a double-ended fixed beam structure, a diaphragm structure, a spring structure, or a dielectric material.

[0079] It should be noted that one end of the cantilever beam structure is fixed and the other end is free. It is usually used for movable electrodes in micro-electromechanical systems (MEMS) and is suitable for occasions requiring sensitive displacement measurement, such as acceleration sensors and pressure sensors. Its advantages are simple structure and easy manufacturing. The double-ended fixed beam structure is characterized by fixed ends of the beam and the middle part can be deformed. It is often used in micro-resonators and micro-switches. Its advantages are good stability and high frequency response, and it can be suitable for high-frequency applications. The diaphragm structure is characterized by being made of thin elastic materials and can deform in-plane or out-of-plane. It is widely used in pressure sensors and microphones. Its advantages are high sensitivity, fast response speed, and ability to withstand large pressure changes. The spring structure is characterized by being able to provide support for the movable part through the spring, such as structures such as coil springs or leaf springs, which are used in environments where mechanical movement and capacitance changes need to be synchronized, such as position sensors or force sensors. Its advantage is that it can provide stable mechanical support while allowing relative movement between electrodes. The advantage of dielectric materials is that different dielectric materials have different dielectric constants and temperature stability, and suitable materials can be selected according to needs.

[0080] In other embodiments of the present application, when the support structure of the capacitive sensor structure 60 is a diaphragm structure or a dielectric material, in an exemplary embodiment, as Figure 3 As shown, the capacitive sensor structure includes a central capacitor, a peripheral capacitor, and two fixed capacitors, wherein the central capacitor, the peripheral capacitor and the two fixed capacitors form a capacitive Wheatstone bridge. Figure 6 As shown, it is a structural schematic diagram of a capacitive sensor structure in an exemplary embodiment, including a central capacitor C1, a peripheral capacitor C2 and two fixed capacitors C3 and C4. It can be understood that the capacitive Wheatstone bridge is a bridge based on the principle of capacitance differential measurement, which is commonly used to measure the capacitance value of a capacitor and other circuit parameters. Its principle is based on the balance condition of the Wheatstone bridge, that is, the product of the resistance and capacitance in the four branches of the bridge is equal. By adjusting the capacitance value in the bridge, the bridge can be balanced to achieve the measurement of the capacitance to be measured. The differential capacitor structure is to improve sensitivity and linearity. Many capacitive accelerometers use a differential capacitor structure, that is, two or more capacitor plates are used to measure relative displacement. This structure can effectively eliminate the influence of common mode noise and temperature drift. In particular, the output voltage of the capacitive Wheatstone bridge is the bridge output voltage Vout.

[0081] In other embodiments of the present application, Figure 4 As shown, the power module 10 further includes a second switch module S2 and a third switch module S3, wherein the first end of the second switch module S2 is connected to the positive electrode V+ of the output voltage of the capacitive sensor structure 60, and the second end is grounded; the first end of the third switch module S3 is connected to the negative electrode V- of the output voltage of the capacitive sensor structure 60, and the second end is grounded; the second switch module S2 is closed in response to the output voltage test signal of V-, and is opened in response to the output voltage test signal of V+; the third switch module S3 is closed in response to the output voltage test signal of V+, and is opened in response to the output voltage test signal of V-. In particular, the output voltage of the capacitive Wheatstone bridge is the bridge output voltage Vout; the driving voltage is recorded as V1.

[0082] It should be noted that the second switch module S2 can be closed or closed in response to the output voltage test signal of V- or V+, and the third switch module S3 can be closed or closed in response to the output voltage test signal of V- or V+, so as to accurately measure the voltage applied to the capacitive sensor structure 60 at a certain moment. Compared with directly measuring the voltage output to the capacitive sensor structure 60, this solution can effectively eliminate the system errors caused by factors such as power supply voltage fluctuations and resistance temperature coefficient, improve the measurement accuracy, and can effectively reduce the influence of external electromagnetic interference on the measurement results, so as to improve the accuracy of the measurement of the voltage applied to the capacitive sensor structure 60 at a certain moment.

[0083] In other embodiments of the present application, the capacitive sensor is a MEMS sensor or an NMES sensor; the capacitive sensor is a capacitive pressure sensor, a capacitive force sensor, a capacitive displacement sensor, a capacitive mass sensor, a capacitive strain sensor, a capacitive flow sensor, a capacitive torque sensor, a capacitive vibration sensor, a capacitive liquid level sensor, a capacitive gyroscope, a capacitive gas sensor, a capacitive magnetic sensor, a capacitive biosensor, a capacitive humidity sensor, a capacitive temperature sensor, a capacitive chemical sensor, a capacitive acceleration sensor, or a capacitive inertial sensor.

