Archive for the ‘Training & Project Guidance’ Category

Scale Of Integration

Wednesday, March 23rd, 2011

Another name for a chip, an integrated circuit (IC) is a small electronic device made out of a semiconductor material. The first integrated circuit was developed in the 1950s by Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor.

Integrated circuits are used for a variety of devices, including microprocessors, audio and video equipment, and automobiles. Integrated circuits are often classified by the number of transistors and other electronic components they contain:

  • SSI (small-scale integration): Up to 100 electronic components per chip
  • MSI (medium-scale integration): From 100 to 3,000 electronic components per chip
  • LSI (large-scale integration): From 3,000 to 100,000 electronic components per chip
  • VLSI (very large-scale integration): From 100,000 to 1,000,000 electronic components per chip
  • ULSI (ultra large-scale integration): More than 1 million electronic components per chip
  • Micro Processor/Controller

    Thursday, March 4th, 2010

    MICROPROCESSOR

    1. A microprocessor, sometimes called a logic chip, is a computer processor on a microchip.

    The microprocessor contains all, or most of, the central processing unit (CPU) functions and is the “engine” that goes into motion when you turn your computer on. A microprocessor is designed to perform arithmetic and logic operations that make use of small number-holding areas called registers. Typical microprocessor operations include adding, subtracting, comparing two numbers, and fetching numbers from one area to another. These operations are the result of a set of instructions that are part of the microprocessor design.

    When your computer is turned on, the microprocessor gets the first instruction from the basic input/output system (BIOS) that comes with the computer as part of its memory. After that, either the BIOS, or the operating system that BIOS loads into computer memory, or an application progam is “driving” the microprocessor, giving it instructions to perform.

     2. For more basics, kindly click the link given below :

    http://www.kids-online.net/learn/click/details/micropro.html

     3. Get the List of Intel’s Microprocessors:

    http://en.wikipedia.org/wiki/List_of_Intel_microprocessors

     4. Wants to know about followings :

     How PCs Work

    How Motherboards Work

    How Semiconductors Work

     Click on this :

     http://computer.howstuffworks.com/microprocessor.htm

     

     

    MICROCONTROLLER

    A microcontroller can be considered a self-contained system with a processor, memory and peripherals and can be used with an embedded system. (Only the software needs be added.) The majority of microcontrollers in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems. These are called embedded systems. While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relays, solenoids, LEDs, small or custom LCD displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other recognizable I/O devices of a personal computer, and may lack human interaction devices of any kind

    A micro-controller is a single integrated circuit, commonly with the following features:

    • central processing unit – ranging from small and simple 4-bit processors to complex 32- or 64-bit processors
    • discrete input and output bits, allowing control or detection of the logic state of an individual package pin
    • serial input/output such as serial ports (UARTs)
    • other serial communications interfaces like I²C, Serial Peripheral Interface and Controller Area Network for system interconnect
    • peripherals such as timers, event counters, PWM generators, and watchdog
    • volatile memory (RAM) for data storage
    • ROM, EPROM, EEPROM or Flash memory for program and operating parameter storage
    • clock generator – often an oscillator for a quartz timing crystal, resonator or RC circuit
    • many include analog-to-digital converters
    • in-circuit programming and debugging support

    Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, and toys. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes.

    Introduction of ELECTRONICS

    Wednesday, October 21st, 2009

    Electronics is a branch of science and technology that deals with the controlled flow of electrons. The ability to control electron flow is usually applied to information handling or device control. Electronics is distinct from electrical science and technology, which deals with the generation, distribution, control and application of electrical power. This distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification possible with a non-mechanical device. Until 1950 this field was called “radio technology” because its principal application was the design and theory of radio transmitters, receivers and vacuum tubes.

    Most electronic devices today use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering. This article focuses on engineering aspects of electronics.  

    Electronic devices and components

    Electronic component

    An electronic component is any physical entity in an electronic system used to affect the electrons or their associated fields in a desired manner consistent with the intended function of the electronic system. Components are generally intended to be connected together, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function (for example an amplifier, radio receiver, or oscillator). Components may be packaged singly or in more complex groups as integrated circuits. Some common electronic components are capacitors, resistors, diodes, transistors, etc.

    Types of circuits

    Circuits and components can be divided into two groups: analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types

    1.      Analog circuits

    Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits.

    The number of different analog circuits so far devised is huge, especially because a ‘circuit’ can be defined as anything from a single component, to systems containing thousands of components.

    Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators.

    One rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance. This type of circuit is usually called “mixed signal” rather than analog or digital.

    Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation. An example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled switch having essentially two levels of output.

    2.     Digital circuits

    Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most common physical representation of Boolean algebra and are the basis of all digital computers. To most engineers, the terms “digital circuit”, “digital system” and “logic” are interchangeable in the context of digital circuits. Most digital circuits use two voltage levels labeled “Low”(0) and “High”(1). Often “Low” will be near zero volts and “High” will be at a higher level depending on the supply voltage in use. Ternary (with three states) logic has been studied, and some prototype computers made.

    Computers, electronic clocks, and programmable logic controllers (used to control industrial processes) are constructed of digital circuits. Digital Signal Processors are another example.

    Building-blocks:

    • Logic gates
    • Adders
    • Binary Multipliers
    • Flip-Flops
    • Counters
    • Registers
    • Multiplexers
    • Schmitt triggers

    Highly integrated devices:

    • Microprocessors
    • Microcontrollers
    • Application-specific integrated circuit (ASIC)
    • Digital signal processor (DSP)
    • Field-programmable gate array (FPGA)

    Heat dissipation and thermal management

    Thermal management of electronic devices and systems

    Heat generated by electronic circuitry must be dissipated to prevent immediate failure and improve long term reliability. Techniques for heat dissipation can include heat sinks and fans for air cooling, and other forms of computer cooling such as water cooling. These techniques use convection, conduction, & radiation of heat energy.

    Noise

    Electronic noise

    Noise is associated with all electronic circuits. Noise is defined as unwanted disturbances superposed on a useful signal that tend to obscure its information content. Noise is not the same as signal distortion caused by a circuit. Noise may be electromagnetically or thermally generated, which can be decreased by lowering the operating temperature of the circuit. Other types of noise, such as shot noise cannot be removed as they are due to limitations in physical properties.

    Electronics theory

    Mathematical methods in electronics

    Mathematical methods are integral to the study of electronics. To become proficient in electronics it is also necessary to become proficient in the mathematics of circuit analysis.

    Circuit analysis is the study of methods of solving generally linear systems for unknown variables such as the voltage at a certain node or the current through a certain branch of a network. A common analytical tool for this is the SPICE circuit simulator.

    Also important to electronics is the study and understanding of electromagnetic field theory.

