Contactor adhesion detection circuit

Abstract

The utility model relates to a contactor adhesion detection circuit. The contactor adhesion detection circuit comprises an acquisition module which comprises a first resistor and a voltage transformer, the third end of the voltage transformer is connected with the second end of the first resistor, and the fourth end of the voltage transformer is connected with the first end of the first resistor; the acquisition module acquires induced voltage according to a loop state between an output live wire and the ground; the signal processing module is connected with the first resistor; the processing module is used for processing the collected induced voltage to obtain a control signal; the control module is connected with the signal processing module; and the controller is used for identifying the control signal and judging whether the contactor is adhered and controlled according to an identification result. The cost of safety detection of the AC charging pile is reduced, and real-time monitoring of the contact point can be realized through the detection circuit.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, in particular to a contactor adhesion detection circuit. Background Art

[0002] One of the key points in the development of electric vehicle industry technology is the construction of charging infrastructure. Charging piles are key equipment for charging electric vehicles and are used to provide electric energy to electric vehicle batteries. The mainboard contactor is a key component in electric vehicles responsible for controlling the flow of current and is responsible for opening or closing the circuit connection between the battery and the drive motor. However, during use, the mainboard contactor may be contaminated by foreign objects such as dust or oxides, resulting in adhesion, which in turn affects the transmission efficiency of electric energy.

[0003] At present, most AC charging pile motherboard contact adhesion detection uses the AC live wire to form a loop with the ground to generate a micro-current to drive the optocoupler, which is converted into high and low level signals and fed back to the microcontroller end, thereby judging the adhesion of the AC charging pile motherboard contactor. Since this solution requires the optocoupler to be driven by current, according to the national standard, the input end of the charging pile must meet higher voltage requirements to the ground, so the optocoupler drive circuit needs to add a high voltage relay to meet the voltage requirements, but the cost of high voltage relays is relatively high and the supply is tight. Utility Model Content

[0004] Based on this, it is necessary to provide a contactor adhesion detection circuit that can detect contact adhesion in an AC high voltage environment.

[0005] In a first aspect, the present application provides a contactor adhesion detection circuit, comprising:

[0006] The acquisition module includes a first resistor and a voltage transformer, wherein the third end of the voltage transformer is connected to the second end of the first resistor, and the fourth end of the voltage transformer is connected to the first end of the first resistor; and is used to acquire the induced voltage according to the loop state between the output live wire and the earth;

[0007] A signal processing module connected to the first resistor; used to process the collected induced voltage to obtain a control signal; and

[0008] The control module is connected to the signal processing module; it is used to identify the control signal and determine whether the contactor is stuck and controlled based on the identification result.

[0009] In one embodiment, the signal processing module includes:

[0010] An operational amplifier module, which is connected to the acquisition module and is used to amplify the induced voltage to obtain a first control signal; and

[0011] The comparator module is connected to the operational amplifier module and is used to obtain a second control signal according to the first control signal and a reference voltage.

[0012] In one embodiment, the operational amplifier module includes an amplifier, a second terminal of the amplifier is connected to the second terminal of the first resistor, and a third terminal of the amplifier is connected to the first terminal of the first resistor.

[0013] In one embodiment, the comparator module includes a comparator, a second resistor and a third resistor, the third end of the comparator is connected to the first end of the amplifier, the second end of the comparator is connected to the first end of the third resistor and the second end of the second resistor, the second end of the third resistor is grounded, and the first end of the second resistor is connected to a power supply.

[0014] In one embodiment, the amplifier and the comparator are arranged on the same chip.

[0015] In one embodiment, the contactor sticking detection circuit further includes:

[0016] The regulation module is arranged between the signal processing module and the control module, and is used to adjust the signal strength output by the signal processing module.

[0017] In one embodiment, the control module includes: a transistor, a second capacitor and a fourth resistor, the first end of the transistor is connected to the signal processing module, the first end of the second capacitor and the first end of the fourth resistor, the second end of the transistor is connected to the second end of the second capacitor and the second end of the fourth resistor and is grounded, and the third end of the transistor is connected to the control module.

[0018] In one embodiment, the acquisition module includes a voltage transformer, a first resistor and a first capacitor, the first end of the voltage transformer is grounded, the second end of the voltage transformer is connected to the live wire output end, the third end of the voltage transformer is connected to the second end of the first resistor and the second end of the first capacitor, and the fourth end of the voltage transformer is connected to the first end of the first resistor and the first end of the first capacitor.

[0019] In one embodiment, the acquisition module includes a first sampling resistor and a second sampling resistor, the first end of the first sampling resistor is connected to the live wire output end, the second end of the first sampling resistor is connected to the second end of the voltage transformer, the second end of the second sampling resistor is connected to the first end of the voltage transformer, and the first end of the second sampling resistor is grounded.

