With the rapid development of industries such as electric vehicles and energy storage, the demand for current detection is also increasing. However, for these scenarios, more sensors such as Hall effect sensors, shunt resistors, current transformers and Rogowski coils are used.

       In some current measurement situations that require extreme accuracy, or when the power system is in a high-interference magnetic field environment, the high accuracy and anti-interference ability of the fluxgate sensor may make it a valuable choice. And as the open-loop fluxgate sensor becomes more popular and its cost decreases, it is expected to have a place in power supply design.

Expensive fluxgate sensors

       In today's electrical equipment, current sensors are very important. This sensor can sense the information of the measured current and transform this information into electrical signals or other forms of information output that meet certain standards according to certain rules. Current sensors have developed into various types according to different application scenarios and technical requirements, including Hall sensors, shunt resistors, current transformers, and flux gates.

       Generally speaking, in power supply design, Hall effect sensors are more commonly used as current sensors due to their simplicity, cost-effectiveness, and adaptability. Hall sensors can directly measure the magnetic field caused by current without complex signal processing, while providing good isolation and safety performance. In addition, Hall sensors have a fast response speed and are suitable for current monitoring in high-frequency switching power supplies.

       Fluxgate sensors may be used in some current measurement applications that require extreme accuracy and sensitivity, such as in high-end power management systems that require high-precision current detection, but they are rarely used in power supply design due to their high cost.

       For example, according to some recent public data in the market, the price of an AC/DC zero fluxgate transformer is about RMB 680, while the price of a closed-loop fluxgate transformer is about RMB 75. The price of an ordinary Hall sensor ranges from a few cents to hundreds of yuan, which means that even a low-end fluxgate sensor may cost many times more than a Hall sensor.

       The high cost is partly due to the fact that the core component of the fluxgate sensor is a high-permeability magnetic core, which is usually made of special magnetic materials, such as giant magnetostrictive alloys (such as Metglas, Permalloy, etc.). These materials have high permeability and low coercivity, but are also relatively expensive.

       At the same time, fluxgate sensors require precise magnetic circuit design and signal processing circuits, especially closed-loop fluxgate sensors, which include a feedback control loop to keep the magnetic core in an unsaturated state. Closed-loop systems require additional hardware and complex signal processing algorithms, increasing the complexity and cost of design and manufacturing.

       Of course, if an open-loop fluxgate sensor design is used, since there is no closed-loop control system, they directly detect the change in the magnetization state of the magnetic core and then convert it into an electrical signal. This simplified design reduces the number of components required and reduces the complexity of signal processing, so it usually has a lower production cost.

       However, even for an open-loop fluxgate sensor, the cost is still not too low. For example, a low-cost open-loop fluxgate current sensor may cost between RMB 50 and RMB 200, while a high-performance open-loop fluxgate sensor with higher accuracy and wider dynamic range may cost RMB 500 to RMB 2,000 or more.

Open-loop fluxgate sensors have development potential

       From a technical point of view, open-loop fluxgate sensors have the characteristics of low zero drift and bias temperature drift, because the magnetic core is in an alternating B-H magnetic field, avoiding the magnetic offset of the fluxgate in the magnetic circuit. This makes them have high accuracy in small current measurement, especially in dynamic characteristics and high resolution.

       Through SENCORUI analysis, the key technology of the magnetic ring design of the open-loop fluxgate current sensor has been verified experimentally. The magnetic ring can increase the current measurement sensitivity by 15.4 times, and the frequency can reach 6.7 kHz, which can meet the requirements of AC and DC complex leakage current detection.

       This means that open-loop fluxgate sensors can be used to measure a variety of AC, DC, pulse and complex signals. They are widely used in industrial fields such as drives, power supplies, power fault detection, new energy, and human contact protection on the photovoltaic array side.

       For example, the ±100A busbar current sensor reference design using an open-loop fluxgate sensor provides a non-intrusive (isolated and lossless) current measurement solution up to ±100A, suitable for applications such as BMS, AC drive control modules, and servo drive control modules.

       The performance of open-loop fluxgate sensors in terms of accuracy, temperature drift, bandwidth, and response time is increasingly valued. Its high accuracy and low drift characteristics give it great potential in the field of high-precision measurement. With the development of electric vehicles and energy storage technology, the market demand for high-precision and high-reliability current measurement is indeed increasing, which provides a potential growth opportunity for open-loop fluxgate sensors. However, in order to truly become mainstream in the market, it is necessary to continue to prove its value in practical applications and show obvious competitive advantages in the competition with traditional sensors.