JPH04121075A - Driving apparatus of piezoelectric actuator - Google Patents

Abstract

PURPOSE:To reduce power consumption and, further, a piezoelectric actuator can be charged and discharged in a short time by a method wherein the driving apparatus of the piezoelectric actuator is composed of a stem-up circuit, a charging circuit and a discharging circuit and a semiconductor device for discharge is provided in the discharging circuit. CONSTITUTION:A trigger signal is outputted to a semiconductor device 2c in a discharging circuit C from a control unit D to close the semiconductor device 2c. By closing the semiconductor device 2c, a current flows to a broken- line direction through a resistor 1c and the semiconductor device 2c in the discharging circuit C and a piezoelectric actuator PA is discharged. It is not necessary to provide an excessively large resistor in the discharging circuit C in order to avoid the discharge of the piezoelectric actuator PA while it is charged and the resistance value of the resistor 1c is properly predetermined. With this constitution, quick discharge can be ensured.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a piezoelectric actuator drive device.

(Prior Art) A piezoelectric actuator is a type of capacitor composed of a dielectric piezoelectric element and two electrodes sandwiching the piezoelectric element. The axial deformation of the piezoelectric actuator is proportional to the charge stored in the piezoelectric actuator, and therefore the output displacement of the piezoelectric actuator is controlled by charging and discharging the piezoelectric actuator.

As shown in Fig. 3, a conventional drive device for charging and discharging such a piezoelectric actuator includes a boost circuit A' equipped with a boost coil and a diode that supplies current only in the direction of charging the piezoelectric actuator. Charging circuit B
' and a discharge circuit C' provided with a -resistance. In this drive device, a booster circuit A
' and charging circuit B' in the direction of the solid line arrow to charge the piezoelectric actuator, and when charging is stopped, the piezoelectric actuator is discharged in the direction of the broken line arrow via the discharge circuit.

(Problem to be solved by the invention) However, in the conventional piezoelectric actuator drive device shown in FIG. 3, current flows through the piezoelectric actuator through the resistance of the discharge circuit at all times, including during charging, so power consumption is large and While charging takes time, discharging during charging must be suppressed (increasing the resistance value in the discharging circuit takes time to discharge, which in turn slows down the operation of the actuator).

Therefore, an object of the present invention is to provide a piezoelectric actuator drive device that consumes less power and can perform charging and discharging in a short time.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a piezoelectric actuator comprising a booster circuit, a charging circuit that allows current to flow only in the direction of charging the piezoelectric actuator, and a discharging circuit. A driving device for a piezoelectric actuator is provided, in which a semiconductor element for discharging is disposed in a discharging circuit.

(Function) In the present invention, the discharging semiconductor element in the discharging circuit is made non-conductive during charging of the piezoelectric actuator and during charge retention from the completion of charging to the time of discharging. Since the discharging semiconductor element is conductive, almost no current flows through the piezoelectric actuator through the discharging circuit during charging and charge retention.

(Example) Hereinafter, the present invention will be described in detail based on the accompanying drawings.

In FIG. 1, PA is a piezoelectric actuator, and 1 is a drive device for the piezoelectric actuator PA according to an embodiment of the present invention. A drive device 1 for a piezoelectric actuator PA includes a known flyback booster circuit A consisting of a booster coil la, a transistor 2a, other resistors, diodes, capacitors, etc., and a charging circuit B to which a diode 1b is connected. , a resistor 1c, a semiconductor element 2c for discharging consisting of an IGBT, and a discharging circuit C connected in series. Further, the output of a control unit D for controlling application of a trigger signal is connected to the base of the transistor 2a and the base of the semiconductor element 2c, respectively. The charging circuit B and the discharging circuit C are connected in parallel to the piezoelectric actuator PA, and the discharging circuit C is grounded.

Furthermore, a resistor 4 is connected between the base and emitter of the semiconductor element 2c.

The operation of the piezoelectric actuator drive device 1 according to the present embodiment configured as described above will be described below with reference to FIGS. 1 and 2.

