Renesas: dedicated motor control circuit technology for automotive MCUs
To increase the range of motor-driven vehicles, it is necessary to boost the energy efficiency of motor control. To achieve this, it is important not only to make mechanical improvements to the motors themselves, but also to enhance the functions and performance of the electronic control units that control the motors. ECUs capable of supporting next-generation EVs, HEVs, and PHEVs require advanced functionality and complex control software, and this results in a substantial increase in the operation processing load placed on the MCUs used in these ECUs. At the same time, automotive MCUs required to restrict the amount of heat they generate in order to maintain a high level of reliability in high-temperature environments. It is therefore necessary to keep the operating frequency of the MCUs’ internal circuits, including the CPU core or cores, relatively low, making them difficult to boost performance.
The newly developed technology is an Intelligent Motor Timer System (IMTS), a dedicated circuit block that can be integrated into automotive microcontrollers for next-generation electric vehicles and hybrid electric vehicles. It performs field-oriented-control operations, which are essential to EV motor control, in a mere 0.8 µs, the world’s fastest rate, which is less than 1/10 the operation processing time of software implementation on a CPU running at the same operating frequency. This contributes to the realization of next-generation high-speed EV motors with excellent energy efficiency and inverter systems with high-speed switching performance to drive them.
Renesas implemented the IMTS as a dedicated circuit block for static processes requiring a high level of responsiveness such as acquisition of sensor data, calculation of control values based on it, and outputting of these values. The IMTS is independent of the CPU and capable of running autonomously, thereby substantially reduces the CPU load of the motor control MCU. The resulting surplus CPU capacity can then be allocated to advanced motor control algorithms designed to boost the energy efficiency of next-generation EVs, HEVs, and PHEVs.
Key features of the new technology include:
- development of dedicated circuit block for static motor control processing and circuit technology enabling autonomous operation
- development of circuit technology providing functional safety required for automotive powertrain control
- development of circuit technology for flexible error correction of external sensor signals
To realize high-precision MCU with highly accurate operation processing, it is essential to acquire highly accurate sensor signal values. Nevertheless, it is impossible to avoid errors from a variety of sources, such as errors caused by the mounting position of the sensors. The newly developed IMTS has a configuration that makes it possible to correct errors in real time using software developed by the user. In addition, the IMTS performs this processing autonomously, so correction processing imposes no load on the CPU. The corrected sensor signal values are used for motor control operations, resulting in more accurate operation processing and better energy efficiency when operating the motor.
Renesas is now testing a prototype 40nm MCU with on-chip flash memory that incorporates the new technologies. It uses an actual motor drive system to confirm operation in an actual system.