In a 48V network the battery is the key element, which supplies the loads, recuperates and stores energy and stabilizes the power net. Even the 12V network is supplied vie a DC/DC converter out of the 48V battery. The BMS is typically integrated within the battery.
Due to the high energy density and the better dynamic in the State of Charge (SoC) typically lithium ion batteries are used as power storage. But the lithium ion batteries are quite sensitive in terms of charging and discharging and have to be monitored and controlled carefully. The key objectives of a BMS are to increase safety and reliability of battery systems, to protect individual cells from damage, manage the battery energy efficiency and prolong battery lifetime. A BMS has to cover several functions such as providing the monitoring and control to protect the battery cells from out of tolerance operating conditions (e.g. overheating). This includes the capability to provide cell balancing to equalize the charge on all cells in the battery. Another task is the survey the SoC to provide the available capacity for the range indication as well as to evaluate the State of Health (SoH) to estimate the remaining lifetime of the battery. The key component of a BMS is the cell monitoring circuit, which monitors each cell, communicates the results and balances the cells when necessary. A battery monitoring unit can also be used to isolate the microcontroller domain to the cell monitoring units and takes over the communication between the microcontroller and the cell monitoring. Further components in BMS are a microcontroller supply, currents sensing unit and pressure sensing unit to detect e.g. a possible thermal runaway in a battery cell.
Complete 48V portfolio
Infineon offers a complete and broad system of chipset solutions – from monitoring/balancing ICs, microcontrollers, transceivers and voltage regulators to sensors and power switches to build up an up to date Battery Management System.
Selected product highlights:
Balancing/Monitoring ICs:The Monitoring and the Balancing ICs are the key components of a BMS. The Monitoring IC is translating the communication from/to the microcontroller UART protocol to the balancing IC using the ISO UART bus. The Monitoring IC can monitor up to 12 cells which voltage values are digitized with a 16-bit Delta-Sigma ADC for each channel synchronously in one measurement cycle. Before the values are sent over the ISO UART a temperature compensation is applied using the integrated stress sensor and calibration values. Additionally the Monitoring IC can read up to five NTC temperature sensors. The ICs are going to be released soon.
Sensors:BMS systems also require precise and robust sensors for sensing the pressure in a battery module as well as for current measurement. With a pressure sensor a thermal runaway of a battery cell can be detected and counter measures can be initiated. Basically, the sensors should take up as little space as possible, have low losses, be flexible, cost-effective, highly precise, and robust and safe in operation over the entire service life. For the BMS the pressure sensors KP256 and KP236N6165 are suitable.
AURIX™ microcontroller:The AURIX™ TC2xx microcontroller family was first introduced into powertrain applications, but with up to 3 TriCore™ processor cores and up to 8MB flash, it has since become highly successful across many automotive applications such as safety, chassis and driver assistance systems. The AURIX™ TC2xx is highly scalable and suitable for a number of 48V applications, it offers ISO 26262 compliance so that it can be used in ASIL-D systems, plus the fact that it’s also used in high voltage applications means that customers can utilise a platform approach. Furthermore, HOT package options are offered, which can be a requirement in some 48V applications in harsh environments.
The successor to the TC2xx, the 40nm AURIX™ TC3xx family, offers a highly compatible future roadmap. It includes up to six independently operating 32-bit TriCore™ processor cores and up to 16MB flash, thus significantly boosting computing performance compared to the AURIX™ TC2xx. The feature rich TC3xx allows designers to upgrade their systems if required and choose from a broad portfolio of scalable memory sizes, peripheral functions, frequencies, temperatures and package options. The first TC3xx devices to be launched; the high end TC38x and the TC39x are already available. A superset approach has been utilized so they are compatible with lower end family members, more of which will be launched throughout 2020, many of which will be suitable for 48V applications.
The TC3xx family, like the TC2xx, offers the ideal combination of real-time capability, and functional safety for ISO 26262 systems up to ASIL-D, with the HOT package being offered throughout. An important enhancement is the inclusion of the Hardware Security Module (HSM) as standard. Security is not just a concern for systems communicating with the outside world, it is now a requirement for some customers, who specify that any microcontroller that communicates via the CAN network requires security. The TC3xx offers the HSM throughout the family, whereas previously it was available only on selected devices on the TC2xx. This offers customers who need security an upgrade path, with the HSM now offering EVITA Full capability, compared to EVITA medium on the TC2xx.
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