PTAB

IPR2016-01600

Semiconductor Components Industries, LLC, doing business as ON Semiconductor v. Power Integrations, Inc.

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1. Case Identification

2. Patent Overview

  • Title: Power Supply Regulator with Variable Current Limit
  • Brief Description: The ’605 patent discloses switch-mode power supply circuits. The technology purports to solve the problem of variations in the actual current limit caused by different input voltages by creating a variable intrinsic current limit threshold that increases during the on-time of the power switch to achieve a more constant output current.

3. Grounds for Unpatentability

Ground 1: Anticipation over de Sartre - Claims 1, 2, 5, and 9 are anticipated by de Sartre under 35 U.S.C. §102.

  • Prior Art Relied Upon: de Sartre (Patent 4,692,853).
  • Core Argument for this Ground: Petitioner argued that the ’605 patent claims were broadened during prosecution from their parent application (which resulted in the ’270 patent). Specifically, the limitation requiring an "approximately constant output current" was removed, leaving only the recitation of a "variable current limit threshold." Petitioner asserted that this broadened claim scope now encompasses prior art that used a variable current limit for different purposes. The petition contended that de Sartre, which was not considered during prosecution or prior litigation, discloses a switch-mode power supply that uses a variable current limit threshold during a safety/start-up mode to protect the power transistor. While the purpose differs from the ’605 patent's stated goal of compensating for input voltage, Petitioner argued that de Sartre’s circuit structure explicitly or inherently discloses every limitation of the challenged claims.
    • Prior Art Mapping:
      • Independent Claim 1: Petitioner mapped the elements of claim 1 to de Sartre's "chopped power supply control circuit." The claimed "comparator" was mapped to de Sartre's comparator 92. Its first input (sensing current) was mapped to input 44, which receives a signal from sense resistor 18 representing the current through the power switch (transistor Tp). Its second input was mapped to the "threshold signal produced by circuit 90," which Petitioner asserted is a variable current limit threshold that increases during the on-time of the switch in safety mode. The claimed "feedback circuit" was mapped to de Sartre's regulation circuit CI2, which monitors the output voltage Vs. The "control circuit" was mapped to the combination of OR gate 60, flip flop 50, and other components in de Sartre, which receive inputs from both the comparator (92) and the feedback circuit (CI2) to generate a control signal (at output 46) that controls the switching of transistor Tp.
      • Dependent Claim 2: This claim adds an oscillator generating a sawtooth waveform, which in turn generates the variable current limit threshold. Petitioner mapped this to de Sartre’s oscillator 82, which generates a sawtooth waveform fed to the "variable threshold elaboration circuit 90" to create the variable threshold.
      • Dependent Claim 5: This claim requires the control circuit to include a latch with a reset input coupled to the comparator's output. Petitioner mapped this to de Sartre's flip flop 50, which functions as a set-reset latch. The reset input 54 is coupled to the output of comparator 92 via OR gate 60.
      • Dependent Claim 9: This claim requires the duty cycle of the control signal to be modulated by the feedback circuit's output. Petitioner argued de Sartre discloses this, as the feedback signal from circuit CI2 controls the reset of flip flop 50, thereby creating "square waves having a variable width" to control the switch, which directly modulates the duty cycle.

4. Key Technical Contentions (Beyond Claim Construction)

  • Scope of "Increases During the On-Time": A central technical argument was that the claim phrase "a variable current limit threshold that increases during the on time of the switch" does not require any specific magnitude or rate of increase. Petitioner contended that any increase, regardless of how slight or for what purpose, satisfies the literal claim language. This argument was framed in contrast to a prior litigation involving the Maige patent, where the Patent Owner had successfully argued that the very slight increase in Maige's threshold during a single on-cycle was effectively "unchanged." Petitioner asserted that de Sartre provides a clearer disclosure with diagrams illustrating the threshold progressively increasing during the switch's on-time.

5. Arguments Regarding Discretionary Denial

  • The petition preemptively addressed potential arguments for discretionary denial by distinguishing the current challenge from prior litigation involving the ’605 patent. It noted that a district court jury found the patent not anticipated by a different reference, Maige (Patent 4,763,238). Petitioner argued that the instant petition should not be denied based on that history because it relies on de Sartre, a different and stronger reference that was not asserted or considered in the prior litigation. The petition asserted that de Sartre's disclosures, particularly its figures, more clearly illustrate a current limit threshold that increases during the on-time of the switch, directly addressing the key point of dispute in the Maige-based litigation.

6. Relief Requested

  • Petitioner requested the institution of an inter partes review (IPR) and the cancellation of claims 1, 2, 5, and 9 of Patent 7,834,605 as unpatentable.