Feature: Power
are becoming popular because of their modularity, scalability and efficiency.
Delivering the power Traditional power architectures are facing challenges in providing more than 200kW to a single rack. Today power is generally brought into the rack at 240VAC, converted to about 400VDC and then stepped down to 48VDC inside the rack, feeding each server board 48V. Tis is further converted to sub-1V levels required by the processors. As compute power increases, this
approach reaches fundamental limits. Modern AI server boards can require several kilowatts, which means feeding tens or hundreds of amps at low voltage. At higher power levels, current quickly becomes unwieldy for standard connectors and cabling – with thermal and mechanical limits. With that in mind, the industry is
moving to deliver power to the server board at much higher voltages. Te 800VDC or ±400VDC architectures result in lower current levels, making the power distribution more practical and efficient. In these early systems, the high voltage
power is usually generated outside of the system, oſten in a dedicated “sidecar” rack, and then distributed to the compute racks.
Rapid growth of artificial intelligence is
forcing a rethink of the data centre power architecture
Depending on the design, the voltage is either converted locally on the server board to intermediate levels like 6V or 12V, or converted to 48V in the rack before distribution. Server boards are extremely valuable
and space-constrained real estate, so any onboard power conversion must be highly compact, low profile and exceptionally efficient, and able to support advanced thermal management strategies.
ISOP architectures for scalable isolation In high-voltage DC systems, the isolation stage needs high efficiency, compact size and robust thermal performance. ISOP converter topologies distribute electrical stress elegantly among multiple modules. Input to converters are series connected in an ISOP arrangement to enable the system to be used from high input voltage, with outputs being parallel connected, to provide high current; see Figure 1. Te
electrical and thermal load on individual components is reduced, as each module handles only a part of the total voltage and power. Resonant LLC converters are very well
suited to this modular concept. Tese converters are designed to operate close to their resonant point, leading to high efficiency and natural voltage, and current sharing between modules. Tis intrinsic balancing behaviour reduces the need for complex control schemes. However, LLC converters usually have a fixed conversion ratio and therefore are best suited for stages where tight voltage regulation is not required. Te ISOP implementations have several
advantages over monolithic designs, such as lower voltage stress on the switching devices, simplified insulation requirements, improved heat distribution and increased power density. Tese features are well suited for the rigorous requirements of AI server power solutions.
Figure 1: The basic ISOP concept is to use low voltage devices in a stacked series of LLC converters with their outputs connected in parallel
www.electronicsworld.co.uk July/August 2026 25
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