Analysis of the self-oscillating series resonant inverter for electronic ballasts

In this paper, we examine the self-oscillating series resonant inverter for electronic ballast applications from a system point of view. By considering the discharge lamp as a linear resistor in steady state, we derive a time-domain closed-form expression of the circuit state variables. Importantly, we observe that the self-oscillating series resonant inverter with lamp loads can be naturally modeled as a relay system. Based on this formulation, the self-oscillating frequencies of the inverter for variable lamp impedance conditions are found via the Tsypkin's locus. The stability of the self-oscillating frequencies is determined in a sampled-data system framework.