Appeal No. 2006-2920 Page 11
Application No. 10/813,501
current flows in a negative direction, opposite to the positive direction of
current flow from the positive terminal of the battery through the field coil
that occurs when field coil 32 is energized by transistor 9 turning ON.
We further note, as pointed out by appellants, that when the voltage
at node Vx lowers (i.e., at the instant when transistor 9 turns off power to
field coil 32) the backflow (i.e., negative) current from field coil 32 initially
begins to flow through parasitic diode 100 (fig. 4) to produce an initial
negative voltage drop (with respect to ground) across resistor 800 at Vs (fig.
4), that triggers comparator 840 to change state and turn ON transistor 10
via the logic of NAND gate 501 and second driving circuit 7 [see brief, page
5, ¶1]. See Asada at col. 3, line 66 through col. 4, line 10:
Thus, the second driving circuit 7 turns off the low-side switching element 10 the
delay time after the battery voltage becomes lower than a regular battery voltage
proportional to the reference voltage, and turns on the same a certain time after the
battery voltage becomes equal to or higher than the regular battery voltage. When
the low-side switching element 10 turns on, and the high-side terminal of the field
coil 32 becomes lower than the ground voltage, back-flow current flows from a
grounded portion through the channel and parasitic diode to the high-side terminal
of the field coil 32. Accordingly, the field coil 32 is supplied from the low-side
switching element 10 with the back-flow current [emphasis added].
After carefully considering all of the evidence before us, we agree with
appellants that Asada fails to disclose the recited limitation of: “configuring a
first circuit of the self-gated transistor to disable the transistor substantially
upon a positive current flow through the transistor” [brief, page 4; reply
brief, page 5; see also claim 1, emphasis added]. We do not find the
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