Tweet

Posted on 17 July 2019

High Energy Savings for Less Money

Free Bodo's Power Magazines!

 

 

 

Low-cost 8-bit MCUs support easy convergence to energy efficient designs

Using sophisticated power concepts based on optimized microcontrollers provide enormous energy saving potentials in various applications. Both improved energy efficiency and reduced system costs are the driving factors in modern motor control designs used in fans, pumps, compressors, geared motors and for power conversion in lighting products or induction cookers.

By Juergen Hoika, Marketing Microcontroller Industrial and Multimarket, Infineon Technologies

 

The implementation of intelligent control concepts like Field Oriented Control (FOC) for electric motors or current control for LED helps to fulfill these demands. Infineon addresses both energy and cost efficiency, expanding its 8-bit microcontroller portfolio with a new series of MCUs providing optimized features, including FOC to enable high energy savings at very low implementation costs.

In industrial nations up to more than half of all electrical energy is consumed by electric motors. Electric motors account for twothirds of industrial electric consumption and about one-fourth of residential electric use. For example improving the efficiency of electric motors can significantly save energy and reduce operating costs. There is an increasing demand for motors with speed control providing higher efficiency (e.g. fans, pumps). The market analysts of IMS Research stated a CAGR of 10% for drive units from 2006 to 2011. This strong growth in industrial drives yields to related growth for microcontrollers with a CAGR of 8.9% in the same time frame.

Beside motor control power electronics help to improve energy efficiency significantly for lighting, induction cooking and air conditioning where the saving potential can exceed 25% (figure 1). The microcontroller is the central element in achieving this. Low cost and easy-to-use microcontroller lower the introduction of high efficient designs with no compromise of the use of sophisticated control methods.

Saving potential using power electronics

Field Oriented Control

FOC - or vector control - is a method to control three-phase AC electrical motors in a way that it can reduce motor size, cost and power consumption. With FOC the efficiency of a motor can be improved significantly. This has a big impact on power consumption, motor dynamics, heat dissipation and noise. A sensor-less FOC on BLDC (Brush Less DC motor) or PMSM (Permanent Magnet Synchronous Motor) provides additional cost benefits compared to sensor based motor control (figure 2). Sensor-less approaches use the back EMF (Electromagnetic Force) of the motor to calculate the rotation angle and rotor position. The back EMF is calculated in the flux estimator, which is based on the voltage model of the system in the two phase reference frame. A single shunt is enough to reconstruct the phase currents.

High energy efficiency at very low cost

The usage of BLDC, PMSM or AC induction motors combined with powerful motor control algorithms running on optimized microcontrollers offer the most energy efficient solutions. For brushless motors, a wide range of motor control system algorithms - including trapezoidal, sinusoidal, and FOC - are available.

Sinusoidal commutation produces smooth motion at slow speeds, but is inefficient at high speeds. Block commutation can be relatively efficient at high speeds, but causes torque ripple at slow speeds. This leads to FOC, which provides the best of both worlds. Using FOC the efficiency of an electrical motor can be increased by up to 95%, providing less power consumption, less noise and excellent torque dynamics. This results in a better efficiency of the inverter, smaller power stage and smaller motor dimensions at the same torque.

The FOC algorithm works by removing time and speed dependencies and allowing the direct and independent control of both magnetic flux and torque. This is done by mathematically transforming the electrical state of the motor into a two-coordinate time-invariant rotating frame using mathematical formulas known as the Clarke and Park transformations. FOC can be used on both AC induction and brushless DC motors to improve their efficiency and performance. It can be applied also to existing motors by upgrading the control system.

Scalable microcontroller family

As low power consumption, higher performance and reduced costs are key drivers of today’s microcontrollers, an 8-bit microcontroller family which offers 16-bit performance at 8-bit costs addresses a huge variety of demanding applications. With the XC800 family (figure 3) Infineon has combined an 8051-core with embedded flash memory of 2KByte to 64KByte and pin-count from 16 (TSSOP16) to 64 (QFP64) pins. To reduce system costs features such as oscillator, voltage regulator, EEPROM and supervisory circuits are integrated. Different flash sizes, scalable peripherals and innovative features like FOC make it easy to select the right product for a dedicated application. The XC800 family provides some powerful peripherals which make this MCUs ideal for various motor control and power conversion applications. These peripherals include a Capture/Compare Unit (CCU6) for flexible PWM generation and an enhanced fast AD converter for precise measurement and hardware synchronization to PWM. In addition some derivates are equipped with a 16- bit vector computer supporting FOC, as an industry first for 8-bit-MCUs. Using the vector computer only about half of the CPU performance is needed to implement FOC, which is also unique in the industry.

Scalable microcontroller portfolio for a broad range of motor control and power conversion applications

The FOC capability - as implemented on the XC886/888, XC878 and the upcoming XC83x products - combines the high-performance 8051 core and a vector computer coprocessor core, which performs 16-bit arithmetic operations. The full programmable vector computer is build by two parallel operating units: the MDU (Multiplication/Division Unit), a 16-bit multiply and divide unit, and the CORDIC, a 16-bit coprocessor dedicated for vector rotation and angular calculations. The interrupt based operation of the vector computer reduces the CPU load. Unlike most competitive FOC implementations that are hard-coded, the XC800 microcontroller based solution offers the added benefit of software re-programmability to give the developers more versatile application options.

