Fluid control valve, fluid control device, and drive circuit

Abstract

To accurately control an output voltage of a piezoelectric actuator without switching the operation mode between charging and discharging of the piezoelectric actuator.SOLUTION: A drive circuit of a piezoelectric actuator includes: a flyback transformer in which a primary winding is connected to a DC power supply and a secondary winding is connected to the piezoelectric actuator; a charge switch connected to the primary winding; a discharge switch connected to the secondary winding; a regenerative capacitor connected to the primary winding, in which discharge energy of the piezoelectric actuator is regenerated; and a switch control unit that controls on / off operations of the charge switch and the discharge switch. The switch control unit controls an applied voltage of the piezoelectric actuator by controlling on / off operations of the charge switch and the discharge switch to repeatedly perform charging and discharging of the piezoelectric actuator.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fluid control valve, a fluid control device, and a drive circuit. [Background technology]

[0002] For example, the flow rate of gas supplied into a chamber in a semiconductor manufacturing process is controlled by a mass flow controller. This mass flow controller includes a fluid control valve equipped with, for example, a piezoelectric actuator, and a flow sensor. The voltage applied to the piezoelectric actuator is controlled so that the deviation between the measured flow rate of the flow sensor and the set flow rate is reduced.

[0003] By the way, when a voltage is applied to a piezoelectric actuator to contract it from an expanded state, it is necessary to discharge the electric charge stored in the piezoelectric actuator. Conventionally, the electric charge discharged from the piezoelectric actuator is consumed as heat, for example, in a resistor in the drive circuit.

[0004] In recent years, gas supply and stop may be repeated at high speed and frequency, such as in the ALD process, and in such cases, the fluid control valve must be opened and closed at high speed. This increases the chances of discharge from the piezoelectric actuator, increasing heat loss in the drive circuit and reducing energy efficiency.

[0005] For this reason, as shown in Patent Document 1, a bidirectional power supply circuit (flyback transformer) that regenerates charge (energy) to the power supply side when the piezoelectric actuator is discharged has been considered. In this bidirectional power supply circuit, the operation mode is changed between output to the secondary side (when the piezoelectric actuator is charged) and regeneration to the primary side (when the piezoelectric actuator is discharged). Specifically, when charging, only the charge switch is turned on and off to charge the piezoelectric actuator, and when discharging, only the discharge switch is turned on and off to discharge from the piezoelectric actuator.

[0006] However, when it is desired to control the voltage to a constant level or within a small voltage range, it is necessary to control the voltage by switching between the charge mode and the discharge mode. This complicates the control of the bidirectional power supply circuit and, in some cases, may cause the output voltage to oscillate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2020-201630 A Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention has been made to solve the above-mentioned problems, and its object is to accurately control the output voltage of a piezoelectric actuator without switching the operating mode when the piezoelectric actuator is charging and discharging. [Means for solving the problem]

[0009] That is, the fluid control valve according to the present invention is a fluid control valve including a piezoelectric actuator and a drive circuit connected to the piezoelectric actuator, the drive circuit including a flyback transformer having a primary winding connected to a DC power supply and a secondary winding connected to the piezoelectric actuator, a charge switch connected to the primary winding and turned on and off to charge the piezoelectric actuator, a discharge switch connected to the secondary winding and turned on and off to discharge the piezoelectric actuator, a regenerative capacitor connected to the primary winding and which regenerates the discharge energy of the piezoelectric actuator, and a switch control unit which controls the on and off operations of the charge switch and the discharge switch, and the switch control unit controls the on and off operations of the charge switch and the discharge switch to repeatedly charge and discharge the piezoelectric actuator, thereby controlling the applied voltage to the piezoelectric actuator.

[0010] With such a fluid control valve, the applied voltage to the piezoelectric actuator is controlled by repeatedly charging and discharging the piezoelectric actuator, so that the output voltage of the piezoelectric actuator can be controlled with high precision without switching the operation mode between charging and discharging the piezoelectric actuator. In particular, in the present invention, when the piezoelectric actuator is controlled at a constant voltage or within a predetermined microvoltage range, there is no need to switch the operation mode between charging and discharging the piezoelectric actuator, so that the output voltage of the piezoelectric actuator can be controlled with high precision.

