🚀 go-pugleaf

NEIL GANDLER (v064mcqs@ubvmsb.cc.buffalo.edu) wrote:

:     Im designing a small power supply. I would like to know if using a 12v
: center tap transformer when full wave rectified and smoothed be more than
: 15 volts to allow a 12 volt regulator 7812 work properly. From my under-
: standing the 78 series regulators need a 3 volt difference atleast. 

The first you must do, is calculate your circuit. 

	You use a center-tapping-trafo. Therefore you have only lost
	of one powerdiode-forward-voltage. From 12VAC you can expect
	about 16VDC with the lost of the diodes forwardvoltage. But
	this is the peak-DC-voltage. The ramp-voltage is given by
	capacitor and the used loadcurrent. The lowest DC-voltage-point
	may be not lower than the DC-outputvoltage of the regulator
	and his worstcase-dropoutputvoltage. 

	The answer:	Yes you can need the center-tapping-trafo
			with 12VAC, but you must know the loadcurrent
			and then you must calculate the value of the
			smoothe-capacitor.

So, I hope I can help you.

Bye Thomas