[0084] In particular, the capacitive sensor includes but is not limited to a MEMS piezoresistive sensor or a NEMS piezoresistive sensor. This embodiment only takes the structure of a MEMS piezoresistive sensor as an example for description.

[0085] In particular, when the piezoresistive sensor is a wireless sensor, the piezoresistive sensor further includes an antenna module and a communication module, and the antenna module and the communication module are used to establish wireless communication with an external test terminal or test equipment.

[0086] It should be noted that the capacitive sensor can be integrated into various micro- and nano-scale devices by virtue of the small size and light weight of MEMS sensors and NMES sensors. Moreover, MEMS sensors and NMES sensors have extremely low power consumption and a long service life. In addition, MEMS sensors and NMES sensors also have the characteristics of high sensitivity and short response time, and can detect tiny changes in real time. They can be applied to environments that require precise measurement and have high-speed dynamic processes, and have higher environmental adaptability.

[0087] In an exemplary embodiment, based on the above-mentioned capacitive sensor, such as Figure 5 As shown, a method for generating a PUF characteristic value of a capacitive sensor is provided, which may include the following steps 102 to 108, wherein:

[0088] Step 102, providing a capacitive sensor and turning on the power of the capacitive sensor, wherein the capacitive sensor includes a power module, a processor, a temperature adjustment module and a capacitive sensor structure; the processor is used to adjust the ambient temperature of the capacitive sensor structure by controlling the temperature adjustment module.

[0089] Step 104: The temperature adjustment module is used to adjust the ambient temperature of the capacitive sensor structure to a plurality of test temperatures.

[0090] Step 106 , measuring the capacitance value of the capacitive sensor structure at each set of test temperatures to obtain multiple sets of capacitance values.

[0091] In order to determine the PUF characteristic value, different capacitance values ​​can be generated by adjusting the ambient temperature. From the perspective of authentication scenarios, CRP can be a set of data from a series of central capacitance and peripheral capacitance values ​​generated at different ambient temperatures. The combined size of the data can range from the smallest 1 data to the entire data set. Figure 6 , which is a graph showing the relationship between ambient temperature and capacitance in an exemplary embodiment, wherein the horizontal axis is ambient temperature and the vertical axis is capacitance. Curve 1 represents the relationship between the central capacitance and the driving voltage, and curve 2 represents the relationship between the peripheral capacitance and the driving voltage.

[0092] Step 108 , using the multiple groups of test temperatures as excitations and the capacitance values ​​at each group of test temperatures as responses to generate PUF characteristic values.

[0093] The above-mentioned method for generating PUF characteristic values ​​of capacitive sensors, through the temperature adjustment module, makes the ambient temperature of the capacitive sensor structure respectively a plurality of test temperatures; the capacitance value of the capacitive sensor structure under each set of ambient temperatures is measured to obtain a plurality of capacitance values, and the plurality of test temperatures are used as excitations, and the capacitance values ​​under each set of test temperatures are used as responses to generate PUF characteristic values, and the capacitance values ​​of the capacitive sensor under different test temperatures are different, and the capacitance values ​​under different test temperatures have unique and stable characteristics, and the test temperature in the capacitive sensor is used as excitation, and the capacitance value under the test temperature is used as a response to generate the PUF characteristic value of the sensor, and no additional design and production costs are required, thus reducing the PUF cost, and further, the response parameters are increased, and the uniqueness of the PUF and the difference of the PUF characteristic values ​​of different sensors are improved. It can also be used for capacitive sensors, as well as anti-counterfeiting, security authentication and device identification including the capacitive sensor to ensure network security.

[0094] In an exemplary embodiment, the capacitance value of the capacitive sensor structure at each set of test temperatures is measured to obtain multiple sets of capacitance values, specifically:

[0095] The output voltage value of the voltage output terminal of the capacitive sensor structure under each set of test temperatures is measured to obtain multiple sets of output voltage values, and the output voltage values ​​are equivalent to the capacitance values.

[0096] Zero external pressure refers to normal atmospheric pressure without any additional external pressure.

[0097] The plurality of test temperatures are used as excitations, and the output voltage values ​​corresponding to the respective test temperatures are used as responses to generate PUF characteristic values.

