Insulation detection circuit for electric automobile

Abstract

The utility model relates to the technical field of new energy automobile safety detection, in particular to an electric automobile insulation detection circuit. The electric automobile insulation detection circuit comprises two detection units. Each detection unit comprises a sampling module, a switch module and an operational amplification module; first ends of the two sampling modules are respectively connected with an anode and a cathode of a power battery pack of the electric automobile, and second ends are respectively connected with first ends of the corresponding switch modules; the second ends of the two switch modules are respectively connected with the first ends of the corresponding operational amplification modules; the second ends of the two operational amplification modules are respectively used as a first detection port and a second detection port; the two operational amplification modules are connected with the same reference voltage. According to the utility model, a special acquisition chip can be avoided, an additional negative pressure acquisition chip can be avoided, a peripheral circuit of the operational amplifier can be simplified, and the reliability of a system can be improved.

Description

Technical Field

[0001] The utility model relates to the technical field of safety detection of new energy vehicles, in particular to an insulation detection circuit of an electric vehicle. Background Art

[0002] With the development of modern industry, electric vehicles (including hybrid vehicles) have experienced rapid growth and are becoming increasingly mature. To meet certain power requirements, electric vehicles require multiple batteries connected in series to form a power battery pack. The total voltage of a power battery pack is generally higher than 100V, and can even reach as high as 800V. Due to the harsh operating environment of electric vehicles, vibration, impact, alternating hot and cold weather, corrosion from various corrosive gases and liquids, and road traffic accidents can all damage the insulation between the internal electrical system of an electric vehicle (such as the power battery pack) and the vehicle body (such as the chassis, etc.), directly affecting the safety of the driver and passengers and the vehicle itself. Therefore, it is of great significance to use an electric vehicle insulation detection circuit to accurately and in real time monitor the insulation performance of the power battery pack to the vehicle body ground to ensure the safety of the driver and passengers, the normal operation of electrical equipment, and the safe operation of the vehicle.

[0003] Currently, electric vehicle insulation detection circuits typically use dedicated acquisition chips to detect the insulation resistance between the two ends of the power battery pack and the vehicle body ground. However, dedicated acquisition chips have high design costs, long procurement cycles, unstable supply, and are subject to various restrictions by chip manufacturers. As a result, their application scope is too narrow and they are difficult to use on a large scale. Secondly, the voltage of the negative electrode of the high-voltage power battery pack relative to the low-voltage vehicle body ground is negative, which requires the addition of an additional negative voltage acquisition chip and the design of specific peripheral circuits for the operational amplifier. In addition, existing circuits use a large number of hardware components, especially inductive devices, which makes the hardware circuit complex and reduces system reliability.

[0004] Therefore, how to avoid using dedicated acquisition chips in electric vehicle insulation detection circuits and avoid adding additional negative pressure acquisition chips, while simplifying the peripheral circuits of operational amplifiers and improving system reliability has become a technical problem that needs to be solved urgently by those skilled in the art. Utility Model Content

[0005] The purpose of the utility model is to provide an electric vehicle insulation detection circuit, which can avoid the use of a dedicated acquisition chip and the addition of an additional negative pressure acquisition chip, while simplifying the peripheral circuit of the operational amplifier and improving the reliability of the system.

[0006] The utility model discloses an insulation detection circuit for an electric vehicle, comprising a first detection unit and a second detection unit;

[0007] The first detection unit includes a first sampling module, a first switch module and a first operational amplifier module; the first end of the first sampling module is connected to the positive electrode of the power battery pack of the electric vehicle, the second end of the first sampling module is connected to the first end of the first switch module, the second end of the first switch module is connected to the first end of the first operational amplifier module, and the second end of the first operational amplifier module serves as a first detection port;

[0008] The second detection unit includes a second sampling module, a second switch module and a second operational amplifier module; the first end of the second sampling module is connected to the negative electrode of the power battery pack of the electric vehicle, the second end of the second sampling module is connected to the first end of the second switch module, the second end of the second switch module is connected to the first end of the second operational amplifier module, and the second end of the second operational amplifier module serves as a second detection port.

