With the rapid development of autonomous driving technology and the commercialization of AI-powered urban mobility, the steering-wheel-free Robotaxi has become a flagship application for next-generation transportation. Its electric powertrain, auxiliary power systems, and safety-critical actuators, serving as the core energy conversion and control units, directly determine the vehicle’s operational efficiency, ride comfort, power consumption, and functional safety. The power MOSFET, as a key switching component in these systems, significantly impacts overall performance, electromagnetic compatibility, power density, and service life through its selection quality. Addressing the high-voltage, high-power, long-duration operation, and stringent safety requirements of Robotaxis, this article proposes a complete, actionable power MOSFET selection and design implementation plan with a scenario-oriented and systematic design approach.
I. Overall Selection Principles: System Compatibility and Balanced Design
The selection of power MOSFETs should not pursue superiority in a single parameter but achieve a balance among electrical performance, thermal management, package size, and reliability to precisely match the overall system requirements.
Voltage and Current Margin Design
Based on the system voltage levels (e.g., 12V/48V low-voltage bus, 400V/800V high-voltage traction platform), select MOSFETs with a voltage rating margin of ≥50% to handle switching spikes, voltage fluctuations, and regenerative braking back-EMF. Ensure sufficient current rating margins according to the load's continuous and peak currents. It is generally recommended that the continuous operating current does not exceed 60%–70% of the device’s rated value.
Low Loss Priority
Loss directly affects energy efficiency, range, and thermal management. Conduction loss is proportional to the on-resistance (Rds(on)), so devices with lower Rds(on) should be chosen. Switching loss is related to gate charge (Q_g) and output capacitance (Coss). Low Q_g and low Coss help increase switching frequency, reduce dynamic losses, and improve EMC performance, crucial for compact motor drives and DC-DC converters.
Package and Heat Dissipation Coordination
Select packages based on power level, space constraints under the vehicle chassis, and thermal conditions. High-power traction applications should use packages with low thermal resistance and low parasitic inductance (e.g., TO220, TO247, DFN). Low-power auxiliary circuits may opt for compact packages (e.g., TO252, SOT) for higher integration. PCB copper heat dissipation, thermal vias, and necessary thermal interface materials to heatsinks or cold plates should be considered during layout.
Reliability and Environmental Adaptability
In continuous public transport service scenarios, devices must withstand harsh automotive environments. Focus should be placed on the device’s operating junction temperature range, avalanche energy rating, electrostatic discharge (ESD) resistance, surge immunity, and parameter stability under thermal cycling and vibration.
II. Scenario-Specific MOSFET Selection Strategies
The main electrical loads of a Robotaxi can be categorized into three critical types: traction motor drive, high-power auxiliary conversion, and safety-critical actuator/ sensor control. Each load type has distinct operating characteristics, requiring targeted selection.
Scenario 1: Traction Inverter & High-Voltage DC-DC Conversion (Power Level: 20kW-100kW+)
The traction inverter and onboard high-voltage DC-DC converters are core to vehicle propulsion and energy distribution, requiring ultra-high efficiency, high power density, and robust reliability under high voltage.
Recommended Model: VBM165R32SE (Single N-MOS, 650V, 32A, TO220)
Parameter Advantages:
Utilizes SJ_Deep-Trench technology, offering an excellent balance of low Rds(on) (89 mΩ @10 V) and high voltage capability, minimizing conduction loss.
Rated voltage of 650V is suitable for 400V bus systems with sufficient margin; continuous current of 32A supports parallel use for higher power.
TO220 package provides good thermal performance and mechanical robustness, facilitating heatsink mounting.
Scenario Value:
Ideal for phases of traction inverter or high-voltage DC-DC converter primary-side switching, enabling high efficiency (>98%) and supporting high switching frequencies for magnetic component miniaturization.
High voltage rating ensures safety and reliability against bus voltage surges.
Design Notes:
Must be used with dedicated high-voltage gate driver ICs featuring isolation and desaturation protection.
Parallel connection requires careful attention to gate drive symmetry and current sharing.
Scenario 2: Low-Voltage, High-Current Auxiliary Power Distribution & DC-DC Synchronous Rectification (Power Level: 1kW-5kW)
Systems like 48V-to-12V DCDC, battery management system (BMS) load switches, and high-power accessory controllers demand extremely low conduction loss to maximize range and minimize heat generation.
Recommended Model: VBQA1301 (Single N-MOS, 30V, 128A, DFN8(5x6))
Parameter Advantages:
Extremely low Rds(on) of 1.2 mΩ (@10 V) using advanced Trench technology, virtually eliminating conduction loss.
Very high continuous current rating of 128A, easily handling peak currents in high-power auxiliary loads.
DFN package offers very low thermal resistance and parasitic inductance, optimal for high-frequency, high-current switching.
