In today's networked world, where connectivity is increasing at an unprecedented rate, a growing number of links occur between systems – a development which was not predicted to that extent. In some cases, the design expectations of these systems are even exceeded, resulting in interference due to daisy chaining and ground loops. This is especially true for power supplies, since these are often neglected up to the last stage of a system or product development, when, fundamental changes to the application are often undesirable or even impossible. Which in turn means that a power supply unit in many cases must provide filter functions beyond the originally envisaged specifications.
In contrast, the increasing energy efficiency requirements have been the driving force to apply faster switching technologies in power supply designs to optimize efficiency, but at the same time bring about a rise in electromagnetic emissions. As a result, the filter components of many power supplies occupy more than 30 % of its total size, making the power supply not only larger but also more expensive compared to soft switching technologies.
Soft switching technologies have existed for decades, with LLC converters processing the most commonly used technology. However, LLC converters have a very limited basic regulation range, which is the reason why they are often used as a second stage with an Active Power Factor Correction (PFC) front-end, which regulates the input voltage of the LLC converter to a specified value so that a better output voltage regulation can be achieved.