Fluid control valve, fluid control device, and drive circuit

Abstract

The present invention provides a fluid control valve, a fluid control device, and a drive circuit capable of accurately controlling an output voltage of a piezoelectric actuator without switching an operation mode during charging and discharging of the piezoelectric actuator, the drive circuit of the piezoelectric actuator comprising: a flyback transformer having a primary coil connected to a DC power supply and a secondary coil connected to a DC power supply; the secondary coil is connected to the piezoelectric actuator; the charging switch is connected to the primary coil; a discharge switch connected to the secondary coil; a recovery capacitor connected to the primary coil and recovering discharge energy of the piezoelectric actuator; and a switch control unit that controls the on / off operation of the charge switch and the discharge switch, the switch control unit controlling the on / off operation of the charge switch and the discharge switch to repeatedly charge and discharge the piezoelectric actuator so as to control the applied voltage of the piezoelectric actuator.

Description

Technical Field

[0001] The invention relates to a fluid control valve, a fluid control device and a driving circuit. Background Art

[0002] For example, in a semiconductor manufacturing process, a mass flow controller controls the flow rate of a gas supplied into a chamber. The mass flow controller includes a fluid control valve and a flow sensor, and the fluid control valve includes, for example, a piezoelectric actuator. In addition, in order to reduce the deviation between the measured flow rate of the flow sensor and the set flow rate, the voltage applied to the piezoelectric actuator is controlled.

[0003] However, when the piezoelectric actuator starts to contract from a state in which it is extended by voltage application, the charge stored in the piezoelectric actuator needs to be discharged. Conventionally, the charge discharged from the piezoelectric actuator is consumed as heat in a resistor in a drive circuit, for example.

[0004] In recent years, there are cases where the supply and stop of gas are repeated at high speed and high frequency, such as in the ALD process. In this case, it is necessary to open and close the fluid control valve at high speed. As a result, the discharge opportunities of the piezoelectric actuator increase, the heat loss in the drive circuit increases, and the energy efficiency deteriorates.

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

[0006] However, when controlling to a constant voltage or controlling within a small voltage range, it is necessary to switch the operation mode between the charging mode and the discharging mode while performing control, so the control of the bidirectional power supply circuit becomes complicated, and in some cases, there is a possibility of output voltage oscillation. Prior art literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-201630 Summary of the invention

[0008] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to control the output voltage of a piezoelectric actuator with high accuracy without switching the operation mode when the piezoelectric actuator is charged and discharged.

[0009] That is, the fluid control valve of the present invention includes a piezoelectric actuator and a driving circuit connected to the piezoelectric actuator, and the fluid control valve is characterized in that it includes: a flyback transformer, a primary coil of which is connected to a DC power supply, and a secondary coil of which is connected to the piezoelectric actuator; a charging switch connected to the primary coil, which is turned on and off to charge the piezoelectric actuator; a discharging switch connected to the secondary coil, which is turned on and off to discharge the piezoelectric actuator; a recovery capacitor connected to the primary coil, which recovers the discharge energy of the piezoelectric actuator; and a switch control unit, which controls the on and off actions of the charging switch and the discharging switch, and the switch control unit controls the charging and discharging of the piezoelectric actuator repeatedly by controlling the on and off actions of the charging switch and the discharging switch, thereby controlling the applied voltage of the piezoelectric actuator.

[0010] According to such a fluid control valve, the piezoelectric actuator is repeatedly charged and discharged, thereby controlling the applied voltage of the piezoelectric actuator, so that the output voltage of the piezoelectric actuator can be controlled with good accuracy without switching the operation mode when the piezoelectric actuator is charged and discharged. In particular, in the present invention, when the piezoelectric actuator is controlled to a constant voltage or a predetermined small voltage range, it is not necessary to switch the operation mode when the piezoelectric actuator is charged and discharged, so the output voltage of the piezoelectric actuator can be controlled with good accuracy.

