Lithium battery protection excitation current generation circuit and lithium battery protection system

Abstract

The application discloses a lithium battery protection excitation current generating circuit and a lithium battery protection system. The excitation current generating circuit comprises: an on-chip control circuit and an off-chip current generating unit. The on-chip control circuit is connected to a voltage output end of a lithium battery and is used for generating a stable controllable control voltage. The off-chip current generating unit is electrically connected to the on-chip control circuit and is connected to the voltage output end of the lithium battery. The off-chip current generating unit outputs an excitation current according to the control voltage of the on-chip control circuit. The technical scheme of the application can effectively reduce heat generation, ensure work clock synchronization and improve detection precision.

Description

Technical Field

[0001] This invention relates to the field of lithium battery protection technology, specifically to an excitation current generation circuit and a lithium battery protection system for lithium battery protection. Background Technology

[0002] Lithium-ion batteries are widely used as energy storage and power devices. To ensure the safety of lithium-ion battery use, assess battery health, and prevent thermal runaway risks, lithium-ion battery management chips have become core supporting components. Electrochemical impedance spectroscopy (EIS) is an important technology for achieving lithium-ion battery life assessment and real-time monitoring of health status. This technology requires applying an excitation current of a specific waveform to the lithium-ion battery and then analyzing the battery's electrochemical characteristics based on the electrical signal response. Therefore, the excitation current generation circuit is an important component for realizing the function of EIS.

[0003] Currently, the industry mainly uses two methods to generate the excitation current. One method involves the excitation current being generated entirely by the on-chip circuitry of the lithium battery management chip, where the excitation current path is integrated within the chip. However, due to the large amplitude of the excitation current, this results in excessively high heat density within the chip, shortening the lifespan of the lithium battery management chip and posing a risk of thermal runaway. Furthermore, due to limitations in chip heating and layout, this method struggles to output large-scale excitation currents, directly leading to lower accuracy in electrochemical impedance spectroscopy monitoring. In addition, parasitic inductance exists in the chip bonding lines and printed circuit board traces, and the detection circuit also has capacitive loads, further exacerbating the limitations of the on-chip integration solution.

[0004] Another approach involves building an off-chip circuit based on discrete components on the printed circuit board to generate the excitation current. This method requires a large number of discrete components, resulting in higher overall hardware costs and occupying a significant amount of circuit board space, which is detrimental to miniaturization design. Furthermore, the on-chip control section and the off-chip current generation section belong to different working units, making it difficult to synchronize their operating clocks. This timing deviation introduces detection errors and reduces the accuracy of electrochemical impedance spectroscopy monitoring. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an excitation current generation circuit for lithium battery protection, which can effectively reduce heat generation, ensure clock synchronization, and improve detection accuracy.

[0006] This application provides an excitation current generation circuit for lithium battery protection, the excitation current generation circuit comprising:

[0007] An on-chip control circuit is connected to the voltage output terminal of the lithium battery and is used to generate a stable and controllable control voltage.

[0008] An external current generation unit is electrically connected to the on-chip control circuit and connected to the voltage output terminal of the lithium battery. The external current generation unit outputs an excitation current according to the control voltage of the on-chip control circuit.

[0009] In one aspect, the on-chip control circuitry includes a bandgap reference module, a filter module, an operational amplifier, a first response transistor, a first on-chip resistor, a second on-chip resistor, a third on-chip resistor, and a buffer.

[0010] The input terminal of the bandgap reference module is connected to the voltage output terminal of the lithium battery, and the output terminal of the bandgap reference module is connected to the non-inverting input terminal of the operational amplifier via the filter module.

[0011] The inverting input terminal of the operational amplifier is connected to the source of the first response transistor and one end of the first internal resistor, respectively. The other end of the first internal resistor is grounded. The output terminal of the operational amplifier is connected to the gate of the first response transistor.

[0012] The second internal resistor and the third internal resistor are connected in series. One end of the series branch is connected to the voltage output terminal of the lithium battery, and the other end of the series branch is connected to the input terminal of the buffer. The drain of the first response transistor is connected to the connection node of the second internal resistor and the third internal resistor.

[0013] In one respect, the first internal resistor, the second internal resistor, and the third internal resistor have the same temperature characteristics.

[0014] In one aspect, both the second internal resistor and the third internal resistor are multi-position adjustable resistors.

