Doubt in simulation of LLC Resonant Converter in LTSpice

[Praveen_Raj]

I'm trying to simulate LLC Resonant Converter, with a (series) resonant freq of 459 kHz.

So if im not wrong, at resonant freq, the gain = 0, and when switching frerq is equal to resonant freq, am supposed to get the best efficiency.

Then when i simulate DC to DC step down llc resonant circuit, with an input voltage of 600v, im some how getting a better efficiency as i increase the switching freq over the resonant freq, does anyone have know why?

Thank you

 

[FvM]

What do you consider as "efficiency" in your simulation? Gain is not efficiency. LLC is designed to achieve voltage variation over a certain range by varying frequency. Lm/Lr ratio if 100:2 is too large for this purpose. Typical transformers have rather 5:1 to 10:1.

 

[Praveen_Raj]

What do you consider as "efficiency" in your simulation? Gain is not efficiency. LLC is designed to achieve voltage variation over a certain range by varying frequency. Lm/Lr ratio if 100:2 is too large for this purpose. Typical transformers have rather 5:1 to 10:1.

efficiency for my purpose is output power (R1) / Input Power.
And the only thing I'm focused on is to decrease switching losses with LLC Resonant Circuit, as im working with very high freq

This is the circuit diagram. And following is the video i kept as reference, and the values of Lr, Lm and Cr are from here.

 

[Praveen_Raj]

if possible, can someone please share a detailed article/book about soft switching with resonant circuits