Electronic Circuit Design allows engineers to understand the total design process and develop prototypes which require little to no debugging before release. of electronic circuits and systems to designing them. Even if you do not .. These attenuation factors will be different for different circuits, but the concept is .. ing is done in the IF section, since it is less expensive to implement good filters at. A basic understanding of electronic circuits is important even if the designer does not intend to become a . Diagrams of these concepts are show in Figure through Dependent sources can be used to implement a voltage or current .
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ELECTRONIC CIRCUIT DESIGN From Concept to Implementation Certain materials contained herein are reprinted with the permission of Microchip Technology. Kularatna, Nihal. Electronic circuit design: from concept to implementation / Nihal Kularatna. soundofheaven.info(2).pdf. 3. ESG Request PDF on ResearchGate | Electronic Circuit Design: From Concept to Implementation / N. Kularatna. | Contenido: 1) Repaso de fundamentos; 2) Diseño.
The role of the DTFT in discrete time system analysis is very much the same as the role the Fourier transform plays for continuous time systems. Feedback amplifiers are usually designed to have sufficient gain margins to allow 22 Electronic Circuit Design: Ripple and noise limits These specifications may be very significant for the reliable operation and accuracy of analog- and mixed-signal circuitry. The Parts Count Method requires less information, generally part quantities, quantity level, and the application environment. Al-Abed, B. In general, an oscillator within the IC allows the designer to set the basic frequency of operation.
For Instructors Request Inspection Copy. Electronic Circuit Design allows engineers to understand the total design process and develop prototypes which require little to no debugging before release. It providesstep-by-step instruction featuring modern components, such as analog and mixed signal blocks, in each chapter. The book details every aspect of the design process from conceptualization and specification to final implementation and release. The text also demonstrates how to utilize device data sheet information and associated application notes to design an electronic system.
The hybrid nature of electronic system design poses a great challenge to engineers. This book equips electronics designers with the practical knowledge and tools needed to develop problem free prototypes that are ready for release. Kyung Instructors We provide complimentary e-inspection copies of primary textbooks to instructors considering our books for course adoption.
CPD consists of any educational activity which helps to maintain and develop knowledge, problem-solving, and technical skills with the aim to provide better health care through higher standards. It could be through conference attendance, group discussion or directed reading to name just a few examples.
We provide a free online form to document your learning and a certificate for your records. Already read this title? Stay on CRCPress. Exclusive web offer for individuals on print book only. From Concept to Implementation. Preview this Book. Electronic Circuit Design: Select Format: Add to Wish List.
Close Preview. Toggle navigation Additional Book Information. Component engineering is responsible for the maintenance of the component database.
The tasks related to the component database include supplier approvals, specifying order codes, creating part numbers, and assigning reliability values for parts. Component engineering also manages component obsolescence issues. Circuit designers must work closely with component engineers during the initial phase of the design cycle. Generally designers should choose components from the preferred component list. They are also directed to choose components with multiple sourcing arrangements.
These steps minimize the risk of production line disruptions in the event a supplier has difficulty delivering the ordered components for production.
However, certain parts Design Process 63 may have a single source. Often these suppliers are reputable manufacturers of components with a proven track record of managing customer relationship in case of discontinuity, substitution, or obsolescence of their products. Failures in time is expressed as failures per hours.
There are two widely used reliability prediction methods: It presents two prediction methods: These methods vary in degree of information needed to apply them. The Part Stress Analysis Method requires a greater amount of detailed information and is applicable during the later design phase when actual hardware and circuits are being designed. The Parts Count Method requires less information, generally part quantities, quantity level, and the application environment.
This method is applicable during the early design phase and during proposal formulation. In general, the Parts Count Method will usually result in a more conservative estimation i. As mentioned earlier, it is the responsibility of the component engineer to include the FIT rate for individual components in the component database.
Moreover, designers can use commercially available software programs to predict accurate reliability figures for their designs. These programs allow the designers to set operating parameters for components and gauge more predictable reliability values for designs.
Some larger companies have formulated company-specific reliability prediction methods, although such methods are fundamentally based on MIL-HDBK They use the field return statistics and corresponding part failures to estimate more realistic or company-specific FIT rates for the components. From Concept to Implementation Designers must select components from this list wherever possible in their designs. The advantages of choosing components from the preferred list are: Although this is true for the majority of the electronic components used in a design, there are other components in the bill of materials BOM where the construction details and expected performance characteristics must be supplied to vendors with the order.
Such components are mainly electromechanical parts, such as cable assemblies, transformers and printed circuit boards. As an example, when ordering a cable assembly, the following can be supplied: The component engineer can then update the component database to include the documentation that is presented to the supplier of the cable assembly when ordering the part.
Production engineering should examine the technology used, component packaging, and component layout and orientation on the PCB. Larger companies employ concurrent engineering concepts, so by the time the design is released for production, the majority of the issues related to production have been sorted out.
This approach helps companies improve their time to market, ensure product quality, and achieve greater financial returns. The two types of testing as far as production is concerned are: Once the PCB is populated with components, in-circuit testing identifies any faulty components, including PCB problems.
Functional testing must be carried out on every product. Functional test specifications are produced and released by designers in consultation with test engineers.
