JPWO2016181946A1 - Recording head drive circuit and image recording apparatus - Google Patents

Abstract

Provided is a recording head drive circuit and an image recording apparatus capable of supplying power more easily and stably to a load element of a recording head while preventing deterioration of a voltage waveform. A recording head drive circuit 30 for supplying a driving voltage corresponding to the operation of the load element to a load element such as an actuator 51 of a recording element provided in the recording head, and an analog input corresponding to the operation of the load element A voltage amplifying unit 31 that amplifies the voltage of the signal Vin to generate the driving voltage signal Vd, a current amplifying unit 33 that amplifies the current of the driving voltage signal and outputs it as the output signal Vout, and feedback according to the voltage of the output signal And a feedback unit 34 that negatively feeds back the signal to the voltage amplification unit.

Description

  The present invention relates to a recording head drive circuit and an image recording apparatus.

  Conventionally, there is an image recording apparatus that records an image on a recording medium by arranging a plurality of recording elements and operating each of the plurality of recording elements. As an image recording apparatus, there is an ink jet recording apparatus that applies pressure to ink and ejects it from a plurality of nozzles. As a mechanism for applying pressure to ink and ejecting it from the nozzle, a piezoelectric element (piezo element) or a diaphragm is provided along the wall surface of the ink flow path (pressure chamber), and voltage is applied to the piezoelectric element to deform it. A piezoelectric element that compresses and deforms the ink flow path, and a resistance element is provided along the ink flow path, and a current is passed through the resistance element to generate heat, thereby heating the ink in the ink flow path and generating bubbles. Thermal type that compresses ink by causing the ink to compress is mainly known.

  Thus, in order to eject ink droplets at an appropriate amount, shape, and speed, it is necessary that the drive voltage waveform applied to the load element such as a piezoelectric element or a resistance element has an appropriate shape. As such a drive waveform, a rectangular wave or a trapezoidal wave is mainly used. In the ink jet recording apparatus, the drive waveform data is converted to analog and appropriately amplified and applied to the load element.

  However, the electric power required for the recording head that operates the arranged recording elements is larger in voltage and current than the electric power used for signal transmission / reception of digital data. Such voltage and current amplification circuits have various bias generation factors and factors that distort the output waveform. On the other hand, Patent Document 1 discloses a technique for outputting voltage waveform data corrected in advance in consideration of the cause of voltage shift and distortion generated in the current amplifier circuit.

Japanese Patent No. 4438393

  However, voltage shifts and voltage waveform distortions do not always occur constantly. The presence / absence and size of these depend on conditions such as the temperature of each element of the circuit and the wiring. Further, in such an image recording apparatus, power is supplied to a load selected according to an ink ejection operation or a non-ejection operation among a number of loads, so that the total of the selected loads greatly changes. Can do. Therefore, in order to obtain a waveform that accurately reflects the voltage deviation and the distortion of the voltage waveform, it is necessary to acquire all these parameters and calculate the correction value, which causes a problem that the control becomes very complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a recording head drive circuit and an image recording apparatus that can supply power more easily and stably to load elements of a recording head while preventing deterioration of the voltage waveform. .

In order to achieve the above object, the present invention described in claim 1
A drive circuit for a printhead that supplies a drive voltage corresponding to the operation of the load element to a load element of a print element provided in the printhead,
A voltage amplifying unit for amplifying the voltage of the analog drive waveform signal according to the operation of the load element to generate a drive voltage signal;
A current amplifying unit that amplifies the current of the drive voltage signal and outputs it as an output signal;
A feedback unit that negatively feeds back a feedback signal corresponding to the voltage of the output signal to the voltage amplification unit;
It is characterized by having.

According to a second aspect of the present invention, in the recording head drive circuit according to the first aspect,
The feedback unit is characterized in that the voltage signal amplified by the voltage amplification unit is combined with the feedback signal and negatively fed back to the voltage amplification unit.

According to a third aspect of the present invention, in the drive circuit for a recording head according to the second aspect,
The feedback unit includes a low-pass unit, and synthesizes a low-frequency component corresponding to the characteristics of the low-pass unit in the feedback signal among the voltage signals amplified by the voltage amplification unit. Yes.

According to a fourth aspect of the present invention, in the drive circuit for a recording head according to any one of the first to third aspects,
The voltage amplifying unit performs an amplifying operation in a plurality of stages including a pre-amplifier and a post-amplifier.

According to a fifth aspect of the present invention, there is provided the recording head drive circuit according to the fourth aspect,
The pre-stage amplifying unit performs differential amplification according to the feedback signal.

A sixth aspect of the present invention is the recording head drive circuit according to the fifth aspect,
An OP amplifier is used for the pre-amplifier unit.

According to a seventh aspect of the present invention, in the drive circuit for a recording head according to any one of the fourth to sixth aspects,
The feedback unit includes a low-pass unit, and synthesizes a low-frequency component corresponding to characteristics of the low-pass unit in the feedback signal among the voltage signals voltage-amplified by the pre-amplifier unit. Yes.

According to an eighth aspect of the present invention, in the drive circuit for a recording head according to any one of the fourth to seventh aspects,
The voltage amplification unit is characterized in that a voltage amplification factor of the rear amplification unit is set larger than a voltage amplification factor of the front amplification unit.

The invention according to claim 9 is the drive circuit for a recording head according to any one of claims 1 to 8, wherein
The voltage amplification unit is configured so that a voltage amplification factor of a component having a frequency higher than a predetermined reference frequency is higher than a voltage amplification factor of a component having a frequency lower than the reference frequency.

According to a tenth aspect of the present invention, in the drive circuit for a recording head according to any one of the first to ninth aspects,
The current amplification unit is characterized in that current amplification is performed by a push-pull operation of two sets of transistors.

According to a eleventh aspect of the present invention, there is provided the recording head drive circuit according to the tenth aspect,
As the transistor, a bipolar transistor is used.

A twelfth aspect of the present invention is the recording head drive circuit according to the tenth or eleventh aspect,
The two sets of transistors are each composed of two or more transistors connected in Darlington connection.

According to a thirteenth aspect of the present invention, in the recording head drive circuit according to the twelfth aspect,
The Darlington connection is an inverted Darlington connection.

According to a fourteenth aspect of the present invention, in the recording head drive circuit according to the thirteenth aspect,
A resistance element that determines an amplification current of a transistor to which the drive voltage signal is input among the transistors connected to the inverted Darlington is provided.

