This invention introduces a compact bidirectional AC-DC converter that merges power factor correction and resonant conversion into a single multilevel stage. By reducing device count, passive size, and DC-link capacitance while achieving soft switching and >98% efficiency, it enables scalable, high-density power conversion for EV charging, grid storage, and aerospace systems.
High-power AC-DC converters are critical for applications like EV charging, renewable energy storage, and aerospace power systems. Conventional designs rely on separate power factor correction (PFC) and DC-DC stages, which increase semiconductor count, capacitor size, and filter complexity. These architectures suffer from switching losses, high voltage stress, and limited scalability, preventing the compact, efficient, and reliable power conversion demanded by next-generation energy systems.
This invention presents a tapped-series multilevel converter where switches are paired with capacitor strings and interconnected by diode networks. The architecture evenly divides voltage stress while enabling bidirectional current across stepped voltage levels. In a three-level implementation, six switches, two capacitors, and two diode strings create three voltage states at AC ports while maintaining capacitor voltage balance. This eliminates the need for a separate PFC stage, reduces DC-link capacitance, and allows soft switching across operating modes. Prototypes have demonstrated functionality under both single-phase and three-phase inputs with high efficiency and reduced harmonic distortion.
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• Reduces semiconductor count by up to 12 devices in 3-phase systems
• Achieves predominantly soft switching with efficiencies above 98%
• Cuts DC-link capacitance size and cost by up to 50%
• Enables smaller filters with lower harmonic distortion and ripple
• Increases power density through reduced size of switches, capacitors, and magnetics
• Reduces device stress, allowing higher-efficiency MOSFET usage
• Scalable to N-level extension for medium-voltage systems
• Supports fully bidirectional power flow for charging and grid export
• Simplifies filter design and reduces EMI via triplen harmonic cancellation
• Lowers bill of materials and system cost with fewer passives and switches
• Bidirectional EV charging and vehicle-to-grid integration
• Grid-tied renewable energy inverters and storage systems
• Medium-voltage industrial motor drives and automation equipment
• Aerospace and aviation lightweight high-density power electronics
• Smart warehouse and logistics vehicle chargers with grid support capability
• US Provisional Application 63/087,174 – Filed 10/02/2020 (Converted)
• US Patent 11,689,115 – Application 17/449,875, Filed 10/04/2021, Granted 06/27/2023, Published as US 2022-0109381 A1
Prototype validated – Demonstrated functionality under both single-phase and three-phase AC inputs with high efficiency and reduced harmonic distortion. TRL ~4–5.
This technology is available for licensing.
Strong potential for adoption in EV charging, grid energy storage, and aerospace industries seeking high-efficiency, compact, and scalable bidirectional power conversion solutions.
Prototype converter data, harmonic distortion test results, and N-level scalability models are available upon request.