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A study on the T5 fluorescent lamp ballast used contour vibration mode piezoelectric transformer using a one-chip microcontroller

The traditional magnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight. In this study, in order to solve the problems, new type of electronic ballast which composed of rectifier, active power factor corrector, series-resonant half bridge inverter, feed back circuit for maintaining constantly current to lamp, protection circuit out of order ballast circuit or piezoelectric transformer and end of lamps life, dimming control, piezoelectric transformer for driving T5 fluorescent lamp were manufactured and using a one chip microcontroller. These ballast circuits could replace magnetic transformer and resonant capacitor with piezoelectric transformers. The proposed electronic ballast operated at high frequency (about 75kHz) showed input power factor of more than 0.995, total harmonic distortion of less than 12% and lamp current crest factor of less than 1.5, respectively. And also, output power and efficiency shown 28W and 85%, respectively. Accordingly, it is considered that the ballast using piezoelectric transformer can replace the typical electronic ballast.