Double-range current measurement system based on solid-state relay

Abstract

The invention discloses a double-range current measurement system based on a solid-state relay, and relates to the technical field of current measurement. The system comprises a closed-loop Hall current sensor, a first shunt resistor, a second shunt resistor, a solid state relay (SSR), a Hall conditioning IC and an external controller. Two shunt resistors with different resistance values are dynamically switched through a solid-state relay, and compatibility of low-current high-precision measurement and high-current wide-range measurement is achieved. The method solves the problems that the precision and range of an existing single-range sensor are difficult to consider, double sensors are high in cost, mechanical relays have defects and the like, has the advantages of low cost, high reliability, good measurement precision and the like, and is suitable for wide-dynamic-range current measurement scenes such as an energy storage system and the like.

Description

Technical Field

[0001] This invention relates to the field of current measurement technology, and in particular to a dual-range current measurement system based on a solid-state relay. Background Technology

[0002] In fields such as energy storage devices, current detection needs to cover a wide range, accurately capturing leakage currents at the milliampere level or even smaller, while reliably monitoring large currents of tens or even hundreds of amperes, with the current dynamic range spanning hundreds or even thousands of times.

[0003] In the existing technology, the following solutions mainly exist: Fixed single-range sensor solution: This solution uses a single-range current sensor to cover the entire current range, employing a sampling circuit with a fixed shunt resistor and a single current sensor. However, this solution struggles to simultaneously achieve high accuracy and a large range. Measuring large currents requires a small-value shunt resistor, resulting in low sampling signal voltage, low resolution, and large measurement errors at low currents. Conversely, using a large shunt resistor to improve accuracy at low currents would lead to excessive voltage drop and power consumption at high currents, potentially causing saturation of the sensor and ADC input.

[0004] Dual-sensor approach: This approach uses two sets of current sensors with different ranges in parallel, one for small current measurement and the other for large current measurement. While this approach optimizes accuracy across different ranges, it requires additional hardware and calibration methods, increasing cost, size, and design complexity.

[0005] Mechanical relay range switching solution: This method uses a mechanical relay to switch the shunt resistor, using a large resistance for small current measurements and a small resistance for large current measurements. However, mechanical relays have drawbacks such as limited contact life, slow switching speed, contact bounce and tumble affecting measurement continuity, large size, and high drive power consumption, making them difficult to meet the needs of frequent and rapid switching and long-life applications.

[0006] Existing technical solutions either struggle to cover the entire current range and guarantee accuracy, require additional hardware and design costs, or suffer from insufficient response and lifespan, failing to fully meet the dual demands of energy storage systems for high accuracy with low current and compatibility with high current. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, this application proposes a dual-range current measurement system based on solid-state relays to solve the problems existing in the prior art.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A dual-range current measurement system based on a solid-state relay includes: Hall effect current sensors are used to detect current signals; The first shunt resistor has a first resistance value and is used for small current measurement; The second shunt resistor has a second resistance value, which is smaller than the first resistance value, and is used for high current measurement. A solid-state relay is connected in series with the second shunt resistor and then in parallel across the first shunt resistor to control whether the second shunt resistor is connected to or disconnected from the measurement circuit. A Hall sensor conditioning chip, connected to the closed-loop Hall current sensor, is used to process the sensor output signal; An external controller, connected to the control terminal of the solid-state relay, is used to control the solid-state relay to turn on and off, thereby achieving range switching; The first shunt resistor has a resistance of 100Ω, corresponding to a small range of 0-3A; the second shunt resistor has a resistance of 3.3Ω, corresponding to a large range of 0-100A.

[0009] As a further technical solution of the present invention: the working modes of the system include: Low current mode: When the current to be measured is within a small range, the external controller controls the solid-state relay to disconnect, and the current signal only passes through the first shunt resistor; High current mode: When the current to be measured exceeds the small range, the external controller controls the solid-state relay to turn on, and the first shunt resistor and the second shunt resistor are connected in parallel.

[0010] As a further technical solution of the present invention: the external controller automatically switches the working mode by detecting the current value in real time: when the current exceeds the preset threshold, it switches to the high current mode; when the current is lower than the preset threshold, it switches to the low current mode.

[0011] As a further technical solution of the present invention: it supports manual control mode, and forces the solid-state relay to turn on and off through software commands or hardware switches to achieve range switching.

[0012] As a further technical solution of the present invention: the solid-state relay can be replaced by a field-effect transistor switch, an optocoupled thyristor switch, an analog switch chip or an electromagnetic relay.

[0013] As a further technical solution of the present invention: the external controller is a microcontroller unit, an analog comparator + trigger circuit, a digital logic circuit, or a programmable logic device.

[0014] As a further technical solution of the present invention: the closed-loop Hall current sensor can be replaced by an open-loop Hall sensor, a current detection circuit based on shunt resistor + amplifier, or a current transformer.

