Grounding detection device and charging device

Abstract

The utility model discloses a grounding detection device and a charging device, and relates to the technical field of charging control. The grounding detection device is arranged in the charging device, the grounding detection device comprises a control module, a voltage dividing module and a differential voltage sampling module, and the voltage dividing module comprises a switch unit. When the switch unit is switched off, the voltage division module outputs a first sampling voltage after voltage division of the first phase line or the neutral line, when the switch unit is switched on, the voltage division module outputs a second sampling voltage after voltage division of the first phase line or the neutral line and the protective ground line, and the switch unit is switched on or switched off based on a grounding detection signal output by the control module; the differential voltage sampling module performs differential sampling on the first sampling voltage when the switch unit is switched off, and performs differential sampling on the second sampling voltage when the switch unit is switched on; the control module determines a grounding detection result based on the differential sampling result of the first sampling voltage and the differential sampling result of the second sampling voltage. The device can improve the accuracy of grounding detection.

Description

Technical Field

[0001] This application relates to the field of charging control technology, and in particular to a grounding detection device and a charging device. Background Technology

[0002] In the electrical system of a charging device, the grounding system is an essential component. Its main function is to guide current to the earth in the event of a fault, thereby protecting personal safety and preventing accidents such as electrical fires. Currently, the grounding system primarily calculates the grounding resistance by measuring the voltage between the protective ground wire and the neutral wire inside the charging device. The grounding resistance value is then used to determine whether the grounding is adequate. Generally, if the grounding resistance exceeds a preset range, the grounding is considered poor.

[0003] However, in some situations, inferring grounding resistance from grounding voltage for grounding detection is inaccurate. For example, when the neutral line is far away or the current on the neutral line is large, the internal resistance of the neutral line itself may introduce an additional voltage drop, leading to inaccurate measured grounding voltage and thus misjudging the grounding detection even when the grounding is good. Furthermore, in a three-phase system with balanced loads, the current flowing through the neutral line can be very small or zero. In this case, even if the grounding is not good, the grounding voltage cannot be effectively detected, making it impossible to determine the true grounding condition. Moreover, in split-phase power systems, the charging device is not connected to the neutral line, making detection methods based on the voltage between the neutral line and the protective ground line unusable. These are all shortcomings of existing grounding detection schemes. Utility Model Content

[0004] In view of this, the embodiments of this application provide a grounding detection device and a charging device, the main purpose of which is to solve the technical problems of inaccurate grounding detection and limited applicability.

[0005] According to one aspect of this application, a grounding detection device is provided, which is disposed in a charging device. The grounding detection device includes a control module, a voltage divider module, and a differential voltage sampling module. The voltage divider module includes a switching unit, wherein...

[0006] The output terminal of the control module is connected to the control terminal of the switching unit, and is used to respond to the ground detection command and output a ground detection signal.

[0007] The first input terminal of the voltage divider module is connected to the first phase line or neutral line, and the second input terminal is connected to the protective ground line through the switching unit. When the switching unit is open, the voltage divider module outputs the first sampled voltage after the first phase line or neutral line is divided. When the switching unit is on, the voltage divider module outputs the second sampled voltage after the first phase line or neutral line and the protective ground line are divided. The switching unit is turned on or off based on the grounding detection signal.

[0008] The first input terminal of the differential voltage sampling module is connected to the output terminal of the voltage divider module, and the second input terminal is connected to the second phase line or the neutral line. It is used to perform differential sampling of the first sampling voltage when the switching unit is open, and differential sampling of the second sampling voltage when the switching unit is on.

[0009] The input terminal of the control module is connected to the output terminal of the differential voltage sampling module, and is used to determine the grounding detection result based on the differential sampling result of the first sampling voltage and the differential sampling result of the second sampling voltage.

[0010] Optionally, the voltage divider module further includes a first voltage divider branch composed of at least one voltage divider resistor, wherein a first end of the first voltage divider branch serves as the first input terminal of the voltage divider module and is connected to the first phase line, and a second end of the first voltage divider branch serves as the output terminal of the voltage divider module and is connected to the first input terminal of the differential voltage sampling module; when the switching unit is turned on, the voltage divider module further includes a second voltage divider branch composed of a grounding resistor; a first end of the second voltage divider branch serves as the second input terminal of the voltage divider module and is connected to the protective ground line, a second end of the second voltage divider branch is connected to the controlled first terminal of the switching unit, and the controlled second terminal of the switching unit serves as the output terminal of the voltage divider module and is connected to the first input terminal of the differential voltage sampling module.

[0011] Optionally, the first input terminal of the voltage divider module is connected to the first phase line; the voltage divider module is used to output the sampled voltage of the first phase line after voltage division as the first sampled voltage when the switching unit is open, and to output the sampled voltage of the first phase line and the protective ground line after voltage division as the second sampled voltage when the switching unit is on.

[0012] Optionally, the voltage divider module further includes a first voltage divider branch composed of at least one voltage divider resistor and a third voltage divider branch composed of at least one voltage divider resistor. The first end of the first voltage divider branch serves as the first input terminal of the voltage divider module and is connected to the first phase line or neutral line. The second end of the first voltage divider branch serves as the output terminal of the voltage divider module and is connected to the first input terminal of the differential voltage sampling module. The first end of the third voltage divider branch serves as the third input terminal of the voltage divider module and is connected to the second phase line or neutral line. The second end of the third voltage divider branch serves as the output terminal of the voltage divider module and is connected to the first input terminal of the differential voltage sampling module. When the switching unit is turned on, the voltage divider module further includes a second voltage divider branch composed of a grounding resistor. The first end of the second voltage divider branch serves as the second input terminal of the voltage divider module and is connected to the protective ground line. The second end of the second voltage divider branch is connected to the controlled first terminal of the switching unit. The controlled second terminal of the switching unit serves as the output terminal of the voltage divider module and is connected to the first input terminal of the differential voltage sampling module.

[0013] Optionally, the first input terminal of the voltage divider module is connected to the first phase line, and the third input terminal is connected to the second phase line; the voltage divider module is used to output the sampled voltage after the first phase line and the second phase line are divided as the first sampled voltage when the switching unit is open, and to output the sampled voltage after the first phase line, the second phase line, and the protective ground line are divided as the second sampled voltage when the switching unit is on; or, the first input terminal of the voltage divider module is connected to the first phase line, and the third input terminal is connected to the neutral line; the voltage divider module is used to output the sampled voltage after the first phase line and the protective ground line are divided as the second sampled voltage when the switching unit is open. The voltage divider module outputs the voltage after the neutral line is divided as the first sampling voltage, and when the switching unit is turned on, it outputs the voltage after the first phase line, neutral line, and protective ground line are divided as the second sampling voltage; or, the first input terminal of the voltage divider module is connected to the neutral line, and the third input terminal is connected to the second phase line; the voltage divider module is used to output the voltage after the neutral line and second phase line are divided as the first sampling voltage when the switching unit is turned off, and to output the voltage after the neutral line, second phase line, and protective ground line are divided as the second sampling voltage when the switching unit is turned on.

