JP2012116098A - Capacitive load driving circuit - Google Patents

Abstract

A carrier ripple is prevented from being superimposed on a drive signal of a capacitive load.
A drive waveform signal is pulse-modulated to generate a modulation signal, and after power amplification, a drive signal generated by passing through a smoothing filter is applied to a capacitive load. In addition, phase lead compensation is performed on the drive signal to generate a feedback signal, and negative feedback is made to the drive waveform signal. The smoothing filter and the capacitive load are connected by a replaceable wiring. When the smoothing filter and the capacitive load are connected by wiring, wiring information regarding the wiring is acquired, and pulse modulation is performed at a carrier frequency corresponding to the wiring information. By so doing, pulse modulation is performed at a carrier frequency corresponding to the wiring, so that it is possible to avoid the carrier ripple from being superimposed on the drive signal.
[Selection] Figure 4

Description

  The present invention relates to a technique for driving a capacitive load such as a piezoelectric element using a drive signal.

  There are many actuators that are configured by a capacitive load such as a piezoelectric element and operate when a drive signal is applied, such as an ejection head mounted on an inkjet printer. If an attempt is made to generate this drive signal using an analog amplifier circuit, a large current flows through the analog amplifier circuit, so that a large amount of power is consumed. As a result, not only does the power efficiency decrease, but the circuit board becomes larger, and further, since the consumed power changes to heat, a large heat dissipation plate is required, and the board becomes larger.

  Therefore, instead of directly amplifying the analog drive signal, the drive waveform signal serving as a reference for the drive signal is pulse-modulated and converted into a modulation signal, and the obtained modulation signal is amplified and then passed through a smoothing filter. A technique for obtaining an amplified drive signal has been proposed (Patent Document 1). Amplification of the modulation signal can be realized simply by switching on / off of the switch. Furthermore, since the smoothing filter can be realized by using an LC circuit in which a coil and a capacitor are combined, in principle, power is not consumed. Therefore, according to the proposed technique, it is possible to generate a drive signal without consuming a large amount of power, and it is possible to reduce the size of the circuit board.

  In the proposed technique, a smoothing filter is configured by the LC circuit, and therefore a peak appears in the gain at the resonance frequency of the LC circuit. Normally, the output peak is suppressed by the resistance value of the electric load or by separately inserting a damping resistor. However, in this method, power is consumed by the resistor. Therefore, it has been proposed to suppress the output peak by performing feedback from the output stage (Patent Document 2). Further, since the signal passing through the smoothing filter is delayed in phase by 180 degrees at the maximum, there is a possibility that the output oscillates if feedback is applied as it is with the signal of the output stage. Therefore, feedback is performed after phase lead compensation is applied to the signal of the output stage.

  Also, when feeding back the signal from the output stage, the resistance of the wiring from the smoothing filter to the capacitive load suppresses the waveform of the drive signal from being gradual (the voltage change of the waveform becomes gentle) Proposal is also made of a technique for applying feedback in consideration of wiring resistance (Patent Document 3), and a technique for switching the carrier frequency for pulse modulation according to the waveform of the drive signal (Patent Document 4) for the purpose of suppressing power consumption. Has been.

JP 2007-168172 A JP 2009-153272 A JP 2005-329710 A JP 2007-190708 A

  However, the conventional techniques such as Patent Document 1 to Patent Document 4 described above have a problem that the ripple (carrier ripple) of the carrier frequency that is removed by the smoothing filter may be superimposed on the drive signal. It was. For this reason, there is a problem that an actuator that is a capacitive load cannot be appropriately driven.

  The present invention has been made to solve at least a part of the above-described problems of the prior art, and provides a technique capable of avoiding a carrier frequency ripple from being superimposed on a drive signal after a smoothing filter. For the purpose.

In order to solve at least a part of the problems described above, the capacitive load driving circuit of the present invention employs the following configuration. That is,
A capacitive load drive circuit that drives a capacitive load by applying a drive signal to the capacitive load having a capacitive component,
A drive waveform signal generating circuit for generating a drive waveform signal which is a reference of the drive signal;
An arithmetic circuit that outputs an error signal by subtracting a feedback signal generated from the drive signal applied to the capacitive load from the drive waveform signal;
A modulation circuit that generates a modulation signal by pulse-modulating the error signal;
A digital power amplifier that amplifies the modulated signal to generate a pulsed power amplified modulated signal;
A smoothing filter that generates the drive signal by smoothing the pulse-wave-shaped power amplification modulation signal;
A phase lead compensation circuit that performs phase lead compensation on the drive signal and outputs the signal after the phase lead compensation as the feedback signal;
Connecting the smoothing filter and the capacitive load, wiring provided to be replaceable,
Wiring information acquisition means for acquiring wiring information which is information about the wiring;
The gist of the invention is that the modulation circuit includes carrier frequency changing means for changing a carrier frequency when the error signal is pulse-modulated based on the wiring information.

