SIDM Piezo Actuator Driving Device and Method

Abstract

To provide a smooth impact drive mechanism (SIDM) piezo actuator driving device which reduces heat generation and power consumption by removing rush current and improves vibration speed.SOLUTION: A piezo actuator driving device 100 includes: a first main switch MT1 and a second main switch MT2 connected in series between first voltage and second voltage and having contacts connected to one end of an inductor LR; a third main switch MT3 and a fourth main switch MT4 connected in series between the first voltage and the second voltage and having contacts connected to the other end of the inductor; and a first resonance switch RT1, a piezo actuator, and a second resonance switch RT2 connected in series between one end and the other end of the inductor. In a resonance period in which the first resonance switch and the second resonance switch are turned on, a resonance loop is formed by connection of the piezo actuator and the inductor, and energy previously charged in the inductor can be provided to the piezo actuator.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a piezoelectric actuator driving device and method, and more particularly, to a SIDM (Smooth Impact Drive Mechanism) piezoelectric actuator driving device and method capable of driving with a gentle piezoelectric actuator vibration method.

Background Art

[0002] FIG. 1 shows a driving circuit 50 of a conventional piezoelectric actuator.

[0003] Referring to FIG. 1, in a conventional piezoelectric actuator driving circuit 50, a piezoelectric actuator P z is charged through main switches MT1 and MT4 between power supplies 10 and 20 to an equivalent capacitor thereof. However, when resonance switches RT1 and RT2 are turned on, resonance occurs between a resonance inductor L R and the equivalent capacitor of the piezoelectric actuator P z to change the voltage polarity of the capacitor, and the main switches MT2 and MT3 on the opposite side are turned on to drive the piezoelectric actuator P z so as to reduce the magnitude of the initial inrush current flowing into the equivalent capacitor thereof. At this time, theoretically, when the resistance in the resonance circuits RT1 and RT2 and the inductor L R is 0, the voltage of the capacitor is charged with voltages having the same magnitude and opposite polarities. At this time, the maximum voltage (V) flowing into the capacitance (C) is given by the following formula according to the maximum current (i) of the inductance (L) of the resonance inductor L R and the capacitance (C) of the capacitor.

[0004]

Equation

[0005] However, due to the internal resistance of the resonance circuit switches RT1 and RT2 and the inductor L REnergy loss occurs due to internal resistance and the like, and due to such losses, the voltage of the opposite polarity flowing into the capacitor during resonance becomes lower than the magnitude of the voltage of the power supply 10. The lower the voltage of the opposite polarity of the capacitor, the larger the inrush current into the capacitor when turning on the main switches MT1, MT4 / MT2, MT3, and the magnitude of this current causes various problems such as large power loss and generation of EMI noise, z which deteriorates the driving operation of the piezo actuator P.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, the present invention has been devised to solve the above-described problems, and an object of the present invention is to provide a SIDM piezo actuator driving device and method that remove the inrush current to the piezo actuator, reduce heat generation and power consumption, and improve the vibration speed as the applied voltage increases.

[0007] Another object of the present invention is to provide a SIDM piezo actuator driving device and method capable of accurate displacement control by inserting an additional pulse for harmonic generation for applying a sawtooth wave (or triangular wave) advantageous for piezo actuator driving.

Means for Solving the Problems

[0008] First, to summarize the features of the present invention, a piezoelectric actuator driving device according to one aspect of the present invention for achieving the above object includes a first main switch and a second main switch connected in series between the first voltage and the second voltage, with a contact connected to one end of an inductor; a third main switch and a fourth main switch connected in series between the first voltage and the second voltage, with a contact connected to the other end of the inductor; and a first resonance switch, the piezoelectric actuator, and a second resonance switch connected in series between one end and the other end of the inductor. During a resonance period in which the first resonance switch and the second resonance switch are turned on, a resonance loop is formed by the connection of the piezoelectric actuator and the inductor, and the energy pre-charged in the inductor can be provided to the piezoelectric actuator.

[0009] Between the forward drive and the reverse drive for the piezoelectric actuator or between the reverse drive and the forward drive, before the formation of the resonance loop during the resonance period, among the first parasitic diode of the first resonance switch composed of a MOSFET and the second parasitic diode of the second resonance switch composed of a MOSFET, a parasitic diode in the current direction flowing through the inductor and a pre-loop formed by the turn-on of the other resonance switch are formed, and it can be driven to eliminate the discontinuity of the current flowing through the inductor at the subsequent moment of the resonance loop.

[0010] Between the forward drive and the reverse drive for the piezoelectric actuator or between the reverse drive and the forward drive, after the formation period of the resonance loop has passed, among the first parasitic diode of the first resonance switch composed of a MOSFET and the second parasitic diode of the second resonance switch composed of a MOSFET, a parasitic diode in the current direction flowing through the inductor and a post-loop formed by the turn-on of the other resonance switch are formed, and after the residual current is discharged from the inductor to the piezoelectric actuator, it can be driven so that the first resonance switch and the second resonance switch are turned off.

[0011] The piezoelectric actuator includes a drive rod coupled to a piezoelectric element and a slider inserted into the drive rod. By driving the piezoelectric element with a drive signal to drive the vibration of the drive rod, the position displacement of the slider can be controlled by the forward and backward movement of the slider due to stick-slip driving.

[0012] The first voltage may be the voltage on the output side of a forward diode connected to the source voltage.

[0013] A drive signal is input as a rectangular wave to both ends of the piezoelectric actuator. The forward or backward movement of the piezoelectric actuator vibration is determined by the magnitudes of the sum of the high intervals and the sum of the low intervals within one period of the drive frequency of the rectangular wave. It may include an additional pulse inserted for harmonic generation at the midpoint of the low interval within one period of the drive frequency.

