Selection of circuit simulation software

Circuit-level simulation analyzes the performance of circuits composed of electronic components, including logic simulation of digital circuits, AC and DC analysis, time domain and frequency domain analysis of analog circuits, etc. The circuit-level simulation must have the support of the component model library containing PSPICE parameters, and the simulation signal and output data replace the signal source and oscilloscope in the actual circuit debugging. Circuit simulation is mainly to test the correctness of the design scheme in terms of function. Circuit simulation technology makes it possible for engineers to fully understand the various characteristics of circuits before the actual electronic system is produced. Now circuit simulation is also widely used in the teaching of electronics in various schools.

There are many types of commercialized circuit simulation software, with different software performance characteristics and application convenience. Choosing the appropriate circuit simulation software according to the needs of engineering and teaching can greatly improve work efficiency and teaching effect.

1. Functional characteristics of circuit simulation technology

Circuit simulation has been widely practiced and proved to be a very effective analysis technique, which is adopted by more and more electronic designers. Circuit simulation technology can play a role in the following aspects.

1. Verify the electronic circuit design

Use circuit simulation technology to quickly simulate and analyze different circuit design schemes to ensure that the design ideas are correct. After the circuit form is determined, sensitivity analysis and tolerance analysis are performed on the circuit component parameters to optimize the circuit parameters and ensure the design quality. Circuit design adopts simulation technology, which can greatly reduce manual labor, shorten design cycle and reduce design cost. For example, there are a large number of complex analyzes in filter design. It will take a lot of time to manually calculate all the data. Using circuit simulation software, results can be obtained within minutes, and the error can be kept within the scope of engineering specifications.

Compared with the traditional circuit measurement method, computer simulation can predict the change process and final result of a specific circuit parameter, so that people can have a deep understanding of the change law of circuit performance. For example, how much impact will the error of component parameters have on product performance? Which component error will have the greatest impact on circuit performance? Using Monte Carlo analysis in circuit simulation technology can quickly draw conclusions. Using worst-case analysis, designers can easily test various extreme conditions and observe the response of the circuit under extreme conditions. Sensitivity analysis enables users to determine the proportion of change in circuit performance parameters such as period, gain, or rise time due to design or component parameter changes.

Circuit simulation technology is especially advantageous in experimental studies where routine measurements are difficult, especially in destructive experiments in real systems. For example, some electronic designs involve high voltage and high current, incorrect design parameters may cause damage to electronic components and hinder the design process. Circuit simulation used in digital circuits also has the characteristics of high efficiency and high precision. Using simulation technology before building the circuit can avoid all kinds of fatal damage and increase the success rate.

As a simulation technique, simulation cannot completely replace the actual measurement of real circuits. However, various parameters produced by simulation have decisive significance in design, and also provide a data basis for physical experiments.

2. Auxiliary teaching for electronics majors

Electronics is a highly experimental subject. It is best to study the principles of electronics simultaneously with experiments to deepen perceptual knowledge. Experiments require measuring instruments and electronic components. When limited by objective conditions, it is an effective method to verify the conclusion of theoretical analysis with circuit simulation. Circuit simulation can record all the data in the analysis, and can easily reproduce various electrical processes, especially some fleeting phenomena. For example, the start-up process of an oscillating circuit is generally only about 1 millisecond. This process cannot be observed on an oscilloscope without a memory function. Using simulation can record the whole process of circuit start-up; for example, circuit simulation software can be used to build various operational circuits and verify the circuit theory of operational amplifiers at any time, which is easier and faster than building experimental circuits. The drawn circuit diagram and the generated simulation curve can be copied to the document, making your experiment report look more convincing.

To study electronic circuits, one must not only master the basic principles and calculation methods, but also pay attention to the cultivation of circuit design, analysis and research and development capabilities. It is usually impossible for laboratories to provide the latest devices from various manufacturers in the world. The circuit simulation can be simulated and analyzed using the model of the new device. The application of circuit simulation technology can also design different forms of training such as verification, testing, design and innovation, so as to cultivate students' various abilities.

3. Learn electronic engineering measurement technology

Measurement is one of the fundamental skills in electronics. There are two requirements for electronic measurement: mastering the operation method of electronic instruments and data collection and analysis.

