Sampling circuit for improving common-mode voltage range
By using a series differential amplifier to enhance the common-mode voltage range of the sampling circuit, the problem of insufficient common-mode voltage range in CSA is solved, achieving higher common-mode voltage processing capability and lower cost, while improving the accuracy and stability of the circuit.
Patent Information
- Application Number
- CN202410618529.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-17
- Publication Date
- 2025-11-18
AI Technical Summary
The limited common-mode voltage range of existing CSA circuits results in high circuit costs and makes it difficult to meet accuracy requirements.
By connecting one or more first and second differential amplifiers in series, the common-mode voltage processing capabilities of the two differential amplifiers are superimposed to directly process higher common-mode voltages without the need for an isolation power supply.
It improves the common-mode voltage range, reduces BOM costs, and enhances circuit accuracy and stability.
Smart Images
Figure CN120979369A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of integrated circuits, and in particular to a sampling circuit for improving the common-mode voltage range. BACKGROUND
[0002] In practical applications, the problem of insufficient common-mode voltage is often encountered. The maximum common-mode voltage of a CSA (Current Sense Amplifier) is usually only 80-100V. If a CSA with higher specifications is selected, the price is often relatively high.
[0003] CSA usually refers to a current sense amplifier. It is a device specifically designed for accurate measurement of current in a circuit. By monitoring the voltage drop across a shunt resistor (a low-value resistor), a CSA can provide information about the size of the current, usually in the form of a voltage output. Such amplifiers are very important in power management, overload protection, and battery charging applications. A CSA can provide high-precision current measurement, which is crucial for ensuring circuit safety and efficiency. SUMMARY
[0004] The purpose of the present application is to provide a sampling circuit for improving the common-mode voltage range, which can meet the accuracy requirements and reduce the overall BOM (Bill of Materials) cost.
[0005] The present application discloses a sampling circuit for improving the common-mode voltage range, comprising:
[0006] a first-stage or more-stage first differential amplifier, the positive input terminal and the negative input terminal of the first-stage first differential amplifier being connected to the first terminal and the second terminal of a sampling resistor respectively, the power supply terminal of the first-stage first differential amplifier being connected to the first terminal of the sampling resistor through a first resistor, the ground terminal of each first differential amplifier being connected to the power supply terminal of the next-stage first differential amplifier through a second resistor, a voltage stabilizing circuit being connected between the ground terminal and the power supply terminal of each first differential amplifier, and the ground terminal of the last-stage first differential amplifier being connected to a constant current source, wherein the voltage at the first terminal of the sampling resistor is a common-mode voltage; and
[0007] a second differential amplifier, the power supply terminal of the second differential amplifier being connected to a reference voltage of the constant current source, the positive input terminal of the second differential amplifier being connected to the output terminal of the last-stage first differential amplifier, and the negative input terminal of the second differential amplifier being connected to the ground terminal of the last-stage first differential amplifier.
[0008] In a preferred embodiment, the constant current source comprises a first transistor, a second transistor, and a third resistor, wherein the collector of the first transistor provides a constant current to the ground terminal of the last stage first differential amplifier, the base of the first transistor, the collector and the base of the second transistor, and one end of the third resistor are connected together, the other end of the third resistor is connected to the reference voltage and the power terminal of the second differential amplifier, the emitter of the first transistor and the emitter of the second transistor are both connected to the ground terminal.
[0009] In a preferred embodiment, the sampling circuit comprises a first stage first differential amplifier, the positive input terminal and the negative input terminal of the first differential amplifier are connected to the first terminal and the second terminal of the sampling resistor respectively, the power terminal of the first differential amplifier is connected to the first terminal of the sampling resistor through a first resistor, a voltage stabilizing circuit is connected between the ground terminal and the power terminal of the first differential amplifier, the ground terminal of the first differential amplifier is connected to a constant current source, the positive input terminal of the second differential amplifier is connected to the output terminal of the first differential amplifier, the negative input terminal of the second differential amplifier is connected to the voltage stabilizing circuit, the ground terminal of the first differential amplifier, and the constant current source.
