Intelligent household electrical appliance battery tester

Abstract

The intelligent household electrical appliance battery tester comprises a to-be-tested battery (1), a lower computer control device used for measuring the internal resistance of the battery and processing, storing and displaying test data in real time, and an upper computer. Wherein the lower computer control equipment comprises a resistance test module; wherein the resistance test module comprises an internal resistance test channel (2), an alternating current differential amplification circuit (3), a coupling drive circuit (4), a phase-locked amplification circuit (5), an alternating current constant current source (6), a multiple feedback type low-pass filter and differential proportion operation circuit (7), a microprocessor MCU (8) and an A / D (analog / digital) conversion circuit (9); the internal resistance test channel (2) is a four-terminal test channel. The intelligent household electrical appliance battery tester system is convenient to use, and the measurement accuracy is greatly improved.

Description

Technical Field

[0001] The present application relates to an intelligent home appliance battery tester system, and more specifically to an intelligent home appliance battery tester system capable of accurately measuring battery internal resistance and voltage with high precision. Background Art

[0002] If a smart appliance's battery fails, it will affect its functionality, necessitating comprehensive online monitoring of key battery parameters. One key indicator of battery health is its internal resistance. Research has shown that changes in internal resistance can indicate impending battery failure, insufficient capacity, or improper charging or discharging. However, measuring battery internal resistance is a technical challenge. Batteries are inherently nonlinear, with internal resistance on the order of milliohms and minimal variation. Furthermore, the electrical signal generated by a battery during operation is a mixed AC / DC signal, making high-precision internal resistance measurement extremely difficult. Measuring battery internal resistance is a complex process, with the DC discharge method and AC impedance method being the most common and reliable methods.

[0003] The DC discharge method involves instantaneously discharging a battery with a high current (typically tens to hundreds of amperes), measuring the instantaneous voltage drop across the battery, and calculating the battery's internal resistance using Ohm's law. This method is widely used in practice, but it imposes significant load impact, shortening battery life. Furthermore, the DC discharge method must be performed in a static or offline state, making online measurement impossible and subject to significant measurement errors.

[0004] The AC impedance method uses an AC signal of a certain frequency applied to both ends of a battery, measuring the current of the AC signal and the voltage drop across the battery. The internal resistance of the battery is calculated using Equation (1). This method does not require discharging the battery and enables safe online monitoring and management, thus not affecting battery performance. However, it is susceptible to interference such as ripple, and factors such as connecting wires can affect accuracy.

[0005]

[0006] Where: I is the modulus of the AC current injected into the battery, U is the modulus of the corresponding current at both ends of the battery, is the phase difference between I and U, and R is the resistance of the battery.

[0007] As can be seen from this, the DC discharge method requires the battery to discharge a large current instantaneously, which requires a large load, causing significant heat generation and making it difficult to design into a portable instrument. The AC impedance method, on the other hand, does not require a discharge load, and the entire instrument does not operate with high currents. It is compact and power-efficient, making it easy to implement portable functions. However, when the AC impedance method is used with a small injection current, the response will be very weak and easily interfered with by noise.

[0008] At present, there is no smart home appliance battery tester system that can accurately measure the internal resistance of the battery with high precision and is easy to carry. Summary of the Invention

[0009] The purpose of the present invention is to develop an intelligent household appliance battery tester system that can quickly and efficiently measure the internal resistance of various types of batteries, thereby providing a simple tool for judging the working performance of batteries.

