JPH04209000A - Piezoelectric element driving circuit - Google Patents

Abstract

PURPOSE:To further make small the peak current than one of the DC/DC converter type piezoelectric element driving circuit and to reduce the size of an inductance by driving the piezoelectric element through a third switching element which is connected to the point located between the inductance and a second switching element which are the parts of the circuit consists of a first switching element, the inductance and the second switching element connected in series. CONSTITUTION:A power supply E, the first switching element S1, the inductance L and the second switching element S2 are connected in series to form the circuit. The third switching element S3 is connected to the point between the inductance L and the second switching element S2 and this third switching element and the piezoelectric element 1 are connected in series. When a transistor Q1 and a transistor Q2 are turned on simultaneously and turning off the transistor Q2 when the current value reaches to a certain value, a current flows to the piezoelectric element 1 through a diode D3 and the transistor Q1 and a voltage Vc drives the piezoelectric element 1. To discharge the piezoelectric element 1, turn on a transistor Q3 and the voltage Vc becomes low and when it reaches zero, a current 12 flows through a diode D2 and the energy is returned to the power supply E. Thus, the peak current becomes smaller than the DC/DC converter type piezoelectric element driving circuit and the size of the inductance becomes small.

Description

[Detailed description of the invention]

[00011

[Field of Industrial Application] The present invention relates to a piezoelectric element drive circuit, and more particularly to a piezoelectric element drive circuit using inductance. The present invention also relates to a piezoelectric element drive circuit using a DC/DC conversion method. [0002] FIG. 15 shows a conventional piezoelectric element drive circuit using a resonant circuit system, and FIG. 16 shows a conventional piezoelectric element drive circuit using a DC/DC conversion system. In the case of a resonant circuit type piezoelectric element drive circuit, as shown in FIG. 15, two parallel transistors Q1 with diodes connected in opposite directions are used.
, O2, which drive the piezoelectric element 1 via an inductance L. That is, during charging, one transistor Q1 is turned off.
N and charges the piezoelectric element 1. During discharging, the other transistor Q2 is turned on to discharge the piezoelectric element 1. [0003] In the case of a DC/DC conversion type piezoelectric element drive circuit, as shown in FIG. 16, there are two transistors Q1 and O2 connected in series, and an inductance L is connected between these transistors. be. The piezoelectric element 1 is charged by setting one transistor Q1 to 0N10FF, and the other transistor Q2 is set to 0N10F.
By performing F, the piezoelectric element 1 is discharged. [0004] Also, FIG. 17 shows a DC/D diagram corresponding to FIG. 16.
This is a conventional example of a C conversion type piezoelectric element drive circuit. 16th
It is shown that other suitable switches may be used in place of the transistors shown. [0005]

[Problem to be Solved by the Invention] In the case of the conventional resonant circuit type piezoelectric element drive circuit shown in FIG. 15, the voltage for driving the piezoelectric element has a relationship of Vc = 2E, so E can be set freely. I can't. Also, FIG. 16 or 17
In the case of the conventional piezoelectric element drive circuit using the DC/DC conversion method shown in , the transistor Q2 is set to 0N10FF to discharge the piezoelectric element 1, but the energy for charging the piezoelectric element 1 is once transferred to the inductance. Because it needs to be stored, the peak current increases and the inductance L
There is a problem in that the size of the core has to become large. [0006] Therefore, the problem of the present invention is that the peak current is D
It is smaller than the C/DC conversion type piezoelectric element drive circuit,
Moreover, the present invention provides a piezoelectric element drive circuit that can reduce the size of inductance L. [0007]

[Means for Solving the Problems] In order to solve such problems, the first invention provides a power source (E), a first switching element (S1), an inductance (L), and a second switching element (E). The inductance (L) and the second switch element (S2) are connected in series with the switch element (S2).
) A piezoelectric element driving device is provided, characterized in that the piezoelectric element (1) is configured to be driven through a third switch element (S3) between the piezoelectric element (1) and the third switch element (S3). [0008] Further, in the second invention, in a piezoelectric element drive circuit using a DC/DC conversion method having one inductance (L) and two switch elements (S1, S2), a power source (E), an inductance ( L), in the circuit leading to the first switch element (S1), the inductance (
The piezoelectric element (1) and the second switching element (S2) are connected in series, bypassing the switching element (L).
There is provided a piezoelectric element drive circuit characterized in that the transistor (Q1) of S1) is grounded. [0009]

