Power Supply Design - Is there a cheaper way? Need help

[FusionITR]

I would suggest replacing D4 and D5 with a bridge?, a half wave rectifier isn't much good at 50/60Hz - a bridge as two full wave rectifiers is MUCH better.

Do you mean replace both D4 and D5 with a single bridge or a bridge bridge replacing each diode?

I ask this because I need to be able to rectify a negative voltage for the negative voltage regulator (the -5V output). If I replace D4 and D5 with a bridge I wont be able to do this.

You do the same as D2 and D3, that's a full wave rectifier, add two more to give the negative half as well - it's normal to use a bridge to do so.

Sorry, to be mean, but if you don't understand such a simple basic circuit perhaps you shouldn't be looking at vastly more complicated switchmode regulators?.

I understand half-wave, full-wave, and bridge rectifiers, (the basics anyway). As far as swicthing regulators, I have to start from somewhere if I want to learn, saying "i dont know anything I give up" is not gonna help me understand them any better :wink: Pouring over the datasheets and asking questions will.

As far as what you are saying, what I am confused about is how you get the negative part of the wave in a bridge rectfier configuration to go to the negative voltage regulator. Maybe I'm just confused by the way youre wording it, do you mind putting up a quick schematic of what you are talking about?

 

[motion]

If I replace D4 and D5 with a bridge I wont be able to do this.

Here is what Nigel is suggesting. I don't know about the transformer voltage though. I think things could get hot for the -5V regulator at full load.