Voltage sampling circuit for battery ripple test

Abstract

The utility model relates to the technical field of battery testing, in particular to a voltage sampling circuit for battery ripple testing. The circuit comprises a blocking and buffering circuit, a voltage dividing and buffering circuit, a filter circuit, a bias voltage circuit and an analog-to-digital conversion unit. The sampling circuit is high in accuracy and good in real-time performance, and key waveforms cannot be lost. In addition, the sampling circuit adopts low-cost components, so that the cost is relatively low.

Description

Technical Field

[0001] The utility model relates to the technical field of battery testing, specifically to a voltage sampling circuit for battery ripple testing. Background Art

[0002] When the electronic system in an electric vehicle is working, especially when the electric drive system is operating under certain conditions of the vehicle, a ripple voltage will be superimposed on the system power supply, including the power battery. Based on specifications and standards, it is necessary to conduct voltage ripple tests on various components of the electric vehicle system, including the power battery. The tests include various forms such as testing the content of the ripple voltage generated when the system or component is working and injecting ripple voltage into the system or component for testing. Regardless of which test form, it is necessary to sample the ripple voltage for data collection, analysis, judgment, and control.

[0003] The ripple voltage is usually an alternating voltage with variable frequency and amplitude. This voltage is superimposed on the DC voltage of the power battery. Traditional ripple voltage sampling circuits usually use direct sampling method, average value sampling method, or effective value measurement method to obtain the data of the alternating voltage.

[0004] For the direct sampling method of ripple voltage, it usually directly samples and measures the superimposed signal of DC and AC. Since the DC voltage of the power battery is much higher than the AC ripple voltage, it is very difficult to achieve good sampling resolution and accuracy for the AC part, that is, the ripple voltage. Moreover, due to the too small AC voltage signal after voltage division, it is easily interfered by noise and has poor accuracy.

[0005] For the average value sampling method, the AC ripple voltage is extracted through a DC blocking circuit, and then the AC signal is amplified and sampled separately, which improves the resolution problem of the direct sampling circuit. After DC blocking, it usually uses a rectifier filter circuit to convert the ripple voltage into a DC signal to obtain the average value of the ripple voltage, and then uses an analog-to-digital converter to measure the DC average value. It has two problems. One is that the introduced filter circuit makes the DC average voltage lag behind the AC voltage, and the real-time performance of the signal and data is poor; the other is that some important information of the waveform, such as peak and valley values, waveform frequency, peak factor, etc., cannot be obtained through the DC average value, especially when the ripple voltage is a non-standard sine voltage.

[0006] For the effective value measurement method, the voltage to be measured is usually connected to an effective value measurement circuit such as AD637 for measurement. Its main disadvantage is the same as that of the average value measurement method, which is poor real-time performance and cannot obtain richer information of the waveform. In addition, limited by the working bandwidth of the effective value measurement circuit, when the frequency of the ripple voltage is relatively high, its accuracy will be worse than that of the average value sampling method. Content of the Utility Model

[0007] The technical problem to be solved by the present utility model is to provide a voltage sampling circuit for battery ripple testing, which has high accuracy, good real-time performance and will not lose key waveforms.

[0008] To solve the above problems, the following technical solutions are provided:

[0009] The voltage sampling circuit for battery ripple testing of the present utility model includes:

[0010] A DC blocking and buffering circuit, which is used to connect to the battery ripple testing system, extract the AC ripple voltage from the battery DC voltage and buffer it to obtain the buffered ripple voltage.

[0011] A voltage dividing and buffering circuit adaptively connected to the DC blocking and buffering circuit, which is used to divide and buffer the buffered ripple voltage to obtain the voltage-divided and buffered ripple voltage.

[0012] A filtering circuit adaptively connected to the voltage dividing and buffering circuit, which is used to filter the voltage-divided and buffered ripple voltage to obtain a signal with a high signal-to-noise ratio.

[0013] An analog-to-digital conversion unit adaptively connected to the filtering circuit, which is used to convert the signal with a high signal-to-noise ratio from analog quantity to digital quantity.

