4 LPC in parallel

[mpmsfilho]

Hello, I just want to know how I can drive 4x LPC-815 diodes at 240mAh but want to use only one driver, how can I do that?

 

[3zuli]

by using 4 drivers set to 240mA, one driver for each doide? :thinking:

 

[Cyparagon]

Or have them in series, and supply the driver with 12V

Parallel is not recommended, because each diode will draw a different current.

 

[mpmsfilho]

I want to use only one driver.

Thanks

 

[jaycey]

Then you want a Flexmod driver available (soon?) from Dr Lava

Wired in series with some resistors.

 

[FireMyLaser]

I'm not sure why you would need the resistors if you connect the diodes in series... Each laser module must be electrically isolated from the heatsink and each other to prevent them from shorting out.

 

[mpmsfilho]

Ok, I can use a AMC7135 with the diodes in parallel?

 

[Bionic-Badger]

Don't use them in parallel, as you can't guarantee that each diode will receive an even amount of current. Even if it worked properly, the AMC7135 can only sink 350mA, so divided four ways would be only 88mA each.

Just buy one of Dr Lava's Microboost drivers, set it for 250mA, and connect it to the four laser diodes in series.

 

[aXit]

Don't use them in parallel, as you can't guarantee that each diode will receive an even amount of current. Even if it worked properly, the AMC7135 can only sink 350mA, so divided four ways would be only 88mA each.

Just buy one of Dr Lava's Microboost drivers, set it for 250mA, and connect it to the four laser diodes in series.

While that would work, FML raises a valid point.

It's easy enough to distribute current equally through the parallel diodes. A resistor in series with each diode.

 

[Xplorer877]

While that would work, FML raises a valid point.

It's easy enough to distribute current equally through the parallel diodes. A resistor in series with each diode.

That would not distribute the current evenly. Only voltage will be evenly supplied across them.

-Tony

 

[aXit]

That would not distribute the current evenly. Only voltage will be evenly supplied across them.

-Tony

No, it will distribute current evenly. While it's not perfect, it's pretty close.

All the diodes are the same, so we can say that the forward voltages of each one are within a small margin.

If V+ is a constant current supply, and the resistors are low value, say... 10ohms, then the current will be split evenly between the laser diodes.

The resistors act as a balancing device, in that if more current started to go through one diode, the resistor in series with it would have a higher voltage drop, encouraging more current to travel through the lower voltage circuits.

Like I said, it's not perfect, and it doesn't work with anything except identical diodes, but it does work.