Internal Name: Three Wire Controller
What’s New: The two windings of a traditional system are wired in series and a center tap brought out from the common connection, so the windings are driven with three power drivers instead of four.
Status: Issued U.S. Nov 3,
2009. PDF version to be available soon.
Why: Unlike the Single-Winding Solenoid approach, there are no performance compromises. This topology eliminates between 25% and 40% of the power driver electronics (depending on the configuration) while retaining 100% of the functionality obtained with the traditional four-wire and four-driver topology, thus reducing costs.
How: The
operation
of a dual-latching solenoid normally calls for only one of the two
windings
to be energized at any given time. If the four wires coming from
the two
windings are interconnected to provide two end leads plus a center tap
common
to both windings, then these three leads can be driven with just three
electronic
driver circuits instead of four. If, for example, a left-hand
winding is
to be driven, then the appropriate voltage differential is applied
between
the left-hand and center drive outputs, while the right-hand drive
output
is driven to match the voltage of the center output. Thus, the
voltage differential
driving the right-hand winding is zero and the winding remains
un-energized.
When the left-hand winding has been energized, done its work, and has
been
shut down, then the right-hand winding can be energized with the needed
voltage
differential while the differential on the left side is maintained at
zero.
If there is overlap in operation of the windings, but such that one
winding
is being shut down as the other winding is simultaneously energized,
then
there is still no performance compromise in going from four drivers to
three.
We see no reason not to employ this topology and eliminate at least 25%
of
the power driver electronics, with no performance compromises. A
simplified
center-tap driver, using diode clamping instead of active pull-up,
increases
the cost savings to about 40% on power electronics while retaining full
capability
except, possibly, in a sensorless configuration, which is now described.
A variation on our patented “Sensorless Position Measurement” invention
is
described in this patent, providing for sensorless measurement and
control
in the three wire context.
Download: Three Wire Drive/Sense for Dual
Solenoid, U.S. 7,612,978
Magnesense LLC Gorham,ME (207) 839-8637
©2005-2009 Joseph Seale