New 4 Channel Highside driver

[edison]

I would go for a 4 channel. Its better to have seperate channels to set bias and gain for each diode. I just finished a 4 watt blue with one of these and is perfect. I had 5v as input voltage and still more then a watt per diode Each diode is different and so its better to buy a quad and use two channels first and ad the other 2 diodes to the other channels later

[bhwollen]

Thanks for your help edison, one more question.

What is the difference between the bias and gain? And how does one go about setting it?

[Badpip]

The bias is the current at 0V modulation input, and the gain is the current at 5V input.

LDs have a lasing threshold current, where they will begin to lase. Below this they just act as a LED.

Lets say you have a diode with 200mA threshold, and 1000mA max current.

To give the best color resolution, the driver is set to start at 200mA by adjusting the bias.

After this, the 1000mA maximum current is set with the gain trimmer.

/Thomas

[bhwollen]

Ah I see, I figured something along those lines. If I were to buy one, would I be able to get you to pre-set it for me if I told you the diodes and current I would like to use?

[planters]

What then is meant by beam suppression. Those "LEDs" still glow with the P3s when they are at the bias setting.

[Badpip]

Ah I see, I figured something along those lines. If I were to buy one, would I be able to get you to pre-set it for me if I told you the diodes and current I would like to use?

Sure, No problem.

What then is meant by beam suppression. Those "LEDs" still glow with the P3s when they are at the bias setting.

Yup, that's where the beam suppression comes into the picture - just tried to keep it simple in my answer above.

Below lasing threshold you have a "LED" - and the blues makes very bright leds before they lase.

Beam suppression turns the diode fully off when the input is at 0V - When it rises, it will jump to the bias setting.

So in the example with 200mA and 1000mA it would go like this: 0-0.2V = 0mA out. 0.2-5V = 200mA to 1000mA.

/Thomas

[planters]

That's what I thought, however I was under the impression that the "just below threshold state" was necessary to maintain a type of readiness to allow fast modulation to the lasing output. No? Or just not significant enough to matter?

[Badpip]

It doesn't matter - laser diodes are FAST. Imagine how fast they are modulated in 10+ GBPS optical networking systems.

The main idea with the threshold setting is to get a wider color palette.

In the example above, without threshold, 0-5V would give you 0-1A. The diode will lase at 200mA, so it will start at 1V modulation input. That's 20% less shades possible.

With beam suppression this is moved to 0.2V, giving you only a 4% smaller range.

DPSS might be another story though.

/Thomas

[planters]

Thanks! Got it.

[kl79]

hello, I own one of your driver, but I have a problem...it's powered with 12V, max current is 1.2A per diode, all is working fine, but if I put the jumpers, the diodes stop lasing (even with 5V mod)...is that normal ?