A multi-level excitation generation system and method for lithium battery impedance measurement

Abstract

The present invention belongs to the technical field of lithium battery measurement, and discloses a multi-level excitation generation system and method for lithium battery impedance measurement, the system comprising: an excitation signal processing module, used for filtering and amplifying the variable frequency excitation signal; a voltage grading module, used for adjusting the voltage of the variable frequency excitation signal after filtering and amplification according to a preset gear; a constant current source module, used for converting the voltage signal after grading adjustment into a constant current signal, and converting the current signal into a stable voltage signal through a grounding resistor; an excitation output module, used for inputting the constant current signal output by the constant current source module as a test current to the battery under test; a grounding resistance grading module, used for switching the test current to grounding resistors with different resistance values ​​according to a preset gear. The present invention can grade the output excitation, and when the battery impedance is small, a large current is used to increase the response voltage of the battery under test, thereby improving the signal-to-noise ratio of the acquisition signal.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery measurement, and in particular to a multi-level excitation generation system and method for lithium battery impedance measurement. Background Art

[0002] In the production and research and development of lithium batteries, accurate EIS (electrochemical impedance spectroscopy) testing in the frequency range of 0.01HZ-10kHZ has become a much-needed link. The test results of each frequency point in the frequency range are crucial for detecting and guiding the optimization of lithium battery performance. The internal resistance of lithium batteries is usually small, most of which are milliohms or even a few tenths of a milliohm. The internal resistance of a PACK composed of lithium batteries is usually tens of milliohms to hundreds of ohms.

[0003] If you want to complete the impedance test of lithium batteries at multiple frequencies, you need a method that can achieve frequency conversion and can perform battery impedance testing from hundreds of milliohms to a few tenths of a milliohm. The premise of this method is to first implement an excitation generation method that supports this test method. The more mature LCR measurement equipment on the market is difficult to meet the precise measurement requirements for low resistance values ​​(especially a few tenths of a milliohm level) under frequency conversion conditions. In addition, the existing technology has deficiencies in achieving high-precision and high-stability excitation current output, and the lack of a stable excitation current will directly affect the accuracy of the battery impedance test. At the same time, the existing technology lacks the excitation current grading function and cannot flexibly adjust the excitation current according to the resistance range being measured, which further limits the maximum improvement of test accuracy and resolution.

[0004] Therefore, how to provide a multi-level excitation generation system and method for lithium battery impedance measurement is a problem that needs to be solved urgently. Summary of the invention

[0005] The embodiment of the present invention provides a multi-level excitation generation system and method for lithium battery impedance measurement, so as to solve the problem that the demand for accurate measurement of low resistance values ​​is difficult to meet in the prior art.

[0006] In order to have a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not a general review, nor is it intended to identify key / important components or to describe the scope of protection of these embodiments. Its only purpose is to present some concepts in a simple form as a prelude to the detailed description that follows.

[0007] According to a first aspect of an embodiment of the present invention, a multi-level excitation generation system for lithium battery impedance measurement is provided.

[0008] In one embodiment, the multi-level excitation generation system for lithium battery impedance measurement includes: a variable frequency signal source module, an excitation signal processing module, a voltage grading module, a constant current source module, an excitation output module, a measured battery and a ground resistance grading module;

[0009] Wherein, the variable frequency signal source module is used to output a variable frequency excitation signal;

[0010] The excitation signal processing module is used to filter and amplify the variable frequency excitation signal;

[0011] The voltage grading module is used to adjust the voltage of the variable frequency excitation signal after filtering and amplification according to the preset gear;

[0012] The constant current source module is used to convert the voltage signal after the step adjustment into a constant current signal, and convert the current signal into a stable voltage signal through a grounding resistor;

[0013] The excitation output module is used to input the constant current signal output by the constant current source module as a test current into the battery under test;

[0014] The grounding resistance grading module is used to switch the test current to grounding resistances with different resistance values ​​according to preset gears;

[0015] The output end of the variable frequency signal source module is electrically connected to the input end of the excitation signal processing module, the output end of the excitation signal processing module is electrically connected to the input end of the voltage grading module, the output end of the voltage grading module is connected to the input end of the constant current source module, the output end of the constant current source module is electrically connected to the input end of the excitation output module, the output end of the excitation output module is electrically connected to the input end of the battery under test, and the output end of the battery under test is electrically connected to the input end of the grounding resistance grading module.

[0016] In one embodiment, the frequency conversion signal source module includes an analog converter IC1, an operational amplifier IC2A, an operational amplifier IC2B, and an operational amplifier IC3A;

[0017] Wherein, the first pin of the analog converter IC1 is connected to the first pin of the operational amplifier IC3A and outputs the voltage V0, the second pin of the operational amplifier IC3A is connected to the thirteenth pin of the analog converter IC1, the third pin of the operational amplifier IC3A is connected to the second pin of the analog converter IC1, the eighth pin of the operational amplifier IC3A is connected to the VCC8 terminal, the fourth pin of the operational amplifier IC3A is connected to the VCC8- terminal, the third pin of the analog converter IC1 is connected to the first pin of the operational amplifier IC2A, the second pin of the operational amplifier IC2A is connected to the fourth pin of the operational amplifier IC3A, the third pin of the operational amplifier IC2A is connected to the VCC8- terminal. The fourth pin of the operational amplifier IC2A is connected to the VCC8- terminal, the eighth pin of the operational amplifier IC2A is connected to the VCC8 terminal, the fifth pin of the analog converter IC1 is connected to the sixth pin of the operational amplifier IC2B, the fifth pin of the operational amplifier IC2B is connected to the external reference voltage input, the seventh pin of the operational amplifier IC2B is connected to the sixth pin of the analog converter IC1, the seventh pin, the eighth pin, the tenth pin and the eleventh pin of the analog converter IC1 are respectively connected to the signal CS, the signal SCLK, the signal DIN and the signal LDAC, the twelfth pin of the analog converter IC1 is grounded, and the fourteenth pin of the analog converter IC1 is connected to the VCC1 terminal.

[0018] In one embodiment, the variable frequency signal source module outputs a variable frequency excitation signal with a frequency variable within a range of 0.01HZ-10KHZ.

[0019] In one embodiment, the excitation signal processing module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C1, a capacitor C2, an operational amplifier IC3B and an operational amplifier IC4A;

[0020] The fifth pin of the operational amplifier IC3B is connected to one end of the resistor R1, the other end of the resistor R1 is grounded, the sixth pin of the operational amplifier IC3B is respectively connected to one end of the resistor R2 and one end of the resistor R3, the other end of the resistor R2 is connected to the output voltage V0, the other end of the resistor R3 is connected to one end of the resistor R4, the other end of the resistor R4 is respectively connected to the seventh pin of the operational amplifier IC3B and one end of the resistor R5, the other end of the resistor R5 is respectively connected to one end of the resistor R6 and the capacitor One end of the capacitor C1 is connected, the other end of the capacitor C1 is grounded, the other end of the resistor R6 is respectively connected to one end of the capacitor C2 and the third pin of the operational amplifier IC4A, the other end of the capacitor C2 is grounded, the second pin of the operational amplifier IC4A is respectively connected to the first pin and one end of the resistor R7, the other end of R7 is connected to one end of the resistor R8, the other end of the resistor R8 outputs a voltage V1, the eighth pin of the operational amplifier IC4A is connected to the VCC8 terminal, and the fourth pin of the operational amplifier IC4A is connected to the VCC8- terminal.