In electronic measurement, a variety of signal generators are used: such as high-frequency signal generators, low-frequency signal generators, and function generators. The signals generated by these instruments can be realized in the circuit simulation software: for example, the transient source can generate various signals of the function generator, and the nonlinear controlled source can generate amplitude modulation waves, etc. By setting the signal parameters of the simulation source, the electrical meaning of various waveforms can be deeply understood.

In the graphics interface of the simulation software, according to the expectation of the measurement results, the display parameters of the waveform are selected, which is equivalent to adjusting each knob of the electronic instrument. The waveform graph produced by circuit simulation has a larger format and more precise coordinates than the oscilloscope screen. The graph measurement tool of the software can perform various measurements on the signal curve, such as the amplitude, frequency, period, phase of the periodic signal and the rise time of the pulse signal, the overshoot amplitude of the signal, etc. The measurement tool is fully graphical, highly interactive, and can automatically calculate various parameters.

Waveform calculators perform mathematical calculations on waveforms. The waveform calculator uses various mathematical symbols and functions to calculate signal data such as average value, differential integral and so on. In most software, using the waveform calculator, complex function expressions can be constructed interactively to generate new waveforms. The measurement results of some simulation software can be marked directly in the chart.

Using virtual instruments in some software (such as Multisim) is very helpful to master the performance and operation of real instruments.

2. Basic performance of circuit simulation software

With the development of microcomputer technology, the level of EDA software based on Windows has been continuously improved. Now there are many different software companies producing circuit simulation products for PC. These products have different technical grades and application positioning. Some software with printed circuit board design as the main application also has embedded simulation components, such as ORCAD's PSPICE, Protel's Simulate, etc. There are many brands dedicated to circuit simulation products, such as Multisim, TINA, ICAP/4, Circuitmaker, and Micro-CAP. Usually these softwares are based on the circuit simulation language PSPICE.

The interfaces and functions of various circuit simulation software have their own characteristics, and the display and processing methods of data are also different. The practical value of circuit simulation software can be evaluated from the following four aspects.

1. Quantity and performance of simulation projects

The number of simulation items is the main index of circuit simulation software. The basic analysis functions of various circuit simulation software include static operating point analysis, transient analysis, DC sweep and AC small signal analysis. Other possible analysis functions include: Fourier analysis, parameter analysis, temperature analysis, Monte Carlo analysis, noise analysis, transfer function analysis, DC and AC sensitivity analysis, distortion analysis, pole and zero analysis, etc. Software with fewer simulation functions such as SIMextrix has only 6 items, while TINA has as many as 20 items. There are about 10 simulation functions of Protel, Orcad, P-CAD and other software. Professional circuit simulation software has more simulation functions, and considers the various needs of electronic design and teaching more thoughtfully. For example, the symbolic analysis of TINA, the component parameter variable and optimization analysis of Pspice and ICAP/4, the network analysis and digital circuit simulation of Multisim, and the error setting of CircuitMaker are all quite distinctive functions.

The PSPICE language is good at analyzing analog circuits, and the processing of digital circuits is not ideal. Various software solutions are not the same: For example, Protel uses Digital SimCode to describe digital components, and uses XSPICE of Georgia University to process digital simulation. Multisim uses collaborative models of analog and digital devices described in VHDL, Verilog, or C code. For the analysis and simulation of pure digital circuits, it is best to use simulation software based on hardware description languages such as VHDL, such as Altera's programmable logic device development software MAX+plus II.

2. Quantity and accuracy of simulation components

The quantity and precision of the simulation components in the software component library determine the applicability and accuracy of the simulation. The component library of circuit simulation software has thousands to 10,000 or 20,000 simulation components, but the component models contained in the software always lag behind the development and application of devices. Therefore, in addition to the component library of the software itself, the website of the component manufacturer is an important source of component models. Designers can customize component models according to the external parameters of the latest devices and build their own component libraries. For teaching workers, the component model library of the software can fully meet the needs of conventional teaching.

