The reflected output voltage comes from only one effect - true transformer "action" that is dependent on the ratio of the input and output winding turns. The reflected voltage magnitude is constant as long as current is flowing in the output winding. There is another phenomenon that is the result of imperfect magnetic coupling between the inductor charging winding (input) and the discharge winding (output). This is called "leakage inductance" and can be modeled, in simple terms, as a small inductor in series with the input winding but not magnetically coupled to anything else. It is this inductance that results in a very high voltage "spike" when the switch turns off. The current through it _does_ "try" to remain constant (equal to the current just before the switch turns off), but since there is nowhere for the stored energy to go that current causes a very high voltage. Again, it has nothing to do with reflected voltage. A "snubber" is used to limit the magnitude of the spike voltage in most practical designs. When the switch turns off you get three distinct voltages at the drain of the MOSFET switch. First you get a high-magnitude narrow spike due to the leakage inductance. Then the reflected secondary voltage appears (it actually started as soon as the FET turned off, but it is sort of "hidden" by the big spike. The reflected voltage will remain nearly constant until all of the energy stored in the inductor ("transformer") has been discharged. The voltage across the output winding is held nearly constant by the voltage on the output capacitor, which changes only a very small amount in any one switching cycle. The reflected voltage is added to or "stacked on top" of the input supply voltage. This stacked voltage is the main consideration when it comes to the voltage rating of the FET. Once the stored energy has been discharged, the FET drain voltage drops back to the voltage on the input filter capacitor. Typically there is some high frequency "ringing" due to resonance between FET and "stray" capacitances and the inductances. If the inductor is not fully discharged before the FET turns ON again, the voltage at the drain remains equal to the "stacked" voltages. Management of the reflected voltage is often a significant consideration in the turns ratio of the inductor ("transformer"). The main consideration in turns ratio is the determination of the inductances required, not input to output voltage ratio. You certainly do not take the approach used for a true transformer. I prefer to think of the magnetic component as an inductor with a charging winding and a discharging winding, not as a "transformer" (though it behaves as such when you really don't want it to) or as a "coupled inductor" because there is no "coupling" between input and output windings in terms of actual power delivery. "Transformer" is a convenient but misleading short word.
You are a natural born teacher! You are incredibly smart, eloquent and have a comfortable way of explaining difficult concepts. You are a lucky young man, you are going to have a bright future.
That why the control circuit is powered from the transformer if there's no oscillation over the transformer the circuit will reset and restart again and sometimes the small resistance that start the controller will burn before because it is calculated to work for a few seconds
This is an excellent presentation. At least for someone already passingly familiar with the relevant concepts, it was extremely clear and easy to follow. F.Y.I., your audio levels are somewhat lower than other channels.
As we're talking about beginners theory class, I'd have also mentioned the damper diode, which would protect the driver from counter-EMF from when it swtiches off. More advanced, there were gate turn-off models in use, where gate voltage turned off the drive, otherwise the driver defaulted in conduction and a no-drive condition would result in overcurrent on the driver. Fortunately, such drivers were quite rare in actual production, as far as I recall, only present in one model Philco television and Sony televisions for a number of years, but not in any other form of flyback circuit in industrial usage.
Snubber circuit wasn't mentioned 15:48 but your explanation is very good I hope you do a project with low voltage input like 40 vdc to explain the work with oscilloscope wave form capture.
I think that when the voltage is stepped up besides turns ratio being the effect of it, that the primary coil itself can have a high BEMF due to the ramp up time being larger than the ramp down time and that as well can effect the secondary BEMF.
I'm trying to learn electronics. Quick question...at time 2:02, what is the purpose of C11 and wouldn't C11 act as a short to an AC input?? Perhaps C11 is chosen to have a high capacitive reactance at 60 HZ and act as virtual open? I quickly figured Xc and came up with approximately 2850 ohms (which could be wrong). Which doesn't seem very high. Either way, what is its purpose?? Thanks in advance!
Thank you bro.. I hope you will do video about forward converters also. I checked almost all your videos and i think you like flyback topology more than others. 😅 is that true?