[0010] In a preferred embodiment, the voltage stabilizing circuit comprises a diode, the cathode of the diode is connected to the power terminal of the first differential amplifier, and the anode of the diode is connected to the ground terminal of the first differential amplifier.
[0011] In a preferred embodiment, the sampling circuit comprises two stages of first differential amplifiers, the positive input terminal and the negative input terminal of the first stage first differential amplifier are connected to the first terminal and the second terminal of the sampling resistor respectively, the power terminal of the first stage first differential amplifier is connected to the first terminal of the sampling resistor through a first resistor, the ground terminal of the first stage first differential amplifier is connected to the power terminal of the second stage first differential amplifier through a second resistor, a first voltage stabilizing circuit is connected between the ground terminal and the power terminal of the first stage first differential amplifier, and a second voltage stabilizing circuit is connected between the ground terminal and the power terminal of the second stage first differential amplifier.
[0012] the positive input terminal of the second differential amplifier is connected to the output terminal of the second stage first differential amplifier, and the negative input terminal of the second differential amplifier is connected to the second voltage stabilizing circuit, the ground terminal of the second stage first differential amplifier, and the constant current source.
[0013] In one preferred embodiment, the first voltage stabilizing circuit comprises a first diode, a cathode of the first diode is connected to a power supply terminal of the first stage first differential amplifier, and an anode of the first diode is connected to a ground terminal of the first stage first differential amplifier; the second voltage stabilizing circuit comprises a second diode, a cathode of the second diode is connected to a power supply terminal of the second stage first differential amplifier, and an anode of the second diode is connected to a ground terminal of the second stage first differential amplifier.
[0014] In one preferred embodiment, the first differential amplifier is implemented as a current sense amplifier.
[0015] In one preferred embodiment, the second differential amplifier is implemented as a current sense amplifier.
[0016] In one preferred embodiment, the second differential amplifier is implemented as an analog-to-digital converter.
[0017] In one preferred embodiment, the common mode voltage ranges from 50V to 100V.
[0018] In the embodiments of the present application, the output of the first differential amplifier is connected to the input of the second differential amplifier, so that the range of the common mode voltage is improved. Since each differential amplifier has its own range of common mode voltage that it can handle, connecting two differential amplifiers in series can make the entire circuit capable of withstanding a higher common mode voltage. The combination of two differential amplifiers solves the problem of insufficient common mode voltage range of a single differential amplifier. This combination method takes advantage of the superposition of the common mode voltage handling capacity of the two differential amplifiers, and can directly handle a higher common mode voltage without the need for an isolated power supply.
[0019] A large number of technical features are described in the specification of the present application, which are distributed in various technical solutions. If all possible combinations of technical features (i.e. technical solutions) of the present application are listed, the specification will be too long. In order to avoid this problem, each technical feature disclosed in the above summary of the present application, each technical feature disclosed in the following embodiments and examples, and each technical feature disclosed in the drawings can be freely combined with each other to form various new technical solutions (these technical solutions should be considered to have been described in the specification), unless such combination of technical features is technically infeasible. For example, features A+B+C are disclosed in one example, features A+B+D+E are disclosed in another example, features C and D are equivalent technical means that play the same role, and can only be used at a time, feature E can be combined with feature C, then the solution of A+B+C+D should not be considered to have been described because it is technically infeasible, and the solution of A+B+C+E should be considered to have been described. BRIEF DESCRIPTION OF DRAWINGS
[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.
[0021] Figure 1 is a structural schematic diagram of a sampling circuit for improving the common-mode voltage range according to an embodiment of the present application.
[0022] Figure 2 is a structural schematic diagram of a sampling circuit for improving the common-mode voltage range according to another embodiment of the present application. DETAILED DESCRIPTION
[0023] In the following description, many technical details are presented in order to make the reader better understand the present application. However, those skilled in the art can understand that the technical solutions claimed by the present application can be realized even without these technical details and based on various changes and modifications of the following embodiments.
