A current sampling circuit based on a voltage type isolation sampling chip

Abstract

This invention discloses a current sampling circuit based on a voltage-type isolation sampling chip, used to achieve isolated sampling of battery current in battery-powered devices. A current signal conversion circuit transmits the battery current signal to a first operational amplifier circuit via a shunt resistor. A second operational amplifier circuit boosts the output voltage of the first operational amplifier circuit to a predetermined value. The first operational amplifier circuit amplifies the voltage signal acquired and converted by the current signal conversion circuit by a predetermined factor before transmitting it to the voltage-type isolation sampling chip circuit. The voltage-type isolation sampling chip circuit detects and isolates the voltage of the input voltage sampling signal during transmission. This current sampling circuit based on a voltage-type isolation sampling chip amplifies and isolates the sampled signal, satisfying the accuracy requirements of isolation sampling while reducing equipment costs.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more specifically to a current sampling circuit based on a voltage-type isolated sampling chip. Background Technology

[0002] In many devices and power systems that use low-voltage batteries, it is often necessary to isolate the current sampling. The reference ground of the current signal in the isolated sampling is not the same as the reference ground of the sampled signal.

[0003] In traditional circuit sampling schemes, one approach is to use a current-mode isolation sampling chip (hereinafter referred to as current-mode) for sampling. The advantages of current-mode sampling are high sampling accuracy and relatively simple circuitry. However, the price of current-mode sampling is almost twice that of voltage-mode sampling (hereinafter referred to as voltage-mode isolation sampling chip), which makes the product less competitive in terms of cost.

[0004] Another approach is to use a current sensor for sampling. The advantages of using a current sensor are low cost and simple peripheral circuitry. However, it suffers from low sampling accuracy, often failing to meet the requirements of the application scenario. Therefore, a circuit solution that balances cost and sampling accuracy is needed, requiring both cost control and the ability to meet the demands of the application. Summary of the Invention

[0005] In view of this, it is necessary to provide a current sampling circuit based on a voltage-type isolated sampling chip that can balance equipment cost and sampling accuracy.

[0006] A current sampling circuit based on a voltage-type isolation sampling chip is used to realize isolated sampling of battery current in battery-powered devices. The current sampling circuit includes a current signal conversion circuit, a first operational amplifier circuit, a reference voltage circuit, a second operational amplifier circuit, and a voltage-type isolation sampling chip circuit. The current signal conversion circuit, the first operational amplifier circuit, and the voltage-type isolation sampling chip circuit are connected in sequence. The reference voltage circuit and the second operational amplifier circuit are connected in sequence. The output terminal of the second operational amplifier circuit is connected to the first operational amplifier circuit.

[0007] The current signal conversion circuit includes a shunt resistor R3 for acquiring the current signal of the main power circuit output by the battery; the first operational amplifier circuit is used to amplify the voltage signal acquired and converted by the current signal conversion circuit by a predetermined factor; the reference voltage circuit is used to provide a reference input voltage for the second operational amplifier circuit; the second operational amplifier circuit is used to amplify the reference input voltage signal by a predetermined factor and transmit it to the first operational amplifier circuit to boost the output voltage of the first operational amplifier circuit; the voltage-type isolation sampling chip circuit is used for voltage detection and isolated transmission of the input voltage sampling signal.

[0008] Preferably, the shunt resistor R3 includes two input terminals and two output terminals. The two input terminals are connected to the main power circuit of the battery output terminal, and the two output terminals are respectively connected to a first resistor R1 and a second resistor R2.

[0009] Preferably, the first operational amplifier circuit includes a first operational amplifier U3-B. The inverting input and non-inverting input of the first operational amplifier U3-B are connected to the output of the current signal conversion circuit through a sixteenth resistor R16 and a seventeenth resistor R17, respectively. The output of the first operational amplifier U3-B is connected to the inverting input of the first operational amplifier U3-B through a parallel fifteenth capacitor C15 and a fifteenth resistor R15. The non-inverting input of the first operational amplifier U3-B is connected to the output of the second operational amplifier circuit through a parallel eighteenth capacitor C18 and a nineteenth resistor R19. The output of the first operational amplifier U3-B is connected to the input of the voltage-type isolated sampling chip circuit through a fourteenth resistor R14.

