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A simpler and more efficient method in switching power supply circuit design
Sep 26, 2018


        The first step in power supply design is to define power requirements, including voltage range, output voltage, and load current. Possible solutions are automatically evaluated and one or two recommendations are presented to the user. This is also the first place where the designer may be in trouble: if the demand is not expressed correctly (for example, if the actual input voltage range is above or below the input value), an unsuitable solution will also be displayed. Users can try multiple sets of requirements, but they must have a clear idea of the system requirements.

 

        Performance evaluation

        Once the circuit components are selected, it is time to evaluate performance. In general, performance evaluation depends on frequency response values (crossover frequency and phase margin), peak current and voltage, and thermal performance values (efficiency, junction temperature, and component temperature). Although these calculations are based on models, the simulation results are well matched to the workbench data.


        Electrical simulation and thermal simulation

        Electrical simulation supports certain solutions. These simulators display a logic diagram that allows the user to further change the component and run the test on the voltage regulator circuit. Existing tests include Bode plots, steady state, line transients, load transients, and startup. (Note that Bode plots can only be used on circuits that use fixed-frequency regulator ICs.) To make online testing more useful, users should carefully review all test conditions. The input voltage and load current may vary for each test, and the default values may not match the user's system. The user must first estimate the expected result, and if the simulation results are different, find out the cause.

       Thermal simulation can be used in many scenarios. The online tool evaluates the voltage regulator circuit implemented on the PCB with a reference design layout. The results of component and board temperatures are displayed in full color images and tables. Since the thermal simulation runs faster (the results can be given in a matter of minutes), the accuracy is naturally not comparable to a detailed CFD (computational fluid dynamics) simulation that takes hours. However, the temperature estimate is typically within 20 °C of the actual value. This is enough to determine the hot spots on the board or component and prevent overheating.


       Test prototype

      The final step before switching the regulator design is to build a prototype for bench testing. Some solutions have support for custom design, while others have reference boards. Online tools have powerful features, and you may have the idea of skipping this step, but don't do this! Most designs work well, but some require careful layout for optimal performance. The actual components of Jingkai source may not match the simulation results precisely, especially after considering their parasitic effects, the actual performance (including the board layout effect) will be slightly different from the simulation results.


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