Liquid dispensing device and drive unit

Abstract

The temperature of the drive circuit is detected appropriately. [Solution] A liquid dispensing device characterized by comprising: a dispensing unit that is driven by a drive signal to dispense liquid; a circuit board on which a drive circuit that generates a drive signal is arranged; a thermistor arranged on the circuit board for detecting the temperature of the drive circuit; and an electrically insulating first heat conductive member arranged on the circuit board, one end of which is connected to the drive circuit and the other end of which is connected to a wire electrically connected to the thermistor.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a drive unit.

Background Art

[0002] There is known a liquid ejection device including a drive circuit that generates a drive signal and a ejection unit that is driven by the drive signal to eject a liquid. In such a liquid ejection device, since the drive signal for driving the ejection unit is a large-amplitude signal, the drive circuit generates heat when generating the drive signal, and the drive circuit becomes hot. When the drive circuit becomes hot, the load related to the drive circuit increases. For this reason, various techniques for detecting the temperature of the drive circuit and reducing the load related to the drive circuit when the drive circuit becomes hot have been proposed. For example, Patent Document 1 discloses a technique of detecting the temperature of an electronic component by arranging a thermistor near the electronic component constituting the drive circuit and stopping the generation of a drive signal by the drive circuit when the electronic component becomes hot.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, according to the conventional technology, since an insulating layer made of an insulating resin such as glass epoxy is interposed between the electronic component and the thermistor, the heat generated by the electronic component cannot be sufficiently transmitted to the thermistor, and there is a possibility that the temperature of the drive circuit cannot be appropriately detected.

Means for Solving the Problems

[0005] To solve the above problems, the liquid dispensing device according to the present invention is characterized by comprising: a dispensing unit that is driven by a drive signal to dispense liquid; a circuit board on which a drive circuit that generates the drive signal is arranged; a thermistor arranged on the circuit board for detecting the temperature of the drive circuit; and an electrically insulating first heat conductive member arranged on the circuit board, one end of which is connected to the drive circuit and the other end of which is connected to a wiring that is electrically connected to the thermistor.

[0006] Furthermore, the drive unit according to the present invention is a drive unit for driving a discharge unit that discharges liquid, and is characterized by comprising: a drive circuit that generates a drive signal for driving the discharge unit; a circuit board on which the drive circuit is arranged; a thermistor arranged on the circuit board for detecting the temperature of the drive circuit; and an electrically insulating first heat conductive member arranged on the circuit board, one end of which is connected to the drive circuit and the other end of which is connected to a wiring electrically connected to the thermistor. [Brief explanation of the drawing]

[0007] [Figure 1] This block diagram shows an example of the configuration of an inkjet printer 1 according to an embodiment of the present invention. [Figure 2] This is a perspective view showing an example of the general internal structure of inkjet printer 1. [Figure 3] This is a cross-sectional view showing an example of the structure of the discharge section D[m]. [Figure 4] This block diagram shows an example of the configuration of head unit 3. [Figure 5] This is a timing chart showing an example of the signals supplied to head unit 3. [Figure 6] This is an explanatory diagram showing an example of an individual designation signal Sd[m]. [Figure 7] This is a block diagram showing an example of the configuration of the drive signal generation circuit 40. [Figure 8] This is a plan view showing an example of the configuration of the drive signal generation unit 4. [Figure 9]It is a cross-sectional view showing an example of the structure of the drive signal generation unit 4. [Figure 10] It is a plan view showing an example of the structure of the drive signal generation unit 4B according to Modification 1 of the present invention. [Figure 11] It is a plan view showing an example of the structure of the drive signal generation unit 4C according to Modification 2 of the present invention. [Figure 12] It is a block diagram showing an example of the configuration of the drive signal generation circuit 40D according to Modification 3 of the present invention. [Figure 13] It is a plan view showing an example of the structure of the drive signal generation unit 4D according to Modification 3 of the present invention. [Figure 14] It is a block diagram showing an example of the configuration of the inkjet printer 1E according to Modification 4 of the present invention. MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in each figure, the dimensions and scales of each part are appropriately different from the actual ones. Further, the embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are imposed. However, the scope of the present invention is not limited to these embodiments unless there is a description to particularly limit the present invention in the following description.

[0009] <<A. Embodiment>> Hereinafter, a liquid ejection device will be described by exemplifying an inkjet printer 1 that ejects ink to form an image on a recording paper PP.

[0010] <<A.1. Outline of Inkjet Printer 1>> Hereinafter, an example of the configuration of the inkjet printer 1 according to the present embodiment will be described while referring to FIGS. 1 to 3.

[0011] FIG. 1 is a functional block diagram showing an example of the configuration of the inkjet printer 1.

[0012] As shown in FIG. 1, the inkjet printer 1 is supplied with print data Img indicating an image to be formed by the inkjet printer 1 from a host computer such as a personal computer or a digital camera. The inkjet printer 1 executes a printing process of forming the image indicated by the print data Img supplied from the host computer on the recording paper PP.

[0013] As shown in FIG. 1, the inkjet printer 1 includes a control unit 2 that controls each part of the inkjet printer 1, a head unit 3 provided with a discharge unit D that discharges ink onto the recording paper PP, a drive signal generation unit 4 provided with a drive signal generation circuit 40 that generates a drive signal Com for driving the discharge unit D, and a conveyance unit 9 for conveying the head unit 3 and the recording paper PP. In this embodiment, the inkjet printer 1 is an example of a "liquid discharge device", the ink is an example of a "liquid", the drive signal generation unit 4 is an example of a "drive unit", and the drive signal generation circuit 40 is an example of a "drive circuit".

[0014] In this embodiment, it is assumed that the inkjet printer 1 includes one or more head units 3. Specifically, in this embodiment, as an example, it is assumed that the inkjet printer 1 includes four head units 3. In the following, for convenience of explanation, there may be cases where, as shown in FIG. 1, an explanation is given by focusing on one of the four head units 3.

[0015] In addition, in the present embodiment, it is assumed that the inkjet printer 1 includes one drive signal generation unit 4 corresponding to one head unit 3. That is, in the present embodiment, it is assumed that the inkjet printer 1 includes four drive signal generation units 4 corresponding to four head units 3. However, the present invention is not limited to such an aspect. The inkjet printer 1 may include two or more drive signal generation units 4 corresponding to one head unit 3. In the following, for convenience of explanation, as shown in FIG. 1, there may be cases where the description is made by focusing on one of the four drive signal generation units 4.

[0016] The control unit 2 is configured to include a control circuit (not shown) and a storage circuit (not shown). The storage circuit is configured to include a volatile memory such as a RAM (Random Access Memory) and a non-volatile memory such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a PROM (Programmable ROM), and stores various information such as the control program of the inkjet printer 1. The control circuit is configured to include one or more CPUs (Central Processing Unit). However, the control circuit may be provided with a programmable logic device such as an FPGA (field-programmable gate array) instead of or in addition to the CPU. Then, the control circuit executes the control program of the inkjet printer 1 stored in the storage circuit and controls each part of the inkjet printer 1 by operating according to the control program. Specifically, the control circuit generates signals for controlling the operations of each part of the inkjet printer 1, such as a designation signal SI, a waveform designation signal dCom, and a conveyance control signal SH.

[0017] Here, the waveform specification signal dCom is a digital signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the ejection unit D. The specification signal SI is a digital signal that specifies the type of operation of the ejection unit D. Specifically, the specification signal SI specifies whether or not to supply the drive signal Com to the ejection unit D, thereby specifying the type of operation of the ejection unit D, such as whether or not ink is ejected from the ejection unit D. The transport control signal SH is a signal for controlling the transport unit 9.

[0018] When printing is performed, the control unit 2 generates signals to control the head unit 3, such as a specified signal SI, based on the print data Img. The control unit 2 also generates signals to control the drive signal generation unit 4, such as a waveform specified signal dCom, when printing is performed. Furthermore, the control unit 2 generates signals to control the transport unit 9, such as a transport control signal SH, when printing is performed. In this way, during printing, the control unit 2 controls the transport unit 9 to move the head unit 3 and the recording paper PP, while adjusting the presence or absence of ink ejection from the ejection unit D, the ink ejection timing, etc., thereby controlling each part of the inkjet printer 1 so that an image corresponding to the print data Img is formed on the recording paper PP.

