Special power supply manufacturers tell you the ten major concerns for the development of switching power supply technology

Edit:Nanjing Fulaixiang Electronics Co., Ltd.UpDate:2018-06-29

Switching power supply has always been a very popular technology in the electronics industry, and its development trend is a problem that everyone must always pay attention to, otherwise it will not keep up with the pace of technological development if not paying attention.Special power supplyThe manufacturer tells you the ten major concerns for the development of switching power supply technology.

Focus one: performance of power semiconductor devices


In 1998, Infineon introduced the cold MOSFET, which adopts a "Super-Junction" structure, so it is also called a super-junction power MOSFET. The working voltage is 600V~800V, the on-state resistance is almost reduced by an order of magnitude, and the switching speed is still maintained. It is a promising high-frequency power semiconductor electronic device.


When the IGBT first appeared, its voltage and current ratings were only 600V and 25A. For a long time, the withstand voltage level was limited to 1200V~1700V. After a long period of research and improvement, the voltage and current ratings of the IGBT have reached 3300V/1200A and 4500V/1800A respectively, and the single-chip withstand voltage of the high-voltage IGBT has reached At 6500V, the upper limit of the working frequency of general IGBT is 20kHz~40kHz. The IGBT manufactured by applying new technology based on punch-through (PT) structure can work at 150kHz (hard switching) and 300kHz (soft switching).


The technological progress of IGBT is actually a compromise between on-state voltage drop, fast switching and high withstand voltage capability. With the difference in technology and structure, IGBT has the following types in the 20-year historical development process: punch-through (PT) type, non-punch-through (NPT) type, soft punch-through (SPT) type, trench type and electric field cut-off (FS) type.

Silicon carbide SiC is an ideal material for power semiconductor device wafers. Its advantages are: forbidden bandwidth, high operating temperature (up to 600°C), good thermal stability, low on-state resistance, good thermal conductivity, extremely small leakage current, PN junction High withstand voltage is conducive to the manufacture of high-frequency high-power semiconductor electronic components with high temperature resistance.


Focus Two: Power Density of Switching Power Supply


Improving the power density of the switching power supply, making it smaller and lighter, is the goal that people are constantly striving to pursue. The high frequency of the power supply is one of the hotspots in the international power electronics industry. Miniaturization and weight reduction of power supplies are particularly important for portable electronic devices (such as mobile phones, digital cameras, etc.). The specific methods to miniaturize the switching power supply include:


One is high frequency. In order to achieve high power density of the power supply, the operating frequency of the PWM converter must be increased, thereby reducing the volume and weight of the energy storage element in the circuit.


The second is the application of piezoelectric transformers. The application of piezoelectric transformers can enable high-frequency power converters to achieve lightness, smallness, thinness and high power density. Piezoelectric transformers use the unique characteristics of "voltage-vibration" transformation and "vibration-voltage" transformation of piezoelectric ceramic materials to transfer energy. Its equivalent circuit is like a series-parallel resonance circuit, which is one of the research hotspots in the field of power conversion.


The third is to use new capacitors. In order to reduce the size and weight of power electronic equipment, we must try to improve the performance of capacitors, increase energy density, and research and develop new capacitors suitable for power electronics and power supply systems, which require large capacitance, small equivalent series resistance, ESR, and volume. Wait a minute.


Focus three: high frequency magnetic and synchronous rectification technology


A large number of magnetic components are used in the power system. The materials, structure and performance of high-frequency magnetic components are different from those of power frequency magnetic components, and there are many problems that need to be studied. The magnetic materials used in high-frequency magnetic components have the following requirements: low loss, good heat dissipation performance, and superior magnetic performance. Magnetic materials suitable for megahertz frequencies have attracted attention, and nanocrystalline soft magnetic materials have also been developed and applied.


After the high frequency, in order to improve the efficiency of the switching power supply, it is necessary to develop and apply soft switching technology. It is a research hotspot in the international power supply industry in the past few decades.


For the soft switching converter with low voltage and high current output, the measure to further improve its efficiency is to try to reduce the on-state loss of the switch. For example, the synchronous rectification SR technology, which uses the reverse connection of the power MOS tube as the switching diode for rectification, instead of the Schottky diode (SBD), can reduce the tube voltage drop and improve the circuit efficiency.


Focus 4: Distributed power supply structure


The distributed power system is suitable for use as a power source for large workstations (such as image processing stations) and large digital electronic switching systems composed of ultra-high-speed integrated circuits. Its advantages are: modularization of dc/dc converter components; easy to achieve N+ 1 Power redundancy, easy to expand the load capacity; can reduce the current and voltage drop on the 48V bus; easy to achieve uniform heat distribution, easy to design for heat dissipation; good transient response; failed modules can be replaced online.


There are two types of distributed power systems, one is a two-level structure, and the other is a three-level structure.


