Self-oscillating electronic ballast analysis via relay systems approach

In this paper, the authors analyze the self-oscillating LC parallel resonant inverter for electronic ballast applications from a system point of view. It is observed that the self-oscillating parallel resonant inverter with lamp loads can be naturally modeled as a relay system with negative hysteresis. Based on this formulation, the self-oscillating frequencies of the circuit are found via the time-domain based Hamel locus. Also, the predicted self-oscillating frequencies via the describing function approach and the Hamel locus approach are compared with the prototype measurement results. It turned out that the accuracy of the frequency prediction via Hamel locus is high, while the accuracy via the describing function is circuit Q dependent