# Calculating Smoothing Capacitance [duplicate]

I'm kinda new in this and I was wondering if I could get some help.

I am trying to build a AC-DC converter, through a full wave rectifier. Ideally a 220V AC source, freq: 50hz stepped down to 22V AC and rectified to a DC voltage but I'm struggling to get a definite formula to calculate the smoothing capacitance. I was planning to channel the output of the rectified DC to a 7812 voltage regulator. Thanks in advance.

• If you would have just searched this site you could have found: electronics.stackexchange.com/questions/176661/… Commented Aug 31, 2016 at 9:09
• 22V AC when rectified will give you about 30V DC. The 7812 will have to drop 18V which may cause overheating if you draw any significant current from it. Commented Aug 31, 2016 at 9:19
• @ Steve G, correct me if I'm wrong but if I was rectifying 22 AC, I would get about 15.55V by using the formula, Vpeak x 0.707? Commented Aug 31, 2016 at 9:28
• AC voltages are normally specified by their RMS, rather than peak, value. Thus the peak is 22 sqrt(2) ~= 31 V, minus a diode drop or two due to rectification and whatever additional drop is acceptable due to load current and the limited size of the smoothing capacitor. Commented Aug 31, 2016 at 9:36
• @ Oleksandr, thanks man!, I didnt know that, i really have to brush up on my fundametals then. Commented Aug 31, 2016 at 9:41