In order to tap the full potential of a 48V Starter Generator, it needs to be integrated into the powertrain. The BSG (Belt-Driven Starter Generator, P0 architecture) was the first system integrated into a 48V Mild-Hybrid vehicle due to the fact it was the lowest system cost and effort required to integrate into an existing car architecture. The P1/P2 and P3 architecture is either a crankshaft mounted or transmission mounted starter generator. From P2 architecture onwards, pure electric driving will be enabled. P4 architecture is being used to allow switch off the combustion engine or pure 48V BEVs. To learn more about a possible P4 system solution for city cars, please download also our whitepaper here!
High Power Inverters & DC/DC require from 1kW up to over 25kW
The below block diagrams show the basic layout of the semiconductors used to control a starter-alternator – the key component in the 48V vehicle electrical system. To power the microcontroller, the system voltage (48V) is reduced to a level common for microcontrollers and other ICs. This is the essential function of the supply IC (safety system supply). It also performs additional tasks in the area of functional safety. For a supply out of the 48V domain a pre regulator (48 V --> below 20 V) is necessary. But also a supply from the 12 V domain is possible. This is depending on the application requirements and a possible functional safety grade. The microcontroller enables both field-oriented control of the electric motor and control of the exciter winding in alternator operation. For this purpose, complex timer units are implemented in the microcontroller. In addition, it communicates with other control units of the vehicle via various communication buses (e.g. via CAN). With appropriate sensors, the rotor position and rotational speed of the electric motor rotor and the currents currently flowing in the inverter are measured and transmitted to the microcontroller. Smart sensor ICs can already process the measured data internally and make this data available to the microcontroller as digital values via a sensor bus. For precise motor control, it is also necessary to transmit the currents in the individual motor phases to the microcontroller. For this purpose, either shunt resistors are used in the inverter or the currents are determined using magnetic field sensors. Lowest RDS(on) MOSFETs are often used as power stage ICs in the 48V vehicle electrical system, which are usually controlled and monitored by dedicated 3-phase drivers and switched to a safe state in an emergency. Other important components, in addition to the motor driver ICs, are high-performance gate driver ICs which, in conjunction with MOSFETs, provide highly reliable battery switches or safety switches for 48V/12V isolation. The 48V vehicle electrical system is electrically coupled to the 12V vehicle electrical system using a DC/DC converter.
Complete 48V portfolio
Infineon offers a complete and broad system of chipset solutions – from microcontrollers, voltage regulators, and transceivers to sensors, smart power drivers and very low-resistance MOSFETs – for 48V starter generator systems.
Selected product highlights:
OPTIREG – voltage regulators:OPTIREG™ Switcher and PMIC are the ideal solution. The Pre-Regulator TLE6389-3G plus the Safety Supply PMIC TLF35584 offer stable supply to the AURIX™. The external safety device not only provides the power supply, but also monitors it and the functional status (e.g. watchdog) of the microcontroller and can be used for switching the system to a safe state (fail safe) in the event of a safety-relevant fault. This increases the availability of the system while allowing the microcontroller's error response to be individually configured.
CAN transceivers and bridge driver ICs:Other important communication and power components for 48V systems are CAN transceivers (e.g. TLE9250VSJ) and bridge driver ICs (e.g. TLE9180):
- TLE9180D-21QK and TLE9180D-31QK: advanced gate driver ICs dedicated to control six external N-channel MOSFETs forming an inverter for high current three phase motor drives application in the automotive sector. A sophisticated high voltage technology allows ICs to support applications for single and mixed battery systems with battery voltages of 12 V, 24 V and 48 V. Bridge, motor and supply related pins can withstand voltages of up to 90 V. Motor related pins can even withstand negative voltage transients down to - 15 V without damage. The TLE9180D-21QK has two integrated current sense amplifier (CSA) for shunt signal conditioning, whereas the TLE9180D-31QK has three CSA. Gain and zero current voltage offset can be adjusted by SPI. The offset can be calibrated. If isolation is required, a discrete component has to be added.
MOSFETs:48V applications are driving a high demand for 80V and 100V MOSFETs for applications such as starter-generators (belt-driven or integrated), DC/DC converters, battery main switches as well as 48V auxiliaries. Infineon's OptiMOS™-5 technology offers a broad portfolio of low RDS(on), scalable MOSFETs in various packages.
For high power requirements the MOSFETs in leadless TOLL package are offered for standard Cu substrates, while as alternative the TOLG package is targeting Al core IM substrates and Cu based substrates in conjunction with very high thermal cycle requirements. Both packages are footprint compatible and provide the highest current capability on a 10x11 mm2 footprint.
Next to these two package options, the TOLT package is supporting top side cooling on ECU level.
For medium and low power requirements like in DC/DC converters or at the 48V auxiliaries, the MOSFETs in 5x6 SSO8 package or in the 3x3 S3O8 package do complement Infineon’s MOSFET portfolio.
Sensors48V systems also require precise and robust sensors for sensing the rotor position of BLDC motors as well as for current measurement. Basically, the sensors should take up as little space as possible, have low losses, be flexible and cost-effective and be highly precise, robust and safe in operation over the entire service life. By way of example, the following sensor portfolio from Infineon:
- XENSIV™ TLE5501: analogue TMR sensors for highly accurate position detection.
Tunnelling Magneto Resistive (TMR) technology is offering high sensing sensitivity with a high output voltage so that no internal amplifier is needed – thus the magnetic sensor can be connected directly to the microcontroller without any further amplification and saving costs for the customers. In addition, TMR technology shows a very low temperature drift reducing external calibration and compensation efforts. The TMR technology is also well known for its low current consumption, which is a low as 2 mA.TLE5501 is used in applications from motors for wipers, pumps and actuators, electric motors in general up to steering angle applications with the highest functional safety requirements.
- XENSIV™ TLE5014SP: iGMR (integrated GMR) based magnetic position angle sensor with a high speed serial interface (SSC interface). It provides high accurate angular position information for various applications in the automotive area. The sensor is available in two versions: qualified according to AEC-Q100 and one AEC-Q100 qualified and ISO26262 compliant with a safety manual and safety analysis summary report available on request.
- XENSIV™ TLE5309D: a diverse redundant angle sensor with analogue outputs.
It combines a Giant Magneto Resistance (GMR) sensor for full 360° angle range with an Anisotropic Magneto Resistance (AMR) sensor for high precision in a flipped configuration in one package. Sine and cosine angle components of a rotating magnetic field are measured by Magneto Resistive (MR) elements. The differential MR bridge signals are independent of the magnetic field strength, and the analogue output is designed for differential or single ended applications. The output voltages are designed to use the dynamic range of an A/D-converter using the same supply as the sensor as voltage reference. The sensor IC is supplied independently by separate supply and ground pins.
- XENSIV™ TLE5501: analogue TMR sensors for highly accurate position detection.
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.
Dual Inverter drive for light electric vehicles
An efficient and low-cost way to implement electric drive in a light vehicle is to use two in-wheel motors and two inverter drives. This study outlines a proposed architecture and the safety standards that the system must meet.