Microcontrollers for Motor Control Systems

Some microcontrollers have been designed to simultaneously control more than one permanent magnet motor in equipment such as air conditioners, washing machines, and dishwashers. Moreover, industrial applications such as general-purpose inverters, uninterruptible power supplies (UPS) as well as heating systems, ventilation systems, and temperature conditioning applications can implement various MCU solutions.

Nowadays microcontrollers (MCUs) represent one of the most essential computing technologies, as their presence is now fundamental in all embedded applications. Electric motor control applications are usually implemented by combining a dedicated motor control unit and a system control unit, both of which use a microcontroller and its related software.

LOW-POWER MCUs

With the need to extend operating time, it is essential to pay attention to the power requirements of all hardware components, especially microcontrollers. In the design phase, designers must understand the compromises they are willing to accept and evaluate the differences in the technological characteristics of the microcontrollers on the market. The technology being these devices is the CMOS. This technology presents both a static and dynamic behavior. There are two fundamental aspects to consider when dealing with this type of technology: the current absorbed when the transistors are not switching (leakage currents) and the current absorbed when the switches don’t work.

The energy requirement of an MCU depends on its operating mode and the environmental conditions in which it is forced to work. A microcontroller has three fundamental operating modes in which it can operate (and therefore energy consumption is a consequence): normal, wait-mode, and stop. Obviously, in normal mode, the microcontroller is fully operational, and this turns out to be the mode. This modality requires higher energy consumption if compared to other modes.

The development of increasingly specific and complete peripherals onboard microcontrollers has allowed the increasingly tight integration of control circuits and the consequent reduction of space and dissipated power.

HIGH-PERFORMANCE DEVICES

Toshiba’s M3H devices incorporate high-performance analog circuits and a wide range of essential functions necessary to support complete motor control. The series includes 64 to 144-pin packages, with 256 up to 512KB of flash memory, and 32KB of data flash memory. The operating frequency is 80MHz. Integrated functions include high-precision analog circuits such as a 12-bit ADC converter with 1.5μs conversion speed and up to 21 channels and an 8-bit and 2-channel DAC. Moreover, Toshiba offers MCU solutions that incorporate a digital RDC, a vector engine (VE) and a one-shot pulse generator. These features improve the efficiency of the algorithm .

The Microchip dsPIC33CK is a dual-core version for motor control. For quick control cycles, it includes registers to reduce the latency, additional instructions to accelerate digital signal processing, tight peripheral coupling, and fast clock. It has small dimension and is available in packages up to 5x5mm 36pin μQFN and up to 12x12mm 80pin TQFP. The processing is up to 100Mips suitable for the control of multiple sensorless and brushless motors that perform field-oriented control algorithms and power factor correction.

Microchip’s 32-bit microcontrollers cover a wide range of motor control applications, from primary 6-step Brushless DC (BLDC) control to advanced sensorless field-oriented control (FOC). The SAM C Cortex®-M0 + (MCU) microcontroller series is based on decades of innovation and experience in built-in Flash microcontroller technology. These devices combine the high-performance motor control and energy efficiency of an ARM Cortex-M0 + MCU with optimized architecture and a set of peripherals. SMART SAM C is ideal for home appliances and other control applications which operate at 5V. CAN-FD, LIN, and automotive qualifications make the SAM C2x series a wise choice for automotive applications such as interior seats, door locks, power windows, and more.

Figure 1: block diagram and application circuit of the SAM C

The SAM C2x series devices are supported in the IDE Microchip / Atmel Studio, Atmel Studio Framework and START for software and configuration examples. For hardware development, the SAM C2x series is supported with an Xplained Pro kit (ATSAMC21-XPRO) which supports additional Arduino-style boards. For BLDC motor control applications, Microchip offers a 24 Volt development platform – ATSAMD21BLDC24V-STK – with a complete power stage and an interchangeable plug-in motor (figure 1).

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Maurizio Di Paolo Emilio is power electronics editor and European correspondent at AspenCore and editor of Power Electronics News.