There are two ways to classify components in circuit simulation software: by component types such as power supplies, diodes, and 74 series, into several categories; or by component manufacturers. Most simulation software has previews of circuit graphic symbols for easy access. Each circuit simulation software has simplified the PSPICE model of the components. For example, the resistance model of PSPICE has three temperature coefficients such as first-order, second-order and exponential. Most software only defines the first two temperature parameters, only TINA defines the three temperature parameters of the resistance, and the resistance of Protel does not define the temperature coefficient; for example, the bipolar transistor has 40 PSPICE model parameters, and Multisim specifies all the parameters , TINA also has 32, and Protel has only 22. Therefore, designs that require high simulation accuracy should use high-precision component models, or modify model parameters based on actual components. The method of viewing and modifying component models varies from software to software. Some component model parameters can be modified in the component attribute box, while others need to open a special model parameter file or interface to modify.

3. Data display and processing capabilities

After running the simulation, a large amount of circuit data will be obtained. There are two ways to display simulation data: list and graph. For example, after calculating the DC static operating point, Protel displays the node voltage, branch current, component consumption function and equivalent resistance of the power supply in a list; Pspice and MicroCAP can mark the voltage, current and power in the circuit diagram. Transient analysis, DC sweep, and AC small-signal analysis generally display the results as graphs. The graph can be printed or saved as a file in a specific format; some software can save the waveform as a common PWL (expressed in time-electrical quantity pair) format file, or export it to Excel. You can also copy the graph line, paste it into the "Drawing" of Windows, and save it as a picture file after processing; or directly paste the graph line into the document of Word, PowerPoint, Authorware and other software.

Each circuit simulation software has different processing capabilities for waveform graph lines. But generally there are the following data processing functions:

(1) Waveform measurement: displayed as different types of coordinate scales (linear, logarithmic, amplitude, decibel, etc.); measure the effective value, root mean square value, peak-to-peak value, average value, maximum value, minimum value, cycle, etc. of the graph .

(2) Graph line calculation: Add, subtract, multiply, divide, differentiate, integrate and other operations on the graph line. Or use the graph variable as the independent variable of the mathematical function to obtain a new mathematical variable.

(3) Modification of graph lines: Make graph lines more beautiful and easier to understand. You can change the thickness, color, style and mark of the graph line; add measurement data point marks and data labels; change the background color of the graph line, the style and color of the coordinates, etc. Some software allows the input of descriptive text in the graph line screen, even Chinese text.

4. Virtual instrument and educational function

Visualized virtual instruments are a feature of circuit simulation software. The most typical example is Multisim, the virtual instrument of this software has reached the highest level of similar software no matter the appearance of the interface or the internal function. Other software with virtual instruments include TINA and EDISON.

Virtual instruments can help learners understand the functions of electronic instruments, and deeply understand the methods and technical essentials of electronic measurement. Master various operation methods of electronic instruments, especially the functions of various control buttons and knobs. The functions of Multisim and TINA virtual instruments have actually surpassed PSPICE itself, and the typical ones are network analyzers and logic analyzers. Network analyzer is a special instrument for analyzing RF components and RF network parameters; while Multisim's logic analyzer has real digital circuit analysis capabilities and meets the technical requirements of actual digital system analysis. Some software also has virtual electromechanical components, such as light bulbs, buttons, relays, contactors and other electrical components, which can be used to construct electromechanical control circuits. Mathematical and analog control devices in the software component library can be used to analyze automatic control principles.

In order to meet the needs of educational units for the teaching of circuit principles, some software has an educational function. It mainly allows users to set some hidden errors on components, so as to improve the ability of training students to analyze and solve problems. For example, Mulisim and TINA can set three parameters of open circuit, short circuit and leakage resistance for components; while CircuitMaker, another circuit simulation product of Altium Company, can do more teaching settings for components and circuits, and can add passwords to prevent users from Modify component properties.

3. How to choose circuit simulation software?

In the production design of electronic engineering or the professional teaching of electronics, there may be different requirements for circuit simulation software, which should be considered from two aspects: software function characteristics and actual work needs.

1. Consider the needs of production and teaching for circuit simulation software.

First of all, the actual production capacity of the software must be considered. What kind of work can be done with this software? Can the model library of the software meet the design needs; what circuit simulation functions does the software have; what output formats the circuit diagram has, whether it is compatible with the company's existing PCB design software; the price of the software and what after-sales services are provided, etc. If the unit's products are more complicated, it is necessary to consider a comprehensive solution from circuit design, analysis, optimization, system simulation, and even electromechanical system design.

