JP2005315225A - Driving circuit and trapezoidal wave generation circuit for micro pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving circuit for a micro pump capable of reducing size and cost with a simple structure. <P>SOLUTION: This circuit includes a capacitor C1, a constant current charging part 51 charging the capacitor with constant current, a constant current discharging part 52 discharging the capacitor with constant current, a buffer part 53 taking out and outputting voltage form at both ends of the capacitor, and a switching part 54 periodically switching and operating the constant current charging part 51 and the constant current discharging part 52. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a driving circuit for a micropump that operates by applying a trapezoidal wave. The present invention has, for example, two throttle channels connected to a chamber and an actuator for increasing or decreasing the volume of the chamber, and the ratio of the channel resistances of the two throttle channels is increased when the volume of the chamber is increased or decreased. It is used to drive a micropump that is configured to change the liquid feed.

  2. Description of the Related Art Conventionally, μ-TAS (Micro Total Analysis System), which applies micromachine technology and refines equipment and methods for chemical analysis and chemical synthesis, has attracted attention. As an element necessary for μ-TAS, there is a micropump that conveys a minute amount of liquid. The present applicant has proposed such a micropump in US Pat. Such a micropump is driven by applying a trapezoidal voltage having a different rise time and fall time to an actuator such as a piezoelectric element.

A drive circuit that generates such a trapezoidal wave (trapezoidal waveform) can be configured by generating a sawtooth wave to clamp the upper limit or by generating a trapezoidal wave from digital data.
JP2001-322099

  However, the conventional drive circuit requires large parts such as an operational amplifier and a coil part, and the circuit is complicated and has a large number of parts. Therefore, there is a limit to downsizing. In particular, when a trapezoidal wave is digitally generated, the scale becomes large because a memory, an arithmetic circuit, a DA converter, a waveform shaping circuit, and the like are necessary.

  A circuit configuration as shown in FIG. 13 is also conceivable.

  That is, in the drive circuit 80 shown in FIG. 13, a rising and falling straight line portion is obtained by an integrating circuit using an operational amplifier (op-amp) AMP1, and a trapezoidal wave is generated. As a result, as shown in FIG. 14, the signal rises by the middle of time T1 when the control signal S1 is “H” and falls by the middle of time T2 when the control signal S1 is “L”. The rise time Tr and the fall time Tf can be adjusted by resistors R10, R11 and the like.

  However, the drive circuit 80 shown in FIG. 13 has a problem that spike-like overshoot occurs in the negative direction when the trapezoidal wave rises as shown in FIG. In order to eliminate this overshoot, it is necessary to use an expensive operational amplifier AMP1 with good characteristics or to add an absorption circuit, and there remains a problem in terms of cost. Further, since the output voltage of the drive circuit is required to be about 50 volts, it is necessary to use the operational amplifier AMP1 that operates at a voltage corresponding to the output voltage, which is disadvantageous in terms of downsizing and cost.

  As described above, conventionally, it is difficult to reduce the size of the drive circuit and to manufacture the drive circuit at a low cost, and there is no problem in experimental use for development and analysis of a micropump. An ultra-small drive circuit could not be incorporated with the micropump as an element.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a micropump drive circuit and a trapezoidal wave generation circuit that can be reduced in size and cost with a simple configuration.

  The drive circuit according to the present invention includes a capacitor, a constant current charging unit for charging the capacitor with a constant current, a constant current discharging unit for discharging the capacitor with a constant current, and a voltage waveform across the capacitor. And a switching unit for periodically switching and operating the constant current charging unit and the constant current discharging unit.

  The constant current charging unit charges the capacitor to the voltage of the DC power source in a time shorter than the first time when the constant current charging unit is switched to operate, and the constant current discharging unit The constant current discharging unit and the constant current discharging unit have respective currents so that the constant current discharging unit discharges the capacitor to a voltage of zero during a time shorter than a second time during which the switching is performed. Is set.

  Preferably, the constant current discharge unit includes a constant current diode or a junction FET.

  The buffer unit is constituted by an emitter follower circuit of a transistor.

  Also, a pulse that periodically switches on and off at a predetermined duty ratio for switching between the operation of charging the capacitor by operating the transistor of the constant current circuit and the operation of discharging the capacitor by the constant current discharging circuit. A circuit for outputting the control signal is provided.

