Three Steps To Get A Switching Power Supply Design

- Dec 26, 2019-

Today, the design of switching power supplies is relatively mature, but how to make the design of switching power supplies simpler still requires a certain amount of energy. Now senior netizens have summed up the following three steps based on their actual combat experience to teach you how to easily design a switching power supply.


The first step in online power supply design is to define the power requirements, including voltage range, output voltage, and load current. Possible solutions are automatically evaluated and one or two recommended solutions are presented to the user. This is also the first place where designers can run into trouble: if the requirements are incorrectly expressed (for example, if the actual input voltage range is higher or lower than the input value), unsuitable solutions are also displayed. Users can try multiple sets of requirements, but they must have a clear concept of system requirements.


When the regulator solution is selected, the components of the circuit can be determined. The tool will display the number of the component. The user can change to a preset alternative or enter a custom component. There are guidelines for component values and all key parasitic values. If a custom component that differs greatly from the recommended value is used, I am afraid that the performance will be greatly reduced.


1 performance evaluation


Once the circuit components are selected, it's time to evaluate performance. Generally, 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 model-based, the simulation results match well with the workbench data.


2 electrical simulation and thermal simulation


Electrical simulation supports some solutions. These emulators display logic diagrams that allow the user to further change components and run tests on the regulated circuit. Existing tests include Bode plot, steady state, line transient, load transient, and start-up. (Note that the Bode plot can only be used for circuits that use fixed-frequency regulator ICs.) To make online testing more useful, users should carefully check all test conditions. The input voltage and load current may change for each test, and the default values may not match the user's system. The user must first estimate the due results, and if the simulation results are different, find out why.


Thermal simulation can be used for many scenarios. The online tool uses a reference design layout to evaluate the voltage regulator circuit implemented on the PCB. The component and board temperature results are displayed in full color graphics and tables. Because thermal simulations run faster (results can be given in a few minutes), the accuracy is naturally less than a detailed CFD (Computational Fluid Dynamics) simulation result that takes hours. However, temperature estimates are generally within 20 ° C of the actual value. This is sufficient for identifying hot spots on circuit boards or components and preventing overheating.


3 test prototype


The final step before designing a switching regulator is to build a prototype for bench testing. Some solutions include custom design support, others have reference design boards. The online tools are powerful, and maybe you have the idea to skip this step-don't do that! Most designs work well, but some require careful layout for optimal performance. The actual components may not exactly match the simulation results, especially after considering their parasitics, the actual performance (including circuit board layout effects) will be slightly different from the simulation results.