[0009] The first operational amplifier module and the second operational amplifier module are both connected to the same reference voltage.

[0010] Optionally, the first sampling module includes a first resistor and a first capacitor; a first end of the first resistor is connected to the positive electrode of the power battery pack, a second end of the first resistor is connected to the first end of the first capacitor, and a second end of the first capacitor is grounded;

[0011] The second sampling module includes a second resistor and a second capacitor; a first end of the second resistor is connected to the negative electrode of the power battery pack, a second end of the second resistor is connected to the first end of the second capacitor, and a second end of the second capacitor is grounded.

[0012] Optionally, the first switch module includes a first switch; a first end of the first switch is connected to the second end of the first resistor, and a second end of the first switch is connected to the first end of the first capacitor;

[0013] The second switch module includes a second switch; a first end of the second switch is connected to the second end of the second resistor, and a second end of the second switch is connected to the first end of the second capacitor.

[0014] Optionally, the first operational amplifier module includes a first operational amplifier; an inverting input terminal of the first operational amplifier is connected to the first terminal of the first capacitor, a positive input terminal of the first operational amplifier is connected to the reference voltage, and an output terminal of the first operational amplifier serves as the first detection port and is connected to an inverting input terminal of the first operational amplifier;

[0015] The second operational amplifier module includes a second operational amplifier; the inverting input terminal of the second operational amplifier is connected to the first end of the second capacitor, the positive input terminal of the second operational amplifier is connected to the reference voltage, and the output terminal of the second operational amplifier serves as the second detection port and is connected to the inverting input terminal of the second operational amplifier.

[0016] Optionally, a third resistor is connected in series between the inverting input terminal of the first operational amplifier and the first terminal of the first capacitor;

[0017] A fifth resistor is connected in series between the inverting input terminal of the second operational amplifier and the first terminal of the second capacitor.

[0018] Optionally, a fourth resistor is connected in series between the inverting input terminal and the output terminal of the first operational amplifier;

[0019] A sixth resistor is connected in series between the inverting input terminal and the output terminal of the second operational amplifier.

[0020] Optionally, the resistance value of the first resistor is the same as the resistance value of the second resistor.

[0021] Optionally, the resistance value of the third resistor is the same as the resistance value of the fifth resistor.

[0022] Optionally, the resistance value of the fourth resistor is the same as the resistance value of the sixth resistor.

[0023] Optionally, the capacitance of the first capacitor is the same as the capacitance of the second capacitor.

[0024] Compared with the prior art, the main differences and effects of this utility model are:

[0025] The utility model adopts an operational amplifier module to improve the anti-interference performance. The output of the operational amplifier module can be collected by a conventional ADC sampling chip or a single-chip AD port. Compared with a dedicated acquisition chip, it has the advantages of low cost, wide application range, and high accuracy. At the same time, the operational amplifier module works in a mode with basically the same gain ratio, which can improve the consistency and stability of the circuit.

[0026] The utility model avoids the existence of negative voltage by adding a reference voltage, and there is no need to add an additional negative voltage acquisition chip. At the same time, there is no need to design a specific peripheral circuit for the operational amplifier to collect the negative voltage, which makes the peripheral circuit of the operational amplifier simpler and greatly improves the reliability of the operational amplifier.

[0027] This solution is easy to implement physically, providing a fundamental guarantee for the safety of electric vehicles. It is suitable for insulation detection and control in the field of new energy vehicles and for applications in engineering circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a module schematic diagram of an electric vehicle insulation detection circuit according to the utility model;

[0029] Figure 2 This is a circuit diagram of an insulation detection circuit for an electric vehicle according to the present utility model;

[0030] Figure 3 This is a schematic diagram of an equivalent circuit of an electric vehicle insulation detection circuit according to the present utility model;

[0031] Figure 4 This is another equivalent circuit diagram of the electric vehicle insulation detection circuit according to the utility model. DETAILED DESCRIPTION

[0032] To make the purpose and technical solutions of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Figure 1 The utility model is a module schematic diagram of an electric vehicle insulation detection circuit.