[0024] In order to make the purpose, technical solutions and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.
[0025] One embodiment of the present application relates to a sampling circuit for improving the common-mode voltage range, which comprises one or more stages of first differential amplifiers and a second differential amplifier. The positive input terminal and the negative input terminal of the first stage of first differential amplifiers are respectively connected to the first end and the second end of a sampling resistor, and the power supply terminal of the first stage of first differential amplifiers is connected to the first end of the sampling resistor through a first resistor. The ground terminal of each stage of first differential amplifiers is connected to the power supply terminal of the next stage of first differential amplifiers through a second resistor. A voltage stabilizing circuit is connected between the ground terminal and the power supply terminal of each stage of first differential amplifiers. The ground terminal of the last stage of first differential amplifiers is connected to a constant current source, wherein the voltage at the first end of the sampling resistor is the common-mode voltage. The power supply terminal of the second differential amplifier is connected to the reference voltage of the constant current source. The positive input terminal of the second differential amplifier is connected to the output terminal of the last stage of first differential amplifiers, and the negative input terminal of the second differential amplifier is connected to the ground terminal of the last stage of first differential amplifiers.
[0026] Common Mode Voltage is the voltage at two or more points in a circuit relative to a common reference point, usually ground or zero potential. In a differential signal system, common mode voltage is particularly important because a differential signal consists of a pair of lines, each carrying a voltage, and the two voltages may share a portion of the voltage relative to a common reference point (such as ground), which is the common mode voltage.
[0027] More specifically, if we have two signal lines A and B, which have voltages VA and VB relative to ground, respectively, then:
[0028] - The differential voltage is the difference between the two signals VA and VB, calculated as Vdiff = VA - VB.
[0029] - The common mode voltage is the average voltage of the two signals VA and VB relative to ground, calculated as VCM = (VA + VB) / 2.
[0030] The concept of common mode voltage is important in many electronic systems, especially when dealing with signal transmission and amplification. Ideally, a differential amplifier or receiver should only be sensitive to the differential voltage and should reject the common mode voltage shared by the two inputs, which helps to improve the quality of the signal and reduce noise. In practical applications, due to external interference or equipment mismatch, common mode voltage can cause noise and errors, so attention should be paid to reducing the impact of common mode voltage during design.
[0031] Figure 1 is a structure diagram of a sampling circuit for boosting the common mode voltage range in an embodiment. The sampling circuit includes a first differential amplifier x1 and a second differential amplifier x2. The positive input terminal and the negative input terminal of the first differential amplifier x1 are connected to the first end and the second end of a sampling resistor R4, respectively. The power supply terminal of the first differential amplifier x1 is connected to the first end of the sampling resistor R4 through a first resistor R1. The ground terminal of the first differential amplifier x1 is connected to a constant current source through a voltage stabilizing circuit. The ground terminal of the first differential amplifier x1 is connected to the constant current source. The voltage at the first end of the sampling resistor R4 is the common mode voltage V2. In an embodiment, the common mode voltage ranges from 50V to 100V.
[0032] In an embodiment, the first differential amplifier x1 is a current sensing amplifier (CSA).
[0033] In an embodiment, the first resistor R1 has a value of, for example, 1K ohm. It should be understood that this value is only an example, and the value of the resistor R1 is not limited to this value, and should be selected according to the specific circuit, for example, it can also be in the range of 1K ohm to 30K ohm, for example, it can also be 3.5K ohm.
