How the Class-E DC-DC Converter will operate?

Thread Starter

pinkyponky

Joined Nov 28, 2019
22
Hello everyone,

I'm studying about the class-e dc/dc converter. I understand half of the functionality and I have some question. Please can you clarify them.

1609621440207.png

From above image I understand that Chock Inductor (Lchoke) and Shunt Capacitor (Cs), the combination of Capacitor (Cseries) and Inductor (Lseries) called it as series resonant network, and Load Resistor (Rload). That's fine.

But, my questions are:
1) what is the use of Shunt Capacitor?. How it is works in this circuit?, Why they are using in the circuit?.
2) Usually DC voltage does not pass through the capacitor, right?. But, how this Vdc passes through the capacitor (Cseries)?.
3) How the DC voltage will convert into AC after the resonant network?, please can anyone explain clearly with waveforms?.
 

bertus

Joined Apr 5, 2008
21,160
Hello,

Is this again a homework question?
If so, post it next time in homework.

Class E is an amplifier class and not a DC-DC converter concept.

From the wiki:
Class E
The class-E amplifier is a highly efficient tuned switching power amplifier used at radio frequencies. It uses a single-pole switching element and a tuned reactive network between the switch and the load. The circuit obtains high efficiency by only operating the switching element at points of zero current (on to off switching) or zero voltage (off to on switching) which minimizes power lost in the switch, even when the switching time of the devices is long compared to the frequency of operation.[20]

The class-E amplifier is frequently cited to have been first reported in 1975.[21] However, a full description of class-E operation may be found in the 1964 doctoral thesis of Gerald D. Ewing.[22] Interestingly, analytical design-equations only recently became known.[23]

https://en.wikipedia.org/wiki/Power_amplifier_classes

Bertus
 

Thread Starter

pinkyponky

Joined Nov 28, 2019
22
Hello,

Is this again a homework question?
If so, post it next time in homework.

Class E is an amplifier class and not a DC-DC converter concept.

From the wiki:
Class E
The class-E amplifier is a highly efficient tuned switching power amplifier used at radio frequencies. It uses a single-pole switching element and a tuned reactive network between the switch and the load. The circuit obtains high efficiency by only operating the switching element at points of zero current (on to off switching) or zero voltage (off to on switching) which minimizes power lost in the switch, even when the switching time of the devices is long compared to the frequency of operation.[20]

The class-E amplifier is frequently cited to have been first reported in 1975.[21] However, a full description of class-E operation may be found in the 1964 doctoral thesis of Gerald D. Ewing.[22] Interestingly, analytical design-equations only recently became known.[23]

https://en.wikipedia.org/wiki/Power_amplifier_classes

Bertus
It is not home work question. I'm learning myself so it is a self study question.
I have go through the all the links that your provided, but there are more questions and they are more explained about the questions only. They are not talking about the regarding my questions?.
 

Marc Sugrue

Joined Jan 19, 2018
211
Hello everyone,

I'm studying about the class-e dc/dc converter. I understand half of the functionality and I have some question. Please can you clarify them.

View attachment 226558

From above image I understand that Chock Inductor (Lchoke) and Shunt Capacitor (Cs), the combination of Capacitor (Cseries) and Inductor (Lseries) called it as series resonant network, and Load Resistor (Rload). That's fine.

But, my questions are:
1) what is the use of Shunt Capacitor?. How it is works in this circuit?, Why they are using in the circuit?.
2) Usually DC voltage does not pass through the capacitor, right?. But, how this Vdc passes through the capacitor (Cseries)?.
3) How the DC voltage will convert into AC after the resonant network?, please can anyone explain clearly with waveforms?.

To try and answer your question though
1. Lchoke and Cs are meant to create a resonant ring which is excited by the switch,
2. Lseries and Cseries is current creating a band pass filter to pass AC (not DC) and the current on Rload would be AC. This is where i suspect theres something missing or wrong on the schematic if DC is your intention
3. I suspect if its DC you want your missing the rectification circuit

https://www.slideserve.com/paloma/resonant-boost-converter-design

https://www.semanticscholar.org/pap...c1bac4a53c8e63d640e9baad9474a9da7a12/figure/1
 
Last edited:

Thread Starter

pinkyponky

Joined Nov 28, 2019
22
To try and answer your question though
1. Lchoke and Cs are meant to create a resonant ring which is excited by the switch,
2. Lseries and Cseries is current creating a band pass filter to pass AC (not DC) and the current on Rload would be AC. This is where i suspect theres something missing or wrong on the schematic if DC is your intention
3. I suspect if its DC you want your missing the rectification circuit

https://www.slideserve.com/paloma/resonant-boost-converter-design

https://www.semanticscholar.org/pap...c1bac4a53c8e63d640e9baad9474a9da7a12/figure/1

I have gained some knowledge with help of you and bertus by go through some materials. Please can you go through my answers and correct me If I'm wrong.
1. Lchoke and Cs are meant to create a resonant ring which is excited by the switch.
[/QUOTE]
You mean that the shunt capacitor we are using just for to create a half-sinusoidal waveform?. Without shunt capacitor we can't able to generate the below waveform?, as shown below.
1609628034408.png
From my understanding, Rising to peak value due to inductor charging and falling to 0V due to inductor discharging. But, here the shunt capacitor not playing any role, right?. Then what is use of shunt capacitor?.

