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electronic technique

According to the principle of electronics, electronic technology is a science that uses electronic devices to design and manufacture circuits with certain functions to solve practical problems, including information electronic technology and power electronic technology. Information electronic technology includes analog electronic technology and digital electronic technology. Electronic technology is a technology for processing electronic signals. The main processing methods are: signal generation, amplification, filtering and conversion.

catalogue

1 electric power

2 Fundamentals of semiconductor devices

3 amplifier circuit

4 arithmetic circuit

5 filter circuit

1 electric power

1. 1, power electronic technology development

1.2 2. Application fields of modern power electronic technology

1.3 3. Development trend of high frequency switching power supply

2 Fundamentals of semiconductor devices

3 amplifier circuit

4 arithmetic circuit

5 filter circuit

Electronic technology-electric power

1, the development of power electronics technology

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.

1. 1 rectifier era

High-power industrial electricity is provided by power frequency (50Hz) alternator, but about 20% of the electricity is consumed in the form of DC. The most typical ones are electrolysis (non-ferrous metals and chemical raw materials need DC electrolysis) and traction (electric locomotives, electric diesel locomotives, subway locomotives, urban trolleybuses, etc.). ) and DC drive (steel rolling, paper making, etc. High-power silicon rectifiers can efficiently convert power frequency alternating current into direct current, so the development and application of high-power silicon rectifiers and thyristors have been greatly developed in the 1960s and 1970s. At that time, there was an upsurge of establishing large-scale silicon rectifier factories in China. At present, large and small silicon rectifier semiconductor manufacturers in China are the products of that era.

1.2 inverter era

In 1970s, there was a worldwide energy crisis in electronic components, and AC motor frequency conversion speed regulation developed rapidly because of its remarkable energy-saving effect. The key technology of variable frequency speed regulation is to convert direct current into alternating current of 0~ 100Hz. In 1970s and 1980s, with the popularization of frequency conversion speed regulating devices, thyristors, high-power transistors (GTR) and high-power inverter gate turn-off thyristors (GT0) became the protagonists of power electronic devices at that time. Similar applications include high voltage DC output, static reactive power dynamic compensation and so on. At this time, power electronics technology has been able to achieve rectification and inverter, but the working frequency is low, limited to the middle and low frequency range.

1.3 frequency converter era

In 1980s, the rapid development of large-scale and ultra-large-scale integrated circuit technology laid the foundation for the development of modern power electronics technology. Combining the precision machining technology of integrated circuit technology with high voltage and high current technology, a number of brand-new fully controlled power devices have emerged. First, the appearance of power M0SFET has driven the development of medium and small power supplies to high frequency, and then the appearance of insulated gate bipolar transistors (IGBT) has brought opportunities for the development of medium and large power supplies to high frequency. The appearance of MOSFET and IGBT marks the transformation from traditional power electronics to modern power electronics. According to statistics, by the end of 1995, power M0SFET and GTR have reached the same level in the market of power semiconductor devices, and it has been concluded that IGBT will replace GTR in the field of power electronics. The development of new devices not only provides high frequency for AC motor variable frequency speed regulation, which makes its performance more perfect and reliable, but also makes modern electronic technology develop to high frequency, which provides an important technical basis for efficient material saving and energy saving of electrical equipment, and realizes small, lightweight, electromechanical integration and intelligence.

2. Application fields of modern power electronics

2. 1 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" plan of US Environmental Protection Agency1June, 992, if the power consumption of desktop personal computers or related peripherals 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.

2.2 High frequency switching power supply for communication

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.

2.3 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.

2.4 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.

2.5 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.

Electronic products: The series of inverter power supply products 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.

2.6 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.

2.7 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.

2.8 Power Active 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.

2.9 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.

3. Development trend of high frequency switching power supply

In the application of power electronics technology and various power supply systems, switching power supply technology is in the core position. For large electroplating power supply, the traditional circuit is bulky and bulky. If Gao Dun switching power supply technology is adopted, its volume and weight will be greatly reduced, the utilization efficiency of power supply will be greatly improved, materials will be saved and costs will be reduced. In electric vehicle and frequency conversion drive, switching power supply technology is indispensable, and the frequency of power supply is changed by switching power supply, so as to achieve nearly ideal load matching and drive control. High-frequency switching power supply technology is the core technology of various high-power switching power supplies (inverter welding machine, communication power supply, high-frequency heating power supply, laser power supply, power operation power supply, etc.). ).