[0014] Wherein, it further includes a bias voltage circuit adaptively connected to the filtering circuit. The bias voltage circuit is used to generate a fixed bias voltage, and the bias voltage is used to pull up the voltage-divided and buffered ripple voltage and then transfer it to the filtering circuit.

[0015] The DC blocking and buffering circuit includes a capacitor C1, a resistor R8 and an operational amplifier U1A. One end of the capacitor C1 is used to connect to the battery ripple testing system to collect the phase voltage of the ripple voltage, and one end of the resistor R8 is used to connect to the battery ripple testing system to collect the neutral line voltage of the ripple voltage. The other end of the capacitor C1 is successively connected in series with resistors R1, R2, R3, R4 and R5 and then connected to the front end of the resistor R6; the other end of the resistor R8 is grounded, and this end of the resistor R8 is successively connected in series with resistors R9, R10, R11 and R12 and then connected to the front end of the resistor R6. The rear end of the resistor R6 is connected to the non-inverting input terminal of the operational amplifier U1A. The output terminal of the operational amplifier U1A is connected to the inverting input terminal of the operational amplifier U1A, and the output terminal of the operational amplifier U1A outputs the buffered ripple voltage.

[0016] The voltage dividing and buffering circuit includes a resistor R7 and an operational amplifier U1B. One end of the resistor R7 is used to receive the buffered ripple voltage. The other end of the resistor R7 is respectively connected to one end of a resistor R15 and the non-inverting input terminal of the operational amplifier U1B. The other end of the resistor R15 is grounded. The output terminal of the operational amplifier U1B is connected to one end of a resistor R17, and the other end of the resistor R17 is connected to the inverting input terminal of the operational amplifier U1B. The output terminal of the operational amplifier U1B forms the ripple voltage after voltage dividing and buffering.

[0017] The bias voltage circuit contains a reference voltage source and an operational amplifier U2B. Pin 1 of the reference voltage source is respectively connected to one end of a resistor R20, pin 2 of the reference voltage source, and one end of a resistor R21. The other end of the resistor R20 is connected to the power supply VCC. The other end of the resistor R21 is respectively connected to one end of a resistor R22 and the non-inverting input terminal of the operational amplifier U2B. The other end of the resistor R22 and pin 3 of the reference voltage source are grounded. The output terminal of the operational amplifier U2B is connected to the inverting input terminal of the operational amplifier U2B, and the output terminal of the operational amplifier U2B forms the bias voltage.

[0018] The filtering circuit contains a resistor R13, a resistor R16, and an operational amplifier U2A. One end of the resistor R13 is used to receive the ripple voltage after voltage dividing and buffering. One end of the resistor R16 is used to receive the bias voltage. The other ends of the resistor R13 and the resistor R16 are both connected to the non-inverting input terminal of the operational amplifier U2A. The output terminal of the operational amplifier U2A is respectively connected to one end of a resistor R19 and one end of a resistor R14. The other end of the resistor R19 is respectively connected to one end of a resistor 18 and the inverting input terminal of the operational amplifier U2A. The other end of the resistor 18 is grounded. A capacitor C3 is connected in parallel across both ends of the resistor R19. The other end of the resistor R14 is respectively connected to one end of a capacitor C2 and the analog-to-digital conversion unit. The other end of the capacitor C2 is grounded.

[0019] The analog-to-digital conversion unit is an analog-to-digital converter or a microcontroller containing an analog-to-digital converter.

[0020] Adopting the above solutions has the following advantages:

[0021] Since the voltage sampling circuit for battery ripple testing of the present utility model adopts a DC-blocking and buffering circuit, the high-voltage DC battery voltage superimposed in the battery ripple voltage is isolated, and the AC battery ripple voltage can be sampled and processed separately. Compared with the direct sampling method that directly samples the original signal with the high-voltage DC battery voltage superimposed, only the small AC signal part needs to be processed. Therefore, the AC gain (amplification factor or voltage division coefficient) of the circuit can be larger. Thus, when using an analog-to-digital converter with the same number of bits, the resolution is higher and the accuracy is better. At the same time, the present utility model does not adopt a rectifying and filtering circuit or an effective value conversion circuit, so the AC instantaneous value of the battery ripple voltage can be directly collected, with good real-time performance, and it can ensure that key waveform information such as the frequency, peak value, and valley value of the waveform is not lost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of the voltage sampling circuit for battery ripple testing of the present utility model;

[0023] Figure 2 is an output waveform diagram of the voltage sampling circuit for battery ripple testing of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present utility model will be further described in detail below with reference to the accompanying drawings.

