Dr Yaakov thanks for the amazing help to give to all of us interested in power conversion. I took inspiration from this video to start designing an llc dcdc converter and I found the power section with magnetic components and switching part rather simple to implement. However I got stuck with the control section when it comes to phase gain loop simulation. I used to do this in frequency domain with conventional pwm loops but the VCO I used to modulate the working frequency of the llc works only in time domain. I am sure there is something to solve this problem in an elegant way rather than do it point by point with different frequency settings. Thanks for your priceless information.
Its amazing, now I can calculate a lot of things for power supplies, now i know why we have specific value of components in Resonant tank circuit, and Helped me to understood the design of Corsair AX1200i, Coolermaster V850V2 PSUs .. Great video
Thank you so much for this simple and effective explanation. I wonder of you are planning to make a lecture on the closed loop control design of the LLC converter
@@sambenyaakov dynamic wireless electric vehicle design...solve a numerical related to design of IPT-SS converter...how to calculate inverter input voltage,Lp,Cp,Ls,Cs....please solve with numerical
Thanks a lot Dr Yaakov! One Q about slide 21: Should it be Amax/Amin = Vmax/Vmin instead? Where am I mistaking? The content looks clear anyway, thanks again!
Dr Ben Yaakov thank you for your help and your patience while you were explained this video,i was wondering if you could explain in 18 "minute,you said that we should not choose the curves desoite they are above the minimum gain,by the meaning we are working in the capacitive region,why we should not operate in this region and what it can causes?.thank you
Thank you for the great explanations for analog circuits. I have a question please: how do you obtain the voltage gain curves like the ones shown at min 11 or 13 for example?
I would like to thank you for the useful information. Second, I have some questions that I hope to get clear answers to help me design my circuit:
1-Could I use an LLC Resonant tank with a multilevel inverter Or it is limited to use on half-bridge and full-bridge only. If I use it with a multilevel, does it affect the waveform of the output of the inverter?
2-What is the output voltage waveform of the resonant tank (VLm)? Is it the same as the waveform of the output voltage of the inverter (Vinv) or different?
Hi Dr Sam, the energy of the leakage inductance Lk should be equal to energy in the output capacitance of the MOSFET. So what happened if energy of Lk is greater or less than energy of capacitance of the MOSFET. Thanks,
@@sambenyaakov Isn't should be the other way? , When Rac is very high , we need to keep very low gain, we move towards the higher frequencies and at some point need pulse skipping due max frequency operational difficulties. Please correct me if i understood wrong
Agreed..Then is it correct to say higher Rac means lower current delivery which means lower Q also means higher operational frequency and at some point as we further go to right side we need pulse skipping?
Hi Mr. Yaakov, thank you for this interesting presentation. I would like to mention one detail: The Rac approach in slide 7 is true as long as Iac is sinusoidal, and this will not be the case since as you point out in slide 10 the switching frequency is above the resonant frequency and hence current will be lagging. Please, can you clarify this point? thanks again.