[0014] Optionally, the differential voltage sampling module includes a differential amplification unit composed of an operational amplifier and resistors. The positive input terminal of the differential amplification unit serves as the first input terminal of the differential voltage sampling module and is connected to the output terminal of the voltage divider module. The positive input terminal of the differential amplification unit is also connected to a constant voltage source through a sampling resistor. The negative input terminal of the differential amplification unit serves as the second input terminal of the differential voltage sampling module and is connected to the second phase line or neutral line. The output terminal of the differential amplification unit is connected to the input terminal of the control module.

[0015] Optionally, the negative input terminal of the differential amplifier unit is connected to the second phase line as the second input terminal of the differential voltage sampling module; the differential amplifier unit is used to receive a first differential sampling voltage between the first sampling voltage and the sampling voltage of the second phase line as the differential sampling result of the first sampling voltage when the switch unit is open, and to receive a second differential sampling voltage between the second sampling voltage and the sampling voltage of the second phase line as the differential sampling result of the second sampling voltage when the switch unit is on; or, the negative input terminal of the differential amplifier unit is connected to the neutral line as the second input terminal of the differential voltage sampling module; the differential amplifier unit is used to receive a first differential sampling voltage between the first sampling voltage and the sampling voltage of the neutral line as the differential sampling result of the first sampling voltage when the switch unit is open, and to receive a second differential sampling voltage between the second sampling voltage and the sampling voltage of the neutral line as the differential sampling result of the second sampling voltage when the switch unit is on.

[0016] Optionally, the differential voltage sampling module further includes a first voltage divider unit and a second voltage divider unit, wherein the first voltage divider unit is connected between the output terminal of the voltage divider module and the positive input terminal of the differential amplifier unit; the second voltage divider unit is connected between the second phase line and the negative input terminal of the differential amplifier unit, or the second voltage divider unit is connected between the neutral line and the negative input terminal of the differential amplifier unit.

[0017] Optionally, the differential voltage sampling module further includes a first filtering unit and / or a first protection unit, wherein the first filtering unit is disposed between the negative input terminal and the output terminal of the differential amplifier unit, and / or, the first filtering unit is disposed between the input terminal and the ground terminal of the control module, and / or, the first filtering unit is disposed between the output terminal and the input terminal of the control module; and / or, the first protection unit is disposed between the output terminal and the power supply terminal of the differential amplifier unit, and between the output terminal and the ground terminal of the differential amplifier unit.

[0018] Optionally, the switching unit includes a switching transistor and a switching isolator. The control terminal of the switching transistor is connected to the output terminal of the control module as the control terminal of the switching unit. The control terminal of the switching transistor is also connected to the output terminal of the control module through a voltage divider resistor and to the ground terminal through a voltage divider resistor. The first terminal of the switching transistor is connected to the ground terminal, the second terminal of the switching transistor is connected to the negative input terminal of the switching isolator, and the positive input terminal of the switching isolator is connected to the power supply terminal. The first output terminal of the switching isolator is connected to the protective ground as the controlled first terminal of the switching unit, and the second output terminal of the switching isolator is connected to the first input terminal of the differential voltage sampling module as the controlled second terminal of the switching unit.

[0019] Optionally, the switching unit further includes a second filtering unit and / or a second protection unit, wherein the second filtering unit is disposed between the control terminal and the ground terminal of the switching transistor; and / or, the second protection unit is disposed between the first output terminal and the second output terminal of the switching isolator.

[0020] According to another aspect of this application, a charging device is provided, wherein the charging device is internally provided with the grounding detection device described in any of the above embodiments.

[0021] By employing the above technical solutions, embodiments of this application provide a grounding detection device and a charging device. The grounding detection device includes a control module, a voltage divider module, and a differential voltage sampling module. The voltage divider module includes a switching unit. When the switching unit is open, the voltage divider module outputs a first sampled voltage after the first phase line or neutral line is divided. When the switching unit is on, the voltage divider module outputs a second sampled voltage after the first phase line or neutral line and the protective ground line are divided. The switching unit is turned on or off based on the grounding detection signal output by the control module. The differential voltage sampling module performs differential sampling on the first sampled voltage when the switching unit is open and differential sampling on the second sampled voltage when the switching unit is on. The control module determines the grounding detection result based on the differential sampling results of the first and second sampled voltages. The aforementioned grounding detection device obtains the grounding resistance by measuring the voltage difference between the measured point voltage on the phase line (or neutral line) and the voltage of the measured point voltage after grounding. The difference between the two measurements lies solely in whether grounding has occurred. Therefore, it effectively avoids the influence of power grid imbalance, voltage drop caused by impedance on transmission cables, and internal parameters of the charging device on the grounding detection results, thereby significantly improving the accuracy of grounding detection under different power grid conditions. Furthermore, the aforementioned grounding detection device does not require connection to the neutral line during grounding detection; it can be connected to either the first or second phase line. Therefore, the device is applicable to various power systems, such as TN, TT, and split-phase transformer systems, thus enhancing its versatility and practicality. It solves the problems of difficult and inaccurate grounding detection for charging devices, providing strong protection for the safe use of charging devices.

[0022] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. Attached Figure Description

[0023] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0024] Figure 1 A schematic diagram of the structure of a grounding detection device provided in the prior art is shown;

[0025] Figure 2 A schematic diagram of the structure of a grounding detection device provided in the prior art is shown;

[0026] Figure 3 A schematic diagram of the structure of a grounding detection device provided in an embodiment of this application is shown;

[0027] Figure 4 A schematic diagram of the structure of a grounding detection device provided in an embodiment of this application is shown;

[0028] Figure 5 A schematic diagram of the structure of a grounding detection device provided in an embodiment of this application is shown;

[0029] Figure 6 A schematic diagram of the structure of a grounding detection device provided in an embodiment of this application is shown;

[0030] Figure 7 A schematic diagram of the structure of a grounding detection device provided in an embodiment of this application is shown;

[0031] Figure 8 A circuit connection diagram of a grounding detection device provided in an embodiment of this application is shown. Detailed Implementation

[0032] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0033] Currently, charging devices are typically installed outdoors. Various unforeseen factors, such as movement, natural aging, and improper installation, can all lead to problems with the grounding continuity of the charging device. For example, the grounding wire of a portable charging device may become loose during transportation or installation; the grounding screws of a fixed charging device may rust due to long-term exposure, affecting grounding continuity; and grounding wires may break during construction. All these factors reduce the reliability of the grounding system and increase the risk of electric shock to users.

[0034] To address the grounding continuity issues caused by the aforementioned factors, existing charging devices are typically designed with grounding detection functions. These functions can immediately stop charging and warn the user upon detecting a grounding fault, thus preventing electric shock accidents caused by poor grounding. Figure 1As shown, a grounding detection scheme for a TN grid system is proposed in the prior art. In this scheme, the neutral line N is connected to the protective grounding line PE at the transformer terminal, and the resistance between the charging device and the PE line is denoted as Rground. The charging device contains capacitors C1 to C4 (these capacitors are usually called Y capacitors). At this time, an induced voltage will be generated on the PE line (hereinafter referred to as C_PE) inside the charging device terminal. Theoretically, since the N line and the PE line are connected through the transformer terminal, the voltage difference between the N line and the C_PE line is the voltage drop on Rground. Based on this, the Rground value can be calculated by measuring the voltage Uground between the N line and the C_PE line, thereby assessing the grounding condition.

