摘要 |
PROBLEM TO BE SOLVED: To obtain a power supply of necessary output voltage by improving reliability of power supply to supply the power to a piezo-drive circuit and by using the power supply of voltage specification which can easily be available in the market. SOLUTION: As the power supply, DC/DC converters 5, 6, 7 are used, the output sides thereof are connected in series and the power is supplied to the piezo-drive circuit 8 from both end portions of the serial circuit. The piezo-drive circuit 8 expands and compresses a piezo-element depending on a control signal from a CPU 10. If the converter 5 fails, the CPU 10 turns OFF the power switch and separates the input side of the converter 5. Since an output voltage of converter 5 becomes 0 V but the converters 6, 7 output the voltage 30 V, the voltage of 60 V can be supplied. The piezo-drive circuit 8 narrows the operation range of the piezo-element 9 depending on drop of voltage to be supplied, but reliability can be improved because the expansion and compression operation is realized without cease of the operation of the piezo-element 9.
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