Differential detection system for a high voltage dc bus and vehicle

Abstract

The application provides a differential detection system of a high-voltage direct-current bus and a vehicle, the system comprising a differential sampling circuit, a first operational amplifier, an isolation circuit and a signal processing circuit; the differential sampling circuit is connected with a positive electrode and a negative electrode of the high-voltage direct-current bus and grounded; the inverting input end of the first operational amplifier is connected with the differential sampling circuit and the output end of the first operational amplifier, and the non-inverting input end of the first operational amplifier is connected with the negative electrode of the high-voltage direct-current bus and the common ground of the differential sampling circuit; the isolation circuit is connected with the first operational amplifier and the differential sampling circuit, and is connected with a power supply voltage and grounded; the signal processing circuit is connected with the isolation circuit, and the signal processing circuit determines the voltage of the high-voltage direct-current bus based on the output current of the isolation circuit. The system performs double-end sampling on the voltage of the high-voltage direct-current bus through differential sampling, has high sampling accuracy, high anti-interference ability, and is provided with the isolation circuit, and thus has high overall use safety.

Description

Technical Field

[0001] This application relates to the field of voltage detection technology, and more specifically, to a differential detection system and vehicle for a high-voltage DC bus. Background Technology

[0002] The energy source for electric vehicles is a high-voltage battery, which transmits direct current (DC) to various electrical devices in the vehicle via a high-voltage direct current bus (HV). To ensure power supply reliability, the voltage of the HV bus needs to be monitored.

[0003] When the voltage of a high-voltage DC bus is detected using a non-isolated detection method in related technologies, the electrical connection between the detection circuit and the circuit under test poses certain safety hazards. In addition, the detection circuit usually uses single-ended sampling, which has weak anti-interference ability and low measurement accuracy. Utility Model Content

[0004] This application provides a differential detection system and vehicle for DC buses, aiming to solve the problems of certain safety hazards, low anti-interference ability and low measurement accuracy when non-isolated detection is used in related technologies.

[0005] In a first aspect, a differential detection system for a high-voltage direct current (HVDC) bus is provided. The differential detection system includes a differential sampling circuit, a first operational amplifier, an isolation circuit, and a signal processing circuit. The first terminal of the differential sampling circuit is connected to the positive terminal of the HVDC bus, the second terminal of the differential sampling circuit is connected to the negative terminal of the HVDC bus, and the third and fourth terminals of the differential sampling circuit are grounded. The differential sampling circuit is used to output a first output voltage. The inverting input terminal of the first operational amplifier is connected to the fourth terminal of the differential sampling circuit and the output terminal of the first operational amplifier to receive the first output voltage. The non-inverting input terminal of the first operational amplifier is connected to the negative terminal of the HVDC bus and the fourth terminal of the differential sampling circuit, all sharing a common ground. The first terminal of the isolation circuit is connected to the output terminal of the first operational amplifier, the inverting input terminal of the first operational amplifier, the fourth terminal of the differential sampling circuit, and the second terminal of the isolation circuit. The third terminal of the isolation circuit is connected to a power supply voltage, and the fourth terminal of the isolation circuit is grounded. The signal processing circuit is connected to the isolation circuit and is used to determine the voltage of the HVDC bus based on the output current of the isolation circuit.

[0006] In the above technical solution, the differential sampling circuit simultaneously measures both the positive and negative terminals of the high-voltage DC bus and calculates the voltage difference between them to output a first output voltage with high sampling accuracy, resulting in high measurement precision. Furthermore, when simultaneously measuring the positive and negative terminals of the high-voltage DC bus using the differential sampling circuit, common-mode noise is suppressed, exhibiting strong anti-interference capabilities. This allows it to output a stable first output voltage to the first operational amplifier, ensuring the reliability of subsequent circuits' detection based on this first output voltage. The first output voltage output by the differential sampling circuit is input to the first operational amplifier, which amplifies it before outputting it to the isolation circuit. This improves the reliability of the voltage connected to the isolation circuit, thereby enhancing the reliability of the output current generated by the isolation circuit based on this voltage. Further, this improves the reliability of subsequent signal processing circuits in determining the voltage of the high-voltage DC bus based on this output current. Thus, this differential detection system can perform dual-terminal isolated detection of the high-voltage DC bus voltage, promptly detecting voltage anomalies with high detection accuracy and reliability. Secondly, by setting up an isolation circuit, electrical isolation between the high-voltage side circuit and the low-voltage side circuit can be achieved, so as to avoid the voltage of the high-voltage DC bus being directly applied to the low-voltage side circuit, which would cause damage to the low-voltage side circuit. While ensuring that the low-voltage side circuit can be used normally, the overall safety of the differential detection system is improved, thereby further ensuring the testing reliability of the differential detection system.

[0007] In conjunction with the first aspect, in some possible implementations, the differential sampling circuit includes a first sampling module, a second sampling module, a second operational amplifier, a first resistor, and a second resistor; one end of the first sampling module serves as the first terminal of the differential sampling circuit and is connected to the positive terminal of the high-voltage DC bus; one end of the second sampling module serves as the second terminal of the differential sampling circuit and is connected to the negative terminal of the high-voltage DC bus; the non-inverting input terminal of the second operational amplifier is connected to the other end of the first sampling module, the inverting input terminal of the second operational amplifier is connected to the other end of the second sampling module, and the output terminal of the second operational amplifier serves as the fourth terminal of the differential sampling circuit and is connected to the inverting input terminal of the first operational amplifier; one end of the first resistor is connected to the non-inverting input terminal of the second operational amplifier and the other end of the first sampling module, and the other end of the first resistor serves as the third terminal of the differential sampling circuit and is grounded; one end of the second resistor is connected to the inverting input terminal of the second operational amplifier and the other end of the second sampling module, and the other end of the second resistor is connected to the common ground of the output terminal of the second operational amplifier.

[0008] In the above technical solution, the first sampling module is used to measure the positive voltage of the high-voltage DC bus, and the second sampling module is used to measure the negative voltage of the high-voltage DC bus. Simultaneously, the first and second sampling modules form a voltage divider network, which divides the voltage between the positive and negative terminals of the high-voltage DC bus, providing a stable intermediate potential, i.e., voltage difference. Compared to acquiring single-ended voltage, acquiring dual-ended voltage through the voltage divider network formed by the first and second sampling modules has higher sampling reliability. Secondly, the high-voltage DC bus is a high-voltage system. The voltage divider resistor network formed by the first and second sampling modules can proportionally attenuate the high voltage to a range that the second operational amplifier can handle, avoiding damage to the second operational amplifier caused by directly connecting the high voltage, which would affect the accuracy of subsequent measurements. In other words, setting up the first and second sampling modules improves measurement reliability. After the second operational amplifier receives the voltage difference from the first and second sampling modules, it amplifies and converts it into a single-ended voltage (i.e., the first output voltage Vin), and then outputs it to the first operational amplifier, thereby improving the reliability of the signal received by the first operational amplifier.

