An intuitive introduction to Phase Shift Full Bridge (PSFB) converters

[@itaygurt]

Dear Prof Yaakov. Thank you for all videos, especially this one which i asked you.

[@sambenyaakov]

👍your are welcome

[@yassin7569]

very beneficial videos

[@sambenyaakov]

Thanks

[@vicentematricardi3596]

Gracias Maestro , un lujo sus clases !!!!!

[@sambenyaakov]

👍🙏

[@kayzrx8]

Great video, Helped me alot and very well explained

[@sambenyaakov]

Thanks

[@edube01]

Thank you for your good explanation of the PSFB converter. But I want to make a precision; in the idle mode the output current will decreases (voltage across this inductor is -Vo) also the inductor current will decreases (curent transformer at 0Voltage).

[@sambenyaakov]

You are correct of course. Thanks for the clarification.

[@PsycosocialSyndrom]

Dear Professor Ben-Yaakov, Thank you for all the knowledge you are constantly providing us! I do have a question about the matter presented in this video: Can you please explain why in the ZVS the body diode of QA will conduct (or "catch" as you said in 8:17). As I see it, on ZVS the capacitance Cds of QB will charge to Vin and Cds of QA will discharge at the same time and when the voltage drop on QB will be equal to Vin the voltage across QA will be zero and we can switch it in zero voltage drop. If QA body diode will be in forward biased that means QB Drain-Source voltage will be Vin + 0.7 (assuming 0.7V forward voltage). is it possible? Your answers and explanations are appreciated. Thank you!

[@sambenyaakov]

"If QA body diode will be in forward biased that means QB Drain-Source voltage will be Vin + 0.7 (assuming 0.7V forward voltage). is it possible?" Yes, this what happens. WE need to allow some spare time to make sure there no shoot through, during the deadtime the body diode is conducting. You ca see it in simulation.

[@PsycosocialSyndrom]

@@sambenyaakov Thanks, I'll try it on a simulation as you suggested. I'm designing a Phase shift topology DCDC converter at the moment and was wondering if you're planning to upload video about PSFB which has a more in depth explanations such as: control method, transformer design and operation modes, serial rectification and current doubler method?

[@suyashverma26]

Thank you so much, professor for the lucid explanation of PSFB converter operation and the enabling of ZVS because of the phase shifting operation. I was trying to simulate this topology and had two queries relating to this: Q1. As the phase shift becomes a degree of freedom in the PSFB converter, what exactly are the use cases for this? Can it be used for selective harmonic elimination, etc.? Q2. As the phase shifting is already helping achieve ZVS, do we still need to intentionally add deadtime in this topology (as we do with usual PWM based converters having bipolar switching for full bridge converter)?

[@vincejison7102]

Great video, professor! I am working on a psfb application and this was very insightful. In some psfb application notes using peak current mode, I see the current signal is measured at the input so that there is no risk of flux walking and saturating the transformer. If we instead moved the current signal measurent to the output, in series with the inductor, do we still run the risk of saturating the transformer and now need DC blocking caps?

[@sambenyaakov]

Yes, you either use PCM or put a capcitor in series at the primary.

[@BigA1]

Thank you for your good explanation of the PSFB converter. Would such a converter also have a capacitor in series with Lr - not for resonance, but to remove any DC current component that may give rise to flux stair-casing in T1. If so, how should the PSFB description be looked at or modified?

[@sambenyaakov]

Yes if voltage mode control is used. No, if current mode.

[@dor7sh]

Can you pleaase elaborate on this? If the current measurment is on the output and not on the transformer is it still possible to remove the capacitors? Or maybe, if we already have a current measurment on the transfomer we can make sure that the control can offset the DC back to 0? @@sambenyaakov

[@esijal]

Thanks Prof for nice explanation, based on my research I found that turn off soft switching is know as ZCS, could you please clarify this?

[@sambenyaakov]

Zero Current Switching, as the name implies is when the current is zero or very small. So how do call the turn off of the HS switch in a BUCK? See kzbin.info/www/bejne/rWXGqX-GoZeKqck

[@esijal]

@@sambenyaakov Thanks professor 🙏

[@sambenyaakov]

@@esijal You think that a refresher video on ZVS ZCS , definitions and implications, will be of interest to those watching my channel?

[@esijal]

@@sambenyaakov Yes dear Professor, especially if it contains popular applications and practical examples for ZVS , Pseudo ZVS, ZCS, and Pseudo ZCS. I appreciate your time to practically differentiate among them. 🙂🙏

[@sambenyaakov]

@@esijal 👍

[@huzaifaahmad2289]

good explanation, thank you

[@sambenyaakov]

Thanks

[@dor7sh]

Thank you Prof. 👏

[@sambenyaakov]

Hi Dor, Thanks. How ae you?

[@dor7sh]

@@sambenyaakov I'm ok. I'm advising on power electronics and energy for a few companies. We should get together some time for coffee.

[@sambenyaakov]

@@dor7sh 👍kzbin.infogaming/emoji/7ff574f2/emoji_u1f60a.png

[@KratosGhostofSparta-pp1cr]

Thank you sir. Could you please name some of the commercial phase-shifted controller? and which one do you suggest? Thank you.

[@sambenyaakov]

There are many on the market. I can't recommend.

[@samuelsam77]

Hi professor thanks for PSFB , can you tell how to reduce gate ringing issues

[@sambenyaakov]

It is a layout problem (inductance) try to increase gate drive resistance.

[@TechTinkerLap-tp7gz]

Nice, Thank you so much

[@sambenyaakov]

Thanks

[@mohithvepa3118]

Sir,during Idling the current direction you mentioned is the opposite and the mosfet will not turn on in the current direction mentioned .Sir , can you confirm this ?

[@sambenyaakov]

To which minute in video are you referring to? Which mosfet will not turn on? Please clarify.

[@mohithvepa3118]

@@sambenyaakov sir during 9:45 QA will not pass the current in the direction mentioned in the slide

[@chakshithbsanil9468]

Hello Professor, at 10:59 time of the video.......the voltage reverses but the current will still be negative since MOSFET Qd is not turned on yet...until gate for MOSFET Qd is given the body diodes of both Qa and Qd is conducting hence current is still negative but voltage is positive....but you have drawn current also as positive...Please clarify this for me Professor.

[@swathi9086]

Sir i have not understood capacitors part,how they came amd why are they charging and discharging

[@sambenyaakov]

When the two transistors are off the inductor current charges the output capacitances.

[@martinmartinmartin2996]

Question ; when designed for a fixed load power" would a PSFB configuration produce LESS spikes than other variable load converters running at the same power? IF NOT why would PSFB ever be considered?

[@sambenyaakov]

Historically, PSFB => DAB => LLC. However, PSFB has advantage in fixed power with large duty cycle due to the lower rms current and economics.

[@sc0or]

Good day, Sir. Considering a ZVS feature (presents in both architectures), what would you advice for an SMPS for audio: LLC or PSFB? Both are supposed to be used with an open loop. In addition I'm planning to go high: 800kHz-1MHz, so PSFB arrears a brick simple, but I'm not sure about which type will give me more clear rail.

[@tamaseduard5145]

👍🙏❤

[@sambenyaakov]

numero uno