First, strong market demand, development has always been an important driving force switching power supply
Switching power supply technology is a power electronics technology, the use of power converters for power conversion, after transform electrical energy to meet all electricity demands. Because of its high efficiency can bring significant economic benefits, and thus attracted the attention of all aspects of the rapidly promotion.
To AC-DC transformation, for example, the traditional use of frequency power conversion technology, compared with control, using high-power high-frequency switch rectifier power supply is a leap forward in technology, it not only easy to get different voltage grade, more importantly, got rid of large bulky body frequency transformer and filter inductor capacitor. As a result of high frequency power conversion, power supply units to significantly reduce the size and weight, which may host size and equipment in coordination and make electric properties are further improved. That is why in 1994 the Ministry of Posts and Telecommunications Woguo original for major policy decisions Yaoqiu communication Lingyutuiguang Shiyong phase-controlled switching power supply to replace the power supply. Years of practice proven, Zhe Yi decision is entirely correct. the use of switching power supply for the country save a lot of copper, steel and covers. Since transformation efficiency, reduce energy consumption and reduce the power room-temperature environment, improve the environment for staff. My extensive use of post and telecommunications sector switching power supply greatly promote its wider application in other areas. It is worth noting that the last two years there's power system DC operating power, is investing 400 billion yuan for the state for urban and rural power grid reconstruction of power supply projects to improve transportation put on distribution power quality, and Ta has Kaishicaiyong switching power supply to replace the traditional Xiang Yi-controlled power supply. Guonei number of communications companies Ru Tong Xun Deng Zhongxing Xi Lie products have been launched one after another. Muqian, Guonei switching power supply manufacturers have Zizhuyanfa and Shengchan 300 over, there were more than a dozen scale. made switching power supply has occupied a considerable market, large companies such as ZTE's power products developed have been widely recognized, quite in the power market competition advantage, and a little start Chukou .
Second, switching power supply 21 Prospects
Energy plays a key role in modern society. Power electronic power conversion technology for its flexible approach, high performance, high power density, high efficiency, in the 21st century will be greatly develop the switching power supply is in the possession of power electronics technology is An important aspect of a large proportion.
1. Semiconductors and circuit switching power supply device is an important support for the development of
Power semiconductor devices power electronics technology is still the "leading", the progress of power electronics has introduced a new must rely on power electronic devices.
Power FET (MOSFET) as conductive unipolar more children significantly reduces the switching time, which can be easily achieved 1MHz switching frequency and the spotlight. But the MOSFET, the device blocking voltage must be added to improve width devices, the drift region, resulting in the device resistance increases rapidly, the device on-state voltage drop increased on-state losses increase, we can only apply to small and medium-power products. In order to reduce on-state resistance, the U.S. unit of IR Company with increased area of the original cell number of ways. such as IR has developed a HEXFET MOSFET, the trench (Trench) of the original cell density has reached 112 million per square inch of the world's highest level of up-state resistance R 3mΩ. Power MOSFET, 500V, TO220 package HEXFET since 1996, its on-state resistance of 50% annual rate of decline. IR has also developed a low gate charge (Qg) of the HEXFET, the faster switching , taking into account the on-state resistance and gate charge reduces both, the R × Qg of 30% per year decline rate. Schottky diodes for the development, the recent use of Trench structure, is expected to show a smaller drop Schottky diode, called TMBS-trench MOS barrier Schottky, which may in very low supply voltage applications, the MOSFET synchronous rectification and competition.
As semiconductor devices silicon material "rule" of semiconductor devices has been more than 50 years, to further tap the potential of silicon performance is difficult. The material of semiconductor devices from the 70's, 80 to 90 years in particular, since the gallium arsenide ( GaAs), semiconductor diamond, silicon carbide (SiC) of the study has a. into the 90s after the study of the silicon carbide to the hot spots. experiment showed that application of SiC semiconductor devices their resistance only Si device 1 / 200; such as high-voltage silicon power MOSFET, conduction voltage drop up to 3 ~ 4V, while the SiC power MOSFET, conduction voltage drop is less than 1V, and turn-off time is less than 10ns. Experiments show that the voltage up to 300V of SiC Shaw Schottky diode (the other electrode of gold, palladium, titanium, cobalt may be), the reverse leakage current of less than 0.1mA/mm, while the reverse recovery time is almost zero.
