JP6662380B2 - Drive circuit of recording head and image recording apparatus - Google Patents

Description

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

  2. Description of the Related Art Conventionally, there is an image recording apparatus that records an image on a recording medium by arranging a plurality of recording elements and operating the plurality of recording elements. 2. Description of the Related Art As an image recording apparatus, there is an ink jet recording apparatus that applies pressure to ink and discharges ink from a plurality of nozzles. As a mechanism for applying pressure to ink and discharging the ink from the nozzles, a piezoelectric element (piezo element) or a vibration plate is provided along the wall surface of the ink flow path (pressure chamber), and a voltage is applied to the piezoelectric element to deform it. A piezo type that compresses and deforms the ink flow path, and a resistive element is provided along the ink flow path, current flows through the resistive element to generate heat, heat the ink in the ink flow path, and generate bubbles. A thermal type in which the ink is compressed by causing the ink to compress is mainly known.

  In order to discharge ink droplets in an appropriate amount, shape and speed as described above, it is necessary that a drive voltage waveform applied to a 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 an ink jet recording apparatus, the drive waveform data is converted into an analog signal, appropriately amplified, and then applied to a load element.

  However, the power required by the printhead that operates the arrayed print elements is larger in voltage and current than the power used for transmitting and receiving digital data signals. In such a voltage or current amplifier circuit, there are various factors for generating a bias and factors for distorting an output waveform. On the other hand, Patent Literature 1 discloses a technique of outputting voltage waveform data corrected in anticipation of the cause of a voltage shift or distortion generated in a current amplifier circuit.

Japanese Patent No. 4438393

  However, voltage deviation and voltage waveform distortion do not always occur constantly. The occurrence and size of these occurrences depend on conditions such as the temperature of each element of the circuit and the wiring. Further, in such an image recording apparatus, since power is supplied to a load selected from a large number of loads in accordance with an ink discharging operation or a non-discharging operation, the total of the selected loads greatly changes. I can do it. Therefore, in order to obtain a waveform that accurately reflects a voltage shift and a voltage waveform distortion, it is necessary to acquire all of these parameters and calculate a correction value, which causes a problem that control becomes extremely complicated.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a recording head drive circuit and an image recording apparatus capable of easily and stably supplying power to a load element of a recording head while preventing a voltage waveform from deteriorating. .

In order to achieve the above object, the present invention is directed to the first aspect of the present invention,
A drive circuit for a printhead that supplies a drive voltage according to the operation of the load element to a load element of a print element provided in the printhead,
A voltage amplification unit that generates a drive voltage signal by amplifying the voltage of the analog drive waveform signal according to the operation of the load element;
A current amplifier that amplifies the current of the drive voltage signal and outputs the output as an output signal;
A feedback unit that performs a negative feedback on the feedback signal corresponding to the voltage of the output signal to the voltage amplification unit;
Equipped with a,
The voltage amplifying unit performs an amplifying operation in a plurality of stages including a pre-stage amplifying unit and a post-stage amplifying unit,
The feedback unit includes a low-pass unit, and among the voltage signals that have been voltage-amplified by the pre-amplification unit, synthesizes a low-frequency component corresponding to the characteristic of the low-pass unit into the feedback signal. I have.
The invention according to claim 2 is
A drive circuit for a printhead that supplies a drive voltage according to the operation of the load element to a load element of a print element provided in the printhead,
A voltage amplification unit that generates a drive voltage signal by amplifying the voltage of the analog drive waveform signal according to the operation of the load element;
A current amplifier that amplifies the current of the drive voltage signal and outputs the output as an output signal;
A feedback unit that performs a negative feedback on the feedback signal corresponding to the voltage of the output signal to the voltage amplification unit;
With
The feedback unit combines the voltage signal amplified by the voltage amplifying unit with the feedback signal and performs negative feedback to an input of the voltage amplifying unit.
It is characterized by:
The invention according to claim 3 is
A drive circuit for a printhead that supplies a drive voltage according to the operation of the load element to a load element of a print element provided in the printhead,
A voltage amplification unit that generates a drive voltage signal by amplifying the voltage of the analog drive waveform signal according to the operation of the load element;
A current amplification unit that amplifies the current of the drive voltage signal by a push-pull operation of two sets of transistors and outputs the amplified output as an output signal;
A feedback unit that performs a negative feedback on the feedback signal corresponding to the voltage of the output signal to the voltage amplification unit;
The driving voltage signal generated by the voltage amplifying unit is added with a bias voltage that is equal to or more than a minimum operating voltage difference for the two sets of transistors of the current amplifying unit to perform an amplifying operation. A bias generator that supplies each of the transistors in the set;
With
The bias generation unit includes a constant current generation unit for making a current flowing to an element that generates the bias voltage constant.
The two sets of transistors are each configured by two or more transistors connected in Darlington, and the Darlington connection is an inverted Darlington connection, and the drive voltage signal of the inverted Darlington connected transistors is A resistance element that determines an amplification current of the input transistor is provided, and the constant current generation unit generates a current equal to an amplification current of the transistor to which the drive voltage signal to which the bias voltage is added is input.
It is characterized by:

According to a fourth aspect of the present invention, in the driving circuit of the recording head according to the third aspect ,
The feedback unit is characterized in that the voltage signal amplified by the voltage amplifying unit is combined with the feedback signal and negatively fed back to the voltage amplifying unit.

According to a fifth aspect of the present invention, in the drive circuit for a print head according to any one of the second to fourth aspects,
The feedback unit includes a low-pass unit, and among the voltage signals voltage-amplified by the voltage amplifying unit, synthesizes a low-frequency component corresponding to the characteristic of the low-pass unit into the feedback signal. I have.

