Abstract: As an important component of communication systems, how to improve the design and production efficiency of secondary power supplies is a problem faced by every power supply designer. With the popularization of the Internet, a power supply design based on the Internet provides us with a new idea. Keywords: secondary power supply, switching power supply, Internet, DC/DC converter 1 Introduction Since the mid-1970s, the technology of transformerless switching power supply has become popular in Europe, America, Japan and other countries around the world. Especially since the 1990s, the rapid development of the communication industry has greatly promoted the development of switching power supplies. The initial switching power supply switching frequency was around 20kHz, slightly higher than the highest audio frequency, and would not bring annoying noise to people. [1] With the rapid development of power electronics technology, high-frequency switching power supplies and their technology have become the mainstream of modern communication power supply systems. In the field of communication power supply, rectifiers are usually called primary power supplies, while DC/DC converters are called secondary power supplies. In traditional power supply design, it takes a long time from the proposal of user needs to the finalization of the actual circuit design. In order to solve the problem of long design cycle of traditional power supply, the United States (MICROSIM) and National Semiconductor (NS) jointly developed a novel online power supply design system (Websim) and released it on its website http://Power.national.com, providing us with a relatively ideal secondary power supply design method. 2 Comparison of traditional power supply design method and Internet-based power supply design method 2.1 High-frequency switching power supply for communication The communication power supply is to convert the single-phase or three-phase AC voltage provided by the mains into DC power with a nominal value of 24V to 48V. At present, in the program-controlled exchange, the traditional phase-controlled voltage regulator has been replaced by high-frequency switching power supply. High-frequency switching power supply (also known as switching rectifier SMR) usually uses high-power high-frequency switching devices MOSFET or IGBT, and the switching frequency is generally controlled in the range of 50 to 100kHz, initially achieving high efficiency and miniaturization. [3] In recent years, the power capacity of switching rectifiers has been continuously expanded, and the single unit capacity has been expanded from 48V/12.5A, 48V/20A to 48V/200A, 48V/400A. There are many types of integrated circuits used in communication equipment, and their required power supply voltages are also different. In the communication power supply system, a high power density high frequency DC/DC isolated power supply module is used to convert the intermediate bus voltage (generally 24V to 48V DC) into the required DC voltage. This can greatly reduce losses, facilitate maintenance, and is very convenient to install and increase capacity. It can generally be directly installed on the standard control board. The requirement for secondary power supply is high power density. As the communication capacity continues to increase, the communication power supply capacity will also continue to increase. [2] In the switching power supply, a fixed DC voltage is converted into a variable DC voltage through a DC/DC converter. At present, the secondary power supply DC/DC converter of the communication power supply has been commercialized. The module adopts high frequency PWM technology, the switching frequency is generally below 500kHz, and the power density is 5W to 20W/in3. Moreover, the use of DC chopper instead of rheostat can save (20 to 30)% of the power. In the switching power supply, the DC chopper not only plays the role of voltage regulation, but also plays the role of effectively suppressing the harmonic current noise on the grid side. With the development of large-scale integrated circuits, power modules are required to be further miniaturized. Therefore, it is necessary to continuously improve the switching frequency and adopt new circuit topologies. Currently, some companies have developed and produced secondary power modules using zero-current switching and zero-voltage switching technologies, which have significantly improved power density. [4] 2.2 Comparison of online power supply design and traditional power supply design methods (1) Traditional power supply design Traditional power supply design first designs the circuit structure and selects the circuit component parameters according to the required circuit parameters; then, it uses CAD software such as PSpice or Electronic Workbench on a computer to simulate and obtain the input and output waveforms, and then analyzes them. This method is relatively intuitive, but it also has its inherent drawbacks, such as: ① The design cycle is relatively long. For slightly more complex switching power supplies with larger power capacities, it generally takes several weeks or even months from component selection, parameter determination, computer simulation, debugging to completion and production; ② The component library of CAD software is not updated quickly enough. Current electronic technology is developing rapidly, while general simulation software has a certain lag; ③ CAD software is not convenient to use. The use of general circuit design software is relatively complex and requires a high level of expertise from the user. Problems such as non-convergence can easily occur during simulation if not careful; ④ If the power supply designer's computer