Test engineering requires test point access to nodes on the circuit to perform tests on discrete components and component modules. This requirement must be factored in during PCB layout. As more and more companies are outsourcing the assembly of products, this may be a department of a contract manufacturing company. Its major responsibilities include ensuring the material required for production is available as and when needed, and negotiating contract agreements with material suppliers.
These contracts determine price, quantities for the contract period, delivery schedule, and lot sizes. Involvement of the purchasing staff during design of a product is mutually beneficial to both departments. The purchasing department can source material for prototype production runs.
It can help designers obtain sample components for design verification. Purchasing can also liaise with component engineering to have new parts qualified and approved through the MRP system.
There are company-specific and generic quality plans that must be followed at all stages of product development. The following plans are applicable to the design process. These cross-functional teams are design engineering electrical and mechanical , production engineering test and manufacturing , and material procurement.
This is carried out after design verification of the product is concluded by the engineering team. At this stage, all relevant documents pertaining to design, testing, and manufacturing have been reviewed and released. The QA department acquires a sample unit from a pilot production run to carry out the testing. The QA tests do not repeat the design verification tests carried out by the design team.
At this stage, the QA team does not expect to uncover any design flaws. However, these tests may include environmental tests, such as temperature cycling, damp heat, vibration, and shock.
Its reviews, audits, and subsequent reports at various stages in the design process help uncover deficiencies in design methodology.
Although it is not essential for all product designs, QA may produce a specific quality plan for the development of the product. It justifies the cost of product design through a business case to company directors. The MRS is produced by marketing and must be made available to engineering prior to initiating detailed design work.
They have the authority to identify and ban unsafe products in the market. In addition to enforcing safety standards, regulatory agencies can enforce mandatory information standards, such as the labeling that appears on products. In most countries, a product cannot be placed in the marketplace if that product does not comply with governing EMC standards and is labeled accordingly.
As the radio frequency spectrum becomes more crowded and the electronic circuitry within products operates at increasingly higher frequencies, such standards have been justifiably imposed on products by regulatory authorities. EMC poses a challenge to designers, and companies must ensure that their design engineers understand EMC by providing training for them so they can engineer designs free from EMC problems.
In this respect, companies may publish their own EMC design guidelines covering rules for technology, PCB layout, mechanical construction, and electrostatic discharge. Alternatively, designers can refer to application notes published by component manufacturers for guidance [3,4].
Solving EMC problems in later stages of the design cycle can be very costly. It may delay production, and companies may be penalized for these delays. Some companies employ engineers who specialize in EMC control to provide guidance and advice to the design team.
It also shows the freedom of designers to take corrective actions at those stages. Note that at later stages designers have few corrective options available to overcome EMC problems, and these options could be prohibitively expensive.
This means that the time designers spend addressing and solving EMC problems at the PCB layout level is justified to guarantee higher-level EMC problems are manageable and correctable.
The folder may also include sales literature, component placements, circuit diagrams, and software versions. Preparation of the compliance folder is a prerequisite to EMC labeling. Some companies obtain the services of external agencies that offer compliance folder management and support. These agencies may even retain the compliance folders and provide complete folder management for their clients. This is a popular service for companies such as importers that lack the technical knowledge and resources to manage the EMC compliance process.
They may also act as the agents for companies when dealing with regulatory issues. They provide component samples, evaluation boards, and expert technical advice to designers. All reputable component manufacturers produce application notes for their components. Application notes provide tested and proven designs as recommended by the component manufacturer.
Designers must be encouraged to refer to application notes during circuit design to ensure performance for the intended application. Furthermore, adherence to application notes offers a design advantage and may shorten design time by reducing debugging and test times. The order code specifies the component name, package type, and packing code. The packing code determines whether the components are packaged in tubes or in tape and reel with specified diameter.
Production engineers must decide on the packing preferences for the component. The QA plan for product design forces the design staff to perform such reviews at every milestone as the design progresses. For example, a design specification review must take place at an early stage in the design process prior to any detailed design work. Reviews empower the design team to embark on the detailed design confidently and with less ambiguity. Proper reviews require time, and reviews should not be rushed through the design process.
These reviews must be done as outlined by the QA plans developed for the design process. Depending on the type of specification being reviewed, the project manager or the team leader would convene a review meeting attended by stakeholders from the different functional areas.
Test plans and subsequent test reports verify the performance of the product against the design specification. Test plans are reviewed by fellow designers in the design department. Test plans can be very descriptive and may describe testing methodologies in detail. The test report is the evidence that can be presented to internal reviewers e. Test reports must show the test configurations in detail, including the equipment used and their calibration status. Test reports must be kept with the project file for a designated period of time as required by company policies.
At this stage, all design-related problems have been rectified after thorough testing of the product. This means that purchasing can procure parts, production engineering can build and assemble the product, and test engineering can test the product without relying on support from those who engineered the design.
This is the objective of the pilot production run. The pilot run includes product quantities for quality assurance and field trials. Even though a review has taken place prior to pilot production, the manufacturing process will find inadequacies in documentation. The pilot production report includes such shortcomings and the respective departments must attend to those discrepancies prior to volume production.