According to a fifteenth aspect of the present invention, in the recording head drive circuit according to any one of the tenth to fourteenth aspects,
The drive voltage signal generated by the voltage amplification unit is added with a bias voltage that is a voltage difference equal to or greater than a minimum operation voltage difference for the two transistors of the current amplification unit to perform amplification operations. It is characterized by comprising a bias generator for supplying each of the pair of transistors.

A sixteenth aspect of the present invention is the recording head drive circuit according to the fifteenth aspect,
The bias generator includes bias transistors corresponding to the two sets of transistors, and adds the operating voltage difference of the bias transistors to the drive voltage signal as the bias voltage of the two sets of transistors. It is characterized by.

According to a seventeenth aspect of the present invention, there is provided the recording head drive circuit according to the sixteenth aspect,
The transistor that performs current amplification by the push-pull operation and the bias transistor that supplies a voltage obtained by adding the bias voltage to the transistor are thermally coupled to each other.

The invention according to claim 18 is the drive circuit of the recording head according to claim 16 or 17,
The biasing transistor and at least a part of the transistor in the current amplifying unit are characterized by being manufactured with uniform characteristics.

According to a nineteenth aspect of the present invention, in the drive circuit for a recording head according to any one of the fifteenth to eighteenth aspects,
The bias generation unit includes a constant current generation unit for making a current flowing to the element generating the bias voltage constant.

A twentieth aspect of the invention is the recording head drive circuit according to the nineteenth aspect,
The two sets of transistors are each composed of two or more transistors connected in Darlington, the Darlington connection is an inverted Darlington connection, and the drive voltage signal is the inverted Darlington connected transistor. A resistance element for determining an amplification current of the input transistor is provided, and the constant current generator generates a current equal to the amplification current of the transistor to which the drive voltage signal to which the bias voltage is added is input. It is characterized by that.

According to a twenty-first aspect of the present invention, in the recording head drive circuit according to any one of the first to twentieth aspects,
With digital / analog converter,
The analog drive waveform signal is obtained by analog-converting a digital signal related to the input drive waveform by the digital / analog conversion unit.

The invention according to claim 22
A drive circuit for a recording head according to any one of claims 1 to 21,
The recording head;
A control unit for controlling the operation of the drive circuit of the recording head;
An image recording apparatus comprising:

  According to the present invention, there is an effect that power can be supplied more easily and stably to the load element of the recording head while preventing the voltage waveform from deteriorating.

1 is a block diagram illustrating a functional configuration of an ink jet recording apparatus that is an embodiment of an image recording apparatus of the present invention. It is a block diagram which shows the structure of a drive circuit. It is a figure explaining the circuit structure of a voltage amplification part. It is a figure which shows the circuit structure of a bias voltage generation part. It is a figure which shows the circuit structure of a current amplifier. It is a figure which shows the circuit structure of a feedback part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a functional configuration of an ink jet recording apparatus which is an embodiment of the image recording apparatus of the present invention.

  The inkjet recording apparatus 1 (image recording apparatus) includes an inkjet head drive unit 100, an inkjet head 50 (recording head), a conveyance drive unit 71, an operation display unit 72, a communication unit 73, and a control unit 80. A bus 90 and the like.

  The drive unit 100 includes a drive waveform signal output unit 10, a digital / analog conversion unit 20 (DAC), a drive circuit 30, and an output selection unit 40, and ink is supplied from each nozzle of the inkjet head 50 at an appropriate timing. Is output to the actuator 51 (load element) of the selected nozzle. The drive waveform signal output unit 10 outputs digital data of a drive waveform corresponding to ink ejection or non-ejection (including interruption or termination of image recording) in synchronization with a clock signal input from an oscillation circuit (not shown). . The DAC 20 converts the drive waveform of the digital data into an analog signal and outputs it to the drive circuit 30 as an input signal Vin (analog drive waveform signal).

The drive circuit 30 amplifies the input signal Vin to a voltage value corresponding to the drive voltage of the actuator 51 to generate a drive voltage signal Vd, and further outputs an output signal Vout obtained by performing current amplification according to the current flowing through the actuator 51. Output.
The output selection unit 40 outputs a switching signal for selecting the actuator 51 that is the output target of the output signal Vout according to the pixel data of the formation target image input from the control unit 80.

  The inkjet head 50 includes a plurality of nozzles, and openings of the plurality of nozzles are arranged in a predetermined pattern on the nozzle surface. The inkjet head 50 forms an image on a recording medium by ejecting ink from the plurality of nozzles in accordance with a drive signal from the drive unit 100. The ink jet head 50 includes actuators 51 for ink ejection operations at a plurality of nozzles (recording elements). Here, a piezoelectric element is used as the actuator 51. This piezoelectric element is provided along the ink flow path to each nozzle, and is deformed by applying the drive voltage output from the drive circuit 30 to change the pressure applied to the ink in the ink flow path. In response to the pressure change, the ink is ejected from the nozzle opening at an appropriate amount, speed, and droplet shape.

  The conveyance driving unit 71 acquires the recording medium before image formation from the paper feeding unit and arranges the recording medium so as to face the nozzle surface of the inkjet head 50, and the recording medium on which the image is formed from a position facing the nozzle surface. Let it drain. When the inkjet head 50 forms an image on the surface of the recording medium by ejecting ink while moving the recording medium, the transport driving unit 71 switches between the driving voltage signal from the inkjet head 50 and the output selection unit 40. The recording medium is conveyed in time with the output of the signal. Examples of the transport driving unit 71 include a unit that places a recording medium on the outer peripheral surface of a cylindrical drum or an endless belt. Note that the recording medium acquired from the paper feeding unit is not limited to paper, and various recording media can be used. For example, cloth, ceramics, plastics, etc. can be used as the recording medium.

  The operation display unit 72 displays status information and menus related to image formation, and accepts input operations from the user. The operation display unit 72 includes, for example, a display screen by a liquid crystal panel, a driver for the liquid crystal panel, and a touch panel provided on the liquid crystal screen, and an operation corresponding to the position where the user performs a touch operation and the type of operation. A detection signal is output to the control unit 80. The operation display unit 72 may further be provided with an LED (Light Emitting Diode) lamp, a push button switch, and the like, and is used for, for example, warning display and main power supply display and operation.

The communication unit 73 performs data transmission / reception with the outside according to a predetermined communication standard.
As communication standards, TCP / IP connection related to communication using a LAN (Local Area Network) cable, wireless LAN (IEEE802.11), Bluetooth (registered trademark), or other short-range wireless communication (IEEE802.15, etc.) or USB Various known methods such as (Universal Serial Bus) connection can be used, and the communication unit 73 includes a connection terminal according to a communication standard that can be used and a hardware (network card) of a driver related to communication connection.

