Current sampling system

Abstract

This utility model discloses a current sampling system. The system includes: a main switch connected in series in the main current path; a sampling switch connected in series with a shunt to form a sampling branch; the sampling branch is connected in parallel with the main current path; and a timing control module connected to the main switch and the sampling switch to generate timing signals and control the on and off states of the main switch and the sampling switch. Through the design of the timing control module, the measured current flows through the main current path most of the time, and through the sampling branch for a small portion of the time. Current sampling is performed when the measured current flows into the shunt. The current sampling system provided in this embodiment, through a dual-switch parallel circuit and appropriate timing control, separates the high-current conduction path from the sampling path, limits the shunt's energizing time to suppress self-heating, and solves the cost-accuracy contradiction of battery testing systems, enabling high-precision high-current sampling at low cost.

Description

Technical Field

[0001] This utility model relates to the field of power electronics detection technology, and in particular to a current sampling system that can improve the sampling accuracy of existing low-cost shunts. Background Technology

[0002] Batteries, as one of the energy storage media, have been widely used in recent years. It is foreseeable that various types of batteries will be further developed, and their production scale will increase exponentially, leading to a surge in demand for high-precision battery testing systems.

[0003] Existing high-precision battery testing systems typically employ high-precision shunts or high-precision current sensors to acquire the output current. However, high-precision current sensors are expensive, especially in multi-channel battery testing systems, where the cost is prohibitive.

[0004] However, low-cost shunts with high current capacity can experience issues such as self-heating and changes in ambient temperature during full-load applications, causing resistance drift to easily exceed 0.05%. Even with temperature compensation algorithms, it is impossible to reliably achieve the required accuracy of 0.02%.

[0005] Therefore, a new solution is urgently needed to improve the sampling accuracy of existing low-cost shunts in order to meet the requirements of high-precision (0.02% accuracy requirement) high current detection. Utility Model Content

[0006] This application provides a current sampling system that solves the technical problems of high cost of high-precision current sensors and insufficient sampling accuracy of low-cost shunts in the prior art, thereby achieving high-precision current sampling at low cost.

[0007] To address the aforementioned technical problems, embodiments of this application provide a current sampling system, including:

[0008] The main switch is connected in series in the main current path;

[0009] A sampling switch is connected in series with a shunt to form a sampling branch; the sampling branch is connected in parallel with the main current path.

[0010] The timing control module, connected to the main switch and the sampling switch, is used to generate timing signals to control the on and off states of the main switch and the sampling switch.

[0011] Preferably, the current sampling system includes a normal state phase and a sampling phase:

[0012] During the normal operation phase, the main switch is turned on, the sampling switch is turned off, current flows through the main switch, and no current flows through the shunt.

[0013] During the sampling phase, the main switch is turned off, the sampling switch is turned on, and the current is diverted to the sampling branch where the shunt is located.

[0014] Preferably, there is an overlapping conduction period between the normal phase and the sampling phase; during the overlapping conduction period, both the main switch and the sampling switch are turned on.

[0015] Preferably, the current sampling system further includes a first terminal block and a second terminal block, wherein after the sampling branch is connected in parallel with the main current path, the two ends of the parallel circuit are respectively connected to the first terminal block and the second terminal block.

[0016] Preferably, the current sampling system further includes a voltage sampling module connected in parallel with the shunt, used to collect the voltage on the shunt.

[0017] Preferably, the current sampling system further includes a temperature compensation module for compensating for the resistance drift of the shunt caused by changes in ambient temperature.

[0018] Preferably, the temperature compensation module includes multiple ambient temperature sensors for real-time monitoring of ambient temperature.

[0019] Preferably, the shunt is equipped with a self-heating temperature sensor for detecting the temperature rise of the shunt itself.

[0020] Preferably, the main switch is any one of a MOSFET module, an IGBT module, a vacuum relay, a composite switch consisting of a relay and a MOSFET, or a composite switch consisting of an optocoupler and a MOSFET.

[0021] Preferably, the sampling switch is any one of a MOSFET module, an IGBT module, a vacuum relay, a composite switch consisting of a relay and a MOSFET, or a composite switch consisting of an optocoupler and a MOSFET.

[0022] The control method for the aforementioned current sampling system is as follows:

[0023] During the normal operation phase, the main switch is turned on and the sampling switch is turned off, allowing current to flow through the main switch while no current flows through the shunt.