[0021] In one embodiment, the voltage grading module includes: a reverse trigger IC5, an analog switch IC6, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18 and a resistor R19;

[0022] The first pin of the reverse trigger IC5 is connected to one end of the resistor R9 and is connected to the external control signal CONTRL1. The other end of the resistor R9 is respectively connected to one end of the resistor R10 and one end of the resistor R11 and is grounded. The other end of R10 is respectively connected to the fifth pin of the reverse trigger IC5 and is connected to the external control signal CONTRL2. The other end of the resistor R11 is connected to the thirteenth pin of the reverse trigger IC5 and is connected to the external control signal CONTRL3. The second pin of the reverse trigger IC5 is connected to the third pin. The fourth pin of the reverse trigger IC5 is connected to the eleventh pin of the analog switch IC6. The sixth pin of the reverse trigger IC5 is connected to the ninth pin. The seventh pin of the reverse trigger IC5 is grounded. The eighth pin of the reverse trigger IC5 is connected to the ninth pin of the analog switch IC6. The tenth pin of the reverse trigger IC5 is connected to the tenth pin of the analog switch IC6. The eleventh pin of the reverse trigger IC5 is connected to the twelfth pin. The fourteenth pin of the reverse trigger IC5 is connected to the VCC14 terminal. The first pin of the analog switch IC6 is respectively connected to one end of the resistor R18 and the One end of the resistor R19 is connected, the other end of the resistor R18 is respectively connected to one end of the resistor R15 and the twelfth pin of the analog switch IC6, the other end of the resistor R15 is respectively connected to one end of the resistor R13 and the fifteenth pin of the analog switch IC6, the other end of the resistor R13 is respectively connected to the fourteenth pin of the analog switch IC6 and connected to the output voltage V1, the other end of the resistor R19 is respectively connected to the fifth pin of the analog switch IC6 and one end of the resistor R16, the other end of the resistor R16 is respectively connected to the second pin of the analog switch IC6 and the One end of the resistor R14 is connected, the other end of the resistor R14 is respectively connected to the fourth pin of the analog switch IC6 and one end of the resistor R17, the other end of the resistor R17 is grounded, the third pin of the analog switch IC6 is connected to one end of the resistor R12, the other end of the resistor R12 outputs the voltage V2, the sixth pin of the analog switch IC6 is grounded, the seventh pin of the analog switch IC6 is connected to the VCC8-terminal, the eighth pin of the analog switch IC6 is grounded, the thirteenth pin of the analog switch IC6 is grounded, and the sixteenth pin of the analog switch IC6 is connected to the VCC8 terminal.

[0023] In one embodiment, the constant current source module includes a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25, a resistor R26, a resistor R27, a resistor R28, a resistor R29, a resistor R30, a resistor R31, a resistor R32, a capacitor C3, a capacitor C4, a capacitor C5, an operational amplifier IC7A, an operational amplifier IC7B, an operational amplifier IC8B, an operational amplifier IC9A and an operational amplifier IC9B;

[0024] Among them, the first pin of the operational amplifier IC7A is respectively connected to the second pin of the operational amplifier IC7A and one end of the resistor R22, the third pin of the operational amplifier IC7A is respectively connected to one end of the resistor R21 and one end of the capacitor C3, the other end of the resistor R21 is connected to the other end of the capacitor C3 and grounded, the eighth pin of the operational amplifier IC7A is connected to the VCC8 end, the fourth pin of the operational amplifier IC7A is connected to the VCC8- end, the other end of the resistor R22 is connected to the fifth pin of the operational amplifier IC8B, the sixth pin of the operational amplifier IC8B is respectively connected to one end of the resistor R23, one end of the resistor R24 ​​and one end of the resistor R23, the other end of the resistor R23 is connected to the sixth pin and the seventh pin of the operational amplifier IC7B, the fifth pin of the operational amplifier IC7B is connected to the output voltage V2, the seventh pin of the operational amplifier IC8B is respectively connected to the other end of the resistor R24, the other end of the resistor R25 and one end of the resistor R27, the The other end of the resistor R27 is respectively connected to the third pin of the operational amplifier IC9A and one end of the resistor R26, the other end of the resistor R26 is respectively connected to the seventh pin and the sixth pin of the operational amplifier IC9B, the fifth pin of the operational amplifier IC9B is respectively connected to one end of the resistor R30, one end of the resistor R31 and one end of the resistor R32 and outputs the voltage V3, the other end of the resistor R31 is connected to the other end of the resistor R32 and is grounded, the other end of the resistor R30 is respectively connected to one end of the resistor R29 and the first pin of the operational amplifier IC9A, the other end of the resistor R29 is respectively connected to one end of the resistor R28 and the second pin of the operational amplifier IC9A, the other end of the resistor R28 is grounded, the eighth pin of the operational amplifier IC9A is connected to one end of the capacitor C4 and connected to the VCC8 terminal, the other end of the capacitor C4 is grounded, the fourth pin of the operational amplifier IC9A is connected to one end of the capacitor C5 and connected to the VCC8-terminal, and the other end of the capacitor C5 is grounded.

[0025] In one embodiment, the excitation output module includes a resistor R33, a resistor R34, a resistor R35, a resistor R36, a resistor R37, a resistor R38, a capacitor C6, a capacitor C7, a capacitor C8, an operational amplifier IC10A, an operational amplifier IC11A, a transistor Q1, a transistor Q2, a transistor Q3, a transistor Q4, a diode D1, a diode D2 and a diode D3;

[0026] Among them, the first pin of the operational amplifier IC10A is connected to one end of the resistor R34 and one end of the capacitor C8, the other end of the capacitor C8 is connected to one end of the resistor R33 and the second pin of the operational amplifier IC10A, the other end of the resistor R33 is connected to the output voltage V4, the third pin of the operational amplifier IC10A is connected to the output voltage V3, the fourth pin of the operational amplifier IC10A is connected to one end of the capacitor C7 and to the VCC5-end, the other end of the capacitor C7 is grounded, the eighth pin of the operational amplifier IC10A is connected to one end of the capacitor C6 and to the VCC5 end, the other end of the capacitor C6 is grounded, the other end of the capacitor R34 is respectively connected to the third pin of the diode D1 and the third pin of the operational amplifier IC11A, the second pin of the diode D1 is connected to the VCC5 end, the first pin of the diode D1 is connected to the VCC5-end, the first pin of the operational amplifier IC11A is respectively connected to the second pin of the operational amplifier IC11A, the cathode of the diode D2 and the diode D 3, the eighth pin of the operational amplifier IC11A is connected to the VCC5 terminal, the fourth pin of the operational amplifier IC11A is connected to the VCC5- terminal, the anode of the diode D2 is connected to one end of the resistor R35 and the base of the transistor Q1 respectively, the other end of the resistor R35 is connected to the VCC5 terminal, the collector of the transistor Q1 is connected to the VCC5 terminal, the emitter of the transistor Q1 is connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to the VCC5 terminal, the emitter of the transistor Q2 is connected to the resistor R35 terminal, and the emitter of the transistor Q2 is connected to the VCC5 terminal. One end of the resistor R37 is connected, the other end of the resistor R37 is connected to one end of the resistor R38 and outputs the voltage V5, the other end of the resistor R38 is connected to the emitter of the transistor Q4, the collector of the transistor Q4 is connected to the VCC5-terminal, the base of the transistor Q4 is connected to the emitter of the transistor Q3, the collector of the transistor Q3 is connected to the VCC5-terminal, the base of the transistor Q3 is respectively connected to the cathode of the diode D3 and one end of the resistor R36, and the other end of the resistor R36 is connected to the VCC5-terminal.