  The control unit 80 controls the overall operation of the inkjet recording apparatus 1. The control unit 80 includes a CPU 81 (Central Processing Unit), a RAM 82 (Random Access Memory), a storage unit 83, and the like. The CPU 81 performs various arithmetic processes related to overall control of the inkjet recording apparatus 1. The RAM 82 provides a working memory space to the CPU 81 and stores temporary data. The storage unit 83 stores a control program executed by the CPU 81, setting data, and the like, and temporarily stores image data to be formed. The storage unit 83 includes a volatile memory such as a DRAM and a non-volatile storage medium such as an HDD (Hard Disk Drive) or a flash memory, and is used properly according to the application.

  The bus 90 is a communication path that transmits and receives data by connecting these components.

Next, the configuration of the drive unit 100 will be described in detail.
FIG. 2 is a block diagram illustrating a functional configuration of the drive unit 100.
Here, the resistor 51 and the capacitor are connected in series as the actuator 51 and are schematically displayed. However, the actuator 51 may be connected in parallel as appropriate according to the actual actuator 51, or may include a coil component. .

  The drive waveform signal output unit 10 includes a controller 11 and a storage unit 12. The controller 11 reads out a digital value corresponding to a change in drive voltage of a drive waveform signal output in synchronization with the clock signal from the storage unit 12 and sequentially outputs it. The storage unit 12 is a nonvolatile memory that holds waveform pattern data of drive waveform signals that can be output by the inkjet recording apparatus 1. This digital value is converted into an analog voltage value by the DAC 20 and becomes an analog signal with a continuous voltage change.

  The DAC 20 is a well-known digital / analog converter, and is provided with a low-pass filter that continuously changes between the discrete values as necessary according to the sampling frequency, the number of bits, etc. of the input digital discrete values. It may be done.

  The output selection unit 40 acquires each pixel data of the image data to be recorded from the control unit 80 in synchronization with the clock signal, and outputs each actuator of the output signal from the drive circuit 30 by a switching signal corresponding to the pixel data. The switching element which switches whether output to 51 is possible or not is provided. Although the pixel data is not particularly limited, here, it is binary data indicating only whether ink is ejected or not, and the output selection unit 40 holds it in raster units in which the ink ejection operation is performed within the same clock cycle. Then, on / off of the switching element is switched according to the binary value. The number of actuators 51 and switching elements corresponding to one drive circuit 30 is, for example, 256 or 1024. Therefore, the more switching elements that are turned on, the more output signals from the drive circuit 30 are supplied (applied). The total load of the actuator 51 is increased.

  The DC voltage conversion unit 60 performs DC / DC conversion of the power supply voltage Vdd into a stable supply voltage Vp and outputs it. Here, the power supply voltage Vdd may be equal to the supply voltage Vp, but is preferably as small as possible within a range in which the signal output to the actuator 51 is not distorted. When the power supply voltage Vdd and the supply voltage Vp are equal, the DC voltage converter 60 may not be provided. The power supply voltage Vdd is supplied from an external power supply (not shown).

  The drive circuit 30 includes a voltage amplifying unit 31, a bias voltage generating unit 32 (bias generating unit), a current amplifying unit 33, a feedback unit 34 (feedback unit), and the like. The driving circuit signal input from the DAC 20 is an actuator. The voltage and current suitable for driving 51 are converted so as to be output.

  The voltage amplifying unit 31 includes a front-stage amplifying unit 311 using an OP amplifier (op-amp) and a rear-stage amplifying unit 312 using a bipolar transistor, and amplifies the driving voltage by two-stage (a plurality of stages) amplification.

FIG. 3 is a diagram illustrating the circuit configuration of the voltage amplification unit 31.
The input signal Vin output from the DAC 20 is input to the non-inverting input of the OP amplifier 311a of the pre-amplifier 311. The feedback signal from the feedback unit 34 is input to the inverting input of the OP amplifier 311a. In this way, differential amplification is performed by the pre-amplifier 311 to stabilize the output voltage. The signal amplified by the OP amplifier 311 a is sent to the feedback unit 34 and also sent to the subsequent stage amplification unit 312.

  The post-stage amplifier 312 further amplifies the voltage signal amplified by the OP amplifier 311a by providing the npn transistor Tr11 and the pnp transistor Tr12 with the emitter grounded between the supply voltage Vp and the ground voltage, respectively. Here, assuming that the amplification factor in the npn transistor Tr11 is 1, that is, voltage amplification is not performed, the resistance values of the resistance element R11 and the resistance element R12 are set to be equal to each other, and these resistance values are appropriately set. This suppresses a decrease in the frequency characteristics of the output voltage (the collector voltage of the npn transistor Tr11). The pnp transistor Tr12 amplifies the voltage as much as possible between the supply voltage Vp and the ground voltage according to the ratio of the resistance values of the resistance element R13 and the resistance element R14, and outputs the drive voltage signal Vd. Here, a resistor element R15 and a capacitor C11 connected in series are connected in parallel to the resistor element R14, and among the input voltage signals, a high frequency equal to or higher than a reference frequency determined by the combined resistance of the resistor elements R14 and R15. For the fluctuation component, the resistance value on the emitter ground side is lowered to the combined resistance of the resistance elements R14 and R15. Thereby, the voltage gain in the high frequency band is higher than the voltage gain in the low frequency band.

Here, in the ink jet recording apparatus 1 of the present embodiment, the voltage amplification factor by the post-stage amplification unit 312 is set larger (higher) than the voltage amplification factor by the pre-stage amplification unit 311. That is, the voltage amplification factor G2 obtained by amplification using the bipolar transistor by the grounded emitter in the rear stage amplification unit 312 is the voltage amplification factor G1 using the OP amplifier 311a in the previous stage amplification unit 311 (including the feedback effect by the feedback unit 34). A closed-loop gain, which is a magnification of the output voltage amplitude from the OP amplifier 311a with respect to the input voltage amplitude to the OP amplifier 311a, and a value obtained by dividing the voltage amplification factor Vout / Vin in the entire drive circuit 30 by the voltage amplification factor G2. Is set to be greater than).
In this way, by suppressing the voltage amplification factor G1 so that the output voltage of the OP amplifier 311a has a smaller amplitude range than the supply voltage to the OP amplifier 311a, distortion of the output signal of the OP amplifier 311a can be prevented, The signal of the drive circuit 30 is stabilized. On the other hand, the voltage amplification factor G2 by the post-stage amplifying unit 312 is determined so that the output voltage has a voltage amplitude close to the supply voltage Vp, so that the amplification can be efficiently performed without increasing the supply voltage Vp. However, if the voltage gain G2 is too large, the gain in the high frequency band decreases, so that the waveform can be compensated without distortion by increasing the voltage gain in the high frequency band as described above. The voltage amplification factor G <b> 2 by the latter stage amplification unit 312 is set, and the remainder is amplified by the previous stage amplification unit 311. A bipolar transistor corresponding to a high voltage and a high slew rate is appropriately selected. The same applies to the bipolar transistors used in the components subsequent to the post-stage amplifier 312. In order to secure the gain in the high frequency band, it is preferable that the input capacity of the bipolar transistor is small.

