Desperatly looking for driver (updated kennan driver?)

[MikePL]

So please correct me if I'm wrong. I only marked the LED connections as the input positive and negative cables can be soldered on the other side of the board.



Please, can someone confirm that these connections are right? I do not want to send my drivers to heaven and have to wait another 3 months for them...

[jtr1962]

So please correct me if I'm wrong. I only marked the LED connections as the input positive and negative cables can be soldered on the other side of the board.



Please, can someone confirm that these connections are right? I do not want to send my drivers to heaven and have to wait another 3 months for them...

That's definitely correct. You can't destroy a buck board by connecting the LED wrong anyway, only by connecting the power leads wrong.

[MikePL]

OK, thanks for help. If anything out of the ordinary happens then I will keep you posted. I've also heard that this driver was to be updated and probably I got the updated version.

[Gryloc]

Was that the reason that it took so long to ship? I am still interested in these, but I am afraid to be stuck waiting. I looked the board over and it seems silly to make the layouts so much more complex. The old driver was so simply laid out, and it is hard to mess things up since the components were pretty spread out. I see the very same components in the new one as the driver before. I studied the new one to see how it compares to the old one, as well as the datasheet schematics, but I could not see where all the traces went (hidden under the IC and hard to see). I think that everything is fine. I hope it is.

-Tony

[MikePL]

They are still marked as 'out of stock' so probably they are shipping the drivers to all those who ordered them long ago.

[PeterC]

Just collected my long oustanding order for 5-off Kennan (KD sku 2982) from the post office. These are of the new build (with diode wires supplied, but not fitted).

Ordered on 7th Jan '08
Delivered on 5th March '08

Patience is obviously required if you order these!

The circuit of the original design was very close to the typical application circuit shown on the Micro-bridge data sheet for the PT4105 (and applied the recommendations about pcb layout given on the sheet). The new design appears to be based on the same application circuit, but has a couple of additional components (with spaces for several more).

It is not easy to see exactly how the components are connected within the circuit! A bright light, magnifier, and continuity meter/DMM will be needed to reverse engineer the design and see exactly what we have.

My initial thoughts, however (if we're lucky), is that the extra pads and pcb tracking may give some scope for easier mods to the driver board than the original one offered (e.g. changing the feedback circuit to alter the current supplied to the LED.

[jtr1962]

My initial thoughts, however (if we're lucky), is that the extra pads and pcb tracking may give some scope for easier mods to the driver board than the original one offered (e.g. changing the feedback circuit to alter the current supplied to the LED.

That's exactly what it looks like to me. See page 5 of the datasheet for some typical dimming methods. The probably have the extra pads so one or even all of these methods may be employed. Good idea since it adds nothing to the cost of manufacture but greatly increases the flexibility.

[MikePL]

Hmmm... I've got a problem. It seems that the connection above is wrong. Today I wired two drivers that way and connected an LED. The LED chip was barely giving some light. I thought that maybe the driver is dead, so I used the other one. I got the same results, the LED was so dim that it was barely visible. Input voltage was 12V from a computer PSU.

So do you have any other suggestions on how to connect the LED wires?

[jtr1962]

Try connecting to the other side of R2 (there's a pad between R1 and R2 which looks like a connection pad). It seems R2 is there to protect the IC. Problem is when you connect directly to pin 8 as per the schematics in the datasheet current will be limited to well under 1 mA due to the presence of R2.

[MikePL]

Thanks for help. It now works absolutely fine. Hooray, I finally have them damn drivers :-)

Edit: just to clarify what connection we are talking about, I've decided to post another image.

This is the right connection of the LED wires:

[jtr1962]

Glad to be of help! Enjoy the drivers!

[space]

Received my two drivers from Kaidomain yesterday, 8th of March. Ordered 12th of January. They have the same pcb's as MikePL, but they have all components except for R6 connected. Will post pictures later. Havn't tried them yet.

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[TorchBoy]

See page 5 of the datasheet for some typical dimming methods. ... all of these methods may be employed.

So the extra IC would be for PWM dimming?

Why do some of these photos have a 22µH inductor and some a 47µH one? (I think those units are right.) I noticed that for the first version too. What difference does more than doubling the value of the inductor make?

[jtr1962]

So the extra IC would be for PWM dimming?

Why do some of these photos have a 22µH inductor and some a 47µH one? (I think those units are right.) I noticed that for the first version too. What difference does more than doubling the value of the inductor make?

Increasing the inductor value just smooths the current to the LED a bit more, that's all. The new version uses a smaller value inductor but has a ceramic cap in parallel with the LED. The capacitor also smooths the current.

Regarding PWM, not sure what extra IC you're referring to here. Can you be more specific? In all the photos I see there's just the PT4105 driver IC. All the rest of the parts are either resistors, inductors, capacitors, or diodes.

[TorchBoy]

The new version uses a smaller value inductor ...

Does it? This pic shows it marked 470, and has the board fully populated except for R6.

Regarding PWM, not sure what extra IC you're referring to here. Can you be more specific? In all the photos I see there's just the PT4105 driver IC. All the rest of the parts are either resistors, inductors, capacitors, or diodes.

Have you noticed that all the photos on the product page are new? In the first photo (link above) it's called IC1 and marked as 82FE.

[jtr1962]

Does it? This pic shows it marked 470, and has the board fully populated except for R6.


Have you noticed that all the photos on the product page are new? In the first photo (link above) it's called IC1 and marked as 82FE.

