With the rapid development of urban air mobility (UAM), electric vertical take-off and landing (eVTOL) air taxis have become a transformative solution for short-range transportation. The propulsion inverter, high-voltage auxiliary power distribution, and critical system load switches, serving as the "propulsion heart, power arteries, and safety synapses" of the vehicle, demand power conversion with utmost efficiency, reliability, and power density. The selection of power MOSFETs is critical for system performance, weight, thermal management, and operational safety. Addressing the stringent requirements of eVTOLs for high thrust-to-weight ratio, extended range, extreme reliability, and harsh operating environments, this article develops a scenario-optimized MOSFET selection strategy.
I. Core Selection Principles and Scenario Adaptation Logic
(A) Core Selection Principles: Four-Dimensional Aerial Adaptation
MOSFET selection requires coordinated adaptation across four dimensions—voltage, loss, package, and reliability—ensuring robust performance under aerial operational stresses:
High Voltage & Robustness: For high-voltage propulsion buses (typically 400V-800V), reserve a rated voltage margin of ≥50% to handle regenerative braking spikes, altitude-related derating, and transients. Prioritize devices with avalanche energy rating and high VDS capability.
Ultra-Low Loss Priority: Prioritize devices with extremely low Rds(on) and optimized gate charge (Qg) to minimize conduction and switching losses. This is paramount for maximizing flight time (range) and reducing thermal load on the limited cooling system.
Package for Harsh Environment: Choose packages with excellent thermal performance (low RthJC) and mechanical robustness (e.g., TO-263, TO-220F) for high-power stages. For distributed load points, compact and vibration-resistant packages (e.g., LFPAK, SOT) are key for power density and reliability.
Military-Grade Reliability: Components must exceed automotive-grade standards, with wide junction temperature range (e.g., -55°C ~ 175°C), high tolerance to vibration, and proven long-term reliability under thermal cycling, adapting to the safety-critical nature of aviation.
(B) Scenario Adaptation Logic: Categorization by Power Train Function
Divide loads into three core aerial scenarios: First, the Main Propulsion Inverter (thrust core), requiring the highest voltage, current, and efficiency. Second, High-Voltage Auxiliary Power Conversion (system support), requiring efficient step-down for avionics and subsystems. Third, Critical System & Safety Load Switching (isolation core), requiring reliable, fast, and independent control of essential loads for redundancy and fault management.
II. Detailed MOSFET Selection Scheme by Scenario
(A) Scenario 1: Main Propulsion Inverter (50kW-200kW per motor) – Thrust Core Device
Propulsion motors demand handling very high continuous and peak phase currents with utmost efficiency and switching frequency to optimize motor control and weight.
Recommended Model: VBL19R20S (N-MOS, 900V, 20A, TO-263)
Parameter Advantages: Super Junction (SJ_Multi-EPI) technology achieves a balanced low Rds(on) of 270mΩ at 10V alongside high voltage blocking (900V). The 20A continuous rating is suitable for multi-parallel configurations in bridge legs. The TO-263 (D2PAK) package offers excellent power handling and thermal interface to heatsinks.
Adaptation Value: Enables efficient inverter design for 400V-600V DC bus systems. Its high voltage rating provides robust protection against transients. When used in parallel, it facilitates scalable power stages, contributing to a power density >20kW/kg for the inverter. Supports high PWM frequencies for precise motor control.
Selection Notes: Verify phase current requirements and design for parallel operation with current sharing. Must be mounted on a liquid-cooled or forced-air heatsink. Requires a dedicated high-performance gate driver with negative voltage turn-off capability for safe operation.
(B) Scenario 2: High-Voltage Auxiliary DC-DC Converter – System Support Device
Isolated or non-isolated DC-DC converters step down the high-voltage bus (e.g., 400V) to low-voltage rails (e.g., 28V, 12V) for avionics, fans, and sensors, demanding high efficiency.
Recommended Model: VBMB1607V3 (N-MOS, 60V, 120A, TO-220F)
Parameter Advantages: Advanced Trench technology achieves an ultra-low Rds(on) of 5mΩ at 10V (38mΩ at 4.5V), minimizing conduction loss. The 120A current rating is exceptional. The TO-220F (fully isolated) package simplifies heatsink mounting and improves isolation safety.
Adaptation Value: Ideal for the synchronous rectification (SR) stage of high-current, low-voltage output DC-DC converters. Its extremely low Rds(on) boosts converter peak efficiency to >97%, directly reducing thermal burden and increasing system-level efficiency. The isolated package enhances design flexibility.
Selection Notes: Perfect for 28V or 48V output power stages. Ensure the driver can provide high peak current for fast switching of this high-power device. Pay close attention to PCB layout to minimize parasitic inductance in the high-di/dt SR loop.
