Low-cost battery pack shunt current acquisition circuit

Abstract

The utility model provides a low-cost battery pack diverter current acquisition circuit, which belongs to the field of new energy automobiles and comprises a diverter, a first filter circuit, a bidirectional ultra-precision current detection amplifier, a second filter circuit and an AFE (analog front end) chip, the diverter is connected to an input end of the bidirectional ultra-precision current detection amplifier through the first filter circuit, and the second filter circuit is connected to an output end of the bidirectional ultra-precision current detection amplifier through the second filter circuit. The output end of the bidirectional ultra-precision current detection amplifier is connected to the analog quantity input end of the AFE chip through a second filter circuit, the reference voltage input end of the bidirectional ultra-precision current detection amplifier is used for reference voltage, and the power supply input port of the bidirectional ultra-precision current detection amplifier is connected to the power supply port of the AFE chip; small voltage differential signals at the two ends of the diverter are filtered and then sent to a bidirectional ultra-precision current detection amplifier, the small voltage differential signals are amplified to a voltage level suitable for processing through internal gain and sent to an AFE chip to calculate the current value and the current direction of the diverter, and the problem that the AFE chip cannot collect the current of the diverter is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of new energy vehicles, in particular to a low-cost current acquisition circuit for a shunt of a battery pack. Background Art

[0002] In a new energy vehicle battery system, it is usually necessary to collect the charging and discharging currents of a power line through a battery management system to monitor and control the charging and discharging processes of a battery pack. The estimation of the remaining battery power is closely related to the working current of the battery pack. When the battery pack is charging, the charging speed and charging time are controlled to protect the health and life of the battery pack. When the battery pack is discharging, the discharging speed and the remaining energy of the battery pack are controlled to ensure that the battery pack will not be over-discharged, thereby extending its service life. As a commonly used current detection device, the principle of a shunt is to connect a micro-ohm-level resistor in series in a bus circuit, and calculate the magnitude of the current according to Ohm's law by measuring the voltage drop.

[0003] The existing shunt current acquisition has the following problems:

[0004] (1) Isolated current sampling circuit: This circuit is composed of a signal acquisition unit, an isolation amplification unit, a signal amplification circuit, and an isolation power supply. The working principle is that when current flows through the shunt, a small voltage signal is generated at both ends of the shunt. After being filtered by the signal acquisition unit, this signal is sent to the isolation amplification unit. After the isolation amplification unit amplifies the acquired signal, it is further amplified to a voltage level suitable for processing by a secondary signal amplification circuit, and then sent to the AD port of a single-chip microcomputer for acquisition and processing. The isolation amplification unit of this circuit requires an isolation power supply circuit to provide an isolation power supply, with a large number of components, occupying the PCB board space and the single-chip microcomputer AD port resources, and having a high cost.

[0005] (2) AFE chip current acquisition circuit: Some AFE chips in the market have built-in current acquisition circuits. The working principle is that when current flows through the shunt, a small voltage signal generated at both ends of the shunt is directly sent to the ISENSE interface of the AFE after being processed by a filtering circuit, and the signal is processed by the AFE. Since the reference ground of the AFE and the reference ground of the shunt are both the high-voltage ground of the battery pack, isolation is not required and the circuit is simple. However, for the new generation of 18-series AFE chips launched by NXP, ADI, etc., the built-in current acquisition function of the AFE chip has been cancelled. Therefore, it is necessary to reconsider a low-cost shunt current acquisition circuit. Content of the Utility Model

[0006] The technical problem to be solved by the utility model is: how to solve the problem that the existing AFE chip cannot collect the shunt current due to the cancellation of the built-in current acquisition function.

[0007] The utility model solves the above technical problems through the following technical solutions: A low-cost current acquisition circuit for a battery pack shunt includes a shunt, a first filter circuit, a bidirectional ultra-precision current detection amplifier, a second filter circuit, and an AFE chip. The shunt is connected to the input end of the bidirectional ultra-precision current detection amplifier through the first filter circuit. The output end of the bidirectional ultra-precision current detection amplifier is connected to the analog input end of the AFE chip through the second filter circuit. The reference voltage input end of the bidirectional ultra-precision current detection amplifier is connected to a reference voltage, and the power input port of the bidirectional ultra-precision current detection amplifier is connected to the power port of the AFE chip.