[0009] Combining the first aspect and the above implementation methods, in some possible implementation methods, the first sampling module includes multiple third resistors connected in series; the end of the first third resistor that is not connected to the third resistor serves as one end of the first sampling module and is connected to the positive terminal of the high voltage DC bus, and the end of the last third resistor that is not connected to the third resistor serves as the other end of the first sampling module and is connected to the non-inverting input terminal of the second operational amplifier and one end of the first resistor.

[0010] And / or,

[0011] The second sampling module includes multiple fourth resistors connected in series; the end of the first fourth resistor that is not connected to any other fourth resistor serves as one end of the second sampling module and is connected to the negative terminal of the high-voltage DC bus, while the end of the last fourth resistor that is not connected to any other fourth resistor serves as the other end of the second sampling module and is connected to the inverting input terminal of the second operational amplifier and one end of the second resistor.

[0012] In the above technical solution, multiple resistors connected in series sample the voltage of the high-voltage DC bus and adjust the voltage of the high-voltage DC bus according to a precise ratio. Furthermore, the circuit structure of the first and second sampling modules, composed of multiple resistors connected in series, is simple, highly reliable, and easy to maintain and debug.

[0013] In combination with the first aspect and the above implementation methods, in some possible implementation methods, the isolation circuit includes a fifth resistor and a linear optocoupler; one end of the fifth resistor serves as the third terminal of the isolation circuit and is connected to the power supply voltage; the linear optocoupler includes a light-emitting diode, a first photodiode, and a second photodiode; the positive terminal of the light-emitting diode is connected to the other end of the fifth resistor; the negative terminal of the light-emitting diode serves as the first terminal of the isolation circuit and is connected to the output terminal of the first operational amplifier, the inverting input terminal of the first operational amplifier, the output terminal of the second operational amplifier, and the negative terminal of the first photodiode; the negative terminal of the first photodiode serves as the second terminal of the isolation circuit; the positive terminal of the first photodiode serves as the fourth terminal of the isolation circuit and is grounded; and the second photodiode is connected to the signal processing circuit.

[0014] In the above technical solution, the linear optocoupler transmits information via optical signals, achieving complete electrical isolation between the high-voltage side circuit (i.e., the differential sampling circuit and the first operational amplifier) ​​and the low-voltage side circuit (i.e., the signal processing circuit), thereby improving the safety of the low-voltage side circuit. The fifth resistor, acting as a feedback resistor, is connected between the output of the first operational amplifier and the first photodiode to form negative feedback and a closed-loop control system, ensuring the stability of the current output to the first photodiode. Furthermore, the linear optocoupler has a fast response time and maintains high linearity between its input and output. This allows it to provide a precise output current to the signal processing circuit based on the output of the differential sampling circuit and the first operational amplifier, ensuring the accuracy and reliability of the signal processing circuit's voltage detection of the high-voltage DC bus based on this output current. Moreover, compared to dedicated isolation amplifier chips, the linear optocoupler has a lower cost.

[0015] In combination with the first aspect and the above implementation methods, in some possible implementation methods, the differential detection system further includes a sixth resistor, one end of which is connected to the output terminal of the second operational amplifier and the other end of the second resistor, and the other end of which is connected to the negative terminal of the light-emitting diode, the output terminal of the first operational amplifier, the inverting input terminal of the first operational amplifier, and the negative terminal of the first photodiode.

[0016] In the above technical solution, the sixth resistor is a current-limiting resistor, used to limit the current output from the second operational amplifier to the first operational amplifier, to avoid the problem of overcurrent damage to the first operational amplifier, and to improve the reliability and service life of the first operational amplifier.

[0017] In combination with the first aspect and the above implementation methods, in some possible implementation methods, the differential detection system further includes a first capacitor, the first plate of the first capacitor is connected to one end of the sixth resistor, the output terminal of the second operational amplifier and the other end of the second resistor, and the second plate of the first capacitor is connected to the non-inverting input terminal of the first operational amplifier and the negative terminal of the high voltage DC bus to ground.

[0018] In the above technical solution, the first capacitor can filter the signal output by the second operational amplifier to filter out high-frequency spike pulses in the circuit, prevent the circuit from oscillating, improve the integrity and accuracy of the first output voltage output to the first operational amplifier, and improve the detection reliability of the subsequent circuit and the differential detection system.

[0019] In combination with the first aspect and the above implementation, in some possible implementations, the differential detection system further includes a second capacitor. The first plate of the second capacitor is connected to the other end of the sixth resistor, the inverting input of the first operational amplifier, and the negative terminal of the first photodiode. The second plate of the second capacitor is connected to the output of the first operational amplifier and the negative terminal of the light-emitting diode.

[0020] In the above technical solution, the second capacitor can filter the signal connected to the first operational amplifier and the isolation circuit to filter out high-frequency spike pulses in the circuit, prevent the circuit from oscillating, improve the integrity and accuracy of the signal connected to the first operational amplifier and the isolation circuit, and improve the detection reliability of the differential detection system.

[0021] In combination with the first aspect and the above implementation methods, in some possible implementation methods, the signal processing circuit includes a voltage conversion unit and a microcontroller unit; the first terminal of the voltage conversion unit is connected to the positive terminal of the second photodiode, the second terminal of the voltage conversion unit is connected to the negative terminal of the second photodiode, and the voltage conversion unit is used to output a second output voltage; the microcontroller unit is connected to the third terminal of the voltage conversion unit, and the microcontroller unit is used to determine the voltage of the high voltage DC bus based on the two output voltages.

[0022] In the above technical solution, the voltage conversion unit converts the output current of the second photodiode into voltage, enabling the voltage conversion unit to output a second output voltage to the microcontroller unit. The microcontroller unit then performs digital-to-analog conversion on the second output voltage to determine the voltage of the high-voltage DC bus. Thus, by converting current into a second output voltage through the voltage conversion unit, and then performing digital-to-analog conversion on this second output voltage through the microcontroller unit to determine the corresponding voltage of the high-voltage DC bus, accurate detection of the high-voltage DC bus voltage is achieved. This allows for timely detection of voltage anomalies, enabling subsequent operators to take appropriate remedial measures based on the anomaly, ensuring stable vehicle operation.

