Re: 6x Blu-ray SLEDS GB! THEY ARE GOING FAST!
A 33 ohm resistor with an AMC powering a 4x gives you 168mA. It varies a little with input voltage and how much current gets bypassed depends on the Vf of he diode at the remaining current. They depend on each other, and the only way to do it safelly is to power the diode fom a proper driver at the desired current, measure the actual output from the AMC, then divide the diode's measured Vf by the current you want to bypass. However i would recommend you bypass 20mA more, just in case, which you did...
Basically you just use Ohm's law. U = R x I..
You want to bypass 150-180mA, to power the diode at 200mA. AMCs vary from 350-380mA!
Then you put the diode on a 317 or a FlexDrive set to 200mA and measure the voltage across it. Let's say you get 6V at 200mA (Rkcstr's gaph says so)
Then you do this: U = R x I -> R = U / I -> R = 6/0.150 (6V divided by 150mA) -> R = 40 ohms
If the AMC puts out EXACTLY 350mA, 40 ohms will give you 200mA current through the diode. But then it will warm up, the Vf will drop and the relationship changes. It's actually very complicated. You could only match it up perfectly using two graphs.
Since you used 33 ohms, (which would bypass 91mA at 3V / with a red diode - is that where you got it?), it bypasses 182mA at 6V, you got a safer current of 168mA through the diode, IF your particular AMC puts out 350 and not 380. If it puts out 380mA, you got 198mA through the diode.
Unfortunatelly the AMC also changes in current with input voltage - the lower the input voltage, the higher the output current for some reason.
Otherwise, you do need output caps on the AMC. The AMC original board doesn't work with output caps, because of the polarity protection. Bridge the protection and you can put a capacitor on the diode directly. If the original polarity protection remains in tact, it doesn't want to start up for some reason, altho it should. But it has something to do with the AMC positive input being at a lower potential than the diode. They should be at the same potential anyway.
In any case, AMC can be a good driver for higher power diodes, where small current changes don't matter. It can be OK for reds, that can either take the current, like open cans, or reds, that you set a little lower than max current.
But it's not good for pushing expensive diodes to their limits. It's not stable enough for that.....
My datasheet says absolute maximum voltage = 7V. But normally it should not be more than 6, so it's not really suitable.