  The bias voltage generator 32 adds a bias voltage to the drive voltage signal Vd obtained by the voltage amplifier 31 with respect to the base voltages input to the two transistors for push-pull operation used in the current amplifier 33, respectively. Thus, the ON state of the transistor of the current amplifying unit 33 is appropriately maintained and the current during idling is reduced.

FIG. 4 is a diagram showing a circuit configuration of the bias voltage generator 32.
The bias voltage generator 32 includes an npn transistor Tr21, a pnp transistor Tr22, and constant current circuits Ic1 and Ic2 (constant current generator).
Each of the npn transistor Tr21 and the pnp transistor Tr22 (collectively referred to as a bias transistor) forms an emitter follower. The pnp transistor Tr22 outputs a high-voltage side drive voltage signal Vdh higher than the voltage value of the drive voltage signal Vd to the current amplifying unit 33 (that is, the minimum operating voltage difference for amplification operation) to the current amplification unit 33, and the npn transistor Tr21. Outputs a low-voltage side drive voltage signal Vdl having a base-emitter voltage lower than the voltage value of the drive voltage signal Vd to the current amplifier 33. That is, the voltage difference between the high-voltage drive voltage signal Vdh and the low-voltage drive voltage signal Vdl is twice the base-emitter voltage. As a result, a base voltage obtained by adding a bias voltage corresponding to the base / emitter voltage of each of the two transistors in the push-pull circuit used in the current amplifying unit 33 as described later (that is, a base / emitter voltage). And supplying an appropriate base current to keep these transistors on and reduce the idling current of the two transistors in the push-pull circuit.

  In the bias voltage generator 32, a constant current circuit Ic2 is connected between the emitter terminal of the pnp transistor Tr22 and the supply voltage Vp, and a constant current circuit Ic1 is connected between the emitter terminal of the npn transistor Tr21 and the ground voltage. It is connected. The constant current circuits Ic1 and Ic2 keep the collector / emitter currents of the pnp transistor Tr22 and the npn transistor Tr21 substantially constant regardless of the voltage value of the input drive voltage signal Vd. This prevents the base / emitter voltage from changing.

  A known circuit is used for the constant current circuits Ic1 and Ic2. In this example, two npn transistors are used, and a constant current circuit is used in which the current flowing through the resistor on the current output side, that is, the voltage drop is maintained to be equal to the base-emitter voltage of the corresponding npn transistor. However, the present invention is not limited to this.

  The current amplifying unit 33 is based on the high voltage side driving voltage signal Vdh and the low voltage side driving voltage signal Vdl obtained by adding a bias voltage to the driving voltage signal Vd obtained by the voltage amplifying unit 31 by the bias voltage generating unit 32. Current output is amplified to generate an output signal Vout. The output signal Vout is output to the actuator 51 via the output selection unit 40.

FIG. 5 is a diagram illustrating a circuit configuration of the current amplifying unit 33.
The current amplifying unit 33 is a push-pull circuit (SEPP) of an emitter follower, and each bipolar transistor (npn transistor Tr31 and pnp transistor Tr32) constituting the emitter follower is further provided with one bipolar transistor (pnp). Transistor Tr33 and npn transistor Tr34) are connected by inverted Darlington to increase the current amplification factor. The current amplifying unit 33 is connected to the npn transistor Tr31 to which the high-voltage drive voltage signal Vdh is input to the base terminal, the pnp transistor Tr32 to which the low-voltage drive voltage signal Vdl is input to the base terminal, and the inverted Darlington connection to the npn transistor Tr31. Pnp transistor Tr33, an npn transistor Tr34 connected to the pnp transistor Tr32 by an inverted Darlington connection, a resistance element R31 provided between the collector terminal of the npn transistor Tr31 and the supply voltage Vp, and a collector terminal of the pnp transistor Tr32 Resistance element R32 provided between the power supply and the ground voltage, and a resistance element R33 and a resistance element R34 for reducing the current during standby, and the emitter of the pnp transistor Tr33 Tha terminal connected to the supply voltage Vp, the emitter terminal of the npn transistor Tr34 is grounded.

  Thus, the npn transistor Tr31 and the pnp transistor Tr32 are preliminarily applied with a bias voltage and input to the base terminal. Therefore, the output signal Vout corresponding to the push-pull operation from the current amplifying unit 33 corresponding to the input signal Vin is maintained and the output voltage waveform is prevented from being distorted. Since the voltage increase / decrease by the bias voltage increases / decreases with the base / emitter voltage of the npn transistor Tr31 and the pnp transistor Tr32, respectively, the voltage of the drive voltage signal Vd finally output from the voltage amplification unit 31 and An output signal Vout having substantially the same voltage is supplied to the actuator 51.

  The resistance elements R31 and R32 keep the amplification current (emitter current) of the npn transistor Tr31 and the pnp transistor Tr32 substantially constant. As a result, the idling current is reduced while suppressing the distortion of the waveform of the output signal Vout. That is, if the collector current (emitter current) of the pnp transistor Tr33 and npn transistor Tr34 is excessively reduced during idling, the emitter current (collector current) of the npn transistor Tr31 and pnp transistor Tr32 becomes further minute correspondingly, and is close to zero. Although it adversely affects the operation of the current amplifying unit 33, particularly the signal output in the high frequency band, the collector currents of the pnp transistor Tr33 and the npn transistor Tr34 can be reduced while preventing this. Further, by using the inverted Darlington connection, the high-voltage side drive voltage signal Vdh and the low-voltage side output from the bias voltage generating unit 32 according to the number of connection stages as in the normal Darlington connection while improving the current amplification factor. Since there is no need to increase the voltage difference from the drive voltage signal Vdl, the maximum voltage amplitude (gain) that can be output is not reduced. As a result, the margin necessary for the supply voltage Vp does not become larger than the maximum voltage amplitude of the output signal Vout, so that the idling current is not increased more than necessary.

