Constant DC current driver from AC?

Thread Starter

tguarriello

Joined Oct 10, 2006
2
I'd like to build a driver circuit that, as simply and economically as possible, takes 120VAC input and drives a variable DC load at a relatively constant .85 to 1.0 Amps peak. The output voltage would have to vary from 20 to 90 volts to deal the load changes and maintain the ~1 amp current flow. Ripple and a little noise is not a problem. Load is resistive (not inductive) and changes very slowly. I'm picturing a basic bridge-capacitor supply feeding a power MOSFET or IGBT circuit that is biased using a shunt (sensing?) resistor. I'm an industrial electrician and haven't done this kinda thing in about 15 years. I was hoping to find some example schematics that might help, but I'm coming up empty handed after about 2 hours of googling. Can anyone help?
 

Thread Starter

tguarriello

Joined Oct 10, 2006
2
Got it! Thanks guys. Good information - After reading through some of this stuff and pulling my old TopSpice program out of the closet (on 5-1/2" disks, so you know how long it's been). I've got a working circuit using a BJT (on paper, anyway).
 

Søren

Joined Sep 2, 2006
472
Hi,

MOSFETs and IGBTs are swithces - can't really bias them the way we can with BJTs.
Ahemmm... Linear audio amplifiers with MOSFET output stages is a myth then ? ;)
And MOSFET (resistive) dimmers can't be done... Hmmm, one of us needs to read up on the subject I'm afraid :)
 

thingmaker3

Joined May 16, 2005
5,084
Søren;21231 said:
Hi,

Ahemmm... Linear audio amplifiers with MOSFET output stages is a myth then ? ;)
And MOSFET (resistive) dimmers can't be done... Hmmm, one of us needs to read up on the subject I'm afraid :)
As I have often said, the universe is full of things I've not heard of.

That's what makes it such a fun place to live in!;)
 
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