Drive signal output circuit and liquid discharge apparatus

Abstract

To provide a drive signal output circuit capable of increasing the frequency of a drive signal.SOLUTION: A drive signal output circuit that outputs a drive signal for driving a capacitive load includes a modulation circuit that modulates a base drive signal that is a base of the drive signal and outputs the modulated signal as a modulation signal, an amplification circuit that amplifies the modulation signal and outputs the amplified modulation signal, and a demodulation circuit that demodulates the amplified modulation signal and outputs the demodulated signal as the drive signal. The demodulation circuit outputs the drive signal from a connection point at which the other end of the inductive circuit and the one end of the capacitive circuit are electrically connected to each other, and the switch circuit switches an inductance value of the inductive circuit between a first inductance value and a second inductance value different from the first inductance value.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a drive signal output circuit and a liquid ejection device. [Background technology]

[0002] Among liquid ejection devices that eject liquid to form images or documents on a medium, those that use piezoelectric elements are known. In such liquid ejection devices, a piezoelectric element is provided corresponding to each of a plurality of nozzles that eject liquid, and each is driven according to a drive signal. When the piezoelectric element is driven, liquid is ejected from the nozzle that is provided corresponding to the piezoelectric element. A sufficient current must be supplied to operate such a piezoelectric element. Therefore, a drive circuit that outputs a drive signal to drive the piezoelectric element includes an amplifier circuit that amplifies the base drive signal, which is the basis of the drive signal.

[0003] For example, Patent Document 1 discloses a liquid ejection device that includes a drive circuit that outputs a drive signal for driving a piezoelectric element and that includes a digital amplifier circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-117050 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology described in Patent Document 1 is not sufficient in terms of realizing a higher frequency drive signal. [Means for solving the problem]

[0006] One aspect of the drive signal output circuit according to the present invention is A drive signal output circuit that outputs a drive signal to drive a capacitive load, a modulation circuit that modulates a base drive signal that is the basis of the drive signal and outputs the modulated signal; an amplifier circuit that amplifies the modulated signal and outputs it as an amplified modulated signal; a demodulation circuit that demodulates the amplified modulated signal and outputs the demodulated signal as the drive signal; Equipped with the demodulation circuit includes an inductive circuit, a capacitive circuit, and a switch circuit; The amplified modulated signal is input to one end of the inductive circuit, The other end of the inductive circuit is electrically connected to one end of the capacitive circuit; the demodulation circuit outputs the drive signal from a connection point where the other end of the inductive circuit and the one end of the capacitive circuit are electrically connected; The switch circuit switches the inductance value of the inductive circuit between a first inductance value and a second inductance value different from the first inductance value.

[0007] One aspect of the liquid ejection device according to the present invention is a discharge unit that discharges liquid by driving a capacitive load; a drive signal output circuit that outputs a drive signal for driving the capacitive load; Equipped with The drive signal output circuit a modulation circuit that modulates a base drive signal that is the basis of the drive signal and outputs the modulated signal; an amplifier circuit that amplifies the modulated signal and outputs it as an amplified modulated signal; a demodulation circuit that demodulates the amplified modulated signal and outputs the demodulated signal as the drive signal; Equipped with the demodulation circuit includes an inductive circuit, a capacitive circuit, and a switch circuit; The amplified modulated signal is input to one end of the inductive circuit, The other end of the inductive circuit is electrically connected to one end of the capacitive circuit; the demodulation circuit outputs the drive signal from a connection point where the other end of the inductive circuit and the one end of the capacitive circuit are electrically connected; The switch circuit switches the inductance value of the inductive circuit between a first inductance value and a second inductance value different from the first inductance value. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of a schematic configuration of a liquid ejection device. [Figure 2] FIG. 2 is a diagram illustrating an example of a functional configuration of the liquid ejection device. [Figure 3] FIG. 2 is a diagram showing a schematic structure of one of a plurality of ejection units included in the ejection head. [Figure 4] 10 is a diagram showing an example of a signal waveform of a drive signal COM. FIG. [Figure 5] FIG. 2 is a diagram illustrating an example of a configuration of a selection control circuit and a plurality of selection circuits. [Figure 6] FIG. 10 is a diagram showing an example of the decoded content in the decoder. [Figure 7] FIG. 2 is a diagram illustrating an example of the configuration of a selection circuit. [Figure 8] FIG. 2 is a diagram illustrating a configuration of a drive signal output circuit. [Figure 9] FIG. 2 is a diagram illustrating an example of the configuration of a demodulation circuit included in a drive signal output circuit. [Figure 10] FIG. 2 is a diagram for explaining the operation of a demodulation circuit. [Figure 11] 10A and 10B are diagrams illustrating an example of a method for controlling a liquid ejection device including a drive signal output circuit. [Figure 12] FIG. 10 is a diagram illustrating a specific example of a drive signal output process. [Figure 13] FIG. 10 is a diagram illustrating a specific example of demodulation processing. [Figure 14] FIG. 10 is a diagram illustrating an example of the configuration of a demodulation circuit according to a first modification. [Figure 15] FIG. 10 is a diagram illustrating an example of the configuration of a demodulation circuit according to a second modification. [Figure 16]FIG. 10 is a diagram illustrating a configuration of a drive signal output circuit according to a second embodiment. [Figure 17] FIG. 10 is a diagram illustrating an example of the configuration of a demodulation circuit according to a second embodiment. [Figure 18] FIG. 10 is a diagram for explaining an example of the operation of the demodulation circuit according to the second embodiment. [Figure 19] FIG. 10 is a diagram illustrating a specific example of demodulation processing according to the second embodiment. [Figure 20] FIG. 10 is a diagram illustrating a configuration of a drive signal output circuit according to a third embodiment. [Figure 21] FIG. 10 is a diagram illustrating an example of the configuration of a demodulation circuit according to a third embodiment. [Figure 22] FIG. 11 is a diagram illustrating a specific example of demodulation processing according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present invention will be described below with reference to the drawings. The drawings used are for the convenience of explanation. Note that the embodiments described below do not unduly limit the content of the present invention as defined in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0010] 1. First embodiment 1.1 Configuration of the liquid ejection device FIG. 1 is a diagram showing an example of the schematic configuration of a liquid ejection device 1. The liquid ejection device 1 of the first embodiment is a serial printing type inkjet printer in which a carriage 21 mounted with a head unit 20 that ejects ink, as an example of a liquid, moves back and forth along a scanning axis and ejects ink onto a medium P that is transported along a transport direction, thereby forming a desired image on the medium P. The medium P used in such a liquid ejection device 1 can be any printing target, such as printing paper, resin film, or fabric. Note that the liquid ejection device 1 is not limited to a serial printing type inkjet printer, but may also be a line printing type inkjet printer. Furthermore, the liquid ejection device 1 is not limited to an inkjet printer, but may also be used in a variety of applications, such as in the manufacture of color filters for liquid crystal displays and the like. the color material ejection device used in forming electrodes for organic EL displays, FEDs (face-emitting displays), etc.; a bioorganic material ejection device used in biochip production; a three-dimensional modeling device; and a textile printing device.

[0011] As shown in FIG. 1, the liquid ejection device 1 includes an ink container 2, a control unit 10, a head unit 20, a moving unit 30, and a transport unit 40.

[0012] The ink container 2 stores multiple types of ink to be ejected onto the medium P. Colors of ink stored in the ink container 2 include black, cyan, magenta, yellow, red, gray, etc. The ink container 2 that stores such ink may be an ink cartridge, a bag-shaped ink pack made of flexible film, or an ink tank that can be refilled with ink.

[0013] The control unit 10 includes a processing circuit such as a CPU (Central Processing Unit) or FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and controls each element of the liquid ejection device 1 including the head unit 20.

[0014] The head unit 20 is mounted on a carriage 21. The carriage 21 is fixed to an endless belt 32 included in a moving unit 30. In addition to the head unit 20, an ink container 2 may be mounted on the carriage 21.

[0015] A control signal Ctrl-H for controlling the head unit 20, output by the control unit 10, is input to the head unit 20 mounted on the carriage 21. Ink stored in the ink container 2 is supplied to the head unit 20 via a tube (not shown). The head unit 20 then ejects the ink supplied from the ink container 2 based on the input control signal Ctrl-H.

[0016] The moving unit 30 includes a carriage motor 31 and an endless belt 32. The carriage motor 31 is driven based on a control signal Ctrl-C input from the control unit 10. The endless belt 32 rotates in accordance with the drive of the carriage motor 31. This causes the carriage 21 fixed to the endless belt 32 to move back and forth along the scanning axis. In other words, the head unit 20 mounted on the carriage 21 moves back and forth along the scanning axis that intersects with the transport direction in which the medium P is transported.

[0017] The transport unit 40 includes a transport motor 41 and a transport roller 42. The transport motor 41 is driven based on a control signal Ctrl-T input from the control unit 10. The transport roller 42 rotates in accordance with the driving of the transport motor 41. As the transport roller 42 rotates, the medium P is transported in the transport direction.

[0018] In the liquid ejection device 1 configured as described above, the head unit 20 mounted on the carriage 21 ejects ink onto the medium P in conjunction with the transport of the medium P by the transport unit 40 and the reciprocating movement of the carriage 21 by the moving unit 30. This causes the ink ejected from the head unit 20 to land at any position on the surface of the medium P. As a result, a desired image is formed on the medium P.

[0019] A specific example of the functional configuration of the liquid ejection device 1 configured as above will be described. Fig. 2 is a diagram showing an example of the functional configuration of the liquid ejection device 1. As shown in Fig. 2, the liquid ejection device 1 has a control unit 10, a head unit 20, a moving unit 30, and a transport unit 40.

[0020] The control unit 10 includes a control circuit 100 .

[0021] When an image signal is input from an external device such as a host computer, the control circuit 100 generates various control signals according to the image signal and outputs them to the corresponding components.

[0022] Specifically, the control circuit 100 generates control signals Ctrl-T and Ctrl-C when an image signal is input and printing is performed on the medium P. The control signal Ctrl-T output by the control circuit 100 is input to a transport motor 41 included in the transport unit 40. The transport motor 41 is driven in response to the control signal Ctrl-T. The driving force of this transport motor 41 transports the medium P along the transport direction. The control signal Ctrl-C output by the control circuit 100 is input to a carriage motor 31 included in the movement unit 30. The carriage motor 31 is driven in response to the control signal Ctrl-C. The driving force of this carriage motor 31 moves the carriage 21 carrying the head unit 20 back and forth along the scanning axis. Note that the transport unit 40 may include one or more transport rotors in addition to the transport motor 41. The transport unit 40 may also include a transport motor driver circuit for converting the control signal Ctrl-T into a predetermined signal that drives the transport motor 41. The moving unit 30 may also include a carriage motor driver circuit for converting the control signal Ctrl-C into a predetermined signal for driving the carriage motor 31 .

[0023] In addition, the control circuit 100 generates a clock signal SCK, a print data signal SI, a latch signal LAT, and a basic drive signal dA as control signals Ctrl-H based on an image signal input from an external device, and outputs them to the head unit 20.

[0024] The head unit 20 includes a drive circuit 50 and a plurality of ejection heads 200 .

[0025] The drive circuit 50 includes a drive signal output circuit 51. A digital base drive signal dA is input to the drive signal output circuit 51 as a control signal Ctrl-H. The drive signal output circuit 51 performs digital-to-analog conversion on the input base drive signal dA and generates and outputs a drive signal COM by class D amplifying the converted analog signal. The drive signal COM output by the drive signal output circuit 51 is input to the ejection head 200. In other words, the base drive signal dA is a signal that forms the basis of the drive signal COM and defines the waveform of the drive signal COM. Here, the base drive signal dA may be any signal that can define the waveform of the drive signal COM, and may be an analog signal.

[0026] The drive circuit 50 also includes a reference voltage output circuit 52. The reference voltage output circuit 52 generates a reference voltage signal VBS, which is a constant DC voltage with a voltage value of 5.5 V, 6 V, or the like, and outputs it to the ejection head 200. This reference voltage signal VBS functions as a reference potential for driving the piezoelectric elements 60 (described below) of the ejection head 200. The potential of such a reference voltage signal VBS is not limited to 5.5 V or 6 V, and may also be ground potential.

[0027] The ejection head 200 includes a selection control circuit 210, a plurality of selection circuits 230, and a plurality of ejection units 600. The plurality of ejection units 600 are provided corresponding to the plurality of selection circuits 230, respectively.

[0028] A clock signal SCK, a print data signal SI, and a latch signal LAT are input to the selection control circuit 210. Based on the input clock signal SCK, print data signal SI, and latch signal LAT, the selection control circuit 210 generates a selection signal S corresponding to each of the multiple selection circuits 230 and outputs it to the corresponding selection circuit 230.

[0029] Each selection circuit 230 receives as input the drive signal COM and a corresponding selection signal S output by the selection control circuit 210. The selection circuit 230 selects or deselects the drive signal COM based on the input selection signal S, thereby generating a drive signal VOUT and supplying the generated drive signal VOUT to the corresponding discharge unit 600. In other words, each selection circuit 230 switches whether or not to supply the drive signal COM to the corresponding discharge unit 600 as the drive signal VOUT.

[0030] Each of the multiple ejection units 600 includes a piezoelectric element 60. One end of the piezoelectric element 60 included in each of the multiple ejection units 600 is supplied with a drive signal VOUT output by the corresponding selection circuit 230. The other end of the piezoelectric element 60 included in each of the multiple ejection units 600 is commonly supplied with a reference voltage signal VBS output by the reference voltage output circuit 52. The piezoelectric element 60 is driven in response to the potential difference between the drive signal VOUT supplied to one end and the reference voltage signal VBS supplied to the other end. An amount of ink corresponding to the drive of this piezoelectric element 60 is ejected from the ejection unit 600.

[0031] 1.2 Discharge head configuration 1.2.1 Discharge section structure An example of the structure of the discharge unit 600 of the discharge head 200 will be described. Fig. 3 is a diagram showing a schematic structure of one of the multiple discharge units 600 of the discharge head 200. As shown in Fig. 3, the discharge unit 600 includes a piezoelectric element 60, a vibration plate 621, a cavity 631, and a nozzle 651.

[0032] The cavity 631 is filled with ink supplied from a reservoir 641. In addition, ink is introduced into the reservoir 641 from the ink container 2 via an ink tube (not shown) and a supply port 661. In other words, the cavity 631 is filled with ink stored in the corresponding ink container 2.

[0033] 3, the vibration plate 621 is displaced by driving the piezoelectric element 60 provided on the upper surface. The internal volume of the cavity 631 filled with ink expands or contracts in accordance with the displacement of the vibration plate 621. In other words, the vibration plate 621 functions as a diaphragm that changes the internal volume of the cavity 631.

[0034] The nozzle 651 is provided in the nozzle plate 632 and is an opening that communicates with the cavity 631. When the internal volume of the cavity 631 changes, an amount of ink corresponding to the change in internal volume is ejected from the nozzle 651.

[0035] Piezoelectric element 60 has a structure in which a piezoelectric body 601 is sandwiched between a pair of electrodes 611 and 612. In piezoelectric body 601 having such a structure, the central portions of electrodes 611 and 612 bend vertically together with diaphragm 621 in response to the potential difference of signals supplied to electrodes 611 and 612.

[0036] For example, a drive signal VOUT is supplied to one of the electrodes 611 or 612 of the piezoelectric element 60, and a reference voltage signal VBS is supplied to the other of the electrodes 611 or 612 of the piezoelectric element 60. When the voltage value of the drive signal VOUT increases, the piezoelectric element 60 bends upward. As the piezoelectric element 60 bends upward, the diaphragm 621 is displaced, and the internal volume of the cavity 631 expands. As a result, ink is drawn in from the reservoir 641. On the other hand, when the voltage value of the drive signal VOUT decreases, the piezoelectric element 60 bends downward. As the piezoelectric element 60 bends downward, the diaphragm 621 is displaced, and the internal volume of the cavity 631 contracts. As a result, an amount of ink corresponding to the degree of contraction is ejected from the nozzle 651.

[0037] That is, the ejection section 600 includes a piezoelectric element 60 that is driven by a drive signal VOUT based on the drive signal COM, and ejects ink when the piezoelectric element 60 is driven.

[0038] 3, the piezoelectric element 60 may have any structure as long as it can eject ink from the ejection portion 600. That is, the piezoelectric element 60 is not limited to the bending vibration structure described above, and may have a structure that uses longitudinal vibration, for example. Furthermore, the piezoelectric element 60 may be configured to bend downward when the voltage value of the drive signal VOUT increases, and to bend upward when the voltage value of the drive signal VOUT decreases.

[0039] 1.2.2 Functional configuration of the drive signal selection circuit Next, the functional configuration of the selection control circuit 210 and the multiple selection circuits 230 of the ejection head 200 will be described. Before describing the functional configuration of the selection control circuit 210 and the multiple selection circuits 230, an example of a drive signal COM controlled to be selected or deselected by the selection control circuit 210 and the multiple selection circuits 230 will be described. FIG. 4 is a diagram showing an example of a signal waveform of the drive signal COM. As shown in FIG. 4, the drive signal COM includes a trapezoidal waveform Adp arranged for each cycle tp from when the latch signal LAT rises until the next rise of the latch signal LAT. The trapezoidal waveform Adp includes a period during which the voltage value is constant at voltage vb, a period during which the voltage value is constant at voltage vt, which is higher than voltage vb, and a period during which the voltage value is constant at voltage vt. That is, the drive signal COM includes a trapezoidal waveform Adp whose voltage value changes between voltage vb and voltage vt and whose voltage value starts at voltage vb and ends at voltage vb during the cycle tp.

[0040] The voltage vb is a voltage value that serves as a reference for the displacement of the piezoelectric element 60. When the voltage value of the drive signal VOUT based on the drive signal COM supplied to the piezoelectric element 60 changes from voltage vb to voltage vt, the piezoelectric element 60 is driven in the upward direction shown in FIG. 3. This causes the vibration plate 621 to be displaced in the upward direction shown in FIG. 3, and the internal volume of the cavity 631 to expand. As a result, ink is drawn from the reservoir 641 into the cavity 631. Thereafter, when the voltage value of the drive signal COM supplied to the piezoelectric element 60 changes from voltage vt to voltage vb, the piezoelectric element 60 is driven in the downward direction shown in FIG. 3. This causes the vibration plate 621 to be displaced in the downward direction shown in FIG. 3, and the internal volume of the cavity 631 to contract. As a result, the ink stored in the cavity 631 is ejected from the nozzle 651.