[0098] In an exemplary embodiment, Figure 7 As shown, the power module includes a battery and a driving voltage adjustment module, and the method further includes:

[0099] Step 202, inputting a plurality of sets of driving voltages to the capacitive sensor structure via the driving voltage adjustment circuit;

[0100] Step 204, measuring the capacitance value of the capacitive sensor structure under each set of driving voltages to obtain multiple sets of capacitance values;

[0101] Step 206 , using the multiple groups of test temperatures and the multiple groups of driving voltages as stimuli, and using the output voltage values ​​corresponding to each group of test temperatures and the output voltage values ​​under each group of driving voltages as responses, to generate PUF characteristic values.

[0102] There may be multiple PUF characteristic values, and one PUF characteristic value may include a test temperature, a driving voltage, and multiple capacitance values ​​under the driving voltage, as shown in Table 1.

[0103] Table 1

[0104]

[0105] In another exemplary embodiment, the output voltage value V0=V+-V-, wherein V+ is the potential of the positive electrode of the voltage output terminal of the capacitive sensor measured when the negative electrode of the voltage output terminal is grounded, and V- is the potential of the negative electrode of the voltage output terminal of the capacitive sensor measured when the positive electrode of the voltage output terminal is grounded.

[0106] Based on this, the present application also provides a method for generating a PUF characteristic value, including steps 302 to 306, wherein:

[0107] Step 302, measuring the potential V+ of the positive electrode of the output voltage end of the capacitive sensor structure when the negative electrode of the output voltage end is grounded under multiple sets of driving voltages at each test temperature, and measuring the potential V- of the negative electrode of the output voltage end when the positive electrode of the output voltage end of the capacitive sensor is grounded, to obtain multiple groups (V+, V-) of multiple sets of driving voltages at each test temperature, wherein the (V+, V-) group under each set of driving voltages is equivalent to the capacitance value under the corresponding driving voltage at the corresponding test temperature.

[0108] Step 304 , measuring and obtaining multiple groups of (V+, V−) groups at multiple groups of driving voltages at multiple groups of test temperatures.

[0109] Step 306 , using multiple groups of test temperatures as stimuli and corresponding (V+, V−) groups under each group of test temperatures as responses to generate PUF characteristic values.

[0110] In the above embodiment, multiple groups of test temperatures are used as excitations, and the capacitive sensor uses the corresponding (V+, V-) groups at different test temperatures as responses to generate PUF characteristic values. The potential of the positive electrode of the output voltage terminal and the potential of the negative electrode of the output voltage terminal at different test temperatures have unique and stable characteristics, so that the PUF characteristic value of the sensor is generated without increasing additional design and production costs, thereby reducing the PUF cost.

[0111] Based on the PUF characteristic value generation method in any of the above embodiments, a PUF key generation method is provided, such as Figure 8 As shown, it includes steps 402 to 406, wherein:

[0112] Step 402: Combine the obtained PUF characteristic values ​​to obtain a plurality of CRP stimulus-response pairs.

[0113] The PUF characteristic value obtained can be determined based on the PUF characteristic value generation method recorded in any of the above embodiments, which will not be described in detail here. CRP: Challenge and Response Pair, refers to the pairing of independent challenges and responses during the device authentication process. The combination method can be implemented by the existing combination method, which will not be described in detail here.

[0114] Exemplarily, the capacitive sensor obtains a PUF characteristic value determined based on the PUF characteristic value generation method recorded in any of the above embodiments, and combines the obtained PUF characteristic values ​​to obtain multiple CRP stimulus-response pairs.

[0115] Step 404: Perform analog-to-digital conversion on the response in the CRP stimulus-response pair to obtain bit data.

[0116] Step 406: Process the bit data using a hash algorithm and combine it with the stimulus data to generate a PUF key.

[0117] Among them, the hash algorithm can convert an input of any length into an output of a fixed length. This output is called a hash value or hash value, which is used for authentication. This method can effectively prevent the key from being predicted or copied, and improve security. The hash algorithm can be, but is not limited to, any one of the SM3, MD5, and RIPEMD algorithms.

[0118] In the above PUF key generation method, the security and reliability of the PUF key can be enhanced by performing analog-to-digital conversion and hash algorithm processing on the CRP stimulus-response pair.

[0119] Furthermore, the PUF key may also be stored in a security verification device of the capacitive sensor to perform security verification on the capacitive sensor.

[0120] Furthermore, the PUF key may be stored in the server to perform security verification on the capacitive sensor.