[0015] In one aspect, the buffer is a voltage follower, and the output of the buffer serves as the voltage output terminal of the on-chip control circuit, outputting a control voltage.

[0016] In one aspect, the off-chip current generation unit includes a second response transistor and an external power resistor;

[0017] One end of the external power resistor is connected to the voltage output terminal of the lithium battery, the other end of the external power resistor is connected to the drain of the second response transistor, the source of the second response transistor is grounded, and the gate of the second response transistor is connected to the voltage output terminal of the on-chip control circuit.

[0018] In one aspect, the filtering module includes: a first filtering resistor, a second filtering resistor, and a filtering capacitor, wherein the first filtering resistor and the second filtering resistor are connected in series, one end of the filtering capacitor is connected to the connection node of the first filtering resistor and the second filtering resistor, and the other end of the filtering capacitor is grounded.

[0019] In addition, to solve the above problems, this application also provides a lithium battery protection system, which includes a lithium battery, a lithium battery management chip, and an excitation current generation circuit as described above. The excitation current generation circuit is integrated on the periphery of the lithium battery management chip and is used to apply an excitation current to the lithium battery.

[0020] The beneficial effects of this invention are as follows: By separating the on-chip control circuit and the off-chip current generation unit, the excitation current does not flow through the chip interior, reducing large current losses within the chip, lowering chip heat generation and heat density, and improving chip operational stability and lifespan. The excitation current is generated by the off-chip unit, not limited by chip area and power consumption, allowing for a larger output excitation current and effectively improving detection accuracy. Furthermore, the control voltage is uniformly generated by the on-chip circuit and directly drives the off-chip current generation unit, ensuring that on-chip and off-chip signals originate from the same source, eliminating detection errors caused by clock asynchrony. Relying on the on-chip circuit for control and the off-chip device for power output eliminates the need for numerous discrete off-chip control components, reducing hardware costs and circuit board footprint. The on-chip circuit only drives the gate capacitor of external devices, resulting in low load pressure, improved circuit transient response and load stability, and adaptability to parasitic inductive and capacitive load conditions. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0022] Figure 1 This is a schematic diagram of the excitation current generation circuit for lithium battery protection in this application. Detailed Implementation

[0023] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0024] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0025] like Figure 1 As shown, this application provides an excitation current generation circuit for lithium battery protection, which includes an on-chip control circuit and an off-chip current generation unit.

[0026] The on-chip control circuit connects to the voltage output terminal of the lithium battery to generate a stable and controllable control voltage. Using the lithium battery output voltage as the power source for the on-chip control circuit eliminates the need for a separate power supply module. The on-chip control circuit relies on this power supply voltage to perform signal processing, outputting a control voltage with adjustable amplitude and stable operation.

[0027] The external current generation unit is electrically connected to the on-chip control circuit and also connected to the voltage output terminal of the lithium battery. The external current generation unit outputs an excitation current based on the control voltage from the on-chip control circuit. The external current generation unit receives the control voltage signal from the on-chip control circuit, uses this as a working control command, and outputs the target excitation current to generate the excitation current.

[0028] This embodiment separates the on-chip control circuitry and the off-chip current generation unit, preventing the excitation current from flowing through the chip's interior. This reduces internal current losses, lowers chip heat generation and heat density, and improves chip stability and lifespan. The excitation current is generated by the off-chip unit, unrestricted by chip area and power consumption, allowing for a larger output current and improved detection accuracy. Furthermore, the control voltage is uniformly generated by the on-chip circuitry and directly drives the off-chip current generation unit, ensuring consistent signals between the on-chip and off-chip circuits and eliminating detection errors caused by clock asynchrony. By relying on on-chip circuitry for control and off-chip device power output, a large number of discrete off-chip control components are eliminated, reducing hardware costs and board space. The on-chip circuitry only drives the gate capacitor of external devices, resulting in lower load stress and improved circuit transient response and load stability, making it suitable for parasitic inductive and capacitive loads.