[0041] Here, the signal waveform of the drive signal COM shown in Figure 4 is an example and is not limited to this, and the drive signal COM may include signal waveforms of various shapes depending on the physical properties of the ink, the ink temperature, the ink ejection amount, the ink ejection period, the type of medium P, the transport speed, etc.

[0042] The selection control circuit 210 outputs a selection signal S to each of the multiple selection circuits 230, which switches whether or not to output the drive signal COM as the drive signal VOUT during the period tp, based on the clock signal SCK, the print data signal SI, and the latch signal LAT. The multiple selection circuits 230 then switch whether or not to output the drive signal COM as the drive signal VOUT based on the input selection signal S. This controls the ejection of ink from the nozzles 651 during the period tp. FIG. 5 is a diagram showing an example of the configuration of the selection control circuit 210 and the multiple selection circuits 230. In the following description, the ejection head 200 will be described as having m ejection units 600.

[0043] A clock signal SCK, a print data signal SI, and a latch signal LAT are input to the selection control circuit 210. The selection control circuit 210 also includes a set of a shift register (S / R) 212, a latch circuit 214, and a decoder 216, each of which corresponds to one of the m ejection sections 600. That is, the selection control circuit 210 includes m shift registers 212, m latch circuits 214, and m decoders 216.

[0044] The print data signal SI is input to the selection control circuit 210 in synchronization with the clock signal SCK. The print data signal SI also includes one-bit print data [SId] for selecting whether or not to eject ink, serially corresponding to each of the m ejection units 600. The print data [SId] included in the print data signal SI is held in m shift registers 212 corresponding to the m ejection units 600. Specifically, the m shift registers 212 corresponding to the piezoelectric elements 60 are cascade-connected, and the serially input print data signal SI is sequentially transferred to the subsequent shift register 212 in accordance with the clock signal SCK. When the print data [SId] is held in the corresponding shift register 212, the clock signal SCK stops. This causes the print data [SId] included in the print data signal SI to be held in the corresponding shift register 212. Note that in FIG. 5, the m shift registers 212 are distinguished from one another by being labeled 1st stage, 2nd stage, ..., mth stage, starting from the upstream side where the print data signal SI is input.

[0045] Each of the m latch circuits 214 simultaneously latches the print data [SId] held in the corresponding shift register 212 at the rising edge of the latch signal LAT. The print data [SId] latched by the latch circuit 214 is then input to the corresponding decoder 216. FIG. 6 is a diagram showing an example of the decoded content in the decoder 216. In a period tp, the decoder 216 generates a signal of a logic level determined by the input print data [SId], shifts the level to a high-amplitude logic, and outputs the signal as a selection signal S. Specifically, when print data [SId]=[1] is input to the decoder 216, the decoder 216 selects dot formation Dt, which forms dots on the medium P, and outputs an H-level selection signal S. When print data [SId]=[0] is input to the decoder 216, the decoder 216 selects dot non-formation NDt, which does not form dots on the medium P, and outputs an L-level selection signal S. The selection signal S output by this decoder 216 is output from the selection control circuit 210.

[0046] The selection signal S output by the selection control circuit 210 is input to the selection circuit 230. A selection circuit 230 is provided corresponding to each of the m ejection units 600. In other words, the ejection head 200 has m selection circuits 230, the same number as the m ejection units 600. FIG. 7 is a diagram showing an example of the configuration of the selection circuit 230. As shown in FIG. 7, the selection circuit 230 includes an inverter 232, which is a NOT circuit, and a transmission gate 234.

[0047] The selection signal S is input to a positive control terminal (not marked with a circle) of the transmission gate 234, and after its logical level is inverted by the inverter 232, is also input to a negative control terminal (marked with a circle) of the transmission gate 234. A drive signal COM is supplied to the input terminal of the transmission gate 234. When an H-level selection signal S is input, the input terminal and output terminal of the transmission gate 234 are electrically connected, and when an L-level selection signal S is input, the input terminal and output terminal are electrically disconnected. That is, when the logical level of the selection signal S is H, the transmission gate 234 outputs the drive signal COM from its output terminal, and when the logical level of the selection signal S is L, the transmission gate 234 does not output the drive signal COM from its output terminal. The signal output to the output terminal of the transmission gate 234 of this selection circuit 230 is supplied as a drive signal VOUT to the piezoelectric element 60 of the corresponding ejection unit 600.

[0048] 1.3 Configuration of the drive signal output circuit 1.3.1 Configuration of the drive signal output circuit Next, the configuration and operation of the drive signal output circuit 51 included in the drive circuit 50 will be described. Fig. 8 is a diagram showing the configuration of the drive signal output circuit 51. As shown in Fig. 8, the drive signal output circuit 51 has an integrated circuit 500, an amplifier circuit 550, a demodulation circuit 560, feedback circuits 570 and 572, a differentiation circuit 580, and a plurality of other circuit elements. The integrated circuit 500 generates gate signals Hgd and Lgd based on a basic drive signal dA that is the basis of the drive signal COM. The amplifier circuit 550 has transistors M1 and M2, and generates an amplified modulation signal AMs by driving the transistors M1 and M2 based on gate signals Hgd and Lgd, and outputs the amplified modulation signal AMs to the demodulation circuit 560. The demodulation circuit 560 demodulates the amplified modulation signal AMs by smoothing it. The signal demodulated by the demodulation circuit 560 is output from the drive signal output circuit 51 as the drive signal COM.

[0049] The integrated circuit 500 has a plurality of terminals including a terminal In, a terminal Bst, a terminal Hdr, a terminal Sw, a terminal Gvd, a terminal Ldr, a terminal Gnd, a terminal Ifb, and a terminal Vfb. The integrated circuit 500 is electrically connected to an external circuit via these plurality of terminals. The integrated circuit 500 also includes a DAC (Digital to Analog Converter) 511, a modulation circuit 510, and a gate drive circuit 520.

[0050] The DAC 511 converts the reference drive signal dA, which is a digital signal that defines the signal waveform of the drive signal COM, into a reference drive signal aA, which is an analog signal, and outputs it to the modulation circuit 510. The signal obtained by amplifying the reference drive signal aA output by the DAC 511 corresponds to the drive signal COM. In other words, the reference drive signal aA is a target signal for the drive signal COM before amplification, and the reference drive signal dA is a target signal for the drive signal COM before amplification and is a signal that defines the shape of the signal waveform of the drive signal COM. The voltage amplitude of the reference drive signal aA output by the DAC 511 is set to, for example, 1V to 2V.

[0051] The modulation circuit 510 generates a modulation signal Ms by modulating the basic drive signal aA and outputs it to the gate drive circuit 520. The modulation circuit 510 includes adders 512 and 513, a comparator 514, an inverter 515, an integral attenuator 516, and an attenuator 517.

[0052] The integral attenuator 516 attenuates and integrates the voltage value of the drive signal COM input via terminal Vfb, and outputs the integrated signal to the negative input terminal of the adder 512. The reference drive signal aA is input to the positive input terminal of the adder 512. The adder 512 generates a voltage signal by subtracting the voltage value of the signal input to the negative input terminal from the voltage value of the signal input to the positive input terminal, and outputs this signal to the positive input terminal of the adder 513. Here, while the maximum value of the voltage amplitude of the reference drive signal aA is about 2 V as mentioned above, the maximum voltage value of the drive signal COM can exceed 40 V. When calculating the deviation, the integral attenuator 516 attenuates the drive signal COM input via terminal Vfb to match the range of the voltage amplitude of the reference drive signal aA with the range of the voltage amplitude of the drive signal COM.

[0053] The attenuator 517 attenuates the high-frequency components of the drive signal COM input via terminal Ifb and supplies the resulting voltage to the negative input terminal of the adder 513. The signal output by the adder 512 is input to the positive input terminal of the adder 513. The adder 513 generates a voltage signal As by subtracting the voltage value of the signal input to its negative input terminal from the voltage value of the signal input to its positive input terminal, and outputs this to the comparator 514. The voltage signal As is a signal obtained by subtracting the voltage value of the signal supplied to terminal Vfb from the voltage value of the base drive signal aA, and then further subtracting the voltage value of the signal supplied to terminal Ifb. Therefore, the voltage signal As is a signal obtained by correcting the deviation, obtained by subtracting the attenuated voltage of the drive signal COM from the target voltage value of the base drive signal aA, using the high-frequency components of the drive signal COM.

[0054] The comparator 514 pulse-modulates the voltage signal As and outputs it as a modulated signal Ms. Specifically, the comparator 514 outputs a modulated signal Ms that goes to H level when the voltage value of the voltage signal As is equal to or greater than a predetermined threshold Vth1 during a period in which the voltage value of the voltage signal As is rising, and goes to L level when the voltage value of the voltage signal As is below a predetermined threshold Vth2 during a period in which the voltage value of the voltage signal As is falling. Here, the thresholds Vth1 and Vth2 are set so that the relationship of threshold Vth1>threshold Vth2 is satisfied. This modulated signal Ms is The frequency and duty ratio change in accordance with the master drive signals dA and aA. That is, by adjusting the modulation gain, which corresponds to the sensitivity of the attenuator 517, it is possible to adjust the amount of change in the frequency and duty ratio of the modulation signal Ms.

[0055] The modulation signal Ms is input to a gate driver 521 included in a gate drive circuit 520. The modulation signal Ms is also input to a gate driver 522 included in the gate drive circuit 520 after its logical level is inverted by an inverter 515. That is, signals whose logical levels are mutually exclusive are input to the gate drivers 521 and 522.

[0056] Here, the timing of the signals input to the gate drivers 521 and 522 may be controlled so that the logic levels do not become H level at the same time. In other words, the above-mentioned "mutually exclusive relationship of logic levels" means that the logic level of the signal input to the gate driver 521 and the logic level of the signal input to the gate driver 522 are not H level at the same time, and includes the case where the logic level of the signal input to the gate driver 521 and the logic level of the signal input to the gate driver 522 are L level at the same time.

[0057] The gate drive circuit 520 includes a gate driver 521 and a gate driver 522 .

[0058] The gate driver 521 generates a gate signal Hgd by level-shifting the modulation signal Ms output by the comparator 514 and outputs it from the integrated circuit 500 via the terminal Hdr. The high-potential side of the power supply voltage of the gate driver 521 is supplied via the terminal Bst, and the low-potential side is supplied via the terminal Sw. The terminal Bst is electrically connected to one end of the capacitor C5 and the cathode of the diode D1. The other end of the capacitor C5 is electrically connected to the terminal Sw. The anode of the diode D1 is electrically connected to the terminal Gvd. The terminal Gvd is also supplied with a voltage signal Vm1, which is a DC voltage of, for example, 7.5 V, generated by a power supply circuit (not shown). As a result, the potential difference between the terminals Bst and Sw is the potential difference across the capacitor C5 and is approximately equal to the voltage value of the voltage signal Vm1. Therefore, the gate driver 521 generates a gate signal Hgd whose H-level voltage value is greater than the voltage value of the terminal Sw by the voltage value of the voltage signal Vm1 and whose L-level voltage value is the voltage value of the terminal Sw according to the logical level of the input modulation signal Ms, and outputs it from the terminal Hdr.

[0059] The gate driver 522 operates at a lower potential side than the gate driver 521. The gate driver 522 generates a gate signal Lgd by level-shifting a signal in which the logical level of the modulation signal Ms output by the comparator 514 is inverted by an inverter 515, and outputs the gate signal Lgd from the integrated circuit 500 via the terminal Ldr. Of the power supply voltages of the gate driver 522, a voltage signal Vm1 is supplied to the high potential side, and ground potential is supplied to the low potential side via the terminal Gnd. The gate driver 522 generates a gate signal Lgd of ground potential, whose H-level voltage value is higher than the voltage value of the voltage signal Vm1 relative to the terminal Gnd and whose L-level voltage value is the voltage value of the terminal Gnd, according to the logical level of the input signal, and outputs the gate signal Lgd from the terminal Ldr.

[0060] As described above, the gate signal Hgd is a signal obtained by level-shifting the voltage value of the modulation signal Ms, and the gate signal Lgd is a signal obtained by inverting the logical level of the modulation signal Ms and then level-shifting the voltage value of the inverted signal. In light of this, the gate signals Hgd and Lgd output by the gate drive circuit 520 can also be considered to be signals obtained by modulating the basic drive signals dA and aA.

[0061] The amplifier circuit 550 includes a pair of transistors M1 and M2, which are N-channel field effect transistors (FETs).

[0062] A voltage signal VHV, which is a DC voltage of, for example, 42 V, is supplied to the drain terminal of the transistor M1. The gate terminal of the transistor M1 is electrically connected to one end of a resistor R1. The other end of the resistor R1 is electrically connected to a terminal Hdr of the integrated circuit 500. That is, a gate signal Hgd output by the integrated circuit 500 is input to the gate terminal of the transistor M1. The source terminal of the transistor M1 is electrically connected to a terminal Sw of the integrated circuit 500. The conduction state between the drain terminal and the source terminal of the transistor M1 is controlled by the gate signal Hgd input to the gate terminal.

[0063] The drain terminal of the transistor M2 is electrically connected to the terminal Sw of the integrated circuit 500. That is, the drain terminal of the transistor M2 and the source terminal of the transistor M1 are electrically connected to each other. The gate terminal of the transistor M2 is electrically connected to one end of the resistor R2. The other end of the resistor R2 is electrically connected to the terminal Ldr of the integrated circuit 500. That is, a gate signal Lgd output by the integrated circuit 500 is input to the gate terminal of the transistor M2. A ground potential is supplied to the source terminal of the transistor M2. The conduction state between the drain terminal and the source terminal of the transistor M2 is controlled by the gate signal Lgd input to the gate terminal.

[0064] In the following description, when the drain terminals and source terminals of transistors M1 and M2 are controlled to be conductive, this may be referred to as "on," and when the drain terminals and source terminals of transistors M1 and M2 are controlled to be non-conductive, this may be referred to as "off."

[0065] In the amplifier circuit 550 configured as described above, when the transistor M1 is controlled to be off and the transistor M2 is controlled to be on, the node to which the terminal Sw is connected is at ground potential. At this time, a voltage signal Vm1 is supplied to the terminal Bst. On the other hand, when the transistor M1 is controlled to be on and the transistor M2 is controlled to be off, the node to which the terminal Sw is connected is at voltage signal VHV. Therefore, a signal having a voltage value equal to the sum of the voltage values ​​of the voltage signals VHV and Vm1 is supplied to the terminal Bst. That is, the gate driver 521 that drives the transistor M1 uses the capacitor C5 as a floating power supply, and the potential at the other end of the capacitor C5, the terminal Sw, changes to the ground potential or the voltage value of the voltage signal VHV depending on the operation of the transistors M1 and M2, so that the gate driver 521 generates a gate signal Hgd whose L level is the voltage value of the voltage signal VHV and whose H level is the sum of the voltage values ​​of the voltage signal VHV and the voltage value of the voltage signal Vm1, and supplies this to the gate terminal of the transistor M1.

[0066] On the other hand, the gate driver 522 that drives the transistor M2 generates a gate signal Lgd whose L level is the ground potential and whose H level is the voltage value of the voltage signal Vm1, regardless of the operation of the transistors M1 and M2, and supplies it to the gate terminal of the transistor M2.

[0067] As described above, the amplifier circuit 550 operates the transistors M1 and M2 in response to the gate signals Hgd and Lgd, thereby amplifying the modulation signal Ms, which is obtained by modulating the basic drive signals dA and aA, in response to the voltage signal VHV. The amplifier circuit 550 then outputs the amplified signal as an amplified modulation signal AMs from the connection point where the source terminal of the transistor M1 and the drain terminal of the transistor M2 are commonly connected. In other words, the amplifier circuit 550 includes the transistors M1 and M2 that are push-pull connected, and when the transistors M1 and M2 are driven, the transistors M1 and M2 are electrically connected. The amplified modulated signal AMs is output from the electrically connected connection point.

[0068] The demodulation circuit 560 includes a filter circuit (not shown in FIG. 8 ) that demodulates and smoothes the amplified modulation signal AMs to generate the drive signal COM. The demodulation circuit 560 then outputs the generated drive signal COM from the drive signal output circuit 51 via the terminal Out. The demodulation circuit 560 also receives the drive voltage detection signal Vdet output by the differentiation circuit 580. The demodulation circuit 560 changes the characteristics of the filter that smooths the amplified modulation signal AMs in accordance with the input drive voltage detection signal Vdet. The demodulation circuit 560 also returns a portion of the current that may be generated when changing the filter characteristics to the propagation path along which the voltage signal VHV propagates as a return voltage signal Vrev. The configuration and operation of the demodulation circuit 560 will be described in detail below.

[0069] The differentiating circuit 580 has a resistor R7 and a capacitor C7. One end of the capacitor C7 is electrically connected to the terminal Out, from which the drive signal COM is output. That is, the drive signal COM is supplied to one end of the capacitor C7. The other end of the capacitor C7 is electrically connected to one end of the resistor R7. The other end of the resistor R7 is supplied with ground potential. The differentiating circuit 580 outputs the drive voltage detection signal Vdet from the connection point where the other end of the capacitor C7 and one end of the resistor R7 are electrically connected. That is, the differentiating circuit 580 constitutes a high-pass filter and outputs the drive voltage detection signal Vdet, which is a signal obtained by differentiating the voltage value of the drive signal COM. The drive voltage detection signal Vdet has a voltage value corresponding to the amount of change in the voltage value of the drive signal COM during a period in which the voltage value of the drive signal COM changes, and outputs the drive voltage detection signal Vdet whose average voltage value is approximately zero during a period in which the voltage value of the drive signal COM is constant. In other words, the differentiating circuit 580 outputs the drive voltage detection signal Vdet according to changes in the voltage value of the drive signal COM. Here, the average voltage value being approximately zero does not necessarily mean zero, but includes a range in which it can be regarded as zero when taking into account variations in the ripple voltage superimposed on the drive signal COM, variations in the circuit elements that make up the various circuits including the differentiating circuit 580, and superimposed noise, etc.

[0070] The feedback circuit 570 includes resistors R3 and R4. One end of the resistor R3 is connected to the terminal Out from which the drive signal COM is output, and the other end of the resistor R3 is connected to the terminal Vfb and one end of the resistor R4. A voltage signal VHV is supplied to the other end of the resistor R4. As a result, the drive signal COM that has passed through the feedback circuit 570 from the terminal Out is fed back to the terminal Vfb in a pulled-up state.

[0071] The feedback circuit 572 includes capacitors C2, C3, and C4 and resistors R5 and R6. One end of the capacitor C2 is connected to the terminal Out from which the drive signal COM is output, and the other end of the capacitor C2 is connected to one end of the resistor R5 and one end of the resistor R6. The other end of the resistor R5 is supplied with ground potential. This allows the capacitor C2 and the resistor R5 to function as a high-pass filter. The cutoff frequency of this high-pass filter is set to, for example, approximately 9 MHz.