    Computer aided design (CAD)

    Electronic design automation

    Today’s electronics engineers have the ability to design circuits using premanufactured building blocks such as power supplies, semiconductors (such as transistors), and integrated circuits. Electronic design automation software programs include schematic capture programs and printed circuit board design programs. Popular names in the EDA software world are NI Multisim, Cadence (ORCAD), Eagle PCB and Schematic, Mentor (PADS PCB and LOGIC Schematic), Altium (Protel), LabCentre Electronics (Proteus) and many others.

    Construction methods

    Electronic packaging

    Many different methods of connecting components have been used over the years. For instance, early electronics often used point to point wiring with components attached to wooden breadboards to construct circuits. Cordwood construction and wire wraps were other methods used. Most modern day electronics now use printed circuit boards made of materials such as FR4, or the cheaper (and less hard-wearing) Synthetic Resin Bonded Paper (SRBP, also known as Paxoline/Paxolin (trade marks) and FR2) – characterised by its light yellow-to-brown colour.

     

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    Electronic Engineering

    Wednesday, October 21st, 2009

    Electronics engineering, also referred to as electronic engineering is an engineering discipline which uses the scientific knowledge of the behavior and effects of electrons to develop components, devices, systems, or equipment (as in electron tubes, transistors, integrated circuits, and printed circuit boards) that uses electricity as part of its driving force. Both terms denote a broad engineering field that encompasses many subfields including those that deal with power, instrumentation engineering, telecommunications, semiconductor circuit design, and many others.

    The term also covers a large part of electrical engineering degree courses as studied at most European universities. In the U.S., however, electrical engineering encompasses all electrical disciplines including electronics. The Institute of Electrical and Electronic Engineers is one of the most important and influential organizations for electronic engineers. Indian universities have separate departments for Electronics Engineering.

    Terminology

    The name electrical engineering is still used to cover electronic engineering amongst some of the older (notably American and Australian) universities and graduates there are called electrical engineers. Some people believe the term ‘electrical engineer’ should be reserved for those having specialized in power and heavy current or high voltage engineering, while others believe that power is just one subset of electrical engineering (and indeed the term ‘power engineering’ is used in that industry) as well as ‘electrical distribution engineering’. Again, in recent years there has been a growth of new separate-entry degree courses such as ‘information engineering’ and ‘communication systems engineering’, often followed by academic departments of similar name. Most European universities now refer to electrical engineering as power engineers and make a distinction between Electrical and Electronics Engineering. Beginning in the 1980s, the term computer engineer was often used to refer to electronic or information engineers. However, Computer Engineering is now considered a subset of Electronics Engineering and the term is now becoming archaic.

    History of electronic engineering

    Electronic engineering as a profession sprang from technological improvements in the telegraph industry in the late 1800s and the radio and the telephone industries in the early 1900s. People were attracted to radio by the technical fascination it inspired, first in receiving and then in transmitting. Many who went into broadcasting in the 1920s were only ‘amateurs’ in the period before World War I.

    The modern discipline of electronic engineering was to a large extent born out of telephone, radio, and television equipment development and the large amount of electronic systems development during World War II of radar, sonar, communication systems, and advanced munitions and weapon systems. In the interwar years, the subject was known as radio engineering and it was only in the late 1950s that the term electronic engineering started to emerge.

    The electronic laboratories (Bell Labs in the United States for instance) created and subsidized by large corporations in the industries of radio, television, and telephone equipment began churning out a series of electronic advances. In 1948, came the transistor and in 1960, the IC to revolutionize the electronic industry. In the UK, the subject of electronic engineering became distinct from electrical engineering as a university degree subject around 1960. Before this time, students of electronics and related subjects like radio and telecommunications had to enroll in the electrical  engineering department of the university as no university had departments of electronics. Electrical engineering was the nearest subject with which electronic engineering could be aligned, although the similarities in subjects covered (except mathematics and electromagnetism) lasted only for the first year of the three-year course.

    Early electronics

    In 1893, Nikola Tesla made the first public demonstration of radio communication. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described and demonstrated in detail the principles of radio communication. In 1896, Guglielmo Marconi went on to develop a practical and widely used radio system. In 1904, John Ambrose Fleming, the first professor of electrical Engineering at University College London, invented the first radio tube, the diode. One year later, in 1906, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode.

    Electronics is often considered to have begun when Lee De Forest invented the vacuum tube in 1907. Within 10 years, his device was used in radio transmitters and receivers as well as systems for long distance telephone calls. In 1912, Edwin H. Armstrong invented the regenerative feedback amplifier and oscillator; he also invented the superheterodyne radio receiver and could be considered the father of modern radio.  Vacuum tubes remained the preferred amplifying device for 40 years, until researchers working for William Shockley at Bell Labs invented the transistor in 1947. In the following years, transistors made small portable radios, or transistor radios, possible as well as allowing more powerful mainframe computers to be built. Transistors were smaller and required lower voltages than vacuum tubes to work. In the interwar years the subject of electronics was dominated by the worldwide interest in radio and to some extent telephone and telegraph communications. The terms ‘wireless’ and ‘radio’ were then used to refer to anything electronic. There were indeed few non-military applications of electronics beyond radio at that time until the advent of television. The subject was not even offered as a separate university degree subject until about 1960.

    Prior to World War II, the subject was commonly known as ‘radio engineering’ and basically was restricted to aspects of communications and RADAR, commercial radio and early television. At this time, study of radio engineering at universities could only be undertaken as part of a physics degree. Later, in post war years, as consumer devices began to be developed, the field broadened to include modern TV, audio systems, Hi-Fi and latterly computers and microprocessors. In the mid to late 1950s, the term radio engineering gradually gave way to the name electronic engineering, which then became a stand alone university degree subject, usually taught alongside electrical engineering with which it had become associated due to some similarities.

    Before the invention of the integrated circuit in 1959, electronic circuits were constructed from discrete components that could be manipulated by hand. These non-integrated circuits consumed much space and power, were prone to failure and were limited in speed although they are still common in simple applications. By contrast, integrated circuits packed a large number — often millions — of tiny electrical components, mainly transistors, into a small chip around the size of a coin.

    Tubes or valves

    The vacuum tube detector

    The invention of the triode amplifier, generator, and detector made audio communication by radio practical. (Reginald Fessenden’s 1906 transmissions used an electro-mechanical alternator.) The first known radio news program was broadcast 31 August 1920 by station 8MK, the unlicensed predecessor of WWJ (AM) in Detroit, Michigan. Regular wireless broadcasts for entertainment commenced in 1922 from the Marconi Research Centre at Writtle near Chelmsford, England.

    While some early radios used some type of amplification through electric current or battery, through the mid 1920s the most common type of receiver was the crystal set. In the 1920s, amplifying vacuum tubes revolutionized both radio receivers and transmitters.

