JP2011178172A - Liquid injector and liquid injection printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid injector which can reduce power consumption. <P>SOLUTION: When outputting a drive waveform signal WCOM as a driving signal COM by pulse modulating the drive waveform signal WCOM by a modulation circuit 26, power amplifying its modulation signal by a digital power amplifier circuit 28, and smoothing the power amplified modulation signal APWM by a smoothing filter 29, if the electric potential of the driving signal COM, which is not necessary to supply a current to an actuator 22 of a capacitive load, is not changed, that is, if the electric potential of the drive waveform signal WCOM does not change, an action stop signal/Disable is set to a low level so that the switching element Q1 on the high side of a digital power amplifier circuit 28, and the switching element Q2 on the low side of the digital power amplifier circuit 28 are both set to OFF states to stop the action of the digital power amplifier circuit 28. Thus, the power consumption quantities of the switching element Q1 on the high side, and the switching element Q2 on the low side as well as a coil L in the smoothing filter 29 can be reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid ejecting apparatus that ejects liquid by applying a drive signal to an actuator, for example, by ejecting a minute liquid from a nozzle of a liquid ejecting head to form fine particles (dots) on a print medium, The present invention is suitable for a liquid jet printing apparatus that prints predetermined characters, images, and the like.

  In a liquid ejection type printing apparatus, an actuator such as a piezoelectric element is provided in order to eject liquid from a nozzle of a liquid ejection head, and a predetermined drive signal must be applied to the actuator. Since this drive signal has a relatively high potential, it is necessary to power-amplify a drive waveform signal serving as a reference for the drive signal by a power amplifier circuit. Therefore, in Patent Document 1 below, a digital power amplifier circuit that has an extremely small power loss and can be downsized as compared with an analog power amplifier is used, and a drive waveform signal is pulse-modulated by a modulation circuit to form a modulation signal. The signal is amplified by a digital power amplification circuit to obtain a power amplification modulation signal, and the power amplification modulation signal is smoothed by a smoothing filter to obtain a drive signal.

JP 2007-168172 A

Incidentally, the drive signal applied to the actuator of the liquid jet printing apparatus or the reference drive waveform signal has a portion (time) in which the potential does not change. The piezoelectric element used as the actuator is a capacitive load, and it is not necessary to supply current to the actuator when the potential of the drive signal does not change. However, in the liquid jet printing apparatus described in Patent Document 1, the digital power amplifier circuit continues to operate even when the potential of the drive signal does not change, and power is consumed by the digital power amplifier circuit and the smoothing filter. There is a problem.
The present invention has been developed paying attention to these problems, and an object thereof is to provide a liquid ejecting apparatus capable of reducing power consumption and a liquid ejecting printing apparatus using the liquid ejecting apparatus. To do.

In order to solve the above problems, a liquid ejecting apparatus of the present invention includes a modulation circuit that modulates a drive waveform signal that is a reference of an actuator drive signal to generate a modulation signal, and amplifies the power by amplifying the modulation signal. A digital power amplifying circuit as a modulation signal; a smoothing filter that smoothes the power amplification modulation signal as the drive signal; and a power amplification stop means that operates when the potential of the actuator is kept constant. It is a feature.
According to this liquid ejecting apparatus, since the operation of the digital power amplifier circuit is stopped when the potential of the actuator is kept constant, that is, when the potential of the drive waveform signal is kept constant, the digital power amplifier circuit and the smoothing filter are used. The power consumption can be reduced.

The digital power amplifier circuit includes a switching element, and the power amplification stop means stops the operation of the digital power amplifier circuit by turning off all the switching elements of the digital power amplifier circuit. It is what.
According to this liquid ejecting apparatus, by turning off all the switching elements of the digital power amplifier circuit, the switching elements can be brought into a high impedance state, thereby suppressing discharge from the actuator that is a capacitive load. can do.
Further, the modulation circuit stops output of the modulation signal when the operation of the digital power amplifier circuit is stopped by the power amplification stop means.
According to this liquid ejecting apparatus, the power consumption of the modulation circuit and the digital power amplification circuit is reduced by stopping the output of the modulation signal itself.

The modulation circuit performs pulse modulation of the drive waveform signal using a first modulation frequency, and the modulation circuit changes the potential of the drive waveform signal from a state where the potential of the drive waveform signal changes. When shifting to a state in which no change occurs, the modulation frequency of pulse modulation is increased more than the first modulation frequency.
According to this liquid ejecting apparatus, the ripple voltage when the operation of the digital power amplifier circuit is stopped can be suppressed, and the potential of the drive signal when the potential does not change can be matched with the target value.

The modulation circuit performs pulse modulation of the drive waveform signal using a first modulation frequency, and the modulation circuit changes the potential of the drive waveform signal from a state where the potential of the drive waveform signal is not changed. When shifting to the changing state, the modulation frequency of the pulse modulation is increased more than the first modulation frequency.
According to this liquid ejecting apparatus, it is possible to suppress a ripple voltage when the operation of the digital power amplifier circuit is resumed.

The high level period of the modulation signal is a first period, the low level period of the modulation signal is a second period, and the modulation circuit changes the potential of the drive waveform signal. When shifting from a non-operating state to a state in which the potential of the drive waveform signal changes, the high-level or low-level period of the modulation signal immediately after the start is set to be half of the first period or the second period. It is a feature.
According to this liquid ejecting apparatus, it is possible to suppress a ripple voltage when the potential of the drive waveform signal changes from a state where it does not change.

The power amplification stop means temporarily restarts the operation of the digital power amplifier circuit while the operation of the digital power amplifier circuit is stopped.
According to this liquid ejecting apparatus, it is possible to suppress a decrease in potential due to self-discharge of an actuator including a capacitive load.
In addition, a memory for storing the driving waveform signal is provided, and the memory stores driving waveform potential difference data.
According to this liquid ejecting apparatus, it is easy to determine whether or not the potential of the drive waveform signal changes.

In addition, a memory for storing the drive waveform signal is provided, and the memory stores drive waveform potential data and information on whether or not the potential of the drive waveform signal is changed.
According to this liquid ejecting apparatus, it is not necessary to determine whether or not the potential of the drive waveform signal changes.

And a memory for storing the drive waveform signal, wherein the memory stores drive waveform potential data, and the power amplification stop means calculates a difference between the drive waveform potential data read from the memory, and the difference is zero. In some cases, the operation of the digital power amplifier circuit is stopped.
According to this liquid ejecting apparatus, the memory capacity may be small.
In addition, the memory stores a modulation frequency by the modulation circuit.
According to this liquid ejecting apparatus, it is possible to freely set the modulation frequency.

