Contour vibration mode piezoelectric transformers were designed and fabricated to the square plate with size of 27.5x27.5x2.6㎟ using PNW-PMN-PZT ceramics. Electrical characteristics of the piezoelectric transformer were investigated for fluorescent lap ballast application. The electrical properties and characteristic temperature rise were measured by oscilloscope and infrared temperature sensor. A 28W fluorescent lamp was successfully driven by the fabricated transformers. The electronic ballast using piezoelectric transformer showed an excellent output power of 28.85[W], efficiency of 86.3% and characteristic temperature rise of 15[$^{C}$].