Hi Sam, I got back around to finishing my LLC converter design. I found a very helpful article by Infineon (URL below). and I outline my work below. My design uses a 48V battery (3.0Vmin, 3.7Vnom, 4.2Vmax, 13S) to 2KW at 175V. The realized design in LTspice that really overdelivers! It can push 15A, 175V, 2.6KW under full load with minimum input voltage, and at no load, max input voltage, It under-delivers, providing 170V. That's good it means I can keep it in regulation with a tighter frequency range. The values I calculated are as follows: Cr = 8.5uF Lr = 1.2uH Lm = 7.2uH Ls = 95uH The *PROBLEM* is the 200A peak currents (guessing around 130A rms, not quite sinusoidal at the max load min input voltage). The primary voltage also resonates up to 130Vpk. This design "works" on paper but does not sound reasonable to me. Where did I go wrong? I picked 3.7V to be the nominal voltage for this design. * Amax = 3.7/3.0 = 1.23 (max load and min input voltage edge case) * Amin = 3.7/4.2 = 0.88 (no load and maximum input voltage edge case) * Fmax = 5 Hz normalized. (arbitrarily chosen to avoid a huge frequency range) * f = 50kHz (arbitrarily chosen so fmax = 250kHz and fmin = 24kHz) *Step 1: find suitable K value.* With no load, Q -> ∞; Amin of 0.88 or less, frequency is limited to 5, 'K' to be no higher than 6. As I understand K should be as high as possible. With K = 6, Amin is 0.86, which is acceptable. *Step 2 and 3: find Qmax and Fmin* The highest Q factor that supports Amax = 1.23 was found to be about 0.4. Q=0.4 allows Amax to reach as high as 1.28, at this peak which occurs at 0.422 Hz (normalized) *Step 4: find Rac_min* Rac_min = 8/π^2 * (Np/Ns)^2 * Vout^2/Pmax Rac_min = 8/π^2 * (48.1V/175V)^2 * 175^2/2000 = 0.9376 *Step 5, lots of arithmetic!* Lr/Cr = Qmax * Rac_min Lr*Cr = (2πf)^-2 Lm=K*Lr Rounded, I end up with the following values: Cr = 8.5uF Lr = 1.2uH Lm = 7.2uH Ls = 95uH Is this correct, and what can be iterated to make this design realizable? www.infineon.com/dgdl/Application_Note_Resonant+LLC+Converter+Operation+and+Design_Infineon.pdf?fileId=db3a30433a047ba0013a4a60e3be64a1
Hi, What is the switching frequency at 48V, nominal power (2kW) and what are the conditions (input voltage frequency and power) when you get the 200A ?
@@sambenyaakov frequency is 24kHz (the minimum), input is 40V, and I just tuned the resistor value to get about 2KW (15.3 ohms) since it is simulated open loop
@@sambenyaakov I agree. But I don't know where I went wrong! K = 6 was chosen since it's a good starting point and I found it offers sufficiently low gain at the high Vin, no load condition, at a frequency only 3 times the nominal. For the record, my design could allow up to K=7.4 with burst mode. but I wanted to play it safe. The normalized AC converter is simulated to find minimum suitable K value. I found that K=0.4 results in a peak of gain of Amax = 1.28, comfortably above the minimum 1.24 for my design. For Rac_min, I use Pmax = 2000W and Vout=175V. I followed it up with your definition using Amax = 1.233 to validate. Rac_min = 8/π^2 * (Np/Ns)^2 * Vout^2/Pmax Rac_min = 8/π^2 * (48.1V/175V)^2 * 175^2/2000 = 0.9376Ω Rac_min = (Amax * VIn_min * 4/(√2pi))^2 / 2000 = 0.9376Ω Solving the equation below, it's telling that inductor will be 14% of the value of the capacitor, or put another way, the capacitor is 7 times greater than the value of the Lr! This is the part that sounds wrong to me: Q = √(Lr/Cr)/Rac_min Lr/Cr = (Qmax * Rac_min)^2 Lr/Cr = (0.4*0.9376Ω)^2 Lr/Cr = 0.1406 Lr = 0.1406*Cr Cr = 7.109*Lr For this ratio to increase, I need to raise Rac_min or Qmax. For those to change, my requirements have to change, as far as I can tell. Of course, I can also just raise the frequency, which will bring Cr down to a manageable value, but then Lr and Lm end up being tiny! I would probably then be looking at a GaN FET design. That might be for a version 2 that features water cooling haha
thank you for this valuable explanation, I have a question for you, is this topology adequate for high power, low output voltages ("The output current variation would be greater than for a PSFB ? Or no ? ")
Very good explanation, just what i was looking for. Is there any video related to ZCS Quasi resonant Buck Converter or ZVS Quasi resonant Boost Converter? Keep on going! Cheers from Venezuela
Thank you for your explanation. Professor, can you please explain the No-Load operation of the Resonant Converters both in Open-Loop and Closed-Loop operation. I have experienced increase in output voltage in the Open-Loop operation, can you please explain this issue?
