12V 0.5A regulated Power supply no IC regulators

[fingers]

Hi,

I need a circuit diagram for a power supply which will give a regulated 12V output under any load, and must be able to deliver at least 350mA. I cannot use IC regulators, short circuit protection needs to be included.
Does anyone have a known working circuit diagram for something like this. I have been trying to make my circuit work, but have had no luck with regulation.

Any help would be very much appreciated.
Thank you.

 

[Nigel Goodwin]

Hi,

I need a circuit diagram for a power supply which will give a regulated 12V output under any load, and must be able to deliver at least 350mA. I cannot use IC regulators, short circuit protection needs to be included.
Does anyone have a known working circuit diagram for something like this. I have been trying to make my circuit work, but have had no luck with regulation.

Presumably this is for a school assignment?.

 

[fingers]

Yes it is. Not hard to guess I suppose! Its a lot harder than I expected it to be.

 

[Nigel Goodwin]

Yes it is. Not hard to guess I suppose! Its a lot harder than I expected it to be.

Post the circuit of what you've done so far, and we can make suggestions - but we're not here to do all your work for you! 8)

 

[fingers]

Here it is, I have replaced the two diodes for a bridge rectifier. My transformer is 2x 15V (about 21Vdc after rectification) without a centre tap. I need a reliable 12V.

 

[Nigel Goodwin]

The 10K resistor is too high to feed the base, it's needs to be a lower value - but be aware of dissipation in the zener diode.

This simple type of regulator will never have great regulation, as there's no feedback - but it's fine for many purposes.