What's the deal with this circuit?

[flashlightlens]

What\'s the deal with this circuit?

This is out of the twin-pack of Costco 1W flashlights (one of which I modded a little here).

I went to mod the second and tore into it a little further. This is the circuit I found (click to view large version):


This seems to be an ever increasingly popular circuit in imported flashlights, like the XM-3. The one I have seems to be a combination of two boards, only one of which is being used for the circuit, and the other for the + contact from the battery tube.

Can anything be done to boost or improve the output of these - maybe to drive a decent 3W?

 

[robk]

Re: What\'s the deal with this circuit?

Interesting, looks identical to the driver in the XM-3, except it uses a TO-92 package for the IC. I'd like to find a source for that IC in the states, but all I can find is HK sources and they want big quantity sales. I had decent results by replacing the 10uH inductor with a 22uH unit. Don't know really what the increase was, but there's another thread with an excel chart of voltage/current/effiency.
[ QUOTE ]
rdshores said:
Here is robk's data for those that may not have Excel.....

[/ QUOTE ]

 

[koala]

Re: What\'s the deal with this circuit?

If you populate the board on the rightside with correct parts you get another complete boost circuit!

 

[robk]

Re: What\'s the deal with this circuit?

Hi Vince!
Yup, I see the silkscreen parts placement. Where do we get the 8505 IC or AIC equivalent? Any sources on your side of the earth?
Thanks,
Rob

 

[koala]

Re: What\'s the deal with this circuit?

Hello rob,
Those circuits are probably Chinese made for their own use. My first choice of sourcing components would be Digikey, localshops here are nothing. Buying from distributors means in quantity of 'K' units.

As for increasing boost, I read someone mention that the circuit is operating in wideopen so there's no sense resistor. The boost depends on the transistor itself.

-vince.

 

[pbarrette]

Re: What\'s the deal with this circuit?

Hi all,

This looks just like the circuit for the Dorcy 1xAAA and there's a lot of info for that circuit floating around these boards. I seem to remember tracking down a part # in another thread for (if I remember correctly) the XM-3 in which we decided that the Chinese IC used was a direct replacement for the AIC chip used in the Dorcy.

If this is the case, then there isn't a whole lot that you can do for this circuit. One option might be to replace the inductor with a 100uH one if it's the normal ~22-47uH one used in these types of circuits. Another, simpler option might be to place a 1-4uF ceramic capacitor in parallel with the existing cap. The lower ESR of the ceramic cap should help to increase the efficiency of the circuit. This will definitely not boost the power much, but it should give you at least a couple more mA or a couple minutes more runtime.

pb