Thanks, Professor! It's an awesome video. But I have a doubt when you explained the V_y = - V_in when the switch is on, you said: "because it's charged to V_in". How could we tell the capacitor has been charged with V_in at that time? It's at 12:07. Many thanks in advance.
Average (not momentary) voltage on any inductor in steady sate, including L1 and L, is zero. Can you see it now that the voltage of the cap is equal to the input voltage?
@@sambenyaakov Great! I think I've seen the trick :) Is it if we take a loop V_in-L_1 -C- L_2- Ground_Vin, it can be concluded that the average voltage charged to the cap is V_in in a period.
Interesting, Professor. The coupling capacitor is not only expensive, but hard to find. The average current through it may be 0 (zero), but the rms current is on par with the output current. I had suspected this since I had an application in which I was using both a buck and a boost converter to provide a variable output (0 to 100V) from a single semi-variable, somewhat fixed, input (10 -14V). The output of the buck would provide the input to the boost! In this case, both the buck and the boost could share the same inductor - what a savings! But this required so much complication from the control circuitry, and I thought there had to be a better way. Hence, to the SEPIC. This would require two inductors - expensive ones, and in my models, coupled inductors work better. But the capacitor, I suspected, had to support a great deal of current for this to work. And in the calculations and the modeling, I needed a capacitor that could support upwards of 10Arms. You cannot find these easily. When we do a search for a product at our favorite electronics suppliers, they simply do not list capacitors with the rms current in mind. You have to sort through them individually. Most manufacturers do not list the rms current of their capacitors in their data sheets, either. Others will advertise that they have high-rms current capacitors, and then you have to sort through their data sheets to find the one you need. Luckily, the SEPIC converter is not to picky about the capacitance, and you have about a decade order of sloppiness (for example, 1 to 10uF) to play with. In the meantime, these big capacitors can run from $2 up to $20 for just one. So this is where we have to consider the economics of choosing one method over the other. In the long term, which one will cost less. In my past, I've seen ceramic capacitors explode and electrolytics (big ones) spew out blue smoke.
Dear Robert. Thanks for comment and for sharing your experience. Yes, capacitors are a sensitive subject. In case you are not aware: th-cam.com/video/8ptGjioWTlM/w-d-xo.html
Thanks! That was a much better presentation than what I had to suffer through almost thirty years ago! I hope you will discus the coupled inductor SEPIC configuration in a future video...
Thanks so much Dr Sam, it is possible Dr. Sam to teach us how we can create netlist for IC, I was trying to create netlist for UC2823A, Is there any recommendations from you now how can I do it. Thanks
Hi Farely, Indeed, you are correct since Vo/Vin is not D but D/(1-D) as indicated few lines above. You are the first one to notice this mistake after 7.5K views! Thanks. Too much woek to redo it. I hope people watching the video will also look up your comment.
@@sambenyaakov There is an option to put on an annotation on the video. It will be very useful because possible that many people will not read the comments.
Thank you for sharing. i have a question about the coupling capacitor polarity. I see schematics showing the + side is towards the input and also they use a big Aluminum Electrolytic cap. however if the output is higher than the input by a few volts, does the capacitor not get reverse biased?
Hi John, just happened to see now your comment which I guess you posted a minute ago. The polarity you indicated is OK. The voltage of the capacitor at the input is higher than the output. A trick to quickly see it is to base the observation on the fact that the AVERAGE voltage on an inductor is zero. So on the left the average voltage seen by the capacitor is Vin, and on the right, ground. You can go through the chore of a detailed analysis, but this will be the answer. Regard Sam
Choose the capacitance to get the ripple level you want on it, normally few percent of Vin, Vout (the smallest of the two) and most important a capacitor that can carry the expected current.
thank you doctor sam for your excellent presentation, however I have a question about the voltage Vx when the switch is off, I didn't understand why is this voltage equal to Vin+V0 during Toff? you neglected the voltage at the terminal of the inductor L1 during Toff? and we know that the average voltage of L1 equal zero during Toff+Ton
@@sambenyaakov sir i have a 2nd review on few days after plzz help me sir ..Total abstract i send to ur mail plz explain methodology and implementation sir
Sam Ben-Yaakov by the way have you ever worked with Cuk-SEPIC hybrid converters? In scientific papersn they are proposed as topology for wind+solar hybrid power
Please explain more regarding current flow through L2 during switch on..as a bigginer I am confused that how can series capacitor charge L2 in a case Vx node grounded???