(C) Scenario 3: Critical System & Safety Load Switch – Isolation Core Device
Critical loads (backup flight controllers, communication modules, safety actuators) require fail-safe, independent, and compact load switches for power sequencing and fault isolation.
Recommended Model: VB2240 (P-MOS, -20V, -5A, SOT23-3)
Parameter Advantages: Ultra-compact SOT23-3 package saves critical board space. Very low Rds(on) of 34mΩ at 4.5V minimizes voltage drop. Low gate threshold voltage (Vth = -0.6V) allows direct, efficient control by 3.3V MCU GPIOs even at low temperatures.
Adaptation Value: Enables distributed, intelligent power management for numerous low-power but critical subsystems. Facilitates implementation of redundancy architectures (e.g., dual-channel power feeds) with independent switching. Fast switching ensures quick response to fault detection commands.
Selection Notes: Confirm load current is well within the -5A rating with margin. Ideal for 12V or lower power rails. For high-side switching with an N-MOS driver, ensure proper level translation. Incorporate inrush current limiting for capacitive loads.
III. System-Level Design Implementation Points
(A) Drive Circuit Design: Matched to Aerial Demands
VBL19R20S: Pair with isolated, high-current gate driver ICs (e.g., Si827x, UCC5350) featuring desaturation detection and soft turn-off. Implement strong negative gate bias (e.g., -5V) for robust turn-off against Miller effect in high-noise environment.
VBMB1607V3: Use a driver with >2A source/sink capability. Optimize gate drive loop layout. A small gate resistor (1-5Ω) can balance switching speed and ringing.
VB2240: Can be driven directly by MCU GPIO with a small series resistor (22-100Ω). For extra robustness in noisy areas, add a simple NPN buffer stage.
(B) Thermal Management Design: Aggressive and Redundant
VBL19R20S (Propulsion): Mandatory liquid cooling or extreme forced air cooling. Use thermal interface material (TIM) with high conductivity. Monitor junction temperature via NTC or driver IC feedback.
VBMB1607V3 (DC-DC): Mount on a dedicated heatsink, either forced-air cooled or coupled to the main cold plate. Size heatsink based on worst-case loss calculations.
VB2240 (Load Switch): Local copper pour is typically sufficient. Ensure overall board airflow for derating.
System-Level: Implement redundant cooling or monitor coolant flow. Position MOSFETs to benefit from primary cooling paths.
(C) EMC and Reliability Assurance for Airworthiness
EMC Suppression:
VBL19R20S: Implement RC snubbers across each switch or phase output. Use laminated DC-link busbars to minimize parasitic inductance. Shield motor cables.
Overall: Implement strict zoning (high-power, low-power, digital). Use ferrite chokes on all cable penetrations. Employ EMI filters at all power inputs/outputs.
Reliability Protection:
Derating: Apply stringent derating rules (e.g., voltage ≤70%, current ≤60% at max junction temperature).
Fault Protection: Implement hardware overcurrent protection (desaturation detection) for VBL19R20S. Use current sense amplifiers or shunts for VBMB1607V3 stage.
Transient Protection: Place TVS diodes at all input power ports and near sensitive load switches (VB2240). Use varistors for surge protection.
IV. Scheme Core Value and Optimization Suggestions
(A) Core Value
Maximized Range & Performance: Ultra-low loss devices directly extend flight time and improve thrust efficiency, a key competitive metric.
Aviation-Grade Safety & Redundancy: The selected devices enable robust, fault-tolerant architectures critical for airworthiness certification.
Optimal Power Density & Weight: The combination of high-performance dies and appropriate packages achieves an excellent balance of power handling and weight, crucial for eVTOLs.
(B) Optimization Suggestions
Higher Power Propulsion: For larger aircraft or higher bus voltages (>600V), consider paralleling VBL19R20S or evaluating 1200V SiC MOSFETs for the next performance leap.
Higher Current Auxiliary Power: For very high-power DC-DC (e.g., >5kW), parallel multiple VBMB1607V3 devices or consider using LFPAK88 packaged devices like VBED1303 for even lower loss.
Integration for Redundancy: Use multi-channel load switch ICs (based on technology like VB2240) for centralized management of critical loads, saving space and simplifying control.
Specialized Environments: For extreme low-temperature high-altitude operation, select variants with guaranteed Vth and Rds(on) performance at -55°C. For the highest reliability zones, seek devices with extended screening or space-grade pedigree.
Conclusion
Power MOSFET selection is central to realizing the efficiency, safety, and reliability targets of eVTOL air taxi propulsion and power systems. This scenario-based selection strategy, focusing on the main inverter, auxiliary power, and critical load switching, provides a practical foundation for robust electrical design. Future development will inevitably leverage Wide Bandgap (WBG) devices like GaN and SiC to push the boundaries of power density and efficiency, enabling the next generation of sustainable urban air transportation.

Detailed Topology Diagrams