JP2011041466A - Drive circuit, liquid jetting device, printer and medical equipment - Google Patents

Abstract

Kind Code: A1 To increase the types of voltage values that can be output while suppressing the number of capacitors.
A plurality of first power storage elements charged by a power source are connected in series to form a series power storage element group. Moreover, a 2nd electrical storage element is charged using this series electrical storage element group. Then, the voltage is applied by connecting the series storage element group to the load while switching between the state where the charged second storage element is connected in series to the series storage element group and the state where the second storage element is not connected in series. If it carries out like this, two types of voltages, the case where the 2nd electrical storage element is connected in series, and the case where it is not connected in series can be output. Here, since two types of voltages can be output for each of a plurality of states in which the number of first power storage elements constituting the series power storage element group is different from each other, the number of voltages that can be output only by providing the second power storage element Can be greatly increased. Thereby, it is possible to output various types of voltages while suppressing the number of power storage elements.
[Selection] Figure 7

Description

  The present invention relates to a technique for driving a load by applying a voltage.

  A technique for driving a load of an electronic element such as a semiconductor element or a dielectric element by applying a voltage is widely used in various apparatuses. For example, in a fluid ejecting apparatus such as an ink jet printer, a fluid is pushed out and ejected from an ejection port by applying a voltage to a piezo element that expands and contracts according to the voltage. Further, in a display device such as a liquid crystal display or an organic EL display, an image is displayed by applying a voltage to the liquid crystal to align liquid crystal molecules or applying a voltage to the organic EL to emit light. Moreover, not only an electronic element but the technique which drives a load by applying a voltage to various loads, such as a motor and an electromagnet, is also used widely.

  In the devices that drive these various loads, the operation of the load is controlled by controlling the waveform (voltage waveform) of the voltage applied to the load. For this reason, it is important to accurately generate the voltage waveform. . For this reason, there is a technology for generating a voltage waveform by preparing a power supply that generates a voltage higher than the maximum voltage of the voltage waveform to be generated and stepping down the voltage from the power supply using a semiconductor element such as a power transistor. Widely used (for example, Patent Document 1). In this technique, it is possible to accurately generate a voltage waveform by controlling a power transistor or the like.

  Further, if a power source having a high output voltage or a power transistor having a high withstand voltage is provided, the apparatus tends to be enlarged. Therefore, a circuit that charges multiple capacitors to the same voltage, increases the voltage by connecting these capacitors in series, and changes the voltage by changing the number of capacitors connected in series (so-called charge pump circuit) ) Has been proposed to reduce the size of the apparatus by omitting power transistors and the like (Patent Document 2).

Japanese Patent Laid-Open No. 11-259969 JP-A-7-130484

  However, the proposed technique has a problem that it is difficult to generate a voltage waveform with high accuracy. That is, since the voltage is changed by changing the number of capacitors connected in series, the number of types of voltage values that can be output is limited to the number of capacitors. Then, since it is necessary to generate a voltage waveform with this limited type of voltage, it is difficult to generate a highly accurate voltage waveform. Of course, it is possible to increase the accuracy of the voltage waveform by outputting more types of voltages with more capacitors, but this time the number of capacitors increases, making it difficult to reduce the size of the circuit. End up.

  The present invention has been made in order to solve the above-described problems of the prior art, and provides a technique for increasing the voltage waveform accuracy by increasing the types of voltage values that can be output while suppressing the number of capacitors. Objective.

In order to solve at least a part of the problems described above, the load driving circuit of the present invention employs the following configuration. That is,
A load driving circuit for driving the load by applying a voltage to the load,
A plurality of first power storage elements that are charged by receiving a supply of voltage from a power source;
A series power storage element group configuring unit that configures a series power storage element group in which the first power storage elements are connected in series by switching a connection state between the plurality of first power storage elements;
A second storage element charging means for charging a second storage element different from the first storage element using the series storage element group;
A first connection state in which the second storage element and the series storage element group are connected to a load in a state where the charged second storage element and the series storage element group are connected in series; and the second storage element, Voltage application means for switching a second connection state in which the series storage element group is connected to the load and disconnecting the series connection with the series storage element group and applying a voltage to the load. Is the gist.