[0015] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1. It achieves full current range coverage in the same sensor, with high accuracy and high resolution in the small current range (milliampere to ampere level) and safe and accurate measurement in the large current range (tens of amperes to hundreds of amperes level), without the need to switch between different sensors, and can obtain complete measurement data from tiny leakage current to large current impact.

[0016] 2. It replaces the two sets of sensors or complex gain control circuits that might have been needed, reducing the number of hardware components, saving PCB space and material costs, while also reducing the difficulty of design and calibration and shortening the development cycle.

[0017] 3. Solid-state relays are used to achieve contactless electronic switching, which ensures the product lifespan for energy storage systems that require long-term monitoring.

[0018] 4. Regardless of the fluctuations in load current, the measurement circuit always operates within its optimal range.

[0019] 5. It has strong versatility and can meet the stringent requirements of current sensing in various occasions. It has broad application prospects and is suitable for multiple fields such as energy storage systems, electric vehicle charging piles, and battery management systems. Attached Figure Description

[0020] Figure 1 This is the schematic diagram of this design. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1, as Figure 1 As shown, a dual-range current measurement system based on a solid-state relay includes: Hall effect current sensors are used to detect current signals; The first shunt resistor has a first resistance value and is used for small current measurement; the resistance value of the first shunt resistor is 100Ω, corresponding to a small range of 0~3A; The second shunt resistor has a second resistance value, which is smaller than the first resistance value, and is used for high current measurement; the resistance value of the second shunt resistor is 3.3Ω, corresponding to a large range of 0~100A; A solid-state relay is connected in series with the second shunt resistor and then in parallel across the first shunt resistor to control whether the second shunt resistor is connected to or disconnected from the measurement circuit. A Hall sensor conditioning chip, connected to the closed-loop Hall current sensor, is used to process the sensor output signal; An external controller is connected to the control terminal of the solid-state relay and is used to control the solid-state relay to turn on and off, thereby achieving range switching.

[0023] The working principle is as follows: Low current mode (low range 3A): When the current to be measured is within a small range (e.g., 0-3A) and high-precision sampling is required, the solid-state relay is in the open state, allowing the entire current signal to pass through the high-resistance RSHUNT_3A. This shunt resistor has a relatively large resistance value, generating a sufficient voltage drop for sensor detection when a small current passes through, resulting in a high-sensitivity and high-resolution output signal. When the current is 3A, the voltage generated across RSHUNT_3A is close to the full-scale voltage of the sensor or subsequent acquisition circuit, effectively utilizing the ADC's dynamic range and ensuring measurement accuracy in the low current range.

[0024] High Current Mode (High Range 100A): When an increase in current is detected that may exceed the small range, the solid-state relay is switched on by controlling the "SW" level logic. After the SSR closes, it is equivalent to connecting the 100Ω resistor of the high-resistance RSHUNT_3A in parallel with the 3.3Ω resistor in another branch. This parallel equivalent resistance is the RHUNT_100A resistor for measuring high current. At this time, the equivalent sampling resistance of the entire sensor is greatly reduced, and it can withstand currents up to 100A without generating excessive voltage drop. Even if the current reaches tens of amperes, the voltage generated by RSHUNT_100A remains within the linear operating range of the sensor, avoiding output saturation and device overheating. In this way, while ensuring the measurement range, some sensitivity is sacrificed (because the voltage generated per unit current is lower in high current mode), but since the focus is mainly on the larger current, the sensor output is still sufficient to accurately measure the large current value.

[0025] SW Range Switching Control Interface: The dual-range switching in this solution can be automatically or manually controlled via an external interface signal. When the system is managed by the MCU, the MCU can determine when to switch ranges based on the real-time detected current value: for example, when the current exceeds a preset threshold, a command is issued to turn on the SSR to switch to the high-current range; when the current drops below the threshold, the SSR is turned off to return to the low-range mode. This automatic control ensures timely and seamless range switching throughout the current change process, without losing important data points. Users can also manually control the range by forcibly selecting the range setting via software commands or hardware switches, according to application requirements.