  In such a capacitive load drive circuit of the present invention, a modulation signal is generated by pulse-modulating a drive waveform signal which is a reference of a drive signal to be applied to the capacitive load, and the obtained modulation signal is power amplified. A drive signal is generated by performing smoothing later. In this way, phase lead compensation is performed on the drive signal applied to the capacitive load to generate a feedback signal, and negative feedback to the drive waveform signal. The smoothing filter and the capacitive load are connected by wiring, and the drive signal output from the smoothing filter is applied to the capacitive load via the wiring. Also, the wiring is replaceable, and when the smoothing filter and the capacitive load are connected by wiring, wiring information regarding the wiring is acquired, and pulse modulation is performed at a carrier frequency according to the wiring information. It has become.

  In this way, the drive signal applied to the capacitive load is negatively fed back with respect to the drive waveform signal serving as a reference for the drive signal, so that the drive signal is prevented from being distorted due to the resonance of the smoothing filter. Can do. Also, when the drive signal is negatively fed back, it is compensated for phase advance compensation (phase advance compensation) and then negatively fed back. Therefore, the drive signal whose phase is delayed by a smoothing filter is driven negatively. The signal output does not become unstable. Further, as will be described in detail later, the frequency at which the carrier ripple is easily superimposed is determined by the wiring. Therefore, if information related to the frequency at which carrier ripple is easily superimposed is stored as wiring information, the wiring information of the connected wiring is obtained and pulse modulation is performed at a carrier frequency that avoids the frequency at which carrier ripple is easily superimposed. I can do it. As a result, it is possible to avoid the carrier ripple from being superimposed on the drive signal.

  In the capacitive load driving circuit of the present invention, information associated with the magnitude or impedance of the inductive component of the wiring may be acquired as wiring information.

  The frequency at which the carrier ripple is easily superimposed is strongly influenced by the size of the inductive component or the impedance of the wiring. Therefore, if information related to the magnitude or impedance of the inductive component of the wiring is acquired as wiring information, pulse modulation can be performed at a carrier frequency that avoids a frequency at which carrier ripple is easily superimposed. It is possible to avoid the ripples from overlapping.

  In the capacitive load driving circuit of the present invention described above, information associated with the length of the wiring may be acquired as wiring information.

  The size of the inductive component of the wiring greatly depends on the length of the wiring. Therefore, if information related to the length of the wiring is stored as wiring information, pulse modulation is performed at a carrier frequency that avoids a frequency at which carrier ripple is easily superimposed, and carrier ripple is not superimposed on the drive signal. It becomes possible to do.

  In the capacitive load driving circuit of the present invention described above, an ID tag describing wiring information may be provided in the wiring.

  By doing this, the operator of the capacitive load driving circuit reads the wiring information described in the ID tag and acquires the wiring information, thereby performing pulse modulation at a carrier frequency that avoids a frequency at which carrier ripples are easily superimposed. As a result, it is possible to avoid the carrier ripple from being superimposed on the drive signal.

  In the capacitive load driving circuit of the present invention described above, a storage medium storing wiring information in a readable manner may be mounted, and the wiring information may be read from the storage medium when the wiring is connected. .

  In this way, wiring information can be read simply by connecting the wiring, and pulse modulation can be performed at a carrier frequency that avoids a frequency at which carrier ripples are easily superimposed. As a result, it is possible to avoid the carrier ripple from being superimposed on the drive signal.

  Further, the above-described capacitive load driving circuit of the present invention may be configured as follows. First, a terminal protrudes from at least the smoothing filter side connector of the wiring, and when the wiring is connected, a drive signal from the smoothing filter is transmitted through the terminal. The connector can also be provided with a terminal that does not relate to the transmission of the drive signal, and the wiring information acquisition means detects whether or not the terminal that is not related to the transmission of the drive signal protrudes from the connector. The wiring information may be acquired.

  In this way, when the wiring is connected, an appropriate carrier frequency can be selected and pulse-modulated depending on whether or not a terminal that is not involved in transmission of the drive signal is provided on the connector. As a result, it is possible to avoid the carrier ripple from being superimposed on the drive signal.