■Charging First, the signal output from the control unit D to the base of the semiconductor element 2c is stopped, and the semiconductor element 2C is brought into a non-conductive state. Next, a trigger signal is similarly applied from the control unit D to the base of the transistor 2a of the booster circuit A for a predetermined period of time, the transistor 2a is made conductive, and a current is caused to flow through the primary coil side of the booster circuit A in the direction of the thin solid line in FIG. Then, an induced current is induced in the direction of the thick solid line in Fig. 1 on the secondary coil side to create a high voltage, which causes the piezoelectric actuator P to
Charge A to a predetermined amount of charge. By repeatedly applying a signal, the bird charges the voltage V of the piezoelectric actuator PA to a rated voltage (for example, 100 OV). Since the semiconductor element 2c is in a non-conductive state, the amount of leakage current passing through the semiconductor element 2c during charging is extremely small, and therefore the piezoelectric actuator PA is discharged in the direction of the broken line in FIG. 1 via the discharge circuit C. The amount can be made extremely small.

As a result, piezoelectric actuator PA can be charged with low power consumption and in a short time.

(2) Stop outputting the trigger signal from the charge retention control unit D to the base of the transistor 2a, and make both the transistor 2a and the semiconductor element 2c non-conductive. In this state, since the semiconductor element 2c is in a non-conductive state, the amount of discharge of the piezoelectric actuator PA in the direction of the broken line in FIG. 1 via the discharge circuit C can be made extremely small as in the case during charging. I can do it. Therefore, it is possible to maintain the charge on the piezoelectric actuator for a long time without discharging the piezoelectric actuator.

(2) By outputting a trigger signal from the discharge control unit L-D to the base of the semiconductor element 2c in the discharge circuit C, the semiconductor element 2c is made conductive. As a result, the resistor IC of the discharge circuit C
A current flows in the direction of the broken line through the semiconductor element 2C, and the piezoelectric actuator PA is discharged. In order to prevent discharge of the piezoelectric actuator during charging, it is not necessary to install an excessive resistance in the discharge circuit C, and the resistance value of the resistor IC is set to an appropriate value. This ensures quick discharge.

Although the present invention has been described in detail above, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and that various modifications can be made within the scope of the invention described in the claims. For example, it is also possible to use an MO3 type FET, a transistor, etc. as the semiconductor element, as long as it satisfies the voltage resistance and leakage current amount. In this case, in order to further reduce the leakage current amount of the semiconductor element during charging and charge retention, that is, the amount of discharge of the piezoelectric actuator, it is preferable to make the chip area as small as possible.

(Effects of the Invention) As explained above, in the present invention, a booster circuit,
In a piezoelectric actuator drive device consisting of a charging circuit that flows current only in the direction of charging the piezoelectric actuator, and a discharging circuit, a semiconductor element for discharging is disposed in the discharging circuit, so that the piezoelectric actuator is By bringing the semiconductor element in the discharge circuit into a non-conductive state, the discharge of the piezoelectric actuator via the discharge circuit at this time can be made extremely small. Therefore, the present invention provides a drive circuit for a piezoelectric actuator that has low power consumption and can perform charging and discharging in a short time.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a driving device for a piezoelectric actuator according to an embodiment of the present invention. FIG. 2 is a time chart of the operation of the drive device of FIG. 1. FIG. 3 is a circuit diagram of a conventional piezoelectric actuator drive device. PA...piezoelectric actuator, 1...piezoelectric actuator drive device, A...boost circuit, B...charging circuit, C...discharging circuit, D...control unit, 2c...semiconductor element. Figure 2

Claims (1)

[Claims] A piezoelectric actuator drive device comprising a booster circuit, a charging circuit that allows current to flow only in the direction of charging the piezoelectric actuator, and a discharge circuit, characterized in that a semiconductor element for discharging is disposed in the discharge circuit. A drive device for a piezoelectric actuator.