[0023] In combination with the first aspect and the above implementation methods, in some possible implementation methods, the differential detection system also includes a Zener diode, with the positive terminal of the Zener diode grounded and the negative terminal of the Zener diode connected to the third terminal of the voltage conversion unit and the microcontroller unit.

[0024] In the above technical solution, the Zener diode can operate in the reverse breakdown region. When the voltage across its terminals exceeds the set Zener voltage, it is worth noting that the Zener diode is connected to ground and a second output voltage respectively. The ground voltage is a stable voltage. That is, when the second output voltage is overvoltage, the Zener diode will conduct and clamp the voltage at the Zener voltage to limit the voltage. The Zener diode ensures that the second output voltage received by the microcontroller is always within a safe operating range, preventing damage to the microcontroller from overvoltage and ensuring the reliability of the microcontroller's use and detection. Secondly, the Zener diode has a fast response speed to voltage changes, quickly clamping transient voltage spikes or short-term overvoltage situations to effectively protect the microcontroller.

[0025] Secondly, this application also provides a vehicle including the differential detection system described in any of the optional embodiments of the first aspect, wherein the differential detection system is connected to a high-voltage DC bus. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the module structure of a differential detection system provided in an embodiment of this application;

[0027] Figure 2 This is a schematic diagram of the circuit structure of a differential detection system provided in an embodiment of this application;

[0028] Figure 3 This is a schematic diagram of the circuit structure of another differential detection system provided in an embodiment of this application;

[0029] Figure 4 This is a schematic diagram of the circuit structure of another differential detection system provided in the embodiments of this application;

[0030] Figure 5 This is a schematic diagram of the circuit structure of another differential detection system provided in the embodiments of this application;

[0031] Figure 6 This is a schematic diagram of the circuit structure of another differential detection system provided in the embodiments of this application;

[0032] Figure 7 This is a schematic diagram of the circuit structure of another differential detection system provided in the embodiments of this application;

[0033] Figure 8 This is a schematic diagram of the circuit structure of another differential detection system provided in the embodiments of this application;

[0034] Figure 9 This is a schematic diagram of the circuit structure of another differential detection system provided in the embodiments of this application.

[0035] In the attached figures, the following labels are used:

[0036] 1. Differential detection system; 11. Differential sampling circuit; 111. First sampling module; 112. Second sampling module; 12. Isolation circuit; 13. Signal processing circuit; 131. Voltage conversion unit; 132. Microcontroller unit;

[0037] HV, High Voltage DC Bus; U1, First Operational Amplifier; U2, Second Operational Amplifier; U3, Third Operational Amplifier; U4, Fourth Operational Amplifier; U5, Linear Optocoupler; R1, First Resistor; R2, Second Resistor; R3, Third Resistor; R4, Fourth Resistor; R5, Fifth Resistor; R6, Sixth Resistor; R7, Seventh Resistor; R8, Eighth Resistor; R9, Ninth Resistor; C1, First Capacitor; C2, Second Capacitor; C3, Third Capacitor; C4, Fourth Capacitor; Dz, Zener Diode; LED, Light Emitting Diode; PD1, First Photodiode; PD2, Second Photodiode; Vin, First Output Voltage; Vout, Second Output Voltage. Detailed Implementation

[0038] The technical solutions in this application will be clearly and thoroughly described below with reference to the accompanying drawings. In the description of the embodiments of this application, unless otherwise stated, " / " means "or," for example, A / B can mean A or B. "And / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, in the description of the embodiments of this application, "multiple" refers to two or more than two.

[0039] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0040] Electric vehicles are increasingly favored by consumers due to their intelligence, low noise, and superior power performance, and are widely used in various fields, replacing traditional gasoline vehicles. Unlike gasoline vehicles, electric vehicles are powered by high-voltage batteries. These batteries transmit DC power to various electrical devices in the vehicle via a high-voltage DC bus, such as the motor drive, air conditioning, and positive temperature coefficient (PTC) heaters. To ensure reliable power supply and prevent damage to electrical equipment caused by excessively high or low voltage on the high-voltage DC bus, it is necessary to monitor the voltage of the high-voltage DC bus.

[0041] Currently, there are two types of high-voltage DC bus voltage detection methods: isolated and non-isolated. Most isolated detection methods in related technologies employ dedicated isolation amplifier chips to electrically isolate the detection circuit and the circuit under test, effectively preventing electrical connection between the high-voltage DC bus and the low-voltage detection circuit. However, isolation amplifiers are relatively expensive, resulting in a high cost for isolated detection solutions, making them unsuitable for cost-sensitive vehicle models, such as low-end vehicles or auxiliary systems.

[0042] In related technologies, non-isolated detection methods for measuring the voltage of high-voltage DC buses do not require expensive isolation amplifier chips, resulting in a simpler circuit structure and lower cost, making them suitable for cost-sensitive vehicle models. However, with non-isolated detection, the detection circuit is electrically connected to the circuit under test, and the voltage of the high-voltage DC bus is directly applied to the low-voltage side circuit. This may damage the low-voltage circuit, affecting its normal operation, and in severe cases, even causing injury to operators, posing certain safety hazards.

[0043] Secondly, the detection circuits in related technologies usually use single-ended sampling, such as using a single-ended resistor to sample the voltage of the high-voltage DC bus. However, single-ended resistor sampling has weak anti-interference capability and low measurement accuracy.

[0044] Therefore, this application provides a differential detection system and vehicle for a high-voltage DC bus. The system performs dual-end sampling of the voltage of the high-voltage DC bus through differential sampling, which has high sampling accuracy, strong anti-interference ability, and is equipped with an isolation circuit, resulting in high overall system safety.

[0045] The differential detection system and vehicle for the high-voltage DC bus provided in this application are described below with reference to the accompanying drawings.

[0046] This application provides a vehicle comprising a high-voltage electrical system and a low-voltage electrical system. The high-voltage electrical system includes a high-voltage battery (e.g., a power battery) to power high-power electrical equipment (e.g., motors, inverters, and other high-voltage components) within the vehicle, enabling normal vehicle operation. The low-voltage electrical system includes a low-voltage battery (e.g., a 12V battery) and a DC-DC converter (DCDC). The DC-DC converter converts the high-voltage electricity from the high-voltage battery to low-voltage electricity to meet the signal transmission / control requirements of the vehicle; further details are omitted here.

[0047] High-voltage batteries typically supply power to high-power electrical equipment via a high-voltage DC bus. When the voltage of the high-voltage DC bus is too high or too low, it can damage the connected high-power equipment, posing a safety hazard. Therefore, the vehicle provided in this application is also equipped with a differential detection system. This system can accurately detect the voltage of the high-voltage DC bus to determine whether the voltage is normal, thereby ensuring the reliability of the power supply to the electrical equipment.

