Bidirectional current isolation sampling device and method and direct current charging pile

Abstract

The invention relates to a bidirectional current isolation sampling device and method and a direct current charging pile, and the device is connected with a direct current bus through a signal collection module, and converts the collected bus current into a first voltage signal; the voltage boosting module is connected with the signal acquisition module and is used for boosting the first voltage signal to a positive value and outputting a second voltage signal; the isolation conversion module is connected with the voltage lifting module, electrically isolates the second voltage signal and outputs a third voltage signal; the signal processing module is connected with the isolation conversion module and converts the third voltage signal into a single-ended signal adaptive to sampling of the analog-to-digital converter; the controller is connected with the signal processing module and used for obtaining the voltage value of the single-end signal and calculating the current value and the transmission direction of the bus current according to the voltage value, the problem that bidirectional current sampling is high in cost or unstable is solved, bidirectional current detection can be independently carried out with lower-cost structural design, and the reliability of the system is improved. And the accuracy of bus current monitoring is improved.

Description

Technical Field

[0001] This application relates to the field of current sampling technology, and in particular to a bidirectional current isolation sampling device, method, and DC charging pile. Background Technology

[0002] In DC charging pile systems, real-time acquisition of bus current is the core technological foundation for achieving dynamic display of charging power, energy metering, and safety protection. Especially in systems supporting V2X (vehicle-to-everything) bidirectional charging and discharging functions, current detection needs to have bidirectional acquisition capabilities to simultaneously meet the monitoring requirements of grid power supply and on-board battery feedback.

[0003] Currently, the industry mainly adopts the following two technical solutions: (1) Integrated solution of finished electricity meter, which directly obtains bus current data through bidirectional DC meter, but the cost is high. (2) Power module communication reading solution, which indirectly obtains output current parameters from power conversion module through communication protocol. This solution depends on the reliability of upstream module and has poor stability.

[0004] There is currently no effective solution to the problems of high cost and instability in bidirectional current sampling in related technologies. Summary of the Invention

[0005] This embodiment provides a bidirectional current isolation sampling device, method, and DC charging pile to solve the problems of high cost and instability of bidirectional current sampling in related technologies.

[0006] In a first aspect, this embodiment provides a bidirectional current isolation sampling device, including a signal acquisition module, a voltage boosting module, an isolation conversion module, a signal processing module, and a controller connected in sequence.

[0007] The signal acquisition module is connected to the DC bus and is used to convert the acquired bus current into a first voltage signal.

[0008] The voltage boosting module is used to boost the first voltage signal to output a second voltage signal, wherein the second voltage signal is a positive value;

[0009] The isolation conversion module is used to electrically isolate the second voltage signal and output a third voltage signal;

[0010] The signal processing module is used to convert the third voltage signal into a single-ended signal that is compatible with the sampling of the analog-to-digital converter;

[0011] The controller is used to acquire the voltage value of the single-ended signal, and to acquire the current value and transmission direction of the bus current based on the voltage value.

[0012] In some embodiments, a temperature acquisition module is also included;

[0013] The temperature acquisition module is connected to the controller and is used to acquire the ambient temperature of the bidirectional current isolation sampling device;

[0014] The controller is used to correct the voltage value according to the ambient temperature, and to obtain the current value and transmission direction of the bus current based on the corrected voltage value.

[0015] In some embodiments, the lifting module includes: a lifting power supply and a lifting circuit;

[0016] The voltage boosting power supply is connected to the voltage boosting circuit and is used to generate a reference voltage;

[0017] The voltage boosting circuit is connected to the signal acquisition module and the isolation conversion module respectively, and superimposes the reference voltage on the first voltage signal to obtain the second voltage signal.

[0018] In some of these embodiments, the lift-up power supply includes: a reference source and a follower;

[0019] The reference source is connected to the follower and is used to output a reference voltage;

[0020] The follower is connected to the voltage boosting circuit and is used to input the reference voltage into the voltage boosting circuit so that the second voltage signal meets the preset voltage range.

[0021] In some embodiments, the signal acquisition module includes: a shunt and a filter circuit;

[0022] The shunt is connected to the positive and negative terminals of the DC bus and is used to collect the bus current and output a DC differential voltage signal.

[0023] One end of the filter circuit is connected to the shunt, and the other end of the filter circuit is connected to the voltage boosting module. It is used to filter the input DC differential voltage signal and output the first voltage signal.

