Olin Lathrop wrote:
> I had a need to produce 10-15V at 20mA or so from a=20
> single AA battery, or maybe two at most.  This is=20
> significant power for an AA cell, so efficiency is=20
> important.  This means it would be desirable to have
> a FET switching the inductor, but that is impossible=20
> to do efficiently on just 1V...

LEDs on your cap for hiking again?

Perhaps LM2623 would be better?

Mike.

AN-1250: Inductive Based Switching Regulator Circuits Provide High
Efficiency White LED Drives=20

AN-1258: LM2623 Boost Converter - A Simple Technology Twist Produces
the Industry's Most Versatile Supply=20

From
http://www1.national.com/ds.cgi/LM/LM2623.pdf

Ratio Adaptive Gated Oscillator Based, DC DC Boost
Converter-Low Vin, Low Ripple, General Purpose.
----------------------------------------------------------
The LM2623 is a high efficiency, general purpose, step-up
DC-DC switching regulator for battery-powered and low input
voltage systems. It accepts an input voltage between 0.8
and 14 volts and converts it into a regulated output voltage.
The LM2623 can be used to generate up to 14 volts using an
inductor and almost any positive voltage using a transformer.
It has an internal .17=A7=D9 N-Channel MOSFET power switch.
Efficiencies up to 90% are achievable with the LM2623.
In order to adapt to a number of applications, the LM2623
allows the designer to vary the output voltage, the operating
frequency (300kHz to 2 MHz) and duty cycle (17% to 90%)
to optimize the part=A1=AFs performance. The selected values can
be fixed or can vary with battery voltage or input to output
voltage ratio. Using these techniques according to the design
guidelines may improve efficiency or reduce parts cost
or both. The LM2623 is a gated oscillator and uses a very
simple, on/off regulation mode to produce good efficiency
and stable operation over a wide operating range. It normally
regulates by skipping switching cycles when it reaches the
regulation limit (Pulse Frequency Modulation). In some applications,
with the proper selection of external feedback
components, it can also regulate cycle to cycle, similar to
Pulse Width Modulated parts. It does this by adjusting the off
time between switching cycles, while maintaining continuous
current through the coil. This cycle to cycle type of PFM
results in very low ripple on the output voltage and/or minimum
sized output capacitors, similar to PWM parts. This
mode also typically maximizes efficiency.
------------------------------

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