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Magnetics Design
08/03/2018 at 15:22 • 0 commentsThe main output inductor after the catch diode is the focus of this design process. I had calculated the of this part using an empirical formula given in the Power Supply Cookbook by Marty Brown , but felt that the estimate was not mathematically sound. So, I searched around and found an app note by TI, AN- 1197. This has detailed mathematical calculations for output inductor calculations.
It has a nice little mathematical algorithm for output inductor calculation geared specifically to buck converters. Lets see where it goes.
Another hurdle that I face is that there seems to be an inverse relationship between the current carrying capability of off the shelf coils and their inductance. The largest current rating I could find for an inductance of 100uH was 3A which is less than the average inductor current and wont work.
Also, I had calculated the inductor current ripple based on an estimate, which I have now discarded in favor of a superior method described in the app note.
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Component Selection/Topology - 2
08/03/2018 at 15:15 • 0 commentsI have selected the majority of parts for the switch mode unit. Now I am stuck on magnetics design and it is proving to be more difficult than I initially thought. The topology I have selected for this unit is a forward-mode buck converter, the selection for which was based upon an app note by ON Semiconductor that I have uploaded to the project files. The main motvation behind doing so was the simplicity of the buck converter as compared to the other option- the flyback converter. Simplcity here is a relative term.
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Component selection and topology.
08/02/2018 at 08:32 • 0 commentsThe semiconductor switches and the related control ic's have been selected. Discrete compenent selection is proving to be difficult as the guide I am following for this design has a cookbook format and the estimate equations for the output choke are approximate at best. Also finding appropriate magnetic elements is proving to be more difficult than semiconductors and ic's.