Brushless DC motor control in just one day
Higher energy efficiency, better dynamics and reduced running noise today constitute important design requirements for motor drives. For this reason, advanced control concepts, such as field oriented control, are also increasingly deployed in drives used for automotive electronics. On the other hand, the effective implementation of these innovative control concepts call for optimised microcontroller architecture and tools that are easy to use. Infineon provides a comprehensive portfolio of application kits with scalable reference designs for motor drives. These kits include all the relevant hardware and software components for Plug&Play designs. These complete solutions comprise microcontrollers, power semiconductors in addition to passive components, plus the documentation such as recommendations for hardware design. Furthermore, the application kits include the reference software and a complete real-time test environment.
Field oriented control
Using FOC, it is possible to boost the efficiency of an electric motor by up to 95%, with reduced power consumption, lower running noise and better dynamics. This in turn improves the efficiency of the inverter, whilst making smaller power stages and motor dimensions with the same speed possible. The FOC algorithm eliminates time and speed dependencies and, in doing so, permits direct and independent control of the magnetic flow and torque. This is achieved via the mathematical conversion of the electric motor status into time-independent rotation coordinates. The corresponding mathematical formulas are known as Clarke and Park transformations. FOC can be used both for AC induction motors as well as for brushless DC motors.
Automotive BLDC Motor Drive Kit
Using the new development kit (Fig. 1), it is possible to quickly realise scalable solutions for the efficient control of 3-phase inverters with BLDC motors. To this end, the kit is based on two efficient automotive microcontrollers, the 8-bit MCU XC886 and the 16-bit MCU XC2236N, both of which support sensor-driven and sensor less control concepts. A new, highly integrated B6 bridge driver, the TLE7184F, is used as an interface to the six N-channel MOSFETs. Besides the complete driver stages, the new driver IC also includes advanced additional and protective functions, which reduce the amount of external circuits required to an absolute minimum.
Fig. 1: The new automotive BLDC motor drive kit from Infineon contains everything that is required for the quick and simple realisation of an efficient motor control for automotive applications. For full resolution, click here.
The kit includes:
– TLE 7184F power board (12 V…24 V/20 A)
– BLDC/PMSM motor
– AC/DC power supply (12 V/2 A)
– Driver card with the XC886
– Driver card with the XC2236N
– USB drive monitor
– CD-ROM with software and documentation
– Cables and connectors for connection to the customer-specific motor
The application circuit is composed of the driver cards with either the XC886 or XC2238N and a 3-phase inverter, which is equipped with the Infineon N-channel MOSFETs and voltage controllers designed for automotive electronics, in addition to the BLDC motor (Fig. 2). The interface between the microcontroller and the power stage is realised with a TLE7184F bridge driver. The new IC from the 3-phase bridge driver family from Infineon can drive up to six external N-channel MOSFETs. Further extensive functions such as e.g. configurable dead time and short-circuit threshold values, in addition to diagnostic and protective functions provide helpful features and significantly reduce the amount of external devices required. What is more, they also ensure a high level of system reliability.
Fig. 2: Block diagram of the application circuit with the driver cards, the inverter with the TLE7184F bridge driver and the motor. For full resolution click here.
To protect the system against polarity reversal, a further P-channel MOSFET, the IPD90P03, has been integrated. Both the supplied BLDC motor and customer-specific motors from 12 V to 24 V (up to 20 A) can be driven by this without any problems.
The kit also includes a complete software package with optimised motor control software and a real-time monitoring tool (digitally isolated). The kit also comprises free development tools and a complete design environment (IDE) with SDCC compiler and debugger facilities. Using the motor control software, it is possible to configure the parameters of a motor quickly and easily.
The software comprises optimised source code for the sensor less field oriented control of the BLDC motor. In addition, V/f control is supported for induction motors (ACIM) to permit rapid evaluation. The DriveMonitor makes it possible to retrieve and modify the control parameters in real time, with the oscilloscope function providing a means of graphically depicting the speed and phase current. The DriveMonitor is a USB stick with JTAG, VCOM (Virtual COM) and CAN interfaces. Whilst the JTAG interface is used for downloading the software and the OCDS debugging, the CAN connection is used for real-time monitoring and configuring the parameters while the application is running.
Optimised microcontrollers and power ICs
With the 8-bit family XC800 and the 16-bit microcontrollers XC2000, Infineon offers scalable solutions for a diverse range of motor control concepts in automotive applications (Fig. 3a). In this regard, the solutions range from block commutation with Hall sensors through to dual field-oriented, sensor less control.
The XC800 family is based on the standard 8051 architecture. The 8-bit microcontrollers offer different sizes of flash memory (2 to 64 KB) and incorporate oscillators, voltage regulators, EEPROM and monitoring/diagnostic circuits in order to reduce the system costs. Its optimised peripherals support different concepts for motor controls and power conversion. It includes an efficient capture compare unit (CCU6) for flexible PWM generation, a high-speed 10-bit AD converter for precision measurements and the hardware synchronisation of the PWM in addition to MultiCAN modules with up to two CAN nodes. The XC800 family features a 16-bit vector computer for trigonometric calculations, in the form required for field oriented control. In addition, it offers scalable package options with 16 to 64 pins and is designed for an extended temperature range with up to 150°C. As such, it is ideally suited for the harsh environments encountered in automotive applications.
The XC2236N belongs to the 16-bit microcontrollers of the XC2000 family, whose performance is comparable with that of 32-bit MCUs. The XC2000 family has been specially developed for automotive applications and is based on the proven C166 architecture. With efficient peripheral functions such as two CAPCOM6 modules and up to two high-speed 12-bit AD converters, the 80-MHz microcontroller is ideal for a diverse range of motor controls in the automotive sector. To this end, besides an efficient MAC unit, it offers 32 up 1600 KB flash memory and 136 KB RAM in scalable package options from 38 up to 176 pins.
In addition to the functions mentioned earlier, the TLE7184F bridge driver (Fig. 3b) also integrates a 5V fixed voltage controller and differential amplifier, which makes connecting to an 8-bit MCU, e.g. the XC886, extremely easy. Likewise, thanks to the integrated operational amplifier, the needed circuits for the shunt-current measurement are minimised, which ultimately leads to a cost and space-optimised design.
Fig. 3: Infineon offers scalable microprocessor and bridge driver families, which support cost/performance-optimised designs. For full resolution click here.
The kit is not only an easy to use reference design for motor drives, but also an ideal training medium. It enables users to test out the advantages and disadvantages of block commutation with Hall sensors compared with sensor less control, and thus to decide which approach best suits their particular application. A video is also available from Infineon, which illustrates just how quickly and easily a complete motor design can be realised with the aid of the kit: https://www.infineon.com/cms/en/product/applications/Motor_Control_Drives/BLCD_CD.html
About the authors:
Ralf Ködel is Product Marketing Manager Automotive Microcontroller at Infineon Technologies. Following his studies of industrial engineering and management, specialising in electrical engineering at the FH Rosenheim University of Applied Sciences, he started his career at Infineon in 2004. Since 2007, he works in product marketing for microcontrollers, which are used in automotive electronics. Ralf.Koedel@infineon.com
Alexander Schmidt is Technical Marketing Manager Automotive Power at Infineon Technologies. After graduating as an engineer in the faculty of electrical engineering/telecommunications, he embarked on his career at Infineon in 2001, initially as an application engineer, working with 16 and 32-bit microcontrollers. Since 2004, he works in technical marketing for automotive semiconductors. Alexander.Schmidt@infineon.com