2. Evaluate the performance of circuit simulation software

The software products of various companies have different sales orientations, and the functions, scalability and prices of circuit simulation software vary greatly.

There are different versions of the same software to suit different business needs with different functions and prices. Ordinary teaching units only need to learn the relevant principles of circuit simulation, and do not have to insist on high performance of the software. Using the student version or educational version of the software can fully meet the needs of daily teaching. As an electronic manufacturer, it is necessary to use the enterprise version or enhanced version of the software, and also consider a series of issues such as product design, production and management, and also have certain requirements for software maintenance and technical support. Therefore, products from large companies should be used as much as possible. Such as ICAP/4, Orcad, etc.; if you have higher comprehensive requirements for circuit design and simulation, you can consider Saber from American Synopsys. Saber is applicable to a wide range of fields, including electronics, power electronics, electrical engineering, mechanical engineering, electro-optics, optics, control systems, and data sampling systems, etc.

3. Select the applicable software according to the teaching needs

In teaching, circuit simulation software is required to clearly display circuit diagrams, signal diagrams and various circuit data. Among all circuit simulation software, Multisim has the most complete simulation components, simulation analysis types and virtual instruments, and is an ideal simulation tool for circuit teaching in schools at all levels. The disadvantage of Multisim is that the circuit diagram screen can only be enlarged to 200%, and the circuit lines are relatively thin, which is not very clear when projected on a large screen. The circuit simulation software that is more suitable for vocational technical schools is TINA 6.0 Simplified Chinese version. Not only the menus and dialog boxes of this software are in Simplified Chinese, but all the help is also written in Chinese, which is easier for students to understand and accept. The display quality of Altium's circuit diagram and simulation diagram interface is relatively good, which is suitable for teachers to use in teaching slide presentations and making illustrations in various documents. Altium is also well suited for teaching printed circuit board design. The advantage of ICAP/4 is that the simulated circuit waveform can be inserted into the circuit diagram, that is, the waveform at any point in the circuit can be displayed. Orcad's Pspice displays the simulated node voltage, branch current, and component power consumption data in the circuit, which is very intuitive; MicroCAP has the most powerful parameter scanning function, and can set up to 20 parameters for scanning analysis. If you are a beginner in electronics, you can use the circuit simulation software Edison with a 3D interface. The software interface is vivid and intuitive, which is quite close to the real image, which is helpful for understanding and understanding the circuit.

4. Dedicated circuit simulation software

In addition to the usual circuit simulation software, there are also some software specially designed for a certain type of design application, such as: Intusoft's power supply simulation design software PowerSupply Designer and magnetic components (design analysis transformers and inductors) design software MagneticsDesigner; Finland APLAC company The software APLAC for RF circuit design and simulation; and the series products of American Ansoft Company, etc. Many semiconductor device manufacturers have also developed special circuit design and simulation software in order to promote their products. Such as Altera's programmable logic device design software Max+PlusI I; TI's switching power supply special design software SWIFT Designer; Linear's circuit simulation and switching power supply design software SwicherCAD, etc.

Summarize

Finally, it should be noted that the development direction of circuit simulation software is no longer limited to the scope of electronics. While enhancing the simulation ability of digital-analog mixed signals, circuit simulation technology is expanding to the fields of power electronics, electro-optics, and even electrical engineering, electromechanical engineering, etc., bringing more convenience to engineering practice and teaching. Circuit simulation technology has a powerful circuit analysis function, basically including all items of electronic test analysis. The number of electronic simulation components, circuit analysis functions and data processing capabilities provided by circuit simulation software from different manufacturers are quite different. The appropriate circuit simulation software should be selected according to the needs of engineering design and professional teaching.

The above are the characteristics and selection suggestions of the circuit simulation software introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have software and hardware function development needs for smart electronic products, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad, including MCU, voice IC, Bluetooth IC and modules, wifi modules. We have hardware design and software development capabilities. Covering circuit design, PCB design, single-chip microcomputer development, software custom development, APP custom development, WeChat official account development, voice recognition technology, Bluetooth wifi development, etc. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS solutions, the development of Bluetooth audio, the development of children's toys, and the development of electronic education products.