A battery internal resistance detection circuit based on mixed signal excitation

Abstract

The utility model discloses a kind of battery internal resistance detection circuit based on mixed signal excitation, comprising: mixed signal excitation source, drive conversion circuit, first voltage measurement circuit, second voltage measurement circuit;Wherein, the mixed signal excitation source, comprising: inverted T type resistance network, first operational amplifier, filter circuit;Wherein, the input end of the inverted T type resistance network is coupled ARM or FPGA, the first voltage measurement circuit is used to measure the voltage of specific resistance both ends, calculate the current flowing through battery;The second voltage measurement circuit is used to measure the voltage of battery both ends, calculate the internal resistance of current flowing through battery.The utility model provides ac component to avoid capacity resistance interference, provides transient response data by providing dc component, and avoid battery damage by direct current step current signal excitation, realize the accurate, nondestructive testing of battery internal resistance and other parameters.

Description

Technical Field

[0001] This utility model relates to the field of battery testing technology, specifically a battery internal resistance detection circuit based on mixed signal excitation. Background Technology

[0002] Battery testing typically employs AC injection and DC discharge methods; however, both methods currently have several drawbacks.

[0003] For the AC injection method, firstly, the injected AC signal is usually small in amplitude, generally around several hundred milliamps, making it difficult to resist interference from system ripple current during online testing. For example, in a UPS system, the second, fourth, and sixth harmonic currents generated during the inverter's inversion process can flow back to the battery, severely affecting the detection accuracy. Data from repeated tests shows that when measuring a 12V battery, the multiple harmonics of a 50Hz / 1A ripple current can affect the measurement accuracy of the monitoring equipment by up to 6.1%. In large UPS systems, the ripple current is often much greater than 1A, greatly limiting the application of the AC injection method in such systems.

[0004] Secondly, existing AC injection methods require measuring AC current signals, voltage response signals, and the phase difference between voltage and current. This increases the complexity of the detection system, introduces more interference factors, and consequently affects measurement accuracy. Furthermore, current technologies typically utilize lock-in amplifiers for small-signal processing; dedicated lock-in amplifier chips are expensive, increasing detection costs and making them unsuitable for cost-sensitive applications.

[0005] Furthermore, the measured internal resistance of a battery varies depending on the frequency of the AC signal, placing extremely high demands on the frequency stability and sine wave purity of the injected signal; otherwise, the test results will be directly affected. However, in practical applications, it is difficult to guarantee that the injected signal always meets these stringent requirements.

[0006] For the DC discharge method, high-current pulse discharge may accelerate battery aging, cannot be detected online in real time, and has low accuracy under dynamic conditions.

[0007] Therefore, existing technologies can no longer meet people's current needs, and based on the current situation, there is an urgent need to improve existing technologies. Utility Model Content

[0008] The purpose of this invention is to provide a battery internal resistance detection circuit based on mixed signal excitation to solve the problems mentioned in the background art.

[0009] This utility model provides a battery internal resistance detection circuit based on mixed signal excitation, comprising: a mixed signal excitation source, a drive conversion circuit, a first voltage measurement circuit, and a second voltage measurement circuit; wherein...

[0010] The hybrid signal excitation source includes: an inverted-T resistor network, a first operational amplifier, and a filter circuit; wherein, the input terminal of the inverted-T resistor network is coupled to an ARM or FPGA, and the output terminal of the inverted-T resistor network is loaded onto the first operational amplifier, and the output terminal of the first operational amplifier is coupled to the filter circuit; the ARM or FPGA sends a DDS signal, which is input to the first operational amplifier through the inverted-T resistor network, and after being filtered by the filter circuit, a composite signal of a low-frequency AC sine wave and a DC step signal is generated;

[0011] The drive conversion circuit includes: an instrumentation amplifier, a drive circuit, and an adjustment circuit; the output of the filter circuit in the mixed signal excitation source is loaded onto the input of the instrumentation amplifier, the output of the instrumentation amplifier is coupled to the drive circuit, and the output of the drive circuit is coupled to the adjustment circuit.

[0012] The output of the drive conversion circuit is coupled to the positive and negative terminals of the battery, wherein the negative terminal of the battery is coupled to ground through a specific resistor.

