With the advancement of robotics and AI, high-end bipedal mobile collaborative robots require exceptional dynamic response, high power density, and ultra-reliability in their actuation and power systems. The selection of power MOSFETs, serving as the core switches for joint motor drives, dynamic bus voltage conversion, and safety-critical module control, directly determines the system's efficiency, torque density, thermal performance, and operational safety. Addressing the stringent requirements for instantaneous high power, compact integration, and functional safety, this article develops a practical and optimized MOSFET selection strategy based on scenario-specific adaptation.
I. Core Selection Principles and Scenario Adaptation Logic
(A) Core Selection Principles: Three-Dimensional Dynamic Adaptation
MOSFET selection requires a balanced focus on three critical dimensions—current capability & switching speed, thermal impedance, and voltage ruggedness—ensuring robust performance under highly dynamic loads:
High Current & Fast Switching: Prioritize devices with very low Rds(on) for minimal conduction loss during high-torque operations and low Qg for efficient high-frequency PWM control of motors, enabling precise and responsive motion.
Superior Thermal Performance: Choose packages with low thermal resistance (RthJC) and designs compatible with effective heatsinking (e.g., TO-220, TO-263) to manage significant heat generated during dynamic acceleration/deceleration and continuous operation.
Voltage Ruggedness with Margin: For common 48V or higher voltage bus systems in robots, select devices with sufficient voltage rating (e.g., ≥100V for 48V bus) to withstand regenerative braking voltage spikes and ensure long-term reliability.
(B) Scenario Adaptation Logic: Categorization by System Function
Divide the power management needs into three core scenarios: First, Joint Actuator Drive (Power & Motion Core), requiring very high continuous and peak current handling. Second, Centralized DC Bus Conversion & Distribution (Power Backbone), requiring high efficiency and power density for stable voltage rails. Third, Safety & Control Module Switching (Safety-Critical), requiring compact, reliable switching for brakes, sensors, or communication isolation.
II. Detailed MOSFET Selection Scheme by Scenario
(A) Scenario 1: Joint Actuator Drive (Peak Power 1kW-3kW) – Power & Motion Core Device
Joint actuators (typically BLDC or PMSM motors) demand handling of very high continuous currents and 3-5 times the peak currents during sudden starts/stops or dynamic impacts.
Recommended Model: VBM1106S (Single-N, 100V, 120A, TO-220)
Parameter Advantages: Trench technology achieves an ultra-low Rds(on) of 6.8mΩ at 10V. Continuous current of 120A (peak much higher) is ideal for high-torque 48V-60V bus actuators. The TO-220 package offers excellent thermal coupling to heatsinks (low RthJC), crucial for managing I²R losses under high dynamic loads.
Adaptation Value: Minimizes conduction loss in the motor phase legs. For a 48V/1.5kW joint motor (~31A continuous), per-device conduction loss can be below 6.5W. Enables high-frequency (>20kHz) PWM for precise current control and smooth, quiet actuator operation, essential for human collaboration.
Selection Notes: Verify motor peak current and bus voltage. A 100V rating provides ample margin for a 48V-60V bus. Must be used with a capable motor driver IC/gate driver and mounted on a substantial heatsink. Ensure gate drive strength (≥2A peak) to switch the moderate Qg quickly.
(B) Scenario 2: Centralized DC Bus Conversion & Distribution – Power Backbone Device
The main DC-DC converters (e.g., 48V to 12V/5V) and power distribution switches require high efficiency and compact size to support the robot's central brain, sensors, and peripherals under varying loads.
Recommended Model: VBGQA1805 (Single-N, 85V, 80A, DFN8(5x6))
Parameter Advantages: SGT technology delivers an excellent Rds(on) of 4.5mΩ at 10V (12mΩ at 4.5V, suitable for 5V logic-driven applications). High current rating (80A) in a compact DFN8 package offers outstanding power density and low parasitic inductance for high-frequency synchronous rectification in buck converters.
Adaptation Value: Dramatically reduces switching and conduction losses in multi-phase buck converters, increasing power supply efficiency to >95% and reducing thermal burden. The small footprint saves valuable PCB space for other critical components. Its performance supports dynamic load changes from various subsystems.
Selection Notes: Ideal for the switching FETs in high-current non-isolated point-of-load (POL) converters. The DFN package requires a well-designed PCB thermal pad with vias for heat dissipation. Ensure proper gate drive voltage (10V recommended) to achieve the lowest Rds(on).
(C) Scenario 3: Safety & Control Module Switching – Safety-Critical Device
Modules such as joint electromagnetic brakes, safety sensor loops, or auxiliary actuator power require reliable, compact, and often high-side (P-MOS) based switching for safe enable/disable and fault isolation.