1 is a front view of a schematic configuration showing an embodiment of a liquid jet printing apparatus using a liquid jet apparatus of the present invention. FIG. 2 is a plan view of the vicinity of a liquid jet head used in the liquid jet printing apparatus of FIG. 1. FIG. 2 is a block diagram of a control device of the liquid jet printing apparatus of FIG. 1. 6 is an explanatory diagram of a drive signal for driving an actuator in each liquid ejecting head. FIG. It is a block diagram of a switching controller. It is a block diagram of the drive circuit of an actuator. FIG. 7 is a detailed block diagram illustrating an example of the drive circuit of FIG. 6. FIG. 8 is an explanatory diagram of a modulation signal, a gate-source signal, and an output signal in the drive circuit of FIG. 7. FIG. 9 is a detailed explanatory diagram of the modulation signal of FIG. 8. FIG. 10 is a detailed explanatory diagram of the modulation signal of FIG. 9. It is a wave form diagram which shows an example of a drive waveform signal. It is explanatory drawing of the memory content which shows 1st Embodiment of this invention. It is a flowchart of the arithmetic processing performed with the controller of FIG. 7 according to the memory content of FIG. It is explanatory drawing of the memory content which shows 2nd Embodiment of this invention. It is a flowchart of the arithmetic processing performed with the controller of FIG. 7 according to the memory content of FIG. It is explanatory drawing of the memory content which shows 3rd Embodiment of this invention. It is a flowchart of the arithmetic processing performed with the controller of FIG. 7 according to the memory content of FIG. FIG. 7 is a detailed block diagram illustrating another example of the drive circuit of FIG. 6.

Next, the first embodiment of the liquid ejecting apparatus according to the invention will be described as applied to a liquid ejecting printing apparatus.
FIG. 1 is a schematic configuration diagram of the liquid jet printing apparatus according to the first embodiment. In the figure, a print medium 1 is conveyed in the direction of an arrow from the left to the right in the figure, and in a printing area in the middle of the conveyance. A line head type printing apparatus to be printed.

  Reference numeral 2 in FIG. 1 denotes a plurality of liquid ejecting heads provided above the conveyance line of the print medium 1, arranged in two rows in the print medium conveyance direction and in a direction intersecting the print medium conveyance direction. And fixed to the head fixing plate 11, respectively. A large number of nozzles are formed on the lowermost surface of each liquid jet head 2, and this surface is called a nozzle surface. As shown in FIG. 2, the nozzles are arranged in rows in the direction intersecting the print medium conveyance direction for each color of the liquid to be ejected. The rows are called nozzle rows, or the row directions are nozzles. Sometimes called the row direction. A line head that extends over the entire length in the direction intersecting the transport direction of the print medium 1 is formed by the nozzle rows of all the liquid jet heads 2 arranged in the direction intersecting the print medium transport direction. When the print medium 1 passes below the nozzle surfaces of these liquid ejecting heads 2, printing is performed by ejecting liquid from a large number of nozzles formed on the nozzle surfaces.

  For example, liquid such as yellow (Y), magenta (M), cyan (C), and black (K) ink is supplied to the liquid ejecting head 2 from a liquid tank (not shown) via a liquid supply tube. The Then, by ejecting a necessary amount of liquid from a nozzle formed in the liquid ejecting head 2 to a necessary portion at the same time, minute dots are formed on the print medium 1. By performing this for each color, printing by one pass can be performed only by passing the print medium 1 conveyed by the conveyance unit 4 once.

  As a method for ejecting the liquid from the nozzle of the liquid ejecting head 2, there are an electrostatic method, a piezo method, a film boiling liquid ejecting method, and the like, and the piezo method is used in the first embodiment. In the piezo method, when a drive signal is given to a piezoelectric element that is an actuator, the diaphragm in the cavity is displaced to cause a pressure change in the cavity, and the liquid is ejected from the nozzle by the pressure change. The liquid ejection amount can be adjusted by adjusting the peak value of the drive signal and the voltage increase / decrease slope. Note that the present invention can be similarly applied to liquid ejection methods other than the piezo method.

  Below the liquid jet head 2, a transport unit 4 for transporting the print medium 1 in the transport direction is provided. The conveying unit 4 is configured by winding a conveying belt 6 around a driving roller 8 and a driven roller 9, and an electric motor (not shown) is connected to the driving roller 8. An adsorption device (not shown) for adsorbing the print medium 1 to the surface of the conveyance belt 6 is provided inside the conveyance belt 6. As this adsorption device, for example, an air suction device that adsorbs the print medium 1 to the conveyance belt 6 by negative pressure, an electrostatic adsorption device that adsorbs the print medium 1 to the conveyance belt 6 by electrostatic force, or the like is used. Accordingly, when only one sheet of the printing medium 1 is fed from the sheet feeding unit 3 to the conveying belt 6 by the sheet feeding roller 5 and the driving roller 8 is rotationally driven by the electric motor, the conveying belt 6 is rotated in the printing medium conveying direction. The print medium 1 is adsorbed to the conveyance belt 6 by the adsorption device and conveyed. While the printing medium 1 is being conveyed, printing is performed by ejecting liquid from the liquid ejecting head 2. The print medium 1 that has finished printing is discharged to the paper discharge unit 10 on the downstream side in the transport direction. The transport belt 6 is attached with a printing reference signal output device composed of, for example, a linear encoder. This printing reference signal output device pays attention to the fact that the transport belt 6 and the print medium 1 that is attracted and transported by the transport belt 6 are moved synchronously, and after the print medium 1 passes through a predetermined position in the transport path. A pulse signal corresponding to the printing resolution required in accordance with the movement of the transport belt 6 is output, and a drive signal is output from the drive circuit described later to the actuator in accordance with the pulse signal, whereby a predetermined position on the print medium 1 is output. A liquid of a predetermined color is ejected onto the print medium 1 and a predetermined image is drawn on the print medium 1 by the dots.

  A control device for controlling the liquid jet printing apparatus is provided in the liquid jet printing apparatus using the liquid jet apparatus according to the first embodiment. As shown in FIG. 3, the control device executes an input interface 61 for reading print data input from the host computer 60, and arithmetic processing such as print processing based on the print data input from the input interface 61. A control unit 62 constituted by a microcomputer, a paper feed roller motor driver 63 for driving and controlling the paper feed roller motor 17 connected to the paper feed roller 5, and a head driver 65 for driving and controlling the liquid ejecting head 2 , An electric motor driver 66 for driving and controlling the electric motor 7 connected to the drive roller 8, a paper feed roller driver 63, a head driver 65, an electric motor driver 66 and a paper feed roller motor 17, the liquid ejecting head 2, An interface 67 for connecting the motor 7 is provided.

  The control unit 62 temporarily stores a CPU (Central Processing Unit) 62a that executes various processes such as a print process, and print data input through the input interface 61 or various data when the print data print process is executed. A random access memory (RAM) 62c that temporarily stores a program such as a print process or a nonvolatile semiconductor memory that stores a control program executed by the CPU 62a. ) 62d. When the control unit 62 obtains print data (image data) from the host computer 60 via the input interface 61, the CPU 62a executes a predetermined process on the print data, and from which nozzle the liquid is ejected. Alternatively, nozzle selection data (drive pulse selection data) indicating how much liquid is to be ejected is calculated, and based on the print data, drive pulse selection data, and input data from various sensors, the paper feed roller motor driver 63, the head A drive signal and a control signal are output to the driver 65 and the electric motor driver 66. By these drive signals and control signals, the paper feed roller motor 17, the electric motor 7, the actuator 22 in the liquid ejecting head 2, etc. are actuated to feed, convey and discharge the print medium 1, and the print medium 1. The printing process is executed. Each component in the control unit 62 is electrically connected through a bus (not shown).

