Preface: Architecting the "Power Heart" for Urban Air Mobility – Discussing the Systems Thinking Behind Power Device Selection in eVTOLs
In the emerging era of Urban Air Mobility (UAM), the performance of an electric Vertical Take-Off and Landing (eVTOL) aircraft, especially for demanding operations like coordinated wedding fleets, hinges on more than just battery energy density and motor power. It critically depends on a supremely reliable, efficient, and lightweight electrical power distribution and conversion system. Core metrics—flight time, payload capacity, safety redundancy, and smooth, quiet operation—are fundamentally governed by the power electronics that manage energy from the high-voltage battery to the propulsion motors and essential avionics.
This article adopts a holistic, safety-critical design mindset to address the core challenges within the eVTOL power chain: how to select the optimal power MOSFETs for the key nodes of high-frequency propulsion inversion, high-voltage distribution/conversion, and critical low-voltage auxiliary power management, under the extreme constraints of ultra-high power density, stringent reliability (DO-254/DO-160 considerations), severe weight limits, and demanding thermal environments.
Within an eVTOL's powertrain, the power conversion modules are the decisive factor for system efficiency, thrust-to-weight ratio, and operational safety. Based on comprehensive analysis of high-voltage handling, high-frequency switching capability, low conduction loss, and compact integration, this article selects three key devices to construct a hierarchical, optimized power solution for aerial fleet applications.
I. In-Depth Analysis of the Selected Device Combination and Application Roles
1. The Thrust Generator Core: VBQE165R20SE (650V, 20A, 150mΩ, DFN8X8, SJ_Deep-Trench) – Main Propulsion Inverter Phase-Leg Switch
Core Positioning & Topology Deep Dive: Designed as the primary switch in multi-phase, high-frequency motor drive inverters for lift and cruise propulsors. Its Super-Junction Deep-Trench technology delivers an exceptional balance of very low Rds(on) and low gate charge (Qg), making it ideal for high-frequency (50kHz-100kHz+) Field-Oriented Control (FOC) or direct drive schemes. The 650V rating is tailored for common 400-500V aircraft battery systems.
Key Technical Parameter Analysis:
Ultra-Low Loss for Maximum Efficiency: An Rds(on) of 150mΩ at 10V VGS ensures minimal conduction loss at high motor phase currents. Combined with fast switching characteristics inherent to SJ technology, it maximizes inverter efficiency, directly extending flight endurance.
Power Density Champion: The DFN8X8 (8x8mm) package offers an outstanding thermal footprint and low parasitic inductance, enabling compact, low-inductance phase-leg layouts essential for high di/dt and dv/dt operation. This is crucial for minimizing inverter volume and weight.
Selection Trade-off: Compared to standard planar MOSFETs or IGBTs, this SJ MOSFET offers significantly lower switching loss at high frequencies, enabling smaller magnetics and filters. It represents the optimal choice for maximizing power density and efficiency in the core propulsion path.
2. The High-Voltage Power Router: VBM18R10S (800V, 10A, 600mΩ, TO220, SJ_Multi-EPI) – High-Voltage DC Link Distribution & Isolated DC-DC Primary Switch
Core Positioning & System Benefit: Serves a dual role: as a solid-state power controller (SSPC) for high-voltage bus segmentation and fault isolation, and as the primary side switch in isolated, high-voltage auxiliary DC-DC converters (e.g., for avionics). Its 800V rating provides robust margin for 600V+ battery systems and voltage transients.
Key Technical Parameter Analysis:
High-Voltage Ruggedness: The 800V VDS and SJ Multi-EPI technology ensure reliable operation in the demanding electrical environment of an eVTOL, where bus voltage can spike during regenerative events or fault conditions.
Balanced Performance: With a moderate Rds(on) of 600mΩ, it handles the relatively lower continuous currents typical of distribution and DC-DC conversion (compared to propulsion) efficiently. The TO-220 package facilitates excellent thermal coupling to a heatsink or cold plate in centralized power units.
System Safety & Redundancy: Enables the implementation of redundant power lanes. It can intelligently disconnect a faulty battery module or power channel under VCU command, enhancing overall system safety and availability—a critical feature for multi-aircraft wedding fleets.
3. The Avionics Guardian: VBA3695 (60V, 4A, 95mΩ, SOP8, Dual-N+N, Trench) – Critical Low-Voltage Avionics & Sensor Power Distribution Switch
Core Positioning & System Integration Advantage: This dual N-channel MOSFET in a single SOP8 package is the cornerstone of intelligent, fault-tolerant power distribution for mission-critical 28V/12V avionics loads, such as Flight Control Computers (FCC), sensors, communication radios, and navigation lighting.
Application Example: Allows independent, software-controlled power sequencing and fast shutdown of individual critical loads in case of anomalies. Enables load shedding strategies to preserve power for essential systems.
PCB Design Value: Dual integration in a compact SOP8 package saves vital PCB real estate in the avionics bay, simplifies gate drive routing for low-side switches, and increases the reliability of the Power Management Unit (PMU).
