고전압 전원공급장치 및 고전압 전자 분야의 기술 기사
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전원공급장치 사용 및 응용
작성자 Cliff Scapellati
High Voltage Power Supplies for Analytical Instrumentation
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작성자 Marcus Foxwell
전자빔 현미경: 스펠만의 역할과 응용 분야
스펠만의 전자빔 현미경 솔루션은 극도의 정확도와 정밀도를 유지하면서 이미징에 필요한 전압을 제공합니다. 전자 현미경은 다양한 산업 분야에서 사용되고 있으며, 일상 생활에 적용되며, 우리 삶 전체에 역할을 합니다. 재료 과학, 의학, 법의학과 같은 분야는 모두 이러한 현미경 사용의 발전으로 혁신되었습니다. 예를 들어 암 연구에서 전자빔 현미경(EBM)은 의사가 비정상적인 세포 구조를 조기에 발견하여 탐지 및 치료를 개선하는 데 도움이 됩니다. 재료 과학에서 과학자는 나노 구조를 탐구하고 이해하여 전자 및 에너지 효율적 기술의 혁신을 주도할 수 있습니다. 법의학에서 잔류물과 섬유에 대한 자세한 분석은 범죄를 해결하는 데 중요한 역할을 합니다. 스펠만은 전자 현미경을 위한 정밀 고전압 솔루션의 세계적 선도 공급업체입니다. 당사의 EBM 솔루션은 극도의 정확도와 정밀도를 유지하면서 전자 빔을 사용하여 이미징을 달성하는 데 필요한 전압을 제공합니다. 단위는 고객의 애플리케이션에 따라 5kV에서 120kV까지 다양합니다. 스펠만의 대부분 제품은 고객을 위한 맞춤형 솔루션으로 구성되어 있지만 표준 범위도 제공됩니다. 매우 자세한 이미징을 위한 강력한 기술. 주사 전자 현미경(SEM)은 매우 세부적인 3차원 이미지를 제공하는 놀라운 정밀도로 널리 인정받고 있습니다. 이들은 고전압 전자 빔을 사용하여 샘플 표면과 상호 작용하고 방출되고 후방 산란된 전자를 감지하여 고해상도 이미지를 생성합니다. SEM의 주요 구성 요소에는 전자 빔 생성, 빔 포커싱, 샘플 상호 작용, 이미지 감지 및 형성이 포함됩니다. 전자빔 생성은 스펠만 EBM 전원 공급 장치(PSU)와 같은 전자총을 사용하여 달성됩니다. 전자는 5kV와 30kV 사이의 일반적인 전압을 사용하여 표본을 향해 가속됩니다. 이를 가속 전압이라고 하며, 스펠만의 EBM PSU의 주요 고전압 출력입니다. SEM의 전압은 최대 75kV에 도달하여 분해능과 샘플 침투 깊이를 높일 수 있습니다. 이 현미경의 일반적인 배율 범위는 20배에서 100만 배입니다. 참고로 일반 광학 현미경의 배율은 2,000배입니다. 빔을 초점 맞추는 과정은 고해상도 이미지 생성을 달성하는 데 매우 중요합니다. 빔은 일련의 전자기 렌즈를 사용하여 세심하게 초점이 맞춰집니다. 그런 다음 빔은 샘플을 스캔하면서 일부 전자와 방사선이 흡수, 편향 또는 방출됩니다. 검출기는 이러한 방출된 전자를 포착하는데, 이를 2차 및 후방 산란 전자라고 합니다. 그런 다음 컴퓨터는 포착된 전자를 사용하여 표본의 이미지를 생성합니다. 반면, 현미경(TEM)은 3차원 이미지를 제공하는 SEM과 달리 원자에 가까운 분해능으로 재료의 내부 구조를 이미징하는 데 중점을 둡니다. TEM은 샘플을 통과하는 전자빔을 통과시켜 2차원 이미지를 생성한 다음 CMOS(보완 금속 산화물 반도체) 카메라로 캡처합니다. 편향된 전자를 감지하는 SEM과 달리 TEM은 샘플을 통과하는 전자를 캡처하여 내부 구성과 형태에 대한 자세한 통찰력을 제공합니다. 이러한 시스템은 매우 높은 수준의 정확도를 유지하면서 수백 킬로볼트 범위의 전압이 필요합니다. 이 유형의 현미경의 일반적인 배율 범위는 50배에서 5천만 배입니다. .
