Testing Solutions for AI Power Electronics

Introduction

Artificial Intelligence has rapidly evolved from experimental research into the backbone of modern innovation — driving breakthroughs in autonomous systems, aerospace, healthcare, and data-driven decision making. As AI models grow larger and more complex, the demand for computational performance has skyrocketed, pushing data centers and server architectures to their physical and electrical limits.

Behind every large-scale AI cluster lies an intricate power network supporting thousands of GPUs, CPUs, and accelerators operating at full capacity. These systems consume massive and rapidly fluctuating amounts of energy, generating electrical and thermal challenges that conventional test methods were never designed to handle. Ensuring that every component — from power supply units to distribution modules — performs reliably under extreme loads is now essential to maintain uptime, safety, and computational accuracy.

At Rexgear , we are at the forefront of this transformation. Our expertise in high-power testing and automation enables engineers and manufacturers to validate next-generation AI servers and power systems with precision, repeatability, and confidence. By combining advanced instrumentation, automated test software, and real-world simulation capabilities, Rexgear helps leading organizations design and qualify the most demanding AI and high-performance computing infrastructures on the planet.

The Architecture of an AI Server

Unlike traditional enterprise servers, AI servers are purpose-built for massively parallel computation. Their architecture is designed to move and process data at extraordinary speeds, but this performance comes with an equally extraordinary demand for power.

At the heart of an AI server lies a dense array of graphics processing units (GPUs) or AI accelerators — sometimes dozens per chassis — each capable of drawing hundreds of watts during peak workloads. Surrounding these compute elements is an intricate power delivery network (PDN) . Multiple high-efficiency power supplies convert AC input into regulated DC rails that feed processors, memory, and interconnects. cooling systems , VRMs (Voltage Regulator Modules) , and redundant backup systems form a delicate balance between electrical performance, thermal management, and reliability.

From a testing perspective, this architecture creates an entirely new landscape of challenges: transient behavior, voltage droops, harmonic distortion, and energy efficiency must all be characterized under real operating conditions. Any instability in the power chain can lead to computation errors, reduced model accuracy, or even catastrophic hardware failure — outcomes that are unacceptable in mission-critical AI environments.

Simplified AI server power architecture

Inside the Power Delivery Network (PDN): From Wall Power to the Silicon

Power in an AI server travels through a carefully engineered hierarchy known as the Power Delivery Network (PDN) — a multilayer system that converts, regulates, and distributes energy from the facility's AC mains all the way down to the millivolt levels used inside GPU and CPU cores.

The process begins with high-efficiency AC-DC power supplies that convert incoming power (typically 208 V or 277 V AC) into intermediate DC voltages such as 12 V or 48 V. These rails are then distributed across the server's backplane and into the mainboard, where a network of copper planes, bus bars, and high-current connectors ensure low-resistance delivery to every subsystem. 

Once the intermediate voltage reaches the processor area, Voltage Regulator Modules (VRMs) take over. Each VRM is a high-frequency DC-DC converter located physically close to the processor socket or accelerator package. Its role is to step down the 12 V or 48 V rail into the precise voltage required by the silicon — often as low as 0.8 V or less — while supplying hundreds of amperes of current with microsecond-level response time.

Modern GPUs and AI accelerators contain multiple power domains , meaning separate VRMs may feed distinct parts of the chip such as compute cores, memory controllers, and high-speed I/O interfaces. These VRMs use advanced topologies (multiphase buck converters, digital controllers, and adaptive compensation) to maintain voltage stability even during sudden current spikes that occur when thousands of cores switch simultaneously.

The final stage of the PDN consists of on-package and on-die decoupling capacitors , which smooth out transient noise and provide instantaneous charge to the transistors inside the chip. Together, this chain — from rack power supply to PCB traces to silicon — forms a dynamic ecosystem where every milliohm and nanohenry matter. Even small parasitic elements in the PDN can cause voltage droops, timing errors, or reduced efficiency, making power integrity testing and validation critical for AI-class hardware.

Why Testing Matters in AI Power Systems

AI servers push hardware far beyond the comfort zone of conventional computing. Power rails fluctuate under unpredictable workloads, GPUs draw hundreds of amperes in microseconds, and even minor transients can ripple through the PDN causing logic errors or performance throttling. In these conditions, reliability is not an assumption — it's a measurable outcome.

