Voltage drop with diodes?

Hi all.

I am hoping someone can point me in the right direction with a "problem" I am having. The scenario is that I have a constant current, voltage regulated 3 channel rgb driver which I run of a 12v ps. Each diode has its own current pot and voltage regulator. The regulator for the red and green gets very hot since these use very little of the 12v supplied. Its not a problem for the 405nm laser since it only has to "eat" 4-5 volts.

Now my question is if it is possible to drop the voltage using 1n400x diodes in series connected right before (+), or after the diode (-), to drop the voltage so less heat is generated. Is there anything I have to be aware of when connecting things this way. Obviously I dont want to fry my lasers and I havent really been able to find any info on using diodes this way, since I dont want to drop the overall voltage.

Hope someone can shed some light on this.

Thx in advance.

NOT connected on the LD (it's possible with linear drivers, but not suggested with switching mode / boost drivers).

But you can connect them in serie with the driver itself (if the driver don't need more than 500/600mA), for lower the power supply voltage of the driver, and the heat dissipated from it (but remember, that part then become dissipated from the diodes).

If your driver needs like 1A or similar, use 3A diodes, like 1N540X serie.

But the driver you have is a single driver for all the 3 lasers ? ..... and it's linear ?

I have no idea what a switch mode driver is. The driver is a 3 channel driver. You can see the schematics for it here: http://c4r0.skrzynka.org/_hv/lasers/RGB_DRV.pdf

Why is it not possible to connect the diodes directly before or after the LD?

LaserAdct said:

I have no idea what a switch mode driver is. The driver is a 3 channel driver. You can see the schematics for it here: http://c4r0.skrzynka.org/_hv/lasers/RGB_DRV.pdf

Why is it not possible to connect the diodes directly before or after the LD?

Click to expand...

This is a current sink circuit as opposed to a linear or switcher voltage regulator current source. This means the regulation happens after the Laser Diode using a MOS-FET. Not sure how to best modify this type of circuit so ill defer to others here. Like HIMNL9 said, with adding diodes all you are doing is moving where the heat is produced ... if the MOS-FETs have proper heatsinks, it may be best to leave it the way it is.

Oh, that one ..... understood ..... yes, it's a sink driver, and for how it's drawn, the TTL signal need to be forced to zero for turn on the laser diode, i see ..... yes, in this schematic you can also add diodes in serie to the laser diode, cause it's a linear driver, but they still need to dissipate heat ..... much better to heatsink very well the mosfets, yes.

Thanks for your replies guys. I think the solution will be to add a bigger heatsink for the mosfets instead of dropping the voltage with diodes.

Regards

Nicki