The design 71 Design Process process also generates production documents as well as user and technical manuals that will be used by production throughout the life cycle of the product.
Documentation ensures the reproducibility and quality of the product. A bill of materials BOM , assembly drawings, component inspection documents, and functional test specifications are some of the documents produced during the design process apart from CAD documentation and data files aiding computer-aided manufacture CAM. Its ownership rests with engineering. Therefore, any changes to the BOM must be done with the consent of engineering.
The BOM defines all necessary components required for assembly of the product. Basically, the BOM is a collection of part numbers; each part number identifies a component. These components can be electronic devices or mechanical items such as brackets, screws, washers, labels, and packaging material.
The part number must also refer to a circuit reference as described in the circuit schematics. Obviously, not all parts in the BOM have circuit references. Each line of the BOM has many fields. Essential fields Screw — BOM ref: T1 Heatsink — BOM ref: The top of the BOM structure will be the part number assigned for the product for customer orders. Below this level, there are assemblies, packaging, manuals, and other documentation.
Functional test specifications can be changed to reduce test time after analyzing failure statistics. Assembly instructions are generated during the design phase and prepared by draftspersons. Assembly instructions are supported by diagrams and photographs, with references to the BOM.
Design Process 73 2. It should contain, among other things, safety precautions, product identification, parts supplied, installation procedures, operating instructions, warranty provisions, frequently asked questions, and product support contacts.
User manuals are not technical manuals and should be written in plain language, avoiding technical jargon wherever possible. Technical writers gather information for the manual from all available design documents. They provide in-depth system-level technical details of the product that are useful for technical support personnel.
Technical manuals may contain, depending on the complexity of the product, an installation guide, functional descriptions of the modules, circuit diagrams and bill of materials, recommended spares, user-configurable features, firmware version and fault diagnostics.
The success of the project depends on how well it is managed by the project manager. Senior management may appoint a dedicated project manager to guide the design process for a complex project where there may be commercial implications for not delivering a desirable product. Alternatively, a team leader can manage a relatively simple product design and assume the role of project manager.
Whatever the case may be, it is necessary to practice established project management principles wherever possible when managing product design. The project manager must be able to justify the resources needed, whether they are monetary, equipment, or personnel. These justifications can be substantiated by providing evidence of resource allocations made to similar projects in the past. The design objective must be a clear and unambiguous statement.
It is essential that the client, 74 Electronic Circuit Design: From Concept to Implementation product marketing, and all other stakeholders agree on the design objective. The scope of the project must remain current until the completion of the project. Project management can identify a range of options in consultation with design experts within design engineering that can lead to successful completion of the project.
These options must be discussed and reviewed with senior management. Changes can have a direct or indirect effect on the project; therefore, changes must be managed and controlled. They can impact resources, design milestones, cost, quality, and material. Once the breakdown of tasks and activities is identified, project management can determine the proper sequence of events and their estimated durations and resource allocations.
The durations and resource requirements for activities can be gauged from similar design tasks completed by designers in the past. Project management must also take contingencies into account when planning the schedule.
The project schedule must mirror the objectives of the project. The schedule must be favorably reviewed by the stakeholders before design activities can begin. Project management must update the Gantt chart regularly to get a snapshot of progress related to the project. Progress must be reviewed at every project meeting to ensure that targeted outcomes and milestones do not slip within the schedule.
The schedule is not a static document. It, too, will change due to a variety of events. Staff may become ill, components may not arrive on time, or testing of the prototypes may be prolonged; such events can have adverse effects on the schedule.
If the changes happen to an event that is in the critical path, it should be examined thoroughly to determine the available options that may help minimize the effect on the schedule. If the change Design Process 75 is due to an inadequacy of resources, project management should be able to negotiate for additional resources. Monitoring the costs of a project is done through cost control. The project team can charge material costs to a specific cost code assigned to the project by the finance department.
Project management must alert higher authorities when cost increases occur. Summary reports sent to senior management at regular intervals must state whether the project is progressing within budget or not. The project scope statement, overall quality policy of the company, project outcomes, and adherence to established product development processes are some of the inputs that can be taken into account when deciding on quality criteria for the project. During the life of the project, a representative from the QA department should work with the project team, performing scheduled and random audits to measure project performance against agreed-to quality criteria.
By monitoring the progress of the project, it is possible to assess individual performances against what was agreed to when the project schedule was formulated. By linking their performances to personal development reviews, designers can be encouraged to complete their tasks as planned.
It is important that project management recognize achievements and establish a plan to reward good performance. The morale of the team can be judged by the progress and enthusiasm displayed by team members throughout the project. If there is low morale, it may be necessary to consult with team members to ascertain the reasons.
The reason may be a project-related issue, such as lack of training. The project closure report outlines achievements against project objectives, lessons learned, and recommendations for future design work. From Concept to Implementation References 1. Lun, T. From Concept to Implementation 3. However, the energy source available for the system may be a commercial AC supply, a battery pack, or a combination of the two.
In some special cases, this energy source may be another DC bus within the system or the universal serial bus USB port of a laptop. In a successful total system design exercise, the power supply should not be considered as an afterthought or the final stage of the design process, because it is the most vital part of a system for good performance under worst-case circumstances. Another serious consideration in system design is the total weight and the volume, and this can be very much dependent on the power supply and the power management system.