    Television

    In 1928 Philo Farnsworth made the first public demonstration of a purely electronic television. During the 1930s several countries began broadcasting, and after World War II it spread to millions of receivers, eventually worldwide. Ever since then, electronics have been fully present in television devices.

    Modern televisions and video displays have evolved from bulky electron tube technology to use more compact devices, such as plasma and LCD displays. The trend is for even lower power devices such as the organic light-emitting diode displays, and it is most likely to replace the LCD and plasma technologies.

    Radar and radio location

    Du ring World War II many efforts were expended in the electronic location of enemy targets and aircraft. These included radio beam guidance of bombers, electronic counter measures, early radar systems etc. During this time very little if any effort was expended on consumer electronics developments.

    Computers

    History of computing hardware

    In 1941, Konrad Zuse presented the Z3, the world’s first functional computer. After the Colossus computer in 1943, the ENIAC (Electronic Numerical Integrator and Computer) of John Presper Eckert and John Mauchly followed in 1946, beginning the computing era. The arithmetic performance of these machines allowed engineers to develop completely new technologies and achieve new objectives. Early examples include the Apollo missions and the NASA moon landing.

    Transistors

    The invention of the transistor in 1947 by William B. Shockley, John Bardeen and Walter Brattain opened the door for more compact devices and led to the development of the integrated circuit in 1959 by Jack Kilby.

    Microprocessors

    In 1969, Ted Hoff conceived the commercial microprocessor at Intel and thus ignited the development of the personal computer. Hoff’s invention was part of an order by a Japanese company for a desktop programmable electronic calculator, which Hoff wanted to build as cheaply as possible. The first realization of the microprocessor was the Intel 4004, a 4-bit processor, in 1969, but only in 1973 did the Intel 8080, an 8-bit processor, make the building of the first personal computer, the MITS Altair 8800, possible. The first PC was announced to the general public on the cover of the January 1975 issue of Popular Electronics. Mechatronics would have a good fortune in the near future.

    ##  In the field of electronic engineering, engineers design and test circuits that use the electromagnetic properties of electrical components such as resistors, capacitors, inductors, diodes and transistors to achieve a particular functionality. The tuner circuit, which allows the user of a radio to filter out all but a single station, is just one example of such a circuit.

    In designing an integrated circuit, electronics engineers first construct circuit schematics that specify the electrical components and describe the interconnections between them. When completed, VLSI engineers convert the schematics into actual layouts, which map the layers of various conductor and semiconductor materials needed to construct the circuit. The conversion from schematics to layouts can be done by software but very often requires human fine-tuning to decrease space and power consumption. Once the layout is complete, it can be sent to a fabrication plant for manufacturing.

    Integrated circuits and other electrical components can then be assembled on printed circuit boards to form more complicated circuits. Today, printed circuit boards are found in most electronic devices including televisions, computers and audio players.

    Typical electronic engineering undergraduate syllabus

    Apart from electromagnetics and network theory, other items in the syllabus are particular to electronics engineering course. Electrical engineering courses have other specialisms such as machines, power generation and distribution. Note that the following list does not include the extensive engineering mathematics curriculum that is a prerequisite to a degree.

    Electromagnetics

    Elements of vector calculus: divergence and curl; Gauss’ and Stokes’ theorems, Maxwell’s equations: differential and integral forms. Wave equation, Poynting vector. Plane waves: propagation through various media; reflection and refraction; phase and group velocity; skin depth. Transmission lines: characteristic impedance; impedance transformation; Smith chart; impedance matching; pulse excitation. Waveguides: modes in rectangular waveguides; boundary conditions; cut-off frequencies; dispersion relations. Antennas: Dipole antennas; antenna arrays; radiation pattern; reciprocity theorem, antenna gain.

    Network analysis

    Network graphs: matrices associated with graphs; incidence, fundamental cut set and fundamental circuit matrices. Solution methods: nodal and mesh analysis. Network theorems: superposition, Thevenin and Norton’s maximum power transfer, Wye-Delta transformation. Steady state sinusoidal analysis using phasors. Linear constant coefficient differential equations; time domain analysis of simple RLC circuits, Solution of network equations using Laplace transform: frequency domain analysis of RLC circuits. 2-port network parameters: driving point and transfer functions. State equations for networks.

    Electronic devices and circuits

    Electronic devices: Energy bands in silicon, intrinsic and extrinsic silicon. Carrier transport in silicon: diffusion current, drift current, mobility, resistivity. Generation and recombination of carriers. p-n junction diode, Zener diode, tunnel diode, BJT, JFET, MOS capacitor, MOSFET, LED, p-i-n and avalanche photo diode, LASERs. Device technology: integrated circuit fabrication process, oxidation, diffusion, ion implantation, photolithography, n-tub, p-tub and twin-tub CMOS process.

    Analog circuits: Equivalent circuits (large and small-signal of diodes, BJTs, JFETs, and MOSFETs. Simple diode circuits, clipping, clamping, rectifier. Biasing and bias stability of transistor and FET amplifiers. Amplifiers: single-and multi-stage, differential, operational, feedback and power. Analysis of amplifiers; frequency response of amplifiers. Simple op-amp circuits. Filters. Sinusoidal oscillators; criterion for oscillation; single-transistor and op-amp configurations. Function generators and wave-shaping circuits, Power supplies.

    Digital circuits: of Boolean functions; logic gates digital IC families (DTL, TTL, ECL, MOS, CMOS). Combinational circuits: arithmetic circuits, code converters, multiplexers and decoders. Sequential circuits: latches and flip-flops, counters and shift-registers. Sample and hold circuits, ADCs, DACs. Semiconductor memories. Microprocessor 8086: architecture, programming, memory and I/O interfacing.

    Signals and systems

    Definitions and properties of Laplace transforms, continuous-time and discrete-time Fourier series, continuous-time and discrete-time Fourier Transform, z-transform. Sampling theorems. Linear Time-Invariant (LTI) Systems: definitions and properties; causality, stability, impulse response, convolution, poles and zeros frequency response, group delay, phase delay. Signal transmission through LTI systems. Random signals and noise: probability, random variables, probability density function, autocorrelation, power spectral density, function analogy between vectors & functions.

    Control systems

    Basic control system components; block diagrammatic description, reduction of block diagrams — Mason’s rule. Open loop and closed loop (negative unity feedback) systems and stability analysis of these systems. Signal flow graphs and their use in determining transfer functions of systems; transient and steady state analysis of LTI control systems and frequency response. Analysis of steady-state disturbance rejection and noise sensitivity.

