Power Integrations Inc v. Semiconductor Components Industries LLC

1. Case Identification

• Case #: IPR2018-01539
• Patent #: 7,944,272
• Filed: August 14, 2018
• Petitioner(s): Power Integrations, Inc.
• Patent Owner(s): Semiconductor Components Industries, LLC
• Challenged Claims: 1-2

2. Patent Overview

• Title: CONSTANT CURRENT CIRCUIT
• Brief Description: The ’272 patent discloses a constant current circuit designed to provide a temperature-compensated output current. The circuit comprises two primary components: a temperature compensation circuit that generates the final output current, and a current supply circuit that provides an input current to the temperature compensation circuit.

3. Grounds for Unpatentability

Ground 1: Claims 1 and 2 are obvious over Tanizawa in view of Ichimaru.

• Prior Art Relied Upon: Tanizawa (Patent 6,316,990) and Ichimaru (Patent 5,430,395).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Tanizawa discloses a temperature compensation circuit that is essentially identical to the one claimed in the ’272 patent. However, Tanizawa’s circuit is supplied by a bias current generated by a simple resistor connected to the power supply voltage (VCC), which makes its output current sensitive to fluctuations in VCC. Ichimaru, in contrast, discloses a self-biased, proportional-to-absolute-temperature (PTAT) constant current circuit that is functionally identical to the current supply circuit of the ’272 patent. This circuit generates a bias current that is substantially independent of the supply voltage. Petitioner asserted that combining Tanizawa's temperature compensation circuit with Ichimaru's supply-independent current supply circuit would result in the circuit claimed in the ’272 patent.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would have recognized that the dependence of an output current on supply voltage, as seen in Tanizawa, is a well-known and undesirable characteristic in constant current circuits. Petitioner contended that a POSITA would combine Tanizawa with Ichimaru to improve Tanizawa’s performance by replacing its VCC-dependent bias current source with Ichimaru’s more stable, VCC-independent PTAT current source. This modification was presented as a known design choice to achieve a predictable improvement in circuit stability.
  • Expectation of Success: Petitioner argued that combining these two known types of circuits was a straightforward application of established design principles. A POSITA would have had a reasonable expectation of success in creating a more stable, temperature-compensated constant current circuit with predictable results.

Ground 2: Claims 1 and 2 are obvious over Tanizawa in view of Shibata.

• Prior Art Relied Upon: Tanizawa (Patent 6,316,990) and Shibata (European Patent Application EP 1881391).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground presented a similar argument to Ground 1, substituting Shibata for Ichimaru. Petitioner again relied on Tanizawa for its disclosure of the core temperature compensation circuit with its VCC-dependent bias current source. Shibata was presented as teaching a self-biased PTAT constant current circuit that, like Ichimaru's, is functionally identical to the current supply circuit claimed in the ’272 patent. Shibata's circuit also generates a bias current that is substantially independent of the supply voltage. Petitioner argued the combination of Tanizawa’s compensation circuit with Shibata’s current supply circuit meets all limitations of the challenged claims.
  • Motivation to Combine: The motivation was identical to that in Ground 1. A POSITA seeking to improve the known supply-voltage sensitivity of Tanizawa’s circuit would be motivated to replace its simple resistor-based bias source. Shibata was offered as another example of a well-known, supply-independent PTAT current source that a POSITA would have readily used to solve this known problem, thereby achieving a more robust and stable constant current circuit.
  • Expectation of Success: As with the first ground, Petitioner contended that a POSITA would have understood that integrating Shibata’s stable current source with Tanizawa’s temperature compensation circuit was a predictable design modification that would successfully yield a circuit with improved supply voltage independence.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under §325(d) would be inappropriate. Although the primary reference, Tanizawa, was considered during the original prosecution of the ’272 patent, it was only applied in the context of an anticipation rejection. Petitioner asserted that its obviousness challenges, which rely on combining Tanizawa with either Ichimaru or Shibata, were never presented to or considered by the Examiner. Because the arguments and the prior art combinations were new, Petitioner contended the petition should not be denied on these grounds.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1 and 2 of the ’272 patent as unpatentable.