[0035] However, real-world situations are usually much more complex than theoretical models. For example, ... Figure 2 As shown, there are actually some impedances on the N line, which can be represented by resistors RN1 and RN2. These resistors can interfere with the accuracy of the Uground measurement. Especially when the N line is long, even with good grounding, the measured Uground is relatively large, mainly due to the voltage drop across resistors RN1 and RN2. In this case, if there is a large current flowing on the N line, even under good grounding conditions, misjudgments may occur.

[0036] On the other hand, refer to Figure 1 In a three-phase power supply system, Uground can only be detected when the system is in a certain degree of imbalance, i.e., when current flows through capacitor C4. If the three phases L1, L2, and L3 are all heavily loaded, bringing the system to a balanced state, then even if Rground is disconnected, Uground may be close to zero, making it impossible to correctly identify whether the ground wire is disconnected. For example, when the charging device is idle, L1 and N are powered by the auxiliary power source on the same line. This is reflected in L2 and L3 having no current, only L1 and N having current, thus creating an imbalance. The induced voltage at this time can reach hundreds of volts. However, when the charging device is charging, the charging current is tens of amps, and the auxiliary power source current is in the milliamp range. In comparison, the milliamp current of the auxiliary power source is too small, reducing the imbalance. Therefore, the induced voltage at this time becomes smaller, only a few volts, and even if Rground is disconnected, it cannot be detected. In addition, for scenarios using split-phase transformers (compliant with UL standards), the charging device is only connected to L1, L2, and the PE line, not the neutral line, therefore, grounding detection cannot be performed. Similarly, in DC charging systems, sometimes only phase lines L1, L2, and L3 are connected. In this configuration, grounding detection is impossible because there is no neutral line. In addition, the introduction of the N line will further increase the complexity and cost of cable laying.

[0037] To address the aforementioned problems, this embodiment proposes a grounding detection device, such as... Figure 3 As shown, the above-mentioned device includes a control module 10, a voltage divider module 20, and a differential voltage sampling module 30, wherein the voltage divider module 20 includes a switching unit 21. In this embodiment, the output terminal of the control module 10 is connected to the control terminal of the switching unit 21, and the control module 10 can be used to respond to a grounding detection command and output a grounding detection signal. The first input terminal of the voltage divider module 20 is connected to the first phase line or neutral line, and the second input terminal is connected to the protective ground line through the switching unit 21. When the switching unit 21 is open, the voltage divider module 20 outputs the first sampled voltage after the first phase line or neutral line is divided; when the switching unit 21 is on, the voltage divider module 20 outputs the second sampled voltage after the first phase line or neutral line and the protective ground line are divided, wherein the switching unit 21 is turned on or off based on the grounding detection signal output by the control module 10. Furthermore, the first input terminal of the differential voltage sampling module 30 is connected to the output terminal of the voltage divider module 20, and the second input terminal is connected to the second phase line or neutral line. The differential voltage sampling module 30 can be used to differentially sample the first sampling voltage when the switching unit 21 is open, and to differentially sample the second sampling voltage when the switching unit 21 is on. Finally, the input terminal of the control module 10 is also connected to the output terminal of the differential voltage sampling module 30, and is used to determine the grounding detection result based on the differential sampling results of the first and second sampling voltages. In this embodiment, the above-mentioned grounding detection device can be installed in a charging device, which can be various charging equipment such as AC charging piles, DC charging piles, charging stations, and charging terminals derived from charging stations.

[0038] Specifically, the aforementioned grounding detection device issues a grounding detection command during grounding detection. This command can be issued periodically or initiated by the user. Furthermore, the control module 10 responds to the grounding detection command by outputting a grounding detection signal to the switching unit 21 of the voltage divider module 20, controlling the switching unit 21 to be in an on or off state. In this embodiment, the first input terminal of the voltage divider module 20 is connected to the first phase line or neutral line, and the second input terminal is connected to the protective ground line through the switching unit 21. When the switching unit 21 is in an off state, the voltage divider module 20 divides the voltage of the first phase line or neutral line and outputs a first sampled voltage. At this time, the first input terminal of the differential voltage sampling module 30 receives the first sampled voltage, and the second input terminal is connected to the second phase line or neutral line. Based on this, the differential voltage sampling module 30 can perform differential sampling of the first sampled voltage and the second phase line or neutral line, and then send this differential sampling result to the control module 10. Subsequently, the control module 10 controls the switching unit 21 to conduct. At this time, the voltage divider module 20 performs voltage division processing on the voltage between the first phase line or neutral line and the protective ground line, and outputs the second sampled voltage. Correspondingly, the differential voltage sampling module 30 performs differential sampling on the second sampled voltage and the second phase line or neutral line, and sends this differential sampling result to the control module 10. Finally, the control module 10 can perform comprehensive analysis based on the differential sampling result of the received first sampled voltage and the differential sampling result of the second sampled voltage. For example, it can compare the difference between the two differential sampling results with a preset threshold to determine the grounding detection result, that is, to determine whether the charging device is properly grounded.

[0039] In this embodiment, the voltage divider module 20 can input one voltage signal as a voltage divider branch connected to the voltage divider module, or it can input two voltage signals as two voltage divider branches connected to the voltage divider module. When the voltage divider module 20 inputs one voltage signal, this voltage signal should be a phase line signal. For example, the voltage divider module can connect any one of the signals L1, L2, and L3 to the voltage divider module for grounding detection. When the voltage divider module 20 inputs two voltage signals, the two voltage signals can be a combination of a phase line and a neutral line signal, or a combination of two phase lines signal. For example, the voltage divider module can connect any combination of L1 and neutral line, L2 and neutral line, L3 and neutral line, L1 and L2, L1 and L3, and L2 and L3 to the voltage divider module for grounding detection. Furthermore, when the switch unit 21 is closed, the switch module 20 can also connect the protective ground wire to the voltage divider module 20 as a voltage divider branch. In this way, the voltage divider module 21 can measure the change in phase line voltage after the circuit is connected to the protective ground wire, thus enabling subsequent grounding detection. This circuit connection method allows the grounding detection device to be configured according to different power grid conditions, effectively improving the device's versatility and practicality.

[0040] It should be noted that the circuit connection method and device selection of each circuit module in the above-mentioned grounding detection device can be determined according to the actual situation, and this embodiment does not impose specific limitations. The circuit function of the grounding detection device provided in this embodiment is mainly realized through the circuit connection relationship between each circuit module, and does not depend on the program module in a certain circuit module. In addition, each circuit module can be implemented by analog circuits or by digital circuits, and for circuit modules that can be embedded with program modules, the implementation of their module functions can be achieved by program modules provided by existing technology. For example, in this embodiment, the method of the control module responding to the grounding detection command and outputting the grounding detection signal, and the method of determining the grounding detection result based on the differential sampling result of the first sampling voltage and the differential sampling result of the second sampling voltage, can both be implemented by program modules provided by existing technology, and are not specifically limited here.

