A current source resonant inverter with improved valley fill circuit for high power factor electronic ballast applications

In the first part of this research, a current source resonant inverter is proposed with the resonant circuit resembles the similar structure of the voltage fed series-parallel loaded resonant (LCC) inverters. The nature of a current source type converter that offers high output impedance is very beneficial to compensate the negative incremental resistance in gaseous discharge lamps. The valley fill circuit is then combined with the proposed inverter to achieve power factor correction and to supply energy to the inverter stage towards the end of the rectified cycle. A new circuit is also proposed and inserted in the valley fill circuit to improve the quality of the line current by further extending the conduction time of the line current.; The second part of this research focuses on developing a novel variable frequency controller that is proposed by modifying the internal circuitry of the 555 timer circuit. This modified 555 circuit is used as a voltage controlled oscillator to continuously regulate the lamp current by varying the switching frequency of the inverter. As a result, high power factor can be achieved while at the same time, the lamp crest factor is also improved. Lamp dimming is achieved by controlling the switching frequency of the proposed inverter. Analytical, simulation and experimental results are presented to verify all the theoretical analysis. (Abstract shortened by UMI.)...