Feature: Power
Figure 2: The EPC91123 – an 800V-12.5V, 6kW, eight-stage ISOP DC-DC converter
Lower voltage operation benefits A major benefit of ISOP configurations is the possibility to use lower voltage semiconductor devices. Te total input voltage can be shared between multiple modules, so that each stage is exposed to a smaller range of voltage. Tis allows the use of faster and more efficient components. Te approach is especially useful when
employing wide bandgap technologies like gallium nitride (GaN). GaN devices are lower voltage, have lower conduction losses, lower gate charge and better switching characteristics than higher voltage devices. Such properties are needed for high-frequency operation and compact system design. For a conventional single-stage converter
stepping down from 800V, the devices must be rated for the full input voltage. In contrast, the ISOP-based approach enables operation with devices rated for much lower voltages, such as 150V GaN transistors, with the benefits of higher efficiency and smaller footprint. Tese devices are also well suited for advanced
thermal management techniques such as direct liquid cooling.
Interleaving and ripple mitigation Te modularity of ISOP systems also allows good ripple reduction using phase interleaving. Tis is done by switching numerous converter modules with equally spaced switching phases so that the total output current is smoothed. Tis method reduces the current ripple amplitude whilst increasing its frequency, thus reducing the output capacitance needs. Te resulting design is more compact, with better transient response and higher overall efficiency – an advantage especially crucial for high current applications characteristic of AI workloads. ISOP topologies divide the load on several channels instead of forcing huge ripple currents through one conversion stage, improving electrical performance and reliability.
A 6kW modular converter An example implementation shows the practical advantages of ISOP-based designs.
26 July/August 2026
www.electronicsworld.co.uk Te EPC91123 is an 800V-12.5V, 6kW,
eight-stage ISOP DC-DC converter that is only 8mm thick, designed to be mounted directly on the server board. Tis converter has a peak efficiency of 98.3% and a full- load efficiency of 97%; see Figure 2. Here the isolation stage of 6kW is achieved by eight identical LLC modules in an ISOP arrangement. Each module converts about 750W, converting an intermediate voltage to a low-voltage output suitable for compute hardware. Te design features compact GaN
devices on primary and secondary sides with synchronous rectification to maximise efficiency. Planar transformers embedded in multilayer PCBs provide isolation and a very low profile. Te surface-mount configuration of
the complete system achieves a minimal footprint and enables advanced cooling strategies. Te experimental validation demonstrates peak efficiency higher than 98% and over 97% at full load conditions, confirming the suitability of this architecture for the high-density AI environments.
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