[0121] It is worth noting that PUF can be used to verify the identity of the device, ensuring that only legitimate devices can access the system or network, and can be used to verify the integrity of the firmware, ensuring that the device loads authenticated firmware when it starts up, preventing malware or firmware tampering, and can also verify the authenticity of the product, etc. In order to ensure the performance and reliability of the capacitive sensor, it is necessary to perform security verification on the capacitive sensor. In an exemplary embodiment, a security verification method for a capacitive sensor is provided, such as Fig. 9 As shown, it includes steps 502 to 510, wherein:

[0122] Step 502: provide a capacitive sensor to be tested, connect a security verification device to the capacitive sensor to be tested, and turn on the power of the capacitive sensor. The security verification device stores a PUF key of the capacitive sensor to be tested generated by the PUF key generation method in the second aspect.

[0123] The PUF key can be generated in the manner described in the above embodiments but is not limited thereto, which will not be described in detail here. The type of the capacitive sensor to be tested can be the capacitive sensor described in any of the above embodiments, and the structure of the capacitive sensor to be tested will not be described in detail here.

[0124] Step 504: Under multiple test temperatures, the security verification device generates a first random number and sends it to the capacitive sensor to be tested. The capacitive sensor to be tested takes the first random number as a challenge and generates a first response.

[0125] The first random number may be generated by a pseudo-random number generator or a time-based random number generator, which is not specifically limited here.

[0126] Step 506: the capacitive sensor to be tested encrypts the first random number to obtain a second response, and sends the second response to the security verification device, where the encryption key of the first random number is the first response.

[0127] Step 508: Use the PUF key stored in the security verification device as a decryption key to decrypt the second response to obtain a second random number.

[0128] Step 510: compare the second random number with the first random number, and if the two are the same, determine that the capacitive sensor to be tested is a security device.

[0129] In the above-mentioned security verification method of the capacitive sensor, by using the PUF key and the challenge-response mechanism, the security verification of the capacitive sensor is achieved, the authenticity of the sensor and the security of the data are ensured, thereby enhancing the security and anti-attack capabilities.

[0130] Furthermore, according to actual application requirements, the security verification of capacitive sensors can be: for the registration of a device (e.g., a capacitive sensor), when used for the first time, the device sends a challenge-response pair (CRP) generated by its PUF to the authentication server. The server compares these CRPs with the pre-stored CRPs to verify the authenticity of the device. If the match is successful, the device will be registered as a legitimate device and assigned a unique identifier.

[0131] Then, for actual application needs, there may be a situation where random numbers are used in combination with challenges in CRP. In this case, the verification server will generate a random number and use it as part of the challenge, combined with the random number and the incentive in CRP. Based on the combination of the random number and the incentive in CRP, the challenge is determined, a response is generated, and the response is returned to the server. The server regenerates the expected response with the same random number and compares it with the received response. In this method, random numbers are introduced on the basis of CRP to ensure that the challenge used for each verification is unique and prevent replay attacks. In addition, random numbers increase the security of the system, making it difficult for attackers to predict or guess the content of the challenge.

[0132] Furthermore, in an exemplary embodiment, a safety verification device for a capacitive sensor is provided, such as Fig.10 As shown, a schematic diagram of the structure of a safety verification device for a capacitive sensor is provided. The safety verification device can use the above-mentioned safety verification method to perform safety verification on the capacitive sensor. The safety verification device includes:

[0133] The memory 1002 is used to store the PUF keys of the multiple capacitive sensors generated in any of the above embodiments.

[0134] The random number generation module 1004 is used to generate a first random number; wherein the first random number is used as an excitation of the capacitive sensor to generate a first response.

[0135] The decryption module 1006 is used to decrypt the second response returned by the capacitive sensor using the PUF key to obtain a second random number; the second response is obtained after the capacitive sensor to be tested encrypts the first random number.

[0136] The comparison module 1008 is used to compare the second random number with the first random number to obtain a comparison result.

[0137] The display module 1010 is used to display the comparison result and / or display the first random number and the second random number.

[0138] Optionally, in an exemplary embodiment, when the capacitive sensor to be tested is a wireless MEMS sensor, the security verification device of the capacitive sensor also includes an antenna module and a communication module. The antenna module enables the device to transmit data wirelessly without physical connection, and the communication module enables it to exchange data with an external system, including sending data collected by the sensor and receiving external instructions.

[0139] The above-mentioned security verification device uses the first random number as the stimulus of the capacitive sensor to be tested to generate a first response, and uses the PUF key to decrypt the second response obtained after encryption based on the first random number to obtain a second random number, and performs security verification on the capacitive sensor to be tested by comparing the first random number with the second random number. This method uses the PUF key and the challenge-response mechanism to achieve security verification of the capacitive sensor, ensure the authenticity of the sensor and the security of the data, thereby enhancing security and anti-attack capabilities.

