Downboy Limits

[rantanplan]

Hi, I´m thinking about using a Downboy (DB1000 and/or DB400)circuit for powering my bike light, that is a bit more "demanding" than a common flashlight. So I´ve some questions about the limits of the downboy circuit, before I think about placing an order /ubbthreads/images/graemlins/wink.gif ...

1. Input voltage 16V - I´m using a 14.4 V Li-Ion battery, that can reach fully loaded up to 16.8 V, under load 16.4 V. Is that still in the tolerance of the circuit? I hope so /ubbthreads/images/graemlins/wink.gif

2. Are there any limits in the total power output, besides max. Vin and max. current?
Possible output requirements could be (converted down from nominal 14.4V Li-Ion):
- 2 or 3 LuxIII @ 1000mA (~12W Output!) with a DB1000
- 2 or 3 LuxIII @ 400mA with a DB400

Can the circuit do the above mentioned jobs?

thanks for your help, rantanplan

 

[Wolfen]

According to Dat2zip Downboy input limit is 16 volts.

 

[dat2zip]

The current revision 3 has 25V input and output capacitors.

The IC input voltage specifications is 18V. You should be safe in this configuration.

The Downboy is taxed the most as Vin goes up, which is just the opposite of Badboy. The Inductor ramp current slope is at worst conditions with higher Vin.

I'd seriously suggest you change the inductor to reduce the di/dt rate. A 10uH DO1608C-103 is recommended for input voltage conditions above 12V.

Wayne

 

[rantanplan]

Ok, thanks for the info /ubbthreads/images/graemlins/smile.gif ... /ubbthreads/images/graemlins/frown.gif

Changing a inductor would be far beyond my soldering skills and equipment /ubbthreads/images/graemlins/wink.gif ... and it would be difficult for me to get this specific inductor here in germany.

Maybe I can use a unmodified Downboy in another project, a single Lux3-Headlamp powered by 7.2V Camcorder Li-Ion Battery. I´ll see ... for my bike light, I´ve alternative solutions.

Thanks, Rantanplan

btw, I didn´t found info about shipping costs in your online shop ... how much is a international shipment (to germany)? thx.

 

[dat2zip]

Shipping is computed based on weight and is shown during checkout.

Wayne

 

[wquiles]

Wayne,

So 16 volts is the max. without any changes to the circuit, right?

This means that 4 rechargable CR123 LiIons in series would kill it unless it is modified?

Will

 

[dat2zip]

The IC is spec'd at 18V Input. I downgraded that to 16V, but, you could push it to 18V if you needed to. The capacitor is rated for 25V putting the IC limiting the upper input voltage.

Four RCR123s should be safe if you don't overcharge the batteries.

Wayne

 

[wquiles]

Thanks Wayne. I tried 4 of these rechargable cells (around 16.5 volts or so) with a DB1000 driving a WX1T and sure enough it works fine /ubbthreads/images/graemlins/goodjob.gif

Will