[0024] In some embodiments, the signal processing module includes: an amplification and filtering circuit and a clamping circuit;

[0025] The amplification and filtering circuit is connected to the isolation conversion module and is used to filter and single-ended the third voltage signal to obtain a single-ended signal.

[0026] The clamping circuit is connected to the amplification and filtering circuit and is used to clamp and protect the single-ended signal.

[0027] Secondly, this embodiment provides a bidirectional current isolation sampling method, applied to any of the bidirectional current isolation sampling devices described in the first aspect, the method comprising:

[0028] Obtain the voltage value of the single-ended signal sent by the signal processing module;

[0029] The voltage value is corrected for temperature drift to obtain the corrected voltage;

[0030] Based on the correction voltage, the current value and transmission direction of the bus current are obtained.

[0031] In some embodiments, the step of performing temperature drift correction on the voltage value to obtain a corrected voltage includes:

[0032] Receive the ambient temperature sent by the temperature acquisition module;

[0033] Based on a preset temperature drift correction function, the correction parameters corresponding to the ambient temperature are calculated;

[0034] The voltage value is added to the correction parameter to obtain the correction voltage.

[0035] In some embodiments, obtaining the current value and transmission direction of the bus current based on the correction voltage includes:

[0036] Based on the correction voltage, the voltage value of the first voltage signal obtained by the signal acquisition module from the bus current sampling is calculated;

[0037] Based on the voltage value of the first voltage signal, the current value and transmission direction of the bus current are obtained.

[0038] Thirdly, this embodiment provides a DC charging pile, including the bidirectional current isolation sampling device described in any of the first aspects above.

[0039] Compared with related technologies, the bidirectional current isolation sampling device, method, and DC charging pile provided in this embodiment, through a signal acquisition module connected to the DC bus, converts the acquired bus current into a first voltage signal; a voltage boosting module connected to the signal acquisition module boosts the first voltage signal to a positive value and outputs a second voltage signal; an isolation conversion module connected to the voltage boosting module electrically isolates the second voltage signal and outputs a third voltage signal; a signal processing module connected to the isolation conversion module converts the third voltage signal into a single-ended signal adapted for analog-to-digital converter sampling; and a controller connected to the signal processing module acquires the voltage value of the single-ended signal and obtains the current value and transmission direction of the bus current based on the voltage value. This solves the problems of high cost or instability in bidirectional current sampling, and enables independent bidirectional current detection with a lower cost structure design, improving the accuracy of bus current monitoring.

[0040] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0041] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0042] Figure 1 This is a structural block diagram of the bidirectional current isolation sampling device in the embodiments of this application;

[0043] Figure 2 This is a schematic diagram of the signal acquisition module in an embodiment of this application;

[0044] Figure 3 This is a schematic diagram of the tire pressure module in an embodiment of this application;

[0045] Figure 4 This is a circuit diagram of the bidirectional current isolation sampling device in a preferred embodiment of this application;

[0046] Figure 5 This is a structural block diagram of the bidirectional current isolation sampling device in a preferred embodiment of this application;

[0047] Figure 6 This is a flowchart illustrating the bidirectional current isolation sampling method in the embodiments of this application.

[0048] Reference numerals: 110, Signal acquisition module; 111, Shunt; 112, Filter circuit; 120, Voltage boosting module; 121, Voltage boosting power supply; 122, Voltage boosting circuit; 130, Isolation conversion module; 131, Isolation operational amplifier circuit; 140, Signal processing module; 141, Amplification and filtering circuit; 142, Clamping circuit; 150, Controller; 151, MCU; 160, Power supply module; 161, Isolation power supply; 162, Low-voltage control power supply; 163, Low-dropout linear regulator; 170, Temperature acquisition module. Detailed Implementation

[0049] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0050] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these” used in this application do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to these processes, methods, products, or devices. Words such as “connected,” “linked,” and “coupled” used in this application are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Normally, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," "third," etc., used in this application are merely to distinguish similar objects and do not represent a specific order of objects.

[0051] This embodiment provides a bidirectional current-isolated sampling device, such as Figure 1 As shown, the bidirectional current isolation sampling device includes: a signal acquisition module 110, a voltage boosting module 120, an isolation conversion module 130, a signal processing module 140, and a controller 150.

