An easy-to-use design tool for engineers


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SiC electronic components are a popular solution for the most demanding industrial, domestic and automotive power supply switching operations. Implementing such circuits requires designers to follow a strict line of mathematical calculations and formulas, which is why UnitedSiC launched the FET-Jet Calculator, a simple online tool that allows selection and comparison of performance across different power applications. It is truly a valuable tool for designers who want to make the best choices. Calculator To use the tool for calculating power systems built by UnitedSiC, just click the link https://info.unitedsic.com/fet-jet on the web page shown in Figure 1. Let’s examine some of its noteworthy features: Easy assessment of the full suite of UnitedSiC FETs and diodes in a variety of energy-based applications; AC-DC: PFC boost, PFC totem, Vienna rectifier; inverter with 2-level voltage source; DC-DC (non-isolated): buck or boost with or without simultaneous correction with 3-level boost; DC-DC (insulated): LLC in full or half-bridge variants, full phase shift bridge, active double bridge with phase control; Support for CCM and BCM management methods; Provides immediate results to facilitate basic design decisions, including overall efficiency, component losses due to dynamic and conductivity causes, junction temperature, stress levels, and number of devices connected in parallel (if any); No registration required Figure 1: Calculator login page The main objective of the online application is to combine power electronics with simplicity of design. Choosing the right SiC device for your needs should be a simple process for the designer. This is one of the primary goals of the FET-Jet Calculator. Helps designers choose UnitedSiC devices and focus more on their project. Allows correct, fast and safe design decisions to be made. All this happens in 3 simple steps: select the application; Select Topology Enter the operating specifications and select the device. Purpose of the calculator The tool that UnitedSiC publishes online and is made available to designers is valuable. Easily identify the optimal UnitedSiC device for your power project. Users only need to select the function and topology of their application, enter the details of the design parameters, and finally, the tool automatically calculates the current, efficiency and circuit losses. The operating temperature and heatsink characteristics are provided as input, to show the expected operating junction temperatures. Users can examine and evaluate, in real time, the effects and consequences of circuit changes by changing the frequency of induction and switching. Additionally, single or parallel devices can be selected to show the relative overall performance of devices with different current ratings. The device warns if the selection is inappropriate or completely wrong, for example when the nominal voltage is insufficient for the selected conditions and topology. These tips help the user to quickly reach a viable and correct solution. All UnitedSiC FETs and Schottky diodes can be selected from sortable tables, which include devices in packages TO-220, TO-247, TO-247/4L, DFN 8×8, and newly manufactured Gen 4 750 V devices. It does not represent This selection is an obstacle to the designer and instead provides further assistance in the final selection of power components. Expected Calculation Solutions Calculation tool is available at https://unitedsic.com/fet-jet/. Here you can enter information about the circuit to be built and designed. The first project highlight involves selecting the following, by selecting the relevant options: AC/DC; DC / DC; DC / DCiso. Equivalent circuits are shown in Figure 2. In detail, the calculator analyzes the following types of solutions: AC / DC DC / DC / Dciso Figure 2: Equivalent circuits related to the three main classes of arithmetic Example: AC / DC converter PFC Here is a simple example of using the calculator via Internet. Some concepts will be explored in more detail later. A general circuit for AC/DC PFC converter design is shown in Figure 3 and includes a typical rectifier bridge, inductor, MOSFET, rectifier diode, and capacitor. Figure 3: AC/DC PFC Converter Design The display has the input data to be entered by the user, on the left, and the output data and calculated parameters, on the right of the display. The calculator provides two menus for choosing the MOSFET and diode model. When choosing electronic components, it is possible to limit the working range of the current. It is also possible to filter the list based on these other additional criteria: nominal voltage; current rating; Package type Serial. For example, we can specify the MOSFET UF3C065040K3S model with the following technical characteristics: Rated voltages: 650 V; Rated current: 54 A; Package: TO-247-3L; RDS (on): 42 mOhm; Maximum operating temperature: 175°C; Low series capacitive value: UF3C/SC. By clicking on the component form, the website displays the relevant page, along with its official data sheet. To select the chosen component and include it in the wiring diagram, click on the point to the left of the same menu. Diode selection includes the same selection criteria. In this case, the UJ3D06560KSD