SolarEgg™: redefining the microinverter architecture for next-generation solar systems

In photovoltaic systems, the market has historically been forced to choose between two different approaches: the installation cost advantage of string inverters and the higher energy harvesting enabled by module-level power electronics, such as microinverters. String inverters benefit from lower upfront system cost and simpler installation economics, but they operate with limited granularity: when one panel is shaded, dirty, mismatched or degraded, the performance of the entire string is significantly affected. Microinverters, on the other hand, maximize the energy extracted from each individual panel and provide superior flexibility, monitoring and fault isolation, but traditionally this has come at the cost of a more complex architecture, higher BOM and higher initial system cost.

Eggtronic developed SolarEgg™ to remove this trade-off.

SolarEgg™ is a proprietary microinverter platform designed to bring the benefits of module-level power conversion — panel-level MPPT, higher energy harvesting, flexible installation and improved resilience to mismatch — into a cost range historically associated with string-based architectures.

The key limitation of conventional microinverters is architectural complexity. Traditional solutions typically require multiple conversion stages, including MPPT, isolated DC/DC conversion, DC/AC conversion and often an unfolding stage, repeated several times for each single microinverter. This increases the number of active and passive components, impacts cost, affects size and can limit large-scale adoption in cost-sensitive solar applications.

Eggtronic’s approach is based on an advanced evolution of the cycloconverter concept. Historically, cycloconverter-based microinverter architectures have been considered attractive for reducing conversion stages and system cost, but they faced a critical implementation challenge: achieving high efficiency and high power density required either expensive, high-performance control ICs, or lower switching frequencies, which increased magnetics size and reduced compactness.

Eggtronic solves this bottleneck by combining SolarEgg proprietary power topology with an EPIC™ controller capable of cost-effectiveness, and operating at very high switching and control frequencies, above 1 MHz.

This enables a microinverter architecture with:

• High energy conversion efficiency in every working point
• Reduced and lower cost BOM
• Smaller magnetics and passive components
• High power density
• Reduced thermal stress
• Simplified system architecture
• Improved scalability for high-volume solar applications

The result is a new class of microinverter platform that preserves the energy-harvesting and flexibility advantages of microinverters while matching the cost-efficiency of string inverters.

Technology comparison: Why SolarEgg™ is different

Technical deep dive: why the SolarEgg™ DAB cycloconverter outperforms conventional LLC-based microinverter architectures

Most conventional microinverter architectures rely on a multi-stage power conversion chain. A typical implementation includes a front-end MPPT boost stage, followed by an isolated resonant DC/DC converter — often based on an LLC topology — and then an unfolding bridge to generate the AC grid waveform. While this approach is well understood, it introduces two structural limitations: conversion losses accumulate across multiple stages, and the bill of materials increases due to the number of power switches, drivers, magnetics, resonant components, controllers and protection circuits required.

SolarEgg™ takes a different architectural path.

At its core, SolarEgg™ is based on Eggtronic’s proprietary single-stage DAB cycloconverter architecture. Instead of processing energy through several cascaded conversion stages, SolarEgg™ performs isolated high-frequency power conversion and grid-synchronized DC/AC generation in a more direct and integrated way.

This is particularly relevant in solar applications, where the operating point changes continuously during the day due to irradiance variation, shading, cloud transients and module mismatch. Conventional LLC-based architectures can be highly efficient around their optimized operating point, but maintaining best-in-class efficiency across a wide input-voltage and load range is challenging. In contrast, the SolarEgg™ DAB cycloconverter is designed to preserve high efficiency across a much broader operating envelope.

The key advantages are:

Native isolated bidirectional power processing
The DAB structure is inherently suited to controlled bidirectional power flow, while providing galvanic isolation through the high-frequency transformer. This makes the architecture well aligned not only with photovoltaic microinverters, but also with future grid-interactive and storage-oriented applications.

Adaptive Zero-Voltage Switching across the operating range
In many power converters, soft-switching conditions are lost at light load or under non-ideal operating points, causing additional switching losses, higher thermal stress and worse EMI behavior. SolarEgg™ is designed to maintain Zero-Voltage Switching across the relevant operating range, enabling a flatter efficiency curve, reduced heat generation and improved electromagnetic performance.

Elimination of the unfolding stage
By using bidirectional GaN devices and a proprietary cycloconverter-based power path, SolarEgg™ can generate the AC waveform without requiring a separate unfolding bridge. This reduces the number of power devices, gate drivers, passive components and control interfaces, directly improving BOM, size, efficiency and reliability.

EPIC™: The control engine behind SolarEgg™

This topology would not be practical with a conventional microcontroller or a standard low-cost ASIC. SolarEgg™ is enabled by Eggtronic’s EPIC™ controller family — mixed-signal power controllers specifically designed for next-generation power conversion.

The critical differentiator is Eggtronic’s proprietary Virtual-ASIC technology. EPIC™ can configure and interconnect analog peripherals, digital peripherals and hardware accelerators to create dedicated, flexible control structures inside the chip. These virtual ASICs can close critical voltage and current feedback loops directly in hardware, at every switching cycle, with extremely low latency and very high control bandwidth, while ensuring the flexibility of microcontroller-based solutions.

This approach offloads the internal RISC-V core from time-critical real-time control tasks. Instead of continuously executing high-frequency control loops in software, the RISC-V core is used to configure the optimized virtual ASICs for each operating condition, manage protocols, supervise I/Os, handle diagnostics and coordinate higher-level system behavior.

