AMC7135 Circuit board @ Kaidomain

Just found this:
http://kaidomain.com/WEBUI/ProductDetail.aspx?TranID=1746

The funny thing is that Kaidomain rates this with 700mA output and the manufacturer only 350mA xD

http://www.micro-bridge.com/AMC7135.asp

edit: Just noticed the board uses 2 regulators in parallel

*DROOLS*
A question I have, is this just a boost/buck circuit, or a boost/buck WITH regulated output? I know they have the runtime diagram on kai, but I'm not sure if that brightness plateau is from the battery or from the regulator.

I just took a chance and ordered a set. The price is for five (5) boards, and ten wires!!!

Did anyone see dimentions for the board?

sparkysko said:

*DROOLS*
A question I have, is this just a boost/buck circuit, or a boost/buck WITH regulated output? I know they have the runtime diagram on kai, but I'm not sure if that brightness plateau is from the battery or from the regulator.

Click to expand...

It's not a boost or buck circuit, but a linear regulator. As far as I can tell from the datasheet (bottom-left graph on page 3), it provides very good regulation as long as Vbattery > Vled + 0.12V.

I just ordered a set plus a couple of CREEs, go to try them out on the CREEs and some K2s I have kicking around.

can you use 2 or more of these on 1 battery? can i use 2 boards to power 2 crees all from 1 18650? i think 3 would just barely exceed the maximum current for an 18650 (2amps) but 2 is ok right?

Whoever gets these, can you please take diameter and overall height measurements of the driver?

Could you also measure the output current to confirm if it's 700mA or 350mA?

moon_lander - the max discharge of most Li-Ion cells is 1.5C, so for a 18650, that's over 3A.

Its parallel 2x 7135 to get 350ma x 2
max Vin :6V
min Vin : 2.7V
so it fits for 2 x CR123A / 1 X Li-ion

If Vin > Vf , its Regulated , however Vin < Vf , its Direct drive
u may consider as a buck circuit

Anyone know how efficient it is?

These are linear regulators, which means that any voltage difference between the LED Vf and the input is dropped and dissipated as heat. The efficiency depends on the ratio of input voltage to output voltage.

If you ran an LED with a Vf of 3.4V from 3 Alkaline cells (4.5V), then the efficiency is 3.4/4.5 = 76%. As the battery voltage drops, the efficiency increases. The closer the input voltage to the LED voltage, the more efficient it will be.

As Carl would say, 'this is freakin awesome'. This will make life much easier for modding noobs that want something more sophisticated than a simple direct drive or resistor. Already looking forward to using this with a Cree and 18650.

mmmflashlights said:

As Carl would say, 'this is freakin awesome'. This will make life much easier for modding noobs that want something more sophisticated than a simple direct drive or resistor. Already looking forward to using this with a Cree and 18650.

Click to expand...

IMVHO it's easy to use an external 350/700 mA switch with this driver. If the 7135s are in parallel, cut the supply path to one circiut, solder two wires to the separated sides of the path and a switch. Press (close) to get 700 mA, release (open) to drive with 350 mA.
Just an idea.

-- M.

but since it is linear this circuit is not very effective like a real buck/boost converter

It can be very efficient given the right battery/LED combination.

Drive a Cree or Seoul (Typical Vf = 3.2V @ 350mA, 3.5V @ 700mA) from 3 NiMH cells or a single Li-Ion, and you're talking about efficiencies of 85-95%. Just as good (or better in many cases) as a switcher.

evan9162 said:

It can be very efficient given the right battery/LED combination.

Drive a Cree or Seoul (Typical Vf = 3.2V @ 350mA, 3.5V @ 700mA) from 3 NiMH cells or a single Li-Ion, and you're talking about efficiencies of 85-95%. Just as good (or better in many cases) as a switcher.

Click to expand...

Er, I think this is a bit optimistic. A dropout voltage of 3.2 + 0.6V is 3.8V which is higher than the nominal lithium voltage of 3.7 and 3 NiCds is 3.6V. There's quite a lot of energy left in the battery @ lower voltages than these.

Linear regs are good when driving strings of LEDs, or when working with a power supply with good long term stability. The problems involved in making efficient use of a battery to drive a single LED are non-trivial.

w

judging by the relative size of the SOT-89 package, the PCB's diameter should be around 19mm. Also the circuit seems to be using two 7135s in parallel, so the output, at least in theory, should put out around 700mA.

7135? - I googled this and got nothing. Datasheet?

w

search for amc7135, its the 4th hit

I guess this is the page moon_lander refeers to http://www.micro-bridge.com/AMC7135.asp. It's no longer the 4th hit on google, it's up to second place. Google works in mysterious ways (especially when half the LED forum googles the same thing)