[0034] In one embodiment, the voltage regulator circuit includes a diode D1. The cathode of the diode D1 is coupled to the power supply terminal of the first differential amplifier x1, and the anode of the diode D1 is coupled to the ground terminal of the first differential amplifier x1, the negative input terminal of the second differential amplifier x2, and a constant current source. This node can be connected to a functional ground (FGND). FGND stands for Functional Ground, which is a reference point for a specific part of the circuit, used for a specific signal or functional module. It can be different from other grounds (such as the power ground PGND) in the circuit, mainly for reducing noise and interference, and improving circuit performance. FGND and other grounds (such as PGND) in the circuit can be physically connected, but they serve different purposes in design. FGND mainly focuses on signal integrity and reducing noise interference, while PGND is mainly the ground point of the power system. In design, these different ground points need to be properly handled to avoid noise and interference.
[0035] The diode D1 is used to control the supply voltage of the first differential amplifier x1, to protect the first differential amplifier x1 from excessive voltage.
[0036] The positive input terminal of the second differential amplifier x2 is connected to the output terminal of the first differential amplifier x1, and the negative input terminal of the second differential amplifier x2 is connected to the anode of the diode D2, the ground terminal of the first differential amplifier x1, and the constant current source. The output VOUT of the second differential amplifier x2 serves as the output of the sampling circuit.
[0037] In one embodiment, the second differential amplifier x2 is a current sense amplifier (CSA).
[0038] In one embodiment, the constant current source includes a first transistor Q1, a second transistor Q2, and a third resistor R3, wherein the collector of the first transistor Q1 provides a constant current to the ground terminal of the first differential amplifier x1, the base of the first transistor Q1, the collector and base of the second transistor Q2, and one end of the third resistor R3 are connected together, the other end of the third resistor R3 is connected to a reference voltage V1 and the power supply terminal of the second differential amplifier x2, and the emitter of the first transistor Q1 and the emitter of the second transistor Q2 are both connected to the ground terminal. The constant current source composed of R2, Q2, and Q1 is used to control the maximum common mode voltage of the first differential amplifier x1, to ensure stable operation of the circuit. In one embodiment, the transistors Q1 and Q2 are implemented by Q2N2222.
[0039] In one embodiment, the value of the third resistor R3 is, for example, 1K ohm. It should be understood that this value is only an example, and the value of the resistor R3 is not limited to this value, and should be selected according to the specific circuit, for example, it can also be in the range of 1K ohm ~ 100K ohm.
[0040] In one embodiment, the reference voltage V1 is 5V. It should be understood that this value is only an example, and the value of the reference voltage V1 is not limited to this value, and should be selected according to the specific circuit, for example, it can also be in the range of 1V to 15V.
[0041] The differential amplifier x1, x2 is implemented by INA199A1. INA199A1 is a current sensing amplifier, which is used to accurately measure the current through a shunt resistor and provide a proportionally amplified output voltage. In this circuit, it is used to measure and amplify the current signal.
[0042] If this sampling circuit uses a differential amplifier INA199A1 (GAIN=50), then the first differential amplifier x1 can withstand a common-mode voltage of 26V, and the second differential amplifier x2 can also withstand a common-mode voltage of 26V. Assuming that the differential-mode input voltage of the first differential amplifier x1 is 1mV, then the output voltage of the first differential amplifier x1 is 50mV, and the output voltage of the second differential amplifier x2 is 5V. Since the first differential amplifier x1 can withstand a maximum common-mode voltage of 26V, the control constant current source can make V(R1)+V(D1)=(x1)VCM, at this time the maximum common-mode voltage is equal to x1(VCM)+x2(VCM)=50V. If the common-mode voltage is still not enough, you can continue to connect the amplifiers in series until the common-mode voltage range is sufficient.
[0043] By connecting two CSAs to each other, the circuit can withstand a common-mode voltage of the sum of the two, thereby greatly improving the common-mode voltage range. Through this design, the circuit can handle higher common-mode voltages without the need for additional isolation measures, which at the same time reduces the cost and improves the accuracy. The total gain of this circuit is the gain of the first differential amplifier x1 multiplied by the gain of the second differential amplifier x2.