[0010] Preferably, the reference voltage circuit includes a reference voltage chip U1, the input terminal of the reference voltage chip U1 is connected to a 5V power supply through an eighth resistor R8, and the VREF terminal of the reference voltage chip U1 is connected to voltage divider resistors R6 and R7 and an eighth capacitor C8.

[0011] The voltage divider resistors R6 and R7 are connected in series and then connected in parallel with the eighth capacitor C8. The VREF terminal of the reference voltage chip U1 is connected to the midpoint of the voltage divider resistors R6 and R7. The two ends of the eighth capacitor C8 are connected to the input terminal of the second operational amplifier circuit.

[0012] Preferably, the second operational amplifier circuit includes a second operational amplifier U3-A. The inverting input terminal of the second operational amplifier U3-A is connected to the negative output terminal of the reference voltage circuit through a ninth resistor R9, and the non-inverting input terminal of the second operational amplifier U3-A is connected to the positive output terminal of the reference voltage circuit through a tenth resistor R10. The output terminal of the second operational amplifier U3-A is connected to the inverting input terminal of the second operational amplifier U3-A through a tenth capacitor C10 and a twelfth resistor R12 connected in parallel. The non-inverting input terminal of the second operational amplifier U3-A is connected to the power supply reference ground BAT_V- through a ninth capacitor C9 and an eleventh resistor R11 connected in parallel.

[0013] Preferably, the voltage-type isolated sampling chip circuit includes a voltage-type isolated sampling chip U2, which includes an input side and an output side;

[0014] The input side of the voltage-type isolated sampling chip U2: the input pin VIN is connected to the output terminal of the first operational amplifier circuit through the fourteenth resistor R14, the seventh capacitor C7 is provided between the input pin VIN and the ground pin GND1, and the ground pin GND1 is connected to the power supply reference ground BAT_V-.

[0015] The output side of the voltage-type isolated sampling chip U2: the positive output terminal OUTP and the negative output terminal OUTN are connected to the load through the fourth resistor R4 and the fifth resistor R5, respectively. The load terminal is connected in parallel with the second capacitor C2, and the ground pin GND2 is connected to the reference ground DGND.

[0016] Preferably, it further includes an operational amplifier chip power supply circuit, which is used to supply power to the operational amplifier chip, including a third operational amplifier U3-C. Pin 8 of the third operational amplifier U3-C is connected to the battery +5V_BAT, and pin 4 of the third operational amplifier U3-C is connected to the battery -5V_BAT.

[0017] In the aforementioned current sampling circuit based on a voltage-type isolation sampling chip, the current signal conversion circuit transmits the battery current signal to the first operational amplifier circuit via a shunt resistor. The second operational amplifier circuit amplifies the reference input voltage signal by a predetermined factor and transmits it to the first operational amplifier circuit, raising the output voltage of the first operational amplifier circuit to a predetermined value. The first operational amplifier circuit amplifies the voltage signal acquired and converted by the current signal conversion circuit by a predetermined factor and transmits it to the voltage-type isolation sampling chip circuit. The voltage-type isolation sampling chip circuit detects and isolates the voltage of the input voltage sampling signal during transmission. This current sampling circuit based on a voltage-type isolation sampling chip amplifies and isolates the sampling signal using an operational amplifier circuit and a voltage-type isolation sampling chip, satisfying the accuracy requirements of isolation sampling while reducing equipment costs. The circuit structure of this invention is easy to implement, low in cost, and readily applicable. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the current sampling circuit based on a voltage-type isolated sampling chip according to an embodiment of the present invention. Figure 1 (Current signal conversion circuit, first operational amplifier circuit and voltage-type isolation sampling chip circuit).