[0027] In one embodiment, the grounding resistance grading module includes resistor R47, resistor R48, resistor R49, resistor R50, resistor R51, resistor R52, resistor R53, resistor R54, resistor R55, resistor R60, resistor R61, resistor R62, resistor R63, resistor R66, resistor R68, resistor R69, resistor R70, resistor R71, resistor R72, field effect transistor Q8, field effect transistor Q9, field effect transistor Q10, optocoupler relay OD4, optocoupler relay OD5, optocoupler relay OD6, analog switch IC12, analog switch IC13 and analog switch IC14;

[0028] The first pin of the analog switch IC12 is respectively connected to the first pin of the analog switch IC13, one end of the resistor R51, the drain of the field effect transistor Q9, the second pin of the optical coupler relay OD5 and the ninth pin of the analog switch IC14, the source of the field effect transistor Q9 is connected to one end of the resistor R50 and is grounded, the other end of the resistor R50 is connected to the gate of the field effect transistor Q9 and is connected to the external control signal CONTRL8, the other end of the resistor R51 is connected to one end of the resistor R52 and is connected to VCC8, the other end of the resistor R52 is connected to the first pin of the optical coupler relay OD5, and the sixth pin of the optical coupler relay OD5 is respectively connected to the optical coupler relay The fourth pin of the optocoupler relay OD6 and the sixth pin of the optocoupler relay OD4 are linked and connected to the signal VBACK, the fourth pin of the optocoupler relay OD5 is connected to one end of the resistor R61 through the resistor R60, and the other end of the resistor R61 is connected to the signal VBACK2, the first pin of the optocoupler relay OD4 is connected to one end of the resistor R49, and the other end of the resistor R49 is respectively connected to one end of the resistor R48 and connected to the VCC8 end, and the other end of the resistor R48 is respectively connected to the drain of the field effect tube Q8, the second pin of the optocoupler relay OD4, the eighth pin of the analog switch IC12, the eighth pin of the analog switch IC13 and the eighth pin of the analog switch IC14 The gate of the field effect transistor Q8 is connected to one end of the resistor R47 and connected to the signal CONTRL7, the other end of the resistor R47 is connected to the source of the field effect transistor Q8 and is grounded, the first pin of the optical coupler relay OD6 is connected to one end of the resistor R55, the other end of the resistor R55 is connected to one end of the resistor R54 and connected to VCC8, the other end of the resistor R54 is respectively connected to the drain of the field effect transistor Q10, the second pin of the optical coupler relay OD6, the sixteenth pin of the analog switch IC12, the sixteenth pin of the analog switch IC13 and the sixteenth pin of the analog switch IC14, the gate of the field effect transistor Q10 is connected to one end of the resistor R53 The second end of the analog switch IC12 is respectively connected to the fifteenth pin of the analog switch IC12, the resistor R66, the resistor R68, the resistor R69, the resistor R70, the resistor R71 and one end of the resistor R72, the other end of the resistor R68 is respectively connected to the second pin of the analog switch IC13 and the fifteenth pin of the analog switch IC14 and connected to the signal VBACK2.The other end of the resistor R69 is respectively connected to the resistor R70, the resistor R71, the other end of the resistor R72, the fifteenth pin of the analog switch IC13 and the second pin of the analog switch IC14 and connected to the signal VBACK3. The other end of the resistor R66 is connected to the tenth pin of the analog switch IC14 and connected to the input signal VBACK1. The third pin of the analog switch IC12 is respectively connected to the fourteenth pin and the sixth pin and connected to the sampling point SAMPLEI+. The fourth pin of the analog switch IC12 and the fourth pin of the analog switch IC13 are both connected to the VCC17- terminal. The fourth pin of the analog switch IC14 is connected to the VCC5- terminal. The fifth pin of the analog switch IC12, the fifth pin of the analog switch IC13 and the fifth pin of the analog switch IC14 are all grounded, the seventh pin of the analog switch IC12 is connected to the seventh pin of the analog switch IC13 through the resistor R66, the thirteenth pin of the analog switch IC12 and the thirteenth pin of the analog switch IC13 are both connected to the VCC17 terminal, the thirteenth pin of the analog switch IC14 is connected to the VCC5 terminal, the third pin of the analog switch IC13 is respectively connected to the fourteenth pin and the sixth pin and connected to the sampling point SAMPLEI-, the third pin of the analog switch IC14 is respectively connected to the fourteenth pin and the eleventh pin and outputs the voltage V4. ,

[0029] In one embodiment, the resistor R66 is a four-terminal Kelvin resistor.

[0030] According to a second aspect of an embodiment of the present invention, a multi-level excitation generation method for lithium battery impedance measurement is provided.

[0031] In one embodiment, the multi-level excitation generation method for lithium battery impedance measurement includes:

[0032] Output variable frequency excitation signal, and filter and amplify the variable frequency excitation signal;

[0033] According to the preset gear, the voltage of the variable frequency excitation signal after filtering and amplification is adjusted in stages;

[0034] Convert the voltage signal after graded adjustment into a constant current signal, and convert the current signal into a stable voltage signal through a grounding resistor;

[0035] The output constant current signal is input into the battery under test as the test current, and the test current is switched to ground resistors with different resistance values ​​according to the preset gear.

[0036] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0037] 1. The present invention can adjust the excitation current level according to the resistance range of the object to be measured, so as to achieve accurate battery impedance measurement, and by selecting a suitable excitation current, ensure that the response voltage of the battery or battery pack to be measured is always within the range that the acquisition circuit can handle. Whether using a larger excitation current to measure low impedance or a smaller excitation current to measure high impedance, a response voltage that is stable in size and easy to handle can be obtained.

[0038] 2. The present invention utilizes the operational amplifier virtual short principle to design the output current source, realizes current output of different gears through ground resistance switching and input voltage switching, meets the test requirements of different resistance ranges, thereby ensuring the test accuracy and adaptability, and provides effective support for the accurate measurement of a wide range of impedance.

[0039] 3. The present invention can grade the output excitation. When the battery impedance is small, a large current is used to increase the response voltage of the battery under test, thereby improving the signal-to-noise ratio of the acquisition signal and increasing the sampling accuracy. At the same time, a constant current source module is added during the output process to ensure the stability of the output voltage, thereby achieving a test resolution of up to 100n ohms.

[0040] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0042] Figure 1 is a principle block diagram of a multi-level excitation generation system for lithium battery impedance measurement according to an exemplary embodiment;

[0043] Figure 2 is a flow chart of a multi-level excitation generation method for lithium battery impedance measurement according to an exemplary embodiment;

[0044] Figure 3 is a schematic diagram of a variable frequency signal source module in a multi-speed excitation generation system for lithium battery impedance measurement according to an exemplary embodiment;

[0045] Figure 4 is a schematic diagram of an excitation signal processing module in a multi-level excitation generation system for lithium battery impedance measurement according to an exemplary embodiment;

[0046] Figure 5 is a schematic diagram of a voltage binning module in a multi-bin excitation generation system for lithium battery impedance measurement according to an exemplary embodiment;

[0047] Figure 6 is a schematic diagram of a constant current source module in a multi-level excitation generation system for lithium battery impedance measurement according to an exemplary embodiment;

[0048] Figure 7 is a schematic diagram of an excitation output module in a multi-level excitation generation system for lithium battery impedance measurement according to an exemplary embodiment;

[0049] Figure 8 It is one of the principle diagrams of a ground resistance grading module in a multi-gradient excitation generation system for lithium battery impedance measurement according to an exemplary embodiment;

[0050] Fig. 9 This is the second schematic diagram of a ground resistance grading module in a multi-gradient excitation generation system for lithium battery impedance measurement according to an exemplary embodiment. DETAILED DESCRIPTION

[0051] The following description and accompanying drawings fully illustrate the specific embodiments of this article so that those skilled in the art can practice them. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. The scope of the embodiments of this article includes the entire scope of the claims, as well as all available equivalents of the claims. Herein, the terms "first", "second", etc. are only used to distinguish one element from another, without requiring or implying any actual relationship or order between these elements. In fact, the first element can also be called the second element, and vice versa. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the structure, device or equipment including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such structure, device or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the structure, device or equipment including the elements. Each embodiment is described in a progressive manner herein, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0052] Each module in the device or system of the present application can be implemented in whole or in part by software, hardware, or a combination thereof. The above modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to the above modules.

[0053] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0054] Figure 1 An embodiment of a multi-level excitation generation system for lithium battery impedance measurement according to the present invention is shown.