  According to another embodiment of the drive circuit of the present invention, a capacitor, a constant current charging unit for charging the capacitor with a constant current, a constant current discharging unit for discharging the capacitor with a constant current, A plurality of buffer units for extracting and outputting voltage waveforms at both ends of the capacitor, and a switching unit for periodically switching and operating the constant current charging unit and the constant current discharging unit, Each of the plurality of buffer units has a circuit that switches between and extracts the voltage waveform and an attenuated voltage waveform obtained by attenuating the voltage waveform at a predetermined ratio, and the plurality of buffer units are configured to output the voltage waveform sequentially. The buffer unit that is not outputting the voltage waveform is controlled to output the attenuated voltage waveform in each cycle.

  Each of the plurality of buffer units includes a first buffer circuit including three resistors and transistors connected in series to divide the voltage waveform, and two of the three resistors. A second buffer circuit configured to include a transistor for outputting a voltage waveform at a connection portion of the two resistors, and a switch circuit for short-circuiting the remaining one of the two resistors. Composed.

  In the driving circuit of one embodiment of the present invention, in the driving circuit according to each aspect, the charging speed of the constant current charging unit is different from the discharging speed of the constant current discharging unit.

  According to the present invention, the micropump drive circuit and the trapezoidal wave generating circuit can be simply configured, and the size and cost can be reduced.

[First Embodiment]
First, the micropump MP used in the first embodiment will be described.

  1 is a plan view schematically showing the configuration of a microfluidic system 1 according to a first embodiment of the present invention, FIG. 2 is a front sectional view of the micropump MP shown in FIG. 1, and FIGS. 3 and 4 are piezoelectric elements. It is a figure which shows the example of the waveform of this drive voltage.

  In FIG. 1, the microfluidic system 1 is configured as a microchip on a silicon substrate 31, and two types of liquids LA and LB pumped by two micropumps MP <b> 1 and MP <b> 2 are joined at the inlet of a flow path 25. , It is configured to feed out from a port (liquid outlet) 27.

  That is, the microfluidic system 1 includes ports (liquid inlets) 11 and 12, channels 13 and 14, openings 15 and 16, chambers 17 and 18, openings 19 and 20, channels 21 and 22, narrow channels 23, 24, 25, a flow path 26, and a port 27.

  Different liquids are supplied to the ports 11 and 12 from other appropriate flow paths or reservoirs. The respective liquids pass through the flow paths 13 and 14 and are pumped by the micro pumps MP1 and MP2 to the flow paths 21 and 22, and further to the narrow flow paths 23 and 24, which are narrower than that. The three narrow channels 23, 24, and 25 form a Y-shaped joint channel, and the two liquids pumped to the narrow channels 23 and 24 merge at the inlet of the narrow channel 25. They join at point GT and are routed through channel 26 and out of port 27 to another suitable channel or reservoir.

  Now, the first micro pump MP1 is connected to the chamber 17 which is a pump chamber and the openings 15 and 19 connecting the chamber 17 and the flow path 13 and the chamber 17 and the flow path 21, respectively. The second micropump MP2 is configured by the openings 16, 20 that connect the flow path 14, the chamber 18 and the flow path 22, respectively.

  Since these two micropumps MP1 and MP2 have the same operation principle and structure, only one of them will be described.

  Referring to FIG. 2, micro pump MP1 uses silicon substrate 31 and forms grooves or depressions for forming chamber 17, openings 15, 19 and flow paths 13, 21 by a photolithography process. A glass substrate 32 serving as a bottom plate or a top plate is bonded to the bottom or top thereof. A piezoelectric element 34 such as PZT (lead zirconate titanate) ceramics is adhered and pasted to the diaphragm (diaphragm) portion of the chamber 17.

  By applying a voltage having a waveform shown in FIG. 3A or FIG. 4A to the piezoelectric element 34 by the drive circuit 36, the diaphragm 31f, which is a silicon thin film, and the piezoelectric element 34 bend and deform in a unimorph mode. Using this, the volume of the chamber 17 is increased or decreased.

