US 8279642B2

US patent 8279642B2, titled "Apparatus for converting direct current to alternating current using an active filter to reduce double-frequency ripple power of bus waveform", was filed on September 21, 2009, and issued on October 2, 2012. The original assignee was Solarbridge Technologies Inc. The current assignees are GRIDSCALE SOLUTIONS, LLC, and Enphase Energy Inc. The inventors are Patrick L. Chapman, Brian T. Kuhn, Robert S. Balog, Jonathan W. Kimball, Philip T. Krein, and Alexander Gray.

Abstract:
The patent describes an inverter for converting an input direct current (DC) waveform from a DC source to an output alternating current (AC) waveform for delivery to an AC grid. This inverter comprises an input converter, an output converter, and an active filter, all electrically coupled to a bus (which can be either a DC or AC bus). The input converter converts the input DC waveform into a bus waveform, and the output converter then converts this bus waveform into the final output AC waveform at the grid frequency. A key feature is the active filter, which reduces double-frequency ripple power on the bus waveform by actively supplying and absorbing power from the bus.

Plain-language overview of independent claims:

• Claim 1: This claim describes an inverter that takes DC power from a source and converts it to AC power for an electrical grid. It includes an "input converter" with a transformer that changes the incoming DC into a bus waveform. An "output converter" then converts this bus waveform into the final AC output at the grid's frequency. Crucially, an "active filter" is connected to the bus. Its job is to reduce unwanted power fluctuations (specifically, "double-frequency ripple power") on the bus by either providing or absorbing power, thus helping to keep the bus voltage steady and tracking a desired signal. This active filter includes a switching circuit connected to an energy storage device.

• Claim 19: This claim focuses on an "apparatus" that includes a solar panel and an inverter. The solar panel generates a DC waveform from sunlight. The inverter, connected to the solar panel, takes this DC waveform and converts it into an AC output. Inside the inverter, there's an "input converter" that transforms the solar cell's DC into a second DC waveform on a DC bus. An "output converter" then converts this second DC waveform into the final AC output. An "active filter" is also connected to the DC bus, reducing the double-frequency ripple power by actively managing power flow to and from the DC bus.

• Claim 31: This claim describes a "power inverter" specifically designed with a DC bus. It has an "input converter" that includes a transformer with primary and secondary windings. A first inverter circuit converts the incoming DC to a first AC waveform on the primary winding, which the transformer then converts to a second AC waveform. A rectifier circuit then converts this second AC waveform into a second DC waveform on the DC bus. An "output converter" takes this second DC waveform from the bus and converts it to an AC output suitable for the grid. Finally, an "active filter" connected to the DC bus works to reduce double-frequency ripple power by supplying and absorbing power as needed.

USPTO Database Search and CAFC 2026 Dockets:
A search of the USPTO database for US patent 8279642B2 confirms the details listed above regarding the patent's information, including its active legal status with an adjusted expiration date of 2030-10-20.

No relevant cases for patent 8279642B2 were found in the CAFC 2026 dockets.US patent 8279642B2, titled "Apparatus for converting direct current to alternating current using an active filter to reduce double-frequency ripple power of bus waveform", was filed on September 21, 2009, and issued on October 2, 2012 [cite: US8279642B2]. The original assignee was Solarbridge Technologies Inc. The current assignees are GRIDSCALE SOLUTIONS, LLC and Enphase Energy Inc. The inventors are Patrick L. Chapman, Brian T. Kuhn, Robert S. Balog, Jonathan W. Kimball, Philip T. Krein, and Alexander Gray [cite: US8279642B2].

Abstract:
The patent describes an inverter for converting an input direct current (DC) waveform from a DC source to an output alternating current (AC) waveform for delivery to an AC grid. This inverter comprises an input converter, an output converter, and an active filter, all electrically coupled to a bus (which can be either a DC or AC bus). The input converter is configured to convert the input DC waveform into a bus waveform, and the output converter then converts this bus waveform into the final output AC waveform at the grid frequency. A key feature is the active filter, which reduces double-frequency ripple power on the bus waveform by actively supplying and absorbing power from the bus [cite: US8279642B2].

Plain-language overview of independent claims:

• Claim 1: This claim describes an inverter that converts a DC input from a source into an AC output for an electrical grid. It includes an input converter (with a transformer) that transforms the DC input into a "bus waveform." An output converter then converts this bus waveform into the final AC output at the grid's frequency. An active filter, connected to the bus, is designed to reduce undesirable double-frequency ripple power by supplying and absorbing power, thereby helping to maintain a stable bus voltage. This active filter specifically contains a switching circuit coupled to an energy storage device [cite: US8279642B2].

• Claim 19: This claim details an "apparatus" consisting of a solar panel and an inverter. The solar panel generates a DC waveform from sunlight. The inverter receives this DC waveform and converts it into an AC output. The inverter's components include an input converter (connected to the solar cell and a DC bus) that converts the solar panel's DC into a second DC waveform on the bus. An output converter then converts this second DC waveform into the final AC output. An active filter is coupled to the DC bus and reduces double-frequency ripple power by managing power flow to and from the DC bus [cite: US8279642B2].

• Claim 31: This claim outlines a power inverter with a DC bus. It features an input converter with a transformer having primary and secondary windings. A first inverter circuit converts the input DC waveform to a first AC waveform on the primary winding, which the transformer then converts to a second AC waveform. A rectifier circuit subsequently converts this second AC waveform into a second DC waveform on the DC bus. An output converter, also connected to the DC bus, converts this second DC waveform into an AC output suitable for the grid. An active filter, electrically coupled to the DC bus, is configured to reduce double-frequency ripple power by supplying and absorbing power from the DC power bus [cite: US8279642B2].

USPTO Database and CAFC 2026 Dockets:
The patent US8279642B2 is listed as "Active" with an adjusted expiration date of October 20, 2030 [cite: US8279642B2]. No relevant cases for patent 8279642B2 were found in the CAFC 2026 dockets.