Powering the future—the hidden heroes of electric vehicle technologies

The automobile industry in Mainland China has developed at an unimaginably rapid pace in recent years and a general trend can be observed in car sales figures. A little more than twenty years ago, automobile production in Mainland China numbered only in the hundreds of thousands, while current automobile output has increased to more than 20 million cars each year. The capacity of the car market in Mainland China has attracted the attention of the world and the development of the automobile electronics industry has brought forth tremendous business opportunities for chip suppliers and distributors.

The development of electric vehicles in China grew at an even more exponential rate: close to 2.9 million EVs were sold in 2016 alone. By 2017, the sales of electric vehicles had exceeded 5.5 million, growing by more than 90% from 2016. As the state now encourages the development of battery electric vehicles, the sales volume of battery electric vehicles (BEV) has more than doubled in 2017 from levels in 2016 and far exceeded the growth in plug-in hybrid electric vehicles (PHEV). The scale of Avnet’s operations in automobile electronics has also continued to grow.

The motor control unit (MCU) is a core component of BEVs. The Shanghai laboratory of Avnet’s Global Design Department is now developing a new solution for the MCUs of electric cars targeted at small or compact passenger cars with a maximum output of 50KW. One particular feature of the motor control solution is that components are selected based on ISO26262 standards which can be used as a reference for the ASIL-D motor control system as well as for rapid evaluation of components such as the main controller chip and driving circuit.

ISO26262 (Road vehicles-Functional safety) is an international standard for automobiles aimed to increase vehicle safety. Functional safety, now a household term, seeks to reduce increasing risks of system failure and random hardware failure. ISO26262 standards include all development phases for functional safety from specification planning, design, implementation, integration, verification, validation and configuration.

ASIL (Automotive Safety Integrity Level) is the safety requirement level for integral parts of the system under ISO26262 standards. Safety requirement levels range from A to D, among which D is the highest level denoting the highest safety requirements. The ASIL-D motor control system is also extremely demanding on hardware and software development processes.

Avnet's motor control solution includes the use of Infineon’s IGBT power module with the model number HybridPACK™1 DC6 and rated at 705V/400A. The main controller chip, an ASIL-D chip, is Infineon’s AURIX™ TC275 triple core processor with lockstep core and other safety functions. Lockstep Core, also an ASIL-D chip, is adopted for power and system monitoring and management. The solution supports different motor interfaces: resolvers, giant magnetoresistance encoders, and optoelectronic encoders, while TC275 supports rotary decoding. The system layout of the solution is shown in the figure below:

Avnet also invested in and installed a new magnetic powder dynamometer for this purpose as shown in the following figure:

The magnetic powder dynamometer is a torque machine used in laboratories that imposes torque load on the tested motor and absorbs its power. It is also the rotational torque-inertia torque converter. The rotating speed sensor and torque sensor are all installed on the dynamometer and they convert the rotation speed and torque of the tested motors to pulse signals and analog signals.

Avnet’s motor control solution includes the main controller chip TC275 which is part of Infineon’s AURIX™ multi-core chip series. The multiple-core structure includes 3 independent 32-bit TriCore processing cores that meet the highest safety standards in the industry—ASIL-D. 65nm embedded flash memory technologies are also adopted to achieve high reliability in the harsh environments of automobile applications. AURIX™ supports multiple communication interfaces and has multiple PWM generator units such as GTM and CCU6. It has VADC and DSADC for different ADC modules as well as comprehensive multiple safety modules such as IOM, HSM, and FCE. It also has high-performance floating-point arithmetic capacity and integrated hardware division units.

The IGBT power module in the solution has a critical role in the motor control of electric vehicles: it is the bridge for energy conversion between the battery system and the motor system. The main chip controls the switch of the IGBT power module and converts the direct current (DC) power stored in the battery into alternate current (AC) to power the vehicle-mounted AC motor. It also converts kinetic energy into electricity when the vehicle brakes to recharge the battery. Infineon’s HybridPACK™1 DC6 module was designed specifically for inverters in electric vehicles. It uses a high-performance ceramic substrate integrated with copper base plate welding and Infineon’s enhanced bonding wire process to significantly improve thermal cycling and power cycling lifetimes.

The driver and controller ICs in the solution are shown in the figure below.

Avnet's new motor control solution for electric vehicles addresses increasing demands for functional safety and is designed to meet ISO26262 standards. The main controller chip, power module and power ICs are all ASIL-D chips. Experimental conditions were also established for analog load tests in the laboratory to better serve the extensive motor control market for electric vehicles in China, a market that will going forward become more regulated and more focused on functional safety. If you are interested, contact Avnet’s regional offices to learn about the detailed technologies and specifications of the solution. It is our goal to provide optimal services for customers across the globe.