  In the micropump MP1, the effective sectional areas of the openings 15 and 19 are smaller than the effective sectional areas of the flow paths 13 and 21. The opening 19 is set so that the flow rate resistance change rate when the pressure in the chamber 17 is increased or decreased is smaller than that of the opening 15. Using such flow path resistance characteristics of the openings 15 and 19, pressure is generated in the chamber 17, and the rate of change in the pressure is controlled, so that the openings 15 in each of the discharge process and the suction process. , 19 can achieve a pumping action that discharges or sucks a larger amount of fluid to the one having a lower flow path resistance.

  Such pressure control of the chamber 17 is realized by controlling the drive voltage supplied to the piezoelectric element 34 and controlling the deformation amount and timing of the diaphragm. That is, the drive voltage is controlled so as to have a trapezoidal wave that rises at a constant speed and is held constant for a predetermined period and then falls at a constant speed. In particular, the two openings of the micropump MP are different in the flow rate resistance change rate with respect to the pressure change as described above. Therefore, by making the rising speed and falling speed of the trapezoidal wave different, Fluid transfer is realized. For example, by applying a driving voltage having the waveform shown in FIG. 3A to the piezoelectric element 34, the piezoelectric element 34 discharges to the side of the flow channel 21, and by applying the driving voltage having the waveform shown in FIG. Discharge to the side.

  3 and 4, the maximum voltage e1 applied to the piezoelectric element 34 is about several volts to several tens of volts, and about 100 volts at the maximum. Times T1 and T7 are about 20 μs, times T2 and T6 are about 0 to several μs, and times T3 and T5 are about 60 μs. Times T4 and T8 may be zero. The frequency of the drive voltage is about 11 KHz. With the drive voltage shown in FIGS. 3A and 4A, a flow rate such as that shown in FIGS. 3B and 4B is obtained in the flow path 21, for example. The flow curves in FIGS. 3B and 4B schematically show the flow rate obtained by the pump operation, and actually the inertial vibration of the fluid is superimposed. Therefore, a curve obtained by superimposing a vibration component on the flow rate curves shown in these figures indicates the actual flow rate obtained.

  The details of the operation principle and manufacturing method of the micropump MP can be referred to Patent Document 1 described above.

  FIG. 5 is a diagram illustrating an example of the configuration of the drive circuit 36 according to the first embodiment, and FIG. 6 is a diagram illustrating a waveform of the drive voltage Vout output from the drive circuit 36.

  5, the drive circuit 36 includes a capacitor C1, a constant current charging unit 51, a constant current discharging unit 52, a buffer unit 53, a switching unit 54, a pulse generating unit 55, a DC power source 56, and the like.

  Referring also to FIG. 6, the constant current charging unit 51 is a constant current circuit for charging the capacitor C <b> 1 by flowing a constant current IC from the DC power source 56. As the capacitor C1, for example, a capacitor having a value of about 1/100 μF to 1 μF, preferably about a few μF of 100 / several μF of 10/10, for example, about 0.1 μF is used. The magnitude of the current IC is, for example, about several mA to several tens mA. The rising characteristic of the drive voltage Vout changes according to the magnitude of the current IC.

  The constant current discharging unit 52 is for discharging the capacitor C1 with a constant current ID. The magnitude of the current ID is, for example, about several mA to several tens mA. The falling characteristic of the drive voltage Vout changes according to the magnitude of the current IC. For the constant current discharge unit 52, for example, a constant current diode or a junction FET is used in order to obtain constant current characteristics.

  The buffer unit 53 takes out the voltage waveform at both ends of the capacitor C1 and outputs it as the drive voltage Vout. The drive voltage Vout is directly applied to the piezoelectric element 34. The buffer unit 53 is configured by, for example, an emitter follower circuit of a transistor.

  The switching unit 54 is for switching and operating the constant current charging unit 51 and the constant current discharging unit 52 based on the control signal S1. In FIG. 5, two contact switches and a logic element symbol for switching between them are functionally shown. However, various circuit elements or components can be used without sticking to these symbols.

  The pulse generator 55 outputs a pulsed control signal S1 that periodically switches on and off (“H” and “L”) at a predetermined duty ratio. The DC power supply 56 supplies the voltage VD to the constant current charging unit 51 and supplies various voltages necessary for the drive circuit 36. For the sake of brevity, the terminals that output the control signals S2 and S3 are shown in FIG. 5, but these are used in a third embodiment to be described later. This is not necessary in the embodiment.