[0019] Figure 2 This is a schematic diagram of the current sampling circuit based on a voltage-type isolated sampling chip according to an embodiment of the present invention. Figure 2 (Reference voltage circuit and second operational amplifier circuit).

[0020] Figure 3This is a schematic diagram of the current sampling circuit based on a voltage-type isolated sampling chip according to an embodiment of the present invention. Figure 3 (Op-amp chip power supply circuit). Detailed Implementation

[0021] This embodiment takes a current sampling circuit based on a voltage-type isolated sampling chip as an example. The present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0022] Please see Figure 1 , Figure 2 and Figure 3 This illustration shows a current sampling circuit based on a voltage-type isolation sampling chip provided by an embodiment of the present invention, used to realize isolated sampling of battery current in a battery-powered device. The current sampling circuit includes a current signal conversion circuit, a first operational amplifier circuit, a reference voltage circuit, a second operational amplifier circuit, and a voltage-type isolation sampling chip circuit. The current signal conversion circuit, the first operational amplifier circuit, and the voltage-type isolation sampling chip circuit are connected in sequence. The reference voltage circuit and the second operational amplifier circuit are connected in sequence. The output terminal of the second operational amplifier circuit is connected to the first operational amplifier circuit.

[0023] The current signal conversion circuit includes a shunt resistor R3 for acquiring the current signal of the main power circuit output by the battery; the first operational amplifier circuit is used to amplify the voltage signal acquired and converted by the current signal conversion circuit by a predetermined factor; the reference voltage circuit is used to provide a reference input voltage for the second operational amplifier circuit; the second operational amplifier circuit is used to amplify the reference input voltage signal by a predetermined factor and transmit it to the first operational amplifier circuit to boost the output voltage of the first operational amplifier circuit; the voltage-type isolation sampling chip circuit is used for voltage detection and isolated transmission of the input voltage sampling signal.

[0024] Preferably, the shunt resistor R3 includes two input terminals and two output terminals. The two input terminals are connected to the main power circuit of the battery output terminal, and the two output terminals are respectively connected to a first resistor R1 and a second resistor R2.

[0025] Specifically, the shunt resistor R3 is connected in series with the battery output terminal in the main power circuit, and the battery output terminal is connected in parallel with the first capacitor C1. The first capacitor C1 is an electrolytic capacitor used for power supply rectification and filtering. It can achieve low-frequency filtering of large-capacity energy storage, has an excellent filtering effect on switching power supply ripple, and improves DC output smoothness by reducing AC ripple coefficient.

[0026] Specifically, in this embodiment, the two input terminals are pins 1 and 4 of the shunt resistor R3, and the two output terminals are pins 2 and 3 of the shunt resistor R3. Pins 1 and 4 of the shunt resistor R3 are connected to the battery output circuit, pin 3 of the shunt resistor R3 is connected to the first resistor R1, and pin 2 of the shunt resistor R3 is connected to the second resistor R2. The first resistor R1 and the second resistor R2 serve to prevent interference.

[0027] Preferably, the first operational amplifier circuit includes a first operational amplifier U3-B. The inverting input and non-inverting input of the first operational amplifier U3-B are connected to the output of the current signal conversion circuit through a sixteenth resistor R16 and a seventeenth resistor R17, respectively. The output of the first operational amplifier U3-B is connected to the inverting input of the first operational amplifier U3-B through a parallel fifteenth capacitor C15 and a fifteenth resistor R15. The non-inverting input of the first operational amplifier U3-B is connected to the output of the second operational amplifier circuit through a parallel eighteenth capacitor C18 and a nineteenth resistor R19. The output of the first operational amplifier U3-B is connected to the input of the voltage-type isolated sampling chip circuit through a fourteenth resistor R14.

