Bill Schertler | August 27, 2015
Power Integrations v. Lee
August 12, 2015
Before: Moore, Mayer, Linn, opinion by Mayer
Power Integrations challenged a decision of the Board of Patent Appeals and Interferences (“board”) affirming the rejection of claims 1, 17, 18 and 19 of US Patent No. 6,249,876 (the ‘876 patent) as anticipated under 35 U.S.C. §102(b). The board’s construction of the claim term “coupled” was not adequately explained. The court vacated and remanded the board’s decision, holding only that the board on remand should carefully and fully assess whether the disputed claims of the ’876 patent are anticipated by the prior art, setting out its reasoning in sufficient detail to permit meaningful appellate review.
The ‘876 patent is directed to a technique for reducing electromagnetic interference by jittering the switching frequency of a switched mode power supply. Representative claim 1 is set forth below.
1. A digital frequency jittering circuit for varying the switching frequency of a power supply, comprising:
an oscillator for generating a signal having a switching frequency, the oscillator having a control input for varying the switching frequency;
a digital to analog converter coupled to the control input for varying the switching frequency; and
a counter coupled to the output of the oscillator, the digital to analog converter coupled to the counter, the counter causing the digital to analog converter to adjust the control input and to vary the switching frequency of the power supply.
The District Court
In 2004, Power Integrations sued Fairchild Semiconductor International, Inc. and related parties (collectively “Fairchild”) in the United States District Court for the District of Delaware, alleging Fairchild had willfully infringed the ’876 patent. A jury found that Fairchild willfully infringed claim 1 of the ‘876 patent and rejected Fairchild’s invalidity defense.
The meaning of the term “coupled” in claim 1 was significant with respect to Fairchild’s invalidity defense. The district court adopted Power Integration’s construction of the term “coupled” as requiring that two circuits be connected in a manner “such that voltage, current, or control signals pass from one to another” with “the recited coupling…present for purposes of control.” However, Power Integrations made clear that its construction did not require a direct connection between circuit elements.
In view of the district court’s claim construction, Fairchild withdrew its anticipation defense, instead arguing at trial that U.S. Patent No. 4,638,417 (“Martin”) rendered claim 1 obvious. After a trial on validity, a second jury returned a verdict that claim 1 of the ’876 patent was not obvious in view of Martin.
Fig. 1 of U.S. Patent No. 4,638,417
On appeal to the Federal Circuit, the jury’s finding that the ‘876 patent was not invalid for obviousness was affirmed. The Federal Circuit noted that the “salient difference” between the ’876 patent and Martin is Martin’s inclusion of an erasable programmable read only memory (“EPROM”) between the counter and the digital to analog converter and “does not teach removing the EPROM . . . as in the ’876 Patent.”
Ex parte Reexamination
While the district court proceedings were pending, the United States Patent and Trademark Office granted Fairchild’s request for ex parte reexamination of claims 1, 17, 18, and 19 of the ’876 patent, where the board affirmed the examiner’s rejection of claim 1 as anticipated by Martin, as well as two other references (Habetler and Wang).
The board concluded, that the term “coupled” meant to “join devices into a single circuit,” and did not preclude the presence of intervening components.
The board rejected Power Integrations’ argument “that the respective counters in Martin, Wang, and Habetler are not coupled to the respective digital to analog converters because all [Martin, Wang, and Habetler] disclose a read only memory (“ROM”) separating a counter from a digital to analog converter.” In the board’s view, Martin, Wang, and Habetler disclosed the limitations of claim 1 because they joined a counter and a digital to analog converter in a single circuit, and the counter “produce[d] a signal that causes a digital to analog converter to adjust control input by utilizing a corresponding memory, the counter (with the corresponding memory) being ‘coupled to’ the digital to analog converter.”
Power Integrations filed a request for rehearing with the board, arguing that the board had “misapprehended” its argument about proper construction of the term coupled. The board denied the request for rehearing, rejecting the contention that it misapprehended Power Integrations’ argument about the proper construction of the term “coupled”.
Power Integration appealed the board’s decision to the Federal Circuit. On appeal to the Federal Circuit, the court concluded that “the board fundamentally misconstrued Power Integrations’ principal claim construction argument and failed to provide a full and reasoned explanation of its decision to reject claim 1 of the ’876 patent as anticipated.”
Central to the court’s conclusion is that Power Integration had consistently argued in all prior proceedings that the “coupled” limitation in claim 1 requires that the counter be connected to the digital to analog converter in a manner that allows it to pass voltage, current, or control signals to instruct the digital to analog converter, and that the counter itself – not a pre-programmed memory – controls the digital to analog converters output to vary the switching frequency.
During reexamination, the board failed to acknowledge the district court’s claim construction or to assess whether its interpretation of the term “coupled” was consistent with the broadest reasonable construction of the term. Instead, the board devoted a substantial portion of its analysis to resolving the question of whether the term “coupled” requires a direct connection between the counter and the digital to analog converter. However, when Power Integrations was before the board it repeatedly acknowledged that the term “coupled” does not preclude the presence of intervening components between the counter and the digital to analog converter. Thus, a significant portion of the board’s opinion was devoted to rejecting an argument that Power Integrations not only never made, but instead expressly disavowed.
The CAFC reasoned “Because so much of the board’s analysis is focused on a red herring – the issue of whether there can be intervening components between the counter and the digital to analog converter – it failed to adequately evaluate Power Integrations’ primary argument, which is that the “coupled” limitation requires that the counter pass control signals, voltage, or current to the digital to analog converter to control it, and that the presence of a memory programmed with data specifying how to vary the switching frequency “uncouples” the counter and the digital to analog converter and severs the requisite control relationship between them.”
The CAFC addressed the different claim construction standards applied by the board and the district court, “There is no dispute that the board is not generally bound by a prior judicial construction of a claim term. Indeed, in reexamination it applies a different claim construction standard than that applied by a district court, affording claims ‘their broadest reasonable interpretation consistent with the specification.’ The fact that the board is not generally bound by a previous judicial interpretation of a disputed claim term does not mean, however, that it has no obligation to acknowledge that interpretation or to assess whether it is consistent with the broadest reasonable construction of the term.”
The court vacated and remanded the board’s decision, holding only that the board on remand should carefully and fully assess whether the disputed claims of the ’876 patent are anticipated by the prior art, setting out its reasoning in sufficient detail to permit meaningful appellate review.
The board is obligated not only to come to a sound decision, but to fully and particularly set out the bases upon which it reached that decision.
To permit effective appellate review, the board’s patentability analyses must be both “clearly disclosed and adequately sustained.”