Driving of 35W(T5) fluorescent lamp by the electronic ballast using piezoelectric transformer

Recently, 40 W fluorescent lamps with 32 mm tube diameter are replaced with 32 W one with 26 mm in diameter to conserve lamp materials and to increase luminance efficiency. Moreover, 35, 28 and 14 W fluorescent lamps with 16 mm in diameter (T5), which are nowadays developed, also may replace 32 W lamps again. Application of slim lamps, however, requires small sized electronic ballast to fulfill the design philosophy of miniaturizing. However, the traditional magnetic ballasts operated at 50-60 Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight In this study, in order to solve these problems, a new type of electronic ballast which is composed of rectifier, active power corrector, series resonant half bridge inverter and piezoelectric transformer was proposed for driving T5 fluorescent lamp. Contour vibration mode piezoelectric transformer with ring/dot electrode structure was fabricated to the size of 27×27×2.5 mm³ by cold isostatic pressing. Driving of piezoelectric transformer was carried out with input region for the ring electrode and output region for the dot electrode. A 35 W (T5) fluorescent lamp was successfully driven by the fabricated ballast with piezoelectric transformer. After driving the lamp for 25 min using the proposed electronic ballast, input power factor of 0.95, efficiency of 90.7%, were shown, respectively, at operating frequency of 79 kHz. And also, output power, efficiency and temperature rise of the piezoelectric transformer, 37.53 W, 92% and 25°C, respectively.