Tiny Blu-Ray power supplies working well!

Hi folks, you might remember some of my posts from a while ago about making a tiny switching power supply to drive the violet LD of the Playstation KES-400A/AA/AAA Blu-Ray diodes.  Well they are finally working well!! (see pix below) Then run great even from a single AAA battery, though I still recommend using 2 to 3 cells for best performance, since high current draw is required for low input voltages.  Efficiencies are typically 80-90% (compared with 50-70% for the old-fashioned passive LM317T regulator & 9v battery).

These circuits work down to just 0.4 volts, so the laser won't die until the batteries are REALLY dead!  The circuit EASILY fits in the venerable Aixis housing - You might even be able to fit TWO in there!  They take an input voltage of anywhere between 0.4v to 5.5v and output 5v regulated through a 10-ohm dropping resistor, which results in safe 42mA through the violet Blu-Ray LD (about 10mW output from my measurements).  They have a simple 3-wire connection (the pic showing one with 5 wires included a touch sensor, but I might abandon that idea).  The size is 0.52" L x 0.36" W x 0.19" Thick (all dim. +/-0.1").  

I can also make 3.3v versions to drive the red portion of the Blu-Ray diode, but for simplicity, I'd recommend using a simple dropping resistor and switch in conjunction with a 2- or 3-cell battery system, and just reserve the more expensive switching supply for the violet LD. (I give schematics on the website below).

You can see documentation, schematics, etc. online at: http://web.mit.edu/cjoye/www/lasers/BluRay1/ (this URL will probably die by the end of this year since I'll be graduating from MIT!), so you can make your own too!

Since I don't have a lot of time to devote to making dozens of these, I will be leaking them slowly on eBay.  Here's the first one:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=190225762021&ssPageName=STRK:MESE:IT&ih=009

Enjoy!
-colin

they look great!
are you hoing to make them into a tiny pointer?

These look very nice,
Would these supply a X-box diode, (405nM), with 100mA @ about 5V?, from a AA Alkaline?
Dark Horse

Dark_Horse said:

These look very nice,
Would these supply a X-box diode, (405nM),  with 100mA @ about 5V?, from a AA Alkaline?
Dark Horse

Click to expand...

Yes, they would drive 100mA, but we'd have to adjust the dropping resistor (no problemo). Actually, this circuit is MORE efficient at 100mA output!!

-c

cdanjo said:

[quote author=Dark_Horse link=1212153839/0#2 date=1212156295]These look very nice,
Would these supply a X-box diode, (405nM),  with 100mA @ about 5V?, from a AA Alkaline?
Dark Horse

Click to expand...

Yes, they would drive 100mA, but we'd have to adjust the dropping resistor (no problemo).  Actually, this circuit is MORE efficient at 100mA output!!

-c[/quote]
How about a pot.

TheMonk said:

[quote author=cdanjo link=1212153839/0#3 date=1212156693]How about a pot.

Click to expand...

A pot by itself in series with an LD is a bit risky if you accideentally turn it too far, plus we'd be talking about something like a 2-ohm pot; Not very standard. Pot's are very large (compared to SMDs), even at 100mA. I find it better to analyze the LD with a precision power supply, current meter and laser power meter and find the point where the efficiency starts to compress. From there you know a good operating current and voltage, so you can easily calculate the needed dropping resistor.

Now using a tiny ~100k pot on the feedback of the switching supply is probably a good idea, but you have to really know what you're doing so you don't burn out your LD!

where you wrote the dealextreme link you should put a reference number.

ignore this post.... my brain is dead tonight ;D

Hey Cdanjo, I made a couple of these circuits of yours, I wanted to ask, the holes on the pcb need to bee connected through the other side? thanks

Look like nice drivers. I think the appeal of a pot is the ability to adjust the laser to whatever current our output you are looking for. Each person is different and it's one of the hazards of doing these mods and pushing out mods to the edge is potentially blowing up our laser diodes. Usually it's a risk that most of us are willing to take to squeeze a little more power from our lasers. D3stroy as an example is running an open in one of my Krytons at 350mw which is probably more than I'd push an open can.

If anyone wants, and cdanjo says its ok, I can get some of these made as kits, no profits from it

I agree with his decision on the fixed resistor for this design. Because it's a voltage regulator and relies on a small dropping resistor for current limiting, the output current will fluctuate depending on the diode voltage drop, which changes as the diode heats up. There is one other issue, each diode has a slightly different voltage drop so it will receive different current from this driver.
In all though, it's a useful small driver for the venerable KES-300A if you're not into adjusting current.

toked323 said:

Hey Cdanjo, I made a couple of these circuits of yours, I wanted to ask, the holes on the pcb need to bee connected through the other side? thanks

Click to expand...

Yes, those are through-plated holes.

As for voltage vs. current regulation, yes, my design is voltage regulated. I tried hard to implement a current regulator (TI TPS75105), but it was so small it was right at the limit of what ExpressPCB.com could do, and I couldn't get it soldered on right, so I gave up and went for voltage regulation. I have considered using the PD part of the laser to give a simple power feedback to the supply, but that wouldn't work well if both violet and red are used simultaneously. I was going for the simplest, minimalist approach first.