[0011] As a specific embodiment, it is preferable that the switch control unit repeatedly performs charging and discharging of the piezoelectric actuator by repeatedly performing a cycle consisting of one on-off operation of the charging switch and one on-off operation of the discharging switch.

[0012] As a specific embodiment, preferably, the switch control unit controls the ratio of the charging energy of a single charge to the discharge energy of a single discharge of the piezoelectric actuator by controlling the on and off actions of the charging switch and the discharging switch, thereby controlling the applied voltage of the piezoelectric actuator.

[0013] As a specific implementation method for controlling the ratio of the charging energy of a single charge to the discharging energy of a single discharge of a piezoelectric actuator, if the primary side switch current value flowing into the charging switch reaches a predetermined primary side peak current value, the switch control unit switches the charging switch from on to off, and if the secondary side switch current value flowing into the discharging switch reaches a predetermined secondary side peak current value, the switch control unit switches the discharging switch from on to off. The switch control unit controls the ratio of the charging energy of a single charge to the discharging energy of a single discharge of the piezoelectric actuator by controlling the ratio of the primary side peak current value to the secondary side peak current value.

[0014] As a specific embodiment of controlling the ratio of the primary side peak current value to the secondary side peak current value, preferably, the switch control unit controls the ratio of the primary side peak current value to the secondary side peak current value based on the output voltage to the piezoelectric actuator.

[0015] Preferably, the switch control unit includes: a primary side peak current setting unit, which 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, which sets the secondary side peak current value by inverting and amplifying the set primary side peak current value through an inverting amplifier circuit; a charging switch driving unit, which drives the charging switch based on the primary side peak current value and the current value flowing through the charging switch; and a discharging switch driving unit, which drives the discharging switch based on the secondary side peak current value and the current value flowing through the discharging switch.

[0016] Preferably, in the secondary side peak current setting unit, by lowering the reference potential input to the non-inverting amplifier terminal of the inverting amplifier circuit, a cycle of repeatedly charging the piezoelectric actuator, a cycle of repeatedly charging and discharging the piezoelectric actuator, and a cycle of repeatedly discharging the piezoelectric actuator are set.

[0017] Furthermore, a fluid control device of the present invention includes: the above-mentioned fluid control valve; a fluid sensor for measuring a fluid flowing in a flow path; and a valve control unit for controlling the fluid control valve based on a measurement value of the fluid sensor.

[0018] Moreover, the driving circuit of the present invention is connected to the piezoelectric actuator, and the driving circuit is characterized in that it includes: a flyback transformer, a primary coil of which is connected to a DC power supply, and a secondary coil of which is connected to the piezoelectric actuator; a charging switch connected to the primary coil and turned on and off to charge the piezoelectric actuator; a discharging switch connected to the secondary coil and turned on and off to discharge the piezoelectric actuator; a recovery capacitor connected to the primary coil and recovering the discharge energy of the piezoelectric actuator; and a switch control unit that controls the on and off actions of the charging switch and the discharging switch, and the switch control unit repeatedly charges and discharges the piezoelectric actuator by alternately turning on and off the charging switch and the discharging switch, and controls the applied voltage of the piezoelectric actuator by controlling the size of the charging energy of a single charge and the discharge energy of a single discharge of the piezoelectric actuator.