[0025] As Figure 1 shown, the voltage sampling circuit for battery ripple testing of the present utility model includes a DC-blocking and buffering circuit 1, a voltage division and buffering circuit 2, a filtering circuit 3, a bias voltage circuit 5, and an analog-to-digital conversion unit 4.

[0026] As Figure 1 shown, the DC-blocking and buffering circuit 1 is used to connect to the battery ripple testing system, extract the AC ripple voltage from the battery DC voltage, and buffer it to obtain the buffered ripple voltage.

[0027] As Figure 1As shown, in this embodiment, the DC-blocking and buffering circuit 1 includes a plug connector J1, a capacitor C1, a resistor R8, and an operational amplifier U1A. One end of the capacitor C1 and one end of the resistor R8 are respectively connected to the 4th pin and the 1st pin of the plug connector J1. During use, the plug connector J1 is plugged into the battery ripple test system. One end of the capacitor C1 is used to collect the phase line voltage of the ripple voltage, and one end of the resistor R8 is used to collect the neutral line voltage of the ripple voltage. The other end of the capacitor C1 is successively connected in series with resistors R1, R2, R3, R4, and R5 and then connected to the front end of the resistor R6. The other end of the resistor R8 is grounded, and this end of the resistor R8 is successively connected in series with resistors R9, R10, R11, and R12 and connected to the front end of the resistor R6. The rear end of the resistor R6 is connected to the non-inverting input terminal of the operational amplifier U1A. The output terminal of the operational amplifier U1A is connected to the inverting input terminal of the operational amplifier U1A, and the output terminal of the operational amplifier U1A outputs the buffered ripple voltage.

[0028] As Figure 1 shown, the voltage-dividing and buffering circuit 2 is connected to the DC-blocking and buffering circuit 1, and the voltage-dividing and buffering circuit 2 is used to perform voltage division and buffering on the buffered ripple voltage to obtain the voltage-divided and buffered ripple voltage.

[0029] As Figure 1 shown, in this embodiment, the voltage-dividing and buffering circuit 2 includes a resistor R7 and an operational amplifier U1B. One end of the resistor R7 is connected to the output terminal of the operational amplifier U1A for receiving the buffered ripple voltage. The other end of the resistor R7 is respectively connected to the resistor R15 and the non-inverting input terminal of the operational amplifier U1B, and the other end of the resistor R15 is grounded. The output terminal of the operational amplifier U1B is connected to one end of the resistor R17, and the other end of the resistor R17 is connected to the inverting input terminal of the operational amplifier U1B. The output terminal of the operational amplifier U1B forms the voltage-divided and buffered ripple voltage.

[0030] As Figure 1 shown, the bias voltage circuit 5 is used to generate a fixed bias voltage, and the bias voltage is used to pull up the voltage-divided and buffered ripple voltage and then transfer it to the filtering circuit 3.

[0031] As Figure 1 shown, in this embodiment, the bias voltage circuit 5 includes a reference voltage source and an operational amplifier U2B. The 1st pin of the reference voltage source is respectively connected to one end of the resistor R20, the 2nd pin of the reference voltage source, and one end of the resistor R21. The other end of the resistor R20 is connected to the power supply VCC, that is, the 12V power supply. The other end of the resistor R21 is respectively connected to one end of the resistor R22 and the non-inverting input terminal of the operational amplifier U2B, and the other end of the resistor R22 and the 3rd pin of the reference voltage source are grounded. The output terminal of the operational amplifier U2B is connected to the inverting input terminal of the operational amplifier U2B, and the output terminal of the operational amplifier U2B forms the bias voltage.