[0019] As shown in Figure 1, the head unit 3 comprises a supply circuit 31 and a head section 32.

[0020] The print head 32 is equipped with M ejection units D. Here, the value M is a natural number satisfying "M≧1". In the following, the m-th ejection unit D among the M ejection units D provided in the print head 32 may be referred to as ejection unit D[m]. Here, the variable m is a natural number satisfying "1≦m≦M". Furthermore, in the following, if a component or signal of the inkjet printer 1 corresponds to ejection unit D[m] among the M ejection units D, the subscript [m] may be added to the code used to represent that component or signal. The supply circuit 31 switches whether or not to supply the drive signal Com to the discharge unit D[m] based on the specified signal SI. Hereinafter, the drive signal Com supplied to the discharge unit D[m] may be referred to as the supply drive signal Vin[m].

[0021] As shown in Figure 1, the drive signal generation unit 4 comprises a drive signal generation circuit 40 and a thermistor TT. Further details will be described later in Figures 8 and 9, but the drive signal generation unit 4 also comprises a heat conduction element XN for transferring heat from the drive signal generation circuit 40 to the thermistor TT, and a drive circuit board 400 on which the drive signal generation circuit 40, thermistor TT, and heat conduction element XN are arranged. In this embodiment, the drive circuit board 400 is an example of a "circuit board," and the heat conduction element XN is an example of a "first heat conduction member."

[0022] As described above, the drive signal generation circuit 40 generates a drive signal Com based on the waveform specification signal dCom and supplies the generated drive signal Com to the head unit 3. The thermistor TT detects the temperature of the drive signal generation circuit 40 and supplies a temperature signal Tmp indicating the detection result to the control unit 2.

[0023] In this embodiment, when printing is being performed, the control unit 2 estimates the temperature of the drive signal generation circuit 40 based on the temperature signal Tmp supplied from the drive signal generation unit 4. The control unit 2 then continues the printing process if the temperature of the drive signal generation circuit 40 estimated based on the temperature signal Tmp is below a predetermined temperature. On the other hand, if the temperature of the drive signal generation circuit 40 estimated based on the temperature signal Tmp becomes higher than the predetermined temperature, the control unit 2 temporarily stops the printing process. Subsequently, the control unit 2 resumes the printing process when the temperature of the drive signal generation circuit 40 estimated based on the temperature signal Tmp returns to below the predetermined temperature.

[0024] Figure 2 is a perspective view showing an example of the schematic internal structure of inkjet printer 1.

[0025] As shown in Figure 2, in this embodiment, we assume that the inkjet printer 1 is a serial printer. Specifically, when the inkjet printer 1 performs a printing process, it transports the recording paper PP in the X1 direction, and while moving the head unit 3 in the Y1 direction which intersects the X1 direction, or in the Y2 direction which is opposite to the Y1 direction, it ejects ink from the head unit 3 to form an image on the recording paper PP according to the print data Img.

[0026] In the following, the X1 direction and its opposite direction, the X2 direction, will be collectively referred to as the "X-axis direction," the Y1 direction intersecting the X-axis direction and its opposite direction, the Y2 direction, will be collectively referred to as the "Y-axis direction," and the Z1 direction intersecting the X-axis and Y-axis directions and its opposite direction, the Z2 direction, will be collectively referred to as the "Z-axis direction." In this embodiment, as an example, the case in which the X-axis direction, Y-axis direction, and Z-axis direction are mutually orthogonal will be described. However, the present invention is not limited to this embodiment. The X-axis direction, Y-axis direction, and Z-axis direction only need to intersect each other. In this embodiment, the Z1 direction is the direction in which ink is ejected from the ejection unit D.

[0027] As shown in Figure 2, the inkjet printer 1 according to this embodiment comprises a housing 100 and a carriage 110 that can reciprocate within the housing 100 in the Y-axis direction.

[0028] As shown in Figure 2, this embodiment assumes that the carriage 110 is equipped with four ink cartridges 120, each corresponding one-to-one with four inks: cyan, magenta, yellow, and black. Furthermore, this embodiment assumes that the carriage 110 is equipped with four head units 3, each corresponding one-to-one with the four ink cartridges 120. Each ejection unit D[m] receives ink from the ink cartridge 120 corresponding to the head unit 3 on which the ejection unit D[m] is located. As a result, each ejection unit D[m] fills itself with the supplied ink, and the ink filled inside the ejection unit D[m] can be ejected from the nozzle N provided in the ejection unit D[m]. Note that the ink cartridges 120 may be located outside the carriage 110.

[0029] As described above, the inkjet printer 1 according to this embodiment includes a transport unit 9. As shown in Figure 2, the transport unit 9 includes a carriage transport motor 91, a media transport motor 92, a media transport mechanism 93, a platen 95, a carriage guide shaft 96, and a carriage transport mechanism 97. The carriage transport motor 91 drives the carriage transport mechanism 97 based on a transport control signal SH. The carriage transport mechanism 97 is, for example, a belt, and transports the carriage 110 in the Y-axis direction based on the drive of the carriage transport motor 91. The carriage guide shaft 96 supports the carriage 110 so that it can reciprocate in the Y-axis direction. The media transport motor 92 drives the media transport mechanism 93 based on a transport control signal SH. The media transport mechanism 93 transports the recording paper PP in the X1 direction by rotating based on the drive of the media transport motor 92. The platen 95 is provided in the Z1 direction of the carriage 110 and supports the recording paper PP being transported by the media transport mechanism 93. In this way, when printing is performed, the transport unit 9 uses the carriage transport motor 91 to reciprocate the head unit 3 and the carriage 110 together along the carriage guide axis 96 in the Y-axis direction, and the media transport motor 92 transports the recording paper PP on the platen 95 in the X1 direction, thereby changing the relative position of the recording paper PP with respect to the head unit 3 and enabling ink to land on the entire surface of the recording paper PP.

[0030] Figure 3 is a schematic partial cross-sectional view of the head portion 32, which is cut to include the discharge portion D [m].

[0031] As shown in FIG. 3, the ejection unit D[m] includes a piezoelectric element PZ[m], a cavity CV[m] filled with ink inside, a nozzle N[m] communicating with the cavity CV[m], and a diaphragm 321. When the piezoelectric element PZ[m] is driven by a supply drive signal Vin[m], the ink in the cavity CV[m] is ejected from the nozzle N[m]. The cavity CV[m] is a space partitioned by a cavity plate 324, a nozzle plate 323 in which the nozzle N[m] is formed, and the diaphragm 321. The cavity CV[m] communicates with a reservoir 325 via an ink supply port 326. The reservoir 325 communicates with an ink cartridge 120 corresponding to the ejection unit D[m] via an ink intake port 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric body Zm[m] provided between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is electrically connected to a power supply line LD set to a predetermined potential VBS. When a supply drive signal Vin[m] is supplied to the upper electrode Zu[m] and a voltage is applied between the upper electrode Zu[m] and the lower electrode Zd[m], the piezoelectric element PZ[m] is displaced in the Z1 direction and the Z2 direction according to the applied voltage, and as a result, the piezoelectric element PZ[m] vibrates. The lower electrode Zd[m] is joined to the diaphragm 321. Therefore, when the piezoelectric element PZ[m] is driven by the supply drive signal Vin[m] and vibrates, the diaphragm 321 also vibrates. Then, the vibration of the diaphragm 321 changes the volume of the cavity CV[m] and the pressure inside the cavity CV[m], and the ink filled in the cavity CV[m] is ejected from the nozzle N[m].

[0032] <<A.2. Configuration and Operation of Head Unit 3>> Hereinafter, an example of the configuration and operation of the head unit 3 will be described while referring to FIGS. 4 to 6.

[0033] FIG. 4 is a block diagram showing an example of the configuration of the head unit 3.

[0034] As shown in Figure 4, the head unit 3 comprises a supply circuit 31 and a head unit 32. The head unit 3 also includes wiring LC to which the drive signal Com is supplied from the drive signal generation unit 4.