[0072] The other end of the resistor R6 is connected to one end of a capacitor C4 and one end of a capacitor C3. The other end of the capacitor C3 is supplied with ground potential. This allows the resistor R6 and the capacitor C3 to function as a low-pass filter. The cutoff frequency of the low-pass filter is set to, for example, approximately 160 MHz.

[0073] As described above, the feedback circuit 572 is configured to include a high-pass filter and a low-pass filter. As a result, the feedback circuit 572 functions as a band-pass filter that passes a predetermined frequency range of the drive signal COM. 2 is connected to the terminal Ifb of the integrated circuit 500. As a result, a signal in which the DC component has been cut out from the high-frequency components of the drive signal COM that has passed through the feedback circuit 572, which functions as a band-pass filter that passes predetermined frequency components, is fed back to the terminal Ifb.

[0074] The drive signal COM output from the terminal Out is a signal obtained by demodulating the amplified modulation signal AMs based on the basic drive signal dA by smoothing it using the demodulation circuit 560. The drive signal COM output from the demodulation circuit 560 is then integrated and attenuated via the feedback circuit 570 and the terminal Vfb, and then fed back to the adder 512. This causes the drive signal output circuit 51 to self-oscillate at a frequency determined by the feedback delay and the feedback transfer function. However, the amount of delay is large using only the feedback path via the terminal Vfb, and therefore, feedback via the terminal Vfb alone may not be enough to increase the frequency of self-oscillation to a level sufficient to ensure the accuracy of the drive signal COM.

[0075] The drive signal output circuit 51 of this embodiment has a path that feeds back the high-frequency component of the drive signal COM via a feedback circuit 572 and terminal Ifb, in addition to the path via terminal Vfb. This reduces the delay in the drive signal output circuit 51 of this embodiment when viewed from the perspective of the entire circuit that makes up the drive signal output circuit 51, and compared to when there is no path via terminal Ifb, it is possible to increase the frequency of the voltage signal As to a level that sufficiently ensures the accuracy of the drive signal COM.

[0076] As described above, the drive signal output circuit 51 of this embodiment is a circuit that outputs a drive signal COM that drives the piezoelectric element 60, and includes a modulation circuit 510 that modulates the base drive signals dA and aA that form the basis of the drive signal COM and outputs it as a modulated signal Ms, an amplification circuit 550 that amplifies the modulated signal Ms and outputs it as an amplified modulated signal AMs, and a demodulation circuit 560 that demodulates the amplified modulated signal AMs and outputs it as the drive signal COM.

[0077] 1.3.2 Demodulation circuit configuration and operation Next, the configuration and operation of the demodulation circuit 560 will be described. FIG. 9 is a diagram showing an example of the configuration of the demodulation circuit 560 included in the drive signal output circuit 51. As shown in FIG. 9, the demodulation circuit 560 includes an inductive circuit 562, a capacitive circuit 564, a switch circuit 566, and a diode D41. The amplified modulation signal AMs is input to one end of the inductive circuit 562, and the other end of the inductive circuit 562 is electrically connected to one end of the capacitive circuit 564. The other end of the capacitive circuit 564 is supplied with a ground potential. In other words, the inductive circuit 562 and the capacitive circuit 564 form a low-pass filter. The amplified modulation signal AMs is smoothed by the low-pass filter formed by the inductive circuit 562 and the capacitive circuit 564, thereby generating the drive signal COM. The demodulation circuit 560 outputs the drive signal COM from the connection point where the other end of the inductive circuit 562 and one end of the capacitive circuit 564 are electrically connected, which is the output point of the low-pass filter.

[0078] Specifically, the inductive circuit 562 includes an inductor L11 and an inductor L12, and the capacitive circuit 564 includes a capacitor C21. An amplified modulation signal AMs is input to one end of the inductor L11 via one end of the inductive circuit 562. The other end of the inductor L11 is electrically connected to one end of the capacitor C21 via one end of the inductive circuit 562 and one end of the capacitive circuit 564. One end of the inductor L12 is electrically connected to one end of the switch circuit 566, and the other end of the switch circuit 566 is electrically connected to one end of the inductor L11. The other end of the inductor L12 is electrically connected to one end of the capacitor C21 via one end of the inductive circuit 562 and one end of the capacitive circuit 564. That is, the inductor L11 and the inductor L12 are connected in parallel between one end and the other end of the inductive circuit 562 via the switch circuit 566. The other end of inductor L11 and the other end of inductor L12 are electrically connected to one end of capacitor C21 via one end of inductive circuit 562 and one end of capacitive circuit 564. In other words, demodulation circuit 560 includes a low-pass filter configured with inductors L11 and L12 connected in parallel and capacitor C21. Demodulation circuit 560 outputs drive signal COM from the output point of the low-pass filter, which is a connection point where the other end of inductor L11, the other end of inductor L12, and one end of capacitor C21 are electrically connected.

[0079] The switch circuit 566 switches the inductance value of the inductive circuit 562 by switching the conduction state between one end of the inductor L11 and one end of the inductor L12.

[0080] Specifically, the switch circuit 566 includes transistors M31 and M32, a capacitor C31, a diode D31, a control circuit 567, and a protection circuit 568. The transistors M31 and M32 are N-channel FETs. The drain terminal of the transistor M32 is electrically connected to one end of the inductor L11, the drain terminal of the transistor M31 is electrically connected to one end of the inductor L12, and the source terminal of the transistor M32 is electrically connected to the source terminal of the transistor M31. A common gate signal Sgd output by the control circuit 567 is input to the gate terminals of the transistors M32 and M31. The conduction state between the drain terminal and the source terminal of the transistors M31 and M32 is controlled by the gate signal Sgd input to the gate terminal.

[0081] The high-potential power supply terminal of the control circuit 567 is electrically connected to one end of a capacitor C31 and the cathode terminal of a diode D31. The other end of the capacitor C31 is electrically connected to a junction between the source terminal of a transistor M31 and the source terminal of a transistor M32. A voltage signal Vm2 is supplied to the anode terminal of the diode D31. That is, the capacitor C31 and the diode D31 form a bootstrap circuit, and a voltage signal Vbt having a voltage value greater than the voltage value at the junction between the source terminal of the transistor M31 and the source terminal of the transistor M32 by the voltage value of the voltage signal Vm2 is output from the junction between the one end of the capacitor C31 and the cathode terminal of the diode D31. Therefore, the high-potential power supply terminal of the control circuit 567 is supplied with a voltage signal Vbt having a voltage value greater than the voltage value at the junction between the source terminal of the transistor M31 and the source terminal of the transistor M32 by the voltage value of the voltage signal Vm2. Here, the voltage signal Vm2 has a voltage value sufficient to drive the transistors M31 and M32, for example, a DC voltage of 7.5 V. In this case, the voltage signal Vm2 may be the same voltage as the voltage signal Vm1 described above, or may be a different voltage.

[0082] The low-potential power supply terminal of the control circuit 567 is electrically connected to the connection point where the source terminal of the transistor M31 and the source terminal of the transistor M32 are connected. That is, the low-potential power supply terminal of the control circuit 567 is supplied with the voltage value of the connection point where the source terminal of the transistor M31 and the source terminal of the transistor M32 are connected.

[0083] The drive voltage detection signal Vdet output by the differentiation circuit 580 is also input to the control circuit 567 as described above. The control circuit 567 compares the voltage value of the input drive voltage detection signal Vdet with a predetermined threshold, and generates a signal that goes to H level when the voltage value of the drive voltage detection signal Vdet is greater than the threshold, and goes to L level when the voltage value of the drive voltage detection signal Vdet is less than the threshold. The control circuit 567 then level-shifts the H level potential of the generated signal to the voltage value of the signal supplied to the power supply terminal on the high potential side, and level-shifts the L level potential of the generated signal to the voltage value of the signal supplied to the power supply terminal on the low potential side, generating a gate signal That is, the control circuit 567 generates a gate signal Sgd whose H level is a voltage value that is greater than the voltage value of the connection point where the source terminals of the transistors M31 and M32 are connected by the voltage value of the voltage signal Vm2, and whose L level is the voltage value of the connection point where the source terminals of the transistors M31 and M32 are connected, and outputs the gate signal Sgd to the gate terminals of the transistors M31 and M32.

[0084] When an H-level gate signal Sgd is input to the transistors M31 and M32, the drain terminal and source terminal of each transistor are controlled to be conductive, and when an L-level gate signal Sgd is input, the drain terminal and source terminal of each transistor are controlled to be non-conductive. That is, when an H-level gate signal Sgd is input to the transistors M31 and M32, the transistors M31 and M32 control one end of the inductor L11 to be conductive and one end of the inductor L12 to be input, and the amplified modulation signal AMs is input to one end of the inductor L12, and when an L-level gate signal Sgd is input, the transistors M31 and M32 control one end of the inductor L11 to be non-conductive and one end of the inductor L12 to be stopped from being input to the one end of the inductor L12. As described above, the control circuit 567 controls the conductive state of the transistors M31 and M32 and the conductive state of the switch circuit 566 in accordance with the drive voltage detection signal Vdet output by the differentiation circuit 580, and the transistors M31 and M32 switch whether or not to input the amplified modulation signal AMs to one end of the inductor L12.

[0085] When the transistors M31 and M32 are controlled to be non-conductive, the inductance value of the inductive circuit 562, which is the inductance value between one end and the other end of the inductive circuit 562, becomes the inductance value of inductor L11, and when the transistors M31 and M32 are controlled to be conductive, the inductance value of the inductive circuit 562, which is the inductance value between one end and the other end of the inductive circuit 562, becomes the combined inductance value of inductors L11 and L12 connected in parallel. That is, the switch circuit 566 controls the conductive state of the transistors M31 and M32 in accordance with the drive voltage detection signal Vdet, thereby switching the inductance value of the inductive circuit 562 between the inductance value of inductor L11 and the combined inductance value of inductors L11 and L12 connected in parallel, which is different from the inductance value of inductor L11.

[0086] The voltage at the connection point between the source terminal of transistor M31 and the source terminal of transistor M32 may fluctuate due to the body diodes of transistors M31 and M32. If the voltage at the connection point between the source terminal of transistor M31 and the source terminal of transistor M32 fluctuates, an abnormality occurs in the voltage of the voltage signal Vbt output by the bootstrap circuit formed by capacitor C31 and diode D31. Such an abnormality in the voltage of the voltage signal Vbt causes an abnormality in the voltage of the gate signal Sgd output by the control circuit 567. If the abnormality in the voltage of the voltage signal Vbt causes the H-level voltage of the gate signal Sgd to exceed the gate breakdown voltage of transistors M31 and M32, an abnormality occurs in transistors M31 and M32. The protection circuit 568 protects transistors M31 and M32 by reducing the risk of overvoltage occurring in the voltage signal Vbt. Such a protection circuit 568 may have any configuration as long as it can limit the voltage value of the voltage signal Vbt so that it does not exceed a predetermined voltage value, and for example, a Zener diode or the like may be used.

[0087] The anode terminal of the diode D41 is electrically connected to one end of the inductor L12 and one end of the switch circuit 566, which is the drain terminal of the transistor M31, and the voltage signal VHV is supplied to the cathode terminal. When one end and the other end of the switch circuit 566 are controlled to be non-conductive during the period when a current flows through the inductor L12 in the direction from the ejection head 200 to the drive signal output circuit 51, that is, when a current flows through the inductor L12 in the direction from the ejection head 200 to the drive signal output circuit 51, When a current flows from the inductor L12 to the drive signal output circuit 51, if the drain and source terminals of the transistor M31 and the drain and source terminals of the transistor M32 are controlled to be non-conductive, an induced electromotive force is generated in the inductor L12 according to the inductance value of the inductor L12 and the current flowing through the inductor L12. As a result, an overvoltage due to the induced electromotive force is generated between one end of the inductor L12 and one end of the switch circuit 566, which is the drain terminal of the transistor M31.

[0088] If the overvoltage generated by this induced electromotive force exceeds the withstand voltage between the drain and source terminals of transistor M31, an abnormality will occur in transistor M31. Diode D41 limits the overvoltage generated between one end of inductor L12 and one end of switch circuit 566, which is the drain terminal of transistor M31, by using voltage signal VHV, and also returns the voltage to voltage signal VHV. This protects transistor M31 from the overvoltage generated by the induced electromotive force in inductor L12, and improves the power utilization efficiency of the liquid ejection device 1 and drive signal output circuit 51.

[0089] In addition, instead of the above-mentioned D41, the demodulation circuit 560 may have a MOS-FET that electrically connects one end of the inductor L12 and one end of the switch circuit 566, which is the drain terminal of the transistor M31, to the propagation path along which the voltage signal VHV propagates, and whose conduction state switches depending on the voltage value of a node to which one end of the inductor L12 and one end of the switch circuit 566 are electrically connected, which is the drain terminal of the transistor M31.

[0090] The operation of the demodulation circuit 560 configured as described above will now be described. Fig. 10 is a diagram for explaining the operation of the demodulation circuit 560. As shown in Fig. 10, the signal waveform of the basic drive signal aA, which is defined by the basic drive signal dA, includes, in a period tp, a period in which the voltage value is constant at voltage dvb, a period in which the voltage value is constant at voltage dvt, a period in which the voltage value changes from voltage dvb to voltage dvt, and a period in which the voltage value changes from voltage dvt to voltage dvb. Here, voltage dvb corresponds to the voltage value of voltage vb of the drive signal COM before amplification, and voltage dvt corresponds to the voltage value of voltage vt of the drive signal COM before amplification.

[0091] At the rising edge of the latch signal LAT, the voltage of the master drive signal aA is constant at voltage dvb. Therefore, the drive signal output circuit 51 operates to maintain the voltage of the drive signal COM it outputs at a constant voltage vb. Because the voltage of the drive signal COM is maintained at a constant voltage vb, the differentiation circuit 580 outputs a drive voltage detection signal Vdet whose average voltage is approximately zero. As a result, the control circuit 567 outputs an L-level gate signal Sgd, and transistors M31 and M32 are controlled to be non-conductive. Therefore, the inductance of the inductive circuit 562 becomes the inductance of inductor L11, and the demodulation circuit 560 outputs the drive signal COM by demodulating the amplified modulation signal AMs using a low-pass filter formed by inductor L11 and capacitor C21.

[0092] Then, at time t1, the voltage value of the basic drive signal aA increases from voltage dvb to voltage dvt. Therefore, the drive signal output circuit 51 operates so that the voltage value of the drive signal COM it outputs increases from voltage vb to voltage vt. At this time, the voltage value of the drive signal COM changes, and the differentiating circuit 580 outputs the drive voltage detection signal Vdet, the voltage value of which increases, due to the increase in the voltage value of the drive signal COM. Then, at time t1a, when the voltage value of the drive voltage detection signal Vdet exceeds the threshold voltage Vbt1, the control circuit 567 switches the logic level of the gate signal Sgd from L level to H level. This controls the transistors M31 and M32 to be conductive. Therefore, the inductance value of the inductive circuit 562 becomes the combined inductance value of the inductors L11 and L12 connected in parallel. That is, at time t1a, the inductance value of the inductive circuit 562 decreases. Then, the demodulation circuit 560 switches the inductance value of the inductors L11 and L12 connected in parallel and the capacitor C The amplified modulation signal AMs is demodulated by a low-pass filter configured by 21 and is output as a drive signal COM.

[0093] Then, at time t2, the voltage value of the basic drive signal aA becomes constant at voltage dvt. Therefore, the drive signal output circuit 51 operates to maintain the voltage value of the output drive signal COM at a constant voltage vt. At this time, as the change in the voltage value of the drive signal COM decreases, the differentiation circuit 580 outputs the drive voltage detection signal Vdet, whose voltage value decreases toward zero. Then, at time t2a, when the voltage value of the drive voltage detection signal Vdet falls below the threshold voltage Vbt1, the control circuit 567 switches the logic level of the gate signal Sgd from H level to L level. This controls the transistors M31 and M32 to be non-conductive. Therefore, the inductance value of the inductor circuit 562 becomes the inductance value of inductor L11. In other words, at time t2a, the inductance value of the inductor circuit 562 increases. Then, the demodulation circuit 560 outputs the drive signal COM, which is obtained by demodulating the amplified modulation signal AMs using a low-pass filter formed by inductor L11 and capacitor C21.

[0094] Subsequently, at time t3, the voltage value of the basic drive signal aA decreases from voltage dvt to voltage dvb. Therefore, the drive signal output circuit 51 operates so that the voltage value of the output drive signal COM decreases from voltage vt to voltage vb. At this time, the voltage value of the drive signal COM changes, and the differentiating circuit 580 outputs a drive voltage detection signal Vdet whose voltage value decreases due to the decrease in the voltage value of the drive signal COM. Then, at time t3a, when the voltage value of the drive voltage detection signal Vdet falls below the threshold voltage Vbt2, the control circuit 567 switches the logic level of the gate signal Sgd from L level to H level. This controls the transistors M31 and M32 to be conductive. Therefore, the inductance value of the inductive circuit 562 becomes the combined inductance value of the inductors L11 and L12 connected in parallel. That is, at time t3a, the inductance value of the inductive circuit 562 decreases. The demodulation circuit 560 demodulates the amplified modulation signal AMs using a low-pass filter formed by inductors L11 and L12 connected in parallel with a capacitor C21, and outputs the drive signal COM.

[0095] Then, at time t4, the voltage of the basic drive signal aA becomes constant at voltage dvb. Therefore, the drive signal output circuit 51 operates to maintain the voltage of the drive signal COM it outputs at a constant voltage vb. At this time, as the change in the voltage of the drive signal COM decreases, the differentiating circuit 580 outputs the drive voltage detection signal Vdet, whose voltage value increases toward zero. Then, at time t4a, when the voltage of the drive voltage detection signal Vdet exceeds the threshold voltage Vbt1, the control circuit 567 switches the logic level of the gate signal Sgd from H level to L level. This causes transistors M31 and M32 to become non-conductive. Therefore, the inductance of the inductive circuit 562 becomes the inductance of inductor L11. That is, at time t4a, the inductance of the inductive circuit 562 increases. Then, the demodulation circuit 560 outputs the drive signal COM, which is obtained by demodulating the amplified modulation signal AMs using a low-pass filter formed by inductor L11 and capacitor C21. Then, at the subsequent rising edge of the latch signal LAT, the period tp ends.

