Fast modulable Laser diode driver with high side current control

[andythemechanic]

Hi everybody,

some time I asked about a modulable driver with high side current monitor ans switching here: http://www.photonlexicon.com/forums/...ead.php?t=7146
From the discussion on this thread a nice driver evolved, which I just finished prototyping and testing. Results look really promising, and I like to share them.
So Voila! Here are the schematic the layout from eagle and a pic of my first test assembly with a bluray laser diode for testing.
Have fun!
In the next post I will show some test results

[andythemechanic]

Here are some test results with a 47Ohm resistor as load. Current is 100mA. I have not testet higher currents so far but simulations point out that with some modifications (change of Resistor R1 and R10) currents up to 10Amps shouldn't be a problem (with proper heatsinking)

[andythemechanic]

Finally some results with a bluray diode, recorded with an ultrafast silicon photodiode (100ps risetime).

[andythemechanic]

As can be seen the driver behaves quite nicely at this low currents. It has the big advantage that the diode is grounded. It has softstart and current limiting.
This was actually my first layout in Eagle and I had quite some fun learning and designing this drive.
A big thanks to Steve (aka mixedgas) for the help with this drive!!!
Hope you enjoy!

Andreas

[chad]

I can't believe I didn't catch this a couple of months ago. Looks good.

How do the drivers work? I saw the pictures of the little projector you finished.

Could you take a couple of pics that might show the modulation of the lasers with your drivers? Maybe a couple of the test patterns?


chad

[andythemechanic]

Could you take a couple of pics that might show the modulation of the lasers with your drivers? Maybe a couple of the test patterns?


chad

Hi Chad,

The pics in the third post here is the actual modulation of a bluray diode recorded with a fast photodiode. I tried to make a simple test to visualize the modulation: I scanned a circle with 400Hz and modulated the diode with a higher harmonic (rectangular). Here are the images at 10kHz and 36kHz Modulation frequency. In real it looks better than with my camera. Also I think the modulation in the scanner is more limited by the noisy AudioDac than the drivers, the above was recorded with a prper function generator.
If you have another testframe (in ILDA format) you would like to see you can PM it to me.
The drivers work really good in my machine. The current limiting feature is really nice when adjusting the drivers, you never have to worry to kill your diodes . They are not so good for pump diodes because these are case positive so you have to isolate them.

Greetings
Andy

[ElektroFreak]

Looks very nice. I'll be trying one of these out for sure!

[andythemechanic]

Looks very nice. I'll be trying one of these out for sure!

If you like to test it, I could send you one for parts cost. I made 8 proto boards and ordered all the parts for 8 drivers. Send me a PM if you're interested!

[ElektroFreak]

PM sent to you!

[flyowynd]

You're my savior, I've got so many issues isolating my red diodes, I will run to my local electronic dealer to buy the components.

High side current drive is very hard to find, and my previous tests with home made one were not very successful.