Vlt Corp. v. Unitrode Corp.
| Citation | 130 F.Supp.2d 178 |
| Decision Date | 24 January 2001 |
| Docket Number | No. 98-CV-11152-PBS.,98-CV-11152-PBS. |
| Parties | VLT CORPORATION and Vicor Corporation, Plaintiffs, v. UNITRODE CORPORATION, Defendant. |
| Court | U.S. District Court — District of Massachusetts |
Robert E. Hillman, Lawrence K. Kolodney, Fish & Richardson, Paul F. Ware, Jr., Douglas C. Doskocil, Daryl L. Wiesen, Goodwin Procter LLP, Boston, MA, for Plaintiffs.
William F. Lee, Dominic E. Massa, Wayne L. Stoner, Hale & Dorr LLP, Paul B. Galvani, Ropes & Gray, Boston, MA, for Defendant.
Plaintiffs VLT Corporation and Vicor Corporation (collectively "Vicor") bring this patent infringement action against Unitrode Corporation ("Unitrode") claiming that Unitrode designed and marketed integrated circuits for use in power supply converters which literally infringe Claims 1 and 5 of U.S. Patent No. Re. 36,098 ("the '098 Patent").
Plaintiffs move for partial summary judgment on the grounds that Unitrode has directly infringed the '098 Patent, that it induced four non-parties to infringe the patent, and that the patent is valid. Unitrode has also moved for summary judgment on the grounds that the patent is anticipated by prior art pursuant to 35 U.S.C. § 102; that it failed to disclose the best mode contemplated by the inventor for practicing his invention; that it is indefinite; and that there is no evidence that Unitrode's actions resulted in any direct patent infringement by any third parties.
After hearing, the Court ALLOWS Vicor's motion for summary judgment on its claim of direct infringement, but DENIES its motion on validity because there is disputed evidence concerning the claim of obviousness. The Court DENIES Unitrode's motions for summary judgment.
The facts that follow are undisputed by the parties, unless otherwise noted:
A. Single ended forward converter technology
The technology at issue is a design for electrical power converters. Power converters function to convert electricity from one voltage to another. The utility of these devices is increasingly evident in many aspects. For example, power converter devices are used to drive personal computers or recharge mobile phone batteries with the electricity from an ordinary household wall plug. A brief review of the relevant electrical power converter technology is necessary to address the competing arguments.
The '098 Patent deals with an improvement on a class of power converters called single-ended forward converters. Figure 1 below, culled from the '098 Patent, illustrates a simplified structure of the single-ended forward converter:
NOTE: OPINION CONTAINING TABLE OR OTHER DATA THAT IS NOT VIEWABLE
The central element is a transformer 11, which has primary and secondary windings surrounding a magnetic core. When the switch 10 is closed, current travels from the terminals of the power source that is to be converted (represented by the small circles at the left of Fig. 1) through the primary winding. As current flows through the primary winding, magnetic "flux" builds up in the transformer's magnetic core. At the same time, a current is induced in the secondary winding which travels to the device to be powered. Whether the current and voltage in the secondary winding are higher than those of the primary winding depends on the ratio of turns between the primary and secondary winding. That is, if the secondary winding has one-half the turns of the primary winding, the resulting voltage will be one-half of the voltage from the original power source.
There is, however, a significant operational limitation on converters of this type. As current flows through the converter, the magnetic flux accumulating in the transformer core will begin to reach a potentially destructive point of "saturation." At some point prior to saturation, the switch 10 must be opened for a period — thus stopping the flow of current — to allow the accumulated flux to reduce. After the flux has reduced, the switch can again be closed to start a new conversion cycle. This process is called "resetting" the transformer core.
The necessity of resetting the core introduces a significant inefficiency into the converter since, during periods of core reset, no power transfer is occurring. In fact, some core reset techniques require the reset intervals to be as long, or longer, than the power transfer intervals. Other techniques cause the magnetic energy associated with flux to be dissipated as heat, rather than to be conserved as useful energy. In addition to being inefficient, the generation of heat is problematic because it requires the converter to be large and bulky to avoid damage to the converter's components resulting from extreme temperatures. This creates an impediment to the goal of miniaturizing the technology.