작성자 Cliff Scapellati
High Voltage Power Supplies for Electrostatic Applications
ABSTRACT High voltage power supplies are a key component in electrostatic applications. A variety of industrial and scientific applications of high voltage power supplies are presented for the scientist, engineer, specifier and user of electrostatics. Industrial processes, for example, require significant monitoring of operational conditions in order to maximize product output, improve quality, and reduce cost. New advances in power supply technology provide higher levels of monitoring and process control. Scientific experiments can also be influenced by power supply effects. Contributing effects such as output accuracy, stability, ripple and regulation are discussed. I. INTRODUCTION The use of high voltage in scientific and industrial applications is commonplace. In particular, electrostatics can be utilized for a variety of effects. Broadly stated, electrostatics is the study of effects produced by electrical charges or fields. The applications of electrostatics can be used to generate motion of a material without physical contact, to separate materials down to the elemental level, to combine materials to form a homogeneous mixture and other practical and scientific uses. By definition, the ability of electrostatic effects to do work requires a difference in electrical potential between two or more materials. In most cases, the energy required to force a potential difference is derived from a high voltage source. This high voltage source can be a high voltage power supply. Today's high voltage power supplies are solid state, high frequency designs, which provide performance and control unattainable only a few years ago. Significant improvements in reliability, stability, control, size reductions, cost and safety have been achieved. By being made aware of these improvements, the user of high voltage power supplies for electrostatic applications can benefit. Additionally, unique requirements of high voltage power supplies should be understood as they can affect the equipment, experiments, process or product they are used in. II. OPERATIONAL PRINCIPLES OF HIGH VOLTAGE POWER SUPPLIES A simplified schematic diagram of a high voltage power supply is shown in Fig. 1. The input voltage source may have a wide range of voltage characteristics. AC sources of 50Hz to 400Hz at less than 24Vac to 480Vac are common. DC sources ranging from 5Vdc to 300Vdc can also be found. It is critical for the user to understand the input voltage requirement as this will impact overall system use and design. Regulatory agencies such as Underwriters Laboratory, Canadian Standards Association, IEC and others are highly involved with any circuits connected to the power grid. In addition to powering the main inverter circuits of the power supply, the input voltage source is also used to power auxiliary control circuits and other ancillary power requirements. The input filter stage provides conditioning of the input voltage source. This conditioning is usually in the form of rectification and filtering in ac sources, and additional filtering in dc sources. Overload protection, EMI, EMC and monitoring circuits can also be found. The output of the input filter is typically a dc voltage source. This dc voltage provides the energy source for the inverter. The inverter stage converts the dc source to a high frequency ac signal. Many different inverter topologies exist for power supplies. The high voltage power supply has unique factors which may dictate the best inverter approach. The inverter generates a high frequency ac signal which is stepped up by the HV transformer. The reason for the high frequency generation is to provide high performance operation with reduced size of magnetics and ripple reduction storage capacitors. A problem is created when a transformer with a high step up ratio is coupled to a high frequency inverter. The high step up ratio reflects a parasitic capacitance across the primary of the high voltage transformer. This is reflected as a (Nsec:Npri)² function. This large parasitic capacitor which appears across the primary of the transformer must be isolated from the inverter switching devices. If not, abnormally high pulse currents will be present in the inverter. Another parameter which is common to high voltage power supplies is a wide range of load operations. Due to the presence of high voltage, insulation breakdown is commonplace. The inverter robustness and control loop characteristics must account for virtually any combination of open circuit, short circuit and operating load conditions. These concerns as well as reliability and cost, must be addressed in the High Voltage Power Supply Inverter topology. The high frequency output of the inverter is applied to the primary of the high voltage step-up transformer. Proper high voltage transformer design requires extensive theoretical and practical engineering. Understanding of magnetics design must be applied along with material and process controls. Much of the specific