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

According to a seventh aspect of the present invention, in the driving circuit of the recording head according to the first or sixth aspect ,
The preamplifier performs differential amplification according to the feedback signal.

According to an eighth aspect of the present invention, in the driving circuit of the recording head according to the seventh aspect ,
An operational amplifier is used for the preamplifier.

According to a ninth aspect of the present invention, in the drive circuit for a recording head according to any one of the sixth to eighth aspects,
The feedback unit includes a low-pass unit, and among the voltage signals that have been voltage-amplified by the pre-amplification unit, synthesizes a low-frequency component corresponding to the characteristic of the low-pass unit into the feedback signal. I have.

According to a tenth aspect of the present invention, in the driving circuit for a recording head according to any one of the first to sixth aspects,
The voltage amplifying unit is characterized in that a voltage gain of the rear-stage amplifying unit is set to be larger than a voltage gain of the front-stage amplifying unit.
According to an eleventh aspect of the present invention, in the driving circuit for a recording head according to the tenth aspect,
The latter-stage amplifier is a combination of two-stage grounded-emitter amplification, and the preceding stage of the two-stage grounded-emitter amplification has an amplification factor of 1.

According to a twelfth aspect of the present invention, in the drive circuit for a recording head according to any one of the first to eleventh aspects,
The voltage amplifying unit is characterized in that a voltage gain of a component having a frequency higher than a predetermined reference frequency is higher than a voltage gain of a component having a frequency lower than the reference frequency.
According to a thirteenth aspect of the present invention, in the driving circuit of the recording head according to the twelfth aspect,
The voltage amplifying unit includes a first resistance element and a capacitor connected in series, and a second resistance element parallel to the first resistance element and the capacitor, wherein the predetermined reference frequency is the first resistance element. And the combined resistance of the second resistance element.

According to a fourteenth aspect of the present invention, in the drive circuit for a recording head according to any one of the first , second , and fourth to thirteenth aspects,
The current amplifying unit performs a current amplification by a push-pull operation of two sets of transistors.

According to a fifteenth aspect of the present invention, in the driving circuit for a recording head according to the fourteenth aspect ,
A bipolar transistor is used as the transistor.

According to a sixteenth aspect of the present invention, in the driving circuit for a recording head according to the fourteenth or fifteenth aspect ,
The two sets of transistors are characterized by being composed of two or more transistors each connected in Darlington.

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

The invention according to claim 18 is a drive circuit for a recording head according to claim 17 , wherein
A resistor element for determining an amplification current of a transistor to which the drive voltage signal is input among the inverted Darlington-connected transistors is provided.

According to a nineteenth aspect of the present invention, in the drive circuit for a recording head according to any one of the fourteenth to eighteenth aspects,
The driving voltage signal generated by the voltage amplifying unit is added with a bias voltage that is equal to or more than a minimum operating voltage difference for the two sets of transistors of the current amplifying unit to perform an amplifying operation. It is characterized in that it comprises a bias generator for supplying each of the transistors of the set.

According to a twentieth aspect of the present invention, in the driving circuit for a recording head according to the third or nineteenth aspect ,
The bias generator includes a bias transistor corresponding to each of the two sets of transistors, and adds the operating voltage difference between 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 twenty- first aspect of the present invention, in the drive circuit for a recording head according to the twentieth aspect ,
A transistor for performing current amplification by the push-pull operation and the bias transistor for supplying a voltage obtained by adding the bias voltage to the transistor are thermally coupled.

According to a twenty-second aspect of the present invention, in the drive circuit for a recording head according to the twentieth or twenty- first aspect,
It is characterized in that at least a part of the bias transistor and the transistor in the current amplification section are manufactured with uniform characteristics.

According to a twenty- third aspect of the present invention, in the recording head drive circuit according to any one of the nineteenth to twenty-second aspects,
The bias generation section includes a constant current generation section for making a current flowing to an element for generating the bias voltage constant.

According to a twenty-fourth aspect of the present invention, in the drive circuit for a recording head according to the twenty- third aspect,
The two sets of transistors are each configured by two or more transistors connected in Darlington, and the Darlington connection is an inverted Darlington connection, and the drive voltage signal of the inverted Darlington connected transistors is A resistance element that determines an amplification current of the input transistor is provided, and the constant current generation unit generates a current equal to an amplification current of the transistor to which the drive voltage signal to which the bias voltage is added is input. It is characterized by:

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

The invention according to claim 26 is
A printhead drive circuit according to any one of claims 1 to 25 ,
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 more easily and stably supplied to a load element of a recording head while preventing deterioration of a voltage waveform.

FIG. 1 is a block diagram illustrating a functional configuration of an inkjet recording apparatus that is an embodiment of an image recording apparatus according to the invention. FIG. 3 is a block diagram illustrating a configuration of a drive circuit. FIG. 3 is a diagram illustrating a circuit configuration of a voltage amplifying unit. FIG. 3 is a diagram illustrating a circuit configuration of a bias voltage generator. FIG. 3 is a diagram illustrating a circuit configuration of a current amplifier. FIG. 3 is a diagram illustrating a circuit configuration of a feedback unit.