[0048] In order for the differential detection system 1 provided in this application to detect the voltage of the high-voltage DC bus HV, in one example, such as Figure 1 As shown, the differential detection system 1 includes a differential sampling circuit 11, a first operational amplifier U1, an isolation circuit 12, and a signal processing circuit 13.

[0049] The first terminal of the differential sampling circuit 11 is connected to the positive terminal HV+ of the high-voltage DC bus HV, and the second terminal of the differential sampling circuit 11 is connected to the negative terminal HV- of the high-voltage DC bus HV. The third and fourth terminals of the differential sampling circuit 11 are grounded. The inverting input terminal of the first operational amplifier U1 is connected to the fourth terminal of the differential sampling circuit 11 and the output terminal of the first operational amplifier U1. The non-inverting input terminal of the first operational amplifier U1 is connected to the negative terminal of the high-voltage DC bus HV and the fourth terminal of the differential sampling circuit 11, all sharing a common ground. The first terminal of the isolation circuit 12 is connected to the output terminal of the first operational amplifier U1, the inverting input terminal of the first operational amplifier U1, the fourth terminal of the differential sampling circuit 11, and the second terminal of the isolation circuit 12. The third terminal of the isolation circuit 12 is connected to the power supply voltage, and the fourth terminal of the isolation circuit 12 is grounded. The signal processing circuit 13 is connected to the isolation circuit 12.

[0050] The differential sampling circuit 11 is used to acquire the voltage of the high-voltage DC bus HV. Specifically, the first and second terminals of the differential sampling circuit 11 are connected to the positive terminal HV+ and the negative terminal HV- of the high-voltage DC bus HV, respectively, resulting in a voltage difference ΔV between the first and second terminals. The differential sampling circuit 11 outputs a first output voltage Vin based on this voltage difference ΔV. This first output voltage Vin is the voltage corresponding to the high-voltage DC bus HV acquired by the differential sampling circuit 11. Thus, the differential sampling circuit 11 simultaneously measures the signal of the high-voltage DC bus HV through both the first and second input terminals and calculates the voltage difference ΔV between them, outputting a first output voltage Vin with high sampling accuracy. Compared to single-ended voltage acquisition, dual-ended measurement offers higher accuracy. Furthermore, when the positive terminal HV+ and negative terminal HV- of the high-voltage DC bus HV are measured simultaneously by the differential sampling circuit 11, if there is the same noise in the two input signals, the noise will be canceled to improve the signal-to-noise ratio, suppress common-mode noise, and have strong anti-interference ability. This enables it to output a stable first output voltage Vin to the subsequent circuit (i.e., the first operational amplifier U1) to ensure the reliability of the detection of the subsequent circuit based on the first output voltage Vin.

[0051] The inverting input of the first operational amplifier U1 is connected to the fourth terminal of the differential sampling circuit 11 to receive the voltage processed by the differential sampling circuit 11. This voltage is then amplified and output to the isolation circuit 12 to improve the reliability of the signal received by the isolation circuit 12. The isolation circuit 12 generates a corresponding output current based on the amplified voltage and outputs it to the signal processing circuit 13. This allows the signal processing circuit 13 to determine the voltage of the high-voltage DC bus HV based on the output current of the isolation circuit 12, thereby achieving isolated detection of the high-voltage DC bus HV.

[0052] The pre-stage circuit of the isolation circuit 12 (i.e., the differential sampling circuit 11 and the first operational amplifier U1) is the high-voltage side circuit, and the post-stage circuit of the isolation circuit 12 (i.e., the signal processing circuit 13) is the low-voltage side circuit. The isolation circuit 12 electrically isolates the high-voltage side circuit from the low-voltage side circuit, preventing the voltage of the high-voltage DC bus HV from being directly applied to the low-voltage side circuit and causing damage. This ensures the normal operation of the low-voltage side circuit and improves the safety of the differential detection system 1.

[0053] It is worth noting that the inverting input terminal of the first operational amplifier U1 is connected to its output terminal, meaning that negative feedback is introduced into the first operational amplifier U1. An ideal operational amplifier exhibits two phenomena: virtual open circuit and virtual short circuit. Under virtual open circuit, the input impedance of the ideal operational amplifier is infinite, therefore the current flowing into the two input terminals of the first operational amplifier U1 is zero, i.e., the input current of the first operational amplifier U1 is zero. Under virtual short circuit, when the ideal operational amplifier operates in the linear region, the voltages at the two input terminals of the first operational amplifier U1 are equal, i.e., both are zero. Therefore, the current flowing through the differential sampling circuit 11 will directly flow to the second terminal of the isolation circuit 12 to ensure the stability of the output current.

[0054] In this example, the differential sampling circuit 11 simultaneously measures both the positive terminal HV+ and the negative terminal HV- of the high-voltage DC bus HV, and calculates the voltage difference ΔV between them to output a first output voltage Vin with high sampling accuracy. Furthermore, when the differential sampling circuit 11 simultaneously measures both the positive and negative terminals HV+ and HV- of the high-voltage DC bus HV, it can suppress common-mode noise and has strong anti-interference capabilities, enabling it to output a stable first output voltage Vin to the first operational amplifier U1. This ensures the reliability of subsequent circuits' detection based on this first output voltage Vin. The first output voltage Vin output by the differential sampling circuit 11 is input to the first operational amplifier U1, which amplifies it before outputting it to the isolation circuit 12. This improves the reliability of the voltage connected to the isolation circuit 12, thereby improving the reliability of the corresponding output current generated by the isolation circuit 12 based on this voltage. Furthermore, this improves the reliability of the subsequent signal processing circuit 13 in determining the voltage of the high-voltage DC bus HV based on this output current. Thus, the differential detection system 1 can perform dual-terminal isolation detection of the voltage of the high-voltage DC bus HV, enabling timely detection of voltage anomalies with high accuracy and reliability. Secondly, the isolation circuit 12 achieves electrical isolation between the high-voltage and low-voltage side circuits, preventing the voltage of the high-voltage DC bus HV from being directly applied to the low-voltage side circuit and causing damage. This ensures the normal operation of the low-voltage side circuit while improving the overall safety of the differential detection system 1, further guaranteeing its testing reliability.

