Detection circuit of insulation resistor of power battery pack and electric automobile

Abstract

The utility model provides a detection circuit for the insulation resistance of a power battery pack and an electric automobile. The detection circuit for the insulation resistance of the power battery pack comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a first switch, a second switch and an acquisition control unit, the first end of the first resistor is electrically connected with the positive electrode of the power battery pack, the second end of the first resistor is electrically connected with the first end of the second resistor and the first collection end of the collection control unit, and the second end of the second resistor is electrically connected with the first end of the third resistor, the first collection end of the collection control unit and the grounding end. The second end of the third resistor is electrically connected with the first end of the fourth resistor and the second acquisition end of the acquisition control unit. The second end of the fourth resistor is electrically connected with the negative electrode of the power battery pack and the second acquisition end of the acquisition control unit. The first switch and the second switch are respectively used for controlling on-off of the positive electrode side and the negative electrode side. The circuit is simple and low in cost.

Description

Technical Field

[0001] The utility model relates to the technical field of electrical insulation, and particularly relates to a detection circuit for the insulation resistance of a power battery pack and an electric vehicle. Background Art

[0002] A power battery pack usually has a relatively high voltage output. For this reason, relevant circuits for the positive and negative electrodes of the power battery pack are usually set respectively to ground, so as to obtain an equivalent resistance with a relatively large value between the positive electrode of the power battery pack and the ground (which can also be understood as the positive electrode insulation resistance) and an equivalent resistance with a relatively large value between the negative electrode of the power battery pack and the ground (which can also be understood as the negative electrode insulation resistance), thereby ensuring the reliable operation of the power system.

[0003] However, during the operation of the power system, affected by the environment, altitude, transient high voltage generated by the external circuit, stress shock, etc., the resistance values of the positive electrode insulation resistance and / or the negative electrode insulation resistance may decrease, resulting in a decrease or failure of the insulation performance. Taking electric vehicles as an example, in current new energy electric vehicles, the voltage platform is generally above 400V. If the insulation performance deteriorates or fails, it will pose a threat to the personal safety of passengers or drivers. If no remedial measures are taken in time, it is very easy to cause harm to passengers or drivers. Therefore, the detection of the resistance value of the insulation resistance is particularly important, and relevant remedial measures can be taken in time when the resistance value decreases.

[0004] The existing detection schemes for the insulation resistance of power batteries include the voltage injection method and the current sensing method. The voltage injection method requires a separate DC power supply, the circuit is more complex, and the cost is higher. The current sensing method requires Hall sensors to be added to the positive and negative electrodes of the bus respectively, which increases the cost and the complexity of the system at the same time. Summary of the Utility Model

[0005] Aiming at the deficiencies in the prior art, the utility model provides a detection circuit for the insulation resistance of a power battery pack and an electric vehicle.

[0006] In a first aspect, in an embodiment, the utility model provides a detection circuit for the insulation resistance of a power battery pack. The detection circuit for the insulation resistance of a power battery pack is used to detect the resistance value of the positive electrode insulation resistance between the positive electrode of the power battery pack and the ground and to detect the resistance value of the negative electrode insulation resistance between the negative electrode of the power battery pack and the ground. The detection circuit for the insulation resistance of a power battery pack includes:

[0007] A first resistor, a second resistor, a third resistor, a fourth resistor, a first switch, a second switch, and an acquisition and control unit;

[0008] The first end of the first resistor is electrically connected to the positive electrode of the power battery pack. The second end of the first resistor is electrically connected to the first end of the second resistor and the first acquisition end of the acquisition control unit respectively. The second end of the second resistor is electrically connected to the first end of the third resistor, the first acquisition end of the acquisition control unit and the ground terminal respectively. The second end of the third resistor is electrically connected to the first end of the fourth resistor and the second acquisition end of the acquisition control unit respectively. The second end of the fourth resistor is electrically connected to the negative electrode of the power battery pack and the second acquisition end of the acquisition control unit respectively;

[0009] The first switch is connected in series with the positive electrode of the power battery pack, the first resistor, the second resistor and the ground terminal to control the on-off of the circuit between the positive electrode of the power battery pack through the first resistor and the second resistor to the ground terminal. The second switch is connected in series with the ground terminal, the third resistor, the fourth resistor and the negative electrode of the power battery pack to control the on-off of the circuit between the negative electrode of the power battery pack through the third resistor and the fourth resistor to the ground terminal.

[0010] In one embodiment, the detection circuit of the insulation resistance of the power battery pack further includes:

[0011] Isolation unit;

[0012] The first input end of the isolation unit is electrically connected to the second end of the first resistor and the first end of the second resistor respectively. The second input end of the isolation unit is electrically connected to the second end of the second resistor, the ground terminal and the first end of the third resistor respectively. The third input end of the isolation unit is electrically connected to the second end of the third resistor and the first end of the fourth resistor respectively. The fourth input end of the isolation unit is electrically connected to the negative electrode of the power battery pack and the second end of the fourth resistor respectively. The first output end and the second output end of the isolation unit are electrically connected to the first acquisition end of the acquisition control unit respectively. The third output end and the fourth output end of the isolation unit are electrically connected to the second acquisition end of the acquisition control unit respectively.

