Development stage of electronic technology

Electronic technology is a new technology developed at the end of 19 and the beginning of the 20th century. It developed most rapidly and was widely used in the 20th century, and became an important symbol of the development of modern science and technology. 1at the end of the 8th century1at the beginning of the 9th century, due to the needs of production development, the research work in electromagnetic phenomena has developed rapidly. 1895, H.A. Lorenz assumed the existence of electrons. 1897, J. J. Thompson discovered electrons through experiments. 1904, J.A.Fleming invented the simplest diode (diode or valve) to detect weak radio signals. 1906, L.D.Forest installed the third electrode (gate) in the diode and invented the transistor with amplification function, which was the most important milestone in the history of early electronics. Several researchers at Bell Laboratories invented the transistor. The world has seen the first sample of 1958 integrated circuit. The appearance and application of integrated circuits mark the development of electronic technology to a new stage.

Electronic technology studies the application of electronic devices and circuits composed of electronic devices. Semiconductor devices are the most basic components of various discrete and integrated electronic circuits. With the rapid development of electronic technology, various new semiconductor devices emerge one after another. The development direction of modern power electronics technology is to change from the traditional power electronics with low frequency technology to the modern power electronics with high frequency technology. Power electronics technology began with silicon rectifier devices in the late 1950s and early 1960s, and its development has gone through rectifier era, inverter era and frequency converter era, which promoted the application of power electronics technology in many new fields. The power semiconductor composite devices with high frequency, high voltage and high current, represented by power MOSFET and IGBT, developed in the late 1980s and early 1990s, indicate that the traditional power electronics technology has entered the modern power electronics era. Efficient green computer power supply

The rapid development of computer technology has led mankind into the information society and promoted the rapid development of power technology. In the 1980s, computers adopted switching power supply in an all-round way, taking the lead in replacing computer power supply. So switching power supply technology has entered the field of electronic and electrical equipment.

With the development of computer technology, green computer and green power supply are put forward. Green computer generally refers to personal computers and related products that are harmless to the environment, and green power supply refers to high-efficiency and energy-saving power supply related to green computers. According to the "Energy Star Program" of the US Environmental Protection Agency 1992 in June, if the power consumption of desktop personal computers or related peripheral devices is less than 30 watts, it meets the requirements of green computers. Improving power efficiency is the fundamental way to reduce power consumption. As far as the current 75% efficient 200-watt switching power supply is concerned, the power supply itself consumes 50 watts of energy.

Communication with High Frequency Switching Power Supply

The rapid development of communication industry has greatly promoted the development of communication power supply. High-frequency miniaturized switching power supply and its technology have become the mainstream of modern communication power supply system. In the field of communication, rectifier is usually called primary power supply, while DC/DC converter is called secondary power supply. The primary power supply is used to convert a single-phase or three-phase AC power grid into a DC power supply with a nominal value of 48V. At present, the traditional phase-controlled stabilized power supply has been replaced by high-frequency switching power supply in the primary power supply of program-controlled switches. High-frequency switching power supply (also known as switching rectifier SMR) works through the high frequency of MOSFET or IGBT, and the switching frequency is generally controlled in the range of 50- 100kHz, which realizes high efficiency and miniaturization. In recent years, the power capacity of switching rectifiers has been continuously expanded, and the single-machine capacity has been expanded from 48V/ 12.5A and 48V/20A to 48V/200A and 48V/400A.

Because there are many kinds of integrated circuits used in communication equipment, their power supply voltages are also different. In the communication power supply system, the high-frequency DC-DC isolated power supply module with high power density is used to convert the intermediate bus voltage (generally 48V DC) into various DC voltages, which can greatly reduce the loss and facilitate maintenance, installation and increase. Generally, it can be directly installed on the standard control panel, and the requirement for secondary power supply is high power density. Due to the continuous increase of communication capacity, the capacity of communication power supply will also increase.

DC-DC converter

A DC/DC converter converts a fixed DC voltage into a variable DC voltage. This technology is widely used in stepless speed change and control of trolleybuses, subway trains and electric vehicles. At the same time, the above control can achieve the performance of acceleration, stability and rapid response, and at the same time, it can save electricity. Replacing rheostat with DC chopper can save energy by 20 ~ 30%. DC chopper can not only adjust the voltage (switching power supply), but also effectively suppress the harmonic current noise on the grid side.

The secondary DC/DC converter of communication power supply has been commercialized. The module adopts high frequency PWM technology, the switching frequency is about 500kHz, and the power density is 5W~20W/in3. With the development of large-scale integrated circuits, the miniaturization of power modules is required, so it is necessary to continuously improve the switching frequency and adopt a new circuit topology. At present, some companies have developed and produced secondary power modules with zero-current switching and zero-voltage switching technology, and the power density has been greatly improved.

Uninterruptible power supply (UPS)

Uninterruptible power supply (UPS) is a kind of high reliability and high performance power supply, which is suitable for computers, communication systems and occasions requiring uninterrupted power supply. The AC mains input is converted into DC through the rectifier, and part of the energy is used to charge the battery, and the other part is converted into AC through the inverter and sent to the load through the transfer switch. In order to provide energy to the load when the inverter fails, another standby power supply is realized through the power transfer switch.