Also, it is important for design engineers to keep in mind that the power supply design may entail many analog design concepts. Most power supply design issues are due to resource and component limitations within the power supply and the power management system. Nonideal components—particularly, passives, commercial limitations to allocate sufficient backup energy storage within the battery pack, unexpected surges and transients from the commercial AC supply, and the fast load current transients—can create extreme and unexpected conditions within the system unless the power management system adequately addresses all the possible worst cases at an early design stage.
Many product design experts choose to have the power supply and the power management system designed at an early stage with estimated parameters, with the actual system blocks powered from the system power supply. This approach may help minimize late-stage disasters in a large design project. When highspeed and power hungry processors were introduced during the mids, much attention was focused on transient response, and industry trends were to mix linear and switching systems to obtain the best of both worlds.
Lowdropout LDO regulators were introduced to power noise-sensitive and fast transient loads in many portable products. In the late s, power management and digital control concepts and many advanced approaches were introduced into the power supply and overall power management . In this chapter we consider design concepts and approaches, with a few design examples of how fundamental design concepts and practices can be applied to develop the power conversion stages and the power management system.
Because of space constraints, for detailed theoretical aspects and deeper design considerations, the reader is referred to the many useful references cited herein. In the modern world of powerhungry products with mixed power supply rail values where a battery pack or another limited capacity alternate energy source is used as the primary or the secondary source, a few additional requirements need to be considered. These are energy-saving aspects, quality of the output with respect to fast load transients, electromagnetic compatibility issues, protection and supervisory aspects, packaging aspects, and communication interfaces.
For the power supply, the design team has two basic choices: The final decision must consider overall cost and the time to deliver. However, when a system becomes quite complex and requires multiple power rails and critical power management, design and build becomes the choice. Distribution becomes more efficient with lower currents, and local power conversion occurs at lower power levels with the many different voltage levels required by individual circuit blocks.
The selected DC bus voltage is determined by the safety requirements. Davis  and Curatolo  provide and overview of DPA concepts, including system cost aspects, Cassani et al. When the overall lineto-load efficiency LTLE is a serious design consideration, designers should carefully account for the efficiencies of individual power supply blocks .
Designing power solutions for line cards in information systems that handle multiple tasks at high speeds is complex. As these boards must process large amounts of data, they incorporate multigigahertz microprocessors, dual-logic application-specific integrated circuits ASICs , and other high-performance devices. These new-generation devices can require two operating voltages per chip: Until recently, these power supply requirements were addressed using multiple single-output isolated DC-DC converters.
However, with rising currents and declining voltages, along with tighter regulation tolerances and faster slew rates, multiple isolated converter solutions are not as effective in such applications.
These isolated converters are not space efficient and can cause higher ohmic losses along long interconnections. Under such conditions, maintaining high overall efficiency and tight point of load POL regulation becomes challenging. To alleviate these issues, now there are integrated building blocks that provide DPA architecture-based solutions for POL requirements.
These are the linear approach, the switching approach, and the charge pump approach. GND 3. Courtesy of Power Electronics Technology . Switching-type DC-DC converters—once the clear choice for 5-V systems—suffer lower efficiency at lower voltages. This situation has led to LDO voltage regulators based on linear designs. Often, combining a switcher and an LDO makes more sense in electronic systems where the DC rail voltages are less than 5 V or 3.
This is mostly due to the rectification losses at very low output voltages. Courtesy of EDN. For many years, designers have used charge pumps for DC-DC conversion in applications for which the regulation tolerance, current conversion efficiency, and noise specifications are not very stringent.
As discussed later, these circuits use capacitors combined with switches to boost or invert the input voltage, and they do not occupy more PCB or silicon area to implement as a single-chip converter . Recent generations of charge pumps have become viable DC-DC conversion methods for cellular phones, portable wireless equipment, notebook computers, and PDAs, where high-density DC-DC conversion is necessary and circuit area is at a premium .
In a practical system, the power supply designer has the possibility of combining these techniques. For an effective overall solution taking all specifications and cost into account, combining a large-capacity bulk SMPS in tandem with LDOs and charge pumps becomes a very effective approach.
In portable application design, the designer should be careful when selecting techniques, and in many situations the method can be a mix of the three techniques discussed. Modern gigahertz-order processors and peripherals generate fast load current transients on their multiple DC rails, and users expect longer run times from batteries.
Therefore, in designing the DC power supply subsystem, one should consider the following: To achieve the above, designers have access to a wide variety of technologies and power management IC families, battery management technologies, architectures, and standards. If the overall system consumes more than 50 W with several DC rail requirements, one has to first carefully analyze the load and have an overall view of its DC rail voltages and the transient behavior of the load.
Courtesy of Power Electronics Technology . The input power source for a case like this will be a Li -ion or Li-polymer rechargeable battery pack.
If this particular system operates from a Li-ion battery, the input operating voltage will be from 3. This operating range is a critical factor in selecting the power supply topologies in the design process. In this kind of product, there are different mixes of blocks, such as the processor, memory, analog front ends, video amplifier, motor, liquid crystal display LCD , CCD module, and backlight for the LCD.