Testing ensures that every part of the power delivery chain performs predictably under stress. It validates power integrity , confirming that voltage droops, ripple, and noise remain within design limits. It verifies efficiency , ensuring minimal energy loss and thermal overhead. It also exposes transient weaknesses that may only appear during rapid load transitions — the same conditions AI models generate during real-world inference and training.

For manufacturers and integrators, thorough testing translates directly into uptime, safety, and data accuracy. A single unstable rail can corrupt a multi-million-parameter computation or trigger cascading shutdowns across a cluster. Therefore, power testing isn't merely a validation step — it's a design discipline that defines the boundary between theoretical performance and real-world reliability.

Testing Architecture for AI Servers

As AI servers evolve to support increasingly dense GPU and CPU clusters, their power delivery networks (PDNs) face extreme demands for stability, efficiency, and redundancy. Validating these systems requires precise control, measurement, and monitoring at every stage — from the power supply units (PSUs) up to the voltage regulator modules (VRMs) and the load consumed by the processors.

This diagram summarizes how Rexgear's integrated test solutions enable engineers to evaluate the full power path of an AI server. Each subsystem — including redundant PSUs, OR-ing and Power Distribution Boards (PDBs), and VRMs — can be tested individually or as part of a complete system-level validation. By using programmable power supplies, electronic loads, and high-performance power analyzers, our setup ensures accurate simulation of real-world operating conditions, from startup transients to dynamic load switching.

Through this approach, engineers can:

• Characterize PSU performance under redundant and parallel configurations.
  
  

• Verify OR-ing and PDB efficiency and fault protection.
  
  

• Validate VRM regulation and transient response under realistic GPU/CPU activity.
  
  

• Measure overall system power efficiency and dynamic behavior with precision instruments.
  
  

Together, these tools provide a complete ecosystem for AI server power testing , helping manufacturers ensure reliability, safety, and performance before deployment in high-density data centers.

VRM Testing — Precision Validation of Power Regulation Performance

The Voltage Regulator Module (VRM) is a critical stage in the AI ​​server's power delivery path, converting intermediate bus voltages (typically 12 V or 48 V) down to the ultra-low core voltages required by GPUs and CPUs — often below 1 V, at hundreds of amperes. Ensuring its accuracy, stability, and transient response is essential for overall system reliability and energy efficiency.

In this test configuration, a programmable DC power supply emulates the upstream bus (PSU output or PDB line), while a programmable DC electronic load replicates the dynamic current demand of the processor rails. This setup allows engineers to precisely characterize how the VRM performs under a wide range of real-world conditions.

Test Objectives

• Voltage Regulation Accuracy: Verify output voltage precision under static and dynamic load conditions.
  
  

• Transient Response: Measure overshoot, undershoot, and recovery time during fast load steps.
  
  

• Efficiency and Thermal Characterization: Quantify conversion efficiency across load levels and monitor thermal behavior.
  
  

• Protection and Fault Tests: Validate OVP, OCP, and OTP protections according to design specifications.
  
  

Test Equipment

• Programmable DC Power Supply (IT6000): Provides a stable and adjustable input source for the VRM under test, supporting wide voltage and current ranges.
  
  

• Programmable DC Electronic Load (N62400 Series Low Voltage High Current DC Electronic Load): Simulates high-speed, variable GPU/CPU current consumption, enabling dynamic step loading and transient analysis, ideal for validating VRM performance under real-world switching activity.
  
  

Through Rexgear's integrated VRM testing solution, engineers can replicate realistic load transients, capture millisecond-scale regulation events, and validate the stability of the entire power delivery network before system integration.

OR-ing & PDB Testing — Validation of Redundant Power Distribution Paths

The OR-ing and Power Distribution Board (PDB) stage manages the transition between multiple redundant power supply units (PSUs) and the downstream voltage regulation modules (VRMs). It ensures that power is delivered continuously even if one or more supplies fail, using OR-ing controllers, diodes, or ideal MOSFETs to isolate and balance current flow between channels.

In this setup, the ITECH IT-M3900C series programmable DC power supplies emulate the redundant PSU outputs of the server. Each output channel represents a different voltage rail — for example 12 V , 12 V Standby (12 VSB) , and 48 V — all feeding into the OR-ing & PDB module.

