PE #40: LLC Resonant DC-DC Converter: Basic Operation and Simulation
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- Опубліковано 10 лип 2024
- This video explains the basic operation of the LLC resonant DC-DC converter. The important points to correctly design and operate the converter are highlighted. The process of Zero Voltage Switching (ZVS) is detailed. An example on how to simulate this converter using LTspice is also presented. The simulation results are used to reinforce the ideas presented in the video.
Thank you very much for sharing this.
You are welcome. Thanks for watching
Oh my god can't believe.... many many thanks 🙏
Thanks for watching!
Been waiting for it. Thanks!
Thank you!
excellent video, very useful!
Thanks!
Thank you sir!
Thanks for watching!
LTspice file is available here: github.com/marcosalonsoelectronics/PE-40
Hello, Marcos!
As always, thanks for your detailed video!
A little question: why we should to use delta value of spikes at 32:34? Isn't the both spikes negative and positive represent losses? Or it represents stored and extracted from Cds energy only?
Yes to the latter question. This is energy handled by Cds. Only the difference between both spikes are losses. These losses are dissipated in the MOSFET's channel. Thanks for watching!
Thank you proff. for the insight. If I want to do synchronous rectification of this LLC converter then how to provide the gate pulse for the other switches. Can you please give me the idea about that?
Usually SR is implemented using auxiliary windings on the transformer to drive the switches but there are also specific ICs for this purpose. See for example the UCC24624
Sir, If I measure voltage across transformer secondary without diode bridge rectifier then I should get a sine wave right? When I did hardware spike across transformer secondary was huge. Is this because switching is not proper?
Hello, if you remove the rectifier the resonant tank will be operating with no load. The waveforms can be strange.
If you want to see sinusoidal waveforms without the rectifier you have to place an equivalent load resistor at the secondary.
Thanks, are there any papers describing High Power charging applications of LLC?. 50kW and above?
Thanks for your question. I have no information on this type of high-power application.
@@MarcosAlonsoElectronics No problem, thank you for all your videos.
Hello! good video! I made experiments - the LLC converter can operate with current density 4A/mm sq.I mean litz wire (wire wound like steel rope)
Hello, thanks for your comment and for sharing your expertise
What about current and voltage at mosfet look like from zvs ? Because vgs and vds show at present only.
The waveforms are shown at 13:57
Thanks for your work. What can you say about ZCS forward converter? This is very interesting theme.
Thanks for your comment. I will think about it.
@Marcos Alonso, for resonant converters (e.g. LLC), how someone can implement a small signal model in simulation? With voltage/current sources, like how is it done in the case of PWM dc dc converters? How could for example the control-output transfer function for an LLC converter be deduced in simulation with a small-signal model (so not using a switching or averaging model, but a small-signal model)? There is such a thing? Can you do a video showing how to do this?
Thanks for the suggestion. To do a dynamic model of the LLC resonant converter is more complicated than a conventional non-resonant DC-DC converter. It is not enough to consider averaged values because the state variable are AC so we need to consider the first harmonic too.
This is a topic that I have in mind for a future video. Thanks!
@Marcos Alonso But you already know how to do the small signal model by calculation and simulation for resonant converters? It would be good then if you could accelerate the creation of these videos on how to calculate and simulate the small signal model for the transfer functions: control-output, audiosusceptibility, input impedance, output impedance, in open loop and closed loop at least in voltage mode control, for these resonant converters. Would you do this?
Sir is there any way we can measure converter input impedance using LTspice?
I was trying with buck converter input impedance by placing series input ac source in the input side but unable to get it ..any suggestions?
Yes, it is possible. The procedure is similar to that shown in video LTspice #6: ua-cam.com/video/JCHiMp47UGw/v-deo.html
You have to inject the modulating signal in series with the input voltage. From the input voltage and input current perturbations you can calculate the input impedance and represent it from the log file data.
This can be interesting for a future video.
@@MarcosAlonsoElectronics I was trying to design the input filter for buck converter so instead of calculating buck converter input impedance analytical ,I was trying with simulation. I tried to search in internet but it seems like no one measuring input impedance using LTspice that make me think how to do it.
@@biswajit681 I will post a video about how to do this soon. This is on my to-do list now.
@@MarcosAlonsoElectronics Many Thanks sir ...
👍👍👍👍👍👍👍👍👍👍
Thanks!
Dear Prof. Alonso, could you please do a similar video on PSFB? Maybe even in Qspice
Hello, thanks for your suggestion. I will consider
Thank you for the reply sir. One more question, sir, why switching frequency chosen as 140kHz instead of 150kHz? Is there any reason, sir?
This was just a possible operating point that was selected to obtain a value of 12 V at the output for a given input voltage. You can choose other points within the switching frequency range. Remember that the switching frequency is our control parameter so it is variable.
Thanks for watching!
@@MarcosAlonsoElectronics thank you very much sir.
As switching frequency is different from resonant frequency then how the resonance occurs in the circuit
Resonant converters usually operate around resonant frequency and not only exactly at resonant frequency.
Bạn có thể cho tôi xin tài liệu mô phỏng LPspice như trên đươc không. Cảm ơn
Tệp mô phỏng hiện có sẵn ở đây:
github.com/marcosalonsoelectronics/PE-40
Cảm ơn bạn đã ghé thăm kênh!
Hi sir, in this video at time 22:33 you said that tdead is >85ns how you calculated . I have calculated using the formula 16*Ceq*fsw*Lm , the values i have taken as Ceq=0.2+0.2=0.4 , fsw=150kHz , Lm=210uH. i am getting 200ns . Kindly clarify the doubt sir.
Hi, thanks for your question. The formula is on the slide at 15:00. Using Ceq~Cds=0.2 nF (only one switch's because 2*Ceq is already considered in the formula), fsw=140 kHz (max. switching frequency), Lm=210 uH. We get t_dead=16*Ceq*fsw*Lm ~ 85 ns.
@@MarcosAlonsoElectronics thank you for the reply sir. One more question sir why switching frequency chosen as 140kHz instead of 150kHz? Is there any reason, sir?
Hai Marcos,
enjoyed the video, what is the component U2?
Hi, thanks for your question. U2 is a voltage controlled oscillator (VCO) from our Simulink-compatible control library. Please, watch videos LTspice #11-14 and #20 for more info on this library. It is available from my website.
@@MarcosAlonsoElectronics Thanks for you reply, please do a video of LLC closed control
Hello sir, I have done this ,can you pls make video on close loop control of LLC
Thanks for the suggestion. I will consider.
Sir what is U3?
U3 is a current sensor available from the Simulink-compatible control library. There is a playlist on this library on my channel. The library is available from my website.
I use it to measure the resonant current as volts so that it can be represented together with the magnetizing current generated by the voltage source.
Hi sir ..is everything alright?? I hope you are doing well
Hi, I am good, thanks for asking!
just very busy these last weeks, not much time to post videos
but please see my last video posted today, thanks!
Or can you please make video on vco
This video shows how to implement a VCO: ua-cam.com/video/BSiRYkqVfqU/v-deo.html