GREAT VIDEO! at 6:38 iron cores are not used in flyback converters. Usually a ferrite core with a GAP. You used the word 'transformer' too much. It should be 'converter' or 'coupled inductor'. After the primary cycle, the energy is stored in the core...not the coil...before the energy goes into the secondary.
My brother was about to tear out plaster - which is very heavy - so there being like four rooms I convinced him to make a mobile unit we could knock the plaster into and move it to a window and slide it out to a dumpster saving us lots of lifting and WORK since that ceiling plaster was POTENTIALIZED some 100 years ago
When speaking of transformer direction, dot, are you referring to current flow direction or electron flow? It’s important, and also confusing. I’ve seen designs where the 2 gets crossed up.
The dot refers to the polarity of the coil. If you push a positive going pulse into the dot side of a transformer, the positive pulse will appear on the dot side of the secondary. The philosophy of the current flow is irrelevant and is not intended to be denoted by the dots. It is strictly for the polarity of the coils, as the current is completely unaware of this mark on the schematic. This is why one shouldn't think of "current flowing through a transformer". It doesn't. It flows through the coils of the transformer. The *energy* flows through the transformer.
@@gcewingTrue. But no engineer talks about electron flow unless in the context of understanding the theory of operation of valves, semiconductor devices. So it's not useful to talk about electron flow in circuit analysis. It is only unqualified people that like to bring up electron flow direction as a way to give the illusion they know what they are talking about.
What are the number of Primary Windings to Secondary Windings needed to start with an Input Voltage of 6 Volts to obtain an Output Voltage of 60.000 Volts?
The number of actual windings is often proprietary (the manufacturer won't tell you exactly how many), but the winding ratio (primary to secondary) can be determined based on an equation (We will go over this in another video later on)
I had forgotten so much of this over 50 years. Actually if the MosFet stays on forever, the primary will saturate, and the current rise will stop (I think).
The current will actually increase faster after the core saturates (because the inductance becomes much lower) until it's limited by other parts of the primary circuit. In practice something will probably overheat and fail, likely the mosfet.
For eagle eyed viewers, who else noticed that there is a bookmark / folder called "Nicolas Cage Nudes" during the theory of operations section from 13: 00 mins in lol
Gravity is a "Physics " word - that's for sure Flat Water and flat oceans and flat lakes on a Curved ball floating in a vacuum with Helicopters that can only fly about 3 miles up because there is not enough DENSITY to provide lift - and if DENSITY goes down with altitude where does that stop ? eventually a dome of nothingness
The reflected output voltage comes from only one effect - true transformer "action" that is dependent on the ratio of the input and output winding turns. The reflected voltage magnitude is constant as long as current is flowing in the output winding.
There is another phenomenon that is the result of imperfect magnetic coupling between the inductor charging winding (input) and the discharge winding (output). This is called "leakage inductance" and can be modeled, in simple terms, as a small inductor in series with the input winding but not magnetically coupled to anything else. It is this inductance that results in a very high voltage "spike" when the switch turns off. The current through it _does_ "try" to remain constant (equal to the current just before the switch turns off), but since there is nowhere for the stored energy to go that current causes a very high voltage. Again, it has nothing to do with reflected voltage. A "snubber" is used to limit the magnitude of the spike voltage in most practical designs.
When the switch turns off you get three distinct voltages at the drain of the MOSFET switch. First you get a high-magnitude narrow spike due to the leakage inductance. Then the reflected secondary voltage appears (it actually started as soon as the FET turned off, but it is sort of "hidden" by the big spike. The reflected voltage will remain nearly constant until all of the energy stored in the inductor ("transformer") has been discharged. The voltage across the output winding is held nearly constant by the voltage on the output capacitor, which changes only a very small amount in any one switching cycle. The reflected voltage is added to or "stacked on top" of the input supply voltage. This stacked voltage is the main consideration when it comes to the voltage rating of the FET. Once the stored energy has been discharged, the FET drain voltage drops back to the voltage on the input filter capacitor. Typically there is some high frequency "ringing" due to resonance between FET and "stray" capacitances and the inductances. If the inductor is not fully discharged before the FET turns ON again, the voltage at the drain remains equal to the "stacked" voltages.