[0055] In order for the differential sampling circuit 11 provided in this application to simultaneously sample the positive terminal HV+ and the negative terminal HV- of the high-voltage DC bus HV, in one example, such as Figure 2As shown, the differential sampling circuit 11 includes a first sampling module 111, a second sampling module 112, a second operational amplifier U2, a first resistor R1, and a second resistor R2. One end of the first sampling module 111 serves as the first terminal of the differential sampling circuit 11 and is connected to the positive terminal HV+ of the high-voltage DC bus HV. One end of the second sampling module 112 serves as the second terminal of the differential sampling circuit 11 and is connected to the negative terminal HV- of the high-voltage DC bus HV. The non-inverting input terminal of the second operational amplifier U2 is connected to the other end of the first sampling module 111, and the inverting input terminal of the second operational amplifier U2 is connected to the other end of the second sampling module 112. The output terminal of the second operational amplifier U2 serves as the fourth terminal of the differential sampling circuit 11 and is connected to the inverting input terminal of the first operational amplifier U1. One end of the first resistor R1 is connected to the non-inverting input terminal of the second operational amplifier U2 and the other end of the first sampling module 111, and the other end of the first resistor R1 serves as the third terminal of the differential sampling circuit 11 and is grounded. One end of the second resistor R2 is connected to the inverting input terminal of the second operational amplifier U2 and the other end of the second sampling module 112, and the other end of the second resistor R2 is connected to the output terminal of the second operational amplifier U2.

[0056] In this example, the first sampling module 111 measures the positive terminal HV+ voltage of the high-voltage DC bus HV, and the second sampling module 112 measures the negative terminal HV- voltage of the high-voltage DC bus HV. Simultaneously, the first sampling module 111 and the second sampling module 112 form a voltage divider network, which divides the voltage between the positive terminal HV+ and the negative terminal HV- of the high-voltage DC bus HV, providing a stable intermediate potential, i.e., the voltage difference ΔV. Compared to acquiring single-ended voltage, acquiring dual-ended voltage through the voltage divider network formed by the first sampling module 111 and the second sampling module 112 has higher sampling reliability. Secondly, since the high-voltage DC bus HV is a high-voltage system, the voltage divider resistor network formed by the first sampling module 111 and the second sampling module 112 can proportionally attenuate the high voltage to a range that the second operational amplifier U2 can handle. This avoids the problem of damage to the second operational amplifier U2 when directly connected to high voltage, which would affect the accuracy of subsequent measurements. In other words, setting up the first sampling module 111 and the second sampling module 112 improves measurement reliability.

[0057] After the second operational amplifier U2 is connected to the voltage difference ΔV between the first sampling module 111 and the second sampling module 112, it amplifies the voltage and converts it into a single-ended voltage (i.e., the first output voltage Vin), and then outputs it to the first operational amplifier U1 to improve the reliability of the signal connected to the first operational amplifier U1.

[0058] Optional, such as Figure 3As shown, the first sampling module 111 includes multiple third resistors R3 connected in series. The end of the first third resistor R3 that is not connected to any other third resistor R3 serves as one end of the first sampling module 111 and is connected to the positive terminal of the high-voltage DC bus HV. The end of the last third resistor R3 that is not connected to any other third resistor R3 serves as the other end of the first sampling module 111 and is connected to the non-inverting input terminal of the second operational amplifier U2 and one end of the first resistor R1. The multiple third resistors R3 connected in series sample the positive terminal HV+ voltage of the high-voltage DC bus HV. By using the multiple third resistors R3 connected in series, the voltage of the high-voltage DC bus HV can be adjusted proportionally. Furthermore, the circuit structure of the first sampling module 111, composed of multiple third resistors R3 connected in series, is simple, highly reliable, and easy to maintain and debug.

[0059] Optional, such as Figure 3 As shown, the second sampling module 112 includes multiple fourth resistors R4 connected in series. The end of the first fourth resistor R4 not connected to any other resistor serves as one end of the second sampling module 112 and is connected to the negative terminal of the high-voltage DC bus HV. The end of the last fourth resistor R4 not connected to any other resistor serves as the other end of the second sampling module 112 and is connected to the inverting input terminal of the second operational amplifier U2 and one end of the second resistor R2. The multiple fourth resistors R4 connected in series sample the negative terminal HV- voltage of the high-voltage DC bus HV, allowing for precise adjustment of the high-voltage DC bus HV voltage. Furthermore, the circuit structure of the second sampling module 112, composed of multiple fourth resistors R4 connected in series, is simple, highly reliable, and easy to maintain and debug.

[0060] To ensure the sampling synchronization of the first sampling module 111 and the second sampling module 112, the third resistor R3 and the fourth resistor R4 are set in the same number. For example, Figure 3 As shown, the first sampling module 111 in this application is provided with three third resistors R3, and the second sampling module 112 is provided with three fourth resistors R4. It should be noted that the first sampling module 111 and the second sampling module 112 may also include other numbers of third resistors R3 and fourth resistors R4; this application does not impose specific limitations on this. This application only uses the differential detection circuit 11, which includes three third resistors R3 and three fourth resistors R4 connected in series, as an example for illustration.

[0061] When the differential detection circuit 11 includes three third resistors R3 and three fourth resistors R4 connected in series, such as Figure 3As shown, the voltage difference ΔV is the voltage difference between nodes H and V. By setting the second resistor R2, the second operational amplifier U2 has negative feedback. Utilizing the virtual short characteristic of the op-amp, it can be known that the voltages at the non-inverting and inverting input terminals of the second operational amplifier U2 are equal. Combining this with the virtual open characteristic of the op-amp, the voltage difference ΔV can be obtained according to formula (1):

[0062] ΔV=Vhv*(R3+R4) / (R3+R3+R3+R4+R4+R4) (1)

[0063] Wherein, Vhv is the voltage between the positive terminal HV+ and the negative terminal HV- of the high-voltage DC bus HV, R3 in (R3+R4) is the resistance value of the third resistor connected to the non-inverting input terminal of the second operational amplifier U2, R4 is the resistance value of the fourth resistor connected to the inverting input terminal of the second operational amplifier U2, and R3 in (R3+R3+R3+R4+R4+R4) is the resistance value of each third resistor connected in series, and R4 is the resistance value of each fourth resistor connected in series.

[0064] Assuming the resistance of the third resistor R3, connected to the non-inverting input of the second operational amplifier U2, is equal to the resistance of the fourth resistor R4, connected to the inverting input of the second operational amplifier U2, and the resistances of the first resistor R1 and the second resistor R2 are equal, then formula (2) is derived:

[0065] Vin=ΔV (2)

[0066] Wherein, Vin is the voltage of the first output voltage.

[0067] Thus, the voltage difference ΔV at the input of the second operational amplifier U2 is equal to the first output voltage Vin of the second operational amplifier U2.