[0011] As a specific embodiment, it is desirable that the switch control unit repeatedly charges and discharges the piezoelectric actuator by repeating a cycle consisting of one on-off operation of the charge switch and one on-off operation of the discharge switch.

[0012] As a specific embodiment, it is desirable that the switch control unit controls the on / off operation of the charge switch and the discharge switch to control the ratio between the charge energy per charge of the piezoelectric actuator and the discharge energy per discharge of the piezoelectric actuator, thereby controlling the applied voltage to the piezoelectric actuator.

[0013] As a specific embodiment of controlling the ratio between the charge energy from one charging of the piezoelectric actuator and the discharge energy from one discharging, the switch control unit switches the charge switch from on to off when a primary side switch current value flowing through the charge switch reaches a predetermined primary side peak current value, and switches the discharge switch from on to off when a secondary side switch current value flowing through the discharge switch reaches a predetermined secondary side peak current value, thereby controlling the ratio between the primary side peak current value and the secondary side peak current value, thereby controlling the ratio between the charge energy from one charging of the piezoelectric actuator and the discharge energy from one discharging.

[0014] As a specific embodiment of controlling the ratio between the primary peak current value and the secondary peak current value, it is desirable that the switch control unit controls the ratio between the primary peak current value and the secondary peak current value based on the output voltage to the piezoelectric actuator.

[0015] It is desirable for the switch control unit to include a primary side peak current setting unit that sets the primary side peak current value based on a voltage command to the piezoelectric actuator and an output voltage to the piezoelectric actuator, a secondary side peak current setting unit that sets the secondary side peak current value by inverting and amplifying the set primary side peak current value using an inverting amplifier circuit, a charge switch drive unit that drives the charge switch based on the primary side peak current value and a current value flowing through the charge switch, and a discharge switch drive unit that drives the discharge switch based on the secondary side peak current value and the current value flowing through the discharge switch.

[0016] In the secondary-side peak current setting unit, it is desirable to set a cycle in which only charging of the piezoelectric actuator is repeated, a cycle in which charging and discharging of the piezoelectric actuator are repeated, and a cycle in which only discharging of the piezoelectric actuator is repeated by lowering a reference potential input to the non-inverting amplification terminal of the inverting amplification circuit.

[0017] In addition, a fluid control device according to the present invention is characterized in that it comprises the above-mentioned fluid control valve, a fluid sensor that measures a fluid flowing in a flow path, and a valve control unit that controls the fluid control valve based on the measurement value of the fluid sensor.

[0018] Furthermore, a drive circuit according to the present invention is a drive circuit connected to a piezoelectric actuator, and includes a flyback transformer having a primary winding connected to a DC power supply and a secondary winding connected to the piezoelectric actuator, a charge switch connected to the primary winding and turned on and off to charge the piezoelectric actuator, a discharge switch connected to the secondary winding and turned on and off to discharge the piezoelectric actuator, a regenerative capacitor connected to the primary winding and for regenerating the discharge energy of the piezoelectric actuator, and a switch control unit that controls the on and off operations of the charge switch and the discharge switch, wherein the switch control unit alternately turns on and off the charge switch and the discharge switch to repeatedly charge and discharge the piezoelectric actuator, and controls the magnitude of the charge energy resulting from one charge and the discharge energy resulting from one discharge of the piezoelectric actuator, thereby controlling the applied voltage to the piezoelectric actuator. Effect of the Invention

[0019] As described above, according to the present invention, the output voltage of the piezoelectric actuator can be controlled with high precision without switching the operation mode between when the piezoelectric actuator is being charged and when it is being discharged. [Brief description of the drawings]

[0020] [Figure 1] 1 is a diagram illustrating a schematic configuration of a fluid control device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating a schematic configuration of a drive circuit according to the embodiment. [Diagram 3] FIG. 4 is a schematic diagram showing the relationship between a first peak current value and a second peak current value in the embodiment. [Figure 4] 4 is a diagram showing a primary side switch current, a secondary side switch current, a voltage of a regenerative capacitor, and a voltage of a piezoelectric actuator in one cycle of operation of the drive circuit of the embodiment. FIG. [Diagram 5]FIG. 1A is a diagram showing the relationship between the first peak current value and the second peak current value when controlled at a constant voltage or a small voltage range in the same embodiment; FIG. 1B is a diagram showing the relationship between the first peak current value and the second peak current value when discharging from a state in which a predetermined voltage is applied; and FIG. 1C is a diagram showing the relationship between the first peak current value and the second peak current value when charging from a state in which a predetermined voltage is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a fluid control device according to the present invention will be described with reference to the drawings. In addition, in any of the drawings shown below, for the purpose of easy understanding, some parts are omitted or exaggerated in schematic form as appropriate. The same components are denoted by the same reference numerals and the description thereof is omitted as appropriate.

