Power Supply Design Questions

[tichris08]

Hi Ray,

I was curious about some of the design changes that happened throughout the years on the OSPI version of the board.

I can see that you started off in 1.2 with a simple half-wave rectifier, moved onto a full wave rectifier and then a bridge. I’m curious to understand what prompted the changes there? Were some users seeing issues with a weaker filter or was this change prompted by something else?

I also see that you started using one additional capacitor of 0.01uF starting with version 1.40. I’m curious to see if this was also prompted by filtering issues or if there’s something else going on.

I assume that D3 is a Zener diode to protect the PI? The Eagle diagram shows it as a regular diode.

Thanks

[Ray]

Actually it has always been half-wave rectifier and has never been full-wave (where did you see the full-wave or bridge?)

The 0.1uF filter caps were added to a number of places as bypass filtered. These help a lot with handling voltage spikes.

D3 is indeed a zener diode.

[tichris08]

Thanks for the reply 🙂

Ah interesting. When I look at in in Eagle, it claims that TVS0 is a bridge in the later versions. Eagle lacks a lot of components, so I’m not terribly surprised 🙂

[Ray]

Some of the components are custom made (i.e. not in the default Eagle library). If you try to edit these components, Eagle will complain that it can’t find the corresponding library.

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