Modern UPS generally adopts pulse width modulation technology and modern power electronic devices such as M0SFET and IGBT, which reduces power supply noise and improves efficiency and reliability. The introduction of microprocessor software and hardware technology can realize intelligent management, remote maintenance and remote diagnosis of UPS.

At present, the maximum capacity of online UPS has reached 600kVA. Ultra-small UPS has also developed rapidly, and its products have specifications such as 0.5kVA, lVA, 2kVA and 3kVA.

Inverter power supply

Inverter power supply is mainly used for variable frequency speed regulation of AC motor, which plays an increasingly important role in electric drive system and has achieved great energy-saving effect. The main circuit of inverter power supply adopts AC -DC- AC scheme. The power frequency power supply is converted into a fixed DC voltage through a rectifier, and then the DC voltage is converted into an AC output with variable voltage and frequency by a PWM high-frequency converter composed of high-power transistors or IGBT. The output waveform of power supply is similar to sine wave, which is used to drive AC asynchronous motor to realize stepless speed regulation.

The series products of inverter power supply below 400kVA in the world have come out. In the early 1980s, Toshiba Corporation of Japan first applied AC variable frequency speed regulation technology to air conditioners. By 1997, its share has reached more than 70% of Japanese household air conditioners. Frequency conversion air conditioner has the advantages of comfort and energy saving. Domestic research on inverter air conditioners began in the early 1990s. 1996 introduced a production line to produce inverter air conditioners, which gradually became a hot spot in R&D and production of inverter air conditioners. It is expected to reach its climax around 2000. In addition to variable frequency power supply, variable frequency air conditioner also needs a compressor motor suitable for variable frequency speed regulation. Optimizing control strategy and selecting functional components are the further development direction of air conditioning variable frequency power supply.

High frequency inverter rectifier welding machine power supply

High frequency inverter rectifier welding machine power supply is a new welding machine power supply with high performance, high efficiency and material saving, which represents the development direction of welding machine power supply today. Because of the commercialization of IGBT large-capacity module, the power supply has a broader application prospect.

Ac -DC- AC -DC (AC -DC- AC -DC) conversion method is mostly used for inverter welding machine power supply. 50Hz alternating current is converted into DC by full-bridge rectification, and the PWM high-frequency conversion part composed of IGBT converts DC into 20kHz high-frequency rectangular wave, which is coupled, rectified and filtered by high-frequency transformer to become a stable DC of power arc.

Due to the harsh working conditions of welding machine power supply, short circuit, arc and open circuit frequently occur, so the working reliability of high frequency inverter rectifier welding machine power supply has become the most critical issue, and it is also the most concerned issue for users. The microprocessor is used as the relevant controller of pulse width modulation (PWM). Through the extraction and analysis of various parameters and information, the purpose of predicting various working States of the system is achieved, and then the system is adjusted and processed in advance, which solves the reliability problem of the current high-power IGBT inverter power supply.

Foreign inverter welding machines have achieved rated welding current of 300A, load duration of 60%, full load voltage of 60~75V, current adjustment range of 5~300A and weight of 29kg.

High power switching high voltage DC power supply

High-power switching high-voltage DC power supply is widely used in electrostatic dust removal, water quality improvement, medical X-ray machine and CT machine and other large equipment. The voltage is as high as 50~l59kV, the current is above 0.5A, and the power can reach 100kW.

Since the 1970s, some Japanese companies have started to adopt inverter technology, which rectifies the commercial power and inverts it to an intermediate frequency of about 3kHz, and then boosts it. In 1980s, the technology of high-frequency switching power supply developed rapidly. Siemens Company of Germany adopts power transistor as the main switching element, which increases the switching frequency of power supply to above 20kHz. Dry-type transformer technology has been successfully applied to high-frequency and high-voltage power supply, eliminating the oil tank of high-voltage transformer and further reducing the volume of transformer system.

China has developed a high voltage DC power supply for electrostatic precipitator. The mains electricity is converted into DC after rectification. DC voltage is converted into high-frequency voltage by full-bridge zero-current switch series resonant inverter circuit, then boosted by high-frequency transformer, and finally rectified into DC high voltage. Under the condition of resistive load, the output DC voltage reaches 55kV, the current reaches 15mA, and the working frequency is 25.6kHz.

Active power filter

When the traditional AC DC converter is put into operation, it will inject a lot of harmonic current into the power grid, causing harmonic loss and interference, and at the same time, the power factor of the equipment network side will deteriorate, which is called "power pollution". For example, with uncontrolled rectification and capacitive filtering, the third harmonic content on the grid side can reach (70-80)%, and the power factor on the grid side is only 0.5-0.6.

Active power filter (APF) is a new type of power electronic device which can dynamically suppress harmonics. It can overcome the shortcomings of traditional LC filter and is a promising harmonic suppression method. The filter consists of a bridge switching power converter and a specific control circuit. The difference from the traditional switching power supply is that (1) not only feeds back the output voltage, but also feeds back the average input current; (2) The current loop reference signal is the product of the voltage loop error signal and the full-wave rectified voltage sampling signal.

