Abstract
This contribution presents a detailed nonlinear analysis of a high-power oscillator that is inductively coupled to an external resonator for power transfer applications. The analytical formulation of a cubic nonlinearity oscillator enables the derivation of the maximum transferred power and the value of the coupling factor at which the oscillation is extinguished. Then, a simple procedure to obtain a Class E oscillator from an initial high efficiency oscillator is presented. The solution curves versus the coupling factor and the elements of the external resonator are easily obtained from the extraction of a bi-variate nonlinear admittance function accounting for the oscillator circuit, which is combined with the passive admittance of the coupled resonator. Very good correspondence has been obtained between simulation and measured results.
Highlights
SEVERAL recent works propose the use of a high-power oscillator as the excitation source of near-field inductive power transfer systems [1]-[4], which avoids the need of both an independent generator and an amplifier
Because in the power transfer application, the output resistive load is located in the external resonator, one can expect the behavior to be different from that of the voltage-controlled oscillator in [6],[7], which had its own output load and was coupled to a high-quality factor resonator
We will analyze the variation of the oscillation frequency and power transfer versus the coupling factor
Summary
SEVERAL recent works propose the use of a high-power oscillator as the excitation source of near-field inductive power transfer systems [1]-[4], which avoids the need of both an independent generator and an amplifier. Most previous works [1]-[4] are devoted to analyze/optimize the efficiency of the transfer process, and, to the best of our knowledge, no detailed investigation has been carried out yet of the variations in the oscillator solution (maximum power transfer, oscillation hysteresis, multivalued operation, etc.) versus the coupling factor. A practical transistor-based oscillator will be considered With this aim, we will use a simple feedback procedure to transform a Class-E amplifier into a high power and high efficiency oscillator. The solution curves (in terms of output power and efficiency) versus the coupling factor or any other parameter of the external resonator will be obtained after the extraction of a bi-variate nonlinear admittance function describing the uncoupled oscillator circuit and a bi-variate DC current function, enabling the efficiency calculation.
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