GaAs has been for some time that a promising material to replace silicon semiconductors. Now experiments show that the superior performance of silicon carbide materials. SiC research it lags behind GaAs, mainly due to the difficulty of making SiC crystals too, when the temperature is higher than 2000 ℃ when, SiC has not yet melted, but at 2400 ℃ SiC has been sublimated into a gas when a. Now is the sublimation method using crystal growth directly from the gas state, the current problem is to further improve the SiC surface with metal contact characteristics and further development of SiC manufacturing process, these issues are expected to be resolved 5 to 10 years. When the application SiC semiconductor devices are manufactured in a wide range applications, the impact on power electronic technology will be revolutionary.
Transformer is the power electronics or switching power supply indispensable in the important parts, planar transformers are available in the past two years a new product. And different from conventional transformers, planar transformers without copper wires and replace them with single or multiple layer printed circuit board, which is far less than the thickness of conventional transformers, can be directly produced in the printed circuit board. Its advantage is the high energy density, thus greatly reducing the volume, equivalent to 20% of conventional transformer; efficiency, typically 97% ~ 99%; high frequency from 50kHz to 2MHz; low leakage inductance (less than 0.2%); low electromagnetic interference (EMI) and so on.
Piezoelectric transformer is the application of mechanical energy → electrical energy → electrical energy of a new transformer, which is the use of piezoelectric ceramic electrostrictive characteristics of the forward and reverse made. Two piezoelectric ceramic close firmly together, will the primary alternating voltage is applied to a piezoelectric ceramic of the horizontal axis, this piece will have a vertical piezoelectric mechanical vibration Ershi another solid combination of piezoelectric film along with a vertical vibration, this time in its horizontal axis the direction of a voltage secondary output voltage. current transformer power is not large, suitable for high voltage and current of smaller applications, such as lighting the lamp starter device. hypervolemic capacitor parts capacitor is the latest development in recent years, United States of Maikeweier has been kept hypervolemic capacitor technology, the world leader. hypervolemic capacitor using a unique metal / carbon electrode technology and advanced non-aqueous electrolyte, is of great Dianji surface He minimum of Xiangduijuli. have been developed to produce a broad scope of application of a variety of super-capacity capacitor modules and components, cell capacity of small to 10F, Tai to 2700F. hypervolemic series capacitor can be easily combined into a high-voltage components or parallel to form high-energy storage group pieces. hypervolemic capacitor components are now available 650V high-voltage high-energy applications.
Super-capacity capacitor has wide application prospects. Use of ultra-capacity capacitor can make semiconductors, paper, textile and other industries highly automated manufacturing systems from power fluctuations and temporary interruptions caused by huge losses; super-capacity capacitors for hospital or utilities and other emergency generator must be used in power supplies, provide bridging power, constitute a short-term uninterruptible power supply. for new electric vehicles or hybrid electric vehicles, super-capacity capacitor can be added even as the battery replacement.
2. Circuit integration and system integration and packaging technology
Power electronic products and circuit development is modular and integrated. With a variety of control functions of the special chip, developing rapidly in recent years, such as power factor correction (PFC) circuit with the control chip; soft switch controlling the ZVS , ZCS chip; phase full-bridge control chip used; ZVT, ZCT PWM control chip special; Parallel flow control chip; current feedback control chips. power semiconductor devices have power integrated circuit (Power IC) and IPM.IPM to IGBT as power switches, will control, drive, protection, detection circuit with encapsulated in a module. due to external wiring, solder joints decreased significantly improved reliability. integrated, modular power supply products to small size, high reliability, to Application of a great convenience.
