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Circuits designed by David Johnson, P.E.
Last Updated on:
Saturday, December 23, 2017 03:21 PM
List of Dave's Circuit Designs
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Voltage Converter; Flyback Converter
Voltage Converter.05v to 6v
Conventional silicon transistors just
can't operate at voltages less than about 0.7v. Old germanium transistors could be
used, but those are hard to these days and most are rather large in size. Some
new n-channel MOSFET devices with very low gate-source threshold voltage can operate
at quite low voltages. I've been experimenting with various devices and came up with
one electronic circuit (shown below), which demonstrates how to boost the low voltage
from a single solar cell to a higher voltage.
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key component in the circuit below is a cheap single logic device from Texas Instruments.
It turns out that TI's 74AUC family of parts can work down to about 0.45 volts. I tried
one of their single schmitt trigger parts and found I was able to make on oscillator
function nicely at 0.5 volts. I then used a charge pump technique and a cheap NPN
transistor to form a low power flyback converter. The circuit can produce about 6 volts at
the output from a 0.5v input. |
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idea is to use this boost circuit to generate the higher starting voltage needed by a much
more powerful DC to DC converter. Once started, part of the converter's output could then
be feed back to the input, to sustain converter operation. This is known as a "bootstrap"
technique. In the future, I hope to post a circuit which can supply several watts of power
from a 0.5v input voltage. This would be ideal for charging a battery using power from a
single large solar cell or several smaller cells wired in parallel. |
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Click
on Drawing Below to view PDF version of Schematic |
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