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 driving unit 100, an inkjet head 50 (recording head), a transport driving 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. 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 the analog signal 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 according to the drive voltage of the actuator 51 to generate a drive voltage signal Vd, and further, as 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 an actuator 51 that is an 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 the 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 according to a drive signal from the drive unit 100. The ink jet head 50 includes an actuator 51 related to an ink ejection operation in each of a plurality of nozzles (printing elements). Here, a piezoelectric element is used as the actuator 51. The piezoelectric element is provided along the ink flow path to each nozzle, and is deformed by applying a drive voltage output from the drive circuit 30 to change the pressure applied to the ink in the ink flow path. In response to this pressure change, the ink is ejected from the nozzle opening in an appropriate amount, speed, and droplet shape.

  The transport drive unit 71 acquires the recording medium before image formation from the paper feeding unit, arranges the recording medium facing the nozzle surface of the inkjet head 50, and moves the recording medium on which the image is formed from the position facing the nozzle surface. Let it drain. In the case where an image is formed on the surface of the recording medium by ejecting ink while the inkjet head 50 moves the recording medium, the transport driving unit 71 switches the driving voltage signal from the inkjet head 50 or the switching by the output selection unit 40. The recording medium is conveyed in synchronization with the signal output. As the transport driving unit 71, for example, a unit that places a recording medium on the outer peripheral surface of a cylindrical drum or an endless belt is used. Note that the recording medium obtained from the paper feeding unit is not limited to paper, and various recording media can be used. For example, cloth, ceramics, plastic, and the like can be used as the recording medium.

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

The communication unit 73 transmits and receives data to and from the outside according to a predetermined communication standard.
The communication standards include TCP / IP connection related to communication using a LAN (Local Area Network) cable, short-range wireless communication (such as IEEE 802.15) such as wireless LAN (IEEE802.11) and Bluetooth (registered trademark), and 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, a driver hardware (network card) related to communication connection, and the like.

  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 the 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 can be selectively used depending on the application.

  The bus 90 is a communication path connecting these components to transmit and receive data.

Next, the configuration of the driving unit 100 will be described in detail.
FIG. 2 is a block diagram illustrating a functional configuration of the driving unit 100.
Here, although a resistance element and a capacitor are connected in series and schematically displayed as the actuator 51, they 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, a storage unit 12, and the like. The controller 11 reads a digital value corresponding to a change in the drive voltage of the drive waveform signal output in synchronization with the clock signal from the storage unit 12 and sequentially outputs the digital value. The storage unit 12 is a non-volatile memory that stores waveform pattern data of a drive waveform signal 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 accompanied by a continuous voltage change.

  The DAC 20 is a well-known digital / analog converter, and is provided with a low-pass filter or the like that continuously changes between the discrete values as needed according to the sampling frequency and the number of bits of the inputted digital discrete values. You may be.

  The output selection unit 40 obtains each pixel data of the image data to be recorded from the control unit 80 in synchronization with the clock signal, and switches each actuator of the output signal from the drive circuit 30 by a switching signal corresponding to the pixel data. A switching element is provided for switching whether output to 51 is possible or not. Although the pixel data is not particularly limited, here, it is binary data indicating only the presence or absence of ink ejection, and the output selection unit 40 holds the pixel data in a raster unit 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 two values. The number of actuators 51 and switching elements corresponding to one drive circuit 30 is, for example, 256 or 1024, and therefore, the more switching elements that are turned on, the more the output signal from the drive circuit 30 is supplied (applied). The total load of the actuator 51 becomes large.

  The DC voltage converter 60 performs DC / DC conversion of the power supply voltage Vdd into a stable supply voltage Vp and outputs the converted voltage. Here, the power supply voltage Vdd may be equal to the supply voltage Vp, but is preferably as small as possible within a range where the signal output to the actuator 51 is not distorted. When the power supply voltage Vdd is equal to the supply voltage Vp, 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, and drives a driving waveform signal input from the DAC 20 by an actuator. A voltage and a current suitable for driving the 51 are converted 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 to a drive voltage by two-stage (multiple-stage) amplification.

FIG. 3 is a diagram illustrating a circuit configuration of the voltage amplifying 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 preamplifier 311. The feedback signal from the feedback unit 34 is input to the inverting input of the OP amplifier 311a. Thus, the differential amplification is performed by the preamplifier 311 to stabilize the output voltage. The signal amplified by the OP amplifier 311a is sent to the feedback unit 34 and also sent to the post-amplification unit 312.

  The rear-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 ground between the supply voltage Vp and the ground voltage, respectively. Here, assuming that the amplification factor of the npn transistor Tr11 is 1, that is, voltage amplification is not performed, the resistance values of the resistance elements R11 and R12 are set equal to each other, and these resistance values are set appropriately. This suppresses a decrease in the frequency characteristics of the output voltage (collector voltage of the npn transistor Tr11). The pnp transistor Tr12 amplifies the voltage within the range between the supply voltage Vp and the ground voltage according to the ratio between the resistance values of the resistance elements R13 and R14, and outputs the drive voltage signal Vd. Here, a resistor R15 and a capacitor C11 connected in series are connected in parallel to the resistor R14, and a high frequency equal to or higher than a reference frequency determined by a combined resistance of the resistors R14 and R15 among the input voltage signals. Is reduced to the combined resistance of the resistance elements R14 and R15. Thus, the voltage gain in the high frequency band is higher than the voltage gain in the low frequency band.