[0022] <Configuration of the fluid control device> The fluid control device 100 of the present embodiment is used, for example, in a semiconductor manufacturing process, and is provided on one or more gas supply lines to control the flow rate of the process gas flowing through each gas supply line.

[0023] Specifically, the fluid control device 100 is a so-called differential pressure mass flow controller (differential pressure MFC), and as shown in FIG. 1, includes a flow path block 2 in which multiple internal flow paths 2R are formed, and a fluid control device 3 mounted on the flow path block 2.

[0024] The flow path block 2 is provided with an inlet port 21 for introducing a fluid into the internal flow path 2R and an outlet port 22 for discharging the fluid from the internal flow path 2R.

[0025] The fluid control device 3 controls the fluid in the internal flow path 2R, and has a flow sensor 31 that measures the flow rate of the fluid flowing through the internal flow path 2R, and a fluid control valve 32 provided upstream of the flow sensor 31. The valve opening of the fluid control valve 32 is feedback-controlled by the control unit 4, which will be described later.

[0026] The flow sensor 31 is a differential pressure type flow sensor, and has an upstream pressure sensor 31a provided upstream of a fluid resistance element 33, such as a restrictor or an orifice, provided in the internal flow path 2R, and a downstream pressure sensor 31b provided downstream of the fluid resistance element 33. A flow rate calculation unit 4a of the control unit 4, which will be described later, calculates a flow rate Q flowing through the internal flow path 2R using the upstream pressure P1 of the fluid resistance element 33 measured by the upstream pressure sensor 31a and the downstream pressure P2 of the fluid resistance element 33 measured by the downstream pressure sensor 31b.

[0027] The fluid control valve 32 is provided upstream of the differential pressure flow sensor 31. The fluid control valve 32 controls the flow rate by moving a valve body back and forth relative to a valve seat using a piezoelectric actuator. Specifically, the fluid control valve 32 includes a valve seat, a valve body that displaces relative to the valve seat, a piezoelectric actuator 32a that displaces the valve body, and a drive circuit 32b that drives the piezoelectric actuator 32a. The piezoelectric actuator 32a is, for example, a laminate of piezoelectric elements and electrodes. The length of the piezoelectric actuator 32a changes according to the voltage applied by the drive circuit 32b. The drive circuit 32b will be described later.

[0028] The control unit 4 has a flow rate calculation unit 4a that calculates a flow rate Q flowing through the internal flow path 2R based on the upstream pressure P1 and the downstream pressure P2, and a valve control unit 4b that controls the fluid control valve 32 based on the flow rate Q calculated by the flow rate calculation unit 4a. The control unit 4 is a so-called computer equipped with, for example, a CPU, a memory, an A / D·D / A converter, and an input / output means, and performs the functions of the flow rate calculation unit 4a, the valve control unit 4b, etc. by executing a flow rate control program stored in the memory and cooperating with various devices.

[0029] The flow rate calculation unit 4a calculates the flow rate Q through the internal flow path 2R from the measured pressures P1 and P2 measured by the upstream pressure sensor 31a and the downstream pressure sensor 31b. That is, the upstream pressure sensor 31a, the fluid resistance element 33, the downstream pressure sensor 31b, and the flow rate calculation unit 4a constitute a so-called pressure-type flow sensor 31. The flow rate calculation formula used by the flow rate calculation unit 4a can be an existing formula. The flow rate Q calculated by the flow rate calculation unit 4a is output to the valve control unit 4b as a measured flow rate.

[0030] The valve control unit 4b performs flow rate feedback control of the opening of the fluid control valve 32 so as to reduce the deviation between the set flow rate set by the user and the measured flow rate Q calculated by the flow rate calculation unit 4a. The valve control unit 4b is a PID controller that receives the deviation between the set flow rate and the measured flow rate and outputs a voltage command to be applied to the fluid control valve 32 by PID calculation.