[0013] In one embodiment, the isolation unit includes a first isolation amplifier and a second isolation amplifier;

[0014] The first input end of the first isolation amplifier is electrically connected to the second end of the first resistor and the first end of the second resistor respectively. The second input end of the first isolation amplifier is electrically connected to the second end of the second resistor, the ground terminal and the first end of the third resistor respectively. The first output end and the second output end of the first isolation amplifier are electrically connected to the first acquisition end of the acquisition control unit respectively;

[0015] The first input terminal of the second isolation amplifier is electrically connected to the second terminal of the third resistor and the first terminal of the fourth resistor respectively. The second input terminal of the second isolation amplifier is electrically connected to the negative electrode of the power battery pack and the second terminal of the fourth resistor respectively. The first output terminal and the second output terminal of the second isolation amplifier are electrically connected to the second acquisition terminal of the acquisition control unit respectively.

[0016] In one embodiment, the detection circuit for the insulation resistance of the power battery pack further includes:

[0017] A first difference calculation unit and a second difference calculation unit;

[0018] The first input terminal of the first difference calculation unit is electrically connected to the first output terminal of the first isolation amplifier. The second input terminal of the first difference calculation unit is electrically connected to the second output terminal of the first isolation amplifier. The output terminal of the first difference calculation unit is electrically connected to the first acquisition terminal of the acquisition control unit to calculate and output the voltage difference between the first input terminal and the second input terminal of the first difference calculation unit;

[0019] The first input terminal of the second difference calculation unit is electrically connected to the first output terminal of the second isolation amplifier. The second input terminal of the second difference calculation unit is electrically connected to the second output terminal of the second isolation amplifier. The output terminal of the second difference calculation unit is electrically connected to the second acquisition terminal of the acquisition control unit to calculate and output the voltage difference between the first input terminal and the second input terminal of the second difference calculation unit.

[0020] In one embodiment, the first difference calculation unit includes a first differential operational amplifier, and the second difference calculation unit includes a second differential operational amplifier;

[0021] The first input terminal of the first differential operational amplifier is electrically connected to the first output terminal of the first isolation amplifier. The second input terminal of the first differential operational amplifier is electrically connected to the second output terminal of the first isolation amplifier. The output terminal of the first differential operational amplifier is electrically connected to the first acquisition terminal of the acquisition control unit;

[0022] The first input terminal of the second differential operational amplifier is electrically connected to the first output terminal of the second isolation amplifier. The second input terminal of the second differential operational amplifier is electrically connected to the second output terminal of the second isolation amplifier. The output terminal of the second differential operational amplifier is electrically connected to the second acquisition terminal of the acquisition control unit.

[0023] In one embodiment, the first switch includes a first optocoupler, and the second switch includes a second optocoupler;

[0024] The photosensitive triode in the first optocoupler is connected in series with the positive electrode of the power battery pack, the first resistor, the second resistor, and the ground terminal. The light-emitting diode in the first optocoupler is electrically connected to the first control terminal of the acquisition control unit, so as to control the on-off of the circuit between the positive electrode of the power battery pack through the first resistor and the second resistor to the ground terminal under the control of the acquisition control unit;

[0025] The photosensitive triode in the second optocoupler is connected in series with the ground terminal, the third resistor, the fourth resistor, and the negative electrode of the power battery pack. The light-emitting diode in the second optocoupler is electrically connected to the second control terminal of the acquisition control unit, so as to control the on-off of the circuit between the negative electrode of the power battery pack through the third resistor and the fourth resistor to the ground terminal under the control of the acquisition control unit.

[0026] In one embodiment, the detection circuit of the insulation resistance of the power battery pack further includes:

[0027] A fifth resistor, a sixth resistor, a third switch, and a fourth switch;

[0028] The first end of the fifth resistor is electrically connected to the positive electrode of the power battery pack and the first end of the first resistor respectively. The second end of the fifth resistor is electrically connected to the ground terminal, the second end of the second resistor, the first end of the sixth resistor, the first end of the third resistor, and the first acquisition terminal of the acquisition control unit respectively. The second end of the sixth resistor is electrically connected to the negative electrode of the power battery pack, the second end of the fourth resistor, and the second acquisition terminal of the acquisition control unit respectively;

[0029] The third switch is connected in series with the positive electrode of the power battery pack, the fifth resistor, and the ground terminal to control the on-off of the circuit between the positive electrode of the power battery pack through the fifth resistor to the ground terminal; the fourth switch is connected in series with the ground terminal, the sixth resistor, and the negative electrode of the power battery pack to control the on-off of the circuit between the negative electrode of the power battery pack through the sixth resistor to the ground terminal.

[0030] In one embodiment, the third switch includes a third optocoupler, and the fourth switch includes a fourth optocoupler;

[0031] The photosensitive triode in the third optocoupler is connected in series with the positive electrode of the power battery pack, the fifth resistor, and the ground terminal. The light-emitting diode in the third optocoupler is electrically connected to the third control terminal of the acquisition control unit, so as to control the on-off of the circuit between the positive electrode of the power battery pack through the fifth resistor to the ground terminal under the control of the acquisition control unit;

[0032] The photosensitive triode in the fourth optocoupler is connected in series with the ground terminal, the sixth resistor, and the negative electrode of the power battery pack. The light-emitting diode in the fourth optocoupler is electrically connected to the fourth control terminal of the acquisition control unit, so as to control the on-off of the circuit between the negative electrode of the power battery pack through the sixth resistor to the ground terminal under the control of the acquisition control unit.