[0028] Specifically, the sixteenth resistor R16, the seventeenth resistor R17, the fifteenth resistor R15, and the nineteenth resistor R19 are external resistors of the first operational amplifier U3-B, the fifteenth capacitor C15 and the eighteenth capacitor C18 are filter capacitors of the first operational amplifier U3-B, and the resistance ratio between the sixteenth resistor R16 and the fifteenth resistor R15 is the amplification factor of the first operational amplifier circuit.

[0029] Specifically, in this embodiment, the resistance of the sixteenth resistor R16 is 62KΩ and the resistance of the fifteenth resistor R15 is 1KΩ, and the amplification factor of the first operational amplifier circuit is 62 times.

[0030] Preferably, the reference voltage circuit includes a reference voltage chip U1, the input terminal of the reference voltage chip U1 is connected to a 5V power supply through an eighth resistor R8, and the VREF terminal of the reference voltage chip U1 is connected to voltage divider resistors R6 and R7 and an eighth capacitor C8.

[0031] The voltage divider resistors R6 and R7 are connected in series and then connected in parallel with the eighth capacitor C8. The VREF terminal of the reference voltage chip U1 is connected to the midpoint of the voltage divider resistors R6 and R7. The two ends of the eighth capacitor C8 are connected to the input terminal of the second operational amplifier circuit.

[0032] Specifically, in this embodiment, the reference voltage chip U1 is an adjustable precision parallel voltage regulator chip AZ431. The AZ431 chip provides an accurate output voltage, unaffected by changes in operating voltage, load, temperature, or time. Reference voltage chips are used in fields requiring high-precision voltage standards, such as high-precision A / D and D / A conversion, sensors, power management, and precision rectification. The AZ431 chip's internal reference keeps the VREF terminal at 2.5V, and the output voltage can be easily set within the range of 2.5V to 36V using an external resistor divider network. It features high accuracy, low output noise, and good temperature stability.

[0033] Specifically, in this embodiment, the voltage divider resistors R6 and R7 form a voltage divider network connected to the output terminal of the reference voltage chip U1 connected in series. The resistance of the voltage divider resistor R6 is 1.2kΩ and the resistance of the voltage divider resistor R7 is 4.99kΩ, so that the output voltage of the reference voltage circuit is stabilized at 3.09V.

[0034] The eighth capacitor C8 serves as a filter.

[0035] Preferably, the second operational amplifier circuit includes a second operational amplifier U3-A. The inverting input terminal of the second operational amplifier U3-A is connected to the negative output terminal of the reference voltage circuit through a ninth resistor R9, and the non-inverting input terminal of the second operational amplifier U3-A is connected to the positive output terminal of the reference voltage circuit through a tenth resistor R10. The output terminal of the second operational amplifier U3-A is connected to the inverting input terminal of the second operational amplifier U3-A through a tenth capacitor C10 and a twelfth resistor R12 connected in parallel. The non-inverting input terminal of the second operational amplifier U3-A is connected to the power supply reference ground BAT_V- through a ninth capacitor C9 and an eleventh resistor R11 connected in parallel.

[0036] Specifically, the ninth capacitor C9 and the tenth capacitor C10 serve as filters, and the second operational amplifier circuit amplifies the output voltage of the reference voltage circuit by a predetermined factor.

[0037] In this embodiment, the amplification factor of the second operational amplifier circuit is R11 / R10, where the resistance of the tenth resistor R10 is 3.6kΩ and the resistance of the eleventh resistor R11 is 1.2kΩ. Therefore, the amplification factor of the second operational amplifier circuit is 1 / 3. That is, the output voltage of the second operational amplifier circuit is 1 / 3 of the output voltage of the reference voltage circuit, and is stable at 1.03V.

[0038] Specifically, the output terminal of the second operational amplifier circuit is connected to the positive input terminal of the first operational amplifier U3-B through the eighteenth capacitor C18 and the nineteenth resistor R19 connected in parallel, thereby boosting the output voltage of the first operational amplifier circuit by 1.03V.