[0055] In this optional embodiment, the multi-level excitation generation system for lithium battery impedance measurement includes: a variable frequency signal source module 1, an excitation signal processing module 2, a voltage grading module 3, a constant current source module 4, an excitation output module 5, a battery under test 6 and a ground resistance grading module 7;

[0056] Wherein, the variable frequency signal source module 1 is used to output a variable frequency excitation signal;

[0057] The excitation signal processing module 2 is used to filter and amplify the variable frequency excitation signal;

[0058] The voltage grading module 3 is used to adjust the voltage of the variable frequency excitation signal after filtering and amplification according to the preset gear (selected gear);

[0059] The constant current source module 4 is used to convert the voltage signal after the step adjustment into a constant current signal, and convert the current signal into a stable voltage signal through a grounding resistor;

[0060] The excitation output module 5 is used to input the constant current signal output by the constant current source module 4 as a test current to the battery under test 6, so that a variable frequency response AC voltage is generated at both ends of the battery under test 6;

[0061] The grounding resistance grading module 7 is used for returning the current to the excitation circuit through the measured battery 6 and to the ground wire of the output circuit through the grounding resistance grading module 7. The grounding resistance grading module 7 switches to different grounding resistors R66 according to the selected gear position;

[0062] The output end of the variable frequency signal source module 1 is electrically connected to the input end of the excitation signal processing module 2, the output end of the excitation signal processing module 2 is electrically connected to the input end of the voltage grading module 3, the output end of the voltage grading module 3 is connected to the input end of the constant current source module 4, the output end of the constant current source module 4 is electrically connected to the input end of the excitation output module 5, the output end of the excitation output module 5 is electrically connected to the input end of the battery under test 6, and the output end of the battery under test 6 is electrically connected to the input end of the grounding resistance grading module 7.

[0063] In this alternative embodiment, if Figure 3 As shown, the frequency conversion signal source module 1 includes an analog converter IC1, an operational amplifier IC2A, an operational amplifier IC2B and an operational amplifier IC3A;

[0064] Wherein, the first pin of the analog converter IC1 is connected to the first pin of the operational amplifier IC3A and outputs the voltage V0, the second pin of the operational amplifier IC3A is connected to the thirteenth pin of the analog converter IC1, the third pin of the operational amplifier IC3A is connected to the second pin of the analog converter IC1, the eighth pin of the operational amplifier IC3A is connected to the VCC8 terminal, the fourth pin of the operational amplifier IC3A is connected to the VCC8- terminal, the third pin of the analog converter IC1 is connected to the first pin of the operational amplifier IC2A, the second pin of the operational amplifier IC2A is connected to the fourth pin of the operational amplifier IC3A, the third pin of the operational amplifier IC2A is connected to the VCC8- terminal. The fourth pin of the operational amplifier IC2A is connected to the VCC8- terminal, the eighth pin of the operational amplifier IC2A is connected to the VCC8 terminal, the fifth pin of the analog converter IC1 is connected to the sixth pin of the operational amplifier IC2B, the fifth pin of the operational amplifier IC2B is connected to the external reference voltage input, the seventh pin of the operational amplifier IC2B is connected to the sixth pin of the analog converter IC1, the seventh pin, the eighth pin, the tenth pin and the eleventh pin of the analog converter IC1 are respectively connected to the signal CS, the signal SCLK, the signal DIN and the signal LDAC, the twelfth pin of the analog converter IC1 is grounded, and the fourteenth pin of the analog converter IC1 is connected to the VCC1 terminal.

[0065] In this optional embodiment, the principle of the variable frequency signal source module 1 is: the analog converter IC1 is a digital-to-analog converter, which can output a variable frequency AC excitation source of 0.01HZ-10KHZ under the control of external signals LDAC, DIN, SCLK, and CS, the operational amplifier IC2 is a DAC external buffer, VREF4096 is an external reference voltage input, the operational amplifier IC3A is a DAC output buffer, and V0 is the output voltage of the variable frequency signal source module 1.

[0066] In this alternative embodiment, if Figure 4 As shown, the excitation signal processing module 2 includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C1, a capacitor C2, an operational amplifier IC3B and an operational amplifier IC4A;

[0067] The fifth pin of the operational amplifier IC3B is connected to one end of the resistor R1, the other end of the resistor R1 is grounded, the sixth pin of the operational amplifier IC3B is respectively connected to one end of the resistor R2 and one end of the resistor R3, the other end of the resistor R2 is connected to the output voltage V0, the other end of the resistor R3 is connected to one end of the resistor R4, the other end of the resistor R4 is respectively connected to the seventh pin of the operational amplifier IC3B and one end of the resistor R5, the other end of the resistor R5 is respectively connected to one end of the resistor R6 and the capacitor One end of the capacitor C1 is connected, the other end of the capacitor C1 is grounded, the other end of the resistor R6 is respectively connected to one end of the capacitor C2 and the third pin of the operational amplifier IC4A, the other end of the capacitor C2 is grounded, the second pin of the operational amplifier IC4A is respectively connected to the first pin and one end of the resistor R7, the other end of R7 is connected to one end of the resistor R8, the other end of the resistor R8 outputs a voltage V1, the eighth pin of the operational amplifier IC4A is connected to the VCC8 terminal, and the fourth pin of the operational amplifier IC4A is connected to the VCC8- terminal.

[0068] In this optional embodiment, the principle of the excitation signal processing module 2 is: the output voltage V0 is the output voltage in the frequency conversion signal source module 1, the operational amplifier IC3 is a reverse amplifier circuit, the resistor R5, the capacitor C1, the resistor R6 and the capacitor C2 form a second-order passive low-pass filter circuit, the operational amplifier IC4 is a follower, and the output voltage V1 is the output voltage of the excitation signal processing module 2.

[0069] In this alternative embodiment, if Figure 5 As shown, the voltage grading module 3 includes: a reverse trigger IC5, an analog switch IC6, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18 and a resistor R19;

[0070] The first pin of the reverse trigger IC5 is connected to one end of the resistor R9 and is connected to the external control signal CONTRL1. The other end of the resistor R9 is respectively connected to one end of the resistor R10 and one end of the resistor R11 and is grounded. The other end of R10 is respectively connected to the fifth pin of the reverse trigger IC5 and is connected to the external control signal CONTRL2. The other end of the resistor R11 is connected to the thirteenth pin of the reverse trigger IC5 and is connected to the external control signal CONTRL3. The second pin of the reverse trigger IC5 is connected to the third pin. The fourth pin of the reverse trigger IC5 is connected to the eleventh pin of the analog switch IC6. The sixth pin of the reverse trigger IC5 is connected to the ninth pin. The seventh pin of the reverse trigger IC5 is grounded. The eighth pin of the reverse trigger IC5 is connected to the ninth pin of the analog switch IC6. The tenth pin of the reverse trigger IC5 is connected to the tenth pin of the analog switch IC6. The eleventh pin of the reverse trigger IC5 is connected to the twelfth pin. The fourteenth pin of the reverse trigger IC5 is connected to the VCC14 terminal. The first pin of the analog switch IC6 is respectively connected to one end of the resistor R18 and the One end of the resistor R19 is connected, the other end of the resistor R18 is respectively connected to one end of the resistor R15 and the twelfth pin of the analog switch IC6, the other end of the resistor R15 is respectively connected to one end of the resistor R13 and the fifteenth pin of the analog switch IC6, the other end of the resistor R13 is respectively connected to the fourteenth pin of the analog switch IC6 and connected to the output voltage V1, the other end of the resistor R19 is respectively connected to the fifth pin of the analog switch IC6 and one end of the resistor R16, the other end of the resistor R16 is respectively connected to the second pin of the analog switch IC6 and the One end of the resistor R14 is connected, the other end of the resistor R14 is respectively connected to the fourth pin of the analog switch IC6 and one end of the resistor R17, the other end of the resistor R17 is grounded, the third pin of the analog switch IC6 is connected to one end of the resistor R12, the other end of the resistor R12 outputs the voltage V2, the sixth pin of the analog switch IC6 is grounded, the seventh pin of the analog switch IC6 is connected to the VCC8-terminal, the eighth pin of the analog switch IC6 is grounded, the thirteenth pin of the analog switch IC6 is grounded, and the sixteenth pin of the analog switch IC6 is connected to the VCC8 terminal.

[0071] In this optional embodiment, the principle of the voltage grading module 3 is: V1 in the voltage grading module 3 is the output voltage of the excitation signal processing module 2; resistors R13, R15, R18, R19, R16, R14 and R17 are grounding voltage-dividing resistors, IC6 is an analog switch, and the fourteenth pin, fifteenth pin, twelfth pin, first pin, fifth pin, second pin, and fourth pin of the analog switch IC6 are key voltage-dividing input points. According to different gear positions, different voltage-dividing inputs can be arbitrarily selected. IC5 is a Schmitt reverse trigger. Under the control of external control signals CONTRL1, CONTRL2, and CONTRL3, the analog switch IC6 can be controlled to select each voltage-dividing point. V2 is the final output voltage of the voltage grading module 3.

