On 19/04/2011 11:50, Oli Glaser wrote:
> Hi all,
>
> I have a battery powered project (either 4xAA/AAA or 3.7V LiPo) which
> has quite a few supply voltages. They are +5, -5, +3.3, and +1.5 - all
> at above 200mA preferably.
> I have spent a night searching through all the major sites to find the
> cheapest solution, as price is an important factor. I have various
> regulators that I like and use often, and obviously have a solution for
> the above, but I would like to hear about how others would approach
> this, for example if anyone knew of a cheap IC that would take care of
> the +3.3 and 1.5V lines, or even a switcher that would do all three
> positive ones. The only multi output regulators I have found are over
> $10, which is quite a bit more than the separate solution.
> Any ideas are most welcome, LDO, switchers, charge pumps, uC based
> switchers, discrete circuits, etc - as long as the price and reliability
> is good. Space is also a big issue though, so I need to avoid large
> footprint or through hole stuff. Efficiency matters, but I thought the
> +3.3 and +1.5 lines could be linear if necessary.
> TIA
>

Multiwinding SMPSU

sec1 3.3V. Feedback Regulate on this, use this with linear reg to get=20
1.5V. Possibly use centre tap winding and two diodes. Don't use 4 diode=20
bridge as the losses are double.
sec2 +6V and -6V approx via two diodes and a pair of LDO regulators. If=20
you want a +5V LDO reg for -5V, then have a second identical winding.

Ensure SMPSU inverter works from 2.5V to 7V input.

If current consumption is low, you could generate the +5V and -5V from=20
the winding feeding 3.3V rectifier(s) via tripler and pair of LDO=20
regulators, or if load is constant and reasonable tolerance allowed just=20
use doubler as voltage drop is over 1V. Possibly add an extra series diode.


--=20
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