Opinion ID: 208680
Heading Depth: 3
Heading Rank: 5

Heading: monitoring the current to the load

Text: Lastly, we address the Commission's ruling regarding the monitoring the current to the load limitation in claim 35. See '258 patent col. 20 ll.9-14 (a third circuit for monitoring the current to the load to generate a second control signal during a second state of circuit operation to cause one of said switching transistors to be maintained OFF). During its infringement analysis, the Commission excluded monitoring voltage from meeting this limitation. Final Determination, slip op. at 51-53. In effect, because a device can indirectly monitor current by monitoring voltage, the Commission limited the monitoring current limitation to instances of directly monitoring current. Thus, although the Commission did not explicitly address the monitoring current limitation under its claim construction section, it effectively construed the limitation. We thus address the parties' dispute regarding this limitation as a claim construction issue. See, e.g., Board of Regents of Univ. of Tex. Sys. v. BENQ Am. Corp., 533 F.3d 1362, 1367 (Fed.Cir.2008) (treating the parties' dispute over a limitation as a claim construction issue because the district court effectively construed the claim phrase in its summary judgment order). Linear argues that the exclusion of indirectly monitoring current is incorrect, arguing that the '258 patent's specification and Ohm's Law [4] support the proposition that monitoring the current to the load in claim 35 can be accomplished either directly or indirectly. In response, AATI contends that the Commission properly rejected Linear's reliance on Ohm's Law and, thus, correctly found that monitoring current could not include monitoring a voltage. We agree with Linear that the Commission improperly narrowed this claim limitation to exclude indirectly monitoring current through the measurement of voltage. The claim limitation does not state directly monitoring current. Rather, it simply reads monitoring the current to the load. '258 patent col. 20 ll.9-10. As such, this limitation should be accorded a scope commensurate with the '258 patent's specification. See, e.g., Tegal Corp. v. Tokyo Electron Am., Inc., 257 F.3d 1331, 1342 (Fed. Cir.2001) (construing a limitation broadly based on the specification). In this case, the '258 patent not only discloses monitoring current directly by using a current comparator, see, e.g., id. col.14 ll.43-61, but also indirectly by some other means. Explicitly, the specification states that other means of detecting current reversals in the inductor current could be used as well, id. col.15 ll.1-10, including generating a feedback signal indicative of current reversal in inductor current ... (see, e.g., resistor R sense in Fig. 7), id. col.15 ll.8-10 (emphases added). Generating a feedback signal based on resistor Rsense measures the voltage across resistor Rsense, therefore indirectly indicat[ing][] current reversal in inductor current by measuring voltage. Thus, the '258 patent expressly contemplates indirectly monitoring current by using a voltage measurement as a proxy. Moreover, once voltage is known, one skilled in the art would recognize that Ohm's Law easily allows current to be calculated, therefore monitoring current indirectly by monitoring voltage. Without support for limiting this limitation as it did, we think the Commission interpreted this limitation incorrectly when it excluded the accused devices. See, e.g., Cohesive Tech., Inc. v. Waters Corp., 543 F.3d 1351, 1367-68 (Fed.Cir.2008) ([I]t is not appropriate for the court to construe a claim solely to exclude the accused device.). Thus, because there is no basis in the patent specification for adding the negative limitationexcluding monitoring voltagewe hold that the Commission erred in construing this limitation. See, e.g., Omega Eng'g, Inc. v. Raytek Corp., 334 F.3d 1314, 1323 (Fed.Cir.2003) (Our independent review of the patent document reveals ... there is no basis in the patent specification for adding the negative limitation. (citations omitted)). In contrast to the Commission's ruling, this limitation can encompass monitoring voltage to indirectly monitor current. In sum, we affirm the Commission's claim construction of switch ... including a pair of synchronously switched switching transistors; second circuit and third circuit; a second control signal ... to cause both transistors to be OFF; and first state of circuit operation and second state of circuit operation. Regarding monitoring the current to the load in claim 35, however, we disagree with the Commission's narrow construction; we hold that this limitation can be satisfied by monitoring voltage to indirectly monitor current.