Dave Tweed wrote:

> Yes, please do. I'd like to see how it compares with one that I came up
> with a few days ago. I need a regulator that can take a battery voltage of
> 3-4 volts and provide 5V at up to 100 mA max with good efficiency. I came
> up with a circuit with 5 res, 2 cap, zener, choke, 1 NPN and 1 PNP.
>
>                                        diode
>     3-4 V o----+------------CCCCC---+---AK----+---+----o 5V @ 100 mA
>                |            68 uH   |         |   |+
>                R                    +------+  R  --- 100uF
>           1000 R                    |  .001|  R  ---
>                R      PNP           |     --- R   |
>                |             100    C     --- |   V
>                +--+---E C---RRRRR--B  NPN  |  |  Gnd
>                |  |    B            E      +--+
>         LM336  Z ---   |            |      |  |
>          -2.5  Z ---   |            V      |  R
>                Z  |.047|    2200   Gnd     |  R
>                |  V    +---RRRRR-----------+  R
>                V Gnd                          |
>               Gnd                             V
>                                              Gnd

> Load regulation seems really solid, but I'm not happy with the efficiency.
> The problem is the base drive of the switching transistor,

I'm not sure I fully understand your boost circuit.
What causes turnoff?? I can see that WHEN the output
has reached spec at 5v it might oscillate around that
point, but when it starts (and output is about 3v)
won't the transistors just turn on and stay on, burning
out the coil??

What efficiency did you get? I think 2-tran circuits
sometimes work better when one tran turns the other
OFF, so you get a distinct "multivibrator" type effect
with fast on/off transitions, timed delays by adding a
cap, and tanking to dump energy forward and back.

Your losses via the PNP are only a couple of mA, so
where are the main losses? Is it switching slowly or
maybe the sat losses in the diode and NPN??
-Roman

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