[0019] As described above, according to the present invention, the output voltage of the piezoelectric actuator can be controlled with high accuracy without switching the operation mode when the piezoelectric actuator is charged and discharged. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a diagram schematically showing the configuration of a fluid control device according to an embodiment of the present invention. Figure 2 It is a diagram schematically showing the configuration of a driving circuit in the same embodiment. Figure 3 Schematic diagram showing the relationship between the primary peak current value and the secondary peak current value in the same embodiment. Figure 4 1 is a diagram showing a primary-side switching current, a secondary-side switching current, a voltage of a recovery capacitor, and a voltage of a piezoelectric actuator in one cycle of operation of the drive circuit according to the same embodiment. Figure 5 (a) is a graph showing the relationship between the primary peak current value and the secondary peak current value when the same embodiment is controlled to a constant voltage or a small voltage range, (b) is a graph showing the relationship between the primary peak current value and the secondary peak current value when the discharge is started from a state where a predetermined voltage is applied, and (c) is a graph showing the relationship between the primary peak current value and the secondary peak current value when the charging is started from a state where a predetermined voltage is applied, according to the same embodiment. Description of Reference Numerals 100…Fluid control device 10…DC power supply 31…Fluid sensor 32…Fluid control valve 32a…Piezoelectric actuator 32b...Drive circuit 4b…Valve control unit 5…Flyback transformer 51…Primary coil 52…Secondary coil 6…Charging switch 7…Discharge switch 8…Recycling capacitors 9…Switch control unit 9a…Primary side peak current setting unit 9b…Secondary side peak current setting unit 91…Inverting amplifier circuit 9c…Charging switch driver 9d…Discharge switch drive unit DETAILED DESCRIPTION

[0021] Hereinafter, one embodiment of the fluid control device of the present invention will be described with reference to the drawings. In order to facilitate understanding, any of the following drawings will be schematically described with appropriate omissions or exaggerations. The same components will be given the same reference numerals and their description will be appropriately omitted.

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

[0023] Specifically, the fluid control device 100 is a so-called differential pressure mass flow controller (differential pressure MFC), such as Figure 1 As shown, the fluid control apparatus 100 includes: a flow path module 2 in which a plurality of internal flow paths 2R are formed; and a fluid control device 3 mounted on the flow path module 2 .

[0024] The flow channel module 2 is provided with an inlet 21 for introducing a fluid into the internal flow channel 2R and a outlet 22 for outleting the fluid from the internal flow channel 2R.

[0025] The fluid control device 3 controls the fluid in the internal flow channel 2R and includes a flow sensor 31 for measuring the flow rate of the fluid flowing in the internal flow channel 2R and a fluid control valve 32 provided on the upstream side of the flow sensor 31. The valve opening of the fluid control valve 32 is feedback-controlled by the control unit 4 described later.

[0026] The flow sensor 31 is a differential pressure flow sensor, and includes an upstream pressure sensor 31a provided on the upstream side of a fluid impedance element 33 such as a restrictor or an orifice provided in the internal flow passage 2R, and a downstream pressure sensor 31b provided on the downstream side of the fluid impedance element 33. The flow rate Q flowing in the internal flow passage 2R is calculated by a flow calculation unit 4a of the control unit 4 described later, using the upstream pressure P1 of the fluid impedance element 33 measured by the upstream pressure sensor 31a and the downstream pressure P2 of the fluid impedance element 33 measured by the downstream pressure sensor 31b.

[0027] The fluid control valve 32 is provided on the upstream side of the differential pressure flow sensor 31. The fluid control valve 32 controls the flow rate by moving the valve core forward and backward relative to the valve seat by a piezoelectric actuator. Specifically, the fluid control valve 32 includes a valve seat, a valve core displaced relative to the valve seat, a piezoelectric actuator 32a displaced by the valve core, and a drive circuit 32b driving the piezoelectric actuator 32a. The piezoelectric actuator 32a is formed by, for example, alternately stacking a piezoelectric element and an electrode. The piezoelectric actuator 32a changes to a length corresponding to the voltage applied by the drive circuit 32b. In addition, the drive circuit 32b will be described later.

[0028] The control unit 4 includes: a flow rate calculation unit 4a that calculates a flow rate Q flowing in the internal flow passage 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 including, for example, a CPU, a memory, an A / D and D / A converter, and an input / output device, and functions as the flow rate calculation unit 4a, the valve control unit 4b, etc. by executing a flow rate control program stored in the memory to link various devices.