[0010] The technical solutions of the present invention are as follows:

[0011] An intelligent home appliance battery tester system includes a battery to be tested, a lower computer control device for measuring the internal resistance of the battery and processing, storing, and displaying the test data in real time, and a host computer;

[0012] The lower computer control device includes a resistance test module; the resistance test module includes an internal resistance test channel, an AC differential amplifier circuit, a coupling drive circuit, a phase-locked amplifier circuit, an AC constant current source, a multiple feedback low-pass filter and a differential proportional operation circuit, a microprocessor MCU and an A / D conversion circuit;

[0013] The internal resistance test channel is a four-terminal test channel;

[0014] The excitation signal source provided by the AC constant current source is injected into both ends of the battery to be tested through the coupling drive circuit and the internal resistance test channel. The generated alternating signal is amplified by the AC differential amplifier circuit to extract the AC component and isolate the DC component. The signal is then passed through a phase-locked amplifier circuit, a multiple feedback low-pass filter, and a differential proportional operation circuit to amplify the signal to a range suitable for testing and filter out large noise signals and high-frequency signals. The extracted effective signal is sent to the microprocessor MCU for acquisition and processing through the A / D conversion circuit.

[0015] The AC constant current source (6) is an AD9833 that outputs a DC voltage signal with a fixed frequency, and then the signal is converted into a constant current source with a constant current through a VI converter.

[0016] Among them, the host computer uses an industrial control computer as the core controller to realize further display, storage and reading of signals.

[0017] Wherein, the lower computer control device is connected to the upper computer via a USB communication loop.

[0018] Wherein, the microprocessor MCU (8) is STM32F103ZET6.

[0019] The present invention offers at least the advantages of ease of use and precise measurement. Furthermore, to reduce noise interference during AC impedance measurement and improve measurement accuracy, the system employs a four-wire AC impedance method to measure the battery's internal resistance. This system, combined with lock-in amplification and filtering techniques, suppresses interference and noise, effectively reducing system errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shows a structural block diagram of the internal resistance test module of the present invention;

[0021] Figure 2 The AD9833 constant voltage sinusoidal signal circuit of the present invention is shown;

[0022] Figure 3 The schematic diagram of the AC signal amplification and filtering circuit of the present invention is shown.

[0023] Figure 4 The phase-locked detection principle diagram of the present invention is shown

[0024] Figure 5 The phase-locked detection circuit of the present invention is shown

[0025] Figure 6 The low-pass filter and differential ratio operation circuit of the present invention are shown

[0026] Figure 7 The four-wire CS connection diagram of the present invention is shown

[0027] Figure 8 The four-wire CS mode serial interface timing diagram of the present invention is shown

[0028] The corresponding relationship between the reference numerals and components is as follows:

[0029] Battery under test 1, internal resistance test channel 2, AC differential amplifier circuit 3, coupling drive circuit 4, phase-locked amplifier circuit 5, AC constant current source 6, multiple feedback low-pass filter and differential proportional operation circuit 7, microprocessor MCU 8, A / D conversion circuit 9. DETAILED DESCRIPTION

[0030] The intelligent home appliance battery tester system includes a battery to be tested (1), a lower-level control device for measuring the battery's internal resistance and processing, storing, and displaying the test data in real time, and a host computer. The lower-level control device is the core control device, not only testing, digitally processing, rapidly storing, reading, and displaying battery parameters, but also centrally managing system power, I / O control, and communication transmission modules to achieve signal separation and transmission. The host computer, with an industrial control computer as its core controller, further displays, stores, and reads the signals.

[0031] The lower computer control device includes a microprocessor module, an internal resistance test module, a voltage test module, a communication module, an LCD touch display module, a storage module, a JTAG module, and a power supply module; wherein the internal resistance test module includes an internal resistance test channel 2, an AC differential amplifier circuit 3, a coupling drive circuit 4, a phase-locked amplifier circuit 5, an AC constant current source 6, a multiple feedback low-pass filter and a differential proportional operation circuit 7, a microprocessor MCU 8, and an A / D conversion circuit 9;

