With the rapid development of robotics and AI-assisted living, smart assisted walking robots have become vital devices for mobility support and logistics. Their power supply and motor drive systems, serving as the "heart and muscles" of the entire unit, must deliver precise, efficient, and highly responsive power conversion for core loads such as joint motors, drive wheels, and various sensor modules. The selection of power MOSFETs directly dictates the system's efficiency, dynamic response, thermal performance, and operational reliability. Addressing the stringent demands of robots for safety, efficiency, compactness, and intelligence, this article centers on scenario-based adaptation to reconstruct the power MOSFET selection logic, providing an optimized solution ready for direct implementation.
I. Core Selection Principles and Scenario Adaptation Logic
Core Selection Principles
Voltage & Current Margin: For common robot bus voltages (12V, 24V, 48V), MOSFET voltage ratings should have a safety margin ≥50%. Current ratings must exceed peak motor/stall currents.
Ultra-Low Loss for Core Drives: Prioritize extremely low Rds(on) and optimized gate charge (Qg) to minimize conduction and switching losses in motor drives, extending battery life.
Package for Power Density & Thermal: Select advanced packages (DFN, SOT, etc.) based on power level and space constraints to achieve high power density and effective heat dissipation.
Robustness for Dynamic Operation: Devices must withstand vibration, repetitive start-stop cycles, and potential load transients, ensuring long-term reliability.
Scenario Adaptation Logic
Based on core load types within a walking robot, MOSFET applications are divided into three main scenarios: Main Drive & Actuator Control (Mobility Core), Auxiliary Actuator & Sensor Power (Function Support), and Safety & Power Management (Critical Control). Device parameters are matched accordingly.
II. MOSFET Selection Solutions by Scenario
Scenario 1: Main Drive & Actuator Control (50W-300W) – Mobility Core Device
Recommended Model: VBGQF1606 (Single-N, 60V, 50A, DFN8(3x3))
Key Parameter Advantages: Utilizes advanced SGT technology, achieving an ultra-low Rds(on) of 6.5mΩ at 10V Vgs. A 50A continuous current rating handles high torque demands for wheel or joint motors.
Scenario Adaptation Value: The DFN8 package offers excellent thermal performance and low parasitic inductance, crucial for high-frequency PWM in compact robot designs. Ultra-low conduction loss maximizes efficiency and battery runtime, while supporting smooth speed control and rapid dynamic response.
Scenario 2: Auxiliary Actuator & Sensor Power – Function Support Device
Recommended Model: VBI5325 (Dual-N+P, ±30V, ±8A, SOT89-6)
Key Parameter Advantages: Integrated complementary N and P-channel pair (30V, 8A). Low Rds(on) (18mΩ N-ch, 32mΩ P-ch @10V). Enables compact H-bridge or half-bridge designs.
Scenario Adaptation Value: The single package simplifies PCB layout for bi-directional control of small motors (e.g., arm joints, head rotation) or solenoid valves. Good thermal performance via SOT89 package supports continuous operation of auxiliary functions.
Scenario 3: Safety & Power Management – Critical Control Device
Recommended Model: VB2120 (Single-P, -12V, -6A, SOT23-3)
Key Parameter Advantages: Very low Rds(on) of 18mΩ at 10V Vgs in a tiny SOT23 package. Low gate threshold (-0.8V) allows easy direct control by low-voltage MCUs.
Scenario Adaptation Value: Ideal for high-side load switching due to P-channel type. Perfect for safety-critical functions like emergency brake control, main power path isolation, or enabling/disabling specific sensor clusters. Its small size minimizes board space for distributed safety controls.
III. System-Level Design Implementation Points
Drive Circuit Design
VBGQF1606: Pair with a dedicated motor driver IC. Ensure strong gate drive with adequate current sourcing/sinking capability. Minimize power loop inductance.
VBI5325: Ensure proper gate drive sequencing for the complementary pair to prevent shoot-through in H-bridge configurations. Use gate resistors for timing control.
VB2120: Can be driven directly by MCU GPIO for simple on/off control. Include base resistor when driven by a bipolar transistor.
Thermal Management Design
Graded Strategy: VBGQF1606 requires significant PCB copper pour, possibly connected to chassis. VBI5325 benefits from moderate copper. VB2120 heat dissipation is manageable via its package and traces due to typically intermittent use.
Derating: Design for 60-70% of continuous current rating under maximum ambient temperature (e.g., 40-50°C inside robot). Monitor junction temperature in main drives.
EMC and Reliability Assurance
EMI Suppression: Use snubber circuits or parallel capacitors for VBGQF1606 in motor drives. Ensure proper decoupling for all MOSFETs.
Protection Measures: Implement robust overcurrent detection for motor drives (VBGQF1606). Use TVS diodes on motor terminals and power inputs. Incorporate ESD protection on control lines (gates).
IV. Core Value of the Solution and Optimization Suggestions
The power MOSFET selection solution for AI-assisted walking robots, based on scenario adaptation logic, achieves comprehensive coverage from core mobility drives to auxiliary functions and critical safety controls. Its core value is threefold:
Maximized Efficiency & Runtime: Using the ultra-low-loss VBGQF1606 for main drives significantly reduces the largest power losses. The efficient VBI5325 for auxiliary actuators further optimizes system-wide energy use. This translates directly to extended operational time per battery charge and reduced heat generation.
Enhanced Agility & Safety: The high-performance drive enables precise and responsive motor control for stable and agile movement. The dedicated safety-control MOSFET (VB2120) facilitates reliable implementation of emergency stops and power management, crucial for user safety.
Optimal Balance of Power Density and Reliability: The selected DFN and SOT packages offer excellent power density for compact robot designs. Combined with sufficient electrical margins and a focus on thermal management, this solution ensures reliable operation under the dynamic and demanding conditions of a walking robot.
In the design of power drive systems for smart assisted walking robots, MOSFET selection is central to achieving efficiency, agility, intelligence, and safety. This scenario-based solution, by accurately matching device characteristics to specific load requirements and incorporating system-level design considerations, provides a actionable technical guide. As robots evolve towards greater autonomy, longer runtime, and more complex interactions, future exploration could focus on integrating current sensing, leveraging even lower Rds(on) technologies, and developing modular power stages, laying a robust hardware foundation for the next generation of high-performance, reliable assisted mobility robots.

Detailed Scenario Topology Diagrams