[0072] In this alternative embodiment, if Figure 6 As shown, the constant current source module 4 includes a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25, a resistor R26, a resistor R27, a resistor R28, a resistor R29, a resistor R30, a resistor R31, a resistor R32, a capacitor C3, a capacitor C4, a capacitor C5, an operational amplifier IC7A, an operational amplifier IC7B, an operational amplifier IC8B, an operational amplifier IC9A and an operational amplifier IC9B;

[0073] Among them, the first pin of the operational amplifier IC7A is respectively connected to the second pin of the operational amplifier IC7A and one end of the resistor R22, the third pin of the operational amplifier IC7A is respectively connected to one end of the resistor R21 and one end of the capacitor C3, the other end of the resistor R21 is connected to the other end of the capacitor C3 and grounded, the eighth pin of the operational amplifier IC7A is connected to the VCC8 end, the fourth pin of the operational amplifier IC7A is connected to the VCC8- end, the other end of the resistor R22 is connected to the fifth pin of the operational amplifier IC8B, the sixth pin of the operational amplifier IC8B is respectively connected to one end of the resistor R23, one end of the resistor R24 ​​and one end of the resistor R23, the other end of the resistor R23 is connected to the sixth pin and the seventh pin of the operational amplifier IC7B, the fifth pin of the operational amplifier IC7B is connected to the output voltage V2, the seventh pin of the operational amplifier IC8B is respectively connected to the other end of the resistor R24, the other end of the resistor R25 and one end of the resistor R27, the The other end of the resistor R27 is respectively connected to the third pin of the operational amplifier IC9A and one end of the resistor R26, the other end of the resistor R26 is respectively connected to the seventh pin and the sixth pin of the operational amplifier IC9B, the fifth pin of the operational amplifier IC9B is respectively connected to one end of the resistor R30, one end of the resistor R31 and one end of the resistor R32 and outputs the voltage V3, the other end of the resistor R31 is connected to the other end of the resistor R32 and is grounded, the other end of the resistor R30 is respectively connected to one end of the resistor R29 and the first pin of the operational amplifier IC9A, the other end of the resistor R29 is respectively connected to one end of the resistor R28 and the second pin of the operational amplifier IC9A, the other end of the resistor R28 is grounded, the eighth pin of the operational amplifier IC9A is connected to one end of the capacitor C4 and connected to the VCC8 terminal, the other end of the capacitor C4 is grounded, the fourth pin of the operational amplifier IC9A is connected to one end of the capacitor C5 and connected to the VCC8-terminal, and the other end of the capacitor C5 is grounded.

[0074] In this optional embodiment, the principle of the constant current source module 4 is: the output voltage V2 in the constant current source module 4 is the output voltage of the voltage grading module 3; IC7 is a two-way follower of a dual operational amplifier, IC8 is a subtractor, the input of the same direction end is the ground potential, and the reverse input is the voltage after V2 follows the buffer, IC9 is a V / I conversion constant current source composed of a dual operational amplifier, which is a positive feedback balanced howland constant current source, and its output current is not affected by the load size, wherein, resistor R26=resistor R27, resistor R28=resistor R29, the output voltage of IC8B is U1, then its output current I=U1 / R30, and the final output voltage of the constant current source module 4 is V3=I*(R31 / / R32).

[0075] In this alternative embodiment, if Figure 7 As shown, the excitation output module 5 includes a resistor R33, a resistor R34, a resistor R35, a resistor R36, a resistor R37, a resistor R38, a capacitor C6, a capacitor C7, a capacitor C8, an operational amplifier IC10A, an operational amplifier IC11A, a transistor Q1, a transistor Q2, a transistor Q3, a transistor Q4, a diode D1, a diode D2 and a diode D3;

[0076] Among them, the first pin of the operational amplifier IC10A is connected to one end of the resistor R34 and one end of the capacitor C8, the other end of the capacitor C8 is connected to one end of the resistor R33 and the second pin of the operational amplifier IC10A, the other end of the resistor R33 is connected to the output voltage V4, the third pin of the operational amplifier IC10A is connected to the output voltage V3, the fourth pin of the operational amplifier IC10A is connected to one end of the capacitor C7 and to the VCC5-end, the other end of the capacitor C7 is grounded, the eighth pin of the operational amplifier IC10A is connected to one end of the capacitor C6 and to the VCC5 end, the other end of the capacitor C6 is grounded, the other end of the capacitor R34 is respectively connected to the third pin of the diode D1 and the third pin of the operational amplifier IC11A, the second pin of the diode D1 is connected to the VCC5 end, the first pin of the diode D1 is connected to the VCC5-end, the first pin of the operational amplifier IC11A is respectively connected to the second pin of the operational amplifier IC11A, the cathode of the diode D2 and the diode D 3, the eighth pin of the operational amplifier IC11A is connected to the VCC5 terminal, the fourth pin of the operational amplifier IC11A is connected to the VCC5- terminal, the anode of the diode D2 is connected to one end of the resistor R35 and the base of the transistor Q1 respectively, the other end of the resistor R35 is connected to the VCC5 terminal, the collector of the transistor Q1 is connected to the VCC5 terminal, the emitter of the transistor Q1 is connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to the VCC5 terminal, the emitter of the transistor Q2 is connected to the resistor R35 terminal, and the emitter of the transistor Q2 is connected to the VCC5 terminal. One end of the resistor R37 is connected, the other end of the resistor R37 is connected to one end of the resistor R38 and outputs the voltage V5, the other end of the resistor R38 is connected to the emitter of the transistor Q4, the collector of the transistor Q4 is connected to the VCC5-terminal, the base of the transistor Q4 is connected to the emitter of the transistor Q3, the collector of the transistor Q3 is connected to the VCC5-terminal, the base of the transistor Q3 is respectively connected to the cathode of the diode D3 and one end of the resistor R36, and the other end of the resistor R36 is connected to the VCC5-terminal.

[0077] In this optional embodiment, the principle of the excitation output module 5 is: the output voltage V3 is the output voltage of the constant current output module, and the output voltage V4 is the feedback voltage of the grounding resistance grading module 7; IC10A is the output operational amplifier, IC11 is the follower, resistor R35, diode D2, diode D3, resistor R36, transistor Q1, transistor Q2, transistor Q3, transistor Q4, resistor R37 and resistor R38 constitute an output power amplifier circuit, V5 is the final output voltage of the excitation output module 5, and the output is applied to the positive electrode of the battery under test.

[0078] In this alternative embodiment, if Figure 8-Figure 9 As shown ( Figure 8 The first end and Fig. 9 Connect the ① end of the Figure 8 The ② end and Fig. 9 The ② end connection in Figure 8 The third end and Fig. 9 ③ end connection), the grounding resistance grading module 7 includes resistor R47, resistor R48, resistor R49, resistor R50, resistor R51, resistor R52, resistor R53, resistor R54, resistor R55, resistor R60, resistor R61, resistor R62, resistor R63, resistor R66, resistor R68, resistor R69, resistor R70, resistor R71, resistor R72, field effect transistor Q8, field effect transistor Q9, field effect transistor Q10, optical coupler relay OD4, optical coupler relay OD5, optical coupler relay OD6, analog switch IC12, analog switch IC13 and analog switch IC14;

