PMP20637: UCD3138 comparison

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Part Number: PMP20637

I watched with great interest comparison video  between Phase Shifted Full Bridge & FB-LLC --- done a while ago by someone at TI

Let us recast some conclusions in light of superb performance of LLC by many new controllers.

#1 the comparison does not mention any output inductor. This is a significant drawback- of any topology which has to handle very low current to high. In a world of GaN devices, the size of any DC inductor will kill the compactness of any product. Not to mention huge loss & then damping one has to do. For small ac ripple filtering, a small inductor can be easily accommodated.

#2 It says that LLC topologies have penalizing output rms  &  ripple and require 9 times more output capacitor. In my model( obtained from mathworks public repository of models in Simulink), & in many of TI's LLC design guides, this does not appear to be true. Especially for high power case of Interleaving & with SR, without the need for DC inductor, LLC  appears to be very competitive.

#3There are key failure modes in PS-FB topologies which is a serious drawback. Also not mentioned.

#4  ZVS is very hard to extend and hard switching is a nuissance.

One thing is very well discussed is the inability of LLC to be synchronized and variable frequency control. I do not know about audio applications, this has not been a problem in my experience in very critical application we handled over decades.

SO unless sync is a requirement, I would proceed with our plans to implement all GaN HB LLC using UCD3138.

Any contrary reviews will be highly appreciated.


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