The power chain in shared mobility EVs is critical for ensuring consistent performance, maximizing vehicle uptime, and minimizing total cost of ownership across diverse driving patterns and users. Unlike privately-owned vehicles, shared cars demand exceptional reliability under frequent start-stop cycles, varying driver behaviors, and the need for rapid turnaround between rentals. A robust and efficient power chain is the cornerstone for achieving dependable daily operation, efficient energy utilization, and long-term durability with minimal maintenance.
The design challenge centers on creating a system that balances cost-effectiveness for large fleets with the rigorous demands of continuous public use. How to select components that offer the best trade-off between performance and price? How to ensure electrical and thermal reliability in a compact, mass-producible package? How to integrate intelligent power management for optimal range and battery health? The answers are embedded in the strategic selection and application of core power semiconductors.
I. Three Dimensions for Core Power Component Selection: Coordinated Consideration of Voltage, Current, and Topology
1. Main Drive Inverter MOSFET: Balancing Performance and Cost for Fleet Vehicles
The key device selected is the VBL17R20S (700V/20A/TO-263, SJ_Multi-EPI).
Voltage Stress and Technology Advantage: For shared EVs typically using 400V DC platforms, a 700V rating provides ample margin for voltage spikes. The Super Junction (SJ_Multi-EPI) technology is the key differentiator. Compared to planar MOSFETs, it offers significantly lower specific on-resistance (RDS(on) of 210mΩ @10V), directly translating to reduced conduction losses during high-torque urban acceleration—a common scenario in shared driving cycles. The TO-263 (D2PAK) package offers a good balance of power handling, thermal performance, and automated assembly compatibility for high-volume manufacturing.
Efficiency and Thermal Considerations: The low RDS(on) minimizes heat generation at typical urban driving currents. This allows for a simpler, more cost-effective thermal interface (e.g., thermal pad to chassis) compared to liquid cooling, reducing system complexity and cost—a vital factor for fleet economics. The fast switching capability of SJ technology also contributes to lower switching losses at moderate frequencies.
2. DC-DC Converter MOSFET: Prioritizing High Current Density and Efficiency
The key device selected is the VBPB1102N (100V/65A/TO-3P, Trench).
High-Power, Compact Auxiliary Power Supply: The primary 12V/24V system in shared EVs powers critical loads like ECUs, lighting, infotainment, and locking systems. The VBPB1102N, with its ultra-low RDS(on) of 18mΩ @10V and high continuous current rating of 65A in the robust TO-3P package, is ideal for the main switch in a 2-3kW DC-DC converter. Its exceptionally low conduction loss is paramount for efficiency, as this converter runs continuously whenever the vehicle is on, directly impacting range.
Reliability in Compact Design: The low loss minimizes the thermal load, enabling a higher power density design. This is crucial for shared vehicle platforms where space is at a premium. The sturdy TO-3P package facilitates reliable mounting to a heatsink, ensuring stable operation over a wide temperature range and under vibration.
3. Load Management and Zone Controller MOSFET: Enabling Intelligent Power Distribution
The key device selected is the VBA3108N (Dual 100V/5.8A/SOP8, N+N Trench).
Intelligent Load Control for Shared Features: Shared vehicles require sophisticated management of numerous auxiliary loads: interior lighting, USB charging ports, telematics modules, and access control systems. The dual N-channel MOSFET in a common-drain configuration within a tiny SOP8 package is perfect for building compact, intelligent switch arrays on zone controllers. Its low RDS(on) (63mΩ @10V per channel) ensures minimal voltage drop and power loss when controlling these loads.
Integration and Diagnostics: The high level of integration saves significant PCB space in body control modules. These switches can be individually controlled by the vehicle's central computer to implement power-saving modes (e.g., shutting down non-essential loads when the car is unrented) and perform diagnostic routines (e.g., detecting lamp outages or short circuits), enhancing fleet management capabilities.
II. System Integration Engineering Implementation
1. Simplified and Robust Thermal Management
A two-tier approach is optimal for cost-sensitive shared fleets.
Tier 1: Chassis-Mounted Cooling: The main drive MOSFET (VBL17R20S) and DC-DC main switch (VBPB1102N) are mounted on dedicated aluminum heatsinks attached to the vehicle chassis or a cold plate, utilizing the vehicle's underbody airflow or a low-speed fan.
Tier 2: PCB-Level Thermal Design: Load management MOSFETs (VBA3108N) rely on careful PCB layout with generous copper pours and thermal vias to dissipate heat to the board and potentially the ECU housing.
2. EMC and Reliability for Diverse Usage
Cost-Effective EMC: Use optimized layout to minimize high-current loop areas. Implement input filters with standard X/Y capacitors and ferrite beads on critical lines. The metal vehicle body provides natural shielding for the power electronics enclosure.
Enhanced Robustness: Implement hardware-based overcurrent protection for all critical switches. Design circuits with derating for voltage and current to accommodate unpredictable driver behavior. Use automotive-grade connectors and environmentally sealed enclosures where necessary.
3. Diagnostics and Fleet Management Integration
Remote Health Monitoring: Leverage the vehicle telematics to report operational parameters like DC-DC converter efficiency trends or error flags from protected load switches. This enables predictive maintenance, scheduling service only when needed, maximizing fleet availability.
Smart Energy Management: The zone controllers using devices like the VBA3108N can execute commands from a central algorithm to reduce phantom drain from auxiliary systems when the vehicle is idle, preserving battery charge for the next user.
III. Performance Verification and Testing Protocol
1. Key Test Items for Shared Mobility
Extended Duty Cycle Testing: Simulate aggressive urban driving cycles representative of shared use, focusing on thermal stability of the power devices.
Rapid Power Cycling Test: Mimic frequent rental intervals with numerous key-on/key-off cycles to test the robustness of the DC-DC converter and load switches.
Environmental Resilience Test: Verify operation across a specified temperature range (-40°C to +85°C) and under sustained vibration.
EMC Conformance Test: Ensure the system does not interfere with key telematics and connectivity systems.
IV. Solution Scalability
1. Adapting to Different Vehicle Segments
City Microcars: Can utilize lower-current variants for the main drive and a lower-power DC-DC. The highly integrated load switch solution remains broadly applicable.
Shared SUVs/Crossovers: May require parallel configuration of the VBL17R20S or a move to a discrete IGBT module for higher power. The DC-DC converter would be scaled up accordingly, potentially using multiple VBPB1102N in parallel.
2. Integration of Fleet-Centric Technologies
Over-the-Air (OTA) Power Management Updates: Future updates could optimize switching parameters or load control strategies based on aggregated fleet data to improve efficiency or reliability.
Advanced Diagnostics: Further integration could allow monitoring of MOSFET RDS(on) drift over time via the drive circuitry, providing direct health indicators for critical power components to the fleet operator.
Conclusion
The power chain design for shared mobility EVs is an exercise in strategic optimization for fleet economics and rugged reliability. The selected component strategy—employing cost-effective SJ MOSFETs for the main drive, ultra-low-loss trench MOSFETs for constant auxiliary power, and highly integrated dual MOSFETs for intelligent load control—creates a foundation for durable, efficient, and manageable electric vehicles. This approach prioritizes low total cost of ownership through component efficiency, reduced thermal management complexity, and enhanced diagnostic capabilities, which are paramount for successful shared mobility operations. As the sector evolves, this power chain framework provides the scalability and intelligence needed to support next-generation shared vehicle platforms.

Detailed Power Chain Topology Diagrams