  The npn transistor Tr31 and the pnp transistor Tr32 used here, and the npn transistor Tr21 and the pnp transistor Tr22 used in the bias voltage generation unit 32 corresponding to them are preferably manufactured with uniform characteristics. . In other words, the electrical characteristics such as the base-emitter voltage and the DC current amplification factor are aligned to generate surplus current according to changes in the bias value due to temperature changes accompanying changes in the amplification current, waveform distortion, and heat. Runaways are prevented. Transistors manufactured with such characteristics are supplied (sold) as a package on the assumption that a plurality (two, etc.) of transistors are used in pairs. Of these transistors, those having different polarities may be complementary. Alternatively, it is possible to simply measure the electrical characteristics of each transistor and use a transistor that matches at a predetermined reference level or higher.

  Furthermore, it is preferable that at least a part of the biasing transistor and the transistor corresponding to the biasing transistor and the corresponding transistor in the current amplifying unit 33 are joined by a predetermined member and thermally coupled. As the predetermined member, a member having high thermal conductivity is preferably used. Corresponding transistors may be formed together on the same substrate.

In the current amplifying unit 33, resistance elements R33 and R34 having a small resistance value are selected so as not to increase the impedance of the output signal Vout.
In addition to the output to the output selection unit 40, the output signal Vout is output (feedback) to the feedback unit 34 as a feedback signal.

  The feedback unit 34 receives the output of the OP amplifier 311a in the voltage amplifying unit 31 and the output signal Vout as a feedback signal, and after adjusting the voltage and frequency band according to the gain, is input to the inverting input of the OP amplifier 311a. Entered.

FIG. 6 is a diagram illustrating a circuit configuration of the feedback unit 34.
The feedback unit 34 includes resistance elements R41, R42, R43 and a capacitor C41.

  The resistance elements R41 and R42 divide the voltage between the output signal Vout and the ground voltage. The divided voltage signal is combined with the voltage signal related to the output of the OP amplifier 311a and input to the inverted output of the OP amplifier 311a. Therefore, the ratio of the resistance values of the resistance elements R41 and R42 is determined according to the voltage amplification factor in the voltage amplification unit 31.

  The output of the OP amplifier 311a is combined with the voltage signal related to the output signal Vout via the resistor element R43 and the capacitor C41 provided in parallel, and returned to the inverting input of the OP amplifier 311a. The resistor element R43 and the capacitor C41 constitute a low-pass filter (low-pass unit, LPF), and the low-frequency component in the output signal of the OP amplifier 311a is superimposed on the output signal Vout by this low-pass filter. It is said. As a result, the phase difference between the inverting input and the non-inverting input due to the negative feedback and the oscillation related to the influence of the frequency component less than the response time of the voltage corresponding to the negative feedback are prevented and included in the output signal Vout. The OP amplifier 311a outputs an appropriate waveform signal in which the influence of the delay component, that is, the capacitive component of the actuator 51, is reduced and the linear response of the output signal Vout is lowered, that is, distortion is suppressed.

As described above, the inkjet recording apparatus 1 of the present embodiment includes the drive circuit 30 that supplies the drive voltage corresponding to the operation of the actuator 51 to the actuator 51 (piezoelectric element) of the nozzle provided in the inkjet head 50. The drive circuit 30 includes a voltage amplifier 31 that amplifies the voltage of the input signal Vin obtained by converting the drive waveform of digital data corresponding to the operation of the actuator 51 into an analog signal and generates the drive voltage signal Vd, and a drive voltage A current amplifying unit 33 that amplifies the current of the signal Vd and outputs it as an output signal Vout, and a feedback unit 34 that negatively feeds back a feedback signal corresponding to the voltage of the output signal Vout to the voltage amplifying unit 31 are provided.
Thus, the waveform of the output signal Vout can be appropriately amplified to a desired voltage amplitude without being distorted from the waveform of the input signal Vin. Accordingly, it is possible to supply power (that is, a voltage waveform with less distortion and a sufficient current) more easily and stably to the load element (actuator 51) of the inkjet head 50 while preventing the voltage waveform from deteriorating. Accordingly, the inkjet head 50 is appropriately operated so that the recorded image does not deteriorate in image quality.

  Further, the feedback unit 34 synthesizes the voltage signal amplified by the voltage amplification unit 31 into a feedback signal and causes the voltage amplification unit 31 to perform negative feedback. As a result, the output signal Vout having a more accurate and stable voltage waveform can be finally suppressed by more accurately suppressing the influence of disturbance such as delay of the feedback signal due to the capacitive component of the actuator 51, power loss and fluctuation of the supply voltage Vp. Can be output.

  In addition, the feedback unit 34 includes a resistance element R43 and a capacitor C41 that form a low-pass section, and a low-frequency component corresponding to the characteristics of the low-pass section is included in the voltage signal that has been voltage amplified by the voltage amplification section 31. The feedback signal is combined and negatively fed back to the voltage amplifier 31. Thereby, the response characteristic with respect to the high frequency component can be adjusted, the oscillation of the signal in the drive circuit 30 can be prevented, and the output signal can be further stabilized.

  In addition, the voltage amplification unit 31 performs an amplification operation in a plurality of stages including the front stage amplification unit 311 and the rear stage amplification unit 312. Therefore, since the voltage amplification factor can be increased as a whole without forcibly increasing the amplification factor of each stage, waveform distortion can be suppressed. In addition, it corresponds to a slew rate (for example, about 100 V / μs depending on a rise time of about 0.5 μsec) required for a voltage difference of a high voltage (for example, 40 to 50 V) used in the inkjet head 50. Easy to form an amplifier circuit. On the other hand, it is difficult for the OP amplifier 311a to provide a large slew rate corresponding to the case where a large voltage amplitude related to the above-described high voltage is required. That is, it is difficult for the OP amplifier 311a to output a signal with a large voltage amplitude accompanied by a waveform pattern that changes voltage at high speed. Therefore, the voltage amplifier 31 can amplify the voltage with a desired waveform while suppressing the distortion of the waveform by combining the amplification using the OP amplifier 311a and the amplification using the bipolar transistor.

  The pre-amplifier 311 performs differential amplification according to the feedback signal. Therefore, as described above, the input signal Vin can be appropriately corrected to obtain a stable and accurate output signal Vout.

  In addition, the OP amplifier 311a is used for the pre-stage amplifier 311 so that differential amplification can be easily performed and oscillation of the differential amplification can be suppressed to obtain a more stable output signal Vout.

