A brief discussion on high-power digital power products

1 Introduction

In the 1960s, switching power supplies came into being and gradually replaced linear regulated power supplies and thyristor phase-controlled power supplies. Over the past 40 years, switching power supply technology has developed and changed rapidly, and has gone through three major technical development stages: application of power semiconductor devices, high frequency and soft switching technology, and comprehensive integration of switching power supply systems. Since the 1980s, the development and research of high frequency and soft switching technology have made power converters more efficient, better performing, lighter, and smaller in size. High frequency and soft switching technology have been one of the hot topics in the international power electronics research community over the past 20 years. In the mid-1990s, integrated power electronic systems and integrated power electronic module technologies began to develop, becoming a problem that the international power electronics industry has been working hard to solve in the past decade. Improving the high efficiency performance of power semiconductor devices, improving the power density of switching power supplies, applying computer-aided design and testing technology, applying high-frequency magnetic integration and synchronous rectification technology, modular distributed power supply structure design, high-density integration of power supply systems, and low-pollution electromagnetic compatibility design are hot topics in modern power supply technology. Power supply digital control has also become a new development trend and has gradually been promoted and applied in power conversion equipment. The industry calls power conversion products that use digital control technology digital power supplies. In recent years, high-power digital power supply technology with digital signal processors as the core control has become a research topic that has attracted the attention of many universities, power electronics technology professional institutions and power system providers. Many related technical papers are published every year at home and abroad. A few power supply manufacturers have begun to gradually launch fully digital power supply products after years of dedicated research and development, especially high-power uninterruptible power supplies and communication power supplies...

High efficiency performance of power semiconductor devices, improving the power density of switching power supplies, application of computer-aided design and testing technology, application of high-frequency magnetic integration and synchronous rectification technology, modular distributed power supply structure design, high-density integration of power supply systems, low-pollution electromagnetic compatibility design, etc. are the hot spots of modern power supply technology. Digital control of power supply has also become a new development trend and has gradually been promoted and applied in power conversion equipment. The industry calls power conversion products using digital control technology digital power supply. In recent years, high-power digital power supply technology with digital signal processor as the control core has become a research topic valued by many universities, power electronics technology professional institutions and power system providers. Many related technical papers are published every year at home and abroad. A few power supply manufacturers have begun to gradually launch fully digital power supply products after years of dedicated research and development, especially high-power uninterruptible power supplies and communication power supplies.

2 Digital Power Overview

2.1 Basic Features

Digital power supply is a new power supply technology that uses digital methods to achieve power supply control, protection and communication interface. Programmable, excellent response characteristics and digital loop control are the three main features that characterize digital power supply. After digitization, the power supply has strong adaptability and flexibility, and has the ability to directly monitor the operating status, which can meet the needs of most power users. The automatic diagnosis and online output adjustment capabilities of digital power supply make debugging and maintenance work easy. Remote diagnosis can also be used to ensure the reliability of the system for continuous operation, and realize fault alarm management, multi-level protection of overvoltage and overcurrent, automatic redundant parallel connection and other functions.

2.2 Comparison between digital power supply and analog power supply

Compared with analog control technology, digital power supply greatly reduces the common errors and aging problems in analog power supply, including the accuracy of analog devices, temperature influence, drift, nonlinear compensation problems, etc. Its stable control parameters make it possible to obtain good consistency without fine adjustment of individual products, with good reliability and manufacturability. Digital control technology based on or high-speed microprocessors, in addition to the characteristics of digital control technology itself, also has its unique advantages due to its faster data processing capabilities, including the realization of more advanced control algorithms, better optimization efficiency, higher data sampling accuracy and control switch adjustment frequency, higher control accuracy and reliability, and excellent system management and Internet network monitoring functions.

The digital power control algorithm based on high speed and high performance is implemented by software. The software operation characteristics make it easier to implement nonlinear control, improve the transient response capability of the power supply, and adopt more optimized control algorithms such as multi-loop control. In many cases, updating the software can realize new topology structures and control algorithms, and changing the power output parameters does not require changing the components on the board. In this way, the reuse rate of the hardware platform can be improved. By designing different software, the new needs of various personalized power systems can be met, thereby shortening the development cycle, reducing development costs, speeding up product launch, and reducing the productive inventory and risks of components. Although digital power has many advantages, there are still some disadvantages that cannot be ignored. Analog control has a small reaction delay to changes in external conditions, while digital power requires a sampling, quantization and processing process to feedback and adjust the changes. Therefore, its response speed to changes in external conditions is generally not as fast as that of analog power. Due to the quantization error of conversion, digital power is also slightly worse than analog power in terms of resolution, bandwidth, voltage compatibility with power components, power consumption, switching frequency, accuracy, efficiency and material cost in low-power power supply systems. However, in the application of large-scale power supply products, with the introduction of high-speed and high-performance dedicated power control technology, high-frequency power supply and soft switching technology are easier to achieve, while the price is constantly decreasing. The digital system it constitutes has a higher degree of integration, and the use of digital power supply solutions is becoming more and more advantageous. The long-term comprehensive cost is not necessarily higher than that of analog power supply, and there is more room for obtaining economic benefits through technology. This is more evident in the market demand for communication power supply, industrial power supply, power control power supply, and uninterruptible power supply for the financial industry and service industry. The economic advantages of digital power supply are more apparent. See Table 1.

