Against the backdrop of the rapid growth of smart healthcare logistics, hospital autonomous delivery robots, as core carriers for medicines, specimens, and supplies, see their operational performance and safety directly determined by the capabilities of their onboard power systems. The traction drive, distributed power distribution, and intelligent module control act as the robot's "power heart and neural network," responsible for precise mobility, stable operation of sensor/computing suites, and safe management of critical functions. The selection of power MOSFETs profoundly impacts system efficiency, thermal performance, safety compliance, and operational reliability. This article, targeting the demanding application scenario of hospital indoor environments—characterized by stringent requirements for safety, low noise, high reliability, and compact size—conducts an in-depth analysis of MOSFET selection considerations for key power nodes, providing a complete and optimized device recommendation scheme.
Detailed MOSFET Selection Analysis
1. VBM1705 (N-MOS, 70V, 100A, TO-220)
Role: Main switch for the motor drive H-bridge or central DC-DC converter stage.
Technical Deep Dive:
Voltage Stress & Drive Efficiency: Designed for 24V or 48V robot battery systems, the 70V-rated VBM1705 provides ample margin for load dump and switching voltage spikes. Utilizing advanced Trench technology, its ultra-low Rds(on) of 5mΩ (at 10V Vgs) minimizes conduction losses in the motor drive phase, which is crucial for extending battery life and reducing heat generation during frequent start-stop and navigation cycles.
Power Density & Thermal Management: With a continuous current rating of 100A, it is well-suited for driving medium-power wheel motors or serving as the main switch in a high-current non-isolated DC-DC converter. The TO-220 package offers an excellent balance between current-handling capability, ease of mounting on a heatsink, and footprint, facilitating a compact and serviceable motor driver design.
Dynamic Performance: The combination of low gate charge and low on-resistance supports PWM frequencies in the tens of kHz range, enabling smooth motor control with low audible noise—a critical requirement for hospital environments.
2. VBGQA3402 (Dual N-MOS, 40V, 90A per Ch, DFN8(5X6)-B)
Role: Intelligent, high-current power distribution for sensor clusters, computing units, or auxiliary actuators.
Extended Application Analysis:
High-Density Power Routing Core: This dual N-channel MOSFET in a compact DFN package integrates two 40V/90A switches. The 40V rating is ideal for 12V or 24V auxiliary power buses within the robot. It enables independent, high-side or low-side switching of two major power-hungry subsystems (e.g., LiDAR/vision system and main computing box), allowing for sequenced power-up/down and individual reset or fault isolation.
Ultra-Low Loss & Thermal Challenge: Featuring an extremely low Rds(on) of 2.2mΩ per channel (at 10V Vgs), it minimizes voltage drop and power loss in the distribution path, maximizing energy delivered to critical loads. The exposed thermal pad of the DFN8 package allows efficient heat transfer to the PCB, which is essential for reliability in a sealed, convection-cooled robot body.
Intelligent Integration: The dual independent channels controlled by the vehicle's main controller enable sophisticated power management policies, such as putting non-critical sensors into low-power sleep mode, enhancing overall system efficiency and intelligence.
3. VBE2625A (Single P-MOS, -60V, -50A, TO-252)
Role: Safety-critical high-side switching, emergency brake control, or main battery disconnect.
Precision Power & Safety Management:
High-Side Safety Switch: This P-channel MOSFET is ideal for applications where a high-side switch is preferred to simplify control or enhance safety. Its -60V rating is more than sufficient for 48V battery systems. It can be used as a controlled main power switch or to drive critical safety loads like an electromagnetic brake directly, ensuring fail-safe operation.
Low-Loss Power Gating: With a low Rds(on) of 20mΩ (at 10V Vgs) and a high continuous current of -50A, it introduces minimal loss in the main power path. Its relatively low gate threshold voltage (Vth: -1.7V) allows for straightforward driving from logic-level signals, often without need for a dedicated driver IC.
Robustness & Form Factor: The TO-252 (DPAK) package provides a good compromise between current capability, ruggedness, and board space savings, suitable for the constrained yet demanding electrical environment of a mobile robot.