Here, in the inkjet recording apparatus 1 of the present embodiment, the voltage amplification rate by the rear amplification section 312 is set to be higher (higher) than the voltage amplification rate by the front amplification section 311. That is, the voltage amplification factor G2 obtained by amplification using the bipolar transistor with the emitter grounded in the rear amplification unit 312 is equal to the voltage amplification factor G1 using the OP amplifier 311a in the front amplification unit 311 (including the effect of feedback by the feedback unit 34). The closed loop gain 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, which is obtained by dividing the voltage gain Vout / Vin of the entire drive circuit 30 by the voltage gain G2. Equal to).
Thus, by suppressing the voltage gain 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 is prevented, The signal of the drive circuit 30 is stabilized. On the other hand, the voltage amplification rate G2 by the rear-stage amplifier 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 unnecessarily. However, if the voltage gain G2 is set too high, the gain in the high frequency band decreases. Therefore, by increasing the voltage gain in the high frequency band as described above, the waveform can be compensated without being distorted. The voltage amplification rate G2 by the rear-stage amplifier 312 is set, and the rest is amplified by the front-stage amplifier 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 each configuration after the post-amplifier 312. In order to secure a gain in a 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 to a base voltage to be input to each of the two transistors for the push-pull operation used in the current amplifier 33. Thus, the ON state of the transistor of the current amplifying unit 33 is appropriately maintained, and the current at the time of idling is reduced.

FIG. 4 is a diagram illustrating a circuit configuration of the bias voltage generation unit 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).
The npn transistor Tr21 and the pnp transistor Tr22 (collectively also referred to as bias transistors) form emitter followers, respectively. The pnp transistor Tr22 outputs a high-side drive voltage signal Vdh higher than the voltage value of the drive voltage signal Vd between the base and the emitter (that is, the minimum operating voltage difference for performing the amplifying operation) to the current amplifying unit 33, and outputs the npn transistor Tr21. Outputs a low-voltage side drive voltage signal Vdl lower than the voltage value of the drive voltage signal Vd between the base and the emitter to the current amplifier 33. That is, the voltage difference between the high-side drive voltage signal Vdh and the low-side drive voltage signal Vdl is twice the base-emitter voltage. As a result, a base voltage (that is, a base-emitter voltage) obtained by adding a bias voltage corresponding to the base-emitter voltage of the transistor to each of two transistors in the push-pull circuit used in the current amplifying unit 33 as described later. To keep these transistors on by passing an appropriate base current 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 current 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 a change in the voltage between the base and the emitter.

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

  The current amplifier 33 is based on the high-side drive voltage signal Vdh and the low-side drive voltage signal Vdl obtained by adding a bias voltage to the drive voltage signal Vd obtained by the voltage amplifier 31 by the bias voltage generator 32. The output signal Vout is generated by amplifying the current. 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 amplification unit 33.
The current amplifying unit 33 is a push-pull circuit (SEPP) of an emitter follower, and further includes one bipolar transistor (pnp transistor Tr31 and one pnp transistor Tr32) as an emitter follower. The transistor Tr33 and the npn transistor Tr34) are connected in inverted Darlington to increase the current amplification factor. The current amplifying unit 33 has an inverted Darlington connection to an npn transistor Tr31 whose high-side drive voltage signal Vdh is input to the base terminal, a pnp transistor Tr32 whose low-side drive voltage signal Vdl is input to the base terminal, and an npn transistor Tr31. Pnp transistor Tr33, npn transistor Tr34 inverted Darlington-connected to pnp transistor Tr32, resistor element R31 provided between collector terminal of npn transistor Tr31 and supply voltage Vp, and collector terminal of pnp transistor Tr32 A resistor R32 provided between the pnp transistor Tr33 and the ground voltage, and a resistor R33 and a resistor R34 for reducing the current during standby. Tha terminal connected to the supply voltage Vp, the emitter terminal of the npn transistor Tr34 is grounded.

  As described above, the bias voltage is added to the npn transistor Tr31 and the pnp transistor Tr32 in advance, and is input to the base terminal. Therefore, the output of the output signal Vout in accordance with the push-pull operation from the current amplifying unit 33 in accordance with the input signal Vin is maintained, thereby preventing the output voltage waveform from being distorted. Since the rise / fall of the voltage corresponding to the bias voltage falls / rises at the voltage between the base and the emitter of the npn transistor Tr31 and the pnp transistor Tr32, respectively, the voltage of the drive voltage signal Vd output from the voltage amplifier 31 and the 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 occurrence of distortion in the waveform of the output signal Vout. That is, if the collector currents (emitter currents) of the pnp transistor Tr33 and the npn transistor Tr34 are excessively reduced at the time of idling, the emitter currents (collector currents) of the npn transistor Tr31 and the pnp transistor Tr32 become correspondingly smaller and approach zero. To adversely affect the operation of the current amplifying unit 33, particularly the output of a signal in a high frequency band. However, it is possible to reduce the collector current of the pnp transistor Tr33 and the npn transistor Tr34 while preventing this. In addition, by using the inverted Darlington connection, the high voltage side drive voltage signal Vdh and the low voltage side which are output from the bias voltage generator 32 according to the number of connection stages as in the normal Darlington connection are improved 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 required for the supply voltage Vp does not increase as compared with the maximum voltage amplitude of the output signal Vout, so that the idling current is not increased more than necessary.

  It is preferable that 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 generator 32 corresponding to these are manufactured with uniform characteristics. . That is, since the electrical characteristics such as the base-emitter voltage and the DC current amplification factor are made uniform, the generation of an excess current according to the change in the bias value due to the temperature change accompanying the change in the amplification current, the distortion of the waveform, and the heat Runaway is prevented. Transistors manufactured with such characteristics are supplied (sold) to the market as a package, for example, assuming that a plurality (two or more) of transistors are used in pairs. In addition, complementary transistors having different polarities may be used. Alternatively, it is also possible to simply measure the electrical characteristics of each transistor and use a transistor that matches at or above a predetermined reference level.