[0035] As shown in Figure 4, the supply circuit 31 comprises M switches WS[1] to WS[M] that correspond one-to-one with M discharge units D[1] to D[M], and a connection state specification circuit 310 that specifies the connection state of each switch. The connection status specification circuit 310 generates a connection status specification signal QS[m] that specifies whether the switch WS[m] is on or off, based on at least some of the signals supplied from the control unit 2: the specification signal SI, the latch signal LAT, the change signal CH, and the clock signal CLK. The switch WS[m] switches between conductivity and non-conductivity between the wiring LC and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m], based on the connection status specification signal QS[m]. In this embodiment, the switch WS[m] is turned on when the connection status specification signal QS[m] is high level and turned off when it is low level. When the switch WS[m] is turned on, the drive signal Com supplied to the wiring LC is supplied to the upper electrode Zu[m] of the discharge section D[m] as the supply drive signal Vin[m].

[0036] Figure 5 is a timing chart s showing an example of various signals, such as the drive signal Com, supplied to the head unit 3.

[0037] As shown in Figure 5, when the inkjet printer 1 performs a printing process, one or more unit periods TP are set as the operating period of the inkjet printer 1. In this embodiment, the inkjet printer 1 can drive each ejection unit D[m] for the printing process during each unit period TP.

[0038] As shown in Figure 5, the control unit 2 outputs a latch signal LAT which has a pulse PLL. This allows the control unit 2 to define a unit period TP as the period from the rising edge of one pulse PLL to the rising edge of the next pulse PLL. The control unit 2 also outputs a change signal CH which has a pulse PLC during the unit period TP. The control unit 2 then divides the unit period TP into a drive period TQ1, from the rising edge of the pulse PLL to the rising edge of the pulse PLC, and a drive period TQ2, from the rising edge of the pulse PLC to the rising edge of the pulse PLL.

[0039] As shown in Figure 5, the designation signal SI includes M individual designation signals Sd[1] to Sd[M] that correspond one-to-one with M ejection units D[1] to D[M]. The individual designation signals Sd[m] specify the mode of operation of the ejection units D[m] in each unit period TP when the inkjet printer 1 performs printing. Prior to each unit period TP, the control unit 2 supplies the designation signal SI, which includes the M individual designation signals Sd[1] to Sd[M], to the connection state designation circuit 310 in synchronization with the clock signal CLK. The connection state designation circuit 310 then generates a connection state designation signal QS[m] based on the individual designation signals Sd[m] in the unit period TP.

[0040] In this embodiment, it is assumed that during a unit period TP in which the printing process is performed, the ejection unit D[m] is capable of forming any of the following dots: a large dot made of ink with an ink amount ξ1, a medium dot made of ink with an ink amount ξ2 less than ξ1, and a small dot made of ink with an ink amount ξ3 less than ξ2.

[0041] Figure 6 is an explanatory diagram illustrating an example of an individual designation signal Sd[m].

[0042] As shown in Figure 6, in this embodiment, the individual designation signal Sd[m] can take any one of four values ​​during the unit period TP in which the printing process is performed: a value of "1" which designates the ejection unit D[m] as the large dot forming ejection unit DP-1, a value of "2" which designates the ejection unit D[m] as the medium dot forming ejection unit DP-2, a value of "3" which designates the ejection unit D[m] as the small dot forming ejection unit DP-3, and a value of "4" which designates the ejection unit D[m] as the non-dot forming ejection unit DP-4. Here, the large dot-forming discharge section DP-1 is the discharge section D that forms large dots in a unit period TP. The medium dot-forming discharge section DP-2 is the discharge section D that forms medium dots in a unit period TP. The small dot-forming discharge section DP-3 is the discharge section D that forms small dots in a unit period TP. The non-dot-forming discharge section DP-4 is the discharge section D that does not form dots in a unit period TP.

[0043] Return to the explanation in Figure 5. As shown in Figure 5, in this embodiment, the drive signal Com has a waveform PA1 provided during the drive period TQ1 and a waveform PA2 provided during the drive period TQ2. Of these, waveform PA1 is a waveform that returns to potential V0, passing through potential VL1 which is lower than potential V0, and potential VH1 which is higher than potential V0. When a supply drive signal Vin[m] having waveform PA1 is supplied to the ejection unit D[m], waveform PA1 is defined so that ink equivalent to ink amount φ1 is ejected from the ejection unit D[m]. Waveform PA2 is a waveform that returns to potential V0, passing through potential VL2 which is lower than potential V0, and potential VH2 which is higher than potential V0. When a supply drive signal Vin[m] having waveform PA2 is supplied to the ejection unit D[m], waveform PA2 is defined so that ink equivalent to ink amount φ2 is ejected from the ejection unit D[m]. In this embodiment, it is assumed that ink quantity ξ1 corresponds to the sum of ink quantity φ1 and ink quantity φ2, ink quantity ξ2 corresponds to ink quantity φ1, and ink quantity ξ3 corresponds to ink quantity φ2.

[0044] Furthermore, in this embodiment, as an example, we assume that when the potential of the supply drive signal Vin[m] supplied to the ejection unit D[m] is high, the volume of the cavity CV[m] in the ejection unit D[m] becomes smaller compared to when the potential is low. Therefore, when the ejection unit D[m] is driven by a supply drive signal Vin[m] having a waveform PA1 or the like, the ink in the ejection unit D[m] is ejected from the nozzle N[m] as the potential of the supply drive signal Vin[m] changes from low to high.

[0045] As shown in Figure 6, when the individual designation signal Sd[m] indicates a value of "1" which designates the ejection unit D[m] as the large dot forming ejection unit DP-1 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal QS[m] to a high level during the drive period TQ1 and the drive period TQ2. In this case, the switch WS[m] is turned on during the drive period TQ1 and the drive period TQ2. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] which has waveforms PA1 and PA2, and ejects ink with an ink amount ξ1 corresponding to a large dot. Furthermore, if the individual designation signal Sd[m] indicates a value of "2" which designates the ejection unit D[m] as the medium dot forming ejection unit DP-2 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal QS[m] to a high level during the drive period TQ1. In this case, the switch WS[m] is turned on during the drive period TQ1. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] having waveform PA1 and ejects ink with an ink amount ξ2 corresponding to the medium dot. Furthermore, if the individual designation signal Sd[m] indicates a value of "3" which designates the ejection unit D[m] as the small dot forming ejection unit DP-3 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal QS[m] to a high level during the drive period TQ2. In this case, the switch WS[m] is turned on during the drive period TQ2. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] having waveform PA2 and ejects ink with an ink amount ξ3 corresponding to a small dot. Also, when the individual designation signal Sd[m] indicates the value "4" that designates the discharge section D[m] as the dot non - forming discharge section DP - 4 in the unit period TP, the connection state designation circuit 310 sets the connection state designation signal QS[m] to the low level throughout the unit period TP. In this case, the switch WS[m] turns off throughout the unit period TP. Therefore, the discharge section D[m] is not driven by the supply drive signal Vin[m] and does not discharge ink in the unit period TP.

[0046] <<A.3. Configuration of the drive signal generation circuit 40>> Hereinafter, an example of the configuration of the drive signal generation circuit 40 and the thermistor TT provided in the drive signal generation unit 4 will be described while referring to FIG. 7.

[0047] FIG. 7 is a block diagram showing an example of the circuit configuration of the drive signal generation circuit 40 and the thermistor TT provided in the drive signal generation unit 4.

[0048] As shown in FIG. 7, the drive signal generation circuit 40 is a class - D amplifier circuit that includes an integrated circuit 41, an amplifier circuit 43, a smoothing circuit 44, a pull - up circuit 45, and a filter circuit 46, and generates a drive signal Com based on the waveform designation signal dCom.

[0049] The integrated circuit 41 is, for example, an LSI (Large Scale Integration), and generates a gate signal SGH and a gate signal SGL based on the waveform designation signal dCom supplied to the terminal tIN via the node nIN. The integrated circuit 41 includes an analog conversion circuit 412, a subtractor 414, an adder 416, an attenuator 418, an integral attenuator 422, a comparator 424, and a gate driver 426.