Hello Professor Ben-Yaakov, ive just recently build a LLC Converter for ~250W, Vin=390V, Vout=24V, half bridge. When i start it up, the control IC goes into soft starting mode and then keeps switching at minimum switching frequency. However, theres no power transfer, output voltage barely goes over 5V (no load at secondary side), although primary side current is very high (~10A ) and perfectly sinusoidal(so there seems to be some resonance). DC link voltage is supplied by a passive 1 phase rectifier, so around 320-330V(i have left out the PFC, hoping it would still somewhat work). Could this be the issue why the converter isnt working if the supply voltage is too far off, which would mean im far off the desired operating region in the voltage-gain-plot, wouldnt it? Best regards
I just had a thought, what if you had a transformer that had not so great K, and you wanted better output regulation, could you slap on a series resonant capacitor with the AC supply (fixed frequency) and improve output voltage regulation? Idea here is to have the the series resonant capacitor resonate with the short-circuit primary inductance. 🤔
The actual value of Lm of the LLC is the external inductor in parallel to the magnetization inductance. In fact, some designers use the magnetization inductnce of the transformer as Lm . This requires the lowering of the permeability of the core by airgap.
I am building a 48V to 115V converter for fun, using flyback transformer core, and I think I can get upwards to 1kW out of it, based on the HF transformer design video. I found in practice at 12V that leakage inductance is going to be an issue for a forward converter so I came here to take advantage of that pesky Lr :) I know nothing about the ferrite core (permeability, reluctance, effective length, Bmax). I found w/ 5 turns & 220nf film capacitor, it oscillates ~50kHz, which works out to Lm ≈ 46uH on the core. I meaured a few times with different numbers of turns and found the inductance does change as expected. With the secondary (same 5 turns 14AWG) I found it rings closer to 10MHz but it was much harder to measure and the ringing was "dirty" , Lr ≈ 1nH although I very much doubt this measurement. Is this the right way to measure the minimum leakage? I can of course always add as needed.
Also, how does the LLC converter react to no load condition? Looks to me the Q will shoot way up and cause problems with gain and resonant voltage rise. Great for my TC's, but not for a converter lol.
Dear Dr. Sam, can you please upload the LLC converter discussions in English ( most of them are in Hebrew) . Thank you in advance. Big fan of your analyis.
Prof. Yaakov, I really appreciate your effort to make this nice video. One question: This first harmonic approach is very convenient and accurate when the current is quite sinusoidal. But when the operating windows are very wide (input/output voltage, current), this is not the case. What approach do you recommend then? Thanks!
Hi Yi Wang, I think in that case you need to consider the contribution of higher order harmonics to the power delivery since it can't be neglected when the current is not sinusoidal... That is the intuitive way to think about it ... For a detailed analysis on this point, have a look on the following IEEE paper in which the authors derived a formula for the gain in that case ... (ieeexplore.ieee.org/document/7172545/).... Hope this helps
Hi Professor, I have a question, please. You marked A_max and A_min on the plot. How did you get them? I'm asking for two reasons 1-I have a V_in of 35-75(v) and V-out of 2(v), and so V_out/V_in is very small while your gain region is around 1. 2- I also saw somewhere that A should be (n).(V_out/V-_n), but in your lecture, we have the gain first, but we calculate n towrds the end. Thank you
The gain is taking care of by transformer. Turns ratio is selected such that at low input you get the required Vout. And then you have the shift of Vin.
@@sambenyaakov I think I finally understand what you meant. which is we should stick to the recommended region shown in the figure, and calculate n based on the vin_min i.e A_max. I hope I'm right. Thank you
Shalom Moshe Nice to hear/read from you. Yes , I know about your designs in Infineon and in fact mentioned your contributions (Including the lossless snubber) in a numbers of my videos. Love to hear how you are doing. Please write to sby@bgu.ac.il
Hi Sam, I built a spreadsheet which computes all component values provided design requirements and operating frequency range! Now the next step is to close the loop. Do you have videos that walk through making it stable? I've noticed that at F_res, the output impedance is very low. But at low or high input voltage requiring boost or buck operation, the output impedance increases due to one of the reactive components dominating, which changes the dymamics of the plant. How is this stabilized? Can I use the same methods and assumptions used for PWM controllers?