[0026] Example 2: Based on Example 1, solid-state relays are not the only usable switching devices. As long as other electronic switching elements (such as switches composed of MOSFETs, electromagnetic relays, optocoupled thyristor switches, analog switch chips, etc.) are used to achieve the same shunt resistor switching function, they all fall within the protection scope of this invention. In Example 3, based on Example 1, the specific connection method of the solid-state relay in the circuit is not limited to that described herein. For example, a single-pole double-throw (SPDT) electronic switch can be used to switch between two shunt resistors, or a parallel / series combination can be used to change the equivalent resistance value. Any switch topology that can achieve the selection of sampling branches with different resistance values ​​to achieve dual-range or multi-range measurement purposes should be considered an equivalent technical solution and protected by this invention. Example 4, based on Example 1, the "small current 3A range" and "large current 100A range" exemplified in this invention are not limiting values; the specific current range can be freely set according to application requirements. Whether it is a lower milliampere-level small range or a higher hundreds of amperes range, as long as the dual-range switching measurement concept described in this solution is adopted, it falls within the protection scope of this invention; Example 5: Based on Example 1, the range switching concept of this solution can be extended to multiple ranges. It is not limited to switching between two ranges; if required by the application, three or even more ranges of different current measurements can be designed. By adding shunt resistor branches and corresponding switching elements, more detailed range coverage can be achieved. This multi-range extension scheme has the same purpose as this invention and is also within the scope of protection. Example 6, based on Example 1, demonstrates that the triggering method for range switching is not limited to external interface commands. Autonomous detection methods can be employed, such as using analog comparator circuits or dedicated monitoring chips to monitor the current in real time. When the current exceeds a predetermined value, the switch automatically switches to a wider range; when the current drops, it switches back to a narrower range. Regardless of whether manual or automatic control is used, as long as the function of range switching based on current magnitude is achieved, it falls within the scope of this invention. Example 7: Based on Example 1, the control unit for implementing range switching control is not limited to an MCU (Microcontroller Unit). It can be any device capable of controlling the switch based on current signals or threshold values. For example, analog comparators with trigger circuits, digital logic circuits, and programmable logic devices (FPGAs / CPLDs) can all replace MCUs to perform the same control function, and their applications fall within the scope of this invention. Example 8, based on Example 1, describes a preferred embodiment of the closed-loop Hall current sensor of the present invention. However, the principle of this dual-range switching is not limited to Hall sensor types. Any technical solution that uses multiple shunt elements in conjunction with a switch to achieve range extension in the current measurement circuit, such as similar improvements to open-loop Hall sensors, current detection circuits based on pure shunt resistors and amplifiers, and current transformers, are also alternative solutions with similar objectives to the present invention and are protected by the present invention.

[0027] This solution primarily addresses the wide-range current sensing requirements of energy storage systems, but its application is not limited to this. The technical concept of this invention can be adopted in any application requiring wide dynamic range current measurement, such as electric vehicle charging stations, battery management systems (BMS), DC power distribution devices, and high-precision power supply testing equipment. Therefore, applying this solution to the aforementioned different scenarios to achieve similar technical effects also falls within the scope of protection of this invention.

[0028] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment have been appropriately combined to form other embodiments that are easy for those skilled in the art to understand.

Claims

1. A dual-range current measurement system based on a solid-state relay, characterized in that, include: Hall effect current sensors are used to detect current signals; The first shunt resistor has a first resistance value and is used for small current measurement; The second shunt resistor has a second resistance value, which is smaller than the first resistance value, and is used for high current measurement. A solid-state relay is connected in series with the second shunt resistor and then in parallel across the first shunt resistor to control whether the second shunt resistor is connected to or disconnected from the measurement circuit. A Hall sensor conditioning chip, connected to the closed-loop Hall current sensor, is used to process the sensor output signal; An external controller, connected to the control terminal of the solid-state relay, is used to control the solid-state relay to turn on and off, thereby achieving range switching; The resistance of the first shunt resistor is 100Ω, corresponding to a small range of 0~3A; The second shunt resistor has a resistance of 3.3Ω, corresponding to a large range of 0 to 100A.

2. The system according to claim 1, characterized in that, The system's operating modes include: Low current mode: When the current to be measured is within a small range, the external controller controls the solid-state relay to disconnect, and the current signal only passes through the first shunt resistor; High current mode: When the current to be measured exceeds the small range, the external controller controls the solid-state relay to turn on, and the first shunt resistor and the second shunt resistor are connected in parallel.

3. The system according to claim 2, characterized in that, The external controller automatically switches operating modes by detecting the current value in real time: when the current exceeds a preset threshold, it switches to high current mode; when the current is lower than the preset threshold, it switches to low current mode.

4. The system according to claim 3, characterized in that, It supports manual control mode, which allows for forced switching of range by using software commands or hardware switches to control the solid-state relay to turn it on and off.

5. The system according to claim 4, characterized in that, The solid-state relay can be replaced by a field-effect transistor switch, an optocoupled thyristor switch, an analog switch chip, or an electromagnetic relay.

6. The system according to claim 1, characterized in that, The external controller is a microcontroller unit, an analog comparator + trigger circuit, a digital logic circuit, or a programmable logic device.

7. The system according to claim 1, characterized in that, The closed-loop Hall current sensor can be replaced by an open-loop Hall sensor, a current detection circuit based on a shunt resistor and amplifier, or a current transformer.

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