Power Supply Design for 5G Base Stations and Edge Data Centers: Why Is Saving Space More Valuable Than Saving Electricity Costs?
Power Design for 5G Base Stations and Edge Data Centers: Why Is “Saving Space” More Valuable Than “Saving Electricity”?
In application scenarios such as rooftop cabinets, street-side cabinets, and building-top sites, physical space is the scarcest operational resource. A single 5G base station cabinet already draws more than 3 kW, while the usable volume of an AAU cabinet is often less than 10 liters. Electricity costs account for only a single-digit percentage of the total cost of ownership over the equipment lifecycle. Every liter of volume reduced and every degree of temperature rise lowered by the power module releases RF unit installation space, battery expansion space, and edge computing node deployment capability—and the combined value of these gains far exceeds the electricity savings from improving power supply efficiency from 96% to 97%.
This is exactly where the core value of silicon carbide (SiC) MOSFETs lies: by increasing switching frequency, the volume of magnetic components and heat sinks is reduced, and the cabinet space saved is left for business workloads, creating greater business returns.
5G Base Station AAU: Increasing Switching Frequency to Gain Space — CM75R035L4X100
The AC/DC PFC stage and high-voltage DC/DC stage of 5G base station power supplies have long faced a set of difficult-to-reconcile contradictions. For conventional silicon superjunction MOSFETs, once the switching frequency exceeds 100 kHz, switching losses deteriorate rapidly. Hardware designers are left with only two choices: either lower the operating frequency, which increases the size of magnetic core components, or accept a higher operating temperature rise and enlarge the heat sink. Both approaches consume a large amount of valuable space inside the cabinet.
SiC MOSFETs break this design trade-off through lower output capacitance and gate charge. Taking the CM75R035L4X100 as an example, the device is rated at 750 V, 54 A, and 35 mΩ in a TO-247-4L Kelvin package. Under the typical 400 V DC bus of telecom power supplies, the device has sufficient voltage derating margin and can raise the PFC circuit switching frequency above 100 kHz.
After the switching frequency is increased, the magnetic core cross-sectional area and winding turns of the PFC inductor and LLC transformer can be reduced accordingly, and the footprint and overall height of the power module decrease. The Kelvin source pin of the TO-247-4L effectively suppresses switching ringing caused by source parasitic inductance. Under high-frequency hard-switching conditions, waveform control remains stable, and no additional snubber circuit is required, further saving PCB space.
For the CCM boost PFC circuit in a 5G macro base station AC/DC, the 750 V voltage rating provides approximately 1.8× voltage margin for a 400 V bus, readily handling lightning surges and switching spikes; the 54 A continuous current covers the switching current stress of a 3 kW-class single-cabinet power topology.
Edge Data Center IBC Stage: Reducing Volume for Density — The Same Device Expands into a Second Application Scenario
The power delivery chain of edge storage servers and street-side edge computing nodes has a system architecture highly similar to that of 5G base station AAUs: 85–264 V AC input is power-factor-corrected by a PFC stage to produce an approximately 400 V DC bus, which is then fed into an isolated intermediate bus converter (IBC).
Inside compact 1U and 2U chassis, cooling airflow is limited. Conventional silicon device solutions can only limit switching frequency to below 100 kHz, and transformers and filter capacitors occupy a large portion of the volume in the power distribution network, reducing overall power density.
The engineering approach of 650–750 V SiC MOSFETs here is completely consistent with that for 5G base stations: rely on higher switching frequency to reduce passive component volume. According to industry measurements, SiC devices can push the switching frequency of edge server IBC circuits to 100–500 kHz, significantly reducing transformer and filter volume and helping the overall system achieve high power density design targets.
The 35 mΩ on-resistance of the CM75R035L4X100 keeps conduction losses within a reasonable range at an operating current of 54 A. At the same time, the extremely low reverse recovery charge of the SiC body diode further reduces switching losses under hard-switching and clamped operating conditions. With lower overall device heat generation, a smaller heat sink can be selected, and fan speed can be reduced—multiple effects together release valuable space for the chassis.
For auxiliary power supplies and bias supply circuits with lower power and stringent space constraints, the CM65R380TFX100 (650 V / 11 A / 380 mΩ) in a TO-220F package can be selected, suitable for low-power auxiliary power supply scenarios.
High-Voltage Auxiliary and Bias Rails: Trading Margin for Reliability — CM170R1KL4X100
In 5G base stations and edge computing equipment, there is another category of power rails that is easily overlooked: gate driver supply, high-voltage bias circuits, capacitor precharge circuits, and auxiliary switching power supplies. These rails do not carry high overall power, but their voltage safety margin cannot be compromised.
When a 400 V DC bus encounters load transients or lightning surges, voltage overshoot occurs, and the peak voltage may approach or even exceed 650 V. Ordinary 650 V-class devices have insufficient derating under such conditions, creating reliability risks.
The CM170R1KL4X100 uses a TO-247-4L package and is rated at 1700 V, 4.8 A, and 1000 mΩ, specifically suited to such high-voltage, low-current auxiliary circuits. The 1700 V blocking voltage provides more than 4× voltage derating for a 400 V bus and offers strong surge withstand capability; the 4.8 A current rating exactly matches the power requirements of auxiliary power supplies, avoiding the cost and volume waste of using an oversized device for low power. The product positioning of this device is high-voltage auxiliary power supply scenarios, with reliability as the priority; it is not recommended for direct use as the main power switching device.
Selection Summary
- For the main power PFC/IBC circuits of 5G base stations and edge data centers: prioritize the CM75R035L4X100 (750 V, 35 mΩ, TO-247-4L) to achieve high-frequency and miniaturized design.
- For low-power auxiliary and bias power supplies: select the CM65R380TFX100 (650 V, TO-220F).
- For high-voltage auxiliary, bias, and capacitor precharge circuits: select the CM170R1KL4X100, relying on its 1700 V high voltage rating to ensure system reliability.
Core design philosophy: Traditional power supply selection often prioritizes calculating conversion efficiency and accounting for electricity cost savings. However, 5G base stations and edge computing equipment are hard-constrained by cabinet space. The volume reduction and power density improvement brought by SiC devices deliver higher business returns than simply saving electricity. Efficiency is an additional benefit; saving space is the core value.