[0008] Preferably, the first filter circuit includes a resistor R1, a resistor R2, a capacitor C1, and a capacitor C2. One end of the shunt is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to one end of the capacitor C1 and the third pin of the bidirectional ultra-precision current detection amplifier. The other end of the shunt is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to one end of the capacitor C2 and the second pin of the bidirectional ultra-precision current detection amplifier. The other ends of the capacitors C1 and C2 are both grounded.

[0009] Preferably, the bidirectional ultra-precision current detection amplifier includes an operational amplifier U1 and resistors R3-R8. One end of the resistor R3 is connected to the other end of the resistor R1, and the other end of the resistor R3 is connected to one end of the resistor R5 and the inverting input end of the operational amplifier U1. The other end of the resistor R5 is connected to the output end of the operational amplifier U1 and then connected to the input end of the second filter circuit. One end of the resistor R4 is connected to the other end of the resistor R2, and the other end of the resistor R4 is connected to the non-inverting input end of the operational amplifier U1 and one end of the resistor R6. The other end of the resistor R6 is connected to one end of the resistor R7 and one end of the resistor R8. The other end of the resistor R7 is connected to the fifth pin of the bidirectional ultra-precision current detection amplifier 30, and the other end of the resistor R8 is grounded.

[0010] Preferably, the second filter circuit includes a resistor R9 and a capacitor C3. One end of the resistor R9 is connected to the output end of the operational amplifier U1, and the other end of the resistor R9 is connected to one end of the capacitor C3 and the analog input end of the AFE chip. The other end of the capacitor C3 is grounded.

[0011] Preferably, it further includes a precision reference voltage chip. The sixth pin and the seventh pin of the bidirectional ultra-precision current detection amplifier are connected and then connected to the precision reference voltage chip. The power input port of the precision reference voltage chip is connected to the power port of the AFE chip.

[0012] Preferably, when the second and third pins of the bidirectional ultra-precision current detection amplifier are shorted, or the voltage difference between the second and third pins is 0, the output voltage of the bidirectional ultra-precision current detection amplifier is equal to the reference voltage. When the second pin is negative relative to the third pin, the output voltage drops below the reference voltage. When the second pin is positive relative to the third pin, the output voltage rises above the reference voltage, achieving bidirectional current measurement.

[0013] Preferably, the current flowing through the shunt is direct current, and the voltage across the shunt is a small voltage differential signal.

[0014] The advantages provided by the present utility model are as follows:

[0015] 1. In the present utility model, the small voltage differential signal generated across the shunt is filtered and then sent to the input port of the bidirectional ultra-precision current detection amplifier. The bidirectional ultra-precision current detection amplifier amplifies the small voltage differential signal to a suitable voltage level through internal gain and then sends it to the analog acquisition port of the AFE chip. By applying a voltage to the reference voltage input terminal of the bidirectional ultra-precision current detection amplifier, bidirectional current measurement can be achieved. The working power supply and the reference voltage input terminal of the bidirectional ultra-precision current detection amplifier are both powered by the AFE chip, eliminating the need for an isolated power supply.

[0016] 2. By adding a bidirectional ultra-precision current detection amplifier and combining it with the AFE chip to achieve current acquisition of the shunt, the present utility model can solve the problem that the current acquisition function of the current AFE chip cannot collect the current of the shunt. Moreover, without the need for an isolated power supply, it can replace the current acquisition method using an isolated operational amplifier and an isolated power supply. The circuit design is simple and easy to implement, which can greatly reduce the design cost of the shunt current acquisition circuit.

[0017] 3. By connecting a precision reference voltage to the reference voltage input terminal of the bidirectional ultra-precision current detection amplifier, the precision reference voltage is used to set the reference input to half-scale to achieve equal ranges in both directions, which can improve the accuracy of current acquisition. Description of the Drawings

[0018] Figure 1 It is the circuit diagram of the low-cost battery pack shunt current acquisition circuit provided in Embodiment 1 of the present utility model;

[0019] Figure 2 It is the circuit diagram of the low-cost battery pack shunt current acquisition circuit provided in Embodiment 2 of the present utility model;

[0020] In the figure: 10 shunt, 20 first filter circuit, 30 bidirectional ultra-precision current detection amplifier, 40 second filter circuit, 50 precision reference voltage, 60 AFE chip. Detailed Embodiment

[0021] In order to make the purpose, technical solution and advantages of the present utility model clearer and more understandable, the technical solution of the present utility model will be clearly and completely described below in conjunction with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present utility model belong to the scope of protection of the present utility model.