    Tools and techniques for LTI control system analysis and design: root loci, Routh-Hurwitz stability criterion, Bode and Nyquist plots. Control system compensators: elements of lead and lag compensation, elements of Proportional-Integral-Derivative controller (PID). Discretization of continuous time systems using Zero-order hold (ZOH) and ADCs for digital controller implementation. Limitations of digital controllers: aliasing. State variable representation and solution of state equation of LTI control systems. Linearization of Nonlinear dynamical systems with state-space realizations in both frequency and time domains. Fundamental concepts of controllability and observability for MIMO LTI systems. State space realizations: observable and controllable canonical form. Ackerman’s function for state-feedback pole placement. Design of full order and reduced order estimators.

    Communications

    Analog communication systems: amplitude and angle modulation and demodulation systems, spectral analysis of these operations, superheterodyne noise conditions.

    Digital communication systems: pulse code modulation (PCM), [[Differential Pulse Code Modulation (DPCM), Delta modulation (DM), digital modulation schemes-amplitude, phase and frequency shift keying schemes (ASK, PSK, FSK), matched filter receivers, bandwidth consideration and probability of error calculations for these schemes, GSM, TDMA.

    Education and training

    Electronics engineers typically possess an academic degree with a major in electronic engineering. The length of study for such a degree is usually three or four years and the completed degree may be designated as a Bachelor of Engineering, Bachelor of Science, Bachelor of Applied Science, or Bachelor of Technology depending upon the university. Many UK universities also offer Master of Engineering (MEng) degrees at undergraduate level.

    The degree generally includes units covering physics, chemistry, mathematics, project management and specific topics in electrical engineering. Initially such topics cover most, if not all, of the subfields of electronic engineering. Students then choose to specialize in one or more subfields towards the end of the degree.

    Some electronics engineers also choose to pursue a postgraduate degree such as a Master of Science (MSc), Doctor of Philosophy in Engineering (PhD), or an Engineering Doctorate (EngD). The Master degree is being introduced in some European and American Universities as a first degree and the differentiation of an engineer with graduate and postgraduate studies is often difficult. In these cases, experience is taken into account. The Master’s degree may consist of either research, coursework or a mixture of the two. The Doctor of Philosophy consists of a significant research component and is often viewed as the entry point to academia.

    In most countries, a Bachelor’s degree in engineering represents the first step towards certification and the degree program itself is certified by a professional body. After completing a certified degree program the engineer must satisfy a range of requirements (including work experience requirements) before being certified. Once certified the engineer is designated the title of Professional Engineer (in the United States, Canada and South Africa), Chartered Engineer or Incorporated Engineer (in the United Kingdom, Ireland, India and Zimbabwe), Chartered Professional Engineer (in Australia) or European Engineer (in much of the European Union).

    Fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. Today most engineering work involves the use of computers and it is commonplace to use computer-aided design programs when designing electronic systems. Although most electronic engineers will understand basic circuit theory, the theories employed by engineers generally depend upon the work they do. For example, quantum mechanics and solid state physics might be relevant to an engineer working on VLSI but are largely irrelevant to engineers working with macroscopic electrical systems.

    Professional bodies

    Professional bodies of note for electrical engineers include the Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Electrical Engineers (IEE), now the Institution of Engineering and Technology(IET). The IEEE claims to produce 30 percent of the world’s literature in electrical/electronic engineering, has over 370,000 members, and holds more than 450 IEEE sponsored or cosponsored conferences worldwide each year.

    Modern electronic engineering

    Electronic engineering in Europe is a very broad field that encompasses many subfields including those that deal with, electronic devices and circuit design, control systems, electronics and telecommunications, computer systems, embedded software etc. Many European universities now have departments of electronics that are completely separate from their respective departments of electrical engineering.

    Subfields

    Electronic engineering has many subfields. This section describes some of the most popular subfields in electronic engineering; although there are engineers who focus exclusively on one subfield, there are also many who focus on a combination of subfields.

    Overview of electronic engineering

    Electronic engineering involves the design and testing of electronic circuits that use the electronic properties of components such as resistors, capacitors, inductors, diodes and transistors to achieve a particular functionality.

    Signal processing deals with the analysis and manipulation of signals. Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a series of discrete values representing the information.

    For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications. For digital signals, signal processing may involve the compression, error checking and error detection of digital signals.

    Telecommunications engineering deals with the transmission of information across a channel such as a co-axial cable, optical fiber or free space.

    Transmissions across free space require information to be encoded in a carrier wave in order to shift the information to a carrier frequency suitable for transmission, this is known as modulation. Popular analog modulation techniques include amplitude modulation and frequency modulation. The choice of modulation affects the cost and performance of a system and these two factors must be balanced carefully by the engineer.

    Once the transmission characteristics of a system are determined, telecommunication engineers design the transmitters and receivers needed for such systems. These two are sometimes combined to form a two-way communication device known as a transceiver. A key consideration in the design of transmitters is their power consumption as this is closely related to their signal strength. If the signal strength of a transmitter is insufficient the signal’s information will be corrupted by noise.

    Control engineering has a wide range of applications from the flight and propulsion systems of commercial airplanes to the cruise control present in many modern cars. It also plays an important role in industrial automation.

    Control engineers often utilize feedback when designing control systems. For example, in a car with cruise control the vehicle’s speed is continuously monitored and fed back to the system which adjusts the engine’s power output accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback.

    Instrumentation engineering deals with the design of devices to measure physical quantities such as pressure, flow and temperature. These devices are known as instrumentation.

    The design of such instrumentation requires a good understanding of physics that often extends beyond electromagnetic theory. For example, radar guns use the Doppler effect to measure the speed of oncoming vehicles. Similarly, thermocouples use the Peltier-Seebeck effect to measure the temperature difference between two points.

    Often instrumentation is not used by itself, but instead as the sensors of larger electrical systems. For example, a thermocouple might be used to help ensure a furnace’s temperature remains constant. For this reason, instrumentation engineering is often viewed as the counterpart of control engineering.

    Computer engineering deals with the design of computers and computer systems. This may involve the design of new hardware, the design of PDAs or the use of computers to control an industrial plant. Computer engineers may also work on a system’s software. However, the design of complex software systems is often the domain of software engineering, which is usually considered a separate discipline.

    Desktop computers represent a tiny fraction of the devices a computer engineer might work on, as computer-like architectures are now found in a range of devices including video game consoles and DVD players.

    Project engineering

    For most engineers not involved at the cutting edge of system design and development, technical work accounts for only a fraction of the work they do. A lot of time is also spent on tasks such as discussing proposals with clients, preparing budgets and determining project schedules. Many senior engineers manage a team of technicians or other engineers and for this reason project management skills are important. Most engineering projects involve some form of documentation and strong written communication skills are therefore very important.

    The workplaces of electronics engineers are just as varied as the types of work they do. Electronics engineers may be found in the pristine laboratory environment of a fabrication plant, the offices of a consulting firm or in a research laboratory. During their working life, electronics engineers may find themselves supervising a wide range of individuals including scientists, electricians, computer programmers and other engineers.