[0031] <Drive circuit 32b of fluid control valve 32> Next, the drive circuit 32b of the fluid control valve 32 will be described in detail with reference to FIG.

[0032] As shown in FIG. 2, the drive circuit 32b includes a flyback transformer 5, a charge switch 6, a discharge switch 7, a regenerative capacitor 8, and a switch control unit 9 that controls the on / off operations of the charge switch 6 and the discharge switch 7.

[0033] The flyback transformer 5 includes a primary winding 51 connected to the DC power supply 10 and a secondary winding 52 connected to the piezoelectric actuator 32a.

[0034] A charging switch 6 that is turned on and off to charge the piezoelectric actuator 32a is connected to the low-voltage side of the primary winding 51. The charging switch 6 is a semiconductor switch such as a field-effect transistor (FET), and a drive command output from a switch control unit 9 is input to the gate of the charging switch 6. A rectifier diode 11 is connected in parallel to the charging switch 6 to pass a current in one direction, from the low-voltage side to the high-voltage side in the primary winding 51.

[0035] A discharge switch 7 that is turned on and off to discharge the piezoelectric actuator 32a is connected to the low-voltage side of the secondary winding 52. The discharge switch 7 is a semiconductor switch such as a field-effect transistor (FET), and a drive command output from a switch control unit 9 is input to the gate of the discharge switch 7. A rectifier diode 12 for passing a current in one direction in the secondary winding 52 from the low-voltage side to the high-voltage side is connected in parallel to the discharge switch 7.

[0036] Furthermore, a regenerative capacitor 8 that regenerates electrical energy (hereinafter, discharge energy) generated by discharging the piezoelectric actuator 32a is connected to the high-voltage side of the primary winding 51. The regenerative capacitor 8 is connected in parallel to the DC power supply 10 in the primary winding 51.

[0037] In addition, a diode 13 is connected on the high-voltage side of the primary winding 51, closer to the DC power supply 10 than the connection point of the regenerative capacitor 8. This diode 13 has an anode connected to the DC power supply 10 side and a cathode connected to the regenerative capacitor 8 side, so that the current generated from the primary winding 51 of the flyback transformer 5 when the piezoelectric actuator 32a is discharged flows only to the regenerative capacitor 8.

[0038] The switch control unit 9 controls the on / off operation of the charge switch 6 and the discharge switch 7. Specifically, the switch control unit 9 controls the on / off operation of the charge switch 6 and the discharge switch 7 to repeatedly charge and discharge the piezoelectric actuator 32a, thereby controlling the voltage applied to the piezoelectric actuator 32a. Here, the charge and discharge of the piezoelectric actuator 32a are repeatedly performed by repeating a cycle consisting of one on / off operation of the charge switch 6 and one on / off operation of the discharge switch 7.

[0039] The switch control unit 9 of this embodiment alternately turns on and off the charge switch 6 and the discharge switch 7 to control the ratio of the charge energy per charge to the discharge energy per discharge of the piezoelectric actuator 32a, thereby controlling the voltage applied to the piezoelectric actuator 32a. The switch control unit 9 controls the primary side switch current I pri is the given primary peak current value I th1 When the charge current reaches the discharge switch 7, the switch control unit 9 switches the charge switch 6 from on to off. sec is the desired secondary peak current value I th2 When the voltage V reaches the threshold voltage Vp, the discharge switch 7 is switched from on to off. Then, the switch control unit 9 controls the output voltage Vp to the piezoelectric actuator 32a. sec Based on this, the primary peak current value I th1 and the secondary peak current value I th2 By controlling the ratio, the ratio between the charging energy in one charging of the piezoelectric actuator 32a and the discharging energy in one discharging of the piezoelectric actuator 32a is controlled.

[0040] As shown in FIG. 2, the switch control unit 9 has a detailed configuration in which an output voltage V sec Based on this, the primary peak current value I th1 A primary-side peak current setting unit 9a sets the primary-side peak current value I th1 is inverted and amplified to obtain the secondary peak current value I th2and a secondary peak current setting unit 9b that sets the primary peak current value I th1 and the current value I flowing through the charging switch 6 pri Based on this, a charging switch driving unit 9c drives the charging switch 6, and a secondary peak current value I th2 and a discharge switch drive unit 9 d that drives the discharge switch 7 based on the value of the current flowing through the discharge switch 7 .

