Server Power Supplies, Power Supply Blades, UPS Systems, PSU Waveform/ Power Analysis and Standard Evaluation

1. Introduction

In recent years, the rapid proliferation of generative AI has accelerated the development of server power supplies in data centers. Generative AI relies on high-performance hardware to process vast amounts of data and execute complex computations—driving demand for specialized hardware components such as GPUs and TPUs* in particular.
These systems consume significantly more power than conventional servers do, making it critical to enhance the power supply infrastructure within data centers.
The introduction of high-performance GPU servers has raised concerns about power capacity per rack, prompting data centers to strengthen their existing infrastructure and adopt new power management solutions. Furthermore, as demand for generative AI continues to grow, power supply systems in data centers are expected to become even more efficient, and various initiatives are underway to support this transition.
* PSU: Power Supply Unit
* GPU: Graphics Processing Unit
* TPU: Tensor Processing Unit

2. Challenges

As adoption of generative AI accelerates, the development of server power supplies in data centers is also progressing— bringing with it several challenges. The deployment of highperformance GPU servers has rapidly increased the power capacity required per rack in data centers. With this surge in power consumption, concerns have emerged about power supply waveform distortion and voltage fluctuations that can impact the stable operation of servers.
To mitigate these risks, uninterruptible power supplies (UPSs) play a vital role. UPS systems ensure continued power delivery during outages or irregularities, helping to protect critical equipment like servers and network devices from data loss or unexpected system shutdowns. So as demand for generative AI continues to grow, data centers are reinforcing their power supply infrastructure and implementing new ways to manage their power.

3. Yokogawa solutions

DL950 ScopeCorder
• Various plug-in modules
• Waveform measurement of high-voltages and high-currents
• Power parameter measurement
• Synchronous measurement of multiple units
DLM3000HD High-Definition Oscilloscope
• Switching loss measurement
WT5000 Precision Power Analyzer
• Basic power accuracy of ±0.03%
• High-precision efficiency measurement
IS8000 Integrated Measurement Software Platform
• Simple comparison with standards
• Detailed waveform confirmation with a zoom display
• Display and comparison of multiple waveform data
• Waveform analysis by calculation

4. Proposal for using the DL950

4.1 Various plug-in modules

The DL950 offers a diverse selection of plug-in modules designed to meet various measurement requirements. These modules range from high-speed, high-precision voltage measurements to temperature, acceleration, strain, frequency, logic, and serial communication data measurements. The modules fit into eight slots on the DL950 main unit, allowing for flexible configurations to suit your specific measurement needs.

Figure 1. DL950 ScopeCorder and various plug-in modules

4.2 Waveform measurement of high voltages and high currents

Taking high-voltage and high-current measurements is essential for power supplies in AI data centers. For highvoltage measurements, the DL950 uses a high-speed 200 MS/s, 14-bit isolated module (720212) paired with a probe for the isolated input module (700929/702902/701947), capable of measuring up to 1,000 V (DC + ACpeak).
For high-current measurements, a combination of a voltage measurement module and an AC/DC split-core current sensor (CT1000S) allows for measurements of up to 1,000 A AC and 1,500 A DC*. The AC/DC split-core current sensor offers easy installation without the need to cut the measurement cable, provides excellent noise immunity, and enables stable large-current measurements over a wide bandwidth.
* Operating environment temperature: Max +40°C.
* The DL950 main unit requires the probe power supply option (/P4 or /P8 option).

Figure 2. AC/DC split core current sensor CT1000S

4.3 Power parameter measurement

The Power Calculation (/G05 option) can calculate up to 118 power parameters for a single system, including voltage RMS value, voltage frequency, active power, reactive power, power factor, and efficiency. It allows for real-time display of both voltage/current waveforms and power parameter trend waveforms on the same time axis.
By setting the calculation interval to align with the input signal edge, calculations can be performed every cycle or half-cycle, enabling measurement of transient voltage/current and power parameters during output transients and fluctuations. Additionally, since the calculated power parameters can be used as trigger sources, fluctuations in voltage, current, and power during instantaneous voltage drops or frequency fluctuations can be monitored. Automatic parameter measurement and cursor-based measurements are also available for power parameters.

