Deciphering the “PWM-resonant converter” proposed by Slobodan Cuk

An intuitive explanation of the “PWM-resonant converter” topology.

[supershaye]

Thank you for this professor. I am studying Power Electronics at university and I have been using your videos since last year. I will probably still be learning from your videos when I start working in industry in a couple of months. I hope you continue to post more videos especially about new converters and magnetics design.

[RaananL]

Clear & Informative presentation. -Thank you very much for sharing your knowledge!

[levnemets]

Dear Professor. This presentation is very informative as usual. I just would like to say, that this topology has significant drawbacks . I simulated a circuit, proposed by prof. S Cuk. For D=50% 12V to 6V at resonant frequency (160kHz) with 40A load. For these conditions, Peak to peak current in output capacitor -80A and RMS current -20A. RMS current in resonant capacitor - 45A. At 50kHz (as it recommended by prof. S. Cuk) peak to peak current in output capacitor is 380A (!) and RMS current is 115A. So, this is a price has to be paid to get rid of inductor in Buck converter. These huge currents make this topology very inefficient and practically unusable.

[premsuthar]

Interesting info. What is reason for two different inductors in two branches of currents ? What equations governs values of Ls and Cs?

[whateverjw]

insight！Fan of your channel! Thank you!

[willgeorge]

Hi Sam Ben-Yaakov
I came to similar conclusion (but Prof Cuk says it's not true) by another route. I always look for problems in a new topology by considering it from another point of view, in this case, from the frequency domain rather than time. Firstly, Prof Cuk has another, previous, variation with the source of the lower fet connected to the supply ground and I consider this version (makes no difference, only serves to put the input and outputs in series. Consider the 2 input side FETs as a 1/2 bridge, (which they are), with asymmetrical PWM as per a standard PSU design that already exists and is understood. the "resonant components " then are a band pass filter, the 2 output diodes are a peak to peak rectifier.supplying the load. Changing the FET drive symmetry changes the level of various harmonics, lowering the fundamental as you move away from symmetry. I said you can't choose the exact switching points to achieve resonance and also for exact output voltage, you can only have ZCS at one value of Vin / Vout, but he denies this, what do you think? I think it is saying the same thing as you via a different route?

[srinivasponnaluri]

Nice circuit. I had also made some alternate circuits without hard turn off. Do contact if interested.

[JadeHare]

Switching capacitors... Sounds to me like the applicationless topologies from the fake China's 1000 talent Ionovici...

No worth to check this video tho~