[0079] The first pin of the analog switch IC12 is respectively connected to the first pin of the analog switch IC13, one end of the resistor R51, the drain of the field effect transistor Q9, the second pin of the optical coupler relay OD5 and the ninth pin of the analog switch IC14, the source of the field effect transistor Q9 is connected to one end of the resistor R50 and is grounded, the other end of the resistor R50 is connected to the gate of the field effect transistor Q9 and is connected to the external control signal CONTRL8, the other end of the resistor R51 is connected to one end of the resistor R52 and is connected to VCC8, the other end of the resistor R52 is connected to the first pin of the optical coupler relay OD5, and the sixth pin of the optical coupler relay OD5 is respectively connected to the optical coupler relay The fourth pin of the optocoupler relay OD6 and the sixth pin of the optocoupler relay OD4 are linked and connected to the signal VBACK, the fourth pin of the optocoupler relay OD5 is connected to one end of the resistor R61 through the resistor R60, and the other end of the resistor R61 is connected to the signal VBACK2, the first pin of the optocoupler relay OD4 is connected to one end of the resistor R49, and the other end of the resistor R49 is respectively connected to one end of the resistor R48 and connected to the VCC8 end, and the other end of the resistor R48 is respectively connected to the drain of the field effect tube Q8, the second pin of the optocoupler relay OD4, the eighth pin of the analog switch IC12, the eighth pin of the analog switch IC13 and the eighth pin of the analog switch IC14 The gate of the field effect transistor Q8 is connected to one end of the resistor R47 and connected to the signal CONTRL7, the other end of the resistor R47 is connected to the source of the field effect transistor Q8 and is grounded, the first pin of the optical coupler relay OD6 is connected to one end of the resistor R55, the other end of the resistor R55 is connected to one end of the resistor R54 and connected to VCC8, the other end of the resistor R54 is respectively connected to the drain of the field effect transistor Q10, the second pin of the optical coupler relay OD6, the sixteenth pin of the analog switch IC12, the sixteenth pin of the analog switch IC13 and the sixteenth pin of the analog switch IC14, the gate of the field effect transistor Q10 is connected to one end of the resistor R53 The second end of the analog switch IC12 is respectively connected to the fifteenth pin of the analog switch IC12, the resistor R66, the resistor R68, the resistor R69, the resistor R70, the resistor R71 and one end of the resistor R72, the other end of the resistor R68 is respectively connected to the second pin of the analog switch IC13 and the fifteenth pin of the analog switch IC14 and connected to the signal VBACK2.The other end of the resistor R69 is respectively connected to the resistor R70, the resistor R71, the other end of the resistor R72, the fifteenth pin of the analog switch IC13 and the second pin of the analog switch IC14 and connected to the signal VBACK3. The other end of the resistor R66 is connected to the tenth pin of the analog switch IC14 and connected to the input signal VBACK1. The third pin of the analog switch IC12 is respectively connected to the fourteenth pin and the sixth pin and connected to the sampling point SAMPLEI+. The fourth pin of the analog switch IC12 and the fourth pin of the analog switch IC13 are both connected to the VCC17- terminal. The fourth pin of the analog switch IC14 is connected to the VCC5- terminal. The fifth pin of the analog switch IC12, the fifth pin of the analog switch IC13 and the fifth pin of the analog switch IC14 are all grounded, the seventh pin of the analog switch IC12 is connected to the seventh pin of the analog switch IC13 through the resistor R66, the thirteenth pin of the analog switch IC12 and the thirteenth pin of the analog switch IC13 are both connected to the VCC17 terminal, the thirteenth pin of the analog switch IC14 is connected to the VCC5 terminal, the third pin of the analog switch IC13 is respectively connected to the fourteenth pin and the sixth pin and connected to the sampling point SAMPLEI-, the third pin of the analog switch IC14 is respectively connected to the fourteenth pin and the eleventh pin and outputs the voltage V4. ,

[0080] In this optional embodiment, the principle of the grounding resistance grading module 7 is: the signal VBACK in the grounding resistance grading module 7 is the negative electrode feedback voltage of the battery; SAMPLEI+ and SAMPLEI- are grounding resistance voltage sampling points, which are used to sample and calculate the excitation current information; resistor R68, resistor R69\\resistor R70\\resistor R71\\resistor R72, and resistor R66 are grounding resistances corresponding to three gears respectively; field effect transistor Q8, optocoupler relay OD4, field effect transistor Q9, optocoupler relay OD5, field effect transistor Q10, optocoupler relay OD6, respectively form three control signals under the control of three external control signals CONTRL7, CONTRL8, and CONTRL9, and the three signals represent three gear selections and cannot be turned on at the same time. When the three signals are turned on respectively, three corresponding input signals VBACK1, VBACK2, and VBACK3 are formed, and the three input signals are respectively connected to the seventh pin, the tenth pin, and the fifteenth pin of the analog switch IC14. When CONTRL7 is at a high level, the field effect transistor Q8 is turned on, the second pin of the optocoupler relay OD4 is pulled low, and the optocoupler relay OD4 is turned on. At this time, VBACK=VBACK1. At the same time, the eighth pins of the analog switches IC12, IC13, and IC14 are pulled low at the same time. At this time, the sixth pin and the seventh pin of the analog switches IC12, IC13, and IC14 are turned on respectively, and the output voltage V4=VBACK1=VBACK. The resistor R66 is a four-terminal Kelvin resistor. The I1 pin and the I2 pin of the resistor R66 are connected to the sampling points SAMPLEI+ and SAMPLEI- respectively through the analog switches IC12 and IC13. In this way, when the grounding resistor (R66) is selected, the current sampling point is also connected to the corresponding two ends of the grounding resistor to sample the excitation current; the output voltage V4 will be fed back to the reverse end of the operational amplifier IC10A in the excitation output module 5 to form a negative feedback closed loop; when CONTRL8 and CONTRL9 are at a high level, the analysis is the same as the other two paths.

[0081] Figure 2 An embodiment of a multi-level excitation generation method for lithium battery impedance measurement according to the present invention is shown.

[0082] In this optional embodiment, the multi-level excitation generation method for lithium battery impedance measurement includes:

[0083] Step S101, outputting a variable frequency excitation signal, and filtering and amplifying the variable frequency excitation signal;

[0084] Step S102, adjusting the voltage of the variable frequency excitation signal after filtering and amplification according to the preset gear;

[0085] Step S103, converting the voltage signal after the step adjustment into a constant current signal, and converting the current signal into a stable voltage signal through a grounding resistor;

[0086] Step S104: input the output constant current signal as a test current to the battery under test, and switch the test current to ground resistors with different resistance values ​​according to a preset gear.

