LLC or LCC converter Selection

[tictac]

Hi all,

I would like to get your advice for designing the power architecture(s) for the following power supply:
Input: 304-456 Vac ( 3 phase)
Output: 50v to 200V - 10A to 100A

I want to select between LLC or LCC converter. which is better for this power and such a output variable current.

Regards

 

[AMSA84]

Hello tictac,

Taking the advantage of your post, 'd like to ask if this kind of converters always need a transformer. From what I have seen, all the examples uses a transformer.

Regards

 

[tictac]

Yes I know about the using of transformer.
I want to know about which is better for good regulation at no load and full load with minimum resonance tank.

 

[Velkarn]

Output: 50v to 200V - 10A to 100A

you need to regulate output voltage from 50 to 200V?

 

[tictac]

Yes I need to have variable voltage from 50 to 200 volts and up to 20kw output power

 

[Velkarn]

at that moment i have designed power supply based on LLC topology (220ac to 24V dc, 100 Wt).
but when i tryed to use LLC topology in another PS with regulated output, i faced problem with regulation. once LLC is not PWM, but freq controled, analysys shows that for quite narrow voltage regulation, very wide freq change needed.

 

[tictac]

at that moment i have designed power supply based on LLC topology (220ac to 24V dc, 100 Wt).
but when i tryed to use LLC topology in another PS with regulated output, i faced problem with regulation. once LLC is not PWM, but freq controled, analysys shows that for quite narrow voltage regulation, very wide freq change needed.

I also have designed power supply based on LLC with L6699 (Vin=220ac Vout=20kv, Iout=10mA) At startup the frequency is high(about 4*F_resonance) after the soft start time, feedback line regulate the outuput voltage proper to load and it goes down near the resonance frequency. L6699 is good selection for LLC but as I know , it is not proper for isolated power supply.
what was your controller IC for LLC? How you calculate Qe and Lr=Lp/Ls ?
Do you use simulation software for your design ? Can you draw Gain-Qe or Gain-Frequency plot for your design?
Can you share with me your information about LLC and above questions?

Regards

 

[Velkarn]

i used L6599 and my power supply is isolated. l6599 and L6699 is similar, so i do`nt see why it is not good for isolated ps.
in designing i used refddesigns and guides from ST.
tomorrow, when i get to my work i try to answer other qwestions.

 

[tictac]

I also worked with L6599 and it has some bug with some features ,So I use L6699.If you see datasheet and application note of L6699 you know it and they improve it.
I also use transformer for increasing output voltage and I use opto-coupler for feedback isolation, but the ground of L6699 is same with ground of Input line voltage (Vac=220v).
I think when you work with 3-phase as your input line the ground of your controller must be isolated from input line (Vac).

Regards

 

[Velkarn]

i tryed to draw Gain-Frequency plot (i do not know it is correct or not)

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for calculating transformer parameters i used ST design guide.
parameters of transformer: Lpri=490u, Lleakage=62u
and what is Qe?

 

[AMSA84]

Hi guys.

I am willing to study resonant converters.

Can you guys help me to know where I can start studying this subjects? Where to start, books, references?

Kind regards.

 

[Velkarn]

AMSA84, search ST site for appnotes AN2644, AN2450 and refdesigns based on L6599, L6699

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and an-1160 from IR

 

[tictac]

i tryed to draw Gain-Frequency plot (i do not know it is correct or not)

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for calculating transformer parameters i used ST design guide.
parameters of transformer: Lpri=490u, Lleakage=62u
and what is Qe?

Thanks you
Can you give me the link of ST design guide?
Q=(Lr/Cr)^0.5*1/Rac and depended to the load.

 

[Velkarn]

LLC resonant half-bridge converter design guideline https://www.st.com/web/en/resource/technical/document/application_note/CD00143244.pdf

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Do you use simulation software for your design ?

i make spice model of power circuit at fixed freqency