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It is well-settled that a party cannot reserve a new claim-construction argument for the post-trial motion stage of litigation.
Prosecution-history estoppel limits the application of the doctrine of equivalents. If a patentee surrenders certain subject matter during prosecution, the patentee is then barred from using the doctrine of equivalents to recover for infringement based on that same subject matter. Prosecution-history estoppel can occur either when the patentee makes a narrowing amendment to the claim or surrenders claim scope through argument to the patent examiner. The application of prosecution-history estoppel is a question of law that an appellate court reviews de novo.
Power Integrations and Fairchild were both manufacturers of power supply controller chips. Power supply controller chips are integrated circuits used in power supplies, such as chargers for electronic devices. These power supplies transformed alternating current ("AC") electricity, which came from an AC outlet, into direct current ("DC") electricity, which was needed to power cell phones, laptops, and other electronic devices. The controversy involved the '079 and '908 patents owned by Power Integrations. The asserted claims of the '079 patent cover switching regulators. During low power periods, prior art switching regulators would skip on/off cycles to decrease the DC power provided; the power remained off during the skipped cycle. However, skipping cycles created loud noise and delivered power in an intermittent fashion. The '079 patent addressed this problem by reducing the frequency of on/off cycles rather than by skipping cycles altogether. The frequency of on/off cycles was determined by feedback signals. For certain range of feedback signals, the frequency of the on/off cycles does not change. Each of the asserted claims requires a "fixed switching frequency for a first range of feedback signals." The '908 patent covered a "power supply controller," which was an integrated circuit that can perform a variety of power-regulation functions. Power Integrations filed suit against Fairchild, alleging infringement of various claims of the '079 patent and the '908 patent. Fairchild argued that the term "fixed" under the district court's construction of "non-varying number of switching cycles per second" requires an absolutely fixed frequency with no variance, even due to operating conditions. The jury found Fairchild literally infringed various claims of the '079 patent and infringed claims 26 and 27 of the '908 patent under the doctrine of equivalents. Fairchild sought judgment as a matter of law that it did not infringe claims of the '079 or '908 patents, or in the alternative a new trial, which the district court denied. Fairchild now appealed the determination of literal infringement of the '079 patent, the determination of infringement under doctrine of equivalents of the '908 patent.
Was there infringement?
It is well-settled that a party cannot reserve a new claim-construction argument for the post-trial motion stage of litigation. When the patentee argued on appeal that the proper claim construction required the chemicals to be permanently removed, we held that because the patentee failed to object to the court's construction or jury instruction with respect to the term 'isolating,' it waived the issue and cannot now raise novel arguments to redefine the scope of the claim." The patentee did not ask the district court to modify the claim construction or accompanying jury instruction. By failing either to request that the district court modify or clarify its claim construction earlier in the litigation proceedings or to object to the jury instructions, Fairchild waived this new claim-construction argument. Dr. Kelley testified that the accused products operate with a non-varying number of cycles per second for a range of operation and that the frequency-hopping products meet the limitation of a "non-varying number of switching cycles per second" because even though the frequency varies over microsecond intervals, the aggregate number of pulses did not vary over each one-second interval. Based on this testimony, a reasonable jury could have concluded that the accused products operate with a "fixed switching frequency" for a certain range of feedback signals under the district court's construction. Thus, substantial evidence supported the jury's verdict of infringement of the '079 patent for all of the accused products. As for the ‘908 patent, prosecution-history estoppel limits the application of the doctrine of equivalents. If a patentee surrenders certain subject matter during prosecution, the patentee is then barred from using the doctrine of equivalents to recover for infringement based on that same subject matter. Prosecution-history estoppel can occur either when the patentee makes a narrowing amendment to the claim or surrenders claim scope through argument to the patent examiner. The application of prosecution-history estoppel is a question of law that an appellate court reviews de novo. Here, the claim language on its face was different than the language of the claims to which the prosecution argument was directed. Claim 26 of the '908 patent covered "a multi-function circuit coupled to receive a signal at a multi-function terminal for adjusting a current limit of a power switch, the multi-function circuit to generate a current limit adjustment signal in response to the signal." The current limit in the '908 patent was externally adjustable and helped prevent a power switch from overloading due to excessive current flow. The '971 patent claimed a "current input circuit coupled to receive a current representative of an input voltage, the current input circuit to generate an enable/disable signal when the current crosses a threshold." The functions performed in the two patents were related but different. Fairchild provided only a cursory argument of why the statement in the '971 patent prosecution history should apply the embodiments claimed in the '908 patent. Fairchild failed to establish that the prosecution history was sufficiently clear as to create an estoppel. Thus, the prosecution-history estoppel did not apply.