| 摘要 |
<P>PROBLEM TO BE SOLVED: To stabilize the operation of a machine element that is driven by a piezo actuator. <P>SOLUTION: A chopper-type circuit performs charge and discharge between a piezo stack 4 and a capacitor 63 that are mounted to the piezo actuator by using a current having a chopping wave with which the current rises, and falls between zero and a peak by repeating turning-on/off of switch elements 64a, 64b. In the circuit, on-periods of the switch elements 64a, 64b are set so that the peak current is monotonously decreased in a period from the start of charging to the termination of the charging and in a period from the start of discharging to the termination of the discharging, and also so that the peak current is gradually decreased from at least halfways of the charging and the discharging. An amount of the charge is increased up to a haflway at one stretch. After that, the amount of the charging is made to approach gently to a target value. Since the current is always changed only in the decreasing direction, the operation of the machine element is stabilized. A resonant oscillating current is prevented from flowing due to a reachable maximum current decreasing in accordance with the progress of charging and discharging. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
