"Series" resonant DC-DC converter

"Series" resonant DC-DC converter

Hi,

Question first:
I can't find any examples of using a series loaded resonant circuit in a basic buck topology. I find many examples in my textbook and other references of using parallel loaded with the basic buck topology. So, now I wonder if the implication that I read that a normal switching converter (e.g. buck) can be converted to a resonant converter by replacing the hard switch with a soft switch (hard switch + resonant LC circuit) is not universally true. Can I use a series loaded resonant circuit in a basic buck topology?




Background info:
I started studying resonant converters. Bob Mammano suggests that series loading is better suited for high voltage, high output impedance applications rather than a parallel loading topology in his paper. Series loaded means the resonant circuit's L and C are in series with the load, so the C is a DC blocking cap.

I think he implies that a normal SMPS switch becomes a resonant switch by following the switch with either a parallel or series loaded resonant circuit, and so they can be "transplanted" into familiar SMPS topologies like the buck converter.

My confusion is that when I tried to find examples of series loaded converters, they all are used as either inverters or rectified and filtered AC waveforms.

- - - Updated - - -

Also, I should mention that I am talking about quasi resonant converters specifically.

Re: "Series" resonant DC-DC converter

Hello,

I think the reason is that a series resonant topology can only transfer AC energy, so you need rectification (as you mentioned also). A buck transfers a DC component, so they are different from eachother. To be honest, I also saw most series resonanit circuits operating as inverters (so not as DC/DC converters). One of the first I saw (and had to debug) was a thyristor half bridge inverter for ultrasonic cleaning.

Mr. Mammano is right, you can convert (almost) all topologies to a resonant version. Generally spoken, peak current and/or peak current does increase when converting from hard switching to a soft switching topology.

You may know that the half or full bridge series loaded converter can be operated as a zero current switching converter (operating below resonance) or a zero voltage switching converter (operating above resonant frequency). the ZVS topology is used frequently in ballast circuits for fluorescent lighting.

Ok, thank you for the help!

I think I may focus my studies on the parallel loading version for now then.