[0096] As described above, in the demodulation circuit 560 of this embodiment, the control circuit 567 outputs an H-level gate signal Sgd when the difference between the voltage value of the drive voltage detection signal Vdet and zero is greater than the threshold voltage Vbt1 or Vbt2 and the absolute value of the voltage value of the drive voltage detection signal Vdet is greater than a predetermined threshold, and outputs an L-level gate signal Sgd when the difference between the voltage value of the drive voltage detection signal Vdet and zero is less than the threshold voltage Vbt1 or Vbt2 and the absolute value of the voltage value of the drive voltage detection signal Vdet is less than the predetermined threshold. Based on the voltage value of det, it is determined whether the voltage value of the drive signal COM, which is the voltage value of the signal waveform defined by the base drive signal dA, is constant or changes, and an H-level gate signal Sgd is output during at least a portion of the period during which the voltage value of the drive signal COM, which is the voltage value of the signal waveform defined by the base drive signal dA, changes, and an L-level gate signal Sgd is output during at least a portion of the period during which the voltage value of the drive signal COM, which is the voltage value of the signal waveform defined by the base drive signal dA, is constant.

[0097] Therefore, the demodulation circuit 560 of this embodiment outputs a drive signal COM obtained by demodulating the amplified modulation signal AMs using a low-pass filter made up of inductors L11, L12 and capacitor C21 connected in parallel during at least a portion of the period in which the voltage value of the drive signal COM, which is the voltage value of the signal waveform defined by the base drive signal dA, changes, and outputs a drive signal COM obtained by demodulating the amplified modulation signal AMs using a low-pass filter made up of inductor L11 and capacitor C21 during at least a portion of the period in which the voltage value of the drive signal COM, which is the voltage value of the signal waveform defined by the base drive signal dA, is constant.

[0098] The absolute value of the voltage value of threshold voltage Vbt1 and the absolute value of the voltage value of threshold voltage Vbt2 may be the same value. Furthermore, the differentiating circuit 580 may have a rectifier circuit that rectifies the drive voltage detection signal Vdet, and the control circuit 567 may output a gate signal Sgd that goes to H level when the voltage value of the signal output by the rectifier circuit is greater than a predetermined threshold, and goes to L level when the voltage value of the signal output by the rectifier circuit is less than the predetermined threshold.

[0099] 1.4 Operation of the liquid ejection device and demodulation circuit A description will now be given of a method for controlling the liquid ejection device 1 including the drive signal output circuit 51 configured as above. Fig. 11 is a diagram showing an example of a method for controlling the liquid ejection device 1 including the drive signal output circuit 51.

[0100] As shown in FIG. 11, when power is supplied to the liquid ejection device 1, the control circuit 100 determines whether a request for image formation on a medium P has occurred (step S1). Here, the request for image formation on a medium P may occur, for example, when an image signal is input from an external device, such as a host computer, external to the liquid ejection device 1, or when a user operates the liquid ejection device 1. If the control circuit 100 determines that a request for image formation on a medium P has not occurred (N in step S1), the liquid ejection device 1 waits until an image formation request occurs. On the other hand, if the control circuit 100 determines that a request for image formation on a medium P has occurred (Y in step S1), the drive signal output circuit 51 executes a drive signal output process (step S2) to output a drive signal COM, and the ejection head 200 executes a liquid ejection process (step S3) to eject ink toward the medium P based on the drive signal COM output by the drive signal output circuit 51 through the drive signal output process.

[0101] Here, the drive signal output process performed by the drive signal output circuit 51 is a process of outputting a drive signal COM obtained by amplifying the signal waveform defined by the basic drive signal dA, which is an amplified drive signal COM obtained by amplifying the signal waveform of the basic drive signal aA. Details of this drive signal output process will be described later. Furthermore, the liquid ejection process performed by the ejection head 200 is a process in which the ejection head 200 ejects liquid onto the medium P based on the drive signal COM output by the drive signal output circuit 51 in the drive signal output process and the print data signal SI and latch signal LAT output by the control circuit 100, and includes, for example, the processes described using Figures 5 to 7.

[0102] After the drive signal output process in step S2 and the liquid ejection process in step S3 are executed, the control circuit 100 determines whether or not image formation, which forms an image on the medium P according to the input image signal, has been completed (step S4). If the control circuit 100 determines that image formation has not been completed (N in step S4), the liquid ejection device 1 The drive signal output process of step S2 and the liquid ejection process of step S3 are executed again. On the other hand, if the control circuit 100 determines that image formation is complete (N in step S4), the liquid ejection device 1 terminates operation, assuming that an image corresponding to the image signal input from the external device has been formed on the medium P. In other words, the liquid ejection device 1 repeatedly executes the drive signal output process of step S2 and the liquid ejection process of step S3 until formation of the image corresponding to the image signal input from the external device, such as a host computer, on the medium P is complete.

[0103] As described above, the control method of the liquid ejection device 1 that ejects ink onto the medium P in this embodiment includes a drive signal output process that outputs a drive signal COM that is an amplified version of the basic drive signals dA and aA, and a liquid ejection process that ejects ink in accordance with the drive signal COM.

[0104] Next, a specific example of the drive signal output process will be described. Fig. 12 is a diagram showing a specific example of the drive signal output process. As shown in Fig. 12, when the drive signal output process starts, the control circuit 100 generates a basic drive signal dA that is the basis of the drive signal COM, and outputs it to the drive signal output circuit 51 (step S21).

[0105] The reference drive signal dA is input to the DAC 511 of the drive signal output circuit 51. The DAC 511 converts the input reference drive signal dA into a reference drive signal aA, which is an analog signal (step S22). The reference drive signal aA is input to the modulation circuit 510. The modulation circuit 510 modulates the input reference drive signal aA and outputs a modulated signal Ms (step S23). The modulated signal Ms output by the modulation circuit 510 and a signal obtained by inverting the logical level of the modulated signal Ms output by the modulation circuit 510 are input to the gate drive circuit 520. The gate drive circuit 520 outputs to the amplifier circuit 550 a gate signal Hgd obtained by level-shifting the input modulated signal Ms, and a gate signal Lgd obtained by level-shifting a signal obtained by inverting the logical level of the input modulated signal Ms. Here, considering that the gate signal Hgd is a signal obtained by level-shifting the modulation signal Ms, and the gate signal Lgd input to the amplifier circuit 550 is a signal obtained by level-shifting a signal in which the logical level of the modulation signal Ms is inverted, the gate signals Hgd and Lgd input to the amplifier circuit 550 are also signals obtained by modulating the basic drive signal aA.

[0106] The amplifier circuit 550 operates in response to the gate signals Hgd and Lgd to output the amplified modulation signal AMs. That is, the amplifier circuit 550 outputs the amplified modulation signal AMs, which is a signal obtained by modulating the basic drive signal aA and amplifying the modulation signal Ms (step S24). The amplified modulation signal AMs output by the amplifier circuit 550 is input to the demodulation circuit 560. The demodulation circuit 560 performs demodulation processing on the input amplified modulation signal AMs (step S25). The demodulation processing performed by the demodulation circuit 560 demodulates the amplified modulation signal AMs and outputs it as the drive signal COM.

[0107] That is, the drive signal output process includes a step in which the modulation circuit 510 outputs a modulated signal Ms obtained by modulating the basic drive signals dA and aA, a step in which the amplifier circuit 550 outputs an amplified modulated signal AMs obtained by amplifying the modulated signal Ms, and a step in which the amplifier circuit 550 outputs a drive signal COM obtained by demodulating the amplified modulated signal AMs.

[0108] Next, a specific example of the demodulation process will be described. FIG. 13 is a diagram showing a specific example of the demodulation process. As shown in FIG. 13, in the demodulation process, the control circuit 567 included in the switch circuit 566 determines whether the voltage value of the drive signal COM is constant or not based on the input drive voltage detection signal Vdet (step S251). Specifically, the differentiation circuit 580 differentiates the voltage value of the drive signal COM, thereby outputting a drive voltage detection signal Vdet whose voltage value is approximately zero during a period in which the voltage value of the drive signal COM is constant, and whose voltage value is positive or negative depending on the amount of change in the voltage value during a period in which the voltage value of the drive signal COM changes. The control circuit 567 determines whether the difference between the voltage value of the drive voltage detection signal Vdet and zero is equal to the threshold voltage Vbt1 or Whether the voltage value of the drive signal COM is constant is determined based on whether it is greater than threshold voltage Vbt2, i.e., whether the absolute value of the voltage value of the drive voltage detection signal Vdet is greater than a predetermined threshold. In other words, in the demodulation process, the control circuit 567 determines whether the voltage value of the drive signal COM is changing or not, based on the differential information of the drive signal COM.

[0109] If the control circuit 567 determines that the voltage value of the drive signal COM is not constant (N in step S251), the control circuit 567 outputs an H-level gate signal Sgd. This controls the transistors M31 and M32 to be conductive (step S252). Therefore, the inductance value of the inductive circuit 562 of the demodulation circuit 560 is controlled to the combined inductance value of the inductors L11 and L12 connected in parallel. That is, during the period in which the voltage value of the drive signal COM changes, including the period in which the voltage value of the drive signal COM changes from voltage vb to voltage vt and the period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb, the demodulation circuit 560 performs a demodulation process to demodulate the amplified modulation signal AMs using the inductive circuit 562 having a combined inductance value of the inductors L11 and L12 connected in parallel that is lower than the inductance value of inductor L11. In other words, during the period when the voltage value of the drive signal COM changes, including the period when the voltage value of the drive signal COM changes from voltage vb to voltage vt, and the period when the voltage value of the drive signal COM changes from voltage vt to voltage vb, a demodulation process is executed to demodulate the amplified modulation signal AMs using inductor L11 and inductor L12 connected in parallel.

[0110] On the other hand, if the control circuit 567 determines that the voltage value of the drive signal COM is constant (Y in step S251), the control circuit 567 outputs an L-level gate signal Sgd. This controls the transistors M31 and M32 to be non-conductive (step S253). Therefore, the inductance value of the inductive circuit 562 of the demodulation circuit 560 is controlled to the inductance value of the inductor L11. That is, during a period in which the voltage value of the drive signal COM is constant and the voltage value of the drive signal COM is controlled to be constant at voltage vb or voltage vt, the demodulation circuit 560 executes a demodulation process to demodulate the amplified modulation signal AMs using the inductor L11. In other words, during a period in which the voltage value of the drive signal COM is constant and the voltage value of the drive signal COM is controlled to be constant at voltage vb or voltage vt, the demodulation process to demodulate the amplified modulation signal AMs using the inductor L11 is executed.

[0111] Here, the piezoelectric element 60 is an example of a capacitive load, the drive signal output circuit 51 is an example of a drive signal output circuit, the inductive circuit 562 is an example of an inductive circuit, the capacitive circuit 564 is an example of a capacitive circuit, and the switch circuit 566 is an example of a switch circuit. Also, the inductor L11 is an example of a first inductor element, the inductor L12 is an example of a second inductor element, the capacitor C21 is an example of a capacitor element, the inductance value of the inductor L11 is an example of a first inductance value, the combined inductance value of the inductors L11 and L12 connected in parallel is an example of a second inductance value, the diode D41 is an example of a diode element, the transistor M1 is an example of a first transistor element, the transistor M2 is an example of a second transistor element, one of the transistors M31 and M32 is an example of a third transistor element, the transistor M32 is an example of a first FET, the transistor M31 is an example of a second FET, and the differentiating circuit 580 is an example of a drive voltage detection circuit. Furthermore, the voltage signal VHV is an example of an amplified power supply voltage, and the drive voltage detection signal Vdet is an example of a voltage change signal.

[0112] 1.5 Effects In recent years, there has been an increasing demand for improved productivity in liquid ejection devices, and in response to this increasing demand, there has been a demand for liquid ejection devices to drive piezoelectric elements that eject ink at high speed and to use drive signals that drive the piezoelectric elements at high frequencies. In response to this demand, a drive signal output circuit configured with a conventional class D amplifier circuit has the advantage of being able to reduce power consumption compared to drive signal output circuits configured with a class A amplifier circuit, a class B amplifier circuit, a class AB amplifier circuit, or the like. However, a new problem has arisen in that it is difficult to reduce the risk of deterioration in the waveform accuracy of the output drive signal and achieve a high-frequency drive signal while maintaining low power consumption, because the demodulation circuit that demodulates the amplified modulated signal and outputs it as a drive signal includes a low-pass filter that includes an inductor and a capacitor.

[0113] Specifically, when attempting to achieve a higher frequency drive signal using a drive signal output circuit configured with a conventional Class D amplifier circuit, it is necessary to change the voltage value of the drive signal in a short time. Therefore, when the voltage value of the drive signal changes, it is necessary to shorten the time it takes for the current flowing through the inductor included in the low-pass filter of the demodulation circuit to reach a predetermined current value, which necessitates reducing the inductance value of the inductor included in the low-pass filter of the demodulation circuit. However, reducing the inductance value of the inductor included in the low-pass filter of the demodulation circuit increases the cutoff frequency of the low-pass filter of the demodulation circuit that demodulates the amplified modulated signal, thereby increasing the voltage amplitude of the ripple voltage superimposed on the drive signal. In other words, reducing the inductance value of the inductor included in the low-pass filter of the demodulation circuit increases the voltage amplitude of the ripple voltage superimposed on the output drive signal, thereby reducing the waveform accuracy of the drive signal. This reduction in waveform accuracy is particularly noticeable during periods when the voltage value of the drive signal remains constant.

[0114] To address this issue, reducing the inductance of the inductor included in the low-pass filter of the demodulation circuit and increasing the capacitance of the capacitor included in the low-pass filter of the demodulation circuit shortens the time it takes for the current flowing through the inductor to reach a predetermined current value and enables the cutoff frequency of the low-pass filter of the demodulation circuit that demodulates the amplified modulated signal to be reduced, thereby reducing the risk of an increase in the voltage amplitude of the ripple voltage superimposed on the drive signal. However, if the capacitance of the capacitor included in the low-pass filter of the demodulation circuit is increased, the current flowing through the inductor increases as the capacitor charges, resulting in increased power consumption in the drive signal output circuit. In other words, if the inductance of the inductor included in the low-pass filter of the demodulation circuit is reduced while maintaining the cutoff frequency of the low-pass filter of the demodulation circuit approximately constant, the capacitance of the capacitor included in the low-pass filter increases, thereby compromising one of the advantages of low power consumption in drive signal output circuits using Class D amplifier circuits.

[0115] As described above, in a drive signal output circuit configured with a class-D amplifier circuit, there is a trade-off between increasing the frequency of the output drive signal, improving the waveform accuracy of the drive signal, and reducing power consumption in the drive signal output circuit. Therefore, in a drive signal output circuit configured with a conventional class-D amplifier circuit, it has been difficult to reduce the risk of deterioration in the waveform accuracy of the output drive signal and achieve a high frequency drive signal while maintaining low power consumption.

[0116] To address this problem, in the drive signal output circuit 51 of the liquid ejection device 1 of the first embodiment, the demodulation circuit 560 has an inductive circuit 562, a capacitive circuit 564, and a switch circuit 566, and the amplified modulation signal AMs is input to one end of the inductive circuit 562, the other end of the inductive circuit 562 is electrically connected to one end of the capacitive circuit 564, and a ground potential is supplied to the other end of the capacitive circuit 564, so that the inductive circuit 562 and the capacitive circuit 564 form a low-pass filter, and the switch circuit 566 switches the inductance value of the inductive circuit 562, which is the inductance value of the low-pass filter formed by the inductive circuit 562 and the capacitive circuit 564. It has a distinctive configuration that allows it to be replaced.

[0117] In the drive signal output circuit 51 of the first embodiment configured as described above, during the period tp during which the time it takes for the current flowing through the inductive circuit 562 to reach a predetermined current value needs to be shortened and the voltage value of the drive signal COM changes, the switch circuit 566 switches the inductance value of the inductive circuit 562 to a smaller value, thereby increasing the frequency of the drive signal COM. During the period during which the ripple voltage superimposed on the signal waveform of the drive signal COM is likely to be significant and the voltage value of the drive signal COM is constant, the switch circuit 566 switches the inductance value of the inductive circuit 562 to a larger value, thereby reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal COM and reducing the risk of deterioration of the signal waveform of the drive signal COM. Furthermore, at this time, the capacitance value of the capacitive circuit 564 remains constant regardless of the operation of the switch circuit 566. This also reduces the risk of increased power consumption in the drive signal output circuit 51.

[0118] That is, in the drive signal output circuit 51 of the liquid ejection device 1 of the first embodiment, the switch circuit 566 has a characteristic configuration in which the switch circuit 566 is the inductance value of a low-pass filter composed of an inductive circuit 562 and a capacitive circuit 564, and switches the inductance value of the inductive circuit 562.This reduces the risk of deterioration in the waveform accuracy of the drive signal COM being output while maintaining the low power consumption of the drive signal output circuit 51, and makes it possible to achieve a high frequency drive signal COM.

[0119] Furthermore, in the drive signal output circuit 51 of the liquid ejection device 1 of this embodiment, the inductive circuit 562 of the demodulation circuit 560 includes an inductor L11 and an inductor L12, and the capacitive circuit 564 of the demodulation circuit 560 includes a capacitor C21. The amplified modulation signal AMs is input to one end of the inductor L11, the other end of the inductor L11 is electrically connected to one end of the capacitor C21, one end of the inductor L12 is electrically connected to one end of the switch circuit 566, the other end of the switch circuit 566 is electrically connected to one end of the inductor L11, the other end of the inductor L12 is electrically connected to one end of the capacitor C21, and a ground potential is supplied to the other end of the capacitor C21. That is, when one end and the other end of the switch circuit 566 are controlled to be non-conductive, the demodulation circuit 560 outputs the drive signal COM obtained by demodulating the amplified modulated signal AMs using a low-pass filter formed by inductor L11 and capacitor C21, and when one end and the other end of the switch circuit 566 are controlled to be conductive, the demodulation circuit 560 outputs the drive signal COM obtained by demodulating the amplified modulated signal AMs using a low-pass filter formed by inductors L11 and L12 connected in parallel and capacitor C21. In other words, the switch circuit 566 switches the inductance value of the inductive circuit 562 in the demodulation circuit 560 between the inductance value of inductor L11 and the combined inductance value of inductors L11 and L12 connected in parallel, which is smaller than the inductance value of inductor L11.