  FIG. 4 shows an example of a drive signal COM that is supplied to the liquid ejecting head 2 from the control device of the liquid ejecting printing apparatus using the liquid ejecting apparatus according to the first embodiment and drives the actuator 22 made of a piezoelectric element. Show. In the first embodiment, a signal whose potential changes centering on the intermediate potential is used. This drive signal COM is a time series connection of drive pulses PCOM as unit drive signals for driving the actuator 22 to eject liquid, and a cavity (pressure chamber) in which the rising portion of the drive pulse PCOM communicates with the nozzle. ) Is expanded and the liquid is drawn in (it can be said that the meniscus is drawn in considering the liquid ejection surface), and the falling portion of the drive pulse PCOM reduces the volume of the cavity to push out the liquid (the liquid Considering the ejection surface, it can be said that the meniscus is extruded). As a result of the liquid being extruded, the liquid is ejected from the nozzle.

  By variously changing the voltage increase / decrease slope and peak value of the drive pulse PCOM consisting of this voltage trapezoidal wave, it is possible to change the amount of liquid drawn in, the speed of drawing in, the amount of liquid pushed out, and the speed of extrusion. Different sizes of dots can be obtained by changing the ejection amount. Therefore, even when a plurality of drive pulses PCOM are connected in time series, a single drive pulse PCOM is selected and supplied to the actuator 22 to eject liquid or select a plurality of drive pulses PCOM to select the actuator. It is possible to obtain dots of various sizes by supplying the liquid 22 and ejecting the liquid a plurality of times. That is, if a plurality of liquids are landed at the same position before the liquid is dried, it is substantially the same as ejecting a large liquid, and the size of the dots can be increased. By combining such techniques, it is possible to increase the number of gradations. Note that the driving pulse PCOM1 at the left end in FIG. This is called microvibration, and is used to suppress or prevent the increase in the viscosity of the nozzle without ejecting liquid.

  In addition to the drive signal COM, the liquid ejection head 2 selects a nozzle to be ejected based on print data as a control signal from the control device of FIG. 3 and connects to the drive signal COM of an actuator 22 such as a piezoelectric element. Drive pulse selection data SI & SP for determining timing, latch signal LAT and channel for connecting the drive signal COM and the actuator 22 of the liquid jet head 2 based on the drive pulse selection data SI & SP after nozzle selection data is input to all nozzles A clock signal SCK for transmitting the signal CH and the drive pulse selection data SI & SP to the liquid jet head 2 as a serial signal is input. Hereinafter, the minimum unit of the drive signal for driving the actuator 22 is referred to as a drive pulse PCOM, and the entire signal in which the drive pulses PCOM are connected in time series is referred to as a drive signal COM. That is, a series of drive signals COM starts to be output in response to the latch signal LAT, and a drive pulse PCOM is output for each channel signal CH.

  FIG. 5 shows a specific configuration of a switching controller built in the liquid ejecting head 2 in order to supply the drive signal COM (drive pulse PCOM) to the actuator 22. The switching controller includes a shift register 211 that stores drive pulse selection data SI & SP for designating an actuator 22 such as a piezoelectric element corresponding to a nozzle that ejects liquid, and a latch circuit that temporarily stores data of the shift register 211. 212 and a level shifter 213 for connecting the drive signal COM to the actuator 22 such as a piezo element by converting the level of the output of the latch circuit 212 and supplying the output to the selection switch 201.

  The drive pulse selection data SI & SP is sequentially input to the shift register 211, and the storage area is sequentially shifted from the first stage to the subsequent stage in accordance with the input pulse of the clock signal SCK. The latch circuit 212 latches each output signal of the shift register 211 by the input latch signal LAT after the drive pulse selection data SI & SP for the number of nozzles is stored in the shift register 211. The signal stored in the latch circuit 212 is converted by the level shifter 213 to a voltage level at which the selection switch 201 at the next stage can be turned on / off. This is because the drive signal COM is higher than the output voltage of the latch circuit 212, and the operating voltage range of the selection switch 201 is set higher accordingly. Accordingly, the actuator 22 such as a piezoelectric element whose selection switch 201 is closed by the level shifter 213 is connected to the drive signal COM (drive pulse PCOM) at the connection timing of the drive pulse selection data SI & SP. In addition, after the drive pulse selection data SI & SP of the shift register 211 is stored in the latch circuit 212, the next print information is input to the shift register 211, and the stored data of the latch circuit 212 is sequentially updated in accordance with the liquid ejection timing. . In addition, the code | symbol HGND in a figure is a ground end of actuators 22, such as a piezoelectric element. Further, even after the actuator 22 such as a piezoelectric element is disconnected from the drive signal COM (drive pulse PCOM) by the selection switch 201, the input voltage of the actuator 22 is maintained at the voltage just before the disconnection.

  FIG. 6 shows a schematic configuration of the drive circuit of the actuator 22. This actuator drive circuit is constructed in the control unit 62 and the head driver 65 in the control circuit. The drive circuit according to the first embodiment is based on the drive waveform data DWCOM stored in advance, and is based on the drive signal COM (drive pulse PCOM), that is, the drive waveform signal WCOM serving as a reference for a signal for controlling the drive of the actuator 22. Drive waveform signal generating circuit 25 for generating the signal, modulation circuit 26 for pulse-modulating the drive waveform signal WCOM generated by the drive waveform signal generating circuit 25, and digital power for amplifying the power of the modulation signal pulse-modulated by the modulation circuit 26 An amplification circuit 28, and a smoothing filter 29 that smoothes the power amplification modulated signal amplified by the digital power amplification circuit 28 and supplies it to the liquid jet head 2 as a drive signal COM (drive pulse PCOM). This drive signal COM (drive pulse PCOM) is sent from the selection switch 201 to the actuator 22. It is fed.

  FIG. 7 shows a specific configuration of the actuator drive circuit. FIG. 7 a shows the drive waveform signal generation circuit 25 and the modulation circuit 26, and FIG. 7 b shows the digital power amplification circuit 28, the smoothing filter 29, and the liquid jet head 2. The drive waveform signal generation circuit 25 stores a drive waveform data of a drive waveform signal composed of digital potential data and the like, and converts the drive waveform data read from the memory 31 into a voltage signal, for a predetermined sampling period. A controller 32 for instructing the frequency, waveform, or waveform output timing of a triangular wave signal to a triangular wave oscillator, which will be described later, and a voltage signal output from the controller 32 are converted to analog and output as a drive waveform signal WCOM. / A converter 33 is provided. The controller 32 also outputs an operation stop signal for stopping the operation of the digital power amplifier circuit 28 toward a gate drive circuit 30 described later in the digital power amplifier circuit 28. It is assumed that the operation of the digital power amplifier circuit 28 is stopped when the operation stop signal / Disable is at a low level.