2.3 Analysis of Digital Power Productization Trend

It can be seen that compared with analog power supply, the technology contained in digital power supply is undoubtedly more complicated, and some new technologies are needed. However, for users, the use of digital power supply is not complicated, and it is easier to use if it is well designed. With the development of technology, some disadvantages of current digital power supply can already meet user needs, but its monitoring and management functions are improved and testability is good, and user maintenance is more convenient, which can greatly reduce the user's operating and management costs. It only requires product designers to have higher design capabilities, which users do not care about. Of course, new products or technologies are often skeptical of users. Can reliability really bring benefits? These need to be guided. Marketing can be solved through free trials or post-payment. Compared with the rapid launch of products that are more adapted to market demand, thereby occupying a broader market, coupled with the technology accumulation effect and rapid product upgrades, reducing bad inventory turnover, and reducing comprehensive production management costs through large-scale production, power product providers will have better long-term economic benefits. Therefore, this high-tech requirement is also very willing to be accepted by power product suppliers who drive market research and development or win benefits with technology. In this way, it is beneficial to both buyers and sellers, thus forming a strong market driving force, and the general trend of power products developing towards full digital control technology in the future will naturally form.

The power digital control technology based on power electronics involves multiple disciplines such as power electronics, automatic control, data processing, and communication technology. Its technical difficulty is naturally not low. Although many technical papers in this area can be searched from academic journals and online media, there are many articles that analyze the principles of power control technology very thoroughly. However, in the process of transforming technical achievements into products and industrialization, its difficulty is even greater than the product digitization process in other industries. This may be one of the main reasons why the concept of fully digital power supply has not been widely used since the beginning of the century. The author's company is a well-known high-tech listed company in China. Its main business is communication equipment products. One of its communication power supply product lines is to develop and produce communication combined power supply, communication uninterruptible power supply and other products. The annual output value of marketing at home and abroad is several billion yuan. The product research and development investment is very large. It has experienced the entire process of high-frequency switching power supply development and accumulated many key technologies and unique technologies. In recent years, a lot of efforts have been made to promote the development of digital power supply technology. From power supply monitoring digitization to power supply control digitization, in-depth research has been carried out, and the ups and downs of product development have been tasted, and good economic benefits have been obtained. This article is based on the research process of the productization of power supply digital control technology in communication power supply and uninterruptible power supply. It briefly introduces some non-principle technical problems that need to be solved in the productization of full digital power supply, from which we can get a glimpse of the practice of productization of technological achievements.

One of the main reasons. The company where the author works is a well-known domestic high-tech listed company. Its main business is communication equipment products. One of its communication power supply product lines is to develop and produce communication combined power supplies, communication uninterruptible power supplies and other products. The annual output value of domestic and foreign sales reaches tens of billions of yuan. The investment in product research and development is huge. It has experienced the entire process of high-frequency switching power supply development and accumulated many key technologies and unique technologies. In recent years, it has made a lot of efforts to promote the development of digital power supply technology. From the digitalization of power supply monitoring to the full digitalization of power supply control, it has conducted in-depth research, tasted the ups and downs in the product development process, and also obtained good economic benefits. This article is based on the productization research process of power supply digital control technology in communication power supply and uninterruptible power supply. It briefly introduces some non-principle technical problems to be solved in the productization of full digital power supply, from which we can get a glimpse of the practice of productization of technical achievements.

3 Productization Case Analysis

3.1 Communication power supply

The important component of the combined power supply for communication is the rectifier module. As the main body of power conversion, the function of the rectifier module is to input sinusoidal AC from the power grid and convert it into low-voltage DC output through rectification. At present, the communication industry has relatively high requirements for power supply and has formulated strict network standards. Performance indicators such as conversion efficiency, input current harmonic content, input power factor, output voltage ripple, output voltage stability, and output dynamic response are all basic parameters that users attach great importance to. Therefore, ordinary rectification and conversion methods are difficult to meet, and measures such as power factor correction and electromagnetic compatibility design are needed. This raises many technical issues. Figure 1 shows the rectifier design technology of a three-phase two-stage circuit structure with no neutral line input.