[0041] The primary-side peak current setting unit 9a determines the voltage command value input from the valve control unit 4b and the output voltage V sec Based on this, the primary peak current value I th1 Set.

[0042] The secondary peak current setting unit 9b sets the primary peak current value I th1 is inverted and amplified by the inverting amplifier circuit 91 to obtain the secondary peak current value I th2 Here, the primary peak current value I th1 A reference potential (fulcrum potential) that is a reference for inverting the primary peak current I th1 and the secondary peak current value I th2 is determined based on the supporting point potential input to the non-inverting amplification terminal of the inverting amplifier circuit 91 as a reference.

[0043] The charging switch driving unit 9c is configured using a flip-flop circuit 92, and a set terminal receives a charging-on pulse (SetPulse1) for turning on the charging switch 6, and a reset terminal receives a primary-side reset pulse (ResetPulse1) for turning off the charging switch 6. A driving command is output from the output terminal of this flip-flop circuit 92 to the gate of the charging switch 6, causing the charging switch 6 to perform an on-off operation.

[0044] The primary side reset pulse is a reset pulse (hereinafter referred to as the primary side on limit pulse (Timelimit1)) for turning off the charge switch 6 before the generation of the discharge on pulse (Setpulse2) for turning on the discharge switch 7, and a current value I pri is the primary peak current value I th1 Specifically, the primary side reset pulse is a signal output by inputting the primary side on limit pulse and the primary side arrival signal to an OR circuit 93. The primary side arrival signal is generated based on the current value I pri and the primary peak current value I th1 This is a High signal that is output from a primary side comparator (comparator) 94 to which the above signals are input.

[0045] The discharge switch driving unit 9d is configured using a flip-flop circuit 95, and a set terminal receives a discharge-on pulse (Setpulse2) for turning on the discharge switch 7, and a reset terminal receives a secondary-side reset pulse (ResetPulse2) for turning off the discharge switch 7. A drive command is output from the output terminal of this flip-flop circuit 95 to the gate of the discharge switch 7, causing the discharge switch 7 to perform an on / off operation.

[0046] The secondary side reset pulse is a reset pulse (hereinafter, referred to as the secondary side on limit pulse (Timelimit2)) for turning off the discharge switch 7 before the generation of the charge on pulse (Setpulse1) for turning on the charge switch 6, and a current value I sec is the secondary peak current value I th2 Specifically, the secondary reset pulse is a signal output by inputting the secondary on limit pulse and the secondary arrival signal to the OR circuit 96. The secondary arrival signal is generated based on the current value I sec and the secondary peak current value I th2This is a High signal that is output from a secondary side comparator (comparator) 97 to which the above signals are input.

[0047] <One Cycle of Operation of the Drive Circuit 32b> Next, one cycle of operation of the drive circuit 32b will be described with reference to Fig. 4. Here, one cycle of operation is an operation of performing one charge and one discharge.

[0048] (1) First, when the charging switch 6 is turned on, a constant current flows through the primary winding 51, and energy (E1=1 / 2×L1×I pri 2 ) is accumulated.

[0049] (2) When the charging switch 6 is turned off, the rectifier diode 12 on the secondary side becomes conductive and a current flows through the secondary winding 52. The energy (E1) stored in the flyback transformer 5 is charged to the piezoelectric actuator 32a, and the voltage of the piezoelectric actuator 32a increases.

[0050] (3) After that, when the discharge switch 7 is turned on, a current flows from the piezoelectric actuator 32a to the secondary winding 52, and energy (E2=1 / 2×L2×I sec 2 At this time, the piezoelectric actuator 32a is discharged.

[0051] (4) When the discharge switch 7 is turned off, the primary side rectifier diode 11 becomes conductive and a current flows through the primary winding 51. The energy (E2) stored in the flyback transformer 5 is charged to the regenerative capacitor 8, and the voltage of the regenerative capacitor 8 increases.

[0052] In the next cycle, energy is stored in the flyback transformer 5 using the energy regenerated in the regenerative capacitor 8 in (4) above.