[0052] The signal acquisition module 110 is connected to the DC bus and is used to convert the acquired bus current into a first voltage signal. Specifically, the signal acquisition module 110 can divide the voltage to output a 0-75mV DC voltage signal, i.e., the first voltage signal. Since the direction of the bus current changes during charging or discharging, the corresponding output first voltage signal can have both positive and negative values.

[0053] The voltage boosting module 120, connected to the signal acquisition module 110, is used to boost the first voltage signal to a positive value so as to output the second voltage signal. Specifically, a constant voltage is superimposed on the first voltage signal. Especially when the first voltage signal is negative, signal superposition can convert the negative voltage at the input terminal into a positive voltage signal input, thereby preventing the subsequent module from being cut off due to negative voltage and failing to output normally. This makes it suitable for scenarios with bidirectional current.

[0054] The isolation conversion module 130, connected to the voltage boosting module 120, is used to electrically isolate the second voltage signal and output a third voltage signal. Specifically, since there is a high voltage on the bus side, the isolation conversion module 130 prevents the risk of high voltage breakdown or leakage, protects the low-voltage circuit and the safety of operators, and achieves electrical isolation and safe signal transmission.

[0055] The signal processing module 140, connected to the isolation conversion module 130, is used to convert the third voltage signal into a single-ended signal suitable for sampling by the analog-to-digital converter. Specifically, the third voltage signal output is a differential signal, which the signal processing module 140 converts into a single-ended signal that is easy for the ADC of the controller 150 to sample.

[0056] The controller 150, connected to the signal processing module 140, is used to sample the voltage value of the single-ended signal and obtain the current value and transmission direction of the bus current based on the voltage value. Specifically, the controller can be a microcontroller MCU 151. The controller 150 deduces the magnitude of the first voltage signal based on the superimposed constant voltage and the gain of each module through which the signal flows, and calculates the actual bus current value and transmission direction by combining the voltage division ratio of the signal acquisition module 110.

[0057] In this embodiment, a signal acquisition module 110, connected to the DC bus, converts the acquired bus current into a first voltage signal; a voltage boosting module 120, connected to the signal acquisition module 110, boosts the first voltage signal to a positive value and outputs a second voltage signal; an isolation conversion module 130, connected to the voltage boosting module 120, electrically isolates the second voltage signal and outputs a third voltage signal; a signal processing module 140, connected to the isolation conversion module 130, converts the third voltage signal into a single-ended signal compatible with analog-to-digital converter sampling; and a controller 150, connected to the signal processing module 140, acquires the voltage value of the single-ended signal and calculates the current value and transmission direction of the bus current based on the voltage value. This solves the problem of high cost or instability in bidirectional current sampling, enabling independent bidirectional current detection with a lower cost structure design, thus improving the accuracy of bus current monitoring.

[0058] In some of these embodiments, see Figure 2 The signal acquisition module 110 includes a shunt 111 and a filter circuit 112. The shunt 111 is connected to the positive and negative terminals of the DC bus and is used to acquire the bus current and output a DC differential voltage signal. One end of the filter circuit 112 is connected to the shunt 111, and the other end of the filter circuit 112 is connected to the voltage boosting module 120. It is used to filter the input DC differential voltage signal and output a first voltage signal.

[0059] Specifically, the shunt 111 can be a 100A 75mV 0.5-class model, with an output DC differential voltage signal of ±75mV. Before the DC differential voltage signal is input to the boost module 120, it is filtered by the filter circuit 112 to improve signal accuracy.

[0060] In some of these embodiments, see Figure 3 The voltage boosting module 120 includes a voltage boosting power supply 121 and a voltage boosting circuit 122. The voltage boosting power supply 121 is connected to the voltage boosting circuit 122 and is used to generate a reference voltage Vref. The voltage boosting circuit 122 is connected to the signal acquisition module 110 and the isolation conversion module 130 respectively, and is used to superimpose the reference voltage Vref onto the first voltage signal to obtain a second voltage signal.

[0061] Specifically, a reference voltage Vref and a first voltage signal Vin are input to the first input terminal of the voltage boosting circuit 122 to obtain the boosted second voltage signal Vin×Gain1+Vref, where Gain1 is the gain of the voltage boosting circuit 122.

[0062] In this embodiment, a stable reference voltage Vref is provided by the boost power supply 121, and the output voltage level is adjusted by the boost circuit 122 to raise the signal level to a higher range so that the signal can adapt to the input requirements of the target device.