A few concepts used in such a system include: Appropriate supply topology selection depends on the input voltage, output voltage, noise, efficiency, cost, and space. The last three items usually compete with each other. The first two restrict the choice of the topology. If the output voltage is always lower than the input voltage, a buck converter or an LDO will work. Otherwise, a buck-boost or a single-ended primary inductance converter SEPIC discussed later will work.
Between these limits, the battery maintains approximately 3. All selections need to be based on these values.
Weighted efficiency is calculated by multiplying each efficiency value by the typical bus power divided by total estimated power ratio. In real-world operation, the example here can have different modes of operation, and for each mode one has to develop a table and analyze and estimate the best options. Then it is necessary to have an estimate of the percentage of the time the camera spends in each mode. For lower-noise considerations, even if an LDO solution is considered in lieu of a switcher , weighted efficiency indicates otherwise for items such as the 3.
Power Electronics Technology . For the 5-V analog bus for the video amp, low-noise operation may be mandatory, but at lower battery voltages such as 3. In this situation, a switcher is to be selected and then followed up with an LDO. After defining the power supply requirements, the designer can start choosing individual ICs required for the system.
For details, see Day  and the data sheets of the relevant ICs [16,17]. By , most cellular phones allowed many features in addition to voice communication.
A trend is for cellular phones to act as MP3 players or to add a micro hard disk or a very large amount of silicon memory. HDD 3. Courtesy of Power Electronics Technology. In the older generation phones the main power rail was 3. Examples are baseband chipsets running from 1. With the common acceptance of mAh Li-based cell phone battery packs, and dealing with packaging problems, thermal management, and noise issues, power management of the product becomes quite critical and the designer has to make a well-informed and critically analyzed approach .
For more discussion on the practical design considerations for portable wireless products, see Armstrong  and Maxim Integrated Products . Then we can add as much secondary information as possible. The more requirement specifications we list, the easier it is to narrow down the available options. Design specifications act as the performance goal that the ultimate power supply must meet in order for the product to meet its overall performance specification.
When developing the specification, the power supply designer must keep in mind what is a reasonable requirement and what is an idealistic requirement. Most specification-related parameters are measurable using common test setups under different environmental conditions.
In developing these specifications, the designer should have a clear idea of the load requirements and steady-state and transient behaviors. In a very simple case where load consumes a few watts to about 50 W in a single- or dual-rail requirement, the load can be supplied by a simple linear or switching supply where only a few of the above items need to be specified. Brown  and Rubadue  provide useful details on specifications and design concepts. A discussion of battery management for longest run time and standby time is beyond the scope of this chapter.
In extreme cases, the load may consist of several complex processors or other mixed signal loads that may require multiple power rails, specialized power management aspects, and ultra-low-voltage DC rails that consume A or more.
Some processor loads may demand digitally controlled adjustable power rails for effective power management. In communication subsystems, the load may demand extra low-noise and low-voltage power rails.
Range of input voltages Product is expected to withstand this range of fluctuations. Frequency for AC input systems or total energy available from a battery pack in mAh or Ah In the case of a battery pack, an off-the-line charger may be designed for the input frequency. In-rush current Important for the start-up conditions. Voltage transients Important for the reliability of the power supply and the load for reliable operation.
Permissible harmonics or power factor Governed by various standardization bodies. Fusing Speed of fusing is based on the I2t rating of the device.
Nominal output voltage The load is expected to operate at this voltage. Average and peak currents RMS values to be used. Stability over a specified period Based on the age of the components. Hold-up time Amount of time the output remains within usable limits when the input source is disconnected temporarily. Output voltage temperature coefficient The stability of the output voltage rails.
Dependent primarily on the reference source stability and the temperature tolerances of the output sampling chain resistors. Output specifications Regulation specifications continued on next page 92 Electronic Circuit Design: Output impedance Represents the Thevenin equivalent resistance of the power supply output. Ripple and noise limits These specifications may be very significant for the reliable operation and accuracy of analog- and mixed-signal circuitry.
Over- and undervoltage limits at the output These specifications indicate the safe operation limits of the load. Output current limit Maximum load current expected. Thermal limits To avoid excessive temperature conditions within the product or the power supply. Power conversion specifications Overall efficiency In battery-powered products and green designs, this is a critical specification.
Thermal dissipation Determines the need for cooling and packaging limitations. Energy conservation and green design aspects Particularly important in high-power loads. Sequencing and resetting of the output rails Critically important specification in multiplerail situations. From Concept to Implementation should have an initial estimate of the load requirements and an idea of the nature of the load in general. The key considerations include: For the simple cases of single- or dual-rail power requirements, there is a choice of three-terminal linear regulator chips; these are low cost and easy to implement, with excellent noise and drift characteristics.
The most useful property is their speed of response to transient loads. There are ways to improve the efficiencies of linear regulators by manipulating the rectifier circuits in the input stages using silicon-controlled rectifiers . Many common loads can tolerate slower responses and greater amounts of high-frequency noise.
For such simple requirements, there are switching regulator solutions where the equivalent of a three-terminal linear IC solution is provided by integrated switching regulator ISR techniques by companies such as Power Trends.
