As industrial collaborative robots evolve towards higher payload capacity, greater precision, and closer human-robot interaction, their internal servo drive and power distribution systems are no longer simple switching units. Instead, they are the core determinants of dynamic performance, motion accuracy, and intrinsic safety. A well-designed power chain is the physical foundation for these robots to achieve smooth torque control, high-efficiency regenerative braking, and robust durability within constrained spaces and demanding operational cycles.
However, building such a chain presents multi-dimensional challenges: How to achieve high power density and low heat generation within compact joint modules? How to ensure the absolute reliability of power devices under conditions of frequent start-stop and overload? How to seamlessly integrate functional safety, thermal management, and intelligent current monitoring for safe collaboration? The answers lie within every engineering detail, from the selection of key components to system-level integration.
I. Three Dimensions for Core Power Component Selection: Coordinated Consideration of Voltage, Current, and Topology
1. Joint Servo Drive MOSFET: The Core of Dynamic Performance and Power Density
The key device is the VBGL1402 (40V/170A/TO-263, Single-N, SGT).
Voltage and Current Stress Analysis: Collaborative robot joint motors typically operate on low-voltage bus systems (24V, 48V, or 72V DC). A 40V VDS rating provides ample margin for a 24V/48V bus, ensuring reliability against voltage spikes. The exceptionally low RDS(on) of 1.4mΩ (at 10V VGS) is critical for minimizing conduction loss (P_cond = I² RDS(on)) during sustained high-torque operation, directly reducing heat generation within the compact joint housing.
Dynamic Response and Efficiency: The SGT (Shielded Gate Trench) technology offers an excellent figure of merit (FOM), balancing low on-resistance and gate charge. This enables high switching frequencies necessary for precise PWM current control in servo drives, while keeping switching losses manageable. The low gate threshold voltage (Vth=3V) ensures compatibility with low-voltage MCU-driven gate drivers.
Thermal Design Relevance: The TO-263 (D²PAK) package offers a superior footprint for heatsinking. Mounting it directly onto a thermally conductive joint housing or a dedicated miniaturized heatsink is essential to manage the heat flux from 170A continuous current capability.
2. Centralized DC Power Distribution MOSFET: The Backbone for Auxiliary Systems and Safety Isolation
The key device is the VBF1638 (60V/35A/TO-251, Single-N, Trench).
Efficiency and Control Logic: This device is ideal for intelligent power distribution modules managing auxiliary systems (vision system LEDs, tool I/O, cooling fans, safety sensors). Its moderate current rating and low RDS(on) (32mΩ at 10V VGS) ensure low voltage drop when switching these loads. It can be used in safety-critical circuits, such as enabling/disabling power to specific joint modules or peripherals based on safety controller signals.
Compactness and Reliability: The TO-251 package provides a robust through-hole mounting option that is more vibration-resistant than SMD-only packages for certain chassis-mounted distribution boards. Its Trench technology ensures stable performance under the variable loads typical of auxiliary systems.
3. Low-Side Drive / Signal-Level Switch MOSFET: The Enabler for Compact Control Electronics
The key device is the VB1210 (20V/9A/SOT23-3, Single-N, Trench).
High-Density Integration for Control Logic: This ultra-small SOT23-3 device is perfect for densely populated main controller or driver PCBs. It serves as a low-side switch for controlling small relays, solenoid valves in grippers, or indicator lights. Its very low on-resistance (11mΩ at 10V VGS) for its package size minimizes heat generation when switching several amps.
Gate Driving Simplicity: The low and consistent gate threshold voltage range (0.5V~1.5V) allows it to be driven directly from microcontroller GPIO pins (3.3V or 5V logic) without needing a level shifter in many cases, simplifying circuit design and saving space.
II. System Integration Engineering Implementation
1. Distributed Thermal Management Strategy
A multi-zone approach is necessary due to space constraints.
Zone 1 (Joint Modules): The VBGL1402 in each joint servo driver must be conductively coupled to the robot arm's structural metal or a dedicated embedded copper heatsink, leveraging the arm as a heat spreader.
Zone 2 (Control Cabinet / Base): Devices like the VBF1638 on the power distribution board require forced air cooling via a system fan or natural convection with strategic board layout and copper pours.
Zone 3 (Controller PCBs): Heat from multiple VB1210 devices and other logic ICs is managed through internal PCB ground/power planes connected to the board's edges or mounting points.
2. Electromagnetic Compatibility (EMC) and Functional Safety Design
Conducted & Radiated EMI Suppression: Use local decoupling capacitors at the drains of all switching MOSFETs. Employ twisted-pair or shielded cables for motor phases and sensitive sensor lines. The compact nature of servo drives demands careful PCB layout with minimized high di/dt loop areas.
