walkingbeard
- Mar 24, 2010
- 6
- Joined
- Mar 24, 2010
- Messages
- 6
Hi,
I'm doing first year Electronics at Queen Mary University of London.
As part of our basic circuits course, we have to design a power supply, based on a rectifier, smoothing cap and voltage regulator.
We can ignore for the moment, the transformation from UK mains voltage (253V maximum).
The rectification and smoothing aren't a problem for me. What I am confused about is the voltage regulator. We have been shown three regulators, two of which we are allowed to use in our project.
I attach the circuits underneath.
As things stand, I have gone for the second one, on the basis that which the first one, you have difficulty in picking components, due to feedback and the fact that a real Zener diode requires a certain current (probably more than I would want at the base of the transistor), in order to reach a near-constant voltage.
I don't think I really know what I'm doing though. Would someone be able to explain to me why I would or wouldn't use these circuits, and how I would go about picking actual components, given that I have to pick values before I even start looking for the components themselves?
I'd be most grateful.
Jack
I'm doing first year Electronics at Queen Mary University of London.
As part of our basic circuits course, we have to design a power supply, based on a rectifier, smoothing cap and voltage regulator.
We can ignore for the moment, the transformation from UK mains voltage (253V maximum).
The rectification and smoothing aren't a problem for me. What I am confused about is the voltage regulator. We have been shown three regulators, two of which we are allowed to use in our project.
I attach the circuits underneath.
As things stand, I have gone for the second one, on the basis that which the first one, you have difficulty in picking components, due to feedback and the fact that a real Zener diode requires a certain current (probably more than I would want at the base of the transistor), in order to reach a near-constant voltage.
I don't think I really know what I'm doing though. Would someone be able to explain to me why I would or wouldn't use these circuits, and how I would go about picking actual components, given that I have to pick values before I even start looking for the components themselves?
I'd be most grateful.
Jack