[0014] Also, according to another aspect of the present invention, a piezoelectric actuator driving method for controlling the position displacement of a slider inserted into a drive rod by driving a piezoelectric element with a drive signal to drive the vibration of the drive rod coupled to the piezoelectric element is such that a drive signal for driving the piezoelectric actuator is input as a rectangular wave, and the forward or backward movement of the piezoelectric actuator vibration is determined by the magnitudes of the sum of the high intervals and the sum of the low intervals within one period of the drive frequency of the rectangular wave. It may include an additional pulse inserted for harmonic generation at the midpoint of the low interval within one period of the drive frequency.

[0015] The width of the additional pulse may be determined such that the ratio of the sum of the high intervals and the sum of the low intervals within one period of the drive frequency of the rectangular wave is determined in the range of 8.5:1.5 to 5.5:4.5.

[0016] And, according to another aspect of the present invention, a piezoelectric actuator driving method for a driving device that applies a first voltage and a second voltage to a first electrode and a second electrode of a piezoelectric actuator, respectively, for forward driving, and applies opposite voltages for reverse driving, includes: a first main switch and a second main switch that are connected in series between the first voltage and the second voltage and whose contacts are connected to one end of an inductor; a third main switch and a fourth main switch that are connected in series between the first voltage and the second voltage and whose contacts are connected to the other end of the inductor; and a first resonance switch, the piezoelectric actuator, and a second resonance switch that are connected in series between one end and the other end of the inductor. Using the driving device, (A) turning on the first main switch and the fourth main switch for the forward driving; (B) turning on the third main switch and the second main switch for the reverse driving; and (C) including a resonance step of turning on the first resonance switch and the second resonance switch between the forward driving and the reverse driving. In the resonance step, a resonance loop is formed by connecting the piezoelectric actuator and the inductor, and the energy previously charged in the inductor can be provided to the piezoelectric actuator.

Advantages of the Invention

[0017] According to the piezoelectric actuator driving device and method of the present invention, it has a structure in which a current is charged in an inductor, and when the current reaches a sufficient level, the resonance switch is turned on to apply a voltage to the piezoelectric actuator equivalent capacitor. For operations after the initial operation, the current in the inductor is replenished by only the amount of energy consumed in the resonance circuit, and it is driven in a form that replenishes the insufficient voltage at both ends of the capacitor with the changed polarity.

[0018] Accordingly, 1) from the perspective of energy, in the conventional invention, in order to replenish the energy consumed when driving a resonant circuit to change the polarity of a piezoelectric actuator equivalent capacitor, a voltage was applied to the capacitor to induce an inrush current. In contrast, in the present invention, the current of the inductor is replenished only by the amount of energy consumed in the resonant circuit. However, due to the nature of the current in the inductor, even when a voltage is applied across the inductor, the current gradually increases from 0. Therefore, unlike when a voltage source is directly applied to the capacitor, there is an advantage that no peak current flows. For example, by removing the inrush current to the piezoelectric actuator in this way, heat generation and power consumption can be reduced. For example, the power consumption can be reduced to about 1 / 10 of the existing driving method and 1 / 3 of the existing eco-driving method when driven by the same voltage.

[0019] 2) Also, by adjusting the magnitude of the current applied to the inductor, a voltage higher than the power supply voltage can be applied across the equivalent capacitor of the piezoelectric actuator, and the voltage input to the piezoelectric actuator can be increased up to 2 to 3 times the maximum (for example, power supply voltage 3.3V -> applied 8V) without a separate DC-DC converter. This has the advantage of being able to improve the vibration speed of the piezoelectric actuator.

[0020] 3) And in the present invention, for the application of a sawtooth wave (or triangular wave) that is advantageous for driving the piezoelectric actuator, additional pulses for harmonic generation are inserted to enable accurate displacement control.

Brief Description of the Drawings

[0021] The accompanying drawings, which are included as a part of the detailed description to assist in understanding the present invention, provide examples of embodiments of the present invention and explain the technical concept of the present invention together with the detailed description.

Figure 1

Figure 2

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Figure 6

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Figure 8

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Figure 10

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Figure 12

Modes for Carrying Out the Invention

[0022] The present invention will be described in detail below with reference to the accompanying drawings. At this time, in the drawings, the same reference numerals are used for the same components as much as possible. Also, detailed descriptions of functions and / or configurations that are already known are omitted. The content disclosed below focuses on the parts necessary for understanding the operations according to various embodiments, and descriptions of elements that may obscure the gist of the description are omitted. Also, some components in the drawings may be exaggerated, omitted, or shown schematically. The sizes of the components do not fully reflect the actual sizes, and therefore, the content described herein is not limited by the relative sizes or intervals of the components depicted in each drawing.

[0023] When describing embodiments of the present invention, if it is determined that specific descriptions of known technologies related to the present invention may obscure the gist of the present invention, the detailed descriptions thereof are omitted. And the terms described hereinafter are terms defined in consideration of the functions in the present invention, and these may vary depending on the intentions or conventions of users, operators, etc. Therefore, the definitions should be given based on the content throughout this specification. The terms used in the detailed description are merely for explaining the embodiments of the present invention and are by no means for limiting. Unless otherwise specified, singular expressions include the meanings of plural forms. In this description, expressions described as "including" or "comprising" are for indicating a certain characteristic, number, step, operation, element, part thereof, or combination, and should not be construed as excluding the existence or possibility of one or more other characteristics, numbers, steps, operations, elements, part thereof, or combination other than those described.