[0022] Embodiment 1

[0023] As Figure 1 shown, this embodiment provides a low-cost shunt current acquisition circuit for a battery pack, including a shunt 10, a first filter circuit 20, a bidirectional ultra-precision current detection amplifier 30, a second filter circuit 40, and an AFE chip 60. The shunt 10 is connected to the input end of the bidirectional ultra-precision current detection amplifier 30 through the first filter circuit 20. The output end of the bidirectional ultra-precision current detection amplifier 30 is connected to the analog input end of the AFE chip 60 through the second filter circuit 40. A reference voltage is input to the reference voltage input end of the bidirectional ultra-precision current detection amplifier 30. The power supply port of the AFE chip 60 is connected to the power input port of the bidirectional ultra-precision current detection amplifier 30 to provide a working voltage for the bidirectional ultra-precision current detection amplifier 30.

[0024] The present utility model filters the small voltage differential signal generated at both ends of the shunt 10 and then sends it to the input port of the bidirectional ultra-precision current detection amplifier 30. The bidirectional ultra-precision current detection amplifier 30 amplifies the small voltage differential signal to a voltage level suitable for processing through internal gain, and then sends it to the analog acquisition port of the AFE chip 60. By applying a voltage to the reference voltage input end of the bidirectional ultra-precision current detection amplifier 30, bidirectional current measurement can be achieved. The working power supply and the reference voltage input end of the bidirectional ultra-precision current detection amplifier 30 are both powered by the AFE chip 60, and there is no need to set up an isolated power supply.

[0025] The present utility model realizes the current acquisition of the shunt 10 by adding a bidirectional ultra-precision current detection amplifier 30 and combining it with the AFE chip 60, which can solve the problem that the current acquisition function of the current AFE chip cannot collect the shunt current, and there is no need to set up an isolated power supply. It can replace the current acquisition method using an isolated operational amplifier and an isolated power supply. The circuit design is simple and easy to implement, and can greatly reduce the design cost of the shunt current acquisition circuit.

[0026] The shunt 10 of the present utility model is used to measure direct current. When direct current passes through the resistor of the shunt, a voltage will be generated at both ends of the resistor. Since the voltage value is small, the small voltage differential signal needs to be amplified before the current value flowing through the shunt can be calculated.

[0027] Continue to refer to Figure 1 , the first filter circuit 20 includes a resistor R1, a resistor R2, a capacitor C1, and a capacitor C2. One end of the shunt 10 is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to one end of the capacitor C1 and the third pin of the bidirectional ultra-precision current detection amplifier 30. The other end of the shunt 10 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to one end of the capacitor C2 and the second pin of the bidirectional ultra-precision current detection amplifier 30. The other ends of the capacitors C1 and C2 are both grounded. By setting the first filter circuit at the input end of the bidirectional ultra-precision current detection amplifier 30, the voltage signal interference generated at both ends of the shunt 10 can be filtered out and the noise can be reduced.

[0028] The model of the bidirectional ultra-precision current detection amplifier 30 is CSA240Q (Analog Semiconductor) or INA240A2QPWRQ1 (TI). The fourth and seventh pins of the bidirectional ultra-precision current detection amplifier 30 are grounded. The sixth pin is connected to the fifth pin. The sixth and seventh pins serve as the reference voltage input ports. The eighth pin is connected to the input end of the second filter circuit, and the output end of the second filter circuit is connected to the analog input end of the AFE chip 60. The fifth pin is connected to the power supply port of the AFE chip 60.

[0029] CSA240Q (Analog Semiconductor) or INA240A2QPWRQ1 (TI) is a precision current detection amplifier with wide common mode, zero drift, and ultra-high common mode rejection ratio (CMRR). Its input end has an enhanced PWM suppression function, and this enhanced PWM suppression function can effectively reduce the influence of common mode transients on the output signal related to the PWM signal. CSA240Q (Analog Semiconductor) or INA240A2QPWRQ1 (TI) has a bandwidth of up to 550 kHz and provides multiple gain version selections: 20V / V, 50V / V, and 100V / V, and the required full-scale output voltage can be optimized according to the expected target current range in the application.