[0029] In one embodiment of this application, the on-chip control circuit includes a bandgap reference module, a filter module, an operational amplifier, a first response transistor, a first on-chip resistor, a second on-chip resistor, a third on-chip resistor, and a buffer. The input terminal of the bandgap reference module is connected to the voltage output terminal of the lithium battery, and the output terminal of the bandgap reference module is connected to the non-inverting input terminal of the operational amplifier via the filter module. The bandgap reference module is powered by the output voltage of the lithium battery and outputs a low-temperature drift and high-stability reference voltage after operation. The reference voltage is filtered by the filter module to remove high-frequency interference signals and then sent to the non-inverting input terminal of the operational amplifier as the reference signal for the entire circuit. The inverting input terminal of the operational amplifier is connected to the source of the first response transistor and one end of the first on-chip resistor, respectively. The other end of the first on-chip resistor is grounded, and the output terminal of the operational amplifier is connected to the gate of the first response transistor. The operational amplifier, the first response transistor, and the first on-chip resistor together form a negative feedback loop. The operational amplifier compares the reference voltage at the non-inverting input terminal and adjusts its own output voltage to control the gate potential of the first response transistor, thereby stabilizing the source potential of the first response transistor and keeping the current flowing through the first on-chip resistor constant. The second and third internal resistors are connected in series. One end of the series branch is connected to the voltage output terminal of the lithium battery, and the other end is connected to the input terminal of the buffer. The drain of the first response transistor is connected to the junction of the second and third internal resistors. The series connection of the second and third internal resistors is then used in the lithium battery voltage circuit. The constant current output by the first response transistor flows through the two series resistors, forming a stable and adjustable voltage drop across the resistors. This voltage signal is then sent to the input terminal of the buffer to provide an adjustable control voltage for subsequent circuits.

[0030] In one embodiment of this application, the first, second, and third internal resistors have the same temperature characteristics. The first, second, and third internal resistors are all selected from the same type of on-chip polysilicon resistors, and their temperature characteristics are identical. That is, the magnitude and trend of their resistance changes with temperature are completely consistent. Even if the ambient temperature changes, the resistance values ​​of the three resistors change synchronously and proportionally, thus ensuring that the voltage and excitation current generated by the circuit are not affected by temperature. When the circuit is working, the excitation current is calculated by combining the resistance ratio of the three types of resistors with the reference voltage. When the ambient temperature changes, the resistance values ​​of the three resistors will shift synchronously according to the same pattern, and the resistance ratio between them remains constant, with the resistance deviations caused by temperature canceling each other out. This ensures that the voltage drop and final excitation current output by the circuit do not change with temperature fluctuations, effectively improving the accuracy of the excitation current output and the overall temperature stability of the circuit, and ensuring the accuracy and reliability of the lithium battery electrochemical impedance spectroscopy detection results.

[0031] In one embodiment of this application, both the second and third internal resistors are multi-level adjustable resistors. Different input resistance values ​​can be switched according to actual needs. After the second and third internal resistors are connected in series, the total series resistance can be adjusted by changing the range. Combined with the constant current-resistance ratio of the preceding stage, the voltage drop generated by the circuit can be continuously changed. Furthermore, the resistance value can be flexibly adjusted by switching ranges, generating various control voltage values ​​and corresponding to multiple levels of excitation current. On the one hand, this can adapt to the electrochemical impedance spectroscopy detection requirements of different operating conditions and different models of lithium batteries, expanding the circuit's applicability; on the other hand, it can refine the current output ranges, improve the adjustment accuracy of the excitation current, and further ensure the detection effect.

[0032] In one embodiment of this application, the buffer is a voltage follower, and its output terminal serves as the voltage output terminal of the on-chip control circuit, outputting the control voltage. In this embodiment, the buffer adopts a voltage follower structure, ensuring that the input voltage and output voltage of the voltage follower are consistent. The buffer's input terminal receives the voltage signal output from the preceding circuit, which, after impedance isolation, is output as the control voltage. The voltage follower features high input impedance and low output impedance, isolating the on-chip circuit from the downstream load, preventing external circuit interference with the stability of the on-chip signal, ensuring accurate transmission of the control voltage, and improving the overall circuit reliability.

[0033] In one embodiment of this application, the off-chip current generation unit includes a second response transistor and an external power resistor. One end of the external power resistor is connected to the voltage output terminal of the lithium battery, and the other end is connected to the drain of the second response transistor. The source of the second response transistor is grounded, and the gate of the second response transistor is connected to the voltage output terminal of the on-chip control circuit. The external power resistor and the second response transistor are connected in series between the lithium battery voltage output terminal and ground. The gate of the second response transistor receives the control voltage output by the on-chip control circuit. The control voltage acts on the second response transistor, changing its conduction level, thereby regulating the current flowing through the external power resistor and the second response transistor. This current is the excitation current used for lithium battery electrochemical impedance spectroscopy detection. The excitation current is formed outside the chip, and the current path does not pass through the chip interior, reducing chip heating and heat density; at the same time, relying on the external power device, a large current can be output, improving detection accuracy.