    Obsolescence of technical skills is a serious concern for electronics engineers. Membership and participation in technical societies, regular reviews of periodicals in the field and a habit of continued learning are therefore essential to maintaining proficiency. And these are mostly used in the field of consumer electronics products.

     

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    Power Electronics

    Wednesday, October 21st, 2009

    Introductions 

    Power electronics is the applications of solid-state electronics for the control and conversion of electric power

    Power electronic converters can be found wherever there is a need to modify the electrical energy form (i.e modify its voltage, current or frequency). Therefore, their power range is from some milliwatts (as in a mobile phone) to hundreds of megawatts (e.g in a HVDC transmission system). With “classical” electronics, electrical currents and voltage are used to carry information, whereas with power electronics, they carry power. Therefore the main metric of power electronics becomes the efficiency.

    The first very high power electronic devices were mercury arc valves. In modern systems the conversion is performed with semiconductor switching devices such as diodes, thyristors and transistors. In contrast to electronic systems concerned with transmission and processing of signals and data, in power electronics substantial amounts of electrical energy are processed. An AC/DC converter (rectifier) is the most typical power electronics device found in many consumer electronic devices, e.g., television sets, personal computers, battery chargers, etc. The power range is typically from tens of watts to several hundred watts. In industry the most common application is the variable speed drive (VSD) that is used to control an induction motor. The power range of VSDs start from a few hundred watts and end at tens of megawatts.

    The power conversion systems can be classified according to the type of the input and output power

    • AC to DC (rectification)
    • DC to AC (inversion)
    • DC to DC (chopping)
    • AC to AC

    Principle                                              

    As efficiency is at a premium in a power electronic converter, the losses that a power electronic device generates should be as low as possible. The instantaneous dissipated power of a device is equal to the product of the voltage across the device and the current through it ( ). From this, one can see that the losses of a power device are at a minimum when the voltage across it is zero (the device is in the On-State) or when no current flows through it (Off-State). Therefore, a power electronic converter is built around one (or more) device operating in switching mode (either On or Off). With such a structure, the energy is transferred from the input of the converter to its output by bursts. To convert the power electronics by using rectifier

    Applications

    Power electronic systems are virtually in every electronic device. For example, around us:

    • DC/DC converters are used in most mobile devices (mobile phone, pda…) to maintain the voltage at a fixed value whatever the charge level of the battery is. These converters are also used for electronic isolation and power factor correction.
    • AC/DC converters (rectifiers) are used every time an electronic device is connected to the mains (computer, television,…)
    • AC/AC converters are used to change either the voltage level or the frequency (international power adapters, light dimmer). In power distribution networks AC/AC converters may be used to exchange power between utility frequency 50 Hz and 60 Hz power grids.
    • DC/AC converters (inverters) are used primarily in UPS or emergency light. During normal electricity condition, the electricity will charge the DC battery. During blackout time, the DC battery will be used to produce AC electricity at its output to power up the appliances.

    Power semiconductor device

    Power semiconductor devices are semiconductor devices used as switches or rectifiers in power electronic circuits (switch mode power supplies for example). They are also called power devices or when used in integrated circuits, called power ICs.

    Most power semiconductor devices are only used in commutation mode (i.e they are either on or off), and are therefore optimized for this. Most of them should not be used in linear operation.

     History 

    Power semiconductor devices first appeared in 1952 with the introduction of the power diode by R.N. Hall. It was made of Germanium and had a voltage capability of 200 volts and a current rating of 35 amperes.

    The thyristor appeared in 1957. Thyristors are able to withstand very high reverse breakdown voltage and are also capable of carrying high current. One disadvantage of the thyristor for switching circuits is that once it is ‘latched-on’ in the conducting state it cannot be turned off by external control. The thyristor turn-off is passive, i.e., the power must be disconnected from the device.

    The first bipolar transistors devices with substantial power handling capabilities were introduced in the 1960s. These components overcame some limitations of the thyristors because they can be turned on or off with an applied signal.

    With the improvements of the Metal Oxide Semiconductor technology (initially developed to produce integrated circuits), power MOSFETs became available in the late 1970s. International Rectifier introduced a 25 A, 400 V power MOSFET in 1978. These devices allow operation at higher frequency than bipolar transistors, but are limited to the low voltage applications.

    The Insulated Gate Bipolar Transistor (IGBT) developed in the 1980s became widely available in the 1990s. This component has the power handling capability of the bipolar transistor, with the advantages of the isolated gate drive of the power MOSFET.

    Common power devices                                                                                     

    Some common power devices are the power diode, thyristor, power MOSFET and IGBT (insulated gate bipolar transistor). A power diode or MOSFET operates on similar principles to its low-power counterpart, but is able to carry a larger amount of current and typically is able to support a larger reverse-bias voltage in the off-state.

    Structural changes are often made in power devices to accommodate the higher current density, higher power dissipation and/or higher reverse breakdown voltage. The vast majority of the discrete (i.e non integrated) power devices are built using a vertical structure, whereas small-signal devices employ a lateral structure. With the vertical structure, the current rating of the device is proportional to its area, and the voltage blocking capability is achieved in the height of the die. With this structure, one of the connections of the device is located on the bottom of the semiconductor [die].

    Common power semiconductor devices

    The realm of power devices is divided into two main categories :

    • The two-terminal devices (diodes), whose state is completely dependent on the external power circuit they are connected to;
    • The three-terminal devices, whose state is not only dependent on their external power circuit, but also on the signal on their driving terminal (gate or base). Transistors and thyristors belong to that category.

    A second classification is less obvious, but has a strong influence on device performance: Some devices are majority carrier devices (Schottky diode, MOSFET), while the others are minority carrier devices (Thyristor, bipolar transistor, IGBT). The former use only one type of charge carriers, while the latter use both (i.e electrons and holes). The majority carrier devices are faster, but the charge injection of minority carrier devices allows for better On-state performance.

    Diodes

    An ideal diode should have the following behaviour:

    • When forward-biased, the voltage across the end terminals of the diode should be zero, whatever the current that flows through it (on-state);
    • When reverse-biased, the leakage current should be zero whatever the voltage (off-state).

    Moreover, the transition between on and off states should be instantaneous.

    In reality, the design of a diode is a trade-off between performance in on-state, off-state and commutation. Indeed, it is the same area (actually the lightly-doped region of a PiN diode) of the device that has to sustain the blocking voltage in off-state and allow current flow in the on-state. As the requirements for the two state are completely opposite, it can be intuitively seen that a diode has to be either optimised for one of them, or time must be allowed to switch from one state to the other (i.e slow down the commutation speed).

    This trade-off between on-state, off-state and switching speed is the same for all power devices. A Schottky diode has excellent switching speed and on-state performance, but a high level of leakage current in off-state. PiN diodes are commercially available in different commutation speeds (so-called fast rectifier, ultrafast rectifier…), but any increase in speed is paid by lower performance in on-state.