[0039] Preferably, the voltage-type isolated sampling chip circuit includes a voltage-type isolated sampling chip U2, which includes an input side and an output side;

[0040] The input side of the voltage-type isolated sampling chip U2: the input pin VIN is connected to the output terminal of the first operational amplifier circuit through the fourteenth resistor R14, the seventh capacitor C7 is provided between the input pin VIN and the ground pin GND1, and the ground pin GND1 is connected to the power supply reference ground BAT_V-.

[0041] The output side of the voltage-type isolated sampling chip U2: the positive output terminal OUTP and the negative output terminal OUTN are connected to the load through the fourth resistor R4 and the fifth resistor R5, respectively. The load terminal is connected in parallel with the second capacitor C2, and the ground pin GND2 is connected to the reference ground DGND.

[0042] Specifically, on the input side of the voltage-type isolation sampling chip U2, the power supply terminal VDD1 is connected to the power supply +5V-BAT, and a fifth capacitor C5 is provided between the power supply terminal VDD1 and the ground pin GND1. The fifth capacitor C5 and the seventh capacitor C7 serve as filters.

[0043] Specifically, on the output side of the voltage-type isolation sampling chip U2, the power supply terminal VDD2 is connected to the power supply +5VD. A third capacitor C3 and a fourth capacitor C4 are connected in parallel between the power supply terminal VDD2 and the ground pin GND2. The third capacitor C3 and the fourth capacitor C4 serve as filters. The fourth resistor R4 and the fifth resistor R5 are anti-interference output resistors. The second capacitor C2 serves as a filter.

[0044] Specifically, in this embodiment, the voltage-type isolation sampling chip U2 adopts the NSI1311 chip. The NSI1311 chip is a high-performance isolation amplifier based on Adaptive OOK encoding capacitive isolation technology. This chip is mainly used for voltage detection and isolation transmission in high-voltage systems, and is especially suitable for application scenarios that require high precision and high anti-interference capability.

[0045] Preferably, it further includes an operational amplifier chip power supply circuit, which is used to supply power to the operational amplifier chip, including a third operational amplifier U3-C. Pin 8 of the third operational amplifier U3-C is connected to the battery +5V_BAT, and pin 4 of the third operational amplifier U3-C is connected to the battery -5V_BAT.

[0046] Specifically, the third operational amplifier U3-C has an eleventh capacitor C11, a twelfth capacitor C12, a thirteenth capacitor C13, and a fourteenth capacitor C14 connected between pins 8 and 4 for filtering. The eleventh capacitor C11 and the thirteenth capacitor C13 are connected in series between pins 8 and 4 of the third operational amplifier U3-C, and the midpoint between the eleventh capacitor C11 and the thirteenth capacitor C13 is connected to the power supply reference ground BAT_V-. The twelfth capacitor C12 and the fourteenth capacitor C14 are connected in series between pins 8 and 4 of the third operational amplifier U3-C, and the midpoint between the twelfth capacitor C12 and the fourteenth capacitor C14 is connected to the power supply reference ground BAT_V-.

[0047] In this embodiment, a current sampling circuit based on a voltage-type isolation sampling chip uses the shunt resistor for current sampling, amplifies the sampled current signal through an operational amplifier circuit, and uses an AZ431 to build a reference circuit to raise the current signal to the input midpoint of the voltage-type isolation sampling chip, thus achieving bidirectional current sampling using a voltage-type isolation chip. This circuit is less expensive than common current-type isolation sampling chip solutions. This circuit is suitable for scenarios requiring current isolation sampling, such as energy storage battery packs, energy storage inverters, and new energy sources.

[0048] The signal conversion circuit requires selecting a suitable shunt resistor based on the battery current range. The output pins of the shunt resistor, namely pins 2 and 3, are the outputs of the signal conversion circuit. These two pins are connected to the input of the first operational amplifier circuit via a resistor (to prevent interference).