[0068] In order for the isolation circuit 12 to generate a corresponding output current based on the signal output from the preceding circuit, in one example, such as Figure 4As shown, the isolation circuit 12 includes a fifth resistor R5 and a linear optocoupler U5. One end of the fifth resistor R5 serves as the third terminal of the isolation circuit 12, connected to the power supply voltage. The linear optocoupler U5 includes a light-emitting diode (LED), a first photodiode (PD) PD1, and a second photodiode PD2. The positive terminal of the LED is connected to the other end of the fifth resistor R5, and the negative terminal of the LED serves as the first terminal of the isolation circuit 12, connected to the output terminal of the first operational amplifier U1, the inverting input terminal of the first operational amplifier U1, the output terminal of the second operational amplifier U2, and the negative terminal of the first photodiode PD1. The negative terminal of the first photodiode PD1 serves as the second terminal of the isolation circuit 12, and the positive terminal of the first photodiode PD1 serves as the fourth terminal of the isolation circuit 12, grounded. The second photodiode PD2 is connected to the signal processing circuit 13.

[0069] In this example, the linear optocoupler U5 transmits information via optical signals, achieving complete electrical isolation between the high-voltage side circuit (i.e., the differential sampling circuit 11 and the first operational amplifier U1) and the low-voltage side circuit (i.e., the signal processing circuit 13), thereby improving the safety of the low-voltage side circuit. The fifth resistor R5, acting as a feedback resistor, is connected between the output of the first operational amplifier U1 and the first photodiode PD1 to form negative feedback and a closed-loop control system, ensuring the stability of the current output to the first photodiode PD1. Furthermore, the linear optocoupler U5 has a fast response time and maintains high linearity between its input and output. This allows it to provide a precise output current to the signal processing circuit 13 based on the outputs of the differential sampling circuit 11 and the first operational amplifier U1, ensuring the accuracy and reliability of the signal processing circuit 13's detection of the voltage Vhv of the high-voltage DC bus HV based on this output current. Moreover, compared to dedicated isolation amplifier chips, the linear optocoupler U5 has a lower cost.

[0070] In one example, such as Figure 5 As shown, the differential detection system 1 also includes a sixth resistor R6. One end of the sixth resistor R6 is connected to the output terminal of the second operational amplifier U2 and the other end of the second resistor R2. The other end of the sixth resistor R6 is connected to the negative terminal of the light-emitting diode LED, the output terminal of the first operational amplifier U1, the inverting input terminal of the first operational amplifier U1, and the negative terminal of the first photodiode PD1.

[0071] In this example, the sixth resistor R6 is a current-limiting resistor, used to limit the current output from the second operational amplifier U2 to the first operational amplifier U1, to avoid the problem of overcurrent damage to the first operational amplifier U1, and to improve the reliability and service life of the first operational amplifier U1.

[0072] Assuming the current in the LED is If, the current generated in the first photodiode PD1 is I1, the current generated in the second photodiode PD2 is I2, and the typical value of the transmission gain k of the linear optocoupler U5 is 1. The inverting input terminal of the first operational amplifier U1 is connected to the output terminal of the first operational amplifier U1, that is, the first operational amplifier U1 introduces negative feedback. According to the two phenomena of virtual open and virtual short of ideal operational amplifiers, the input voltage of the first operational amplifier U1 is equal, both being 0. Therefore, the current flowing through the sampling circuit 11 will flow directly to the negative terminal of the second photodiode PD2. At this time, the current I1 generated in the first photodiode PD1 can be obtained according to formula (3):

[0073] I1=Vin / R6 (3)

[0074] Where Vin is the voltage of the first output voltage, and R6 is the resistance of the sixth resistor. At this time, the current I1 on the first photodiode PD1 depends only on the value of the first output voltage Vin and the value of the sixth resistor R6, and is independent of the light output characteristics of the light-emitting diode LED.

[0075] Correspondingly, the current I2 generated on the second photodiode PD2 can be obtained according to formula (4):

[0076] I2=K*I1 (4)

[0077] Where K is the transmission gain of the linear optocoupler, and K = 1. This corresponds to the current I2 of the second photodiode PD2, which is the output current of the isolation circuit 12, and this output current is then output to the subsequent circuit.

[0078] To improve the reliability of the first output voltage Vin from the second operational amplifier U2 to the first operational amplifier U1, in one example, such as Figure 5 As shown, the differential detection system 1 also includes a first capacitor C1. The first plate of the first capacitor C1 is connected to one end of the sixth resistor R6, the output terminal of the second operational amplifier U2, and the other end of the second resistor R2. The second plate of the first capacitor C1 is connected to the non-inverting input terminal of the first operational amplifier U1 and the negative terminal HV- of the high-voltage DC bus HV, which are grounded together.

[0079] In this example, the first capacitor C1 can filter the signal output by the second operational amplifier U2 to filter out high-frequency spike pulses in the circuit, prevent the circuit from oscillating, and improve the integrity and accuracy of the first output voltage Vin output to the first operational amplifier U1, thereby improving the detection reliability of the subsequent circuit and the differential detection system 1.

[0080] To improve the reliability of the signals connected to the isolation circuit 12, in one example, such as Figure 5As shown, the differential detection system 1 also includes a second capacitor C2. The first plate of the second capacitor C2 is connected to the other end of the sixth resistor R6, the inverting input terminal of the first operational amplifier U1, and the negative terminal of the first photodiode PD1. The second plate of the second capacitor C2 is connected to the output terminal of the first operational amplifier U1 and the negative terminal of the light-emitting diode LED.

[0081] In this example, the second capacitor C2 can filter the signals connected to the first operational amplifier U1 and the isolation circuit 12 to filter out high-frequency spike pulses in the circuit, prevent the circuit from oscillating, improve the integrity and accuracy of the signals connected to the first operational amplifier U1 and the isolation circuit 12, and improve the detection reliability of the differential detection system 1.

[0082] In order for the signal processing circuit 13 to determine the voltage of the high-voltage DC bus HV based on the output current of the isolation circuit 12, in one example, such as Figure 6 As shown, the signal processing circuit 13 includes a voltage conversion unit 131 and a microcontroller unit 132. The first terminal of the voltage conversion unit 131 is connected to the positive terminal of the second photodiode PD2, and the second terminal of the voltage conversion unit 131 is connected to the negative terminal of the second photodiode PD2. The voltage conversion unit 131 is used to output a second output voltage Vout. The microcontroller unit 132 is connected to the third terminal of the voltage conversion unit 131, and the microcontroller unit 132 is used to determine the voltage of the high-voltage DC bus HV based on the two output voltages Vout.