    Switches

    The trade-off between voltage, current and frequency ratings also exists for the switches. Actually, all power semiconductors rely on a PiN diode structure to sustain voltage. This can be seen in above figure. The power MOSFET has the advantages of the majority carrier devices, so it can achieve very high operating frequency, but can’t be used with high voltages. As it is a physical limit, no improvement is expected from silicon MOSFET concerning their maximum voltage ratings. However, its excellent performance in low voltage make it the device of choice (actually the only choice) for applications below 200 V. By paralleling several devices, it is possible increase the current rating of a switch. The MOSFET is particularly suited to this configuration because its positive thermal coefficient of resistance tends to balance current between individual devices.

    The IGBT is a recent component, so its performance improves regularly as technology evolves. It has already completely replaced the bipolar transistor in power applications, and the availability of power modules (in which several IGBT dice are connected in parallel) makes it attractive for power levels up to several megawatts, pushing further the limit where thyristors and GTO become the only option. Basically, an IGBT is a bipolar transistor driven by a power MOSFET: it has the advantages of being a minority carrier device (good performance in on-state, even for high voltage devices), with the high input impedance of a MOSFET (it can be driven on or off with a very low amount of power). Its major limitation for low voltage applications is the high voltage drop it exhibits in on-state (2 to 4 V). Compared to the MOSFET, the operating frequency of the IGBT is relatively low (few devices are rated over 50 kHz), mainly because of a so-called ‘current-tail’ problem during turn-off. This problem is caused by the slow decay of the conduction current during turn-off resulting from slow recombination of large number of carriers, which flood the thick ‘drift’ region of the IGBT during conduction. The net result is that the turn-off switching loss of an IGBT is considerably higher than its turn-on loss. Generally, in datasheet, turn-off energy is mentioned as a measured parameter and one has to multiply that number with the switching frequency of the intended application to estimate the turn-off loss.

    At very high power levels, thyristor-based devices (SCR, GTO,  MCT) are still the only choice. Though driving a thyristor is somewhat complicated, as this device can only be turned on. It turns off by itself as soon as no more current flows through it. This requires specific circuit with means to divert current, or specific applications where current is known to cancel regularly (i.e Alternating Current). Different solution have been developed to overcome this limitation (Mos Controlled Thyristors, Gate Turn Off thyristor…). These components are widely used in power distribution applications.

    Parameters of power semiconductor devices

    Various parameters are as follows :

    1. Breakdown voltage: Often the trade-off is between breakdown voltage rating and on-resistance because increasing the breakdown voltage by incorporating a thicker and lower doped drift region leads to higher on-resistance.
    2. On-resistance: Higher current rating lowers the on-resistance due to greater numbers of parallel cells. This increases overall capacitance and slows down the speed.
    3. Rise and fall times for switching between on and off states.
    4. Safe-operating area (from thermal dissipation and “latch-up” consideration)
    5. Thermal resistance: This is actually an often-ignored but extremely important parameter from practical system design point of view. Semiconductors do not perform well at elevated temperature but due to large current conduction, all power semiconductor device heat up. Therefore it needs to be cooled by removing that heat continuously. Packaging interface provides the path between the semiconductor device and external world to channelize the heat outside. Generally, large current devices have large die and packaging surface area and lower thermal resistance.

    Research and development

    Packaging

    The role of packaging is to:

    • connect a die to the external circuit;
    • provide a way to remove the heat generated by the device;
    • protect the die from the external environment (moisture, dust);

    Many of the reliability issues of power device are either related to excessive temperature of fatigue due to thermal cycling. Research is currently carried out on the following topics:

    • improve the cooling performance.
    • improve the resistance to thermal cycling by closely matching the Coefficient of thermal expansion of the packaging to that of the silicon.
    • increase the maximum operating temperature of the packaging material.

    Research is also ongoing on electrical issues such as reducing the parasitic inductance of packaging. This inductance limits the operating frequency as it generates losses in the devices during commutation.

    Low-voltage MOSFETs are also limited by the parasitic resistance of the packages, as their intrinsic on-state resistance can be as low as one or two milliohms.

    Some of the most common type of power semiconductor packages include TO-220, TO-247, TO-262, TO-3, D2Pak, etc.

    Improvement of structures

    IGBTs are still under development and we can expect increased operating voltages in the future. At the high-power end of the range, MOS-Controlled Thyristor are promising devices. A major improvement over conventional MOSFET structure is achieved by employing superjunction charge-balance principle to the design. Essentially, it allows the thick drift region of a power MOSFET to be heavily doped (thereby reducing the electrical resistance for electron flow) without compromising the breakdown voltage. An adjacent region of similarly doped (but of opposite carrier polarity – holes) is created within the structure. These two similar but opposite doped regions effectively cancel out their mobile charge and develop a ‘depleted region’ which supports the high voltage during off-state. On the other hand, during conducting state, the higher doping of the drift region allows easier flow of carrier thereby reducing on-resistance. Commercial devices, based on this principle, have been developed by International Rectifier and Infineon in the name of CoolMOSTM.

    Wide band-gap semiconductors

    The major breakthrough in power semiconductor devices is expected from the replacement of silicon by a wide band-gap semiconductor. At the moment, silicon carbide (SiC) is considered to be the most promising. SiC Schottky diodes with a breakdown voltage of 1200 V are commercially available, as are 1200 V JFETs. As both are majority carrier devices, they can operate at high speed. Bipolar devices are being developed for higher voltages, up to 20 kV. Among its advantages, silicon carbide can operate at higher temperature (up to 400°C) and has a lower thermal resistance than silicon, allowing better cooling.

    • Bipolar junction transistor
    • Bootstrapping
    • FGMOS
    • Power electronics
    • Power MOSFET
    • Dimmer
    • Gate turn-off thyristor
    • IGBT
    • Integrated gate-commutated thyristor
    • Thyristor
    • Triac
    • Voltage regulator

     

    # For MORE, E-mail to info@makcissolutions.com . 

    Power electronics is the applications of solid-state electronics for the control and conversion of electric power.

     Introductions

    Power electronic converters can be found wherever there is a need to modify the electrical energy form (i.e modify its voltage, current or frequency). Therefore, their power range is from some milliwatts (as in a mobile phone) to hundreds of megawatts (e.g in a HVDC transmission system). With “classical” electronics, electrical currents and voltage are used to carry information, whereas with power electronics, they carry power. Therefore the main metric of power electronics becomes the efficiency.

