Need Help with Designing 120-24 V, 21 A AC-DC Convereter for Voltage level Conversion

Thread Starter


Joined Dec 2, 2012
Hello Everone,
I am working on a project that requires me to convert AC voltage to regulated DC supply for DC loads upto 500 W. Below are the important specifications for my converter design.

Input Voltage 120VAC
Output Voltage 24VDC
Output Current 21.0Amps
Load Regulation +/-0.5%
Line Regulation +/-0.5%
Ripple/Noise: 10mV Peak-Peak
Overload Protection 105-135%, Pulse Mode
Input-Output Isolation 1000VDC minimum
Efficiency 75% or better
Oper. Temperature with Derating: -40 to +60 DegC typical

I am thinking to use a center tap isolating transformer after the AC power source (use two diode arrangement for rectification) and use some sort of filters (LC-flters) and and finally employ use DC-DC converter thereafter. My challenge is to what shall I use as a switch for the DC-DC converter. I was thinking about using MOSFET. With it, I need to come up with some kind of design to control the cycle (some sort of PWM circuitry). I would really appreciate if anyone could help me with this stage of my project.

Thank you so much,



Joined Sep 7, 2009
Tell us whether this is a school assignment or a work assignment. Believe it or not, it would significantly change the answer I would have to give on it.

Also: tell us what kind of "safety" specs it has to meet. size and weight limits?

The best approach would be an offline half-bridge converter. This is a very difficult design for a novice.