expertise involves managing the high number of secondary turns, and the high secondary voltages. Due to these factors, core geometry, insulation methods and winding techniques are quite different than conventional transformer designs. Some areas of concern are: volts/turn ratings of the secondary wire, layer to layer insulating ratings, insulating material dissipation factor, winding geometry as it is concerned with parasitic secondary capacitance and leakage flux, impregnation of insulating varnish to winding layers, corona level and virtually all other conventional concerns such as thermal margins, and overall cost. The high voltage multiplier circuits are responsible for rectification and multiplication of the high voltage transformer secondary voltage. These circuits use high voltage diodes and capacitors in a "charge pump" voltage doubler connection. As with the high voltage transformer, high voltage multiplier design requires specific expertise. In addition to rectification and multiplication, high voltage circuits are used in the filtering of the output voltage, and in the monitoring of voltage and current for control feedback. Output impedance may intentionally be added to protect against discharge currents from the power supply storage capacitors. These high voltage components are typically insulated from ground level to prevent arc over. The insulation materials vary widely, but typical materials are: air, SF6, insulating oil, solid encapsulants (RTV, epoxy, etc.). The insulating material selection and process control may be the most important aspect of a reliable high voltage design. Control circuits keep all of the power stages working together. Circuit complexity can range from one analog I.C. to a large number of I.C.’s and even a microprocessor controlling and monitoring all aspects of the high voltage power. However, the basic requirement which every control circuit must meet is to precisely regulate the output voltage and current as load, input power, and command requirements dictate. This is best accomplished by a feedback control loop. Fig. 2 shows how feedback signals can be used to regulate the output of the power supply. Conventional regulation of voltage and current can be achieved by monitoring the output voltage and current respectively. This is compared to a desired (reference) output signal. The difference (error) between the feedback and reference will cause a change in the inverter control device. This will then result in a change of power delivered to the output circuits. In addition to the voltage and current regulation, other parameters can be precisely regulated. Controlling output power is easily accomplished by an (X) (Y) = Z function, (V I = W), and comparing it to the desired output power reference. Indeed, any variable found within Ohm's law can be regulated, (resistance, voltage, current and power). In addition, end process parameters can be regulated if they are affected by the high voltage power supply (i.e. coatings, flow rates, etc.). III. HIGH VOLTAGE REGULATION The importance of a regulated source of high voltage and/or constant current is critical to most applications involving electrostatics. Variations in output voltage or current can have direct effects on the end results and, therefore, must be understood as a source of error. In high voltage power supplies, the voltage references that are used to program the desired output can be eliminated as a source of significant error by the use of highly stable voltage reference I.C.s. Typical specifications of better than 5ppm/°C are routine. Similarly, analog I.C.s (op amps, A/D D/A's, etc.) can be eliminated as a significant source of error by careful selection of the devices. There remains one component, unique to high voltage power supplies, which will be the major source of stability errors: the high voltage feedback divider. As seen in Fig. 1, the high voltage feedback divider consists of a resistive divider network. This network will divide the output voltage to a level low enough to be processed by the control circuits. The problem of stability in this network results from the large resistance of the feedback resistors. Values of >100 Meg Ohms are common. This is to reduce power dissipation in the circuit and reduce the effects of temperature change due to self heating. The large resistance and the high voltage rating requires unique technology specific to high voltage resistors. The unique high voltage resistor must be "paired" with a low value resistor to insure ratio tracking under changes of temperature, voltage, humidity and time. In addition, the high value of resistance in the feedback network means a susceptibility to very low current interference. It can be seen that currents as low as 1 X 10-9 amps will result in >100ppm errors. Therefore, corona current effects must seriously be considered in the design of the resistor and the resistor feedback network. Also, since much of the resistor technology is based on a ceramic core or substrate, piezoelectric effects must also be