[0029] The flow rate calculation unit 4a calculates the flow rate Q flowing in the internal flow channel 2R based on 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 impedance element 33, the downstream pressure sensor 31b and the flow rate calculation unit 4a constitute a so-called pressure-type flow rate sensor 31. In addition, the calculation formula of the flow rate used in the flow rate calculation unit 4a can use an existing calculation formula. In addition, 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 feedback control on 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 inputs 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 through PID calculation.

[0031] <Drive Circuit 32b of Fluid Control Valve 32> Next, refer to Figure 2 The drive circuit 32b of the fluid control valve 32 is described in detail.

[0032] like Figure 2 As shown, the drive circuit 32 b includes a flyback transformer 5 , a charging switch 6 , a discharging switch 7 , a recovery capacitor 8 , and a switch control unit 9 for controlling the on and off operations of the charging switch 6 and the discharging switch 7 .

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

[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 coil 51. The charging switch 6 is a semiconductor switch such as a field effect transistor (FET), and a drive command output from the switch control unit 9 is input to the gate. A rectifier diode 11 is connected in parallel to the charging switch 6, and the rectifier diode 11 allows current to flow in one direction from the low voltage side to the high voltage side in the primary coil 51.

[0035] In addition, 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 coil 52. The discharge switch 7 is a semiconductor switch such as a field effect transistor (FET), and a drive command output from the switch control unit 9 is input to the gate. A rectifier diode 12 is connected in parallel to the discharge switch 7, and the rectifier diode 12 allows current to flow in the secondary coil 52 in one direction from the low voltage side to the high voltage side.

[0036] A recovery capacitor 8 for recovering electric energy (hereinafter, discharge energy) generated by discharge of the piezoelectric actuator 32 a is connected to the high voltage side of the primary coil 51 . The recovery capacitor 8 is connected in parallel to the DC power supply 10 in the primary coil 51 .

[0037] Furthermore, a diode 13 is connected to the high voltage side of the primary coil 51, closer to the DC power supply 10 than the connection point of the recovery capacitor 8. The anode of the diode 13 is connected to the DC power supply 10, and the cathode is connected to the recovery capacitor 8. When the piezoelectric actuator 32a is discharged, the current generated from the primary coil 51 of the flyback transformer 5 flows only to the recovery capacitor 8.

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

[0039] The switch control unit 9 of this embodiment controls the ratio of the charging energy of one charge to the discharging energy of one discharge of the piezoelectric actuator 32a by alternately turning the charging switch 6 and the discharging switch 7 on and off, thereby controlling the applied voltage of the piezoelectric actuator 32a. pri Reaching the predetermined primary side peak current value I th1 , the switch control unit 9 switches the charging switch 6 from on to off. In addition, if the secondary side switch current value I flowing into the discharge switch 7 sec Reaching the predetermined secondary side peak current value I th2 , the switch control unit 9 switches the discharge switch 7 from on to off. Furthermore, the switch control unit 9 is based on the output voltage V sec , control the primary side peak current value I th1 The secondary side peak current value I th2The ratio of the charging energy of one charge to the discharging energy of one discharge of the piezoelectric actuator 32a is thereby controlled.

[0040] As the detailed structure of the switch control unit 9, Figure 2 As shown, the primary side peak current setting unit 9a is provided, based on the output voltage V sec Set the primary side peak current value I th1 The secondary side peak current setting unit 9b, by setting the primary side peak current value I th1 Inverting amplification to set the secondary side peak current value I th2 Charging switch driving unit 9c, based on the primary side peak current value I th1 and the current value I flowing through the charging switch 6 pri , driving the charging switch 6; and the discharging switch driving unit 9d, based on the secondary side peak current value I th2 and the current value flowing through the discharge switch 7, driving the discharge switch 7.

