Common anode diodes and their drivers.

[DMills]

Hi all,
Just a thought, but having seen the pain people go through with insulating the cans on multi diode rigs to allow the use of low side drive on positive supplies, the following thought occurred.

Why not use a negative supply and connect the anode (and can) directly to ground?

Something like this:


Obviously not complete, but it shows I think the basic concept.

You could even use an off the shelf low side driver if you got a little sneaky with the modulation input (I like current mode for getting such things across unknown voltage drops myself, but there are many ways to do it).

This would allow for one of those multi diode rigs to be built without needing to fart around insulating every diode mount (with the associated loss of thermal goodness).

Just a thought.

Regards, Dan,

[edison]

i think this is a good idea esspecially when you have -24v already in your projector.

I,m not very good at electronics but maybe shrad can have a look at it.

i will send him a PM

[DMills]

24V is a bit high if you want good efficiency, but a small switcher (which could be common to multiple diodes) would take care of that in short order.
Must draw it sometime....

Regards, Dan.

[RedlumX]

Why not use a negative supply and connect the anode (and can) directly to ground?

Because it's the wrong way around... the can must go to minus.

[DMills]

Because it's the wrong way around... the can must go to minus.

Then it is a common cathode diode and you can just use a trivial high side driver in the obvious way.
I really cannot see any combination that really warrants all the pratting around with insulation that seems to go on around here.

Regards, Dan.

[shrad]

a switching, isolated diode driver would guarantee that... see linear appnotes about "current sources for fiber optics lasers"

[andyf97]

Because it's the wrong way around... the can must go to minus.

Are they like this in DVD drives?

[The_Doctor]

I think most drives use a negative-grounded can because it's easier and cheaper to be safe in their standard negative ground cases. My driver design is specifically intended to work the same way. Negative ground with high side drive is nice. Insulating a mount isn't that hard either, specially if you're using a TEC which does it anyway.