Distributed switching power supply system

The distributed power supply system takes low-power modules and large-scale control integrated circuits as basic components, and uses the latest theoretical and technical achievements to form a modular and intelligent high-power power supply, which makes strong electricity and weak electricity closely combined, reduces the development pressure of high-power components and high-power devices (centralized) and improves production efficiency.

In the early 1980s, the research of distributed high-frequency switching power supply system basically focused on the parallel technology of converters. In the middle and late 1980s, with the rapid development of high-frequency power conversion technology, various converter topologies appeared one after another. The combination of large-scale integrated circuit and power device technology makes it possible to integrate small and medium-sized power devices, thus rapidly promoting the development of distributed high-frequency switching power supply system. Since the late 1980s, this direction has become a research hotspot in the field of international power electronics. The number of papers is increasing year by year, and the application field is expanding.

Distributed power supply mode has the advantages of energy saving, reliability, high efficiency, economy and convenient maintenance. It has been gradually adopted by large computers, communication equipment, aerospace, industrial control and other systems, and it is also the most ideal power supply mode for ultra-high-speed integrated circuit low-voltage power supply (3.3V). In high-power occasions, such as electroplating, electrolytic power supply, electric locomotive traction power supply, intermediate frequency induction heating power supply, motor driving power supply and other fields, it also has broad application prospects. The application of electronic technology in the field of transportation is mainly the application of transportation system. At present, the electric locomotive is changing from the traditional DC motor drive to the traditional AC motor drive, mainly using GTO control devices, and the rectifier and inverter are controlled by PWM, so the input current can be sine wave. At present, many countries are developing maglev trains driven by linear synchronous motors. Once this technology is mature and successfully applied, it will bring a revolution to transportation, which will not only help shorten the time, but also make an important contribution to energy conservation and emission reduction. Motor technology can also be used in automobile engines. In modern cars, mechanical or electromechanical fuel injection systems tend to be eliminated, and electronic fuel injection devices are widely used because of their excellent performance. The electronic fuel injection device can automatically ensure that the engine is always in the best working state, so that its output power can save fuel and purify the air to the maximum extent under certain conditions. At the same time, the best working conditions are obtained through experiments and input into the memory. When the engine starts to work, according to the air flow measured by the sensor and the oxygen content in the exhaust pipe, it runs according to the pre-programmed operation program, and then the engine is controlled to be in the best working state.

At present, automotive electronic technology has developed to the fourth generation, that is, small systems including electronic technology (including microcomputer technology), optimal control technology, sensor technology, network technology, electromechanical integration coupling cross technology and other comprehensive technologies have entered the mature stage of commodity production from the scientific research stage (such as centralized control of braking, steering and suspension, centralized control of engine and transmission). At the same time, intelligent integrated sensors and intelligent actuators will be put into practice, and digital signal processing methods will be applied to speech recognition, safety collision, timely diagnosis and navigation systems. The greening of power supply system has two meanings: first, it saves electricity significantly, that is, it saves power generation capacity, and power generation is an important cause of environmental pollution, so saving electricity can reduce environmental pollution; Secondly, these power sources can't (or less) pollute the power grid. The International Electrotechnical Commission (IEC) has formulated a series of standards, such as IEC555, IEC9 17, IECl000 and so on. In fact, many power electronic energy-saving devices often become the pollution sources of the power grid: injecting serious high-order harmonic current into the power grid, reducing the total power factor, multi-peak voltage coupling of the power grid, and even missing corners and distortion. At the end of the 20th century, various schemes of active filter and active compensator were born, and there were many methods to correct power factor. These laid the foundation for mass production of various green switching power supply products in 2 1 century.

Modern power electronics technology is the basis of the development of switching power supply technology. With the continuous emergence of new power electronic devices and circuit topologies suitable for higher switching frequency, modern power supply technology will develop rapidly under the impetus of practical needs. Under the traditional application technology, the performance of switching power supply is affected by the performance limitation of power devices. In order to give full play to the characteristics of various power devices and minimize the influence of device performance on the performance of switching power supply, new power supply circuit topology and new control technology can make the power switch work in zero voltage or zero current state, thus greatly improving the working frequency, improving the working efficiency of switching power supply and designing a switching power supply with excellent performance.

In a word, power electronics and switching power supply technologies are constantly developing due to application requirements, and the emergence of new technologies will update many application products and open up more updated application fields. The realization of high frequency, modularization, digitalization and greening of switching power supply will mark the maturity of these technologies and realize the combination of high efficiency and high quality electricity consumption. In recent years, with the development of communication industry, the domestic market demand of switching power supply for communication with switching power supply technology as the core exceeds 2 billion RMB, attracting a large number of domestic and foreign scientific and technological personnel to carry out research and development. It is the general trend that switching power supply replaces linear power supply and phased power supply. Therefore, the domestic market of electric power supply system, which also has a demand of 10 billion output value, is starting and will soon develop. There are many other special power supplies and industrial power supplies with switching power supply technology as the core waiting for people to develop.