[0024] Also, terms such as first and second may be used to describe various components, but these components are not limited by the terms such as first and second, and these terms are only used for the purpose of distinguishing one component from another.

[0025] Figure 2 is a diagram illustrating the components of the piezoelectric actuator 150 of the present invention.

[0026] Referring to FIG. 2, the piezoelectric actuator 150 of the present invention may include a piezoelectric element 10, a drive rod 20 coupled to the piezoelectric element 10, and a slider 30 inserted into the drive rod 20. Such a piezoelectric actuator 150 is an element that can control the vibration of the drive rod 20 by a PWM drive signal V to cause a displacement of the position of the slider 30, and is applied in various fields for precise motion control, such as focus adjustment of a camera module and automotive fuel injection.

[0027] For example, if a PWM drive signal V is applied to the piezoelectric element 10, the piezoelectric element 10 can vibrate the drive rod 20 in the forward or backward direction by the drive signal V. At this time, the slider 30 is fitted to the drive rod 20 and coupled so as to slide. However, if the movement of the drive rod 20 in the forward or backward direction is controlled to be slow, since the frictional force between the drive rod 20 and the slider 30 is greater than the inertial force of the slider 30, the drive rod 20 and the slider 30 are configured to move together as one (referred to as a stick state). If the movement of the drive rod 20 in the forward or backward direction is controlled to be faster than a threshold value, since the frictional force between the drive rod 20 and the slider 30 is smaller than the inertial force of the slider 30, the slider 30 remains in its original position and the drive rod 20 is configured to move smoothly (referred to as a slip state). By appropriately controlling the vibration speed of the drive rod 20 in the forward or backward direction in such a manner, it becomes possible to control the relative position displacement of the slider 30.

[0028] FIG. 3 is a diagram for explaining a piezoelectric actuator driving device 100 according to an embodiment of the present invention.

[0029] Referring to FIG. 3, a piezoelectric actuator driving device 100 according to an embodiment of the present invention includes, for driving a piezoelectric actuator 150, a first main switch MT1, a second main switch MT2, a third main switch MT3, a fourth main switch MT4, a first resonance switch RT1, and an inductor L Rand includes a circuit having a second resonance switch RT2. The piezo actuator driving device 100 may further include a forward diode BD connected between the source voltage 190 and the first voltage 110.

[0030] The switches, namely, the first main switch MT1, the second main switch MT2, the third main switch MT3, the fourth main switch MT4, the first resonance switch RT1, and the second resonance switch RT2 may be elements such as MOSFETs (Metal Oxide Silicon Field Effect Transistors), IGBTs (Insulated Gate Transistors). In this case, as shown in the figure, parasitic diodes D of the first main switch MT1, the second main switch MT2, the third main switch MT3, and the fourth main switch MT4, which are formed in manufacturing, and parasitic diodes D1 and D2 of the first resonance switch RT1 and the second resonance switch RT2 may be included.

[0031] Also, these switches may be composed of BJT (Bipolar Junction Transistor) elements. In this case, the parasitic diodes D of the first main switch MT1, the second main switch MT2, the third main switch MT3, and the fourth main switch MT4 are not included, and the parasitic diodes D1 and D2 of the first resonance switch RT1 and the second resonance switch RT2 are not included either.

[0032] As described below, unless otherwise specified, when the switch is composed of BJT elements, it may be driven without the parasitic diodes D, D1, and D2 as described above. Of course, unless otherwise specified, the switch may be composed of a combination of IGBTs, MOSFETs, BJTs, etc.

[0033] However, the resonance loop circuit (RT1, RT2, L) of the present invention including the piezo actuator 150 R,150) operating mode, even when the switch is composed of BJT elements, a diode (hereinafter referred to as the forward diode) D1 connected in parallel to the first resonant switch RT1 and a diode (hereinafter referred to as the reverse diode) D2 connected in parallel to the second resonant switch RT2 may be added. Therefore, in the description of this operating mode, the case where the forward diode D1 and the reverse diode D2 are added and driven will be described.

[0034] As described above, depending on the element structure of the switch, the gate, drain / source terminals of the IGBT / MOSFET element can correspond to the base, emitter / collector (or collector / emitter) terminals of the BJT element.

[0035] As shown in FIG. 2, the piezoelectric actuator 150 is a piezoelectric element that vibrates by a drive signal when a drive signal V is applied to both end electrodes, and is applied in various fields for precise motion control such as focus adjustment of a camera module and automotive fuel injection. The piezoelectric actuator 150 may be interpreted as an electrical equivalent circuit including an inherent parasitic inductance (Lp), a charge capacitance (Cp), a parasitic resistance (Rp) corresponding to a mechanical load, and a parasitic stray capacitance (Cs) due to the influence of electrodes and surrounding conductors. For example, the resonant frequency is determined by the inductance (Lp) and the capacitance (C = Cp + Cs). If the mechanical load is small, the resistance (Rp) decreases, and if the mechanical load is large, the resistance (Rp) increases.

[0036] Hereinafter, when a first voltage 110 (for example, 3.3 V) and a second voltage 120 (for example, ground voltage) are applied to both end electrodes of the piezo actuator 150, that is, the first electrode (for example, the left electrode in FIG. 3) and the second electrode (for example, the right electrode in FIG. 3), it is referred to as forward driving (for example, driving that vibrates to the right in FIG. 2). Further, when opposite voltages, that is, the second voltage 120 (for example, ground voltage) and the first voltage 110 (for example, 3.3 V) are applied to both end electrodes of the piezo actuator 150, that is, the first electrode (for example, the left electrode in FIG. 3) and the second electrode (for example, the right electrode in FIG. 3), it is referred to as reverse driving (for example, driving that vibrates to the left in FIG. 2).

