| 摘要 |
PROBLEM TO BE SOLVED: To prevent the efficiency reduction and heat generation increase of a piezoelectric transformer due to the abnormal vibration of the piezoelectric transformer, since a conventional device cannot detect the harmonic constituent of the drive voltage and output voltage of the piezoelectric transformer. SOLUTION: High-pass filter circuits 17 and 18 detect the input drive voltage of a piezoelectric transformer 12 and the harmonic constituent of an output voltage. A comparator 19 compares a reference voltage VrefC with the output signal of the high-pass filter circuit 17. A comparator 21 compares a reference voltage VrefD with the output signal of the high-pass filter circuit 18. An OR gate 23 obtains the logic sum of each output signal of the comparators 19 and 21 and outputs it to an LED-lighting circuit 25 through a level retention circuit 24. When the high frequency constituent is generated in the drive voltage or output voltage of the piezoelectric transformer 12, and at least either harmonic constituent exceeds a reference level, and the LED of the LED-lighting circuit 25 stays on. |