[0013] The first voltage measurement circuit includes a protection circuit, an instrumentation amplifier circuit, a differential amplifier circuit, and a first ADC. The two ends of the specific resistor are first coupled to the protection circuit and then coupled to the instrumentation amplifier circuit. The output terminal of the instrumentation amplifier circuit is coupled to the differential amplifier circuit, and the output terminal of the differential amplifier circuit is coupled to the first ADC. The first voltage measurement circuit is used to measure the voltage across the specific resistor and calculate the current flowing through the battery.

[0014] The second voltage measurement circuit includes the first voltage measurement circuit, a secondary amplifier circuit, and a second ADC; the second voltage measurement circuit is further coupled to the output of the first voltage measurement circuit, and the output of the secondary amplifier circuit is coupled to the second ADC; the second voltage measurement circuit is used to measure the voltage across the battery and calculate the internal resistance flowing through the battery.

[0015] When the input signal to the battery is a low-frequency AC sinusoidal current signal, the first voltage measuring circuit measures the voltage across a specific resistor as V1, and the current flowing through the battery is I1 = V1 / R1; when the input signal to the battery is a DC step signal current signal, the first voltage measuring circuit measures the voltage across a specific resistor as V2, and the current flowing through the battery is I2 = V2 / R1.

[0016] When a low-frequency AC sinusoidal current signal is input to the battery, the voltage across the battery terminals in the second voltage measurement circuit is V3, and the battery's internal resistance R... 交== V3 / I1; When the input to the battery is a DC step current signal, the second voltage measuring circuit measures the voltage across the battery as V4, and the battery's internal resistance R... 直 ==V4 / I2;

[0017] Finally, the final battery internal resistance value R is output through weighted fusion. 内 =NR 交 +MR 直 Where N is the proportion of AC component in the battery design and M is the proportion of DC component.

[0018] The present invention has the following advantages: by providing an AC component to avoid capacitive interference, providing a DC component to provide transient response data, and using a DC step current signal to avoid battery damage, the present invention achieves accurate and non-destructive testing of parameters such as battery internal resistance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the hybrid signal excitation source circuit structure of this utility model;

[0020] Figure 2 This is a schematic diagram of the drive conversion circuit structure of this utility model;

[0021] Figure 3 This is a schematic diagram of the positive and negative terminal connection circuit of the battery of this utility model;

[0022] Figure 4 This is a schematic diagram of the first voltage measurement circuit of this utility model;

[0023] Figure 5 This is a schematic diagram of the second voltage measurement circuit of this utility model. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the present utility model without creative effort are within the protection scope of the present utility model.

[0025] This utility model provides the following technical solution: a battery internal resistance detection circuit based on hybrid signal excitation, comprising:

[0026] refer to Figure 1A mixed-signal excitation source includes: an inverted-T resistor network, a first operational amplifier, and a filter circuit; wherein, the input terminal of the inverted-T resistor network is coupled to the DAC of an ARM or FPGA, and the output terminal of the inverted-T resistor network is loaded onto the first operational amplifier, and the output terminal of the first operational amplifier is coupled to the filter circuit.

[0027] The ARM or FPGA sends a DDS signal, which is input to the first operational amplifier through an inverted T resistor network. After being amplified by the first operational amplifier, the DDS signal is transmitted to the filter circuit. After being filtered by the filter circuit, a composite signal of a low-frequency AC sine wave (such as 10Hz) and a DC step signal is generated.

[0028] Among them, DDS: Direct Digital Frequency Synthesis is a digitally driven frequency synthesis technology. With its high resolution, fast switching speed and excellent flexibility, it has become the core technology of modern function generators, arbitrary waveform generators, local oscillators of communication systems, etc.

[0029] The basic idea of ​​DDS is to pre-store the digital form of an ideal waveform (such as the amplitude value of a sine wave) in a memory (ROM), then read these data in a certain order at extremely high speed, and then convert them into analog waveforms through a digital-to-analog converter (DAC).

[0030] refer to Figure 2 The drive conversion circuit includes: an instrumentation amplifier, a drive circuit, and an adjustment circuit;

[0031] The output of the filter circuit is applied to the input of the instrumentation amplifier, the output of the instrumentation amplifier is coupled to the drive circuit, and the output of the drive circuit is coupled to the adjustment circuit.

