Preface: Architecting the "Energy Heart" for Urban Air Mobility – Discussing the Systems Thinking Behind Power Device Selection
In the transformative era of electrification reshaping urban transportation, the energy system of a premium passenger-grade eVTOL or low-altitude commuter aircraft is far beyond a mere assembly of battery cells and controllers. It is, more critically, an ultra-reliable, high-power-density, and intelligent electrical energy "hub." Its defining performance metrics—exceptional climb/cruise efficiency, robust and responsive thrust output, and flawless support for vital avionics—are fundamentally anchored in the power conversion and management architecture. This article adopts a holistic, co-optimization design philosophy to dissect the core challenges within the power chain of AAM vehicles: how, under the extreme constraints of specific power, ultimate reliability, stringent EMI/EMC standards, and harsh operational environments, can we select the optimal power semiconductor portfolio for the three critical nodes: the main propulsion inverter, high-voltage DC-DC/power distribution, and low-voltage auxiliary power management?
I. In-Depth Analysis of the Selected Device Combination and Application Roles
1. The Propulsion Powerhouse: VBP165C40 (650V SiC MOSFET, 40A, TO-247) – Main Propulsion Inverter Phase-Leg Switch
Core Positioning & Topology Deep Dive: Engineered as the core switch in a high-voltage (e.g., 800V bus) three-phase inverter driving high-RPM permanent magnet synchronous motors (PMSMs). Silicon Carbide technology is non-negotiable here for its ultra-fast switching, enabling high PWM frequencies (>50kHz) crucial for minimizing motor current ripple, torque pulsation, and filter passive size. The 650V rating provides robust margin for 400-500V battery systems and regenerative braking transients.
Key Technical Parameter Analysis:
Ultra-Low Conduction & Switching Loss: An RDS(on) of 50mΩ (@18V) ensures minimal conduction loss. Combined with SiC's inherently low Qg and Qrr, total losses are dramatically reduced compared to Si IGBTs or Super-Junction MOSFETs, directly translating to extended range and reduced thermal management burden.
High-Temperature Capability: SiC's superior material properties allow operation at higher junction temperatures, enhancing system power density and overload capability.
Selection Trade-off: Compared to high-current Si IGBTs (excessive switching loss at high frequency) or Si SJ-MOSFETs (higher Qrr, limited dV/dt), this SiC MOSFET represents the optimal balance for achieving maximum propulsion efficiency and power density in performance-critical aerial applications.
2. The High-Voltage Power Router: VBPB16R47SFD (600V SJ-Multi-EPI, 47A, TO-3P) – High-Voltage Non-Isolated DCDC / Intelligent Power Distribution Switch
Core Positioning & System Benefit: Serves as the primary switching element in high-voltage, high-power non-isolated DC-DC converters (e.g., for battery cell balancing, bus voltage regulation) or as a solid-state power controller (SSPC) for high-voltage load distribution (e.g., de-icing systems, high-power avionics). Its advanced Super-Junction Multi-EPI technology offers an excellent balance of low RDS(on) (70mΩ) and fast body diode performance.
Key Technical Parameter Analysis:
Efficiency & Ruggedness Balance: The low on-resistance minimizes conduction loss in continuously operating converters. The robust package and technology provide strong avalanche energy rating and dV/dt immunity, essential for the harsh electrical environment of an aircraft.
Fast Intrinsic Diode: Reduces reverse recovery losses in hard-switching topologies, improving converter efficiency and reliability without requiring external Schottky diodes.
Selection Rationale: For applications where the highest switching speed of SiC is not mandated but superior performance to standard planar MOSFETs is required, this SJ-MOSFET offers a cost-optimized, high-reliability solution for managing and converting high-voltage power within the aircraft.
3. The Auxiliary Power Conductor: VBED1806 (80V Trench MOSFET, 90A, LFPAK56) – Low-Voltage, High-Current Auxiliary Power Distribution & Non-Isolated DCDC Switch
Core Positioning & System Integration Advantage: Acts as the core switch for high-current, low-voltage (e.g., 28V or 48V) auxiliary power networks. Its extremely low RDS(on) of 6mΩ (@10V) is critical for minimizing voltage drop and power loss in paths supplying high-demand loads like flight control actuators, cabin environmental systems, or high-power communication units.
Key Technical Parameter Analysis:
Ultimate Conduction Performance: The ultra-low RDS(on) ensures virtually lossless power delivery, maximizing usable energy for critical systems and minimizing heat generation in confined spaces.
Advanced Package: The LFPAK56 (TO-263 variant) package offers an excellent thermal resistance-to-footprint ratio, facilitating efficient heat sinking through the PCB to the aircraft structure or cold plate.
Drive Optimization: Although RDS(on) is extremely low, gate charge (Qg) must be carefully managed with a capable driver to ensure swift switching, minimizing transition losses in PWM-controlled applications like point-of-load converters.