[0044] The differential amplifier x1, x2 can be replaced by a CSA240 amplifier with PWM rejection, which uses the first stage to process AC CMR and the second stage to process VCM range. The second differential amplifier x2 can be replaced by a CSD or, to improve the common-mode voltage input range of the CSD. The second differential amplifier x2 can also be replaced by an ADC, and then a digital isolation chip is used to transmit the collected data.
[0045] This sampling circuit indeed solves the problem of insufficient common-mode voltage range of a single CSA by combining two CSAs. This combination method takes advantage of the superposition of the common-mode voltage handling capability of the two CSAs. Specifically, the circuit achieves an increase in the common-mode voltage range by connecting the output of differential amplifier x1 to the input of differential amplifier x2. Since each CSA has its own common-mode voltage range that it can handle, connecting two CSAs in series allows the entire circuit to withstand a higher common-mode voltage.
[0046] The signals processed by traditional sampling circuits can involve high voltages or high common-mode voltages, which can interfere with or damage other parts of the circuit. In order to protect the circuit and the user, it is necessary to separate different parts of the circuit by isolating the power supply to ensure that the high voltage part does not affect the overall circuit. This sampling circuit, through reasonable design, uses the first differential amplifier x1 and the second differential amplifier x2 to jointly bear the common-mode voltage. Through this design, the circuit can directly handle higher common-mode voltages without the need for an isolated power supply. Isolated power supplies are usually used to electrically isolate inputs and outputs or different circuit parts to avoid high voltage damage to the circuit or affect accuracy. This sampling circuit achieves the ability to handle high common-mode voltages through internal design, thus eliminating the need for additional isolation measures.
[0047] Figure 2 is another embodiment of a sampling circuit that increases the common-mode voltage range.
[0048] In one embodiment, the sampling circuit includes two stages of first differential amplifiers and second differential amplifiers, i.e., a first stage of first differential amplifier x1, a second stage of first differential amplifier x2, and a second differential amplifier x3. The positive input terminal of the first stage of first differential amplifier x1 is connected to the first end of the sampling resistor R4, the negative input terminal of the first stage of first differential amplifier x1 is connected to the second end of the sampling resistor R4, the power supply terminal of the first stage of first differential amplifier x1 is connected to the first end of the sampling resistor R4 through the first resistor R1, the ground terminal of the first stage of first differential amplifier x1 is connected to the power supply terminal of the second stage of first differential amplifier x2 through the second resistor R2, and the ground terminal and the power supply terminal of the first stage of first differential amplifier x1 are connected to the second voltage stabilizing circuit.
[0049] In one embodiment, the first voltage stabilizing circuit includes a first diode D1. Specifically, the cathode of the first diode D1 is coupled to the power supply terminal of the first differential amplifier x1, and the anode of the first diode D1 is coupled to the ground terminal of the first differential amplifier x1.
[0050] In one embodiment, the second voltage stabilizing circuit includes a second diode D2. Specifically, the cathode of the second diode D2 is coupled to the power supply terminal of the first differential amplifier x2, and the anode of the second diode D2 is coupled to the ground terminal of the first differential amplifier x2.
[0051] It should be understood that the voltage stabilizing circuit of the present application is not limited to the form of a diode, and any circuit capable of controlling the power supply voltage of the first differential amplifier is within the protection scope of the present application.
[0052] In one embodiment, the second resistor R2 has a value of, for example, 1K ohm. It should be understood that this value is only an example, and the value of the resistor R2 is not limited to this value, and should be selected according to the specific circuit, for example, it can also be in the range of 1K ohm~100K ohm, for example, it can also be 5K ohm, 30K ohm, etc.
[0053] The positive input terminal of the second differential amplifier x3 is connected to the output terminal of the second-stage first differential amplifier x2, and the negative input terminal of the second differential amplifier x3 is connected to the anode of the second diode D2, the ground terminal of the second-stage first differential amplifier x2, and the constant current source.