Scenario Value:
Perfect for main power path switching in BMS, high-current DC-DC converter synchronous rectification, or controlling high-power peripherals (e.g., climate compressor drivers), boosting system efficiency above 97%.
Compact size supports high power density design in crowded electronic control units (ECUs).
Design Notes:
PCB layout is critical: the exposed pad must be soldered to a large, thick copper area (recommended ≥500 mm²) with multiple thermal vias.
Requires a strong gate driver (capability ≥3A) to fully utilize its fast switching potential.
Scenario 3: Sensor, Communication Module & Actuator Control (Power Level: <500W)
Numerous low-to-medium power loads such as LiDAR, radar, computing unit power sequencing, and door/window actuators require compact, efficient, and MCU-friendly switches with good reliability.
Recommended Model: VBE1337 (Single N-MOS, 30V, 15A, TO252)
Parameter Advantages:
Low Rds(on) of 37 mΩ (@10 V) ensures minimal voltage drop and power loss.
Low gate threshold voltage (Vth ~1.7V) allows direct drive by 3.3V/5V microcontrollers without level shifters.
TO252 package provides a good balance of compact size, moderate thermal performance, and ease of assembly.
Scenario Value:
Enables intelligent power domain management for sensors and ECUs, allowing sleep/wake-up control to reduce quiescent power.
Suitable for driving medium-power actuators (e.g., brake pump motors, fan blowers) directly or via a driver stage.
Design Notes:
Add a small series gate resistor (e.g., 22Ω-100Ω) to dampen ringing when driven by an MCU.
For inductive loads, incorporate freewheeling diodes and snubber networks.
III. Key Implementation Points for System Design
Drive Circuit Optimization
High-Voltage/Power MOSFETs (e.g., VBM165R32SE): Use isolated gate driver ICs with sufficient drive current (≥2A) and integrated protection features (UVLO, DESAT). Focus on minimizing gate loop inductance.
Low-Voltage/High-Current MOSFETs (e.g., VBQA1301): Employ non-isolated but powerful gate drivers placed very close to the MOSFET. Use Kelvin connection for gate drive if possible.
Low-Power MOSFETs (e.g., VBE1337): Ensure MCU GPIO can provide adequate peak current; use gate series resistors and local decoupling.
Thermal Management Design
Tiered Strategy: Use liquid-cooled cold plates or large heatsinks for traction inverter MOSFETs (VBM165R32SE). For VBQA1301, rely on thick PCB copper layers connected to chassis ground or a heatsink via thermal pads. For VBE1337, natural convection via PCB copper is often sufficient.
Monitoring: Implement junction temperature estimation or direct sensing for critical MOSFETs to enable derating or shutdown.
EMC and Functional Safety Enhancement
Noise Suppression: Use RC snubbers across drain-source for high-voltage switches. Place ferrite beads on gate and power lines. Ensure proper shielding and grounding.
Protection Design: Incorporate TVS diodes at all input/output ports and gate pins. Implement hardware overcurrent, overtemperature, and short-circuit protection with fast response times (<1µs) for ASIL compliance.
Redundancy: For safety-critical functions, consider using redundant MOSFETs or driver paths.
IV. Solution Value and Expansion Recommendations
Core Value
Maximized Range and Efficiency: The combination of ultra-low Rds(on) (VBQA1301) and optimized high-voltage devices (VBM165R32SE) minimizes system losses, directly extending vehicle range.
Enhanced Functional Safety and Availability: Robust device selection paired with protection designs supports ASIL-B/C levels. Independent control of power domains (using VBE1337) improves system availability and fault isolation.
High Power Density and Reliability: Compact packages and efficient thermal design allow for smaller ECUs, while automotive-grade reliability ensures operation over a long service life.
Optimization and Adjustment Recommendations
Higher Power Traction: For 800V systems or higher power ratings, consider MOSFETs with 750V-900V ratings (e.g., VBP175R07) or parallel more VBM165R32SE devices.
Higher Integration: For space-constrained zones, consider using dual MOSFETs in smaller packages or Intelligent Power Modules (IPMs) that integrate drivers and protection.
Extreme Environments: For under-hood or exposed locations, select devices with wider temperature ranges and enhanced moisture resistance coatings.
Advanced Topologies: For next-generation zonal architectures, combine selected MOSFETs with multi-phase buck/boost controllers for optimal power delivery.
The selection of power MOSFETs is a cornerstone in designing the power and drive systems for AI City Robotaxis. The scenario-based selection and systematic design methodology proposed herein aim to achieve the optimal balance among efficiency, reliability, safety, and power density. As technology evolves, future exploration may include wide-bandgap devices (SiC, GaN) for even higher efficiency and switching frequencies, paving the way for lighter, longer-range, and more intelligent autonomous vehicles. In the era of smart urban mobility, superior hardware design remains the foundational enabler for safety, performance, and user trust.

Detailed Topology Diagrams