Automotive electrification revolution: efficient current sensors and intelligent controller solutions

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With the automotive industry fully embracing the wave of electric vehicles (EVs), traditional fuel sources and power systems are undergoing a disruptive transformation. This transition not only drives rapid development of charging infrastructure but also presents new challenges in vehicle performance, production efficiency, and cost control. Among these challenges, a critical area that cannot be overlooked is the demand for high-performance current sensors and controllers. Against this backdrop, Melexis has launched a series of high-performance current sensor and controller solutions, leveraging its deep technical expertise and innovation capability. These products not only meet the stringent requirements of the electric vehicle industry for current monitoring and control but also achieve industry-leading levels in reliability, accuracy, and cost-effectiveness.

The operational efficiency of electric vehicle batteries is crucial

The core of electric vehicle development lies in high-voltage systems, with battery operating voltages reaching up to 400V in current models and expected to increase to 800V in the next generation. Therefore, ensuring the safe and efficient operation of these batteries is paramount. This includes electric motors and actuators, as well as charging infrastructure, heaters, and Battery Management Systems (BMS), with current sensors being a fundamental part of these systems. These devices need to operate under normal conditions and provide accurate current feedback, which is crucial for the efficient operation of electric vehicles.

BMS plays a vital role in ensuring the safe and efficient operation of batteries. This includes interpreting parameters to ensure that the batteries operate within safe limits and carefully balancing individual cells during charging/discharging cycles. In electric vehicles, BMS is used to determine factors such as State of Charge (SoC), State of Health (SoH), and State of Functionality (SoF), which are crucial for maintaining safety, estimating charging times, and determining electric vehicle range.

Current sensors are also crucial for ensuring that electric vehicle batteries remain in optimal operating conditions. The ideal operating temperature range for typical electric vehicle power packs is between 15°C and 35°C. Temperatures that are too high or too low can decrease battery efficiency, thereby reducing the driving range of electric vehicles. Most electric vehicles use a combination of PTC heaters, electric compressors, and fans to manage thermal conditions. Current sensors provide necessary feedback to the battery control system to precisely regulate the thermal management system. They also offer diagnostic capabilities to identify abnormal operating conditions, such as excessive current draw.

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The functionality of electric vehicle charging ports is also crucial

On the other hand, the electrification of automobiles has also spurred specific requirements for car charging ports. Due to the high frequency of use, these ports not only need to be highly reliable but also need to clearly display the charging status to the driver. To meet these needs, an increasing number of car manufacturers are beginning to install LED lights in the charging port area.

These lights are used not only to indicate the charging status but also to alert users to any potential malfunction through simple changes in light effects. This design allows users to receive clear and intuitive indications at the charging connection point, enabling them to quickly understand the battery level or whether there are any safety risks.

The electrification of powertrains has significantly increased the complexity of car designs, leading to additional functional requirements for the latest charging port designs. This includes monitoring the open/close status of the charging port cover and sensing the temperature of high-voltage connectors.

To meet the diverse demands of automotive electrification applications, Melexis has meticulously introduced a range of sensor and driver products. These products, with their outstanding features and functionalities, have brought unprecedented innovation and development to the electric vehicle industry. Below, we will provide you with a detailed introduction to the unique aspects of these products.

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Current sensors: key elements to enhance battery operation efficiency and safety

Firstly, the MLX91220 from Melexis is an isolated integrated Hall effect current sensor IC with dual overcurrent detection (OCD) capabilities, designed for currents ranging from 0 to 50A and requiring only a 5V power supply. This sensor IC achieves a perfect blend of small size, low impedance, high bandwidth, and isolation, while maintaining excellent overall performance. It is recognized as one of the most straightforward fully integrated current sensor ICs available in the market.

The MLX91220 is capable of directly sensing the current flowing through the package leadframe, which minimizes thermal losses and makes it suitable for various standard solutions. It supports two measurement modes: proportional mode, which meets the needs of different applications requiring output voltage to be adjusted proportionally, and fixed mode (differential), which fulfills specific requirements using a reference voltage.

To meet diverse application requirements, Melexis has also introduced the MLX91221 version, which operates on a 3.3V power supply. This version is particularly suitable for scenarios such as DC fast charging, AC wall-mounted charging stations / ICCB, onboard chargers (OBC), DC-DC converters, and similar applications.

Furthermore, the MLX91230/MLX91231, as standout members of Melexis' third-generation current sensor family, represent intelligent Hall effect current sensors. They comply with ASIL standards, enabling simultaneous measurement of current, voltage, and temperature on a single chip. Equipped with dedicated 32 KB flash memory, they provide an ideal choice for safety-critical applications. Their robust diagnostic capabilities significantly alleviate the burden on integrators when developing safety mechanisms, including built-in on-chip overcurrent detection.

In terms of accuracy, the MLX91230 offers ±0.5% accuracy within a temperature range of -40°C to 125°C, while the MLX91231 surpasses this with an accuracy of up to ±0.25%. Additionally, automatic gain control supported by the MCU can cover a wider dynamic range, and onboard flash memory allows for customized software deployment and extensive compensation for system flaws. Both sensors are packaged in SOIC8, enabling direct connection to a 12V battery or measurement and diagnostics via local interconnect network (LIN) bus or UART.