  As the modulation circuit 26, a known pulse width modulation (PWM) circuit is used. Therefore, the modulation circuit 26 includes a triangular wave oscillator 34 that outputs a triangular wave signal serving as a reference signal in accordance with the frequency, waveform, and waveform output timing instructed by the controller 32, and the drive output from the D / A converter 33. The waveform signal WCOM is compared with the triangular wave signal output from the triangular wave oscillator 34, and a pulse duty modulation signal that is on-duty is output when the drive waveform signal WCOM is larger than the triangular wave signal. The frequency of the triangular wave signal (reference signal) is defined as a modulation frequency (generally called a carrier frequency). The modulation circuit 26 may be a known pulse modulation circuit such as a pulse density modulation (PDM) circuit.

  The digital power amplifying circuit 28 is based on a half-bridge output stage 21 composed of a high-side switching element Q1 and a low-side switching element Q2 for substantially amplifying power and a modulation signal from the modulation circuit 26. And a gate drive circuit 30 for adjusting the gate-source signals GH and GL of the low-side switching element Q2 and the low-side switching element Q2. In the digital power amplifier circuit 28, when the modulation signal is at a high level, the gate-source signal GH of the high-side switching element Q1 is at a high level, and the gate-source signal GL of the low-side switching element Q2 is at a low level. Therefore, the high-side switching element Q1 is turned on and the low-side switching element Q2 is turned off. As a result, the output Va of the half bridge output stage 21 becomes the supply voltage VDD. On the other hand, when the modulation signal is at a low level, the gate-source signal GH of the high-side switching element Q1 is at a low level, and the gate-source signal GL of the low-side switching element Q2 is at a high level. The side switching element Q1 is turned off and the low side switching element Q2 is turned on. As a result, the output Va of the half-bridge output stage 21 becomes zero.

  In this way, when the high-side switching element Q1 and the low-side switching element Q2 are digitally driven, current flows through the on-state switching element, but the resistance value between the drain and the source is very small, and the loss is almost none. Does not occur. Further, since no current flows through the switching element in the off state, no loss occurs. Accordingly, the loss itself of the digital power amplifier circuit 28 is extremely small, and a switching element such as a small MOSFET can be used.

  When the operation stop signal / Disable output from the controller 32 is at a low level, the gate drive circuit 30 turns off both the high-side switching element Q1 and the low-side switching element Q2. As described above, when the digital power amplifier circuit 28 operates, either the high-side switching element Q1 or the low-side switching element Q2 is turned on. Turning off both the high-side switching element Q1 and the low-side switching element Q2 is synonymous with stopping the operation of the digital power amplifier circuit 28, and is electrically composed of a piezoelectric element that is a capacitive load. The actuator 22 is maintained in a high impedance state. When the actuator 22 is maintained in a high impedance state, the electric charge stored in the actuator 22 that is a capacitive load is maintained, and the charge / discharge state is maintained or suppressed to a slight self-discharge.

  As the smoothing filter 29, a secondary filter composed of one capacitor C and a coil L was used. The smoothing filter 29 attenuates and removes the modulation frequency generated by the modulation circuit 26, that is, the frequency component of pulse modulation, and outputs the drive signal COM (drive pulse PCOM) having the waveform characteristics as described above. Although FIG. 7 is shown as a circuit for easy understanding, the drive waveform signal generation circuit 25 and the modulation circuit 26 are constructed by programming performed in the control unit 62 of FIG. Further, the smoothing filter 29 can be configured using a stray inductance or stray capacitance generated in the circuit wiring, or an actuator, and is not necessarily formed into a circuit. The memory 31 is formed in the ROM 62d.

  FIG. 8 shows a control mode of digital power amplification performed in the first embodiment. The upper part of FIG. 8 shows a normal digital power amplification state as a conventional example, and the lower part of FIG. 8 shows an example of digital power amplification control of the first embodiment. In the conventional digital power amplification that has been conventionally performed, the digital power amplification circuit is always operated even if the potential of the drive signal COM does not change. For example, a digital power amplifier circuit used in the audio field is based on the premise that the input constantly changes, and therefore does not stop operating. On the other hand, since the actuator 22 such as a piezoelectric element is a capacitive load, it is not necessary to pass a current when the potential of the drive signal COM does not change. Nevertheless, if the high-side switching element Q1 and the low-side switching element Q2 of the digital power amplifier circuit 28 are kept on and off, the high-side switching element Q1, the low-side switching element Q2 and the coil L of the smoothing filter 29 Power is consumed.

  Therefore, in the first embodiment, as shown in the truth table of Table 1 below, when the potential of the drive signal COM (the same applies to the drive waveform signal WCOM before power amplification) does not change, the operation stop signal / Disable Is set to a low level to stop the operation of the digital power amplifier circuit 28, and both the high-side switching element Q1 and the low-side switching element Q2 are turned off. When both the high-side switching element Q1 and the low-side switching element Q2 are turned off, the actuator 22, which is a capacitive load, is maintained in a high impedance state, and the self-discharge is maintained in a slight state. In the first embodiment, when the operation of the digital power amplifier circuit 28 is stopped, that is, when the potential of the drive signal COM (drive waveform signal WCOM) does not change, the modulation signal PWM is not output (maintained at a low level). . Thereby, the power consumption of the modulation circuit 26 and the gate drive circuit 30 can also be reduced.

  Incidentally, both the high-side switching element Q1 and the low-side switching element Q2 of the digital power amplifier circuit 28 cannot be turned off only by not outputting the modulation signal PWM (maintaining at a low level). This is because when the modulation signal PWM is at a low level, the gate-source signal GH of the high-side switching element Q1 is at a low level, but the gate-source signal GL of the low-side switching element Q2 is at a high level. This is because the high-side switching element Q1 is turned off and the low-side switching element Q2 is turned on. Therefore, when the operation stop signal / Disable is at a low level, the gate drive circuit 30 is low in both the gate-source signal GH of the high-side switching element Q1 and the gate-source signal GL of the low-side switching element Q2. Level.

  FIG. 9 shows details of the PWM modulation performed by the modulation circuit 26. FIG. 9a shows a state in which the potential of the drive waveform signal WCOM gradually increases and then decreases after being held constant. FIG. 9b shows a state in which the potential of the drive waveform signal WCOM gradually decreases and gradually increases after being held constant. In the first embodiment, when the drive waveform signal WCOM increases or decreases, when the potential of the drive waveform signal WCOM is changed to a state where the potential does not change, the modulation frequency of pulse modulation is used. Increase (triangular wave signal TRI frequency). Similarly, when the drive waveform signal WCOM increases, decreases, or when the potential of the drive waveform signal WCOM changes from a state where the potential does not change to a state where the potential changes, the modulation frequency of the pulse modulation (triangular wave) Signal TRI frequency). Specifically, when the modulation frequency of the normal pulse modulation (triangular wave signal TRI frequency) is 500 kHz and the potential of the drive waveform signal WCOM is changed to a state where the potential does not change, and the drive waveform signal WCOM The modulation frequency (triangular wave signal TRI frequency) of pulse modulation when shifting from a state where the potential is not changed to a state where the potential is changed is set to 1000 kHz. By doing so, the ripple voltage of the drive signal COM in each transition period can be suppressed, and in particular, the potential of the drive signal when the potential does not change can be matched with the target value. Note that the switching of the modulation frequency is not limited to two stages, and the number of switching stages may be further increased or gradually changed.