[0063] In some of these embodiments, see Figure 4 The voltage boosting power supply 121 includes a reference source U4 and a follower U5. The reference source U4 is connected through the follower U5 and is used to output a reference voltage Vref. The follower U5 is connected to the voltage boosting circuit 122 and is used to input the reference voltage into the voltage boosting circuit 122.

[0064] Specifically, the reference source U4 can be a reference chip such as TL431 or REF3025, which generates the required reference voltage Vref through a voltage divider resistor. To ensure accuracy, the reference source U4 and the voltage divider resistor can be selected with an accuracy of 0.5% or 0.1%. The boost power supply 121 also includes a resistor R11. One end of the resistor R11 is connected to the reference source U4, and the other end of the resistor R11 is connected to the power supply. The resistor R11 is a current-limiting resistor and also bears the voltage drop from the power supply voltage to Vref. To ensure that the voltage after the reference passes through the voltage divider resistor is not affected by external circuitry, a follower U5 is provided to buffer and isolate the voltage and improve its load-carrying capacity.

[0065] In some of these embodiments, see Figure 4 The voltage boosting circuit 122 includes: a first operational amplifier U1, a first resistor R3, and a second resistor R4.

[0066] The first input terminal of the first operational amplifier U1 is connected to the output terminal of the follower through the first resistor R3; the first input terminal of the first operational amplifier U1 is also connected to the first potential terminal V of the signal acquisition module 110. i+ The connection is made between the second input terminal of the first operational amplifier U1 and the second potential terminal V of the signal acquisition module 110. i- Connection: The output terminal of the first operational amplifier U1 is connected to the second input terminal of the first operational amplifier U1 through the second resistor R4.

[0067] Specifically, the voltage boosting circuit 122 also includes input resistors R1 and R2, and capacitor C1, which filters the input signal. The first resistor R3 and the second resistor R4 are feedback resistors; for ease of calculation, R1=R2 and R3=R4 are generally set. The output of the first operational amplifier U1 is typically Vout=(R4 / R2)×Vin, where Vin=V i+ -V i- .

[0068] In some of these embodiments, see Figure 4The isolation conversion module 130 employs an isolation operational amplifier circuit 131, which includes a second operational amplifier U2 (i.e., the isolation operational amplifier), a resistor R5, and a capacitor C4. The first input terminal of the isolation operational amplifier U2 is connected to the output terminal of the first operational amplifier U1 through resistor R5; the first input terminal of the isolation operational amplifier U2 is also grounded through capacitor C4. The second input terminal of the isolation operational amplifier U2 is grounded. The first and second output terminals of the isolation operational amplifier U2 are respectively connected to an amplification and filtering circuit 141 to convert the differential signal output by U2 into a single-ended signal.

[0069] The isolation operational amplifier U2 has an input limit of 250mV and a voltage rise reference Vref of 120mV. The four resistors R1, R2, R3, and R4 have the same value. The gain 1 of the first operational amplifier U1 is 1. This ensures that the input voltage range of U2 is 45-195mV, which is within U2's good linear range, avoiding distortion issues in the small-signal input stage. U2 can be equipped with an NSI1200C with an 8x gain (Gain 2 = 8), outputting a differential signal of 0.36-1.56V.

[0070] In some of these embodiments, see Figure 4 The signal processing module 140 includes an amplification and filtering circuit 141 and a clamping circuit 142.

[0071] The amplification and filtering circuit 141 is connected to the isolation conversion module 130 and is used to filter and single-ended the third voltage signal to obtain a single-ended signal.

[0072] Specifically, the amplification and filtering circuit 141 includes a third operational amplifier U3, resistors R6, R7, R8, and R9, and capacitors C5 and C6. The first input terminal of the third operational amplifier U3 is connected to the first output terminal of the isolation operational amplifier U2 through resistor R6; the first input terminal of the third operational amplifier U3 is also connected to GND through resistor R9 and capacitor C5. The second input terminal of the third operational amplifier U3 is connected to the second output terminal of the isolation operational amplifier U2 through resistor R7. The output terminal of the third operational amplifier U3 is connected to the clamping circuit 142; the output terminal of the third operational amplifier U3 is also connected to the second input terminal of the third operational amplifier U3 through resistor R8 and capacitor C6. R6 and R7 are the differential input resistors of U3, R8 and R9 are the feedback resistors, and C5 and C6 are the feedback capacitors connected in parallel across the feedback resistors. Their purpose is to compensate for phase and prevent self-oscillation. For ease of calculation, R6 = R7, R8 = R9, Gain2 = R8 / R7, and the gain is set to 1.8 times, i.e., Gain3 = 1.8.