considered. It can be demonstrated that vibrating a high voltage power supply during operation will impose a signal, related to the vibration frequency, on the output of the power supply. IV. AUXILIARY FUNCTIONS INVOLVES WITH THE HIGH VOLTAGE POWER SUPPLY . In many applications of high voltage, additional control functions may be required for the instrument. The power supply designer must be as familiar with the electrostatics application as the end user. By understanding the application, the power supply designer can incorporate important functions to benefit the end process. A typical feature that can be implemented into a high voltage power supply is an "ARC Sense" control. Fig. 3 shows a schematic diagram of an arc sense circuit. Typically, a current sensing device such as a current transformer or resistor is inserted in the "low voltage side" of the high voltage output circuits. Typically, the arc currents are equal to: I = (E/R) where I = Arc current in amperes. E = Voltage present at high voltage capacitor.. R = Output limiting resistor in ohms. The arc current is usually much greater than the normal dc current rating of the power supply. This is due to keeping the limiting resistance to a minimum, and thereby the power dissipation to a minimum. Once the arc event is sensed, a number of functions can be implemented. "Arc Quench" is a term which defines the characteristic of an arc to terminate when the applied voltage is removed. Fig. 4 shows a block diagram of an arc quench feature. If shutdown is not desired on the first arc event, a digital counter can be added as shown in Fig. 5. Shutdown or quench will occur after a predetermined number of arcs have been sensed. A reset time must be used so low frequency arc events are not accumulated in the counter. Example: A specification may define an arc shutdown if eight arcs are sensed within a one minute interval. A useful application of the arc sense circuit is to maximize the applied voltage, just below the arcing level. This can be accomplished by sensing that an arc has occurred and lowering the voltage a small fraction until arcing ceases. Voltage can be increased automatically at a slow rate. (Fig. 6). Another feature which can be found in the high voltage power supply is a highly accurate current monitor circuit. For generic applications this monitor feature may only be accurate to milliamperes, or microamperes. However, in some electrostatic applications accuracy down to femtoamperes may be required. This accuracy can be provided by the high voltage monitoring circuits. However, the user of the power supply usually must specify this requirement before ordering. V. GENERATING CONSTANT CURRENT SOURCES In many electrostatic applications, a constant current created by corona effects is desirable. This can be accomplished in a number of unique ways. A constant current source can be broadly defined as having a source impedance much larger than the load impedance it is supplying. Schematically it can be shown as in Fig. 7: Practically stated, as R2 changes impedance there is negligible effect on the current through R1. Therefore, R1 and R2 have a constant current. In a single power supply application, this can be accomplished two ways. The first is to provide an external resistor as the current regulating device. The second is to electronically regulate the current using the current feedback control as shown in Fig. 2. In applications where multiple current sources are required, it may not be practical to have multiple power supplies. In this case, multiple resistors can be used to provide an array of current sources. This is typically used where large areas need to be processed with the use of electrostatics. Fig. 8 shows this scheme. CONCLUSION This paper presented information useful to electrostatic applications using high voltage power supplies. The high voltage power supply has concerns which differentiate it from conventional power supplies. The designer of high voltage power supplies can be a key resource for the user of electrostatics. Significant control features can be offered by the high voltage power supply. In addition, safety aspects of high voltage use require important attention. High voltage sources can be lethal. The novice user of high voltage should be educated on the dangers involved. A general guideline for safety practices is found in IEEE standard 510-1983 "Recommended Practices for Safety in High Voltages and High Power Testing [4]". REFERENCES: [1] C. Scapellati, "High Voltage Power Supplies for Analytical Instrumentation", Pittsburgh Conference, March 1995. [2] D. Chambers and C. Scapellati , "How to Specify Today's High Voltage Power Supplies", Electronic Products Magazine, March 1994. [3]D. Chambers and C. Scapellati, "New High Frequency, High Voltage Power Supplies for Microwave Heating Applications", Proceedings of the 29th Microwave Power Symposium, July 1994. [4]IEEE Standard 510-1983, IEEE Recommended Practices for Safety In High Voltage and High Power Testing. Click here to Download article PDF.