Thank you sir, Good video, i got to know more about SEPIC. can you upload more videos on SEPIC like its controlling and its Application like in Solar MPPT?
Thanks, Professor! It's an awesome video. But I have a doubt when you explained the V_y = - V_in when the switch is on, you said: "because it's charged to V_in". How could we tell the capacitor has been charged with V_in at that time? It's at 12:07.
Many thanks in advance.
Average (not momentary) voltage on any inductor in steady sate, including L1 and L, is zero. Can you see it now that the voltage of the cap is equal to the input voltage?
@@sambenyaakov Great! I think I've seen the trick :) Is it if we take a loop V_in-L_1 -C- L_2- Ground_Vin, it can be concluded that the average voltage charged to the cap is V_in in a period.
@@dinleepound9466 👍
Great video again Professor. Thank you!😀
Thanks again!
Thank you for an excellent explanation.
Interesting, Professor. The coupling capacitor is not only expensive, but hard to find. The average current through it may be 0 (zero), but the rms current is on par with the output current. I had suspected this since I had an application in which I was using both a buck and a boost converter to provide a variable output (0 to 100V) from a single semi-variable, somewhat fixed, input (10 -14V). The output of the buck would provide the input to the boost! In this case, both the buck and the boost could share the same inductor - what a savings!
But this required so much complication from the control circuitry, and I thought there had to be a better way. Hence, to the SEPIC. This would require two inductors - expensive ones, and in my models, coupled inductors work better. But the capacitor, I suspected, had to support a great deal of current for this to work. And in the calculations and the modeling, I needed a capacitor that could support upwards of 10Arms. You cannot find these easily.
When we do a search for a product at our favorite electronics suppliers, they simply do not list capacitors with the rms current in mind. You have to sort through them individually. Most manufacturers do not list the rms current of their capacitors in their data sheets, either. Others will advertise that they have high-rms current capacitors, and then you have to sort through their data sheets to find the one you need. Luckily, the SEPIC converter is not to picky about the capacitance, and you have about a decade order of sloppiness (for example, 1 to 10uF) to play with.
In the meantime, these big capacitors can run from $2 up to $20 for just one. So this is where we have to consider the economics of choosing one method over the other. In the long term, which one will cost less.
In my past, I've seen ceramic capacitors explode and electrolytics (big ones) spew out blue smoke.
Dear Robert. Thanks for comment and for sharing your experience. Yes, capacitors are a sensitive subject. In case you are not aware: th-cam.com/video/8ptGjioWTlM/w-d-xo.html
Thanks! That was a much better presentation than what I had to suffer through almost thirty years ago! I hope you will discus the coupled inductor SEPIC configuration in a future video...
Thanks. Will try. Meanwhile see th-cam.com/video/Y0WWj2dO_h8/w-d-xo.html
Sir, Kindly make the video on state space model and transfer function of coupled inductor SEPIC converter please.
Perhaps. Have you seen this? www.ee.bgu.ac.il/~pel/pdf-files/jour97.pdf
Awesome explanation. Very didatic. Congratulation.
Thanks for comment
Thanks so much Dr Sam, it is possible Dr. Sam to teach us how we can create netlist for IC,
I was trying to create netlist for UC2823A,
Is there any recommendations from you now how can I do it.
Thanks
Tricky. Especially since it is a very HF device. For basic simulation you can model the central units: amplifier, modulator, driver
how much should be the ripple voltage across coupling capacitor need to consider, in sepic converter?
I think you made a mistake. Iav(L1) = Io *D/(1-D)
Thanks Farley. Can you pinpoint the time in video strip you are referring to?
Sam Ben-Yaakov It's at 11:30,bottom right corner
Hi Farely,
Indeed, you are correct since Vo/Vin is not D but D/(1-D) as indicated few lines above. You are the first one to notice this mistake after 7.5K views! Thanks. Too much woek to redo it. I hope people watching the video will also look up your comment.
@@sambenyaakov There is an option to put on an annotation on the video. It will be very useful because possible that many people will not read the comments.