[0024] During the sampling phase, the main switch is turned off, the sampling switch is turned on, and the current is shunted to the sampling branch where the shunt is located; the voltage across the shunt is collected.

[0025] After sampling is completed, switch back to the normal phase;

[0026] During a control cycle, the current sampling system is in the normal state for most of the time and in the sampling state for a small portion of the time.

[0027] Preferably, there is an overlapping conduction period between the normal phase and the sampling phase; during the overlapping conduction period, both the main switch and the sampling switch are turned on.

[0028] Preferably, the duration of the overlapping conduction period is 1 μs to 100 μs.

[0029] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0030] The current sampling system provided in this embodiment separates the high current conduction path from the sampling path through a dual-switch parallel circuit and appropriate timing control, limits the shunt power-on time to suppress self-heating, and solves the contradiction between cost and accuracy in battery testing systems. It can achieve high-precision high current sampling at low cost.

[0031] From a technical perspective, this invention can improve the sampling accuracy of shunts at a low cost, making low-cost multi-channel high-current testing systems possible. From an application perspective, this invention can significantly reduce the cost of high-precision high-current multi-channel battery / cell testing systems, facilitating large-scale deployment of testing systems, accelerating the transition to full electrification, and has broad application prospects and significant economic benefits. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0033] Figure 1 This is a schematic diagram of the current sampling system provided in the embodiments of this application;

[0034] Figure 2 This is a timing control flowchart provided in the embodiments of this application.

[0035] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0036] This application provides a current sampling system that solves the technical problems of high cost of high-precision current sensors and insufficient sampling accuracy of low-cost shunts in the prior art, thereby achieving high-precision current sampling at low cost.

[0037] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0038] Shunt circuits currently exhibit the following main types of resistance drift:

[0039] First, there is the inherent variation in its resistance value, which can be resolved through calibration.

[0040] Secondly, there is the resistance drift caused by ambient temperature, which can be resolved by calibration at multiple temperature points;

[0041] Furthermore, there is the resistance drift caused by self-heating during high-current detection. The error caused by the shunt's self-heating is often above 0.1%, which is the most difficult to solve. Self-heating drift is not a simple linear error; it involves three coupled effects: Joule heating is proportional to the square of the power, the nonlinearity of heat conduction, and the hysteresis of the temperature coefficient. Due to the complexity of thermal equilibrium time, such as in pulsed current scenarios, traditional temperature compensation methods may completely fail.

[0042] This application proposes the following scheme:

[0043] By using a dual-switch parallel circuit and appropriate timing control, the high-current conduction path and sampling path are separated, and the shunt power-on time is limited to suppress self-heating. In this way, high-precision current sampling can be achieved at low cost.

[0044] To better understand the above technical solutions, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses consistent with some aspects of this application as detailed in the appended claims.

[0045] Example 1

[0046] Figure 1 This is a schematic diagram of the current sampling system provided in the embodiments of this application. The current sampling system includes:

[0047] The main switch K1 is connected in series in the main current path;

[0048] Sampling switch K2 is connected in series with shunt R1 to form a sampling branch; the sampling branch is connected in parallel with the main current path.

[0049] The timing control module is connected to the main switch K1 and the sampling switch K2, and is used to generate timing signals to control the on and off of the main switch K1 and the sampling switch K2.

[0050] The timing control module is designed so that the measured current passes through the main current path most of the time and passes through the sampling branch for a small portion of the time. Current sampling and detection are performed when the measured current flows into the shunt R1.

[0051] Furthermore, the current sampling system also includes a voltage sampling module, connected in parallel with the shunt R1, for sampling the voltage on the shunt R1.

[0052] Furthermore, the current sampling system also includes: a first terminal A and a second terminal B. After the sampling branch is connected in parallel with the main current path, the two ends of the parallel circuit are respectively connected to the first terminal A and the second terminal B.

[0053] In this way, the entire current sampling system can be connected in series with the current being measured to perform current detection. Based on the voltage across shunt R1 and the resistance of shunt R1, the sampling current can be calculated.

[0054] During testing, the measured current flows through the main current path (main switch K1) for the vast majority of the time (more than 70%), and only for a very short time does the current flow through the sampling branch (sampling switch K2 and shunt R1). Current detection is performed when the current flows into the shunt R1.

