Sold/Expired New Design - Off the Shelf SSC P7 current regulator (PWM, buck or buck/boost) needed.

[ronanski]

Hello,

Any/all ideas appreciated - new design.

Looking for an "off the shelf" buck high-efficiency PWM true current regulator for SSC P7 which will regulate (not just limit) the LED current to 2.8A optionally with PWM dimming and optionally with thermal / current compensation (for derating).

I have two applications - focusing on the portable applicaiton currently which is a head mounted two LED torch (all custom made) with 2X SSC P7's - I have a choice of two bins/Vf's:

DSVN (I): 5000-5700K, Vf 3.25-3.50V, 800-900lm
DSXP (K): 6300-7000K,Vf 3.75-4.00V, 800-900lm

I'm at the age where I can't easily solder the small SMD components, so I am avoiding developing my own custom PWM current regulator board. I have the technical know-how just not the SMD skills nor time to spare.

I've not settled on a battery, but it will probably be a Li-Po mounted in my backpack. My battery can be 12VDC nominal (11-15V) or 6VDC (5-8V) or even some other voltage. It would be great to find an buck/boost OTS driver which had a much wider input range (eg 3.7V-30V) but this is optional.

I need to maintain the full 2.8A LED current for 4H so I am designing the system with a 12AH (plus) LiIoPo battery.

Recently I ordered a couple of the KAI SSC P7 regulators, but unfortunately these are no better than a series resistor with poor current regulation (http://www.kaidomain.com/ProductDetails.aspx?ProductId=1770) giving me a dimming LED over the battery charge (not an option). This is not an indirect complaint against KAI, it was my fault that I didn't research the AMC7135 linear regulator IC these things are based on before I purchased (I've asked KAI/sales if they have a better switching driver in the meantime).

I am looking for a true switching/PWM buck current regulator. It may require an external switch as most IC's I've seen are not capable of 2.8A continuous. My headlamp design needs to maintain full SSC P7 brightness for the 4H charge of the battery.

I do not have to house the driver inside a flashlight since this is an OEM, so the board can be square, rectangular, etc (I'll mount in a separate enclosure in my backpack).

I'm very suprised how hard it has been to find such a driver for the P7 since it has been in production awhile.

I've looked at the LM3401 or LM3485 (national) or LT3478 (Linear Tech) IC's but the eval boards (which I'd consider using in a short run prototype) don't fit well with the 2.8 A or so needed by the P7.

Maybe a topic for a new thread, but optionally I'd like to consider a supercapicator to replace the LiIoPo battery. I think Maxwell makes them and they may be competitive space wise but probably not cost-wise.

Any ideas?

Thank you,

Ronan/Andrionix

 

[Blindasabat]

I am looking for something similar, a 2S2P Cree MC-E which will be ~6.6V times two 1200mA drives. You need 6.5-8V (depending on your LED) at 2.8A if you run in series, or 3.25-4V at 5.6A in parallel.

I am not an expert, but I have been going through the Sandwich Shoppe ( http://theledguy.chainreactionweb.com/http://www.theledguy.com ) converter boards all day, and I don't know aof anything that can do the 5.6A thing. They do have the Shark Buck 3A that can drive up to 3A but you need to supply a higher voltage than your LEDs total Vf. You can adjust the output below 3A with the onboard trimpot - how accurately you can hit 2.8A is anybody's guess(?). It looks like it can drive the two P7 in series at up to 3A as long as your battery can supply 24 Watts while staying over ~8V.

Somebody please correct me if I'm wrong.

I may get the Shark buck 3A to drive my 2S2P MC-E (~6.5V) with a 7.2V battery pack or drive a parallel MC-E off a 6V NiMH pack.

 

[LEDobsession]

I recently came across something of this nature and I may also be using it in the near future.

http://www.led-tech.de/en/LED-Controlling/Constant-Current-Power-Supply/PowerLine-SLIM-Constant-Current-Power-Supply--2800mA,-30V--LT-1291_118_119.html

Maybe this will be of some help.

 

[Bimmerboy]

Hi Ronan,

:welcome:

This area of the forum is for buy/sell/trade, so it'd be a good idea to ask a mod to move this thread to either Flashlight Electronics - Batteries Included (which would be my first choice for this topic), or Homemade and Modified Lights.

That said, there are four choices that I know of which may fit your needs. The hipFlex by TaskLED, the Shoppe's Shark Buck mentioned above, a popular driver made by CPF member Der Wichtel, and the hipCC (also by taskled... no UI, so you'll also need a d2Flex for PWM dimming).

The Powerline Slim by led-tech.de (also mentioned above) will place tight restrictions on your power supply since it's a linear type driver. It has a 1V drop, but doesn't like input of more than 2V above LED Vf. If I understand correctly, that only allows your battery pack to drop 1V during it's full runtime... and that's assuming you're able to get a perfect match of Vin to Vf in the first place. Definitely go with the other drivers.

At this time, I know a bit more about the taskled stuff than the others, so I can say that the efficiency charts look very good, especially at higher total operating voltages. And the UI is pretty darn awesome.

Good luck in your quest, and don't forget to ask a mod for help moving the thread!

 

[chuckolson]

There's a MAX16804 PWM current control chip made for up to 350mA automotive use, but it will operate down to 5.5V input. It chops at about 200 Hz and has a dimming line. The chip senses current with a differential pair and they show an application circuit for ampere-level operation driving a power transistor base with the chip output, the LED in the collector, and sensing resistor in the emitter connected to supply (-). I figure it will work with a couple of series 18650's to get the voltage up and maybe another pair in parallel to get the current up.

All this is a lot of work compared to just direct driving it with two 18650's in parallel for about 7.5 watt operation - - or add another parallel 18650 and it might get you up to the 10 watt max input level, but unregulated, of course. Three cells might overdrive the P7 a bit after recharge, so I would tend to stop at two cells and be safe. Of course heat extraction would be top priority for this kind of operation.

Parallel cells puts it into a side-by-side cell configuration, which I've always preferred to in-line cylindrical for in-pocket EDC. You might want to look up my 4/29/04 post in the "Homemade and Modified Lights" section entitled "A 3-Watt Flashlight" for a packaging style that solves the heat removal problem and uses side-by-side cells. A version with the P7 and Lithiums should be real nice.

Whatever you decide, good luck - -

Chuck

 

[cmacclel]

I recently came across something of this nature and I may also be using it in the near future.

http://www.led-tech.de/en/LED-Contr...wer-Supply--2800mA,-30V--LT-1291_118_119.html

Maybe this will be of some help.

This is a buck driver but if I'm reading it correctly you can only have a maximum of 2v over the LED forward voltage. If so that's not very good!

Mac