It is explanatory drawing which showed the structure of the liquid ejecting apparatus carrying the capacitive load drive circuit of a present Example. It is explanatory drawing which showed the circuit structure of the capacitive load drive circuit of a present Example. It is explanatory drawing which showed the mechanism in which a carrier ripple generate | occur | produces under the influence of the induction component (and resistance component) which a wiring cable has. FIG. 3 is a circuit diagram showing a part of the capacitive load driving circuit of the first embodiment. It is explanatory drawing which summarized a mode that a carrier frequency was changed corresponding to the wiring information of ID tag. It is explanatory drawing which showed the reason which can avoid that a carrier ripple is superimposed by changing a carrier frequency according to wiring information. It is explanatory drawing which illustrated the other aspect of 1st Example. It is the circuit diagram which showed a part of capacitive load drive circuit of 2nd Example. It is the circuit diagram which showed a part of capacitive load drive circuit of 3rd Example.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Device configuration:
B. Circuit configuration of capacitive load drive circuit:
C. Mechanism for generating carrier ripple:
D. Capacitive load driving circuit of the first embodiment:
E. Capacitive load driving circuit of the second embodiment:
F. Capacitive load driving circuit of the third embodiment:

A. Device configuration :
FIG. 1 is an explanatory diagram showing a configuration of a liquid ejecting apparatus 100 equipped with a capacitive load driving circuit 200 of the present embodiment. As shown in the figure, the liquid ejecting apparatus 100 is roughly divided into an ejecting unit 110 that ejects liquid, a supply pump 120 that supplies the liquid ejected from the ejecting unit 110 toward the ejecting unit 110, and the ejecting unit 110. And a control unit 130 for controlling the operation of the supply pump 120. The liquid ejecting apparatus 100 is an example of a water jet knife as a surgical tool used for excising or incising a living tissue by ejecting pulsed liquid from the ejecting unit 110.

  The injection unit 110 has a structure in which a metal rear block 114 is overlapped on a metal front block 113 and screwed, and a circular liquid passage pipe 112 is erected on the front surface of the front block 113. An injection nozzle 111 is inserted at the tip of the liquid passage tube 112. A thin disk-shaped liquid chamber 115 is formed on the mating surface of the front block 113 and the rear block 114, and the liquid chamber 115 is connected to the ejection nozzle 111 via the liquid passage tube 112. In addition, an actuator 116 composed of a laminated piezoelectric element is provided inside the rear block 114. The ejection unit 110 and the control unit 130 are connected by a wiring cable 150, and a drive signal is supplied from the capacitive load driving circuit 200 in the control unit 130 to the actuator 116 via the wiring cable 150. Further, one end side of the wiring cable 150 is attached to the injection unit 110 by a connector 152, and the other end side of the wiring cable 150 is attached to the control unit 130 by a connector 154. For this reason, the distribution cable 150 can be replaced with various distribution cables 150 having different lengths and characteristics. The wiring cable 150 corresponds to “wiring” in the present invention, and the actuator 116 corresponds to “capacitive load” in the present invention.

  The supply pump 120 sucks up the liquid through the tube 121 from the liquid tank 123 in which the liquid to be ejected (water, physiological saline, chemical liquid, etc.) is stored, and then the liquid in the ejection unit 110 through the tube 122. Supply into the chamber 115. For this reason, the liquid chamber 115 is filled with the liquid.

  When a drive signal is applied from the control unit 130 to the actuator 116, the actuator 116 extends and the liquid chamber 115 is compressed, and as a result, the liquid filled in the liquid chamber 115 is pulsed from the ejection nozzle 111. Is injected into. The extension amount of the actuator 116 depends on the voltage applied as the drive signal. Accordingly, in order to eject a pulsed liquid having a desired characteristic, it is necessary to apply an accurate drive signal to the actuator 116. Therefore, in order to generate such a drive signal, a capacitive load drive circuit 200 as described below is mounted in the control unit 130.