II. System Integration Design and Expanded Key Considerations
1. Topology, Drive, and Control Loop Synergy
Propulsion Inverter & Motor Controller: The gate drive for the VBP165C40 SiC MOSFETs must be ultra-low inductance, with precise dead-time control and active short-circuit protection, tightly synchronized with the high-performance motor controller executing Field-Oriented Control (FOC) or Direct Torque Control (DTC).
High-Voltage Power Management: Controllers for converters or SSPCs using VBPB16R47SFD must ensure smooth switching, with telemetry (current, temperature) fed back to the Vehicle Management Computer (VMC) for health monitoring and predictive maintenance.
Digital Auxiliary Load Management: The VBED1806 can be controlled via a dedicated Power Distribution Unit (PDU) microcontroller, enabling intelligent load shedding, priority-based sequencing, and millisecond-level fault isolation for critical 28V/48V systems.
2. Hierarchical and Aggressive Thermal Management Strategy
Primary Heat Source (Liquid Cold Plate): The VBP165C40 SiC modules in the propulsion inverter are the highest power density heat source, demanding direct integration with a liquid cooling jacket designed for high-altitude operation.
Secondary Heat Source (Forced Air/Liquid Coupled): Converters built with VBPB16R47SFD may utilize forced air cooling or share a secondary liquid cooling loop, depending on power levels and location within the airframe.
Tertiary Heat Source (PCB Conduction to Chassis): The VBED1806 and its associated PDU circuitry will rely on heavy copper planes, thermal vias, and direct mounting to a thermally conductive chassis or cold wall to dissipate heat.
3. Engineering Details for Aerospace-Grade Reliability
Electrical Stress & EMI Mitigation:
VBP165C40: Utilize low-inductance busbar design and optimized RC snubbers to manage voltage overshoot from motor winding inductance at high dV/dt.
VBPB16R47SFD: Implement careful layout to minimize parasitic loop inductance. Use gate resistors to tailor switching speed for an optimal EMI/efficiency trade-off.
All Devices: Employ robust gate protection (clamp Zeners, TVS) against transients.
Conservative Derating Practice:
Voltage Derating: Operational VDS/VDC stress should be ≤ 70-80% of rated BVDSS for MOSFETs and VCE for IGBTs, considering all transients.
Current & Thermal Derating: All current ratings must be derated based on worst-case junction temperature, using transient thermal impedance curves. Target maximum Tj < 125°C or lower as per reliability requirements. Pay special attention to single-event burnout (SEB) thresholds for high-voltage devices.
III. Quantifiable Perspective on Scheme Advantages
Quantifiable Efficiency & Range Gain: For a 200kW peak propulsion system, employing VBP165C40 SiC MOSFETs over best-in-class Si IGBTs can reduce total inverter losses by 40-60% at typical operating points, directly increasing mission range or payload capacity.
Quantifiable Power Density & Weight Savings: The combination of high-efficiency SiC and compact packages (LFPAK56, TO-3P) reduces heatsink mass and volume. Using VBED1806 for multiple high-current rails consolidates components, potentially reducing PDU weight by over 30% compared to discrete solutions.
Lifecycle Reliability & Cost: Selecting devices with robust technology (SiC, SJ-Multi-EPI) and applying stringent aerospace derating minimizes in-flight failure risk, reducing maintenance costs and maximizing vehicle availability, a critical metric for commercial AAM operations.
IV. Summary and Forward Look
This scheme provides a vertically optimized power chain for high-end passenger AAM vehicles, addressing the triumvirate of propulsion, high-voltage management, and auxiliary distribution with purpose-selected devices. Its core philosophy is "performance-matched system optimization":
Propulsion Level – Focus on "Ultimate Switching Performance": Leverage SiC technology to maximize system efficiency and power density, the key drivers for viable flight.
High-Voltage Power Level – Focus on "Robust Efficiency & Control": Utilize advanced SJ-MOSFETs for reliable and efficient management of the high-voltage electrical bus.
Auxiliary Power Level – Focus on "Ultimate Conduction & Integration": Employ ultra-low RDS(on) devices in advanced packages to minimize losses and space in constantly operating auxiliary systems.
Future Evolution Directions:
Higher Voltage & Integrated SiC Power Modules: As bus voltages trend toward 1000V+ for reduced cable weight, 1200V+ SiC half-bridge or phase-leg modules will become essential.
Wide-Bandgap for All High-Power Stages: Adoption of GaN HEMTs for very high-frequency auxiliary DC-DC converters, pushing power density boundaries further.
Fully Integrated Smart Power Switches: The use of Intelligent Power Switches (IPS) with embedded diagnostics, protection, and communication (e.g., SENT, CAN FD) for both high-voltage and low-voltage distribution, enabling true prognostics and health management (PHM).
This framework serves as a foundational guide, which engineers must refine based on specific aircraft parameters: operational voltage (e.g., 800V), peak/continuous power profiles, mission duty cycles, and the exact thermal management architecture, to realize a certifiable, high-performance AAM energy system.

Detailed Topology Diagrams