High performance at lowest cost

The two new MCU series XC82x and XC83x of the XC800 family enable a very costeffective implementation of energy saving control concepts with single unit prices starting at about 0.40 Euro (@ 100k units). The XC82x derivates integrate a MDU and a fast ADC to provide a fast PWM unit for sinusoidal commutation with hall sensors, while the XC83x devices (figure 4) in addition integrate an enhanced vector computer (MDU and CORDIC) to provide full hardware supported FOC functionality.

Block diagram of the XC83x series with new and enhanced peripherals

For optimized motor control like sensor less FOC of a BLDC or PMSM a configurable reference code (PWM frequency, motor parameters and current measurement scaling) is available with following features: 16-bit arithmetic, PI controller with anti-wind-up limit and 24-bit data storage, flux calculation with 32-bit resolution and fast control loop calculation with <150µs.

Following requirements are key for the power conversion in lighting applications (like current control for LED or power control and ignition in HID) and in single switch topologies with quasi resonant control like in induction cooking: High resolution PWM, fast ADC measurements, autonomous peripherals, and comparators for control loop and for protection.

To address these needs the XC82x/XC83x MCUs provide a CapCom6 unit clocked at 48MHz and a fast 16-MHz ADC with a sample time of only 125ns and a conversion time of about 820ns. The direct hardware link between ADC and CCU6 (figure 5) provides a powerful PWM control. In addition the integrated ADC limit checker realizes a digital comparator with 8-bit resolution. Furthermore an ADC “Out of Range” comparator is implemented.

Direct hardware link between ADC and CAPCOM6 unit provide a powerful PWM control

The new microcontrollers are optimized for low pin count packages (figure 6) to reduce board space and costs. Features supporting a low pint count include an integrated oscillator (48 MHz), integrated ADC reference voltage (1.25V), bidirectional port structure for half duplex connectivity at one pin, only 3 pins dedicated for power supply (VDDC, VDDP, VSSP), OCDS debug support via single pin DAP and the non volatile configuration of the boot mode.

The new XC82x-XC83x devices are optimized for low pin count

Furthermore the new low-cost XC82x and XC83x series offer several new features to provide additional value including touch sense and LED matrix control, RTC with 32kHz and 75kHz oscillator and high current pads for direct drive of stepper gauges.

Ready to go - for energy efficient designs

The effective implementation and execution of the innovative motor control concepts needs an optimized microcontroller architecture and ease of use tools. Infineon does not only offer powerful scalable microcontrollers, but also provides complete solutions with the related tool chain. In addition a broad portfo lio of application kits, which ease the evaluation and implementation of hardware and software solutions for high efficient motor drives, is offered. The provided application kits and tool chain support the fast implementation of the new motor control techniques on the microcontrollers. A complete portfolio of reference systems for motor drive applications is available supporting the whole range of algorithms from block commutation to FOC.

All offered application kits contain a free tool chain (compiler, real time debugging environment, etc.) and offer Plug&Play design as all related hardware and software parts are provided. A complete solution with microcontrollers, power semiconductors and passive components is provided. Complementary comprehensive documentation with hardware design examples is included the application kits.

The kits are ready to be used with DAvE Drive, a unique auto code generator for motor drives. DAvE Drive is an application code generator available for the company’s 8-bit MCU families. It helps to reduce the software development time for motor drives due to fast and easy configuration of complex control algorithms like FOC. Designers of motor controls can quickly focus on application- specific software, such as the programming of drive functions. The DAvE Drive software tool generates complete algorithms with documented source code and does not derive from precompiled libraries. It also enables the fast adaption for customer specific motors. The motor type can be selected from a library or defined by setting the key characteristics like nominal voltage, phase inductivity or resistance. Using DAvE Drive the parameters for speed and current control can be easily adapted.

Conclusion

The need of higher efficient motor drives and power conversion solutions results in an increasing demand of related microcontrollers. Infineon’s MCUs of the XC800 family offer scalable solutions for different types of motor control methods ranging from block commutation for BLDC motors with Hall sensor or sensor less, FOC for BLDC motors or PMSMs and both FOC and PFC (Power Factor Control). Further reference code and application kits for lighting applications and induction cooking are in development.

A complete tool chain and dedicated application kits pave the way to high efficient designs based on this optimized microcontrollers and enable short time-to-market. The new 8-bit series XC82x and XC83x addresses a broad spectrum of extremely cost effective applications and provide significantly energy savings. Engineering samples of these low cost devices will be available from March 2010 on.

Please visit Embedded World 2010 to get more information about XC82x and XC83x from Infineon´s experts.

 

Further information on Infineon’s microcontroller offering at: www.infineon.com/microcontrollers

 

 

VN:F [1.9.17_1161]
Rating: 0.0/6 (0 votes cast)

This post was written by:

- who has written 155 posts on PowerGuru - Power Electronics Information Portal.


Contact the author

Leave a Response

You must be logged in to post a comment.