An intuitive explanation of ZVS, ZCS and pseudo ZVS

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An intuitive explanation of ZVS, ZCS and pseudo ZVS

Рет қаралды 11,181

11 ай бұрын

Please note: This video was trimmed to delete a section that included inaccuracies. A corrected version will be uploaded later on. Sorry.

Пікірлер: 32

@GHOTIME 11 ай бұрын

Very helpful Professor. Thank you for your continuous effort in spreading knowledge!

@sambenyaakov 11 ай бұрын

Thanks

@tseckwr3783 11 ай бұрын

Thanks again Professor.

@sambenyaakov 11 ай бұрын

Thanks

@aviperi7 4 ай бұрын

שלום שמואל, תודה רבה על הסרטונים, מעשיר מאוד. אשמח אם אוכל להתייעץ אתך בנוגע למעגל HB ואחריו LC resonance tank, הספק גבוה.

@sambenyaakov 4 ай бұрын

בהחלט. sam.benyaakov@gmail.com

@akosbuzogany2752 11 ай бұрын

I had a similar issue few weeks ago with a high voltage generator on the primary side of the transformer. Those high current peaks as on the graph at 15:23 didn't seem to appear due the frequency itself, they were rather dependent of the point where the switching met the ringing of the circuit (based on the inductance of the primary coil and the MOSFET capacitance probably). The worst case was when I tried to force the current by turning it on when it had to counteract the current slope generated by the ringing of the preceding excitation. Even if it was not the strongest, first period of the ringing but a later one, the sharp current peaks were present. By tuning the timing of the excitation and the ringing I was able to reduce those peaks near to zero, just as on the upper part of the picture. Could my issue had some completely different cause than you addressed in this presentation? In my circuit there was a simple N-MOSFET pulling down the primary coil.

@sambenyaakov 11 ай бұрын

Thanks for sharing. It appears that the tuning did the job of achieving soft switching.

@fala-at 11 ай бұрын

Dear Professor, I do not understand why the main loss is the product of drain voltage and current during hard switching turn-on. What with the capacitance parallel to the transistor which is discharging through the transistor during the transistor turn-on?

@sambenyaakov 11 ай бұрын

You have keen eyes. Thanks. There is a problem with the explanation. I was carried away. This part was deleted and I plan to post a correction video.

@fala-at 11 ай бұрын

@@sambenyaakov Dear Professor, thank you for the reply. I'm looking forward to this video. I want to precise my question. In kzfaq.info/get/bejne/f52Aqa-EqJPPqnU.html you describe hard switching turn-on. In simulation results, we can see the current of the transistor (M1) which is the current of the inductor and reverses recovering current of the diode. This current and the transistor voltage cause the switching power losses. But what with the energy stored in the capacitance of the transistor M1 ? Why we do not observe the current which discharge the transistor capacitance like in flyback kzfaq.info/get/bejne/f52Aqa-EqJPPqnU.html ?

@sambenyaakov 11 ай бұрын

You are correct, there is an additional loss due to the discharge of the Coss. I am not sure if LTspice takes tis current into account when plotting the power loss.

@fala-at 11 ай бұрын

@@sambenyaakov thank you.

@tamaseduard5145 11 ай бұрын

👍🙏❤️

@sambenyaakov 11 ай бұрын

👍🙏😊

@chaiyonglim 10 ай бұрын

for Buck or Boost converter, beside switching loss, is BCM mode always outperform CCM in term of overall efficiency? Or it limit in low-moderate load current case as BCM need very large ripple results in high Irms*dcr loss?

@sambenyaakov 10 ай бұрын

At higher currents the conduction loss increase due to the high rms values.

@hjjeon6812 11 ай бұрын

Thanks professor. Pls doublecheck the slide 9, it looks the overlap loss waveform of Rg=1ohm needs to be corrected to that of Rg=50ohm.

@sambenyaakov 11 ай бұрын

Thanks for comment. I am sorry, but this slide has inaccuracies. I have deleted this section. I will post a correcting video.

@SergiuCosminViorel 10 ай бұрын

But if i need to control the impact of the noise generated by the source, i need fixed frequency of commutation.

@sambenyaakov 10 ай бұрын

You mean synchronizing to another source? Well, you can use a variable inductor as in kzfaq.info/get/bejne/oNN5l7yq0rWbonk.html

@SergiuCosminViorel 10 ай бұрын

@@sambenyaakov I knew about all these, separate aspects, but never thought about putting it together. Very smart!

@panditji8823 11 ай бұрын

Hi Sir, nay u help to design transformer for flyback converter in step byxstep process.

@sambenyaakov 11 ай бұрын

Have you seen kzfaq.info/get/bejne/j5aHis1jybXDmGw.html ?

@kammarianurag3687 10 ай бұрын

Sir, in the very first slide you have shown diode across the MOSFET. Is it body diode or external diode because the current direction is reversed.

@sambenyaakov 10 ай бұрын

These are body diodes. he graph shows the magnitude of the current not polarity as is clear from the narration.

@rajatsankhla8993 11 ай бұрын

Is zvs turn off really helpfull? Why would one do that, if i were to transfer current to upper device.?

@sambenyaakov 11 ай бұрын

In PWM converters the duty cycle controls the power transfer so do have to turn on and off the transistors, unless I did not understand the question.

@Telectronics 11 ай бұрын

If you hit resonance exactly at the LLC converter you destroy your switches from overvoltage right ?

@sambenyaakov 11 ай бұрын

No, you dont, The voltage is clamped to the bus and the current depends on the load. Working at a slightly higher frequency than resonance is the best.

@Telectronics 11 ай бұрын

I see then it´s best to put the frequency slightly above resonance for normal operation and for short circuit protection pushing the frequency way higher because as you say we still have ZVS benefit at higher frequencies. Thanks for the nice video !

@sambenyaakov 11 ай бұрын

Indeed