New highest efficiency step down converter

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Wow, this seems to be the driver I have dreamt of. Will have to build an aleph light now, will have to buy pilas, will go /ubbthreads/images/graemlins/broke.gif.
Girl friend will /ubbthreads/images/graemlins/Christo_pull_hair.gif, I'll be alone and need a lot of /ubbthreads/images/graemlins/grouphug.gif with other cpf'ers.

Chrisse
 
This converter board currently is being planned on maintaining target size that will fit in the ECan, Anode contact backside, components all topside. Current thinking is it will not be Sandwich compatible with the dual connector setup.

Since it has low voltage drop out to protect the battery, it won't support the dual stage switch as planned. This shouldn't be a problem if one used a zero ohm resistor board to eliminate the two stage mode. Since the Aleph is modular, you could have zero as one of your board options to support this configuration. It would be nice if we can work out a two stage configuration for this and since the jury is not out yet and we have not done an exhaustive testing of this board we won't jell the layout and consider it final for now.

This board like the Downboy/Badboy will have a low value sense resistor to set the output current. Thus, this board will be able to support many runtime/brightness combinations. If you don't need 1A to the LED and would prefer a longer runtime a Wiz2 750 or a Wiz2500 could be made. The lower output drives will mean the efficiency would go up as well.

The IC footprint is like many of the newer parts and comes in a leadless package. It's more power in less space, and is a much better thermal package.

Due to the IC packaging technology it takes a good solid 45minutes to 1 hour to hand produce one of these gems. I will not hand make these boards unless the price tag of $45.00 would not bother folks.

I've ordered new soldering tips and hopefully that will help make soldering these package styles easier.

As soon as all the mechanical details can be worked out, a run will be scheduled for the local CM shop. Pricing and delivery has not been set yet.

Wayne
 
Now there's something i never thought id live to see; a runtime chart with McGizmo's name on it /ubbthreads/images/graemlins/eek.gif

$45 dollar price point would not bother me, please put my name down for a few.
 
Tyler,
I have been experimenting with some 2 stage switches and resistor values and 10 ohms on 2x123 gets you a low level that graphs rather erratic but is a lower level and longer run time. I also tried a 7.5 ohm to stage on a Pila 150S and it also gives you a lower output and might actually serve as a method of detecting when the battery is about run its course. I have not been able to confirm it but I think towards the end, the low will either flash or be nothing and yet the high would still work. /ubbthreads/images/graemlins/icon3.gif I am not willing yet to give up on a dual level with this driver but I believe the low voltage shut off is a fixed feature. For use with the Li-Ion's this shut off is a good feature since as I understand it, even marginal current drain on the cells if accidentally left on can draw the voltage down to a point that the cell has been damaged.

I wish I understood these circuits better! In the case of the 2x123, you can see that the driver will allow light out of the front until the 2.7 volts has been reached. In the case of 2x123, this is a set of pretty depleated batteries I think!

The one working sample I have is in a Aleph 3 and getting an excess of 6000 lux for more than an hour and a half from 2x123 is pretty dang cool! /ubbthreads/images/graemlins/thumbsup.gif SInce the Aleph 3 is all about throw anyway, not having a *great* low level is not as disappointing as it would be on a more general purpose platform like the Aleph 2 or Aleph 1. I don't think the wiz2 will displace the DownBoy on 2x123 for general purpose, multi level outputs. 30 hours of viable low level output on a DB-2x123 is not to be thrown out with the wash! Same with the SDC although I have not confirmed its runtime nature on low level ( kj? Mike?).

My gut feeling is that the wiz2 will be pulled off the bench in special team play when one is either after max efficiency on high, constant current output or more specifically when one is after max efficiency and max brightness on high constant current output. The higher the efficiency, the lower the thermal output from the driver and the better suited the driver is for longer constant on service.

Now we have even more choices; that's good and bad! /ubbthreads/images/graemlins/icon15.gif I am real glad that I had moved into the Aleph LE system prior to these new drivers coming out! At least with a removable LE, one can consider multiple engines in a system. One possible strategy would be a LED based HOLE and LOLE (think HOLA and LOLA /ubbthreads/images/graemlins/tongue.gif ) and since a picture is worth many words:

Aleph-system.jpg
 
A half length of the cylindrical foam from a SF LA container nests the LE perfectly in the SC2 carrier! /ubbthreads/images/graemlins/thumbsup.gif
 
So .. this NewWiz is only for 2x123 and a LuxI or LuxIII and is a buck/boost driver with high efficiency and deadly long runtime?
No 5W.
No 1x123.
No 2-stage (yet).

Correct?

bk
 
Bernhard,

Your aversion to rechargeables has caused you to leave out the primary reason for this driver's existance! Namely Li-Ion cells. But aside from that, you are correct, maybe???? I don't knowif the 6V limit is on Vin or Vout or both? Can this driver boost to a 5W?

OK, I'll back off and let Wayne explain the driver.:o
 
This driver input and output max voltage is 6V. So, no 5W with this driver. Not for this size. There are many other ICs and options to drive a 5W with high efficiency. It's just there are very few ICs that are small enough and that will do the job correctly and in the limited real estate provided. Typically only the newer IC's meet these requirements.

