As high-end explosion-proof collaborative robots evolve towards greater dexterity, higher payload-to-weight ratios, and fail-safe operation in hazardous environments, their internal motor drive and power distribution systems are no longer mere functional blocks. Instead, they are the core determinants of motion smoothness, operational safety, and long-term maintenance-free reliability. A meticulously designed power chain is the physical foundation for these robots to achieve precise torque control, efficient thermal performance, and intrinsic safety under strict ATEX/IECEx standards.
However, building such a chain presents multi-dimensional challenges: How to achieve high-efficiency power conversion within extremely compact joint spaces? How to ensure absolute reliability and minimal heat generation to prevent ignition risks? How to seamlessly integrate robust short-circuit protection, precise current sensing, and intelligent power sequencing? 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 Motor Drive MOSFET: The Core of Motion Precision and Efficiency
Key Device: VBL1615 (60V/75A/TO-263, Single N-Channel)
Voltage & Current Stress Analysis: Collaborative robots typically operate on safe low-voltage DC systems (e.g., 24V or 48V). A 60V-rated device provides ample margin for voltage spikes induced by long cable runs or motor regeneration within the joint module. The high continuous current rating of 75A and pulse current capability are crucial for delivering peak torque required for acceleration and heavy payload handling, all while adhering to strict derating rules for safety-critical applications.
Dynamic Characteristics and Loss Optimization: The extremely low on-resistance (RDS(on) as low as 11mΩ @10V) is paramount. It minimizes conduction losses, which is the primary source of heat in the cramped joint space. Lower heat generation directly reduces the thermal management burden and lowers the surface temperature of the joint—a critical factor for explosion-proof certification. The Trench technology ensures fast switching, enabling high-frequency PWM for smooth, quiet motor operation and precise current control.
Thermal & Mechanical Design Relevance: The TO-263 (D2PAK) package offers an excellent balance between power handling, thermal performance (via board mounting to a heatsink), and a compact footprint suitable for joint drive PCB design. Its robust construction withstands the continuous vibration present in robotic operation.
2. Compact Power Management & Isolation MOSFET: The Enabler for Miniaturized Safety
Key Device: VBQA2157N (-150V/22A/DFN8(5x6), Single P-Channel)
System-Level Functionality: This P-Channel MOSFET is instrumental in implementing high-side load switches, reverse polarity protection, and safe power domain isolation—essential functions in an explosion-proof design where fault containment is vital. Its -150V drain-source voltage rating allows it to safely handle voltages in 48V or isolated auxiliary power systems with significant margin.
Efficiency and Space Savings: The ultra-compact DFN8 package, with a footprint of just 5x6mm, is ideal for space-constrained control boards within the robot's base or arm. Despite its size, it maintains a low RDS(on) of 65mΩ @10V, ensuring minimal voltage drop and power loss in power path control applications. This facilitates the design of highly integrated, distributed power management nodes.
Reliability in Harsh Environments: The advanced package offers good thermal performance for its size and is suitable for automated assembly processes, enhancing manufacturing reliability. Its use simplifies circuit design for safe shutdown sequences and isolation of sub-systems during fault detection.
3. Centralized Power Distribution MOSFET: The Backbone of Robust System Power
Key Device: VBM1607V1.6 (60V/120A/TO-220, Single N-Channel)
High-Current Handling Capability: This device is designed for main power distribution points, such as the primary bus switch or the final drive stage for a high-torque joint. Its exceptionally low RDS(on) of 5mΩ @10V and high current rating of 120A set a benchmark for minimizing conduction loss in high-current paths, which is fundamental for maximizing system runtime and efficiency.
Thermal Management Simplicity: The TO-220 package is a classic choice for applications requiring significant heat dissipation. It can be easily mounted to a chassis heatsink or a dedicated cooler, allowing the power distribution unit to handle large, sustained currents while keeping junction temperatures within safe limits. This predictable thermal performance is easier to validate for safety standards.
System Protection Relevance: Its robust construction and high current capability make it a reliable component for implementing hardware-based overcurrent protection circuits. When used as a low-side switch with a current shunt, it enables precise, fast-acting motor phase or system total current protection.
II. System Integration Engineering Implementation
1. Thermal Management for Intrinsic Safety
The primary design goal is to keep all surface temperatures below the ignition temperature of the specified gas group. A multi-pronged approach is used:
Joint Modules: The VBL1615 is mounted on a small, localized heatsink coupled to the robot arm's structure, using thermally conductive but electrically isolating pads. Thermal simulation must ensure hot spots remain within limits.
Central Power Unit: The VBM1607V1.6 is mounted on a primary chassis heatsink, potentially with low-speed fan assistance if enclosed in a pressurized or sealed control cabinet.
Board-Level Components: For VBQA2157N and other ICs, careful PCB layout with thick copper pours and thermal vias is essential to spread heat to the board's ground plane, which acts as a secondary heatsink.