[0055] Thus, by separating the high-current conduction path from the sampling path through timing control, it can be ensured that the shunt R1 only has a very short time to receive a large current. By limiting the energizing time of the shunt R1 to suppress self-heating, the current loss and heat generation can be greatly reduced, thereby making the temperature of the shunt R1 close to the ambient temperature.

[0056] In this way, the resistance of the shunt R1 only has the first two drift cases (the dispersion of its own resistance and the resistance drift caused by the ambient temperature), and these two cases can be solved through calibration during the production stage, thereby greatly improving the sampling accuracy of the shunt.

[0057] Figure 2 The diagram shown is an exemplary timing control diagram. The operation of the current sampling system is as follows:

[0058] (1) Normal stage

[0059] From time T0 to time T1, the main switch K1 is turned on and the sampling switch K2 is turned off. Current flows through the main switch K1, and no current flows through the shunt R1.

[0060] (2) Sampling phase

[0061] From time T1 to time T2, the control level of sampling switch K2 gradually transitions from low to high, and sampling switch K2 is turned on. At the same time, main switch K1 remains on, with an overlap time Δt ≥ 1μs, where Δt = T3 - T2.

[0062] From time T3 to time T4, the control level of main switch K1 gradually transitions from high to low, and main switch K1 is turned off. Simultaneously, sampling switch K2 remains on, and current is shunted to the sampling branch where shunt R1 is located. Before sampling switch K2 is turned off, i.e. Figure 2 Before time T5, the voltage across the shunt R1 is collected (the sampling window is after time T4 and before time T5).

[0063] The overlapping conduction period is designed to ensure smooth current switching. The overlapping time Δt can be adaptively adjusted according to the frequency of the measured current. For example, Δt is 1μs to 100μs.

[0064] The sampling window time can be adaptively adjusted according to the frequency of the measured current. For example, the sampling window is 1ms to 10ms.

[0065] (3) Switching phase

[0066] From time T5 to time T6, the control level of sampling switch K2 gradually transitions from high level to low level, and sampling switch K2 is turned off.

[0067] At the start of the next cycle, the main switch K1 is turned on, and all the current flows back to the main current path where the main switch K1 is located, starting the normal phase of the next cycle.

[0068] In the timing diagram above, T6 > T5 > T4 > T3 > T2 > T1 > T0.

[0069] In one cycle of control timing, the main switch K1 is high for more than 70% of the time, and the control timing signal of the sampling switch K2 is largely complementary to that of the main switch K1. At the same time, when the main switch K1 and the sampling switch K2 switch on and off, a short overlapping conduction period (Δt, when both the main switch K1 and the sampling switch K2 are on) is designed to ensure that the current switching is not abrupt and to avoid fluctuations in the circuit under test.

[0070] The control cycle can be adaptively adjusted according to the frequency of the measured current. Note that the temperature rise of the shunt R1 should be less than 0.1℃.

[0071] In a preferred embodiment, the shunt R1 is equipped with a self-heating temperature sensor to detect the temperature rise of the shunt R1 itself. When the temperature rise of the shunt R1 is ≥0.1℃, the sampling switch K2 is turned off, and the main switch K1 is turned on to switch from the sampling stage back to the normal stage.

[0072] In one optional implementation, the main switch K1 and the sampling switch K2 can be low-resistance MOSFET modules, for example, with an internal resistance of <0.5mΩ and a withstand current of ≥120% of the measured current.

[0073] In another alternative implementation, the main switch K1 and the sampling switch K2 can also be composed of IGBT modules, vacuum relays, composite switches consisting of relays and MOSFETs (such as the EV200+AUIRFS8409 module manufactured by Tyco), or composite switches consisting of optocouplers and MOSFETs (such as the Si828xCC-IS module manufactured by Silicon Labs).

[0074] Furthermore, the current sampling system also includes a temperature compensation module, which is used to compensate for the resistance drift of the shunt R1 caused by changes in ambient temperature.

[0075] The temperature compensation module includes multiple ambient temperature sensors for real-time monitoring of the ambient temperature and for compensating the resistance of the shunt R1 according to a preset temperature compensation algorithm. The temperature compensation algorithm can employ existing mature technologies.

[0076] During the production phase, the shunt R1 is calibrated at multiple temperature points (-10℃–80℃), and a resistance-temperature lookup table is established and stored in the temperature compensation module. The temperature compensation module accurately compensates for resistance changes in the shunt R1 under different ambient temperatures, further improving sampling accuracy.