[0033] In one embodiment, the acquisition control unit includes a single-chip microcomputer, which includes a single-chip microcomputer AD acquisition unit and a control unit that are electrically connected to each other;

[0034] The first acquisition terminal of the single-chip microcomputer AD acquisition unit is electrically connected to the second terminal of the first resistor, the first terminal of the second resistor, the second terminal of the second resistor, the first terminal of the third resistor, and the ground terminal respectively. The second acquisition terminal of the single-chip microcomputer AD acquisition unit is electrically connected to the second terminal of the third resistor, the first terminal of the fourth resistor, the second terminal of the fourth resistor, and the negative electrode of the power battery pack respectively.

[0035] In a second aspect, in one embodiment, the present utility model provides an electric vehicle, which includes a power battery pack and a detection circuit for the insulation resistance of the power battery pack in any of the above embodiments.

[0036] Through the above detection circuit for the insulation resistance of the power battery pack and the electric vehicle, multiple resistors and switches are provided to detect the insulation resistance in the form of bridge resistor voltage division. The circuit is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following will briefly introduce the drawings required for description in the embodiments. Obviously, the following drawings are only some embodiments of the present utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 It is a schematic structural diagram of a detection circuit for the insulation resistance of a power battery pack in an embodiment of the present utility model;

[0039] Figure 2 It is a schematic structural diagram of a detection circuit for the insulation resistance of a power battery pack including an isolation amplifier in an embodiment of the present utility model;

[0040] Figure 3 It is a schematic structural diagram of a detection circuit for the insulation resistance of a power battery pack including a differential operational amplifier in an embodiment of the present utility model;

[0041] Figure 4 It is an equivalent circuit diagram of disconnecting S1, S2, S3, and S4 in an embodiment of the present utility model;

[0042] Figure 5 It is an equivalent circuit diagram of closing S1, S2, and S3 in an embodiment of the present utility model;

[0043] Figure 6 It is an equivalent circuit diagram of closing S1, S2, and S4 in an embodiment of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of this application, "a plurality" means two or more, unless otherwise specifically defined. In this application, the term "exemplary" is used to mean "serving as an example, illustration, or description". Any embodiment described as "exemplary" in this application is not necessarily to be construed as more preferred or more advantageous than other embodiments. In order for any person skilled in the art to implement and use the present invention, the following description is given. In the following description, details are set forth for the purpose of explanation. It should be understood that those of ordinary skill in the art can recognize that the present invention can be implemented without the use of these specific details. In other instances, well-known structures and processes are not described in detail to avoid unnecessary details from obscuring the description of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope that conforms to the principles and features disclosed in this application.

[0046] In a first aspect, as Figure 1 shown, in one embodiment, the present invention provides a detection circuit for the insulation resistance of a power battery pack. The detection circuit for the insulation resistance of the power battery pack is used to detect the resistance value of the positive insulation resistance RP of the positive electrode BAT+ of the power battery pack to the ground and detect the resistance value of the negative insulation resistance RN of the negative electrode BAT0 of the power battery pack to the ground. The detection circuit for the insulation resistance of the power battery pack includes:

[0047] The first resistor R3, the second resistor R4, the third resistor R5, the fourth resistor R6, the first switch S3, the second switch S4, and the acquisition control unit (in one embodiment, the acquisition control unit includes a single-chip microcomputer, and the single-chip microcomputer includes a single-chip microcomputer AD acquisition unit and a control unit that are electrically connected to each other. In Figure 1 it, the connection relationship between the acquisition control unit and other devices is represented by the single-chip microcomputer AD acquisition unit).

[0048] The first end of the first resistor R3 is electrically connected to the positive electrode BAT+ of the power battery pack. The second end of the first resistor R3 is respectively electrically connected to the first end of the second resistor R4 and the first acquisition end of the single-chip microcomputer AD acquisition unit. The second end of the second resistor R4 is respectively electrically connected to the first end of the third resistor R5, the first acquisition end of the single-chip microcomputer AD acquisition unit, and the ground terminal PGND. The second end of the third resistor R5 is respectively electrically connected to the first end of the fourth resistor R6 and the second acquisition end of the single-chip microcomputer AD acquisition unit. The second end of the fourth resistor R6 is respectively electrically connected to the negative electrode BAT0 of the power battery pack and the second acquisition end of the single-chip microcomputer AD acquisition unit.

[0049] Among them, in Figure 1 it, the voltage-dividing network formed by the first resistor R3, the second resistor R4, the third resistor R5, and the fourth resistor R6 has a total of four nodes with voltage outputs, and directly outputs to the single-chip microcomputer AD acquisition unit. Therefore, two first acquisition ends and two second acquisition ends are respectively provided for the single-chip microcomputer AD acquisition unit mentioned above, so as to meet the voltage acquisition of the four nodes.