B. Capacitive load drive circuit configuration:
FIG. 2 is an explanatory diagram showing a circuit configuration of the capacitive load driving circuit 200 mounted on the control unit 130. As shown in the figure, the capacitive load drive circuit 200 includes a drive waveform signal generation circuit 210 that outputs a drive waveform signal (hereinafter referred to as WCOM) serving as a reference for the drive signal, and the WCOM received from the drive waveform signal generation circuit 210. An arithmetic circuit 220 that outputs an error signal (hereinafter referred to as dWCOM) based on a feedback signal (hereinafter referred to as dCOM), which will be described later, and a modulation that performs pulse modulation on the dWCOM from the arithmetic circuit 220 and converts it into a modulated signal (hereinafter referred to as MCOM). A circuit 230, a digital power amplifier 240 that digitally amplifies the MCOM from the modulation circuit 230 to generate a power amplification modulation signal (hereinafter referred to as ACOM), and receives the ACOM from the digital power amplifier 240 to remove the modulation component. After that, a drive signal (hereinafter referred to as COM) is supplied to the actuator 116 of the injection unit 110. That a smoothing filter 250, in addition to compensating for advancing the phase with respect to the COM output from the low pass filter 250 (phase lead compensation), and a phase lead compensation circuit 260 generates a dCOM (feedback signal).

  Of these, the drive waveform signal generation circuit 210 includes a waveform memory storing WCOM data and a D / A converter, and converts data read from the waveform memory into an analog signal by the D / A converter. To generate a WCOM (drive waveform signal). The arithmetic circuit 220 outputs a signal obtained by subtracting dCOM from the WCOM thus output as dWCOM (error signal). Conversely, the drive waveform signal generation circuit 210 reads WCOM (drive waveform signal) as digital data from the waveform memory storing the WCOM data, and after converting the dCOM into digital data by an A / D converter, the signal processing circuit The calculation circuit 220 may be used to subtract dCOM from WCOM by digital calculation to generate dWCOM (error signal) as digital data. In that case, the modulation circuit 230 is configured by a digital circuit using the signal processing circuit so that dWCOM is handled as digital data.

  The modulation circuit 230 generates (pulse modulation) a pulse-like MCOM (modulation signal) by comparing dWCOM with a triangular wave having a fixed period. Here, the base frequency (carrier frequency) of the triangular wave used for pulse modulation can be changed by control from the carrier frequency changing means 280. Then, the carrier frequency changing unit 280 changes the carrier frequency based on the wiring information acquired by the wiring information acquiring unit 270 (information on the wiring cable 150 connecting the ejection unit 110 and the control unit 130). Although described later in detail, it is possible to avoid the carrier ripple from being superimposed on COM by changing the carrier frequency at the time of pulse modulation based on the wiring information.

  The MCOM obtained by the modulation circuit 230 is input to the digital power amplifier 240. The digital power amplifier 240 includes two switch elements (such as MOSFETs) that are push-pull connected, a power source, and a gate driver that drives these switch elements. When MCOM is in the high state, the high-side switch element is turned on, the low-side switch element is turned off, and the power supply voltage Vdd is output as ACOM. When the MCOM is in the Low state, the high-side switch element is turned off, the low-side switch element is turned on, and the ground voltage is output as ACOM. As a result, the MCOM that changes in a pulse waveform between the operating voltage of the modulation circuit 230 and the ground is amplified to an ACOM that changes in a pulse waveform between the power supply voltage Vdd and the ground. In this amplification, since only the ON / OFF of the two switch elements connected in a push-pull manner is switched, it is possible to greatly suppress the power loss as compared with the case where the analog waveform is amplified. As a result, not only can the power efficiency be improved, but there is no need to provide a large heat sink for heat dissipation, and the circuit can be miniaturized.

  The power-amplified ACOM (power amplification modulation signal) is converted into COM (drive signal) by passing through a smoothing filter 250 constituted by an LC circuit, and is applied to the actuator 116 via the wiring cable 150. Further, COM is negatively fed back to the arithmetic circuit 220, but the phase of COM is delayed with respect to WCOM by passing through the smoothing filter 250. Therefore, instead of simply negatively feeding back COM, compensation (phase lead compensation) is performed to advance the phase through a phase lead compensation circuit 260 constituted by a capacitor and a resistor, and the obtained signal is set as dCOM and the arithmetic circuit 220. Negative feedback. The detailed configuration of the wiring information acquisition unit 270 will be described later.

  Here, as shown in FIG. 2, the wiring cable 150 also has an inductive component and a resistance component. Therefore, due to this influence, it seems that some deviation occurs between the COM output from the smoothing filter 250 and the signal (hereinafter referred to as RCOM) actually applied to the actuator 116. When actually examined, it has been found that carrier ripple can be superimposed on the RCOM actually applied to the actuator 116 due to the influence of the inductive component (and the resistance component) of the wiring cable 150. Here, the carrier ripple means a signal component of a carrier signal (triangular wave signal) used for pulse modulation included in the RCOM applied to the actuator 116. Hereinafter, this point will be described in detail.

