Obviousness

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 7939967

This analysis considers combinations of prior art references that would render the independent claims of US Patent 7939967 (Claims 1, 9, and 14) obvious to a person having ordinary skill in the art (PHOSITA) as of the filing date (June 25, 2009). The primary motivation for combining these references would be to improve efficiency in redundant power supply systems while maintaining continuous power delivery.

Independent Claim 1: Apparatus

Claim 1 describes an apparatus with:

1. A first power supply coupled to an electrical load and a first source, configured to issue an alert signal for a failure in the first source.
2. A second power supply coupled to the electrical load and a second source, configured to transition from a lesser output level to a greater output level in response to an activation signal.

Combination 1: US5894413A (Sony) in view of US20090224603A1 (Perper)

• US5894413A (Sony - "Redundant power supply switchover circuit") discloses a redundant power supply system with a main power supply (MPS) and a sub power supply (SPS) connected in parallel to a load. [cite: US5894413A, Abstract] It includes a voltage detection circuit to detect a drop in the MPS's output voltage (indicative of a failure condition) and a switchover control circuit that switches the SPS to start up when the MPS fails. [cite: US5894413A, Abstract] This reference clearly teaches:
  • A first power supply (MPS) coupled to a load and a first source, detecting a failure, and implicitly issuing an alert signal (via the voltage detection and switchover control).
  • A second power supply (SPS) coupled to the load and a second source, which "starts up" in response to the detection of the MPS failure (activation signal).
• US20090224603A1 (Perper - "Energy conserving (stand-by mode) power saving design for battery chargers and power supplies") teaches a power supply or battery charger with an "always on" sensing circuit and a main circuit that is "normally in a stand-by mode to conserve energy." [cite: US20090224603A1, Abstract] When the sensing circuit detects a "need for operation," the main circuit transitions into a "full operation mode." [cite: US20090224603A1, Abstract] This reference explicitly teaches:
  • A power supply capable of operating at a "lesser output level" (stand-by mode) and transitioning to a "greater output level" (full operation mode).
  • This transition occurs in response to an activation signal (detection of a "need for operation").
  • The motivation for this design is "to conserve energy." [cite: US20090224603A1, Abstract]

Motivation to Combine:
A PHOSITA, seeking to improve the energy efficiency of the redundant power supply system described by Sony (US5894413A), would find it obvious to incorporate the energy-saving standby mode taught by Perper (US20090224603A1). Sony's system, if its sub power supply (SPS) is fully active while the main power supply (MPS) operates, would be less efficient than if the SPS operated in Perper's standby mode, only transitioning to full output when the MPS fails. Therefore, a PHOSITA would be motivated to configure Sony's SPS to operate at a "lesser output level" (standby) for energy conservation, and then transition to a "greater output level" (normal operation) upon receiving the activation signal (i.e., the detected failure of the MPS from Sony's voltage detection circuit). This combination directly addresses the elements of Claim 1.

Dependent Claims 2 and 8:
Claim 2 adds that the first power supply provides operating power to the electrical load while the second power supply transitions. Claim 8 further specifies this power comes from "internal energy storage." The patent in suit itself acknowledges that "the use of output filtering, buffering or energy storage capacitors within power supplies is a common practice, and no additional elaboration is required in this regard" to provide conditioned power during transitions. [cite: US7939967B2, Description, First Illustrative Method, at 206] Therefore, a PHOSITA implementing the combined Sony and Perper system to ensure uninterrupted power during a fault condition would, as a matter of routine design and general knowledge, incorporate conventional energy storage (e.g., capacitors) into the primary power supply to bridge any brief power gaps during the transition of the standby power supply. This predictable outcome of combining known elements using known methods to achieve a known function (uninterrupted power) renders these dependent claims obvious.

Independent Claim 9: System

Claim 9 outlines a system with an electrical load, a first power supply, and a second power supply, both coupled to independent sources and the load. Both power supplies are configured to:

1. Provide an alert signal for an anomalous condition in their respective independent sources.
2. Transition from a lesser output level to a greater output level in response to a respective activation signal.