Sorry, I didn't even look at the product page until now, so I really had no idea what you were referring to. Electronically, there's not much difference between a 22µH and a 47µH inductor. It was probably a matter of one part being cheaper or more available than the other. IC1 is probably a voltage regulator but it could also be a transistor or a diode mislabeled as an IC. It does indeed look like it has something to do with PWM. If I had to guess, I'd say it's a transistor which pulls the FB pin high in order to turn the LED off via a PWM signal.

[MikePL]

Hmm... I wonder what those extra components add to the driver? All the drivers I have are just like the one in the photo on top of the page. No IC1 no resistors... but I have the R6

[TorchBoy]

IC1 is probably a voltage regulator but it could also be a transistor or a diode mislabeled as an IC. It does indeed look like it has something to do with PWM. If I had to guess, I'd say it's a transistor which pulls the FB pin high in order to turn the LED off via a PWM signal.

Sounds good. 3 pins, so I wouldn't think diode.

Hmm... I wonder what those extra components add to the driver? All the drivers I have are just like the one in the photo on top of the page. No IC1 no resistors... but I have the R6

And it's just a link. Apparently a board tuneable for multiple applications. We could do with some sort of application notes for this particular board.

If the set resistor is 0.2 ohms, is the output now 1A instead of the old 750mA?

[mike2g]

I'm sorry but the workings of this board is beyond me. Does anyone know what resistor could be used to replace the supplied 0.2ohm one that would produce 350mA?

[TorchBoy]

The datasheet says a 0.57 ohm resistor will give a fixed 350mA output. (I haven't received the new version of the board yet, so I haven't seen if there's an easier way provided by all the new resistors etc.)

[mhahn@hvc.rr.com]

I got some of the new Kennans with IC1, R4, and R5, but no R6. The extra parts make the driver shut down for input voltages below 6.2 volts. My guess is these parts are designed to shut down the driver when 2 Li-Ion cells driving it get below their safe operating voltage.

It seems you can pretty easily bypass this "feature" by shorting out R4. Or else by removing IC1, R4, R5 and then installing a piece of wire for R6. I'm a little bummed to have to be doing this on the drivers I got. I really like being able to drive a LED off of 4 NiMh batteries, and with IC1 installed, that's not gonna happen.

Mark

[TorchBoy]

Or else by removing IC1, R4, R5 and then installing a piece of wire for R6.

Sounds like what the initial run of this new version had, as per the pic posted by MikePL.

Nice deductive work, BTW.

[space]

I've tried to make a schematic of the boards I received and taken a few pictures. One of my boards has a 22uH and the other a 47uH inductor. They also have different R2, one 5k1 the other 3k.

As far as I can read from the datasheet (PT4105), the CE-pin (chip enable) needs at least 1.5V to "start" the chip. When going below 0.3V it will shut down again. I agree with Mark that the R4+5+7 and IC1 have the task of regulating the voltage to the CE-pin and thereby enabling / disabling the PT4105 at certain supply voltages. By changing/adjusting these resistors one probably could change shutdown voltage to what ever one like.











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[nein166]

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Awesome Picture!
Oh and thanks for the the schematic. Changing the shutdown voltage would save my cells when running on multiple Li-Ions.

[TorchBoy]

So are these in stock or aren't they? Has anyone had any shipped since the web site started claiming they are in stock again?

[mhahn@hvc.rr.com]

So I finally tried removing IC1, R7 and R5 (if you pull off IC1 and R5 you don't need to bother with R4), then I shorted out R6. Everything seems to work fine.

But I noticed something different. With R1 set at .200 ohms, the driver drives the LED with about 1 amp of current. So the LED runs a lot brighter than previous versions of the driver (the old version of the driver ran at around .8 amps I think).

The LED now runs a bit hotter, which I would expect. And the driver chip now gets pretty warm, like too hot to touch after a few minutes. I looked up absolute max current for the driver chip and it's listed as 1.5 amps. But the recommended operating current is less than .7 amps.

Anybody try running one of these for a long time? My tests have all been pretty short, less than an hour. I'm wondering if these drivers are going to be more failure prone due to the higher current.

Mark

[TorchBoy]

If the set resistor is 0.2 ohms, is the output now 1A instead of the old 750mA?

But I noticed something different. With R1 set at .200 ohms, the driver drives the LED with about 1 amp of current. So the LED runs a lot brighter than previous versions of the driver (the old version of the driver ran at around .8 amps I think).

Thank you for that confirmation. The datasheet indicates it shouldn't be run at 1A with less than 9V in, so I'm a little surprised at that change.

[MikePL]

I have one more question about this driver. Can it be powered without the LED connected on the other end? I heard that some drivers need an output in order not to burn. I am about to make a light and I would like to have a switch which would either power one LED or three. While switching there is always a 'gap' which lasts 0.2s and I would like to know it such a repeated switching can damage it.

[jtr1962]

I have one more question about this driver. Can it be powered without the LED connected on the other end? I heard that some drivers need an output in order not to burn. I am about to make a light and I would like to have a switch which would either power one LED or three. While switching there is always a 'gap' which lasts 0.2s and I would like to know it such a repeated switching can damage it.

In general, step-up drivers are the ones in danger of burning out if no load is connected. What happens is that the output voltage increases without limits until it exceeds the ratings of the pass element or the output capacitor. Once that happens, you get catastrophic failure (in layman's terms lots of smelly smoke). Some step-up drivers have output voltage limits to prevent this from happening.

Since this isn't a step-up driver, but rather a step-down one, this failure mode can't happen. With nothing connected the pass MOSFET will simply be driven at maximum duty cycle, and the output voltage will be a little less than the input voltage. This can't harm anything.

[TorchBoy]

Some step-up drivers have output voltage limits to prevent this from happening.

Would a zener diode do that job?