[0034] like Figure 1 As shown, the electric vehicle insulation detection circuit includes a first detection unit 10 and a second detection unit 20 .

[0035] The first detection unit 10 includes a first sampling module 101, a first switch module 102, and a first operational amplifier module 103. The first end of the first sampling module 101 is connected to the positive electrode of the power battery pack 30 of the electric vehicle, the second end of the first sampling module 101 is connected to the first end of the first switch module 102, the second end of the first switch module 102 is connected to the first end of the first operational amplifier module 103, and the second end of the first operational amplifier module 103 serves as the first detection port.

[0036] The second detection unit 20 includes a second sampling module 201, a second switch module 202, and a second operational amplifier module 203. The first end of the second sampling module 201 is connected to the negative electrode of the power battery pack 30 of the electric vehicle, the second end of the second sampling module 201 is connected to the first end of the second switch module 202, the second end of the second switch module 202 is connected to the first end of the second operational amplifier module 203, and the second end of the second operational amplifier module 203 serves as the second detection port.

[0037] The first operational amplifier module 103 and the second operational amplifier module 203 are both connected to the same reference voltage (not shown).

[0038] The utility model adopts an operational amplifier module to improve the anti-interference performance. The output of the operational amplifier module can be collected by a conventional ADC sampling chip or a single-chip AD port. Compared with a dedicated acquisition chip, it has the advantages of low cost, wide application range, and high accuracy. At the same time, the operational amplifier module works in a mode with basically the same gain ratio, which can improve the consistency and stability of the circuit.

[0039] The utility model avoids the existence of negative voltage by adding a reference voltage, and there is no need to add an additional negative voltage acquisition chip. At the same time, there is no need to design a specific peripheral circuit for the operational amplifier to collect the negative voltage, which makes the peripheral circuit of the operational amplifier simpler and greatly improves the reliability of the operational amplifier.

[0040] This solution is easy to implement physically, providing a fundamental guarantee for the safety of electric vehicles. It is suitable for insulation detection and control in the field of new energy vehicles and for applications in engineering circuits.

[0041] Figure 2 The utility model is a circuit diagram of an electric vehicle insulation detection circuit.

[0042] like Figure 2 As shown, and reference Figure 1 The first sampling module 101 includes a first resistor R1 and a first capacitor C1. The first end of the first resistor R1 is connected to the positive electrode Bat+ of the power battery pack 30, and the second end of the first resistor R1 is connected to the first end of the first capacitor C1. The second end of the first capacitor C1 is connected to ground PE. It is understood that ground PE can be a vehicle body ground such as the vehicle chassis. The first resistor R1 can be referred to as the positive-side sampling resistor, and the first capacitor C1 can be referred to as the positive-side post-sampling filter capacitor.

[0043] The second sampling module 201 includes a second resistor R2 and a second capacitor C2. The first end of the second resistor R2 is connected to the negative electrode Bat- of the power battery pack 30, the second end of the second resistor R2 is connected to the first end of the second capacitor C2, and the second end of the second capacitor C2 is connected to ground PE. The second resistor R2 can be referred to as the negative-side sampling resistor, and the second capacitor C2 can be referred to as the negative-side post-sampling filter capacitor.

[0044] In one embodiment, the resistance of the first resistor R1 is the same as the resistance of the second resistor R2. For example, the resistance of the first resistor R1 and the resistance of the second resistor R2 are 990 kΩ±0.1%.

[0045] In one embodiment, the capacitance of the first capacitor C1 and the capacitance of the second capacitor C2 are the same. As an example, the capacitance of the first capacitor C1 and the second capacitor C2 may be 10nF±10%.

[0046] Continue as Figure 2 As shown, the first switch module 102 includes a first switch IC1. A first end of the first switch IC1 is connected to a second end of a first resistor R1, and a second end of the first switch IC1 is connected to a first end of a first capacitor C1.