[0087] The present invention is not limited to the structures which have been described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A multi-level excitation generation system for lithium battery impedance measurement, characterized in that: The system comprises: a variable frequency signal source module (1), an excitation signal processing module (2), a voltage grading module (3), a constant current source module (4), an excitation output module (5), a battery to be tested (6) and a ground resistance grading module (7); Wherein, the variable frequency signal source module (1) is used to output a variable frequency excitation signal; The excitation signal processing module (2) is used to filter and amplify the variable frequency excitation signal; The voltage stepping module (3) is used to adjust the voltage of the variable frequency excitation signal after filtering and amplification according to a preset step; The constant current source module (4) is used to convert the voltage signal after step adjustment into a constant current signal, and convert the current signal into a stable voltage signal through a grounding resistor; The excitation output module (5) is used to input the constant current signal output by the constant current source module (4) as a test current into the battery under test (6); The grounding resistance grading module (7) is used to switch the test current to grounding resistances with different resistance values ​​according to a preset gear; The output end of the variable frequency signal source module (1) is electrically connected to the input end of the excitation signal processing module (2), the output end of the excitation signal processing module (2) is electrically connected to the input end of the voltage grading module (3), the output end of the voltage grading module (3) is connected to the input end of the constant current source module (4), the output end of the constant current source module (4) is electrically connected to the input end of the excitation output module (5), the output end of the excitation output module (5) is electrically connected to the input end of the battery under test (6), and the output end of the battery under test (6) is electrically connected to the input end of the grounding resistance grading module (7); The excitation signal processing module (2) comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C1, a capacitor C2, an operational amplifier IC3B and an operational amplifier IC4A; Wherein, the fifth pin of the operational amplifier IC3B is connected to one end of the resistor R1, and the other end of the resistor R1 is grounded; the sixth pin of the operational amplifier IC3B is respectively connected to one end of the resistor R2 and one end of the resistor R3, and the other end of the resistor R2 is connected to the output voltage V0; the other end of the resistor R3 is connected to one end of the resistor R4, and the other end of the resistor R4 is respectively connected to the seventh pin of the operational amplifier IC3B and one end of the resistor R5; the other end of the resistor R5 is respectively connected to one end of the resistor R6 and one end of the capacitor C1, and the other end of the capacitor C1 is grounded; the other end of the resistor R6 is respectively connected to one end of the capacitor C2 and the third pin of the operational amplifier IC4A, and the other end of the capacitor C2 is grounded; the second pin of the operational amplifier IC4A is respectively connected to the first pin and one end of the resistor R7, and the other end of R7 is connected to one end of the resistor R8, and the other end of the resistor R8 outputs the voltage V1; The excitation output module (5) includes a resistor R33, a resistor R34, a resistor R35, a resistor R36, a resistor R37, a resistor R38, a capacitor C6, a capacitor C7, a capacitor C8, an operational amplifier IC10A, an operational amplifier IC11A, a transistor Q1, a transistor Q2, a transistor Q3, a transistor Q4, a diode D1, a diode D2 and a diode D3; Among them, the first pin of the operational amplifier IC10A is connected to one end of the resistor R34 and one end of the capacitor C8, the other end of the capacitor C8 is connected to one end of the resistor R33 and the second pin of the operational amplifier IC10A, the other end of the resistor R33 is connected to the output voltage V4, the third pin of the operational amplifier IC10A is connected to the output voltage V3, the fourth pin of the operational amplifier IC10A is connected to one end of the capacitor C7 and to the VCC5-end, the other end of the capacitor C7 is grounded, the eighth pin of the operational amplifier IC10A is connected to one end of the capacitor C6 and to the VCC5 end, the other end of the capacitor C6 is grounded, the other end of the capacitor R34 is respectively connected to the third pin of the diode D1 and the third pin of the operational amplifier IC11A, the second pin of the diode D1 is connected to the VCC5 end, the first pin of the diode D1 is connected to the VCC5-end, the first pin of the operational amplifier IC11A is respectively connected to the second pin of the operational amplifier IC11A, the cathode of the diode D2 and the diode D 3, the eighth pin of the operational amplifier IC11A is connected to the VCC5 terminal, the fourth pin of the operational amplifier IC11A is connected to the VCC5- terminal, the anode of the diode D2 is connected to one end of the resistor R35 and the base of the transistor Q1 respectively, the other end of the resistor R35 is connected to the VCC5 terminal, the collector of the transistor Q1 is connected to the VCC5 terminal, the emitter of the transistor Q1 is connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to the VCC5 terminal, the emitter of the transistor Q2 is connected to the resistor R35 terminal, and the emitter of the transistor Q2 is connected to the VCC5 terminal. One end of the resistor R37 is connected, the other end of the resistor R37 is connected to one end of the resistor R38 and outputs the voltage V5, the other end of the resistor R38 is connected to the emitter of the transistor Q4, the collector of the transistor Q4 is connected to the VCC5- terminal, the base of the transistor Q4 is connected to the emitter of the transistor Q3, the collector of the transistor Q3 is connected to the VCC5- terminal, the base of the transistor Q3 is respectively connected to the cathode of the diode D3 and one end of the resistor R36, and the other end of the resistor R36 is connected to the VCC5- terminal; The grounding resistance grading module (7) comprises a resistor R47, a resistor R48, a resistor R49, a resistor R50, a resistor R51, a resistor R52, a resistor R53, a resistor R54, a resistor R55, a resistor R60, a resistor R61, a resistor R62, a resistor R63, a resistor R66, a resistor R68, a resistor R69, a resistor R70, a resistor R71, a resistor R72, a field effect transistor Q8, a field effect transistor Q9, a field effect transistor Q10, an optical coupler relay OD4, an optical coupler relay OD5, an optical coupler relay OD6, an analog switch IC12, an analog switch IC13 and an analog switch IC14; The first pin of the analog switch IC12 is respectively connected to the first pin of the analog switch IC13, one end of the resistor R51, the drain of the field effect transistor Q9, the second pin of the optical coupler relay OD5 and the ninth pin of the analog switch IC14, the source of the field effect transistor Q9 is connected to one end of the resistor R50 and is grounded, the other end of the resistor R50 is connected to the gate of the field effect transistor Q9 and is connected to the external control signal CONTRL8, the other end of the resistor R51 is connected to one end of the resistor R52 and is connected to VCC8, the other end of the resistor R52 is connected to the first pin of the optical coupler relay OD5, and the sixth pin of the optical coupler relay OD5 is respectively connected to the optical coupler relay The fourth pin of the optocoupler relay OD6 and the sixth pin of the optocoupler relay OD4 are linked and connected to the signal VBACK, the fourth pin of the optocoupler relay OD5 is connected to one end of the resistor R61 through the resistor R60, and the other end of the resistor R61 is connected to the signal VBACK2, the first pin of the optocoupler relay OD4 is connected to one end of the resistor R49, and the other end of the resistor R49 is respectively connected to one end of the resistor R48 and connected to the VCC8 end, and the other end of the resistor R48 is respectively connected to the drain of the field effect tube Q8, the second pin of the optocoupler relay OD4, the eighth pin of the analog switch IC12, the eighth pin of the analog switch IC13 and the eighth pin of the analog switch IC14 The gate of the field effect transistor Q8 is connected to one end of the resistor R47 and connected to the signal CONTRL7, the other end of the resistor R47 is connected to the source of the field effect transistor Q8 and is grounded, the first pin of the optical coupler relay OD6 is connected to one end of the resistor R55, the other end of the resistor R55 is connected to one end of the resistor R54 and connected to VCC8, the other end of the resistor R54 is respectively connected to the drain of the field effect transistor Q10, the second pin of the optical coupler relay OD6, the sixteenth pin of the analog switch IC12, the sixteenth pin of the analog switch IC13 and the sixteenth pin of the analog switch IC14, the gate of the field effect transistor Q10 is connected to one end of the resistor R53 The second end of the analog switch IC12 is respectively connected to the fifteenth pin of the analog switch IC12, the resistor R66, the resistor R68, the resistor R69, the resistor R70, the resistor R71 and one end of the resistor R72, the other end of the resistor R68 is respectively connected to the second pin of the analog switch IC13 and the fifteenth pin of the analog switch IC14 and connected to the signal VBACK2.The other end of the resistor R69 is respectively connected to the resistor R70, the resistor R71, the other end of the resistor R72, the fifteenth pin of the analog switch IC13 and the second pin of the analog switch IC14 and connected to the signal VBACK3. The other end of the resistor R66 is connected to the tenth pin of the analog switch IC14 and connected to the input signal VBACK1. The third pin of the analog switch IC12 is respectively connected to the fourteenth pin and the sixth pin and connected to the sampling point SAMPLEI+. The fourth pin of the analog switch IC12 and the fourth pin of the analog switch IC13 are both connected to the VCC17- terminal. The fourth pin of the analog switch IC14 is connected to the VCC5- terminal. The fifth pin of the switch IC12, the fifth pin of the analog switch IC13 and the fifth pin of the analog switch IC14 are all grounded, the seventh pin of the analog switch IC12 is connected to the seventh pin of the analog switch IC13 through the resistor R66, the thirteenth pin of the analog switch IC12 and the thirteenth pin of the analog switch IC13 are both connected to the VCC17 terminal, the thirteenth pin of the analog switch IC14 is connected to the VCC5 terminal, the third pin of the analog switch IC13 is respectively connected to the fourteenth pin and the sixth pin and connected to the sampling point SAMPLEI-, the third pin of the analog switch IC14 is respectively connected to the fourteenth pin and the eleventh pin and outputs the voltage V4;, The output voltage V3 is the output voltage of the constant current source module (4); The signal VBACK in the grounding resistance grading module (7) is the negative electrode feedback voltage of the battery; SAMPLEI+ and SAMPLEI- are grounding resistance voltage sampling points, which are used to sample and calculate the excitation current information; the field effect transistor Q8, the optical coupler relay OD4, the field effect transistor Q9, the optical coupler relay OD5, the field effect transistor Q10, the optical coupler relay OD6, respectively form three control signals under the control of the three external control signals CONTRL7, CONTRL8, and CONTRL9, the three signals represent three gear selections and cannot be turned on at the same time. When the three signals are turned on respectively, three corresponding input signals VBACK1, VBACK2, and VBACK3 are formed.