[0050] The analog conversion circuit 412 is a DAC (digital to analog converter) that converts the digital waveform specification signal dCom into an analog signal Aa. The voltage amplitude of signal Aa is, for example, about 0 to 2 volts, and the drive signal Com is obtained by amplifying this voltage by about 20 times. In other words, signal Aa is the signal before amplification of the drive signal Com. The integrating attenuator 422 outputs a signal Ax obtained by attenuating the signal SN1 input to terminal t1 (described later) and then integrating it. The subtractor 414 outputs a signal Ab, which represents the potential obtained by subtracting the potential of signal Aa from the potential of signal Ax. The attenuator 418 outputs a signal Ay, which is the signal SN2 input to terminal t2 (described later) with its high-frequency components attenuated. The adder 416 outputs a signal As, which represents the potential obtained by adding the potentials of signal Ab and signal Ay. Comparator 424 outputs a modulated signal Ms obtained by pulse-modulating signal As. Specifically, comparator 424 outputs a modulated signal Ms that becomes high level when signal As's voltage rises above threshold voltage Vth1, and low level when signal As's voltage falls below threshold voltage Vth2. The threshold voltages Vth1 and Vth2 are set to the relationship 'Vth1 > Vth2'.

[0051] The power supply voltage for the circuit from the analog conversion circuit 412 to the comparator 424 is a low voltage, such as 3.3 volts. In contrast, the drive signal Com has a large amplitude, sometimes exceeding 40 volts. Therefore, the integrating attenuator 422 attenuates the signal SN1, which has an amplitude corresponding to the drive signal Com, to match the amplitude range of the signal Ax to the amplitude range of the signal in the circuit from the analog conversion circuit 412 to the comparator 424. Furthermore, although a digital signal is used as an example to describe the waveform specification signal dCom in this embodiment, the waveform specification signal dCom can be any signal that defines the target value for generating the drive signal Com. For example, an analog signal Aa may be used as the waveform specification signal dCom. If signal Aa is the waveform specification signal dCom, the integrated circuit 41 may be configured without including the analog conversion circuit 412.

[0052] The gate driver 426 outputs a gate signal SGH, obtained by converting the modulated signal Ms to a specific amplitude, to node nH via terminal tH. The gate driver 426 also outputs a gate signal SGL, obtained by converting the inverted logic level of the modulated signal Ms to a specific amplitude, to node nL via terminal tL.

[0053] The amplification circuit 43 includes, for example, transistors TrH and TrL, and generates an amplified signal Az, which is a signal obtained by amplifying the modulated signal Ms, based on the gate signals SGH and SGL output from the integrated circuit 41. In this embodiment, as an example, it is assumed that transistors TrH and TrL are field-effect transistors. More specifically, in this embodiment, it is assumed that N-channel type metal-oxide-semiconductor field-effect transistors (MOSFETs) are used as transistors TrH and TrL.

[0054] The gate signal SGH, output from gate driver 426 to terminal tH, is input to the gate gate gt of transistor TrH via node nH and resistor RGH. Similarly, the gate signal SGL, output from gate driver 426 to terminal tL, is input to the gate gate gt of transistor TrL via node nL and resistor RGL. The logic levels of gate signals SGH and SGL are mutually exclusive. Here, "mutually exclusive" means that the signal level of gate signal SGH supplied to the gate gate gt of transistor TrH and the signal level of gate signal SGL supplied to the gate gate gt of transistor TrL can never be high at the same time; in other words, transistors TrH and TrL can never be turned on at the same time. Transistor TrH turns on when the potential of its gate gate gt is high, and turns off when the potential of its gate gate gt is low. The transistor TrL turns on when the potential of its gate electrode gt is high, and turns off when the potential of its gate electrode gt is low.

[0055] The drain electrode dt of transistor TrH is electrically connected to node nV, which is set to the high-potential power supply potential VHV, and the source electrode st is electrically connected to node nD. The source electrode st of transistor TrL is electrically connected to node nG, which is set to ground potential, and the drain electrode dt is electrically connected to node nD. Alternatively, the source electrode of transistor TrL may be electrically connected to the power supply line LD, which is set to potential VBS.

[0056] As described above, transistor TrH turns on when the gate signal SGH supplied to the gate electrode gt is high level and turns off when it is low level. Transistor TrL turns on when the gate signal SGL supplied to the gate electrode gt is high level and turns off when it is low level. Therefore, the node nD that electrically connects the source electrode st of transistor TrH and the drain electrode dt of transistor TrL outputs an amplified signal Az, which is the modulated signal Ms amplified.

[0057] In this embodiment, transistors TrH and TrL are examples of "two transistors," transistor TrH is an example of a "first transistor," transistor TrL is an example of a "second transistor," power supply potential VHV is an example of a "first potential," node nV is an example of a "first potential line," ground potential is an example of a "second potential," and node nG is an example of a "second potential line."

[0058] An electrolytic capacitor Cd is connected to node nV, to which the power supply potential VHV is supplied. One end (terminal tD1) of the electrolytic capacitor Cd is electrically connected to node nV, and the other end (terminal tD2) is electrically connected to node nG, which is set to ground potential. In this embodiment, the electrolytic capacitor Cd is, for example, a large-capacity aluminum electrolytic capacitor, which suppresses potential fluctuations at node nV and stabilizes the power supply potential VHV. Terminals tD1 and tD2 will be described later in Figure 8.

[0059] The smoothing circuit 44 is an LPF (Low Pass Filter) that smooths the amplified signal Az to generate a drive signal Com, and outputs the generated drive signal Com to node nX. The smoothing circuit 44 includes an inductor L0 and a capacitor C0. One end (terminal tL1) of the inductor L0 is electrically connected to node nD, and the other end (terminal tL2) is electrically connected to node nX. One end (terminal tC1) of the capacitor C0 is electrically connected to node nX, and the other end (terminal tC2) is electrically connected to node nG, which is set to ground potential. Node nX is electrically connected to wiring LC. Terminals tL1 and tL2, and terminals tC1 and tC2 will be described later in Figure 8.

[0060] The pull-up circuit 45 feeds back the signal SN1, which is the drive signal Com output to node nX, to terminal t1. The pull-up circuit 45 includes a resistor R1, one end of which is electrically connected to node nX and the other end of which is electrically connected to terminal t1, and a resistor R2, one end of which is electrically connected to terminal t1 and the other end of which is electrically connected to node nV, which is set to the power supply potential VHV.

[0061] The filter circuit 46 is a Band Pass Filter (BPF) and feeds back a signal SN2, which is obtained by cutting the DC component from the frequency components of a predetermined band of the drive signal Com, to terminal t2. The filter circuit 46 comprises a resistor R3, a capacitor C1 with one end electrically connected to node nX and the other end electrically connected to one end of resistor R3, a resistor R4 with one end electrically connected to one end of resistor R3 and the other end electrically connected to node nG which is set to ground potential, a capacitor C2 with one end electrically connected to the other end of resistor R3 and the other end electrically connected to node nG which is set to ground potential, and a capacitor C3 with one end electrically connected to the other end of resistor R3 and the other end electrically connected to terminal t2. Of these, capacitor C1 and resistor R4 function as a High Pass Filter (HPF) that allows high-frequency components of the drive signal Com above the cutoff frequency to pass through. Furthermore, resistor R3 and capacitor C2 function as an LPF (Low Pass Filter) that allows low-frequency components of the drive signal Com below the cutoff frequency to pass through. In this embodiment, the cutoff frequency of the HPF is set lower than the cutoff frequency of the LPF in the filter circuit 46. Therefore, the filter circuit 46 allows frequency components of the drive signal Com that are above the cutoff frequency of the HPF and below the cutoff frequency of the LPF to pass through. In addition, because the filter circuit 46 is equipped with capacitor C3, the signal from which the DC component has been cut off from the frequency components of the drive signal Com that have passed through the HPF and LPF is fed back to terminal t2.