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

[0042] The secondary-side peak current setting unit 9b uses the inverting amplifier circuit 91 to convert the primary-side peak current value I set by the primary-side peak current setting unit 9a to th1 Inverting amplification to set the secondary side peak current value I th2 Here, a reference potential (branch potential) is input from the branch potential setting section 90 to the non-inverting amplifier terminal of the inverting amplifier circuit 91. The reference potential is set to set the primary side peak current value I th1 Here, if Figure 3 As shown in FIG. 1 , the primary side peak current value I is determined based on the support point potential input to the non-inverting amplifier terminal of the inverting amplifier circuit 91. th1 and the secondary side peak current value I th2 .

[0043] The charging switch driving unit 9c is composed of a trigger circuit 92, and a charging on pulse (SetPulse1) for turning on the charging switch 6 is input to the set terminal, and a primary side reset pulse (ResetPulse1) for turning off the charging switch 6 is input to the reset terminal. A driving instruction is output from the output terminal of the trigger circuit 92 to the gate of the charging switch 6, so that the charging switch 6 performs an on-off operation.

[0044] In addition, before the discharge on pulse (Setpulse2) for turning on the discharge switch 7 is generated, based on the reset pulse (hereinafter, the primary side on threshold pulse (Timelimit1)) for turning off the charge switch 6 and the current value I flowing through the charge switch 6 pri The peak current value I reaches the primary side th1 The primary side arrival signal (ThreshPulse1) is used to generate a primary side reset pulse. Specifically, the primary side reset pulse is a signal output by inputting the primary side on-threshold pulse and the primary side arrival signal to the OR circuit 93. In addition, the primary side arrival signal is a signal output by inputting the current value I flowing through the charging switch 6. pri and the primary side peak current value I th1 The primary side comparator (comparator) 94 outputs a high level signal.

[0045] The discharge switch driving unit 9d is composed of a trigger circuit 95, and a discharge on pulse (Setpulse2) for turning on the discharge switch 7 is input to the set terminal, and a secondary side reset pulse (ResetPulse2) for turning off the discharge switch 7 is input to the reset terminal. A drive command is output from the output terminal of the trigger circuit 95 to the gate of the discharge switch 7, so that the discharge switch 7 performs an on-off operation.

[0046] In addition, before the charge on pulse (Setpulse1) for turning on the charge switch 6 is generated, based on the reset pulse (hereinafter, secondary side on threshold pulse (Timelimit2)) for turning off the discharge switch 7 and the current value I sec The secondary side peak current value I th2 The secondary side arrival signal (ThreshPulse2) is used to generate a secondary side reset pulse. Specifically, the secondary side reset pulse is a signal output by inputting the secondary side turn-on critical pulse and the secondary side arrival signal to the OR circuit 96. In addition, the secondary side arrival signal is a signal output by inputting the current value I flowing through the discharge switch 7. sec and the secondary side peak current value I th2 The secondary side comparator 97 outputs a high level signal.

[0047] <One Cycle of Operation of Driving Circuit 32b> Next, refer to Figure 4 The operation of one cycle of the driving circuit 32b will be described. Here, the operation of one cycle is an operation of performing one charge and one discharge.

[0048] (1) First, if the charging switch 6 is turned on, a constant current flows to the primary coil 51, and the energy (E1 = 1 / 2 × L1 × I pri2 ) is stored in the flyback transformer 5.

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

[0050] (3) Thereafter, if the discharge switch 7 is turned on, current flows from the piezoelectric actuator 32a to the secondary coil 52, and the energy (E2 = 1 / 2 × L2 × I sec 2 ) is stored in the flyback transformer 5. At this time, the piezoelectric actuator 32a is discharged.

[0051] (4) When the discharge switch 7 is turned off, the rectifying diode 11 on the primary side is turned on, and current flows to the primary coil 51. The energy (E2) stored in the flyback transformer 5 is charged to the recovery capacitor 8, and the voltage of the recovery capacitor 8 increases.

[0052] In the next cycle, the energy recovered in the recovery capacitor 8 in the above-mentioned (4) is used to store energy in the flyback transformer 5 .

