Is the following regulator valid, safe and efficient?
The transformer is a dual 7V output toroidal. So B1 is supposed to rectify out 14v and B2 taps the "center" to produce 7V.
INAE and I've never used dual bridges in a tapped arrangement like this so I thought I should ask before playing around with mains like this.
UPDATE:
The following is the circuit corrected as discussed but without the regulators:
This is supposed to model the Amgis L01-6310 14V/7V transformer to see what sort of voltages might be supplied to the 12V/5V regulators (because I should have used a 12V/6V part since Vpeak of 14V is *1.414 = 19.8V. Secondaries have 7 ohms series resistance per datasheet. I have never modeled a transformer in LTSpice before but I reasoned the turns ratio is 120 / 14 = 8.57 squared = 73.5 but this seemed to be off by a factor of 2 so I figured the primary is wired in parallel for 120V mains so I doubled the ratio to 147 / 1.
Green is the 14V tap. Blue is the 7V tap. Red and light blue shows the load on the outputs.
So it seems I get 16V and 7.2V which isn't too bad. If it comes out to 16V thats only a 4V drop. But I don't think the 12V load will be loaded much. If I only load it with ~25 mA, I get 18V which is 6V * 0.025 = 150 mW.
INAE so this could all be wildly wrong. IIWAE it would probably still be wrong.
Best Answer
The second bridge rectifier (the one connected to the center tap) is actually completely redundant. You can just connect the input of the regulator directly to the center tap, and it will get half the voltage, full-wave rectified by the two left-hand diodes of the other bridge.