[0032] As Figure 1 shown, the filtering circuit 3 is connected to the voltage dividing and buffering circuit 2 and the bias voltage circuit 5, superimposes the bias voltage and the divided ripple voltage, and reduces the noise of the signal through filtering to obtain a signal with a high signal-to-noise ratio for the analog-to-digital conversion unit 4 to process.

[0033] As Figure 1 shown, in this embodiment, the filtering circuit 3 includes a resistor R13, a resistor R16, and an operational amplifier U2A. One end of the resistor R13 is connected to the output terminal of the operational amplifier U1B for receiving the divided and buffered ripple voltage. One end of the resistor R16 is connected to the output terminal of the operational amplifier U2B for receiving the bias voltage. The other ends of the resistor R13 and the resistor R16 are both connected to the non-inverting input terminal of the operational amplifier U2A. The output terminal of the operational amplifier U2A is respectively connected to one ends of a resistor R19 and a resistor R14. The other end of the resistor R19 is respectively connected to one end of a resistor 18 and the inverting input terminal of the operational amplifier U2A. The other end of the resistor 18 is grounded, and a capacitor C3 is connected in parallel across both ends of the resistor R19. The other end of the resistor R14 is respectively connected to one end of a capacitor C2 and the analog-to-digital conversion unit 4, and the other end of the capacitor C2 is grounded.

[0034] As Figure 1 shown, the analog-to-digital conversion unit 4 is connected to the filtering circuit 3 for converting the signal with a high signal-to-noise ratio from analog to digital.

[0035] As Figure 1 shown, in this embodiment, the analog-to-digital conversion unit 4 is a single-power-supply analog-to-digital converter or a microcontroller including an analog-to-digital converter. The analog-to-digital conversion unit 4 is connected to one end of the resistor R14 connected to the capacitor C2.

[0036] The advantages of a voltage sampling circuit for battery ripple testing disclosed by the present utility model are high resolution, high precision, good accuracy, low cost, and no loss of key waveform information. The above advantages are achieved by blocking direct current, using low-cost components, and directly converting the processed alternating current signal from analog to digital instead of converting it to direct current. The waveform diagram plotted from the sampled data of a 100 kHz ripple voltage is as Figure 2 shown.

[0037] The first-stage circuit of the voltage sampling circuit for battery ripple testing in this solution uses a DC-blocking and buffering circuit 1, which isolates the high-voltage DC battery voltage superimposed on the battery ripple voltage, thus enabling separate sampling and processing of the AC battery ripple voltage. Since the DC signal (DC battery voltage) is relatively large while the AC signal (battery ripple voltage) is relatively small, compared with the direct sampling method that directly samples the original signal with the high-voltage DC battery voltage superimposed, this design only needs to process the small AC signal part. Therefore, the AC gain (amplification factor or voltage division coefficient) of the circuit can be larger. As a result, when using an analog-to-digital converter with the same number of bits, the resolution is higher and the accuracy is better.

[0038] The voltage division and buffering circuit 2, bias circuit, and filtering circuit 3 used in the voltage sampling circuit for battery ripple testing in this solution are all composed of ordinary low-cost operational amplifiers and ordinary resistors and capacitors, with low cost.

[0039] The AC signal processed by the voltage sampling circuit for battery ripple testing in this solution directly enters an analog-to-digital converter or a microcontroller containing an analog-to-digital converter for analog-to-digital conversion, without adding a rectifier and filter circuit 3 or an RMS conversion circuit in the middle. Therefore, the AC instantaneous value of the battery ripple voltage can be directly collected, and thus key waveform information such as the frequency, peak value, and valley value of the waveform can be ensured not to be lost.

Claims

1. A voltage sampling circuit for battery ripple test, comprising: A DC isolation and buffer circuit is used to connect to a battery ripple test system, extract the AC ripple voltage from the battery DC voltage and buffer it to obtain a buffered ripple voltage; A voltage divider and buffer circuit adaptively connected to the DC isolation and buffer circuit, used for performing voltage divider buffering on the buffered ripple voltage to obtain a voltage divider and buffered ripple voltage; A filter circuit adapted to be connected to the voltage divider and buffer circuit, used for filtering the ripple voltage after voltage division and buffering to obtain a signal with a high signal-to-noise ratio; The analog-to-digital conversion unit adaptively connected to the filtering circuit is used to convert the analog quantity to the digital quantity of the signal with high signal-to-noise ratio.

