Motor control circuit for automotive MCUs targets next-gen EVs

February 09, 2017 // By Graham Prophet
Renesas Electronics (Tokyo, Japan) has announced that it has developed an Intelligent Motor Timer System (IMTS), a dedicated circuit block that can be integrated into automotive microcontrollers (MCUs) for next-generation electric vehicles (EVs) and hybrid electric vehicles (HEVs).

Renesas says it will equip automotive microcontrollers with this dedicated motor control circuitry; objectives include boosting the energy efficiency of next-generation electric vehicles. Compared to a software implementation, the circuit block will reduces operation time to 10% or less while providing functional safety. Its functional block diagram is shown above, and contrasted with a conventional layout, below.

The IMTS performs field-oriented-control operations in 0.8 µsec, claimed as the fastest available. This contributes to the realization of next-generation high-speed EV motors with energy efficiency and inverter systems with high-speed switching performance to drive them. The circuit also enables functional safety support required for the automotive powertrain field.

With the increasingly stricter fuel efficiency requirements in the recent years, EVs, HEVs, and plug-in hybrid electric vehicles (PHEVs) have come to account for an increasing share of the total number of vehicles produced. To increase the range of such motor-driven vehicles, it is necessary to boost the energy efficiency of motor control.

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, so it 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.

Motor control requires a succession of static processing involving field-oriented-control operations, in which the motor current value and angle value are acquired during each control period managed by the MCU's internal timer circuit and control values are determined for the next control period; and PWM output generated based on the control values. When multiple types of motor control are operating at the same time, the resulting processing load can consume up to the equivalent of up