  The constant current charging unit 51 is switched to operate at the first time TC, which is equal to the time when the control signal S1 is “L”, but at a shorter time Tr. The value of the current IC is set so that the capacitor C1 is charged to the voltage VD of the DC power supply 56. The second time TD when the constant current discharging unit 52 is switched to operate, which is equal to the time when the control signal S1 is “H”, but at a shorter time Tf, is constant current discharging unit 52. The value of the current ID is set so that the capacitor C1 is discharged to zero voltage.

The micropump shown in FIG. 2 can transport fluid to either side of the openings 15 and 19 depending on the driving waveform as described above, but turbulence occurs near the opening 19 where cavitation is difficult to occur. For reasons such as difficulty, it is preferable that the sheet is transported to the opening 19 side, and the transport to the opening 19 side is the forward direction (M1). The drive circuit has a charging rate of the constant current charging unit 51 and a discharging rate of the constant current discharging unit 52 so as to generate a waveform (FIG. 3 in this example) that can realize fluid transfer in the positive direction more suitable for transfer. It is preferred that they are designed differently. Therefore, in this example, the charging speed is set to be higher than the discharging speed, and the piezoelectric element quickly presses the fluid in the chamber and slowly returns to the original state.


Thus, according to the drive circuit 36, a trapezoidal wave can be easily generated at both ends of the capacitor C1 by charging the capacitor C1 by the constant current charging unit 51 and discharging the capacitor C1 by the constant current discharging unit 52. . The buffer 53 can easily extract the waveform and output it as the drive voltage Vout without affecting the waveform of the capacitor C1. The drive circuit 36 has a simple circuit configuration, and can be reduced in size and cost by being mounted on a small substrate. Therefore, for example, it is possible to arrange the drive circuit 36 at a position indicated by a broken line in FIG.
[Second Embodiment]
Next, a second embodiment will be described. In the second embodiment, only the part relating to the drive circuit 36B is different from that of the first embodiment, and the description of the other parts is omitted. The same applies to the following embodiments.

  FIG. 7 is a diagram illustrating an example of the configuration of the drive circuit 36B according to the second embodiment. In the second embodiment, the drive circuit 36B is shown more specifically than in the first embodiment. In FIG. 7, the pulse generator and the DC power supply are not shown.

  As shown in FIG. 7, the drive circuit 36B includes a capacitor C1, a constant current charging unit 51B, a constant current discharging unit 52B, a buffer unit 53B, a switching unit 54B, and the like.

  The constant current charging unit 51B includes a transistor Q4 and resistors R1 to R3. The constant current discharge unit 52B includes a constant current element G1 such as a constant current diode. The buffer unit 53B includes a transistor Q5 and resistors R4 to R5. The switching unit 54B includes transistors Q1 to Q3 and resistors R6 to R8.

When the control signal S1 is “L”, the transistor Q1 is turned off and the transistor Q3 is turned on. As a result, a bias voltage obtained by dividing the voltage VD by the resistors R1 and R2 is applied to the base of the transistor Q4. When the saturation voltage between the collector and the emitter when the transistor Q3 is on is substantially zero, the bias voltage VB applied to the base of the transistor Q4 is approximately
VB = VD × R2 / (R1 + R2)
It becomes.

At this time, the collector current Ic1 flowing through the transistor Q4 takes into consideration the base-emitter voltage Vbe of the transistor Q4.
Ic1 = [VD−VD × R2 / (R1 + R2) −Vbe] / R3
It becomes.

  The collector current Ic1 becomes a constant current IC and charges the capacitor C1. The voltage VC of the capacitor C1 rises with a linear slope. When the voltage VC reaches almost the voltage VD, it is saturated and does not change with the value of the voltage VD.

  When the control signal S1 is switched to “H”, the transistor Q4 is turned off and the transistor Q2 is turned on at the same time. Thereby, the electric charge accumulated in the capacitor C1 starts discharging at a specific current value of the constant current element G1. The voltage drops with a constant slope until the voltage VC of the capacitor C1 becomes zero (ground level), and when the voltage becomes zero, the value is held.