You can use same method as in PWM but after getting the small signal response and then checking over the envelope of the operating points. Have you seen ruclips.net/video/amRqIgH10Rg/видео.html ?
What happens with formulas when you need sinus signal on output? I'm trying to create sinus kV on output with capacitive load but I don't know how to define Lm of transformer?
@@sambenyaakov sorry I did not get it, let say the range of input volt is 350-400 volt and the switching frequency Fsw is 100 kHz, How the Fs min and Fs max will be after doing whole calculation and finding the Fr, Cr ,Lr and Lm. thanks in advance
When calculating Rac, min you are using Vin, min and Amax. This is clear because Qmax is going to happen with Amax and Rac, min. Now when calculating Lr and Cr using resonant frequency fr, have I understood correctly that with these values then at fr I Will get gain Amax?
@@sambenyaakov thank you for your reply, do you have a video about LLC resonating with a small inductive load (10u(H)) ? . I am learning about an LLC converter with output as current control (as a current source) to power one motor phase. (specifically the Slotless Self-Bearing Permanent-Magnet Motor, it's a 6 phase motor, I plan to use 6 LLC converters)
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I never expected to learn this concept in such a easy manner, thanks a lot professor.
Thanks, I appreciate it.
A very enjoyable presentation. I particularly liked the way you used the normalized resonant graphd.
Hi David, Thanks for comment.
Dr Yaakov thanks for the amazing help to give to all of us interested in power conversion. I took inspiration from this video to start designing an llc dcdc converter and I found the power section with magnetic components and switching part rather simple to implement. However I got stuck with the control section when it comes to phase gain loop simulation. I used to do this in frequency domain with conventional pwm loops but the VCO I used to modulate the working frequency of the llc works only in time domain. I am sure there is something to solve this problem in an elegant way rather than do it point by point with different frequency settings. Thanks for your priceless information.
Have you seen ruclips.net/video/amRqIgH10Rg/видео.html
Thank you Dr. Yaakov for this simple yet effective explanation. At 16.12, Amax/Amin = Vin,max/Vin,min = Vac,max/Vac,min.
Its amazing, now I can calculate a lot of things for power supplies, now i know why we have specific value of components in Resonant tank circuit, and Helped me to understood the design of Corsair AX1200i, Coolermaster V850V2 PSUs .. Great video
Thanks for sharing
Thank you so much for this simple and effective explanation. I wonder of you are planning to make a lecture on the closed loop control design of the LLC converter
Have you seen ruclips.net/video/amRqIgH10Rg/видео.html ?
Great video again Dr. Sam
Thanks again.
@@sambenyaakov dynamic wireless electric vehicle design...solve a numerical related to design of IPT-SS converter...how to calculate inverter input voltage,Lp,Cp,Ls,Cs....please solve with numerical
Outstanding Job.
Thanks for all🙂
very impressive explanation, thank you sir.
Thanks.
Thanks a lot Dr Yaakov! One Q about slide 21: Should it be Amax/Amin = Vmax/Vmin instead? Where am I mistaking? The content looks clear anyway, thanks again!
Thanks. It is OK, you need max gain when Vin is min.
Dr Ben Yaakov thank you for your help and your patience while you were explained this video,i was wondering if you could explain in 18 "minute,you said that we should not choose the curves desoite they are above the minimum gain,by the meaning we are working in the capacitive region,why we should not operate in this region and what it can causes?.thank you
Not sure I follow your question. The desired operational mode is when the current lags to get ZVS
Thank you for the great explanations for analog circuits. I have a question please: how do you obtain the voltage gain curves like the ones shown at min 11 or 13 for example?
LTspice simulation, small signal on first harmonics model.
I would like to thank you for the useful information.