[0053] <Overall Operation of Drive Circuit 32b> When the piezoelectric actuator 32a is charged with a predetermined voltage and the fluid control valve 32 is maintained at a predetermined opening (when controlled at a constant voltage or a small predetermined voltage range), as shown in FIG. 5(a), the switch control unit 9 controls the primary peak current value I th1 and the secondary peak current value I th2 The charging switch 6 and the discharging switch 7 are repeatedly turned on and off with a one-to-one relationship between the charging energy to the piezoelectric actuator 32a and the discharging energy from the piezoelectric actuator 32a. The charging energy to the piezoelectric actuator 32a and the discharging energy from the piezoelectric actuator 32a are thus in a one-to-one relationship, the applied voltage to the piezoelectric actuator 32a is constant, and the fluid control valve 32 is maintained at a predetermined opening.

[0054] When discharging the piezoelectric actuator 32a from a state in which a predetermined voltage is applied thereto to change the opening degree, as shown in FIG. 5(b), the switch control unit 9 changes the primary peak current value I th1 and the secondary peak current value I th2 In comparison with the secondary peak current I th2 The ratio of the charge energy to the discharge switch 7 is increased, and the charge switch 6 and the discharge switch 7 are repeatedly turned on and off. As a result, the discharge energy from the piezoelectric actuator 32a becomes greater than the charge energy to the piezoelectric actuator 32a, the voltage applied to the piezoelectric actuator 32a decreases, and the opening of the fluid control valve 32 changes.

[0055] Here, when discharging the piezoelectric actuator 32a, the primary peak current value I set by the primary peak current setting unit 9a may vary depending on the discharge voltage. th1 In this case, a high signal is output from the primary side comparator 94, so that the charging switch 6 continues to be turned off and the discharging switch 7 repeatedly turns on and off, and only the discharging operation is performed.

[0056] In addition, when the opening degree is changed by charging the piezoelectric actuator 32a from a state in which a predetermined voltage is applied to the piezoelectric actuator 32a, as shown in FIG. 5(c), the switch control unit 9 changes the primary side peak current value I th1 and the secondary peak current value I th2 The primary peak current I th1 The ratio of the charge switch 6 to the discharge switch 7 is increased, and the charge switch 6 and the discharge switch 7 are repeatedly turned on and off. As a result, the charge energy to the piezoelectric actuator 32a becomes greater than the discharge energy from the piezoelectric actuator 32a, the voltage applied to the piezoelectric actuator 32a increases, and the opening of the fluid control valve 32 changes.

[0057] Here, when the piezoelectric actuator 32a is charged, the secondary peak current value I set by the secondary peak current setting unit 9b may vary depending on the charging voltage. th2 In this case, a high signal is output from the secondary side comparator 97, so that the discharge switch 7 continues to be turned off and the charge switch 6 repeatedly turns on and off, and only the charge operation is performed.

[0058] <Effects of this embodiment> As described above, according to the fluid control device 100 of this embodiment, the piezoelectric actuator 32a is repeatedly charged and discharged, and the magnitude of the charge energy per charging and the discharge energy per discharging of the piezoelectric actuator 32a is controlled to control the voltage applied to the piezoelectric actuator 32a. Therefore, the output voltage of the piezoelectric actuator 32a can be precisely controlled without switching the operating mode between charging and discharging the piezoelectric actuator 32a.

[0059] <Other embodiments> For example, in the above embodiment, the driving circuit 32b is configured from an analog circuit, but it may be configured from a digital circuit that exerts the functions of each part of the analog circuit.

[0060] Furthermore, in the secondary-side peak current setting unit 9b, by lowering the reference potential input to the non-inverting amplification terminal of the inverting amplification circuit 91, it may be possible to arbitrarily set a cycle in which only the charging of the piezoelectric actuator 32a is repeated, a cycle in which the charging and discharging of the piezoelectric actuator 32a is repeated, and a cycle in which only the discharging of the piezoelectric actuator 32a is repeated.

[0061] Furthermore, the flow rate control device in the above embodiment is a differential pressure mass flow controller, but may be a thermal mass flow controller.

[0062] Furthermore, the fluid control valve in the above embodiment is used in a mass flow controller, which is a fluid control device, but it may be used in various valves such as a pressure control valve of a pressure control device or a shutoff valve.