System-Level Design and Application Recommendations
Drive Circuit Design Key Points:
Motor Drive Switch (VBM1705): Requires a dedicated half-bridge or H-bridge driver with sufficient current capability to achieve fast switching and minimize cross-conduction. Careful attention to gate loop layout is necessary to prevent oscillation.
High-Current Distribution Switch (VBGQA3402): Can be driven by a standard gate driver IC. Ensure the driver can source/sink adequate peak current to handle the high gate charge of parallel MOSFETs if used for a single high-current channel. Use Kelvin source connections if possible for precise current sensing.
High-Side Safety Switch (VBE2625A): Simple to drive, often via a small N-MOSFET or bipolar transistor level shifter. Incorporate a pull-up resistor on the gate to ensure definite turn-off in case of MCU fault.
Thermal Management and EMC Design:
Tiered Thermal Design: VBM1705 requires attachment to a chassis-mounted heatsink or the robot's baseplate. VBGQA3402 relies on a well-designed PCB thermal pad connected to internal ground planes or a localized metal core. VBE2625A benefits from a generous copper pour on the PCB.
EMI Suppression: Employ gate resistors to control the switching speed of VBM1705, reducing motor drive dv/dt noise. Place high-frequency decoupling capacitors close to the drain-source of VBGQA3402. Use ferrite beads on the power lines to sensitive sensor modules powered through these switches.
Reliability Enhancement Measures:
Adequate Derating: Operate MOSFETs at no more than 60-70% of their rated voltage and current in continuous operation. Monitor the case temperature of VBM1705, especially during high-torque maneuvers.
Multiple Protections: Implement hardware overcurrent protection (e.g., desat detection for VBM1705, current sense amplifiers for VBGQA3402 branches) and fast software fault handling. The high-side switch (VBE2625A) should be part of a watchdog or safety controller circuit.
Enhanced Protection: Use TVS diodes on all battery-input and motor-output lines. Ensure proper creepage and clearance for onboard voltages, considering potential condensation in hospital environments.
Conclusion
In the design of efficient, safe, and intelligent power systems for hospital autonomous delivery robots, power MOSFET selection is key to achieving reliable navigation, long endurance, and safe interaction within a sensitive environment. The three-tier MOSFET scheme recommended in this article embodies the design philosophy of high efficiency, compact integration, and functional safety.
Core value is reflected in:
Full-Stack Efficiency & Drive Performance: From high-efficiency motor drive and control (VBM1705), to ultra-low-loss intelligent power distribution for avionics (VBGQA3402), and down to robust safety power gating (VBE2625A), a complete, efficient, and controllable energy pathway from battery to all loads is constructed.
Intelligent Operation & Functional Safety: The dual N-MOS enables granular power management of subsystems, while the P-MOS provides a reliable safety switch. This offers a hardware foundation for energy optimization, diagnostic reporting, and implementing safe states, significantly enhancing robot availability and operational safety.
Hospital Environment Adaptability: Device selection balances current handling, low loss, and compact packaging. Coupled with optimized thermal design and EMI mitigation, it ensures quiet, reliable, and interference-free operation within hospital wards and corridors.
Future-Oriented Scalability: The modular power architecture and selected devices allow for adaptation to different robot payloads and operational durations by scaling battery voltage or using parallel devices.
Future Trends:
As hospital robots evolve towards higher levels of autonomy (L4), collaborative operation, and wireless charging, power device selection will trend towards:
Increased adoption of integrated motor driver ICs or Intelligent Power Modules (IPMs) for even more compact designs.
Use of MOSFETs with integrated current and temperature sensing for enhanced diagnostics and predictive maintenance.
GaN devices may be considered for ultra-high-frequency onboard DC-DC converters to achieve the ultimate power density for future compute-intensive AI processing units.
This recommended scheme provides a complete power device solution for hospital autonomous delivery robots, spanning from battery to motor and sensors, and from main power conversion to intelligent safety switching. Engineers can refine and adjust it based on specific battery voltage (24V/48V), motor power rating, and required safety integrity levels (SIL) to build robust, efficient, and safe robotic carriers that support the future of smart healthcare logistics.

Detailed Topology Diagrams