  Further, the feedback unit 34 includes a resistance element R43 and a capacitor C41 that form a low-pass section, and a low-frequency component corresponding to the characteristics of the low-pass section is included in the voltage signal that has been voltage-amplified by the pre-stage amplifier 311. Combined with the feedback signal. Therefore, it is possible to adjust the response characteristic with respect to the high frequency component, and in particular, to prevent the oscillation due to the amplification operation of the OP amplifier 311a and to stabilize the output signal.

  In the voltage amplification unit 31, the voltage amplification factor G <b> 2 of the rear amplification unit 312 is determined to be larger than the voltage amplification factor G <b> 1 of the front amplification unit 311. Therefore, it is possible to cause the pre-amplifier 311 to function by giving priority to the improvement of the stability related to the feedback described above, and it is possible to effectively amplify the voltage by the post-amplifier 312.

  Further, the voltage amplification unit 31 is configured such that the voltage amplification factor of a component having a frequency higher than a predetermined reference frequency is higher than the voltage amplification factor of a component having a frequency lower than the reference frequency. Therefore, the amplification factor on the high frequency side, which is likely to be lowered by applying feedback, is improved, and while accurately amplifying and outputting the distortion of the drive waveform with a lot of high frequency components such as a rectangular wave and a trapezoidal wave, the output is performed. The stability of 30 can be improved.

  Further, since the current amplifying unit 33 performs current amplification by push-pull operation of two sets of transistors, an output obtained by performing current amplification while maintaining a driving waveform more efficiently while suppressing idling current than amplification by one transistor. A signal Vout can be generated.

  Further, a bipolar transistor is used as the transistor used in the current amplifying unit 33, so that a voltage amplitude that can be secured with respect to the power supply voltage can be secured wider than that of the FET. Accordingly, the power consumption can be further reduced by setting the power supply voltage lower than that of the FET.

  Further, since the two sets of transistors used in the current amplifying unit 33 are each composed of two or more transistors connected in Darlington, the current can be stably amplified greatly with an easy circuit configuration.

  Further, by using the inverted Darlington connection as the Darlington connection, an increase in the bias voltage can be suppressed as compared with the normal Darlington connection. Therefore, it is possible to efficiently increase the current amplification factor while suppressing an increase in the power supply voltage related to the increase in the bias voltage. In addition, since the current related to the operation of the bias voltage generator 32 can be suppressed, the power consumption can be suppressed. Further, by combining the inverted Darlington connection and the feedback of the output signal Vout, current amplification can be efficiently performed while suppressing the ease of oscillation.

  In addition, the resistance is determined so as to determine the emitter currents of the npn transistor Tr31 and the pnp transistor Tr32 to which the drive voltage signal Vd (the high-voltage side drive voltage signal Vdh and the low-voltage side drive voltage signal Vdl) is input among the transistors connected by the inverted Darlington connection. Since the elements R31 and R32 are provided, an appropriate current amplification factor can be maintained regardless of the input voltage. As a result, no more current than necessary is passed. In particular, by supplying an appropriate minute current to the resistance elements R31 and R32, the emitter currents of the npn transistor Tr31 and the pnp transistor Tr32 can be maintained even when the idling current of the pnp transistor Tr33 and the npn transistor Tr34 is reduced to the limit. Accordingly, it is possible to appropriately maintain the waveform (frequency characteristic) of the output signal Vout while reducing current consumption by reducing the idling current.

  Further, with respect to the drive voltage signal Vd generated by the voltage amplifying unit 31, a voltage difference equal to or greater than the minimum base / emitter voltage (operation voltage difference) for the two transistors of the current amplifying unit 33 to perform the amplifying operation. A bias voltage generator 32 is provided to which a certain bias voltage is added and supplied to the two sets of transistors. As a result, a situation in which the output signal Vout from the current amplifying unit 33 is not turned off does not occur, so that the distortion of the output signal Vout related to the on / off switching can be prevented.

  The bias voltage generator 32 includes an npn transistor Tr21 and a pnp transistor Tr22 as bias transistors respectively corresponding to the two sets of transistors related to the above-described push-pull operation, and a base-emitter voltage of the bias transistor. Is added to the drive voltage signal Vd as the bias voltage of the two sets of transistors described above, thereby generating and outputting the high-voltage drive voltage signal Vdh and the low-voltage drive voltage signal Vdl. Thus, unlike the case where a fixed value is used as a bias voltage using a diode or a resistance element, an appropriate bias voltage can be set according to the operation of the transistor of the current amplifying unit 33 and the heat generated by the operation. Therefore, it is possible to appropriately reflect the bias voltage that changes according to the heat generation (temperature), to prevent unnecessary heat generation and current consumption, and to suppress the occurrence of thermal runaway. Also, by setting the bias voltage as described above, since the output signal Vout from the current amplifying unit 33 is not turned off, it is not necessary to set the bias voltage larger than necessary, so that the idling current can be reduced.

  In addition, a transistor that performs current amplification by a push-pull operation in the current amplifying unit 33, and a bias transistor that supplies a high-voltage side drive voltage signal Vdh and a low-voltage side drive voltage signal Vdl obtained by adding a bias voltage to the transistor, Are combined. Thereby, the temperature of the corresponding transistors is kept substantially the same, and the offset of the bias voltage due to the temperature change according to the heat generated during the operation of the corresponding transistors between the bias voltage generation unit 32 and the current amplification unit 33. It is possible to suppress power consumption and stably reduce power consumption.

  The npn transistor Tr21 and pnp transistor Tr22 of the bias voltage generator 32 and the npn transistor Tr31 and pnp transistor Tr32 (including the pnp transistor Tr33 and npn transistor Tr34 as necessary) in the current amplifier 33 have characteristics. In other words, it is possible to use products that are manufactured in a uniform manner, that is, those that have complementary polarity, those that are complementary, those that are sold in the same package and those that have the same polarity, and that are matched. Electrical characteristics such as emitter-to-emitter voltage can be aligned. As a result, it is possible to more effectively prevent an unnecessarily large amount of current from locally flowing in accordance with changes in current and temperature, and further accompanying oscillation and thermal runaway.

  Further, the bias voltage generator 32 includes constant current circuits Ic1 and Ic2 for making constant currents flowing to the npn transistor Tr21 and the pnp transistor Tr22 that generate the bias voltage. As a result, the bias voltage can be kept constant by suppressing the change in the amount of current according to the voltage change of the input drive voltage signal Vd. In addition, this makes it possible to generate and output an output signal Vout with less distortion while efficiently reducing power consumption by limiting the amount of current to an appropriate minimum amount.