  Further, in the first embodiment, the high-level or low-level period of the modulation signal PWM immediately after the start of the transition from the state in which the potential of the drive waveform signal WCOM is not changed to the state in which the potential is changed is changed to the original modulation signal. The half of the PWM period. Specifically, as shown in FIG. 10, when the drive waveform signal WCOM is greater than the triangular wave signal TRI, the modulation signal PWM is high level, and when the drive waveform signal WCOM is smaller than the triangular wave signal TRI, the modulation signal PWM is low level. Therefore, if the output of the modulation signal PWM is started from the lower vertex of the triangular wave signal TRI, the high level period can be halved. Further, if the output of the modulation signal PWM is started from the top of the triangular wave signal TRI, the low level period can be halved. For example, in FIG. 9A, the waveform of the triangular wave signal TRI from the controller 32 to the triangular wave oscillator 34 is changed from the controller 32 so that the triangular wave signal TRI starts from the upper apex at the same time as the decrease starts from the state where the potential of the drive waveform signal WCOM is constant. The waveform output timing is instructed. On the other hand, in FIG. 9B, the waveform of the triangular wave signal TRI from the controller 32 to the triangular wave oscillator 34 is started from the controller 32 so that the triangular wave signal TRI starts from the lower vertex at the same time as the increase starts from the state where the potential of the drive waveform signal WCOM is constant. The waveform output timing is instructed. And by doing in this way, the ripple voltage of the drive signal COM in each transition period is suppressed.

  In the first embodiment, while the operation of the digital power amplifier circuit 28 is stopped, the operation of the digital power amplifier circuit is temporarily resumed. Specifically, the operation stop signal / Disable is set to the high level to restart the operation of the gate drive circuit 30, and the modulation signal PWM is also output from the modulation circuit 26 to output the high-side switching element Q1 of the digital power amplifier circuit 28. The low-side switching element Q2 is turned on / off. The operation of the digital power amplifier circuit 28 is stopped when the potential of the drive waveform signal WCOM is not changed. Therefore, the operation of the digital power amplifier circuit 28 is also stopped by the potential of the drive signal COM supplied to the actuator 22. It is the same as the potential before and after being applied. By doing so, it is possible to suppress a decrease in potential due to self-discharge of the actuator 22 composed of a capacitive load.

For example, as shown in FIG. 11, the drive waveform signal WCOM has a potential of 0 to 0 in period 0, 2 V in period 3, 4 V in period 4, 6 V in period 5, and 6 in period 6. Is 8V, the potential of period 7 to period 11 is 10V, the potential of period 12 is 8V, the potential of period 13 is 6V, the potential of period 14 is 4V, the potential of period 15 is 2V, and the potential of period 16 to period 18 is 0V In this case, the memory 31 stores data as shown in FIG. In the first embodiment, the potential difference between the periods is stored as the output voltage difference value Vd, and the modulation frequency (PWM frequency in the figure) fpwm in each period is stored.
FIG. 13 is a flowchart of arithmetic processing performed by the controller 32 using the data stored in the memory 31 of FIG. In this calculation process, first, in step S1, the previous potential value Vs is cleared.

In step S2, the memory address counter N is cleared.
In step S3, the waveform data (output voltage difference value) Vd at the address N is read from the memory 31.
Next, the process proceeds to step S4, where it is determined whether or not the waveform data (output voltage difference value) Vd read in step S3 is waveform end data. If not, the process proceeds to step S5.

  In step S5, the waveform data (output voltage difference value) Vd read in step S3 is determined. At this time, when the immediately preceding output voltage difference value Vd is 0 and the currently read output voltage difference value Vd is 0, the state in which the potential of the drive waveform signal WCOM has not changed continues. As a thing, it transfers to step S6. If the immediately preceding output voltage difference value Vd is not 0 and the currently read output voltage difference value Vd is 0, it is determined that the potential of the drive waveform signal WCOM has changed to step S11. Migrate to When the output voltage difference value Vd immediately before is 0 and the currently read output voltage difference value Vd is a positive value, the potential of the drive waveform signal WCOM has shifted from an unchanged state to an increased state. As shown in FIG. Further, when the immediately preceding output voltage difference value Vd is 0 and the currently read output voltage difference value Vd is a negative value, the potential of the drive waveform signal WCOM has shifted from a state where it does not change to a decrease state. As shown in FIG. In other cases, that is, when the immediately preceding output voltage difference value Vd is not 0 and the currently read output voltage difference value Vd is not 0, the process proceeds to step S15.

In step S6, the modulation frequency fpwm read from the memory 31 is determined. At this time, if the immediately preceding modulation frequency fpwm is 0 and the currently read modulation frequency fpwm is not 0, it is determined that the operation of the digital power amplifier circuit 28 is temporarily resumed, and the process proceeds to step S7. If the immediately preceding modulation frequency fpwm is not 0 and the currently read modulation frequency fpwm is 0, the operation of the digital power amplifier circuit 28 is stopped and the process proceeds to step S8. When the immediately preceding modulation frequency fpwm is 0 and the currently read modulation frequency fpwm is 0, the operation of the digital power amplifier circuit 28 is continued to be stopped, and the process proceeds to step S10.
In Step S7, the original duty cycle of the modulation signal PWM is output in half, and the process proceeds to Step S9.
In step S9, the operation stop signal / Disable is set to a high level to operate the digital power amplifier circuit 28 and the modulation circuit 26, and the process proceeds to step S12.

In step S8, the process waits until the end of the modulation cycle, and proceeds to step S10.
Also in step S11, the process waits until the end of the modulation period, and proceeds to step S10.
In step S10, the operation stop signal / Disable is set to a low level, the operations of the digital power amplifier circuit 28 and the modulation circuit 26 are stopped, and the process proceeds to step S12.

On the other hand, in step S13, by adjusting the waveform of the triangular wave signal TRI and the waveform output timing as described above, the high level period of the modulation signal PWM is set to half of the high level period of the original modulation signal, and output. The process proceeds to step S15.
Further, in step S14, by adjusting the waveform of the triangular wave signal TRI and the waveform output timing as described above, the low level period of the modulation signal PWM is set to half the low level period of the original modulation signal, and output. The process proceeds to step S15.
In step S15, the current potential value V is calculated by adding the output voltage difference value Vd to the previous potential value Vs, and the process proceeds to step S16.