    The first very high power electronic devices were mercury arc valves. In modern systems the conversion is performed with semiconductor switching devices such as diodes, thyristors and transistors. In contrast to electronic systems concerned with transmission and processing of signals and data, in power electronics substantial amounts of electrical energy are processed. An AC/DC converter (rectifier) is the most typical power electronics device found in many consumer electronic devices, e.g., television sets, personal computers, battery chargers, etc. The power range is typically from tens of watts to several hundred watts. In industry the most common application is the variable speed drive (VSD) that is used to control an induction motor. The power range of VSDs start from a few hundred watts and end at tens of megawatts.

    The power conversion systems can be classified according to the type of the input and output power

    • AC to DC (rectification)
    • DC to AC (inversion)
    • DC to DC (chopping)
    • AC to AC

    Principle                                              

    As efficiency is at a premium in a power electronic converter, the losses that a power electronic device generates should be as low as possible. The instantaneous dissipated power of a device is equal to the product of the voltage across the device and the current through it ( ). From this, one can see that the losses of a power device are at a minimum when the voltage across it is zero (the device is in the On-State) or when no current flows through it (Off-State). Therefore, a power electronic converter is built around one (or more) device operating in switching mode (either On or Off). With such a structure, the energy is transferred from the input of the converter to its output by bursts. To convert the power electronics by using rectifier

    Applications

    Power electronic systems are virtually in every electronic device. For example, around us:

    • DC/DC converters are used in most mobile devices (mobile phone, pda…) to maintain the voltage at a fixed value whatever the charge level of the battery is. These converters are also used for electronic isolation and power factor correction.
    • AC/DC converters (rectifiers) are used every time an electronic device is connected to the mains (computer, television,…)
    • AC/AC converters are used to change either the voltage level or the frequency (international power adapters, light dimmer). In power distribution networks AC/AC converters may be used to exchange power between utility frequency 50 Hz and 60 Hz power grids.
    • DC/AC converters (inverters) are used primarily in UPS or emergency light. During normal electricity condition, the electricity will charge the DC battery. During blackout time, the DC battery will be used to produce AC electricity at its output to power up the appliances.

    Power semiconductor device

    Power semiconductor devices are semiconductor devices used as switches or rectifiers in power electronic circuits (switch mode power supplies for example). They are also called power devices or when used in integrated circuits, called power ICs.

    Most power semiconductor devices are only used in commutation mode (i.e they are either on or off), and are therefore optimized for this. Most of them should not be used in linear operation.

     History

    Power semiconductor devices first appeared in 1952 with the introduction of the power diode by R.N. Hall. It was made of Germanium and had a voltage capability of 200 volts and a current rating of 35 amperes.

    The thyristor appeared in 1957. Thyristors are able to withstand very high reverse breakdown voltage and are also capable of carrying high current. One disadvantage of the thyristor for switching circuits is that once it is ‘latched-on’ in the conducting state it cannot be turned off by external control. The thyristor turn-off is passive, i.e., the power must be disconnected from the device.

    The first bipolar transistors devices with substantial power handling capabilities were introduced in the 1960s. These components overcame some limitations of the thyristors because they can be turned on or off with an applied signal.

    With the improvements of the Metal Oxide Semiconductor technology (initially developed to produce integrated circuits), power MOSFETs became available in the late 1970s. International Rectifier introduced a 25 A, 400 V power MOSFET in 1978. These devices allow operation at higher frequency than bipolar transistors, but are limited to the low voltage applications.

    The Insulated Gate Bipolar Transistor (IGBT) developed in the 1980s became widely available in the 1990s. This component has the power handling capability of the bipolar transistor, with the advantages of the isolated gate drive of the power MOSFET.

    Common power devices                                                                                     

    Some common power devices are the power diode, thyristor, power MOSFET and IGBT (insulated gate bipolar transistor). A power diode or MOSFET operates on similar principles to its low-power counterpart, but is able to carry a larger amount of current and typically is able to support a larger reverse-bias voltage in the off-state.

    Structural changes are often made in power devices to accommodate the higher current density, higher power dissipation and/or higher reverse breakdown voltage. The vast majority of the discrete (i.e non integrated) power devices are built using a vertical structure, whereas small-signal devices employ a lateral structure. With the vertical structure, the current rating of the device is proportional to its area, and the voltage blocking capability is achieved in the height of the die. With this structure, one of the connections of the device is located on the bottom of the semiconductor [die].

    Common power semiconductor devices

    The realm of power devices is divided into two main categories :

    • The two-terminal devices (diodes), whose state is completely dependent on the external power circuit they are connected to;
    • The three-terminal devices, whose state is not only dependent on their external power circuit, but also on the signal on their driving terminal (gate or base). Transistors and thyristors belong to that category.

    A second classification is less obvious, but has a strong influence on device performance: Some devices are majority carrier devices (Schottky diode, MOSFET), while the others are minority carrier devices (Thyristor, bipolar transistor, IGBT). The former use only one type of charge carriers, while the latter use both (i.e electrons and holes). The majority carrier devices are faster, but the charge injection of minority carrier devices allows for better On-state performance.

    Diodes

    An ideal diode should have the following behaviour:

    • When forward-biased, the voltage across the end terminals of the diode should be zero, whatever the current that flows through it (on-state);
    • When reverse-biased, the leakage current should be zero whatever the voltage (off-state).

    Moreover, the transition between on and off states should be instantaneous.

    In reality, the design of a diode is a trade-off between performance in on-state, off-state and commutation. Indeed, it is the same area (actually the lightly-doped region of a PiN diode) of the device that has to sustain the blocking voltage in off-state and allow current flow in the on-state. As the requirements for the two state are completely opposite, it can be intuitively seen that a diode has to be either optimised for one of them, or time must be allowed to switch from one state to the other (i.e slow down the commutation speed).

    This trade-off between on-state, off-state and switching speed is the same for all power devices. A Schottky diode has excellent switching speed and on-state performance, but a high level of leakage current in off-state. PiN diodes are commercially available in different commutation speeds (so-called fast rectifier, ultrafast rectifier…), but any increase in speed is paid by lower performance in on-state.

    Switches

    The trade-off between voltage, current and frequency ratings also exists for the switches. Actually, all power semiconductors rely on a PiN diode structure to sustain voltage. This can be seen in above figure. The power MOSFET has the advantages of the majority carrier devices, so it can achieve very high operating frequency, but can’t be used with high voltages. As it is a physical limit, no improvement is expected from silicon MOSFET concerning their maximum voltage ratings. However, its excellent performance in low voltage make it the device of choice (actually the only choice) for applications below 200 V. By paralleling several devices, it is possible increase the current rating of a switch. The MOSFET is particularly suited to this configuration because its positive thermal coefficient of resistance tends to balance current between individual devices.

