Converting 380 V Bus to Low Voltage for Point-of-Load Applications

With rising power consumption in data centers and telecom systems, improving energy efficiency is of prime concern because reducing power wastage translates into big dollar savings. While there have been numerous proposals floated to improve overall efficiency and drastically cut power consumption, high-voltage DC power distribution is one that is gaining support from several agencies, including the EPA, Green Grid, Electric Power Research Institute (EPRI), and the EMerge Alliance. As a result, there are several studies extoling the virtues of 380 VDC distribution in data center servers and telecom equipment. Of particular note is (1) a white paper by Vicor¹ that shows why high-voltage DC power distribution is an attractive solution to the energy consumption dilemma in data centers and (2) a 380 VDC distribution standard developed by the EMerge Alliance.

In support of the high-voltage DC distribution standard, several power supply vendors have introduced wide-input, high- to low-voltage DC/DC converters for point-of-load (POL) applications in servers and other systems. These include Artesyn Embedded Technologies, TDK-Lambda Americas, and Vicor Corp. Besides serving the need, some of these high-voltage DC/DC converters also raise the performance bar in terms of efficiency, density, reliability, and flexibility.

High step-down converters

Artesyn, for instance, has readied half- and full-brick converters for high-voltage DC/DC conversion that lend themselves to 380 VDC distribution architecture. In the full-brick category, the AIF12 series offers isolated, single-output DC/DC modules, providing up to 600 W output with a maximum baseplate operating temperature of 100°C without de-rating. In addition, it features full safety isolated low-voltage secondary-side control and Astec Linear Programming (ALP), as well as permitting adjustment of module parameters via I²C bus. The 600 W model AIF12W300N-L in this series can handle an input DC range of 250 V to 420 V and deliver regulated 48 VDC output at 12.5 A with low-output ripple and noise. Typical efficiency is 90 percent.

In the half-brick space (Figure 1), the company offers fully-featured AIH series modules that are capable of delivering 250 W output power while providing monitoring, protection, and adjustment capabilities, as well as communication facilities for use when storing valuable end-user information.

Like the AIF series, the AIH models also handle a wide input range of 250 to 420 VDC and can deliver single isolated and regulated outputs of 12 or 24 VDC. While the 12 V model AIH20 is tailored to offer 20 A output current, the 24 VDC model AIH10 provides 10 A output current. Both the units are housed in modules measuring 2.40 x 2.30 x 0.50 in. (61.0 x 58.4 x 12.7 mm).

Figure 1: Artesyn’s half-brick AIH model handles wide-input range of 250 to 420 VDC and delivers single isolated and regulated outputs of 12 or 24 VDC.

Similarly, TDK-Lambda Americas has also crafted isolated full-brick high-voltage DC/DC converter modules with 450 to 600 W output power and nominal single-output voltages of 12, 24, 28, or 48 VDC. The wide-input PAF600F280 series is rated for maximum power output of 600 W with input-voltage range of 200 to 400 VDC. Typical peak efficiency is 91 percent. While the unit is rated to operate up to the baseplate temperature of 100°C, the model needs some derating at 100°C base-plate temperature (Figure 2).

Figure 2: TDK-Lambda’s wide-input PAF600F280 can operate up to 100°C baseplate temperature, but needs some derating at 100°C.

Bus converter modules

Similarly, Vicor has developed a variety of isolated unregulated bus converter modules, labeled BCM®, to step-down 380 – 400 VDC input to standard 48 V or 12 VDC output. The output from these modules is used to power non-isolated POL regulators. A good example is BCM384T480T325A00, a 384 VDC to 48 VDC bus converter incorporating zero-voltage/zero-current switching (ZVS/ZCS)-based sine amplitude converter (SAC) topology to realize high efficiency with high power density. Thus, implementing fixed, high-frequency (>1 MHz) soft switching, the unit offers over 96 percent efficiency with a power density of >1,000 W/in.³ to deliver up to 325 W (average) output power. Housed in the manufacturer’s VI Chip® package, the module is compatible with standard pick-and-place and surface-mount assembly processes. Per the product datasheet, the VI Chip package provides flexible thermal management through its low junction-to-case and junction-to-board thermal resistance, as well as low-impedance interconnect to system board.

Recently, employing advances in power packaging, the manufacturer has further extended the power handling capability of high-voltage BCM modules while concurrently enhancing the power density and efficiency of the high step-down ratio DC/DC converter. With a nominal input voltage of 380 V and a K-factor of 1/8, Vicor’s new BCM in ChiP package (Figure 3) offers an isolated 48 V distribution bus with a peak efficiency of 98 percent. With its input range of 260 to 410 VDC, the new BCM supports outputs ranging from 32.5 V to 51.25 VDC.

Figure 3: Vicor’s new BCM in ChiP package raises the density and efficiency bars.

Offered in the 6123 ChiP package, the new 380 VDC VI Chip BCM BCM380y475x1K2A30 measures 63 x 23 mm, with a height of only 7.3 mm. Initially offered as a through-hole device, package options will also include SMD variants, according to the manufacturer. ChiP BCMs can be paralleled to provide multi-kW arrays and are capable of bi-directional operation to support battery backup and renewable energy applications. Standard BCM features include under-over-voltage lockout, over-current, short circuit, and over-temperature protection. ChiP BCMs incorporate digital telemetry and control features that can be configured to meet customer requirements.

“The roll-out of high-voltage DC distribution infrastructure is yielding reduced power consumption and operational costs for datacom and industrial facilities,” said Stephen Oliver, Vicor’s VP of the VI Chip product line.

In systems where an intermediate bus voltage of 12 VDC is required, Vicor is offering B384F120T30, a 384 VDC to 12 VDC bus converter in VI Chip package (Figure 4), delivering high efficiency (>95 percent) and power density (1,017 W/in.³). The module is rated to deliver up to 300 W output power with no output filtering required. Due to its high-conversion efficiency and safe operating temperature range, the BCM does not require a discrete heatsink in typical applications, according to the product’s datasheet.

Figure 4: This 384 VDC to 12 VDC BCM achieves a power density of 1,017 W/in.³ in a VI Chip package compatible with standard pick-and-place and surface-mount assembly processes.

However, if 48 V bus voltage must be further dropped to 12 VDC, Vicor’s IBC series provides the requisite step-down with peak efficiency close to 98 percent from an eighth-brick footprint and up to 300 W of output power. A converter for this application is Vicor’s IB050E120T32N1-00, an IBC module that provides 12 VDC output from a 48 VDC input with the ability to handle an input voltage range of 38 to 60 VDC with an input-to-output isolation of 2,250 VDC.

In summary, a high-voltage DC distribution ecosystem is now emerging. As more system designers tap the benefits of high-voltage DC distribution, more manufacturers will join the fray to make 380 VDC input DC/DC converters cost-effective and competitive. For more information on the products discussed in this article, use the links provided to access product pages on the Hotenda website.

  1. White paper “High-voltage DC distribution is key to increased system efficiency and renewable-energy opportunities” Stephen Oliver, Vice President, VI Chip Product Line, Vicor Corp.
  2. High Voltage DC Distribution Improves Data Center Efficiency” by Ashok Bindra, Hearst Electronic Products.