[0037] As shown in FIG. 3, the first main switch MT1 and the second main switch MT2 are connected in series between the first voltage 110 and the second voltage 120, and the contact thereof is the inductor L R and is connected to one end of.

[0038] The third main switch MT3 and the fourth main switch MT4 are connected in series between the first voltage 110 and the second voltage 120, and the contact thereof is the inductor L R and is connected to the other end of.

[0039] The first resonance switch RT1, the piezo actuator 150, and the second resonance switch RT2 are connected in series between the first electrode and the second electrode of the piezo actuator 150.

[0040] As described above, the piezo actuator driving device 100 may further include a forward diode BD connected between the source voltage 190 and the first voltage 110. At this time, the first voltage 110 is the voltage on the output side of the forward diode BD connected to the source voltage 190. When the diode BD is ideal, the first voltage 110 and the source voltage 190 may be the same, but there may be a slight difference (for example, 0.7 V) substantially. The diode BD, when either one of both ends of the inductor L R is larger than the first voltage 110, together with the operation of the parasitic diodes D1 / D2, the inductor LR It is possible to prevent a short circuit between the [component] and the source voltage 190 and leakage of current.

[0041] FIG. 4 is a timing diagram for explaining the operation of the drive device 100 of FIG. 3.

[0042] FIG. 5 is a reference diagram for explaining the states of the forward drive and the reverse drive of the drive device 100 of FIG. 3.

[0043] Referring to FIGS. 4 and 5, first, during periods t1 and t2 in FIG. 4, as shown in 410 of FIG. 5, by control signals S(MT1) and S(MT4) of a control device (not shown) applied as a logical high voltage to respective gate terminals, the first main switch MT1 and the fourth main switch MT4 are turned on (MT3 / MT2 / RT1 / RT2 are turned off), and forward driving of the piezo actuator 150 (for example, driving that vibrates to the right in FIG. 2) may be performed.

[0044] Also, during periods t6 and t7, as shown in 430 of FIG. 5, by control signals S(MT3) and S(MT2) of the control device applied as a logical high voltage to respective gate terminals, the third main switch MT3 and the second main switch MT2 are turned on (MT1 / MT4 / RT1 / RT2 are turned off), and reverse driving of the piezo actuator 150 (for example, driving that vibrates to the left) may be performed.

[0045] In the present invention, between such forward driving (MT1, MT4 turned on) and reverse driving (MT3, MT2 turned on), during period t3 or t8 (resonance period) in FIG. 4, as shown in 420 or 440 of FIG. 5, the first resonance switch RT1 and the second resonance switch RT2 are turned on to cause resonance. This is performed when control signals S(RT1) and S(RT2) of the control device applied to respective gate terminals are applied as a logical high voltage. That is, during the resonance period, a resonance loop is formed by the connection of the piezo actuator 150 and the inductor L R to form a resonance loop due to the connection of the inductor L RThe energy previously charged is provided to the piezoelectric actuator 150 so that it can be driven. Also, the inductor L R By adjusting the magnitude of the current applied to, during the resonance period, the voltage of the inductor L R is applied to the piezoelectric actuator 150, and a voltage higher than the power supply voltage 110 can be applied across the equivalent capacitor of the piezoelectric actuator 150. Thus, there is an advantage that the voltage input to the piezoelectric actuator 150 can be increased up to 2 to 3 times maximum (for example, when the power supply voltage is 3.3 V -> applied 8 V) without a separate DC-DC converter, and thereby the vibration speed of the piezoelectric actuator 150 can be improved.

[0046] In the present invention, by placing the resonance period in which the first resonance switch RT1 and the second resonance switch RT2 are turned on between the forward drive (MT1 / MT4 turn-on) and the reverse drive (MT3 / MT2 turn-on), or between the reverse drive (MT3 / MT2 turn-on) and the forward drive (MT1 / MT4 turn-on) as described above, a resonance loop circuit (RT1, RT2, L R , 150) in which resonance occurs is formed so that the resonance loop is formed, and the polarity direction of the capacitance at both ends of the piezoelectric actuator 150 (see 430 and 440 in FIG. 5) can be charged in advance in the driving direction.

[0047] That is, when the first resonance switch RT1 and the second resonance switch RT2 are turned on after the forward drive (MT1, MT4 turn-on) and before the reverse drive (MT3, MT2 turn-on), a resonance loop is formed by the piezoelectric actuator 150 and the inductor L R and resonance (resonance period T = 2π(LC)) occurs between the capacitance (C) of the piezoelectric actuator 150 and the inductance (L) of the inductor L R 1 / 2)(For example, when ignoring the parasitic inductance (Lp)), the capacitance polarities at both ends of the piezoelectric actuator 150 can be pre-charged in the negative drive direction (for example, -+)

[0048] Also, if the first resonance switch RT1 and the second resonance switch RT2 are turned on after the negative drive (MT3, MT2 turn on) and before the positive drive (MT1, MT4 turn on), a resonance loop is formed between the piezoelectric actuator 150 and the inductor L R and the capacitance (C) of the piezoelectric actuator 150 and the inductance (L) of the inductor L R generate resonance (resonance period T = 2π(LC) 1 / 2 ), and the capacitance polarities at both ends of the piezoelectric actuator 150 can be pre-charged in the positive drive direction (for example, +-).