[0050] The first switch S3 is connected in series with the positive electrode BAT+ of the power battery pack, the first resistor R3, the second resistor R4, and the ground terminal PGND to control the on / off of the line between the positive electrode BAT+ of the power battery pack, through the first resistor R3 and the second resistor R4, to the ground terminal PGND; the second switch S4 is connected in series with the ground terminal PGND, the third resistor R5, the fourth resistor R6, and the negative electrode BAT0 of the power battery pack to control the on / off of the line between the negative electrode BAT0 of the power battery pack, through the third resistor R5 and the fourth resistor R6, to the ground terminal PGND.

[0051] Among them, in Figure 1 it, the first switch S3 is connected in series between the first resistor R3 and the second resistor R4. In other embodiments, the first switch S3 can also be connected in series between the positive electrode BAT+ of the power battery pack and the first resistor R3; similarly, in Figure 1 it, the second switch S4 is connected in series between the second resistor R4 and the third resistor R5. In other embodiments, the second switch S4 can also be connected in series between the third resistor R5 and the fourth resistor R6, or, connected in series between the fourth resistor R6 and the negative electrode BAT0 of the power battery pack.

[0052] Among them, the first resistor R3 and the second resistor R4 form a voltage dividing network between the positive electrode BAT+ and the ground terminal PGND of the power battery pack, and the third resistor R5 and the fourth resistor R6 form a voltage dividing network between the negative electrode BAT0 and the ground terminal PGND of the power battery pack. The two groups together form a bridge resistor network. The first switch S3 and the second switch S4 can be conducted respectively, so as to output corresponding voltage values to the AD acquisition unit of the single-chip microcomputer respectively, and then enable the control unit in the acquisition control unit to process the acquired voltage values to obtain the resistance values of the positive insulation resistor RP and the negative insulation resistor RN respectively.

[0053] Through the above detection circuit of the insulation resistance of the power battery pack, multiple resistors and switches are set, and the detection of the insulation resistance is realized in the way of bridge resistor voltage division. The circuit is simple and the cost is low.

[0054] In one embodiment, the detection circuit of the insulation resistance of the power battery pack further includes an isolation unit.

[0055] The first input terminal of the isolation unit is electrically connected to the second terminal of the first resistor and the first terminal of the second resistor respectively. The second input terminal of the isolation unit is electrically connected to the second terminal of the second resistor, the ground terminal and the first terminal of the third resistor respectively. The third input terminal of the isolation unit is electrically connected to the second terminal of the third resistor and the first terminal of the fourth resistor respectively. The fourth input terminal of the isolation unit is electrically connected to the negative electrode of the power battery pack and the second terminal of the fourth resistor respectively. The first output terminal and the second output terminal of the isolation unit are electrically connected to the first acquisition terminal of the acquisition control unit respectively. The third output terminal and the fourth output terminal of the isolation unit are electrically connected to the second acquisition terminal of the acquisition control unit respectively.

[0056] Among them, from the above connection relationship, it can be seen that the four output nodes corresponding to the first resistor, the second resistor, the third resistor and the fourth resistor are output to the acquisition control unit through the isolation unit.

[0057] Among them, the isolation unit mainly plays the role of electrical isolation. Since the power battery pack is on the high-voltage side and the acquisition control unit is on the low-voltage side, if there is no electrical isolation, interference is likely to occur, which will affect the acquisition control unit and even damage the acquisition control unit.

[0058] Among them, in this embodiment, the isolation unit can directly adopt an isolation transformer. Since the isolation transformer realizes the voltage transmission through the electromagnetic induction between the primary winding and the secondary winding, it can better realize electrical isolation and enable the input and output to maintain the same proportional relationship, so as to meet the subsequent calculation requirements.

[0059] As Figure 2 shown, in one embodiment, the isolation unit includes a first isolation amplifier and a second isolation amplifier (as Figure 2the isolation amplifier 1 and the isolation amplifier 2 therein);

[0060] The first input terminal of the isolation amplifier 1 is electrically connected to the second terminal of the first resistor R3 and the first terminal of the second resistor R4 respectively. The second input terminal of the isolation amplifier 1 is electrically connected to the second terminal of the second resistor R4, the ground terminal PGND and the first terminal of the third resistor R5 respectively. The first output terminal and the second output terminal of the isolation amplifier 1 are electrically connected to the first acquisition terminal of the acquisition control unit (in the same embodiment as above, in this embodiment, the connection relationship between the acquisition control unit and other devices is represented by the single-chip microcomputer AD acquisition unit).

[0061] The first input terminal of the isolation amplifier 2 is electrically connected to the second terminal of the third resistor R5 and the first terminal of the fourth resistor R6 respectively. The second input terminal of the isolation amplifier 2 is electrically connected to the negative electrode BAT0 of the power battery pack and the second terminal of the fourth resistor R6 respectively. The first output terminal and the second output terminal of the isolation amplifier 2 are electrically connected to the second acquisition terminal of the single-chip microcomputer AD acquisition unit.

[0062] Among them, the isolation amplifier is a special amplifier used to provide electrical isolation between the input signal and the output signal. It usually consists of two parts: an isolation element (such as an optocoupler, an isolation transformer, etc.) between the input terminal and the output terminal and an amplification circuit. The isolation amplifier is usually applied to occasions where signals need to be isolated and amplified, such as in industrial control systems, measuring instruments, medical equipment and other fields. Its functions include electrical isolation, signal amplification, signal transmission, etc.

