High-frequency class-D converter driving with feedback capacitors for electrodeless fluorescent lamps

This paper presents a novel class-D converter for electrodeless fluorescent lamps (EFLs) in the several megahertz frequency. The proposed converter is a self-oscillating type and it uses the feedback capacitors to supply the gate voltages to the switching devices of a half-bridge inverter via gate circuits. The converter is suitable not only for a conventional EFL but also a choke-coil-less type which uses an exciting coil instead of a choke coil. The oscillating frequency is changed depending on DC voltages, especially in the choke-coil-less type. In this case, the gate circuits compensates both the off interval of the switching devices and a phase angle in order to stabilize the power factor. A prototype EFL with and without the choke coil operated steadily on the frequency of 2.5 MHz, and the temperature of the MOSFET could be kept below 55°C for both cases