Recommended Model: VBE2216 (Single-P, -20V, -40A, TO-252)
Parameter Advantages: Trench P-MOS technology with low Rds(on) of 16mΩ at 4.5V. A -40A continuous current rating is robust for brakes or medium-power auxiliary devices. The low gate threshold voltage (Vth = -0.8V) allows for relatively easy drive from low-voltage MCUs (3.3V/5V). The TO-252 (D-PAK) package offers a good balance of power handling and footprint.
Adaptation Value: Enables efficient high-side switching for 12V/24V safety circuits (e.g., joint brakes). The fast switching capability ensures quick engagement/release of brakes (<10ms), critical for safe stop. The P-MOS configuration simplifies drive circuitry compared to using an N-MOS for high-side switching.
Selection Notes: Verify the controlled module's voltage and inrush current. The -20V rating is suitable for 12V systems with margin. Can be driven directly by an MCU GPIO for smaller loads or via a simple NPN buffer for larger ones. Include freewheeling diodes for inductive loads like brake coils.
III. System-Level Design Implementation Points
(A) Drive Circuit Design: Matching Dynamic Needs
VBM1106S: Pair with robust three-phase gate driver ICs (e.g., DRV8353) with ample drive current (>2A). Minimize power loop inductance in motor phase legs. Use gate resistors to fine-tune switching speed and control EMI.
VBGQA1805: In buck converters, pair with a dedicated controller/synchronous driver. Ensure a low-impedance gate drive path. A small gate-source capacitor (e.g., 1nF) may help damp high-frequency oscillations.
VBE2216: For MCU direct drive, use a series gate resistor (e.g., 10Ω-47Ω). For higher current switching, implement an NPN transistor level shifter circuit. A pull-up resistor on the gate ensures defined off-state.
(B) Thermal Management Design: Aggressive and Tiered
VBM1106S (Joint Drive): Mandatory external heatsinking. Use thermal interface material and possibly forced air cooling across the heatsink, especially for joints with high duty-cycle movements.
VBGQA1805 (Power Conversion): Rely on a high-quality PCB thermal design: use the maximum recommended copper area (≥150mm²) under the DFN pad, multiple thermal vias to inner layers, and possibly a bottom-side heatsink if space allows.
VBE2216 (Safety Switch): For continuous high-current use, a small heatsink on the TO-252 tab or a generous copper pour is recommended. For intermittent use (e.g., brake control), the package may suffice with good PCB copper.
(C) EMC and Reliability Assurance for Harsh Dynamic Environment
EMC Suppression:
VBM1106S: Use low-ESR ceramic capacitors (100nF) very close to the drain-source terminals. Consider an RC snubber across the motor phases if needed. Shield motor cables.
Power Stages: Use common-mode chokes on all input power lines. Ensure proper grounding and isolation between noisy power stages and sensitive digital/control areas.
Reliability Protection:
Overcurrent Protection: Implement precise phase current sensing (shunt + amplifier) with hardware comparators for immediate fault shutdown in motor drives.
Overvoltage Protection: At the main 48V+ bus input, use TVS diodes or varistors to clamp regenerative braking spikes exceeding the MOSFETs' ratings.
Redundancy & Monitoring: For safety-critical switches (VBE2216), consider current monitoring and temperature sensing on the heatsink or PCB near the device.
IV. Scheme Core Value and Optimization Suggestions
(A) Core Value
Dynamic Performance Maximized: Enables high-torque density and fast-responding joints while maintaining thermal stability, directly contributing to the robot's agility and payload capacity.
System Efficiency Optimized: High-efficiency conversion and low-loss switching extend operational battery life and reduce the size/cost of the thermal management system.
Safety & Integration Balanced: Provides robust and controllable switching for functional safety elements while leveraging advanced packages (DFN) for space-saving integration of power conversion.
(B) Optimization Suggestions
Higher Power/Voltage Adaptation: For robots using an 80V+ bus or higher power joints, consider VBM16R32S (600V, 32A, SJ-MOS) for its excellent Rds(on) and voltage rating.
Integration Upgrade: For highly integrated joint modules, explore using pre-assembled motor drive power stages (IPMs) or pairing the selected MOSFETs with driver ICs in compact multi-chip modules (MCMs).
Space-Constrained High-Current: In very dense designs, VBGQA1303 (30V, 85A, DFN) could be evaluated for lower-voltage (e.g., 12V/24V) high-current auxiliary actuators, offering even lower Rds(on).
Conclusion
Strategic MOSFET selection is pivotal to unlocking the high dynamic performance, efficiency, and safety required by next-generation bipedal collaborative robots. This scenario-based strategy provides a clear roadmap for matching device capabilities to critical robotic functions—from high-power actuation to intelligent power distribution and safety control. Future exploration into wide-bandgap (SiC) devices for ultra-high-efficiency main bus conversion and advanced integrated power modules will further push the boundaries of robot power density and intelligence.

Detailed MOSFET Application Diagrams