[0041] The above embodiments obtain the grounding resistance by comparing the voltage at the measured point on the phase line (or neutral line) with the voltage difference after the measured point voltage on the phase line (or neutral line) is divided by grounding. The difference between the two measurements lies only in whether grounding has occurred. Therefore, it can effectively avoid the influence of power grid imbalance, voltage drop caused by impedance on transmission cables, and internal parameters of the charging device on the grounding detection results, thereby effectively improving the accuracy of grounding detection and the accuracy of detection under different power grid conditions. Furthermore, when performing grounding detection, the above device does not need to be connected to the neutral line; it can be connected to the first and second phase lines instead. Therefore, the above grounding detection device is applicable to various power systems, such as TN systems, TT systems, and split-phase transformer systems, thus improving the versatility and practicality of the grounding detection device. In summary, this solution solves the problems of difficult, inaccurate, and limited applicable scenarios in charging device grounding detection, providing strong protection for the safe use of charging devices.

[0042] In one embodiment, such as Figure 4 As shown, the voltage divider module 20 includes a switching unit 21 and a first voltage divider branch 22 composed of at least one voltage divider resistor. When the switching unit 21 is turned on, the voltage divider module 20 also includes a second voltage divider branch 23 composed of a grounding resistor. In this embodiment, the first end of the first voltage divider branch 22 serves as the first input terminal of the voltage divider module 20 and is connected to the first phase line, and the second end of the first voltage divider branch 22 serves as the output terminal of the voltage divider module 20 and is connected to the first input terminal of the differential voltage sampling module 30. Further, when the switching unit 21 is turned on, the first end of the second voltage divider branch 23 serves as the second input terminal of the voltage divider module 20 and is connected to the protective ground line, the second end of the second voltage divider branch 23 is connected to the controlled first terminal of the switching unit 21, and the controlled second terminal of the switching unit 21 serves as the output terminal of the voltage divider module 20 and is connected to the first input terminal of the differential voltage sampling module 30.

[0043] Specifically, in this embodiment, the voltage divider module 20, in addition to the switching unit 21, also includes a first voltage divider branch 22 composed of at least one voltage divider resistor, and a second voltage divider branch 23 composed of a grounding resistor, which is connected when the switching unit 21 is closed. One end of the first voltage divider branch 22 serves as the input terminal of the voltage divider module 20 and is directly connected to the first phase line, while the other end serves as the output terminal and is connected to the input terminal of the differential voltage sampling module 30. It is used to provide the differential voltage sampling module 30 with a voltage divider signal for the first phase line when the switching unit 21 is open. Further, when the switching unit 21 is closed, the second voltage divider branch 23 is activated. One end of it is connected to the protective ground line, and the other end is connected to one controlled terminal of the switching unit 21. Simultaneously, the other controlled terminal of the switching unit 21 serves as the output of the voltage divider module 20 and is connected to the differential voltage sampling module 30, providing the differential voltage sampling module 30 with a voltage divider signal between the first phase line and the protective ground line.

[0044] The above embodiment, by incorporating a switching unit, a first voltage divider branch, and a second voltage divider branch within the voltage divider module, can achieve flexible voltage division processing of the first phase line voltage and the protective ground line voltage by combining the switching function of the switching unit. This circuit effectively improves the accuracy of grounding detection, avoids interference from external factors on the grounding detection results, and enhances the stability and reliability of the system. Furthermore, this circuit does not require connection to a neutral line, effectively reducing circuit costs. Simultaneously, it is flexibly applicable to various power system environments such as TN systems, TT systems, and split-phase transformer systems, exhibiting strong versatility and flexibility.

[0045] In one embodiment, such as Figure 4 As shown, the first input terminal of the voltage divider module 20 is connected to the first phase line. In this connection mode, the voltage divider module can output the sampled voltage of the first phase line after voltage division as the first sampled voltage when the switch unit 21 is off, and output the sampled voltage of the first phase line and the protective ground line after voltage division as the second sampled voltage when the switch unit 21 is on.

[0046] Specifically, in this embodiment, the first input terminal of the voltage divider module 20 is connected to the first phase line. With this connection, when the switch unit 21 is in the off state, the voltage divider module 20 divides the voltage of the first phase line and outputs the divided sampled voltage, i.e., the first sampled voltage; when the switch unit 21 is on, the voltage divider module 20 divides the voltage between the first phase line and the protective ground line and outputs the divided sampled voltage, i.e., the second sampled voltage. This circuit connection allows the voltage divider module 20 to flexibly adjust its output according to the state of the switch unit 21 and provides the necessary voltage signal for the subsequent differential voltage sampling module.

[0047] The above embodiment, by connecting the first input terminal of the voltage divider module to the first phase line, enables precise voltage sampling of the first phase line voltage and the voltage between the first phase line and the protective ground line. This circuit improves the accuracy of grounding detection and avoids safety hazards caused by poor grounding. Furthermore, this circuit is applicable to various power system environments, exhibiting strong versatility and adaptability.

[0048] In one embodiment, such as Figures 5 to 7 As shown, the voltage divider module 20 includes a switching unit 21, a first voltage divider branch 22 composed of at least one voltage divider resistor, and a third voltage divider branch 24 composed of at least one voltage divider resistor. When the switching unit 21 is turned on, the voltage divider module 20 also includes a second voltage divider branch 23 composed of a grounding resistor. In this embodiment, the first end of the first voltage divider branch 22 serves as the first input terminal of the voltage divider module 20 and is connected to the first phase line or neutral line, and the second end of the first voltage divider branch 22 serves as the output terminal of the voltage divider module 20 and is connected to the first input terminal of the differential voltage sampling module 30. The first end of the third voltage divider branch 24 serves as the third input terminal of the voltage divider module 20 and is connected to the second phase line or neutral line, and the second end of the third voltage divider branch 24 serves as the output terminal of the voltage divider module 20 and is connected to the first input terminal of the differential voltage sampling module 30. Furthermore, when the switching unit 21 is turned on, the first end of the second voltage divider branch 23 is connected to the protective ground as the second input terminal of the voltage divider module 20, the second end of the second voltage divider branch 23 is connected to the controlled first terminal of the switching unit 21, and the controlled second terminal of the switching unit 21 is connected to the first input terminal of the differential voltage sampling module 30 as the output terminal of the voltage divider module 20.

[0049] Specifically, in this embodiment, the voltage divider module 20 includes, in addition to the switching unit 21, a first voltage divider branch 22 composed of at least one voltage divider resistor, a third voltage divider branch 24 composed of at least one voltage divider resistor, and a second voltage divider branch 23 composed of a grounding resistor connected when the switching unit 21 is turned on. For example, referring to... Figure 8 The voltage divider module may include a switching unit consisting of a switching transistor Q45 and a switching isolator U43, a first voltage divider branch consisting of voltage divider resistors R750, R751 and R752, a third voltage divider branch consisting of voltage divider resistors R753, R754 and R755, and a second voltage divider branch consisting of a grounding resistor R747 connected when both the switching transistor Q45 and the switching isolator U43 are turned on.