[0077] Furthermore, those skilled in the art can add functional branches to the above-mentioned current sampling system as needed to meet advanced requirements in different scenarios. These functional branches include, but are not limited to, overcurrent protection branches, temperature compensation branches, self-calibration branches, anti-interference and reliability enhancement branches, and communication interface branches.

[0078] Testing showed that the shunt self-heating of the current sampling system provided in this embodiment is greatly reduced, the temperature drift error is less than 0.005%, and the overall accuracy reaches 0.02%.

[0079] The current sampling system provided in this embodiment, through dual-switch timing control, compresses the shunt energizing time to the millisecond level, fundamentally suppressing shunt self-heating. Combined with multi-temperature point calibration, it enables the low-cost shunt to achieve an accuracy of 0.02%, resolving the cost-accuracy contradiction in multi-channel battery testing systems.

[0080] From a technical perspective, this invention can improve the sampling accuracy of shunts at a low cost, making low-cost multi-channel high-current testing systems possible. From an application perspective, this invention can significantly reduce the cost of high-precision high-current multi-channel battery / cell testing systems, facilitating large-scale deployment of testing systems and accelerating the transition to full electrification.

[0081] Through the above-mentioned technical solution, this utility model achieves low-cost and high-precision high-current detection, which has broad application prospects and significant economic benefits.

[0082] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection or an indirect connection through an intermediate medium, or the internal connection of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0083] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0084] The above description is merely a preferred embodiment of this application and does not constitute any limitation on this application in any form or substance. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of this application, and these improvements and additions should also be considered within the scope of protection of this application. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of this application are equivalent embodiments of this application; furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of this application still fall within the scope of the technical solution of this application.

Claims

1. A current sampling system, characterized in that, include: The main switch (K1) is connected in series in the main current path; The sampling switch (K2) is connected in series with the shunt (R1) to form the sampling branch; The sampling branch is connected in parallel with the main current path; The timing control module is connected to the main switch (K1) and the sampling switch (K2) and is used to generate timing signals to control the on and off states of the main switch (K1) and the sampling switch (K2).

2. The current sampling system as described in claim 1, characterized in that, The current sampling system includes a normal phase and a sampling phase: During the normal operation phase, the main switch (K1) is turned on, the sampling switch (K2) is turned off, current flows through the main switch (K1), and no current flows through the shunt (R1). During the sampling phase, the main switch (K1) is turned off, the sampling switch (K2) is turned on, and the current is diverted to the sampling branch where the shunt (R1) is located.

3. The current sampling system as described in claim 2, characterized in that, There is an overlapping conduction period between the normal phase and the sampling phase; during the overlapping conduction period, both the main switch (K1) and the sampling switch (K2) are turned on.

4. The current sampling system as described in claim 1, characterized in that, The current sampling system further includes a first terminal (A) and a second terminal (B). After the sampling branch is connected in parallel with the main current path, the two ends of the parallel circuit are respectively connected to the first terminal (A) and the second terminal (B).

5. The current sampling system according to any one of claims 1 to 4, characterized in that, The current sampling system also includes a voltage sampling module connected in parallel with the shunt (R1) for collecting the voltage on the shunt (R1).

6. The current sampling system according to any one of claims 1 to 4, characterized in that, The current sampling system also includes a temperature compensation module, which is used to compensate for the resistance drift of the shunt (R1) caused by changes in ambient temperature.

7. The current sampling system as described in claim 6, characterized in that, The temperature compensation module includes multiple ambient temperature sensors for real-time monitoring of ambient temperature.

8. The current sampling system according to any one of claims 1 to 4, characterized in that, The shunt (R1) is equipped with a self-heating temperature sensor to detect the temperature rise of the shunt (R1) itself.

9. The current sampling system according to any one of claims 1 to 4, characterized in that, The main switch (K1) can be any one of the following: MOSFET module, IGBT module, vacuum relay, composite switch composed of relay and MOSFET, or composite switch composed of optocoupler and MOSFET.

10. The current sampling system according to any one of claims 1 to 4, characterized in that, The sampling switch (K2) can be any one of the following: MOSFET module, IGBT module, vacuum relay, composite switch composed of relay and MOSFET, or composite switch composed of optocoupler and MOSFET.

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