Combination 2: US4860188A (Texas Instruments) in view of US20090224603A1 (Perper)

• US4860188A (Texas Instruments - "Redundant power supply control") describes a redundant system with "two DC-DC power supplies connected in parallel to provide power to a load." [cite: US4860188A, Abstract] It teaches a master/slave configuration where "Both the master and slave power supplies have substantially the same output voltage and current characteristics." [cite: US4860188A, Description, Col. 2, lines 17-19] Crucially, it states that "Should the master power supply fail, the slave power supply assumes the master role... Should the slave power supply fail, the master power supply continues to operate." [cite: US4860188A, Description, Col. 2, lines 20-25] This demonstrates a bidirectional redundant system where either supply can detect a fault (anomalous condition) in its source and the other can take over, implying the capacity for both to issue alerts and respond to activation signals.
• US20090224603A1 (Perper - "Energy conserving (stand-by mode) power saving design...") again provides the teaching of operating a power supply in an energy-saving standby (lesser output) mode and transitioning to a full (greater output) operation mode when activated. [cite: US20090224603A1, Abstract]

Motivation to Combine:
A PHOSITA, seeking to improve the energy efficiency of the bidirectional redundant power supply system taught by Texas Instruments (US4860188A), would recognize that continuously operating both master and slave power supplies at full output or shared load can be inefficient. Perper (US20090224603A1) provides a clear solution for energy conservation through a standby mode. [cite: US20090224603A1, Abstract] It would be obvious to modify the power supplies in Texas Instruments' system to incorporate Perper's standby functionality. For instance, one power supply could operate in an energy-saving standby mode (lesser output) and transition to full operation (greater output) when an anomalous condition of the other supply's source is detected (alert signal from the failing unit serving as an activation signal). Given the symmetrical nature of redundancy described by Texas Instruments, this standby functionality could be applied to either power supply, making the system bidirectional in terms of alerts and transitions.

Dependent Claim 11:
Claim 11 specifies that the power supplies are configured to provide operating power for an amount of time sufficient for the other to transition. As with dependent claims 2 and 8, this is a standard design consideration for maintaining uninterrupted power in redundant systems, commonly achieved using internal energy storage (e.g., capacitors), a practice well-known in the art at the time of the invention.

Independent Claim 14: Method

Claim 14 describes a method including:

1. Asserting a signal responsive to an anomalous condition of a first independent source (energizing a first power supply).
2. Transitioning a second power supply from a standby output level to a normal output level responsive to the signal (second power supply energized by a second independent source).
3. Providing operating power from the first power supply to an electrical load during the transitioning.

Combination 3: US5894413A (Sony) in view of US20090224603A1 (Perper) and general knowledge in the art.

• US5894413A (Sony) teaches the method step of detecting a main power supply failure and initiating a switchover to a sub power supply in response to that failure. [cite: US5894413A, Abstract] This covers "asserting a signal responsive to an anomalous condition."
• US20090224603A1 (Perper) explicitly teaches the method step of a power supply (main circuit) being "normally in a stand-by mode to conserve energy" and transitioning to a "full operation mode" when a "need for operation" is detected. [cite: US20090224603A1, Abstract] This covers "transitioning a second power supply from a standby output level to a normal output level responsive to the signal."
• General knowledge in the art: As noted previously and within the specification of US7939967, "the use of output filtering, buffering or energy storage capacitors within power supplies is a common practice" for providing conditioned power and preventing interruptions during power supply changes. [cite: US7939967B2, Description, First Illustrative Method, at 206] This covers "providing operating power from the first power supply to an electrical load during the transitioning."

Motivation to Combine:
A PHOSITA would be motivated to implement the method of managing redundant power supplies for increased energy efficiency while ensuring continuous operation. By combining the fault detection and switchover initiation methods of Sony (US5899413A) with the energy-saving standby and transition method of Perper (US20090224603A1), the PHOSITA would arrive at the method claimed in Claim 14. The use of internal energy storage to bridge power gaps during transition is a well-known engineering solution for ensuring uninterrupted power in such systems, making this step an obvious design choice when combining these known methods.