[0140] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0141] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0142] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0143] In one embodiment, a computer device is further provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above method embodiments when executing the computer program.

[0144] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0145] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it may be directly on the other component or there may also be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the specification of this application are for illustrative purposes only and do not represent the only implementation method.

[0146] In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or equipment.

[0147] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first feature is directly in contact with the second feature, or the first feature and the second feature are indirectly in contact through an intermediate medium. Moreover, a first feature being “above”, “above” or “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below” or “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0148] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more related listed items.

[0149] The technical features of the above embodiments can be combined without changing the basic principles of the present application. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0150] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of patent protection of the present application shall be subject to the attached claims.

Claims

1. A method for generating a PUF characteristic value of a capacitive sensor, characterized in that: include: Providing a capacitive sensor and turning on the power of the capacitive sensor, wherein the capacitive sensor includes a power module, a processor, a temperature adjustment module and a capacitive sensor structure; The processor is used to adjust the ambient temperature of the capacitive sensor structure by controlling the temperature adjustment module; The temperature adjustment module is used to adjust the ambient temperature of the capacitive sensor structure to a plurality of test temperatures. Measuring and obtaining the capacitance value of the capacitive sensor structure at each set of test temperatures to obtain multiple sets of capacitance values; Using the multiple groups of test temperatures as excitations and the capacitance values ​​at each group of test temperatures as responses, generating PUF characteristic values; The capacitance value of the capacitive sensor structure at each set of test temperatures is measured to obtain multiple sets of capacitance values, specifically: Measure and obtain the output voltage value of the voltage output terminal of the capacitive sensor structure at each set of test temperatures to obtain multiple sets of output voltage values, wherein the output voltage value is equivalent to the capacitance value; The generating of the PUF characteristic value is specifically as follows: taking the multiple groups of the test temperatures as excitations and taking the corresponding output voltage values ​​under each group of test temperatures as responses to generate the PUF characteristic value; wherein the output voltage value V0=V+-V-, wherein V+ is the potential of the positive electrode of the voltage output end measured when the negative electrode of the voltage output end of the capacitive sensor is grounded, and V- is the potential of the negative electrode of the voltage output end measured when the positive electrode of the voltage output end of the capacitive sensor is grounded.

2. The PUF feature value generation method according to claim 1, characterized in that: The capacitive sensor structure includes a central capacitor, a peripheral capacitor, and two fixed capacitors, and the central capacitor, the peripheral capacitor and the two fixed capacitors form a capacitive Wheatstone bridge.

3. The PUF feature value generation method according to claim 2, characterized in that: The power module includes a battery and a driving voltage adjustment module, and the method further includes: Inputting a plurality of sets of driving voltages to the capacitive sensor structure via the driving voltage adjustment circuit; Measuring and obtaining the capacitance value of the capacitive sensor structure under each set of driving voltages to obtain multiple sets of capacitance values; The generating of the PUF characteristic value specifically comprises taking the multiple groups of the test temperatures and the multiple groups of driving voltages as stimuli, taking the output voltage values ​​corresponding to each group of test temperatures and the output voltage values ​​under each group of driving voltages as responses, and generating the PUF characteristic value.

4. The PUF feature value generation method according to claim 3, characterized in that: The multiple sets of capacitance values ​​are obtained, specifically: Measure the potential V+ of the positive electrode of the output voltage end of the capacitive sensor structure when the negative electrode of the output voltage end is grounded under multiple sets of driving voltages at each test temperature, and measure the potential V- of the negative electrode of the output voltage end when the positive electrode of the output voltage end of the capacitive sensor is grounded, to obtain multiple sets of (V+, V-) of multiple sets of driving voltages at each test temperature, wherein the (V+, V-) set under each set of driving voltages is equivalent to the capacitance value under the corresponding driving voltage at the corresponding test temperature; Multiple groups of (V+, V-) at multiple groups of driving voltages at multiple groups of test temperatures are measured.

5. The method for generating a PUF characteristic value according to claim 4, characterized in that: The capacitive sensor is a MEMS sensor or an NMES sensor; the capacitive sensor is a capacitive pressure sensor, a capacitive force sensor, a capacitive displacement sensor, a capacitive mass sensor, a capacitive strain sensor, a capacitive flow sensor, a capacitive torque sensor, a capacitive vibration sensor, a capacitive liquid level sensor, a capacitive gyroscope, a capacitive gas sensor, a capacitive magnetic sensor, a capacitive biosensor, a capacitive humidity sensor, a capacitive temperature sensor, a capacitive chemical sensor, a capacitive acceleration sensor, or a capacitive inertial sensor.