[0083] In this example, the voltage conversion unit 131 converts the output current of the second photodiode PD2 into voltage, enabling it to output a second output voltage Vout to the microcontroller unit 132. The microcontroller unit 132 then performs a digital-to-analog conversion on the second output voltage Vout to determine the voltage of the high-voltage DC bus HV. Thus, by converting current into a second output voltage Vout through the voltage conversion unit 131, and then performing a digital-to-analog conversion on Vout by the microcontroller unit 132 to determine the corresponding voltage of the high-voltage DC bus HV, accurate detection of the high-voltage DC bus HV is achieved. This allows for timely detection of voltage anomalies, enabling subsequent operators to take appropriate remedial measures to ensure stable vehicle operation.

[0084] In order for the voltage conversion unit 131 to convert the output current into a second output voltage Vout, in one example, such as Figure 7As shown, the voltage conversion unit 131 includes a third operational amplifier U3 and a seventh resistor R7. The non-inverting input terminal of the third operational amplifier U3 serves as the first terminal of the voltage conversion unit 131 and is connected to the positive terminal of the second photodiode PD2. The power input terminal of the third operational amplifier U3 serves as the second terminal of the voltage conversion unit 131 and is connected to the negative terminal of the second photodiode PD2. The output terminal of the third operational amplifier U3 serves as the third terminal of the voltage conversion unit 131 and is connected to the microcontroller unit 132 and the inverting input terminal of the third operational amplifier U3. One end of the seventh resistor R7 is connected to the non-inverting input terminal of the third operational amplifier U3 and the positive terminal of the second photodiode PD2, and the other end of the seventh resistor R7 is grounded.

[0085] In this example, the third operational amplifier U3 can output a second output voltage Vout corresponding to its current-based output to the microcontroller unit 132.

[0086] In another example, such as Figure 8 As shown, the voltage conversion unit 131 may include a fourth operational amplifier U4, an eighth resistor R8, and a third capacitor C3. The non-inverting input of the fourth operational amplifier U4 serves as the first terminal of the voltage conversion unit 131 and is connected to the positive terminal of the second photodiode PD2. The inverting input of the fourth operational amplifier U4 serves as the second terminal of the voltage conversion unit 131 and is connected to the negative terminal of the second photodiode PD2. The output of the fourth operational amplifier U4 serves as the third terminal of the voltage conversion unit 131 and is connected to the microcontroller unit 132. One end of the eighth resistor R8 is connected to the inverting input of the fourth operational amplifier U4, and the other end of the eighth resistor R8 is connected to the output of the fourth operational amplifier U4 and the microcontroller unit 132. The first plate of the third capacitor C3 is connected to one end of the eighth resistor R8 and the inverting input of the fourth operational amplifier U4, and the second plate of the third capacitor C3 is connected to the other end of the eighth resistor R8, the output of the fourth operational amplifier U4, and the microcontroller unit 132.

[0087] In this example, the reliability of the output voltage Vout corresponding to the current output can be determined by the fourth operational amplifier U4. The first output voltage Vout can be obtained according to formula (5):

[0088] Vout = I2R8 (5)

[0089] R8 is the resistance value of the eighth resistor.

[0090] Formula (6) can be derived from the above formulas (1) to (5):

[0091] Vout / Vin=kR8 / R6 (6)

[0092] According to formula (6), the gain of the second output voltage Vout can be achieved by adjusting the values ​​of the sixth resistor R6 and the eighth resistor R8. When the resistance values ​​of the sixth resistor R6 and the eighth resistor R8 are set to be the same, then Vout / Vin=k. Combining formulas (1) and (2), the relationship between the second output voltage Vout and the high voltage DC bus voltage Vhv can be obtained as formula (7):

[0093] Vout=Vhv*k(R3+R4) / (R3+R3+R3+R4+R4+R4) (6)

[0094] Therefore, there is a linear relationship between the second output voltage Vout and the voltage Vhv of the high-voltage DC bus HV under test, and their ratio can be adjusted by changing the resistance values ​​of multiple voltage divider resistors R3 and R4. Correspondingly, the microcontroller unit 132 can calculate the voltage Vhv of the high-voltage DC bus HV under test based on the second output voltage Vout output by the fourth operational amplifier U4, thus achieving accurate detection of the high-voltage DC bus HV.

[0095] In one example, such as Figure 8 As shown, the differential detection system 1 also includes a Zener diode Dz, the positive terminal of which is grounded, and the negative terminal of which is connected to the third terminal of the voltage conversion unit 131 and the microcontroller unit 132.

[0096] In this example, the Zener diode Dz operates in the reverse breakdown region. When the voltage across its terminals exceeds the set Zener voltage, it's worth noting that the Zener diode Dz is connected to ground and the second output voltage Vout, respectively. The ground voltage is a stable voltage. That is, when the second output voltage Vout is overvoltage, the Zener diode Dz will conduct and clamp the voltage at the Zener voltage, thus limiting the voltage. The Zener diode Dz ensures that the second output voltage Vout received by the microcontroller 132 is always within a safe operating range, preventing damage to the microcontroller 132 from overvoltage and ensuring the reliability of its use and detection. Furthermore, the Zener diode Dz responds quickly to voltage changes, rapidly clamping transient voltage spikes or short-term overvoltage situations to effectively protect the microcontroller 132.

[0097] To further improve the integrity of the signals output to the microcontroller 132, in one example, such as Figure 9 As shown, the differential detection system 1 also includes a ninth resistor R9 and a fourth capacitor C4. One end of the ninth resistor R9 is connected to the third terminal of the voltage conversion unit 131, and the other end of the ninth resistor R9 is connected to the microcontroller unit 132. The first plate of the fourth capacitor C4 is connected to the other end of the ninth resistor R9 and the microcontroller unit 132, and the second plate of the fourth capacitor C4 is grounded.

[0098] In this example, the fourth capacitor C4 and the ninth resistor R9 can filter the signal output by the voltage conversion unit 131 to attenuate the high-frequency noise in the second output voltage Vout, improve the integrity and accuracy of the second output voltage Vout output to the microcontroller unit 132, and further ensure the detection reliability of the differential detection system 1.

[0099] Optionally, the microcontroller unit 132 may be a microcontroller unit (MCU).

