Maybe dump the caps via an inductance [hopefully low R losses?].
Maybe monitor the current and switch it off as some of the H-bridge motor
drivers do? Except that uses some wasteful circuitry to achieve it.
John K.
----- Original Message -----
From: "John Rehwinkel" <jreh...@mac.com>
...clip....
I was thinking about this and display efficiency. Obviously, efficiency
would improve if anode resistors are dispensed with, but then it's left to
the power supply to monitor and control current through a negative
resistance. David's watch does this directly, by incorporating current
feedback into the power supply. However, David's watch is direct drive. I
was thinking about how to do this with a multiplexed watch.
What I came up with is a little nuts, and probably would do horrible things
to tube life, but I haven't tried it yet. I was thinking of using a circuit
like the General Radio 1538 Strobotac, which has a cute way of building up
charge for its flashtube by running a flyback type converter with a pulse
train, charging up a storage capacitor incrementally until it has the
desired amount of energy (they also claim nearly 100% efficiency, as their
device can operate from batteries as well). This would be an interesting
concept for a multiplexed nixie display: configure the cathode drivers, then
dump a packet of charge into an anode capacitor. If the voltage is high
enough, ionization should be gratifyingly fast. Since the capacitor is
small, the total amount of energy would be limited. However, this would be
running a nixie rather like a flashtube, with brief, high-current pulses.
The duty cycle would be tiny, but the overload would be great. What this
would do to tube lifetime, I don't know. It might be just fine, it might
blast the cathode to pieces in hours.
...clip...
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