ISRs are able to provide buck, boost, or inverting voltage values from a single DC bus supply such as 5 V . Further to examples given in Section 3. Some of these are powered by a few AA cells from which different voltages need to be generated. See Figure 3. Adapted from Narveson . Reed Business Information, a division of Reed Elsevier.
All rights reserved. In CMOS digital circuits, the power consumption is proportional to V2, and this fact encourages chip designers to develop processors that operate with lower rail voltages .
To achieve these rates, most modern high-power processors have digital command signals based on four- to five-bit code to command a voltage regulator module VRM to output different voltages to power the processor. For more details, see Mannion . The VRM is capable of adjusting its own output voltage under the command code bits from the processor within the range of values specified by the processor.
With the load demands of extremely high current slew rates, the VRM should be capable of responding quickly with low-ESR capacitors at the output. The PCB track inductances can jeopardize the required slew rate; thus, designers must pay special attention to PCB layout. For details, see Brown , Gentchev , and Wong et al. In most processor-based systems, power rails have typical value combinations such as 1.
Common themes are sequential power-up, ratiometric method, and output tracking or simultaneous or coincidental power-up. This technique can be used to delay the start-up of the second rail at some predetermined time after the first rail is turned on.
Switching off can be based on the same principle in the reverse order . The two rails are turned on simultaneously, reaching regulation at their respective set points at the same time.
In this method, the two rails are controlled with different slew rates. Around , Intel shipped processors with technology to allow the central processing unit CPU to slow down, suspend, or shut down part or all of the system platform, or even the CPU itself, to preserve and extend battery life.
The history and technical details related to this process are available in Kolinski et al. The ACPI specification provides a platform-independent, industry-standard approach to operating system—based power management. ACPI-compliant computers require the generation of these multiple voltages at various current ratings as the system transitions between sleep states. The ACPI defines six possible discrete system operating states, which are referred to as S0 to S5, in order of highest to lowest power consumption.
In addition, this may even provide the option of freeing the designer from the burden of getting safety approvals for the product. Until the late s, wall plug-in supplies were limited to less than 25 W, but as of this capability has grown to about W. Most low-power, older versions were linear regulator based, but recent energy-saving and related standards worldwide have pushed these products to adopt switch mode designs.
From Concept to Implementation details on external power supplies, international power converter requirements, and recent energy saving standards, see Everett , Forrester , and Jovalusky . Note the isolation indicated in the feedback and control block, which is essential for this purpose. Within the past two decades, because of the emphasis placed on power quality issues, PFC as applicable to the nonlinear behavior of the input current waveform of a rectifier has become an important issue.
When the switch S1 is closed, the circuit may be operated at a nominal line of V AC. When the switch is open, D1 to D4 form a full-bridge rectifier capable of rectifying a nominal V AC line and producing the same V DC output voltage.
In many universal input systems, there is an automatic changeover capability built into the design. One is the energy storage in capacitors C1 and C2. The other is the resistor R1 and special components such as negative temperature coefficient NTC thermistors for the purpose of inrush current limiting.
From Concept to Implementation where VRMS is the rms AC input voltage, Iload is the average load current, f is the line frequency, and C is the value of the effective smoothing capacitor. For diodes, maximum forward rectification current capability, peak inverse voltage PIV capability, and the surge current capability to withstand the peak current associated with turn-on are the most important specifications. Proper calculation and selection of the input rectifier filter capacitors are very important, because this will influence performance parameters such as low-frequency AC ripple at the output power supply and the holdover time.
Normally, high-grade electrolytic capacitors with high ripple current capacity and low ESR need to be used with a minimum working voltage of V DC. Fuses are categorized by three major parameters: The current rating of a fuse is the RMS value or the maximum DC value that it must exceed before blowing. The voltage rating of a fuse is not necessarily linked to the supply voltage. The voltage across the fuse element under these conditions depends on the supply voltage and the type of circuit.
For example, a fuse in series with an inductive circuit may see voltages several times greater than the supply voltage during the clearance transient. The I 2 t rating of a fuse is defined by the amount of energy that must be dissipated in the fuse element to cause it to melt.
This is sometimes referred to as the prearcing let-through current. To melt the fuse element, heat energy must be dissipated in the element more rapidly than it can be conducted away. This requires a defined current and time product. The heat energy dissipated in the fuse element is estimated in watt-seconds or joules , or I 2 Rt for a particular fuse with an internal resistance of R. As the fuse resistance is a constant, this is proportional to I 2 t, normally referred to as the I 2 t rating for a particular fuse or the prearcing energy.
It should be noted that the I 2 t energy can be as much as 20 times greater in a slow-blow fuse of the same DC current rating. For example, a A fuse can have an I 2 t rating ranging from 5 A2s for a fast fuse to A2s for a slow fuse. For high-power semiconductors such as power diodes and transistors, manufacturers indicate a value of I 2 t, from 10 ms for 50 Hz or 8.
Comparing this value with the fuse I 2 t permits us to verify the protection . These currents are caused by the charging of the filter capacitors, which at turn-on present a low impedance to the AC lines, generally limited by the ESR plus the total input resistance within the charging path. If no protection is employed, these surge currents may approach very large values to blow the input fuses.