[0073] Clamping circuit 142, connected to amplification and filtering circuit 141, is used to clamp and protect single-ended signals. Specifically, when the external common-mode input of U2 experiences overvoltage or the power supply V1 is abnormal, a 2.6V VFailsafe fault voltage will be output. To ensure that the Vadc voltage is between V1 and GND and to prevent damage to the controller 150 port, clamping diodes D1 and D2 are set before the input of controller 150. One end of clamping diode D1 is connected to power supply V1, and the other end of clamping diode D1 is connected to the output of the third operational amplifier U3; one end of clamping diode D2 is connected to the output of the third operational amplifier U3, and the other end of clamping diode D2 is connected to GND.

[0074] Furthermore, the output of the third operational amplifier U3 is connected to the clamping circuit 142 via an RC filter circuit, which includes a resistor R10 and a capacitor C7. The RC filter circuit provides signal filtering while also providing external voltage storage for the ADC input inside the controller 150.

[0075] In some of these embodiments, see Figure 5 The bidirectional current isolation sampling device also includes: a power supply module 160; the power supply module 160 includes an isolation power supply 161 and a low-voltage control power supply 162.

[0076] One end of the isolation power supply 161 is connected to the low-voltage control power supply 162, and the other end of the isolation power supply 161 is connected to the voltage boosting module 120 and the isolation conversion module 130 respectively, for providing isolated power supply to each module.

[0077] The low-voltage control power supply 162 is also connected to the isolated operational amplifier circuit 131 and the controller 150. Furthermore, the power module 160 also includes a low-dropout regulator (LDO) 163, through which the low-voltage control power supply 162 is connected to the MCU 151 of the controller 150. The LDO 163 reduces the voltage from 5V to 3.3V to power the MCU 151.

[0078] Specifically, the input voltage V1 and output voltage V2 of the isolation power supply 161 are 5V, which are used to safely isolate the high-voltage side of the external sampling and the internal low-voltage side, protect the internal low-voltage control circuit, protect personal safety, and block common-mode interference.

[0079] Among them, V2 of the isolation power supply 161 is connected to the power supply terminals of the reference source U4, the follower U5, the differential operational amplifier U1 and the isolation operational amplifier U2, respectively, and V1 of the low-voltage control power supply 162 is connected to the third operational amplifier U3, the clamping diode D1 and the low-dropout linear regulator 163, respectively.

[0080] In some of these embodiments, see Figure 5 The bidirectional current isolation sampling device also includes a temperature acquisition module 170. The temperature acquisition module 170, connected to the controller 150, is used to acquire the ambient temperature of the bidirectional current isolation sampling device. The controller 150 is used to correct the voltage value based on the ambient temperature, and to obtain the bus current value and transmission direction based on the corrected voltage value. The temperature acquisition module 170 is also connected to a low-dropout linear regulator 163.

[0081] Specifically, this embodiment uses three operational amplifiers (U1, U2, and U3) and a reference follower operational amplifier. The gain temperature drift and nonlinear temperature drift of these operational amplifiers differ. To achieve more precise measurement requirements, the influence of ambient temperature on the system gain can be used for superposition calibration. The temperature acquisition module 170 typically uses an NTC or PT1000 for ambient temperature acquisition.

[0082] This embodiment also provides a bidirectional current isolation sampling method, applied to the bidirectional current isolation sampling device in any of the above embodiments, specifically applied to the controller 150 side, see [link to documentation]. Figure 6 The method includes:

[0083] Step S610: Obtain the voltage value of the single-ended signal sent by the signal processing module 140.

[0084] Step S620: Perform temperature drift correction on the voltage value to obtain the corrected voltage.

[0085] Step S630: Based on the correction voltage, obtain the current value and transmission direction of the bus current.

[0086] In this embodiment, the voltage value can be obtained regardless of whether the bus current is in the forward or reverse direction. In order to achieve more precise measurement requirements, the current value and current direction on the bus side are accurately recovered by superimposing calibration through ambient temperature.

[0087] In some embodiments, based on step S620, temperature drift correction is performed on the voltage value to obtain a corrected voltage, including:

[0088] Step S621: Receive the ambient temperature sent by the temperature acquisition module 170.

