Piezoelectric transformer with pulse dropping technique for high voltage generation

This paper describes implementation design and analysis of piezoelectric transformer with pulse dropping technique to produce high voltage. The main contribution is the implementation of pulse dropping mode in inverter switching mechanism to decrease heat of piezoelectric transformer during the high voltage generation. Piezoelectric transformer fed by inverter in this work is dedicated to generate high voltage in high frequency. How ever, load current drawn from the transformer causes temperature rise and deterioration of internal elements of piezoelectric. As operating temperature reach the maximum limit, the output voltage of piezoelectric becomes non sinusoidal and decreases in magnitude. In pulse dropping technique, there are two modes in period of inverter switching. The first mode is called as power injection and the second is called as relaxation period. The experiments was carried out by a high frequency inverter, power MOSFET as power electronic switch, KW06-559 infra red thermometer to detect temperature of piezoelectric transformer, and resistive-capacitive component as a load. Without the use of pulse dropping technique during experiment, the temperature of piezoelectric reached the maximum limit at 70°C, voltage output was unstable and the piezoelectric was easy to crack. It was found that first mode maintained high voltage output at 2.45 kV peak to peak and the second mode successfully maintained the average temperature of piezoelectric in the range of 35-40°C.