Hello,

I'm using the circuit shown in the figure to produce a +/- 15 V supply for powering some op amps. I tested this circuit using a center tapped transformer without any load connected to it. The circuit seems to draw too much current. A 6 A fuse blew, which definitely shouldn't be happening. I implemented this circuit in breadboard and PCB, but the results stayed the same. However, my PSpice simulation says I should be getting a +/- 15 V output.

Narrowing it down, I am getting the +15 V section (when I tried a partial implementation) but the -15 V section seems to be the source of the problem. What am I doing wrong?

 

hi,
With a CT transformer you dont need two bridge rectifiers, you are effectively shorting thru your double bridge.

E

 

Your bridge rectifiers are fighting each other. You only need one, like this:-

 

Thanks! I'll try them out!

Although I still don't completely get how the bridge rectifiers clash... is it because the ground line both sources and sinks current? (In my understanding of the circuit?)

 

It's the connection at C1 and C2. You have one bridge sending its negative there and the other bridge sending its positive there, and they are also connected through the transformer. Too many current paths!

You need to simplify. It only takes 4 diodes to do this job.

 

I still don't completely get how the bridge rectifiers clash..

Consider the half-cycle when the bottom of L3 is +ve and the top of L2 is -ve. There is a short circuit via D6 and D9.

 

Consider the half-cycle when the bottom of L3 is +ve and the top of L2 is -ve. There is a short circuit via D6 and D9.

Umm... Whoops...

 

The PSpice simulation likely worked because the short circuit just created a very large current but the voltage was still okay, since the components are ideal (diodes that can carry infinite current and not blow). If you look at the diode currents you will likely see very large values.