Re: 7815 Regulators. Voltage margin?

Posted by strewel_peterson on Jul 19, 2020; 8:44pm
URL: http://guitar-fx-layouts.238.s1.nabble.com/7815-Regulators-Voltage-margin-tp48987p48996.html

16v AC is a sine wave: it goes from about -22.5 to +22.5 volts: if you take the average of the voltage squared (which cunningly makes the negatives positive, then take the square roiot of that, you get16.

What this means is that at peak positive on the incoming AC you get 22.5 volts, the diode takes 0.5 v or so, and the reservoir cap could therefore charge up to 22v.

So long as the circuit isn't trying to drain the reservoir cap faster than it charges from the AC, you would see a voltage somewhere between 16 and 22  at the input of the regulator - should be high enough to guarantee 15v out.

At least, I think that's what happens!

Cheers.