Electrical energy is the highest quality energy source in the history of human civilization. It is thanks to the full development and utilization of electrical energy that humanity has been able to enter such a developed industrialized and information-based society. Although humanity has made remarkable achievements in the generation, transmission, and utilization of electrical energy, how to utilize it more rationally, efficiently, accurately, and conveniently remains a major problem that needs to be solved.
The birth and development of power electronics technology has brought about a revolutionary change in how humans use electricity and has greatly changed people’s concept of using electricity. In the world, the proportion of total electricity consumption that has been transformed and regulated by power electronic devices has become an important indicator for measuring the level of electricity consumption. At present, the global average of this indicator is 40%, and it will reach 80% by 2010[1]. This poses a new challenge to power electronics technology.
However, the development of power electronics technology has now reached a crossroads, with the contradiction between the complexity of power electronic devices and their wide range of applications becoming increasingly acute. On the one hand, numerous fields require the extensive use of power electronic devices, while on the other hand, the diverse applications of power electronic devices mean that their design, production, and maintenance require a great deal of human and material resources, creating a significant obstacle to their popularization and promotion, and becoming a bottleneck for the advancement of power utilization technology.
Currently, the international power electronics community generally believes that power electronics integration technology is the most promising way to overcome the obstacles facing the development of power electronics technology and further expand the application fields of power electronics technology.
The concept of power electronics integration has been around for over 10 years. The early approach was monolithic integration, which embodied the concept of System on Chip (SOC), where the main circuit, drive, protection, and control circuits were all manufactured on the same silicon chip. Due to the significant differences in manufacturing processes between high-voltage, high-current main circuit components and other low-voltage, low-current circuit components, as well as issues related to high-voltage isolation and heat transfer, monolithic integration is very difficult and is currently only used in the low-power range. In the medium-to-high power range, only hybrid integration can be used, where multiple bare dies of devices with different processes are packaged in a module. The widely used power electronic power modules and intelligent power modules (IPMs) embody this idea. Around 1997, the US government, military, and some renowned scholars in the field of power electronics jointly proposed the concept of Power Electronic Building Block (PEBB) [1-4], clarifying integration as the future development direction of power electronics technology and pushing the research on power electronics integration technology to a climax.
2. The significance of integration
The research on integrated technology will determine the future rise and fall of power electronics technology, which can be understood by comparing it with the development history of electronic technology.
Looking back at the trajectory of electronic technology development, before the advent of microelectronics, marked by integrated circuits, the design, manufacturing, and maintenance of electronic devices faced similar challenges. The emergence of microelectronics encapsulated the most significant difficulties and the vast majority of the workload in electronic design within integrated circuits, greatly reducing the difficulty of device design, manufacturing, and maintenance. Any engineer with a basic engineering education could easily design electronic devices for their respective technical fields, significantly increasing the automation level of production. Integration greatly expanded the application scope of electronic technology, permeating all aspects of production and daily life, leaving its mark on numerous products. This expansion of application areas, in turn, greatly propelled the advancement of the technology itself. Due to public acceptance, financial and technological support, industrial backing, and a huge market, electronic technology created numerous technological darlings that embody its full essence, such as computers, mobile phones, digital cameras, and MP3 players.
History often repeats itself in surprising ways, and people can learn from it. Just like 30 years ago, power electronics also needs to step out of the ivory tower created by power electronics engineers and become a powerful tool that engineers with basic skills can master in different industries. Only in this way can we expect greater development and a more brilliant future. The way to achieve this goal is integration [2]. Through integration, the technical difficulties and main design work encountered in the design of existing power electronic devices, such as components, circuits, control, electromagnetics, materials, and heat transfer, can be solved in the integrated module, making the application system design simple to select the appropriate standardized modules and assemble them [3]. This revolutionary technology will divide the current power electronics technology field into two different branches: integrated module manufacturing technology and system application technology. The former focuses on solving the problems of module design and manufacturing, and overcomes the main difficulties in power electronics technology through the close intersection and integration of multiple different disciplines; while the latter solves the problem of combining modules into systems for various wide and diverse specific applications. With the development of this technology, the design and manufacturing of integrated modules will become the main focus of research in power electronics itself, while system application technology will gradually become a general skill mastered and used by engineers in various industries with basic qualifications. They will design and implement power electronic systems distributed across various devices according to the application problems addressed in their respective industries. Consequently, the power electronics industry will also show a trend of differentiation, with the manufacturing of integrated modules becoming the main focus, while the share of pure power electronic device manufacturing will gradually decrease, with more penetration into other industries. However, this does not mean the shrinkage of the entire industry. On the contrary, due to the widespread application of modules in various fields, like integrated circuits, the power electronics industry is expected to experience even more vigorous development than it does now.