작성자 Spellman High Voltage Electronics Corporation
Bulletin STP-783, Standard Test Procedure for High Voltage Power Supplies (circa July 1983)
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작성자 The Institute of Electrical and Electronics Engineers
IEEE Std 510-1983 IEEE Recommended Practices for Safety in High Voltage and High Power Testing
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작성자 Paul Treglia and Clive McNamara
Next Generation in High Voltage Power Feed Equipment
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작성자 Derek Chambers and Cliff Scapellati
Specifying High Voltage Power Supplies
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작성자 Clifford Scapellati and Paul Treglia
High Voltage Power Supply Technology for Use in Power Feed Applications
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작성자 Boris Sasic, Sam Pindrys and Jim Willsey
Functional Role of X-ray Generators in Industrial Applications
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작성자 Cliff Scapellati
A Product Development Process For High Voltage Power Supplies
ABSTRACT: Applications requiring high voltage power sources are growing at a healthy rate. In most cases the high voltage power supply must be custom designed for a particular application. In addition, market pressure for reduced cost, increased power, and higher reliability require significant research for new, innovative approaches. . The intent of the paper is to familiarize the user and specifier of high voltage power supplies to the development process, thereby improving future development programs. A typical development time for these new designs will be less than one year. An analysis of this development process is discussed. The development process must include: specification of the product, material and labor cost goals, vendor and component issues, process control analysis, electrical/mechanical/material engineering, definition of experiments, stress testing, safety analysis, regulatory requirements, prototype construction and testing, production documentation, design review milestones, and production start up. These requirements are presented with real world applications involving high voltage insulation systems, packaging concepts, high voltage testing, and electronic designs. I. INTRODUCTION: The foundation of any specific product development process is its ability to apply the general methods of project management. Project management tools will allow the successful execution of the process. In general, project management will coordinate all resources required to define, plan, execute, and evaluate the project. The decision to undertake a project may be complex. However, once the decision is made to move forward on a project, the decision to apply methods of project management is easy. By definition, a project signifies that important strategic goals are at stake. Without proper project management the goals will not be achieved. . In the area of high voltage power supply product development, a rigorous and detailed process has been defined and executed with a high success rate. Many areas of work, experimentation, and testing have been proceduralized specifically for high voltage. II. PRODUCT DEFINITION AND CONCEPTUALIZATION: Typically, high voltage power supplies are specified by the next level system designer. Rarely are marketing specifications the basis of the product definition. This greatly simplifies the task of finalizing specifications and getting approval to start the project. The next level system can be defined as the equipment the high voltage power supply will be used in. The system design team will be required to work closely with the engineers designing the high voltage power supply. In most cases, technical discussions can yield a sufficient specification in a matter of days. Other contract issues may cause delayed start to projects and need to be given proper attention. A. Product Conceptualization: In parallel with the technical and specification discussion, a conceptual approach will take form. Initially, relaying on existing platform technologies is the best method to reduce risks. Risk reduction analysis at this phase can save significant cost and time further into the project. Risk analysis needs to be considered for the benefit of both parties. Neither party will benefit by unwarranted and unnecessary risks. However, it requires great discipline to overcome the lure of conceptualizing an approach that may seem novel and exciting. Many engineers will fail this test and may pay a price by having program delays, reliability problems and cost overruns. Of course basic research and development cannot be sacrificed and must be carried out separately from the development efforts. The product development process can be crippled if new R&D needs to be accomplished during its phase. B. The Iterative Design Process: As stated above, using an existing platform product is the best way to minimize risks. However, even with platform products, some new design concepts will be needed. These will typically involve: new mechanical packaging, new interface circuitry, auxiliary power requirements (filament or grid supplies), etc. Initially, these new ideas will be the starting point for design details. However, if not continuously updated, these "first approach" ideas will invariable not yield the best