Migrating to Digital Power Conversion and Management for a Greener Future

Smart energy implies a level of intelligence in the generation, distribution and consumption of power. To some extent this has been imposed upon utility companies by governments, but it goes much deeper than mere legislation. A wider social conscience means it now influences how power is handled in all of its forms and at every level.

The ‘smarts’ increasingly embedded within meters, appliances, machinery and even buildings are intended to help get energy under control. An expanding global population and limited fossil fuels, compounded by the negative impact on the environment from exploiting those resources, is causing the world’s energy landscape to change.

Renewable energies are becoming more relevant. The IEA recently published data indicating how the key areas of energy generation and consumption are furthering the objectives of the Paris Agreement. Electric vehicles, solar PV and onshore wind farms are meeting current expectations, while other initiatives including carbon capture and storage and improved efficiency in coal-fired power generation are not. Indicators for other forms of renewable energy such as nuclear power and energy storage show more effort is required, as do end markets such as transport, industry, and consumer applications such as appliances and lighting.

A large factor in energy inefficiencies is the conversion stage which naturally incurs losses, but techniques and technologies being developed can help minimize them.  The industry continues to transition to a digital domain, which offers greater control, flexibility and efficiency than a purely analog approach. As a result of this transition, there are a growing number of solutions available that combine a range of features specifically targeting power conversion.

Monitoring energy usage

Smart meters are now being rolled out in many countries to give consumers greater control over their energy usage and to help utility companies monitor demand to ensure they only produce enough energy to meet that demand. The more utility companies know about consumer habits, the easier it is for them to adopt a more environmentally responsible approach to energy generation and distribution. While the term ‘smart meter’ covers this application space, they can vary significantly in their functionality. Some may simply pass data back to the utility provider, while others may offer the homeowner full visibility into their energy usage.

The FM4 S6E2Dx family of microcontrollers from Cypress Semiconductor is aimed at OEMs looking to develop a system that can interface to a smart meter and provide a wealth of information. It can form the heart of a Home Energy Management System (HEMS) as shown in Figures 1 and 2. It integrates an ARM Cortex-M4F core with a graphics subsystem, along with a host of other peripherals to support wired and wireless interfaces.

Figure 1: The Home Energy Management System Controller from Cypress Semiconductor offers the perfect platform for developing smart energy solutions.

Figure 2: The HEMS Controller from Cypress Semiconductor, featuring the FM4 S6E2Dx microcontroller.

Within the same family, the FM0+ S6E1A1 series is optimized for energy management in a different form, motor control. Digital control of Brushless DC Motors (BLDCs) and Permanent Magnet Synchronous Motors (PMSMs) is an area of energy management that is prime for optimization. Both types of motor are present in a growing number of industrial machines and consumer appliances, and have been the subject of efforts to improve energy efficiency for some time. Field Oriented Control (FOC) is a technique that makes driving and controlling PMSMs and BLDCs much more efficient, however it does require a relatively higher level of processing power. The FM0+ S6E1A series is ideally suited to FOC of BLDC and PMSM motors, applications that are fully supported with design guides from the manufacturer, Cypress Semiconductor.

Figure 3: The FM0+ S6E1A1 integrates everything needed to develop FOC based BLDC and PMSM motor control solutions.

Power conversion

While some electrical appliances run from an AC supply, many more need a stepped-down and regulated DC supply, making the use of Switched Mode Power Supplies (SMPSs) widespread. The move to digital control has enabled OEMs to produce smaller and more efficient SMPSs, and efforts continue to further improve efficiency in this key area.

The dsPIC33F family of Digital Signal Controllers (DSCs) from Microchip is positioned for intelligent power conversion, offering dynamic control and loop adjustment, predictive control loop algorithms, and operational flexibility for different power levels. This level of digital control is intended to remove the need for a standard analog control loop while offering greater control. Regulation is controlled by the software running on the DSC, supporting digital compensation algorithms for non-linear predictive and adaptive control. In short, the power supply is much better equipped to handle changes in input power and loads in order to operate at optimal efficiency under a wide range of conditions. In this scenario, the algorithms running on the DSC use feedback gathered using high-speed and high-bandwidth ADCs in conjunction with high-speed PWMs. The PWM module on the dsPIC33F is able to directly drive all common power supply topologies while executing digital compensation algorithms on the processing core.

As Figure 4 shows, the dsPIC33F is also able to implement Power Factor Correction through a Boost-PFC algorithm, using average current mode control. By calculating the product of the rectified input voltage, the output voltage error compensator and the output of the voltage feed-forward, the reference current is derived digitally. Even when running this application, the dsPIC33F has plenty of processing headroom for other application software.

Figure 4: The dsPIC33F is able to implement complex and adaptive digital power control with processing headroom to spare.

Fully integrated solutions

There are many aspects to power with conversion, distribution and application being the general divisions, but each with its own particular variants. It may not be reasonable to expect a single device to be applicable to all of these areas, but there are solutions that come close.

One such example is the PAC5223 from Active Semi, which is part of a wider family of Power Application Controller (PAC) devices that have been optimized for the new wave of smart energy appliances and equipment (Figure 5). Based on an ARM Cortex-M0 core, it features Active Semi’s proprietary technology including the Multi-Mode Power Manager, Application Specific Power Drivers and Configurable Front End.

Figure 5: The PAC5233 Power Application Controller offers an impressive level of integrated features covering most power conversion and management applications.

The Multi-Mode Power Manager is described as an ‘all in one’ solution for multiple types of power sources, featuring a multi-mode switching supply controller that can be used in buck, SEPIC or AD/DC Flyback mode, as well as handling up to four linear regulated voltage supplies. The Application Specific Power Drivers include high-side and low-side gate drivers capable of implementing half-bridge, H-bridge, 3-Phase, and general purpose control. The Configurable Front End includes all of the analog functionality needed in a power application, including programmable differential and single-ended gain amplifiers, digital-to-analog converters and comparators. It can also accept multiple analog input signals and even provides amplification for sensor inputs.

The applications addressed by the PAC family are extensive and include general purpose high-voltage system controllers, home appliances, power tools, motor controllers, LED lighting controllers, and uninterruptible power supplies. It can also be used in solar micro-inverters, as well as a wide range of industrial applications. Figure 6 shows a typical application.

Figure 6: The PAC52xx in a typical application.

The PAC5223 is also supported by the HYDRA-X23/X23S development platform which is intended to support engineers developing power applications. Like its namesake, the development kit accepts different ‘heads’ to extend its functionality, while the main kit (or ‘body’) offers breakout connectors for easy access to all of the PAC5223’s peripherals.

Conclusion

Getting ‘smart’ about power involves a migration to digital control wherever possible. So important is this new power paradigm that governments are enacting legislation to ensure it occurs before the climate suffers irrevocable damage.

The electronic engineering community has an important role to play in this migration by adopting digital control in all applicable situations. The semiconductor industry is working hard to make that simpler through highly integrated devices and full-featured development kits.

References

1. https://en.wikipedia.org/wiki/Paris_Agreement
2. http://www.iea.org
3. Field Oriented Control of BLDCs and PMSMs using the FM0+ S6E1A1