However, sometimes a very unique and specialized power supply is needed. Many companies try to design their own. Some succeed, but many incur significant expenses and lose valuable time to market because they simply don't know how to design power systems that are stable, reliable, can be mass-produced, and operate for extended periods. They often don't know when to design it themselves and when to buy what they need.
When to Buy:
Many times, you're told to "cut that $40 item from the network system to reduce costs." After all, it's just a power supply, and any junior engineer can make it, right? Often, organizations with core competencies outside of power electronics lack the training, personnel, or testing equipment, and are unaware of the associated problems. They dive headfirst into an area they're not prepared to navigate. The mistake lies in assuming that power supplies are simple components that anyone can design. Why are some companies outsourcing manufacturing to EMSI suppliers? Simply put, it costs them less, and they can do a better job than what's done in-house. Keep in mind, too, that their customers may have more demanding clients than you do. Quality, reliability, and cost have been enhanced in the manufacturing process, and therefore, the overall cost can be reduced by purchasing pre-assembled power supplies.
When to build
your own power supply? Sometimes you can't avoid having to build your own power supply. When does it make sense to build your own power supply?
• If you cannot purchase something that meets your business needs.
• If the requirement for designing your own power supply can be managed with readily available semiconductors or on-chip power module components, with good support from application engineering staff and design software tools.
• If you have access to the appropriate testing equipment and have the experience and time to do the job correctly.
• There is time to do things right.
• If purchasing a power supply is truly too expensive for the application and you are going to build something that will make a significant difference.
Although excellent resources are available, the best advice regarding the use of reference designs is that you should not place the design responsibility solely on your component suppliers without some internal effort. The designer and the company with the product are ultimately responsible for the final system or product. Do not proceed without conducting sufficient testing and evaluation of the design, and ensuring that the design will perform under specified time and temperature conditions. Perform a hands-on product evaluation and/or simulation. Do not rely solely on a semiconductor supplier's reference design or proceed directly to volume production.
Regardless of the technology or control topology used, companies should invest in training, design tools, testing equipment, and software to validate the design and exceed the expectations of the intended application. Excellent resources are available, often free of charge or with minimal investment of time and resources. Vendors can provide reference designs, evaluation tables, and design software, often at no cost. In many cases, they will also supply Gerber files that can be imported into your own system, ready to go.
Design Considerations If You “Build” Your Own
Power Supply: There are some questions you should ask yourself before building your own power supply or power electronics system. First, it’s important to consider what type of power converter system you need. This determines the level of complexity of the overall design effort, the risks involved, and the regulatory requirements. Do you have the right test equipment? Frequency response analyzers, electronic loads, electrical safety testers, and other specialized equipment are needed, and many simply don’t have these items readily available. Do you have experienced staff with the appropriate skills to design power supplies? Consider magnetism, PCB design, grounding, and the necessary shielding techniques. The autorouter will need to be powered off, and manual design skills will be required. Safety separation techniques must be incorporated into the design to meet leakage guidelines.
Start by asking yourself if it's offline or DC-DC. Is it isolated or non-isolated? Is it commercially available with proven performance? Parts with integrated materials may be available. At lower power levels, components from semiconductor companies are now highly integrated; many even contain the inductor inside the package, forming what is commonly called a PSIP or power supply module. If the design requires isolation, do you have the expertise and equipment to perform electrical safety testing on the designs, adhering to global safety specifications and standards? Do you know how to design magnetism with the required safety agency clearances and permits? Consider operating hours—will it be a 24/7 high-reliability application? It might make sense to purchase if high-power offline, isolated components are needed, proven out-of-the-box reliability is required, and the volumes aren't sufficient to justify a DIY effort.
Obtaining safety approvals is costly and time-consuming. If the product will be shipped internationally, it will need a wide input voltage range of 85 to 265 Vac 50-60 Hz and will require approvals for worldwide acceptance. Are you prepared for the cost and delays? Do you have safety experts on staff who are familiar with regulatory requirements and testing procedures? Consider EMI-RFI. Switched-mode power supplies can generate a lot of noise, especially if they are not properly designed. Regulatory bodies have no sense of humor or sympathy for poorly designed switched-mode power supplies.
Manufacture with more tools and resources than ever before.
If, after considering these issues, you decide to manufacture your power supply, it is strongly recommended that you involve suppliers as early as possible in the definition, selection, and design process. The sooner you seek support and assistance, the more time you will have to do things in an organized manner, with greater flexibility and more options. A project schedule loses flexibility the closer we get to the prototype and production phase.
With energy efficiency regulations increasingly becoming a system-level consideration, addressing power electronics at the very beginning of the process is critical. Don't choose the wrong part, topology, or circuit just to have stock units already assembled with faults. Nothing has to be designed in a vacuum; there are plenty of resources available to help you successfully implement your design in the right situations. If you're designing your own power supply, the good news is that there's more support than ever. New developments in technology, available from Mouser, include products for many power converter levels. There are plenty of resources available to help you successfully implement your custom design in the right situations. Whether you're buying or building, Mouser offers products from over 450 suppliers with resources available for any power level and is ready to help.
With over 25 years of experience in the electronics and semiconductor industry, Kevin has held semiconductor product positions at Freescale Semiconductor, Fairchild Semiconductor, ON Semiconductor, and Motorola Semiconductor. Kevin also has extensive experience as a design engineer in medical electronics and military electronics.
Author:
By Kevin Parmenter, Contributing Author, Mouser Electronics