[0032] Connect a constant-current, low-frequency sinusoidal AC signal to the positive and negative terminals of the battery under test 1. Due to the capacitive component in the battery's internal resistance R, the injected current signal I generates a response voltage signal U, and there is a phase difference θ between the two signals. Based on the principle analysis, the internal resistance of the battery is: In the formula, cosθ is a non-zero constant coefficient, and I is the input constant current signal. The key to testing the value of R is to measure the size of the corresponding signal U. Since the amplitude of the response signal is very small, it is easily submerged in noise and difficult to process. The system inputs the response voltage signal through differential amplification into the phase-locked amplifier circuit and low-pass filter circuit to obtain the voltage drop generated by the purely resistive part of the battery. After this voltage passes through the A / D conversion circuit, it is sent to the CPU for processing. The obtained value is the internal resistance of the battery under test. The structural diagram of the internal resistance test module is shown in the figure. Figure 1 shown.

[0033] 1) AC constant current source 6

[0034] The AC method for online measurement of battery internal resistance requires an ideal constant current source module to output an AC constant current signal connected to both ends of the battery. Since the internal resistance of the battery is very small, the constant current source must have low distortion and sufficient stability. Based on these requirements, we choose AD9833 to output a DC voltage signal with a fixed frequency. Then, through the VI converter, the signal is converted into a constant current source with a constant current. Figure 2 Design schematic for constant current source.

[0035] The AD9833 chip is a fully integrated DDSDIANLU. Its internal components mainly include a phase accumulator (28 bits), a sine lookup table, a digital-to-analog converter (DAC), and a low-pass filter (LPF). The reference clock is provided by an external crystal oscillator. The phase register and adder constitute the core part of the AD9833 chip, namely the 28-bit phase accumulator. When the chip is running, the phase accumulator is equivalent to a counter. First, the frequency control word L sets a unit increment. The clock signal acts as a switch to automatically increase the phase accumulator output by one unit increment. When the accumulator increment reaches its own specified value, a count overflow is automatically generated. At this time, the overflow frequency is the output frequency of the signal generated by the AD9833 chip. Figure 2 This is the AD9833 constant voltage sinusoidal signal circuit.

[0036] The AD9833 outputs a constant-voltage sinusoidal signal, so it needs to be converted into a constant-current signal through a V / I conversion (voltage / current conversion). This solution uses the OPA564Z as the core chip for the V / I conversion. To prevent the response voltage from being too high or too low, which could damage the circuit, two Schottky diodes are connected to the output of the V / I converter for protection.

[0037] 2) AC differential amplifier circuit 3

[0038] AC differential amplifier circuit 3 is the first part of the AC response signal processing module. Because the AC voltage signal generated by the lithium battery is weak, it must be pre-amplified and filtered before being input into the correlator. The pre-amplifier filter in this solution consists of an AC differential amplifier and a bandpass filter.

[0039] The AC differential amplifier circuit uses the AD620, a high-performance instrument amplifier with stable performance and adjustable gain. Its amplification factor is determined by the feedback resistor RG between pins 1 and 8. This resistor is selected using an analog switch, and the amplification factor is selected by the microcontroller to keep the signal within the optimal acquisition voltage range. After amplification, the signal is detected by a bandpass filter, resulting in a 0.4-3kHz bandpass signal, which is then fed to the next-stage phase-locked amplifier circuit. Figure 3 This is the schematic diagram of the AC signal amplification and filtering circuit.

[0040] 3) Phase-locked amplifier circuit 5

[0041] After AC differential amplification, the AC signal is then passed through the phase-locked amplifier circuit 5 for phase-locked amplification. This circuit performs phase-sensitive detection on AC signals. Its key control chip is the phase-locked amplifier. The phase-locked amplifier has two input signals and one output signal: the input signal and a reference signal. The output signal is amplified by the chip based on the frequency of the reference signal. This allows for selective amplification of the signal amidst noise interference, significantly reducing noise interference and improving the detection signal-to-noise ratio.

[0042] In this solution, ATMEL's AD630 chip is used to perform phase-locked amplification on the battery internal resistance measurement signal. The signal processing application range of the high-precision balanced modulator AD630 includes: synchronous detection, phase detection, balanced modulation and mediation, orthogonal detection, lock-in amplification, phase-sensitive detection and square wave multiplication.