[0047] The first switch IC1 can be referred to as a main positive circuit switch. In one embodiment, the first switch IC1 is an optocoupler.

[0048] The second switch module 202 includes a second switch IC2 . A first end of the second switch IC2 is connected to the second end of the second resistor R2 , and a second end of the second switch IC2 is connected to the first end of the second capacitor C2 .

[0049] The second switch IC2 can be referred to as a main negative circuit switch. In one embodiment, the second switch IC2 is an optocoupler.

[0050] Continue as Figure 2 As shown, the first operational amplifier module 103 includes a first operational amplifier Q1. The inverting input terminal of the first operational amplifier Q1 is connected to the first terminal of the first capacitor C1, the positive input terminal of the first operational amplifier Q1 is connected to the reference voltage VREF, the output terminal of the first operational amplifier Q1 serves as a first detection port to obtain the voltage V1, and the output terminal of the first operational amplifier Q1 is also connected to the inverting input terminal of the first operational amplifier Q1.

[0051] The second operational amplifier module 203 includes a second operational amplifier Q2. The inverting input terminal of the second operational amplifier Q2 is connected to the first terminal of the second capacitor C2, the non-inverting input terminal of the second operational amplifier Q2 is connected to the reference voltage VREF, the output terminal of the second operational amplifier Q2 serves as a second detection port for obtaining the voltage V2, and the output terminal of the second operational amplifier Q2 is also connected to the inverting input terminal of the second operational amplifier Q2.

[0052] Continue as Figure 2 As shown, a third resistor R3 is connected in series between the inverting input terminal of the first operational amplifier Q1 and the first terminal of the first capacitor C1. A fifth resistor R5 is connected in series between the inverting input terminal of the second operational amplifier Q2 and the first terminal of the second capacitor C2.

[0053] The third resistor R3 and the fifth resistor R5 can provide current limiting protection for the circuit. In one embodiment, the resistance of the third resistor R3 and the fifth resistor R5 are the same. For example, the resistance of the third resistor R3 and the fifth resistor R5 can be 10kΩ±0.1%.

[0054] Continue as Figure 2 As shown, a fourth resistor R4 is connected in series between the inverting input terminal and the output terminal of the first operational amplifier Q1, and a sixth resistor R6 is connected in series between the inverting input terminal and the output terminal of the second operational amplifier Q2.

[0055] The fourth resistor R4 and the sixth resistor R6 may be referred to as negative feedback resistors. In one embodiment, the resistance of the fourth resistor R4 and the sixth resistor R6 are the same. For example, the resistance of the fourth resistor R4 and the sixth resistor R6 may be 1 kΩ±0.1%.

[0056] Continue as Figure 2 As shown, the electric vehicle insulation detection circuit includes four loops.

[0057] In the first circuit, the first end of the first resistor R1 is connected to the positive electrode Bat+ of the power battery pack 30 (the connection end can be recorded as end 1), the second end of the first resistor R1 is connected to the first end of the first switch IC1, the second end of the first switch IC1 is connected to the first end of the first capacitor C1 (the connection end can be recorded as end 2), the second end of the first capacitor C1 is connected to the vehicle body ground (the connection end can be recorded as end 4), the first end of the third resistor R3 is connected to end 2, and the second end of the third resistor R3 is connected to the inverting input end of the first operational amplifier Q1 (the connection end can be recorded as end 3).

[0058] In the second circuit, the first end of the second resistor R2 is connected to the negative electrode Bat- of the power battery pack 30 (the connection end can be recorded as terminal 6), the second end of the second resistor R2 is connected to the first end of the second switch IC2, the second end of the second switch IC2 is connected to the first end of the second capacitor C2 (the connection end can be recorded as terminal 5), the second end of the second capacitor C2 is connected to terminal 4, the first end of the fifth resistor R5 is connected to terminal 5, and the second end of the fifth resistor R5 is connected to the inverting input terminal of the second operational amplifier Q2 (the connection end can be recorded as terminal 7).