Thank you for great explanation
Thanks
Very good explanation sir.
Thanks
great video - thanks
Thanks
Thank you Sir. It's very useful.
Thanks
Thank you for sharing. i have a question about the coupling capacitor polarity. I see schematics showing the + side is towards the input and also they use a big Aluminum Electrolytic cap. however if the output is higher than the input by a few volts, does the capacitor not get reverse biased?
Hi John, just happened to see now your comment which I guess you posted a minute ago. The polarity you indicated is OK. The voltage of the capacitor at the input is higher than the output. A trick to quickly see it is to base the observation on the fact that the AVERAGE voltage on an inductor is zero. So on the left the average voltage seen by the capacitor is Vin, and on the right, ground. You can go through the chore of a detailed analysis, but this will be the answer.
Regard
Sam
I am asking in terms of percentage of input or o.p voltage?
5%-10% will be OK
Very good explanation! thanks for the video😁
Thanks
Hi Dr Sam. Can we have a resonance phenomena on Vy using the first harmonic method ?
I am not sure I am following your question. Please expand.
On Vy there is a AC voltage after the high pass capacitor, so with Harmonic decomposition tool, we can have a resonance frequency with L2 and C.
The C is large to keep the ripple at low value so the resonant frequency is very low as compared to the pwm switching frequency.
Thanks so much Dr Sam, how we size the series capacitance?
Which topology ?
Sam Ben-Yaakov the series capacitor for SEPIC Convert
Choose the capacitance to get the ripple level you want on it, normally few percent of Vin, Vout (the smallest of the two) and most important a capacitor that can carry the expected current.
Sam Ben-Yaakov Hi Dr Sam , I am asking about the series capacitor of SEPIC Converter between the 2 inductors
Yes, my answer was related to this capacitor. You need to keep the ripple low and worry about the AC current passing through it
thank you doctor sam for your excellent presentation, however I have a question about the voltage Vx when the switch is off, I didn't understand why is this voltage equal to Vin+V0 during Toff? you neglected the voltage at the terminal of the inductor L1 during Toff? and we know that the average voltage of L1 equal zero during Toff+Ton
Hi Ayoub, please indicate the time on video you are referring to.
It's at 7:50 thank you
Hi Ayoub
Going back from Vo you add the average voltage of capacitor which is Vin
Thank you for your response
Small correction @1:30 the correct equation is V= (-) L di/dt . The (-) is missing. Respect.
Why? For the labeled directions of V and I the equation is correct.
Oops ! Missed your arrows ! My mistake.
For a whatever my excuse is worth : your arrow for V is a bit un-conventional !Regards.
Sir plzz explain implementation and methodology of a pfc bridgeless SEPIC converter with multiplier cell for universal input voltage applications
Wow. Please send me a reference to what you mean?
@@sambenyaakov sir plz tell me ur mail id ...i send to a document
@@chitti3786 sby@bgu.ac.il
@@sambenyaakov tqsmch sir
@@sambenyaakov sir i have a 2nd review on few days after plzz help me sir ..Total abstract i send to ur mail plz explain methodology and implementation sir
Thank you for the nice explanation!
Thanks for comment.
Sam Ben-Yaakov by the way have you ever worked with Cuk-SEPIC hybrid converters? In scientific papersn they are proposed as topology for wind+solar hybrid power
Please explain more regarding current flow through L2 during switch on..as a bigginer I am confused that how can series capacitor charge L2 in a case Vx node grounded???
Capacitor C is charges and imposes an almost constant voltage on L2
Capacitor C is charged and imposes an almost constant voltage on L2.
Nicely explaination
😊
Thanks sir
👍🙏
Thank you sir, Good video, i got to know more about SEPIC.
can you upload more videos on SEPIC like its controlling and its Application like in Solar MPPT?
Thanks for comment. I will see what I can do.
Thank you sir.
shouldnt Ilavg be -io and not io???????????for the given configuration.
The direction og I(L2) is indeed reversed. Thanks.
The direction of I(L2) is indeed reversed
also below that it is written iL1(avq)=Io*Vo/Vin=Io*D but shouldnt it be Io*D/1-D as Vo/Vin=D/1-D ?????????