PTAB

IPR2026-00165

Monolithic Power Systems Inc v. Reed Semiconductor Corp

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petition

1. Case Identification

2. Patent Overview

  • Title: Power Supply Apparatus
  • Brief Description: The ’955 patent discloses a power supply apparatus designed to reduce the impact of switching noise on its internal reference voltage source. The purported novelty lies in an arrangement where a linear regulator stabilizes an input voltage and supplies its regulated output voltage to power both a reference voltage source and the controller for a switching power supply.

3. Grounds for Unpatentability

Ground 1: Obviousness over Lotfi and Kha - Claims 1, 7-9 are obvious over Lotfi, alone or in view of Kha.

  • Prior Art Relied Upon: Lotfi (Patent 7,015,544) and Kha (Patent 5,428,286).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Lotfi teaches all limitations of claims 1 and 7. Lotfi discloses a power converter with a linear regulator (235) that provides a regulated bias voltage (Vbias) derived from an input voltage (Vin). This Vbias is supplied as the power supply voltage to both the "bandgap reference circuit 260" (the claimed reference voltage source) and the "PWM comparator 255" (the claimed controller of the switching power supply). Petitioner asserted this directly maps to the core architecture of the ’955 patent. Furthermore, because the PWM comparator is powered by Vbias, the input voltage Vin is not directly supplied to the controller, satisfying another key limitation. For claim 7, Petitioner argued Lotfi discloses implementing its controller on a single semiconductor substrate.
    • Motivation to Combine (for §103 grounds): For claims 8 and 9, which require a step-up switching regulator, Petitioner contended that while Lotfi discloses a buck (step-down) converter, it also states that other topologies are within its scope. Kha teaches that various switching topologies, including the boost (step-up) converter, were well-known and basic options. A POSITA would combine Lotfi with the teachings of Kha by replacing Lotfi's buck converter with a boost converter for any application requiring an output voltage higher than the input voltage, which was a routine design choice.
    • Expectation of Success (for §103 grounds): A POSITA would have a high expectation of success because substituting a boost converter for a buck converter was a well-understood modification with predictable results. The upstream control components taught by Lotfi (linear regulator, reference circuit) operate independently of the downstream switching topology and would function as intended after the substitution.

Ground 2: Obviousness over Doluca, Burstein, and Kha - Claims 1, 7-9 are obvious over Doluca in view of Burstein, and further in view of Kha.

  • Prior Art Relied Upon: Doluca (Patent 5,528,132), Burstein (Patent 6,271,652), and Kha (Patent 5,428,286).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Doluca discloses the high-level architecture of claim 1: a DC-DC converter with a switching power supply, a controller, and a linear regulator whose output (VR) powers the controller. Doluca explicitly teaches that the input voltage (VIN) is not directly supplied to the controller. However, Doluca treats its linear regulator as a "black box" without implementation details. Burstein supplies these missing details, disclosing a well-known "prior art" voltage regulator that includes a "bandgap reference circuit 11" (the claimed reference voltage source). Critically, Burstein teaches that the regulator's own stabilized output voltage (VR) is used to power its internal bandgap reference circuitry. Therefore, combining Doluca’s architecture with Burstein’s standard regulator implementation discloses all elements of claim 1. For claim 7, both Doluca and Burstein teach implementation on a single semiconductor substrate.
    • Motivation to Combine (for §103 grounds): A POSITA seeking to implement Doluca's system would be motivated to use a known, standard linear regulator design, as Doluca provides no specific circuit. Burstein describes a "prior art" regulator design that was well-known and suitable for providing the "accurate, and stable" voltage required by Doluca's controller. The combination represents the straightforward implementation of a conceptual block diagram with a known, off-the-shelf circuit design. For claims 8 and 9 (step-up), the motivation to further combine with Kha is the same as in Ground 1: a POSITA would recognize that Doluca’s buck topology could be replaced with a boost topology like Kha’s for applications requiring voltage step-up.
    • Expectation of Success (for §103 grounds): The combination of Doluca and Burstein would predictably result in a functional power converter, as Burstein's regulator would simply perform its known function of supplying a stable voltage. Further adding Kha's teachings by swapping converter topologies was a routine modification with predictable outcomes.

4. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1, 7, 8, and 9 of the ’955 patent as unpatentable.