[0049] In the present invention, during the time other than the resonance period after the positive drive (MT1, MT4 turn on) and the negative drive (MT3, MT2 turn on), the control signals S(RT1) and S(RT2) of the control device are provided as a logical low voltage, and the first resonance switch RT1 and the second resonance switch RT2 are turned off. However, there is a period during which either one of the first resonance switch RT1 and the second resonance switch RT2 is turned on for a predetermined time in the pre-loop period before the resonance period and the pre-loop period after the resonance period.

[0050] That is, in the pre-loop period t2 that partially overlaps with the positive drive (MT1, MT4 turn on) before the resonance period t3, the first resonance switch RT1 is turned on in advance. After the resonance period t3, the second resonance switch RT2 is turned off, but a post-loop period t4 during which the turn-on of the first resonance switch RT1 is maintained for a predetermined time may be included.

[0051] Also, even in the negative direction drive (MT3, MT2 turned on), the second resonance switch RT2 is pre - turned on during a pre - loop period t7 that partially overlaps with the negative direction drive (MT3, MT2 turned on) before the resonance period t8. After the resonance period t8, the first resonance switch RT1 is turned off, but a post - loop period t9 may be included during which the turn - on of the second resonance switch RT2 is maintained for a predetermined time.

[0052] Furthermore, by pre - turning on the first resonance switch RT1 during such a pre - loop period t2, before the resonance loop is formed during the resonance period, the second parasitic diode D2 in the current direction flowing through the inductor L R and a pre - loop is formed by the turn - on of the first resonance switch RT1 on the other side of the resonance circuit, and it can be driven so as to eliminate the discontinuity of the current flowing through the inductor L R at the moment of the subsequent resonance loop. That is, using the second parasitic diode D2 of the second resonance switch RT2 composed of an element having a parasitic diode such as a MOSFET or IGBT, it can be driven so as to eliminate the discontinuity of the current flowing through the inductor L R at the moment of the resonance loop.

[0053] Also, during such a post - loop period t4, by maintaining the turn - on state of the first resonance switch RT1 for a predetermined time, even after the formation period of the resonance loop has passed, the second parasitic diode D2 in the current direction flowing through the inductor L R and a post - loop is formed by the turn - on of the first resonance switch RT1 on the other side of the resonance circuit. After discharging the residual current from the inductor L R to the piezo - actuator 150, it can be driven so that the first resonance switch RT1 and the second resonance switch RT1 are turned off. That is, using the second parasitic diode D2 of the second resonance switch RT2 composed of an element having a parasitic diode such as a MOSFET or IGBT, after the resonance loop, for a predetermined time, the inductor L RResidual current can be discharged from the piezo actuator 150.

[0054] Similarly, by pre-turning on the second resonant switch RT2 during the pre-loop period t7, before the resonant loop is formed during the resonant period, the inductor L R forms a pre-loop due to the turn-on of the first parasitic diode D1 in the current direction flowing through it and the turn-on of the second resonant switch RT2 on the other side of the resonant circuit. Subsequently, at the moment of the resonant loop, the inductor L R can be driven to eliminate the discontinuity of the current flowing through it. That is, using the first parasitic diode D1 of the first resonant switch RT1 composed of an element having a parasitic diode such as a MOSFET or IGBT, at the moment of the resonant loop, the inductor L R can be driven to eliminate the discontinuity of the current flowing through it.

[0055] Also, similarly, during the post-loop period t9, by maintaining the turn-on state of the second resonant switch RT2 for a predetermined period, even after the formation period of the resonant loop has passed, the inductor L R forms a post-loop due to the turn-on of the first parasitic diode D1 in the current direction flowing through it and the turn-on of the second resonant switch RT2 on the other side of the resonant circuit. After discharging the residual current from the inductor L R to the piezo actuator 150, the first resonant switch RT1 and the second resonant switch RT1 can be driven to turn off. That is, using the first parasitic diode D1 of the first resonant switch RT1 composed of an element having a parasitic diode such as a MOSFET or IGBT, after the resonant loop, the residual current from the inductor L R to the piezo actuator 150 can be discharged for a predetermined time.

[0056] On the one hand, as also described in FIG. 2, the piezo actuator 150 includes a drive rod 20 coupled to the piezo element 10 and a slider 30 inserted into the drive rod 20. By driving the piezo element 10 with a drive signal V to drive the vibration of the drive rod 20, the displacement of the slider 30 over time can be controlled by the forward and backward movement of the slider 30 due to stick-slip driving.

[0057] The drive signal V may be a signal applied to both ends of the piezo actuator 150 by control signals S(MT1), S(MT2), S(MT3), S(MT4) of a control device (not shown). Such a drive signal is input as a rectangular wave to both ends of the piezo actuator 150, and the forward or backward vibration of the piezo actuator 150 is determined by the magnitudes of the sum of the high intervals and the sum of the low intervals within one cycle of the drive frequency of the rectangular wave. As will be described later, by inserting an additional pulse at the midpoint of the low interval within one cycle of the drive frequency, a sawtooth wave (or triangular wave) advantageous for driving the piezo actuator 150 can be applied.

[0058] FIG. 6 is a diagram for explaining the drive signal V and displacement applied to the piezo actuator 150 of the present invention.

[0059] Referring to FIG. 6, for example, if a rectangular wave PWM drive signal V is applied to the piezoelectric element 10, the piezoelectric element 10 can vibrate the drive rod 20 in the forward or backward direction by the drive signal V. At this time, the slider 30 is fitted to the drive rod 20 and coupled so as to slide. However, if the movement of the drive rod 20 in the forward or backward direction is controlled to be slow, since the frictional force between the drive rod 20 and the slider 30 is larger than the inertial force of the slider 30, the drive rod 20 and the slider 30 are configured to move together as one (referred to as a stick state). If the movement of the drive rod 20 in the forward or backward direction is controlled to be faster than the threshold value, since the frictional force between the drive rod 20 and the slider 30 is smaller than the inertial force of the slider 30, the slider 30 remains in its original position and the drive rod 20 is configured to move smoothly (referred to as a slip state). By such a method, it becomes possible to appropriately control the vibration speed of the drive rod 20 in the forward or backward direction and to control the relative position displacement of the slider 30.