[Operation] In the first invention, as shown in FIG. 2(a), the transistor Q1 and the transistor Q2 are simultaneously turned ON1 and
When the transistor Q2 is turned off when a certain current value is reached, a current flows to the piezoelectric element 1 through the diode D3 and the transistor Q1, and the voltage Vc rises as shown in FIG. ON1, when the transistor Q2 is turned off when a certain current value is reached, a current flows to the piezoelectric element 1 through the diode D3 and the transistor Q1, the voltage Vc rises as shown, and the piezoelectric element 1 is driven. [00101 As shown in FIG. 2(b), when discharging the piezoelectric element 1, when the transistor Q3 is turned on, the voltage Vc
When the voltage Vc decreases and becomes zero, a current 2 flows through the diode D2 and the energy is returned to the power source E side. Further, in the second invention, when driving (charging) the piezoelectric element 1, if the transistor Q1 is turned on and then turned off, the currents I+ and I2 become as shown in FIG. It is powered (charged) by During discharging, as shown in FIG. 7(b), the transistor Q
2 is turned off for a certain period of time, the piezoelectric element 1 is discharged. [00111

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a first embodiment of a piezoelectric element drive circuit of the present invention. The first switching element S1 includes a transistor Q1 and a diode D1 connected in parallel to the transistor. The first switching element S1 includes a transistor Q1 and a diode D1 connected in parallel to the transistor. Similarly, the second switch element S2 and the third switch element S3 are also connected to transistors O2 and Q3, respectively.
and diodes D2 and D3 connected in parallel to these transistors. [00121 In a circuit in which a power supply E, a first switch element S1, an inductance L, and a second switch element S2 are connected in series, a third switch is connected between the inductance L and the second switch element S2. The third switch element S3 is connected, and the piezoelectric element 1 is connected in series with this third switch element. As shown in FIG. 2(a), when transistor Q1 and transistor Q2 are simultaneously turned ON1 and transistor Q2 is turned OFF when a certain current value is reached, current flows to piezoelectric element 1 through diode D3 and transistor Q1, and voltage Vc rises as shown in the figure, and the piezoelectric element 1 is driven. [0013] As shown in FIG. 2(b), when discharging the piezoelectric element 1, when the transistor Q3 is turned on, the voltage Vc
When the voltage Vc drops to zero, a current I2 flows through the diode D2, and the energy is returned to the power source E side. As a result, the peak current can be made smaller than that of a piezoelectric element drive circuit using the DC/DC conversion method, and the size of the inductance L can be made smaller. [00141 FIG. 3 shows a second embodiment of the piezoelectric element drive circuit of the present invention. The difference from Embodiment 1 is that the third switching element S3 in Embodiment 1 is arranged in parallel with the first switching element S1 on the side closer to the power supply E than the inductance, and the transistors and diodes of these switching elements are This is the point where these are connected in series. The effects are the same as in Example 1. [00151 FIG. 4 shows a third embodiment of the piezoelectric element drive circuit of the present invention. The difference from Example 2 is that the first switching element S1 and the third switching element S3 are arranged closer to the piezoelectric element 1 than the inductance. The effect is the same as that of Example 1 or Example 2. FIG. 5 shows a fourth embodiment of the piezoelectric element drive circuit of the present invention. The difference from Example 1 is that a thyristor THI is used instead of the transistor of the switching element S1. Thyristor TH
Ql can be used as the pulse to turn on 1. Compared to other circuits using transistors, this has the advantage that only two drive signal lines are required. [0016] Similarly, in the first to third embodiments described above, a Mos FET can be used instead of a transistor. Embodiment 5 of the present invention is shown in FIG. 6, which shows a DC/D converter having one inductance and two switching elements.
This is a piezoelectric element drive circuit using the C conversion method. Power supply E,
In the circuit that leads to the first switching element 81, the inductance L is bypassed and the piezoelectric element 1
and a second switch element S2 are connected in series. Transistor Q1 of switch element S1 is grounded. [0017] When driving (charging) the piezoelectric element 1, if the transistor Q1 is turned on and then turned off, the current I+
, I2 are as shown in Fig. 7(a), and piezoelectric element 1
is driven (charged) by voltage Vc. Further, during discharging, as shown in FIG. 7(b), when the transistor Q2 is turned off for a certain period of time, the piezoelectric element 1 is discharged. [0018] FIG. 8 is a circuit similar to the embodiment of FIG. 6, in which one switch element S1 in FIG. 6 is placed closer to the power source E than the inductance. The embodiments shown in FIGS. 6 to 8 have the advantage that an NPN transistor can be used as one transistor, resulting in lower costs and simpler configuration of the drive circuit (on the NPN side). [00191 FIG. 9 shows a piezoelectric element drive circuit, which turns off the discharging transistor when the voltage falls below zero during discharge of the piezoelectric element 1, that is, when the drive pulse during driving is too long. The piezoelectric element is charged/discharged by turning transistors Q1 and Q2 alternately 0N10FF (Figure 10).
, if the ON time of transistor Q2 is long, the voltage VC will swing from positive to negative (FIG. 11). Therefore, the transistor Q3 is used to prevent the voltage Vc from becoming negative. (Figure 12). [00201 FIGS. 13 and 14 are modifications of the embodiment shown in FIG. 9. The same effects as the embodiment shown in FIG. 9 are achieved. According to the embodiments shown in FIGS. 9 and 13 and 14, it is necessary to adjust the ON time of Q2 in the piezoelectric element 1 due to variations in the transformer.
Since the voltage Vc can be discharged regardless of the time, the control circuit can be easily constructed. [0021]