[0054] In one embodiment, the constant current source includes a first transistor Q1, a second transistor Q2, and a third resistor R3, wherein the collector of the first transistor Q1 provides a constant current to the ground terminal of the second-stage first differential amplifier x2, the base of the first transistor Q1, the collector and base of the second transistor Q2, and one end of the third resistor R3 are connected, the other end of the third resistor R3 is connected to the reference voltage V1 and the power supply terminal of the second differential amplifier x2, and the emitter of the first transistor Q1 and the emitter of the second transistor Q2 are both connected to the ground terminal. The constant current source composed of R2, Q2, Q1 is used to control the maximum common mode voltage of the first differential amplifiers x1, x2, and ensure the stable operation of the circuit.
[0055] In the present embodiment, by connecting the three differential amplifiers x1, x2, and x3 to each other, the common mode voltage that the circuit can withstand is the sum of the three, thereby greatly improving the common mode voltage range. Through this design, the circuit can handle higher common mode voltages without the need for additional isolation measures, which at the same time reduces the cost and improves the precision. If the common mode voltage is still not enough, more stages of first differential amplifiers can be connected in series until the common mode voltage range is sufficient, and the common mode voltage can even be infinitely increased.
[0056] It is to be noted that the relationship terms such as first and second, and the like, used in the specification are merely intended to distinguish one entity or operation from another, and are not necessarily required to be taken literally, unless expressly so defined by the claims. Moreover, the term "comprising" or "including" or any other variant is intended to cover non-exclusive inclusions, such that processes, methods, articles, or apparatuses that comprise, include, or are otherwise including a series of elements are not required to include only those elements that are directly enumerated, or that are otherwise required. An element preceded by "comprises... a" does not, without further constraints, foreclose the existence of additional identical elements other than the one preceeding the term. The term "a" or "an" or "the" preceding an element or intervention is intended to foreclose only the existence of one element or one intervention whereas "comprising", "including", and "having" (or with, or containing) are intended to foreclose the existence of only that one element or one intervention. Where the application recites a process, method, article or apparatus that comprises, includes or has a series of elements, the terms "comprising", "including" and "having" are intended to indicate that the process, method, article or apparatus includes the elements that are directly enumerated, but not excluding additional elements. The term "consisting of" is intended to foreclose the existence of additional elements other than those that are directly enumerated. The term "consisting essentially of" is intended to foreclose the existence of additional elements other than those that are directly enumerated, but does not foreclose the existence of additional elements that are equivalent to those that are directly enumerated. The term "comprising" is intended to mean that the process, method, article or apparatus includes the recited elements, but not excluding additional elements. The term "a" or "an" is intended to foreclose the existence of more than one of the element that is preceded by the term. The term "plurality" is intended to mean two or more. The term "multiple" is intended to mean two or more.
[0057] The term "coupled to" and its derivatives can be used herein. "Coupled" can mean that two or more elements are in direct physical or electrical contact. However, "coupled" can also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other, and can mean that one or more other elements are coupled or connected between the elements that are said to be coupled to each other.
[0058] This specification includes the combination of various embodiments described herein. Individual recitation of embodiments (e.g., "one embodiment" or "some embodiments" or "the preferred embodiment") does not necessarily refer to the same embodiment; however, such embodiments are not mutually exclusive, unless otherwise indicated or as is clear from the context. It is noted that the word "comprising" is used herein in the broadest sense to mean that the process, method, article, or apparatus includes the recited elements, but not excluding additional elements.
[0059] All documents mentioned in this specification are hereby incorporated by reference in their entirety to provide additional description of the application. In addition, it should be appreciated that the above description is intended to be illustrative, and not restrictive, of the application. Many embodiments of the present application will be apparent to those of ordinary skill in the art upon reviewing the above description. The scope of the application should, therefore, be determined not with reference to the above description, but instead with reference to the appended claims, along with their full scope of equivalents.
