Hi Chalee, that comes from looking at the square wave input into the circuit. This waveform has 50% duty cycle and ranges in a value from 0 to +Vdc. It has a DC offset of Vdc/2. If we remove the DC offset (because it will be blocked by the series capacitor), the waveform becomes a 0-average equivalent square wave that spans from -Vdc/2 to +Vdc/2. Therefore, the peak amplitude of the waveform is Vdc/2. We use this peak value of the 0-averaged square wave to generate the peak amplitude of the 1st harmonic. Hope this helps. Best wishes on your design. -Dr. K
thanks sir, if we consider it as CLLLC resonant converter means that we have the L and C in second part of trans, should we consider them in resonant frequency formula, also in quality factor? can u please guide me? thanks
I have. Watched many of your videos. Very educational... can you provide info- or tutorial how SWITCHING woks in a MRI; SGA ( SWITCHABLE GRADIENT AMPLIFIER) which is IGBT based. explained polarity/ WAVEFORMS before are going of the amp. Thanks to
Abhishek, if the question is can we have two inductors in parallel to create Lr? The answer is yes, but when inductance is in parallel the overall inductance value is 1/(1/L1 + 1/L2). One reason to place in parallel is to increase the current capability if you have to use an "off-the-shelf" inductor that has lower current ratings than required. Is there a reason to place two inductors in parallel?
A MATLAB script was used to compute and plot the functions. The equations are well known and can be found in most application notes that cover the design of series resonant converters. Best wishes on your design. -Dr. K
This is great to know the steady state gain equations, but what about dynamics? Very important for compensation. There are a number of reactive components so I would expect this to be a fairly high order system.
The LLC converter is probably best modeled as a 3rd order system and yes there is a transient (dynamic) aspect at start-up and if/when the load changes. If the load is inductive, then the model order is higher. Once feedback is added for regulation, we have a dynamic component associated with the feedback loop elements. This becomes a nonlinear feedback control system. All of this is too much for a 15 minute video. Therefore, I just presented the basics. Best wishes on your designs. -Dr. K
@@powerelectronicswithdr.k1017 Are there some guides or application notes I could follow up with to help with design of a compensation network for LLC converter? I've heard there may be methods of current mode control rather than voltage mode control.
@@power-max Sure, OnSemi has a good application note, but I can no longer find a link on their website. It is titled "Introduction to LLC Resonant Converter," AND90107/D by Vaclav Drda. There is a complete section on the control methods and discuss both the voltage and current based feedback control. This reference also briefly discusses the start-up (transient) behavior. Another reference on control is from TI. Here's a link to a TI reference on the compensation design for the series LLC converter www.ti.com/lit/an/slua582a/slua582a.pdf. Please keep in mind that you are often adjusting the switching frequency of the front-end bridge. These adjustments are made based on either the output voltage (voltage controlled) and/or the output current (current controlled). Often voltage control is done with an outer-loop (slower) and current control is done via an inner-loop (faster). I would also recommend studying control concepts of VCOs and PLLs. There are some overlap in control technology when regulating an LLC converter. The control and regulation is an additional layer of complexity beyond the power electronics topology. Perhaps a new channel called Power Control with Dr. K? lol Best wishes on your designs. -Dr K
@@powerelectronicswithdr.k1017 Thank you for these references! I have gotten pretty acclimated with the power electronics side of the LLC converter, from hobby experience with building DRSSTC Tesla coil and building a spreadsheet calculator that computes component values for a set of design goals (Vin, Vout, optimal operating condition, power, etc) Something I found while trying to build a step up LLC converter is that the inductance and capacitance value for the LC portion become unrealistic for a step-up converter (for building a high power inverter) and I think I can resolve this by moving the LLC components to the secondary side of the transformer, but then I cannot leverage the leakage reactance or magnetizing reactance of an "integrated magnetic element" for a very compact design. Would there be a better topology for a step up converter or do you think I did something wrong?