[0049] The reference voltage circuit takes a +5V voltage (+5V-BAT) referenced to the negative terminal of the battery as its input. This 5V voltage is adjusted to 3.09V using an AZ431 chip and voltage divider resistors. The output of this reference voltage circuit needs to be connected to a second operational amplifier circuit. This second operational amplifier circuit further adjusts the input voltage and connects to the first operational amplifier circuit, providing a reference voltage for its output signal. Both the first and second operational amplifier circuits require external power supplies to operate, necessitating an operational amplifier chip power supply circuit. This circuit connects a positive 5V power supply (+5V-BAT) and a negative 5V power supply (-5V-BAT) referenced to the negative terminal of the battery to pins 8 and 4 of the operational amplifier chip, respectively.

[0050] The circuit described above converts the signal output from the shunt resistor into a signal that can be directly used as the input to the voltage-type isolation sampling chip. By connecting the output of the first operational amplifier circuit to the input of the voltage-type isolation sampling chip circuit, the entire circuit is formed.

[0051] The technical differences between voltage-mode and current-mode sampling are as follows: current-mode sampling enables bidirectional sampling with a very small input signal range, typically -250mV to +250mV, thus achieving high-precision sampling; voltage-mode sampling is limited to single-phase sampling and has a wider input range, with the NSI1311's input range being 0.1V to 2V. Therefore, we need to design the circuit described above to process the signal output from the shunt resistor. To achieve bidirectional sampling, the signal needs to be boosted by a reference voltage. The reference voltage circuit and the second operational amplifier circuit boost the signal by 1.03V, ensuring the signal outputs around 1.03V without exceeding the input range of the voltage-mode chip. Simultaneously, to improve accuracy, the first operational amplifier circuit amplifies the signal by 10 times, making it close to the voltage-mode input range and guaranteeing the accuracy of isolated sampling.

[0052] In the aforementioned current sampling circuit based on a voltage-type isolation sampling chip, the current signal conversion circuit transmits the battery current signal to the first operational amplifier circuit via a shunt resistor. The second operational amplifier circuit amplifies the reference input voltage signal by a predetermined factor and transmits it to the first operational amplifier circuit, raising the output voltage of the first operational amplifier circuit to a predetermined value. The first operational amplifier circuit amplifies the voltage signal acquired and converted by the current signal conversion circuit by a predetermined factor and transmits it to the voltage-type isolation sampling chip circuit. The voltage-type isolation sampling chip circuit detects and isolates the voltage of the input voltage sampling signal during transmission. This current sampling circuit based on a voltage-type isolation sampling chip amplifies and isolates the sampling signal using an operational amplifier circuit and a voltage-type isolation sampling chip, satisfying the accuracy requirements of isolation sampling while reducing equipment costs. The circuit structure of this invention is easy to implement, low in cost, and readily applicable.