  The transistor Q5 constitutes an emitter follower circuit and operates as a voltage buffer for the capacitor C1. In order to obtain a desired trapezoidal wave, as described with reference to FIG. 6, the rising is completed at a time Tr within a time TC in which the control signal S1 is “L”, and a flat time Thf is provided. . Then, the discharge is completed at a time Tf within a time TD in which the control signal S1 is “H”, and a ground level flat time Tlf is provided.

The drive circuit 36B can be configured by a general small component that is commercially available, has a simple circuit configuration, and can be mounted on a small substrate. Therefore, it is advantageous for downsizing and cost reduction. For example, as compared with the case where an operational amplifier is used, since the transistor is small, the area of the mounting substrate can be reduced and the cost can be reduced. In addition, there is no problem such as overshoot that occurs when an integrated wave is generated by an operational amplifier, and a trapezoidal wave having an almost ideal waveform can be generated.
[Modification]
FIG. 8 is a diagram illustrating an example of a configuration of a drive circuit 36BB according to a further modification of the second embodiment.

  As shown in FIG. 8, in the drive circuit 36BB of the modification, a constant current operation function defined by a depletion type junction FET Q6 and a resistor R9 is used as the constant current discharge part 52BB. The other parts are the same as those of the drive circuit 36B.

By adjusting the value of the resistor R9, the magnitude of the current ID during discharge can be adjusted. Therefore, a potentiometer or a trimmer may be used as the resistor R9.
[Third Embodiment]
Next, a third embodiment will be described. In the first and second embodiments above, the drive circuits 36, 36B, and 36BB used for the basic driving method of the micropump MP have been described. In the third embodiment, two micropumps MP1 and MP2 are provided. An application example in the case of driving will be described.

  That is, in the microfluidic system 1 shown in FIG. 1, two types of liquids LA and LB are fed into the narrow flow paths 23 and 24 by the two micropumps MP1 and MP2, respectively, and merged at the junction point GT. In the third embodiment, the two types of liquids LA and LB are not continuously fed to the junction point GT, but are intermittently fed alternately.

  That is, while one micropump MP1 is driven to pump the liquid LA, the other micropump MP2 is not driven, while the other micropump MP2 is driven to pump the liquid LB. The micro pump MP1 is not driven. As a result, the two types of liquids LA and LB are alternately and intermittently sent to the confluence point GT.

  At this time, when one micropump MP1 is driven and the liquid LA is being pumped and the other micropump MP2 is stopped without being driven at all, the narrow flow path downstream from the junction point GT. While being fed to 25, the liquid LA also enters the narrow channel 24 on the non-driven side, and the liquid LB flows backward.

  Therefore, when mixed by such a method, the mixed liquid of the liquid LA which has flowed backward and the liquid LB to be transferred next is sent to the confluence point GT, and 20-30% of the mixed liquid is the other. It becomes difficult to obtain an accurate mixing ratio by flowing back to the liquid LA side.

  Therefore, in the third embodiment, as shown in FIG. 9, a minute driving voltage (driving pulse) is also applied to the micropump MP on the non-liquid feeding side to perform fine operation.

  That is, as shown in FIG. 9, while driving one micropump MP1 and pumping the liquid LA, a minute drive voltage is applied as a bias to the other micropump MP2, and the other micropump MP2 is driven. While the liquid LB is being pumped, a minute driving voltage is applied as a bias to one micropump MP1.

  When the control is performed in this way, the pressure at which the liquid pumped by the micropump MP tries to flow backward is balanced with the pressure of the liquid on the non-liquid feeding side. As a result, the liquid is pumped without flowing back. All of the liquid is sent to the narrow channel 25 on the downstream side.

  Therefore, it is possible to accurately obtain the liquid mixing ratio as intended. In addition, there is no liquid backflow, and all the liquid is sent to the narrow channel 25 on the downstream side, so that the flow rate as a whole is increased and the flow rate efficiency is improved.

  Specifically, for example, when both the liquids LA and LB have a viscosity of 1 cps, a driving voltage of 50 V is applied for pressure feeding, whereas a minute driving voltage of 20 V is applied to the side to be finely operated. .