[0050] In this embodiment, the first end of the first voltage divider branch 22 serves as the first input terminal of the voltage divider module 20 and is connected to the first phase line or neutral line. Its second end serves as the output terminal of the voltage divider module 20 and is connected to the first input terminal of the differential voltage sampling module 30. Simultaneously, the first end of the third voltage divider branch 24 serves as the third input terminal of the voltage divider module 20 and is connected to the second phase line or neutral line. Its second end also serves as the output terminal of the voltage divider module 20 and is connected to the first input terminal of the differential voltage sampling module 30. Furthermore, when the switching unit 21 is turned on, the first end of the second voltage divider branch 23 serves as the second input terminal of the voltage divider module 20 and is connected to the protective ground line. Its second end is connected to the controlled first terminal of the switching unit 21. The controlled second terminal of the switching unit 21 then serves as the output terminal of the voltage divider module 20 and is again connected to the first input terminal of the differential voltage sampling module 30. Through the above circuit, the voltage divider module 20 can adjust the voltage divider path according to the state of the switching unit 21, thereby outputting different sampling voltages.

[0051] The above embodiments, by incorporating a switching unit and multiple voltage divider branches within the voltage divider module, enable precise voltage sampling of the first phase line or neutral line, the second phase line or neutral line, and the protective ground line voltage. By connecting multiple voltage divider branches for sampling, the circuit can more accurately determine the grounding status of the power system, improving detection accuracy and reliability. Furthermore, the circuit offers good flexibility and adaptability, allowing for adjustments to its connection method based on different power system environments, thus enhancing the flexibility of the device's application.

[0052] In one embodiment, such as Figure 5 As shown, the first input terminal of the voltage divider module 20 is connected to the first phase line, and the third input terminal is connected to the second phase line. In this connection configuration, the voltage divider module 20 can be used to output the sampled voltage after the first and second phase lines are divided as the first sampled voltage when the switching unit 21 is open, and to output the sampled voltage after the first phase line, the second phase line, and the protective ground line are divided as the second sampled voltage when the switching unit 21 is on. Alternatively, as... Figure 6 As shown, the first input terminal of the voltage divider module 20 is connected to the first phase line, and the third input terminal is connected to the neutral line. In this connection configuration, the voltage divider module 20 can be used to output the sampled voltage after the first phase line and neutral line are divided as the first sampled voltage when the switching unit 21 is open, and to output the sampled voltage after the first phase line, neutral line, and protective ground line are divided as the second sampled voltage when the switching unit 21 is on. Alternatively, as... Figure 7As shown, the first input terminal of the voltage divider module 20 is connected to the neutral line, and the third input terminal is connected to the second phase line. In this connection configuration, the voltage divider module 20 can be used to output the sampled voltage after the neutral line and the second phase line are divided as the first sampled voltage when the switching unit 21 is open, and to output the sampled voltage after the neutral line, the second phase line, and the protective ground line are divided as the second sampled voltage when the switching unit 21 is on.

[0053] Specifically, in this embodiment, the voltage divider module 20 has a first input terminal and a third input terminal. The first input terminal can be connected to the first phase line or the neutral line, and the third input terminal can be connected to the second phase line or the neutral line. The second terminals of the first voltage divider branch (connected to the first phase line or the neutral line) and the third voltage divider branch (connected to the second phase line and the neutral line) are both connected to the measured point. The voltage at the measured point is used as the output of the voltage divider module. That is, by using the same components and second-terminal connection points for the first and third voltage divider branches, the first and third terminals of the first and third voltage divider branches, i.e., the first and third input terminals of the voltage divider module 20, are interchangeable. In this way, users can complete voltage detection without following specific rules when wiring, resulting in high fault tolerance and simple operation. Furthermore, when the switch unit 21 is in the open state, the voltage divider module 20 can output the voltage sampling voltage between the first phase line and the second phase line, the first phase line and the neutral line, or the neutral line and the second phase line, i.e., the first sampling voltage, depending on the connection of the input terminals. When the switching unit 21 is turned on, the voltage divider module 20 can include the protective ground wire in the voltage division range and output a voltage divider sampling voltage that includes the first phase wire, the second phase wire, the neutral wire (depending on the input connection), and the protective ground wire, i.e., the second sampling voltage. Through the above circuit connection method, the voltage divider module 20 can flexibly adjust its output according to different power system configurations and detection requirements, thereby providing strong data support for subsequent voltage sampling and grounding status judgment.

[0054] The above embodiments, by designing different circuit connection methods for the voltage divider module, can achieve accurate voltage sampling of multi-phase line voltages and protective ground voltages in the power system. Based on this, the circuit can effectively improve the accuracy and reliability of voltage monitoring, avoiding safety hazards caused by poor grounding. Secondly, by setting the constituent components and second-terminal connection points of the first and third voltage divider branches to be the same, the fault tolerance rate for user installation can be increased, simplifying installation. Furthermore, the circuit has high versatility and adaptability, suitable for different power system configurations and monitoring needs, and provides strong protection for the safe operation of the power system.

[0055] In one embodiment, such as Figure 8As shown, the differential voltage sampling module includes a differential amplification unit composed of an operational amplifier U44B and resistors. The resistors include a feedback resistor R764 between the negative input and output terminals of the operational amplifier U44B. The positive input terminal of the differential amplification unit serves as the first input terminal of the differential voltage sampling module and is connected to the output terminal of the voltage divider module. The positive input terminal of the differential amplification unit is also connected to a constant voltage source Vref via a sampling resistor R760. The negative input terminal of the differential amplification unit serves as the second input terminal of the differential voltage sampling module and is connected to the second phase line or neutral line. The output terminal of the differential amplification unit is connected to the input terminal PE_DET_AD of the control module.

[0056] Specifically, in this embodiment, the positive input terminal of the differential amplifier unit is connected to the output terminal of the voltage divider module and serves as its first input terminal to receive one voltage signal. Simultaneously, its positive input terminal is also connected to a constant voltage source Vref through a sampling resistor R760 to ensure the stability and accuracy of the input signal. Furthermore, the negative input terminal of the differential amplifier unit serves as its second input terminal, connected to the second phase line or neutral line, and is used to receive another voltage signal. In this embodiment, the output signal of the differential amplifier unit can be output to the input terminal PE_DET_AD of the control module for subsequent processing and analysis.

[0057] The above embodiment, by setting a differential amplifier unit in the differential voltage sampling module, can effectively amplify the voltage difference between the two input terminals while suppressing common-mode signal interference, thereby improving the signal-to-noise ratio of the sampled signal. Furthermore, the negative input terminal of the differential amplifier unit is connected as the second input terminal to the second phase line or neutral line, and the positive input terminal is connected as the first input terminal to the first phase line or neutral line. Since the voltage values ​​of the phase line or neutral line are related to the voltage system of the preceding stage, using the phase line and neutral line as the reference voltage of the negative input terminal is stable. If the ground line is used as the reference voltage, it will be unstable due to the induced voltage at the left end of the grounding resistor R747 being affected by changes in the power grid state, leading to inaccurate measurements. Therefore, the above circuit, by setting the phase line or neutral line as the negative input terminal of the differential amplifier unit and setting the voltage of the phase line or neutral line as the differential reference voltage, can enhance the stability and reliability of the input signal, enabling the differential voltage sampling module to operate stably in complex electrical environments. In addition, introducing a constant voltage source Vref can adjust the output voltage of the operational amplifier to the sampling range of the MCU.