[0120] In the drive signal output circuit 51 of the first embodiment having the demodulation circuit 560 configured as described above, during the period of the cycle tp during which it is desired to shorten the time until the current flowing through the inductive circuit 562 reaches a predetermined current value and during which the voltage value of the drive signal COM changes, the switch circuit 566 switches the inductance value of the inductive circuit 562 to the combined inductance value of the inductors L11 and L12 connected in parallel, thereby reducing the inductance value of the inductive circuit 562 and realizing a high frequency of the drive signal COM; during the period of the cycle tp during which a ripple voltage superimposed on the signal waveform of the drive signal COM may be significantly generated and during which the voltage value of the drive signal COM is constant, the switch circuit 566 switches the inductance value of the inductive circuit 562 to the inductance value of inductor L11, thereby increasing the inductance value of the inductive circuit 562 and realizing a high frequency of the drive signal COM; This reduces the risk of the signal waveform of the drive signal COM being degraded by a ripple voltage superimposed on the waveform. Furthermore, at this time, the capacitance value of the capacitive circuit 564 is constant at the capacitance value of the capacitor C21, regardless of the operation of the switch circuit 566. Therefore, the risk of an increase in power consumption in the drive signal output circuit 51 is also reduced.

[0121] As a result, in the drive signal output circuit 51 of the first embodiment of the liquid ejection device 1 having the demodulation circuit 560 of this configuration, the risk of deterioration in the waveform accuracy of the drive signal COM to be output can be reduced while maintaining the low power consumption of the drive signal output circuit 51, and a high frequency drive signal COM can be achieved.

[0122] Here, the inductance value of inductor L11 is preferably larger than the inductance value of inductor L12. That is, the inductance value of inductor L12 is preferably smaller than the inductance value of inductor L11. This allows the combined inductance value of inductors L11 and L12 connected in parallel to be made sufficiently smaller than the inductance value of inductor L11. As a result, during the period in which the voltage value of drive signal COM changes, the time required for the current flowing through inductive circuit 562 to reach a predetermined current value can be further shortened, thereby achieving an even higher frequency for drive signal COM.

[0123] Furthermore, the on-resistance of the transistors M1 and M2 included in the amplifier circuit 550 may be greater than the on-resistance of the transistors M31 and M32 included in the switch circuit 566. That is, the on-resistance of the transistors M31 and M32 included in the switch circuit 566 may be smaller than the on-resistance of the transistors M1 and M2 included in the amplifier circuit 550. As described above, the drive frequency of the transistors M1 and M2 is approximately several MHz, while the drive frequency of the transistors M31 and M32 is approximately several tens of kHz to 100 kHz. Therefore, elements with a larger input capacitance and therefore a lower on-resistance can be selected for the transistors M31 and M32 compared to the transistors M1 and M2. Furthermore, using elements with a lower on-resistance for the transistors M31 and M32 can further shorten the time required for the current flowing through the inductive circuit 562 to reach a predetermined current value during a period in which the voltage value of the drive signal COM changes. Furthermore, by using elements with low on-resistance as the transistors M31 and M32, the risk of distortion in the signal waveform of the drive signal COM due to the on-resistance of the transistors M31 and M32 is reduced, and since the losses in the transistors M31 and M32 are reduced, further power savings in the drive signal output circuit 51 can be achieved.

[0124] Furthermore, in the control method of the liquid ejection device 1 of the first embodiment, during a period in which the voltage value of the drive signal COM is constant and the voltage value of the drive signal COM is controlled to be constant at voltage vb or voltage vt, the demodulation circuit 560 performs a demodulation process to demodulate the amplified modulation signal AMs using an inductive circuit 562 with the inductance value of inductor L11, and during a period in which the voltage value of the drive signal COM changes and the voltage value of the drive signal COM changes from voltage vb to voltage vt and from voltage vt to voltage vb, the demodulation circuit 560 performs a demodulation process to demodulate the amplified modulation signal AMs using an inductive circuit 562 with a combined inductance value of inductor L11 and inductor L12 connected in parallel, which is lower than the inductance value of inductor L11.

[0125] As a result, during the period tp, when it is desired to shorten the time it takes for the current flowing through the inductive circuit 562 to reach a predetermined current value, and during the period when the voltage value of the drive signal COM changes, the inductance value of the demodulation circuit 560 can be reduced, the frequency of the drive signal COM can be increased, and the ripple voltage superimposed on the signal waveform of the drive signal COM during the period tp becomes apparent. During periods when a significant change in voltage is likely to occur and when the voltage value of the drive signal COM is constant, the inductance value of the demodulation circuit 560 can be increased, reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal COM and reducing the risk of degradation of the signal waveform of the drive signal COM. Furthermore, because the capacitance value of the capacitive circuit 564 is constant at this time, the risk of an increase in power consumption in the drive signal output circuit 51 is also reduced. That is, the control method for the liquid ejection device 1 of the first embodiment switches the inductance value of the inductive circuit 562, which is the inductance value of the low-pass filter composed of the inductive circuit 562 and the capacitive circuit 564, based on the voltage value of the drive signal COM. This reduces the risk of degradation of the waveform accuracy of the drive signal COM to be output while maintaining low power consumption of the drive signal output circuit 51 and enables the drive signal COM to have a high frequency.

[0126] Furthermore, in the control method of the liquid ejection device 1 of the first embodiment, during a period in which the voltage value of the drive signal COM is constant and the voltage value of the drive signal COM is controlled to be constant at voltage vb or voltage vt, a demodulation process is executed to demodulate the amplified modulation signal AMs using inductor L11, and during a period in which the voltage value of the drive signal COM changes and the voltage value of the drive signal COM changes from voltage vb to voltage vt, and during a period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb, a demodulation process is executed to demodulate the amplified modulation signal AMs using inductor L11 and inductor L12 connected in parallel.

[0127] As a result, during the period tp when it is desired to shorten the time it takes for the current flowing through the inductive circuit 562 to reach a predetermined current value and when the voltage value of the drive signal COM changes, the inductance value of the inductive circuit 562 is switched to the combined inductance value of the inductors L11 and L12 connected in parallel, thereby reducing the inductance value of the demodulation circuit 560 and enabling the drive signal COM to have a higher frequency; and during the period during the period tp when a significant ripple voltage may be generated that is superimposed on the signal waveform of the drive signal COM and when the voltage value of the drive signal COM is constant, the inductance value of the inductive circuit 562 is switched to the inductance value of inductor L11, thereby increasing the inductance value of the demodulation circuit 560 and enabling the voltage amplitude of the ripple voltage that is superimposed on the signal waveform of the drive signal COM to be reduced, thereby reducing the risk of the signal waveform of the drive signal COM being deteriorated. Furthermore, at this time, because the capacitance value of the capacitive circuit 564 is constant at the capacitance value of the capacitor C21 regardless of the operation of the switch circuit 566, there is also a reduced risk of an increase in power consumption in the drive signal output circuit 51. As a result, the control method for the liquid ejection device 1 of the first embodiment having the demodulation circuit 560 configured as described above can reduce the risk of deterioration in the waveform accuracy of the drive signal COM to be output, while maintaining low power consumption in the drive signal output circuit 51, and can achieve a higher frequency for the drive signal COM.

[0128] 1.6 Variations In the liquid ejection device 1, drive signal output circuit 51, and control method for the liquid ejection device 1 of the first embodiment described above, the inductive circuit 562 of the demodulation circuit 560 has inductors L11 and L12 connected in parallel, and the switch circuit 566 switches between using the inductance value of inductor L11 as the inductance value of the inductive circuit 562 or using the combined inductance value of the inductors L11 and L12 connected in parallel as the inductance value of the inductive circuit 562. However, this is not limited to this configuration as long as the inductance value of the inductive circuit 562, which constitutes a low-pass filter in the demodulation circuit 560, can be switched.

[0129] 1.6.1 Variation 1 14 is a diagram showing an example of the configuration of a demodulation circuit 560 of Modification 1. As shown in FIG. 14, in the demodulation circuit 560 of Modification 1, an inductive circuit 562a of the demodulation circuit 560 has inductors L11a and L12a connected in series, and a switch circuit 566a The inductance value of the inductor L11a is used as the inductance value of the inductive circuit 562a, or the combined inductance value of the inductors L11a and L12a connected in series is used as the inductance value of the inductive circuit 562a.

[0130] Specifically, as shown in FIG. 14 , the demodulation circuit 560 of Modification 1 includes an inductive circuit 562a, a capacitive circuit 564, and a switch circuit 566a. The inductive circuit 562a includes an inductor L11a and an inductor L12a, and the capacitive circuit 564 includes a capacitor C21. The amplified modulation signal AMs is input to one end of the inductor L11a, and the other end of the inductor L11a is electrically connected to one end of the inductor L12a, which is electrically connected to one end of the capacitor C21. The switch circuit 566a has one end electrically connected to one end of the inductor L12a, and the other end of the switch circuit 566a is electrically connected to the other end of the inductor L12a. The demodulation circuit 560 outputs the drive signal COM from the connection point where the other end of the inductor L12a and one end of the capacitor C21 are electrically connected.

[0131] In demodulation circuit 560 of modification 1 configured as described above, the inductance value of inductive circuit 562a is switched to a combined inductance value of inductors L11a and L12a connected in series during a period when switch SWa included in switch circuit 566a is controlled to be non-conductive, and is switched to an inductance value of inductor L11a that is smaller than the combined inductance value of inductors L11a and L12a connected in series during a period when switch SWa included in switch circuit 566a is controlled to be conductive. That is, switch circuit 566a switches the inductance value of inductive circuit 562 by switching the conductive state of both ends of inductor L12a.

[0132] In the drive signal output circuit 51 having the demodulation circuit 560 of variant example 1 configured as described above, during the period of the cycle tp when it is desired to shorten the time it takes for the current flowing through the inductive circuit 562a to reach a predetermined current value and when the voltage value of the drive signal COM changes, the switch circuit 566a switches the inductance value of the inductive circuit 562a to the inductance value of inductor L11a, thereby reducing the inductance value of the inductive circuit 562a and achieving a high frequency of the drive signal COM; during the period of the cycle tp when a noticeable ripple voltage superimposed on the signal waveform of the drive signal COM may occur and when the voltage value of the drive signal COM is constant, the switch circuit 566a switches the inductance value of the inductive circuit 562a to the combined inductance value of inductor L11a and inductor L12a connected in series, thereby increasing the inductance value of the inductive circuit 562a, thereby reducing the risk of the signal waveform of the drive signal COM being deteriorated by the ripple voltage superimposed on the signal waveform of the drive signal COM. Furthermore, at this time, the capacitance value of the capacitive circuit 564 is constant at the capacitance value of the capacitor C21, regardless of the operation of the switch circuit 566a. This reduces the risk of an increase in power consumption in the drive signal output circuit 51. In other words, the same effects as those of the liquid ejection device 1 and drive signal output circuit 51 of the first embodiment described above are achieved.

[0133] Furthermore, in the control method of the liquid ejection device 1 having the demodulation circuit 560 of Modification 1, during a period in which the voltage value of the drive signal COM is constant and the voltage value of the drive signal COM is controlled to be constant at voltage vb or voltage vt, the demodulation circuit 560 executes a demodulation process to demodulate the amplified modulation signal AMs using an inductive circuit 562a having a combined inductance value of inductor L11a and inductor L12a connected in series. In other words, during a period in which the voltage value of the drive signal COM is constant and the voltage value of the drive signal COM is controlled to be constant at voltage vb or voltage vt, a demodulation process is executed to demodulate the amplified modulation signal AMs using inductor L11a and inductor L12a connected in series.

[0134] On the other hand, during the period in which the voltage value of the drive signal COM changes, including the period in which the voltage value of the drive signal COM changes from voltage vb to voltage vt and the period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb, the demodulation circuit 560 executes a demodulation process to demodulate the amplified modulation signal AMs using the inductor L11a, inductor circuit 562a having the inductance value of inductor L11a. In other words, during the period in which the voltage value of the drive signal COM changes, including the period in which the voltage value of the drive signal COM changes from voltage vb to voltage vt and the period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb, the demodulation process to demodulate the amplified modulation signal AMs is executed using inductor L11a.

[0135] The method for controlling the liquid ejection device 1 that has the demodulation circuit 560 configured as described above and executes the demodulation process described above also achieves the same effects as the method for controlling the liquid ejection device 1 of the first embodiment described above.

[0136] Note that switch SWa included in switch circuit 566a may have a configuration that is capable of switching the conduction state between one end and the other end of inductor L12a, and may have the same configuration as the above-described switch circuit 566. In this case, control circuit 567 included in switch SWa may output gate signal Sgd that goes to H level when the voltage value of the input drive voltage detection signal Vdet is greater than a predetermined threshold and goes to L level when the voltage value of the input drive voltage detection signal Vdet is smaller than the threshold, or may output gate signal Sgd that goes to H level when the voltage value of the input drive voltage detection signal Vdet is smaller than the threshold and goes to L level when the voltage value of the input drive voltage detection signal Vdet is greater than the threshold.

[0137] In variant example 1, inductive circuit 562a is an example of an inductive circuit, inductor L11a is an example of a first inductor element, inductor L12a is an example of a second inductor element, capacitor C21 is an example of a capacitor element, the inductance value of inductor L11 is an example of a first inductance value, and the combined inductance value of inductors L11 and L12 connected in series is an example of a second inductance value.

[0138] 1.6.2 Variation 2 Fig. 15 is a diagram showing an example of the configuration of a demodulation circuit 560 of Modification 2. As shown in Fig. 15, in demodulation circuit 560 of Modification 2, inductive circuit 562b included in demodulation circuit 560 has inductors L11b and L12b, and switch circuit 566b switches between using the inductance value of inductor L11b as the inductance value of inductor L12b as the inductance value of inductive circuit 562b.

[0139] 15, the demodulation circuit 560 of the second modification includes an inductive circuit 562b, a capacitive circuit 564, and a switch circuit 566b. The inductive circuit 562b includes an inductor L11b and an inductor L12b, and the capacitive circuit 564 includes a capacitor C21. One end of the inductor L11b is electrically connected to one end of a switch SWb1 included in the switch circuit 566b, one end of the inductor L12b is electrically connected to one end of a switch SWb2 included in the switch circuit 566b, and the other end of the inductor L11b and the other end of the inductor L12b are electrically connected to one end of the capacitor C21. The amplified modulation signal AMs is input to an input end of the switch circuit 566b, which is a connection point electrically connecting the other end of the switch SWb1 and the other end of the switch SWb2. That is, the switch circuit 566b outputs the amplified modulation signal AMs input to the connection point where the other end of the switch SWb1 and the other end of the switch SWb2 are electrically connected from one end of the switch SWb1 or one end of the switch SWb2. The connection point of the switch circuit 566b corresponds to an input terminal to which the amplified modulated signal AMs is input, and one end of the switch SWb1 and one end of the switch SWb2 correspond to output terminals that output the amplified modulated signal AMs. The switch circuit 566b switches between electrically connecting one end and the other end of the switch SWb1 and electrically connecting one end and the other end of the switch SWb2, and the demodulation circuit 560 outputs the drive signal COM from the connection point where the other end of the inductor L11b, the other end of the inductor L12b, and one end of the capacitor C21 are electrically connected.

[0140] In the demodulation circuit 560 of Modification 2 configured as described above, the switches SWb1 and SWb2 are controlled to be exclusively conductive. Specifically, the switches SWb1 and SWb2 each have a configuration similar to that of the switch circuit 566 described above. One of the control circuit 567 included in the switch SWb1 and the control circuit 567 included in the switch SWb2 outputs a gate signal Sgd that goes to an H level when the voltage value of the input drive voltage detection signal Vdet is greater than a predetermined threshold and goes to an L level when the voltage value of the input drive voltage detection signal Vdet is less than the threshold, and the other of the control circuit 567 included in the switch SWb1 and the control circuit 567 included in the switch SWb2 outputs a gate signal Sgd that goes to an H level when the voltage value of the input drive voltage detection signal Vdet is less than the threshold and goes to an L level when the voltage value of the input drive voltage detection signal Vdet is greater than the threshold.

[0141] In the demodulation circuit 560 of the second modification configured as described above, the inductance value of the inductive circuit 562b is switched to the inductance value of the inductor L11b during a period when the switch SWb1 included in the switch circuit 566b is controlled to be conductive and the switch SWb2 is controlled to be non-conductive, and is switched to the inductance value of the inductor L12b during a period when the switch SWb1 included in the switch circuit 566b is controlled to be non-conductive and the switch SWb2 is controlled to be conductive. That is, the switch circuit 566b switches the inductance value of the inductive circuit 562b by switching the conductive states of the switches SWb1 and SWb2.

[0142] In the drive signal output circuit 51 having the demodulation circuit 560 of Modification 2 configured as described above, during the period tp during which the time it takes for the current flowing through the inductive circuit 562b to reach a predetermined current value needs to be shortened and the voltage value of the drive signal COM changes, the switch circuit 566b selects and switches the smaller of the inductance values ​​of inductor L11b and inductor L12b as the inductance value of the inductive circuit 562b. This reduces the inductance value of the inductive circuit 562b and achieves a higher frequency of the drive signal COM. On the other hand, during the period during which the ripple voltage superimposed on the signal waveform of the drive signal COM is likely to be significant and the voltage value of the drive signal COM is constant, the switch circuit 566b selects and switches the larger of the inductance values ​​of inductor L11b and inductor L12b as the inductance value of the inductive circuit 562b. This increases the inductance value of the inductive circuit 562b, reducing the risk of the signal waveform of the drive signal COM being degraded by ripple voltage superimposed on the signal waveform of the drive signal COM. Furthermore, at this time, the capacitance value of the capacitive circuit 564 is constant at the capacitance value of the capacitor C21, regardless of the operation of the switch circuit 566b. This also reduces the risk of an increase in power consumption in the drive signal output circuit 51. In other words, the same effects as those of the liquid ejection device 1 and drive signal output circuit 51 of the first embodiment described above are achieved.

[0143] In the control method of the liquid ejection device 1 having the demodulation circuit 560 of the second modification, the voltage value of the drive signal COM is constant for a period in which the voltage value of the drive signal COM is controlled to be constant at the voltage vb or the voltage vt, and the demodulation circuit 560 In other words, during a period in which the voltage value of the drive signal COM is constant and the voltage value of the drive signal COM is controlled to be constant at voltage vb or voltage vt, a demodulation process is executed in which the amplified modulated signal AMs is demodulated using the inductor element with the larger inductance value of the inductor L11b or the inductance value of the inductor L12b.

