A low-size multi-power-level single-transistor ballast for low pressure fluorescent lamps, using a piezoelectric transformer

A 5 to 18 Watts multi-power level demonstrator with a transoner-type piezoelectric transformer (PT) has been built in class-E topology to show the full functionality of a low-size low-cost instant start ballast for fluorescent lamps. Zero-voltage switching was achieved for different output power levels (different tubes), at nominal input voltage of 230 V AC, including tolerances, using one and the same PT sample and ballast circuit. The PT was 8 mm thick, and had a diameter of 19 mm. The used switch, a 1200 V fieldstop-IGBT, 1 A-type, shows losses of 716 mW for 16.8 Watts output power, at a frequency of 119 kHz. The converter efficiency (without rectifiers) has been accordingly 89.5%.