[0020] In one embodiment, the acquisition module further includes a first diode, a second end of the first diode is connected to a first end of the second sampling resistor, and a first end of the first diode is grounded.

[0021] The contactor adhesion detection circuit includes a collection module, including a first resistor and a voltage transformer, the third end of the voltage transformer is connected to the second end of the first resistor, and the fourth end of the voltage transformer is connected to the first end of the first resistor; used to collect the induced voltage according to the loop state between the output live wire and the earth; a signal processing module, connected to the first resistor; used to process the collected induced voltage to obtain a control signal; and a control module, connected to the signal processing module; used to identify the control signal, and judge whether the contactor is adhesion controlled by the identification result. When a loop is formed between the output live wire and the earth through the voltage transformer, an induced current is generated at the rear end of the transformer, and an induced voltage is generated at both ends of the first resistor. After being processed by the signal processing module, a fixed frequency control signal is generated, and the control signal is input into the control module. According to the continuity of the control signal, it is judged whether the contactor is adhesion controlled, which reduces the cost of monitoring the adhesion of the contact point of the AC charging pile, avoids faults and abnormalities caused by human operation, and effectively improves the detection reliability and detection efficiency through real-time detection of the monitoring circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of module connection of a contactor adhesion detection circuit in one embodiment;

[0023] Figure 2 is a circuit diagram of a contactor adhesion detection circuit in one embodiment;

[0024] Figure 3 FIG. 4 is a circuit diagram of a contactor adhesion detection circuit in another embodiment.

[0025] Explanation of the accompanying drawings: acquisition module 100; signal processing module 200; control module 300; regulation module 400; first resistor R1; second resistor R2; third resistor R3; fourth resistor R4; fifth resistor R5; sixth resistor R6; seventh resistor R7; eighth resistor R8; ninth resistor R9; tenth resistor R10; eleventh resistor R11; twelfth resistor R12; thirteenth resistor R13; fourteenth resistor R14; fifteenth resistor R15; sixteenth resistor R16; seventeenth resistor R17; eighteenth resistor R18; nineteenth resistor R19; first capacitor C1; second capacitor C2; third capacitor C3; fourth capacitor C4; fifth capacitor C5; transistor Q; voltage transformer T; amplifier U1A; comparator U1B; diode D. DETAILED DESCRIPTION

[0026] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0028] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0029] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0030] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0031] like Figure 1 and Figure 2 As shown, Figure 1 FIG. 1 shows a schematic diagram of module connection of a contactor adhesion detection circuit in an embodiment. Figure 2 A circuit diagram of a contactor adhesion detection circuit in an embodiment is shown. In one embodiment, the contactor adhesion detection circuit includes an acquisition module, including a first resistor and a voltage transformer, the third end of the voltage transformer is connected to the second end of the first resistor, and the fourth end of the voltage transformer is connected to the first end of the first resistor; used to collect the induced voltage according to the loop state between the output live wire and the earth; a signal processing module, connected to the first resistor; used to process the collected induced voltage to obtain a control signal; and a control module, connected to the signal processing module; used to identify the control signal, and determine whether the contactor is adhesion controlled according to the identification result.

[0032] The contactor adhesion detection circuit is used to detect the contactor state, and includes an acquisition module 100, a signal processing module 200 and a control module 300. The signal processing module 200 is connected to the acquisition module 100, and the control module 300 is connected to the signal processing module 200. The acquisition module 100 is connected to the contactor to collect voltage signals, and transmits the voltage signals to the signal processing module 200. After being processed by the signal processing module 200, the control signals are transmitted to the control module 300, so that the control module 300 identifies the control signals and determines whether the contactor is adhesion controlled by the identification results.

[0033] In this embodiment, the contactor adhesion detection circuit reduces the cost of monitoring the adhesion of the contact points of the AC charging pile, avoids faults and abnormalities caused by human operation, and effectively improves the detection reliability and efficiency through real-time detection by the monitoring circuit.

[0034] In one embodiment, the signal processing module 200 includes an operational amplifier module 220, which is connected to the acquisition module 100 and is used to amplify the induced voltage to obtain a first control signal; and a comparator module 240, which is connected to the operational amplifier module 220 and is used to obtain a second control signal based on the first control signal and a reference voltage.