  Also, various mixing ratios can be obtained by changing the duty ratio, which is the ratio between the normal driving voltage and the minute driving voltage. For example, when the duty ratio is 1: 1, the mixing ratio is 1: 1, but when the duty ratio is 1: 2, as shown in FIG. 10, the mixing ratio is 1: 2. Although not shown, when the duty ratio is 1:10, the mixing ratio is 1:10.

  In the third embodiment, a drive circuit 36C for driving the two micropumps MP1 and MP2 as such is used.

  FIG. 11 is a diagram illustrating an example of the configuration of the drive circuit 36C of the third embodiment, and FIG. 12 is a diagram illustrating waveforms of the drive voltages Vout1 and Vout2 output from the drive circuit 36C.

  In FIG. 11, the driving circuit 36C includes a capacitor C1, a constant current charging unit 51C, a constant current discharging unit 52C, first buffer circuits 53C1 and 53C2, second buffer circuits 57C1 and 57C2, switch circuits 58C1 and 58C2, and a switching unit. 54C and the like.

  Among these, the basic configurations and operations of the capacitor C1, the constant current charging unit 51C, the constant current discharging unit 52C, and the switching unit 54C are the same as those of the drive circuit 36B described above.

  The drive circuit 36C is provided with a plurality of buffer units, ie, first buffer circuits 53C1 and 53C2, second buffer circuits 57C1 and 57C2, and a plurality of switch circuits 58C1 and 58C2.

  Each of the first buffer circuits 53C1 and 53C2 includes three resistors R41 to R43 and R44 to 46 and transistors Q51 and Q54 connected in series to divide the voltage VC of the capacitor C1. The second buffer circuits 57C1 and 57C2 are transistors Q52 and 55 for outputting a voltage waveform at a connection portion of two resistors R41 to R42 and R44 to 45 among the three resistors R41 to R43 and R44 to 46, respectively. It is comprised including. The switch circuits 58C1 and 58C2 are for short-circuiting the remaining one of the resistors R43 and R46.

  The pulse generator 55 (see FIG. 5) outputs control signals S2 and S3 that are switched on and off (“H” and “L”) at a predetermined period (TE + TF). The control signals S2 and S3 are signals in which “H” and “L” are inverted from each other.

  From the second buffer circuits 57C1 and 57C2, a normal voltage waveform whose peak value is the voltage VD and an attenuated voltage waveform obtained by attenuating it at a predetermined ratio are switched according to the on / off of the control signals S2 and S3. Drive voltages Vout1 and Vout2 are output.

That is, referring to FIGS. 11 and 12, when control signal S2 is “H” and control signal S3 is “L”, transistor Q53 is on and transistor Q56 is off. The drive voltages Vout1 and Vout2 output from the transistors Q52 and Q55 constituting the emitter follower are respectively the peak values VDL1 and VDH2,
VDL1 = VD × (R42) / (R41 + R42)
VDH2 = VD × (R45 + R46) / (R44 + R45 + R46)
It becomes.

Further, when the control signal S2 is “L” and the control signal S3 is “H”, the drive voltages Vout1 and Vout2 have peak values VDH1 and VDL2, respectively.
VDH1 = VD × (R42 + R43) / (R41 + R42 + R43)
VDL2 = VD × (R45) / (R44 + R45)
It becomes.

  Here, by setting R41 = R44, R42 = R45, and R43 = R46, the peak values of the trapezoidal waves of the drive voltages Vout1 and Vout2 are alternately equal voltage values according to the on / off of the control signals S2 and S3. (VDH1 = VDH2, VDL1 = VDL2) is output. Depending on how the values of the resistors R41 to R46 are set, driving voltages having various peak values can be obtained.

  The switching frequency of the control signals S2 and S3 is about several Hz to several KHz, and when the voltage value VDH is about 50 volts, the voltage value VDL is about 20 volts. The voltage values VDH and VDL may be set to different values, and the two drive voltages Vout1 and Vout2 may be different from each other.

  In the drive circuit 36C, a bipolar transistor is used as a transistor, but a field effect transistor (FET), other various transistors, or semiconductor elements may be used instead.

