Hi all,

I only " translated " , a power supply schematic for an halogen lamp - 45 W , about 4A under 12V.

In fact, i plan also to use it for more projects .

http://electronics-diy.com/electronic_schematic.php?id=981

It would be great, if someone could check my schematic copy.

Of course, ( 15 * 1,414) - 2 is only 19,21 V .

Thanks a lot.

jm

 

It would be great, if someone could check my schematic copy.

It will output a voltage that varies slightly with varying load - in my book, that doesn't work as a regulator.

It is very easy to check it yourself - read the datasheet.

 

your better using a Pnp series pass transistor, than npn.

 

Hello,

As dd told you, better use a PNP transistor as pass transistor.
This picture from the hamradio magazine " FUNK Amateur march 2016" shows you the effect of using the PNP pass transistor:



Sorry for the german text, but the images are clear.

Bertus

 

Hi

You might consider using a step down (buck) controller with external switch.

 

Hello,

As dd told you, better use a PNP transistor as pass transistor.
This picture from the hamradio magazine " FUNK Amateur march 2016" shows you the effect of using the PNP pass transistor:
Bertus

I've seen that 7805 pass PNP diagram before in the datasheet for the 78xxs and I couldn't figure out why that PNP doesn't have a base resistor. It seemed a bit odd but I figured there was something I didn't understand.

 

Hi,

As usual, thanks a lot for your replies.

Great site.

jm

 

I've seen that 7805 pass PNP diagram before in the datasheet for the 78xxs and I couldn't figure out why that PNP doesn't have a base resistor. It seemed a bit odd but I figured there was something I didn't understand.

I've seen that 7805 pass PNP diagram before in the datasheet for the 78xxs and I couldn't figure out why that PNP doesn't have a base resistor. It seemed a bit odd but I figured there was something I didn't understand.

I'm guessing your worried about the base current? The 317 acts as the base resistor. The circuit has no short circuit protection anymore as it is. You could add a little resistor in the base to current limit the transistor again.