solution. . Simply Stated: Never go with your first idea. It will become outdated quickly once the conceptual design starts to take form. The technique which is best used during these early phases is an iterative design process. Whereby initial concepts are continuously updated as the details take form. From an outside vantage point, the iterations may seem to cause project delays. But in the long run, this process will result in a more solid foundation to insure the strength of the project in its final phases. . At every critical iteration, the user or specifier must participate in the design change. This further insures the validation of the product. III. PROJECT PLANNING: Clearly defining the scope of a project is as important as the conceptualization and design of the product. Without a clear understanding of the "who, what, where, when, why, and how", a project can go off course. This can basically be seen as the business side of the project management. "Business" can be seen as a taboo subject to some technical people. This is perfectly understandable and needs to be factored into the decision making process used by the technical design team. Here, the project manager must have full understanding of the strategic business goals associated with the success of the project. The project manager must continually weigh business issues with technical issues. Difficult judgments and decisions will have to be made. It is here that the defined scope of the program will help guide in decision making. In all cases, the project manager must attempt to impart the business strategy and scope to all team members. In many cases, this will allow "buy in" when judgments are made, or a strategic course change is required. In some cases, team members will not relate to the business strategy and scope of the project. This is natural and must be managed. A. The Work Breakdown Structure: The work breakdown structure (WBS) is a concept routinely used in classical project management. The WBS clearly defines, in a hierarchal manner, the work to be performed. In larger projects, the details of work may not find their way into a formal WBS analysis. However, in small to moderate sized projects, (such as the development of a high voltage power supply), all WBS details should be made visible. In larger projects the WBS tasks may be assigned to groups or departments, but in the small to moderate sized projects, tasks should always be clearly assigned to an individual. Examples of this type of detail would be: printed wiring board design, magnetics design, experimental definitions and analysis, parts list creation, etc. An example of a WBS for a printed wiring board is shown below: 1.0 CONTROL PWB DESIGN . 1.1 Electrical Design . 1.1.1 Controller EE . 1.1.2 Diagnostics . 1.1.3 Interface . 1.2 PWB Layout Design . 1.2.1 Mechanical Area Study . 1.2.2 Component Symbols Created . 1.2.3 Routing Etc. Based on the WBS outline, the individual or group can now pursue their assigned task by organizing the time and resources required for completion. B. Resource Allocation: It is a requirement of the development process that qualified resources be assigned. Invariably, the quantity and capabilities of the team members will determine the success or failure of the project. Insufficient resources, or the unavailability of assigned resources will result in the delayed completion of WBS tasks. Even if sufficient resources are available, capability limits of the individual may also delay task completion. . When assigning resources to tasks, it is critical to specify the project and task goals. They must be specifically defined, assigned clearly to an individual who will be responsible, and with a time base for completion.. . Other influencing factors may effect resources and cause delays. Outside services such as consultants, subcontractors, or vendors can seriously hamper progress if their performance is not acceptable. When individuals are responsible for multiple products or projects, unexpected conflicts will occur. For example, a product that has completed its development phases suddenly requires a redesign or changes. This type of unexpected resource loading is typical, but very difficult to manage. Whenever possible, product support engineers should be used to support non-development activities. C. Project Schedules: The project schedule is another critical tool for managing the project. A number of project scheduling systems can be used.(1) In this specific process, a project master schedule is implemented using a project planning bar chart or GANTT chart. Here tasks are indicated in order with a sequential time base. The order of the tasks can follow the WBS. This helps to keep the WBS and schedule in one data base for easier management. Once again, as in the case of the WBS, it is important to include as many detailed tasks as practical into the project schedule. Otherwise, these tasks can easily be forgotten. Examples of these types of tasks are: Design Review Milestones and Preparation Material and Cost Tracking . Material Ordering . Process Documentation . Shipping Packaging Design . Test Equipment and Procedures . ESS Testing . Manufacturing Tooling . Manufacturing Drawings Release . Etc. When creating the project schedule it is important to have the project team understand and agree on the time allocations assigned