Applied to SolarEgg™, this enables several system-level advantages:

Switching frequencies above 1 MHz
High-speed deterministic control allows SolarEgg™ to operate stably above 1 MHz. This dramatically reduces the size of the transformer and inductive components, lowering magnetics cost, copper content, weight and overall system volume.

Lower control ripple and smaller capacitors
The ability to close cycle-by-cycle feedback loops with very low latency reduces control ripple and dynamic error. This allows the system to reduce the size and cost of capacitive elements while preserving stable operation and power quality.

Proprietary Variable Frequency Modulation
EPIC™ enables Eggtronic’s proprietary Variable Frequency Modulation strategy, which dynamically minimizes reactive currents and preserves soft-switching conditions. The result is a high and flat efficiency profile across operating conditions, together with excellent grid waveform quality and THD below 3%.

Precise timing for bidirectional GaN devices
SolarEgg™ is a topology that requires extremely accurate timing, including fine dead-time control and fast gate-drive coordination. EPIC™ provides the deterministic timing needed to fully exploit bidirectional GaN devices, reduce switching losses and maintain safe, efficient operation at high frequency.

In summary, SolarEgg™ is not simply a different power topology. It is a tightly integrated combination of proprietary power architecture, high-frequency GaN operation and EPIC™ real-time mixed-signal control. This is what allows Eggtronic to achieve microinverter-level energy harvesting with a simplified single-stage architecture, reduced BOM, compact magnetics and industry-leading efficiency.

Record efficiency with cost-optimized components

The SolarEgg™ 500W reference design achieves a 96.1% CEC weighted efficiency, with a remarkably flat efficiency curve from light load to full load. This is a critical point for solar applications, where the converter rarely operates at a single fixed point and must maintain high performance across changing irradiance, temperature and module conditions.

Importantly, these results are achieved while using cost-optimized bidirectional GaN devices, including devices based on Renesas GaN technology, with twice higher on-resistance than the devices typically selected for peak-performance demonstrators. This was an intentional engineering choice: the goal was not to build a laboratory prototype using the most expensive components available, but to prove that the patented SolarEgg™ architecture itself is the key enabler of high efficiency, reduced BOM and compact implementation.

In other words, the performance comes primarily from the topology, the control strategy and the EPIC™ controller — not from over-engineering the power stage with high-cost components.

Higher reliability through fewer components

In power electronics, what is not present in the system cannot fail. SolarEgg™ simplified BOM is therefore not only a cost advantage, but also a reliability advantage.

The single-stage DAB cycloconverter architecture reduces the number of power conversion blocks, active switches, gate drivers, magnetic components and passive elements typically required in conventional multi-stage microinverters. This directly reduces component count, assembly complexity and potential failure points.

The reliability benefits are structural:

Lower heat generation
High conversion efficiency reduces thermal losses, limiting the need for large, expensive and bulky heat sinks.

Lower component stress
Reduced operating temperatures help extend the lifetime of electrolytic or film capacitors, magnetic components and other thermally sensitive parts.

More compact mechanical design
High-frequency operation and reduced magnetics size enable a compact architecture, which is particularly valuable for outdoor module-level installations exposed to temperature cycles, humidity and mechanical stress.

Soft-switching operation
Adaptive Zero-Voltage Switching reduces switching losses, electrical stress and EMI, improving both efficiency and long-term robustness.

Where SolarEgg™ delivers the highest value

SolarEgg™ is particularly valuable in installations where conventional string architectures show their limitations and where standard microinverters remain constrained by cost or complexity.

Typical high-value use cases include:

• Roofs with multiple orientations
• Partially shaded installations caused by trees, chimneys, antennas or nearby buildings
• Fragmented rooftops with irregular module placement
• Systems expected to expand progressively over time
• Installations requiring module-level monitoring and localized maintenance
• Residential and commercial applications where energy harvesting, safety, compactness and cost must be optimized together

In these scenarios, module-level power conversion can unlock higher energy yield and greater design flexibility. SolarEgg™ aims to deliver these advantages with a simplified architecture and a cost structure designed for broader adoption.

Opportunity for solar OEMs

For solar system manufacturers, the 500W SolarEgg™ reference design — ERD00718 — provides a highly optimized starting point to accelerate product development.

The platform is designed to support:

• Fast time-to-market through a pre-validated reference architecture
• High weighted efficiency with a flat operating profile
• Excellent cost and performance of the EPIC IC controller
• Reduced BOM and simplified system architecture
• Compact module-level integration
• Scalability across different power ratings with limited redesign effort
• Grid-compliant operation, including THD below 3%
• A clear path toward differentiated microinverter products

For OEMs, SolarEgg™ is not only a reference design; it is a technology platform that can be adapted to specific cost, power, grid and mechanical requirements.

Conclusion

SolarEgg™ addresses the historical trade-off between string inverters and conventional microinverters. String inverters offer low upfront cost but limited module-level optimization. Traditional microinverters provide superior energy harvesting and flexibility, but with higher BOM, higher complexity and higher system cost.

SolarEgg™ is designed to bridge this gap.

It combines a proprietary single-stage DAB cycloconverter architecture, high-frequency GaN operation and EPIC™ real-time mixed-signal control to deliver module-level energy harvesting with high efficiency, reduced BOM cost, compact magnetics and strong scalability.

The result is a microinverter platform that brings high-performance module-level power conversion closer to the cost structure required for mass-market solar adoption.