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Power Technology Roadmap Charts Parametric Trends for DC/DC Converters

Von Ashok Bindra

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Power supply users increasingly demand more effective, smaller and lower-cost solutions. Users also seek advances in circuit design, components, and packaging and assembly techniques to meet changing consumer needs. The Power Sources Manufacturers Association (PSMA) recently responded by developing its seventh technology roadmap, the 2011 PSMA Power Technology Roadmap (PTR), for product groups such as AC/DC front-end power supplies, external AC/DC supplies, isolated and non-isolated DC/DC converters. ²

PSMA created the roadmap to provide insight into power technology and power delivery trends and prepare users and manufacturers for changes in the industry. It consists of presentations and workshops by leading power source experts in power architectures, components and technology, and market forces. Since applications also drive the performance specifications of power supply products, the roadmap also includes a new segment on application trends. This piece covers important metrics, market drivers and challenges in computing, communications, digital power, industrial, lighting, medical, military and solar photovoltaic (PV) power.

“The breadth and depth of the presentations, commentary and discussions are unprecedented and together capture the technical trends and issues facing the industry today,” said Aung Thet Tu, product line director at Fairchild Semiconductor and co-chair of the PSMA organizing committee, during his plenary talk at the Applied Power Electronics Conference (APEC) 2011¹ this year.

At the conference, co-chair Carl Blake said, “Adding the third segment of applications provides a more comprehensive look at the dependency between multiple segments of technology, products, components and applications.”

Isolated DC/DC converters

According to the PSMA PTR, in the isolated DC/DC converter industry, half-brick form factor continues to decline in popularity because power supply designers favor smaller quarter- and eighth-brick sizes. However, the roadmap indicates that sixteenth-brick sizes are also gaining momentum in some applications that are less cost sensitive.

While the telecommunications sector continues to use 48/60 V as standard input voltages, 48 V is still the narrow input range for computing and networking. Meanwhile, other industries, such as industrial and military, increasingly drive other input voltage ranges (Table 1).

PSMA Voltage Requirements

Table 1: Estimated input and output voltage requirements for a variety of fully regulated, isolated bricks and other form factors, along with drivers and barriers. (Source: PSMA.)

The PSMA roadmap shows that single-output converters still dominate the landscape and are used in more than 95 percent of power supply designs. Although improved switching technology, controllers and integrated assembly methods continue to improve efficiency and increase power density, price reductions will continue to impact the adoption rate of single-output converters.

The roadmap predicts that communication interfaces will begin to change from serial to parallel as designers increasingly adopt protocols such as PMBus for communications and control of microcontrollers. Power supply designers will increasingly use PMBus as digital control proliferates.

Non-isolated DC/DC Converters

The voltage necessary for electronic loads, such as processors, DSPs and memory and logic ICs is continuing to decrease into the sub one-volt region. In addition, electronic loads require tighter voltage set point windows, lower output voltage ripple, faster transient response and reduced noise generation (Table 2).

PSMA VIN, IOUT

Table 2: Projected input voltage range (VIN) and output current (IOUT) ratings for non-isolated DC/DC converters through 2015. (Source: PSMA.)

Power density is continuing to increase and, as a result, emerging non-isolated DC/DC converters must operate at higher switching frequencies to reduce component size, use better package thermal performance and deliver improved efficiency.

Consequently, PSMA suggests that offerings in power-supply-in-a-package (PSiP) and power-supply-on-a-chip (PwrSoC) will continue to emerge. Integrating a smaller inductor within a package continues to be an important factor for a viable PSiP, along with other passive components. However, unlike PSiP, the inductor is external to the PwrSoC chip.

Because the PSiP encompasses all components to deliver a complete DC/DC converter solution, it is gaining momentum for non-isolated point-of-load (POL) designs where efficiency and density are paramount.

Power components

To meet new requirements by decreasing dynamic power losses and further improve conversion efficiency of power supplies, power semiconductor suppliers continue to improve the area-specific on-resistance RDS (on) of MOSFETs. However, a new trend is to reconsider the common figure of merit (FOM), which was traditionally defined as input gate charge (Cg) multiplied by RDS (on). According to the PTR, designers are finding that Coss/Qoss may be a better metric for low-voltage POL converters running above 400 kHz and high-voltage applications in general.

Meanwhile, suppliers are developing new die-bond techniques and materials to continuously improve power package performance.

For example, GaN-based FETs are generating tremendous interest in DC/DC converter design and manufacturing because of the benefits of gallium nitride (GaN), including lower specific on-resistance, higher breakdown voltages, higher switching frequencies and improved system efficiency and power density. In fact, International Rectifier and Efficient Power Conversion recently announced the availability of GaN-on-Silicon (GaN-on-Si)-based FETs up to 200 V.

Both manufacturers are touting GaN-on-Si-based FETs as replacements for silicon MOSFETs in voltage converters to increase efficiency and power density. Efficient Power Conversion recently demonstrated how its enhancement-mode GaN or eGaN FETs can handle high step-down ratios in a single stage with unprecedented efficiency and power density. (See Digi-Key’s Product Training Modules) The manufacturer attributes this performance to dramatic improvements in FOM with higher switching capability, no stored charge and no reverse recovery. This allows POL DC/DC converters with necessary high step-down ratios to generate 1.8 V or lower from a 48-V bus voltage.

Many other suppliers are expected to follow with 600-V-or-higher GaN offerings. Market research firm Yole Développement identified manufacturers planning to join the race at 600 V and above, including Furukawa, GaN Systems, MicroGaN, Panasonic, Sanken, and Toshiba. According to Yole Développement, the inflection point for GaN market ramp-up will occur early next year, leading to a $50-million-plus market by 2013 and expanding to $350 million by 2015.

Copies of the printed and CDROM versions of roadmap were shared with PSMA regular and associate member companies as a benefit of their membership. PSMA affiliate members and non-members can purchase the report from the PSMA website.

References:
  1. Plenary talk by Aung Thet Tu, Co-Chairman of PSMA Power Technology Roadmap committee, APEC 2011
  2. PSMA Power Technology Roadmap report 2011 on CD, How2Power Bookstore.

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Über den Autor

Ashok Bindra

Über den Verlag

Electronic Products

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