[0035] The operational amplifier module 220 includes an amplifier U1A, a fifth resistor R5 and a third capacitor C3, the second end of the amplifier U1A is connected to the second end of the first resistor R1, the second end of the amplifier U1A is connected to the first end of the fifth resistor R5, the second end of the fifth resistor R5 is connected to the first end of the amplifier U1A, and the third end of the amplifier U1A is connected to the first end of the first resistor R1. Further, the fourth end of the amplifier U1A is a power supply end, the fourth end of the amplifier U1A is connected to the first end of the third capacitor C3 and the power supply, the second end of the third capacitor C3 is grounded, and the fifth end of the amplifier U1A is grounded. The comparator module 240 includes a comparator U1B, a second resistor R2 and a third resistor R3, the third end of the comparator U1B is connected to the first end of the amplifier U1A, the second end of the comparator U1B is connected to the first end of the third resistor R3 and the second end of the second resistor R2, the second end of the third resistor R3 is grounded, and the first end of the second resistor R2 is connected to the power supply. After the amplifier module 220 amplifies the voltage signal, it is transmitted to the comparator module 240 through the sixth resistor R6 and the fourth capacitor C4. The first end of the sixth resistor R6 is connected to the first end of the amplifier U1A and the second end of the fifth resistor R5. The second end of the sixth resistor R6 is connected to the first end of the fourth capacitor C4 and the third end of the comparator U1A. The second end of the fourth capacitor C4 is grounded. Schematically, the resistance of the second resistor R2 is 100K, the resistance of the third resistor R3 is 10K, the resistance of the fifth resistor R5 is 1M, and the resistance of the sixth resistor R6 is 1K; the third capacitor C3 is 0.1uF / 50V, and the fourth capacitor C4 is 1nF / 50V.

[0036] When the contactor is adhered or in contact, a loop is formed between the output live wire and the earth through the voltage transformer T, and a magnetic field is generated by the current in the loop flowing through the primary winding; the secondary winding senses the generated magnetic field and generates an induced current. The induced current passes through the secondary winding, directly generates an induced voltage at the first end and the second end of the first resistor R1, and outputs the induced voltage to the amplifier module. In order to measure and detect the generated induced voltage, the amplifier module 220 amplifies the induced voltage, schematically, the voltage signal can be amplified 1000 times. The amplified induced voltage is input to the comparator module 240, and the signal output by the amplifier module 220 can be used as the first input, and the second input can be a reference voltage value (reference value). When the induced voltage amplified by the amplifier module 220 is compared with the reference voltage, the comparator will output a corresponding control signal according to the relationship between the two, and the control signal is input to the control module 300. Schematically, the voltage transformer T model is ZMPT107, which can convert a smaller voltage, and a larger resistance can be used for the live wire to earth loop.

[0037] In this embodiment, the induced voltage is amplified by the amplifier module 220, so that the weak induced signal can be amplified to a level suitable for subsequent processing and judgment. The comparator module can compare the amplified induced voltage with the set reference voltage value, so as to realize the judgment of the contactor state, which helps to improve the accuracy and stability of the signal and ensure that the subsequent comparator module can make accurate judgments; by inputting the control signal output by the comparator into the control module 300, the real-time monitoring and control of the contactor state can be realized, which helps to improve the reliability of the system, and also provides real-time feedback information for subsequent maintenance and fault handling.

[0038] In one embodiment, the amplifier U1A and the comparator U1B are arranged on the same chip. The first end and the second end of the first resistor R1 are respectively connected to the third end of the chip and the second end of the chip, and the voltage signal is transmitted to the amplifier module 220. The amplifier U1A obtains an amplified signal after amplifying the voltage signal. The amplified signal is transmitted to the third end of the chip again through the first end of the chip, the sixth resistor R6, and the fourth capacitor C4. The chip processes the received amplified signal. At this time, the chip acts as a comparator and outputs a control signal to the control module 300. The control module 300 determines whether the contactor is controlled by adhesion according to the continuity of the control signal.

[0039] In this embodiment, the chip integrating the amplifier and the comparator can realize a more compact and simplified circuit design, reduce the number of components, and reduce the volume and power consumption of the system. Under high voltage conditions, the stability and reliability of the overall circuit can be improved, and the space occupied by each module on the circuit board can be reduced, which helps to meet the space restrictions of the circuit board under high voltage conditions.

[0040] like Figure 3 As shown, Figure 3 A circuit diagram of a contactor adhesion detection circuit having a control module 400 in an embodiment is shown. The control module 400 includes a transistor Q, a second capacitor C2, a fourth resistor R4, and a seventh resistor R7, a first end of the transistor Q is connected to the signal processing module 200, a first end of the second capacitor C2, and a first end of the fourth resistor R4, a second end of the transistor Q is connected to a second end of the second capacitor C2 and a second end of the fourth resistor R4 and is grounded, a third end of the transistor Q is connected to a second end of the seventh resistor R7 and the control module 300, and a first end of the seventh resistor R7 is connected to a power supply.