[0034] In one embodiment of this application, the filtering module includes a first filtering resistor, a second filtering resistor, and a filtering capacitor. The first and second filtering resistors are connected in series, one end of the filtering capacitor is connected to the connection node of the first and second filtering resistors, and the other end of the filtering capacitor is grounded. The filtering module constitutes a π-type low-pass filter network. The reference voltage output from the bandgap reference module passes through two stages of resistors in sequence. High-frequency noise signals are discharged to ground through the filtering capacitor, leaving only stable low-frequency effective signals for transmission to subsequent stages. This effectively filters out high-frequency noise and interference signals in the reference voltage, improves the purity of the reference signal input to the operational amplifier, avoids control voltage fluctuations caused by noise, ensures stable excitation current output, and further improves the accuracy of electrochemical impedance spectroscopy detection.

[0035] To further illustrate the technical solution of this application, an example is given: Vbat is the battery voltage of the lithium battery; the battery voltage Vbat of the lithium battery generates an extremely low temperature drift reference voltage Vref via a bandgap reference module, the value of which is 1.224V; the first filter resistor is R1, the second filter resistor is R2, the filter capacitor is C1, the first response transistor M1 and Rpoly1 form a feedback loop, and the first response transistor M1 is an NMOS transistor; the magnitude of the feedback loop voltage V1 is:

[0036] V1=Vref*Av*Rpoly1*(1 / gm+Rpoly1) / [Av*Rpoly1*(1 / gm+Rpoly1)+1]

[0037] Where Av is the operational amplifier gain, and gm is the transconductance of the first response transistor M1. When Av and Rpoly1 are sufficiently large, V1 = Vref. Transconductance is a core electrical parameter of the field-effect transistor, denoted by gm, and measured in Siemens. It characterizes the transistor's ability to control the drain current with respect to the gate-source voltage. Assuming the drain-source voltage remains stable, the transconductance value is equal to the ratio of the change in drain current to the change in gate-source voltage, reflecting the efficiency of converting a voltage signal into a current signal.

[0038] V1 is controlled by negative feedback loop to stabilize the voltage, thereby generating an internal stable bias current I1. The bias current I1 passes through the second internal resistor Rpoly2 and the third internal resistor Rpoly3 to generate a fixed voltage drop ΔV, the magnitude of which is: ΔV=[(Rpoly2+Rpoly3) / Rpoly1]*V1. The second internal resistor Rpoly2 and the third internal resistor Rpoly3 are both multi-level adjustable resistors, generating a controllable voltage drop ΔV.

[0039] At this point, the voltage V2 = Vb - ΔV; according to the virtual short and virtual open characteristics of the operational amplifier; the magnitude of the Eisp voltage, Eisp, is equal to V2; the Eisp voltage is the voltage to ground at the output pin Eisp in this circuit. This pin is the excitation control signal output terminal for lithium battery electrochemical impedance spectroscopy detection, and is the node voltage through which the on-chip control circuit transmits control commands to the off-chip current generation unit. Eisp is the drive output terminal, responsible for outputting control voltage to adjust the excitation current; Eisn is the sampling input terminal, responsible for transmitting the measured current signal back inward. The two constitute a paired signal link for drive and sampling. The operational amplifier in this application possesses two major electrical characteristics: virtual short and virtual open. Virtual short means that the potentials of the non-inverting and inverting input terminals of the operational amplifier are approximately equal, and the potential difference between the two terminals approaches zero; virtual open means that the current flowing into the non-inverting and inverting input terminals of the operational amplifier is approximately zero, and the input terminals draw almost no current. Relying on the above characteristics, this circuit can stably establish a negative feedback working state, accurately replicate the reference voltage, and generate a stable bias signal.

[0040] Relying on the real-time sampling function of the sampling input terminal Eisn, the circuit can dynamically correct the control voltage output on the chip.