[0063] Electrical isolation: The isolation amplifier can effectively isolate the input signal and the output signal, avoiding signal interference and electrical grounding problems.

[0064] Signal amplification: The isolation amplifier can amplify the input signal so as to output a signal with a larger amplitude, thereby meeting the requirements of subsequent circuits or devices.

[0065] Signal transmission: The isolation amplifier can transmit signals between the input and the output, and by introducing the isolation element, the interference and noise in signal transmission can be reduced.

[0066] In one embodiment, the detection circuit of the insulation resistance of the power battery pack further includes:

[0067] a first difference calculation unit and a second difference calculation unit;

[0068] The first input terminal of the first difference calculation unit is electrically connected to the first output terminal of the first isolation amplifier. The second input terminal of the first difference calculation unit is electrically connected to the second output terminal of the first isolation amplifier. The output terminal of the first difference calculation unit is electrically connected to the first acquisition terminal of the acquisition control unit to calculate and output the voltage difference between the first input terminal and the second input terminal of the first difference calculation unit.

[0069] The first input terminal of the second difference calculation unit is electrically connected to the first output terminal of the second isolation amplifier. The second input terminal of the second difference calculation unit is electrically connected to the second output terminal of the second isolation amplifier. The output terminal of the second difference calculation unit is electrically connected to the second acquisition terminal of the acquisition control unit to calculate and output the voltage difference between the first input terminal and the second input terminal of the second difference calculation unit.

[0070] As mentioned in the above embodiments, the first isolation amplifier and the second isolation amplifier can be directly connected to the acquisition control unit. However, this method requires the acquisition control unit to calculate each voltage value to obtain the terminal voltage of the corresponding resistor, and then complete the calculation of the insulation resistance value. In this embodiment, the first difference calculation unit and the second difference calculation unit can be set to determine the voltage difference between the first input terminal and the second input terminal of the first isolation amplifier, that is, the terminal voltage of the second resistor, by means of hardware, and determine the voltage difference between the first input terminal and the second input terminal of the second isolation amplifier, that is, the terminal voltage of the fourth resistor, by means of hardware. It should be noted that the four output nodes corresponding to the first resistor, the second resistor, the third resistor, and the fourth resistor are directly output to the acquisition control unit, or the four corresponding output nodes are output to the acquisition control unit through the first isolation amplifier and the second isolation amplifier. There are two first acquisition terminals and two second acquisition terminals corresponding to the acquisition control unit respectively. In this embodiment, since the first difference calculation unit and the second difference calculation unit are used to determine the terminal voltages of the second resistor and the fourth resistor respectively, only one first acquisition terminal and one second acquisition terminal of the acquisition control unit are required.

[0071] Among them, the difference calculation unit can adopt devices such as differential amplifiers.

[0072] As Figure 3 shown, in one embodiment, the first difference calculation unit includes a first differential operational amplifier, and the second difference calculation unit includes a second differential operational amplifier (such as Figure 3 the differential operational amplifiers 1 and 2 in

[0073] The first input terminal of the differential operational amplifier 1 is electrically connected to the first output terminal of the isolation amplifier 1. The second input terminal of the differential operational amplifier 1 is electrically connected to the second output terminal of the isolation amplifier 1. The output terminal of the differential operational amplifier 1 is electrically connected to the first acquisition terminal of the single-chip microcomputer AD acquisition unit.

[0074] The first input terminal of the differential operational amplifier 2 is electrically connected to the first output terminal of the isolation amplifier 2, the second input terminal of the differential operational amplifier 2 is electrically connected to the second output terminal of the isolation amplifier 2, and the output terminal of the differential operational amplifier 2 is electrically connected to the second acquisition terminal of the single-chip microcomputer AD acquisition unit.

[0075] Among them, a differential operational amplifier is a special type of operational amplifier specifically designed to calculate the difference between two input signals. It has two input terminals, namely the non-inverting input terminal (+IN) and the inverting input terminal (-IN), and an output terminal. The differential operational amplifier usually has the characteristics of high gain, high input impedance, and low output impedance, and can amplify the input signals and calculate the difference between them.

[0076] In one embodiment, the first switch includes a first optocoupler, and the second switch includes a second optocoupler;

[0077] The phototransistor in the first optocoupler is connected in series with the positive electrode of the power battery pack, the first resistor, the second resistor, and the ground terminal. The light-emitting diode in the first optocoupler is electrically connected to the first control terminal of the acquisition control unit to control the on / off of the circuit between the positive electrode of the power battery pack through the first resistor and the second resistor to the ground terminal under the control of the acquisition control unit;

[0078] The phototransistor in the second optocoupler is connected in series with the ground terminal, the third resistor, the fourth resistor, and the negative electrode of the power battery pack. The light-emitting diode in the second optocoupler is electrically connected to the second control terminal of the acquisition control unit to control the on / off of the circuit between the negative electrode of the power battery pack through the third resistor and the fourth resistor to the ground terminal under the control of the acquisition control unit.