Second, I have some questions that I hope to get clear answers to help me design my circuit:
1-Could I use an LLC Resonant tank with a multilevel inverter Or it is limited to use on half-bridge and full-bridge only. If I use it with a multilevel, does it affect the waveform of the output of the inverter?
2-What is the output voltage waveform of the resonant tank (VLm)? Is it the same as the waveform of the output voltage of the inverter (Vinv) or different?
1. I guess you can a MV configuration but I don't recall seeing one
2 Yes
Hi Dr Sam, the energy of the leakage inductance Lk should be equal to energy in the output capacitance of the MOSFET.
So what happened if energy of Lk is greater or less than energy of capacitance of the MOSFET.
Thanks,
Thank you, know it's easier to see why some manufacturers of resonant chip controllers use pulse skipping as Rac approaches zero.
Indeed.
@@sambenyaakov Isn't should be the other way? , When Rac is very high , we need to keep very low gain, we move towards the higher frequencies and at some point need pulse skipping due max frequency operational difficulties. Please correct me if i understood wrong
@@jacobs7281 Change in Rac does not reuire change of voltage gain (A) but current delivery which affects Q.
Agreed..Then is it correct to say higher Rac means lower current delivery which means lower Q also means higher operational frequency and at some point as we further go to right side we need pulse skipping?
Hi Mr. Yaakov, thank you for this interesting presentation. I would like to mention one detail: The Rac approach in slide 7 is true as long as Iac is sinusoidal, and this will not be the case since as you point out in slide 10 the switching frequency is above the resonant frequency and hence current will be lagging. Please, can you clarify this point? thanks again.
Hi Eduard, A sinusoidal waveform is found not only at the resonant frequency but also around it as long as you don't approach the third harmonics.
Thank you for such a clear and concise explanation. Can you please review vac min expression at 19:50? I think it should be 2/pi, not 4/pi.
First harmoni of a square wave 4/pi
Yes, that I agree. But it is a half bridge with input Vin. So, either vin/2 or 2/pi should be in the equation.
You got me there. You are correct! I hope other will notice your correction. Thanks.
Good stuff Sam. How to determine Lm from the coupling inductor?
Lm is just the total inductance you measure at the primary. This assumes a low leakage inductance.
Hi Sam, I got back around to finishing my LLC converter design. I found a very helpful article by Infineon (URL below). and I outline my work below. My design uses a 48V battery (3.0Vmin, 3.7Vnom, 4.2Vmax, 13S) to 2KW at 175V. The realized design in LTspice that really overdelivers! It can push 15A, 175V, 2.6KW under full load with minimum input voltage, and at no load, max input voltage, It under-delivers, providing 170V. That's good it means I can keep it in regulation with a tighter frequency range.
The values I calculated are as follows:
Cr = 8.5uF
Lr = 1.2uH
Lm = 7.2uH
Ls = 95uH
The *PROBLEM* is the 200A peak currents (guessing around 130A rms, not quite sinusoidal at the max load min input voltage). The primary voltage also resonates up to 130Vpk. This design "works" on paper but does not sound reasonable to me. Where did I go wrong?
I picked 3.7V to be the nominal voltage for this design.
* Amax = 3.7/3.0 = 1.23 (max load and min input voltage edge case)
* Amin = 3.7/4.2 = 0.88 (no load and maximum input voltage edge case)
* Fmax = 5 Hz normalized. (arbitrarily chosen to avoid a huge frequency range)
* f = 50kHz (arbitrarily chosen so fmax = 250kHz and fmin = 24kHz)
*Step 1: find suitable K value.*
With no load, Q -> ∞; Amin of 0.88 or less, frequency is limited to 5, 'K' to be no higher than 6. As I understand K should be as high as possible.
With K = 6, Amin is 0.86, which is acceptable.