[0032] Since the signal output by the mixed signal excitation source is a voltage signal, it needs to be converted into a current signal by a drive conversion circuit. The voltage signal is first amplified by an instrumentation amplifier and then adjusted by an adjustment circuit to generate a current signal of low-frequency AC sine wave and DC step signal. The adjustment circuit consists of two sets of resistors connected in parallel and is used to adjust the magnitude of the output current signal.

[0033] In this embodiment, the driving circuit can be composed of two transistors connected by a common base. The driving circuit improves the driving capability of the instrumentation amplifier and, together with the adjustment circuit, adjusts the magnitude of the output current signal.

[0034] refer to Figure 3The output terminal of the drive conversion circuit is coupled to the positive and negative terminals of the battery. The negative terminal of the battery is coupled to ground through a specific resistor. In this embodiment, since the current value output by the drive conversion circuit to the battery can only be adjusted to an approximate range by adjusting the circuit, although the range of this current value is very small, it is not accurate enough. Therefore, a specific resistor is set, and the current value flowing through the battery can be accurately calculated by measuring the voltage across the specific resistor.

[0035] refer to Figure 4 The first voltage measurement circuit includes a protection circuit, an instrumentation amplifier circuit, a differential amplifier circuit, and a first ADC. The two ends of the specific resistor are first coupled to the protection circuit and then coupled to the instrumentation amplifier circuit. The output terminal of the instrumentation amplifier circuit is coupled to the differential amplifier circuit, and the output terminal of the differential amplifier circuit is coupled to the first ADC.

[0036] In this embodiment, in the first voltage measurement circuit, the protection circuit is used to protect the instrumentation amplifier and differential amplifier circuit from damage. (Refer to...) Figure 4 The protection circuit uses a reverse-connected series diode. By setting the power supply voltage of the protection circuit to the same voltage (VCC) as the power supply voltage of the instrumentation amplifier, the instrumentation amplifier circuit will be damaged when the voltage across the protection circuit is greater than VCC. Therefore, the voltage flowing through the protection circuit must not be greater than VCC.

[0037] In this embodiment, the voltage across a specific resistor can be measured by the first voltage measurement circuit, and the current flowing through the battery can be calculated. Since the signal input to the battery by the drive conversion circuit is a low-frequency AC sine wave and a DC step signal current signal, the voltage across the specific resistor measured by the first voltage measurement circuit also has two results: when the input is a low-frequency AC sine wave current signal, the voltage across the specific resistor is V1, and the current flowing through the battery is I1 = V1 / R1; when the input is a DC step signal current signal, the voltage across the specific resistor is V2, and the current flowing through the battery is I2 = V2 / R1.

[0038] refer to Figure 5 The second voltage measurement circuit includes the first voltage measurement circuit, a secondary amplifier circuit, and a second ADC. The second voltage measurement circuit is formed by coupling the secondary amplifier circuit to the output of the first voltage measurement circuit, and the output of the secondary amplifier circuit is coupled to the second ADC. The second voltage measurement circuit is used to measure the voltage across the battery terminals. Because the internal resistance of the battery varies, if the internal resistance is within the normal range, the first ADC can directly read the voltage from the output of the differential amplifier circuit when measuring the voltage across the battery terminals. If the internal resistance of the battery is too low, the voltage needs to be amplified by the secondary amplifier circuit before the second ADC reads the voltage from the output of the secondary amplifier circuit.

[0039] Similarly, since the signal input to the battery from the drive conversion circuit is a low-frequency AC sine wave and a DC step signal current signal, the second voltage measurement circuit will also produce two results regarding the voltage across the battery: when the input is a low-frequency AC sine wave current signal, the voltage across the battery is V3, and the battery's internal resistance R... 交 == V3 / I1; When the input is a DC step current signal, the voltage across the battery is V4, and the battery's internal resistance R... 直 ==V4 / I2;

[0040] In this embodiment, since the battery is designed with an AC component of N and a DC component of M, the final battery internal resistance value R is output through weighted fusion. 内 =NR 交 +MR 直 Where N and M are percentages, for example, if the AC component accounts for 70% and the DC component accounts for 30%, then R 内 =0.7R 交 +0.3R 直 .

