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I'm designing a H-bridge driven by two IR2110 MOSFET drivers and using four NMOS (IRFS SL7440) transistors. The goal is to transfer power via the two magnetically coupled coils. I am driving the MOSFET drivers at 50 kHz which is the resonant frequency of this magnetically coupled system via the formula: $$ f_{res} = \frac{1}{2*\pi*\sqrt{L*C}} $$

Filling in L=30 uH and C=338 nF gives approximately 50 kHz. Below is a picture of my schematic, (the first coil is marked by red dots, the second coil is marked by yellow dots) enter image description here

The problem I encounter is that the current through and voltage over the second coil is too low and too spiked. Below are two LTspice simulations that show the difference in current and voltage between the output of the H-bridge (=first coil=L1), and the second coil (=L2). enter image description here enter image description here (The current through the first coil is marked in green, while the current through the second coil is marked in deep blue, idem for the voltage plot)

I've tried different resonant frequencies, and changing the coils' characteristics accordingly but the drop in voltage and current remains.

Where could this unwanted drop in power come from?

Edward-__-
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  • What convinced you to use series secondary tuning and no, you are not measuring the voltage across the secondary coil. – Andy aka Dec 04 '22 at 10:37
  • There doesn't seem to be much sign of resonance occuring. Most designs would use parallel receiver resonance. You might be getting lost in the detail. It would be easier to investigate the coils at this stage if you simply drove the tuned primary with a voltage source, rather than investing effort in simulating the whole driver/H-bridge thing. What coupling k are you assuming between the coils? – Neil_UK Dec 04 '22 at 10:45
  • [Full bridge rectifier and resonance for wireless power transfer in the receiver circuit](https://electronics.stackexchange.com/a/641774/20218) – Andy aka Dec 04 '22 at 11:06
  • what is coupling factor between the coils? Why are you using series resonance, should use a parallel resonant network. And the resonant frequency of a coupled coil with inductance L and capacitance C is \$\frac{1}{\sqrt{(1+k)LC}}\$ – sarthak Dec 04 '22 at 11:11
  • Further at your frequency your inductor is impedance is very low ~9Ohm. Maybe increase the inductance as well. – sarthak Dec 04 '22 at 11:13
  • Coupling factor is set to 1, thus the ideal case. – Edward-__- Dec 04 '22 at 11:14
  • If you want to see the effect of resonance, set the coupling factor down to something sensible for wireless charging. Wityh a coupling of 1, you might just as well be using only the inductors, it's called a transformer. – Neil_UK Dec 04 '22 at 13:48

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