C. Mechanism for generating carrier ripple:
FIG. 3 is an explanatory diagram showing a mechanism in which carrier ripple occurs due to the influence of the inductive component (and resistance component) of the wiring cable 150. FIG. 3A shows a circuit configuration from ACOM to RCOM. Let Llpf be the inductance of the coil of the smoothing filter 250, and let Clpf be the capacitance of the capacitive component of the smoothing filter 250. Similarly, let Rc and Lc be the resistance value and inductance of the wiring on one side. Furthermore, the capacitance of the capacitive load is Cload.

Also, for convenience, the transfer function of the coil of the smoothing filter 250 is set as Z1, the transfer function of the forward side of the wiring cable 150 (the side sending from the smoothing filter 250 to the actuator 116) is set as Za, and the return side of the wiring cable 150 is connected to the actuator 116. If the transfer function of the part including the actuator 116 (the side returning from the actuator 116 to the ground of the capacitive load driving circuit 200) is Zb, Z1, Za and Zb are respectively given by the following equations.
Z1 = s · Llpf
Za = Rc + s · Lc
Zb = 1 / (s.Cload) + (Rc + s.Lc)
Further, in the circuit configuration shown in FIG. 3A, the transfer function of transfer elements (capacitance components of the reciprocating portion of the wiring cable 150 and the actuator 116 and the smoothing filter 250) connected in series to the coil of the smoothing filter 250. Z2 is given by the following equation.
Z2 = {1 / (s · Clpf)} // {2 (Rc + s · Lc) + 1 / (s · Cload)}
Here, s is a Laplace operator, which is an imaginary unit j multiplied by an angular frequency ω. // is a parallel composite symbol representing the composite impedance of parallel connection.
Then, the transfer function H between ACOM and RCOM is given by the equation of FIG.

  FIG. 3C shows an example of the gain-frequency characteristic of the transfer function H. In FIG. 3C, it is assumed that the resistance per unit length (= 2 × Rc) of the wiring cable 150 is about several hundred milliΩ and the inductance per unit length (= 2 × Lc) is about several μH. The gain-frequency characteristics obtained with various wiring lengths are illustrated.

  The broken line shown in FIG. 3C is the gain-frequency characteristic when the length of the wiring cable 150 is 2 [m (meter)], and the alternate long and short dash line is the gain when the length is 1 [m]. -It is a frequency characteristic, and a dashed-two dotted line is a gain-frequency characteristic in the case of 0.5 [m]. A solid line represents a gain-frequency characteristic when the wiring cable 150 is not provided. As shown in the figure, when the actuator 116 (capacitive load) is connected via the wiring cable 150, resonance due to the inductance of the wiring cable 150 and the capacitive load occurs on the higher frequency side than the resonance frequency f0 of the smoothing filter 250. appear. Further, when the length of the wiring cable 150 is changed, the inductance value of the wiring cable 150 changes, so that the resonance frequency fc changes. Therefore, depending on the length of the wiring cable 150 to be connected, the resonance peak may approach (or match) the carrier frequency at the time of pulse modulation, and a very large carrier ripple may remain in the drive signal applied to the actuator 116. Can happen.

  For example, the power supply voltage of the digital power amplifier 240 is set to 100 V, and the wiring cable 150 connecting the smoothing filter 250 and the actuator 116 is connected in various lengths between 0.5 [m] and 2 [m]. Shall be. If the inductance of the wiring cable 150 is 0 (corresponding to the case where the cable length is 0 [m]), as shown in the solid line gain-frequency characteristics shown in FIG. The gain at is -40 db, and the carrier ripple remaining in the drive signal is 1 Vpp. However, when the cable length of the wiring cable 150 is 0.5 [m], the gain at the carrier frequency fc is −40 db, and when the cable length is 1 [m], it is −20 db, and the cable length is 2 [m]. ] Is −45 db. Carrier ripples remaining in the drive signal are 1 Vpp, 10 Vpp, and 0.56 Vpp, respectively. Although the ACOM amplified by the digital power amplifier 240 is smoothed through the smoothing filter 250, the carrier ripple may be superimposed on the drive signal due to the mechanism described above.

  If the carrier ripple is superimposed, the actuator 116 cannot be driven appropriately. However, if a damping resistor is inserted in the wiring, power is consumed by the resistor, so that power efficiency is lowered. Further, if the characteristics of the smoothing filter 250 are changed so that the frequency component of the carrier ripple is further suppressed, the resonance frequency f0 of the smoothing filter 250 is lowered, so that the signal frequency band cannot be secured. On the contrary, if the carrier frequency at the time of pulse modulation is increased, carrier ripple can be suppressed, but this causes an increase in switching loss at the time of pulse modulation or at the time of amplification of the modulation signal. Therefore, in order to apply a drive signal without carrier ripple to the actuator 116 without such problems, the following method is employed.