    The IGBT is a recent component, so its performance improves regularly as technology evolves. It has already completely replaced the bipolar transistor in power applications, and the availability of power modules (in which several IGBT dice are connected in parallel) makes it attractive for power levels up to several megawatts, pushing further the limit where thyristors and GTO become the only option. Basically, an IGBT is a bipolar transistor driven by a power MOSFET: it has the advantages of being a minority carrier device (good performance in on-state, even for high voltage devices), with the high input impedance of a MOSFET (it can be driven on or off with a very low amount of power). Its major limitation for low voltage applications is the high voltage drop it exhibits in on-state (2 to 4 V). Compared to the MOSFET, the operating frequency of the IGBT is relatively low (few devices are rated over 50 kHz), mainly because of a so-called ‘current-tail’ problem during turn-off. This problem is caused by the slow decay of the conduction current during turn-off resulting from slow recombination of large number of carriers, which flood the thick ‘drift’ region of the IGBT during conduction. The net result is that the turn-off switching loss of an IGBT is considerably higher than its turn-on loss. Generally, in datasheet, turn-off energy is mentioned as a measured parameter and one has to multiply that number with the switching frequency of the intended application to estimate the turn-off loss.

    At very high power levels, thyristor-based devices (SCR, GTO,  MCT) are still the only choice. Though driving a thyristor is somewhat complicated, as this device can only be turned on. It turns off by itself as soon as no more current flows through it. This requires specific circuit with means to divert current, or specific applications where current is known to cancel regularly (i.e Alternating Current). Different solution have been developed to overcome this limitation (Mos Controlled Thyristors, Gate Turn Off thyristor…). These components are widely used in power distribution applications.

    Parameters of power semiconductor devices

    Various parameters are as follows :

    1. Breakdown voltage: Often the trade-off is between breakdown voltage rating and on-resistance because increasing the breakdown voltage by incorporating a thicker and lower doped drift region leads to higher on-resistance.
    2. On-resistance: Higher current rating lowers the on-resistance due to greater numbers of parallel cells. This increases overall capacitance and slows down the speed.
    3. Rise and fall times for switching between on and off states.
    4. Safe-operating area (from thermal dissipation and “latch-up” consideration)
    5. Thermal resistance: This is actually an often-ignored but extremely important parameter from practical system design point of view. Semiconductors do not perform well at elevated temperature but due to large current conduction, all power semiconductor device heat up. Therefore it needs to be cooled by removing that heat continuously. Packaging interface provides the path between the semiconductor device and external world to channelize the heat outside. Generally, large current devices have large die and packaging surface area and lower thermal resistance.

    Research and development

    Packaging

    The role of packaging is to:

    • connect a die to the external circuit;
    • provide a way to remove the heat generated by the device;
    • protect the die from the external environment (moisture, dust);

    Many of the reliability issues of power device are either related to excessive temperature of fatigue due to thermal cycling. Research is currently carried out on the following topics:

    • improve the cooling performance.
    • improve the resistance to thermal cycling by closely matching the Coefficient of thermal expansion of the packaging to that of the silicon.
    • increase the maximum operating temperature of the packaging material.

    Research is also ongoing on electrical issues such as reducing the parasitic inductance of packaging. This inductance limits the operating frequency as it generates losses in the devices during commutation.

    Low-voltage MOSFETs are also limited by the parasitic resistance of the packages, as their intrinsic on-state resistance can be as low as one or two milliohms.

    Some of the most common type of power semiconductor packages include TO-220, TO-247, TO-262, TO-3, D2Pak, etc.

    Improvement of structures

    IGBTs are still under development and we can expect increased operating voltages in the future. At the high-power end of the range, MOS-Controlled Thyristor are promising devices. A major improvement over conventional MOSFET structure is achieved by employing superjunction charge-balance principle to the design. Essentially, it allows the thick drift region of a power MOSFET to be heavily doped (thereby reducing the electrical resistance for electron flow) without compromising the breakdown voltage. An adjacent region of similarly doped (but of opposite carrier polarity – holes) is created within the structure. These two similar but opposite doped regions effectively cancel out their mobile charge and develop a ‘depleted region’ which supports the high voltage during off-state. On the other hand, during conducting state, the higher doping of the drift region allows easier flow of carrier thereby reducing on-resistance. Commercial devices, based on this principle, have been developed by International Rectifier and Infineon in the name of CoolMOSTM.

    Wide band-gap semiconductors

    The major breakthrough in power semiconductor devices is expected from the replacement of silicon by a wide band-gap semiconductor. At the moment, silicon carbide (SiC) is considered to be the most promising. SiC Schottky diodes with a breakdown voltage of 1200 V are commercially available, as are 1200 V JFETs. As both are majority carrier devices, they can operate at high speed. Bipolar devices are being developed for higher voltages, up to 20 kV. Among its advantages, silicon carbide can operate at higher temperature (up to 400°C) and has a lower thermal resistance than silicon, allowing better cooling.

    • Bipolar junction transistor
    • Bootstrapping
    • FGMOS
    • Power electronics
    • Power MOSFET
    • Dimmer
    • Gate turn-off thyristor
    • IGBT
    • Integrated gate-commutated thyristor
    • Thyristor
    • Triac
    • Voltage regulator

     

    # For MORE, E-mail to info@makcissolutions.com .

    Marine electronics

    Wednesday, October 21st, 2009

    Marine electronics refers to electronics devices designed and classed for use in the marine environment where even small drops of salt water will destroy electronics devices. Therefore the majority of these types of devices are either water resistant or waterproof. A wide variety of marine electronics are available in the marketplace today. Reviews and reports on marine chartplotters, autopilots, VHF radios, network chartplotters, fish finders, and a wide range of handheld devices can be found at Marine Electronics Reviews

    The term marine electronics is used for areas such as

    • Ship
    • Yacht

    Marine electronics devices are

    • Chartplotter
    • Marine VHF radio
    • Autopilot/Self-steering gear
    • Fishfinder/Sonar
    • Radar
    • GPS
    • Electronic compass
    • Satellite television
    • Marine fuel management

    Communication

    The electronics devices communicate by using a protocol defined by NMEA. NMEA has two standards available

    • NMEA 0183
    • NMEA 2000

    NMEA 0183 is based on a serial communication network. NMEA 2000 is a Controller-area network based technology.

    Also different suppliers of marine electronics have their own communications protocol

    • Simrad has SimNet
    • Raymarine has SeaTalk
    • Furuno has NavNet
    • Stowe has Dataline

    Companies

    The international companies selling marine electronics for ships and yachts alphabetically are

    • Airmar
    • FuelTrax
    • Furuno
    • Maretron
    • Raymarine Marine Electronics
    • Simrad in Kongsberg Maritime
    • Simrad Yachting in Navico
    • Stowe Marine
    • Tinley Electronics

    Companies developing marine electronics products are

    • Egersund Marine Electronics
    • Kongsberg Maritime
    • Navico

     

    # For MORE E-mail to info@makcissolution.com .