[0060] That is, the forward or backward vibration of the piezoelectric actuator 150 may be determined by the magnitudes of the sum of the high intervals and the sum of the low intervals within one period of the driving frequency of the rectangular wave of the driving signal V. As shown in FIG. 6, the case where the magnitudes of the sum of the high intervals and the sum of the low intervals within one period of the driving frequency of the rectangular wave of the driving signal V are 7:3 is exemplified. In the high interval of the rectangular wave of the driving signal V, as shown in the same figure, the piezoelectric element 10, that is, the displacement (L) of the driving rod 20 with time (small gradient) causes the driving rod 20 and the slider 30 to move forward at a relatively slow speed. In the low interval of the rectangular wave of the driving signal V, as shown in the same figure, the piezoelectric element 10, that is, the generation of the displacement (L) of the driving rod 20 in the opposite direction (large gradient) causes the driving rod 20 to move backward at a high speed, and the position of the slider 30 can be increasingly displaced in the forward direction (610). In order to cause such displacement of the slider 30, in addition to the case where the magnitude ratio of the sum of the high intervals and the sum of the low intervals within one period of the driving frequency of the rectangular wave of the driving signal V is 7:3, the duty ratio may be determined in the range of 8.5:1.5 to 5.5:4.5 (that is, as A:B, when A is a real number between 5.5 and 8.5, B = 10 - A). In particular, theoretically, if the magnitudes of the sum of the high intervals and the sum of the low intervals within one period of the driving frequency of the rectangular wave are 5:5, the displacement of the slider 30 cannot be caused and it can be located at the original position.

[0061] Thus, roughly speaking, when the magnitudes of the sum of the high intervals and the sum of the low intervals within one period of the driving frequency of the rectangular wave of the driving signal V are 7:3, forward displacement is obtained, and when they are 3:7, backward displacement is obtained. The waveform of the driving signal V may be generated as a sawtooth wave and applied to the piezoelectric element 10. However, in this case, a large voltage of several tens of volts or more is required, and an increase in power and additional components are required, so it is generally not a commonly used method.

[0062] FIG. 7 is an illustration of a board diagram for the transfer function of the piezoelectric actuator 150 of the present invention.

[0063] Referring to FIG. 7, as seen in the Bode diagram between the input and output when a rectangular drive signal V is input to the piezoelectric actuator 150, it appears as a system with a damping ratio close to 0 as in a second-order system. At this time, if the frequency of the input waveform (for example, 1 MHz) is appropriately selected and a rectangular wave having a duty ratio of 3:7, 7:3, or similar thereto is applied, higher-order harmonics of the fourth order or higher that interfere with the triangular wave are attenuated by the second-order system filter, and relatively large second- and third-order harmonics appear. Thus, the displacement (L) over time of the output end of the piezoelectric actuator 150, that is, the piezoelectric element 10 or the drive rod 20, can be obtained in the form of a triangular wave (see FIG. 6).

[0064] However, when adjusting the drive frequency, if the frequency is driven lower than the resonance frequency of the piezoelectric actuator 150 in order to obtain large second- and third-order harmonics, the fundamental wave decreases and a large amplitude cannot be obtained. On the other hand, if the frequency is increased near the resonance frequency in order to obtain a large amplitude, the attenuation of the second- and third-order harmonics becomes severe, and the desired displacement in the form of a triangular wave over time cannot be obtained at the output end of the piezoelectric actuator 150.

[0065] That is, as in the example of the drive signal (V') in FIG. 6, when a rectangular wave with severe attenuation of the second- and third-order harmonics and a gentle slope for both is applied as the drive signal, that is, when the drive signal (V') with reduced second- and third-order harmonics is applied to the piezoelectric actuator 150, the displacement (L') of the output end of the piezoelectric actuator 150, that is, the piezoelectric element 10 or the drive rod 20, cannot be obtained in the form of a triangular wave over time, but is applied in the form of a sine wave and cannot cause the displacement of the slider 30 (see FIG. 6). At this time, the displacement speed of the piezoelectric element 10, that is, the drive rod 20, does not appear as required, and the forward or backward displacement of the slider 30 cannot be caused (610).

[0066] That is, it can be understood that if the drive signal V of a rectangular wave does not contain sufficiently large second- and third-order harmonics, a satisfactory triangular wave at the output terminal cannot be obtained.

[0067] FIG. 8 is a diagram for explaining an additional pulse 810 inserted for harmonic generation at the midpoint of the low interval within one period of the drive frequency in the drive signal (V1) of the present invention.

[0068] Referring to FIG. 8, when a drive signal for driving the piezoelectric actuator 150 is input as a rectangular wave, at the midpoint of the low interval within one period (T) of the drive frequency (at the center of 2A), the piezoelectric actuator 150 can be driven using a drive signal (V2) including an additional pulse 810 inserted for harmonic generation. The width (2B) of the additional pulse 810 may be determined to be smaller than the half width (A) of the low interval within the one period (T) from the midpoint of the low interval within one period (T) of the drive frequency to both sides (B < A) and applied.