D. Capacitive load driving circuit of the first embodiment:
FIG. 4 is a circuit diagram showing a part of the capacitive load driving circuit 200 of the first embodiment. In the first embodiment, an ID tag 160 corresponding to the cable length (or cable characteristic) of the distribution cable 150 is provided on the distribution cable 150. When the control unit 130 is activated, the operator of the liquid ejecting apparatus 100 reads the wiring information (cable length, cable characteristics, etc.) described in the ID tag 160 and sets ON / OFF of the switch 272 to set the carrier frequency. Wiring information is input to the changing means 280. Then, the carrier frequency changing unit 280 changes the carrier frequency based on the input wiring information. The modulation circuit 230 performs pulse modulation of dWCOM using the changed carrier frequency.

  FIG. 5 is an explanatory diagram summarizing how the carrier frequency is changed in accordance with the wiring information of the ID tag 160. Here, the length of the wiring cable 150 is described as the wiring information. For example, when the cable length that is the wiring information is x [m (meter)], the operator of the liquid ejecting apparatus 100 sets the switch 272 to OFF. Then, the carrier frequency changing means 280 selects the carrier frequency fcx1. Further, when the cable length as the wiring information is 2x [m] or 4x [m], the carrier frequency fcx2 is selected by setting the switch 272 to ON. By doing so, it is possible to avoid the carrier ripple from being superimposed on the drive signal to the actuator 116 for the following reason. In FIG. 5, the cable length is described as the wiring information. However, the wiring information may be a simple number or symbol, or may be a setting state of the switch 272. . In the first embodiment, the switch 272 corresponds to the “wiring information acquisition unit” in the present invention.

  FIG. 6 is an explanatory diagram illustrating the reason why it is possible to avoid the carrier ripple from being superimposed by changing the carrier frequency according to the wiring information. Here, there are three types of wiring cables 150 that may be connected, x [m], 2x [m], and 4x [m]. Then, when each wiring cable 150 is used, the resonance frequency of the resonance generated between the wiring cable 150 and the actuator 116 can be examined in advance.

  In FIG. 6, the gain-frequency characteristic when the wiring cable 150 of x [m] is connected is indicated by a two-dot chain line. Further, the gain-frequency characteristic when the 2x [m] wiring cable 150 is connected is indicated by a one-dot chain line, and the gain-frequency characteristic of the 4x [m] wiring cable 150 is indicated by a broken line. Here, the resonance frequency of the smoothing filter 250 is determined from a necessary signal frequency band, and cannot be lowered further. In other words, the amount of attenuation in the high frequency region cannot be designed to be larger than that. In the characteristic of the smoothing filter 250 determined as described above, in the ideal state where the wiring cable 150 is not connected, the frequency (minimum frequency) that can satisfy the specification value of the carrier ripple of the application at the minimum is shown in FIG. fcmin "is displayed. Further, from the viewpoint of suppressing switching loss, that is, from the viewpoint of preventing destruction due to heat generation of the switch element, there is a frequency at which the carrier frequency cannot be increased further. In FIG. 6, such a frequency (maximum frequency) is displayed as “fcmax”. The carrier frequency at the time of pulse modulation needs to be designed between the lowest frequency fcmin and the highest frequency fcmax. Therefore, two types of carrier frequencies fcx1 and fcx2 are set between the lowest frequency fcmin and the highest frequency fcmax while being spaced apart from each other. Further, if the gain at the carrier frequency is −40 db or less, the carrier ripple is not noticeable.

  As is apparent from FIG. 6, when the wiring cable 150 having a cable length of x [m] is connected, the gain can be suppressed to −40 db by setting the carrier frequency to fcx1. Further, when the wiring cable 150 having a cable length of 2x [m] or 4x [m] is connected, the gain at the carrier frequency can be suppressed to -40 db or less by setting the carrier frequency to fcx2. Therefore, as shown in FIG. 5, the carrier frequency is set for the cable length of the wiring cable 150 (that is, wiring information). This makes it possible to avoid the carrier ripple from being superimposed on the drive signal to the actuator 116 when any of the wiring cables 150 of x "m" to 4x "m" is connected. As the two types of carrier frequencies fcx1 and fcx2 set in advance, a minimum frequency fcmin and a maximum frequency fcmax may be set.