[0053] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A current sampling circuit based on a voltage type isolated sampling chip, for realizing isolated sampling of battery current in a device powered by a battery, characterized in that, It includes a current signal conversion circuit, a first operational amplifier circuit, a reference voltage circuit, a second operational amplifier circuit, and a voltage-type isolation sampling chip circuit. The current signal conversion circuit, the first operational amplifier circuit, and the voltage-type isolation sampling chip circuit are connected in sequence. The reference voltage circuit and the second operational amplifier circuit are connected in sequence. The output terminal of the second operational amplifier circuit is connected to the first operational amplifier circuit. The current signal conversion circuit includes a shunt resistor R3, which is used to acquire the current signal of the main power circuit output by the battery. The first operational amplifier circuit amplifies the voltage signal acquired and converted by the current signal conversion circuit by a predetermined factor; the reference voltage circuit provides a reference input voltage to the second operational amplifier circuit; the second operational amplifier circuit amplifies the reference input voltage signal by a predetermined factor and transmits it to the first operational amplifier circuit to increase the output voltage of the first operational amplifier circuit, so that the output signal is within the input range of the voltage-type isolation sampling chip; the voltage-type isolation sampling chip circuit is used for voltage detection and isolated transmission of the input voltage sampling signal. The voltage-type isolation sampling chip circuit includes a voltage-type isolation sampling chip U2, which includes an input side and an output side. The input side of the voltage-type isolated sampling chip U2: the input pin VIN is connected to the output terminal of the first operational amplifier circuit through the fourteenth resistor R14, the seventh capacitor C7 is provided between the input pin VIN and the ground pin GND1, and the ground pin GND1 is connected to the power supply reference ground BAT_V-. The output side of the voltage-type isolation sampling chip U2: the positive output terminal OUTP and the negative output terminal OUTN are connected to the load through the fourth resistor R4 and the fifth resistor R5, respectively. The load terminal is connected in parallel with the second capacitor C2, and the ground pin GND2 is connected to the reference ground DGND. The shunt resistor R3 includes two input terminals and two output terminals. The two input terminals are connected to the main power circuit of the battery output terminal, and the two output terminals are respectively connected to a first resistor R1 and a second resistor R2.

2. The current sampling circuit based on a voltage-type isolated sampling chip as described in claim 1, characterized in that, The first operational amplifier circuit includes a first operational amplifier U3-B. The inverting input and non-inverting input of the first operational amplifier U3-B are connected to the output of the current signal conversion circuit through the sixteenth resistor R16 and the seventeenth resistor R17, respectively. The output of the first operational amplifier U3-B is connected to the inverting input of the first operational amplifier U3-B through the fifteenth capacitor C15 and the fifteenth resistor R15 connected in parallel. The non-inverting input of the first operational amplifier U3-B is connected to the output of the second operational amplifier circuit through the eighteenth capacitor C18 and the nineteenth resistor R19 connected in parallel. The output of the first operational amplifier U3-B is connected to the input of the voltage-type isolated sampling chip circuit through the fourteenth resistor R14.

3. The current sampling circuit based on a voltage-type isolated sampling chip as described in claim 1, characterized in that, The reference voltage circuit includes a reference voltage chip U1. The input terminal of the reference voltage chip U1 is connected to a 5V power supply through an eighth resistor R8. The VREF terminal of the reference voltage chip U1 is connected to the midpoint of the voltage divider resistors R6 and R7. The voltage divider resistors R6 and R7 are connected in series and then connected in parallel with the eighth capacitor C8. The two ends of the eighth capacitor C8 are connected to the input terminal of the second operational amplifier circuit.

4. The current sampling circuit based on a voltage-type isolated sampling chip as described in claim 2, characterized in that, The second operational amplifier circuit includes a second operational amplifier U3-A. The inverting input terminal of the second operational amplifier U3-A is connected to the negative output terminal of the reference voltage circuit through a ninth resistor R9, and the non-inverting input terminal of the second operational amplifier U3-A is connected to the positive output terminal of the reference voltage circuit through a tenth resistor R10. The output terminal of the second operational amplifier U3-A is connected to the inverting input terminal of the second operational amplifier U3-A through a tenth capacitor C10 and a twelfth resistor R12 connected in parallel. The non-inverting input terminal of the second operational amplifier U3-A is connected to the power supply reference ground BAT_V- through a ninth capacitor C9 and an eleventh resistor R11 connected in parallel.

5. The current sampling circuit based on a voltage-type isolated sampling chip as described in claim 4, characterized in that, It also includes an operational amplifier chip power supply circuit, which is used to supply power to the first operational amplifier U3-B and the second operational amplifier U3-A. The operational amplifier chip power supply circuit includes a third operational amplifier U3-C. Pin 8 of the third operational amplifier U3-C is connected to the battery +5V_BAT, and pin 4 of the third operational amplifier U3-C is connected to the battery -5V_BAT.

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