Claims
1. A sampling circuit for improving the common-mode voltage range, characterized in that, include: The system comprises one or more stages of first differential amplifiers. The positive and negative input terminals of the first stage first differential amplifier are connected to the first and second terminals of a sampling resistor, respectively. The power supply terminal of the first stage first differential amplifier is connected to the first terminal of the sampling resistor through a first resistor. The ground terminal of each stage first differential amplifier is connected to the power supply terminal of the next stage first differential amplifier through a second resistor. A voltage regulator circuit is connected between the ground terminal and the power supply terminal of each stage first differential amplifier. The ground terminal of the last stage first differential amplifier is connected to a constant current source. The voltage at the first terminal of the sampling resistor is a common-mode voltage. as well as The second differential amplifier has its power supply terminal connected to the reference voltage of the constant current source, its positive input terminal connected to the output terminal of the last stage first differential amplifier, and its negative input terminal connected to the ground terminal of the last stage first differential amplifier.
2. The circuit according to claim 1, characterized in that, The constant current source includes a first transistor, a second transistor, and a third resistor. The collector of the first transistor provides a constant current to the ground terminal of the last stage first differential amplifier. The base of the first transistor, the collector and base of the second transistor, and one end of the third resistor are connected. The other end of the third resistor is connected to the reference voltage and the power supply terminal of the second differential amplifier. The emitters of the first transistor and the second transistor are both connected to ground.
3. The circuit according to claim 1, characterized in that, The sampling circuit includes a first-stage differential amplifier. The positive and negative input terminals of the first differential amplifier are connected to the first and second terminals of a sampling resistor, respectively. The power supply terminal of the first differential amplifier is connected to the first terminal of the sampling resistor through a first resistor. A voltage regulator circuit is connected between the ground terminal and the power supply terminal of the first differential amplifier. The ground terminal of the first differential amplifier is connected to a constant current source. The positive input terminal of the second differential amplifier is connected to the output terminal of the first differential amplifier. The negative input terminal of the second differential amplifier is connected to the voltage regulator circuit, the ground terminal of the first differential amplifier, and the constant current source.
4. The circuit according to claim 3, characterized in that, The voltage regulator circuit includes a diode, the cathode of which is connected to the power supply terminal of the first differential amplifier, and the anode of which is connected to the ground terminal of the first differential amplifier.
5. The circuit according to claim 1, characterized in that, The sampling circuit includes two stages of first differential amplifiers. The positive and negative input terminals of the first stage first differential amplifiers are connected to the first and second terminals of the sampling resistor, respectively. The power supply terminal of the first stage first differential amplifier is connected to the first terminal of the sampling resistor through the first resistor. The ground terminal of the first stage first differential amplifier is connected to the power supply terminal of the second stage first differential amplifier through the second resistor. A first voltage regulator circuit is connected between the ground terminal and the power supply terminal of the first stage first differential amplifier. A second voltage regulator circuit is connected between the ground terminal and the power supply terminal of the second stage first differential amplifier. The positive input terminal of the second differential amplifier is connected to the output terminal of the second stage first differential amplifier, and the negative input terminal of the second differential amplifier is connected to the second voltage regulator circuit, the ground terminal of the second stage first differential amplifier, and the constant current source.
6. The circuit according to claim 5, characterized in that, The first voltage regulator circuit includes a first diode, the cathode of which is connected to the power supply terminal of the first stage first differential amplifier, and the anode of which is connected to the ground terminal of the first stage first differential amplifier; the second voltage regulator circuit includes a second diode, the cathode of which is connected to the power supply terminal of the second stage first differential amplifier, and the anode of which is connected to the ground terminal of the second stage first differential amplifier.
7. The circuit according to claim 1, characterized in that, The first differential amplifier is implemented using a current-sensing amplifier.
8. The circuit according to claim 1, characterized in that, The second differential amplifier is implemented using a current-sensing amplifier.
9. The circuit according to claim 1, characterized in that, The second differential amplifier is implemented using an analog-to-digital converter.
10. The circuit according to claim 1, characterized in that, The common-mode voltage ranges from 50V to 100V.