Е-Публикации
Технически университет - София

Abstract: In this paper, the authors present an analysis of the behavior of circuit configurations of step-up transformer-based LC oscillators suitable for building input stages of low-power self-oscillating boost DC–DC converters for energy harvesting systems. The circuit configuration under consideration is based on a Meissner oscillator, and unlike it, the oscillator includes a step-up transformer and a JFET transistor operating in a triode mode of operation with a variable transconductance. Based on an analysis of the circuit in steady-state operating mode, the second-order characteristic equation was determined, and the self-oscillation conditions were identified. Then, the behavior of the oscillator during self-oscillation and the change in the transconductance of the transistor were studied. Based on a theoretical analysis, taking into account the nonlinearities of the transistor, formulas were obtained for the initial value of the transconductance and amplitude of the output voltage in the steady-state operating mode. As a result of the obtained analytical expressions, a design procedure was proposed for given requirements for the output parameters. Moreover, from the performed simulations and experimental testing of the sample electronic circuits, the values for the main electrical parameters were obtained in reasonable agreement with the results of the calculations, using the proposed analytical expressions. To illustrate the effectiveness of the presented theoretical analyses and the proposed design procedure, a photoelectric-based self-oscillating DC–DC converter using a step-up transformer-based LC oscillator as an input stage is developed. Low-power amorphous silicon photovoltaic panels have been used as sources of electrical energy. As a result of the performed simulation studies and experimental testing, the FoM coefficient is obtained to be 300% at an external load equal to 20 kΩ. The proposed electronic system also provides a backup power supply circuit in case of insufficient illumination of the photovoltaic panels.

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