Has anyone had experience making a (negative) regulating version of the DDL ?

[chefla]

You guys might want to try the LT3015 from Linear. It is a true negative regulator and good for up to 1.5 Amps.

 

[midias]

LM337 Neg regulator built it used it and currently using it for my 635nm pen

 

[rhd]

So instead of this:

v+ ===> reg ===> diode ===> v-

You are doing this:

v+ ===> diode ===> reg ===> v-

The end result should be the same.

Something has been driving me nuts here, and it all has to do with where we get the (-) feed for the driver.

The only thing that makes sense in my head, is from the battery (+). But that doesn't *actually* make sense in my head.

Excuse the awfulness of this drawing:

 

[jib77]

The driver's negative becomes the common positive plane, it should be tied to the battery positive or case.

 

[rhd]

The driver's negative becomes the common positive plane, it should be tied to the battery positive or case.

I guess my gut was correct. It's just hard to get my head around the ground coming from battery positive. It makes sense though.

Thanks Jib

 

[kiyoukan]

if you want a negative regulating driver capable of 2a and softstart send me a msg.

 

[Wolfman29]

Yeah - I actually have a build using one of these with the IR diode you sent me, rhd. Why didn't you just ask for how I used the driver? XD

 

[Elektrotechniker]

I like this thread.

 

[foulmist]

can anyone tell me if this is possible with a switching driver?

AX2002 IC for example???

I am trying to use that with a case positive diode? :thinking::thinking:

 

[midias]

can anyone tell me if this is possible with a switching driver?

AX2002 IC for example???

I am trying to use that with a case positive diode? :thinking::thinking:

Well buck boost are not going to let you do it exactly the same if you have a data sheet I could probably help you more.

 

[foulmist]

yes I do:

 

[foulmist]

Ok so it's 3:30 am here now in Bulgaria... and I am not sleeping

I decided to test this with LM1117 and it kinda works but not exactly!

So I made my own PCB according to the diagram I double and triple checked
everything :

B+ to case
B- to Adj pin and cap's negative
Vin to diode's negative and cap's negative

I set the current to nearly 380mA. ..~370mA something
I connected the test load, connected the adjustable power supply,
pushed the button and now comes the funny stuff

when I was cranking up the voltage from 0V to 6V i got a steady current
going up! Good for now.. at 6V I got to the 370mA.. So I started cheering ..
then I turned the voltage up and WHOA?! the current suddenly dropped to
250mA and stayed there no matter how many volts I fed it with....

when I returned to 6V input I got my 370mA current again...

so I decided to see how does it behave on my 150mW IR diode..
it's maximum current is 380mA.. and I have set it to almost there..

now I stared from 0V again and when I reached 4.7V the current
was 370mA so I decided to stop cranking the voltage up and see what
happens next..

at some moments later what I saw was that the current was slowly
starting to rise due to heat... the hotter the diode and driver got the
more current was going in.. from 370mA it went to 380mA and I turned it off..
don't want to kill my diode

because if had crossed the border of regulation... I think it's not regulating
properly when connected after the diode... I don't know how it turned out
for you guys but for me it didn't work.. maybe LM317 behaves differently in
this manner but my LM1117 doesn't... :gun::cryyy:

well I just wanted to share that with you ... if you have any suggestions or thoughts pls share

I am going to get some sleep now ... it's almost 4am ..... goodnight :can:

p.S. I guess that's why there are negative rail regulators and positive rail regulators and not just
ONE of them if it worked both ways don't you think??
I think this was doomed from the beginning ...

 

[Kizdawg]

Sorry to jump in I'm a dweeb at electronix.. I wired a few arduino's but nothing special.. I need an RHD crash course in electronics... and from what I have read I'm there... Thx RHD.