[0079] As mentioned in the above embodiment, the power battery pack is the high-voltage side and the acquisition control unit is the low-voltage side. Therefore, electrical isolation between the high-voltage side and the low-voltage side can be achieved through the isolation unit, thereby improving the system reliability. To make the system more efficient, the first switch and the second switch are usually controllable devices, that is, they can be controlled by the acquisition control unit to achieve automatic conduction and disconnection. However, in this way, the power battery pack and the acquisition control unit are connected, and there is a risk of interference. In view of this situation, an optocoupler is selected as the switch in this embodiment, and the electrical isolation function of the optocoupler is used to achieve electrical isolation between the power battery pack and the acquisition control unit. Of course, in other embodiments, the switch can also be a relay, a contactor, etc.

[0080] As Figure 3 shown, in one embodiment, the detection circuit of the insulation resistance of the power battery pack further includes a fifth resistor R1, a sixth resistor R2, a third switch S1, and a fourth switch S2.

[0081] The first end of the fifth resistor R1 is electrically connected to the positive electrode BAT+ of the power battery pack and the first end of the first resistor R3 respectively. The second end of the fifth resistor R1 is electrically connected to the ground terminal PGND, the second end of the second resistor R4, the first end of the sixth resistor R2, the first end of the third resistor R5, and the first acquisition terminal of the single-chip microcomputer AD acquisition unit (specifically, through the isolation amplifier 1 and the differential operational amplifier 1 to the first acquisition terminal of the single-chip microcomputer AD acquisition unit). The second end of the sixth resistor R2 is electrically connected to the negative electrode BAT0 of the power battery pack, the second end of the fourth resistor R6, and the second acquisition terminal of the single-chip microcomputer AD acquisition unit (specifically, through the isolation amplifier 2 and the differential operational amplifier 2 to the second acquisition terminal of the single-chip microcomputer AD acquisition unit).

[0082] The third switch S1 is connected in series with the positive electrode BAT+ of the power battery pack, the fifth resistor R1, and the ground terminal PGND to control the on / off of the line between the positive electrode BAT+ of the power battery pack through the fifth resistor R1 to the ground terminal PGND; the fourth switch S2 is connected in series with the ground terminal PGND, the sixth resistor R2, and the negative electrode BAT0 of the power battery pack to control the on / off of the line between the negative electrode BAT0 of the power battery pack through the sixth resistor R2 to the ground terminal PGND.

[0083] Among them, if there are only the first resistor R3, the second resistor R4, the third resistor R5, and the fourth resistor R6, when the equivalent resistance values of the positive insulation resistor RP and the negative insulation resistor RN decrease due to a single-ended fault, for example, the positive insulation resistor RP decreases from 10 MΩ to 10 KΩ due to a single-ended fault, while the negative insulation resistor RN is still 10 MΩ. Based on the voltage division relationship between the two, the voltage on the positive electrode side is extremely small, so that when the voltage is detected through the first resistor R3, the second resistor R4, the third resistor R5, and the fourth resistor R6 subsequently, only an extremely small voltage can be obtained on the positive electrode side, which may exceed the acquisition range of the single-chip microcomputer AD acquisition unit, resulting in the inability to perform the entire detection process. In this embodiment, the fifth resistor R1 and the sixth resistor R2 are added. When detection is required, the third switch S1 and the fourth switch S2 are closed, and by using the voltage division of the fifth resistor R1 and the sixth resistor R2, whether the positive insulation resistor RP or the negative insulation resistor RN has a single-ended fault, a suitable voltage value can be obtained at the subsequent stage, thus ensuring the reliability of the detection.

[0084] In one embodiment, the third switch includes a third optocoupler, and the fourth switch includes a fourth optocoupler;

[0085] The photosensitive triode in the third optocoupler is connected in series with the positive electrode of the power battery pack, the fifth resistor, and the ground terminal. The light-emitting diode in the third optocoupler is electrically connected to the third control terminal of the acquisition control unit to control the on / off of the line between the positive electrode of the power battery pack through the fifth resistor to the ground terminal under the control of the acquisition control unit;

[0086] The photosensitive triode in the fourth optocoupler is connected in series with the ground terminal, the sixth resistor, and the negative electrode of the power battery pack. The light-emitting diode in the fourth optocoupler is electrically connected to the fourth control terminal of the acquisition control unit, so as to control the on-off of the circuit between the negative electrode of the power battery pack and the ground terminal through the sixth resistor under the control of the acquisition control unit.

[0087] Among them, for the purpose of using the optocoupler as the switch, reference can be made to the above-mentioned embodiments, which will not be elaborated here.

[0088] In order to make the technical solutions in the above embodiments clearer, a principle description is given below, which can be referred to Figures 3 to 6 .

[0089] Among them, in the static state, S1-S4 are all in the off state. At this time, the circuit will not reduce the insulation performance of the whole vehicle, and the equivalent circuit is as Figure 4 ;

[0090] Closing S1, S2, S3, the equivalent circuit is as Figure 5

[0091] According to Kirchhoff's first law:

[0092] I1 + I2 + I3 = I4 + I5, (Equation 1).

[0093] By collecting Ueb, calculate Uab:

[0094]

[0095] Given the voltage BAT from BAT+ to BAT0, calculate Ubc:

[0096] Ubc = BAT - Uab, (Equation 3).