[0059] In the third loop, the first end of the fourth resistor R4 is connected to the 3 terminal, the second end of the fourth resistor R4 is connected to the output terminal of the first operational amplifier Q1 (the connection terminal can be recorded as the 8 terminal), the positive input terminal of the first operational amplifier Q1 is connected to the reference voltage VREF, and the reverse input terminal of the first operational amplifier Q1 is connected to the 3 terminal.

[0060] In the fourth loop, the first end of the sixth resistor R6 is connected to the 7th terminal, the second end of the sixth resistor R6 is connected to the output terminal of the second operational amplifier Q2 (the connection terminal can be recorded as the 9th terminal), the positive input terminal of the second operational amplifier Q2 is connected to the reference voltage VREF, and the reverse input terminal of the second operational amplifier Q2 is connected to the 7th terminal.

[0061] The utility model is composed of only components such as resistors, capacitors, optocouplers and operational amplifiers, has a simple structure, is easy to implement, avoids inductive components, effectively avoids the influence of parasitic equivalent series resistance inside inductive components in physical circuits, improves the reliability of the system, and does not require additional calibration.

[0062] Figure 3 The utility model is an equivalent circuit diagram of an electric vehicle insulation detection circuit.

[0063] exist Figure 3 In the example, the first switch IC1 is closed and the second switch IC2 is open. Figure 3 As shown, according to the voltage of V1 obtained from the first detection port, the voltage of U1 can be inferred, as shown in formula (1):

[0064]

[0065] According to the voltage of U1 and the voltage U of the power battery pack, the voltage of U2 can be obtained, as shown in formula (2):

[0066] U2=U-U1 (2)

[0067] Let N1 be the ratio of voltage U1 to voltage U2, as shown in formula (3):

[0068]

[0069] Among them, R X is the insulation resistance of the positive electrode of the power battery pack to the vehicle body ground, R Y It is the insulation resistance between the negative pole of the power battery pack and the vehicle body ground.

[0070] Figure 4 This is another equivalent circuit diagram of the electric vehicle insulation detection circuit according to the utility model.

[0071] exist Figure 4 In the example, the first switch IC1 is open and the second switch IC2 is closed. Figure 4 As shown, based on the voltage of V2 obtained from the second detection port (since the operational amplifier introduces the reference voltage VREF, V2 will not have a negative voltage reading), the voltage of U3 can be inferred, as shown in formula (4):

[0072]

[0073] Considering that the voltage between the negative electrode of the power battery pack and the vehicle body ground is negative, the negative voltage can be converted into a positive voltage through the reference voltage VREF. Formula (4) is transformed as follows:

[0074]

[0075] According to the voltage of U3 and the voltage U of the power battery pack, the voltage of U4 can be obtained, as shown in formula (5):

[0076] U4=U-U3 (5)

[0077] Let N2 be the ratio of voltage U3 to voltage U4, as shown in formula (6):

[0078]

[0079] Let R1+R3=R2+R5=R, then according to equations (3) and (6), we can get R X and R Y The resistance value is shown in equations (7) and (8):

[0080]

[0081] The utility model controls the switch states of the first switch IC1 and the second switch IC2 to obtain the voltage V1 of the first detection port and the voltage V2 of the second detection port respectively, and can infer R X and R Y The smaller value of the two can indicate the insulation performance of the power battery pack to the vehicle body ground.

[0082] As mentioned above, since the present invention introduces a reference voltage VREF into the operational amplifier, V2 will not have a negative voltage reading. Moreover, according to the above formula (4) and the variant (4'), it can be seen that the present invention can convert a negative voltage into a positive voltage during the calculation process through the reference voltage VREF, thereby eliminating the need for an additional negative voltage sampling chip. At the same time, it also simplifies the peripheral circuit of the operational amplifier and avoids complex calculations.