[0062] As described above, the drive signal generation circuit 40 generates the drive signal Com by smoothing the amplified signal Az at the node nD with the smoothing circuit 44. The drive signal Com is integrated and subtracted by the integrator attenuator 422 and then fed back to the subtractor 414. Therefore, self-oscillation occurs at a frequency determined by the delay in the smoothing circuit 44, the delay in the integrator attenuator 422, and the feedback transfer function. However, since the delay amount of the feedback path via the terminal t1 is large, the self-oscillation frequency cannot be increased to such an extent that the accuracy of the waveform of the drive signal Com can be sufficiently ensured only by the feedback via the terminal t1. In contrast, in the present embodiment, a path for feeding back the high-frequency component of the drive signal Com via the terminal t2 is provided separately from the path via the terminal t1, so that the delay of the feedback in the entire drive signal generation circuit 40 can be reduced. That is, in the present embodiment, the frequency of the signal As obtained by adding the signal Ay, which is the high-frequency component of the drive signal Com, to the signal Ab can be increased as compared with the case where there is no path via the terminal t2, so that the accuracy of the drive signal Com can be sufficiently ensured.

[0063] As shown in FIG. 7, one end (terminal tT1) of the thermistor TT is electrically connected to the node nT, and the other end (terminal tT2) is electrically connected to the node nG. The electrical resistance value between the terminals tT1 and tT2 of the thermistor TT is a value corresponding to the temperature of the thermistor TT. Therefore, the temperature of the thermistor TT can be specified based on the potential difference between the terminals tT1 and tT2 of the thermistor TT or the current flowing between the terminals tT1 and tT2 of the thermistor TT. In the present embodiment, as an example, it is assumed that the temperature signal Tmp supplied from the thermistor TT to the control unit 2 is a signal indicating the potential of the node nT determined based on the potential difference between the terminals tT1 and tT2 (that is, the potential difference between the node nG and the node nT). Note that the terminals tT1 and tT2 will be described later with reference to FIG. 8.

[0064] <<Configuration of Drive Signal Generation Unit 4>> The configuration of the drive signal generation unit 4 will be described below with reference to Figures 8 and 9.

[0065] Figure 8 is a plan view showing an example of the wiring pattern of the drive signal generation circuit 40 and thermistor TT in a plan view of the drive circuit board 400 on which the drive signal generation circuit 40 is provided, which is part of the drive signal generation unit 4. Note that in Figure 8, some electronic components of the drive signal generation circuit 40 are omitted from the description. Also, although Figure 8 illustrates the case where the drive circuit board 400 is provided on a plane with the Z1 direction as the normal direction, the present invention is not limited to this embodiment. The normal direction of the drive circuit board 400 may be any direction.

[0066] As shown in Figure 8, terminal tIN of integrated circuit 41 is connected to node nIN. Terminal tH of integrated circuit 41 is electrically connected to the gate electrode gt of transistor TrH via node nH, and terminal tL of integrated circuit 41 is electrically connected to the gate electrode gt of transistor TrL via node nL. Furthermore, the source electrode st of transistor TrL is electrically connected to node nG. The drain electrode dt of transistor TrL is electrically connected to the source electrode st of transistor TrH and to terminal tL1 of inductor L0 via node nD. Terminal tL2 of inductor L0 is electrically connected to terminal tC1 of capacitor C0 via node nX. Terminal tC2 of capacitor C0 is electrically connected to node nG. Furthermore, the drain electrode dt of transistor TrH is electrically connected to terminal tD1 of electrolytic capacitor Cd via node nV. Terminal tD2 of electrolytic capacitor Cd is electrically connected to node nG.

[0067] As shown in Figure 8, terminal tT1 of the thermistor TT is connected to node nT. Terminal tT2 of the thermistor TT is connected to node nG. Node nT supplies a temperature signal Tmp to the control unit 2, which indicates a value corresponding to the temperature of the thermistor TT.

[0068] As shown in Figure 8, a heat conduction element XN is arranged on the drive circuit board 400. The heat conduction element XN has terminals tX1 and tX2, which transfer heat between terminals tX1 and tX2 and electrically insulate terminals tX1 and tX2 from each other. Terminal tX1 of the heat conduction element XN is connected to node nV. Terminal tX2 of the heat conduction element XN is connected to node nT. In other words, in this embodiment, the heat conduction element XN thermally connects node nV and node nT while electrically disconnecting node nV and node nT. In this embodiment, node nV is an example of a "connection wire".

[0069] Therefore, in this embodiment, the heat generated from the drain electrode dt of transistor TrH is transmitted to the thermistor TT via node nV, the heat conduction element XN, and node nT. This makes it possible in this embodiment to use the temperature signal Tmp output from the thermistor TT as a signal that accurately represents the temperature of transistor TrH in the drive signal generation circuit 40.

[0070] Figure 9 is a cross-sectional view showing an example of the configuration of the drive signal generation unit 4. Specifically, Figure 9 is a cross-sectional view of the drive signal generation unit 4, taken when the drive circuit board 400 is viewed in the Z1 direction, with a cross section that includes a broken line passing through the transistor TrH, the heat conduction element XN, and thermistor TT.

[0071] As shown in Figure 9, the drive signal generation unit 4 comprises a drive circuit board 400, a drive signal generation circuit 40 including a transistor TrH, a thermistor TT, and a heat conductive element XN.

[0072] The drive circuit board 400 has an upper substrate surface 4001 on which the drive signal generation circuit 40 is provided, and a lower substrate surface 4002 which is the surface opposite to the upper substrate surface 4001. In this embodiment, it is assumed that the drive circuit board 400 is a multilayer substrate. Specifically, in this embodiment, the drive circuit board 400 has multiple layers between the upper substrate surface 4001 and the lower substrate surface 4002, including a surface layer 401, an insulating layer 402, a wiring layer 403, and a protective layer 404.

[0073] The surface layer 401 is a layer including the upper substrate surface 4001 and is composed of wiring 401L and resist 401R. The wiring 401L is made of a conductive material such as copper or aluminum. The resist 401R is made of an insulating resin such as epoxy resin. The insulating layer 402 is provided between the surface layer 401 and the lower substrate surface 4002, and consists of wiring 402L and an insulating portion 402R. The wiring 402L is made of a conductive material such as copper or aluminum. The insulating portion 402R is made of an insulating resin such as epoxy resin. The wiring layer 403 is provided between the insulating layer 402 and the lower substrate surface 4002, and consists of wiring 403L and an insulating portion 403R. The wiring 403L is made of a conductive material such as copper or aluminum. The insulating portion 403R is made of an insulating resin such as epoxy resin. The protective layer 404 is a layer including the lower substrate surface 4002 and is composed of an insulating resin such as epoxy resin. In this embodiment, it is assumed that the wiring pattern of the drive signal generation circuit 40 described in Figure 8 consists of wiring 401L, wiring 402L, and wiring 403L.

[0074] As shown in Figure 9, the thermistor TT comprises a thermistor body AT, terminal tT1, and terminal tT2.

[0075] The thermistor body AT is a conductive material having an electrical resistance value corresponding to the temperature of the thermistor body AT. Terminal tT1 electrically connects the thermistor body AT to the portion of node nT that is patterned as wiring 401L. Terminal tT2 electrically connects the thermistor body AT to the portion of node nG that is patterned as wiring 401L.

[0076] As shown in Figure 9, the thermal conductive element XN comprises a thermal conductive element body AN, terminal tX1, and terminal tX2.

[0077] The thermal conductive element body AN is an insulating material that has thermal conductivity. Specifically, in this embodiment, the thermal conductive element body AN has a higher thermal conductivity than any of the insulating components included in the drive circuit board 400, namely the resist 401R, the insulating part 402R, the insulating part 403R, and the protective layer 404. Furthermore, in this embodiment, the thermal conductive element body AN has a thermal conductivity of 50% or more of the thermal conductivity of each of the conductive components included in the drive circuit board 400, namely the wiring 401L, the wiring 402L, and the wiring 403L. For example, in this embodiment, aluminum nitride is used as the thermal conductive element body AN. As shown in Figure 9, in this embodiment, it is assumed that the heat conduction element body AN is positioned at a location in the Z2 direction relative to the upper substrate surface 4001, with a gap between it and the upper substrate surface 4001.

