ENGINEERING FEATURE

Immaculate Conversion – Evolution of AC/DC and DC/DC Power Supplies

The increasingly complex demands placed on modern power architectures are at odds with the ever present pressures on cost and time to market. To satisfy these conflicting requirements, engineers are turning to power conversion and distribution solutions that are dedicated to meeting the needs of industry-standard hardware platforms and even specific device types such as FPGAs and processors. Here, Arrow examines available options for system and board designers to quickly configure solutions to system power requirements.

AC-DC Conversion – Focus on Power Density

Compact, board-mounted power supplies are frequently chosen to provide an AC/DC front end in distributed power architectures. With high power densities and high operating efficiencies, these units deliver a convenient solution to 48V bulk supply or 12V intermediate bus supply. Available supplies in industry-standard form-factors range from sub-50W 2” x 4” models to 200W within the 3” x 5” footprint. Among the dominant design trends for these units, achieving a low profile minimises airflow shadowing and thereby increases cooling for other devices downstream of the power supply.

As ever, high power density is the holy grail. However, many units now entering the market are designed to operate at full rated power with low airflow, equivalent to only a few CFM. This can save the system designer from being forced to locate the power supply adjacent to the cooling fan, or alternatively can allow a lower cooling fan specification.


Figure 1 – Power-One PLP75 Power Supply

These principles are clearly seen in the latest AC/DC board mounted supplies from Power-One, which includes the BLP55, MPB80, PLP75, MPB125 and MPB150 models. High efficiencies and advanced thermal management techniques allow the PLP75, for example, to operate at 75W with only 5 CFM forced-air cooling or 65W with convection cooling. The range includes single- and multi-output configurations, providing a choice of 5V, 15V or 24V outputs as well as the more common 12V or 48V outputs.

Similarly, the Astec and Artesyn ranges from Emerson Network Power offer a comprehensive selection of low profile 3” x 5” AC/DC supplies from 65W to 150W designed for low airflow operation. Among these, the TLP150 has a profile of only 1.25” (31.8mm) and delivers its full 150W with airflow of 200LFM. Like larger, rack mount front ends, the TLP150 also provides a 12V output for powering fans in addition to the main output channel, together with an optional auxiliary ‘always-on’ 5V output for applications that require standby operation. There are also extensive control and monitoring features.


Figure 2: Astec TLP150 150W Power Supply

The complete Astec/Artesyn board mounted AC/DC range also includes units approved for low power medical, dental and laboratory applications. Medical versions of the TLP150, NLP65 and NLP110 carry full safety approval to EN/UL60601 and UL2601. IEC and CSA approvals also help to accelerate design in time and reduce system compliance costs.

C&D Technologies has a wide range of multi-output and single-output AC/DC power supplies up to 500W and beyond. As an example, the NX301 is a compact, 300W, power factor corrected, multiple output power supply. All outputs are fully isolated and regulated. Active current sharing circuitry, together with control functions and alarm options simplifies N+1 and redundant applications. The peak current ratings of the auxiliary outputs are capable of handling fan and disk drive applications.

DC/DC Power – Device-specific PoLs Arrive

Moving on to power distribution options at the board level, major developments include the adoption of high power density PoLs to satisfy the complete power supply requirements for specific ICs on the board. These tend to be aimed at the major functional ICs including microprocessors, ASICs, FPGAs and the latest memory devices, which can impose exacting requirements for multiple power rails. In addition to these dedicated PoLs, a variety of non isolated converters, displaying high power density and advanced features such as protection capabilities or voltage sequencing, are required to power other digital and analogue devices on the board.

One example is the new VRM11.X family of DC/DC Converters from C&D Technologies, which is dedicated to providing power for next generation Intel processors.


Figure 3: C&D Technologies VRM11.X Family

The VRM11.X family is fully compliant with Intel’s VRM11.0 power specification and represents a proven power solution. Comprising six models, the range offers a choice of form factors and power level options to give designers and developers a high degree of flexibility as well as reducing risk and time to market. The modules take advantage of system airflow for optimal cooling and provide a cost effective, space saving alternative to embedded voltage regulators. Both 80A and 150A current options are available. Combined with a choice of either 1U or 2U form factors, these features allow the VRM11.X family to address most next generation Intel processor power applications. The availability of three versions with ‘no load line’ gives even more flexibility for other applications such as custom ASIC designs where low voltage, high output current and tight regulation are needed.

Multi Processor PoLs

For densely populated multiprocessor systems, the PTH04040W from Texas Instruments is a high-performance 60A rated, non isolated power module, which uses the latest multi-phase switched mode topology to operate at up to 93% efficiency. The PTH04040W operates over an input voltage range of 2.95V to 5.5V, and can be set to any output voltage from 0.8V to 2.5V using a single external resistor. The combination of a wide input voltage and wide output adjust range serves high performance applications built using either a 3.3V or 5V distribution bus. These modules offer high levels of flexibility, including on/off inhibit and margin up/down controls, differential remote output voltage sensing for tight load regulation, and an output over current and over temperature shutdown. Importantly, the PTH04040W incorporates the Texas Instruments Auto-Track™ feature, which allows the outputs of multiple modules to track a common voltage during power-up and power-down transitions. This greatly simplifies the sequencing of voltages for VLSI ICs that operate from multiple power rails.