In step S16, the current potential value V calculated in step S15 is output to the D / A converter 33, and the process proceeds to step S17.
In step S17, the modulation frequency fpwm read from the memory 31 is output to the modulation circuit 26 (triangular wave oscillator 34), and the process proceeds to step S18.
In step S18, the operation stop signal / Disable is set to high level, the digital power amplifier circuit 28 and the modulation circuit 26 are operated, and the process proceeds to step S19.

In step S19, the current potential value V is updated and stored as the previous potential value Vs, and then the process proceeds to step S12.
In step S12, the process waits until the read timing of the memory 31, and proceeds to step S20.
In step S20, the memory address counter N is incremented, and then the process proceeds to step S3.

  According to this arithmetic processing, the operation of the digital power amplifier circuit 28 is stopped when there is no change in the potential of the drive signal COM that does not require supplying current to the actuator 22, that is, when the potential of the drive waveform signal WCOM does not change. As a result, the power consumption in the coil L in the high-side switching element Q1 and the low-side switching element Q2 and the smoothing filter 29 constituting the digital power amplifier circuit 28 can be reduced.

Further, by turning off both the high-side switching element Q1 and the low-side switching element Q2 of the digital power amplifier circuit 28, the high-side switching element Q1 and the low-side switching element Q2 can be brought into a high impedance state. Thereby, the discharge from the actuator 22 which is a capacitive load can be suppressed.
When the operation of the digital power amplifier circuit 28 is stopped, the power consumption of the modulation circuit 26 and the gate drive circuit 30 of the digital power amplifier circuit 28 is reduced by stopping the output of the modulation signal PWM itself.

Further, when shifting from the state in which the potential of the drive waveform signal WCOM is changed to the state in which the potential is not changed, the ripple when the operation of the digital power amplifier circuit 28 is stopped by increasing the modulation frequency fpwm of the pulse modulation. The voltage can be suppressed, and the potential of the drive signal COM when the potential does not change can be matched with the target value.
Further, when shifting from the state in which the potential of the drive waveform signal WCOM is not changed to the state in which the potential is changed, the ripple when the operation of the digital power amplifier circuit 28 is resumed by increasing the modulation frequency fpwm of the pulse modulation. Voltage can be suppressed.

Further, the high-level period of the modulation signal PWM immediately after the start of transition from the state in which the potential of the drive waveform signal WCOM is not changed to the state in which the potential changes in the increasing direction is set to be half of the high-level period of the original modulation signal. By doing so, the ripple voltage can be suppressed.
Further, the low level period of the modulation signal PWM immediately after the start of transition from the state in which the potential of the drive waveform signal WCOM is not changed to the state in which the potential is changed in a decreasing direction is set to be half of the low level period of the original modulation signal. By doing so, the ripple voltage can be suppressed.

Further, by temporarily resuming the operation of the digital power amplifier circuit 28 while the operation of the digital power amplifier circuit 28 is stopped, it is possible to suppress a potential drop due to self-discharge of the actuator 22 composed of a capacitive load. Become.
Further, since the drive waveform signal WCOM is stored in the memory 31 as data of the output voltage difference value Vd, it is easy to determine whether or not the potential of the drive waveform signal WCOM changes.
Further, the modulation frequency fpwm by the modulation circuit 26 is also stored in the memory 31, so that the modulation frequency fpwm can be set freely.

  Next, a second embodiment of the liquid ejecting apparatus of the invention will be described. The liquid ejecting apparatus according to the present embodiment is applied to the liquid ejecting printing apparatus as in the first embodiment, and includes a schematic configuration, the vicinity of the liquid ejecting head, a control device, a drive signal, a switching controller, and an actuator. The drive circuit, modulation signal, gate-source signal, and output signal are the same as those in the first embodiment. In the second embodiment, the contents of data stored in the memory 31 and the arithmetic processing performed by the controller 32 using the stored data are different.

For example, assuming that the waveform of the drive waveform signal is the same as that of FIG. 11 of the first embodiment, data having the contents shown in FIG. 14 is stored in the memory 31 in the second embodiment. The data stored in the memory 31 in the second embodiment includes the output voltage value (drive waveform potential data) V of the drive waveform signal WCOM in each period, the drive waveform states D0 and D2 in each period, and the modulation frequency in each period ( In FIG. 14, the PWM frequency) fpwm is stored. The drive waveform states D0 and D2 are represented by 3-bit data, [000] indicates that the potential of the drive waveform signal WCOM has not changed, and [011] indicates that the potential of the drive waveform signal WCOM has not changed. [111] indicates that the potential of the drive waveform signal WCOM continues to change, and [010] indicates that the potential of the drive waveform signal WCOM has changed from a state where it has not changed. [101] indicates that the operation of the digital power amplifier circuit 28 is temporarily resumed, [100] indicates that the operation of the digital power amplifier circuit 28 is stopped, and [001] indicates driving. It shows that the potential of the waveform signal WCOM changes in a decreasing direction from a state in which it does not change.
FIG. 15 is a flowchart of arithmetic processing performed by the controller 32 using the data stored in the memory 31 of FIG. In this calculation process, first, in step S101, the previous potential value Vs is cleared.

In step S102, the memory address counter N is cleared.
In step S103, the waveform data (output voltage value) V at the address N is read from the memory 31.
Next, the process proceeds to step S104, where it is determined whether or not the waveform data (output voltage value) V read in step S103 is waveform end data. If the waveform data is waveform end data, the arithmetic processing is terminated. Otherwise, the process proceeds to step S105.

  In step S105, the drive waveform states D0 and D2 read in step S103 are determined. At this time, if the drive waveform states D0 and D2 are [101], it is determined that the operation of the digital power amplifier circuit 28 is temporarily resumed, and the process proceeds to step S107. On the other hand, if the drive waveform states D0 and D2 are [100], the operation of the digital power amplifier circuit 28 is stopped and the process proceeds to step S108. On the other hand, if the drive waveform states D0 and D2 are [000], the operation of the digital power amplifier circuit 28 is stopped and the process proceeds to step S110. If the drive waveform states D0 and D2 are [010], the process proceeds to step S111 on the assumption that the potential of the drive waveform signal WCOM has changed from the change state to the non-change state. When the drive waveform states D0 and D2 are [011], it is determined that the potential of the drive waveform signal WCOM has changed from an unchanged state to an increased state, and the process proceeds to step S113. If the drive waveform states D0 and D2 are [001], the process proceeds to step S114 on the assumption that the potential of the drive waveform signal WCOM has changed from a state in which the drive waveform signal WCOM has not changed. If the drive waveform states D0 and D2 are [00 *] (* is either 0 or 1), the process proceeds to step S116 because it is in another state.

In step S107, the original duty cycle of the modulation signal PWM is halved and output, and the process proceeds to step S109.
In step S109, the operation stop signal / Disable is set to the high level to operate the digital power amplifier circuit 28 and the modulation circuit 26, and the process proceeds to step S112.

In step S108, the process waits until the end of the modulation period, and proceeds to step S110.
Also in step S111, the process waits until the end of the modulation period, and proceeds to step S110.
In step S110, the operation stop signal / Disable is set to the low level, and the operations of the digital power amplifier circuit 28 and the modulation circuit 26 are stopped, and the process proceeds to step S112.