[0144] On the other hand, during the period when the voltage value of the drive signal COM changes, including the period when the voltage value of the drive signal COM changes from voltage vb to voltage vt and the period when the voltage value of the drive signal COM changes from voltage vt to voltage vb, the demodulation circuit 560 executes a demodulation process to demodulate the amplified modulation signal AMs using the inductive circuit 562b having the smaller inductance value of the inductor L11b or the inductor L12b. In other words, during the period when the voltage value of the drive signal COM changes, including the period when the voltage value of the drive signal COM changes from voltage vb to voltage vt and the period when the voltage value of the drive signal COM changes from voltage vt to voltage vb, the demodulation process to demodulate the amplified modulation signal AMs is executed using the inductor element having the smaller inductance value of the inductor L11b or the inductor L12b.

[0145] The method for controlling the liquid ejection device 1 that has the demodulation circuit 560 configured as described above and executes the demodulation process described above also achieves the same effects as the method for controlling the liquid ejection device 1 of the first embodiment described above.

[0146] The inductive circuit 562b is an example of an inductive circuit, the inductor L11b is an example of a first inductor element, the inductor L12b is an example of a second inductor element, the capacitor C21 is an example of a capacitor element, the inductance value of the inductor L11b is an example of a first inductance value, the inductance value of the inductor L12b is an example of a second inductance value, one end of the switch SWb1 is an example of a first output terminal, one end of the switch SWb2 is an example of a second output terminal, and the connection point where the other end of the switch SWb1 and the other end of the switch SWb2 are electrically connected is an example of an input terminal.

[0147] 2. Second embodiment Next, a liquid ejector 1 and a drive signal output circuit 51 of a second embodiment will be described. The liquid ejector 1 of the second embodiment differs from the liquid ejector 1 of the first embodiment in that a switch circuit 566 of a demodulation circuit 560 switches the inductance value of an inductive circuit 562 in accordance with the determination result of whether the value of the basic drive signal dA is constant, in addition to the determination result of whether the voltage value of the drive signal COM is constant based on a drive voltage detection signal Vdet output by a differentiation circuit 580. In describing the liquid ejector 1 and drive signal output circuit 51 of the second embodiment, similar components to those of the liquid ejector 1 and drive signal output circuit 51 of the first embodiment are denoted by similar reference numerals, and their description will be omitted or simplified.

[0148] FIG. 16 is a diagram showing the configuration of a drive signal output circuit 51 of the second embodiment. As shown in FIG. 16, the drive signal output circuit 51 of the second embodiment further includes a differentiation circuit 530 in addition to the drive signal output circuit 51 of the first embodiment. A reference drive signal dA is input to the differentiation circuit 530. The differentiation circuit 530 generates a reference drive differentiated signal DdA that goes to H level when the value of the input reference drive signal dA changes and goes to L level when the value of the input reference drive signal dA does not change, and outputs the signal to the demodulation circuit 560. Note that the differentiation circuit 530 may also receive a reference drive signal aA instead of the reference drive signal dA, generate a reference drive differentiated signal DdA that goes to H level during periods when the voltage value of the input reference drive signal aA changes, and goes to L level during periods when the voltage value of the input reference drive signal aA is considered constant, and output the signal to the demodulation circuit 560.

[0149] 17 is a diagram illustrating an example of the configuration of a demodulation circuit 560 according to the second embodiment. As illustrated in FIG. 17, the master drive differential signal DdA is input to a control circuit 567 included in a switch circuit 566 of the demodulation circuit 560. The control circuit 567 generates a gate signal Sgd, the logic level of which changes depending on the logic level of the master drive differential signal DdA and the voltage value of the drive voltage detection signal Vdet, and outputs the gate signal Sgd to transistors M31 and M32. Specifically, when the logic level of the master drive differential signal DdA switches from L level to H level, the control circuit 567 sets the logic level of the gate signal Sgd to H level. Thereafter, when the voltage value of the drive voltage detection signal Vdet falls below a predetermined threshold, the control circuit 567 sets the logic level of the gate signal Sgd to L level.

[0150] An example of the operation of the demodulation circuit 560 of the second embodiment configured as described above will now be described. FIG. 18 is a diagram illustrating an example of the operation of the demodulation circuit 560 of the second embodiment. As shown in FIG. 18, at the rising edge of the latch signal LAT, the voltage value of the master drive signal aA is constant at voltage dvb, so the differentiation circuit 530 outputs an L-level master drive differentiated signal DdA, and the drive signal output circuit 51 operates so that the voltage value of the drive signal COM it outputs is constant at voltage vb. At this time, because the voltage value of the drive signal COM is controlled to be constant at voltage vb, the differentiation circuit 580 outputs a drive voltage detection signal Vdet whose average voltage value is approximately zero. Therefore, the control circuit 567 outputs an L-level gate signal Sgd, and transistors M31 and M32 are controlled to be non-conductive. Therefore, the inductance value of the inductive circuit 562 becomes the inductance value of the inductor L11, and the demodulation circuit 560 outputs the drive signal COM obtained by demodulating the amplified modulation signal AMs using a low-pass filter formed by the inductor L11 and the capacitor C21.

[0151] At a subsequent time t11, the voltage value of the signal waveform of the reference drive signal aA, which is a signal waveform defined by the reference drive signal dA, rises from voltage dvb to voltage dvt. That is, at time t11, the value of the reference drive signal dA changes. Accordingly, the differentiation circuit 530 switches the logic level of the reference drive differentiated signal DdA from L level to H level. As the logic level of the reference drive differentiated signal DdA switches from L level to H level, the control circuit 567 switches the logic level of the gate signal Sgd from L level to H level. As a result, the transistors M31 and M32 are controlled to be conductive, and the inductance value of the inductive circuit 562 becomes the combined inductance value of the inductors L11 and L12 connected in parallel. That is, at time t11, the inductance value of the inductive circuit 562 decreases. The demodulation circuit 560 demodulates the amplified modulation signal AMs using a low-pass filter formed by inductors L11 and L12 connected in parallel with a capacitor C21, and outputs the drive signal COM.

[0152] Furthermore, at time t11, the voltage value of the signal waveform of basic drive signal aA, which is a signal waveform defined by basic drive signal dA, increases from voltage dvb to voltage dvt, causing the drive signal output circuit 51 to operate so that the voltage value of the drive signal COM it outputs increases from voltage vb to voltage vt. At this time, the change in the voltage value of the drive signal COM, that is, the increase in the voltage value of the drive signal COM, causes the voltage value of the drive voltage detection signal Vdet output by the differentiation circuit 580 to increase. Then, at time t11a, the voltage value of the drive voltage detection signal Vdet exceeds the threshold voltage Vbt1. At this time, the control circuit 567 continues to output an H-level gate signal Sgd.

[0153] At a subsequent time t12, the signal waveform defined by the base drive signal dA, that is, the voltage value of the signal waveform of the base drive signal aA, becomes constant at voltage dvt. That is, at time t12, the value of the base drive signal dA does not change and becomes constant. Therefore, the differentiation circuit 530 switches the logic level of the base drive differentiated signal DdA from H level to L level. At this time, the control circuit 567 continues to output the H level gate signal Sgd. Also, at time t12, the signal waveform defined by the base drive signal dA, that is, the voltage value of the signal waveform of the base drive signal aA, becomes constant at voltage dvt. Since the voltage value is constant at voltage dvt, the drive signal output circuit 51 operates to maintain the voltage value of the output drive signal COM constant at voltage vt. At this time, because the amount of change in the voltage value of the drive signal COM becomes smaller, the voltage value of the drive voltage detection signal Vdet output by the differentiation circuit 580 decreases toward zero. Then, at time t12a, when the voltage value of the drive voltage detection signal Vdet falls below the threshold voltage Vbt1, the control circuit 567 switches the logic level of the gate signal Sgd from H level to L level. This causes transistors M31 and M32 to become non-conductive, and the inductance value of the inductive circuit 562 becomes the inductance value of inductor L11. In other words, at time t12a, the inductance value of the inductive circuit 562 increases. Then, the demodulation circuit 560 outputs the drive signal COM by demodulating the amplified modulation signal AMs using a low-pass filter formed by inductor L11 and capacitor C21.

[0154] At a subsequent time t13, the voltage value of the signal waveform of the reference drive signal aA, which is a signal waveform defined by the reference drive signal dA, decreases from voltage dvt to voltage dvb. That is, at time t13, the value of the reference drive signal dA changes. Accordingly, the differentiation circuit 530 switches the logic level of the reference drive differentiated signal DdA from L level to H level. As the logic level of the reference drive differentiated signal DdA switches from L level to H level, the control circuit 567 switches the logic level of the gate signal Sgd from L level to H level. As a result, the transistors M31 and M32 are controlled to be conductive, and the inductance value of the inductive circuit 562 becomes the combined inductance value of the inductors L11 and L12 connected in parallel. That is, at time t13, the inductance value of the inductive circuit 562 decreases. The demodulation circuit 560 demodulates the amplified modulation signal AMs using a low-pass filter formed by inductors L11 and L12 connected in parallel with a capacitor C21, and outputs the drive signal COM.

[0155] Furthermore, at time t13, the voltage value of the signal waveform of basic drive signal aA, which is a signal waveform defined by basic drive signal dA, decreases from voltage dvt to voltage dvb, causing the drive signal output circuit 51 to operate so that the voltage value of the drive signal COM it outputs decreases from voltage vt to voltage vb. At this time, the change in the voltage value of the drive signal COM, that is, the decrease in the voltage value of the drive signal COM, causes the voltage value of the drive voltage detection signal Vdet output by the differentiation circuit 580 to decrease. Then, at time t13a, the voltage value of the drive voltage detection signal Vdet falls below the threshold voltage Vbt2. At this time, the control circuit 567 continues to output the H-level gate signal Sgd.

[0156] At a subsequent time t14, the signal waveform defined by the reference drive signal dA, that is, the signal waveform of the reference drive signal aA, has a constant voltage dvb. That is, at time t14, the value of the reference drive signal dA remains constant and unchanged. Therefore, the differentiation circuit 530 switches the logic level of the reference drive differentiated signal DdA from H level to L level. At this time, the control circuit 567 continues to output the H level gate signal Sgd. Also, at time t14, the signal waveform defined by the reference drive signal dA, that is, the signal waveform of the reference drive signal aA, has a constant voltage dvb, and the drive signal output circuit 51 operates so that the voltage value of the drive signal COM it outputs remains constant at voltage vb. At this time, because the amount of change in the voltage value of the drive signal COM becomes smaller, the voltage value of the drive voltage detection signal Vdet output by the differentiation circuit 580 rises toward zero. Then, at time t14a, when the voltage value of the drive voltage detection signal Vdet exceeds the threshold voltage Vbt2, the control circuit 567 switches the logic level of the gate signal Sgd from H level to L level. As a result, the transistors M31 and M32 are controlled to be non-conductive, and the inductance value of the inductive circuit 562 becomes the inductance value of the inductor L11. That is, at time t14a, the inductance value of the inductive circuit 562 increases. Then, the demodulation circuit 560 demodulates the amplified modulation signal AMs using a low-pass filter formed by the inductor L11 and the capacitor C21. The drive signal COM is output, and the period tp ends at the subsequent rising edge of the latch signal LAT.

[0157] As described above, in the liquid ejection device 1 and drive signal output circuit 51 of the second embodiment, when the value of the base drive signal dA changes from a non-changing state to a changing state, the control circuit 567 determines that this is a period in which the voltage value of the drive signal COM changes, that is, a period in which the voltage value of the drive signal COM changes from voltage vb to voltage vt, and a period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb, and outputs an H-level gate signal Sgd that controls transistors M31 and M32 to be conductive.When the voltage value of the drive signal COM changes from a changing state to a non-changing state, the control circuit 567 determines that this is a period in which the voltage value of the drive signal COM is constant, and that the voltage value of the drive signal COM is controlled to be constant at voltage vb or voltage vt, and outputs an L-level gate signal Sgd that controls transistors M31 and M32 to be non-conductive.

[0158] 18, the change in the voltage value of the signal waveform defined by the reference drive signal dA lags behind the change in the voltage value of the signal waveform of the reference drive signal aA. In the liquid ejection device 1 and drive signal output circuit 51 of the second embodiment, when the value of the reference drive signal dA changes from a static state to a changing state, it is determined that this is a period in which the voltage value of the drive signal COM changes, that is, a period in which the voltage value of the drive signal COM changes from voltage vb to voltage vt, and a period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb. By outputting an H-level gate signal Sgd that controls the transistors M31 and M32 to be conductive, it is possible to detect that the voltage value of the drive signal COM changes before the voltage change of the signal waveform of the drive signal COM, and to reduce the inductance value of the inductive circuit 562 of the demodulation circuit 560. As a result, the delay in the change in voltage value of the drive signal COM relative to the change in voltage value of the signal waveform defined by the base drive signal dA is reduced relative to the change in voltage value of the signal waveform of the base drive signal aA, thereby enabling the drive signal COM to have an even higher frequency.

[0159] Next, a control method for a liquid ejection device 1 having a drive signal output circuit 51 of a second embodiment will be described. In the control method for a liquid ejection device 1 having a drive signal output circuit 51 of the second embodiment, the demodulation process method is different from the control method for the liquid ejection device 1 of the first embodiment. FIG. 19 is a diagram showing a specific example of the demodulation process of the second embodiment. As shown in FIG. 19, in the demodulation process of the second embodiment, the control circuit 567 of the switch circuit 566 determines whether the value of the base drive signal dA is constant based on the input base drive differential signal DdA (step S261). Specifically, if the logic level of the input base drive differential signal DdA is low, the control circuit 567 determines that the value of the base drive signal dA is constant, and if the logic level of the input base drive differential signal DdA is high, the control circuit 567 determines that the value of the base drive signal dA is not constant.

[0160] Then, when the control circuit 567 determines that the value of the reference drive signal dA is not constant (N in step S261), that is, when the control circuit 567 determines that the value of the reference drive signal dA is changing, the control circuit 567 outputs an H-level gate signal Sgd. This controls the transistors M31 and M32 to be conductive (step S262). Therefore, the inductance value of the inductive circuit 562 of the demodulation circuit 560 is controlled to the combined inductance value of the inductors L11 and L12 connected in parallel.

[0161] On the other hand, if the control circuit 567 determines that the value of the basic drive signal dA is constant (Y in step S261), the control circuit 567 determines whether the voltage value of the drive signal COM is constant or not based on the drive voltage detection signal Vdet (step S263). Then, if the control circuit 567 determines that the voltage value of the drive signal COM is not constant (N in step S263), that is, if the control circuit 567 determines that the voltage value of the drive signal COM is changing, The control circuit 567 outputs an H-level gate signal Sgd. This controls the transistors M31 and M32 to be conductive (step S262). Therefore, the inductance value of the inductive circuit 562 included in the demodulation circuit 560 is controlled to be the combined inductance value of the inductors L11 and L12 connected in parallel.

[0162] On the other hand, if the control circuit 567 determines that the voltage value of the drive signal COM is constant (Y in step S263), the control circuit 567 outputs an L-level gate signal Sgd. This controls the transistors M31 and M32 to be non-conductive (step S264). Therefore, the inductance value of the inductive circuit 562 included in the demodulation circuit 560 is controlled to the inductance value of the inductor L11.

[0163] That is, in the control method of the liquid ejection device 1 of the second embodiment, the control circuit 567 determines, in the demodulation process, based on the differential information of the base drive signal dA, whether the voltage value of the signal waveform defined by the base drive signal dA, that is, the voltage value of the drive signal COM based on the base drive signal dA, is in a state where it changes or does not change. Then, when the value of the base drive signal dA changes from a state where it does not change, the control circuit 567 determines that this is a period where the voltage value of the drive signal COM changes, that is, a period where the voltage value of the drive signal COM changes from voltage vb to voltage vt, and a period where the voltage value of the drive signal COM changes from voltage vt to voltage vb, and outputs an H-level gate signal Sgd that controls the transistors M31 and M32 to be conductive. When the voltage value of the drive signal COM changes from a state where it does change to a state where it does not change, this is a period where the voltage value of the drive signal COM is constant at voltage vb or voltage vt, and outputs an L-level gate signal Sgd that controls the transistors M31 and M32 to be non-conductive.

[0164] In the control method of the liquid ejector 1 of the second embodiment described above, when the value of the base drive signal dA changes from a static state to a changing state, it is determined that this is a period in which the voltage value of the drive signal COM changes, that is, a period in which the voltage value of the drive signal COM changes from voltage vb to voltage vt, and a period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb, and by outputting an H-level gate signal Sgd that controls transistors M31 and M32 to be conductive, it is possible to detect that the voltage value of the drive signal COM changes before the voltage change of the signal waveform of the drive signal COM and reduce the inductance value of the inductive circuit 562 of the demodulation circuit 560. As a result, the delay in the change in the voltage value of the drive signal COM relative to the change in the voltage value of the signal waveform of the base drive signal aA, which is the change in the voltage value of the signal waveform defined by the base drive signal dA, is reduced, and it is possible to achieve an even higher frequency of the drive signal COM.

[0165] Note that step S262 shown in FIG. 19 corresponds to step S252 shown in FIG. 13, step S263 shown in FIG. 19 corresponds to step S251 shown in FIG. 13, and step S264 shown in FIG. 19 corresponds to step S253 shown in FIG. 13.

[0166] 3. Third embodiment Next, a liquid ejection device 1 and a drive signal output circuit 51 of a third embodiment will be described. The liquid ejection device 1 of the third embodiment differs from the liquid ejection devices 1 of the first and second embodiments in that the switch circuit 566 of the demodulation circuit 560 switches the inductance value of the inductive circuit 562 in accordance with the amount of change in the voltage value per predetermined time of the signal waveform of the basic drive signal aA, which is defined by the basic drive signal dA, and the number of piezoelectric elements 60 driven by the drive signal VOUT corresponding to the drive signal COM, in addition to the result of the determination of whether the voltage value of the drive signal COM is constant based on the drive voltage detection signal Vdet output by the differentiation circuit 580. Note that, in describing the liquid ejection device 1 and drive signal output circuit 51 of the third embodiment, it is necessary to consider the liquid ejection device 1 and drive signal output circuit 51 of the first and second embodiments. The same components as those in the circuit 51 are denoted by the same reference numerals, and the description thereof will be omitted or simplified.

[0167] FIG. 20 is a diagram showing the configuration of a drive signal output circuit 51 of the third embodiment. As shown in FIG. 20, the drive signal output circuit 51 of the third embodiment has a differentiation circuit 531. The base drive signal aA is input to the differentiation circuit 531. The differentiation circuit 531 differentiates the signal waveform of the input base drive signal aA to generate a base drive differentiated signal DaA, and outputs it to a demodulation circuit 560. Furthermore, as shown in FIG. 20, the demodulation circuit 560 included in the drive signal output circuit 51 of the third embodiment also receives as input a print data signal SI output by the control circuit 100.

