Power Supply for Data Centers How 1 MW per Server Rack Is to Become a Reality in the Future

Related Vendors

Infineon Technologies AG

Rittal GmbH & Co. KG

FAULHABER Drive Systems

Wuxi InfiMotion Technology Co., Ltd.

While traditional server racks have so far managed with 40 to 100 kilowatts, artificial intelligence is increasing power requirements to previously unimaginable levels. The vision is: one megawatt per rack. However, to ensure that this figure is not just a marketing figure, fundamental problems with the power supply need to be solved.

Traditionally, power is supplied to the data center via alternating current, which is fed into the racks and broken down by power supply units for each individual server board. However, this architecture means that the energy is converted several times: from high voltage AC to low voltage AC, then to 48 volts DC and finally directly to the supply voltage of the chips. Each stage generates losses. Even efficient power supply units rarely achieve more than 90 percent; standard devices often achieve 80 to 85 percent. This sounds high at first glance, but in a rack with a 100 kilowatt load, ten percent loss already means ten kilowatts that are converted exclusively into heat. With a target value of one megawatt per rack, the same efficiency would mean over 100 kilowatts of waste heat from the power supply units alone. As much as the entire energy requirement of a small company.

A new Approach

Infineon is working with partners such as Nvidia on a power architecture that radically reduces the number of converter stages. Instead of carrying alternating current to the rack, direct current of up to 800 volts is to be supplied directly to the cabinets. Only there is a targeted conversion to the required operating voltages carried out. This centralization of power distribution not only reduces the amount of cabling and space required, but above all the losses. Fewer conversion stages mean greater efficiency.

Infineon is launching power supply units and backup modules with a significantly higher power density on the market. While small power supply units with a few kilowatts per server or per blade were previously common, central power supply units with 12 kilowatts and more are now taking center stage. Combined with the latest semiconductor technology based on silicon carbide and gallium nitride, efficiency is increasing noticeably. Instead of 80 percent, values in excess of 95 percent will be possible in the future. The difference sounds small, but on the scale of entire data centers, it makes the difference between manageable operation and an energy guzzler that is no longer economically viable.

Semiconductors in Transition

The breakthrough for the 800-volt DC power supply in the rack is based on decisive advances in power semiconductors. Classic silicon transistors quickly reach their limits at high voltages and currents: On-resistance increases, switching losses increase and thermal stresses further degrade performance. Wide-bandgap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) fundamentally change the picture. Their larger bandgap not only allows higher reverse voltages, but also a significantly lower specific on-state resistance (R_DS(on)) and considerably lower switching losses. SiC MOSFETs can operate reliably in the 800 V range without massive heat losses. GaN components go one step further by enabling extremely high switching frequencies. This significantly reduces the size of passive components such as coils and capacitors and makes the power modules more compact and efficient overall.

This technological basis enables modern power supply units and DC/DC converters to achieve efficiencies of over 95%, whereas previous silicon solutions usually remained at 80-90%. The lower losses and better thermal stability make cooling and operational management much easier. Without wide bandgap materials, efficient 800 V DC architectures would be almost impossible to implement in the rack.

Infineon is also using this semiconductor expertise to lead the way in the next generation of battery backup units (BBUs). The roadmap ranges from modular 4 kW solutions to the world's first 12 kW BBU, which achieves a power density up to 400 percent higher than the industry standard. These backup modules not only offer a particularly efficient and scalable power supply for AI server racks, but also reliably protect sensitive hardware from voltage peaks and current anomalies.

Cooling is also Crucial

With SiC- and GaN-based solutions, Infineon is creating the basis for power up to 800 volts to be fed directly into the rack, where it is available with minimal losses. However, even if the losses are drastically reduced by wide bandgap semiconductors, cooling remains a decisive factor. This is because every percent of waste heat adds up to enormous amounts of energy for megawatt outputs. This is where providers such as Rittal come into play, using direct liquid cooling systems to ensure that the thermal load is reliably dissipated - only the combination of an efficient power supply and modern cooling technology makes the 1 MW server rack truly realistic.

One megawatt per server rack is therefore not just a question of cooling, but above all a question of electrical efficiency. Every kilowatt hour that is not lost in heat can be used directly for computing power. If the power supply is rethought, with high-voltage direct current right into the rack and high-density power modules directly at the chips, then the megawatt rack moves from a vision to reality. (mr)