Chin Chang

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 Tsypkins locus. The stability of the self-oscillating frequencies is determined in a sampled-data system framework.

Self-oscillating electronic ballast analysis using the relay systems approach

In this paper, the authors analyze the self-oscillating LC parallel resonant inverter for electronic ballast applications from a control 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 turns out that the accuracy of the frequency prediction via the Hamel locus approach is high, while the accuracy via the describing function approach is circuit Q-value dependent.

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.

Voltage-fed half-bridge resonant converter for multiple lamp independent operation

In this paper, we explore the voltage-fed half-bridge LLC resonant converter for multiple lamp parallel independent operation (ILO). Based on the observation of almost invariant voltage gain relation with the resonant tank input impedance phase angle for different number of lamps, we propose the so-called phase-shift based control method. With this method, multiple lamp ILO is achieved under voltage-fed half-bridge LLC resonant converter with zero-voltage-switching (ZVS). Experimental results are presented for instant start 4-lamp TL70 F32T8.