@@power-max Typically, a transformer is used as part of the design of a resonant converter, and this allows you to boost or buck the input into the desired output range. The transformer provides isolation and is also wound to provide the shunt inductance in the LLC resonant converter. Fine regulation of the output voltage is then done via control of the switching frequency. Texas Instruments has a great spreadsheet tool for doing the initial design and parameter calculations for an LLC converter www.ti.com/tool/UCC25600-DESIGN-CALC. This works pretty well. There are also numerous resources on winding the resonant converter transformers that you can research. Best wishes.
Hi Srinivas, sure. Power Electronics by Daniel Hart is very good www.amazon.com/Power-Electronics-Daniel-Hart-Professor/dp/0073380679, Dr. Ned Mohan's book is also very good www.amazon.com/Power-Electronics-Course-Ned-Mohan/dp/1118074807. When I teach Power Electronics, I will reference materials from Texas Instruments Power Topologies Handbook, www.ti.com/seclit/ug/slyu036/slyu036.pdf. Hope this helps. Best wishes on your designs. -Dr. K
Hello Enes, there is still resistance. As an example, a series RLC circuit will operate at resonance when the frequency of the driving source is sqrt(1/LC). At this frequency, the voltage and current are in phase and the load looks purely resistive to the source. Re is the equivalent resistance of the load as reflected back through the rectifier and secondary transformer of the resonant converter. Hope this helps. -Dr. K
Wonderful explaination
Love the retro music! 🕺
Thank you :)
This is the shortest but powerful
Thank you
Where does the term Vdc/2 come from when you are deriving an output voltage for Half-Bridge Series LC output equation?
Hi Chalee, that comes from looking at the square wave input into the circuit. This waveform has 50% duty cycle and ranges in a value from 0 to +Vdc. It has a DC offset of Vdc/2. If we remove the DC offset (because it will be blocked by the series capacitor), the waveform becomes a 0-average equivalent square wave that spans from -Vdc/2 to +Vdc/2. Therefore, the peak amplitude of the waveform is Vdc/2. We use this peak value of the 0-averaged square wave to generate the peak amplitude of the 1st harmonic. Hope this helps. Best wishes on your design. -Dr. K
thanks sir, if we consider it as CLLLC resonant converter means that we have the L and C in second part of trans, should we consider them in resonant frequency formula, also in quality factor? can u please guide me? thanks
amazing job man , co clear
Aakash, thank you. Best wishes on your design. -Dr. K
Best Ever
I have. Watched many of your videos.
Very educational... can you provide info- or tutorial how SWITCHING woks in a MRI;
SGA ( SWITCHABLE GRADIENT AMPLIFIER) which is IGBT based. explained polarity/ WAVEFORMS before are going of the amp.
Thanks
to
I think at 3:00 the negative sign before 1/ωCR accidentally became positive, right?
Great
Very good classes, ty
Thank you.
nice information sir,
if we adding a one more inductor in parallel with main inductor what is the benefits?.
and how zvs and zcs take place sir
Abhishek, if the question is can we have two inductors in parallel to create Lr? The answer is yes, but when inductance is in parallel the overall inductance value is 1/(1/L1 + 1/L2). One reason to place in parallel is to increase the current capability if you have to use an "off-the-shelf" inductor that has lower current ratings than required. Is there a reason to place two inductors in parallel?
@@powerelectronicswithdr.k1017 ok sir, i got it thank you sir.
sir i want to know about the ZVS and ZCS difference in this converter.
Would you please tell me how those graphs are obtained, Sir? What software/simulation tool did you used to obtain those graohs?
A MATLAB script was used to compute and plot the functions. The equations are well known and can be found in most application notes that cover the design of series resonant converters. Best wishes on your design. -Dr. K
This is great to know the steady state gain equations, but what about dynamics? Very important for compensation. There are a number of reactive components so I would expect this to be a fairly high order system.
