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Astral Driver - Boost, Buck, & Sepic

hakzaw1

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Subscribing--Ready to place orders--len
 



paul1598419

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I take it you are going to use a PCB with a high thermal conductivity. Is this the only way to heat sink these ICs? I would still prefer to not use the bottom of the board if components will allow. Are the pots you are using multi-turn pots? Just trying to get a picture of the buck driver's ability to adjust from 1.1 amps to 6 amps. I would need to be able to get within a 100 mA scale. If it can do better, then that's wonderful. :thanks:
 

astralist

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I take it you are going to use a PCB with a high thermal conductivity. Is this the only way to heat sink these ICs? I would still prefer to not use the bottom of the board if components will allow. Are the pots you are using multi-turn pots? Just trying to get a picture of the buck driver's ability to adjust from 1.1 amps to 6 amps. I would need to be able to get within a 100 mA scale. If it can do better, then that's wonderful. :thanks:
Just like the specification i wrote, the components are only on the top side of PCB, leaving th bottom side of PCB flat so that you can mount it on some heatsink perfectly, thus maximizing heat transfer.

it is actually a single turn pot
if we look at the graph, adjusting the higher current will be a challenge.

If you want to fine tune specifically for higher current, you can change the pot to 1k pot, so it will strech the 80-100% graph to 0-100%
 

Richie89

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Will you offer them with leads already soldered on for a little extra mullah, for people that are too impatient to do themselves like me :O
 

Benm

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@paul:
@Benm:
You mean the PicoDrive right?
This driver is unique, the input voltage allows it to run with boost and sepic topology. With one lithium battery it can supply about 800mA+ to 5V load, with two lithium battery, you can get a double output current.
Making the DC-DC switching boost converter with regulated current is actualy just like making a sepic converter, the output voltage is depends on the load, the voltage will increased as the current trying to reach the set/limit current. The limitation lies on the capability/flexibility of the IC. The SuperDrive LV for example, can only have minimum output voltage of 2.9V regardless of the current, so that it can regulates itself properly and the max input.
Let's say i have a laser diode that has a forward drop of 3.8 volts and requires 400 mA to operate. Would this driver work from a lithium cell that starts out at 4.2 volts and then discharges all the way to 3.0 volts (before safety circuits cut it off)?

Given the small footprint that would be pretty amazing. Such drivers often have buck-boost or boost-buck topolgy with some more or less fixed intermediary voltage. This works fine if you have the space to build them (like in solar charge controllers where the panels mpp could be below or above the battery voltage depending on light intensity), but putting that into a cubic-centimeter like envelope would be a challenge even for only a few watts.
 

astralist

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It should work like that, given the buck-boost topology.
Also, the maximum output capability is determined by the input to output voltage ratio and the internal current limit, and also efficiency.

when it's operating in buck mode, output current will be on its max capability.
But when in boost mode, the battery and converter must try hard to achieve stable constant current output until it finally unable to keep the stable current output i.e the current will be decreased from its original setting by the potentiometer.

It's quite hard to estimate output current capability vs Vin for the buck-boost/sepic converter with current regulated scheme, not until i do a proper testing.
I'll update the current graph once it's been tested.
 

paul1598419

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To get a SEPIC topology in such a small package, I imagine you are using coupled inductors instead of individual ones. I am a bit concerned with this type of topology for an LD driver circuit, but that may just be my over concern talking. I look forward to your tests and results.
 

paul1598419

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He did say about the 17th of this month. IDK if he is ahead is schedule, but my best guess is probably not.
 

CDBEAM777

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OK then....I have been waiting for something like this !!! The Superdrive LV....YES !!!!!

A compact and corrected NUBM044 EDC....PACKED TIGHT !!!!!!!

Hmmmm....SO....we harvest the Cree XML2 ( 145mm x 41mm)....and add optics to the front....hmmmm....maybe add 40mm more...so....we end up at 185mm....'bout 7" long.....OK !!

A little on the long side for an EDC....but....Still OK......

The XML2 takes a single 26650 LiPo....and has an external charging jack !!

Not sure the switch will stand up to 5A....but....whada want for 12 bucks !!!!


Just add this to my EVER growing list !!!!

Needs a name !!! hmmmmm.... ????:crackup::crackup:

THANX Astralist !!!!

CDBEAM
 

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paul1598419

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Hi CDBEAM. Nice to see you again. Yeah, I just bought the 445nm cylindrical lens trio from Techhood. Still want to know if anyone else has bought a set of these. The center lens corrects in the 90 degree axis to the others. I have a pair of the 6X from Opt lasers too. Have the diode and need to decide what to put it in. I'm thinking of using my empty MS-SSW-II where I will have the room to add the clear tube to add the optics to. That should make an aesthetic build.
 

astralist

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Sorry for late reply, i have a news for you all:

Due to Ramadan and Ied Mubarak, i need to postpone the payment :(

I just paid the component and assembly service by now (5 July 2017), due to small quantity order and assembly services (total combined of 100 units of all three driver: 50-25-25) it's quite whopping with combined USD2.4k lol
It will be cheaper if i solder/reflow it myself, but not sure if i'll be able to do it because of fine pitch QFN components. :banghead:

And about the PicoDrive:
Due to out of stock and the minimum order of the IC, i am unable to get the boost/buck for now, hence the IC has been replaced with boost-only IC with same board size and output max ~800mA
I'll be sure to design another boost/buck laser driver later :beer:
 

CDBEAM777

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Hi Paul....yea...this will be a nice driver...small...boost....high amp....great if it all comes together !!! Good Luck Astralist...and THANX !!! Just another project....added to a LONG LIST. !!

CDBEAM
 




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