cicuit design questions

[chikkenguy]

there are a couple things i have not been able to figure out about the design of this power supply. any help would be very much appreciated.

1. what purpose do the .01uf caps around the diode bridge for the b+/- supply serve? they are too small to act as ripple filters, arent they?

2. this is sort of a bigger question perhaps: how does the rectification circuit for the +48v supply work? what purpose do the 1800uf caps serve? does that section function as a voltage doubling circuit? how about the .01uf caps there too? why couldnt you just eliminate d5 and d11 and let d6 and d10 do the rectification job?

[tpryan]

The .01uF caps are to suppress any switching noise from the diodes. Whether or not this is actually a problem is somewhat controversial, but they're easy enough to add and don't cost very much. They don't improve performance in any way I can measure, but seeing them on the schematic makes some people feel better.

C8, C21, D5, D6, D10, and D11 form a full wave voltage doubler. Eliminating D5 and D11 would remove the charging path for C8 and C21. Do a google search for all the information on circuit action you could want.

[chikkenguy]

could you explain at all why you chose to use a voltage doubling circuit instead of a more straight forward rectification scheme?

[tpryan]

A full wave doubler is straightforward. Voltage doublers are a good solution where you need a voltage higher than what's available from the transformer, but with little current draw. It's a very common way to get +48V for phantom power.