BOE Technology Group Co Ltd v. Bishop Display Tech LLC

1. Case Identification

• Case #: IPR2025-01331
• Patent #: 8,093,830
• Filed: July 28, 2025
• Petitioner(s): BOE Technology Group Co., Ltd.
• Patent Owner(s): Bishop Display Tech LLC
• Challenged Claims: 1-5

2. Patent Overview

• Title: Semiconductor Light Source Driving Apparatus
• Brief Description: The ’830 patent discloses a driving apparatus for a semiconductor light source, such as an LED. The apparatus uses a feedback control loop that adjusts the output voltage of a voltage source based on both the detected output current and the detected impedance of the light source to maintain stable performance.

3. Grounds for Unpatentability

Ground 1: Obviousness over Ghanem in view of Nishimura - Claims 1-5 are obvious over Ghanem in view of Nishimura.

• Prior Art Relied Upon: Ghanem (Patent 6,285,139) and Nishimura (Patent 7,332,699).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Ghanem taught a complete semiconductor light source driving apparatus with a feedback control loop. Ghanem’s circuit included a light source (LEDs), a voltage source, an output voltage controller (power factor controller 19), an output current detector (current sensor circuit 10), and a current comparator (comparator 48), thus meeting most limitations of independent claims 1 and 5. The key difference identified was the ’830 patent’s requirement for an "impedance detecting section" whose output is used to control the voltage. Petitioner asserted Nishimura explicitly taught this missing element, disclosing a circuit that measures an LED’s operating current and voltage to estimate its dynamic impedance. Petitioner argued that adding Nishimura’s impedance detection circuit to Ghanem’s apparatus would render the claimed invention obvious. For dependent claim 2, which requires a "divider," Petitioner contended Nishimura taught this by disclosing that impedance is calculated by dividing voltage by current. For dependent claims 3 and 4, Petitioner argued Ghanem’s multipliers and latches met the limitations for a "gain circuit" and "compensator."
  • Motivation to Combine: Petitioner asserted a person of ordinary skill in the art (POSITA) would combine Ghanem and Nishimura to improve the performance and reliability of Ghanem’s circuit. Ghanem recognized the need to compensate for impedance changes but used an indirect method (a thermistor). Nishimura provided a superior, direct method of measuring impedance by sensing voltage and current. A POSITA would have been motivated to replace Ghanem’s indirect approach with Nishimura’s more accurate direct measurement to better regulate output power and maintain constant brightness, which was the stated goal of both references.
  • Expectation of Success: A POSITA would have had a reasonable expectation of success because applying Nishimura’s known technique of impedance detection to Ghanem’s known LED driver circuit was a straightforward integration of compatible, conventional circuit components to achieve the predictable result of more accurate feedback control.

Ground 2: Obviousness over Tripathi in view of Nishimura - Claims 1-2 and 5 are obvious over Tripathi in view of Nishimura.

• Prior Art Relied Upon: Tripathi (Patent 7,262,559) and Nishimura (Patent 7,332,699).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Tripathi disclosed a power supply for LEDs that met most limitations of the challenged claims. Tripathi’s circuit included an LED light source (10), a voltage source (AC/DC converter 22, power converter 23), an output voltage controller (feedback controller 27), an output current detector (LED current sensor 25), and a current comparator function within the feedback controller. Similar to the argument in Ground 1, Petitioner contended that Tripathi lacked an explicit impedance detecting section whose output is used for control. Nishimura was again relied upon to supply this teaching, disclosing the estimation of dynamic impedance from measured voltage and current to account for temperature and aging effects.
  • Motivation to Combine: Petitioner argued a POSITA would have been motivated to incorporate Nishimura’s impedance detection into Tripathi’s circuit to enhance its functionality. While Tripathi’s circuit regulated current, it did not explicitly account for impedance changes due to factors like temperature and aging, which Tripathi acknowledged were issues. Nishimura directly addressed this problem by teaching the use of dynamic impedance measurement for control. A POSITA would combine the teachings to improve Tripathi's design, creating a more robust driver circuit that maintains stable brightness by compensating for impedance variations, thereby achieving a known objective using known techniques.
  • Expectation of Success: A POSITA would have reasonably expected success in this combination. Both references operate in the same field of LED driver circuits and use standard feedback control principles. Implementing Nishimura’s impedance calculation using Tripathi’s already-sensed voltage and current signals would have been a predictable modification to improve system reliability.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under §325(d) is inappropriate because the grounds rely on prior art (Ghanem, Tripathi, Nishimura) that was not before the Examiner during the original prosecution. Petitioner contended the Examiner’s allowance was based on the "best prior art of record" lacking an impedance detecting section, a deficiency directly cured by the newly cited references.
• Petitioner further argued that discretionary denial under §314(a) based on the Fintiv factors is unwarranted. Petitioner asserted that the co-pending district court litigation is at a very early stage, with a trial date set for January 2027, making it likely that a Final Written Decision (FWD) from the IPR would issue before trial. Petitioner also stipulated that, if the IPR is instituted, it would not pursue the same invalidity grounds in the district court litigation.

5. Relief Requested

• Petitioner requested the institution of an inter partes review and the cancellation of claims 1-5 of Patent 8,093,830 as unpatentable under 35 U.S.C. §103.