[0168] 21 is a diagram showing an example of the configuration of a demodulation circuit 560 of the third embodiment. As shown in Fig. 21, the base drive differential signal DaA and the print data signal SI are input to a control circuit 567 included in a switch circuit 566 of the demodulation circuit 560. The control circuit 567 then outputs a gate signal Sgd whose logic level can be switched based on the drive voltage detection signal Vdet output by the differentiation circuit 580, the base drive differential signal DaA, and the print data signal SI, thereby switching the inductance value of the inductive circuit 562 of the demodulation circuit 560.

[0169] Specifically, the control circuit 567 determines whether the voltage value of the input base drive differential signal DaA is equal to or greater than a predetermined threshold. The base drive differential signal DaA output by the differentiation circuit 531 is a signal obtained by differentiating the signal waveform of the base drive signal aA, and the voltage value of the base drive differential signal DaA is proportional to the amount of change per predetermined time in the voltage value of the signal waveform of the base drive signal aA. In other words, when the voltage value of the signal waveform of the base drive signal aA changes rapidly, the voltage value of the base drive differential signal DaA, which is the differential value of the signal waveform of the base drive signal aA, increases, and when the voltage value of the signal waveform of the base drive signal aA changes slowly, the voltage value of the base drive differential signal DaA, which is the differential value of the signal waveform of the base drive signal aA, decreases. The control circuit 567 determines whether the voltage value of the base drive differential signal DaA is equal to or greater than a predetermined threshold value, thereby determining whether the amount of change in voltage value per predetermined time of the signal waveform of the base drive signal aA, which is defined by the base drive signal dA, i.e., the amount of change per predetermined time of the voltage value of the drive signal COM, is steeper or slower than the predetermined threshold value.

[0170] The control circuit 567 also calculates the number of piezoelectric elements 60 to which a drive signal VOUT corresponding to the drive signal COM is supplied, based on the input print data signal SI. As described above, the print data signal SI includes 1-bit print data [SId] for selecting whether or not to eject ink, serially corresponding to each of the m ejection units 600. The print data [SId] included in the print data signal SI is [1] when ink is to be ejected from the ejection unit 600 and the drive signal VOUT corresponding to the drive signal COM is supplied to the piezoelectric elements 60 of the ejection unit 600, and is [0] when ink is not to be ejected from the ejection unit 600 and the drive signal VOUT corresponding to the drive signal COM is not supplied to the piezoelectric elements 60 of the ejection unit 600. Based on the input print data signal SI, the control circuit 567 counts the number of print data [SId] where print data [SId] = [1] or the number of print data [SId] where print data [SId] = [0] out of the m-bit print data [SId] corresponding to the m ejection sections 600, thereby calculating the number of piezoelectric elements 60 to which the drive signal VOUT corresponding to the drive signal COM is supplied.

[0171] Here, the m piezoelectric elements 60 of the m ejection sections 600 are connected in parallel to the propagation path of the drive signal COM output by the drive signal output circuit 51 via the selection circuit 230. Therefore, the number of piezoelectric elements 60 to which the drive signal VOUT corresponding to the drive signal COM is supplied is proportional to the load capacitance connected to the propagation path of the drive signal COM. In other words, the control circuit 567 calculates the number of piezoelectric elements 60 to which the drive signal VOUT corresponding to the drive signal COM is supplied based on the input print data signal SI, thereby Calculate the load capacity to be connected.

[0172] The control circuit 567 then switches the inductance value of the inductive circuit 562 of the demodulation circuit 560 by outputting a gate signal Sgd whose logic level can be switched depending on the determination result of whether the voltage value of the drive signal COM is constant or not, which is determined based on the drive voltage detection signal Vdet output by the differentiation circuit 580, the determination result of whether the amount of change in the voltage value of the drive signal COM per specified time, which is determined based on the basic drive differentiation signal DaA, is steeper or slower than a specified threshold, and the calculation result of the load capacitance connected to the propagation path of the drive signal COM, which is calculated based on the print data signal SI. In other words, the switch circuit 566 switches the inductance value of the inductive circuit 562 between the inductance value of inductor L11 and the combined inductance value of inductors L11 and L12 connected in parallel, based on not only whether the voltage value of the drive signal COM is constant but also the amount of change per specified time in the voltage value of the signal waveform defined by the base drive signal dA, which is the amount of change per specified time in the voltage value of the signal waveform of the base drive signal aA, and the load capacitance connected to the propagation path along which the drive signal COM propagates.

[0173] If the amount of change per specified time in the voltage value of the signal waveform defined by the base drive signal dA is small, and if the load capacitance connected to the propagation path of the drive signal COM is small, the current value of the current flowing through the inductive circuit 562 will be small. In the liquid ejection device 1 and drive signal output circuit 51 of the third embodiment, the switch circuit 566 switches between setting the inductance value of the inductor L11 or the combined inductance value of the parallel-connected inductors L11 and L12 as the inductance of the inductor circuit 562 based on the amount of change per predetermined time in the voltage value of the signal waveform defined by the basic drive signal dA, which is the amount of change per predetermined time in the voltage value of the signal waveform of the basic drive signal aA, and the load capacitance connected to the propagation path along which the drive signal COM propagates, in addition to determining whether the voltage value of the drive signal COM is constant. This allows the inductance value of the inductor circuit 562 to be set to the inductance value of inductor L11 even during a period in which the voltage value of the drive signal COM is changing, as long as the current flowing through the inductive circuit 562 is small. This reduces the risk of ripple voltage being superimposed on the signal waveform of the drive signal COM during a period in which the voltage value of the drive signal COM is changing, improving the waveform accuracy of the signal waveform of the output drive signal COM.

[0174] Next, a control method for a liquid ejection device 1 having a drive signal output circuit 51 of a third embodiment will be described. In the control method for a liquid ejection device 1 having a drive signal output circuit 51 of the third embodiment, the demodulation process is different from the control methods for the liquid ejection device 1 of the first and second embodiments. FIG. 22 is a diagram showing a specific example of the demodulation process of the third embodiment. As shown in FIG. 22, in the demodulation process of the third embodiment, the control circuit 567 of the switch circuit 566 determines whether the value of the base drive signal dA is constant based on the input base drive differential signal DaA (step S271). Specifically, the voltage value of the base drive differential signal DaA becomes approximately zero for a certain period of time, and becomes a signal with a voltage value corresponding to the amount of change per predetermined time during the certain period in which the voltage value of the base drive signal aA changes. The control circuit 567 determines whether the voltage value of the base drive signal aA is constant, and therefore whether the value of the base drive signal dA is constant, based on whether the voltage value of the input base drive differential signal DaA is approximately zero.

[0175] If the control circuit 567 determines that the value of the base drive signal dA is constant (Y in step S271), that is, if the control circuit 567 determines that the value of the base drive signal dA has not changed, the control circuit 567 determines whether the voltage value of the drive signal COM is constant based on the drive voltage detection signal Vdet (step S272).

[0176] If the control circuit 567 determines that the value of the base drive signal dA is not constant (N in step S271), or if the control circuit 567 determines that the voltage value of the drive signal COM is not constant (N in step S272), the control circuit 567 determines whether the amount of voltage change per predetermined time of the base drive signal aA is greater than a predetermined value based on the voltage value of the base drive differential signal DaA (step S273).Furthermore, if the control circuit 567 determines that the amount of voltage change per predetermined time of the base drive signal aA is less than a predetermined value (N in step S273), the control circuit 567 determines whether the number of piezoelectric elements 60 driven by the drive signal COM, which are load capacitances connected to the propagation path of the drive signal COM, is greater than a predetermined number based on the print data signal SI (step S274).

[0177] If the control circuit 567 determines that the amount of voltage change per predetermined time of the basic drive signal aA is greater than a predetermined value (Y in step S273), or if the control circuit 567 determines that the number of piezoelectric elements 60 driven by the drive signal COM is greater than a predetermined number (Y in step S274), the control circuit 567 outputs an H-level gate signal Sgd. This controls the transistors M31 and M32 to be conductive (step S275). Therefore, the inductance value of the inductive circuit 562 included in the demodulation circuit 560 is controlled to the combined inductance value of the inductors L11 and L12 connected in parallel.

[0178] On the other hand, if the control circuit 567 determines that the voltage value of the drive signal COM is constant (Y in step S272), or if the control circuit 567 determines that the number of piezoelectric elements 60 driven by the drive signal COM is less than a predetermined number (N in step S274), the control circuit 567 outputs an L-level gate signal Sgd. This controls the transistors M31 and M32 to be non-conductive (step S276). Therefore, the inductance value of the inductive circuit 562 in the demodulation circuit 560 is controlled to the inductance value of the inductor L11.

[0179] As described above, in the control method of the liquid ejection device 1 of the third embodiment, during the period in which the voltage value of the drive signal COM changes, when the amount of change in the voltage value of the base drive signal aA per unit time is smaller than a predetermined threshold during the period in which the voltage value of the drive signal COM changes from voltage vb to voltage vt, and during the period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb, if the amount of change in the voltage value of the base drive signal aA per unit time is smaller than a predetermined threshold, the amplified modulation signal AMs is demodulated by the inductive circuit 562 of the inductance value of inductor L11.Furthermore, when the number of piezoelectric elements 60 driven by the drive signal COM is smaller than a predetermined threshold quantity, during the period in which the voltage value of the drive signal COM changes from voltage vb to voltage vt, and during the period in which the voltage value of the drive signal COM changes from voltage vt to voltage vb, the amplified modulation signal AMs is demodulated by the inductive circuit 562 of the inductance value of inductor L11.

[0180] As described above, when the amount of change per predetermined time in the voltage value of the signal waveform defined by the reference drive signal dA is small, and when the amount of change per predetermined time in the voltage value of the signal waveform of the reference drive signal aA is small, and when the load capacitance connected to the propagation path of the drive signal COM is small, the current value of the current flowing through the inductive circuit 562 is small. In the control method of the liquid ejection device 1 of the third embodiment, even during a period in which the voltage value of the drive signal COM changes, when the current value of the current flowing through the inductive circuit 562 is small, and when the amount of change per predetermined time in the voltage value of the signal waveform of the reference drive signal aA is small, and when the load capacitance connected to the propagation path of the drive signal COM is small, by setting the inductance value of the inductor 562 to the inductance value of inductor L11, the risk of ripple voltage being superimposed on the signal waveform of the drive signal COM during a period in which the voltage value of the drive signal COM changes is reduced, and the waveform accuracy of the signal waveform of the output drive signal COM is improved.

[0181] In the control method of the liquid ejection device 1 having the drive signal output circuit 51 of the third embodiment, when the amount of change per predetermined time in the voltage value of the signal waveform defined by the base drive signal dA is small, and the load capacitance connected to the propagation path of the drive signal COM is small, the inductance value of the inductive circuit 562 is set to the inductance value of the inductor L11. However, in the demodulation process, only one of the following may be performed: a determination of whether the amount of change per predetermined time in the voltage value of the signal waveform defined by the base drive signal dA is small, or a determination of whether the load capacitance connected to the propagation path of the drive signal COM is small.

[0182] 19, step S272 shown in FIG. 22 corresponds to step S251 shown in FIG. 13 and step S263 shown in FIG. 19, step S275 shown in FIG. 22 corresponds to step S252 shown in FIG. 13 and step S262 shown in FIG. 19, and step S276 shown in FIG. 22 corresponds to step S253 shown in FIG. 13 and step S264 shown in FIG. 19.

[0183] Although the embodiments and modifications have been described above, the present invention is not limited to these embodiments and can be embodied in various forms without departing from the spirit of the present invention. For example, the above embodiments can be combined as appropriate.

[0184] The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects). The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments or that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0185] The following can be derived from the above-described embodiment.

[0186] One aspect of the drive signal output circuit is A drive signal output circuit that outputs a drive signal to drive a capacitive load, a modulation circuit that modulates a base drive signal that is the basis of the drive signal and outputs the modulated signal; an amplifier circuit that amplifies the modulated signal and outputs it as an amplified modulated signal; a demodulation circuit that demodulates the amplified modulated signal and outputs the demodulated signal as the drive signal; Equipped with the demodulation circuit includes an inductive circuit, a capacitive circuit, and a switch circuit; The amplified modulated signal is input to one end of the inductive circuit, The other end of the inductive circuit is electrically connected to one end of the capacitive circuit; the demodulation circuit outputs the drive signal from a connection point where the other end of the inductive circuit and the one end of the capacitive circuit are electrically connected; The switch circuit switches the inductance value of the inductive circuit between a first inductance value and a second inductance value different from the first inductance value.

[0187] In this drive signal output circuit, during a period when it is desired to shorten the time it takes for the current flowing through the inductive circuit to reach a predetermined current value, the switch circuit switches the inductance value of the inductive circuit to a small value, thereby realizing a high frequency drive signal, and during a period when a significant ripple voltage may be superimposed on the signal waveform of the drive signal, the switch circuit switches the inductance value of the inductive circuit to a large value, thereby reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal and reducing the risk of deterioration of the signal waveform of the drive signal. Since the capacitance value of the capacitive circuit is constant, the possibility of an increase in power consumption in the drive signal output circuit is reduced.

[0188] In one aspect of the drive signal output circuit, the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; The amplified modulated signal is input to one end of the first inductor element, the other end of the first inductor element is electrically connected to one end of the capacitor element; one end of the second inductor element is electrically connected to one end of the switch circuit; the other end of the second inductor element is electrically connected to the one end of the capacitor element; the other end of the switch circuit is electrically connected to the one end of the first inductor element; The demodulation circuit may output the drive signal from a connection point where the other end of the first inductor element, the other end of the second inductor element, and the one end of the capacitor element are electrically connected.

[0189] In this drive signal output circuit, during a period when it is desired to shorten the time it takes for the current flowing through the inductive circuit to reach a predetermined current value, the switch circuit switches the inductance value of the inductive circuit to the combined inductance value of the first inductor element and the second inductor element connected in parallel, thereby achieving a high frequency drive signal, and during a period when a significant ripple voltage superimposed on the signal waveform of the drive signal may occur, the switch circuit switches the inductance value of the inductive circuit to the inductance value of the first inductor element as the inductance value of the inductive circuit, thereby reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal and reducing the risk of deterioration of the signal waveform of the drive signal.Furthermore, at this time, because the electrostatic capacitance value of the capacitor element in the capacitive circuit is constant, the risk of an increase in power consumption in the drive signal output circuit is also reduced.

[0190] In one aspect of the drive signal output circuit, the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; The amplified modulated signal is input to one end of the first inductor element, the other end of the first inductor element is electrically connected to one end of the second inductor element; the other end of the second inductor element is electrically connected to one end of the capacitor element; one end of the switch circuit is electrically connected to the one end of the second inductor element; the other end of the switch circuit is electrically connected to the other end of the second inductor element; The demodulation circuit may output the drive signal from a connection point where the other end of the second inductor element and the one end of the capacitor element are electrically connected.

[0191] In this drive signal output circuit, during a period when it is desired to shorten the time it takes for the current flowing through the inductive circuit to reach a predetermined current value, the switch circuit switches the inductance value of the inductive circuit to the inductance value of the first inductor element, thereby achieving a high frequency drive signal, and during a period when a significant ripple voltage superimposed on the signal waveform of the drive signal may occur, the switch circuit switches the inductance value of the inductive circuit to the combined inductance value of the first inductor element and the second inductor element connected in series, thereby reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal and reducing the risk of deterioration of the signal waveform of the drive signal.Furthermore, at this time, because the electrostatic capacitance value of the capacitor element in the capacitive circuit is constant, the risk of an increase in power consumption in the drive signal output circuit is also reduced.

[0192] In one aspect of the drive signal output circuit, the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; one end of the first inductor element is electrically connected to a first output terminal of the switch circuit; one end of the second inductor element is electrically connected to a second output terminal of the switch circuit; the other end of the first inductor element and the other end of the second inductor element are electrically connected to one end of the capacitor element; The amplified modulated signal is input to an input terminal of the switch circuit, the switch circuit switches between electrically connecting the input terminal and the first output terminal and electrically connecting the input terminal and the second output terminal; The demodulation circuit may output the drive signal from a connection point where the other end of the first inductor element, the other end of the second inductor element, and the one end of the capacitor element are electrically connected.

[0193] In this drive signal output circuit, during a period when it is desired to shorten the time it takes for the current flowing through the inductive circuit to reach a predetermined current value, the switch circuit switches the inductance value of the inductive circuit to the smaller inductance value of the first inductor element or the second inductor element, thereby achieving a higher frequency of the drive signal, and during a period when a significant ripple voltage superimposed on the signal waveform of the drive signal may occur, the switch circuit switches the inductance value of the inductive circuit to the larger inductance value of the first inductor element or the second inductor element, thereby reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal and reducing the risk of deterioration of the signal waveform of the drive signal.Furthermore, at this time, because the electrostatic capacitance value of the capacitor element in the capacitive circuit is constant, the risk of an increase in power consumption in the drive signal output circuit is also reduced.

[0194] In one aspect of the drive signal output circuit, The inductance value of the first inductor element may be greater than the inductance value of the second inductor element.

[0195] In one aspect of the drive signal output circuit, the amplifier circuit amplifies the modulated signal in accordance with an amplified power supply voltage, and outputs the amplified modulated signal; The demodulation circuit may include a diode element having an anode terminal electrically connected to the one end of the second inductor element and the one end of the switch circuit and having a cathode terminal to which the amplified power supply voltage is supplied.

[0196] In this drive signal output circuit, the influence of the induced electromotive force generated in the demodulation circuit can be reduced.

[0197] In one aspect of the drive signal output circuit, the amplifier circuit includes a first transistor element and a second transistor element that are push-pull connected, and outputs the amplified modulated signal by driving the first transistor element and the second transistor element; the switch circuit includes a third transistor element that switches whether or not the amplified modulation signal is input to the one end of the second inductor element; The on-resistance of the third transistor element may be smaller than the on-resistance of the first transistor element and the on-resistance of the second transistor element.

[0198] In this drive signal output circuit, the waveform precision of the drive signal can be further improved.

[0199] In one aspect of the drive signal output circuit, the switch circuit includes a first n-channel FET and a second n-channel FET, a drain terminal of the first FET electrically connected to the one end of the first inductor element; a drain terminal of the second FET electrically connected to the one end of the second inductor element; a source terminal of the first FET electrically connected to a source terminal of the second FET; A common gate drive signal may be input to the gate terminal of the first FET and the gate terminal of the second FET.

[0200] In this drive signal output circuit, the stability of the operation of the switch circuit can be improved.