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

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

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

FIG. 6 is a diagram illustrating a circuit configuration of the feedback unit 34.
The feedback section 34 has 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 between 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 of the output signal Vout via the resistor R43 and the capacitor C41 provided in parallel, and is returned to the inverted input of the OP amplifier 311a. The resistance element R43 and the capacitor C41 form a low-pass filter (low-pass section, LPF), and the low-frequency filter superimposes a low-frequency component of the output signal of the OP amplifier 311a on the output signal Vout to provide a feedback signal. It is said. This prevents the phase shift 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 shorter than the response time of the voltage corresponding to the negative feedback, and is included in the output signal Vout. The effect 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 reduced, that is, an appropriate waveform signal in which distortion is suppressed is output from the OP amplifier 311a.

As described above, the inkjet recording apparatus 1 of the present embodiment includes the drive circuit 30 that supplies a drive voltage according 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 amplifying unit 31 that amplifies a voltage of an input signal Vin obtained by converting a drive waveform of digital data according to an operation of the actuator 51 into an analog signal to generate a drive voltage signal Vd; A current amplifying unit 33 amplifies the current of the signal Vd and outputs it as an output signal Vout, and a feedback unit 34 for negatively feeding back a feedback signal corresponding to the voltage of the output signal Vout to the voltage amplifying unit 31.
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. Therefore, it is possible to more easily and stably supply power (that is, a voltage waveform with less distortion and a sufficient current) to the load element (actuator 51) of the inkjet head 50 while preventing the voltage waveform from deteriorating. Therefore, the image quality is not deteriorated in the recorded image by operating the inkjet head 50 appropriately.

  The feedback unit 34 combines the voltage signal amplified by the voltage amplifying unit 31 into a feedback signal and feeds back the voltage signal to the voltage amplifying unit 31. As a result, the output signal Vout having a more accurate and stable voltage waveform can be obtained by more accurately suppressing the effects of disturbances such as the delay of the feedback signal, power loss, and fluctuation of the supply voltage Vp due to the influence of the capacitive component of the actuator 51. Can be output to

  Further, the feedback unit 34 includes a resistance element R43 and a capacitor C41 forming a low-pass unit, and outputs a low-frequency component corresponding to the characteristic of the low-pass unit from the voltage signal amplified by the voltage amplifying unit 31. The signal is combined with the feedback signal and negatively fed back to the voltage amplifier 31. This makes it possible to adjust the response characteristics to high-frequency components, prevent signal oscillation in the drive circuit 30, and make the output signal more stable.

  Further, the voltage amplifying unit 31 performs an amplifying operation in a plurality of stages including the pre-amplifying unit 311 and the post-amplifying unit 312. Therefore, the voltage amplification factor can be increased as a whole without forcibly increasing the amplification factor of each stage, so that waveform distortion can be suppressed. Further, it corresponds to a slew rate (for example, about 100 V / μs according to 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. It is easy to form an amplifier circuit. On the other hand, in the OP amplifier 311a, it is difficult to provide a large slew rate corresponding to a case where a large voltage amplitude related to the high voltage is required. That is, it is difficult for the OP amplifier 311a to output a signal having a large voltage amplitude with a waveform pattern that changes voltage at high speed. Therefore, the voltage amplifying unit 31 can amplify a voltage with a desired waveform while suppressing waveform distortion by combining amplification using the OP amplifier 311a and amplification using a bipolar transistor.

  The preamplifier 311 performs differential amplification according to the feedback signal. Therefore, as described above, it is possible to obtain a stable and accurate output signal Vout by performing appropriate correction on the input signal Vin.

  In addition, the use of the OP amplifier 311a in the preamplifier 311 facilitates differential amplification and suppresses the oscillation of the differential amplification to obtain a more stable output signal Vout.

  The feedback unit 34 includes a resistance element R43 and a capacitor C41 that form a low-pass unit, and outputs a low-frequency component corresponding to the characteristic of the low-pass unit from the voltage signal amplified by the preamplifier 311. Combine with the feedback signal. Therefore, it is possible to adjust the response characteristic to the high frequency component, and in particular to prevent the oscillation due to the amplifying operation of the OP amplifier 311a to further stabilize the output signal.

  In the voltage amplifying unit 31, the voltage gain G2 of the rear-stage amplifier 312 is set to be larger than the voltage gain G1 of the front-stage amplifier 311. Therefore, the first-stage amplifier 311 can function with priority given to the improvement of the stability related to the feedback, and the second-stage amplifier 312 can effectively amplify the voltage.

  Further, the voltage amplifying unit 31 is configured such that the voltage gain of a component having a frequency higher than a predetermined reference frequency is higher than the voltage gain of a component having a frequency lower than the reference frequency. Therefore, the amplification factor on the high frequency side, which tends to be reduced by applying feedback, is improved, and the drive waveform is amplified and output with high accuracy while keeping the distortion of the drive waveform having many high frequency components such as a rectangular wave and a trapezoidal wave small. 30 can be improved in stability.

  Further, since the current amplifying unit 33 performs the current amplification by the push-pull operation of the two transistors, the output obtained by performing the current amplification while maintaining the driving waveform more efficiently while suppressing the idling current than the amplification by one transistor. The 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. Therefore, the power consumption can be suppressed lower by setting the power supply voltage lower than that of the FET.

  Further, since the two sets of transistors used in the current amplifying section 33 are each configured by two or more transistors connected in Darlington, a large current can be stably amplified with a simple circuit configuration.