B. The Vinciarelli invention and the prior art
Dr. Patrizio Vinciarelli ("Vinciarelli"), the president and chairman of Vicor Corporation, devised a solution to the inefficiencies of the single-ended forward converter by creating a core reset technique that increases power transfer intervals and minimizes energy dissipation. Vinciarelli filed his initial patent application for the invention on February 4, 1982. Based on the this application, the United States Patent and Trademark Office ("PTO") issued U.S. Patent No. 4,441,146 ("the '146 Patent"). In 1995 Vinciarelli resubmitted the patent to the PTO in a "reissue" proceeding pursuant to 35 U.S.C. § 251. From that proceeding the PTO issued the '098 Patent, three claims of which are the subject of this suit.
A simple form of the Vinciarelli invention is represented below as Figure 4a from the '098 Patent:
NOTE: OPINION CONTAINING TABLE OR OTHER DATA THAT IS NOT VIEWABLE
The figure incorporates the elements of the single ended forward converter and adds three new elements. One is a capacitor 20, an energy storing device. The second is an additional switch 21, which is "in series" with the capacitor. The third new element, represented simply by a box, is the "control" consisting of a circuit 22 that dictates when the new switch 21 is opened and closed.
During operation, switch 10 (the "primary switch") is closed to initiate the energy conversion cycle. As energy is transferred between the primary and secondary windings, the new switch 21 (the "auxiliary" or "reset" switch) remains open, thereby disconnecting the capacitor from the transformer. When it is time to initiate core reset, the primary switch is opened and the auxiliary switch is closed. The reset process itself takes place in two phases. During the first phase, magnetic flux that has built up during the energy conversion process flows out of the transformer into the capacitor, reducing the magnetic energy and flux in the core to zero.1 During the second phase, energy flows from the capacitor back into the transformer, causing the flux to increase, but with reversed polarity.2 Through this process the energy stored in the transformer has been decreased to zero and increased again (albeit from the opposite direction), filling the core with "negative flux." On the next conversion cycle, the core's capacity for magnetic flux buildup has thus been doubled — i.e, the positive flux first neutralizes the negative flux from the previous reset interval (bringing the core to a neutral flux condition) and then builds up to its maximum positive value. The reset mechanism draws the name "magnetizing current mirror" from this back-and-forth flow of magnetizing current. When the reset is complete, the auxiliary switch is opened and the primary switch is closed to start a new conversion cycle. Modern high-frequency power converters repeat this process hundreds of thousands of times per second.
Although Vinciarelli was not aware of it at the time he filed the '146 Patent, the basic contours of his invention described up to this point are the same as core reset techniques embodied in the earlier works of two individuals. In 1981, a short time before Vinciarelli filed the application for the '146 Patent, an engineer named Bruce Carsten ("Carsten") published an article describing the use of current mirror to reset a converter's transformer core. Some actual converters that were designed by Mr. Carsten prior to the Vinciarelli patent application and that incorporated a current mirror mechanism were located during the course of this litigation in a mountaintop shack in Alaska. Also, in 1981 a Soviet engineer named Polikarpov received a Soviet patent that described a similar method of core reset.
C. The switch timing properties
The aspect of the device in dispute here, however, is not the magnetizing current mirror itself; rather, the dispute centers around the timing by which the primary and auxiliary switches open and close. While the ordinary operation of the current mirror's core reset mechanism goes part of the way toward achieving a reset that is non-dissipative in nature, the switches themselves are additional sources of dissipation of energy as heat. That is, these switches act to some degree as capacitors and therefore store energy at various times during the conversion cycle. This characteristic is referred to as a "parasitic capacitance." If a switch is closed and conducting current while this parasitic capacitance is charged with energy, that energy will be dissipated as heat. However, according to Vicor, if a short delay is provided between the opening of the auxiliary switch and the closing of the primary switch, the reversed flow of the magnetizing current can be used to discharge the primary switch's parasitic capacitance without heat dissipation. Neither the Carsten article nor the Soviet patent describes the use or advantage of such a switch-timing delay. Moreover, the Carsten converters located during this litigation did not exhibit these properties when tested by the parties.
Vicor contends that the limitations of certain claims in the '098 Patent require such a delay and...
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