Management of the reflected voltage is often a significant consideration in the turns ratio of the inductor ("transformer"). The main consideration in turns ratio is the determination of the inductances required, not input to output voltage ratio. You certainly do not take the approach used for a true transformer.
I prefer to think of the magnetic component as an inductor with a charging winding and a discharging winding, not as a "transformer" (though it behaves as such when you really don't want it to) or as a "coupled inductor" because there is no "coupling" between input and output windings in terms of actual power delivery. "Transformer" is a convenient but misleading short word.
Thank you for such a detailed comment :)
This is really a Beginner friendly class. Thank you.
I'm glad you found it helpful!
You are a natural born teacher! You are incredibly smart, eloquent and have a comfortable way of explaining difficult concepts. You are a lucky young man, you are going to have a bright future.
Thanks, that's very kind of you!
great breakdown.
thank you :)
Thank you for the explanation; you made the Flyback circuit so much easier to understand.
Glad to hear that!
If the mosfet stays on, the inductor will saturate, the current will rise steeply, and the magic smoke will come out.
exactly :)
Maybe this is the reason to put the rezistor in primary?
Ah, THAT magic stuff???
If they just sold it in the spray cans to get it back 🤔🤔🤔🥸
That why the control circuit is powered from the transformer if there's no oscillation over the transformer the circuit will reset and restart again and sometimes the small resistance that start the controller will burn before because it is calculated to work for a few seconds
Explained very well. Great video
Glad you liked it!
This is an excellent presentation. At least for someone already passingly familiar with the relevant concepts, it was extremely clear and easy to follow.
F.Y.I., your audio levels are somewhat lower than other channels.
Thanks! I'll work on getting my audio levels better, I appreciate the feedback.
As we're talking about beginners theory class, I'd have also mentioned the damper diode, which would protect the driver from counter-EMF from when it swtiches off.
More advanced, there were gate turn-off models in use, where gate voltage turned off the drive, otherwise the driver defaulted in conduction and a no-drive condition would result in overcurrent on the driver. Fortunately, such drivers were quite rare in actual production, as far as I recall, only present in one model Philco television and Sony televisions for a number of years, but not in any other form of flyback circuit in industrial usage.
Interesting info, thanks for sharing!
This was great! thank you for taking the time.
Glad you enjoyed it!
Great video. Very nice work. you are good at this.
Thank you very much!
Thanks. Good info; especially the part about this type of converter being more or less failsafe if the MOSFET or similar were to fail short.
Glad it helped :)
Thank you for making this video!
Glad it was helpful!
Great video. Does it make a difference on how the transformer is wound?
The short answer is yes. I will be making a video that talks about transformers in more detail.
You should build a ZVS flyback circuit and describe the process as you go and show the variables in design. The ZVS circuit is so cool.
That's a great idea - I'll add it to my list of future videos!
Your content is promising.
I clicked doubtedly, but remained voluntarily.
Keep up sir bro. You gonna make it far🫡
Thanks for the support!
Snubber circuit wasn't mentioned 15:48 but your explanation is very good I hope you do a project with low voltage input like 40 vdc to explain the work with oscilloscope wave form capture.
There will be another video on the snubber circuit coming out soon!
Actually life changing info
you are actually a life changing human being
$3
Thanks for the explanation!!
You are very welcome :)
I think that when the voltage is stepped up besides turns ratio being the effect of it, that the primary coil itself can have a high BEMF due to the ramp up time being larger than the ramp down time and that as well can effect the secondary BEMF.
thank you for your insight and knowledge :)
Cool vid!
thank you :)
I'm trying to learn electronics. Quick question...at time 2:02, what is the purpose of C11 and wouldn't C11 act as a short to an AC input?? Perhaps C11 is chosen to have a high capacitive reactance at 60 HZ and act as virtual open? I quickly figured Xc and came up with approximately 2850 ohms (which could be wrong). Which doesn't seem very high. Either way, what is its purpose??
Thanks in advance!
C11 is referred to as an "x-capacitor", and its purpose is explained in this video: ua-cam.com/video/q7z0ht7eCig/v-deo.html
Thanks for explanation!!!!!
You're welcome, glad you found it helpful!
Yeah it's really help full ❤❤❤❤@@RGBEngineering
And what is switching the mosfet??. Key to the whole thing.