Several methods are widely employed in introducing a high impedance to the AC line at turn-on. Initially, the thermistor resistance is high, which limits the inrush. Courtesy of Power Electronics Technology; Bell . From Concept to Implementation through the thermistor, it heats up and the resistance decreases for normal operation.
The FET limits the inrush by turning on slowly as its gate capacitor charges. The input filter charges through the resistor until the relay is commanded to connect the filter to the converter and short the resistor. Each of these has its advantages and drawbacks . The value of L1 is typically 5 to 10 times larger than L2. More details of this technique are discussed by Bell , giving attention to the design of the magnetics.
If the waveforms are not aligned, the power factor PF is less than 1; if they are aligned, the PF is greater than 1. In most cases, PF-corrected designs can achieve PF values of 0.
Given this simple explanation, it is also necessary to appreciate the case of nonsinusoidal rectifier currents, which can generate many harmonics of the line frequency waveform. In practice, sometimes it is reasonable to assume that the input voltage waveform is purely sinusoidal, despite any distortions in the current waveform.
With this discussion, we can appreciate the regulatory bodies defining the limits of harmonics generated by electrical systems connected to the AC utility grid. In practical cases of off-line SMPS systems, the fundamental idea is to use a power MOSFET switch and an inductor in the series path of the charging capacitor to artificially align the voltage and charging current waveforms.
A power factor control IC that switches the MOSFET at higher frequency smoothes out the current waveform and aligns its fundamental component with the input voltage waveform. Courtesy of EDN; Zuk . It is important to note that the main smoothing capacitor Cin has now moved further toward the DC-DC converter stage. Figure 3. For details of this application case, see Zuk ; Sandler et al.
However, when low-noise requirements and fast transient response at the output side are required, LDOs are considered as follow-on blocks or postregulator circuit blocks. The following section provides an overview of techniques available and important design considerations.
For complete theory and analysis of switch mode and linear converters, the reader should refer to the bibliography at the end of the chapter. As discussed in Section 3. The switching converter topology has a major bearing on the conditions in which the power supply can operate safely and on the amount of power it can deliver. Cost versus performance tradeoffs are also needed in selecting a suitable converter topology for an application.
The primary factors that determine the choice of topology are whether DC isolation is needed, the peak currents and voltages the power switches are subjected to, the voltages applied to transformer primaries, cost, and reliability.
Some relative merits and demerits of the converter topologies and typical applications are summarized in Table 3. The industry has settled on several primary topologies for a majority of applications. The boundaries Electronic Circuit Design: Nonisolated basic converters buck, boost, and buck-boost types are generally used for lower-power PCB-level converter circuits and are not so popular for higher-power applications.
Isolated versions such as forward mode, flyback, and bridge types are generally used for applications where higher power, galvanic isolation, and multiple output rails are required. Because of the advantages of operation in buck or boost modes without inversion, SEPIC converters are gaining popularity in battery-powered applications.
The following sections provide an overview of important design aspects of these topologies. The power switch in the forward topology is ground referenced also called a low-side switch , whereas in buck topology the switch source terminal floats on the switching node. The main advantage of the forward topology is that it provides isolation and the capability to provide step-up or step-down function.
One important design consideration in this topology is the magnetizing inductance and the need to reset the transformer core. The value of LM can be measured at the primary terminals with the secondary winding open-circuited.
The peak current in LM is proportional to the maximum flux density within the core, and a given core can handle only a Design of DC Power Supply and Power Management limited flux density before saturation occurs. At saturation, a rapid reduction of inductance occurs.
The other element added to the transformer model is LL, and this can be measured at the primary terminals with the secondary winding s short-circuited. This term represents the stray value, which does not couple primary to secondary. With careful design, this value can be kept small and the effect on the converter is limited to voltage spikes on the power switch. A few techniques are available for this purpose. The common method is to have an additional winding and a diode for core resetting.
A few advanced techniques used for solving the same problem are active clamp reset and resonant reset forward converters. Mappus , King and Gehrke , and Hariharan and Schie  provide analysis and design aspects of the active clamp reset techniques.
Hariharan and Schie  and Khasiev  detail the important design aspects of resonant reset forward converters. In multiple output applications, the addition of a secondary winding, a diode, and an output capacitor is all that is required for an additional output. Flyback converter operation can lead to confusion if the designer approaches the design of its magnetics as if it were a transformer.
Except for the case of multiple output windings, the magnetics in a flyback converter are not a transformer. An easy way to view this is as an energy bucket that is alternately filled when the switch is on and dumped when the switch is off. In other words, a flyback magnetic sometimes called a transformer choke is an energy-in, energy-out power transfer device where input and output windings do not conduct current simultaneously.
A gapped core is used in general to have adequate leakage inductance at the input side for energy storage during the switch-on period. The primary specifications for an off-line flyback power supply design, such as a power adapter for a notebook computer or a PDA, are based on the following: Power Electronics Technology [45,47,48].
Adapted from , courtesy of Power Electronics Technology. VDC min Dmax 3. The core set and the gap must be chosen for an AL product that supports a reasonable number of turns in such a way that it meets the other requirements as well .