In addition, the two sets of transistors related to the push-pull operation in the current amplifying unit 33 are configured by two or more transistors each connected in Darlington, and the Darlington connection is an inverted Darlington connection, and the inverted Darlington connection. The resistance elements R31 and R32 determine the emitter currents of the npn transistor Tr31 and the pnp transistor Tr32 to which the driving voltage signal Vd (the high-voltage driving voltage signal Vdh and the low-voltage driving voltage signal Vdl) is input, respectively, among the connected transistors. Each of the emitters of the pnp transistor Tr32 and the npn transistor Tr31 to which the low-voltage side drive voltage signal Vdl and the high-voltage side drive voltage signal Vdh to which a bias voltage is applied is input to the constant current circuits Ic1 and Ic2, respectively. Over current to generate a (collector current) equal current. Here, the equal current means the accuracy of the current that can be set by the constant current circuits Ic1 and Ic2, the fluctuation of the current allowed by the constant current circuits Ic1 and Ic2, the error of the resistance elements R33 and R34, the npn transistor Tr31, This means a range that can be set in consideration of an error that can occur depending on various factors, such as a change in bias voltage that cannot be eliminated by the pnp transistor Tr32.
As a result, the base / emitter voltage in the transistor of the current amplifying unit 33 and the base / emitter voltage in the bias voltage generating unit 32 can be equalized. An output signal Vout with less distortion can be generated and output while reducing power consumption well.

  Further, the DAC 20 is provided, and the input signal Vin is obtained by analog conversion of the input digital signal related to the drive waveform by the DAC 20. Therefore, the input signal Vin can be generated easily and stably.

  The inkjet recording apparatus 1 according to the embodiment of the image recording apparatus of the present invention includes a drive circuit 30, an inkjet head 50, and a control unit 80 that controls the operation of the drive circuit 30. Accordingly, while preventing deterioration of the voltage waveform, power is more easily and stably supplied to the load (actuator 51) of the inkjet head 50, and the ink image is ejected accurately and appropriately, thereby stabilizing the image quality of the formed image. Can be improved.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above embodiment, the output of the OP amplifier 311a and the output of the current amplifying unit 33 are combined and fed back to the OP amplifier 311a via the feedback unit 34. Absent. However, when an OP amplifier is used as the voltage amplification unit 31, it is more preferable to feed back the output of the OP amplifier 311a from the viewpoint of preventing oscillation.

  In the above embodiment, as the voltage amplification unit 31, the front stage amplification unit 311 using the OP amplifier 311a and the rear stage amplification unit 312 using the bipolar transistor are combined, but the voltage amplification unit 31 is not limited to two stages. There may be one stage or a plurality of stages of three or more stages. Further, the circuit configuration is not limited to the same as the above embodiment. An FET or the like may be used. Further, voltage amplification may be performed without using the OP amplifier 311a. In this case, for example, a differential amplifier circuit may be configured using only bipolar transistors. Further, when the OP amplifier 311a is not used, a configuration in which the drive voltage signal Vd output from the post-stage amplifier 312 is output to the feedback unit 34 can be assumed.

  In the above-described embodiment, only the low frequency component of the output of the OP amplifier 311a is selectively fed back. The presence / absence and range of the frequency selection are appropriately determined in various conditions such as the ink ejection frequency of the inkjet recording apparatus 1. It only has to be set.

  Further, the voltage amplification factors of the pre-amplifier 311 and the post-amplifier 312 may be appropriately set according to the required total voltage amplification factor, the number of amplification stages, and the like.

  Similarly, the frequency dependency of the voltage amplification factor in the voltage amplification unit 31 depends on the relationship between the gain characteristics with respect to the frequencies of the pre-amplification unit 311 and the post-amplification unit 312 and the ink ejection frequency of the inkjet recording apparatus 1. Accordingly, the gain can be appropriately changed. If a sufficient gain can be obtained without increasing the amplification factor of the high frequency component, it is not necessary to set the amplification factor of the high frequency component high. Conversely, the amplification factor may be changed more finely for each frequency according to the gain characteristics.

  In the above embodiment, the current amplifying unit 33 is configured using a bipolar transistor. However, an FET may be used, or a field effect transistor (FET) and a bipolar transistor may be used in combination. However, it is easier to ensure a wide voltage amplitude between the supply voltage Vp and the ground voltage by using a bipolar transistor than by using an FET. That is, it is not necessary to set the supply voltage Vp higher than the required voltage amplitude, and as a result, the power consumption related to the idling current can be reduced.

  Further, the transistor is not limited to the inverted Darlington connection in two stages, but may be connected in three or more stages, or a normal Darlington connection may be made. Further, other well-known amplifier circuit configurations different from the Darlington connection may be used as long as the accuracy and stability of the output signal can be maintained.

  In the above embodiment, the bias voltage is generated in the bias voltage generation unit 32 by using a bipolar transistor of the same package or complementary as the bipolar transistor used in the current amplification unit 33. However, the diode, LED, resistor A bias voltage may be generated using an element or the like or in combination. In this case, in order to prevent thermal runaway, it is necessary to give a slight margin to the set bias voltage or to change the bias voltage according to the temperature state.

  In the above embodiment, the bipolar transistors of the same package and / or complementary used in the bias voltage generating unit 32 and the current amplifying unit 33 are thermally coupled. However, they must be thermally coupled. is not.

  In the above-described embodiment, the collector currents of the npn transistor Tr21 and the pnp transistor Tr22 in the bias voltage generation unit 32, that is, the base current (bias current) are kept substantially uniform using the constant current circuits Ic1 and Ic2. However, as these constant current circuits Ic1 and Ic2, other known constant current circuits may be used, or a simple adjustment of the bias current using a resistance element or the like may be used.

  In the above embodiment, the DAC 20 converts the digital signal related to the drive waveform to analog and amplifies the voltage and current. However, the analog signal is acquired from the outside, and the analog signal is simply amplified and output. Alternatively, on the contrary, the DAC 20 and the drive circuit 30 may be provided together on the same substrate (chip). Further, the drive waveform signal output unit 10 may also be provided on the same substrate (chip) as the drive circuit 30.

  In the above embodiment, only the ink ejection is switched. However, the ink ejection amount may be switched in a plurality of stages. In this case, the number of types of drive waveforms can be increased, or ink can be ejected once by combining a plurality of drive waveforms.