For the fully digital communication power rectifier module, the technical issues that need to be solved during the productization process include but are not limited to the above-mentioned technical issues. Since its control has realized most of the signal acquisition and digitization, some signal acquisition circuits can be omitted in the design of monitoring communication components and shared with the information required for control.

3.2 Uninterruptible Power Supply

Uninterruptible power supply has a very broad market both at home and abroad, especially the double conversion online type, which is widely favored by users for its good input and output performance, and occupies most of the market, and its proportion continues to expand. The important components of the online type are the rectifier and the inverter. The two components are the main body of power conversion. The function of the rectifier is to input the sinusoidal AC from the power grid, transform it into high-voltage DC through rectification, and then the inverter completes the conversion of high-voltage DC into stable AC output.

Similarly, the communications industry has relatively high performance requirements and has formulated strict human network standards. Performance indicators such as conversion efficiency, input current harmonic content, input power factor, output voltage harmonic content, output voltage regulation accuracy, and output voltage dynamic response are all basic needs that users attach great importance to. Therefore, ordinary rectification and conversion methods are difficult to meet, and measures such as inversion and design are needed. This has raised many new technical issues.

As for the technology required for the commercialization of uninterruptible power supply, compared with the rectifier, most of them can be regarded as high-power power supply, and their technical composition structure is different. From the technical structure diagram shown in the figure, it can be seen that compared with the rectifier module, there is an additional "bypass control" component, and a "conversion" component replaces the "two-conversion component" of the rectifier, which is actually a "one-conversion component". The technical difficulty in inverter control is also much greater than that of rectifier control. Figure 2 shows the distributed bypass three-phase input and three-phase output sine wave online or module design technology structure.

4 Key points for commercialization of digital control technology achievements

4.1 Technical development requirements

Some of the technical items listed above may overlap or cross in actual product development. Technical topics such as "power factor correction function control algorithm", "high-efficiency soft switch control algorithm" and "output voltage high-precision voltage regulation control algorithm" have been deeply studied in many colleges and universities. Generally speaking, there is basically no problem in principle, which is also the focus of power digital technology. It just needs to be verified in practice. In the process of technology moving towards productization, since the actual circuit implementation and input and output environment are not ideal models, there are often deviations or even large differences between the results of theoretical simulation and the productization situation. It is always necessary to introduce a lot of engineering ideas to deal with and solve them, such as "signal acquisition and correction design technology", "control technology when input voltage is unbalanced", "output DC voltage midpoint balance control technology", whether there is a neutral line in the input and output, rapid protection of input and output abnormal conditions, and various logic function realizations, etc. In the process of product development, the solution of these non-pure principle technical problems always requires multi-level comprehensive application development on some basic technologies, and needs to be designed and continuously supplemented and improved according to the business needs of the product. According to the traditional waterfall development model, this often requires more R&D resources and takes longer R&D time.

4.2 Productization process management reference

It is self-evident that the development process of digital high-power power supply products requires a large investment of resources. However, the proportion of software development in the development process is relatively larger than that of low-power digital power supply, and it is mainly the development of embedded software, some of which are highly related to hardware. However, apart from these technical and algorithm parts related to circuit topology, software development is easier to achieve modularization. There is a lot of work that can be gradually accumulated and transplanted on different hardware platforms. Some proven and mature modules can be shared in different products to enhance the competitiveness of the company's core technology. For software development, the realization of user functional requirements can completely follow the usual software development model, such as incremental model and iterative model.

General software development process management tools as well as software development, testing and verification tools and methods can be applied. The improvement of software development process capability maturity will also improve the product development process capability maturity, and the quality of the product will steadily improve. Through the improvement and enhancement of process capability, the dependence of product quality on the personal capabilities of a few R&D personnel can be weakened. Through project management, each part of the technology required for the product can be more professional and the capability level can be improved faster. Through team operation, its technical capability level will be determined by the overall capability of the team. If the team operation is relatively successful, the overall capability of the team can reach or exceed the highest level of the team members. In this way, the final product R&D capability can be as good as possible in all aspects, and the final product R&D quality will naturally be good. In fact, this kind of team operation management has relatively mature models in many companies, and the general team management model is also applicable, which can be used as a reference.

5 Conclusion

Through independent pre-research of key technologies, we will concentrate superior resources on project development, lay a solid foundation, master core technologies, and form a technical platform for R&D work that takes a long time, affects product performance, and has greater technical risks. We will develop general comprehensive application technologies and functional realizations as a series of product optimization and improvement projects, and then choose the right time to integrate them according to market demand conditions. Only through such a productization process can we successfully develop popular products with rich functions, excellent performance, exquisite process technology, high reliability, easy use and maintenance, good economy, and users are willing to accept.