Inductor-less piezoelectric transformer electronic ballast for linear fluorescent lamp

This paper presents a cost-effective piezoelectric transformer based ballast circuit that is designed to drive a linear fluorescent lamp without dependence on any magnetic devices. This innovative circuit uses a radial vibration mode piezoelectric transformer or Transoner(R) to replace the inductor and the capacitors of the resonant tank portion in conventional electronic ballast circuits in order to effectively reduce the component number and cost. By fully utilizing the characteristics of the radial vibration mode piezoelectric transformer, the switches of the ballast circuit can work in a ZVS (zero-voltage switching) condition thus significantly reducing the turn-on switching losses when compared to a hard-switching topology. In addition, the inherent input capacitance of the radial vibration mode piezoelectric transformer enhances circuit operation by serving as a turn-off snubber for the half-bridge switches. This decreases turn-off voltage spiking thus reducing the turn-off losses for the half-bridge switches of the proposed circuit. Through these innovative circuit techniques, the proposed circuit provided 32-watts of power at commendable efficiency of around 90% when utilizing a standard 110-volt 60-Hz line as the power source and a 4-foot 40-watt linear fluorescent lamp as a load.