Then the secondary turns are calculated from the following: For more details related to these design approaches, see Leman  and Power Integrations, Inc. In this design approach, current waveform parameter K P simplifies calculations for both continuous and discontinuous modes . For critical mode control—based design approaches, see Basso .
In this kind of design, for the best performance in charging a battery, the constant voltage mode CVM , constant power mode CPM , and constant current mode CIM are combined. It is also possible to use either an active clamp or RCD clamp approach for transformer demagnetizing, and critical mode conduction is used on the boundary of the CVM and CPM regions .
Lower values are needed for Zeners with higher IZT. Courtesy of Power Integrations, Inc. They are inexpensive because the transformer which really works as a coupled inductor is part of the output filter and generating multiple outputs merely requires the addition of another secondary winding along with diodes and output filter capacitors.
However, at power levels greater than W, because of excessive peak currents in the switching transistor and excessive voltages across the switches, this topology reaches its limitations. In these situations the two-transistor forward converter approach is a solution. Design aspects and calculation guidelines for the two-transistor forward converter are available in Gauen [59,60].
In general, full-bridge topology is used for very high-power applications, and it is quite important to consider the losses in the circuits and the design complications due to their high-side switches operating with their source terminals in the case of MOSFETs or emitters in IGBTs or power transistors at floating levels.
Gate driver ICs help solve this problem. In general, losses are contributed by many different sources, the important ones being: Using a simple calculation based on an Excel sheet, the designer can determine where optimization can be achieved.
In a larger-capacity power supply, the percentage values may be different. If constant current control is used. Courtesy of Power Electronics Technology; Jovalusky . For example, in half- or full-bridge circuits based on MOSFETs, low-side n channel transistors need to be driven by a positive gate voltage with respect to the ground plane, but the high-side transistor gate needs to be driven by a positive voltage with respect to its source terminals, which will be at floating voltage values.
Gate driver circuits are useful in any switching system topology where two switches operate at high and low sides. To justify the use of these for efficient power circuit designs, the designer should understand and pay adequate attention to the parasitic capacitances at the gate input . In some of these, optoisolators are used for electrical isolation between the drive side and the power stage. Several years ago the author was asked to develop a DC-DC converter based on the following specifications: Adapted from Clemente, S.
For initial startup requirements, a simple auxiliary power supply of 15 V was proposed. Once the V DC output appeared, an auxiliary winding in the planar transformer would handle overpowering of the control and supervisory circuits.
From Concept to Implementation From Concept to Implementation a smaller PCB area after carefully considering the simplicity achievable by the pulse transformers. In achieving a low component count and associated high reliability, it was necessary to drop the temptation to use standard logic IC-based supervisory circuits and use a component count optimized simple comparator circuit-based subcircuit. Although SEPIC circuits require more components than buck or boost converters, they allow operation with fewer cells in the battery, where the cost of extra components is usually offset by the savings in the battery.
SEPIC topologies possess the following advantages: A more detailed analysis [69,70] with design approach can be found in Dixon [67,68,71], Nuefeld , and Rahban . Courtesy of Power Electronics Technology; Nuefeld . Another useful practical consideration for easy construction and lower cost in SEPIC circuits is to have the two nearly equal inductors coupled [69,71]. However, due to its circuit complexity, it had not found application in low-power DC-DC converters until about the early s.
All resonant control circuits keep the pulse width constant and vary the frequency, whereas all PWM control circuits keep the frequency constant and vary the pulse width. From Concept to Implementation have been designed to operate with switching frequencies generally in the range of 50 kHz to more than kHz. However, increasing the switching frequency, although allowing for miniaturization, leads to increased switching stresses and losses.
This leads to a reduction in efficiency. The detrimental effects of the parasitic elements also become more pronounced as the switching frequency is increased. Resonant circuits in power supplies can also operate in two modes: In the continuous mode, the circuit operates either above or below resonance.
This is a truly resonant technique, but it is not commonly used in power supplies because of its high peak currents and voltages. In the discontinuous mode, the control circuit generates pulses having a fixed on-time but at varying frequencies determined by the load requirements. This mode of operation does not generate continuous current flow in the tuned circuit. This is the common mode of operation in a majority of resonant converters and is called the quasi-resonant mode of operation. The power switch is turned on and off in the same manner as in PWM converters, but the tank circuit forces the current through the switch into a sinusoidal form.
The actual conduction period of the switch is governed by the resonant frequency, fr, of the tank circuit. The main advantages of the quasi-resonance arise from the near-sinusoidal switching currents and voltages. The operation of a quasi-resonant switching power supply is analogous to a PWM supply of the same topology.
The difference lies in the fact that the switching waveform in quasi-resonant supplies has been preshaped into a sinusoidal form. With PWM converters, there is simultaneous conduction of current and voltage during part of the switching period. In resonant conversion, switching can be achieved at either the zero current point or the zero voltage point of the sinusoidal switching waveform, thus minimizing the switching losses.
However, increasing the switching frequency is accompanied by increasing switching stresses and detrimental effects due to parasitics.
Because resonant circuits generate sinusoids, designers can operate the power switches either at zero current or at zero voltage points in the resonant waveform. Based on this, there are two types of resonant switches: