JP6245346B2 - Driving circuit and driving method for driving a liquid discharge head - Google Patents

Description

  The present invention relates to a driving circuit and a driving method for driving a liquid discharge head.

  Ink jet printers that record images and documents by ejecting ink onto a print medium from a plurality of nozzles of a print head are widely used. In such an ink jet printer, an actuator provided corresponding to each nozzle of the print head is driven according to a drive signal, whereby a predetermined amount of ink is ejected from the nozzle at a predetermined timing.

  For the drive signal for driving the actuator of the print head, for example, the drive waveform signal that becomes the reference of the drive signal is pulse-modulated by a pulse density modulation (PDM) method to obtain a modulation signal, and the modulation signal is power amplified. Then, it is generated by smoothing the power amplification modulation signal as a power amplification modulation signal (see, for example, Patent Document 1).

JP 2010-114711 A JP 2007-168172 A

  The drive signal generated as described above generally includes ripple noise corresponding to the oscillation frequency of pulse modulation. Here, since the pulse density modulation method is a self-excited modulation method, the oscillation frequency varies according to the signal level (voltage level). Therefore, depending on the oscillation timing, even if the waveform of the input signal is the same, the waveform of the output drive signal may be different due to the shift in the position where the ripple noise is superimposed. Thus, when generating a drive signal for driving an actuator using pulse modulation by the pulse density modulation method, there is a problem that waveform reproducibility may be deteriorated. When the waveform reproducibility of the drive signal is lowered, the ink ejection stability is lowered.

  Such a problem is not limited to a print head in an inkjet printer, but is common when driving a liquid discharge head having a plurality of nozzles that discharge liquid and a plurality of actuators provided corresponding to the plurality of nozzles. It was an issue.

  The present invention has been made to solve the above-described problems, and is used when driving a liquid discharge head having a plurality of nozzles that discharge liquid and a plurality of actuators provided corresponding to the plurality of nozzles. The object is to improve the waveform reproducibility of the drive signal.

In order to solve at least a part of the above problems, the present invention can be realized as the following forms or application examples. As a first aspect of the present invention, a driving circuit for driving a plurality of actuators is provided. The drive circuit includes a modulation circuit that modulates a drive waveform signal that is a reference of a drive signal for driving the actuator to generate a modulation signal, and digital power that amplifies the modulation signal to generate a power amplification modulation signal. An amplification circuit; and a smoothing filter that smoothes the power amplification modulation signal to obtain the drive signal. Here, the modulation circuit determines an oscillation start timing of pulse modulation in the modulation circuit based on a latch signal for latching a selection signal for selecting the actuator driven by the drive signal from a shift register. Moreover, a drive circuit for driving a plurality of actuators is provided as a second embodiment of the present invention. The drive circuit includes a modulation circuit that modulates a drive waveform signal that is a reference of a drive signal for driving the actuator to generate a modulation signal, and digital power that amplifies the modulation signal to generate a power amplification modulation signal. An amplification circuit; and a smoothing filter that smoothes the power amplification modulation signal to obtain the drive signal. Here, the modulation circuit determines an oscillation start timing of pulse modulation in the modulation circuit based on a channel signal that specifies an output timing of each drive pulse constituting the drive waveform signal.

Application Example 1 A drive circuit for driving a liquid discharge head having a plurality of nozzles that discharge liquid and a plurality of actuators provided corresponding to the plurality of nozzles,
A modulation circuit that modulates a drive waveform signal that is a reference of a drive signal for driving the actuator by a pulse density modulation method,
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,
The modulation circuit determines the oscillation start timing based on a predetermined signal synchronized with the drive waveform signal.

  In this drive circuit, since the modulation circuit determines the oscillation start timing based on a predetermined signal synchronized with the drive waveform signal, the oscillation start timing of the modulation circuit is synchronized with the drive waveform signal, and the drive output from the drive circuit The ripple noise included in the signal also becomes noise corresponding to the period and waveform of the drive waveform signal. Therefore, this drive circuit improves the waveform reproducibility of the drive signal when driving a liquid discharge head having a plurality of nozzles that discharge liquid and a plurality of actuators provided corresponding to the plurality of nozzles. Can do.

[Application Example 2] The driving circuit according to Application Example 1,
The predetermined signal specifies a latch signal for latching a selection signal for selecting a nozzle to eject liquid from a shift register of the liquid ejection head, and an output timing of each driving pulse constituting the driving waveform signal. A driving circuit that is at least one of a channel signal to be generated and a timing signal generated according to the position of the liquid discharge head.

  In this drive circuit, the modulation circuit can determine the oscillation start timing based on a signal synchronized with the drive waveform signal.

Application Example 3 The driving circuit according to Application Example 1 or Application Example 2,
The digital power amplifier circuit has a plurality of switching elements,
The actuator is a capacitive load;
The drive circuit includes stop control means for performing stop control to stop the operation of the digital power amplifier circuit by turning off the plurality of switching elements in a predetermined period according to the drive waveform signal,
The drive circuit, wherein the modulation circuit determines the oscillation start timing regardless of whether the operation of the digital power amplifier circuit is stopped.

  In this drive circuit, it is possible to improve the waveform reproducibility of the drive signal while reducing power consumption by stopping the operation of the digital power amplifier circuit.

Application Example 4 The driving circuit according to Application Example 3,
The stop control means restarts the operation of the digital power amplifier circuit when the oscillation start timing is determined by the modulation circuit when the operation of the digital power amplifier circuit is stopped.

  In this drive circuit, it is possible to improve the waveform reproducibility of the drive signal while reducing power consumption by stopping the operation of the digital power amplifier circuit.

  The present invention can be realized in various modes. For example, a drive circuit and a drive method for driving a liquid discharge head, a liquid discharge apparatus having such a liquid discharge head and a drive circuit, and the same The present invention can be realized in the form of a control method, a computer program for realizing the functions of these methods or apparatuses, a recording medium on which the computer program is recorded, and the like.

It is explanatory drawing which shows schematic structure of the printing system in the Example of this invention. 2 is an explanatory diagram showing a schematic configuration centering on a control unit 40 of the printer 100. FIG. FIG. 6 is an explanatory diagram illustrating an example of various signals supplied to the print head 60. 4 is an explanatory diagram illustrating a configuration of a switching controller 61 of a print head 60. FIG. 2 is an explanatory diagram showing a schematic configuration of a drive circuit 80 for driving a print head 60. FIG. 3 is an explanatory diagram showing functional blocks of a modulation circuit 82. FIG. 5 is an explanatory diagram showing an example of a specific functional configuration of a drive circuit 80. FIG.

  Next, embodiments of the present invention will be described based on examples.

A. Example:
FIG. 1 is an explanatory diagram showing a schematic configuration of a printing system according to an embodiment of the present invention. The printing system of the present embodiment includes a printer 100 and a host computer 90 that supplies print data PD to the printer 100. The printer 100 is connected to the host computer 90 via the connector 12.

  The printer 100 of this embodiment is an ink jet printer that is one of liquid ejecting apparatuses that eject liquid. The printer 100 forms ink dots on a print medium by ejecting ink as a liquid, thereby recording characters, figures, images, and the like according to the print data PD.

  As shown in FIG. 1, the printer 100 includes a carriage 30 on which a print head 60 is mounted, a moving mechanism that performs main scanning for reciprocating the carriage 30 along a direction parallel to the axis of the platen 26, and a print medium. A transport mechanism that performs sub-scanning to transport the paper P in a direction intersecting the main scanning direction (sub-scanning direction), an operation panel 14 for performing various instruction / setting operations related to printing, and each unit of the printer 100 are controlled. And a control unit 40. The carriage 30 is connected to the control unit 40 via a flexible cable (FFC) (not shown).

  The transport mechanism that transports the paper P has a paper feed motor 22. The rotation of the paper feed motor 22 is transmitted to the paper transport roller (same) via a gear train (not shown), and the paper P is transported along the sub-scanning direction by the rotation of the paper transport roller.

  The moving mechanism for reciprocating the carriage 30 includes an endless drive belt between the carriage motor 32, a slide shaft 34 that is laid in parallel to the axis of the platen 26, and slidably holds the carriage 30, and the carriage motor 32. And a pulley 38 for tensioning 36. The rotation of the carriage motor 32 is transmitted to the carriage 30 via the drive belt 36, whereby the carriage 30 reciprocates along the slide shaft 34. The printer 100 detects an position of the carriage 30 (print head 60) along the main scanning direction, and an encoder (not shown) that outputs a pulse signal to the control unit 40 as the carriage motor 32 rotates. It has. Based on the pulse signal output from the encoder, the control unit 40 generates a timing signal PTS that defines the input timing of the drive signal selection signal SI & SP to the shift register 63 described later.

  The carriage 30 stores a plurality of inks each having a predetermined color (for example, cyan (C), light cyan (Lc), magenta (M), light magenta (Lm), yellow (Y), and black (K)). Ink cartridge 70 is mounted. The ink stored in the ink cartridge 70 mounted on the carriage 30 is supplied to the print head 60. The print head 60 includes a plurality of nozzles that eject ink and actuators (nozzle actuators) that are provided corresponding to the nozzles. In this embodiment, a piezo element (piezoelectric element) is used as the nozzle actuator. When the nozzle actuator is driven by a drive signal to be described later, the vibration plate in the cavity (pressure chamber) communicating with the nozzle is displaced to cause a pressure change in the cavity, and the ink from the corresponding nozzle is changed by the pressure change. Is discharged. By adjusting the peak value of the drive signal used for driving the nozzle actuator and the voltage increase / decrease slope, the ink ejection amount (that is, the size of the dots to be formed) can be adjusted.

  FIG. 2 is an explanatory diagram showing a schematic configuration centering on the control unit 40 of the printer 100. The control unit 40 includes an interface 41 for inputting print data PD and the like input from the host computer 90, and a control unit 42 that executes predetermined arithmetic processing based on the print data PD input via the interface 41. , A paper feed motor driver 43 for driving and controlling the paper feed motor 22, a head driver 45 for driving and controlling the print head 60, a carriage motor driver 46 for driving and controlling the carriage motor 32, the drivers 43, 45 and 46, and the paper And an interface 47 for connecting the feed motor 22, the print head 60, and the carriage motor 32.

  The control unit 42 includes a CPU 51 that executes various arithmetic processes, a RAM 52 that temporarily stores and expands programs and data, and a ROM 53 that stores programs executed by the CPU 51. Various functions by the control unit 42 are realized by the CPU 51 operating based on a program stored in the ROM 53. Note that at least a part of the functions of the control unit 42 may be realized by operating an electric circuit included in the control unit 42 based on the circuit configuration.

  When the control unit 42 obtains the print data PD from the host computer 90 via the interface 41, the control unit 42 executes a predetermined process on the print data PD to eject ink from which nozzle of the print head 60, or which Generates nozzle selection data (drive signal selection data) that defines whether or not a certain amount of ink is to be ejected, and outputs control signals to the drivers 43, 45, and 46 based on the print data PD, drive signal selection data, etc. To do. The drivers 43, 45, and 46 output drive signals for driving the paper feed motor 22, the print head 60, and the carriage motor 32, respectively. For example, the head driver 45 supplies a later-described clock signal SCK, latch signal LAT, drive signal selection signal SI & SP, channel signal CH, and drive signal COM to the print head 60. The paper feed motor 22, the print head 60, and the carriage motor 32 operate according to the drive signal, whereby the printing process on the paper P is executed.

  FIG. 3 is an explanatory diagram illustrating an example of various signals supplied to the print head 60. The drive signal COM is a signal for driving a nozzle actuator provided in the print head 60. The drive signal COM is a signal in which drive pulses PCOM (drive pulses PCOM1 to PCOM4) as a minimum unit (unit drive signal) of the drive signal for driving the nozzle actuator are continuous in time series. A set of four drive pulses PCOM of the drive pulses PCOM1 to PCOM4 corresponds to one pixel (print pixel).

  Each drive pulse PCOM is composed of a voltage trapezoidal wave. The rising portion of each drive pulse PCOM is a portion for enlarging the volume of the cavity communicating with the nozzle and drawing ink (which can be said to draw a meniscus in terms of the ink ejection surface), and the falling edge of the drive pulse PCOM. The portion is a portion for reducing the volume of the cavity and pushing out the ink (which can be said to push out the meniscus in terms of the ink ejection surface). Therefore, ink is ejected from the nozzles by driving the nozzle actuator according to the drive pulse PCOM.

  In the drive signal COM, the waveforms (voltage increase / decrease slope and peak value) of the drive pulses PCOM2 to PCOM4 are different from each other. When the waveform of the drive pulse PCOM supplied to the nozzle actuator is different, the ink drawing amount and drawing speed, the ink pushing amount and the pushing speed are different, and the ink discharge amount (that is, the ink dot size) is different. It becomes. By selecting one or a plurality of drive pulses PCOM from the drive pulses PCOM2 to PCOM4 and supplying them to the nozzle actuator, ink dots of various sizes can be formed. In this embodiment, the drive signal COM includes a drive pulse PCOM1 called micro vibration. The drive pulse PCOM1 is used when only ink is drawn and no extrusion is performed, for example, when the viscosity increase of the nozzle is suppressed.

  The drive signal selection signal SI & SP is a signal that selects a nozzle that ejects ink based on the print data PD and determines the connection timing of the nozzle actuator to the drive signal COM. The latch signal LAT and the channel signal CH are signals for connecting the drive signal COM and the nozzle actuator of the print head 60 based on the drive signal selection signal SI & SP after the nozzle selection data for all the nozzles is input. As shown in FIG. 3, the latch signal LAT and the channel signal CH are signals synchronized with the drive signal COM. That is, the latch signal LAT is a signal that becomes a high level corresponding to the start timing of the drive signal COM, and the channel signal CH is a high level that corresponds to the start timing of each drive pulse PCOM constituting the drive signal COM. Is a signal. Output of a series of drive signals COM is started according to the latch signal LAT, and each drive pulse PCOM is output according to the channel signal CH. The clock signal SCK is a signal for transmitting the drive signal selection signal SI & SP to the print head 60 as a serial signal.

  FIG. 4 is an explanatory diagram showing the configuration of the switching controller 61 of the print head 60. The switching controller 61 is constructed in the print head 60 in order to supply a drive signal COM (drive pulse PCOM) to the nozzle actuator 67. The switching controller 61 has a shift register 63 that stores the drive signal selection signal SI & SP, a latch circuit 64 that temporarily stores the data of the shift register 63, and level-converts the output of the latch circuit 64 and supplies it to the selection switch 66. A level shifter 65 and a selection switch 66 for connecting the drive signal COM to the nozzle actuator 67 are provided.

  The drive register selection signal SI & SP is sequentially input to the shift register 63, and the area stored in accordance with the input pulse of the clock signal SCK is sequentially shifted to the subsequent stage. Note that the input of the drive signal selection signal SI & SP to the shift register 63 is executed according to the timing signal PTS described above. The latch circuit 64 latches the output signals of the shift register 63 according to the input latch signal LAT after the drive signal selection signals SI & SP for the number of nozzles are stored in the shift register 63. The signal stored in the latch circuit 64 is converted by the level shifter 65 into a voltage level at which the selection switch 66 at the next stage can be switched (ON / OFF). The nozzle actuator 67 corresponding to the selection switch 66 that is closed (becomes connected) by the output signal of the level shifter 65 is connected to the drive signal COM (drive pulse PCOM) at the connection timing of the drive signal selection signal SI & SP. Further, after the drive signal selection signal SI & SP input to the shift register 63 is latched by the latch circuit 64, the next drive signal selection signal SI & SP is input to the shift register 63, and the latch circuit 64 receives the ink discharge timing. Update stored data sequentially. According to the selection switch 66, even after the nozzle actuator 67 is disconnected from the drive signal COM (drive pulse PCOM), the input voltage of the nozzle actuator 67 is maintained at the voltage just before the disconnection. In addition, the symbol HGND in FIG. 4 is the ground end of the nozzle actuator 67.

  FIG. 5 is an explanatory diagram showing a schematic configuration of a drive circuit 80 for driving the print head 60. The drive circuit 80 is a circuit that generates the drive signal COM described above and supplies it to the nozzle actuator 67 of the print head 60, and is constructed in the control unit 42 and the head driver 45 (see FIG. 2) in the control unit 40. ing. The drive circuit 80 includes a drive waveform signal generation circuit 81, a modulation circuit 82, a digital power amplification circuit (so-called class D amplifier) 83, and a smoothing filter 87.

  The drive waveform signal generation circuit 81 generates a drive waveform signal WCOM that serves as a reference for the drive signal COM that drives the nozzle actuator 67 based on the drive waveform data DWCOM stored in advance. In this embodiment, the drive waveform signal generation circuit 81 outputs an operation stop signal / Disable for stopping the operation of the digital power amplifier circuit 83 to a gate drive circuit 84 described later in the digital power amplifier circuit 83. . The drive waveform signal generation circuit 81 functions as stop control means in the present invention.

  The modulation circuit 82 performs pulse modulation on the drive waveform signal WCOM generated by the drive waveform signal generation circuit 81 and outputs a modulation signal MS. FIG. 6 is an explanatory diagram showing functional blocks of the modulation circuit 82. The modulation circuit 82 of this embodiment is a so-called ΔΣ modulation circuit that performs pulse modulation by a pulse density modulation (PDM) method. The modulation circuit 82 compares the input signal with a predetermined value and outputs a modulation signal MS that becomes a high level when the input signal is equal to or higher than the predetermined value, and the input signal and output signal of the comparator 822 A subtractor 824 that calculates the error ER, a delay 826 that delays the error ER, and an adder 828 that adds the delayed error ER to the drive waveform signal WCOM that is the original signal. The modulation signal MS output from the modulation circuit 82 is a signal that represents a waveform by the density of pulses.

  Further, as shown in FIG. 6, in the present embodiment, the above-described latch signal LAT is input to the comparator 822 of the modulation circuit 82. The comparator 822 outputs the modulation signal MS at a timing according to the latch signal LAT. As a result, the oscillation operation of the modulation circuit 82 is once cleared, and the oscillation operation is started at a timing according to the latch signal LAT. This will be described in detail later.

  In the pulse width modulation (PWM) method, which is another typical pulse modulation method, the oscillation frequency is constant (triangular wave frequency), which is very similar to the drive signal for the print head nozzle actuator. In particular, when operating at a high frequency (for example, 5 MHz), there is a problem that the waveform reproducibility of a low level input signal is particularly poor. In contrast, the pulse density modulation method used in this embodiment is a self-excited modulation method, and the oscillation frequency varies according to the input signal level. Specifically, the oscillation frequency in the pulse density modulation method is highest when the input signal level is an intermediate value, and decreases as the input signal level increases or decreases from the intermediate value. Therefore, in the pulse density modulation method, it is possible to suppress a decrease in waveform reproducibility even when the input signal is at a low level. In addition, the pulse density modulation method does not require an external circuit for generating a high-frequency signal unlike the pulse width modulation method, and thus has an advantage in system configuration, for example, that it is relatively easy to make a single chip.

  The digital power amplification circuit 83 (FIG. 5) amplifies the modulation signal MS output from the modulation circuit 82 and outputs a power amplification modulation signal. The digital power amplifier circuit 83 performs switching based on a half-bridge output stage 85 including a high-side switching element Q1 and a low-side switching element Q2 for substantially amplifying power and a modulation signal MS from the modulation circuit 82. And a gate drive circuit 84 for adjusting the gate-source signals GH and GL of the elements Q1 and Q2. In the digital power amplifier circuit 83, when the modulation signal MS is at a high level, the high-side switching element Q1 is turned on because the gate-source signal GH is at a high level, and the low-side switching element Q2 is between the gate and source. The signal GL becomes a low level and is turned off. As a result, the output of the half bridge output stage 85 becomes the supply voltage VDD. On the other hand, when the modulation signal MS is at a low level, the high-side switching element Q1 is turned off because the gate-source signal GH is at a low level, and the low-side switching element Q2 has a gate-source signal GL at a high level. Becomes the ON state. As a result, the output of the half-bridge output stage 85 becomes zero.

  When the operation stop signal / Disable output from the drive waveform signal generation circuit 81 described above is at a low level, the gate drive circuit 84 turns off both the switching elements Q1 and Q2. Turning off both of the switching elements Q1 and Q2 is synonymous with stopping the operation of the digital power amplifier circuit 83, and the nozzle actuator 67, which is an electrically capacitive load, is maintained in a high impedance state. It will be. When the nozzle actuator 67 is maintained in a high impedance state, the electric charge stored in the nozzle actuator 67 which is a capacitive load is retained, and the charge / discharge state is maintained (or suppressed to a very slight self-discharge). ). In this embodiment, 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 the low level, and the high-side switching element Q1 and the low-side switching element Both Q2 are turned off, and the operation of the digital power amplifier circuit 83 is stopped. Since the nozzle actuator 67 is a capacitive load, even if the power consumption is reduced by such stop control, there is no substantial effect on the printing process.

  The smoothing filter 87 smoothes the power amplification modulation signal output from the digital power amplification circuit 83 to generate a drive signal COM (drive pulse PCOM), and supplies the drive signal COM to the nozzle actuator 67 via the selection switch 66 of the print head 60. (See FIG. 4). In this embodiment, a low-pass filter (low-pass filter) using a combination of a capacitor C and a coil L is used as the smoothing filter 87. The smoothing filter 87 attenuates and removes the modulation frequency component generated in the modulation circuit 82, and outputs the drive signal COM (drive pulse PCOM) having the waveform characteristics as described above. In general, the drive signal COM output from the smoothing filter 87 includes ripple noise corresponding to the oscillation frequency of the modulation circuit 82 and the like.

  FIG. 7 is an explanatory diagram showing an example of a specific functional configuration of the drive circuit 80. As described above, the modulation circuit 82 of this embodiment is a pulse density modulation type modulation circuit, and the latch signal LAT is input to the comparator (CMP). The drive circuit 80 of the present embodiment is a negative feedback type circuit using a general error amplifier, but a circuit that emphasizes high frequency components (a high pass filter (HP-F) and a high frequency boost (G)) and And a circuit (shown as “IFB”) for feeding back the high frequency component.

  Here, as described above, in the drive circuit 80 of this embodiment, the latch signal LAT is input to the comparator 822 of the modulation circuit 82 (see FIGS. 6 and 7), and the comparator 822 receives the latch signal LAT. In response, the modulation signal MS is output. As a result, the oscillation operation of the modulation circuit 82 is once cleared, and the oscillation operation is started at a timing according to the latch signal LAT. Since the latch signal LAT is a signal synchronized with the drive waveform signal WCOM, the modulation circuit 82 determines the oscillation start timing of the pulse modulation based on the signal (latch signal LAT) synchronized with the drive waveform signal WCOM. .

  When the oscillation start timing of the modulation circuit 82 is determined based on the signal synchronized with the drive waveform signal WCOM, the oscillation start timing of the modulation circuit 82 is synchronized with the drive waveform signal WCOM. Therefore, the ripple noise included in the drive signal COM output from the drive circuit 80 also becomes noise corresponding to the cycle and waveform of the drive waveform signal WCOM. Therefore, if the waveform of the drive waveform signal WCOM input to the modulation circuit 82 is the same, the waveform of the drive signal COM (signal including ripple noise) output from the drive circuit 80 is the same. As described above, in the drive circuit 80 of this embodiment, the modulation circuit 82 determines the oscillation start timing of pulse modulation based on the signal (latch signal LAT) synchronized with the drive waveform signal WCOM. As a result, the ink ejection stability can be improved.

  Further, in the drive circuit 80 of the present embodiment, the modulation circuit 82 is based on the latch signal LAT, that is, a signal (see FIG. 3) that defines the output start timing of the set of drive pulses PCOM1 to PCOM4 constituting the drive signal COM. Since the oscillation start timing of pulse modulation is determined, the waveform reproducibility in each cycle of the drive signal COM can be improved satisfactorily.

  Further, in the drive circuit 80 of the present embodiment, the modulation circuit 82 determines the oscillation start timing of pulse modulation based on a signal (latch signal LAT) synchronized with the drive waveform signal WCOM. Even when the accuracy of the mechanical mechanism of the printer 100 is low, the influence on the waveform reproducibility of the drive signal COM can be suppressed.

  Further, in the drive circuit 80 of the present embodiment, the operation of the digital power amplifier circuit 83 is stopped by turning off both the switching elements Q1 and Q2 by the operation stop signal / Disable output from the drive waveform signal generation circuit 81 described above. Stop control is performed. In this embodiment, even when the operation of the digital power amplifier circuit 83 is stopped, the modulation circuit 82 determines the oscillation start timing of pulse modulation based on the signal (latch signal LAT) synchronized with the drive waveform signal WCOM. To do. Therefore, the oscillation start timing of the modulation circuit 82 is always synchronized with the drive waveform signal WCOM regardless of whether stop control is being performed. Therefore, in the drive circuit 80 of the present embodiment, the waveform reproducibility of the drive signal can be improved even when the power consumption is reduced by the stop control of the operation of the digital power amplifier circuit 83.

B. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

B1. Modification 1:
The configuration of the printer 100 in the above embodiment is merely an example and can be variously modified. For example, in the above-described embodiment, a piezo element (piezoelectric element) is used as the nozzle actuator 67, but instead of the piezo element, ink is generated by another element such as a magnetostrictive element or a heating element (heater) disposed in the ink passage. Other actuators such as a mechanism for ejecting ink using bubbles generated in the passage may be used.

  In the above embodiment, the printer 100 receives the print data PD from the host computer 90 and performs the printing process. Instead, the printer 100, for example, receives image data acquired from a memory card or a predetermined value. The print data PD may be generated based on the image data acquired from the digital camera via the interface, the image data acquired by the scanner, and the like to perform the printing process.

  In the above embodiment, the printer 100 moves the print head 60 back and forth in a predetermined direction (main scanning direction) with respect to the continuous paper P positioned in the print area, and the paper P is used as the main paper P. Although it is assumed that the printer performs printing while repeating the operation (sub-scanning) for conveying in the conveying direction that intersects the scanning direction, the present invention is a so-called impact printer that performs printing on cut paper, and the lower surface of the print head. The present invention can also be applied to a so-called line printer that performs printing while transporting a sheet in a direction intersecting the sheet width direction under a nozzle row arranged side by side over the sheet width.

  The present invention can also be applied to apparatuses other than ink jet printers as long as the apparatus discharges a liquid (including a liquid material in which particles of functional material are dispersed and a fluid such as a gel). Examples of such liquid ejection devices include electrode materials and color materials used in the manufacture of textile printing devices for applying patterns to fabrics, liquid crystal displays, EL (electroluminescence) displays, surface-emitting displays, color filters, and the like. Such as a device that discharges a liquid material containing the above material in a dispersed or dissolved form, a device that discharges bioorganic materials used in biochip manufacturing, a device that discharges a liquid used as a precision pipette, a watch, a camera, etc. A device that ejects lubricating oil pinpoint to a precision machine, a device that ejects a transparent resin liquid such as an ultraviolet curable resin to form a micro hemispherical lens (optical lens) used in optical communication elements, etc., a substrate For example, an apparatus for discharging an etching solution such as an acid or an alkali in order to etch the above may be used.

  In the above embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. Good.

  In addition, when part or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, a hard disk, etc. It also includes an external storage device fixed to the computer.

B2. Modification 2:
In the above embodiment, the modulation circuit 82 determines the pulse modulation oscillation start timing based on the latch signal LAT. However, if the signal is synchronized with the drive waveform signal WCOM, the pulse modulation oscillation is performed based on other signals. The start timing may be determined. For example, the modulation circuit 82 may determine the pulse modulation oscillation start timing based on the above-described channel signal CH that specifies the output timing of each drive pulse PCOM constituting the drive waveform signal WCOM, The oscillation start timing of pulse modulation may be determined based on the timing signal PTS generated according to the position.