Dedicated FPGA PoLs

When powering modern FPGA processors, the availability of a dedicated PoL converter provides numerous benefits compared to designing with discrete components. These include a simplified design, higher system reliability and PCB real estate savings by using fewer components, in addition to greater efficiency and simplified EMC compliance (due to the lower number of PCB tracks). Astec and Artesyn, for example, have developed a series of DC/DC converters explicitly designed to support FPGA core and I/O voltages from 0.9V to 3.3V at currents from 1A to 30A. These types of power solutions greatly simplify and eliminate a number of steps in the process that board level designers would have to take to power FPGAs and allow designers to focus on the core system requirements.

Indeed, matching PoLs to FPGAs has gone a stage further, as a number of the Astec/Artesyn parts have now been identified by Altera as being suitable for use with the company’s Stratix®, Cyclone™ and MAX® series of FPGAs. The LDO03C series of DC/DC converters have been identified for use with core and I/O currents of 1.0A to 2.5A, while the LDO06C series meets requirements for currents from 2.5A to 5A. Currents in the region of 5A to 10A are addressed using the LDO10C series. For higher currents of 10A to 15A and 15A to 30A, the SMT15E and SMT30E PoL DC/DC converters provide the best respective solutions.


Figure 4: Astec and Artesyn Ranges are Matched to Altera FPGAs

The LDO0x and SMTxx devices are high density converters designed to provide good efficiency and performance, minimum footprint and wide output-voltage trim or adjustment range. Wide input voltage ranges, integrated protection functionality and remote on/off are provided as standard.

As a further aid to designers, Arrow has compiled a cross-reference guide that consolidates details of these devices into a single document.


Figure 5: PoL Cross Reference Guide for Altera FPGAs

With a view to reducing the time to develop system-level power solutions to satisfy industry standard platforms such as the Advanced Telecommunications Computing Architecture (ATCA), Power-One offers the Z-One® family of PoL converters. As an example, the 60A ZY8160 is the newest and highest current digital PoL module in the Z-One range, and is ideal for communications and server applications. As an I²C programmable DC/DC converter, the ZY8160 provides industry leading power management capabilities with no cost or space premium. ZY8160-based systems can reduce development time, components and PCB traces by up to 90%.


Figure 6: Power-One Z-One GUI

The ZY8160 can be used with ZM7000 Series Digital Power Managers (DPMs) to completely eliminate external components for sequencing, tracking, protection, monitoring and reporting. All parameters are programmed via the industry-standard I²C communication bus, which also enables ‘on the fly’ parameter updates at any time during system development or service without requiring hardware changes. In addition, performance parameters can be monitored via a Graphical User Interface (GUI).

General Purpose PoL Trends

PoL converters to address the full range of board level power requirements are, of course, many and varied. Some of the newest examples to be introduced by major manufacturers include the Tyco PicoTLynx series of power modules.


Figure 7: Tyco PicoTLynx Series

These are non-isolated DC/DC converters featuring high power density, capable of delivering up to 6A of output current with fast transient response. Advantages include a wide DC input voltage range from 2.4V to 5.5V and a precisely regulated output voltage from 0.6V to 3.63V. The output voltage is programmable via an external resistor. Features include remote On/Off, overcurrent and over-temperature protection. The APTH versions also feature output voltage sequencing. A new feature, the Tunable-Loop™, allows the user to optimise the dynamic response of the converter to match the load.

Other advantages of the PicoTLynx series include very high efficiency and superior thermal performance.

Custom Power Supply Services

Despite the obvious advantages of adopting off the shelf power modules, in practice there are often requirements to configure a tailored power solution. That is why, in addition to the industry’s widest range of standard power conversion products, Arrow also provides a variety of custom power supply design and configuration services. These include design and implementation of PCBs, sheet metal and cable assemblies, installation of products such as fans, heatsinks, LEDs, switches and relays, product testing and documentation, project management and technical support.

Combined with in-house competencies to configure modular power supply families from numerous suppliers, Arrow’s custom power supply service delivers a fully outsourced solution.

The service is operated by qualified Arrow design engineers and performed within ESD-controlled, ISO9002-accredited facilities that are safety certified by UL, VDE, CSA and TUV. This enables a smooth interface with customers’ own quality management systems, and is able to deliver solutions within as little as two weeks and without a large price premium over equivalent standard products.

Conclusion

The advent of the distributed power architecture, bringing the advantages of modularity and configurability, has allowed system designers to adopt an application specific approach to power supply design. However, the increasing complexity of the power supply demands imposed by the latest advanced ICs – which typically have multiple power domains to maximise energy efficiency – make power supply design as challenging as ever.

To help engineers respond to these challenges, and deliver timely and cost-effective solutions, power supply specialists are responding with turnkey solutions dedicated to commonly used devices and platforms. While this is a significant new trend, the perennial goals of reduced footprint, increased power density and greater conversion efficiency remain at the forefront of all power supply designers’ minds.

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