Appeal No. 2006-2920 Page 12
Application No. 10/813,501
examiner’s arguments persuasive regarding the comparator offset voltages
and associated delays. In particular, we do not agree with the examiner’s
finding that the negative input terminal of the comparator must be a positive
voltage (i.e., with respect to ground) in order to turn OFF transistor 841. To
the contrary, we find the negative terminal of comparator 840 never attains
a positive voltage potential above ground. We find that the examiner is
confusing a positive voltage with respect to ground (and associated positive
current flow) with a positive voltage potential occurring between comparator
inputs Vs and Vr.
We note that comparator 840 changes state according to whether the
voltage (Vs) at the inverting (-) input crosses above or below the reference
voltage (Vr) at the non-inverting (+) input. We agree with appellants that
this point will occur when both comparator input voltages are still negative
(i.e., with respect to ground potential). Therefore, we agree with appellants
that there is a negative current flowing through transistor 841 at the instant
in time when transistors 841 and 10 are disabled when Vs becomes more
positive than Vr, but where both Vs and Vr are negative voltages with
respect to ground potential. We find that this point of disablement occurs
when the field coil backflow current is almost fully discharged and
approaching ground potential but where the negative voltage Vs dropped
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