[0030] The bidirectional ultra-precision current detection amplifier 30 includes an operational amplifier U1 and resistors R3 - R8. One end of resistor R3 serves as the third pin of the bidirectional ultra-precision current detection amplifier 30 and is connected to the other end of resistor R1. The other end of resistor R3 is connected to one end of resistor R5 and the inverting input terminal of operational amplifier U1. The other end of resistor R5 is connected to the output terminal of operational amplifier U1 and then to the input terminal of the second filter circuit. One end of resistor R4 serves as the second pin of the bidirectional ultra-precision current detection amplifier 30 and is connected to the other end of resistor R2. The other end of resistor R4 is connected to the non-inverting input terminal of operational amplifier U1 and one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R7 and one end of resistor R8. The other end of resistor R7 is connected to the fifth pin of the bidirectional ultra-precision current detection amplifier 30, and the other end of resistor R8 is grounded.

[0031] The second filter circuit 40 includes resistor R9 and capacitor C3. One end of resistor R9 is connected to the output terminal of operational amplifier U1. The other end of resistor R9 is connected to one end of capacitor C3 and the analog input terminal of the AFE chip 60. The other end of capacitor C3 is grounded. By setting the second filter circuit at the output terminal of the bidirectional ultra-precision current detection amplifier 30, the interference at the output terminal of the bidirectional ultra-precision current detection amplifier 30 can be further filtered out, reducing the noise.

[0032] The AFE chip 60 uses an existing chip, which is used to collect the analog quantity after being amplified and processed by the bidirectional ultra-precision current detection amplifier 30, thereby calculating the current value and current direction flowing through the shunt, and providing a working power supply for the bidirectional ultra-precision current detection amplifier 30 without the need to set up an additional isolated power supply.

[0033] Working principle: After the current flows through the shunt 10, the voltage generated at both ends of the shunt 10 is processed by the first filter circuit, and then the voltage is input to the third pin (IN - pin) and the second pin (IN + pin) of the bidirectional ultra-precision current detection amplifier 30. The eighth pin (OUT pin) of the bidirectional ultra-precision current detection amplifier 30 outputs a voltage analog quantity to the analog input terminal of the AFE chip. The AFE chip 60 calculates the current value and current direction flowing through the shunt. The seventh pin (REF1) of the bidirectional ultra-precision current detection amplifier 30 is grounded, and the sixth pin (REF2) is connected to the fifth pin to achieve bidirectional current measurement.

[0034] Embodiment 2

[0035] As Figure 2As shown, the difference between this embodiment and Embodiment 1 is that: in this embodiment, the reference voltage input terminal of the bidirectional ultra-precision current detection amplifier 30 is connected to the precision reference voltage chip 50. The sixth and seventh pins of the bidirectional ultra-precision current detection amplifier 30 are connected together and then connected to the precision reference voltage chip 50. The precision reference voltage chip 50 provides a reference voltage for the bidirectional ultra-precision current detection amplifier 30. The power input port of the precision reference voltage chip 50 is connected to the power port of the AFE chip 60. The AFE chip 60 provides the operating power supply for both the bidirectional ultra-precision current detection amplifier 30 and the precision reference voltage chip 50 at the same time.

[0036] The model of the precision reference voltage chip 50 is REF3025 (TI). Other chips with or capable of realizing the same function can also be used to set the reference input to half range to achieve equal ranges in both directions. When the input pins of the bidirectional ultra-precision current detection amplifier 30 are short-circuited or the input is 0V, that is, the second and third pins are short-circuited, or the voltage difference between the second and third pins is 0, the output voltage of the eighth pin is equal to the reference voltage. When the second pin is negative relative to the third pin, the output voltage drops below the reference voltage. When the second pin is positive relative to the third pin, the output voltage rises above the reference voltage, thus realizing bidirectional current measurement. By connecting the precision reference voltage chip 50 to the reference voltage input terminal of the bidirectional ultra-precision current detection amplifier 30, the precision reference voltage chip 50 can provide a stable, accurate, and reliable reference voltage, with very low temperature drift, noise, and drift characteristics, etc., to meet application scenarios with high requirements for precision and stability, and can maintain the stability of the output voltage under different working conditions, avoiding output voltage deviation caused by factors such as temperature change and power supply voltage fluctuation, thereby improving the precision of current acquisition.