[0097] Given Uab and Ubc, using Ohm's law, transform Equation 1:

[0098]

[0099] Closing S1, S2, S4, the equivalent circuit is shown in Figure 6

[0100] According to Kirchhoff's first law:

[0101] I1’ + I2’ = I4’ + I5’ + I6’, (Equation 5).

[0102] By collecting Ufc’, calculate Ubc’:

[0103]

[0104] Given the voltage BAT' from BAT+ to BAT0, calculate Uab':

[0105] Uab' = BAT′ - Ubc', (Equation 7).

[0106] Given Uab' and Ubc', using Ohm's law, transform Equation 1:

[0107]

[0108] (Equation 4) and (Equation 8) form a system of equations to find the values of RP and RN:

[0109]

[0110] In a second aspect, in an embodiment, the present invention provides an electric vehicle, including a power battery pack and a detection circuit for the insulation resistance of the power battery pack in any of the above embodiments.

[0111] Through the above electric vehicle, multiple resistors and switches are provided to implement the detection of the insulation resistance in the form of bridge resistor voltage division, with a simple circuit and low cost.

[0112] In the above embodiments, the descriptions of the various embodiments have their own focuses. For the parts not detailed in a certain embodiment, reference can be made to the detailed descriptions of other embodiments above, which will not be elaborated here.

[0113] The above has introduced in detail a detection circuit for the insulation resistance of a power battery pack and an electric vehicle provided by the present invention. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those skilled in the art, based on the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

[0114] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should all be considered as within the scope described in this specification.

Claims

1. A detection circuit for insulation resistance of a power battery pack, characterized in that: The insulation resistance detection circuit of the power battery pack is used to detect the resistance value of the positive electrode insulation resistance of the positive electrode of the power battery pack to the ground and to detect the resistance value of the negative electrode insulation resistance of the negative electrode of the power battery pack to the ground. The insulation resistance detection circuit of the power battery pack includes: A first resistor, a second resistor, a third resistor, a fourth resistor, a first switch, a second switch and a collection control unit; The first end of the first resistor is electrically connected to the positive electrode of the power battery pack, the second end of the first resistor is electrically connected to the first end of the second resistor and the first collection terminal of the collection control unit, the second end of the second resistor is electrically connected to the first end of the third resistor, the first collection terminal of the collection control unit and the ground terminal, the second end of the third resistor is electrically connected to the first end of the fourth resistor and the second collection terminal of the collection control unit, and the second end of the fourth resistor is electrically connected to the negative electrode of the power battery pack and the second collection terminal of the collection control unit; The first switch is connected in series with the positive electrode of the power battery pack, the first resistor, the second resistor and the ground terminal to control the on-off of the line between the positive electrode of the power battery pack through the first resistor and the second resistor to the ground terminal; the second switch is connected in series with the ground terminal, the third resistor, the fourth resistor and the negative electrode of the power battery pack to control the on-off of the line between the negative electrode of the power battery pack through the third resistor and the fourth resistor to the ground terminal.

2. The detection circuit of the insulation resistance of the power battery pack according to claim 1, characterized in that: The detection circuit of the insulation resistance of the power battery pack also includes: Isolation unit; The first input end of the isolation unit is electrically connected to the second end of the first resistor and the first end of the second resistor, respectively; the second input end of the isolation unit is electrically connected to the second end of the second resistor, the ground end, and the first end of the third resistor, respectively; the third input end of the isolation unit is electrically connected to the second end of the third resistor and the first end of the fourth resistor, respectively; the fourth input end of the isolation unit is electrically connected to the negative electrode of the power battery pack and the second end of the fourth resistor, respectively; the first output end of the isolation unit and the second output end of the isolation unit are electrically connected to the first acquisition end of the acquisition control unit, respectively; the third output end of the isolation unit and the fourth output end of the isolation unit are electrically connected to the second acquisition end of the acquisition control unit, respectively.

3. The detection circuit of the insulation resistance of the power battery pack according to claim 2, characterized in that: The isolation unit includes a first isolation amplifier and a second isolation amplifier; The first input end of the first isolation amplifier is electrically connected to the second end of the first resistor and the first end of the second resistor respectively, the second input end of the first isolation amplifier is electrically connected to the second end of the second resistor, the ground end and the first end of the third resistor respectively, and the first output end of the first isolation amplifier and the second output end of the first isolation amplifier are electrically connected to the first acquisition end of the acquisition control unit respectively; The first input end of the second isolation amplifier is electrically connected to the second end of the third resistor and the first end of the fourth resistor, respectively; the second input end of the second isolation amplifier is electrically connected to the negative electrode of the power battery pack and the second end of the fourth resistor, respectively; and the first output end of the second isolation amplifier and the second output end of the second isolation amplifier are electrically connected to the second acquisition end of the acquisition control unit, respectively.