  Further, since the resistors R43 and R46 connected to the ground are short-circuited by the switch circuits 58C1 and 58C2, the circuit is simplified. However, the peak level of the drive voltage Vout can be increased by short-circuiting the other resistors R. You may change it. Further, various other circuit configurations can be employed instead of the first buffer circuits 53C1 and 53C2, the second buffer circuits 57C1 and 57C2, and the switch circuits 58C1 and 58C2. It is possible to provide three or more first buffer circuits, second buffer circuits, and switch circuits corresponding to three or more micropumps MP.

  According to the drive circuit 36C of the third embodiment, the two micropumps MP1 and MP2 are driven to alternately and intermittently send the two types of liquids LA and LB, so that there is no liquid backflow, and the intended target is achieved. The liquid mixing ratio can be obtained accurately. Various mixing ratios can be obtained by changing the duty ratio of the control signals S2 and S3.

  The drive circuit 36C, like the drive circuits 36 and 36B described above, has a simple circuit configuration and is advantageous for downsizing and cost reduction.

  In each of the above embodiments, the drive circuit 36, 36B, 36BB, 36C, the micro pump MP, the configuration of the whole or each part of the micro fluid device 1, the structure, shape, dimensions, number, material circuit configuration, circuit constant, characteristics, etc. These can be appropriately changed in accordance with the spirit of the present invention. In addition, the whole or part of the driver circuit can be an integrated circuit.

  The microfluidic system 1 according to the embodiment described above can be applied to various fields other than the field of μ-TAS. For example, it can be used as a transport means for liquid fuel used in a fuel cell or the like. The drive circuit or trapezoidal wave generation circuit according to the present invention can be applied to uses other than the driving of the micropump.

  The drive circuit according to the present invention drives a micropump to transport or supply a test solution or liquid in various fields such as environment, food, biochemistry, immunology, hematology, genetic analysis, synthesis, drug discovery, and fuel. It can be used for processing.

  In addition, the trapezoidal wave generating circuit according to the present invention includes the above-described micropump drive circuit, and includes a motor drive for driving a rotating body such as a communication device or a recording medium that requires a trapezoidal wave. It can be used for various purposes.

It is a top view which shows typically the structure of the microfluidic system which concerns on this invention. It is front sectional drawing of the micropump shown in FIG. It is a figure which shows the example of the waveform of the drive voltage of a piezoelectric element. It is a figure which shows the example of the waveform of the drive voltage of a piezoelectric element. It is a figure which shows the example of a structure of the drive circuit of 1st Embodiment. It is a figure which shows the waveform of the drive voltage output from a drive circuit. It is a figure which shows the example of a structure of the drive circuit of 2nd Embodiment. It is a figure which shows the example of a structure of the modification of a drive circuit. It is a figure which shows the example of the waveform of a drive voltage. It is a figure which shows the other example of the waveform of a drive voltage. It is a figure which shows the example of a structure of the drive circuit of 3rd Embodiment. It is a figure which shows the waveform of the drive voltage output from a drive circuit. It is a figure which shows the example of a structure of a drive circuit. It is a figure which shows the drive waveform obtained by the drive circuit of FIG.

Explanation of symbols

1 Microfluidic device 34 Piezoelectric element 36, 36B, 36BB, 36C Drive circuit 51 Constant current charging unit (constant current charging circuit)
52 Constant current discharge part (constant current discharge circuit)
53 Buffer section (buffer circuit)
53C1, 53C2 First buffer circuit (buffer unit)
54 switching section 55 pulse generating section (circuit that outputs a control signal)
56 DC power supply 57C1, 57C2 Second buffer circuit (buffer unit)
58C1, 58C2 Switch circuit MP1, MP2 Micro pump C1 Capacitor G1 Constant current element (constant current diode)
Q6 Junction FET
R resistance Q transistor

Claims (10)