[0053] <Overall Operation of Driving 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 (controlled to a constant voltage or a small predetermined voltage range), as shown in FIG. Figure 5 As shown in (a), the switch control unit 9 sets the primary side peak current value I th1 and the secondary side peak current value I th2 The ratio of the charging energy to the piezoelectric actuator 32a and the discharging energy from the piezoelectric actuator 32a becomes 1:1, and the charging switch 6 and the discharging switch 7 are repeatedly turned on and off. In addition, the small predetermined voltage range is, for example, a range of ±10% relative to the entire range of the applied voltage of the actuator. As a result, the charging energy to the piezoelectric actuator 32a and the discharging energy from the piezoelectric actuator 32a become 1:1, the applied voltage of the piezoelectric actuator 32a becomes constant, and the fluid control valve 32 maintains a predetermined opening.

[0054] When the piezoelectric actuator 32a is caused to discharge from a state where a predetermined voltage is applied so as to change the opening degree, as shown in FIG. Figure 5 As shown in (b), the switch control unit 9 has a primary side peak current value I th1 The secondary side peak current value I th2 The secondary side peak current value I is increased by th2The ratio of the charging switch 6 and the discharging switch 7 is repeatedly turned on and off. As a result, the discharge energy from the piezoelectric actuator 32a is greater than the charging energy to the piezoelectric actuator 32a, the applied voltage to the piezoelectric actuator 32a is reduced, and the opening degree of the fluid control valve 32 changes.

[0055] Here, when the piezoelectric actuator 32a is discharged, there is a primary side peak current value I set by the primary side peak current setting unit 9a according to the discharge voltage. th1 In this case, since the primary-side comparator 94 outputs a high-level signal, the charging switch 6 continues the OFF operation, and the discharging switch 7 repeatedly turns on and off, thereby performing only the discharging operation.

[0056] In addition, when the piezoelectric actuator 32a is charged from a state where a predetermined voltage is applied so as to change the opening degree, as shown in FIG. Figure 5 As shown in (c), the switch control unit 9 has a primary side peak current value I th1 The secondary side peak current value I th2 The primary side peak current value I is increased by th1 The charging switch 6 and the discharging switch 7 are repeatedly turned on and off at a ratio of , thereby causing the charging energy to the piezoelectric actuator 32a to be greater than the discharging energy from the piezoelectric actuator 32a, increasing the applied voltage to the piezoelectric actuator 32a and changing the opening of the fluid control valve 32.

[0057] Here, when the piezoelectric actuator 32a is charged, there is a secondary side peak current value I set by the secondary side peak current setting unit 9b according to the charging voltage. th2 In this case, since the secondary-side comparator 97 outputs a high-level signal, the discharge switch 7 continues to be turned off, and the charge switch 6 repeatedly turns on and off, thereby performing only the charging operation.

[0058] <Effects of the present embodiment> In this way, according to the fluid control device 100 of this embodiment, the piezoelectric actuator 32a is repeatedly charged and discharged, and the charging energy of a single charge and the discharge energy of a single discharge of the piezoelectric actuator 32a are controlled, thereby controlling the applied voltage of the piezoelectric actuator 32a. Therefore, the output voltage of the piezoelectric actuator 32a can be controlled with good precision without switching the action mode when the piezoelectric actuator 32a is charged and discharged.

[0059] <Other Implementation Methods> For example, in the above-described embodiment, an example is shown in which the driving circuit 32 b is configured by an analog circuit, but it may be configured by a digital circuit that performs the functions of each part of the analog circuit.

[0060] In addition, it can also be configured that in the secondary side peak current setting unit 9b, by lowering the reference potential input to the non-inverting amplifier terminal of the inverting amplifier circuit 91, a cycle of repeatedly charging the piezoelectric actuator 32a, a cycle of repeatedly charging and discharging the piezoelectric actuator 32a, and a cycle of repeatedly discharging the piezoelectric actuator 32a can be arbitrarily set.