[0041] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery internal resistance detection circuit based on mixed signal excitation, characterized in that, include: A mixed-signal excitation source includes: an inverted-T resistor network, a first operational amplifier, and a filter circuit; wherein the input terminal of the inverted-T resistor network is coupled to an ARM or an FPGA, and the output terminal of the inverted-T resistor network is loaded onto the first operational amplifier, and the output terminal of the first operational amplifier is coupled to the filter circuit. The ARM or FPGA sends a DDS signal, which is input to the first operational amplifier through an inverted T resistor network. After being filtered by the filter circuit, a composite signal of low-frequency AC sine wave and DC step signal is generated. The drive conversion circuit includes: an instrumentation amplifier, a drive circuit, and an adjustment circuit; The output of the filter circuit is applied to the input of the instrumentation amplifier, the output of the instrumentation amplifier is coupled to the drive circuit, and the output of the drive circuit is coupled to the adjustment circuit. The output of the drive conversion circuit is coupled to the positive and negative terminals of the battery, wherein the negative terminal of the battery is coupled to ground through a specific resistor. The first voltage measurement circuit includes a protection circuit, an instrumentation amplifier circuit, a differential amplifier circuit, and a first ADC. The two ends of the specific resistor are first coupled to the protection circuit and then coupled to the instrumentation amplifier circuit. The output terminal of the instrumentation amplifier circuit is coupled to the differential amplifier circuit, and the output terminal of the differential amplifier circuit is coupled to the first ADC. The first voltage measurement circuit is used to measure the voltage across a specific resistor and calculate the current flowing through the battery; The second voltage measurement circuit includes the first voltage measurement circuit, a secondary amplifier circuit, and a second ADC; the second voltage measurement circuit is formed by coupling the secondary amplifier circuit to the output of the first voltage measurement circuit, and the output of the secondary amplifier circuit is coupled to the second ADC. The second voltage measurement circuit is used to measure the voltage across the battery terminals and calculate the internal resistance flowing through the battery.

2. The battery internal resistance detection circuit based on mixed signal excitation according to claim 1, characterized in that: The drive conversion circuit converts the voltage signal into a current signal, generating a low-frequency AC sine wave and a DC step signal current signal.

3. The battery internal resistance detection circuit based on mixed signal excitation according to claim 1, characterized in that: The adjustment circuit consists of two sets of resistors connected in parallel, used to adjust the magnitude of the output current signal.

4. The battery internal resistance detection circuit based on mixed signal excitation according to claim 1, characterized in that: The driving circuit can be composed of two transistors connected by a common base to improve the driving capability of the instrumentation amplifier, and the magnitude of the output current signal can be adjusted in conjunction with the adjustment circuit.

5. A battery internal resistance detection circuit based on mixed signal excitation according to claim 1, characterized in that: The protection circuit uses a reverse-connected series diode, and the power supply voltage of the protection circuit is set to the same voltage as the power supply voltage of the instrumentation amplifier, so as to protect the instrumentation amplifier and differential amplifier circuit from damage.

6. The battery internal resistance detection circuit based on mixed signal excitation according to claim 1, characterized in that: When the input to the battery is a low-frequency AC sinusoidal current signal, the first voltage measurement circuit measures the voltage across a specific resistor as V1, and the current flowing through the battery is I1 = V1 / R1. When the input to the battery is a DC step current signal, the first voltage measurement circuit measures the voltage across a specific resistor as V2, and the current flowing through the battery is I2 = V2 / R1.

7. A battery internal resistance detection circuit based on mixed signal excitation according to claim 1, characterized in that: When measuring the voltage across the battery terminals, if the battery's internal resistance is within the normal range, the second voltage measurement circuit directly reads the voltage from the output of the differential amplifier circuit via the first ADC. If the battery's internal resistance is too low, the second voltage measurement circuit reads the voltage from the output of the secondary amplifier circuit through the second ADC.

8. A battery internal resistance detection circuit based on mixed signal excitation according to claim 1, characterized in that: When a low-frequency AC sinusoidal current signal is input to the battery, the voltage across the battery terminals in the second voltage measurement circuit is V3, and the battery's internal resistance R... 交 ==V3 / I1; When a DC step current signal is input to the battery, the second voltage measurement circuit measures the voltage across the battery as V4, and the battery's internal resistance R... 直 ==V4 / I2; The final battery internal resistance value R is output through weighted fusion. 内 =NR 交 +MR 直 Where N is the proportion of AC component in the battery design and M is the proportion of DC component.

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