TMR sensor solution for ultra-precise monitoring of electric vehicle batteries

[Introduction]The battery level indicator is a basic function configuration of a hybrid electric vehicle (xEV). The battery monitoring function can accurately measure the remaining battery capacity and help to accurately estimate the driving distance. As the power consumption of electric vehicles increases, more accurate battery monitoring functions will be required in the future. The current sensor is one of the components that affects the monitoring performance of the electric vehicle battery.

The challenges of battery monitoring are critical to avoiding ‘battery drain’

Generally speaking, when the battery is depleted, the electric car cannot continue to drive. Especially on highways, it is critical to avoid running out of power, otherwise it may lead to major traffic accidents, not only endangering personal safety, but also causing serious traffic jams. To avoid this, automakers and transportation infrastructure companies offer a variety of services, including showing drivers accurate battery drain estimates and providing information about battery charging service and parking areas. These ancillary services will also be further enhanced with the popularization of electric vehicles and the development of power supply infrastructure in the future.

To effectively estimate battery consumption, high-accuracy battery monitoring is critical. Reliable information on remaining drivable distance can be difficult to obtain without an accurate measurement of remaining battery capacity. In addition, improving the accuracy of battery monitoring can not only check the battery charge and discharge status in relation to the remaining battery capacity, but also help to extend battery life by avoiding situations that impair battery performance.

battery monitoring

TMR sensor solution for ultra-precise monitoring of electric vehicle batteries

Battery monitoring solution detects high currents up to 1200 A with less than 1% error

Among various current sensors*1 used for battery monitoring, closed-loop current sensors are usually used for measurement. Closed-loop current sensors have a large magnetic core consisting of coils that generate magnetic flux for sensing. However, the use of such a sensor compromises the flexibility of the battery monitoring design and does not reduce vehicle weight.

A new closed-loop tunnel magnetoresistance (TMR)*2 current sensor developed by TDK addresses these issues, using a coreless sensor. The magnetic detection part of the TMR current sensor (consisting of TMR elements, coils and resistors) and an application-specific integrated circuit (ASIC)*3 are all integrated in one package, enabling high-precision measurement of large currents up to 1200 A in a non-contact manner without error Less than 1% (full scale). In addition, its small size and low power consumption enable unprecedented high-precision battery monitoring.

Traditional closed-loop sensors and TMR current sensors

By integrating the TMR element, coil, magnetic detection section and ASIC into a single package, size and power consumption are reduced.

This new TMR current sensor was developed by fully utilizing TDK Group’s TMR element technology and TDK-Micronas’ magnetic sensor design technology, demonstrating its strong technical strength. The TMR current sensor (product name: CUR 423x) will support high-precision battery monitoring and further promote the popularity of electric vehicles.

Comparison of Characteristics of Magnetic Sensor Elements

The TMR element produces an output (that is, the value that the element outputs after detecting the strength and variation of the magnetic field and converting it into an electrical signal) than other sensor elements such as AMR (Anisotropic Magnetoresistive) elements and GMR (Giant Magnetoresistive) elements output is higher.

TMR current sensor CUR 423x

The CUR 423x is a non-contact magnetic field sensor for high DC and high AC current measurements in the automotive and industrial sectors. This is the first Micronas-branded product developed using TDK TMR technology. For more information, visit the Product Center.

the term

1. Types of current sensors: There are many types of current sensors, including “shunt resistance type”: the current value is obtained by passing the current through a small resistance value resistor and measuring the voltage between the two ends; and “closed loop type”: the feedback current passes through The second winding makes the magnetic field generated by the input current constant zero.

2. TMR (Tunnel Magnetoresistance) is a phenomenon that magnetically changes the tunneling current through an insulating film; components applying this mechanism have higher magnetoresistance (magnetoresistance reflects sensitivity) and can be more accurate than conventional components read high-density signals.

3. ASIC (Application-Specific Integrated Circuit) refers to an integrated circuit designed for specific applications such as signal processing, in which multiple functional circuits are integrated.

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