On the other hand, in step S113, by adjusting the waveform of the triangular wave signal TRI and the waveform output timing as described above, the high level period of the modulation signal PWM is set to half the high level period of the original modulation signal, and output. The process proceeds to step S116.
Further, in step S114, by adjusting the waveform of the triangular wave signal TRI and the waveform output timing as described above, the low level period of the modulation signal PWM is set to half the low level period of the original modulation signal, and output. The process proceeds to step S116.
In step S116, the output voltage value V read in step S103 is output to the D / A converter 33, and the process proceeds to step S117.

In step S117, the modulation frequency fpwm read from the memory 31 is output to the modulation circuit 26 (triangular wave oscillator 34), and the process proceeds to step S118.
In step S118, the operation stop signal / Disable is set to the high level, the digital power amplifier circuit 28 and the modulation circuit 26 are operated, and the process proceeds to step S112.
In step S112, the process waits until the read timing of the memory 31, and proceeds to step S20.
In step S120, the memory address counter N is incremented, and then the process proceeds to step S103.

  According to this arithmetic processing, in addition to the effect of the first embodiment, the drive waveform signal WCOM is stored in the memory 31 as the output voltage value (drive waveform potential data) V, and the drive waveform state (drive) Information on whether or not the potential of the waveform signal is changed) Since D0 and D2 are also stored, it is not necessary to determine whether or not the potential of the drive waveform signal WCOM changes.

Next, a third embodiment of the liquid ejecting apparatus of the invention will be described. The liquid ejecting apparatus according to the third embodiment is applied to the liquid ejecting printing apparatus as in the first embodiment, and includes a schematic configuration, the vicinity of the liquid ejecting head, a control device, a drive signal, a switching controller, The actuator drive circuit, modulation signal, gate-source signal, and output signal are the same as in the first embodiment. In the third embodiment, the contents of data stored in the memory 31 and the arithmetic processing performed by the controller 32 using the stored data are different. For example, assuming that the waveform of the drive waveform signal is the same as that of FIG. 11 of the first embodiment, data having the contents shown in FIG. 16 is stored in the memory 31 in the third embodiment. The data stored in the memory 31 in the third embodiment stores the output voltage value (drive waveform potential data) V of the drive waveform signal WCOM in each period and the modulation frequency (PWM frequency in FIG. 16) fpwm in each period. ing.
FIG. 17 is a flowchart of arithmetic processing performed by the controller 32 using the data stored in the memory 31 of FIG. In this calculation process, first, in step S201, the previous potential value Vs is cleared.

In step S202, the memory address counter N is cleared.
In step S203, the waveform data (output voltage value) V at the address N is read from the memory 31.
Next, the process proceeds to step S204, where it is determined whether or not the waveform data (output voltage value) V read in step S203 is waveform end data. If the waveform data is waveform end data, the arithmetic processing is terminated. Otherwise, the process proceeds to step S205.

  In step S205, the waveform data (output voltage value) V read in step S203 is determined. At this time, the value obtained by subtracting the previous output voltage value V from the previous output voltage value V is 0, and the value obtained by subtracting the previous output voltage value V from the currently read output voltage value V is 0. In this case, the process proceeds to step S206 assuming that the state in which the potential of the drive waveform signal WCOM has not changed continues. Further, the value obtained by subtracting the output voltage value V immediately before the previous output voltage value V is not 0, and the value obtained by subtracting the previous output voltage value V from the currently read output voltage value V is 0. In some cases, it is determined that the potential of the drive waveform signal WCOM has not changed, and the process proceeds to step S211. Further, the value obtained by subtracting the immediately preceding output voltage value V from the immediately preceding output voltage value V is 0, and the value obtained by subtracting the immediately preceding output voltage value V from the currently read output voltage value V is a positive value. In this case, the process proceeds to step S213 assuming that the drive waveform signal WCOM has changed from the state in which the potential of the drive waveform signal WCOM does not change to the increase state. Also, the value obtained by subtracting the output voltage value V immediately before from the previous output voltage value V is 0, and the value obtained by subtracting the previous output voltage value from the currently read output voltage value V is a negative value. In such a case, it is assumed that the potential of the drive waveform signal WCOM has changed from a state in which the potential does not change, and the process proceeds to step S214. In other cases, the process proceeds to step S216.

  In step S206, the modulation frequency fpwm read from the memory 31 is determined. At this time, if the immediately preceding modulation frequency fpwm is 0 and the currently read modulation frequency fpwm is not 0, it is determined that the operation of the digital power amplifier circuit 28 is temporarily resumed, and the process proceeds to step S207. If the immediately preceding modulation frequency fpwm is not 0 and the currently read modulation frequency fpwm is 0, the operation of the digital power amplifier circuit 28 is stopped and the process proceeds to step S208. If the immediately preceding modulation frequency fpwm is 0 and the currently read modulation frequency fpwm is 0, the operation of the digital power amplifier circuit 28 is continued and the process proceeds to step S210.

In step S207, the on-duty period of the original modulation signal PWM is halved and output, and the process proceeds to step S209.
In step S209, the operation stop signal / Disable is set to the high level to operate the digital power amplifier circuit 28 and the modulation circuit 26, and the process proceeds to step S212.
In step S208, the process waits until the end of the modulation period, and proceeds to step S210.
Also in step S211, the process waits until the end of the modulation period, and proceeds to step S210.
In step S210, the operation stop signal / Disable is set to a low level, the operations of the digital power amplifier circuit 28 and the modulation circuit 26 are stopped, and the process proceeds to step S12.

On the other hand, in step S213, by adjusting the waveform of the triangular wave signal TRI and the waveform output timing as described above, the high level period of the modulation signal PWM is set to half the high level period of the original modulation signal, and output. The process proceeds to step S216.
Further, in step S214, by adjusting the waveform of the triangular wave signal TRI and the waveform output timing as described above, the low level period of the modulation signal PWM is set to half of the low level period of the original modulation signal, and output. The process proceeds to step S216.
In step S216, the output voltage value V read in step S203 is output to the D / A converter 33, and the process proceeds to step S217.

In step S217, the modulation frequency fpwm read from the memory 31 is output to the modulation circuit 26 (triangular wave oscillator 34), and the process proceeds to step S218.
In step S218, the operation stop signal / Disable is set to the high level, the digital power amplifier circuit 28 and the modulation circuit 26 are operated, and the process proceeds to step S212.
In step S212, the process waits until the read timing of the memory 31, and proceeds to step S220.
In step S220, the memory address counter N is incremented, and then the process proceeds to step S203.

  According to this arithmetic processing, in addition to the effects of the first and second embodiments, the drive waveform signal WCOM is stored in the memory 31 as the output voltage value (drive waveform potential data) V, and the controller 32 reads out from the memory 31. Since the difference of the output voltage value (drive waveform potential data) V is calculated and the difference of the output voltage value (drive waveform potential data) V is 0, the operation of the digital power amplifier circuit 28 is stopped. The capacity of 31 may be small.