[0078] The terminal tX1 is connected to the heat conduction element main body AN and is also connected to the portion of the node nV patterned as the wiring 401L. In the present embodiment, the terminal tX1 is made of the same material as the heat conduction element main body AN. However, the terminal tX1 may be made of a material different from that of the heat conduction element main body AN. For example, the terminal tX1 may be made of a conductive material such as the same material as the wiring 401L. In addition, it is preferable that the terminal tX1 has a thermal conductivity of 50% or more of the thermal conductivity of each of the wirings 401L, 402L, and 403L. Further, it is preferable that the terminal tX1 has a higher thermal conductivity than any of the resist 401R, the insulating portions 402R and 403R, and the protective layer 404. The terminal tX2 is connected to the heat conduction element main body AN and is also connected to the portion of the node nT patterned as the wiring 401L. In the present embodiment, the terminal tX2 is made of the same material as the heat conduction element main body AN. However, the terminal tX2 may be made of a material different from that of the heat conduction element main body AN. For example, the terminal tX2 may be made of a conductive material such as the same material as the wiring 401L. In addition, it is preferable that the terminal tX2 has a thermal conductivity of 50% or more of the thermal conductivity of each of the wirings 401L, 402L, and 403L. Further, it is preferable that the terminal tX2 has a higher thermal conductivity than any of the resist 401R, the insulating portions 402R and 403R, and the protective layer 404.

[0079] <<Summary of Embodiment A.5.>> Thus, according to this embodiment, the heat generated at the drain electrode dt of the transistor TrH is transmitted to the thermistor TT via the node nV, the heat conduction element XN, and the node nT. In this embodiment, the thermal conductivity of the heat conduction element XN is higher than the thermal conductivity of insulating components such as the resist 401R in the drive circuit board 400. Therefore, according to this embodiment, the ratio of the amount of heat transmitted to the thermistor TT in the heat generated at the drain electrode dt of the transistor TrH can be increased as compared with the aspect where the heat conduction element XN is not provided. Thereby, according to this embodiment, the temperature signal Tmp output from the thermistor TT can be made a signal that accurately represents the temperature of the transistor TrH in the drive signal generation circuit 40 as compared with the aspect where the heat conduction element XN is not provided.

[0080] <<B. Modified Example>> Each of the above embodiments can be variously modified. Specific modification modes are exemplified below. Two or more modes arbitrarily selected from the following examples can be appropriately combined within a range where they do not conflict with each other. In the modified examples exemplified below, for elements whose actions and functions are equivalent to those of the embodiment, the reference numerals referred to in the above description are used, and the detailed description of each is appropriately omitted.

[0081] <<Modified Example 1>> In the above-described embodiment, the aspect in which the heat conduction element XN is connected to the node nV and the node nT has been exemplified and described, but the present invention is not limited to such an aspect. For example, the heat conduction element XN may be connected to the node nD and the node nT.

[0082] FIG. 10 is a cross-sectional view showing an example of the drive signal generation unit 4B according to this modified example.

[0083] As shown in Figure 10, the drive signal generation unit 4B differs from the drive signal generation unit 4 according to the embodiment in that it is equipped with a heat conduction element XN-B instead of a heat conduction element XN. The heat conduction element XN-B differs from the heat conduction element XN according to the embodiment in that it is connected to node nD and node nT instead of node nV and node nT. Specifically, the heat conduction element XN-B has a terminal tX1 connected to node nD and a terminal tX2 connected to node nT. The heat conduction element XN-B transfers heat between terminals tX1 and tX2, and electrically insulates terminals tX1 and tX2. In other words, in this modified example, the heat conduction element XN-B thermally connects node nT and node nD, while electrically disconnecting node nT and node nD. In this modified example, node nD is an example of a "connection wire".

[0084] Thus, in this modified configuration, the heat generated from the source electrode st of transistor TrH, the heat generated from the drain electrode dt of transistor TrL, and the heat generated from inductor L0 are transmitted to the thermistor TT via node nD, the heat conduction element XN-B, and node nT. This makes it possible to make the temperature signal Tmp output from the thermistor TT a signal that accurately represents the temperature of the transistors TrH and TrL and inductor L0, which are electronic components in the drive signal generation circuit 40 that generate a large amount of heat.

[0085] <<Modification 2>> In the embodiments and modified example 1 described above, the thermal conductive element XN (and thermal conductive element XN-B) is described as being connected to node nT for the purpose of transferring heat to the thermistor TT, but the present invention is not limited to such embodiments. For example, the thermal conductive element may be provided to dissipate heat generated in the drive signal generation circuit 40.

[0086] Figure 11 is a cross-sectional view showing an example of a drive signal generation unit 4C according to this modified example.

[0087] As shown in Figure 11, the drive signal generation unit 4C differs from the drive signal generation unit 4 according to the embodiment in that, in addition to the heat conduction element XN, it also includes a heat dissipation heat conduction element YN. The heat dissipation heat conduction element YN has terminals tY1 and tY2, which transfer heat between terminals tY1 and tY2 and electrically insulate terminals tY1 and tY2. Terminal tY1 of the heat dissipation heat conduction element YN is connected to node nV. Terminal tY2 of the heat dissipation heat conduction element YN is connected to node nG. In other words, in this modified example, the heat dissipation heat conduction element YN thermally connects node nV and node nG while electrically disconnecting node nV and node nG.

[0088] In this modified example, the heat dissipation thermal conductive element YN has the same configuration as the thermal conductive element XN. That is, in this modified example, the heat dissipation thermal conductive element YN comprises a main body made of aluminum nitride and terminals tY1 and tY2 having the same configuration as terminals tX1 and tX2.

[0089] As described above, in this modified example, the heat generated from the drain electrode dt of the transistor TrH is transmitted to node nG via node nV and the heat dissipation thermal conductive element YN, and the heat is dissipated from node nG. As a result, in this embodiment, compared to the embodiment in which the heat dissipation thermal conductive element YN is not provided, the heat generated in the drive signal generation circuit 40 can be dissipated more efficiently. In this modified example, the heat dissipation thermal conductive element YN is an example of a "second thermal conductive member", node nG is an example of "heat dissipation wiring", and node nV is an example of "connection wiring".

[0090] <<Modification 3>> In the embodiments and modifications 1 and 2 described above, the case in which the drive signal generation circuit 40 is a Class D amplifier circuit was used as an example, but the present invention is not limited to such embodiments. The drive signal generation circuit 40 may be an amplifier circuit other than a Class D amplifier circuit, for example, a Class AB amplifier circuit.

[0091] Figure 12 is a block diagram showing an example of the circuit configuration of the drive signal generation circuit 40D and thermistor TT included in the drive signal generation unit 4D according to this modified example.

[0092] As shown in Figure 12, the drive signal generation circuit 40D comprises an analog conversion circuit 41D, an amplification circuit 43D, and an electrolytic capacitor Cd, and generates a drive signal Com based on a waveform specification signal dCom. Specifically, the drive signal generation circuit 40D generates the drive signal Com by, for example, class-AB amplification of the input signal obtained by analog conversion of the waveform specification signal dCom.

[0093] The analog conversion circuit 41D outputs a waveform specification signal QB, which includes a base supply signal QBH and a base supply signal QBL, based on a digital waveform specification signal dCom. Specifically, the analog conversion circuit 41D converts the waveform specification signal dCom into an analog input signal and generates a base supply signal QBH, which is an analog signal indicating a potential based on the potential of the input signal, and a base supply signal QBL, which is an analog signal indicating a potential based on the potential of the input signal but lower than the base supply signal QBH. The analog conversion circuit 41D then outputs the base supply signal QBH to node nH from output terminal tQH and the base supply signal QBL to node nL from output terminal tQL.

[0094] The amplifier circuit 43D is a so-called push-pull circuit comprising an NPN bipolar transistor TBH and a PNP bipolar transistor TBL, and generates a drive signal Com based on the base supply signal QBH and the base supply signal QBL.

[0095] The bipolar transistor TBH has its base electrode wB electrically connected to the output terminal tQH, from which the base supply signal QBH is supplied. The collector electrode wC of the bipolar transistor TBH is electrically connected to node nV, which is set to the power supply potential VHV, and the emitter electrode wE is electrically connected to node nD, which supplies the drive signal Com. The bipolar transistor TBH turns on, for example, when the potential of the base supply signal QBH rises, thereby increasing the potential of the drive signal Com. The bipolar transistor TBH turns off, for example, when the potential of the base supply signal QBH is constant, and when the potential of the base supply signal QBH falls.