[0041] In one embodiment, the contactor adhesion detection circuit also includes a control module 400, which is arranged between the signal processing module 200 and the control module 300, and is used to adjust the signal strength output by the signal processing module 200. The control module 400 regulates the control signal processed by the signal processing module 200, and outputs a control signal with stable waveform and frequency to the control module 300. The control module 400 is connected to the control module 300 through the eighth resistor R8, the first end of the eighth resistor R8 is connected to the third end of the transistor Q and the first end of the seventh resistor R7, and the second end of the eighth resistor R8 is connected to the control module 300. Wherein, GND (Ground, grounding) represents the ground terminal. Schematically, the capacitance of the second capacitor C2 is 1nF / 50V, the resistance of the fourth resistor R4 is 10K, the resistance of the seventh resistor R7 is 4.7K, and the resistance of the eighth resistor R8 is 1K.

[0042] After the induced voltage is processed by the amplifier module 220 and the comparator module 240 in the signal processing module 200, a control signal is obtained, and the control signal is input to the transistor through the eighteenth resistor R18 and the nineteenth resistor R19. The first end of the comparator U1B is connected to the second end of the eighteenth resistor and the first end of the nineteenth resistor, the first end of the eighteenth resistor is connected to the power supply, the second end of the eighteenth resistor is connected to the first end of the nineteenth resistor, and the second end of the nineteenth resistor is connected to the first end of the transistor Q. The control signal includes high and low levels, and the transistor Q is driven by the high and low levels. The transistor Q generates a square wave signal with a fixed frequency and inputs the square wave signal with a fixed frequency to the control module 300. Schematically, the model of the transistor Q is SS8050, the resistance value of the eighteenth resistor is 10K, and the resistance value of the nineteenth resistor is 1K.

[0043] In this embodiment, the control signal output by the signal processing module 200 is further processed and optimized by the setting of the control module 400, and the amplitude of the output signal of the comparator U1B is enhanced. When a higher amplitude is required to drive the subsequent circuit, the triode can provide additional amplification factors and increase the signal amplitude, thereby meeting the high amplitude signal requirements, helping to ensure the matching and adaptability of signal transmission, and reducing signal distortion and loss.

[0044] In one embodiment, the acquisition module 100 includes a voltage transformer T, a first resistor R1, a first capacitor C1, a first sampling resistor and a second sampling resistor, the first sampling resistor includes a ninth resistor R9, a tenth resistor R10 and an eleventh resistor R11, and the second sampling resistor includes a twelfth resistor R12, a thirteenth resistor R13 and a fourteenth resistor R14. The first end of the ninth resistor R9 is connected to L-OUT (live line output end), the second end of the ninth resistor R9 is connected to the first end of the tenth resistor R10, the second end of the tenth resistor R10 is connected to the first end of the eleventh resistor R11, the second end of the eleventh resistor R11 is connected to the second end of the voltage sensor L, the first end of the voltage transformer T is connected to the second end of the twelfth resistor R12, the first end of the twelfth resistor R12 is connected to the second end of the thirteenth resistor R13, the first end of the thirteenth resistor R13 is connected to the second end of the fourteenth resistor R14, and the first end of the fourteenth resistor R14 is connected to the ground line. The third end of the voltage transformer T is connected to the second end of the first resistor R1 and the second end of the first capacitor C1, and the fourth end of the voltage transformer T is connected to the first end of the first resistor R1 and the first end of the first capacitor C1. Wherein, the first end of the voltage sensor T and the second end of the voltage sensor T are located at the primary winding of the voltage sensor T, and the third end of the voltage sensor T and the fourth end of the voltage sensor T are located at the secondary winding of the voltage sensor T. Schematically, the model of the voltage transformer T is ZMPT107, the resistance of the first resistor R1 is 49.9R, the capacitance of the first capacitor C1 is 0.1uF / 50V, the resistance of the ninth resistor R9 is 2M, the resistance of the tenth resistor R10 is 2M, and the resistance of the eleventh resistor R11 is 2M, the resistance of the twelfth resistor R12 is 2M, the resistance of the thirteenth resistor R13 is 2M, and the resistance of the fourteenth resistor R14 is 2M.

