AC to Point of Load: One Stop Shop v Different Manufacturers

January 4, 2013
By

Connecting power supplies and convertersDo you remember situations when you just couldn’t get electronic systems to work, even when everything you have read and know says they should be plug-and-play compatible? Or have you upgraded your computer to a newer version of the operating system, only to find your printers or other peripherals no longer work? And when you called the service hotlines of the different vendors it was always the fault of the other one. Or you were told that you are the only one in the whole world having this problem. And when you search the internet you find out that you share the same problem with hundreds or even thousands of users. The frustration levels increase with the hours you spend trying the solutions offered on the forums by self-styled “experts”. Something usually ends up in the bin. Or out the window!

Connecting power supplies and converters together is certainly not as complex as some connections we need to make as a design engineer. Nevertheless different topologies, input and output impedances of the individual converters, their reaction to dynamic loads and the transfer function of the feedback loops can become critical factors in a system. Whilst you are likely to get the system to work with a variety of different converters, it isn’t as easy to optimize your system for efficiency, power density and thermal management.

DC-DC converters have negative input impedances and can draw quite a high current during startup. Additional storage capacitors can make the situation worse. If this is not considered properly during the design your system may oscillate. If you don’t get it right, your system will never start up as one of the converters will go into overcurrent mode. In this case a special start up sequence may be necessary.

Another issue may come up in an AC to load where you’re connecting together in one system AC-DC, DC-DC and non-isolated point-of -load converters from various manufacturers. If different hard switching topologies – with different switching frequencies – are used the EMI noise spectrum could be above the required limits. That’s a possibility even if the filters suggested by the manufacturers are used.

Different tolerances for the components used inside the various converters can also be challenging. We’re all aware of situations when a system has been working without any problems for a long time and then suddenly a new production lot does not pass the final test. Quite often this is due to a component change or several components being at the limit of their specified tolerances. It may take hours or days to find out the reason and organize the necessary corrective action.

On the other hand, there are advantages if the parts within the power design are supplied from one manufacturer. You have more assurance that all of the devices will work together because the devices have been tested during their development and in the application labs. Any component change will be thoroughly tested in combination with other converters or input/output modules connected to a specific device. There also may be many other customers using the same or a similar configuration as you. Therefore, your power system is not unique, and the company’s applications support team will know your configuration and the specific operating conditions.

There is another significant advantage to using one vendor for all of your converter stages. Let’s take microprocessors as an example. You can optimize your system to achieve the highest efficiency by using the components specifically designed for a high voltage bus system or a pre-regulated 48V distribution bus. That means you no longer have to deal with the significant power losses on cables and PCB traces generated by high currents under low line conditions. You could also select downstream bus converters with a narrow input voltage range and therefore much better efficiency and higher power levels. A factorized power™ bus allow you to not only reduce the power losses by more than 50% but also move a major part of these losses away from the microprocessor to areas where they cannot do any harm.

Lastly, with one manufacturer for all the parts of the power chain, you have one single point of contact for all your questions.

Other Vicor PowerBlog Posts:

Back to Basics: Handling High Input Transients

Back to Basics: Meeting EMI for AC-DC Systems

Webinar Rebroadcast: Best Practices Using DC-DC Bricks

What’s the Problem with AC-DC Front Ends?

Check All the Options and Find the Power Product for you

Comments are closed.

Find out more about our Cool-Power Buck Regulators subscribe to vicor newsletter Contact Us

Get Connected