[0083] It should be noted that in the claims and description of this patent, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "including a" does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0084] In the accompanying drawings, some structural or method features may be shown in a particular arrangement and / or order. However, it should be understood that such a particular arrangement and / or order may not be required. Rather, in some embodiments, these features may be arranged in a manner and / or order different from that shown in the illustrative drawings. In addition, the inclusion of structural or method features in a particular figure does not imply that such features are required in all embodiments, and in some embodiments, these features may not be included, may be modified, or may be combined with other features.

[0085] Although the present invention has been illustrated and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

1. An electric vehicle insulation detection circuit, characterized in that: comprising a first detection unit and a second detection unit; The first detection unit includes a first sampling module, a first switch module and a first operational amplifier module; the first end of the first sampling module is connected to the positive electrode of the power battery pack of the electric vehicle, the second end of the first sampling module is connected to the first end of the first switch module, the second end of the first switch module is connected to the first end of the first operational amplifier module, and the second end of the first operational amplifier module serves as a first detection port; The second detection unit includes a second sampling module, a second switch module and a second operational amplifier module; the first end of the second sampling module is connected to the negative electrode of the power battery pack of the electric vehicle, the second end of the second sampling module is connected to the first end of the second switch module, the second end of the second switch module is connected to the first end of the second operational amplifier module, and the second end of the second operational amplifier module serves as a second detection port. The first operational amplifier module and the second operational amplifier module are both connected to the same reference voltage.

2. The electric vehicle insulation detection circuit according to claim 1, characterized in that: The first sampling module includes a first resistor and a first capacitor; a first end of the first resistor is connected to the positive electrode of the power battery pack, a second end of the first resistor is connected to the first end of the first capacitor, and a second end of the first capacitor is grounded; The second sampling module includes a second resistor and a second capacitor; a first end of the second resistor is connected to the negative electrode of the power battery pack, a second end of the second resistor is connected to the first end of the second capacitor, and a second end of the second capacitor is grounded.

3. The electric vehicle insulation detection circuit according to claim 2, characterized in that: The first switch module includes a first switch; a first end of the first switch is connected to the second end of the first resistor, and a second end of the first switch is connected to the first end of the first capacitor; The second switch module includes a second switch; a first end of the second switch is connected to the second end of the second resistor, and a second end of the second switch is connected to the first end of the second capacitor.

4. The electric vehicle insulation detection circuit according to claim 3, characterized in that: The first operational amplifier module includes a first operational amplifier; an inverting input terminal of the first operational amplifier is connected to the first end of the first capacitor, a positive input terminal of the first operational amplifier is connected to the reference voltage, and an output terminal of the first operational amplifier serves as the first detection port and is connected to the inverting input terminal of the first operational amplifier; The second operational amplifier module includes a second operational amplifier; the inverting input terminal of the second operational amplifier is connected to the first end of the second capacitor, the positive input terminal of the second operational amplifier is connected to the reference voltage, and the output terminal of the second operational amplifier serves as the second detection port and is connected to the inverting input terminal of the second operational amplifier.

5. The electric vehicle insulation detection circuit according to claim 4, characterized in that: A third resistor is connected in series between the inverting input terminal of the first operational amplifier and the first terminal of the first capacitor; A fifth resistor is connected in series between the inverting input terminal of the second operational amplifier and the first terminal of the second capacitor.

6. The electric vehicle insulation detection circuit according to claim 4, characterized in that: A fourth resistor is connected in series between the inverting input terminal and the output terminal of the first operational amplifier; A sixth resistor is connected in series between the inverting input terminal and the output terminal of the second operational amplifier.

7. The electric vehicle insulation detection circuit according to claim 2, characterized in that: The resistance value of the first resistor is the same as the resistance value of the second resistor.

8. The electric vehicle insulation detection circuit according to claim 5, characterized in that: The resistance value of the third resistor is the same as the resistance value of the fifth resistor.

9. The electric vehicle insulation detection circuit according to claim 6, characterized in that: The resistance value of the fourth resistor is the same as the resistance value of the sixth resistor.

10. The electric vehicle insulation detection circuit according to claim 2, characterized in that: The capacitance of the first capacitor is the same as the capacitance of the second capacitor.

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