[0045] When the contactor is in contact or sticking, a loop consisting of L-OUT (live wire output end), the ninth resistor R9, the tenth resistor R10, the eleventh resistor R11, the voltage transformer T, the twelfth resistor R12, the thirteenth resistor R13, the fourteenth resistor R14 and the ground wire is formed in the acquisition module 100. At the same time, an induced current is generated in the secondary winding of the voltage transformer T, that is, an induced voltage is generated on both sides of the first resistor R1, and the induced voltage is transmitted to the signal processing module 200 for signal processing. The induced voltage is transmitted to the signal processing module 200 through the fifteenth resistor R15, the sixteenth resistor R16 and the seventeenth resistor R17, the first end of the fifteenth resistor R15 is connected to the first end of the first resistor R1 and the first end of the first capacitor C1, the second end of the fifteenth resistor R15 is connected to the second end of the sixteenth resistor R16 and the signal processing module 200, the first end of the sixteenth resistor R16 is grounded, the first end of the seventeenth resistor R17 is connected to the second end of the first resistor R1 and the second end of the first capacitor C1, and the second end of the seventeenth resistor R17 is connected to the signal processing module 200. Schematically, the resistance of the fifteenth resistor R15 is 1K, the resistance of the sixteenth resistor R16 is 1M, and the resistance of the seventeenth resistor R17 is 1K.

[0046] In a feasible implementation, the acquisition module 100 includes a diode D, a second end of the diode D is connected to a first end of the fourteenth resistor R14, and a first end of the diode D is connected to a ground line. Specifically, the model of the diode D is an M7 diode.

[0047] In the description of this specification, the descriptions with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", etc., mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the utility model. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0048] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0049] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A contactor adhesion detection circuit, characterized in that: include: The acquisition module comprises a first resistor and a voltage transformer, wherein the third end of the voltage transformer is connected to the second end of the first resistor, and the fourth end of the voltage transformer is connected to the first end of the first resistor; and is used to acquire the induced voltage according to the loop state between the output live wire and the earth; A signal processing module, connected to the first resistor, used for processing the collected induced voltage to obtain a control signal; and The control module is connected to the signal processing module and is used to identify the control signal and determine whether the contactor is controlled by adhesion according to the identification result.

2. The contactor adhesion detection circuit according to claim 1, characterized in that: The signal processing module comprises: an operational amplifier module, the operational amplifier module being connected to the acquisition module and configured to amplify the induced voltage to obtain a first control signal; and A comparator module, the comparator module is connected to the operational amplifier module, and is used to obtain a second control signal according to the first control signal and a reference voltage.

3. The contactor adhesion detection circuit according to claim 2, characterized in that: The operational amplification module includes an amplifier, a second end of the amplifier is connected to the second end of the first resistor, and a third end of the amplifier is connected to the first end of the first resistor.

4. The contactor adhesion detection circuit according to claim 2, characterized in that: The comparator module includes a comparator, a second resistor and a third resistor, the third end of the comparator is connected to the first end of the amplifier, the second end of the comparator is connected to the first end of the third resistor and the second end of the second resistor, the second end of the third resistor is grounded, and the first end of the second resistor is connected to a power supply.

5. The contactor adhesion detection circuit according to claim 3 or 4, characterized in that: The amplifier and the comparator are arranged on the same chip.

6. The contactor adhesion detection circuit according to claim 1, characterized in that: The contactor adhesion detection circuit also includes: The regulating module is arranged between the signal processing module and the control module, and is used to regulate the signal strength output by the signal processing module.

7. The contactor adhesion detection circuit according to claim 6, characterized in that: The regulation module includes: a transistor, a second capacitor and a fourth resistor, the first end of the transistor is connected to the signal processing module, the first end of the second capacitor and the first end of the fourth resistor, the second end of the transistor is connected to the second end of the second capacitor and the second end of the fourth resistor and is grounded, and the third end of the transistor is connected to the control module.

8. The contactor adhesion detection circuit according to claim 1, characterized in that: The acquisition module includes a voltage transformer, a first resistor and a first capacitor. The first end of the voltage transformer is grounded, the second end of the voltage transformer is connected to the live wire output end, the third end of the voltage transformer is connected to the second end of the first resistor and the second end of the first capacitor, and the fourth end of the voltage transformer is connected to the first end of the first resistor and the first end of the first capacitor.

9. The contactor adhesion detection circuit according to claim 8, characterized in that: The acquisition module includes a first sampling resistor and a second sampling resistor, wherein the first end of the first sampling resistor is connected to the live wire output end, the second end of the first sampling resistor is connected to the second end of the voltage transformer, the second end of the second sampling resistor is connected to the first end of the voltage transformer, and the first end of the second sampling resistor is grounded.

10. The contactor adhesion detection circuit according to claim 9, characterized in that: The acquisition module further includes a first diode, a second end of the first diode is connected to a first end of a second sampling resistor, and a first end of the first diode is grounded.

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