[0069] FIG. 8 shows an example where the ratio of the sum of the high intervals and the sum of the low intervals within one period of the drive frequency of the rectangular wave in the drive signal (V1) without the additional pulse 810 is 3:7, but it is not limited thereto, and the pulse width may be determined so that the ratio is determined within the range of 1.5:8.5 to 4.5:5.5.

[0070] Also, when driving the piezoelectric actuator 150 using the drive signal (V2) including the additional pulse 810, the pulse width may be determined so that the ratio of the sum of the high intervals and the sum of the low intervals within one period of the drive frequency of the rectangular wave including the additional pulse 810 is determined within the range of 8.5:1.5 to 5.5:4.5 (forward displacement generation), and the pulse width may be determined so that the ratio of the sum of the high intervals and the sum of the low intervals within one period of the drive frequency of the rectangular wave including the additional pulse 810 is determined within the range of 1.5:8.5 to 4.5:5.5 (backward displacement generation).

[0071] The driving method as shown in FIG. 8 may be applied to the circuit of FIG. 3, and may also be applied to a conventional circuit as shown in FIG. 1. In addition, it may be applied to various devices for driving the piezo actuator 150. That is, the piezo element 10 is driven by the driving signal (V2), and by driving the vibration of the driving rod 20 coupled to the piezo element 10, the position displacement of the slider 30 is controlled by the forward and backward movement of the slider 30 due to stick-slip driving. It can be applied to all driving methods of the piezo actuator 150 for this purpose.

[0072] FIG. 9 is an illustration of the signal waveform actually applied to the piezo actuator 150 when no additional pulse is inserted into the driving signal (V1) of the present invention.

[0073] FIG. 10 is an illustration of the signal waveform actually applied to the piezo actuator 150 when an additional pulse is inserted into the driving signal (V2) of the present invention.

[0074] Referring to FIGS. 9 and 10, it was confirmed that in the driving signal (V2) into which the additional pulse 810 is inserted, compared to the driving signal (V1) into which no additional pulse is inserted, a much higher value power spectrum (dB) is shown in the second and third harmonic regions around the resonance frequency in the frequency analysis. This can be confirmed by passing through a second-order system with ζ (DAMPING RATIO) = 0.02.

[0075] FIG. 11 shows a partial enlargement of the driving signal (V1) and the piezo displacement (L1) when no additional pulse is inserted in FIG. 9.

[0076] FIG. 12 shows a partial enlargement of the driving signal (V2) and the piezo displacement (L2) when an additional pulse is inserted in FIG. 10.

[0077] Referring to FIGS. 11 and 12, in the drive signal (V2) in which the additional pulse 810 is inserted as compared to the drive signal (V1) in which no additional pulse is inserted, the output end of the piezoelectric actuator 150, that is, the displacement (L2) of the piezoelectric element 10 or the drive rod 20 over time is obtained in the form of a triangular wave, and it becomes possible to cause displacement of the slider 30. In the drive signal (V1) in which no additional pulse is inserted, displacement (L1) of the drive rod 20 in a sine wave form occurs, and displacement of the slider 30 cannot be controlled.

[0078] As described above, the drive method presented in the present invention further places the additional pulse 810 in the middle portion corresponding to 1 / 2 in the period of the side having a long duty in the drive waveform having an existing 3:7 or a similar duty, thereby utilizing a method of significantly increasing the magnitudes of the second and third harmonics. Therefore, according to the drive method presented in the present invention, a sufficiently large ratio of triangular waves or sawtooth waves can be applied to the output end of the piezoelectric actuator 150, that is, the piezoelectric element 10 or the drive rod 20, even in SIDM drive using resonance.

[0079] In other words, according to the piezoelectric actuator driving device 100 according to the present invention, the inductor L R is charged with current, and when the current reaches a sufficient level, the resonance switches RT1 and RT2 are turned on so that the piezoelectric actuator 150 and the like apply a voltage to the capacitor. The subsequent operations except for the initial operation are driven in a form of replenishing the voltage lacking at both ends of the capacitor with the voltage having the opposite polarity by replenishing the current to the inductor L R (RT1, RT2, L R ) by an amount of energy consumed in the resonance circuit.

[0080] Thereby, 1) from the perspective of energy, in the conventional invention, in order to replenish the energy consumed when driving the resonance circuit to change the polarity of the piezoelectric actuator equivalent capacitor, a voltage was applied to the capacitor to induce an inrush current, whereas in the present invention, the resonance circuit (RT1, RT2, L RThe current of inductor L is replenished only by the amount of energy consumed in R ( ), but due to the properties of the current in inductor L R , even if a voltage is applied across inductor L R , the current gradually increases from 0. Therefore, unlike when a voltage source is directly applied to a capacitor, there is an advantage that no peak current flows. For example, by removing the inrush current to the piezo actuator 150 in this way, heat generation and power consumption can be reduced. For example, the power consumption can be reduced to about 1 / 10 of the existing driving method and 1 / 3 of the existing eco-driving method when driven by the same voltage.

[0081] 2) Also, by adjusting the magnitude of the current applied to inductor L R , a voltage higher than the power supply voltage can be applied across the equivalent capacitor of the piezo actuator 150, and the voltage input to the piezo actuator 150 can be increased up to 2 to 3 times the maximum (for example, power supply voltage 3.3V -> applied 8V) without a separate DC-DC converter. This has the advantage of improving the vibration speed of the piezo actuator 150.

[0082] 3) And in the present invention, for the application of a sawtooth wave (or triangular wave) advantageous for driving the piezo actuator 150, an additional pulse for harmonic generation is inserted to enable accurate displacement control.