Circuitry in the direction of the system further Fazhan . As now the inverter is for 200 ~ 300 parts assembled together to become a Xitong. This approach time-consuming and labor and costly, also do Tijihenxiao Nan Yu . U.S. VICOR produced by the first generation of the power module production technology, power, magnetic components and packaging technologies limit the volume, density has been unable to exceed cubic inch 80W. In recent years, introduced the second generation of the power module, the internal structure also changed for the module type, to a high degree of integration and fully computerized. power density has reached a per cubic inch 120W. power module contains only the first generation device 1 / 3, the 115 was reduced to 35. the second generation of power modules The control circuit contains only two components, known as the "brain" (Brain). "brain" is two thick film circuit, by the VICOR's own self-development and production of clean room, the total volume of only 0.1in3, replaced The first generation of products of about 100 control elements, the volume reduced by 60%. the second generation of products is another breakthrough in the improvement of transformers, shielded structure and the copper core, the primary and secondary coil around both sides of the split The temperature is very low. parasitic capacitance and common-mode noise is very low. transformer processing power density per cubic inch 1000W, temperature rise of only 3 ℃. the second generation power device die soldered directly to the substrate to replace the The first generation of TO-200 package, you can improve the cooling efficiency and reduce parasitic inductance, capacitance and resistance. the second generation product of integration clearly raised, but not the system integration. Professor Li Zeyuan leadership of the United States Power Electronic Systems Center (Center of Power Electronics Sys tems, referred to as CPES) has proposed the idea of systems integration, information transmission, control and power semiconductor devices all integrated to form the connection between the components to increase reliability without wires, using three-dimensional method of heat dissipation to improve the cooling, it is possible to power from low power (hundreds of watts ~ kW) to achieve high power (tens of kilowatts and above). the result of system integration can change the current semi-automatic, semi-manual assembly process may be completely automated production, which can reduce the cost, there is generally conducive to the promotion application. Professor Li Zeyuan Zhengzai application of this Shexiang, to CPES Jiehe several universities in the U.S. specialty, doing system integration of electrical Qudong. System Integration of Di Yibu yes Ba inverse Transformer made a module, drive circuit, protection circuit be put to; second step is to do with the inverter and the motor to form a system integration. there is but one example, Intel's microprocessor is the leading These years of development trend is faster, lower voltage, current capacity need has been increasing. Muqian Intel microprocessors working voltage is 2 ~ 3V/10A, operating frequency is 300MHz. expected even after two years take two years, its voltage will be reduced to 1V, the current 30 ~ 50A, operating frequency of 1GHz. is that it is close to the microprocessor to switch power supply, switching power supply in order to quickly provide current to the microprocessor speed This may still meet the requirements of existing microprocessors. but in the future lower voltage microprocessor, current increases faster when the current solution will not meet its requirements. Three years ago, Professor Li Zeyuan proposed solve Wen Ti, Bi Xu Jie He will switch with the power supply and microprocessor. Today, Intel Corporation most Jieshou the Zheyi Xiangfaerzai Jijicucheng matter. raised the idea is: switching power supply combined with the Weichuliqi Zhu Ji Jin Mi board below. that the size of switching power supply and microprocessor to be equal to the switching power supply and now a few times great than the microprocessor. how to reduce the size? it is facing new challenges!
Can be expected, the following questions are eternal switching power supply development direction:
(1) switching power supply frequency is higher, so be fast dynamic response, with high-speed microprocessor is required; is also an important way to reduce the volume.
(2) to reduce the size of the transformer inductance, capacitance should decrease the volume.
(3) speed, the heat is reduced, heat will be easy, easy to achieve high power density.
Power Electronics Technology is important to support science and technology, according to the U.S. President on Science and Technology Advisory Committee suggested that the national key science and technology has seven areas: energy, environmental protection, information and communications, life sciences, materials and transportation. No one in each field and power electronics are not related, are playing an important role, and switching power supply is an important aspect of which has a far-reaching prospects.