[/QUOTE]
2. Lseries and Cseries is current creating a band pass filter to pass AC (not DC) and the current on Rload would be AC. This is where i suspect theres something missing or wrong on the schematic if DC is your intention.
[/QUOTE]
From this, what I understand is that, When the Switch_off, the current will flow through the LC circuit so the output will have a positive half cycle of sinusoidal waveform. When the Switch_on, the energy stored in the Cs will discharge through the LC circuit with negative polarity (when discharging the capacitor the polarity will change) so the output will be negative half cycle of sinusoidal waveform. Thus, we have a full sinusoidal waveform across the load resistor.
 
Last edited:

Thread Starter

pinkyponky

Joined Nov 28, 2019
22
What I understand I drawn below, please correct me if I'm wrong and can you help me by explaining the rest of the circuit.

1609631944174.png
 

Thread Starter

pinkyponky

Joined Nov 28, 2019
22
Hello again,

I have learned and I understand about the LC Oscillator tank circuit from the below video. They explained when the L and C elements are in parallel. But, in the class-E amplifier circuit the L and C elements are in series. So I'm not still understanding that how the series L and C elements will be charged and discharged?, please any one can explain me how these elements will be charged and discharged with the current directions and polarity as explain in the below video?. And also still not understanding why the shunt capacitor is used?.
I have been trying a lot to understand the functionality of the Class-E amplifier and trucked here at this point. If you have 10min time I will also available in the Microsoft Teams to discuss about this.
 
Last edited:

Marc Sugrue

Joined Jan 19, 2018
211
1. Lchoke and Cs are meant to create a resonant ring which is excited by the switch.
You mean that the shunt capacitor we are using just for to create a half-sinusoidal waveform?. Without shunt capacitor we can't able to generate the below waveform?, as shown below.
View attachment 226573
From my understanding, Rising to peak value due to inductor charging and falling to 0V due to inductor discharging. But, here the shunt capacitor not playing any role, right?. Then what is use of shunt capacitor?.

[/QUOTE]
2. Lseries and Cseries is current creating a band pass filter to pass AC (not DC) and the current on Rload would be AC. This is where i suspect theres something missing or wrong on the schematic if DC is your intention.
[/QUOTE]
From this, what I understand is that, When the Switch_off, the current will flow through the LC circuit so the output will have a positive half cycle of sinusoidal waveform. When the Switch_on, the energy stored in the Cs will discharge through the LC circuit with negative polarity (when discharging the capacitor the polarity will change) so the output will be negative half cycle of sinusoidal waveform. Thus, we have a full sinusoidal waveform across the load resistor.
[/QUOTE]

1. For the waveform on drain of the switch the 'rate of change' for the voltage will be controlled by Cs, The 'rate of change' in current flow will be controlled by the Choke. They work together. Post #4 is very insightful as to its operation as simulated in LT spice. My advice would be to simulate the circuit in post #4 to get a better understanding as all the information is present to replicate the simlation.

2. When the switch turns off the choke will flyback to continue the flow of current. The 'rate of change' in votage it flybacks will be limited by Cs which is what you see as the rising edge of Toff. At some point the enegy in the choke will run dry and the voltage will start to fall, again the rate of change is limited by Cs which is the falling edge of Toff. This changing voltage is generating a AC current with a funamental frequency but also a lot of harmonic content which is no use. The band pass (Notch) filter removes the unwanted harmonics from the drain waveform to put the chosen frequencies onto the load (the capacitor cseries removes low frequencies and DC offsets and Lseries blocks high frequency haromonics leaving in this case the fundamental harmonic).

The post by #4 by Bertus shows a lot of this very nicely.

https://www.electronics-tutorials.ws/accircuits/series-resonance.html

https://electricalacademia.com/electronics/band-pass-notch-filter-circuit-theory/#:~:text=The bandpass and notch (or,response curves in Figure 1.&text=In each case, the filtering,characteristics of the LC circuits.

https://www.elprocus.com/series-and-parallel-lc-circuit-resonance/
 
Last edited:

Thread Starter

pinkyponky

Joined Nov 28, 2019
22
To try and answer your question though
1. Lchoke and Cs are meant to create a resonant ring which is excited by the switch,
2. Lseries and Cseries is current creating a band pass filter to pass AC (not DC) and the current on Rload would be AC. This is where i suspect theres something missing or wrong on the schematic if DC is your intention
3. I suspect if its DC you want your missing the rectification circuit

https://www.slideserve.com/paloma/resonant-boost-converter-design

https://www.semanticscholar.org/pap...c1bac4a53c8e63d640e9baad9474a9da7a12/figure/1
I have simulate the circuit and I have one question from the simulation. I have attached the circuit and simulation waveform below.
1609700466909.png

[/QUOTE]
1. Lchoke and Cs are meant to create a resonant ring which is excited by the switch,
[/QUOTE]
As you told that the Lchoke (here L1) and parallel/shunt capacitor (here C1) are meant to create a resonant ring meaning that the sinusoidal wave?. Resonant ring means what?.