[0089] Step S622: Calculate the correction parameters corresponding to the ambient temperature based on the preset temperature drift correction function.

[0090] Step S623: Add the voltage value to the correction parameter to obtain the correction voltage value.

[0091] Specifically, by selecting typical samples of 3Pcs or more and placing them within the required operating temperature range of the entire machine, sampling and statistics are performed every 20°C. A standard mV signal reference source is used to simulate current input, and the current value converted by the MCU151 is collected. The output under different inputs is averaged, and the average current deviation α at different temperatures is statistically calculated, establishing an α-t table. Theoretically, the error caused by temperature drift can be fitted using the linear equation: Δi = at + b. Curve fitting is performed using partial data from the α-t table to obtain 'a' and 'b', and the remaining data in the table are used for feedback verification and correction. Therefore, the formula for calculating the corrected voltage value is: Vadc1 = Vadc + Δi, where Vadc1 is the corrected voltage value, Vadc is the voltage value before correction, and Δi is the correction parameter. This formula correlates temperature t with Vadc, enabling calibration of different temperature drift values ​​at different temperatures.

[0092] In some embodiments, step S630, based on the correction voltage, obtains the current value and transmission direction of the bus current, including:

[0093] Step S631: Based on the correction voltage, calculate the voltage value of the first voltage signal obtained by the signal acquisition module 110 from the bus current sampling.

[0094] Step S632: Based on the voltage value of the first voltage signal, obtain the current value and transmission direction of the bus current.

[0095] Specifically, based on the superimposed reference voltage Vref and the gain of each module through which the signal flows, the first voltage signal is deduced, and combined with the voltage division ratio of the signal acquisition module 110, the actual bus current value and transmission direction are calculated.

[0096] This embodiment also provides a DC charging pile, including the bidirectional current isolation sampling device in any of the above embodiments.

[0097] In this embodiment, a signal acquisition module 110, connected to the busbar, converts the acquired busbar current into a differential voltage signal and outputs a first voltage signal. A voltage boosting module 120, connected to the signal acquisition module 110, boosts the first voltage signal to a positive value and outputs a second voltage signal. An isolation conversion module 130, connected to the voltage boosting module 120, electrically isolates the second voltage signal and outputs a third voltage signal. A signal processing module 140, connected to the isolation conversion module 130, converts the third voltage signal into a single-ended signal compatible with analog-to-digital converter sampling. A controller 150, connected to the signal processing module 140, samples the voltage value of the single-ended signal and calculates the busbar current based on the voltage value. This solves the problem of high cost or instability in bidirectional current sampling, enabling independent bidirectional current detection with a lower-cost structural design, thus improving the accuracy of busbar current monitoring.

[0098] The present embodiment will now be described and illustrated through preferred embodiments. Figure 4 and Figure 5 This is a schematic diagram of the bidirectional current isolation sampling device in this preferred embodiment.

[0099] like Figure 4 and Figure 5 As shown, the preferred embodiment of this bidirectional current isolation sampling device includes: a signal acquisition module 110, a voltage boosting module 120, an isolation conversion module 130, a signal processing module 140, a controller 150, a temperature acquisition module 170, and a power supply module 160.

[0100] The signal acquisition module 110 includes a shunt 111 and a filter circuit 112. The boost converter module 120 includes a boost power supply 121 and a boost circuit 122. The isolation conversion module 130 includes an isolation operational amplifier circuit 131. The signal processing module 140 includes an amplification and filtering circuit 141 and a clamping circuit 142. The controller 150 includes an MCU 151. The power supply module 160 includes an isolated power supply 161, a low-voltage control power supply 162, and a low-dropout linear regulator 163.