  Further, by using the inverted Darlington connection as the Darlington connection, it is possible to suppress an increase in the bias voltage 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 according 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, 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 easiness of oscillation.

  Further, among the transistors connected in inverted Darlington, the driving voltage signal Vd (the high-voltage driving voltage signal Vdh and the low-voltage driving voltage signal Vdl) is input to each of the npn transistor Tr31 and the pnp transistor Tr32 so as to determine the emitter current. Since the elements R31 and R32 are provided, an appropriate current amplification factor can be maintained regardless of the input voltage. As a result, an unnecessary current does not flow. In particular, by applying 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. Therefore, it is possible to appropriately maintain the waveform (frequency characteristics) of the output signal Vout while reducing the idling current to suppress current consumption.

  Further, with respect to the drive voltage signal Vd generated by the voltage amplifying unit 31, the voltage difference is equal to or more than the minimum base-emitter voltage (operating voltage difference) for the two sets of transistors of the current amplifying unit 33 to perform the amplifying operation. There is provided a bias voltage generator 32 to which a certain bias voltage is added and supplied to each of the two sets of transistors. This does not cause a situation in which the output signal Vout from the current amplifying unit 33 is turned off, so that it is possible to prevent the output signal Vout from being distorted due to on / off switching.

  The bias voltage generator 32 has 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 the 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, thereby generating and outputting the high-voltage drive voltage signal Vdh and the low-voltage drive voltage signal Vdl. This makes it possible to set an appropriate bias voltage according to the operation of the transistor of the current amplifying unit 33 and the heat generated in the operation, unlike the case where a fixed value is used as the bias voltage using a diode, a resistor, or the like. Therefore, it is possible to appropriately reflect the bias voltage that changes according to heat generation (temperature), to prevent unnecessary heat generation and current consumption, and to further suppress the occurrence of thermal runaway. Also, by setting such a bias voltage, it is not necessary to set the bias voltage higher than necessary in order not to turn off the output signal Vout from the current amplifying unit 33, so that the idling current can be reduced.

  Further, 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-side drive voltage signal Vdh and a low-side drive voltage signal Vdl in which a bias voltage is added to the transistor, respectively, Are combined. As a result, the temperatures of the corresponding transistors are 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 generating unit 32 and the current amplifying unit 33. And power consumption can be reduced stably.

  The npn transistor Tr21 and the pnp transistor Tr22 of the bias voltage generation unit 32 and the npn transistor Tr31 and the pnp transistor Tr32 of the current amplifying unit 33 (including the pnp transistor Tr33 and the npn transistor Tr34 as necessary) have characteristics. By being manufactured in parallel, that is, complementary ones of different polarities, and those of the same polarity that are sold in the same package or matched are used, the base / Electrical characteristics such as emitter-to-emitter voltage can be made uniform. As a result, it is possible to more effectively prevent an unnecessary current from flowing locally in accordance with a change in the current or the temperature, and further cause an oscillation or a thermal runaway accompanying the change.

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

Further, two sets of transistors related to the push-pull operation in the current amplifying unit 33 are each configured by two or more transistors connected in Darlington, and the Darlington connection is an inverted Darlington connection. Among the connected transistors, the resistance elements R31 and R32 are set so as to 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. The constant current circuits Ic1 and Ic2 are provided with a low-voltage drive voltage signal Vdl and a high-voltage drive voltage signal Vdh to which a bias voltage is added, respectively, and each of the pnp transistor Tr32 and the npn transistor Tr31 has an emitter. Over current to generate a (collector current) equal current. Here, the equal current means the accuracy of the current that can be set in the constant current circuits Ic1 and Ic2, the fluctuation of the current allowed in the constant current circuits Ic1 and Ic2, the error of the resistance elements R33 and R34, the npn transistor Tr31 and This means a range that can be set in consideration of an error that can occur according to various factors, such as a change in bias voltage that cannot be completely eliminated by the pnp transistor Tr32 or the like.
As a result, the voltage between the base and the emitter in the transistor of the current amplifying unit 33 and the voltage between the base and the emitter in the bias voltage generating unit 32 can be made equal. It is possible to generate and output the output signal Vout with little distortion while reducing power consumption well.

  The DAC 20 is provided, and the input signal Vin is obtained by converting the input digital signal of the drive waveform into an analog signal by the DAC 20. Therefore, the input signal Vin can be easily and stably generated.

  Further, 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 for controlling the operation of the drive circuit 30. Accordingly, while preventing the voltage waveform from deteriorating, the power (actuator 51) of the ink jet head 50 is more easily and stably supplied with electric power, and discharges appropriate ink droplets with high accuracy to stabilize the image quality of the formed image. Can be improved.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible.
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. However, it is not always necessary to combine the two and feed them back. Absent. However, when an OP amplifier is used for the voltage amplifying unit 31, it is more preferable to feed back the output of the OP amplifier 311a from the viewpoint of preventing oscillation.

  Further, in the above embodiment, as the voltage amplifying unit 31, the former-stage amplifying unit 311 using the OP amplifier 311a and the latter-stage amplifying unit 312 using the bipolar transistor are combined, but the present invention is not limited to two stages. One or three or more stages may be used. 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. In a case where the OP amplifier 311a is not used, a mode in which the drive voltage signal Vd output from the post-amplifying unit 312 is output to the feedback unit 34 can be assumed.

  Further, in the above embodiment, only the low frequency component of the output of the OP amplifier 311a is selectively fed back. However, the presence or absence and the range of the frequency selection are appropriately determined under various conditions such as the ink ejection frequency of the inkjet recording apparatus 1. It should just be set.