[/QUOTE]
2. Lseries and Cseries is current creating a band pass filter to pass AC (not DC) and the current on Rload would be AC. This is where i suspect theres something missing or wrong on the schematic if DC is your intention
[/QUOTE]
As you told that, Is the Lseries and Cseries is only used for filter out the unwanted harmonics?. These elements not used for AC signal generation right?.

3) How the DC current converted to the AC current when passing through the parallel capacitor (C1) from the above simulation?.
 
Last edited:

Thread Starter

pinkyponky

Joined Nov 28, 2019
22
You mean that the shunt capacitor we are using just for to create a half-sinusoidal waveform?. Without shunt capacitor we can't able to generate the below waveform?, as shown below.
View attachment 226573
From my understanding, Rising to peak value due to inductor charging and falling to 0V due to inductor discharging. But, here the shunt capacitor not playing any role, right?. Then what is use of shunt capacitor?.
2. Lseries and Cseries is current creating a band pass filter to pass AC (not DC) and the current on Rload would be AC. This is where i suspect theres something missing or wrong on the schematic if DC is your intention.
[/QUOTE]
From this, what I understand is that, When the Switch_off, the current will flow through the LC circuit so the output will have a positive half cycle of sinusoidal waveform. When the Switch_on, the energy stored in the Cs will discharge through the LC circuit with negative polarity (when discharging the capacitor the polarity will change) so the output will be negative half cycle of sinusoidal waveform. Thus, we have a full sinusoidal waveform across the load resistor.
[/QUOTE]

1. For the waveform on drain of the switch the 'rate of change' for the voltage will be controlled by Cs, The 'rate of change' in current flow will be controlled by the Choke. They work together. Post #4 is very insightful as to its operation as simulated in LT spice. My advice would be to simulate the circuit in post #4 to get a better understanding as all the information is present to replicate the simlation.

2. When the switch turns off the choke will flyback to continue the flow of current. The 'rate of change' in votage it flybacks will be limited by Cs which is what you see as the rising edge of Toff. At some point the enegy in the choke will run dry and the voltage will start to fall, again the rate of change is limited by Cs which is the falling edge of Toff. This changing voltage is generating a AC current with a funamental frequency but also a lot of harmonic content which is no use. The band pass (Notch) filter removes the unwanted harmonics from the drain waveform to put the chosen frequencies onto the load (the capacitor cseries removes low frequencies and DC offsets and Lseries blocks high frequency haromonics leaving in this case the fundamental harmonic).

The post by #4 by Bertus shows a lot of this very nicely.

https://www.electronics-tutorials.ws/accircuits/series-resonance.html

https://electricalacademia.com/electronics/band-pass-notch-filter-circuit-theory/#:~:text=The bandpass and notch (or,response curves in Figure 1.&text=In each case, the filtering,characteristics of the LC circuits.

https://www.elprocus.com/series-and-parallel-lc-circuit-resonance/
[/QUOTE]

[/QUOTE]
The post by #4 by Bertus shows a lot of this very nicely.
[/QUOTE]
I have simulated the circuit as per the post by #4. But I have a question and posted at #11, please can you answer that.
 

Marc Sugrue

Joined Jan 19, 2018
211
https://electricalacademia.com/electronics/band-pass-notch-filter-circuit-theory/#:~:text=The bandpass and notch (or,response curves in Figure 1.&text=In each case, the filtering,characteristics of the LC circuits.
I have simulate the circuit and I have one question from the simulation. I have attached the circuit and simulation waveform below.
View attachment 226641
1. Lchoke and Cs are meant to create a resonant ring which is excited by the switch,
[/QUOTE]
As you told that the Lchoke (here L1) and parallel/shunt capacitor (here C1) are meant to create a resonant ring meaning that the sinusoidal wave?. Resonant ring means what?.

[/QUOTE]
2. Lseries and Cseries is current creating a band pass filter to pass AC (not DC) and the current on Rload would be AC. This is where i suspect theres something missing or wrong on the schematic if DC is your intention
[/QUOTE]
As you told that, Is the Lseries and Cseries is only used for filter out the unwanted harmonics?. These elements not used for AC signal generation right?.

3) How the DC current converted to the AC current when passing through the parallel capacitor (C1) from the above simulation?.
[/QUOTE]

1. Its a resonant circuit, by resonant ring i meant L1 & C1 are chosen to give the fundamental frequency you require - they define the operating frequency of the amplifier https://www.daycounter.com/Calculators/LC-Resonance-Calculator.phtml one word of note is that as this is a high frequency circuit the capacitance of the Mosfet Vds will be significant.
2. Correct its a filter to clean the harmonic content for the desired output. The pass band would be set to the resonance in 1. to achieve low harmonic output. The intent is to get a nice sine wave output but if too many harmonics pass through that won't be the case.
 
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