[0061] Furthermore, the flow 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 of the above-described embodiment is used as a mass flow controller of a fluid control device, but may be various valves such as a pressure control valve of a pressure control device and a shutoff valve.

[0063] In addition, various modifications and combinations of the embodiments may be made without departing from the spirit of the present invention.

Claims

1. A fluid control valve, comprising a piezoelectric actuator and a drive circuit connected to the piezoelectric actuator, wherein the fluid control valve is characterized in that: The driving circuit comprises: a flyback transformer, wherein the primary coil is connected to a DC power supply and the secondary coil is connected to the piezoelectric actuator; A charging switch connected to the primary coil and turned on and off to charge the piezoelectric actuator; A discharge switch connected to the secondary coil, which is turned on and off to discharge the piezoelectric actuator; A recovery capacitor connected to the primary coil to recover the discharge energy of the piezoelectric actuator; as well as a switch control unit, controlling the on and off actions of the charging switch and the discharging switch, The switch control unit controls the on and off operations of the charge switch and the discharge switch to repeat charging and discharging of the piezoelectric actuator, thereby controlling the applied voltage of the piezoelectric actuator.

2. The fluid control valve according to claim 1, characterized in that: The switch control unit repeatedly performs charging and discharging of 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. The fluid control valve according to claim 1 or 2, characterized in that: The switch control unit controls the on / off operation of the charging switch and the discharging switch to control the ratio of the charging energy of one charge to the discharging energy of one discharge of the piezoelectric actuator, thereby controlling the applied voltage of the piezoelectric actuator.

4. The fluid control valve according to claim 3, characterized in that: If the primary-side switch current value flowing into the charging switch reaches a predetermined primary-side peak current value, the switch control unit switches the charging switch from on to off. If the secondary-side switch current value flowing into the discharge switch reaches a predetermined secondary-side peak current value, the switch control unit switches the discharge switch from on to off. The switch control unit controls the ratio of the charging energy of one charge to the discharging energy of one discharge of the piezoelectric actuator by controlling the ratio of the primary-side peak current value to the secondary-side peak current value.

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

6. The fluid control valve according to claim 4 or 5, characterized in that: The switch control unit comprises: a primary-side peak current setting unit that sets the primary-side peak current value based on an output voltage to the piezoelectric actuator; A secondary side peak current setting unit sets the secondary side peak current value by inverting and amplifying the set primary side peak current value through an inverting amplifier circuit; a charging switch driving unit, configured to drive the charging switch based on the primary-side peak current value and a current value flowing through the charging switch; and The discharge switch driving unit drives the discharge switch based on the secondary side peak current value and a current value flowing through the discharge switch.

7. The fluid control valve according to claim 6, characterized in that: In the secondary side peak current setting unit, by lowering the reference potential input to the non-inverting amplifier terminal of the inverting amplifier circuit, a cycle of only repeatedly charging the piezoelectric actuator, a cycle of repeatedly charging and discharging the piezoelectric actuator, and a cycle of only repeatedly discharging the piezoelectric actuator are set.

8. A fluid control device, characterized in that: include: The fluid control valve according to any one of claims 1 to 7; A fluid sensor, which measures the fluid flowing in the flow channel; as well as The valve control unit controls the fluid control valve based on the measurement value of the fluid sensor.

9. A driving circuit connected to a piezoelectric actuator, the driving circuit comprising: a flyback transformer, wherein the primary coil is connected to a DC power supply and the secondary coil is connected to the piezoelectric actuator; A charging switch connected to the primary coil and turned on and off to charge the piezoelectric actuator; A discharge switch connected to the secondary coil, which is turned on and off to discharge the piezoelectric actuator; A recovery capacitor connected to the primary coil to recover the discharge energy of the piezoelectric actuator; as well as a switch control unit, controlling the on and off actions of the charging switch and the discharging switch, The switch control unit controls the charging switch and the discharging switch to repeat charging and discharging of the piezoelectric actuator, thereby controlling the applied voltage of the piezoelectric actuator.

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