[0058] In one embodiment, such as Figure 5 and Figure 7As shown, the negative input terminal of the differential amplifier unit is connected to the second phase line as the second input terminal of the differential voltage sampling module 30. In this connection method, the differential amplifier unit can be used to receive the first differential sampling voltage between the first sampling voltage and the sampling voltage of the second phase line as the differential sampling result of the first sampling voltage when the switching unit 21 is open, and to receive the second differential sampling voltage between the second sampling voltage and the sampling voltage of the second phase line as the differential sampling result of the second sampling voltage when the switching unit 21 is on. Alternatively, as... Figure 6 As shown, the negative input terminal of the differential amplifier unit is connected to the neutral line as the second input terminal of the differential voltage sampling module 30. In this connection configuration, the differential amplifier unit can receive the first differential sampling voltage between the first sampling voltage and the sampling voltage of the neutral line as the differential sampling result of the first sampling voltage when the switch unit 21 is open, and receive the second differential sampling voltage between the second sampling voltage and the sampling voltage of the neutral line as the differential sampling result of the second sampling voltage when the switch unit 21 is on.

[0059] Specifically, in this embodiment, the negative input terminal of the differential amplifier unit serves as the second input terminal of the differential voltage sampling module 30, which can be connected to the second phase line (such as...). Figure 5 and Figure 7 (as shown), it can also be connected to the neutral line (such as...) Figure 6 (As shown). When the negative input terminal of the differential amplifier unit is connected to the second phase line, the differential amplifier unit can acquire the first differential sampling voltage between the first sampling voltage and the second phase line voltage when the switch unit 21 is in the off state, and use this as the differential sampling result of the first sampling voltage. When the switch unit 21 is on, the differential amplifier unit can acquire the second differential sampling voltage between the second sampling voltage and the second phase line voltage, and use this as the differential sampling result of the second sampling voltage. If the negative input terminal of the differential amplifier unit is changed to be connected to the neutral line, then under different states of the switch unit 21, the differential amplifier unit will acquire the differential voltage between the first sampling voltage and the neutral line voltage, and the differential voltage between the second sampling voltage and the neutral line voltage, respectively, and use these as the corresponding differential sampling results.

[0060] The above embodiment enables differential sampling of two different sampling voltages by flexibly connecting the differential amplifier unit to the second phase line or the neutral line. This circuit not only improves the accuracy and stability of voltage sampling and effectively suppresses common-mode noise interference, but also allows the system to accurately acquire the differential voltage between the sampling voltage and the reference voltage (second phase line or neutral line) under different switching unit states, thus providing reliable data support for subsequent grounding detection.

[0061] In one embodiment, the differential voltage sampling module further includes a first voltage divider unit and a second voltage divider unit. The first voltage divider unit is connected between the output terminal of the voltage divider module and the positive input terminal of the differential amplifier unit, and the second voltage divider unit is connected between the second phase line and the negative input terminal of the differential amplifier unit; alternatively, the second voltage divider unit is connected between the neutral line and the negative input terminal of the differential amplifier unit.

[0062] Specifically, the first voltage divider unit is connected between the output terminal of the voltage divider module and the positive input terminal of the differential amplifier unit, thus serving as a voltage divider. The second voltage divider unit is connected between the second phase line (or neutral line, depending on the specific design) and the negative input terminal of the differential amplifier unit, also serving as a voltage divider. In this embodiment, the first and second voltage divider units are symmetrically arranged, a design that ensures the balance and stability of the circuit. For example, referring to... Figure 8 The first voltage divider unit consists of resistors R756, R757, and R758 connected in series, and the second voltage divider unit consists of resistors R761, R762, and R763 connected in series. These resistors collectively reduce the voltage on the phase line or neutral line, thus ensuring that the voltage input to the differential amplifier unit is sufficiently low so that the voltage output from the differential amplifier unit conforms to the MCU's sampling range. The sampling resistor R760 and the feedback resistor R764 also contribute to the voltage division, ensuring that the output voltage of the differential amplifier unit conforms to the MCU's sampling range. The differential voltage sampling module also includes a current limiting unit, which is implemented by the filter resistor R759. The current limiting unit prevents excessive current from entering the MCU, thus avoiding damage to the MCU.

[0063] The above embodiments, by introducing a first voltage divider unit and a second voltage divider unit, can gradually reduce the high voltage to a range that the MCU can sample. The gradual voltage reduction using multiple resistors avoids the problem of excessively large resistor size caused by a single resistor performing voltage reduction. The current limiting unit controls the output current of the differential amplifier unit, thereby preventing MCU damage or performance degradation due to excessive current.

[0064] In one embodiment, the differential voltage sampling module further includes a first isolation unit and a second isolation unit. The first isolation unit is connected in series with the first voltage divider unit between the output terminal of the voltage divider module and the positive input terminal of the differential amplifier unit. The second isolation unit is connected in series with the second voltage divider unit between the second phase line and the negative input terminal of the differential amplifier unit, or the second isolation unit is connected in series with the second voltage divider unit between the neutral line and the negative input terminal of the differential amplifier unit.

[0065] Specifically, the first isolation unit and the first voltage divider unit are connected in series between the output of the voltage divider module and the positive input of the differential amplifier unit, serving both isolation and voltage division functions. Similarly, the second isolation unit and the second voltage divider unit are connected in series between the second phase line (or neutral line, depending on the specific design) and the negative input of the differential amplifier unit, also achieving signal isolation and voltage division. In this embodiment, the first and second isolation units are symmetrically arranged, ensuring circuit balance and stability. For example, referring to… Figure 8 The first isolation unit can be composed of isolation capacitor C474, and the second isolation unit can be composed of isolation capacitor C475. As electrical isolation devices, they have high-voltage withstand characteristics. Furthermore, the first voltage divider unit is composed of resistors R756, R757, and R758 connected in series, and the second voltage divider unit is composed of resistors R761, R762, and R763 connected in series. These resistors collectively reduce the voltage on the phase line or neutral line, thereby ensuring that the voltage input to the differential amplifier unit is low enough so that the voltage output from the differential amplifier unit conforms to the sampling range of the MCU. The sampling resistor R760 and the feedback resistor R764 also have a voltage divider effect, ensuring that the output voltage of the differential amplifier unit conforms to the sampling range of the MCU.

[0066] The differential voltage sampling module also includes a current limiting unit, which is provided by a filter resistor R759. The current limiting unit is used to prevent excessive current from entering the MCU, which could damage the MCU.

[0067] The above embodiments, by introducing a first isolation unit, a first voltage divider unit, a second isolation unit, a second voltage divider unit, and a current limiting unit, can significantly improve the reliability and safety of the differential voltage sampling module. Specifically, the voltage divider unit uses multiple resistors to gradually reduce the high voltage to a voltage range that the MCU can sample; this gradual voltage reduction by multiple resistors avoids the problem of excessively large resistor size caused by a single resistor performing voltage reduction. The isolation unit effectively provides electrical isolation between the high and low voltage levels. The current limiting unit controls the output current of the differential amplifier unit, thereby preventing MCU damage or performance degradation due to excessive current.

[0068] In one embodiment, the differential voltage sampling module further includes a first filtering unit and / or a first protection unit. The first filtering unit is disposed between the negative input terminal and the output terminal of the differential amplifier unit, and / or between the input terminal and the ground terminal of the control module, and / or between the output terminal of the differential amplifier unit and the input terminal of the control module. Alternatively, the first protection unit is disposed between the output terminal and the power supply terminal of the differential amplifier unit, and also between the output terminal and the ground terminal of the differential amplifier unit.