  Alternatively, more types (three or more types) of carrier frequencies may be set between the lowest frequency fcmin and the highest frequency fcmax, and the carrier frequency may be set according to the wiring information of the ID tag 160. .

  FIG. 7 is an explanatory diagram illustrating another aspect of the first embodiment for selecting a carrier frequency according to wiring information from among three or more types of carrier frequencies. FIG. 7A shows a state where three types of carrier frequencies fcx1, fcx2, and fcx3 are set between the lowest frequency fcmin and the highest frequency fcmax. FIG. 7B shows a state in which one of the carrier frequencies is selected by setting two switches according to the cable length (wiring information) described in the ID tag 160. Yes. If the types of carrier frequencies are increased in this way, a more appropriate carrier frequency can be selected according to the connected wiring cable 150.

E. Capacitive load driving circuit of the second embodiment:
In the first embodiment described above, the wiring information described in the ID tag 160 has been described as the carrier frequency selected by the operator of the liquid ejecting apparatus 100 setting the switch 272. On the other hand, it is also possible to transmit the wiring information to the carrier frequency changing means 280 simply by connecting the wiring cable 150 and set the carrier frequency. In the second and third embodiments described below, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 8 is a circuit diagram showing a part of the capacitive load driving circuit 200 of the second embodiment in which the carrier frequency corresponding to the wiring information is set by connecting the wiring cable 150. In the second embodiment, the connector 154 connected to the control unit 130 side (capacitive load drive circuit 200 side) of the wiring cable 150 is a male connector, and the control unit 130 side (capacitive load drive circuit 200 side). The connector is a female connector. The connector 154 on the side of the wiring cable 150 is provided with a terminal 274a and a terminal 274b. When the wiring cable 150 is connected to the control unit 130 (capacitive load driving circuit 200), the terminal 274a is output from the smoothing filter 250. The terminal 274b is connected to the ground line.

  As shown in FIG. 8, in the second embodiment, another terminal 274c is also provided on the connector 154 on the control unit 130 (capacitive load drive circuit 200) side of the wiring cable 150. The terminal 274c is configured to short-circuit a contact provided on the capacitive load drive circuit 200 side when the wiring cable 150 is connected to the control unit 130 (capacitive load drive circuit 200). That is, if the terminal 274c is provided in the connector 154, the contact of the capacitive load drive circuit 200 is short-circuited, and if the terminal 274c is not provided, the contact of the capacitive load drive circuit 200 is disconnected. Therefore, wiring information can be stored depending on whether or not the terminal 274c is provided in the connector 154 of the wiring cable 150.

  Then, the carrier frequency changing means 280 detects the wiring information according to the contact state when the wiring cable 150 is connected, and sets the carrier frequency. For example, when the cable length is x [m], the connector 154 is not provided with the terminal 274c, and when the cable length is 2x [m] or 4x [m], the terminal 274c is provided. When the wiring cable 150 is connected, if the contact is short-circuited, the carrier frequency fcx1 is selected. If the contact is not short-circuited, the carrier frequency fcx2 is selected. Similarly to the above, it is possible to set a carrier frequency corresponding to the wiring cable 150.

  In the above description, since the wiring information is stored depending on the presence / absence of one terminal 274c, the wiring information is 1-bit information, and one of the two types of carrier frequencies fcx1 and fcx2 is selected. be able to. On the other hand, if the wiring information is stored depending on the presence / absence of the plurality of terminals 274c, the number of bits of the wiring information increases, so that an appropriate carrier frequency can be set from other types of carrier frequencies. .

F. Capacitive load driving circuit of the third embodiment:
In the second embodiment described above, the wiring information is stored according to the presence / absence of the terminal 274c provided on the connector 154 of the wiring cable 150. On the other hand, a ROM (storage medium) storing wiring information may be mounted in advance on the connector 154 on the control unit 130 (capacitive load drive circuit 200) side of the wiring cable 150.

  FIG. 9 is a circuit diagram showing a part of the capacitive load driving circuit 200 of the third embodiment in which a ROM storing wiring information is mounted in the connector 154 of the wiring cable 150. In the third embodiment, the ROM 162 is mounted on the connector 154 of the wiring cable 150 on the capacitive load driving circuit 200 side, and the capacitive load driving circuit 200 has a ROM data read circuit 276 that reads data from the ROM 162. Is provided.