3. 1 high frequency

Theoretical analysis and practical experience show that the volume and weight of transformers, inductors and capacitors of electrical products are inversely proportional to the square root of power frequency. Therefore, when we increase the frequency from 5~l0%Hz to 400 times of 20kHz, the volume and weight of electrical equipment will generally drop to 5 ~ 10% of the power frequency design. Inverter rectifier welding machine and switching rectifier for communication power supply are based on this principle. Similarly, various DC power supplies such as electroplating, electrolysis, electro-machining, charging, floating charging and power switch-off in the traditional "rectification industry" can also be transformed into "switching power supplies" according to this principle, and the main materials can be saved by more than 90% and the electric energy can be saved by more than 30%. Due to the gradual increase of the upper limit of the working frequency of power electronic devices, many traditional high-frequency devices using electron tubes have been solidified, which has brought remarkable economic benefits of energy-saving, water-saving and material-saving, and can also reflect the value of technical content.

3.2 Modularization

Modularity has two meanings, one is modularity of power devices, and the other is modularity of power supply units. Our common device modules, including one unit, two units, six units to seven elements, including switching devices and anti-parallel freewheeling diodes, are essentially "standard" power modules (SPM). In recent years, some companies also put the driving and protection circuits of switching devices into power modules to form an "intelligent" power module (IPM), which not only reduces the volume of the whole machine, but also facilitates the design and manufacture of the whole machine. In fact, due to the continuous improvement of frequency, the influence of lead parasitic inductance and parasitic capacitance is more and more serious, which causes greater electrical stress (such as overvoltage and overcurrent burr) to the device. In order to improve the reliability of the system, some manufacturers have developed "user-specific" power module (ASPM), which installs almost all the hardware of the whole machine in a module in the form of chips, so that there is no traditional lead connection between components. This module has been designed strictly and reasonably in the aspects of heat, electricity and machinery, and has reached a perfect position. It is similar to the user-specific integrated circuit (ASIC) in microelectronics. As long as the control software is written into the microprocessor chip in the module, and then the whole module is fixed on the corresponding radiator, a new switching power supply device is formed. It can be seen that the purpose of modularization is not only to facilitate the use and reduce the volume of the whole machine, but also to cancel the traditional connection and minimize the parasitic parameters, so as to minimize the electrical stress borne by the device and improve the reliability of the system. In addition, due to the limitation of device capacity and the consideration of increasing redundancy and improving reliability, high-power switching power supply generally adopts multiple independent module units working in parallel and adopts current sharing technology. All modules share the load current. Once one module fails, other modules will share the load current equally. This not only improves the power capacity, but also meets the requirements of large current output under the condition of limited device capacity. Moreover, the reliability of the system is greatly improved by adding redundant power modules with less power than the whole system. Even if a single module fails, it will not affect the normal work of the system and will provide sufficient time for repair.

3.3 Digitization

In the traditional power electronics technology, the control part is designed and operated according to analog signals. In the 1960s and 1970s, power electronics technology was based entirely on analog circuits. However, digital signals and digital circuits are becoming more and more important, and digital signal processing technology is becoming more and more mature, showing more and more advantages: it is convenient for computer processing and control, avoiding analog signal distortion, reducing the interference of stray signals (improving anti-interference ability), facilitating software package debugging and remote sensing and telemetry, and facilitating the implantation of technologies such as self-diagnosis and fault tolerance. Therefore, in the 1980s and 1990s, analog technology is still useful for the design of various circuits and systems, especially for the solution of PCB layout, electromagnetic compatibility (EMC) and power factor correction (PFC), but for intelligent switching power supply, digital technology is indispensable when computer control is needed.

3.4 Greening

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. [ 1]

Electronic Technology-Fundamentals of Semiconductor Devices

Overview of electronic technology semiconductor

Semiconductors are materials whose conductivity can be controlled, ranging from insulators to conductors. No matter from the perspective of science and technology or economic development, the importance of semiconductors is enormous. Today, most electronic products, such as computers, mobile phones or digital recorders, are closely related to semiconductors. Common semiconductor materials include silicon, germanium, gallium arsenide, etc. Among all kinds of semiconductor materials, silicon is the most influential one in commercial applications.

semiconductor diode

Bipolar transistor

field-effect tube

Electronic technology-amplifier circuit

Discrete amplifier circuit

Basic connection of unipolar triode amplifier circuit

Basic connection of unipolar MOS transistor amplifier circuit

Interpolar coupling amplifier and multipole amplifier circuit

Integrated operational amplifier circuit

Push-pull amplifier

Current source circuit

Composite pipe structure