[0069] Specifically, the first filtering unit can be located between the negative input and output terminals of the differential amplifier unit, and / or between the input and ground terminals of the control module, and / or between the output terminal of the differential amplifier unit and the input terminal of the control module, and is used to filter out high-frequency noise and interference in the sampled signal, thereby improving the purity and stability of the signal. Furthermore, the first protection unit can be located at the output terminal of the differential amplifier unit to protect the differential amplifier unit from damage. For example, referring to... Figure 8 The filtering unit includes filter capacitors C476 and C477, and filter resistor R759. Filter capacitor C477 can be used alone or in combination with filter resistor R759 and another filter capacitor C476 to form a low-pass filter circuit, filtering out high-frequency noise in the signal. Furthermore, a diode D95 is connected between the differential amplifier circuit and the power supply and ground terminals. By using diode D95, in case of abnormal output signal conditions, such as excessively high or low voltage, the diode can be turned on or off, protecting the differential amplifier unit from damage and enhancing the circuit's reliability and safety.

[0070] The above embodiments, by incorporating a first filtering unit and a first protection unit into the differential voltage sampling module, can significantly improve the performance and reliability of the module. The first filtering unit effectively filters out high-frequency noise and interference in the sampled signal, improving signal purity and stability. The first protection unit enhances the module's protection capabilities and can promptly cut off or limit harmful currents in abnormal situations, protecting the differential amplifier unit and other circuit components from damage and extending the module's lifespan.

[0071] In one embodiment, such as Figure 8 As shown, the switching unit includes a switching transistor and a switching isolator. The control terminal of the switching transistor serves as the control terminal of the switching unit and is connected to the output terminal of the control module. The control terminal of the switching transistor is also connected to the output terminal of the control module and to the ground terminal via a voltage divider resistor. The first terminal of the switching transistor is connected to the ground terminal, the second terminal of the switching transistor is connected to the negative input terminal of the switching isolator, the positive input terminal of the switching isolator is connected to the power supply terminal, the first output terminal of the switching isolator serves as the first controlled terminal of the switching unit and is connected to the protective ground wire, and the second output terminal of the switching isolator serves as the second controlled terminal of the switching unit and is connected to the first input terminal of the differential voltage sampling module.

[0072] Specifically, such as Figure 8As shown, the switching unit can be designed using a combination of switching transistors and switching isolation devices. The control terminal of the switching transistor Q45 serves as the control terminal of the switching unit, connected to the output terminal PE_DET_CTR of the control module, and used to receive ground detection signals to achieve switching action. Simultaneously, the control terminal of the switching transistor Q45 is also connected to the output terminal PE_DET_CTR of the control module through voltage divider resistor R746, and to the ground terminal through voltage divider resistor R749. The voltage divider resistors divide the ground detection signal, reducing the voltage at the output terminal PE_DET_CTR of the control module, thereby controlling whether the switching transistor Q45 is turned on, and thus controlling whether the switching isolation device is turned on. At the same time, resistors R746 and R749 provide a release path when external signal interference generates high voltage on the capacitor, guiding it to the ground terminal, preventing the switching transistor Q45 from turning on. Therefore, resistors R746 and R749 also have the function of maintaining system stability. Furthermore, the first terminal of the switching transistor Q45 is grounded, and the second terminal is connected to the negative input terminal of the switching isolator U43. The positive input terminal of the switching isolator U43 is connected to the power supply terminal VCC through a current-limiting resistor R748 to ensure that the current is reasonably limited when the switch is activated, protecting the diode in the switching isolator U43 from damage by large currents. The first output terminal of the switching isolator U43, as the first controlled terminal of the switching unit, is connected to the protective ground, and the second output terminal, as the second controlled terminal of the switching unit, is connected to the first input terminal of the differential voltage sampling module and is used to transmit voltage signals when the switch is turned on.

[0073] The above embodiments, by incorporating a switching transistor and a switching isolation device in the switching unit, enable flexible control of the input signals to the control module. The voltage divider resistor reduces the voltage surge of the control signal on the switching transistor, improving the reliability of the switching unit. Simultaneously, the switching isolation device provides electrical isolation and enhances system safety, preventing current leakage or short circuits due to faults.

[0074] In one embodiment, such as Figure 8 As shown, the switching unit further includes a second filtering unit and / or a second protection unit. The second filtering unit is disposed between the control terminal and the ground terminal of the switching transistor, and / or the second protection unit is disposed between the first output terminal and the second output terminal of the switching isolator.

[0075] Specifically, such as Figure 8 As shown, the switching unit also includes a second filtering unit and / or a second protection unit. The second filtering unit is located between the control terminal and the ground terminal of the switching transistor Q45. It can be used to filter out high-frequency noise and interference in the control signal and ensure that the switching transistor Q45 can receive a stable and accurate ground detection signal, such as... Figure 8The filter capacitor C473 is used in the circuit. The second protection unit is located between the first and second output terminals of the switching isolator U43. When an abnormal voltage occurs at the output terminal of the switching isolator U43, such as excessively high voltage, it limits the abnormal voltage to a safe range through the breakdown and conduction of the bidirectional breakdown diode, thus protecting subsequent circuits from damage. Figure 8 The bidirectional breakdown diode D94 in the middle.

[0076] The above embodiments, by incorporating a second filtering unit and a second protection unit into the switching unit, can significantly improve the performance and reliability of the switching unit. The second filtering unit effectively filters out high-frequency noise and interference in the control signal, ensuring that the switching transistor receives clear and accurate control commands, thereby improving the accuracy and stability of the switching action. The second protection unit enhances the self-protection capability of the switching unit and can respond promptly to abnormal voltage conditions, limiting the abnormal voltage to a safe range, thus preventing circuit damage or safety accidents caused by excessive voltage.

[0077] In one embodiment, a charging device is provided, which includes the grounding detection device described in any of the above embodiments. In this embodiment, the charging device can be an AC charging station, a DC charging station, a charging pile, a charging terminal derived from the charging pile, or other charging equipment. For specific implementations of the charging device, please refer to the grounding detection device described in any of the above embodiments, which will not be repeated here.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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.

[0079] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A grounding detection device, characterized in that, The grounding detection device is installed in the charging device. The grounding detection device includes a control module, a voltage divider module, and a differential voltage sampling module. The voltage divider module includes a switching unit. The output terminal of the control module is connected to the control terminal of the switching unit, and is used to respond to the ground detection command and output a ground detection signal. The first input terminal of the voltage divider module is connected to the first phase line or neutral line, and the second input terminal is connected to the protective ground line through the switching unit. When the switching unit is open, the voltage divider module outputs the first sampled voltage after the first phase line or neutral line is divided. When the switching unit is on, the voltage divider module outputs the second sampled voltage after the first phase line or neutral line and the protective ground line are divided. The switching unit is turned on or off based on the grounding detection signal. The first input terminal of the differential voltage sampling module is connected to the output terminal of the voltage divider module, and the second input terminal is connected to the second phase line or the neutral line. It is used to perform differential sampling of the first sampling voltage when the switching unit is open, and differential sampling of the second sampling voltage when the switching unit is on. The input terminal of the control module is connected to the output terminal of the differential voltage sampling module, and is used to determine the grounding detection result based on the differential sampling result of the first sampling voltage and the differential sampling result of the second sampling voltage.