[0096] The bipolar transistor TBL has its base electrode wB electrically connected to the output terminal tQL, from which the base supply signal QBL is supplied. The bipolar transistor TBL also has its collector electrode wC electrically connected to node nG, which is set to ground potential, and its emitter electrode wE electrically connected to node nD, which supplies the drive signal Com. The bipolar transistor TBL turns on, for example, when the potential of the base supply signal QBL decreases, thereby decreasing the potential of the drive signal Com. Conversely, the bipolar transistor TBL turns off, for example, when the potential of the base supply signal QBL is constant, and when the potential of the base supply signal QBL increases.

[0097] The electrolytic capacitor Cd is a capacitor that supplies current to the amplification circuit 43D. Specifically, of the two electrodes of the electrolytic capacitor Cd, one terminal tD1 is electrically connected to node nV, which is set to the power supply potential VHV, and to the collector electrode wC of the bipolar transistor TBH, while the other terminal tD2 is electrically connected to node nG, which is set to the ground potential.

[0098] Thermistor TT has one terminal tT1 electrically connected to node nT, and the other terminal tT2 electrically connected to node nG.

[0099] Figure 13 is a plan view showing an example of the configuration of the drive signal generation unit 4D according to this modified example.

[0100] As shown in Figure 13, terminal tIN of the analog conversion circuit 41D is connected to node nIN, to which the waveform specification signal dCom is supplied. Output terminal tQH of the analog conversion circuit 41D is electrically connected to the base electrode wB of the bipolar transistor TBH via node nH, and output terminal tQL of the analog conversion circuit 41D is electrically connected to the base electrode wB of the bipolar transistor TBL via node nL. Furthermore, the collector electrode wC of bipolar transistor TBL is electrically connected to node nG. The emitter electrode wE of bipolar transistor TBL is electrically connected to the emitter electrode wE of bipolar transistor TBH via node nD. Furthermore, the collector electrode wC of the bipolar transistor TBH is electrically connected to terminal tD1 of the electrolytic capacitor Cd via node nV. Terminal tD2 of the electrolytic capacitor Cd is electrically connected to node nG.

[0101] As shown in Figure 13, terminal tT1 of the thermistor TT is connected to node nT. Terminal tT2 of the thermistor TT is connected to node nG. Node nT supplies a temperature signal Tmp, which indicates a value corresponding to the temperature of the thermistor TT, to the control unit 2.

[0102] As shown in Figure 13, terminal tX1 of the heat conduction element XN is connected to node nV. Terminal tX2 of the heat conduction element XN is connected to node nT. In other words, in this modified example, the heat conduction element XN thermally connects node nV and node nT, while electrically disconnecting node nV and node nT.

[0103] Therefore, in this modified example, the heat generated from the collector electrode wC of the bipolar transistor TBH is transmitted to the thermistor TT via node nV, the heat conduction element XN, and node nT. This makes it possible to use the temperature signal Tmp output from the thermistor TT as a signal that accurately represents the temperature of the bipolar transistor TBH in the drive signal generation circuit 40.

[0104] In this modified example, bipolar transistors TBH and TBL are examples of "two transistors," bipolar transistor TBH is an example of a "first transistor," bipolar transistor TBL is an example of a "second transistor," and node nV is an example of a "connection wire."

[0105] <<Modification 4>> In the embodiments and modifications 1 to 3 described above, the drive signal generation unit 4 is provided separately from the head unit 3 as an example; however, the present invention is not limited to this embodiment. The drive signal generation unit 4 may be mounted on the head unit 3.

[0106] Figure 14 is a functional block diagram showing an example of the configuration of the inkjet printer 1E according to this modified example.

[0107] As shown in Figure 14, the inkjet printer 1E differs from the inkjet printer 1 according to the embodiment in that it includes a head unit 3E instead of a head unit 3. The head unit 3E differs from the head unit 3 according to the embodiment in that, in addition to the supply circuit 31 and the head unit 32, it includes a drive signal generation unit 4 which includes a drive signal generation circuit 40 and a thermistor TT.

[0108] In this modified example, as in the embodiment, the temperature signal Tmp output from the thermistor TT can be used as a signal that accurately represents the temperature of the drive signal generation circuit 40.

[0109] <<Modification Example 5>> In the above-described embodiments and modification examples 1 to 4, it is assumed that the inkjet printer 1 is a serial printer, but the present invention is not limited to such a mode. The inkjet printer 1 may be a so-called line printer in which a plurality of nozzles N are provided in the head unit 3 so as to extend wider than the width of the recording paper PP. In this case, the head unit 3 does not reciprocate inside the housing 100, and the relative positional relationship between the head unit 3 and the housing 100 does not change.

[0110] <<C. Supplementary Note>> Aspects related to the above description are appended below. For the sake of easy understanding of each aspect, hereinafter, the reference numerals in the drawings are appended in parentheses for convenience, but this is not intended to limit the present invention to the illustrated aspects.

[0111] <<Supplementary Note 1>> The inkjet printer 1 according to Supplementary Note 1 includes a discharge unit D that is driven by a drive signal Com to discharge ink, a drive circuit board 400 on which a drive signal generation circuit 40 that generates the drive signal Com is disposed, a thermistor TT that is disposed on the drive circuit board 400 and detects the temperature of the drive circuit board 400, and an electrically insulating heat conduction element XN that is disposed on the drive circuit board 400 and is connected to a node nT in which one terminal tX1 is connected to the drive signal generation circuit 40 and the other terminal tX2 is electrically connected to the thermistor TT.

[0112] According to Supplementary Note 1, since the heat conduction element XN transfers the heat generated by the drive signal generation circuit 40 to the thermistor TT, the temperature of the drive signal generation circuit 40 can be detected more accurately as compared with an aspect not provided with the heat conduction element XN.

[0113] <<Supplementary Note 2>> The inkjet printer 1 according to Supplementary Note 2 is the inkjet printer 1 according to Supplementary Note 1, and the heat conduction element XN is made of aluminum nitride.

[0114] According to Appendix 2, the thermal conductive element XN can achieve both electrical insulation and thermal conductivity.

[0115] <<Note 3>> The inkjet printer 1 according to Appendix 3 is the inkjet printer 1 according to Appendix 1 or 2, characterized in that the drive signal generation circuit 40 includes an amplification circuit 43 comprising transistors TrH and TrL for amplifying an input signal including gate signals SGH and SGL to generate a drive signal Com, and one terminal tX1 of the thermal conductive element XN is connected to node nV electrically connected to transistor TrH, or node nD electrically connected to transistor TrL.

[0116] According to Appendix 3, the heat conduction element XN transfers heat generated by transistors TrH or TrL, which generate a large amount of heat in the drive signal generation circuit 40, to the thermistor TT. Therefore, compared to the configuration without the heat conduction element XN, the temperature of the drive signal generation circuit 40 can be detected more accurately.

[0117] <<Note 4>> The inkjet printer 1 according to Appendix 4 is the inkjet printer 1 according to Appendix 1 to 3, wherein the drive signal generation circuit 40 includes an amplification circuit 43 comprising transistors TrH and TrL for amplifying an input signal including gate signals SGH and SGL to generate a drive signal Com, wherein transistor TrH is electrically connected to node nV set to power supply potential VHV, transistor TrL is electrically connected to node nG set to ground potential, and one terminal tX1 of the heat conduction element XN is connected to node nV or node nD which is electrically connected to transistor TrH.

[0118] According to Appendix 4, the heat conduction element XN transfers heat generated by the transistor TrH, which generates a large amount of heat in the drive signal generation circuit 40, to the thermistor TT. Therefore, compared to the configuration without the heat conduction element XN, the temperature of the drive signal generation circuit 40 can be detected more accurately.

[0119] <<Note 5>> The inkjet printer 1 according to Appendix 5 is the inkjet printer 1 according to Appendix 1 to 4, wherein the drive signal generation circuit 40 includes an amplification circuit 43 comprising field-effect transistors transistors TrH and TrL for amplifying an input signal including gate signals SGH and SGL to generate a drive signal Com, and one terminal tX1 of the thermal conductive element XN is connected to node nV electrically connected to the drain electrode dt of transistor TrH, or to node nD electrically connected to the drain electrode dt of transistor TrL.