Functional Safety Integration: Collaborative robots must comply with standards like ISO 10218-1 and ISO/TS 15066. The power distribution MOSFETs (e.g., VBF1638) can be part of Safe Torque Off (STO) or other category 3/PLd safety circuits. Redundant current monitoring using shunts or Hall sensors on each joint motor phase is critical for overload and collision detection.
3. Reliability Enhancement for Continuous Operation
Electrical Stress Protection: Snubber circuits across motor terminals may be needed for longer cable runs to joint motors. Flyback diodes are mandatory for all inductive loads (relays, solenoids) switched by devices like the VB1210.
Fault Diagnosis: Implement hardware overcurrent protection on each motor phase. Monitor heatsink temperature in each joint. The low RDS(on) of the selected MOSFETs themselves contributes to reliability by reducing thermal stress under normal operation.
III. Performance Verification and Testing Protocol
1. Key Test Items and Standards
Dynamic Performance Test: Measure step response, settling time, and torque ripple under varying loads to validate the precision enabled by the fast-switching, low-loss power devices.
Thermal Cycling Test: Subject the robot to repeated high-duty-cycle movements in an environmental chamber to validate thermal management from joint to control cabinet.
EMC Test: Ensure compliance with industrial standards (e.g., IEC 61000-6-2, -6-4) to prevent interference with nearby sensitive equipment.
Endurance and Lifetime Test: Execute millions of repetitive motion cycles on a test bench to simulate years of operation, monitoring for degradation in MOSFET parameters or joint temperature rise.
Functional Safety Validation: Rigorously test all safety-related circuits, including power isolation via distribution switches, to verify performance to the required Performance Level (PL).
2. Design Verification Example
Test data from a 10kg payload collaborative robot arm (Bus voltage: 48VDC, Ambient temp: 25°C) shows:
Joint Driver Efficiency: Peak efficiency of the servo drive (using VBGL1402) exceeded 98% at rated torque.
Thermal Performance: Under continuous peak torque operation, the VBGL1402 case temperature stabilized at 85°C with conduction to the aluminum joint housing.
System Response: The low gate charge of the VB1210 enabled sub-microsecond switching for control signals, contributing to fast system-level safety response.
The power distribution system (using VBF1638) operated without fault during 100,000 cycle load switching tests.
IV. Solution Scalability
1. Adjustments for Different Payloads and Kinematics
Low Payload (<5kg) / SCARA Robots: May use lower current rated MOSFETs in smaller packages (e.g., SO-8 variants like VBBC1309) for joint drives, reducing joint size further.
High Payload (>15kg) / Heavy-Duty Collaborative Arms: May require parallel operation of VBGL1402 devices per joint or transition to power modules for currents beyond 200A. The centralized power distribution would need higher current switches.
Mobile Collaborative Robots (Cobots on AGVs): The entire power system must be optimized for energy efficiency. The high efficiency of the selected MOSFETs directly extends battery life.
2. Integration of Cutting-Edge Technologies
Intelligent Power Health Monitoring (IPHM): Future systems can monitor the on-state resistance (RDS(on)) of key MOSFETs like the VBGL1402 over time. A gradual increase can predict end-of-life or cooling system degradation, enabling predictive maintenance.
Wide Bandgap (GaN) Technology Roadmap:
Phase 1 (Current): The selected Silicon-based MOSFETs (SGT/Trench) offer the optimal balance of performance, cost, and reliability for mainstream collaborative robots.
Phase 2 (Next 2-3 years): Adoption of GaN HEMTs for the joint servo drives in premium models. This could enable switching frequencies in the MHz range, drastically reducing the size of motor inductors and filters, and allowing for even more compact joint designs.
Phase 3 (Future): Integration of monolithic half-bridge GaN ICs with drivers, further simplifying design and maximizing power density.
Conclusion
The power chain design for industrial collaborative robots is a meticulous balancing act between power density, thermal performance, control precision, and functional safety. The tiered optimization scheme proposed—employing a high-current, low-loss SGT MOSFET for dynamic joint control, a robust Trench MOSFET for safe and efficient power distribution, and an ultra-compact Trench MOSFET for high-density logic control—provides a scalable and reliable foundation for cobots of various scales and applications.
As collaborative robots become more intelligent and demand greater autonomy, their power management will trend towards greater decentralization and intelligence at the joint level. Engineers must adhere to stringent industrial and functional safety standards while employing this framework, preparing for the eventual integration of Wide Bandgap semiconductors and advanced predictive health monitoring.
Ultimately, excellent robotic power design is felt, not seen. It translates into smoother, more precise, and safer human-robot collaboration, higher throughput, and lower total cost of ownership through exceptional reliability. This is the true value of engineering precision in powering the next generation of intelligent automation.

Detailed Topology Diagrams