2. The grounding detection device according to claim 1, characterized in that, The voltage divider module further includes a first voltage divider branch consisting of at least one voltage divider resistor, wherein, The first end of the first voltage divider branch is connected to the first phase line as the first input terminal of the voltage divider module, and the second end of the first voltage divider branch is connected to the first input terminal of the differential voltage sampling module as the output terminal of the voltage divider module. When the switching unit is turned on, the voltage divider module further includes a second voltage divider branch composed of a grounding resistor; the first end of the second voltage divider branch is connected to the protective ground wire as the second input terminal of the voltage divider module, the second end of the second voltage divider branch is connected to the controlled first terminal of the switching unit, and the controlled second terminal of the switching unit is connected to the first input terminal of the differential voltage sampling module as the output terminal of the voltage divider module.

3. The grounding detection device according to claim 2, characterized in that, The first input terminal of the voltage divider module is connected to the first phase line; the voltage divider module is used to output the sampled voltage of the first phase line after voltage division as the first sampled voltage when the switching unit is open, and to output the sampled voltage of the first phase line and the protective ground line after voltage division as the second sampled voltage when the switching unit is on.

4. The grounding detection device according to claim 1, characterized in that, The voltage divider module further includes a first voltage divider branch composed of at least one voltage divider resistor, and a third voltage divider branch composed of at least one voltage divider resistor, wherein, The first end of the first voltage divider branch is connected to the first phase line or neutral line as the first input terminal of the voltage divider module, and the second end of the first voltage divider branch is connected to the first input terminal of the differential voltage sampling module as the output terminal of the voltage divider module. The first end of the third voltage divider branch is connected to the second phase line or neutral line as the third input terminal of the voltage divider module, and the second end of the third voltage divider branch is connected to the first input terminal of the differential voltage sampling module as the output terminal of the voltage divider module. When the switching unit is turned on, the voltage divider module further includes a second voltage divider branch composed of a grounding resistor; the first end of the second voltage divider branch is connected to the protective ground wire as the second input terminal of the voltage divider module, the second end of the second voltage divider branch is connected to the controlled first terminal of the switching unit, and the controlled second terminal of the switching unit is connected to the first input terminal of the differential voltage sampling module as the output terminal of the voltage divider module.

5. The grounding detection device according to claim 4, characterized in that, The voltage divider module has its first input terminal connected to the first phase line and its third input terminal connected to the second phase line. When the switching unit is open, the voltage divider module outputs a sampled voltage (after the first and second phase lines are divided) as a first sampled voltage; and when the switching unit is closed, it outputs a sampled voltage (after the first, second, and protective ground lines are divided) as a second sampled voltage. Alternatively... The voltage divider module has its first input terminal connected to the first phase line and its third input terminal connected to the neutral line. When the switching unit is open, the voltage divider module outputs a sampled voltage (after the first phase line and neutral line are divided) as a first sampled voltage; and when the switching unit is closed, it outputs a sampled voltage (after the first phase line, neutral line, and protective ground line are divided) as a second sampled voltage. Alternatively... The first input terminal of the voltage divider module is connected to the neutral line, and the third input terminal is connected to the second phase line. The voltage divider module is used to output the sampled voltage after the neutral line and the second phase line are divided as the first sampled voltage when the switching unit is open, and to output the sampled voltage after the neutral line, the second phase line and the protective ground line are divided as the second sampled voltage when the switching unit is on.

6. The grounding detection device according to any one of claims 1 to 5, characterized in that, The differential voltage sampling module includes a differential amplification unit composed of an operational amplifier and resistors, wherein, The positive input terminal of the differential amplifier unit is connected to the output terminal of the voltage divider module as the first input terminal of the differential voltage sampling module. The positive input terminal of the differential amplifier unit is also connected to a constant voltage source through a sampling resistor. The negative input terminal of the differential amplifier unit is connected to the second phase line or neutral line as the second input terminal of the differential voltage sampling module; the output terminal of the differential amplifier unit is connected to the input terminal of the control module.

7. The grounding detection device according to claim 6, characterized in that, The negative input terminal of the differential amplifier unit is connected to the second phase line as the second input terminal of the differential voltage sampling module; the differential amplifier unit is used to receive a first differential sampling voltage between the first sampling voltage and the sampling voltage of the second phase line as the differential sampling result of the first sampling voltage when the switching unit is open, and to receive a second differential sampling voltage between the second sampling voltage and the sampling voltage of the second phase line as the differential sampling result of the second sampling voltage when the switching unit is on; or... The negative input terminal of the differential amplifier unit is connected to the neutral line as the second input terminal of the differential voltage sampling module. The differential amplifier unit is used to receive the first differential sampling voltage between the first sampling voltage and the sampling voltage of the neutral line as the differential sampling result of the first sampling voltage when the switch unit is off, and to receive the second differential sampling voltage between the second sampling voltage and the sampling voltage of the neutral line as the differential sampling result of the second sampling voltage when the switch unit is on.

8. The grounding detection device according to claim 6, characterized in that, The differential voltage sampling module further includes a first voltage divider unit and a second voltage divider unit, wherein... The first voltage divider unit is connected between the output terminal of the voltage divider module and the positive input terminal of the differential amplifier unit; The second voltage divider unit is connected between the second phase line and the negative input terminal of the differential amplifier unit, or the second voltage divider unit is connected between the neutral line and the negative input terminal of the differential amplifier unit.

9. The grounding detection device according to claim 6, characterized in that, The differential voltage sampling module further includes a first filtering unit and / or a first protection unit, wherein, The first filtering unit is disposed between the negative input terminal and the output terminal of the differential amplifier unit, and / or, the first filtering unit is disposed between the input terminal and the ground terminal of the control module, and / or, the first filtering unit is disposed between the output terminal of the differential amplifier unit and the input terminal of the control module; and / or, The first protection unit is disposed between the output terminal and the power supply terminal of the differential amplifier unit, and between the output terminal and the ground terminal of the differential amplifier unit.

10. The grounding detection device according to claim 1, characterized in that, The switching unit includes a switching transistor and a switching isolation device, wherein, The control terminal of the switching transistor is connected to the output terminal of the control module as the control terminal of the switching unit. The control terminal of the switching transistor is also connected to the output terminal of the control module through a voltage divider resistor, and to the ground terminal through a voltage divider resistor. The first terminal of the switching transistor is connected to the ground terminal, the second terminal of the switching transistor is connected to the negative input terminal of the switching isolation device, and the positive input terminal of the switching isolation device is connected to the power supply terminal. The first output terminal of the switch isolation device is connected to the protective ground as the first controlled terminal of the switch unit, and the second output terminal of the switch isolation device is connected to the first input terminal of the differential voltage sampling module as the second controlled terminal of the switch unit.

11. The grounding detection device according to claim 10, characterized in that, The switching unit further includes a second filtering unit and / or a second protection unit, wherein, The second filter unit is disposed between the control terminal and the ground terminal of the switching transistor; and / or, The second protection unit is disposed between the first output terminal and the second output terminal of the switch isolation device.

12. A charging device, characterized in that, The charging device is internally equipped with a grounding detection device as described in any one of claims 1 to 11.

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