This is my first question on stackexchange so if I do anything wrong, please let me know :-)
So my situation is the following:
I am working on a power supply module where I need 7 separated +28V DC outputs up to 25A. My current design incorporates of a small transformer-rectifier-regulator module with adjustable output that I want to use as a "pilot module". Then feed the output voltage of this "pilot module" into 7 "power modules" where on each of them it will steer a NPN transistor. The NPN transistor I'm thinking of using is the 2N3771 in TO3 package, rated at 50V, 30A, 150W.
Now I need to convert the 230V AC from my mains into a lower DC voltage for the power transistor emitter. Traditionally I would do that using a transformer, followed by a rectifier and smoothing cap. However, in this case I could see that getting very costly and hard to obtain, both using 7 different transformers or 1 big (huge) transformer.
So I was thinking about replacing the mains-transformer-rectifier-capacitor with mains-rectifier-capacitor-MOSFET and control the MOSFET with a pwm signal. Would this work? What would be the advantages and drawbacks of this approach? If I use a transformer, the output current will be lower then the input current while with a MOSFET this wouldn't happen. So could I double the load on the MOSFET given it will only be switched on half the time? Or would the peak current damage the MOSFET?
Thanks to everyone taking the time to read and answer this already :-)