Excellent Resources Narrow the Make-or-Buy Decision for Power Supplies

By Landa Culbertson, Contributing Author, Mouser Electronics

In today's energy conscious, high tech environment - the performance of the power supply, historically disregarded as just a basic necessity, has arguably taken center stage. Consider for example, the U.S. Department of Energy's $37.7 Million USD investment in an ARPA-E program that seeks to increase energy efficiency of power conversion systems and enable high efficiency, high power density power electronics across all applications from consumer, mobile, and computing to wireless infrastructure, lighting, industrial, and automotive. The effort is driven by the department's assessment that by 2030, 80% of the country's electricity could flow through power converters, as compared to just 30% in 2005.

In the not too distant past, it was generally an automatic decision to choose to purchase a ready-made power supply over designing one at the component level when given the choice. However, as the importance of the power supply has risen in recent years, amazing tools and resources from semiconductor suppliers have become available to support component-level power supply designers seeking to differentiate their end product based on power technology. These same assets can aid the designer tasked with unique requirements that would not be met by off-the-shelf products. It is now more worthwhile than ever to spend the time to carefully evaluate the make versus buy decision for power supplies.

Why Buy?

Purchased power supplies provide the following great advantages:

• Lower cost: The component bill of materials (BOM) of a power supply is high compared with buying a complete off-the-shelf product due to volume manufacturing. For example, the BOM of a 30-amp 5-volt power supply is about 5 times the cost of purchasing a commercial power supply.
• Time to market: You can get to market faster by saving development time and applying resources to your core competencies instead.
• Safety and regulatory compliance certifications: Off-the-shelf power supplies remove the expense, time, and challenge associated with seeking agency approvals. Regulations are also subject to change, and a purchased power supply is guaranteed to meet standards at the time of purchase. Some approvals to consider are:
  • Worldwide Electrical Safety Standards
  • Worldwide EMC/EMI Standards
  • Global Power Consumption and Efficiency Regulations for External Power Supplies and Battery Chargers
  • Application-Specific Certifications such as Medical and ITE Certification
• Quality and Reliability: Commercial power supplies have been rigorously tested over line, load, temperature, shock, and vibration specifications. Some products are even backed by extended warranties.
• Second sourcing: By choosing products offered in industry-standard form factors such as quarter-brick, half-brick, and full-brick, you can realize the benefits of having alternate sources.

Commercial power supplies are readily available. TDK-Lambda, with 36 years of experience, is one notable provider. The company takes pride in offering an extensive collection of highly reliable products, including the ZWS-BP Series of 150W - 240W compact, lightweight, high efficiency, open frame, AC-DC power supplies. Offering 200% peak power capability (280W - 480W), this series meets global safety standards for a universal input (85-265VAC) and less than 0.5mA earth leakage current, meets EMC/EMI standards including power factor correction requirements, and comes with a 5 year warranty. The TDK-Lambda portfolio also includes the MWS65 Series of 55-67W AC-DC power supplies with Medical and ITE certifications including BF (Body Floating) rating for applications where the equipment may come in direct contact with the patient, such as blood pressure monitors and ultrasound equipment. For DC-DC applications, TDK-Lambda recently introduced the PH-A280 Series of converters for 50W, 75W, 100W, and 150W output power levels from a 200 to 425VDC input. These devices come in industry standard quarter-brick modules and are ideal for liquid, air cooled, and conduction cooled systems given their wide temperature range of -40 to 100°C. The series is also backed by a 5 year warranty.

For DC-DC, make sure to also take a look at Murata Power Solutions, currently the world's largest supplier of DC-DC converter modules. The NCM6 Series of isolated 6W single and dual output DC-DC converters, the SPM15 Series of isolated 15W DC-DC converters, and the SPM25 Series of isolated 25W DC-DC converters are amongst the company's latest introductions. All of these products feature small footprints for board mounting. NCM6 is encapsulated for superior thermal performance, and SPM15/25 are potted in a metal can for low electromagnetic interference emission, protection from harsh environments such as high humidity, and resistance to mechanical stresses such as vibration and shock.

Making Your Own Power Supply is Easier than Ever Before

Here are some of the latest design tools and resources available to assist both expert and new power supply designers:

Texas Instruments

• PowerLab™ Reference Design Library: Use the online PowerLabâ„¢ Power Reference Designs Selection Tool to input your design criteria including AC or DC input, isolated or non-isolated, input and output voltage ranges, and output current, as well as other advanced search criteria such as application or topology to search TI's database of over 1200 reference designs. These are designs that have actually been built and tested by TI, and have downloadable documentation including circuit schematic, printed circuit board (PCB) layout, BOM, test report, and gerber files.
• Power Stage Designer™ 2.1: This online tool helps you to design the power stage of the most commonly used switchmode power supplies. Choose the topology (buck, boost, flyback, etc) and input your design criteria, and the tool will show you the recommended values for the inductor/and or transformer as well as provide helpful insight on the duty cycle, input power, losses on the diodes, current ripple, and more.
• WEBENCH® Power Designer: End-to-end power supply design is really just a matter of clicks using this online design and simulation tool. Simply input your design requirements, select your optimization preference from high efficiency, small footprint, to low BOM cost, and the tool will return your design options for module, integrated, and controller-based solutions. From there, select one or more designs to electrically and thermally simulate, as well as optimize components. Finally, export your schematic and layout to popular CAD formats for hardware prototyping.

Figure 1: Screenshot of TI's WEBENCH Power Designer Tool

Maxim Integrated

• EE-Sim Design Generation and Simulation Tool: Maxim's online tool allows you to input your design requirements, change from default to preferred components, and simulate your design. Use the checkout feature to see the availability of components and pricing at your favorite distributor, including Mouser. Save or print your schematic and BOM.

Infineon Technologies

• SupIRBuck® Design Tool: Infineon's online DC-DC design tool takes basic parameters and any special requirements entered by the user and generates solution recommendations from which the user chooses the best fit for the application. The tool produces a detailed schematic and BOM, with the ability to fine tune. Features include a full AC analysis, modeling of key voltage and current waveforms, transient performance modeling, re-arranging of component layout, a detailed thermal analysis, and power dissipation analysis.

onsemi

• GreenPoint® Design Tool: The GreenPoint online design simulation tool from onsemi is currently dedicated to LED Lighting drivers in AC-DC, DC-DC, or linear applications.
• Power Supply WebDesigner: Topologies supported by Fairchild's online power supply design tool include primary-side regulated flyback converters, secondary-side regulated flyback converters, switch-mode power supplies, AC-DC off-line power supplies, isolated buck-boost converters, forward isolated buck converters, and DC-DC isolated converters. Just enter basic design requirements or use the tool to optimize parameters. The tool enables you to analyze and simulate the design and then automatically generates a schematic and BOM.

Though power supply design should always be undertaken with care and is still considered an art by many seasoned designers, given the new tools and resources available now, making your own supply is easier to achieve than ever before. Whether you ultimately decide to make or buy, Mouser is here to help. Mouser carries products from over 600 suppliers to enable you during the evaluation and development process.