At the output side, the ITECH IT6000C bidirectional DC power supply acts as a programmable load or VRM emulator, an IT8000 DC load can also be used for this purpose , allowing the engineer to draw controlled current and replicate downstream system behavior. This bidirectional capability enables both sourcing and sinking current, making it ideal for characterizing voltage transitions, backfeed protection, and fault recovery scenarios.

Test Objectives

• Redundancy and OR-ing Validation: Confirm proper current sharing and isolation between PSU channels.
  
  

• Voltage Drop & Reverse Current Tests: Measure diode or MOSFET voltage drop and verify that no backfeed occurs during channel switching.
  
  

• Efficiency & Thermal Evaluation: Assess conduction losses and thermal behavior across OR-ing stages.
  
  

• Fault Tolerance Testing: Simulate PSU failure or disconnection and verify uninterrupted output delivery.
  
  

Equipment Used

• ITECH IT-M3900C Series Bidirectional DC Power Supplies – Simulate multiple PSU outputs with precise voltage and current control (12 V / 12 VSB / 48 V).
  
  

• ITECH IT6000 Bidirectional DC Power Supply or IT8000 DC Load – Operates as a controllable load or VRM simulator, capable of both sourcing and sinking current for dynamic transition testing.
  
  

This configuration enables comprehensive OR-ing and PDB validation , ensuring reliable power redundancy, seamless failover behavior, and efficient current management across high-density AI server power architectures.

PSU Testing — Input Grid Simulation and Efficiency Characterization

The Power Supply Unit (PSU) is the foundation of any AI server's power delivery system. It converts AC grid input into multiple regulated DC rails such as 12 V , 12 V Standby , and 48 V , feeding downstream stages like the OR-ing board and VRM modules. Validating PSU performance ensures that the system can deliver consistent power, maintain high efficiency, and meet safety and redundancy standards under real-world operating conditions.

In this configuration, the ITECH IT7900 regenerative grid simulator emulates the AC mains input of the server. It provides a fully programmable, single-phase power source capable of simulating voltage sags, frequency variations, and transient events to evaluate PSU robustness and compliance with grid standards.

On the DC side, three ITECH IT-M3900C series bidirectional power supplies or IT-M3800 DC Electronic loads emulate the server's internal power rails , drawing programmable current to simulate real operational load profiles across 12 V , 12 VSB , and 48 V outputs. A high-precision power analyzer (87400) is connected between the input and output to measure voltage, current, power factor, harmonics, and efficiency in real real time.

Test Objectives

• Input Performance & Power Quality: Evaluate PSU response to AC line variations, dips, and phase distortions.
  
  

• Output Regulation & Stability: Verify voltage accuracy and current capability across all DC rails.
  
  

• Efficiency & Power Loss Analysis: Measure input vs. output power to calculate conversion efficiency and identify thermal losses.
  
  

• Protection Testing: Validate PSU behavior under overcurrent, short-circuit, and brownout conditions.
  
  

Equipment Used

• ITECH IT7900 Regenerative Grid Simulator – Provides controlled AC input with programmable voltage, frequency, and harmonic distortion to simulate real-world grid behavior.
  
  

• ITECH IT-M3900C Series Bidirectional Power Supply – Simulate multiple server DC rails (12 V / 12 VSB / 48 V) with adjustable current, enabling steady-state and dynamic load tests.
  
  

• 87400 Power Analyzer – Captures high-accuracy measurements of input/output power, PF, THD, and efficiency for comprehensive PSU characterization.
  
  

This setup allows engineers to perform complete PSU validation , from AC input compliance to DC output performance and overall efficiency, ensuring that each unit meets the stringent power integrity demands of modern AI servers.

Power Efficiency & 80 PLUS Validation

Beyond functional validation, this configuration also supports compliance testing for energy-efficiency standards such as 80 PLUS and Energy Star . By combining the IT7900 grid simulator , IT-M3900C bidirectional PS , and a precision power analyzer , engineers can accurately measure input and output power under various load levels (20%, 50%, 80%, and 100%). These measurements determine the PSU's conversion efficiency , power factor, and total harmonic distortion—key metrics required to certify high-efficiency power supplies.

Through this setup, Rexgear's test solutions enable manufacturers to validate compliance, optimize power conversion stages, and ensure that each PSU meets the demanding performance and sustainability goals of modern AI data centers.