2. The voltage sampling circuit for battery ripple test according to claim 1, characterized in that: It also includes a bias voltage circuit adaptively connected to the filter circuit, the bias voltage circuit is used to generate a fixed bias voltage, and the bias voltage is used to pull up the ripple voltage after voltage division and buffering and then pass it to the filter circuit.

3. The voltage sampling circuit for battery ripple test according to claim 2, characterized in that: The DC isolation and buffer circuit includes a capacitor C1, a resistor R8 and an operational amplifier U1A; one end of the capacitor C1 is used to be connected to a battery ripple test system for collecting the phase line voltage of the ripple voltage, and one end of the resistor R8 is used to be connected to a battery ripple test system for collecting the neutral line voltage of the ripple voltage; the other end of the capacitor C1 is connected in series with resistors R1, R2, R3, R4 and R5 once, and then connected to the front end of resistor R6; the other end of the resistor R8 is grounded, and this end of the resistor R8 is connected in series with resistors R9, R10, R11 and R12 once, and is connected to the front end of resistor R6, and the rear end of resistor R6 is connected to the in-phase input end of the operational amplifier U1A; the output end of the operational amplifier U1A is connected to the reverse input end of the operational amplifier U1A, and the output end of the operational amplifier U1A outputs the buffered ripple voltage.

4. The voltage sampling circuit for battery ripple test according to claim 2, characterized in that: The voltage divider and buffer circuit includes a resistor R7 and an operational amplifier U1B; one end of the resistor R7 is used to receive the buffered ripple voltage, the other end of the resistor R7 is respectively connected to a resistor R15 and the in-phase input end of the operational amplifier U1B, and the other end of the resistor R15 is grounded; the output end of the operational amplifier U1B is connected to one end of the resistor R17, and the other end of the resistor R17 is connected to the reverse input end of the operational amplifier U1B; the output end of the operational amplifier U1B forms the voltage divided and buffered ripple voltage.

5. The voltage sampling circuit for battery ripple test as claimed in claim 2, characterized in that: The bias voltage circuit includes a reference voltage source and an operational amplifier U2B; pin 1 of the reference voltage source is respectively connected to one end of a resistor R20, pin 2 of the reference voltage source and one end of a resistor R21, the other end of the resistor R20 is connected to a power supply VCC, the other end of the resistor R21 is respectively connected to one end of a resistor R22 and the non-inverting input end of the operational amplifier U2B, the other end of the resistor R22 and pin 3 of the reference voltage source are grounded; the output end of the operational amplifier U2B is connected to the inverting input end of the operational amplifier U2B, and the output end of the operational amplifier U2B forms the bias voltage.

6. The voltage sampling circuit for battery ripple test according to claim 2, characterized in that: The filtering circuit includes a resistor R13, a resistor R16 and an operational amplifier U2A; one end of the resistor R13 is used to receive the ripple voltage after the voltage division buffering, one end of the resistor R16 is used to receive the bias voltage, and the other end of the resistor R13 and the other end of the resistor R16 are both connected to the in-phase input end of the operational amplifier U2A; the output end of the operational amplifier U2A is respectively connected to one end of the resistor R19 and the resistor R14, the other end of the resistor R19 is respectively connected to one end of the resistor 18 and the inverting input end of the operational amplifier U2A, the other end of the resistor 18 is grounded, and the two ends of the resistor R19 are connected in parallel with a capacitor C3; the other end of the resistor R14 is respectively connected to one end of the capacitor C2 and the analog-to-digital conversion unit, and the other end of the capacitor C2 is grounded.

7. The voltage sampling circuit for battery ripple test according to claim 2, characterized in that: The analog-to-digital conversion unit is an analog-to-digital converter or a microcontroller including an analog-to-digital converter.

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