LCC versus LLC converters: Part II. Basic characteristics

[@alanhillsplasmatweeter7318]

This is very helpful Prof. Ben-Yaakov. I have looked at a TI paper that covers this topic and your description has helped my understanding. Thank you!!

[@sambenyaakov]

Thanks. Glad it was helpful!

[@venkataratnamv6989]

Hi sam. I am very very excited to watch all your videos. I have referred many of your papers for my research studies. Your work helped me a lot.

[@sambenyaakov]

Thanks for encouragement. Comments lie yours keep me going. If not a member, please join www.linkedin.com/groups/13606756/

[@audiokees4045]

Hi there Ben. Here I am again. A question did arrive again, I am not as far and close to a actual design, when mine pcb router is ready I can mill it and build it. The biggest no clear question was the transformer, but now I get it after read a lot of papers, unfortunately most are LLC and for this I have much more clarity about the transformer and there are tools. I did read for LCC the transformer just needs big enough to not load the current source like resonance tank to much, as a LLC has the transformer included, LCC is different, it needs a high impedance transformer because of the current source behavior, I did see nicely when I make the inductance bigger the current source voltage just get higher but the current through stays quite the same, to some ex tense, that is what current sources do. I have done it with a calculator who is on the internet who can calculate resonance and Q, did calculate the load resistance for low and high load and sim that. Quite interesting, I have now 15 amps 20 volts, and the 350 v and 2 x 130 volts regulated in sim, as for the transformer, just make it big as possible not to load the Lr Cs Cp to much, it is a current source, and yes I do now this from audio amp designs. I have now a transformer who is 1200 uH primary and use the N/S square to calculate the secondary inductance's, nice to see when I go lower I need a different (lower) Q and tank, use a LLC tool who do also transformer calculations I can just use that, so I can see if it fit on the transformer. But with a lcr calculator and a transformer with 1000 or more uH I get good results, I did see there is a spot where higher inductance's do not give more benefit so I use that what is just below that border. and the signals looking very good. The max power give 3,1 amps in primary mosfets, with low load it get to very low value,s but do stuck on min 0.8 amps. the Cs capacitor in tank does get 1.1 Kv when start up, but when idle it is just above 400 volts, that startup current is also high what is quite normal, a problem all resonance converters have, electronics do take care of that starting on high frequencies. I can sim that by the way it is in the model. Resonance converters are nice things, using a q loaded resonance tank as a current source or a voltage source being a frequency driven power resistor to the transformer, and use the circulating current to discharge mosfet capacitance to allow soft switching. But the design is tricky, but I get the hang a little, I am more concerned about the high voltages I need to be careful. So I go make a protection with a switch who shuts off in milliseconds when i touch wrong. Oke yes I have alwasy repair the old tv sets, holding high voltages, so I do now I have to be carefull, but when 67 as I am now, things can be more easy forgotten, I wish you a nice day.

[@sambenyaakov]

Thanks for sharing. 67 is young🙂

[@audiokees4045]

@@sambenyaakov Well thank you friend. I have by the way get the LLC supply from eBay for the audio amp, 2 x 60 volts 10 amps. Just for curiosity because I like building myself, but it was cheap and I play with it., but when connect it open it go in burst mode. that is audible. So I guess I go remove the feedback and set the supply open loop around the hot spot where voltage keeps quite stable, this way I get no trouble anymore and burst mode is gone. The seller have delete the ic names and the names of the drive mosfets, I do not understand because it is easy to track. Have a nice day.

[@karastom2304]

Thanks so much Dr. Sam, please can you describe the physics of Q factor and how we can improve it and its important in resonance. Thanks.

[@sambenyaakov]

Q is the ratio between the reactive and real energy, you don't necessarily want to increase it at all times. Sometime a high Q will cause more losses due to the circulating reactive energy.