[0083] As described above, the present invention has been described by specific matters such as specific components, limited embodiments, and drawings, but this is only provided to assist a more general understanding of the present invention. The present invention is not limited to the above embodiments, and those having ordinary knowledge in the field to which the present invention pertains can make various modifications and deformations without departing from the essential characteristics of the present invention. Therefore, the idea of the present invention should not be defined only by the described embodiments, and in addition to the claims described later, any technical idea with a modification equivalent or equivalent to this claim should also be interpreted as being included in the scope of rights of the present invention.

Description of Symbols

[0084] 150 Piezo Actuator 110 First Voltage 120 Second Voltage MT1~MT4 Main Switch RT1, RT2 Resonance Switch L R Inductor

Claims

1. A piezoelectric actuator driving device, comprising: a first main switch and a second main switch that are connected in series between a first voltage and a second voltage and whose contacts are connected to one end of an inductor; a third main switch and a fourth main switch that are connected in series between the first voltage and the second voltage and whose contacts are connected to the other end of the inductor; and a first resonance switch, the piezoelectric actuator, and a second resonance switch that are connected in series between one end and the other end of the inductor, forming a resonance loop by connecting the piezoelectric actuator and the inductor during a resonance period in which the first resonance switch and the second resonance switch are turned on, and providing energy previously charged in the inductor to the piezoelectric actuator, between a forward drive and a reverse drive for the piezoelectric actuator or between the reverse drive and the forward drive, before the formation of the resonance loop during the resonance period, Among the first parasitic diode of the first resonance switch composed of a MOSFET and the second parasitic diode of the second resonance switch composed of a MOSFET, a parasitic diode in the current direction flowing through the inductor and a pre-loop formed by the turn-on of the other resonance switch are formed, and the piezoelectric actuator driving device drives to eliminate the discontinuity of the current flowing through the inductor at the moment of the subsequent resonance loop.

2. A piezoelectric actuator driving device, comprising: a first main switch and a second main switch that are connected in series between a first voltage and a second voltage and whose contacts are connected to one end of an inductor; a third main switch and a fourth main switch that are connected in series between the first voltage and the second voltage and whose contacts are connected to the other end of the inductor; and a first resonance switch, the piezoelectric actuator, and a second resonance switch that are connected in series between one end and the other end of the inductor, forming a resonance loop by connecting the piezoelectric actuator and the inductor during a resonance period in which the first resonance switch and the second resonance switch are turned on, and providing energy previously charged in the inductor to the piezoelectric actuator, between a forward drive and a reverse drive for the piezoelectric actuator or between the reverse drive and the forward drive, after the formation period of the resonance loop has passed, Of the first parasitic diode of the first resonant switch composed of a MOSFET and the second parasitic diode of the second resonant switch composed of a MOSFET, the parasitic diode in the current direction flowing through the inductor and the after-loop formed by the turn-on of the other resonant switch are formed, and after discharging the residual current from the inductor to the piezoelectric actuator, the first resonant switch and the second resonant switch are driven to turn off, The piezoelectric actuator driving device according to claim 1.

3. The piezoelectric actuator includes a drive rod coupled to a piezoelectric element and a slider inserted into the drive rod, and drives the piezoelectric element by a drive signal to drive the vibration of the drive rod, thereby controlling the position displacement of the slider by the forward and backward movement of the slider by stick-slip driving. The piezoelectric actuator driving device according to claim 1 or 2.

4. The first voltage is the voltage on the output side of the forward diode connected to the source voltage. The piezoelectric actuator driving device according to claim 1 or 2.

5. A drive signal is input to both ends of the piezoelectric actuator in a rectangular wave, and the forward or backward movement of the piezoelectric actuator vibration is determined by the magnitudes of the sum of the high intervals and the sum of the low intervals within one period of the drive frequency of the rectangular wave. Including an additional pulse inserted for harmonic generation at the midpoint of the low interval within one period of the drive frequency. The piezoelectric actuator driving device according to claim 1 or 2.

6. The pulse width of the additional pulse is determined such that the ratio of the sum of the high intervals and the sum of the low intervals within one period of the drive frequency of the rectangular wave is determined in the range of 8.5:1.5 to 5.5:4.

5. The piezoelectric actuator driving device according to claim 5.

7. A piezoelectric actuator driving method for a driving device that performs forward driving by applying a first voltage and a second voltage to a first electrode and a second electrode of a piezoelectric actuator, respectively, and reverse driving by applying opposite voltages, respectively. The driving device includes a first main switch and a second main switch connected in series between the first voltage and the second voltage, and the contact is connected to one end of the inductor; A third main switch and a fourth main switch connected in series between the first voltage and the second voltage, and the contact is connected to the other end of the inductor; and A first resonance switch, the piezo actuator, and a second resonance switch, which are connected in series between one end and the other end of the inductor; (A) turning on the first main switch and the fourth main switch for the forward drive; (B) turning on the third main switch and the second main switch for the reverse drive; and (C) including a resonance stage of turning on the first resonance switch and the second resonance switch between the forward drive and the reverse drive, forming a resonance loop by connecting the piezo actuator and the inductor in the resonance stage, and providing the energy pre-charged in the inductor to the piezo actuator, between the forward drive and the reverse drive for the piezo actuator or between the reverse drive and the forward drive, before the formation of the resonance loop during the resonance period when the first resonance switch and the second resonance switch are turned on, A piezo actuator driving method for driving so as to eliminate the discontinuity of the current flowing through the inductor at the moment of the subsequent resonance loop, by forming a pre-loop due to the parasitic diode in the current direction flowing through the inductor and the turn-on of the other-side resonance switch among the first parasitic diode of the first resonance switch composed of MOSFET and the second parasitic diode of the second resonance switch composed of MOSFET.

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