4. The detection circuit of the insulation resistance of the power battery pack according to claim 3, characterized in that: The detection circuit of the insulation resistance of the power battery pack also includes: a first difference calculation unit and a second difference calculation unit; The first input end of the first difference calculation unit is electrically connected to the first output end of the first isolation amplifier, the second input end of the first difference calculation unit is electrically connected to the second output end of the first isolation amplifier, and the output end of the first difference calculation unit is electrically connected to the first acquisition end of the acquisition control unit, so as to calculate the voltage difference between the first input end and the second input end of the first difference calculation unit and output it; The first input terminal of the second difference calculation unit is electrically connected to the first output terminal of the second isolation amplifier, the second input terminal of the second difference calculation unit is electrically connected to the second output terminal of the second isolation amplifier, and the output terminal of the second difference calculation unit is electrically connected to the second acquisition terminal of the acquisition control unit to calculate the voltage difference between the first input terminal and the second input terminal of the second difference calculation unit and output it.

5. The detection circuit of the insulation resistance of the power battery pack according to claim 4, characterized in that: The first difference calculation unit includes a first differential operational amplifier, and the second difference calculation unit includes a second differential operational amplifier; The first input end of the first differential operational amplifier is electrically connected to the first output end of the first isolation amplifier, the second input end of the first differential operational amplifier is electrically connected to the second output end of the first isolation amplifier, and the output end of the first differential operational amplifier is electrically connected to the first acquisition end of the acquisition control unit; The first input terminal of the second differential operational amplifier is electrically connected to the first output terminal of the second isolation amplifier, the second input terminal of the second differential operational amplifier is electrically connected to the second output terminal of the second isolation amplifier, and the output terminal of the second differential operational amplifier is electrically connected to the second acquisition terminal of the acquisition control unit.

6. The insulation resistance detection circuit of the power battery pack according to any one of claims 1 to 5, characterized in that: The first switch includes a first optical coupler, and the second switch includes a second optical coupler; The photosensitive transistor in the first optical coupler is connected in series with the positive electrode of the power battery pack, the first resistor, the second resistor and the ground terminal, and the light-emitting diode in the first optical coupler is electrically connected to the first control terminal of the acquisition control unit, so as to control the on-off of the line between the positive electrode of the power battery pack through the first resistor and the second resistor to the ground terminal under the control of the acquisition control unit; The phototransistor in the second optocoupler is connected in series with the ground terminal, the third resistor, the fourth resistor and the negative electrode of the power battery pack, and the light-emitting diode in the second optocoupler is electrically connected to the second control terminal of the acquisition control unit to control the on / off of the line between the negative electrode of the power battery pack through the third resistor and the fourth resistor to the ground terminal under the control of the acquisition control unit.

7. The insulation resistance detection circuit of the power battery pack according to any one of claims 1 to 5, characterized in that: The detection circuit of the insulation resistance of the power battery pack also includes: a fifth resistor, a sixth resistor, a third switch and a fourth switch; The first end of the fifth resistor is electrically connected to the positive electrode of the power battery pack and the first end of the first resistor respectively, the second end of the fifth resistor is electrically connected to the ground terminal, the second end of the second resistor, the first end of the sixth resistor, the first end of the third resistor and the first acquisition terminal of the acquisition control unit respectively, and the second end of the sixth resistor is electrically connected to the negative electrode of the power battery pack, the second end of the fourth resistor and the second acquisition terminal of the acquisition control unit respectively; The third switch is connected in series with the positive electrode of the power battery pack, the fifth resistor and the ground terminal to control the on-off of the line between the positive electrode of the power battery pack through the fifth resistor to the ground terminal; the fourth switch is connected in series with the ground terminal, the sixth resistor and the negative electrode of the power battery pack to control the on-off of the line between the negative electrode of the power battery pack through the sixth resistor to the ground terminal.

8. The detection circuit of the insulation resistance of the power battery pack according to claim 7, characterized in that: The third switch includes a third optical coupler, and the fourth switch includes a fourth optical coupler; The photosensitive transistor in the third photocoupler is connected in series with the positive electrode of the power battery pack, the fifth resistor and the ground terminal, and the light-emitting diode in the third photocoupler is electrically connected to the third control terminal of the acquisition control unit, so as to control the on-off of the line between the positive electrode of the power battery pack through the fifth resistor and the ground terminal under the control of the acquisition control unit; The phototransistor in the fourth optocoupler is connected in series with the ground terminal, the sixth resistor and the negative electrode of the power battery pack, and the light-emitting diode in the fourth optocoupler is electrically connected to the fourth control terminal of the acquisition control unit to control the on-off of the line between the negative electrode of the power battery pack through the sixth resistor to the ground terminal under the control of the acquisition control unit.

9. The detection circuit for insulation resistance of a power battery pack according to any one of claims 1 to 5, characterized in that: The acquisition control unit includes a single chip microcomputer, and the single chip microcomputer includes a single chip microcomputer AD acquisition unit and a control unit electrically connected to each other; The first acquisition end of the single-chip AD acquisition unit is electrically connected to the second end of the first resistor, the first end of the second resistor, the second end of the second resistor, the first end of the third resistor and the ground end, respectively; the second acquisition end of the single-chip AD acquisition unit is electrically connected to the second end of the third resistor, the first end of the fourth resistor, the second end of the fourth resistor and the negative electrode of the power battery pack, respectively.

10. An electric vehicle, characterized in that: A detection circuit for the insulation resistance of a power battery pack and the power battery pack according to any one of claims 1 to 9.

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