3. Different levels and forms of integration technology
In general, the integration of power electronic devices and systems can be divided into three different levels and forms:
1) Monolithic integration refers to the fabrication of power devices, drive, control, and protection circuits in power electronic circuits onto a single silicon wafer using semiconductor integrated circuit processing methods, embodying the concept of SOC (System on Chip). This integration method offers the highest integration density and is suitable for mass production and automated manufacturing, effectively reducing costs, size, and weight. However, it faces significant challenges due to the substantial differences in manufacturing processes between high-voltage, high-current main circuit components and other low-voltage, low-current circuit components, as well as issues related to high-voltage isolation and heat transfer. Therefore, monolithic integration is very difficult and currently only has applications in the low-power range, such as TopSwitch. With the development of new semiconductor materials and processing technologies, it will inevitably move towards larger power levels in the future.
2) Hybrid integration involves using packaging techniques to encapsulate multiple silicon chips, each containing power devices, drive, protection, and control circuitry, into a single module, forming a relatively independent unit with partial or complete functionality. This integration method effectively addresses issues such as the combination of circuits from different processes and high-voltage isolation, achieving high integration density and significantly reducing size and weight. However, it still faces challenging technical challenges related to distributed parameters, electromagnetic compatibility, and heat transfer, and it cannot yet effectively reduce costs or achieve high reliability. Therefore, it is currently primarily used in medium-power applications, with a trend towards higher power applications. A typical example of hybrid integration is the Integrated Power Device (IPM). In a sense, hybrid integration represents a compromise between integration density and technical difficulty, based on current technological capabilities. It has strong practical significance and is currently the mainstream approach in power electronics integration technology.
3) System integration, also known as system-level integration, is a commonly used integration solution in the field of engineering technology. It involves organically combining and assembling existing entities into a complete system. In the field of power electronics, system integration generally refers to the organic combination of multiple circuits or devices into a fully functional power electronic system, such as a communication power supply system. System integration is functional integration, characterized by low integration degree and technical difficulty, making it easy to implement. However, due to its low integration degree, its size and weight cannot be significantly reduced compared to independent devices and circuits. Furthermore, its composition is still mainly based on discrete components, making design and manufacturing more complex, and the advantages of integration cannot be clearly demonstrated. Currently, system integration technology is mostly used in systems with high power and complex structures and functions.
Currently, the concept of integration discussed in the international power electronics community generally refers to monolithic integration and hybrid integration, and rarely includes the level of system integration.
4 Major Research Institutions
Currently, some of the more influential research institutions in the field of international power electronics integration include: the Center for Power Electronic Systems (CPES) [1,2], the Department of Electrical Engineering at Cornell University [3], the Power Electronics Research Group at the University of Arkansas [5], and the Spanish National Microelectronics Research Center [6]. Some powerful companies, such as General Electric (GE) [7], International Rectifier (IR), Semikron, and ABB, have also joined the field.
CPES currently holds a central position in this field of research, covering the widest range of topics and producing the largest number of publications and research results, thus leading the mainstream research direction of international power electronics integration technology to a certain extent. The goal of CPES is to integrate all circuits and components in a power electronic system, including main circuits, sensors, drives, protection, control, and communication interfaces, through high-density hybrid integration and multi-layer interconnection, forming a universal standardized integrated power electronic module (IPEM) for constructing various application systems.
The domestic academic community has already paid great attention to power electronics integration technology and reached a consensus that, with the government's promotion, research on power electronics integration technology in my country should be carried out as soon as possible. Some scholars from Tsinghua University, Zhejiang University and Xi'an Jiaotong University have started to conduct research from different perspectives[8], but in general, it is still in the initial stage.
The National Natural Science Foundation of China has approved the key project "Theoretical and Key Technology Research on Power Electronics System Integration," to be undertaken by Zhejiang University, Xi'an Jiaotong University, and Xi'an Power Electronics Technology Research Institute, and officially launched in January 2003. Although the funding amount of the National Natural Science Foundation project is not large, the establishment of this project has profound significance, marking the official start of research on power electronics integration technology in my country.
This section primarily studies application system design based on standardized integrated modules. Its content includes selecting appropriate modules according to the application, addressing the stability issues of multi-module systems, and optimizing the system design. Since a standardized series of modules has not yet been established, current research in this field mainly attempts to establish demonstration systems composed of modules to prove the feasibility and effectiveness of the power electronics integration concept.
A successful example is the integrated AC motor, in which a frequency converter with a power of about 1kW is integrated into the housing of the AC asynchronous motor, thus giving the motor adjustable speed performance, small size and high efficiency.
In addition, there are distributed power systems that employ integrated technologies, etc.
5. Conclusion
This article provides an overview of the concept, significance, and development of power electronics integration technology, details the major research institutions and research content in this field both domestically and internationally, and draws the following conclusions:
1) Power electronics integration technology is currently the most important research direction in the field of power electronics technology. It will inevitably become a research hotspot in the future and, to some extent, determine the future rise and fall of power electronics technology.
2) Monolithic integration, hybrid integration, and system integration can be seen as different levels and forms of power electronics integration. Currently, monolithic integration is limited to the low-power range, while hybrid integration or a combination of hybrid and system integration is mostly used in the medium-power field, and system integration still dominates in the high-power field. Due to their higher integration and better performance, monolithic integration and hybrid integration are the main development directions of future integration technologies.
3) At present, we should base ourselves on the existing level of technology, adopt reasonable integration degree and integration form according to the actual situation, and promote the practical application and industrialization of integration technology as soon as possible.