[0100] In summary, the differential sampling circuit 11 simultaneously measures both the positive terminal HV+ and the negative terminal HV- of the high-voltage DC bus HV, and calculates the voltage difference ΔV between them to output a first output voltage Vin with high sampling accuracy. Furthermore, when simultaneously measuring both terminals HV+ and HV- of the high-voltage DC bus HV using the differential sampling circuit 11, common-mode noise is suppressed, resulting in strong anti-interference capabilities. This allows it to output a stable first output voltage Vin to the first operational amplifier U1, ensuring the reliability of subsequent circuit detection based on this first output voltage Vin. The first output voltage Vin output by the differential sampling circuit 11 is input to the first operational amplifier U1, which amplifies it before outputting it to the isolation circuit 12. This improves the reliability of the voltage connected to the isolation circuit 12, thereby increasing the reliability of the corresponding output current generated by the isolation circuit 12 based on this voltage. Furthermore, this enhances the reliability of the subsequent signal processing circuit 13 in determining the voltage of the high-voltage DC bus HV based on this output current. Thus, the differential detection system 1 can perform dual-terminal isolation detection of the voltage of the high-voltage DC bus HV, enabling timely detection of voltage anomalies with high accuracy and reliability. Secondly, the isolation circuit 12 achieves electrical isolation between the high-voltage and low-voltage side circuits, preventing the voltage of the high-voltage DC bus HV from being directly applied to the low-voltage side circuit and causing damage. This ensures the normal operation of the low-voltage side circuit while improving the overall safety of the differential detection system 1, further guaranteeing its testing reliability.

[0101] Through the above description of the embodiments, those skilled in the art will understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0102] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0103] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A differential detection system for a high-voltage DC bus, characterized in that, The differential detection system includes: A differential sampling circuit, wherein the first terminal of the differential sampling circuit is connected to the positive terminal of the high-voltage DC bus, the second terminal of the differential sampling circuit is connected to the negative terminal of the high-voltage DC bus, and the third and fourth terminals of the differential sampling circuit are grounded, and the differential sampling circuit is used to output a first output voltage; The first operational amplifier has its inverting input terminal connected to the fourth terminal of the differential sampling circuit and the output terminal of the first operational amplifier to receive the first output voltage. The non-inverting input terminal of the first operational amplifier is connected to the negative terminal of the high-voltage DC bus and the fourth terminal of the differential sampling circuit to ground. An isolation circuit is provided, wherein a first terminal of the isolation circuit is connected to the output terminal of the first operational amplifier, the inverting input terminal of the first operational amplifier, a fourth terminal of the differential sampling circuit, and a second terminal of the isolation circuit; a third terminal of the isolation circuit is connected to a power supply voltage; and a fourth terminal of the isolation circuit is grounded. A signal processing circuit is connected to the isolation circuit, and the signal processing circuit is used to determine the voltage of the high voltage DC bus based on the output current of the isolation circuit.

2. The differential detection system according to claim 1, characterized in that, The differential sampling circuit includes: The first sampling module, one end of which is connected to the positive terminal of the high-voltage DC bus as the first terminal of the differential sampling circuit; The second sampling module, one end of which serves as the second terminal of the differential sampling circuit, is connected to the negative terminal of the high-voltage DC bus. The second operational amplifier has its non-inverting input connected to the other end of the first sampling module, its inverting input connected to the other end of the second sampling module, and its output connected to the fourth terminal of the differential sampling circuit and the inverting input of the first operational amplifier. A first resistor, one end of which is connected to the non-inverting input of the second operational amplifier and the other end of the first sampling module, and the other end of which serves as the third terminal of the differential sampling circuit and is grounded; and, The second resistor has one end connected to the inverting input of the second operational amplifier and the other end of the second sampling module, and the other end connected to the output of the second operational amplifier.

3. The differential detection system according to claim 2, characterized in that, The first sampling module includes multiple third resistors connected in series; The end of the first third resistor that is not connected to the third resistor serves as one end of the first sampling module and is connected to the positive terminal of the high voltage DC bus. The end of the last third resistor that is not connected to the third resistor serves as the other end of the first sampling module and is connected to the non-inverting input terminal of the second operational amplifier and one end of the first resistor. And / or, The second sampling module includes multiple fourth resistors connected in series; The end of the fourth resistor located at the first position that is not connected to the fourth resistor serves as one end of the second sampling module and is connected to the negative terminal of the high-voltage DC bus. The end of the fourth resistor located at the last position that is not connected to the fourth resistor serves as the other end of the second sampling module and is connected to the inverting input terminal of the second operational amplifier and one end of the second resistor.

4. The differential detection system according to claim 2, characterized in that, The isolation circuit includes: The fifth resistor, one end of which serves as the third terminal of the isolation circuit, is connected to the power supply voltage; and, A linear optocoupler, comprising a light-emitting diode (LED), a first photodiode, and a second photodiode, wherein the anode of the LED is connected to the other end of the fifth resistor, the cathode of the LED serves as the first terminal of the isolation circuit and is connected to the output terminal of the first operational amplifier, the inverting input terminal of the first operational amplifier, the output terminal of the second operational amplifier, and the cathode of the first photodiode, the cathode of the first photodiode serves as the second terminal of the isolation circuit, the anode of the first photodiode serves as the fourth terminal of the isolation circuit and is grounded, and the second photodiode is connected to the signal processing circuit.

5. The differential detection system according to claim 4, characterized in that, The differential detection system also includes: The sixth resistor has one end connected to the output terminal of the second operational amplifier and the other end of the second resistor, and the other end of the sixth resistor is connected to the negative terminal of the light-emitting diode, the output terminal of the first operational amplifier, the inverting input terminal of the first operational amplifier, and the negative terminal of the first photodiode.

6. The differential detection system according to claim 5, characterized in that, The differential detection system also includes: The first capacitor has its first plate connected to one end of the sixth resistor, the output terminal of the second operational amplifier, and the other end of the second resistor. The second plate of the first capacitor is connected to the non-inverting input terminal of the first operational amplifier and the negative terminal of the high-voltage DC bus.

7. The differential detection system according to claim 5, characterized in that, The differential detection system also includes: The second capacitor has its first plate connected to the other end of the sixth resistor, the inverting input of the first operational amplifier, and the negative terminal of the first photodiode. The second plate of the second capacitor is connected to the output of the first operational amplifier and the negative terminal of the light-emitting diode.

8. The differential detection system according to any one of claims 4-7, characterized in that, The signal processing circuit includes: A voltage conversion unit, wherein a first terminal of the voltage conversion unit is connected to the positive terminal of the second photodiode, and a second terminal of the voltage conversion unit is connected to the negative terminal of the second photodiode, the voltage conversion unit being used to output a second output voltage; and, A microcontroller unit is connected to the third terminal of the voltage conversion unit, and the microcontroller unit is used to determine the voltage of the high voltage DC bus based on the second output voltage.

9. The differential detection system according to claim 8, characterized in that, The differential detection system also includes: A Zener diode, the positive terminal of which is grounded, and the negative terminal of which is connected to the third terminal of the voltage conversion unit and the microcontroller unit.

10. A vehicle, characterized in that, The vehicles include: The differential detection system according to any one of claims 1 to 9, wherein the differential detection system is connected to a high-voltage DC bus.

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