| 摘要 |
PROBLEM TO BE SOLVED: To obtain a small-sized, high-efficiency piezoelectric transformer having a high boosting ratio specifying the ratio of the resonance resistance of a generating part to the resonance resistance of a driving part. SOLUTION: A piezoelectric transformer has construction provided with input electrodes 3, 4 for applying voltage to a lead zirconate titanate family piezoelectric ceramic 1 for example, and an output electrode 5 for taking power out. The input electrodes 3, 4 are formed in a driving part where vibration by an inverse piezoelectric effect of the piezoelectric ceramic 1 is excited, and the output electrode is formed in the generating part where vibration is taken out as power by a normal piezoelectric effect. In the piezoelectric transformer, the ratio Rg/Rd of the resonance resistance Rg of the generating part to the resonance frequency Rd of the driving part is determined to be 30 or less. If the ratio exceeds 30, the efficiency lowers and becomes lower than 80%, and a calorific value on the occasion of driving the piezoelectric transformer increases, and operation of an inverter for liquid crystal back light becomes unstable. Accordingly, a piezoelectric transformer small-sized, capable of producing large output power, and high-efficiency is obtained, if the ratio Rg/Rd<30 is satisfied.
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