diode was chosen, it has the following characteristics: rated voltage: 650 V; Rated current: 10 A; Package: TO-247-3L; Maximum operating temperature: 175°C; very high conversion speed; Series: UJ3D. Then enter some operating parameters (as shown in Figure 4): Rated power [VA]Line to neutral RMS voltage [V]The number of legs of the DC voltage jumper [V]switching frequency [Hz]Input current ripple [%]Number of Parallel FETs Number of Parallel Diodes Rdson Type Rthjc Type Heatsink Temperature [° C]FET Rthcs (insulator pad) [K / W]Diode Rthcs (Isolator Pad) [K / W]Figure 4: Some data to be entered to calculate the AC/DC PFC transformer processing takes two or three seconds max to show the final results. The final calculations are very useful and are shown in Figure 5. They are divided into the following categories: Calculated parameters FET Rdson adjusted by temperature [Ohm]Losses in FET junction temperature and temperature [° C]Diode junction temperature and temperature losses [° C]Total loss and efficiency of the leg [W]sum [W]Semiconductor efficiency [%]Figure 5: Results and output data displayed by the calculator for AC / DC PFC converter It is clear that the parameters calculated by the program are not the same for all simulations. Each transformer model has its own classes of calculated parameters. Efficiency is one of the most important parameters. All calculation and solution methods provide a very important parameter that appears as a final result, which is efficiency. It depends on various parameters and is always a very crucial and important point, especially with regard to power supplies and transformers. Example of a Boost converter with the following features: FET selection: UF3SC065040D8S diode selection: UJ3D1210TS power rating [W]: 3000 input voltage [V]: 325 Output Voltage [V]: 600 inductances [uH]: 800 Rdson: Typical heatsink temperature [° C]: 70 provides an efficiency of 99.55%, also shown in Figure 6. Figure 6: One of the most important parameters that the calculator provides is efficiency Another very important parameter is the “ripple” current of the inductor which, in this case, can be entered by the user as data Enter. The inductance ripple current is used as the input parameter to improve shunt loss estimates. Calculator accuracy How accurate is the FET-Jet Calculator? There are certainly some trade-offs between accuracy, ease of use, and speed. You cannot have all of these requirements at the same time. The FET-Jet Calculator appropriately adjusts these parameters by minimizing errors as possible and by performing simplifications that allow fast results with low precision losses for typical applications. Accuracy is sufficient for the intended purpose of the FET-Jet Calculator, a tool for selecting and comparing power supplies, in order to use the most suitable components in your projects. The FET-Jet Calculator does not distinguish between input power and output power. The efficiency of a power semiconductor, in most solutions, is high enough to make the small difference between the input and output power negligible. So the nominal power can be thought of as the output power. System characterization and conclusions Power switching devices are now an established fact and are increasingly used by designers. Power transformers and power supply systems using multi-phase integrated circuits (MOSFETs) and diodes with SiC are becoming more and more popular. In fact, the designers felt that there was no correct and complete calculator, which could check, in one package, all kinds of connections. For engineers working with SiC for the first time or those looking for the best SiC device to fit their designs, this calculator is a quick and easy way to evaluate UnitedSiC FETs in a large variety of power structures, thus speeding up research and development and avoiding wasted time creating simulations Advanced if unsuitable devices are selected. It only takes a few clicks to point designers in the right direction and get the perfect design. This calculator will be revamped and updated soon with useful graphics implementation that will cover various parameters, such as currents, temperatures, input and output voltages, and efficiencies. Currently, the system characterization can be done manually, changing the values ​​and plotting the results on a spreadsheet, as can be seen in Figure 7. The example involves building a Buck Converter CCM system using the following characteristics: FET selection: UF3SC065007K4S Diode selection: UJ3D1250K Power rating [W]: 500 input voltage [V]: from 15 to 100 output voltage [V]: 12 Number of legs: 1 inductance [uH]: 75 switching frequency [Hz]Number of Parallel FETs: 75000 Number of Parallel Diodes: 1 Number of Parallel Diodes: 1 Rdson Type: Rthjc Typical Type: Max Heatsink Temperature [° C]: 80 ft Rthcs (insulating pad) [K / W]: 0.6 Ruthx Diode (Isolator Pad) [K / W]: 0.6 The purpose of the simulation is to see how the efficiency of the system interacts with the change in the input power voltage. The graph shows two curves with switching frequency of 75 kHz and 200 kHz. Measurements under different conditions give the following results: Figure 7: A simple example of a Buck system project and its efficiency curves according to the input voltage and switching frequency.


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