2. The multi-level excitation generation system for lithium battery impedance measurement according to claim 1, characterized in that: The frequency conversion signal source module (1) comprises an analog converter IC1, an operational amplifier IC2A, an operational amplifier IC2B and an operational amplifier IC3A; Wherein, the first pin of the analog converter IC1 is connected to the first pin of the operational amplifier IC3A and outputs the voltage V0, the second pin of the operational amplifier IC3A is connected to the thirteenth pin of the analog converter IC1, the third pin of the operational amplifier IC3A is connected to the second pin of the analog converter IC1, the eighth pin of the operational amplifier IC3A is connected to the VCC8 terminal, the fourth pin of the operational amplifier IC3A is connected to the VCC8- terminal, the third pin of the analog converter IC1 is connected to the first pin of the operational amplifier IC2A, the second pin of the operational amplifier IC2A is connected to the fourth pin of the operational amplifier IC3A, the third pin of the operational amplifier IC2A is connected to the VCC8- terminal. The fourth pin of the operational amplifier IC2A is connected to the VCC8- terminal, the eighth pin of the operational amplifier IC2A is connected to the VCC8 terminal, the fifth pin of the analog converter IC1 is connected to the sixth pin of the operational amplifier IC2B, the fifth pin of the operational amplifier IC2B is connected to the external reference voltage input, the seventh pin of the operational amplifier IC2B is connected to the sixth pin of the analog converter IC1, the seventh pin, the eighth pin, the tenth pin and the eleventh pin of the analog converter IC1 are respectively connected to the signal CS, the signal SCLK, the signal DIN and the signal LDAC, the twelfth pin of the analog converter IC1 is grounded, and the fourteenth pin of the analog converter IC1 is connected to the VCC1 terminal.

3. The multi-level excitation generation system for lithium battery impedance measurement according to claim 2, characterized in that: The variable frequency signal source module (1) outputs a variable frequency excitation signal with a frequency variable within a range of 0.01 Hz to 10 kHz.

4. The multi-level excitation generation system for lithium battery impedance measurement according to claim 3, characterized in that: The eighth pin of the operational amplifier IC4A is connected to the VCC8 terminal, and the fourth pin of the operational amplifier IC4A is connected to the VCC8- terminal.

5. The multi-level excitation generation system for lithium battery impedance measurement according to claim 4, characterized in that: The voltage grading module (3) comprises: a reverse trigger IC5, an analog switch IC6, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18 and a resistor R19; The first pin of the reverse trigger IC5 is connected to one end of the resistor R9 and is connected to the external control signal CONTRL1. The other end of the resistor R9 is respectively connected to one end of the resistor R10 and one end of the resistor R11 and is grounded. The other end of R10 is respectively connected to the fifth pin of the reverse trigger IC5 and is connected to the external control signal CONTRL2. The other end of the resistor R11 is connected to the thirteenth pin of the reverse trigger IC5 and is connected to the external control signal CONTRL3. The second pin of the reverse trigger IC5 is connected to the third pin. The fourth pin of the reverse trigger IC5 is connected to the eleventh pin of the analog switch IC6. The sixth pin of the reverse trigger IC5 is connected to the ninth pin. The seventh pin of the reverse trigger IC5 is grounded. The eighth pin of the reverse trigger IC5 is connected to the ninth pin of the analog switch IC6. The tenth pin of the reverse trigger IC5 is connected to the tenth pin of the analog switch IC6. The eleventh pin of the reverse trigger IC5 is connected to the twelfth pin. The fourteenth pin of the reverse trigger IC5 is connected to the VCC14 terminal. The first pin of the analog switch IC6 is respectively connected to one end of the resistor R18 and the One end of the resistor R19 is connected, the other end of the resistor R18 is respectively connected to one end of the resistor R15 and the twelfth pin of the analog switch IC6, the other end of the resistor R15 is respectively connected to one end of the resistor R13 and the fifteenth pin of the analog switch IC6, the other end of the resistor R13 is respectively connected to the fourteenth pin of the analog switch IC6 and connected to the output voltage V1, the other end of the resistor R19 is respectively connected to the fifth pin of the analog switch IC6 and one end of the resistor R16, the other end of the resistor R16 is respectively connected to the second pin of the analog switch IC6 and the One end of the resistor R14 is connected, the other end of the resistor R14 is respectively connected to the fourth pin of the analog switch IC6 and one end of the resistor R17, the other end of the resistor R17 is grounded, the third pin of the analog switch IC6 is connected to one end of the resistor R12, the other end of the resistor R12 outputs the voltage V2, the sixth pin of the analog switch IC6 is grounded, the seventh pin of the analog switch IC6 is connected to the VCC8-terminal, the eighth pin of the analog switch IC6 is grounded, the thirteenth pin of the analog switch IC6 is grounded, and the sixteenth pin of the analog switch IC6 is connected to the VCC8 terminal.

6. The multi-level excitation generation system for lithium battery impedance measurement according to claim 5, characterized in that: The constant current source module (4) comprises a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25, a resistor R26, a resistor R27, a resistor R28, a resistor R29, a resistor R30, a resistor R31, a resistor R32, a capacitor C3, a capacitor C4, a capacitor C5, an operational amplifier IC7A, an operational amplifier IC7B, an operational amplifier IC8B, an operational amplifier IC9A and an operational amplifier IC9B; Among them, the first pin of the operational amplifier IC7A is respectively connected to the second pin of the operational amplifier IC7A and one end of the resistor R22, the third pin of the operational amplifier IC7A is respectively connected to one end of the resistor R21 and one end of the capacitor C3, the other end of the resistor R21 is connected to the other end of the capacitor C3 and grounded, the eighth pin of the operational amplifier IC7A is connected to the VCC8 end, the fourth pin of the operational amplifier IC7A is connected to the VCC8- end, the other end of the resistor R22 is connected to the fifth pin of the operational amplifier IC8B, the sixth pin of the operational amplifier IC8B is respectively connected to one end of the resistor R23, one end of the resistor R24 ​​and one end of the resistor R23, the other end of the resistor R23 is connected to the sixth pin and the seventh pin of the operational amplifier IC7B, the fifth pin of the operational amplifier IC7B is connected to the output voltage V2, the seventh pin of the operational amplifier IC8B is respectively connected to the other end of the resistor R24, the other end of the resistor R25 and one end of the resistor R27, the The other end of the resistor R27 is respectively connected to the third pin of the operational amplifier IC9A and one end of the resistor R26, the other end of the resistor R26 is respectively connected to the seventh pin and the sixth pin of the operational amplifier IC9B, the fifth pin of the operational amplifier IC9B is respectively connected to one end of the resistor R30, one end of the resistor R31 and one end of the resistor R32 and outputs the voltage V3, the other end of the resistor R31 is connected to the other end of the resistor R32 and is grounded, the other end of the resistor R30 is respectively connected to one end of the resistor R29 and the first pin of the operational amplifier IC9A, the other end of the resistor R29 is respectively connected to one end of the resistor R28 and the second pin of the operational amplifier IC9A, the other end of the resistor R28 is grounded, the eighth pin of the operational amplifier IC9A is connected to one end of the capacitor C4 and connected to the VCC8 terminal, the other end of the capacitor C4 is grounded, the fourth pin of the operational amplifier IC9A is connected to one end of the capacitor C5 and connected to the VCC8-terminal, and the other end of the capacitor C5 is grounded.

7. The multi-level excitation generation system for lithium battery impedance measurement according to claim 6, characterized in that: The resistor R66 is a four-terminal Kelvin resistor.

8. A multi-level excitation generation method for lithium battery impedance measurement, using the multi-level excitation generation system for lithium battery impedance measurement according to any one of claims 1 to 7, characterized in that: The method includes: Output variable frequency excitation signal, and filter and amplify the variable frequency excitation signal; According to the preset gear, the voltage of the variable frequency excitation signal after filtering and amplification is adjusted in stages; Convert the voltage signal after graded adjustment into a constant current signal, and convert the current signal into a stable voltage signal through a grounding resistor; The output constant current signal is input into the battery under test as the test current, and the test current is switched to ground resistors with different resistance values ​​according to the preset gear.

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