According to the present invention as described above, the peak current is smaller than that of a piezoelectric element drive circuit based on the DC/DC conversion method, so that the core size of the inductance L is reduced. Furthermore, the power supply voltage E can be freely selected.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a first embodiment of a piezoelectric element drive circuit of the present invention.

FIG. 2 is a schematic diagram showing the operation of the first embodiment. 1. FIG. 3 is a schematic diagram of a second embodiment of the piezoelectric element drive circuit of the present invention, similar to the embodiment of FIG.

4 is a schematic diagram of a third embodiment of the piezoelectric element drive circuit of the present invention, similar to the embodiment of FIG. 3; FIG.

FIG. 5 is a schematic diagram of a fourth embodiment of the piezoelectric element drive circuit of the present invention.

FIG. 61 is a schematic diagram of an embodiment of a piezoelectric element drive circuit of the present invention using a DC/DC conversion method. FIG. 7 is a diagram showing the operation of the piezoelectric element drive circuit according to the embodiment of FIG. 6;

FIG. 8 is a schematic diagram of a modification of the embodiment of FIG. 6;

FIG. 9 is a schematic diagram of another embodiment of the piezoelectric element drive circuit of the present invention.

FIG. 10 is a diagram for explaining the operation of the embodiment of FIG. 9;

FIG. 11 is a diagram for explaining the operation of the embodiment of FIG. 9;

FIG. 12 is a diagram for explaining the operation of the embodiment of FIG. 9;

13 is a schematic diagram of a variant similar to the embodiment of FIG. 9; FIG.

14 is a schematic diagram of another variant similar to the embodiment of FIG. 9; FIG.

FIG. 15 is a schematic diagram of a piezoelectric element drive circuit using a conventional resonant circuit method.

FIG. 16 is a schematic diagram of a piezoelectric element drive circuit using a conventional DC/DE conversion method.

FIG. 17 is a schematic diagram of another piezoelectric element drive circuit using the conventional DC/DE conversion method.

[Explanation of symbols]

1 Piezoelectric element S Switch element Q Transistor D Diode E Power supply Vc voltage L Inductance

[Figure 7]

Claims (2)

[Claims] Claim 1: A power source (E) and a first switch element (S1
), inductance (L), and second switch element (
S2) is connected in series to drive the piezoelectric element (1) from between the inductance (L) and the second switch element (S2) via the third switch element (S3). A piezoelectric element drive circuit characterized in that it is configured as follows. 2. In a piezoelectric element drive circuit using a DC/DC conversion method having one inductance (L) and two switching elements (S1, S2), a power source (E), an inductance (L), a first In the circuit leading to the switch element (S1), the piezoelectric element (1) and the second switch element (S2) are connected in series, bypassing the inductance (L), and the transistor (S1) of one switch element (S1) is connected in series.
Q1) is a piezoelectric element drive circuit characterized by being grounded.