[0201] In one aspect of the drive signal output circuit, a drive voltage detection circuit that outputs a voltage change signal corresponding to a change in the voltage value of the drive signal; The switch circuit may switch the inductance value of the inductive circuit between the first inductance value and the second inductance value in response to the voltage change signal.

[0202] In one aspect of the drive signal output circuit, The switch circuit may switch the inductance value of the inductive circuit between the first inductance value and the second inductance value based on a change in the voltage value of a signal waveform defined by the base drive signal and a load capacitance connected to a propagation path along which the drive signal propagates.

[0203] This drive signal output circuit can further improve the waveform accuracy of the output drive signal.

[0204] One aspect of the liquid ejection device is a discharge unit that discharges liquid by driving a capacitive load; a drive signal output circuit that outputs a drive signal for driving the capacitive load; Equipped with The drive signal output circuit a modulation circuit that modulates a base drive signal that is the basis of the drive signal and outputs the modulated signal; an amplifier circuit that amplifies the modulated signal and outputs it as an amplified modulated signal; a demodulation circuit that demodulates the amplified modulated signal and outputs the demodulated signal as the drive signal; Equipped with the demodulation circuit includes an inductive circuit, a capacitive circuit, and a switch circuit; The amplified modulated signal is input to one end of the inductive circuit, The other end of the inductive circuit is electrically connected to one end of the capacitive circuit; the demodulation circuit outputs the drive signal from a connection point where the other end of the inductive circuit and the one end of the capacitive circuit are electrically connected; The switch circuit switches the inductance value of the inductive circuit between a first inductance value and a second inductance value different from the first inductance value.

[0205] In this liquid ejection device, during a period in which it is desired to shorten the time it takes for the current flowing through the inductive circuit to reach a predetermined current value, the switch circuit switches the inductance value of the inductive circuit to a small value, thereby realizing a high frequency drive signal, and during a period in which a significant ripple voltage may be generated on the signal waveform of the drive signal, the switch circuit switches the inductance value of the inductive circuit to a small value. By switching the capacitance value to a larger value, the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal is reduced, reducing the risk of deterioration of the signal waveform of the drive signal.Furthermore, since the capacitance value of the capacitive circuit is constant, the risk of an increase in power consumption in the drive signal output circuit is also reduced.

[0206] In one aspect of the liquid ejection device, the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; The amplified modulated signal is input to one end of the first inductor element, the other end of the first inductor element is electrically connected to one end of the capacitor element; one end of the second inductor element is electrically connected to one end of the switch circuit; the other end of the second inductor element is electrically connected to the one end of the capacitor element; the other end of the switch circuit is electrically connected to the one end of the first inductor element; The demodulation circuit may output the drive signal from a connection point where the other end of the first inductor element, the other end of the second inductor element, and the one end of the capacitor element are electrically connected.

[0207] In this liquid ejection device, during a period in which it is desired to shorten the time it takes for the current flowing through the inductive circuit to reach a predetermined current value, the switch circuit switches the inductance value of the inductive circuit to the combined inductance value of the first inductor element and the second inductor element connected in parallel, thereby achieving a high frequency drive signal, and during a period in which a significant ripple voltage superimposed on the signal waveform of the drive signal may occur, the switch circuit switches the inductance value of the inductive circuit to the inductance value of the first inductor element as the inductance value of the inductive circuit, thereby reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal and reducing the risk of deterioration of the signal waveform of the drive signal.Furthermore, at this time, because the electrostatic capacitance value of the capacitor element in the capacitive circuit is constant, the risk of an increase in power consumption in the drive signal output circuit is also reduced.

[0208] In one aspect of the liquid ejection device, the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; The amplified modulated signal is input to one end of the first inductor element, the other end of the first inductor element is electrically connected to one end of the second inductor element; the other end of the second inductor element is electrically connected to one end of the capacitor element; one end of the switch circuit is electrically connected to the one end of the second inductor element; the other end of the switch circuit is electrically connected to the other end of the second inductor element; The demodulation circuit may output the drive signal from a connection point where the other end of the second inductor element and the one end of the capacitor element are electrically connected.

[0209] In this liquid ejection device, during a period when it is desired to shorten the time it takes for the current flowing through the inductive circuit to reach a predetermined current value, the switch circuit switches the inductance value of the inductive circuit to the inductance value of the first inductor element, thereby achieving a high frequency drive signal, and during a period when a significant ripple voltage superimposed on the signal waveform of the drive signal may occur, the switch circuit switches the inductance value of the inductive circuit to the combined inductance value of the first inductor element and the second inductor element connected in series, thereby reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal and reducing the risk of deterioration of the signal waveform of the drive signal.Furthermore, at this time, because the electrostatic capacitance value of the capacitor element in the capacitive circuit is constant, the risk of an increase in power consumption in the drive signal output circuit is also reduced.

[0210] In one aspect of the liquid ejection device, the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; one end of the first inductor element is electrically connected to a first output terminal of the switch circuit; one end of the second inductor element is electrically connected to a second output terminal of the switch circuit; the other end of the first inductor element and the other end of the second inductor element are electrically connected to one end of the capacitor element; The amplified modulated signal is input to an input terminal of the switch circuit, the switch circuit switches between electrically connecting the input terminal and the first output terminal and electrically connecting the input terminal and the second output terminal; The demodulation circuit may output the drive signal from a connection point where the other end of the first inductor element, the other end of the second inductor element, and the one end of the capacitor element are electrically connected.

[0211] In this liquid ejection device, during a period in which it is desired to shorten the time it takes for the current flowing through the inductive circuit to reach a predetermined current value, the switch circuit switches the inductance of the inductive circuit to the smaller inductance value of the first inductor element or the second inductor element, thereby achieving a higher frequency of the drive signal, and during a period in which a significant ripple voltage superimposed on the signal waveform of the drive signal may occur, the switch circuit switches the inductance of the inductive circuit to the larger inductance value of the first inductor element or the second inductor element, thereby reducing the voltage amplitude of the ripple voltage superimposed on the signal waveform of the drive signal and reducing the risk of deterioration of the signal waveform of the drive signal.Furthermore, at this time, because the electrostatic capacitance value of the capacitor element in the capacitive circuit is constant, the risk of an increase in power consumption in the drive signal output circuit is also reduced.

[0212] In one aspect of the liquid ejection device, The inductance value of the first inductor element may be greater than the inductance value of the second inductor element.

[0213] In one aspect of the liquid ejection device, the amplifier circuit amplifies the modulated signal in accordance with an amplified power supply voltage, and outputs the amplified modulated signal; The demodulation circuit may include a diode element having an anode terminal electrically connected to the one end of the second inductor element and the one end of the switch circuit and having a cathode terminal to which the amplified power supply voltage is supplied.

[0214] In this liquid ejection device, the influence of the induced electromotive force generated in the demodulation circuit can be reduced.

[0215] In one aspect of the liquid ejection device, the amplifier circuit includes a first transistor element and a second transistor element that are push-pull connected, and outputs the amplified modulated signal by driving the first transistor element and the second transistor element; the switch circuit includes a third transistor element that switches whether or not the amplified modulation signal is input to the one end of the second inductor element; The on-resistance of the third transistor element may be smaller than the on-resistance of the first transistor element and the on-resistance of the second transistor element.

[0216] In this liquid ejection device, the waveform precision of the drive signal can be further improved.

[0217] In one aspect of the liquid ejection device, the switch circuit includes a first n-channel FET and a second n-channel FET, a drain terminal of the first FET electrically connected to the one end of the first inductor element; a drain terminal of the second FET electrically connected to the one end of the second inductor element; a source terminal of the first FET electrically connected to a source terminal of the second FET; A common gate drive signal may be input to the gate terminal of the first FET and the gate terminal of the second FET.

[0218] In this liquid ejection device, the stability of the operation of the switch circuit can be improved.

[0219] In one aspect of the liquid ejection device, a drive voltage detection circuit that outputs a voltage change signal corresponding to a change in the voltage value of the drive signal; The switch circuit may switch the inductance value of the inductive circuit between the first inductance value and the second inductance value in response to the voltage change signal.

[0220] In one aspect of the liquid ejection device, The switch circuit may switch the inductance value of the inductive circuit between the first inductance value and the second inductance value based on a change in the voltage value of a signal waveform defined by the base drive signal and a load capacitance connected to a propagation path along which the drive signal propagates.

[0221] In this liquid ejection device, the waveform precision of the output drive signal can be further improved. [Explanation of symbols]

[0222] 1...liquid ejection device, 2...ink container, 10...control unit, 20...head unit, 21...carriage, 30...movement unit, 31...carriage motor, 32...endless belt, 40...transport unit, 41...transport motor, 42...transport roller, 50...drive circuit, 51...drive signal output circuit, 52...reference voltage output circuit, 60...piezoelectric element, 100...control circuit, 200...ejection head, 210...selection control circuit, 212...shift register, 214...latch circuit, 216...decoder, 230...selection circuit, 232...inverter, 234...transmission gate, 500...integrated circuit, 510...modulation circuit, 512, 513...adder, 514...comparator, 515...inverter, 516...integral attenuator, 517...attenuator, 520 ...Gate drive circuit, 521, 522...Gate driver, 530, 531...Differentiation circuit, 550...Amplification circuit, 560...Demodulation circuit, 562...Inductive circuit, 564...Capacitive circuit, 566...Switch circuit, 567...Control circuit, 568...Protection circuit, 570, 572...Feedback circuit, 580...Differentiation circuit, 600...Discharge portion, 601...Piezoelectric element, 611, 612...Electrodes, 621...Vibration Moving plate, 631...cavity, 632...nozzle plate, 641...reservoir, 651...nozzle, 661...supply port, C2 to C5, C7, C21, C31...capacitors, D1, D31, D41...diodes, L11, L12...inductors, M1, M2, M31, M32...transistors, P...medium, R1 to R7...resistors, SWa, SWb1, SWb2...switches

Claims

1. A drive signal output circuit that outputs a drive signal to drive a capacitive load, a modulation circuit that modulates a base drive signal that is the basis of the drive signal and outputs the modulated signal; an amplifier circuit that amplifies the modulated signal and outputs it as an amplified modulated signal; a demodulation circuit that demodulates the amplified modulated signal and outputs the demodulated signal as the drive signal; Equipped with the demodulation circuit includes an inductive circuit, a capacitive circuit, and a switch circuit; The amplified modulated signal is input to one end of the inductive circuit, The other end of the inductive circuit is electrically connected to one end of the capacitive circuit; the demodulation circuit outputs the drive signal from a connection point where the other end of the inductive circuit and the one end of the capacitive circuit are electrically connected; the switch circuit switches the inductance value of the inductive circuit between a first inductance value and a second inductance value different from the first inductance value; A drive signal output circuit comprising:

2. the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; The amplified modulation signal is input to one end of the first inductor element, the other end of the first inductor element is electrically connected to one end of the capacitor element; one end of the second inductor element is electrically connected to one end of the switch circuit; the other end of the second inductor element is electrically connected to the one end of the capacitor element; the other end of the switch circuit is electrically connected to the one end of the first inductor element; the demodulation circuit outputs the drive signal from a connection point where the other end of the first inductor element, the other end of the second inductor element, and the one end of the capacitor element are electrically connected.

2. The drive signal output circuit according to claim 1, wherein:

3. the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; The amplified modulation signal is input to one end of the first inductor element, the other end of the first inductor element is electrically connected to one end of the second inductor element; the other end of the second inductor element is electrically connected to one end of the capacitor element; one end of the switch circuit is electrically connected to the one end of the second inductor element; the other end of the switch circuit is electrically connected to the other end of the second inductor element; the demodulation circuit outputs the drive signal from a connection point where the other end of the second inductor element and the one end of the capacitor element are electrically connected.

2. The drive signal output circuit according to claim 1, wherein:

4. the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; one end of the first inductor element is electrically connected to a first output terminal of the switch circuit; one end of the second inductor element is electrically connected to a second output terminal of the switch circuit; the other end of the first inductor element and the other end of the second inductor element are electrically connected to one end of the capacitor element; The amplified modulated signal is input to an input terminal of the switch circuit, the switch circuit switches between electrically connecting the input terminal and the first output terminal and electrically connecting the input terminal and the second output terminal; the demodulation circuit outputs the drive signal from a connection point where the other end of the first inductor element, the other end of the second inductor element, and the one end of the capacitor element are electrically connected.

2. The drive signal output circuit according to claim 1, wherein:

5. The inductance value of the first inductor element is greater than the inductance value of the second inductor element.

3. The drive signal output circuit according to claim 2.

6. the amplifier circuit amplifies the modulated signal in accordance with an amplified power supply voltage, and outputs the amplified modulated signal; the demodulation circuit includes a diode element having an anode terminal electrically connected to the one end of the second inductor element and the one end of the switch circuit and having a cathode terminal to which the amplified power supply voltage is supplied; 3. The drive signal output circuit according to claim 2.

7. the amplifier circuit includes a first transistor element and a second transistor element that are push-pull connected, and outputs the amplified modulated signal by driving the first transistor element and the second transistor element; the switch circuit includes a third transistor element that switches whether or not the amplified modulation signal is input to the one end of the second inductor element; an on-resistance of the third transistor element is smaller than an on-resistance of the first transistor element and an on-resistance of the second transistor element; 3. The drive signal output circuit according to claim 2.

8. the switch circuit includes a first n-channel FET and a second n-channel FET, a drain terminal of the first FET electrically connected to the one end of the first inductor element; a drain terminal of the second FET electrically connected to the one end of the second inductor element; a source terminal of the first FET electrically connected to a source terminal of the second FET; a common gate drive signal is input to the gate terminal of the first FET and the gate terminal of the second FET; 3. The drive signal output circuit according to claim 2.

9. a drive voltage detection circuit that outputs a voltage change signal corresponding to a change in the voltage value of the drive signal; the switch circuit switches the inductance value of the inductive circuit between the first inductance value and the second inductance value in response to the voltage change signal; 2. The drive signal output circuit according to claim 1, wherein:

10. the switch circuit switches the inductance value of the inductive circuit between the first inductance value and the second inductance value based on a change in a voltage value of a signal waveform defined by the basic drive signal and a load capacitance connected to a propagation path along which the drive signal propagates.

2. The drive signal output circuit according to claim 1, wherein:

11. a discharge unit that discharges liquid by driving a capacitive load; a drive signal output circuit that outputs a drive signal that drives the capacitive load; Equipped with The drive signal output circuit a modulation circuit that modulates a base drive signal that is the basis of the drive signal and outputs the modulated signal; an amplifier circuit that amplifies the modulated signal and outputs it as an amplified modulated signal; a demodulation circuit that demodulates the amplified modulated signal and outputs the demodulated signal as the drive signal; Equipped with the demodulation circuit includes an inductive circuit, a capacitive circuit, and a switch circuit; The amplified modulated signal is input to one end of the inductive circuit, The other end of the inductive circuit is electrically connected to one end of the capacitive circuit; the demodulation circuit outputs the drive signal from a connection point where the other end of the inductive circuit and the one end of the capacitive circuit are electrically connected; the switch circuit switches the inductance value of the inductive circuit between a first inductance value and a second inductance value different from the first inductance value; A liquid ejection device characterized by:

12. the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; The amplified modulation signal is input to one end of the first inductor element, the other end of the first inductor element is electrically connected to one end of the capacitor element; one end of the second inductor element is electrically connected to one end of the switch circuit; the other end of the second inductor element is electrically connected to the one end of the capacitor element; the other end of the switch circuit is electrically connected to the one end of the first inductor element; the demodulation circuit outputs the drive signal from a connection point where the other end of the first inductor element, the other end of the second inductor element, and the one end of the capacitor element are electrically connected. The liquid ejection device according to claim 11 .

13. the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; The amplified modulation signal is input to one end of the first inductor element, the other end of the first inductor element is electrically connected to one end of the second inductor element; the other end of the second inductor element is electrically connected to one end of the capacitor element; one end of the switch circuit is electrically connected to the one end of the second inductor element; the other end of the switch circuit is electrically connected to the other end of the second inductor element; the demodulation circuit outputs the drive signal from a connection point where the other end of the second inductor element and the one end of the capacitor element are electrically connected. The liquid ejection device according to claim 11 .

14. the inductive circuit includes a first inductor element and a second inductor element; the capacitive circuit includes a capacitor element; one end of the first inductor element is electrically connected to a first output terminal of the switch circuit; one end of the second inductor element is electrically connected to a second output terminal of the switch circuit; the other end of the first inductor element and the other end of the second inductor element are electrically connected to one end of the capacitor element; The amplified modulated signal is input to an input terminal of the switch circuit, the switch circuit switches between electrically connecting the input terminal and the first output terminal and electrically connecting the input terminal and the second output terminal; the demodulation circuit outputs the drive signal from a connection point where the other end of the first inductor element, the other end of the second inductor element, and the one end of the capacitor element are electrically connected. The liquid ejection device according to claim 11 .

15. The inductance value of the first inductor element is greater than the inductance value of the second inductor element. The liquid ejection device according to claim 12 .

16. the amplifier circuit amplifies the modulated signal in accordance with an amplified power supply voltage, and outputs the amplified modulated signal; the demodulation circuit includes a diode element having an anode terminal electrically connected to the one end of the second inductor element and the one end of the switch circuit and having a cathode terminal to which the amplified power supply voltage is supplied; The liquid ejection device according to claim 12 .

17. the amplifier circuit includes a first transistor element and a second transistor element that are push-pull connected, and outputs the amplified modulated signal by driving the first transistor element and the second transistor element; the switch circuit includes a third transistor element that switches whether or not the amplified modulation signal is input to the one end of the second inductor element; an on-resistance of the third transistor element is smaller than an on-resistance of the first transistor element and an on-resistance of the second transistor element; The liquid ejection device according to claim 12 .

18. the switch circuit includes a first n-channel FET and a second n-channel FET, a drain terminal of the first FET electrically connected to the one end of the first inductor element; a drain terminal of the second FET electrically connected to the one end of the second inductor element; a source terminal of the first FET electrically connected to a source terminal of the second FET; a common gate drive signal is input to the gate terminal of the first FET and the gate terminal of the second FET; The liquid ejection device according to claim 12 .

19. a drive voltage detection circuit that outputs a voltage change signal corresponding to a change in the voltage value of the drive signal; the switch circuit switches the inductance value of the inductive circuit between the first inductance value and the second inductance value in response to the voltage change signal; The liquid ejection device according to claim 11 .

20. the switch circuit switches the inductance value of the inductive circuit between the first inductance value and the second inductance value based on a change in a voltage value of a signal waveform defined by the basic drive signal and a load capacitance connected to a propagation path along which the drive signal propagates. The liquid ejection device according to claim 11 .

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