Electrical characteristics of central driving type piezoelectric transformers with different electrode distributing

In this study, three kinds of central driving type piezoelectric transformers, Types A, B and C with different electrode distributing were investigated by using impedance analyses. With the increase of the input electrode area, the resonant resistance of input section decreased and the effective electromechanical coefficient increased. With the decrease of the length of the generator section, the resonant resistance of generator section increased and the effective electromechanical coefficient decreased. The voltage step-up ratio increased with the increase of the ratio of the input and output resonant resistance. The temperature rise of Type A was lower because the impedance matching between the load resistance and the output impedance was achieved. Taking into consideration of the mechanical quality factor (Qm), the output impedance (Zout) and the temperature rise (ΔT) of each transformer, Type A with the input electrode length ratio of 1:1:1 could be selected as the optimum structure to drive the LCD backlight.