*Step 2 and 3: find Qmax and Fmin*
The highest Q factor that supports Amax = 1.23 was found to be about 0.4. Q=0.4 allows Amax to reach as high as 1.28, at this peak which occurs at 0.422 Hz (normalized)
*Step 4: find Rac_min*
Rac_min = 8/π^2 * (Np/Ns)^2 * Vout^2/Pmax
Rac_min = 8/π^2 * (48.1V/175V)^2 * 175^2/2000 = 0.9376
*Step 5, lots of arithmetic!*
Lr/Cr = Qmax * Rac_min
Lr*Cr = (2πf)^-2
Lm=K*Lr
Rounded, I end up with the following values:
Cr = 8.5uF
Lr = 1.2uH
Lm = 7.2uH
Ls = 95uH
Is this correct, and what can be iterated to make this design realizable?
www.infineon.com/dgdl/Application_Note_Resonant+LLC+Converter+Operation+and+Design_Infineon.pdf?fileId=db3a30433a047ba0013a4a60e3be64a1
Hi, What is the switching frequency at 48V, nominal power (2kW) and what are the conditions (input voltage frequency and power) when you get the 200A ?
@@sambenyaakov frequency is 24kHz (the minimum), input is 40V, and I just tuned the resistor value to get about 2KW (15.3 ohms) since it is simulated open loop
@@power-max Something is wrong with the design. 24kHz seems awfully low for the Lm you use.
@@sambenyaakov I agree. But I don't know where I went wrong! K = 6 was chosen since it's a good starting point and I found it offers sufficiently low gain at the high Vin, no load condition, at a frequency only 3 times the nominal. For the record, my design could allow up to K=7.4 with burst mode. but I wanted to play it safe.
The normalized AC converter is simulated to find minimum suitable K value. I found that K=0.4 results in a peak of gain of Amax = 1.28, comfortably above the minimum 1.24 for my design.
For Rac_min, I use Pmax = 2000W and Vout=175V. I followed it up with your definition using Amax = 1.233 to validate.
Rac_min = 8/π^2 * (Np/Ns)^2 * Vout^2/Pmax
Rac_min = 8/π^2 * (48.1V/175V)^2 * 175^2/2000 = 0.9376Ω
Rac_min = (Amax * VIn_min * 4/(√2pi))^2 / 2000 = 0.9376Ω
Solving the equation below, it's telling that inductor will be 14% of the value of the capacitor, or put another way, the capacitor is 7 times greater than the value of the Lr! This is the part that sounds wrong to me:
Q = √(Lr/Cr)/Rac_min
Lr/Cr = (Qmax * Rac_min)^2
Lr/Cr = (0.4*0.9376Ω)^2
Lr/Cr = 0.1406
Lr = 0.1406*Cr
Cr = 7.109*Lr
For this ratio to increase, I need to raise Rac_min or Qmax. For those to change, my requirements have to change, as far as I can tell.
Of course, I can also just raise the frequency, which will bring Cr down to a manageable value, but then Lr and Lm end up being tiny! I would probably then be looking at a GaN FET design. That might be for a version 2 that features water cooling haha
@@power-max Without going into details (sorry too busy) it would deem to me the the turns ratio of the transformer and frequency are not optimized.
thank you for this valuable explanation, I have a question for you, is this topology adequate for high power, low output voltages ("The output current variation would be greater than for a PSFB ? Or no ? ")
In general the performance of the LLC is better than that of PSFB. But it works best with narrower input voltage and load current.
Thank you sir.
Most welcome
Very good explanation, just what i was looking for. Is there any video related to ZCS Quasi resonant Buck Converter or ZVS Quasi resonant Boost Converter? Keep on going! Cheers from Venezuela
Have you seen ruclips.net/video/w4cxLPl2Wsg/видео.html
@@sambenyaakov yeah, that was the first one i saw. Thanks anyways
Thank you for your explanation. Professor, can you please explain the No-Load operation of the Resonant Converters both in Open-Loop and Closed-Loop operation. I have experienced increase in output voltage in the Open-Loop operation, can you please explain this issue?
Charging of parasitic inductances can cause an increase in output voltage.
Hello Professor Ben-Yaakov,
ive just recently build a LLC Converter for ~250W, Vin=390V, Vout=24V, half bridge.
