Here we go, I found a voltage regulator that might do the trick: Linear's LTC3526.
This is how the chip compares to a AA battery.
Its switching frequency is 1MHz, so it wouldn't need a large inductor.
A suitable inductor would be roughly 2x the size of the chip.
It needs 0.68V to start up, but once running, it'll keep operating down to 0.5V.
Efficiency below 1mA is 40-90%, but above 1mA it stays ≥90%.
Typical operating current is 0.25mA.
Maximum current rating is 0.55A - not bad there. Linear makes pretty nice regulators.
Specs on keyboard operating/standby current are tough to find.
What I did get:
- NuVision and M-Edge keyboards: 2.5mA operating current, 0.3mA standby, and 0.040mA sleep.
- Generic Amazon keyboard: 5mA operating current, 2.5mA standby, 0.2mA sleep.
So if you've got a decent keyboard, that little voltage regulator will, by itself, use roughly as much power as your keyboard uses in standby, or potentially 6x as much power as the keyboard itself if the keyboard is sleeping. (The regulator would still be running, and at such a low power draw, it would be at around 70% efficiency.)
But there's a minor detail that I've left out: That nice chip + the inductor, assuming production-scale quantities, would be about $1.75. I don't know how low Linear will go on quantity discounts, but from what I've seen, they like to keep a good reign on their sale prices. Add in a few cents for the resistors and capacitors that are also needed, and a few cents for some kind of sturdy metal contact for the + terminal, and something for the tiny PCB, and something for fabricating the metal clip, and something for the labor needed to assemble it all, and you're well beyond a $2.50 sale price.
Or go with a larger and cheaper regulator chip
if there's still room for it.
The little footprint on the diagram shown above is
only the chip itself. Things like that normally require some additional space around them that's covered in copper on the PCB, in order to help draw heat away from the device.
We have some IP in some of the IC circuits that are in there, but the key is we’ve been able to miniaturize the boost circuit to a point that no one else has been able to achieve
Yes, because no one else
cares, at least for this application.
1) Some people will keep buying alkalines because using rechargeables requires too much thinking. The placebo effect will be strong with these people.
1a) Some people will keep buying alkalines because rechargeables are "way too expensive" simply due to the initial purchase cost. Fine, keep wasting money.*
2) People will buy NiMH cells, which completely eliminate the need for this little booster.
3) If this is meant for use with low-drain devices, which inherently use very few batteries in the first place, then it doesn't make sense either. If your keyboard or remote or clock uses 2 AAs a year, you're probably looking at $0.50-$1.50/year in batteries. So. What.
* Low-drain devices are one place where NiMH might not make sense, simply because they use so few batteries in the first place. NiMH pays for itself with each recharge. If you're only charging once a year, versus once every 2 weeks or so, it might be awhile before you see payback for the batteries and the charger. If you go cheap on the charger, it might be harder on the batteries each time they're charged, reducing their lifespan. Cheap rechargeables aren't good either - less capacity, lousier discharge curves, lower output voltage, and shorter life.
Batteroo Eventually the batterys natural, unboosted output drops to 1.3 voltsbut Batteriser keeps it at 1.5 volts for another month. Now youve realized a 3x increase in battery life. And so on, and so on. Roohparvar says Batteriser can continue to deliver a 1.5 volt charge in batteries that have discharged down to 0.6 volts. There are more than eight 0.1 volt steps between 0.6 and 1.5 volts, so, in grossly simplified terms, the Batteriser can extend operational battery life somewhere around a factor of eight.
given that NiMHs start at 1.2V.
Facebook
Twitter