The MLX91230/MLX91231 are suitable for DC current sensing, integrating integrated voltage and temperature (IVT) measurement functions, featuring built-in microcontrollers, and supporting safety applications, making them ideal for electric vehicle battery management and distribution systems. They can be used in various scenarios such as 12V/24V battery sensor chips, 48V/HV battery management systems, for monitoring battery state of charge (SoC), state of health (SoH), and state of function (SoF). They are also applicable in intelligent battery disconnect units, battery junction boxes, power relay components, excitation fuses, high-voltage relays or contactors, and domain controllers.

In addition, Melexis has introduced the MLX91208, a programmable current detection chip packaged in a standard SO-8 format. Leveraging Melexis' patented IMC-Hall technology, it achieves high sensitivity by detecting the magnetic field intensity parallel to the chip surface generated by current, providing high-speed analog signal output with a response time as low as 3µs.

The MLX91208 fully complies with automotive-grade standards, particularly suitable for isolated DC, AC, and AC/DC current detection up to 250 kHz. Its unique design significantly reduces drift within the chip's lifespan, ensuring long-term stable performance. Additionally, the transmission characteristics of the MLX91208 can be fully programmed by customers to compensate for mechanical/magnetic errors that may occur during assembly processes.

Finally, the MLX91218 is another high-speed, high-precision IMC-Hall® current sensor chip with dual OCD functionality, flexible 3.3V/5V power supply voltage, and high signal-to-noise ratio (SNR), which helps simplify module design. It utilizes IMC-Hall® technology with a flexible U-shaped shield to effectively resist interference and can measure currents in the range of 200A to 2000A. Its 400 kHz bandwidth and fast response make it an ideal choice for high-speed applications such as motor control, inverters, and converters.

To further simplify the design and implementation of current sensing solutions, Melexis also offers current sensor simulators that use IMC-Hall® technology to assist customers in making informed decisions regarding device and shield selection.

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Switch and LED driver controllers: the perfect combination of flexibility and high performance

Melexis has introduced the unique Hall switch MLX92292, which not only performs switching and latching functions but also precisely detects lateral magnetic fields, overcoming the limitation of only detecting orthogonal magnetic fields in the market. This controller supports ASIL B safety integrity level and complies with ISO26262 standards. Its built-in comprehensive diagnostic mechanisms further enhance its safety. The flexible programming options allow OEM customers to choose pre-programmed units or utilize end-of-line (EOL) programming to personalize configuration for maximizing system optimization.

The MLX92292 is available in 3-lead TSOT or TO92 package modes and operates in a wide voltage range of 3.3V to 18V, making it versatile for various application environments. Particularly noteworthy is its extremely low power consumption (typically only 7µA), making it highly suitable for battery-powered applications, especially in scenarios where vehicle engines are not running, effectively reducing battery drain. Programmable sleep time further enhances its energy-saving effectiveness.

Additionally, Melexis has introduced the MLX81118, an intelligent 24-channel LED driver chip with an integrated LIN interface. It not only meets ASIL (ISO 26262) standards but also achieves ASIL B level of system integration, providing robust functional safety assurance for electric vehicle charging ports. The MLX81118 is particularly suitable for ambient lighting applications, with its LIN interface conforming to multiple international standards and supporting automatic addressing, offering significant convenience for system integration.

The MLX81118 features an integrated intelligent microcontroller unit (MCU) and flash memory, providing flexibility in system design and facilitating future functionality updates. With its 16-bit PWM (frequency of 500 Hz), it can precisely control LED brightness, enabling static illumination and basic dynamic LED light effects. Notably, it can diagnose each LED by monitoring its temperature through measuring the LED threshold voltage, ensuring stable system operation.

Combining the MLX92292 with the MLX81118 unlocks significant potential for enhancing user experience. By connecting the output of the MLX92292 Hall sensor chip to the GPIO of the MLX81118, the status of the charging port cover position can be monitored in real time by the vehicle's body domain controller (BDC) through the LED driver chip's LIN interface. This intelligent integration not only reduces the number of connections to the vehicle's BDC but also allows changes in the charging port cover position to directly trigger LED responses.

For example, in nighttime or low-light conditions, when the charging port cover is opened, the MLX92292 can quickly detect this status change and activate surrounding LEDs for illumination through the MLX81118. This intelligent response ensures that the driver can clearly see the charging port's location under any lighting conditions, significantly enhancing the user experience.

Conclusion

The operation of electric vehicles is continuously seeking higher efficiency to accelerate charging times and extend the vehicle's range. Through more precise current measurement, optimizing current regulation control systems, and improving battery thermal management, efficiency can be enhanced. Melexis offers various current sensors and controllers that can assist in improving the operational efficiency of electric vehicles. It's worth further exploring the details of these products for manufacturers of electric vehicle-related products.

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