[0041] The voltage Vout across the external power resistor Rout is:

[0042] Vout=Vbat-Eisp=Vbat-V2=ΔV=[(Rpoly2+Rpoly3) / Rpoly1]*Vref;

[0043] Since the second internal resistor Rpoly2 and the third internal resistor Rpoly3 are multi-stage controllable resistors, a controllable voltage is obtained across the external power resistor Rout, resulting in a controllable excitation current Iout: Iout = [(Rpoly2 + Rpoly3) / Rpoly1] * Vref / Rout; the external lithium battery is connected to one end of the external power resistor Rout; the other end of the external power resistor Rout is connected to the drain of the second response transistor M2, the source of the second response transistor M2 is grounded, and the gate of the second response transistor M2 is connected to the pin of the drive output terminal Eisp.

[0044] From the above formula and reasoning, it can be seen that this application uses an internal controllable resistor to control the generation of control voltage, and the control voltage then generates an excitation current through an external power resistor.

[0045] This application discloses a lithium battery protection system, comprising a lithium battery, a lithium battery management chip, and an excitation current generation circuit. The excitation current generation circuit is integrated around the lithium battery management chip and is used to apply an excitation current to the lithium battery. This lithium battery protection system uses the lithium battery as the monitoring object, with the lithium battery management chip as the core control unit, and the excitation current generation circuit arranged around the lithium battery management chip. During system operation, the excitation current generation circuit generates an excitation current based on its own circuit structure and applies this excitation current to the lithium battery, working with the lithium battery management chip to complete protection-related functions such as lithium battery electrochemical impedance spectroscopy detection and health status monitoring. Arranging the excitation current generation circuit around the chip retains the original control functions of the lithium battery management chip while avoiding chip overheating issues through an external architecture. The overall system structure is rationally laid out, capable of stably outputting multiple levels of excitation current, improving the accuracy of lithium battery status monitoring and overall operational safety.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. An excitation current generation circuit for lithium battery protection, characterized in that, The excitation current generation circuit includes: An on-chip control circuit is connected to the voltage output terminal of the lithium battery and is used to generate a stable and controllable control voltage. An external current generation unit is electrically connected to the on-chip control circuit and connected to the voltage output terminal of the lithium battery. The external current generation unit outputs an excitation current according to the control voltage of the on-chip control circuit.

2. The excitation current generating circuit according to claim 1, characterized in that, The on-chip control circuit includes a bandgap reference module, a filter module, an operational amplifier, a first response transistor, a first on-chip resistor, a second on-chip resistor, a third on-chip resistor, and a buffer; The input terminal of the bandgap reference module is connected to the voltage output terminal of the lithium battery, and the output terminal of the bandgap reference module is connected to the non-inverting input terminal of the operational amplifier via the filter module. The inverting input terminal of the operational amplifier is connected to the source of the first response transistor and one end of the first internal resistor, respectively. The other end of the first internal resistor is grounded. The output terminal of the operational amplifier is connected to the gate of the first response transistor. The second internal resistor and the third internal resistor are connected in series. One end of the series branch is connected to the voltage output terminal of the lithium battery, and the other end of the series branch is connected to the input terminal of the buffer. The drain of the first response transistor is connected to the connection node of the second internal resistor and the third internal resistor.

3. The excitation current generating circuit according to claim 2, characterized in that, The first internal resistor, the second internal resistor, and the third internal resistor have the same temperature characteristics.

4. The excitation current generating circuit according to claim 2, characterized in that, Both the second and third internal resistors are multi-position adjustable resistors.

5. The excitation current generating circuit according to claim 2, characterized in that, The buffer is a voltage follower, and its output terminal serves as the voltage output terminal of the on-chip control circuit, outputting the control voltage.

6. The excitation current generating circuit according to any one of claims 1 to 5, characterized in that, The off-chip current generation unit includes a second response transistor and an external power resistor; One end of the external power resistor is connected to the voltage output terminal of the lithium battery, the other end of the external power resistor is connected to the drain of the second response transistor, the source of the second response transistor is grounded, and the gate of the second response transistor is connected to the voltage output terminal of the on-chip control circuit.

7. The excitation current generating circuit according to claim 1, characterized in that, The filtering module includes a first filtering resistor, a second filtering resistor, and a filtering capacitor. The first filtering resistor and the second filtering resistor are connected in series. One end of the filtering capacitor is connected to the connection node of the first filtering resistor and the second filtering resistor, and the other end of the filtering capacitor is grounded.

8. A lithium battery protection system, characterized in that, The lithium battery protection system includes a lithium battery, a lithium battery management chip, and an excitation current generation circuit according to any one of claims 1 to 7. The excitation current generation circuit is integrated on the periphery of the lithium battery management chip and is used to apply an excitation current to the lithium battery.

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