A capacitor,
A constant current charging unit for charging the capacitor with a constant current;
A constant current discharge unit for discharging the capacitor with a constant current;
A buffer unit for extracting and outputting a voltage waveform across the capacitor; and
A switching unit for periodically switching and operating the constant current charging unit and the constant current discharging unit;
A driving circuit for a micropump characterized by comprising: A capacitor,
A constant current charging unit for charging the capacitor by passing a constant current from a DC power supply;
A constant current discharging unit for discharging the capacitor with a constant current;
A buffer unit for extracting and outputting a voltage waveform across the capacitor; and
A switching unit for switching and operating the constant current charging unit and the constant current discharging unit based on a control signal,
In a time shorter than a first time during which the constant current charging unit is switched to operate, the constant current charging unit charges the capacitor to the voltage of the DC power source, and the constant current discharging unit operates. The constant current discharging unit and the constant current discharging unit have respective currents set so that the constant current discharging unit discharges the capacitor to a voltage of zero during a time shorter than the second time during which switching is performed. Become
A drive circuit for a micropump characterized by the above. The constant current discharge unit is configured to include a constant current diode,
The driving circuit for the micropump according to claim 2. The constant current discharge unit is configured to have a junction FET,
The driving circuit for the micropump according to claim 2. The buffer unit is configured by an emitter follower circuit of a transistor.
The micropump drive circuit according to claim 2. A capacitor,
A constant current charging circuit including a transistor for charging the capacitor by supplying a constant current from a DC power supply;
A constant current discharge circuit configured to include a constant current element for discharging the capacitor with a constant current;
A buffer circuit including a transistor for extracting and outputting a voltage waveform across the capacitor; and
For switching between the operation of charging the capacitor by operating the transistor of the constant current circuit and the operation of discharging the capacitor by the constant current discharge circuit, a pulse-like state in which on / off is periodically switched at a predetermined duty ratio A circuit for outputting a control signal,
In a time shorter than the first time when the operation is switched to charge the capacitor, the constant current charging circuit is switched to the operation of charging the capacitor to the voltage of the DC power source and discharging the capacitor. In a time shorter than the second time, the constant current discharging circuit is configured to set respective currents of the constant current charging circuit and the constant current discharging circuit so that the capacitor is discharged to zero voltage.
A drive circuit for a micropump characterized by the above. A capacitor,
A constant current charging unit for charging the capacitor with a constant current;
A constant current discharging unit for discharging the capacitor with a constant current;
A plurality of buffer units for extracting and outputting a voltage waveform at both ends of the capacitor;
A switching unit for periodically switching and operating the constant current charging unit and the constant current discharging unit,
Each of the plurality of buffer units includes a circuit that switches and extracts the voltage waveform and an attenuated voltage waveform obtained by attenuating the voltage waveform at a predetermined ratio,
The plurality of buffer units are switched at a predetermined cycle so as to sequentially output the voltage waveforms, and the buffer units not outputting the voltage waveform are controlled to output the attenuated voltage waveform in each cycle. ,
A drive circuit for a micropump characterized by the above. A capacitor,
A constant current charging unit for charging the capacitor by passing a constant current from a DC power supply;
A constant current discharging unit for discharging the capacitor with a constant current;
A plurality of buffer units for extracting and outputting a voltage waveform at both ends of the capacitor;
A switching unit for switching and operating the constant current charging unit and the constant current discharging unit based on a control signal,
Each of the plurality of buffer units includes a first buffer circuit configured to include three resistors and transistors connected in series to divide the voltage waveform, and two resistors of the three resistors. A second buffer circuit configured to include a transistor for outputting a voltage waveform at a connection portion of the first and second switches, and a switch circuit for short-circuiting the remaining one of the two resistors.
A drive circuit for a micropump characterized by the above. The charging rate of the constant current charging unit is different from the discharging rate of the constant current discharging unit,
9. The micropump driving circuit according to claim 1, wherein the driving circuit is a micropump driving circuit. A capacitor,
A constant current charging unit for charging the capacitor by passing a constant current from a DC power supply;
A constant current discharging unit for discharging the capacitor with a constant current;
A buffer unit for extracting and outputting a voltage waveform across the capacitor; and
A switching unit for switching and operating the constant current charging unit and the constant current discharging unit based on a control signal,
In a time shorter than a first time during which the constant current charging unit is switched to operate, the constant current charging unit charges the capacitor to the voltage of the DC power source, and the constant current discharging unit operates. The constant current discharging unit and the constant current discharging unit are set to have respective currents set so that the constant current discharging unit discharges the capacitor to a voltage of zero during a time shorter than the second time during which switching is performed. Become
A trapezoidal wave generating circuit characterized by that.

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