[0120] According to Appendix 5, the heat conduction element XN transfers heat generated by transistors TrH or TrL, which generate a large amount of heat in the drive signal generation circuit 40, to the thermistor TT. Therefore, compared to the configuration without the heat conduction element XN, the temperature of the drive signal generation circuit 40 can be detected more accurately.

[0121] <<Note 6>> The inkjet printer 1 according to Appendix 6 is the inkjet printer 1 according to Appendix 1 to 4, characterized in that the drive signal generation circuit 40 includes an amplification circuit 43 comprising field-effect transistors transistors TrH and TrL for amplifying an input signal including gate signals SGH and SGL to generate a drive signal Com, and one terminal tX1 of the thermal conductive element XN is connected to node nD which is electrically connected to the source electrode st of transistor TrH.

[0122] According to Appendix 6, the heat conduction element XN transfers heat generated by the transistor TrH, which generates a large amount of heat in the drive signal generation circuit 40, to the thermistor TT. Therefore, compared to the configuration without the heat conduction element XN, the temperature of the drive signal generation circuit 40 can be detected more accurately.

[0123] <<Note 7>> The inkjet printer 1 according to Appendix 7 is the inkjet printer 1 according to Appendix 1 or 2, characterized in that the drive signal generation circuit 40 includes an amplification circuit 43D comprising a bipolar transistor TBH and a bipolar transistor TBL for amplifying a waveform specification signal QB, which is an input signal including a base supply signal QBH and a base supply signal QBL, to generate a drive signal Com, and one terminal tX1 of the thermal conductive element XN is connected to a node nV that is electrically connected to the collector electrode wC of the bipolar transistor TBH.

[0124] According to Appendix 7, the heat conduction element XN transfers heat generated by the bipolar transistor TBH, which generates a large amount of heat in the drive signal generation circuit 40, to the thermistor TT. Therefore, compared to the configuration without the heat conduction element XN, the temperature of the drive signal generation circuit 40 can be detected more accurately.

[0125] <<Note 8>> The inkjet printer 1 according to Appendix 8 is an inkjet printer 1 according to Appendix 1 or 2, wherein the drive signal generation circuit 40 includes an amplification circuit 43D comprising bipolar transistors TBH and TBL for amplifying a waveform specification signal QB, which is an input signal including a base supply signal QBH and a base supply signal QBL, to generate a drive signal Com, and one terminal tX1 of the thermal conductive element XN is connected to the emitter electrode wE of the bipolar transistor TBH and a node nD that is electrically connected to the emitter electrode wE of the bipolar transistor TBL.

[0126] According to Appendix 8, the heat conduction element XN transfers heat generated by the bipolar transistors TBH and TBL, which generate a large amount of heat in the drive signal generation circuit 40, to the thermistor TT. Therefore, compared to the configuration without the heat conduction element XN, the temperature of the drive signal generation circuit 40 can be detected more accurately.

[0127] <<Note 9>> The inkjet printer 1 according to Appendix 9 is an inkjet printer 1 according to Appendix 1 to 8, characterized in that it comprises an electrically insulating heat dissipation heat conductive element YN, one of which terminals tY1 is connected to a drive signal generation circuit 40 and the other terminal tY2 is connected to a node nG which is a heat dissipation wiring.

[0128] According to Appendix 9, compared to the configuration without the heat conduction element XN, the heat generated by the drive signal generation circuit 40 can be dissipated more efficiently. [Explanation of Symbols]

[0129] 1... Inkjet printer, 2... Control unit, 3... Head unit, 4... Drive signal generation unit, 40... Drive signal generation circuit, 41... Integrated circuit, 43... Amplifier circuit, 44... Smoothing circuit, C0... Capacitor, Cd... Electrolytic capacitor, D... Discharge unit, L0... Inductor, TrH... Transistor, TrL... Transistor, TT... Thermistor, XN... Thermal conductive element.

Claims

1. A dispensing unit that is driven by a drive signal to dispense liquid, A circuit board on which a drive circuit that generates the aforementioned drive signal is arranged, A thermistor is placed on the circuit board and detects the temperature of the drive circuit, An electrically insulating first thermal conductive member is arranged on the circuit board, with one end connected to the drive circuit and the other end connected to wiring electrically connected to the thermistor. Equipped with, A liquid dispensing device characterized by the following features.

2. The first heat conductive member is made of aluminum nitride. The liquid dispensing device according to claim 1, characterized in that...

3. The drive circuit includes an amplification circuit comprising two transistors for amplifying the input signal to generate the drive signal. One end of the first heat conductive member is connected to a connecting wire electrically connected to at least one of the two transistors. The liquid dispensing device according to claim 1, characterized in that...

4. The two transistors mentioned above are A first transistor electrically connected to a first potential line set to a first potential, It includes a second transistor electrically connected to a second potential line set to a second potential lower than the first potential, The aforementioned transistor is the first transistor. The liquid dispensing device according to claim 3, characterized in that...

5. The aforementioned transistor is a field-effect transistor. The aforementioned connection wiring is electrically connected to the drain electrode of the field-effect transistor. The liquid dispensing device according to claim 3, characterized in that...

6. The aforementioned transistor is a field-effect transistor. The aforementioned connection wiring is electrically connected to the source electrode of the field-effect transistor. The liquid dispensing device according to claim 3, characterized in that...

7. The aforementioned transistor is a bipolar transistor. The aforementioned connection wiring is electrically connected to the collector electrode of the bipolar transistor. The liquid dispensing device according to claim 3, characterized in that

8. The aforementioned transistor is a bipolar transistor. The aforementioned connection wiring is electrically connected to the emitter electrode of the bipolar transistor. The liquid dispensing device according to claim 3, characterized in that

9. The circuit board is provided with an electrically insulating second heat conductive member, one end of which is connected to the drive circuit and the other end of which is connected to the heat dissipation wiring on the circuit board. A liquid dispensing device according to any one of claims 1 to 8, characterized in that

10. A drive unit that drives a discharge unit that discharges liquid, A drive circuit that generates a drive signal to drive the discharge unit, A circuit board on which the aforementioned drive circuit is arranged, A thermistor is placed on the circuit board and detects the temperature of the drive circuit, An electrically insulating first thermal conductive member is arranged on the circuit board, with one end connected to the drive circuit and the other end connected to wiring electrically connected to the thermistor. Equipped with, A drive unit characterized by the following features.

11. The first heat conductive member is made of aluminum nitride. The drive unit according to claim 10, characterized in that

12. The drive circuit includes an amplification circuit comprising two transistors for amplifying the input signal to generate the drive signal. One end of the first heat conductive member is connected to a connecting wire electrically connected to at least one of the two transistors. The drive unit according to claim 10, characterized in that

13. The two transistors mentioned above are A first transistor electrically connected to a first potential line set to a first potential, It includes a second transistor electrically connected to a second potential line set to a second potential lower than the first potential, The aforementioned transistor is the first transistor. The drive unit according to claim 12, characterized in that

14. The aforementioned transistor is a field-effect transistor. The aforementioned connection wiring is electrically connected to the drain electrode of the field-effect transistor. The drive unit according to claim 12, characterized in that

15. The aforementioned transistor is a field-effect transistor. The aforementioned connection wiring is electrically connected to the source electrode of the field-effect transistor. The drive unit according to claim 12, characterized in that

16. The aforementioned transistor is a bipolar transistor. The aforementioned connection wiring is electrically connected to the collector electrode of the bipolar transistor. The drive unit according to claim 12, characterized in that

17. The aforementioned transistor is a bipolar transistor. The aforementioned connection wiring is electrically connected to the emitter electrode of the bipolar transistor. The drive unit according to claim 12, characterized in that

18. The circuit board is provided with an electrically insulating second heat conductive member, one end of which is connected to the drive circuit and the other end of which is connected to the heat dissipation wiring on the circuit board. A drive unit according to any one of claims 10 to 17, characterized in that

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