Compensation in wireless power transfer -circuit topology

[eeefreakians]

in the above schematic whether i need a external compensation network(separate L and C) with primary coil? or the capacitor should resonate with primary coil?


pls elaborate it? i have attached a schematic whether it is correct?

similarly for secondary also

 

[eeefreakians]

help me learn mre in this svm. pls post correct schematic

 

[FvM]

Incomplete schematic. You need to know the inductor coupling to calculate the resonant circuit.

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You need to know the coil parameters.

 

[D.A.(Tony)Stewart]

• In order to have maximal power transfer theorem satisfied, load impedance must be matched to source.
• Since can assume charging a battery is very low load impedance, <1Ω
• we know free space impedance is relatively high,
• the mutual coupling must be relatively high for efficiency,<1 but >0.5 we assume the two loop gaps are much less than their diameters.
• we know if excitation frequency is off by fc/Q of the SRF, fc of the coils or at least betwen the twin peaks then the amplitude will drop by -3dB so we want not too high a Q, or freq error , maybe Q=1 under max load. and <100 at no load
• We an assume the source is low impedance but if it comes from a COmmon collector current source , it becomes the reactance at fc, so topology of driver is critical
• We want to prevent saturation of magnetics so air coil may be initially selected or computed otherwise
• In order to provide a low resonant impedance in series, L must be small and C large with very low ESR
• when you compute your power transfer losses, consider a tapped coil for step up voltage on primary and step down voltage on secondary such that coupling imoedance in series can be transformed by the turns ratio.
• with an autotransformer *Dual-loop* antenna coupling, I believe it is easier to match impedances of battery to sourc and keep freq. within FCC /IEC limits
• this way transfer current is low but higher voltage then with a few turn tap only, current is boosted by turns ratio while v is dropped.
• measure/calc source/load impedance for maximal power transfer when matched Z
• this will 50% efficient max but higher power, thus if higher efficiency is desired, use a higher turns ratio so source Z is much lower than Zbat charger

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when matched Z this will 50% efficient max but higher power, thus if higher efficiency is desired, use a higher turns ratio as a non-resonant current source With a Voc and Vload =%80Voc , much like a PV current source in MPT except RF rather than DC.

 

[eeefreakians]

can anyone give numerical example for it8-O

 

[FvM]

If you are analyzing a specific wireless power transfer system, you should know about the coil parameters.

In most cases, the coupling will be considerably smaller than 1. In this case, you can start the calculation with uncoupled coils, in terms of your initial question, the series capacitor will resonate with primary coil inductance. Adding a coupling will slightly detune the resonators, if the coils involve a core or magnetic shield (e.g. like the Qi standard), you'll observe a significant inductance increment and need to re-tune the circuit. Qi does this by adapting the transmitter frequency.

 

[eeefreakians]

could someone post the schematic for wireless power transfer with compensation§

 

[D.A.(Tony)Stewart]

depends which topology you want.
BE-ON or BE-BY

ON as in on top of inductive transfer , more efficient but close proximity
BY as in near but less critical gap and less efficiency using resonant mode.

BE as in B field Emitter