When i start it up, the control IC goes into soft starting mode and then keeps switching at minimum switching frequency.
However, theres no power transfer, output voltage barely goes over 5V (no load at secondary side), although primary side current is very high (~10A ) and perfectly sinusoidal(so there seems to be some resonance).
DC link voltage is supplied by a passive 1 phase rectifier, so around 320-330V(i have left out the PFC, hoping it would still somewhat work). Could this be the issue why the converter isnt working if the supply voltage is too far off, which would mean im far off the desired operating region in the voltage-gain-plot, wouldnt it?
Best regards
It seems the the range of frequency is wrong and the converter locks into a a bad operating point.
I just had a thought, what if you had a transformer that had not so great K, and you wanted better output regulation, could you slap on a series resonant capacitor with the AC supply (fixed frequency) and improve output voltage regulation? Idea here is to have the the series resonant capacitor resonate with the short-circuit primary inductance. 🤔
This would change it to a sort of resonant converter.
Thanks a lot. I was however wondering if transformer inductance (both primary and secondary) should be taken into calculations?
They should be absorbed in Lm
@@sambenyaakov you mean that lm should be greater than transformer primary inductance, in order to be neglegible in comparison?
The actual value of Lm of the LLC is the external inductor in parallel to the magnetization inductance. In fact, some designers use the magnetization inductnce of the transformer as Lm . This requires the lowering of the permeability of the core by airgap.
@@sambenyaakov thanks for your answer
I am building a 48V to 115V converter for fun, using flyback transformer core, and I think I can get upwards to 1kW out of it, based on the HF transformer design video. I found in practice at 12V that leakage inductance is going to be an issue for a forward converter so I came here to take advantage of that pesky Lr :)
I know nothing about the ferrite core (permeability, reluctance, effective length, Bmax). I found w/ 5 turns & 220nf film capacitor, it oscillates ~50kHz, which works out to Lm ≈ 46uH on the core. I meaured a few times with different numbers of turns and found the inductance does change as expected. With the secondary (same 5 turns 14AWG) I found it rings closer to 10MHz but it was much harder to measure and the ringing was "dirty" , Lr ≈ 1nH although I very much doubt this measurement.
Is this the right way to measure the minimum leakage? I can of course always add as needed.
Also, how does the LLC converter react to no load condition? Looks to me the Q will shoot way up and cause problems with gain and resonant voltage rise. Great for my TC's, but not for a converter lol.
It seems that you have a lot of fun. At no load operation is forces to burst mode.
Dear Dr. Sam, can you please upload the LLC converter discussions in English ( most of them are in Hebrew) . Thank you in advance. Big fan of your analyis.
too time consuming. I will try to add some more formation of LLC.
Thank you very much. I am looking forward to it. How to design a LLC converter from scratch is a very interesting topic for me :)
Prof. Yaakov, I really appreciate your effort to make this nice video. One question: This first harmonic approach is very convenient and accurate when the current is quite sinusoidal. But when the operating windows are very wide (input/output voltage, current), this is not the case. What approach do you recommend then? Thanks!
Hi Yi Wang, I think in that case you need to consider the contribution of higher order harmonics to the power delivery since it can't be neglected when the current is not sinusoidal... That is the intuitive way to think about it ... For a detailed analysis on this point, have a look on the following IEEE paper in which the authors derived a formula for the gain in that case ... (ieeexplore.ieee.org/document/7172545/).... Hope this helps
Hi Mr. Mohsen, thanks for this information. will check this paper for sure.
Go with LCC for wide input/output , but the efficiency is not as great as LLC.
Hi Professor, I have a question, please. You marked A_max and A_min on the plot. How did you get them? I'm asking for two reasons 1-I have a V_in of 35-75(v) and V-out of 2(v), and so V_out/V_in is very small while your gain region is around 1. 2- I also saw somewhere that A should be (n).(V_out/V-_n), but in your lecture, we have the gain first, but we calculate n towrds the end. Thank you
The gain is taking care of by transformer. Turns ratio is selected such that at low input you get the required Vout. And then you have the shift of Vin.
