# How a Special Box Turns Solar Panel Power into Home Electricity > This patent describes a device that takes the unique direct current (DC) electricity from each layer of a special multi-layer solar panel and converts it into alternating current (AC) electricity usable in homes, making sure to get the most power out of each layer. - **Patent:** US 9391457 - **Original title:** Apparatus and method for producing AC power - **Owner:** Sunlight Photonics - **Granted:** 2016 - **Status:** Active - **Times cited:** 1 - **Field:** renewable_energy, consumer_electronics, semiconductors, electrical_engineering ## What it does This patent describes an electrical power conversion device that takes direct current (DC) energy from a multi-junction solar cell and turns it into alternating current (AC) energy. A multi-junction solar cell has several layers, or "junctions," each producing its own DC electricity. The device has multiple input pairs (Claim 1) to receive DC energy from each of these different junctions. It then uses multiple DC-to-AC inverting circuits (Claim 1), one for each input, to convert that DC energy into AC. An important part is the Maximum Power Point Tracking (MPPT) circuit (Claim 1), which ensures that the device always pulls the most power possible from the solar cell junctions. For example, if a multi-junction solar cell has three layers, this device would have three separate inputs and three separate DC-to-AC inverting circuits, each optimized to convert the power from its specific layer. ## What it does NOT cover - Does not cover power conversion devices for single-junction solar cells. - Does not cover systems that combine the DC outputs from different junctions before converting them to AC. - Does not cover converting DC power from sources other than multi-junction solar cells. - Does not cover power conversion without an MPPT circuit to maximize energy harvest. - Does not cover devices where the power conversion components are not housed within a single package (Claim 1). ## The clever bit The novelty lies in individually managing and converting the DC output from each separate junction within a multi-junction solar cell, rather than treating the entire cell as a single DC source. This allows for more precise Maximum Power Point Tracking and conversion for each layer, maximizing overall energy yield. ## Real-world examples 1. Concentrated photovoltaic (CPV) systems 2. Spacecraft solar arrays 3. High-efficiency solar panels for specialized applications 4. Microinverters designed for multi-junction cells ## Why it matters Multi-junction solar cells are known for their high efficiency, especially in concentrated solar power or specialized applications like spacecraft. This patent addresses a challenge with these cells: optimizing power extraction from each individual junction. By converting each junction's output separately, the device can maximize the overall energy harvested, even if different junctions are performing differently due to varying light conditions or degradation. This approach can lead to more efficient solar power systems, particularly in niche high-performance solar markets. ## Frequently asked questions ### What does How a Special Box Turns Solar Panel Power into Home Electricity cover? This patent describes a device that takes the unique direct current (DC) electricity from each layer of a special multi-layer solar panel and converts it into alternating current (AC) electricity usable in homes, making sure to get the most power out of each layer. ### Who owns patent US 9391457? Sunlight Photonics owns this patent, granted in 2016. ### When does this patent expire? This patent is expected to expire on September 28, 2032, when the invention enters the public domain. ### What is patent US 9391457 cited by? This patent has been cited by 1 later patents that build on its ideas. ### What problem does this patent solve? Multi-junction solar cells are known for their high efficiency, especially in concentrated solar power or specialized applications like spacecraft. This patent addresses a challenge with these cells: optimizing power extraction from each individual junction. By converting each junction's output separately, the device can maximize the overall energy harvested, even if different junctions are performing differently due to varying light conditions or degradation. This approach can lead to more efficient solar power systems, particularly in niche high-performance solar markets. ### What does this patent NOT cover? Does not cover power conversion devices for single-junction solar cells. **Full plain-English explainer:** https://patentbrief.org/patent/us/9391457/apparatus-and-method-for-producing-ac-power **Original patent:** https://patents.google.com/patent/US9391457 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How to Make High-Efficiency Solar Cells with Stacked Layers](https://patentbrief.org/patent/us/9287431/superstrate-sub-cell-voltage-matched-multijunction-solar-cells) — This patent describes a solar cell design that stacks two different types of light-absorbing layers, cadmium telluride and silicon, connecting them in parallel to capture more sunlight efficiently. - [Solar Cells Made of Stacking Layers with Different Energy Gaps](https://patentbrief.org/patent/us/8912428/high-efficiency-multijunction-ii-vi-photovoltaic-solar-cells) — This patent describes a solar cell built by stacking multiple layers, each designed to capture a different part of the light spectrum for maximum energy conversion, achieving high efficiency. - [Solar Cells with Built-in Smart Electronics on the Back](https://patentbrief.org/patent/us/9293619/smart-photovoltaic-cells-and-modules) — This patent describes a solar cell design that integrates electronic components, like a bypass switch, directly onto the back of the cell to improve performance, especially when parts of the cell are shaded. - [How the First Practical Silicon Solar Cell Works](https://patentbrief.org/patent/us/2780765/solar-cell-photovoltaic) — A 1954 invention by Bell Labs researchers that created the first silicon-based solar cell capable of converting sunlight into enough electricity to power everyday devices. - [How Amorphous Silicon Changed Solar Power](https://patentbrief.org/patent/us/4064521/semiconductor-device-having-a-body-of-amorphous-silicon) — This 1976 patent describes using a specific form of non-crystalline silicon to create cheap, thin semiconductor devices like solar cells.