Usually a variable PWM
Check out this video on regulator ICs: ua-cam.com/video/B7wOFzCd6LA/v-deo.html
variable PWM OSCILLATOR.
PWM is just a description of what is happening to the signal.
Operative word is oscillator.
Thank you bro..
I hope you will do video about forward converters also.
I checked almost all your videos and i think you like flyback topology more than others. 😅 is that true?
I like all converters equally :)
GREAT VIDEO!
at 6:38 iron cores are not used in flyback converters. Usually a ferrite core with a GAP.
You used the word 'transformer' too much. It should be 'converter' or 'coupled inductor'.
After the primary cycle, the energy is stored in the core...not the coil...before the energy goes into the secondary.
Thanks for the info!
You are absolutely right. Transformer does not store energy in the core while flyback coupled inductors do.
LEGEND
thank you :)
Where do we get the term "flyback" from? Something to do with tubes, you think?
yes, from what I am aware, this topology was originally used in TV power supplies; they had vacuum tubes or something to light up.
Thanks for a great video... One question what simulation software do you use?
www.falstad.com/circuit/circuitjs.html
Very Helpful. Thx. Will watch several times to internalize. Cheers.
Glad it helped!
My brother was about to tear out plaster - which is very heavy - so there being like four rooms I convinced him to make a mobile unit we could knock the plaster into and move it to a window and slide it out to a dumpster saving us lots of lifting and WORK since that ceiling plaster was POTENTIALIZED some 100 years ago
When speaking of transformer direction, dot, are you referring to current flow direction or electron flow? It’s important, and also confusing. I’ve seen designs where the 2 gets crossed up.
I am referring to conventional current flow.
The dot refers to the polarity of the coil. If you push a positive going pulse into the dot side of a transformer, the positive pulse will appear on the dot side of the secondary. The philosophy of the current flow is irrelevant and is not intended to be denoted by the dots. It is strictly for the polarity of the coils, as the current is completely unaware of this mark on the schematic. This is why one shouldn't think of "current flowing through a transformer". It doesn't. It flows through the coils of the transformer. The *energy* flows through the transformer.
It doesn't matter which current convention you use as long as you're consistent.
@@gcewingTrue. But no engineer talks about electron flow unless in the context of understanding the theory of operation of valves, semiconductor devices.
So it's not useful to talk about electron flow in circuit analysis.
It is only unqualified people that like to bring up electron flow direction as a way to give the illusion they know what they are talking about.
What are the number of Primary Windings to Secondary Windings needed to start with an Input Voltage of 6 Volts to obtain an Output Voltage of 60.000 Volts?
The number of actual windings is often proprietary (the manufacturer won't tell you exactly how many), but the winding ratio (primary to secondary) can be determined based on an equation (We will go over this in another video later on)
I had forgotten so much of this over 50 years. Actually if the MosFet stays on forever, the primary will saturate, and the current rise will stop (I think).
Yes, in real life, the ESR of the MOSFET and primary-side of the transformer will limit the current.
The current will actually increase faster after the core saturates (because the inductance becomes much lower) until it's limited by other parts of the primary circuit. In practice something will probably overheat and fail, likely the mosfet.
Galvanic isolation?
Yes, this circuit provides galvanic isolation between the input and output.
pls share the ti topologies.pdf
It doesn't look like they have it anymore. I will upload it to the RGB Engineering Patreon page :)
www.patreon.com/posts/ti-power-117089174?Link&
Thank you so much for an eloquently explained lecture on this topic, you made it so easy to understand and digest 😃
Glad it was helpful!
Immencely
For eagle eyed viewers, who else noticed that there is a bookmark / folder called "Nicolas Cage Nudes" during the theory of operations section from 13: 00 mins in lol
Clap your diodes if you have a variac!
Gravity is a "Physics " word - that's for sure Flat Water and flat oceans and flat lakes on a Curved ball floating in a vacuum with Helicopters that can only fly about 3 miles up because there is not enough DENSITY to provide lift - and if DENSITY goes down with altitude where does that stop ? eventually a dome of nothingness
Adult content don't make adults better.
Meditating the word of GOD does. JESUS CHRIST loves us.