2. Electromagnetic Compatibility (EMC) and Functional Safety Design
Conducted & Radiated Emissions: Use multilayer PCBs with dedicated power and ground planes. Implement local decoupling ceramics near each MOSFET. Ferrite beads on motor leads and shielded cables for all external connections are mandatory to contain noise, which is critical in sensitive industrial environments.
Functional Safety & Protection: Designs must target at least SIL 2/PLe levels. Implement redundant current sensing (shunt + Hall) for motor drives using VBL1615. Use the VBQA2157N in conjunction with monitoring circuits to implement safe torque off (STO) power isolation paths. All gate drives must have undervoltage lockout (UVLO) and dedicated overcurrent shutdown comparators with response times <1µs.
3. Reliability Enhancement for 24/7 Operation
Electrical Stress Protection: Snubber circuits across motor terminals and TVS diodes on all power inputs are necessary to absorb regenerative energy and voltage transients. Gate protection zeners are used for all MOSFETs.
Fault Diagnosis: Implement comprehensive monitoring of MOSFET health by periodically checking on-resistance (via VDS sensing during known current) and heatsink temperatures. Predictive algorithms can flag degradation before failure.
III. Performance Verification and Testing Protocol
1. Key Test Items and Standards
Explosion-Proof Certification Testing: The entire system, including surface temperatures of power components under worst-case load, must be validated per ATEX/IECEx standards for the intended zone.
Extended Temperature & Thermal Cycling: Test from -20°C to +70°C (or wider per spec) to ensure performance and reliability across the operational range.
Vibration and Shock Testing: Perform according to ISO 9283 and other robotic standards to ensure mechanical integrity of solder joints and mounts.
EMC Immunity Testing: Must robustly pass IEC 61000-4 series tests (ESD, EFT, Surge) to ensure operation is not disrupted by industrial noise.
Continuous Operational Endurance Test: Run for thousands of hours under a dynamic load profile simulating repetitive pick-and-place cycles to assess long-term reliability.
2. Design Verification Example
Test data from a 10kg payload explosion-proof collaborative robot joint (Bus voltage: 48VDC, Ambient temp: 40°C) shows:
Joint Drive Efficiency: The inverter stage using VBL1615 achieved >98% efficiency at rated continuous torque, with junction temperature rise maintained below 40°C.
Power Distribution Loss: The main bus switch (VBM1607V1.6) contributed less than 0.3% total system loss under full load.
System Response: The protection circuitry using VBQA2157N achieved fault isolation within 3µs, meeting stringent safety requirements.
The system successfully passed surface temperature tests for Group IIB T4 certification.
IV. Solution Scalability
1. Adjustments for Different Payloads and Form Factors
Low Payload (<5kg) / Cobots: Can utilize VBL1615 for all joints, with potentially smaller packages for very small joints. Central distribution may use lower-current devices.
High Payload (>15kg) / Industrial Arms: May require parallel connection of VBL1615 or stepping up to higher-current modules in TO-247 packages for the main joints. The VBM1607V1.6 remains ideal for central power switching.
Mobile/AGV-integrated Arms: Emphasis shifts to ultra-low quiescent current in power management. The VBQA2157N becomes key for intelligent power gating of unused modules to conserve energy.
2. Integration of Cutting-Edge Technologies
Wide Bandgap (GaN) Exploration: For next-generation ultra-compact and efficient joints, GaN HEMTs (e.g., 100V ratings) can be evaluated to replace traditional MOSFETs like the VBL1615, enabling higher switching frequencies, smaller filters, and even lower losses.
Predictive Health Management (PHM): Leverage motor current signature analysis and MOSFET on-resistance monitoring data to predict bearing wear and power device aging, transitioning from preventive to predictive maintenance.
Domain-Centralized Power Architecture: Evolve from distributed joint drives to a centralized, multi-axis servo drive platform. This would utilize high-current, multi-channel power stages, where the selection principles for safety, efficiency, and thermal performance remain paramount but are integrated at a system level.
Conclusion
The power chain design for high-end explosion-proof collaborative robots is a systems engineering task dominated by the triumvirate of Safety, Precision, and Density. The tiered optimization scheme proposed—prioritizing high efficiency and compactness in joint drives (VBL1615), enabling miniaturized safety control in power management (VBQA2157N), and ensuring robust, low-loss power distribution (VBM1607V1.6)—provides a foundational blueprint for reliable robotic design in hazardous environments.
As robotics move towards more integrated joints and smarter power domains, the underlying requirements for component reliability, thermal performance, and protective control only intensify. It is recommended that engineers adhere rigorously to functional safety standards and explosion-proof certification processes while applying this framework, leaving ample design margin and preparing for the integration of next-generation wide-bandgap semiconductors.
Ultimately, excellent robotic power design is felt, not seen. It manifests as smooth, precise motion, cool-running joints, and unwavering reliability over thousands of hours in challenging conditions. This is the true value of engineering precision in enabling automation to work safely, side-by-side with humans, anywhere.

Detailed Topology Diagrams