This driver will work on a 1X123 and a 1W/3W, or a 2X123 and a 1W/3W combo.

It will also handle all the odd combos like 3AA, 3C, 3D 4AA, 2 L91s etc. Any battery voltage that is greater than 2.7 and less than 6V can be used with this driver and there is no Vf restriction. An Vf Bin code, J,K,L,M...

Yes, the 2.5V shutdown is internal to the IC and there is no way around it since it was specifically designed for Li-ion and to protect deep discharge.

Wayne
 
Wayne,
It will work on JSB's Li-Ion 123 size but won't the voltage drop on a CR123 take you donw below the 2.7 volts?
 
Wayne, what about driving an Sbin 5watt?

Thanks for all the work on this board. I've been trying to switch everything to Li-ion.
 
Can we put two drivers in series with two Li-Ion cell powering them?? /ubbthreads/images/graemlins/blush.gif
 
I'm just giving you some general input range. You need to take into account the internal battery resistance and output power to determine if a configuration will work.

Stripping out the configurations, the technical preliminary specifications are:

Vin: 2.5V - 6V.
Iout: 400ma - 1A (Set by a low value sense resistor).
Vout max: ~6V.
Vin max: 6V.
Iin max: ~2A NOTE1

NOTE1: Due to size constraints the Iin limit is dictated by the inductor and not the IC. For those serious hackers out there, substituting a larger inductor will allow you to pull more power.

cy,

I would without a doubt totally discourage any 5W usage at all with this driver. The IC is a low voltage device and the semiconductor process has been optimized for usage in the 3-5V range. Operating the semiconductor fabrication beyond the 6V limit will probably kill the IC. Like I mentioned above, there are more elegant solutions for driving the 5W.

Don,

You are correct in that a regular 123 has been shown to not be able to support high current demands. That doesn't preclude one from making a wiz2 400 and a 123 combo. The 400, 500 and 750mA Wiz2 drivers might be fine with a 123 even tho you may not get the full battery usage. But, in a pinch, if you were using R123s and the light pooped out a regular 123 could stave off a very dark situation. I know it's marginal. 1A from the 123 would drop the battery voltage to 2.5V right off the getgo. So, only light duty versions would be applicable for this usage.

That would also apply to 2 NiMH AAs or even 2 regular AAs. Fresh they might be 3V open no load, but, under load could drop to 2.6V or so. That's been my experience with the testing I've done on the bench. Under these conditions you might get 10 minutes of runtime before it cuts off and I mean it cuts off. Right at the corner is very interesting. The IC cuts off. Since the load has been disconnected, the battery voltage rises and the IC starts up again. This results in a flashing light mode. It's definitely a warning to change the batteries.

Remember that your applied application dead battery condition should be 2.5V or higher. In that way you will squeeze all the juice out of the battery. If your take a 2AA battery setup the dead state has been accepted at around 1V/cell or 2V. That is below the 2.5V minimum input and you will not tap all of a 2AA setup.

A R123, Li-ion, Pila etc start full charged around 4.2V and are considered dead somewhere below 3V.

A 3AA or 3 alkaline would start at 4.5V which is within the 2.5V - 6V range and the dead battery state would be 1V * 3 or 3V. That too is within the 2.5V - 6V range and would be a good combination. So, 3AA, 3C, 3Ds would all be great candidates with this driver. Mag3C, Mag3D, Mag4C, Mag4D all 2X123 lights. 1X123 using JSB's Li-ion batteries. I think that should help enlighten some ideas and general constraints of where this driver could be used.

The end target of the board diameter is to keep it the same size as the BB, DB and MM series. Currently the prototypes are a tad bigger.

Wayne
 
[ QUOTE ]
dat2zip said:

Yes, the 2.5V shutdown is internal to the IC and there is no way around it since it was specifically designed for Li-ion and to protect deep discharge.

Wayne

[/ QUOTE ]

Wayne, does this also mean you see no way of implementing a two-stage option for lights with this converter?

Chrisse
 
Chrisse,
I believe a two stage switch can be utilized but I have my concerns about a *common* solution and the stability of the solution. From testing one sample, I found that 15 ohms was too much resistance and 7.5 ohmswas not enough. I settled on 10 ohms and did a run test on the Aleph 3 which was puting out a lux of just over 6000 on high:

Aleph3-NWiz-2x123-Low-10ohms.jpg


You can see that the 10 ohm does give you extended play at reduced output. You can also see that the graph is rather erattic. The one down spike early on was due to the tail cap not being tightened enough and I asume as it heated up, the switch turned off. I happened to walk by and see the light off and tightened the cap getting it turned backon again. /ubbthreads/images/graemlins/icon15.gif

I did not monitor the beam so I don't knowwhat was going on with some of the *strange* sections of the graph. Frankly, 10 ohms is too high of a low for my way of thinking and I don't know how much current was going through the switch but the head of the light was at roughly room temperature whereas the tail cap was very warm! When I get a chance, I want to try a 12.5 ohm switch and see if it will drop the driver out of regulation but still have enough voltage to keep the LED going. It ain't over yet!!

I have been using this light with the 10 ohm switch and the low level is relatively low enough to be of use I believe but I think lower would be better still.
 
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