  Next, a modified example of the actuator drive circuit described above will be described. FIG. 18 is a block diagram illustrating another example of the actuator drive circuit. This actuator drive circuit is similar to the actuator drive circuit of FIG. 7, and the same reference numerals are given to the same components, and detailed description thereof is omitted. In the actuator drive circuit of FIG. 7, the controller 32 outputs an operation stop signal / Disable to the gate drive circuit 30, and when the operation stop signal / Disable is at a low level, the high-side switching element Q1 of the digital power amplifier circuit 28 is output. The low-side switching element Q2 is turned off, and the operation of the digital power amplifier circuit 28 is stopped. This is because, as described above, there is only one gate drive circuit 30, and for example, the gate-source signal GL to the low-side switching element Q2 is inverted by inverting the gate-source signal GH to the high-side switching element Q1. This is because the gate-source signals GH and GL to the high-side switching element Q1 and the low-side switching element Q2 cannot be set to the low level.

  Therefore, in this modification, the gate drive circuit 30 is provided in each of the high-side switching element Q1 and the low-side switching element Q2. The comparator 35 outputs a pulse modulation signal PWMP that is high when the drive waveform signal WCOM is greater than the triangular wave signal TRI and its inverted pulse modulation signal PWMN, and outputs the pulse modulation signal PWMN of the high side switching element Q1. A pulse modulation signal PWMP is output to the gate drive circuit 30, and an inverted pulse modulation signal PWMN is output to the gate drive circuit 30 of the low-side switching element Q2. When the digital power amplifier circuit 28 is stopped, that is, when the potential of the drive waveform signal WCOM does not change, the controller 32 holds both the modulation signals PWMP and PWMN output from the comparator 35 at a low level. As a result, the gate-source signals GH and GL output from the two gate drive circuits 30 both become low level, and both the high-side switching element Q1 and the low-side switching element Q2 are turned off. The operation and operation stop of the digital power amplifier circuit 28 are as shown in the truth table of Table 2 below.

  In the first to third embodiments, only the case where the liquid ejecting apparatus of the present invention is used in a line head type liquid ejecting printing apparatus has been described in detail. The present invention can be similarly applied to the liquid jet printing apparatus.

  In addition, the liquid ejecting apparatus of the present invention may be a liquid other than ink (including a liquid material in which particles of functional material are dispersed and a fluid such as a gel) and a fluid other than a liquid (fluid) It is also possible to embody a liquid ejecting apparatus that ejects a solid that can be ejected as For example, a liquid material ejecting apparatus that ejects a liquid material that contains materials such as electrode materials and color materials used in the manufacture of liquid crystal displays, EL (electroluminescence) displays, surface-emitting displays, color filters, and the like in a dispersed or dissolved form. Further, it may be a liquid ejecting apparatus that ejects a bio-organic matter used for biochip manufacturing, or a liquid ejecting apparatus that ejects a liquid that is used as a precision pipette and serves as a sample. In addition, transparent resin liquids such as UV curable resins for forming liquid injection devices that inject lubricating oil onto precision machines such as watches and cameras, micro hemispherical lenses (optical lenses) used in optical communication elements, etc. Examples include a liquid ejecting apparatus that ejects a liquid onto a substrate, a liquid ejecting apparatus that ejects an etching solution such as acid or alkali to etch the substrate, a fluid ejecting apparatus that ejects a gel, and a powder such as toner. It may be a fluid ejection recording apparatus that ejects a solid. The present invention can be applied to any one of these injection devices.

  1 is a print medium, 2 is a liquid ejecting head, 3 is a paper feed unit, 4 is a transport unit, 5 is a paper feed roller, 6 is a transport belt, 7 is an electric motor, 8 is a drive roller, 9 is a driven roller, 10 is A paper discharge unit, 11 is a head fixing plate, 21 is a half-bridge output stage, 22 is an actuator, 25 is a drive waveform signal generation circuit, 26 is a modulation circuit, 28 is a digital power amplification circuit, 29 is a smoothing filter, 30 is a gate drive Circuit, 31 memory, 32 controller, 33 D / A converter, 34 triangular wave oscillator, 35 comparator, 65 head driver

Claims (12)

A modulation circuit that modulates a drive waveform signal that serves as a reference for the drive signal of the actuator to generate a modulation signal;
A digital power amplifier circuit that amplifies the modulated signal to obtain a power amplified modulated signal;
A smoothing filter that smoothes the power amplification modulation signal to obtain the drive signal;
A liquid ejecting apparatus comprising: power amplification stopping means that operates when the potential of the actuator is kept constant.   The digital power amplifier circuit includes a switching element, and the power amplification stop unit stops the operation of the digital power amplifier circuit by turning off all the switching elements of the digital power amplifier circuit. The liquid ejecting apparatus according to claim 1.   The liquid ejecting apparatus according to claim 1, wherein the modulation circuit stops the output of the modulation signal when the operation of the digital power amplification circuit is stopped by the power amplification stop unit.   The modulation circuit performs pulse modulation of the drive waveform signal using a first modulation frequency, and the modulation circuit does not change the potential of the drive waveform signal from the state where the potential of the drive waveform signal changes. 4. The liquid ejecting apparatus according to claim 1, wherein when transitioning to a state, the modulation frequency of pulse modulation is increased more than the first modulation frequency. 5.   The modulation circuit performs pulse modulation of the drive waveform signal using a first modulation frequency, and the modulation circuit changes the potential of the drive waveform signal from a state where the potential of the drive waveform signal does not change. 5. The liquid ejecting apparatus according to claim 1, wherein when transitioning to a state, a modulation frequency of pulse modulation is increased more than the first modulation frequency. 6.   The high level period of the modulation signal is a first period, and the low level period of the modulation signal is a second period. In the modulation circuit, the potential of the drive waveform signal does not change. When shifting from a state to a state in which the potential of the drive waveform signal changes, the high-level or low-level period of the modulation signal immediately after the start is set to the first period or half of the second period The liquid ejecting apparatus according to any one of claims 1 to 5.   The liquid ejection according to claim 1, wherein the power amplification stop unit temporarily restarts the operation of the digital power amplifier circuit while the operation of the digital power amplifier circuit is stopped. apparatus.   The liquid ejecting apparatus according to claim 1, further comprising a memory that stores the drive waveform signal, wherein the memory stores drive waveform potential difference data.   8. The memory according to claim 1, further comprising a memory for storing the driving waveform signal, wherein the memory stores driving waveform potential data and information indicating whether or not the potential of the driving waveform signal is changing. The liquid ejecting apparatus according to any one of the above.   A memory for storing the drive waveform signal, wherein the memory stores drive waveform potential data, and the power amplification stop means calculates a difference of the drive waveform potential data read from the memory, and the difference is 0 The liquid ejecting apparatus according to claim 1, wherein the operation of the digital power amplifier circuit is stopped.   The liquid ejecting apparatus according to claim 8, wherein a modulation frequency by the modulation circuit is stored in the memory.   A liquid jet printing apparatus comprising the liquid jet apparatus according to claim 1.

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