[0043] For the AD630 chip as a lock-in amplifier, the circuit implementation in this system is relatively simple and has high measurement accuracy. The measurement principle is as follows: Figure 4 As shown, the phase-locked detection circuit is as follows Figure 5 shown.

[0044] 4) Multiple feedback low-pass filter and differential proportional operation circuit 7

[0045] The low-pass filter is the last link in the signal processing part. Its purpose is to filter the converted half-wave signal to obtain a stable and ideal signal effective value, that is, a DC voltage signal. This system uses OP37 to build an active low-pass filter. The DC voltage signal will enter the next level differential proportional operation circuit. The output voltage varies in the range of 0V to 2.5V, which is convenient for the AD converter to collect signals. The circuit of this part is as follows Figure 6 shown.

[0046] 5) A / D conversion circuit 9

[0047] The final stage of signal measurement is the A / D conversion circuit. The module uses the AD7980, a 16-bit, successive approximation analog-to-digital converter (ADC) operating from a single power supply. The device integrates a low-power, high-speed, 16-bit sampling ADC and a versatile serial port. On the rising edge of CNV, the device samples the analog input voltage difference between IN+ and IN-, ranging from 0V to REF. The reference voltage, REF, is externally supplied and scales linearly with the supply voltage (VDD), power consumption, and throughput rate, independent of the device's power supply.

[0048] In this circuit, two AD7980s are used to measure internal resistance and voltage respectively. Based on the device's technical parameters, the circuit uses a four-wire CS mode to connect the two AD7980s to the microcontroller via SPI. The connection diagram is shown in the figure. Figure 7 The corresponding timing is shown as Figure 8 shown.

[0049] The performance test of the developed device was carried out, and the test results showed that this was an effective assessment of the design completion of the device. The test results showed that the design of the device met the design requirements.

[0050] Although the present invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from the scope of the present invention. Additionally, modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from the essential scope of the present invention. Therefore, embodiments of the present invention are not limited to the specific embodiment(s) disclosed herein as the best mode for practicing the present invention.

Claims

1. An intelligent home appliance battery tester, comprising a battery to be tested (1), a lower computer control device for measuring the internal resistance of the battery and processing, storing, and displaying the test data in real time, and an upper computer; in, The lower computer control device includes a resistance test module; wherein the resistance test module includes an internal resistance test channel (2), an AC differential amplifier circuit (3), a coupling drive circuit (4), a phase-locked amplifier circuit (5), an AC constant current source (6), a multiple feedback low-pass filter and a differential proportional operation circuit (7), a microprocessor MCU (8) and an A / D conversion circuit (9); The internal resistance test channel (2) is a four-terminal test channel; The excitation signal source provided by the AC constant current source (6) is injected into the two ends of the battery to be tested through the coupling drive circuit and the internal resistance test channel. The generated alternating signal is amplified by the AC differential amplifier circuit to extract the AC component and isolate the DC component. The signal is then amplified to a range suitable for testing by a phase-locked amplifier circuit, a multiple feedback low-pass filter and a differential proportional operation circuit. The signal can be filtered out with large noise signals and high-frequency signals. The extracted effective signal is sent to the microprocessor MCU for collection and processing through the A / D conversion circuit.

2. The smart home appliance battery tester according to claim 1, wherein: The AC constant current source (6) is an AD9833 that outputs a DC voltage signal with a fixed frequency, and then passes through a VI converter to convert the signal into a constant current source with a constant current.

3. The smart home appliance battery tester according to claim 1, wherein: The host computer uses an industrial control computer as the core controller to further display, store and read the signal.

4. The smart home appliance battery tester according to claim 1, wherein: The lower computer control device is connected to the upper computer via a USB communication loop.

5. The smart home appliance battery tester according to claim 1, wherein: The microprocessor MCU (8) is STM32F103ZET6.

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