  In the above embodiment, a piezoelectric ink jet recording apparatus using a piezoelectric element as a load element has been described as an example. However, a thermal ink jet that applies pressure by bubbling ink by heat generated by a resistance element or the like. The present invention can also be applied to a recording apparatus. In the case of using the piezo type, the influence of the capacitive load of the piezoelectric element is more likely to appear on the feedback signal than the thermal type, and therefore the output signal Vout and the output voltage signal of the OP amplifier 311a are combined and negatively fed back. The effect of improving the stability due to this tends to become more prominent.

  In the above embodiment, the inkjet recording apparatus in which nozzles for ejecting ink are arranged as recording elements has been described as an example. However, other images that record images by operating a plurality of arranged recording elements are described. The present invention can also be applied to a recording apparatus such as an LED printer.

The circuit configuration described above is a basic part, and a resistor element, a capacitor, and the like can be provided at various well-known locations in order to stabilize the signal.
In addition, the specific details shown in the above embodiment can be appropriately changed without departing from the gist of the present invention.

  The present invention can be used in a recording head drive circuit and an image recording apparatus.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 10 Drive waveform signal output part 11 Controller 12 Memory | storage part 20 DAC (digital / analog converting part)
DESCRIPTION OF SYMBOLS 30 Drive circuit 31 Voltage amplification part 32 Bias voltage generation part 33 Current amplification part 34 Feedback part 40 Output selection part 50 Inkjet head 51 Actuator 60 DC voltage conversion part 71 Conveyance drive part 72 Operation display part 73 Communication part 80 Control part 81 CPU
82 RAM
83 Storage unit 90 Bus 100 Drive unit 311 Preamplifier 311a OP amplifier 312 Postamplifier C11, C41 Capacitors Ic1, Ic2 Constant current circuits R11-R15, R31-R34, R41-R43 Resistive elements Tr11, Tr12, Tr21, Tr22, Tr31 to Tr34 Transistor Vd Drive voltage signal Vdd Power supply voltage Vdh High side drive voltage signal Vdl Low side drive voltage signal Vin Input signal Vout Output signal Vp Supply voltage

Claims (22)

A drive circuit for a printhead that supplies a drive voltage corresponding to the operation of the load element to a load element of a print element provided in the printhead,
A voltage amplifying unit for amplifying the voltage of the analog drive waveform signal according to the operation of the load element to generate a drive voltage signal;
A current amplifying unit that amplifies the current of the drive voltage signal and outputs it as an output signal;
A feedback unit that negatively feeds back a feedback signal corresponding to the voltage of the output signal to the voltage amplification unit;
A drive circuit for a recording head, comprising:   2. The recording head drive circuit according to claim 1, wherein the feedback unit combines the voltage signal amplified by the voltage amplification unit with the feedback signal and negatively feeds back to the voltage amplification unit.   The feedback unit includes a low-pass unit, and combines the feedback signal with a low-frequency component corresponding to the characteristics of the low-pass unit out of the voltage signal voltage amplified by the voltage amplification unit. A drive circuit for a recording head according to claim 2.   4. The drive circuit of the recording head according to claim 1, wherein the voltage amplifying unit performs an amplifying operation in a plurality of stages including a pre-amplifier and a post-amplifier.   The recording head drive circuit according to claim 4, wherein the pre-amplifier performs differential amplification in accordance with the feedback signal.   6. The recording head drive circuit according to claim 5, wherein an OP amplifier is used for the pre-amplifier.   The feedback unit includes a low-pass unit, and synthesizes a low-frequency component corresponding to a characteristic of the low-pass unit in the feedback signal among the voltage signals voltage-amplified by the pre-stage amplifier unit. A drive circuit for a recording head according to any one of claims 4 to 6.   8. The recording head according to claim 4, wherein the voltage amplification unit is set such that a voltage amplification factor of the rear amplification unit is larger than a voltage amplification factor of the front amplification unit. 9. Drive circuit.   The voltage amplification unit is configured such that a voltage amplification factor of a component having a frequency higher than a predetermined reference frequency is higher than a voltage amplification factor of a component having a frequency lower than the reference frequency. Item 9. The recording head drive circuit according to any one of Items 1 to 8.   The recording head drive circuit according to claim 1, wherein the current amplifying unit performs current amplification by a push-pull operation of two sets of transistors.   11. The recording head drive circuit according to claim 10, wherein a bipolar transistor is used as the transistor.   12. The recording head drive circuit according to claim 10, wherein each of the two sets of transistors includes two or more transistors connected in a Darlington connection.   13. The recording head drive circuit according to claim 12, wherein the Darlington connection is an inverted Darlington connection.   14. The recording head drive circuit according to claim 13, further comprising a resistance element for determining an amplification current of a transistor to which the drive voltage signal is input among the transistors connected to the inverted Darlington.   The drive voltage signal generated by the voltage amplification unit is added with a bias voltage that is a voltage difference equal to or greater than a minimum operation voltage difference for the two transistors of the current amplification unit to perform amplification operations. 15. The drive circuit for a recording head according to claim 10, further comprising a bias generation unit that supplies each pair of transistors.   The bias generator includes bias transistors corresponding to the two sets of transistors, and adds the operating voltage difference of the bias transistors to the drive voltage signal as the bias voltage of the two sets of transistors. 16. A drive circuit for a recording head according to claim 15, wherein:   17. The recording head according to claim 16, wherein the transistor that performs current amplification by the push-pull operation and the bias transistor that supplies a voltage obtained by adding the bias voltage to the transistor are thermally coupled. Driving circuit.   18. The recording head drive circuit according to claim 16, wherein at least a part of the bias transistor and the transistor in the current amplifying unit are manufactured with uniform characteristics.   19. The recording head according to claim 15, wherein the bias generation unit includes a constant current generation unit configured to make a current to flow to the element that generates the bias voltage constant. Drive circuit.   The two sets of transistors are each composed of two or more transistors connected in Darlington, the Darlington connection is an inverted Darlington connection, and the drive voltage signal is the inverted Darlington connected transistor. A resistance element for determining an amplification current of the input transistor is provided, and the constant current generator generates a current equal to the amplification current of the transistor to which the drive voltage signal to which the bias voltage is added is input. 20. The recording head driving circuit according to claim 19, wherein the recording head driving circuit is a recording head driving circuit. With digital / analog converter,
The recording head according to claim 1, wherein the analog drive waveform signal is obtained by analog-converting a digital signal related to an input drive waveform by the digital / analog conversion unit. Drive circuit. A drive circuit for a recording head according to any one of claims 1 to 21,
The recording head;
A control unit for controlling the operation of the drive circuit of the recording head;
An image recording apparatus comprising:

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