Personally I would not recommend that driver. I don't believe it is a constant current driver. I am assuming that is how it is for both a blue ray and a 445 with no pot adjustments. With higher voltage forward it drops current and if that is correct then it is dangerous if the battery has a voltage spike on start up especially with a 405 diode. I have also had many customers have problems with them. I would just grab a ben boost.:beer:
This driver.
Of course it isn't a constant-current driver. Neither is the current user-adjustable.
I have a couple of those drivers and from what I've measured, the output current is inversely proportional to Vdrop across the load.
Increase the Vdrop and the current drops. There's no sudden 'spike' as the driver tries to 'probe' the load.
For all intents and purposes they're fine for 445nm diodes but if you want to slap one across a 12x, you're wasting a
lot of the diode's potential.
They can't boost very far (~5V tops) but they can deliver a full amp at 4.2V or so. By 4.5V you're looking at 700mA out, and it rolls off from there.
Now, as for your original question of mA versus mW -- there are several factors that come into play.
Firstly, for an absolutely fair comparison, the diode's Vf must always be met. If not, efficiency begins to decrease and your measurements go out the window.
Secondly, you also have to take optics into account -- are you measuring current before collimation, or after? Depending on the lens, you could be looking at 5 to 10% attenuation.
Now, for
actual mA versus mW, it depends on every diode. You can find threads out there of experimental data, and that's how you get a rough estimate of what input current nets you what output power.
For example, we all know that 1A into a projector diode produces roughly 1W of output power. Similarly, 250mA into a LPC-815 will give you roughly 200mW out.
If you're ever lucky enough to be able to get hold of a manufacturer's
datasheet for a diode, you'll see they list a Typical Working Current given a set of conditions (in this one, it's 'CW, Po=120mW').
That means, for a typical diode, 200mA in will net you 120mW out. That figure may vary from diode to diode (hence the Min and Max values).
Sometimes, you can even get a
graph of mA input for mW output. That one isn't by a manufacturer (it's actually test data from O-Like), but nonetheless, once you have one of those it becomes very easy to interpolate output power from those. Just read the value you want off the axes.
Of course, that's given that the diode's Vdrop is met at all times.
That's why this driver has two 'modes of operation', so to speak.
It
can push close to 1A at 4.5V Vf, but it
can't do so at 6V for a 12x. Instead, it trades off boost voltage for current. As the voltage increases, the voltage decreases.
If you fed a 12x diode a whole amp at 6V, you'd get
magic smoke. If the diode survived, you'd get roughly 1.1W of 405nm.
But the driver can't deliver 1A at 6V Vf, so the diode is safe. At that voltage, the highest current the driver can push drops to 250mA or so, which is well within the safe range for a 12x diode.