to a task. If the time estimates are not credible, the team members may reject ownership and the task will not be completed. In addition to the team members, senior management should be informed, and individual projects should be loaded into a long term department master schedule. IV. DESIGN REVIEW GUIDELINES: The design review forum is a critical part of a project. During these forums, a project review is undertaken in order to inform concerned parties, who are not directly associated with the project team, on the progress of the project. It is important that these design reviews reinforce and amend the progress of the team. In no way can the design review replace daily and weekly project management. By their nature, design reviews occur only at critical phases of a project. Project delays will occur if important decisions are delayed until the design review milestones. A successful technique used for short term review is weekly team meetings. In this forum, the critical team members meet weekly and resolve issues quickly. This group is typically 8-12 people and consist of: project manager, electrical engineers, mechanical engineers, lab personnel, quality control, sales/marketing, and representatives from manufacturing departments. . In the process used for the high voltage power supply development, specific requirements for each design review are required and a checklist is used to insure completion of these requirements. Important design reviews milestones are defined and it is very useful when the end user of the equipment attends design reviews. These milestones occur at the following phases of the project: A. Conceptual Design Review: The conceptual design review occurs early in the project. At this stage, product concepts are reviewed along with the specification requirements. Some of the specific requirements of the conceptual design review are: Design Compatibility with Specifications . Mechanical Design Concepts . Mechanical Outline Drawings. Electrical Design Concepts . Heat Dissipation Concepts . Software/Hardware Architecture . Reliability and Environmental Stress Screening (ESS) . Manufacturability . Technical and Cost Risks . Testing and Maintenance . Program Schedule . Material and Labor Cost Estimates Each of these are discussed and reviewed. Inevitably, new tasks are required as questions are raised. These tasks are tracked as "Action Items", and are assigned to an individual along with a completion date. All action items are reviewed at the weekly meetings. This helps to insure prompt attention to these tasks. B. Critical Design Review: The critical design review occurs mid-way in the project. Here, detailed design data, experimental data, and breadboard hardware review takes place. Many topics covered in the conceptual design review will be reviewed again. However, at this phase the level of detail should be such as to clearly define and identify the product. These details can be described as: . Preliminary Performance Data (to the specification) . Mechanical Design Detailed Drawings . Electrical Schematics . Heat Dissipation and Efficiency Data . Software Specifications . ESS Test Plan . Engineering Acceptance Test Procedure (ATP) . EMC Test Plan . Breadboard Demonstration . Actual Material Costs and Project Expenditures . Once again, action items are assigned. Previous action items from previous design reviews are discussed and hopefully all issues resolved. C. Final Design Review: At this point in the project, verification of the product is reviewed. A completed acceptance test procedure is made available and any open performance or reliability issues are discussed. As before, items from previous design reviews are discussed and hard evidence of completion is presented. V. ISO9000 STANDARDS: The process for high voltage power supply design described here operates under the umbrella of the ISO9000 quality system. Specifically, this process was required to be proceduralized to sections 4.3, Contract Review, 4.4, Design Control, and 4.5, Documentation and Data Control, of the ISO9001 International Standard. It can be demonstrated that all parts of the development process address the ISO standards. Contract review is established early on during the technical specification and project conceptualization phase. Since the high voltage power supply has been defined as a customer driven requirement, the customer is involved in all aspects of the initial review. Changes throughout the product life impact the customer and supplier manage the changes. Design control adherence will naturally occur if the project planning, design review, and resource allocation are followed and properly documented. Design verification and design validation requires special attention. Many items covered in the design reviews will document the design verification. Design validation can be accomplished by in house testing to recreate the end user's conditions, or by receiving successful detailed test reports from the end user. . Although documentation and data control may not directly be required during a product development project, important critical documents are created and need to be controlled early on in the project. This will minimize uncertainty when the product release to manufacturing is done. Click here to Download article PDF.
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