Applications Push Input Voltages of DC-DC Converters Higher

With power consumption and the cost of power increasing exponentially, datacenters are rapidly migrating toward high voltage DC power distribution because of their increasing need to reduce power distribution losses and improve overall system efficiency.

Likewise, to minimize the use of copper for high power transmission, three-phase circuits are popular in datacenters and datacom facilities in Europe. Such applications revolve around three-phase distribution at 380 or 415VAC with a basic AC-DC front-end connected to each phase. The high DC voltage generated from this scheme is distributed throughout the system for further conversion.

High voltage DC power distribution is gaining traction in the commercial and military EV/HEV market. Military hybrid electric vehicles (HEVs) traditionally operated by a stack of Li-ion type batteries are incorporating power distribution systems that are driven by input voltages in the range of 600V. As a result, such systems must incorporate bus converters that down convert the high voltage input from the batteries to 28 VDC output as a bus for powering other functions in the vehicle.

Stringent standards for ruggedness, transient response, safety and other factors, has generated specifications that define the characteristics of the 600 VDC electrical system. Labeled MIL-PRF-GCS600A, and approved by the Department of Defense (DoD), these specifications provide a system of requirements for the electrical characteristics and safety of high voltage power distribution subsystems in military ground vehicles.

With voltages as high as 600V, safety becomes paramount. The designer must ensure that DC-DC converters used in these systems meet the isolation requirements of the application. In addition, minimizing EMI interference and curbing transients and surges at high voltages raises its own set of engineering challenges. In fact, tackling such issues in high voltage circuits can present a significant barrier to entry for most power supply vendors.

And with the availability of high voltage – 800+V – power components like Silicon Carbide MOSFETs and high breakdown voltage capacitors, existing designs can be upgraded to meet the DC-DC conversion needs of high voltage applications with 400V and higher DC input voltages. The concept of selectively strapping the primary of two power trains in series or parallel to accommodate wide input ranges is another Vicor proprietary approach well worth exploring.

But ultimately, power supply makers need to understand more fully the market opportunities and then choose to either re-examine and rework existing approaches or develop a brand new power scheme to enable power system designers to efficiently and cost effectively meet these new power challenges.

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