  In addition, the voltage amplification factors of the front-stage amplification unit 311 and the rear-stage amplification unit 312 may be appropriately set according to the required total voltage amplification ratio, the number of amplification stages, and the like.

  Similarly, the frequency dependence of the voltage amplification rate in the voltage amplifying unit 31 depends on the characteristics of the gain with respect to the frequencies of the pre-amplifying unit 311 and the post-amplifying unit 312 and the correspondence between the ink ejection frequency of the inkjet recording apparatus 1 and the like. 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 gain may be finely changed for each frequency in accordance with the gain characteristics.

  Further, in the above embodiment, the current amplifying unit 33 is configured using a bipolar transistor, but an FET may be used, or a field effect transistor (FET) and a bipolar transistor may be used in combination. However, using a bipolar transistor makes it easier to secure a wide voltage amplitude between the supply voltage Vp and the ground voltage than using a FET. That is, there is no need to set the supply voltage Vp higher than the required voltage amplitude, and as a result, the power consumption relating to the idling current can be reduced.

  Further, the transistors are not limited to the case where the transistors are connected in inverted Darlington in two stages, but may be connected in three or more stages or normal Darlington connection. In addition, another well-known amplifier circuit configuration 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-described embodiment, the bias voltage is generated in the bias voltage generator 32 by using the bipolar transistor of the same package and complementary as the bipolar transistor used in the current amplifier 33. However, the diode, the LED, and the resistor The bias voltage may be generated by using an element or the like or in combination. In this case, in order to prevent thermal runaway, it is necessary to provide a margin for the set bias voltage or to change the bias voltage according to the temperature state.

  In the above embodiment, the same package and / or the complementary bipolar transistor used in the bias voltage generator 32 and the current amplifier 33 are thermally coupled. is not.

  In the above embodiment, the collector currents of the npn transistor Tr21 and the pnp transistor Tr22 in the bias voltage generator 32, that is, the base currents (bias currents) are kept substantially uniform using the constant current circuits Ic1 and Ic2. However, as these constant current circuits Ic1 and Ic2, other well-known constant current circuits may be used, or a circuit that simply adjusts the bias current more easily by 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 into an analog signal to amplify the voltage and the current. However, the analog signal is obtained from the outside, and the analog signal is simply amplified and output. Alternatively, the DAC 20 and the drive circuit 30 may be provided collectively on the same substrate (chip). Further, the drive waveform signal output unit 10 may be provided on the same substrate (chip) as the drive circuit 30.

  Further, in the above embodiment, only the ejection or non-ejection of the ink is switched, but the ejection amount of the ink may be switchable in a plurality of stages. In this case, it is possible to increase the types of driving waveforms or to perform one-time ink ejection by combining a plurality of driving waveforms.

  Further, in the above-described embodiment, a piezo-type ink jet recording apparatus using a piezoelectric element as a load element has been described as an example. However, a thermal ink jet recording apparatus that applies pressure by causing bubbles to form ink by heat generated by a resistance element or the like. The present invention can be applied to a recording device. When the piezo method is used, the influence of the capacitive load of the piezoelectric element is more likely to appear in the feedback signal than in the thermal method, so that the output signal Vout and the output voltage signal of the OP amplifier 311a are combined and negatively fed back. Thus, the effect of improving stability tends to be more remarkable.

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

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

  INDUSTRIAL APPLICATION This invention can be utilized for the drive circuit of a recording head, and an image recording apparatus.

Reference Signs List 1 inkjet recording device 10 drive waveform signal output unit 11 controller 12 storage unit 20 DAC (digital / analog conversion unit)
Reference Signs List 30 drive circuit 31 voltage amplifying unit 32 bias voltage generating unit 33 current amplifying unit 34 feedback unit 40 output selecting unit 50 inkjet head 51 actuator 60 DC voltage converting unit 71 transport driving unit 72 operation display unit 73 communication unit 80 control unit 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 to R15, R31 to R34, R41 to R43 resistance 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 (26)