[0063] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0064] 100... Fluid control device 10...DC power supply 31 Fluid sensor 32 Fluid control valve 32a···Piezo actuator 32b Drive circuit 4b Valve control section 5 Flyback transformer 51 Primary winding 52 Secondary winding 6. Charging switch 7 Discharge switch 8. Regenerative capacitor 9 Switch control section 9a Primary side peak current setting section 9b Secondary side peak current setting section 91 Inverting amplifier circuit 9c Charging switch drive unit 9d Discharge switch drive unit

Claims

1. A fluid control valve including a piezoelectric actuator and a drive circuit connected to the piezoelectric actuator, The drive circuit includes: a flyback transformer having a primary winding connected to a DC power supply and a secondary winding connected to the piezoelectric actuator; a charge switch connected to the primary winding and turned on and off to charge the piezoelectric actuator; a discharge switch connected to the secondary winding and turned on and off to discharge the piezoelectric actuator; a regenerative capacitor connected to the primary winding for regenerating discharge energy of the piezoelectric actuator; a switch control unit that controls an on / off operation of the charge switch and the discharge switch, The switch control unit controls an on / off operation of the charge switch and the discharge switch to repeatedly charge and discharge the piezoelectric actuator, thereby controlling the voltage applied to the piezoelectric actuator.

2. 2. The fluid control valve according to claim 1, wherein the switch control unit repeatedly charges and discharges the piezoelectric actuator by repeating a cycle consisting of one on-off operation of the charging switch and one on-off operation of the discharging switch.

3. 3. The fluid control valve according to claim 1, wherein the switch control unit controls an on / off operation of the charging switch and the discharging switch to control a ratio between charging energy in one charging of the piezoelectric actuator and discharging energy in one discharging of the piezoelectric actuator, thereby controlling the applied voltage to the piezoelectric actuator.

4. The switch control unit is When a primary side switch current value flowing through the charging switch reaches a predetermined primary side peak current value, the charging switch is switched from on to off; When a secondary-side switch current value flowing through the discharge switch reaches a predetermined secondary-side peak current value, the discharge switch is switched from on to off, 4. The fluid control valve according to claim 3, wherein a ratio between the charging energy in one charging of the piezoelectric actuator and the discharging energy in one discharging of the piezoelectric actuator is controlled by controlling a ratio between the primary side peak current value and the secondary side peak current value.

5. 5. The fluid control valve according to claim 4, wherein the switch control unit controls a ratio between the primary peak current value and the secondary peak current value based on a voltage command to the piezoelectric actuator and an output voltage to the piezoelectric actuator.

6. The switch control unit is a primary peak current setting unit that sets the primary peak current value based on an output voltage to the piezoelectric actuator; a secondary peak current setting unit that inverts and amplifies the set primary peak current value by an inverting amplifier circuit to set the secondary peak current value; a charge switch drive unit that drives the charge switch based on the primary peak current value and a current value flowing through the charge switch; 6. The fluid control valve according to claim 4, further comprising a discharge switch drive unit that drives the discharge switch based on the secondary peak current value and a value of a current flowing through the discharge switch.

7. 7. The fluid control valve according to claim 6, wherein the secondary-side peak current setting unit sets a cycle in which only charging of the piezoelectric actuator is repeated, a cycle in which charging and discharging of the piezoelectric actuator are repeated, and a cycle in which only discharging of the piezoelectric actuator is repeated, by lowering a reference potential input to a non-inverting amplification terminal of the inverting amplification circuit.

8. A fluid control valve according to any one of claims 1 to 7; A fluid sensor for measuring a fluid flowing through a flow path; a valve control unit that controls the fluid control valve based on a measurement value of the fluid sensor.

9. A drive circuit connected to the piezoelectric actuator, a flyback transformer having a primary winding connected to a DC power supply and a secondary winding connected to the piezoelectric actuator; a charge switch connected to the primary winding and turned on and off to charge the piezoelectric actuator; a discharge switch connected to the secondary winding and turned on and off to discharge the piezoelectric actuator; a regenerative capacitor connected to the primary winding for regenerating discharge energy of the piezoelectric actuator; a switch control unit that controls an on / off operation of the charge switch and the discharge switch, The switch control unit controls the charge switch and the discharge switch to repeatedly charge and discharge the piezoelectric actuator, thereby controlling the voltage applied to the piezoelectric actuator.

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