[0101] Shunt 111 is connected to the positive and negative terminals of the DC bus to collect the bus current and output a DC differential voltage signal. One end of filter circuit 112 is connected to shunt 111, and the other end is connected to boost circuit 122 to filter the input DC differential voltage signal and output a first voltage signal. Boost power supply 121 is connected to boost circuit 122 to generate a reference voltage. Boost circuit 122 is also connected to isolation operational amplifier circuit 131 to superimpose the reference voltage onto the first voltage signal to obtain a second voltage signal. Isolation operational amplifier circuit 131 is connected to amplification and filtering circuit 141 to convert the second voltage signal into a third voltage signal. Amplification and filtering circuit 141 is connected to MCU 151 via clamping circuit 142 to filter and single-ended the third voltage signal to obtain a single-ended signal. Clamping circuit 142 is used to clamp and protect the single-ended signal. MCU151 acquires the single-ended signal output from amplification and filtering circuit 141 and calculates the voltage value based on the single-ended signal. MCU151 is connected to temperature acquisition module 170 to calculate correction parameters based on the acquired ambient temperature. The voltage value is then added to the correction parameters to obtain the corrected voltage value. Low-voltage control power supply 162 outputs 5V. One end of isolation power supply 161 is connected to low-voltage control power supply 162, and the other end of isolation power supply 161 is connected to boost power supply 121, boost circuit 122, and isolation operational amplifier circuit 131 for isolated power supply. Low-dropout linear regulator 163 is connected to low-voltage control power supply 162 at one end and to temperature acquisition module 170 and MCU151 at the other end to reduce the 5V voltage to 3.3V. Low-voltage control power supply 162 is also connected to amplification and filtering circuit 141.

[0102] Detailed hardware circuit design, such as Figure 4 As shown, Rshunt is a shunt 111 that collects the bus current and voltage. Commonly used values ​​are 75mV or 45mV; this preferred embodiment uses a 100A 75mV 0.5-class model. The voltage boosting circuit 122 includes a first operational amplifier U1, a precision operational amplifier used to convert the differential voltage signal of Rshunt into a common-mode signal. A voltage boosting reference Vref is superimposed at the positive input terminal of U1. C1 is the input filter capacitor, R1 and R2 are input resistors, and R3 and R4 are feedback resistors. For ease of calculation, R1=R2, R3=R4, and Vout=(R4 / R2)×Vin.

[0103] T1 is an isolated power supply 161 with a 5V input (V1) and a 5V output (V2). The V2 terminal of T1 is connected to a boost power supply 121 to generate a reference voltage. The boost power supply 121 typically uses a reference source U4 (such as a TL431 or REF3025 reference chip) to generate the required reference voltage through a voltage divider resistor. The boost power supply 121 also includes a current-limiting resistor R11, which also handles the voltage drop from V2 to Vref. To ensure that the reference voltage after passing through the voltage divider resistor is not affected by external circuitry, the boost power supply 121 also includes a follower U5, which serves as a buffer for isolation and to improve load capacity.

[0104] The isolation operational amplifier circuit 131 includes an isolation operational amplifier U2. Since the input limit of the isolation operational amplifier U2 is 250mV, the voltage rise reference Vref is set to 120mV. At the same time, the four resistors R1-R4 have the same value, and Gain1 is 1. This makes the input voltage range of U2 45-195mV, which is within the good linear range of U2, avoiding the distortion problem of the operational amplifier in the small signal stage of the input. The component selected for U2 is NSI1200C, with a gain of 8, that is, Gain2=8, and the output is a differential signal of 0.36-1.56V.

[0105] The amplification and filtering circuit 141 includes a precision operational amplifier U3, differential input resistors R6 and R7, feedback resistors R8 and R9, and feedback capacitors C5 and C6 connected in parallel across the feedback resistors to compensate for phase and prevent self-oscillation. For ease of calculation, R6=R7, R8=R9, Gain2=R8 / R7, and the gain is set to 1.8 times, i.e., Gain3=1.8. The amplification and filtering circuit 141 also includes an RC filter circuit 112 composed of R10 and C7, which provides signal filtering and external voltage storage for the ADC input of the MCU151. Since a 2.6V VFailsafe fault voltage will be output when the external common-mode input of U2 is over-voltage or the power supply is abnormal, clamping diodes D1 and D2 are designed to ensure that the Vadc voltage is between V1 and GND and to avoid damage to the MCU151 port.

[0106] In summary, the signal chain transfer function is:

[0107] ;

[0108] The theoretical Vadc voltage of this preferred embodiment is 0.648-2.808V, with a certain margin above and below to ensure that the device can be used even under 1.1 times overcurrent conditions.

[0109] Based on the ambient temperature obtained by the temperature acquisition module 170, the MCU151 further calculates the correction parameter Δi according to the temperature drift correction function, and calibrates the acquired voltage value Vadc to obtain the corrected voltage value Vadc1=Vadc+Δi.

[0110] Finally, the MCU151 calculates the input current Vin of the device based on Vadc1, and converts it into the actual sampled bus current value according to the resistance ratio of the shunt 111 (75mV 100A) using the formula Vin×100 / 75mV.

