PTAB

IPR2017-01453

Power Integrations Inc v. Semiconductor Components Industries LLC

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: High-Speed Reflected Signal Detection for Primary-Side Controlled Power Converters
  • Brief Description: The ’841 patent discloses controllers for switch-mode power converters that regulate their output using primary-side control. The technology addresses the problem of oscillating energy in the reflected signal from the transformer's auxiliary winding, which can delay accurate signal detection and slow down regulation. The invention uses a discharging circuit to quickly dissipate this oscillating energy at the beginning of the power transistor's off-period, enabling faster and more precise control.

3. Grounds for Unpatentability

Ground 1: Anticipation by Bonte - Claims 5-7 are anticipated by Bonte under 35 U.S.C. §102(b).

  • Prior Art Relied Upon: Bonte (Patent 5,305,192).
  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that Bonte, which teaches a primary-side controlled flyback converter, discloses every limitation of claims 5, 6, and 7. Bonte was not considered during the original prosecution of the ’841 patent. Like the ’841 patent, Bonte addresses the problem of erroneous initial spikes in the feedback voltage caused by leakage inductance and discloses a "leakage inductance spike blanking circuit" to eliminate these effects for a fixed period at the start of the "switch off" time.

    • Claim 5 (Independent): Petitioner asserted that Bonte anticipates claim 5 by disclosing a controller for a power converter with a power transistor.

      • Switching Circuit: Bonte’s switching regulator control circuit (405) was identified as the claimed switching circuit. It generates a switching signal to drive a power transistor (switch 412) in response to a detection signal (VBIAS) from the transformer's bias winding, thereby regulating the power converter.
      • Discharging Circuit: Petitioner mapped Bonte's "leakage inductance spike blanking circuit 710" to the claimed discharging circuit. This circuit is coupled to a supply terminal (VBIAS) that is powered by the transformer's reflected signal. Petitioner argued this circuit is coupled to discharge a current sourced from the supply terminal during a delay time that starts from a falling edge of the switching signal, as Bonte explicitly states it "suppresses the error signal...for a fixed period of time at the start of 'switch off' time."

    • Claim 6 (Dependent): Petitioner argued that Bonte anticipates the additional limitations of claim 6, which further define the discharging circuit.

      • Comparison Circuit: Bonte's differential amplifier circuit (705) was argued to be the claimed comparison circuit. It compares a feedback signal (FB), which is correlated to the supply terminal voltage, with a threshold reference voltage (4.5V) to generate an error signal that ultimately controls the discharging function.
      • Transistor: Bonte's transistor (Q49 in FIG. 11B) was mapped to the claimed transistor. This transistor is coupled to the comparison circuit (via amplifier 1125, which corresponds to amplifier 705) and discharges current from the supply terminal in response to a discharging signal generated by the blanking circuit.

    • Claim 7 (Dependent): Petitioner asserted that Bonte anticipates the further limitation of claim 7, which adds a pulse generation circuit.

      • Pulse Generation Circuit: Petitioner mapped Bonte's capacitor (DC1 in FIG. 11B) to the claimed pulse generation circuit. Bonte states that the length of time the blanking circuit remains on is set by this capacitor, giving rise to a 1.5 micro-second pulse. This pulse is generated in response to the falling edge of the switching signal (FFQ signal), and the pulse signal is coupled to control the discharging transistor (Q49 via Q54), thereby meeting all limitations of the claim.

4. Relief Requested

  • Petitioner requested the institution of an inter partes review (IPR) and the cancellation of claims 5, 6, and 7 of the ’841 patent as unpatentable.