B3. Modification 3:
In the above embodiment, stop control for stopping the operation of the digital power amplifier circuit 83 is performed according to the operation stop signal / Disable. However, stop control is not necessarily performed.

  Further, when the stop control is performed, when the switching elements Q1 and Q2 are both turned off in response to the low level operation stop signal / Disable and the operation of the digital power amplifier circuit 83 is stopped, the latch signal LAT When the oscillation start timing of the modulation circuit 82 is determined based on (or another signal synchronized with the drive waveform signal WCOM), the operation of the digital power amplifier circuit 83 may be forcibly restarted. Even in this case, it is possible to improve the waveform reproducibility of the drive signal while reducing the power consumption by stopping the operation of the digital power amplifier circuit 83.

B4. Modification 4:
Of the constituent elements in the above-described embodiments, examples, and modifications, elements other than those described in the independent claims are additional elements, and can be omitted or combined as appropriate.

DESCRIPTION OF SYMBOLS 12 ... Connector 14 ... Operation panel 22 ... Paper feed motor 26 ... Platen 30 ... Carriage 32 ... Carriage motor 34 ... Sliding shaft 36 ... Drive belt 38 ... Pulley 40 ... Control unit 41 ... Interface 42 ... Control part 43 ... Paper feed motor Driver 45 ... Head driver 46 ... Carriage motor driver 47 ... Interface 51 ... CPU
52 ... RAM
53 ... ROM
DESCRIPTION OF SYMBOLS 60 ... Print head 61 ... Switching controller 63 ... Shift register 64 ... Latch circuit 65 ... Level shifter 66 ... Selection switch 67 ... Nozzle actuator 70 ... Ink cartridge 80 ... Drive circuit 81 ... Drive waveform signal generation circuit 82 ... Modulation circuit 83 ... Digital Power amplification circuit 84 ... Gate drive circuit 85 ... Half bridge output stage 87 ... Smoothing filter 90 ... Host computer 100 ... Printer 822 ... Comparator 824 ... Subtractor 826 ... Delay 828 ... Adder WCOM ... Drive waveform signal CH ... Channel signal LAT ... Latch signal COM ... Drive signal PTS ... Timing signal

Claims (4)

A drive circuit for driving the actuator over the multiple,
A modulation circuit that modulates the signal a drive waveform signal as a reference of a drive signal for driving the actuator pulse modulated and,
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,
The modulation circuit determines a pulse modulation oscillation start timing in the modulation circuit based on a latch signal for latching a selection signal for selecting the actuator driven by the drive signal from a shift register .   A drive circuit for driving a plurality of actuators,
  A modulation circuit that modulates a drive waveform signal that is a reference of a drive signal for driving the actuator into a modulation signal by pulse modulation;
  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,
  The said modulation circuit is a drive circuit which determines the oscillation start timing of the pulse modulation in the said modulation circuit based on the channel signal which specifies the output timing of each drive pulse which comprises the said drive waveform signal. A method for driving the actuator over the multiple,
A modulation step of the modulation signal a drive waveform signal as a reference of a drive signal for driving the actuator pulse modulated and,
A power amplification step of amplifying the modulation signal to obtain a power amplification modulation signal;
Smoothing the power amplification modulation signal to make the drive signal,
The modulation process is based on a latch signal for latching a selection signal for selecting the actuator to be driven by the drive signal from the shift register, including the step of determining the oscillation start timing of a pulse modulation in the modulation step,
Method.   A method for driving a plurality of actuators, comprising:
  A modulation step of modulating a drive waveform signal, which is a reference of a drive signal for driving the actuator, into a modulation signal by pulse modulation;
  A power amplification step of amplifying the modulation signal to obtain a power amplification modulation signal;
  Smoothing the power amplification modulation signal to make the drive signal,
  The modulation step includes a step of determining an oscillation start timing of pulse modulation in the modulation step based on a latch signal for latching a selection signal for selecting the actuator driven by the drive signal from a shift register.
Method.

Images