Reason for Dual N-Channel Configuration: While requiring a gate drive above the source voltage (often using a simple charge pump or bootstrap circuit), N-channel MOSFETs offer significantly lower Rds(on) for the same die size compared to P-channel devices. This configuration is chosen for its superior efficiency in managing the continuous, vital power flows to avionics, where every watt of loss matters.
II. System Integration Design and Expanded Key Considerations
1. Topology, Drive, and Control Loop
Propulsion Inverter & Motor Controller Synergy: The gate drivers for the VBQE165R20SE must be ultra-fast, low-inductance, and placed in close proximity to achieve precise PWM timing for smooth motor torque. Their status and temperature must be monitored by the Motor Control Unit (MCU).
High-Voltage Management: The VBM18R10S, when used as an SSPC, requires a robust, isolated gate driver with clear fault feedback to the Vehicle Management System (VMS). In DC-DC applications, its switching must be synchronized with the converter controller.
Intelligent Avionics Power Sequencing: The gates of the VBA3695 are controlled by the VMS or a dedicated PMU, enabling programmable soft-start, priority-based power-up, and microsecond-level overcurrent protection to safeguard sensitive avionics.
2. Hierarchical Thermal Management Strategy
Primary Heat Source (Liquid Cold Plate Integration): The VBQE165R20SE arrays in the propulsion inverter are the highest power density heat sources. They must be directly mounted on a liquid-cooled cold plate designed for minimal thermal impedance.
Secondary Heat Source (Forced Air/Liquid Cooling): The VBM18R10S devices in the high-voltage power distribution unit may be consolidated on a shared heatsink, cooled by forced air or a secondary liquid loop.
Tertiary Heat Source (Conduction to Chassis): The VBA3695 and associated avionics PMU circuitry rely on thermal vias and PCB conduction to transfer heat to the aircraft structure or a localized heatsink.
3. Engineering Details for Reliability Reinforcement
Electrical Stress Protection:
VBQE165R20SE: Requires careful layout to minimize stray inductance. RC snubbers may be necessary across each switch to dampen high-frequency ringing caused by package and loop inductance.
VBM18R10S: Needs clamping circuits (TVS/varistors) at its drain to handle voltage spikes from long cable inductance in the distribution harness.
VBA3695: Loads like avionic solenoids or motors require freewheeling diodes.
Enhanced Gate Protection: All gate drives must be protected against overshoot and undershoot with Zener diodes. Series resistors must be optimized for EMI and switching loss trade-offs.
Derating Practice:
Voltage Derating: VBM18R10S VDS stress should be kept below 640V (80% of 800V). VBQE165R20SE stress below 520V.
Current & Thermal Derating: All device currents must be derated based on worst-case junction temperature, using transient thermal impedance curves. Maximum Tj during continuous operation should be conservatively targeted (e.g., <110°C) to ensure long-term reliability under all flight profiles.
III. Quantifiable Perspective on Scheme Advantages and Competitor Comparison
Quantifiable Efficiency & Weight Improvement: Using VBQE165R20SE in a 100kW per motor propulsion inverter can reduce total switching and conduction losses by over 25% compared to standard MOSFETs, directly increasing hover time. The compact package reduces inverter weight and volume.
Quantifiable Safety & Integration Improvement: Using VBA3695 to manage dual redundant power paths for avionics saves >40% PCB area versus discrete solutions, while providing independent fault isolation—directly improving system-level Functional Safety metrics.
Lifecycle & Operational Reliability: The selected high-reliability-appropriate devices, combined with robust protection and derating, minimize in-flight failure risks, ensuring high dispatch reliability for the commercial air wedding service.
IV. Summary and Forward Look
This scheme provides a cohesive, optimized power chain for eVTOL air wedding fleets, addressing the unique needs from high-voltage propulsion to fault-tolerant avionics. Its essence is "performance-critical optimization with safety-first integration":
Propulsion Level – Focus on "Ultra-High Frequency & Density": Leverage best-in-class SJ MOSFETs for maximum efficiency and minimal inverter size/weight.
High-Voltage Distribution Level – Focus on "Robustness & Safety": Utilize high-voltage SJ devices for reliable energy routing and isolation, forming the backbone of electrical system safety.
Avionics Power Level – Focus on "Fault-Tolerant Intelligence": Employ integrated multi-channel switches for compact, smart, and redundant management of critical loads.
Future Evolution Directions:
Gallium Nitride (GaN) HEMTs: For next-generation ultra-high frequency (>500kHz) propulsion and ultra-compact DC-DC converters, GaN devices can further reduce losses and passive component size.
Fully Integrated Smart Power Switches: Adoption of IPS or IntelliFETs with built-in diagnostics, current sensing, and protection for both high-voltage distribution and low-voltage avionics paths will simplify design and enhance system health monitoring.
Engineers can refine this framework based on specific eVTOL parameters: battery voltage (e.g., 800V), total propulsion power, redundancy architecture (e.g., triplex), and thermal management strategy, to design optimal power systems for safe and spectacular urban air mobility.

Detailed Power Chain Topology Diagrams