@@sambenyaakov I think I finally understand what you meant. which is we should stick to the recommended region shown in the figure, and calculate n based on the vin_min i.e A_max. I hope I'm right. Thank you
Sam
This is Moshe domb
Nice to see your presentation
Did a lot of LLC DESIGNS myself in Infineon
How are u doing now days
Cordially
Moshe
Shalom Moshe
Nice to hear/read from you. Yes , I know about your designs in Infineon and in fact mentioned your contributions (Including the lossless snubber) in a numbers of my videos. Love to hear how you are doing. Please write to sby@bgu.ac.il
I have gone through this video many times, I have a question that why Lm is not being used on Qmax and fr calculations??..Thank You
Lm comes in by the choosing of the Lm/Lr ratio
Hi Sam, I built a spreadsheet which computes all component values provided design requirements and operating frequency range! Now the next step is to close the loop. Do you have videos that walk through making it stable?
I've noticed that at F_res, the output impedance is very low. But at low or high input voltage requiring boost or buck operation, the output impedance increases due to one of the reactive components dominating, which changes the dymamics of the plant. How is this stabilized? Can I use the same methods and assumptions used for PWM controllers?
You can use same method as in PWM but after getting the small signal response and then checking over the envelope of the operating points. Have you seen ruclips.net/video/amRqIgH10Rg/видео.html ?
@@sambenyaakovI have not, thanks for the pointer!
Hi sir
How you plotted the gain versus freq
And innductance ratio curves
This was done on an equivalent circuit using Rac
Hello sir, you have shown resonant tank gain with the normalized switching frequency. how can i get that plots?
Write to me at sby@bgu.ac.il
@@sambenyaakov Can I send a general question about mosfet turn off spike to your email id?
What happens with formulas when you need sinus signal on output? I'm trying to create sinus kV on output with capacitive load but I don't know how to define Lm of transformer?
Calculate Rac and continue from there.
@@sambenyaakov Not sure then Rac=8*Xc/PI^2 (Xc=1/2*pi*C)?
how to calculate or know the range of switching frequency Fsmin, Fsmax that the converter can work on ?
Explained in video. Depends on the expected input voltage variations.
@@sambenyaakov sorry I did not get it, let say the range of input volt is 350-400 volt and the switching frequency Fsw is 100 kHz, How the Fs min and Fs max will be after doing whole calculation and finding the Fr, Cr ,Lr and Lm. thanks in advance
@@salahalatai8255 Isn't it clear here? ruclips.net/video/ZWwZBHV0ynY/видео.html
@@sambenyaakov not yet, I got maximum gain and min gain. But I wonder what depends on for drawing a line to intersect with the x-axis?
When calculating Rac, min you are using Vin, min and Amax. This is clear because Qmax is going to happen with Amax and Rac, min. Now when calculating Lr and Cr using resonant frequency fr, have I understood correctly that with these values then at fr I Will get gain Amax?
Indeed.
Dear sir
How to avoid bifurcation issue in bidirectional wireless power transfer in ev battery charging
Bifurcation is invoked by high ripple. See www.ee.bgu.ac.il/~pel/pdf-files/conf45.pdf
@@sambenyaakov
Thank you sir
wr=2*pi*fr, right ?
Correct. So?
can i use LLC converter to transfer power to very small inductance motor? thanks sir
Yes. Notice that in a motor there is a back EMF not just inductance.
@@sambenyaakov thank you for your reply, do you have a video about LLC resonating with a small inductive load (10u(H)) ? . I am learning about an LLC converter with output as current control (as a current source) to power one motor phase. (specifically the Slotless Self-Bearing Permanent-Magnet Motor, it's a 6 phase motor, I plan to use 6 LLC converters)
@@nguyencuong-ye1gn Sorry I have no experience with LLC driving motors . I am not clear what is your idea. LLC is normally used for DC-DC conversion.