  When the wiring cable 150 is connected to the capacitive load drive circuit 200 of the control unit 130 and the control unit 130 is activated, the ROM data read circuit 276 provided in the capacitive load drive circuit 200 stores it in the ROM 162. Wiring information is read and input to the carrier frequency changing means 280. Then, based on the correspondence as shown in FIG. 5 or FIG. 7B, a carrier frequency corresponding to the wiring information is selected, and pulse modulation is performed at the carrier frequency. In this way, since pulse modulation can be performed at a carrier frequency corresponding to the wiring cable 150, it is possible to avoid the carrier ripple from being superimposed on the drive signal applied to the actuator 116.

  Although the capacitive load drive circuits of various embodiments have been described above, the present invention is not limited to all the embodiments described above, and can be implemented in various modes without departing from the scope of the invention. For example, by applying the capacitive load driving circuit of this embodiment to various electronic devices including medical devices such as a fluid ejection device used for forming a microcapsule containing a medicine or a nutrient, power efficiency is improved. A miniaturized electronic device can be provided. The present invention can also be suitably applied to a capacitive load driving circuit that is mounted on an ink jet printer and drives an ejection nozzle that ejects ink.

DESCRIPTION OF SYMBOLS 100 ... Liquid injection apparatus, 110 ... Injection unit, 111 ... Injection nozzle,
112 ... Liquid passage tube, 113 ... Front block, 114 ... Rear block,
115 ... Liquid chamber, 116 ... Actuator, 120 ... Supply pump,
121 ... Tube, 122 ... Tube, 123 ... Liquid tank,
130 ... Control unit 150 ... Wiring cable 152 ... Connector
154 ... Connector, 160 ... ID tag, 162 ... ROM,
200: Capacitive load drive circuit, 210 ... Drive waveform signal generation circuit,
220 ... arithmetic circuit, 230 ... modulation circuit, 240 ... digital power amplifier,
250 ... smoothing filter, 260 ... compensation circuit, 270 ... wiring information acquisition means,
272 ... switch, 274a-c ... terminal,
276 ... ROM data read circuit, 280 ... carrier frequency changing means

Claims (7)

A capacitive load drive circuit that drives a capacitive load by applying a drive signal to the capacitive load having a capacitive component,
A drive waveform signal generating circuit for generating a drive waveform signal which is a reference of the drive signal;
An arithmetic circuit that outputs an error signal by subtracting a feedback signal generated using the drive signal applied to the capacitive load from the drive waveform signal;
A modulation circuit that generates a modulation signal by pulse-modulating the error signal;
A digital power amplifier that amplifies the modulated signal to generate a pulsed power amplified modulated signal;
A smoothing filter that generates the drive signal by smoothing the pulse-wave-shaped power amplification modulation signal;
A phase lead compensation circuit that performs phase lead compensation on the drive signal and outputs the signal after the phase lead compensation as the feedback signal;
Connecting the smoothing filter and the capacitive load, wiring provided to be replaceable,
Wiring information acquisition means for acquiring wiring information which is information about the wiring;
A capacitive load driving circuit comprising: carrier frequency changing means for changing a carrier frequency when the modulation circuit performs pulse modulation on the error signal based on the wiring information.   The capacitive load driving circuit according to claim 1, wherein the wiring information is information associated with the magnitude or impedance of an inductive component included in the wiring.   The capacitive load driving circuit according to claim 1, wherein the wiring information is information associated with the length of the wiring.   The capacitive load drive circuit according to claim 1, wherein the wiring is provided with an ID tag on which the wiring information is written. A capacitive load driving circuit according to any one of claims 1 to 3,
A storage medium storing the wiring information in a readable manner is mounted on the wiring.
The capacitive load driving circuit, wherein the wiring information acquisition means is means for reading the wiring information from the storage medium. A capacitive load driving circuit according to any one of claims 1 to 3,
At least the smoothing filter side connector of the wiring is provided with a terminal projecting the drive signal from the smoothing filter,
The capacitive load drive circuit, wherein the wiring information acquisition means is means for acquiring the wiring information by detecting whether or not a terminal to which the drive signal is not transmitted projects from the connector. A capacitive load driving circuit according to any one of claims 1 to 6,
A supply pump for supplying liquid;
An injection unit having a liquid chamber into which the liquid supplied from the supply pump flows, an actuator that is the capacitive load, and an injection nozzle that injects the liquid that has flowed into the liquid chamber;
With
When the drive signal is applied to the actuator, the liquid that has flowed into the liquid chamber is ejected in a pulse form from the ejection nozzle.
Liquid ejector.

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