Focus five: PFC converter


Since the input end of the ac/dc conversion circuit has rectifier components and filter capacitors, when the sinusoidal voltage is input, the power factor of the electronic equipment powered by the single-phase rectifier power supply is only 0.6 to 0.65 on the grid side (AC input end). Using PFC (power factor correction) converters, the grid-side power factor can be increased to 0.95 to 0.99, and the input current THD is less than 10%. It not only controls the harmonic pollution of the power grid, but also improves the overall efficiency of the power supply. This technology is called Active Power Factor Correction APFC. Single-phase APFC has been developed earlier at home and abroad, and the technology has been relatively mature; although there are many types of topology and control strategies for three-phase APFC, they still need to be researched and developed.


Generally, a high-power factor ac/dc switching power supply consists of a two-stage topology. For low-power ac/dc switching power supplies, the two-stage topology is generally low in efficiency and high in cost.


If the input power factor requirements are not particularly high, combine the PFC converter and the subsequent dc/dc converter into a topology to form a single-stage high power factor ac/dc switching power supply. Only one main switch tube can be used. The power factor is corrected to above 0.8 and the output DC voltage is adjustable. This topology is called a single-tube single-stage or S4PFC converter.


Focus 6: Voltage Regulator Module VRM


The voltage regulator module is a type of low-voltage, high-current output dc-dc converter module that provides power to the microprocessor.


Now that the speed and efficiency of data processing systems are increasing day by day, in order to reduce the electric field strength and power consumption of the microprocessor IC, the logic voltage must be reduced. The logic voltage of the new generation of microprocessors has been reduced to 1V, and the current is as high as 50A-100A. Therefore, the requirements for VRM are: low output voltage, large output current, high current change rate, fast response, etc.


Focus Seven: Fully Digital Control


The control of the power supply has been controlled by analog control and mixed analog-digital control, and has entered the fully digital control stage. Full digital control is a new development trend, which has been applied in many power conversion equipment.


But in the past, digital control was used less in dc/dc converters. In the past two years, high-performance full-digital control chips for power supplies have been developed, and the cost has been reduced to a reasonable level. Many companies in Europe and the United States have developed and manufactured digital control chips and software for switching converters.


The advantages of full digital control are: digital signals can be calibrated in smaller quantities than mixed analog-digital signals, and the chip price is lower; accurate digital correction of current detection errors can be carried out, and voltage detection can be more accurate; fast Flexible control design.


Concern eight: electromagnetic compatibility


The EMC problem of high frequency switching power supply has its particularity. The di/dt and dv/dt generated by the power semiconductor switch tube during the switching process cause strong conducted electromagnetic interference and harmonic interference. Some conditions will also cause strong electromagnetic field (usually near field) radiation. Not only seriously pollutes the surrounding electromagnetic environment, but also causes electromagnetic interference to nearby electrical equipment, and may also endanger the safety of nearby operators. At the same time, the internal control circuit of the power electronic circuit (such as the switching converter) must also be able to withstand the EMI generated by the switching action and the interference of the electromagnetic noise on the application site. The above-mentioned peculiarities, coupled with the specific difficulties in EMI measurement, in the field of electromagnetic compatibility of power electronics, there are many cutting-edge topics of cross-border science to be studied. Many universities at home and abroad have carried out research on electromagnetic interference and electromagnetic compatibility of power electronic circuits, and have achieved many gratifying results. Research results in recent years have shown that the source of electromagnetic noise in switching converters mainly comes from the voltage and current changes produced by the switching action of the main switching device. The faster the change rate, the greater the electromagnetic noise.


Focus Nine: Design and Test Technology


Modeling, simulation and CAD are a new design tool. In order to simulate the power system, a simulation model must be established first, including power electronic devices, converter circuits, digital and analog control circuits, and magnetic components and magnetic field distribution models. The thermal model, reliability model and EMC model of the switch tube must also be considered. . Various models are very different, and the development direction of modeling is: digital-analog hybrid modeling, hybrid hierarchical modeling, and combining various models into a unified multi-level model.


The CAD of the power supply system includes main circuit and control circuit design, device selection, parameter optimization, magnetic design, thermal design, EMI design and printed circuit board design, reliability estimation, computer-aided synthesis and optimization design, etc. The use of simulation-based expert system for power system CAD can make the designed system perform better, reduce design and manufacturing costs, and perform manufacturability analysis. This is one of the development directions of simulation and CAD technology in the 21st century. In addition, the development, research and application of technologies such as thermal testing, EMI testing, and reliability testing of power systems should also be vigorously developed.


Focus ten: system integration technology


The manufacturing characteristics of power supply equipment are: many non-standard parts, high labor intensity, long design cycle, high cost, low reliability, etc., and users require the power supply products produced by the manufacturer to be more practical, lighter and smaller, and lower in cost. These conditions put power manufacturers under tremendous pressure and urgently need to carry out research and development of integrated power modules, so that the goals of standardization, modularization, manufacturability, mass production, and cost reduction of power supply products can be achieved. In fact, in the development process of power integration technology, it has gone through the development stages of modularization of power semiconductor devices, integration of power and control circuits, and integration of passive components (including magnetic integration technology). In recent years, the development direction is to integrate the low-power power supply system on a chip, which can make the power supply products more compact, smaller in size, and reduce the lead length, thereby reducing the parasitic parameters. On this basis, integration can be achieved, with all components and control and protection integrated in one module.

Special power supply manufacturers summarized the ten major concerns for the development of switching power supply technology for you! hope it is of help to you!