Figure 3. Examples of single-phase voltage and current waveforms, along with power parameter calculations

4.4 Synchronous measurement of multiple units

You can connect up to four subunits to a single main unit via fiber-optic cables, expanding the system to a maximum of 160 channels. Measurement start/stop, trigger timing, and sample clock can all be synchronized across the units.

Figure 4. Example of connecting five DL950 units

Measured data can also be displayed as waveforms on the IS8000 integrated measurement software platform. The IS8000 consolidates control and data acquisition for multiple measuring instruments, enhancing reliability and efficiency.
Additionally, post-measurement data analysis can be conveniently performed on a single display.

5. Proposal for using the DLM3000HD

5.1 Switching loss measurement

Switching losses in power devices are typically calculated based on the product of voltage and current in the turn-on/ off section, and power calculations using current and constants such as ON resistance (RDS(on)) and saturation voltage (VCE(sat)) during the conduction phase. However, the switching loss calculation function in the DLM series’ power supply analysis function can easily perform these calculations.

For instance, when measuring a MOSFET, the following losses can be readily calculated as power [W] and electric energy [J or Wh] by entering the voltage, current-level values, isolating the switching section, and specifying the ON resistance value:

• Turn-on loss
• Conduction loss
• Turn-off loss
• Total of the above

The DLM series allows you to zoom in on any two points simultaneously. This enables focused analysis of the turn-on/ off area within the cycle of interest, as shown in Fig. 5, where ringing and noise conditions can be observed.

Figure 5. Switching losses are obtained by focusing on a single

6. Proposal for using the WT5000

6.1 Highly accurate power measurement with a basic power accuracy of ±0.03%

The WT5000 offers a total measurement accuracy of ±0.03% (50/60 Hz), which is among the highest in the world. When measuring currents with high RMS wave heights, minimizing range error is important. This is why the WT5000 provides a minimum range error and a power accuracy of ±(0.01% of reading + 0.02% of range) (50/60 Hz), ensuring highly precise power measurements. Thanks to its modular design, the WT5000 allows you to replace or add your own input modules. The system offers three different input options (dedicated current sensor input, 30-A rated input, or 5-A rated input), enabling flexible measurement of a wide range of current amplitudes with a single unit.

Figure 6. WT5000 input elements (3 types) mounted

6.2 High-precision efficiency measurement of AC/DC and DC/DC conversion

AI data center power supplies typically contain several conversion circuits. Suppressing harmonics is crucial because they are connected to a standard AC commercial power supply, and suppression is achieved by including a power factor correction (PFC) circuit. Additionally, a DC/DC converter is used to regulate the DC voltage level. These conversion circuits require designs that minimize power loss, and the WT5000, with its multi-channel input capability, is ideal for measuring the efficiency of each circuit with precision. This ensures optimal performance.

Figure 7. Example of WT5000 and CT1000S connection

7. Proposal for using the IS8000

7.1 Simple comparison of measurement parameter response times with standards

A simple comparison can be performed to check if the response time of a measurement parameter is within the specified standard. By reading a measurement data CSV file and a standard reference line CSV file (which must be prepared in advance), the two datasets can be overlaid for easy comparison to determine whether the response time meets the standard.*
* This is a simplified comparison method, as it involves waveform comparison under the assumption that the measured waveforms are reproducible. Prior verification in the customer’s environment is required.

Figure 8. Example of comparison with standard values

7.2 Detailed waveform confirmation with a zoom display

You can zoom in on up to four waveforms at the same time.
This allows for simultaneous observation of waveform rise and fall characteristics in greater detail.

Figure 9. Example of up to four simultaneously displayed zoomed waveforms

7.3 Display and comparison of multiple waveform data on the same time axis

You can display data measured with the DLM series oscilloscope or DL ScopeCorder by synchronizing the time axis of each dataset during offline analysis. In addition to synchronization with absolute time or the start/end of a waveform, the reference time axis can also be synchronized based on the trigger position information of each waveform.
Displaying the trigger position as a reference helps in analyzing the relationship between events before and after triggering.

Figure 10. Example of two files displayed using the trigger position as a reference point

7.4 Waveform analysis by calculation

After confirming the waveform, you can perform not only parameter and cursor measurements but also waveform calculations and FFT analysis using the extended calculation option.

Figure 11. Example of parameter measurement