The LLC converter is probably best modeled as a 3rd order system and yes there is a transient (dynamic) aspect at start-up and if/when the load changes. If the load is inductive, then the model order is higher. Once feedback is added for regulation, we have a dynamic component associated with the feedback loop elements. This becomes a nonlinear feedback control system. All of this is too much for a 15 minute video. Therefore, I just presented the basics. Best wishes on your designs. -Dr. K
@@powerelectronicswithdr.k1017 Are there some guides or application notes I could follow up with to help with design of a compensation network for LLC converter? I've heard there may be methods of current mode control rather than voltage mode control.
@@power-max Sure, OnSemi has a good application note, but I can no longer find a link on their website. It is titled "Introduction to LLC Resonant Converter," AND90107/D by Vaclav Drda. There is a complete section on the control methods and discuss both the voltage and current based feedback control. This reference also briefly discusses the start-up (transient) behavior. Another reference on control is from TI. Here's a link to a TI reference on the compensation design for the series LLC converter www.ti.com/lit/an/slua582a/slua582a.pdf. Please keep in mind that you are often adjusting the switching frequency of the front-end bridge. These adjustments are made based on either the output voltage (voltage controlled) and/or the output current (current controlled). Often voltage control is done with an outer-loop (slower) and current control is done via an inner-loop (faster). I would also recommend studying control concepts of VCOs and PLLs. There are some overlap in control technology when regulating an LLC converter. The control and regulation is an additional layer of complexity beyond the power electronics topology. Perhaps a new channel called Power Control with Dr. K? lol Best wishes on your designs. -Dr K
@@powerelectronicswithdr.k1017 Thank you for these references!
I have gotten pretty acclimated with the power electronics side of the LLC converter, from hobby experience with building DRSSTC Tesla coil and building a spreadsheet calculator that computes component values for a set of design goals (Vin, Vout, optimal operating condition, power, etc)
Something I found while trying to build a step up LLC converter is that the inductance and capacitance value for the LC portion become unrealistic for a step-up converter (for building a high power inverter) and I think I can resolve this by moving the LLC components to the secondary side of the transformer, but then I cannot leverage the leakage reactance or magnetizing reactance of an "integrated magnetic element" for a very compact design. Would there be a better topology for a step up converter or do you think I did something wrong?
@@power-max Typically, a transformer is used as part of the design of a resonant converter, and this allows you to boost or buck the input into the desired output range. The transformer provides isolation and is also wound to provide the shunt inductance in the LLC resonant converter. Fine regulation of the output voltage is then done via control of the switching frequency. Texas Instruments has a great spreadsheet tool for doing the initial design and parameter calculations for an LLC converter www.ti.com/tool/UCC25600-DESIGN-CALC. This works pretty well. There are also numerous resources on winding the resonant converter transformers that you can research. Best wishes.
Hi sir ....could you suggest any book name on design of power converts or ...any reference
Hi Srinivas, sure. Power Electronics by Daniel Hart is very good www.amazon.com/Power-Electronics-Daniel-Hart-Professor/dp/0073380679, Dr. Ned Mohan's book is also very good www.amazon.com/Power-Electronics-Course-Ned-Mohan/dp/1118074807. When I teach Power Electronics, I will reference materials from Texas Instruments Power Topologies Handbook, www.ti.com/seclit/ug/slyu036/slyu036.pdf. Hope this helps. Best wishes on your designs. -Dr. K
@@powerelectronicswithdr.k1017 thanks a lot...sir for your reply
what is Re?
When operating at resonant frequency, R=0, so IL goes to infinite values, sorry I didn't understand.
Hello Enes, there is still resistance. As an example, a series RLC circuit will operate at resonance when the frequency of the driving source is sqrt(1/LC). At this frequency, the voltage and current are in phase and the load looks purely resistive to the source. Re is the equivalent resistance of the load as reflected back through the rectifier and secondary transformer of the resonant converter. Hope this helps. -Dr. K
@@powerelectronicswithdr.k1017 yess thank you , understand now :)
The background music is way too loud
I wouldn't trust this logan dude
Great
Thank you. -Dr. K