hey guys, ive got to make a voltage regulator for a uni project. it has to use hysterisis and produce 9v out from a 16Vrms AC powerpack over a 15 ohm load. It also needs overload protection, ive drawn up the attached circuit, i think it will work and filled in some of the values i know but im stuck for the others, any help would be great.
15072
Redbelly98
Aug20-08, 04:29 PM
I'm not qualified to analyze a circuit like that, but what about using a simple 9Vdc regulator after cap C6?
mgb_phys
Aug20-08, 04:39 PM
I think that's cheating!
berkeman
Aug20-08, 04:56 PM
hey guys, ive got to make a voltage regulator for a uni project. it has to use hysterisis and produce 9v out from a 16Vrms AC powerpack over a 15 ohm load. It also needs overload protection, ive drawn up the attached circuit, i think it will work and filled in some of the values i know but im stuck for the others, any help would be great.
15072
Couple comments:
-- Usually I would put the current sensing resistor in the + feed, right before Q1. Having it in the negative return complicates the grounding of this non-isolated buck converter.
-- I'm not sure about the snubber on the flywheel diode. I've never used one, and generally haven't seen them used in bucks. It will lower your efficiency at least. Why do you have it there?
-- It seems like you should consider putting a bit of hysteresis in your comparator circuit. I'm not generally comfortable with comparator circuits without at least some postitive feedback hysteresis.
berkeman
Aug20-08, 04:57 PM
I'm not qualified to analyze a circuit like that, but what about using a simple 9Vdc regulator after cap C6?
I get the feeling that the assignment is to design a switching regulator, rather than a linear regulator.
berkeman
Aug20-08, 04:58 PM
Couple comments:
-- Also, is there a reason that you are using a Darlington for Q1? That will impact your efficiency pretty significantly.
Quiz Question: Why?
.
Redbelly98
Aug20-08, 07:14 PM
... what about using a simple 9Vdc regulator after cap C6?
I think that's cheating!
I get the feeling that the assignment is to design a switching regulator, rather than a linear regulator.
Whoops, my bad!
berkeman
Aug20-08, 07:19 PM
Couple comments:
-- It seems like you should consider putting a bit of hysteresis in your comparator circuit. I'm not generally comfortable with comparator circuits without at least some postitive feedback hysteresis.
Another Quiz Question for the original poster (OP) -- Why do I say this about comparator hysteresis?