[@tbd-w1c]

Thank you professor Yaakov for the amazing two videos on the resonant converters. Are you aware of any articles or videos that use the first harmonic approximation to design LCC and/or PRC converters from beginning to end?

[@sambenyaakov]

There care some but I can't member details off hand. Sorry.

[@kenhenderson7858]

Hi Sam, your videos on these topics have been a great help in understanding LCC & LLC converters! I have seen several wireless power converters that use LCCL-LC topology with a LC tank running at resonance followed by CL-LC transformer arrangement to get constant current or voltage output. The load damps the main LC tank, so what I don't understand is what happens if the load is disconnected or the transformer wire breaks. It seems that the main LC tank will resonate to large voltage/current and burn the driving stage. Any ideas on how they handle this situation? thanks for any comments!

[@sambenyaakov]

Most papers on subject are academic. They normally do not worry about such petty issues😊

[@kenhenderson7858]

@@sambenyaakov Yes, I agree. I have been looking at LLC resonant controller chips and they measure the tank capacitor voltage then increase the frequency if the cap voltage becomes too large. That seems a reasonable way to handle it.

[@MrDefiler82]

Thank you very much! Your material is amazing! As far as I understood, the LCC converters are more preferable for step-up operations, because the currents at high side are not so high and the inductance after rectifier should be especially bulky. Am I right ?

[@sambenyaakov]

Not really, OK in step down

[@chiefrunningfist]

Another very informative vid professor, thanks! Is it possible/optimal to implement a LCC (+ output LC filter) when working with a variable Vin (Vin; 0.5Vin), as well as a dynamic load? When comparing the various resonant topologies, it seems in the LCC case, you could adjust gain to create a constant Vout of Vin/2 (Amin = 0.5; Amax= 1.0) while the load went from light to heavy, easier than if using an LLC topology and trying to do the same thing? Is this correct understanding? I get that you can vary your gain by adjusting the switch freq, but how to deal with variable Q(s) while simultaneously maintaining necessary gain? How to navigate high Qs? When setting Z = 1, and trying to design a variable output supply, it seems that Qs will span at least an order, but then regardless what you decide to (and are able to) change Z to youll have a high Qs at heavy load?? Do you have any vids on variable Q? Thanks again.

[@sambenyaakov]

"Do you have any vids on variable Q" Not really. Aside from the gain and control issues, the efficiency is not less important so avoiding high Q and high rms currents is a consideration when choosing the topology. is

[@marcinszajner2924]

This is great material!

[@sambenyaakov]

😊

[@alexandrsemenkoff6935]

Hi Professor! Very interesting videos! How is T1 calculated for LCC converter?

[@sambenyaakov]

Ti is really s coupled inductor. See kzbin.info/www/bejne/g2SydoBsodOZiKc

[@alexandrsemenkoff6935]

Sorry, I put it wrong. How to calculate transformer primary inductance T1 for LCC converter. Because it is parallel to the capacitor

[@abiramsam8673]

Hi I have a doubt is it possible to have a single stage ac dc converter with LLC???

[@sambenyaakov]

I am not sure it can be done in a practical way.

[@girloftigerland6888]

Dear Professor ,Recently i have started my thesis ganfet with LLC ,your videos are helping me alot 🫡

[@sambenyaakov]

Thanks. I am happy to learn. Don't hesitate to call upon ne if you think I can be of help. Good luck with your studies.

[@girloftigerland6888]

@@sambenyaakov Dear Professor ,I got a confusion ,My full thesis work will be on LLC circuit and on pcb i am using Gan Fet.before making the LLC my prof asked me to add L ,C,R to the PCB's Half bridge as testing/operation.i cant understand what would be the reason.

[@engineeringadventures1229]

Hi professor. I watch your videos and take them as reference for my study and experiments. Is there any possibility you can be my mentor? I am keen on learning and open for all possible ways.

[@sambenyaakov]

I really don't have the time but if you ask a question I will try to answer.