configuration is not high enough, it will take a long time to perform a simulation. (2) Internet-based power supply design methods and their characteristics. MICROSIM, in collaboration with NS, developed the Websim online power supply design system. It is the first comprehensive online resource for power management design in the international semiconductor industry. The system's functions include component selection, circuit design, demo board ordering, and online sample simulation. Its advantages are: ① Short design cycle: Websim directly provides the circuit after the input voltage requirement, eliminating the need for users to design circuit topology and calculate circuit parameters. Furthermore, only minor modifications to the given typical application circuit are required to obtain the desired circuit, thus enabling power supply design to be completed in a very short time; ② Cost savings: Users can use the supercomputers and simulation software provided on the website to complete the power supply design, eliminating dependence on expensive software and workstations. This ensures both calculation accuracy and cost savings; ③ Convenience and intuitiveness: Websim does not require high user expertise. Users only need a basic understanding of switching power supply circuits and a basic concept of the waveforms of key nodes to design a circuit that meets the requirements. A deep understanding of complex simulation software is not necessary. 3 Webench Software Tool and Its Application Demonstration Webench is a set of tools used by power supply design engineers. It has Websim functionality and provides interactive tools that can select, simulate, and order samples to achieve time-saving power supply design. Websim is a browser-based simulation tool. It can achieve the following functions: (1) real-time feedback of power supply line performance; (2) obtain steady state, start-up, line transient response, load transient response, loop gain measurement, and trend prediction; (3) measurement data processing and waveform display. Taking a three-output DC/DC converter with a minimum input of 20V and a maximum of 22V and outputs of +5V (1A), +10V (0.5A), and -15V (0.2A) as an example, typical design steps are given. 3.1 Obtaining information from Power.national.com First, enter the following in the browser's address bar: Http://power.national.com and select Webench. If it is the first time a user logs in, the system will ask you to enter an email address as your account and send you a confirmation email. After the identity is confirmed, you can use the website. The website will allocate a "MyWebench" disk space to each official user to store personal simulations, design bills of materials, online component distribution and demonstration boards. In the future, users can obtain all information of their personal account through personalized "MyAccount", such as the ChangePassword function. 3.2 Select components with solutionselector (1) After logging into Webench correctly, a dialog box will appear, requiring the user to set various design requirements values ​​for the switching power supply in each column, including setting the maximum and minimum input voltage of the power supply, the range of ambient temperature changes, and the output voltage and current values ​​of each group of the switching power supply. In this example, the requirement is to design a single-input, three-output Flybach type switching power supply. (2) After the design requirements are submitted, the system will automatically list the various PWM integrated chips produced by NS that can form the output requirements and the confirmation boxes for the design requirements, as shown in Table 1. The datasheet for the LM2585 obtained from the website shows its internal structure as shown in Figure 1, which meets the design requirements. Therefore, we select the LM2585, and after submission, a dialog box as shown in Table 2 appears. Selecting the three-output circuit (+ (Out1), + (Out2), - (Out3)) and submitting again yields the circuit shown in Figure 2. In this circuit, component parameters can be changed to achieve the desired circuit performance. 3.3 After setting the circuit parameters, we can select the circuit state to be measured from the Control Panel for simulation. After the simulation, simply move the mouse over the desired point to obtain the voltage waveform; move the mouse over the desired point to obtain the current waveform. Circuit component parameters can be changed at any time to achieve the required circuit performance. If the performance meets the requirements, the circuit parameters can be determined, and after actual research and testing, a final product can be formed. In the circuit shown in Figure 2, we select the steady-state state for simulation. After completion, we measure the output voltages (Vout1, Vout2, Vout3), obtaining the output waveforms as shown in Figure 3, providing a basis for further analysis of the average value and ripple of the output voltage. The test values ​​are shown in Table 3, indicating that the design requirements are met. Table 3 Output Test Values ​​4 Summary From the above analysis, we can see that the online power supply design described in this paper has significant advantages compared to traditional power supply designs. This power supply design also has its disadvantages, namely, a greater limitation on the selection of components. However, its idea of ​​combining traditional power supply design with the Internet is worth learning from. It is believed that in the near future, as more and more integrated chip manufacturers adopt this method for circuit design, it will greatly facilitate the design and production of a wide range of users.