电气技术专业英语

1. 电气技术专业英语 朱一纶 主编 中国电力出版社

2. Unit 14 Electronic Design Application 课件制作: 吴岱曦

3. Index • Text • 1. What is EDA • 2. What is EWB? • 3. Design with Protel 99

4. Reading materials • 1. Power systems CAD • 2. Simulation • 3. SPICE

5. Exercises • 1. Put the Phrases into English • 2. Put the Phrases into Chinese • 3. Sentence Translation • 4. Translation

6. Text

7. 1. What is EDA • Electronic design application (EDA) is the category of tools for designing and producing electronic systems (Fig 14.1 are some interfaces of EDA) ranging from printed circuit boards (PCBs) to integrated circuits. This is sometimes referred to as ECAD (electronic computer-aided design) or just CAD.

8. Fig 14.1 Some interfaces of EDA

9. While early EDA focused on digital circuitry, many new tools incorporate analog design, and mixed systems. This is happening because there is now a trend to place entire electronic systems on a single chip.

10. Current digital flows are extremely modular. The front ends produce standardized design descriptions that compile into invocations of "cells", without regard to the cell technology.

11. Cells implement logic or other electronic functions using a particular integrated circuit technology. Fabricators generally provide libraries of components for their production processes, with simulation models that fit standard simulation tools.

12. Analog EDA tools are much less modular, since many more functions are required, they interact more strongly, and the components are (in general) less ideal.

13. The circuit design is the very first step of actual design of an electronic circuit. Typically sketches are drawn on paper, and then entered into a computer using a schematic editor. Therefore schematic entry is said to be a front-end operation of several others in the design flow.

14. Despite the complexity of modern components – huge ball grid arrays and tiny passive components – schematic capture is easier today than it has been for many years.

15. CAD software is easier to use and is available in full-featured expensive packages, very capable mid-range packages that sometimes have free versions and completely free versions that are either open source or directly linked to a printed circuit board fabrication company.

16. 2. What is EWB? • Electronics Workbench is a design tool that provides you with all the components and instruments necessary to create board-level designs. Fig 14.2 is the interface of EWB.

17. It has complete mixed analog and digital simulation and graphical waveform analysis, allowing you to design your circuit and then analyze it using different simulated instruments and analysis options. • It is fully integrated and interactive, thus you can change your circuits quickly, allowing fast and repeated what-if analysis.

18. Fig 14.2 The interface of EWB

19. 1. Circuit Simulation Mechanism • After you create a circuit schematic and turn on the power or click the simulate button, the solution of the circuit and generation of the data you see on instruments such as the oscilloscope is the role of the simulator.

20. More specifically, the simulator is the part of Electronics Workbench that calculates a numerical solution to a mathematical representation of a circuit you created.

21. For this calculation to occur, each component in a circuit is represented by a mathematical model. Mathematical models link the schematic in the circuit window with the mathematical representation for simulation.

22. The accuracy of the component models determines the degree to which simulation results match real-world circuit performance.

23. The mathematical representation of a circuit is a set of simultaneous, nonlinear differential equations. The main task of the simulator is to solve these equations numerically. A SPICE-based simulator transforms the nonlinear differential equations into a set of nonlinear algebraic equations.

24. These equations are further linearized using the modified Newton-Raphson method. The resulting set of linear algebraic equations is efficiently solved using the sparse matrix processing LU factorization method.

25. 2. Four Stages of Circuit Simulation • The simulator in Electronics Workbench, like other general-purpose simulators, has four main stages: input, setup, analysis and output.

26. At the input stage, after you have built schematic, assigned values and chosen an analysis, the simulator reads information about your circuit. • At the setup stage, the simulator constructs and checks a set of data structures that contain a complete description of your circuit.

27. At the analysis stage, the circuit analysis specified in the input stage is performed. This stage occupies most of CPU execution time and actually is the core of circuit simulation. The analysis stage formulates and solves circuit equations for the specified analyses and provides all the data for direct output or post-processing.

28. At the output stage, you view the simulation results. You can view results on instruments such as the oscilloscope, or on graphs that appear when you run an analysis from the Analysis menu or when you choose Analysis/Display Graphs.

29. 3. Design with Protel 99 • Several electronic design applications exist to both create schematics of a circuit and transfer them to a working PCB layout. Here we discuss the design of a circuit using Protel 99SE（Fig 14.3）.

30. Fig 14.3 The process of design with Protel 99 SE

31. 1. Start Protel and select File/New. Use a MS Access Database and give it a name – this will create a Design Database file (extension .DDB) that contains all the parts of your design.

32. 2. The Database has its own internal File System – go into the Documents Folder, select File/New and create a new Schematic Document that will describe our circuit.

33. This consists of placing symbols that represent the individual components in the design and connecting their individual connections, or nodes, to one another.

34. 3. We are now ready to check our design to make sure there are no errors. This can be done using what called an Electrical Rule Check (ERC). It can be found under Tools/ERC.

35. 4. We are now ready to actually create a PCB from this schematic. There is no information about physical data in a schematic – orientation, spacing.The only data that will be sent to the PCB document besides a list of what nodes are connected to each other (a netlist) are the number of pins on each part, and the Footprint for each part.

36. 5. We can first layout the components. Clicking a component and dragging the mouse will allow you to move the component. Pressing the Space Bar while doing this causes it to rotate.

37. You should try to place the components reasonably close together (save surface area), and in a manner that ensures that the connections cross each other as little as possible. This will make it easier for Protel to route the design.

38. 6. We now need to tell Protel's AutoRouter to work only in the Top Layer and select AutoRoute/All, and hit Route All. The Board should Route.

39. 7. Now we can run a Design Rule Check (DRC), which will ensure that we have no short circuits, that everything is routed, etc. It can be accessed from Tools/Design Rule Check.

40. The PCB design is now complete. All that remains is to transfer the PCB out of Protel in a format that can be understood by the PCB manufacture.

41. This is the End of the Text

42. Reading materials

43. 1. Power systems CAD • Power systems CAD refers to computer-aided design (CAD) software tools that are used to design and simulate complex electrical power systems.

44. Electrical power systems CAD tools are used by electrical power systems engineers, a distinct discipline of electrical engineering.

45. According to the Institute of Electrical and Electronics Engineers (IEEE), there are 21,000 power systems engineers worldwide focused on improving electrical grids, eliminating blackouts, and reducing electrical accidents.

46. Such engineering expertise is instrumental to preserving the critical power needs of modern digital society, e.g. transportation, communications, computing, etc.

47. Power systems CAD tools have following virtue: • Providing a design foundation that allows power systems to be created quickly • Enabling design engineers to test the safety and integrity of their design concepts • Allowing design engineers to create a repository if proven design elements that can be reused in future projects

48. Thus power systems CAD software products allow organizations to develop higher-quality power systems designs. The electrical power systems CAD process, frequently called power systems "modeling," typically consists of two distinct stages:

49. 1．The design stage, in which an electric systems model is created. • 2．The simulation or analysis stage, in which software simulation programs are used to test the integrity of the design; these simulation programs test how the model would behave in real-world operation by checking for specific types of design or operational problems.

50. It is important to note that this is an iterative process, in which simulation results will suggest ways that the design should be modified to increase safety, reliability, and serviceability.