[0111] Through the combination of the above hardware and software, the measured current can achieve an average theoretical accuracy of 0.5% in the range of 5A-100A (depending on the shunt 111), and an accuracy of less than 1% over the entire temperature range. It can also ensure good linearity under low current conditions.

[0112] In this preferred embodiment, a three-stage operational amplifier architecture is used, along with a boost power supply 121 to boost the input voltage, thereby achieving bidirectional current detection. At the same time, with the help of ambient temperature calibration logic, the function of sampling the actual current more accurately under wide temperature range operating conditions is achieved, while also having an absolute advantage in cost.

[0113] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0114] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0115] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0116] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A bidirectional current isolation sampling device, characterized in that, It includes a signal acquisition module, a voltage boosting module, an isolation conversion module, a signal processing module, and a controller connected in sequence; The signal acquisition module is connected to the DC bus and is used to convert the acquired bus current into a first voltage signal. The voltage boosting module is used to boost the first voltage signal to output a second voltage signal, wherein the second voltage signal is a positive value; The isolation conversion module is used to electrically isolate the second voltage signal and output a third voltage signal; The signal processing module is used to convert the third voltage signal into a single-ended signal that is compatible with the sampling of the analog-to-digital converter; The controller is used to acquire the voltage value of the single-ended signal, and to acquire the current value and transmission direction of the bus current based on the voltage value.

2. The bidirectional current isolation sampling device according to claim 1, characterized in that, Also includes: Temperature acquisition module; The temperature acquisition module is connected to the controller and is used to acquire the ambient temperature of the bidirectional current isolation sampling device; The controller is used to correct the voltage value according to the ambient temperature, and to obtain the current value and transmission direction of the bus current based on the corrected voltage value.

3. The bidirectional current isolation sampling device according to claim 1, characterized in that, The lifting module includes: a lifting power supply and a lifting circuit; The voltage boosting power supply is connected to the voltage boosting circuit and is used to generate a reference voltage; The voltage boosting circuit is connected to the signal acquisition module and the isolation conversion module respectively, and superimposes the reference voltage on the first voltage signal to obtain the second voltage signal.

4. The bidirectional current isolation sampling device according to claim 3, characterized in that, The voltage boosting power supply includes: a reference source and a follower; The reference source is connected to the follower and is used to output a reference voltage; The follower is connected to the voltage boosting circuit and is used to input the reference voltage into the voltage boosting circuit so that the second voltage signal meets the preset voltage range.

5. The bidirectional current isolation sampling device according to claim 1, characterized in that, The signal acquisition module includes: a splitter and a filter circuit; The shunt is connected to the positive and negative terminals of the DC bus and is used to collect the bus current and output a DC differential voltage signal. One end of the filter circuit is connected to the shunt, and the other end of the filter circuit is connected to the voltage boosting module. It is used to filter the input DC differential voltage signal and output the first voltage signal.

6. The bidirectional current isolation sampling device according to claim 1, characterized in that, The signal processing module includes: an amplification and filtering circuit and a clamping circuit; The amplification and filtering circuit is connected to the isolation conversion module and is used to filter and single-ended the third voltage signal to obtain a single-ended signal. The clamping circuit is connected to the amplification and filtering circuit and is used to clamp and protect the single-ended signal.

7. A bidirectional current isolation sampling method, applied to the bidirectional current isolation sampling device according to any one of claims 1 to 6, characterized in that, The method includes: Obtain the voltage value of the single-ended signal sent by the signal processing module; The voltage value is corrected for temperature drift to obtain the corrected voltage; Based on the correction voltage, the current value and transmission direction of the bus current are obtained.

8. The method according to claim 7, characterized in that, The step of performing temperature drift correction on the voltage value to obtain the corrected voltage includes: Receive the ambient temperature sent by the temperature acquisition module; Based on a preset temperature drift correction function, the correction parameters corresponding to the ambient temperature are calculated; The voltage value is added to the correction parameter to obtain the correction voltage.

9. The method according to claim 7, characterized in that, The step of obtaining the current value and transmission direction of the bus current based on the correction voltage includes: Based on the correction voltage, the voltage value of the first voltage signal obtained by the signal acquisition module from the bus current sampling is calculated; Based on the voltage value of the first voltage signal, the current value and transmission direction of the bus current are obtained.

10. A DC charging pile, characterized in that, Includes the bidirectional current isolation sampling device according to any one of claims 1 to 6.

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