• Magnetics Design

    Araib Irshad • 08/03/2018 at 15:22 • 0 comments

    The 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.

  • Component Selection/Topology - 2

    Araib Irshad • 08/03/2018 at 15:15 • 0 comments

    I 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.

  • Component selection and topology.

    Araib Irshad • 08/02/2018 at 08:32 • 0 comments

    The 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.