A drive circuit for a printhead that supplies a drive voltage according to the operation of the load element to a load element of a print element provided in the printhead,
A voltage amplification unit that generates a drive voltage signal by amplifying the voltage of the analog drive waveform signal according to the operation of the load element;
A current amplifier that amplifies the current of the drive voltage signal and outputs the output as an output signal;
A feedback unit that performs a negative feedback on the feedback signal corresponding to the voltage of the output signal to the voltage amplification unit;
Equipped with a,
The voltage amplifying unit performs an amplifying operation in a plurality of stages including a pre-stage amplifying unit and a post-stage amplifying unit,
The feedback unit includes a low-pass unit, and among the voltage signals amplified by the pre-amplification unit, synthesizes a low-frequency component corresponding to the characteristic of the low-pass unit with the feedback signal. Drive circuit for the recording head. A drive circuit for a printhead that supplies a drive voltage according to the operation of the load element to a load element of a print element provided in the printhead,
A voltage amplification unit that generates a drive voltage signal by amplifying the voltage of the analog drive waveform signal according to the operation of the load element;
A current amplifier that amplifies the current of the drive voltage signal and outputs the output as an output signal;
A feedback unit that performs a negative feedback on the feedback signal corresponding to the voltage of the output signal to the voltage amplification unit;
Equipped with a,
The drive circuit for a print head, wherein the feedback unit combines the voltage signal amplified by the voltage amplifying unit with the feedback signal and performs negative feedback to an input of the voltage amplifying unit . A drive circuit for a printhead that supplies a drive voltage according to the operation of the load element to a load element of a print element provided in the printhead,
A voltage amplification unit that generates a drive voltage signal by amplifying the voltage of the analog drive waveform signal according to the operation of the load element;
A current amplification unit that amplifies the current of the drive voltage signal by a push-pull operation of two sets of transistors and outputs the amplified output as an output signal;
A feedback unit that performs a negative feedback on the feedback signal corresponding to the voltage of the output signal to the voltage amplification unit;
The driving voltage signal generated by the voltage amplifying unit is added with a bias voltage that is equal to or more than a minimum operating voltage difference for the two sets of transistors of the current amplifying unit to perform an amplifying operation. A bias generator that supplies each of the transistors in the set;
Equipped with a,
The bias generation unit includes a constant current generation unit for making a current flowing to an element that generates the bias voltage constant.
The two sets of transistors are each configured by two or more transistors connected in Darlington, and the Darlington connection is an inverted Darlington connection, and the drive voltage signal of the inverted Darlington connected transistors is A resistance element that determines an amplification current of the input transistor is provided, and the constant current generation unit generates a current equal to an amplification current of the transistor to which the drive voltage signal to which the bias voltage is added is input. A driving circuit for a recording head, comprising: 4. The drive circuit of claim 3 , wherein the feedback unit combines the voltage signal amplified by the voltage amplifying unit with the feedback signal and performs negative feedback to the voltage amplifying unit. 5. The feedback unit includes a low-pass unit, and among the voltage signals amplified by the voltage amplifying unit, synthesizes a low-frequency component corresponding to characteristics of the low-pass unit into the feedback signal. The printhead driving circuit according to claim 2 . The driving circuit according to claim 2, wherein the voltage amplifying unit performs an amplifying operation in a plurality of stages including a front-stage amplifying unit and a rear-stage amplifying unit. The preamplifier section, a driving circuit of the recording head according to claim 1 or 6, wherein performing the differential amplification in response to the feedback signal. 8. The drive circuit for a recording head according to claim 7 , wherein an OP amplifier is used in the pre-amplifier. The feedback unit includes a low-pass unit, and among the voltage signals amplified by the pre-amplification unit, synthesizes a low-frequency component corresponding to the characteristic of the low-pass unit with the feedback signal. The driving circuit for a recording head according to any one of claims 6 to 8 , wherein: Wherein the voltage amplifying unit, according to any one of claims 1,6～9 voltage amplification factor of the post-stage amplifying unit, characterized in that it is defined greater than the voltage gain of the preamplifier unit Drive circuit for recording head. 11. The recording head drive circuit according to claim 10, wherein the rear-stage amplifier is a combination of two-stage grounded emitter amplification, and the front-stage of the two-stage grounded emitter amplification has an amplification factor of 1. . The voltage amplifying unit is configured so that a voltage gain of a component having a frequency higher than a predetermined reference frequency is higher than a voltage gain of a component having a frequency lower than the reference frequency. Item 12. The recording head drive circuit according to any one of Items 1 to 11 . The voltage amplifying unit includes a first resistance element and a capacitor connected in series, and a second resistance element parallel to the first resistance element and the capacitor, wherein the predetermined reference frequency is the first resistance element. 13. The recording head driving circuit according to claim 12, wherein said driving circuit is determined by a combined resistance of said second resistance element. 14. The drive circuit according to claim 1 , wherein the current amplifying unit performs a current amplification by a push-pull operation of two sets of transistors. 15. The driving circuit according to claim 14 , wherein a bipolar transistor is used as the transistor. 16. The driving circuit according to claim 14, wherein the two sets of transistors each include two or more transistors connected in Darlington. 17. The drive circuit according to claim 16 , wherein the Darlington connection is an inverted Darlington connection. 18. The drive circuit according to claim 17, further comprising a resistor element that determines an amplification current of a transistor to which the drive voltage signal is input among the inverted Darlington-connected transistors. The driving voltage signal generated by the voltage amplifying unit is added with a bias voltage that is equal to or more than a minimum operating voltage difference for the two sets of transistors of the current amplifying unit to perform an amplifying operation. 19. The drive circuit for a print head according to claim 14 , further comprising a bias generator that supplies each of the sets of transistors. The bias generator includes a bias transistor corresponding to each of the two sets of transistors, and adds the operating voltage difference between the bias transistors to the drive voltage signal as the bias voltage of the two sets of transistors. 20. The recording head drive circuit according to claim 3, wherein: 21. The recording head according to claim 20 , wherein a 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. Drive circuit. 22. The printhead drive circuit according to claim 20, wherein at least a part of the bias transistor and the transistor in the current amplifying unit are manufactured with uniform characteristics. 23. The recording head according to claim 19 , wherein the bias generation section includes a constant current generation section for making a current flowing to an element generating the bias voltage constant. Drive circuit. The two sets of transistors are each configured by two or more transistors connected in Darlington, and the Darlington connection is an inverted Darlington connection, and the drive voltage signal of the inverted Darlington connected transistors is A resistance element that determines an amplification current of the input transistor is provided, and the constant current generation unit generates a current equal to an amplification current of the transistor to which the drive voltage signal to which the bias voltage is added is input. 24. The recording head drive circuit according to claim 23, wherein: It has a digital / analog converter,
The recording head according to any one of claims 1 to 24 , wherein the analog drive waveform signal is obtained by converting a digital signal related to an input drive waveform into an analog signal by the digital / analog converter. Drive circuit. A printhead drive circuit according to any one of claims 1 to 25 ,
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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