6. A capacitive sensor PUF key generation method, characterized in that: include: Combining the PUF characteristic values ​​obtained by the PUF characteristic value generation method according to any one of claims 1 to 4 to obtain a plurality of CRP stimulus-response pairs; Performing analog-to-digital conversion on the response in the CRP stimulus-response pair to obtain bit data; The bit data is processed using a hash algorithm and combined with the stimulus data to generate a PUF key.

7. The method for generating a capacitive sensor PUF key according to claim 6, characterized in that: The method also includes storing the PUF key in a security verification device of the capacitive sensor.

8. A safety verification method for a capacitive sensor, characterized in that: include: A capacitive sensor to be tested is provided, a security verification device is connected to the capacitive sensor to be tested, and a power supply of the capacitive sensor is turned on, wherein the security verification device stores a PUF key of the capacitive sensor to be tested generated by the PUF key generation method according to claim 6 or claim 7; Under multiple test temperatures, the security verification device generates a first random number and sends it to the capacitive sensor to be tested, and the capacitive sensor to be tested takes the first random number as a challenge and generates a first response; The capacitive sensor to be tested encrypts the first random number to obtain a second response, and sends the second response to the security verification device, where the encryption key of the first random number is the first response; Decrypting the second response using the PUF key stored in the security verification device as a decryption key to obtain a second random number; The second random number is compared with the first random number, and if the two are the same, it is determined that the capacitive sensor to be tested is a safety device.

9. A safety verification device for a capacitive sensor, characterized in that: The safety verification device can use the safety verification method described in claim 8 to perform safety verification on the capacitive sensor, and the safety verification device includes: A memory for storing PUF keys of multiple capacitive sensors generated by the method of claim 6 or claim 7; A random number generation module, used to generate a first random number; A decryption module, configured to decrypt a second response returned by the capacitive sensor using the PUF key to obtain a second random number; A comparison module, used for comparing the second random number with the first random number to obtain a comparison result; A display module is used to display the comparison result and / or display the first random number and the second random number.

10. A capacitive sensor, characterized in that: The PUF characteristic value generation method can be applied to any one of claims 1 to 4, wherein the capacitive sensor comprises: a power module, a processor, a storage module, an interface module, a temperature adjustment module, and a capacitive sensor structure; the power module is used to provide power to the processor, the storage module, the interface module, the temperature adjustment module, and the capacitive sensor structure, and the temperature adjustment module comprises a temperature detection module and a heating resistor arranged in the capacitive sensor structure area; the processor is electrically connected to the capacitive sensor structure, and is used to calculate the capacitance value of the capacitive sensor structure, and is used to control the working state of the power module, and the processor is also used to respond to a first test signal of an external test device, and adjust the ambient temperature of the capacitive sensor structure by controlling the temperature of the heating resistor; Wherein, when the capacitive sensor is in a testing state, the battery supplies power to the heating resistor, and when the capacitive sensor is in a working state, the battery stops supplying power to the heating resistor.

11. The capacitive sensor according to claim 10, characterized in that: The power module includes: a battery, a first switch module and a voltage adjustment module. The first switch module controls the voltage adjustment module to output a corresponding driving voltage in response to a second test signal sent by the processor.

12. The capacitive sensor according to claim 11, characterized in that: The voltage adjustment module includes k voltage output nodes, and resistors R1, R2...Rk connected in series in sequence, k is a positive integer, and a voltage output node is arranged between two adjacent resistors. The first switch module responds to the second test signal sent by the processor and selects to connect the corresponding voltage output node to control the voltage adjustment module to output the corresponding driving voltage.

13. The capacitive sensor according to claim 12, characterized in that: The power supply module also includes a second switch module and a third switch module, wherein the first end of the second switch module is connected to the positive electrode V+ of the output voltage end of the capacitive sensor structure, and the second end is grounded; the first end of the third switch module is connected to the negative electrode V- of the output voltage end of the capacitive sensor structure, and the second end is grounded; the second switch module is closed in response to the output voltage test signal of V-, and is opened in response to the output voltage test signal of V+; the third switch module is closed in response to the output voltage test signal of V+, and is opened in response to the output voltage test signal of V-.

Images