[0037] Working principle: After the current flows through the shunt 10, the voltage generated at both ends of the shunt 10 is processed by the first filter circuit, and then the voltage is input to the third pin (IN- pin) and the second pin (IN+ pin) of the bidirectional ultra-precision current detection amplifier 30. The eighth pin (OUT pin) of the bidirectional ultra-precision current detection amplifier 30 outputs a voltage analog quantity to the analog quantity input terminal of the AFE chip. The AFE chip 60 calculates the current value and current direction flowing through the shunt. The seventh pin (REF1) and the sixth pin (REF2) of the bidirectional ultra-precision current detection amplifier 30 are connected together and then connected to the precision reference voltage chip 50 to achieve bidirectional current measurement.

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-cost battery pack shunt current acquisition circuit, characterized by: The invention comprises a shunt (10), a first filtering circuit (20), a bidirectional ultra-precision current detection amplifier (30), a second filtering circuit (40), and an AFE chip (60). The shunt (10) is connected to the input end of the bidirectional ultra-precision current detection amplifier (30) via the first filtering circuit (20), the output end of the bidirectional ultra-precision current detection amplifier (30) is connected to the analog input end of the AFE chip (60) via the second filtering circuit (40), the reference voltage input end of the bidirectional ultra-precision current detection amplifier (30) is connected to the reference voltage, and the power input port of the bidirectional ultra-precision current detection amplifier (30) is connected to the power port of the AFE chip (60).

2. The low-cost battery pack shunt current acquisition circuit according to claim 1, characterized in that: The first filtering circuit (20) comprises a resistor R1, a resistor R2, a capacitor C1, and a capacitor C2; one end of the shunt (10) is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the capacitor C1 and the third pin of the bidirectional ultra-precision current detection amplifier (30); the other end of the shunt (10) is connected to one end of the resistor R2, the other end of the resistor R2 is connected to one end of the capacitor C2 and the second pin of the bidirectional ultra-precision current detection amplifier (30); and the other ends of the capacitors C1 and C2 are both grounded.

3. The low-cost battery pack shunt current acquisition circuit according to claim 2, characterized in that: The bidirectional ultra-precision current detection amplifier (30) includes an operational amplifier U1 and resistors R3-R8, one end of the resistor R3 is connected to the other end of the resistor R1, the other end of the resistor R3 is connected to one end of the resistor R5 and the inverting input end of the operational amplifier U1, the other end of the resistor R5 is connected to the output end of the operational amplifier U1 and then to the input end of the second filter circuit, one end of the resistor R4 is connected to the other end of the resistor R2, the other end of the resistor R4 is connected to the non-inverting input end of the operational amplifier U1 and one end of the resistor R6, the other end of the resistor R6 is connected to one end of the resistor R7 and one end of the resistor R8, the other end of the resistor R7 is connected to the fifth pin of the bidirectional ultra-precision current detection amplifier (30), and the other end of the resistor R8 is grounded.

4. The low-cost battery pack shunt current acquisition circuit according to claim 3, characterized in that: The second filtering circuit (40) comprises a resistor R9 and a capacitor C3, one end of the resistor R9 is connected to the output end of the operational amplifier U1, the other end of the resistor R9 is connected to one end of the capacitor C3 and the analog input end of the AFE chip (60), and the other end of the capacitor C3 is grounded.

5. The low-cost battery pack shunt current acquisition circuit according to claim 1, characterized in that: It also includes a precision reference voltage chip (50), the sixth pin and the seventh pin of the bidirectional ultra-precision current detection amplifier (30) are connected to the precision reference voltage chip (50), and the power input port of the precision reference voltage chip (50) is connected to the power port of the AFE chip (60).

6. The low-cost battery pack shunt current acquisition circuit according to claim 5, characterized in that: When the second pin and the third pin of the bidirectional ultra-precision current detection amplifier (30) are short-circuited, or the voltage difference between the second pin and the third pin is 0, the output voltage of the bidirectional ultra-precision current detection amplifier (30) is equal to the reference voltage; when the second pin is negative relative to the third pin, the output voltage drops below the reference voltage; when the second pin is positive relative to the third pin, the output voltage rises above the reference voltage, thereby achieving bidirectional current measurement.

7. The low-cost battery pack shunt current acquisition circuit according to claim 1, characterized in that: The current flowing through the shunt (10) is direct current, and the voltage across the two ends of the shunt (10) is a small voltage differential signal.

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