  The load driving circuit of the present invention includes a plurality of first power storage elements that are charged by a power source, and the plurality of first power storage elements are connected in series to form a series power storage element group. In addition, the second power storage element is charged by connecting the series power storage element group to the second power storage element. When the series storage element group is connected to the load and a voltage is applied to the load, the series storage element group and the second storage element are connected in a state where the charged second storage element and the series storage element group are connected in series. A voltage is applied by switching between a state in which the element is connected to the load and a state in which the series connection between the second storage element and the series storage element group is disconnected and the series storage element is connected to the load.

  A series storage element group in which a plurality of first storage elements are connected in series generates a voltage different from each of the first storage elements. Therefore, the second storage element charged using the first storage element is the first storage element. The voltage value is different. Then, when the voltage is output using these power storage elements, only the first power storage elements are connected in series (when only the series power storage element group is used), and the second power storage in addition to the first power storage elements. Voltages having different voltage values are output when the elements are connected in series (when the second storage element is connected in series to the series storage element group). As a result, the number of voltages that can be output can be increased. As a result, the gradation of the output voltage is improved, and as a result, the accuracy of the voltage waveform can be increased. The series storage element group may take a plurality of modes in which the number of the first storage elements constituting the series storage element group is different. For each of the modes, the series storage element group and the second storage element are It is possible to output two types of voltages depending on whether or not they are connected in series. For this reason, it is possible to greatly increase the number of voltages that can be output simply by providing the second power storage element, and it is possible to output various types of voltages while suppressing the number of power storage elements.

  The storage element may be any element as long as it is an element that is charged and generates a voltage. For example, it may be an element that generates a voltage by storing an electric field when it is charged and supplied with a charge like a capacitor, or stores chemical energy inside like a secondary battery. The element which generates a voltage by this may be sufficient.

  Moreover, in the load drive circuit of the present invention described above, when the first power storage element is disconnected from the load and charged, the second power storage element may be connected to the load.

  If it carries out like this, since the 1st electrical storage element can be charged in the state which applied the voltage to the load using the voltage of the 2nd electrical storage element, even when charging the 1st electrical storage element, voltage is applied to the load. It is possible to maintain the state in which is applied.

Moreover, the load drive circuit of the present invention described above can be grasped as the following mode. That is,
A first power storage element that is charged by receiving a voltage from a power source;
A second power storage element that is charged by receiving a voltage from the power source;
A series power storage element group constituting means constituting a series power storage element group in which the first power storage element and the second power storage element are connected in series;
A third storage element charging means for charging a third storage element different from the first storage element and the second storage element by using the series storage element group;
In a state where the charged third storage element and the series storage element group are connected in series, a first connection state in which the third storage element and the series storage element group are connected to a load, and the third storage element A load comprising: voltage applying means for switching a second connection state in which the series storage element group is connected to the load in a state in which the series connection with the series storage element group is disconnected, and applying a voltage to the load It can be grasped as a drive circuit.

  The load drive circuit of this aspect includes a first power storage element and a second power storage element that are charged by a power source, and the first power storage element and the second power storage element are connected in series to form a series power storage element group. Constitute. Further, the third power storage element is charged by connecting the series power storage element group to the third power storage element. When the series storage element group is connected to the load and a voltage is applied to the load, the series storage element group and the third storage element are connected in a state where the charged third storage element and the series storage element group are connected in series. A voltage is applied by switching between a state in which the element is connected to the load and a state in which the series connection between the third power storage element and the series power storage element group is disconnected and the series power storage element group is connected to the load.

  The series storage element group in which the first storage element and the second storage element are connected in series generates a voltage different from that of the first storage element and the second storage element. The first power storage element and the second power storage element have different voltages. Therefore, when only the series storage element group is used (when only the first storage element and the second storage element are used) and when the third storage element is connected in series in addition to the series storage element group, different voltages are used. Is output. As a result, the number of types of voltage values can be increased to improve the gradation of the output voltage, and as a result, the accuracy of the voltage waveform can be increased.

  In addition, if the load driving circuit of the present invention described above is used, liquid can be appropriately ejected from the ejection nozzle by driving an actuator provided in the ejection nozzle, and therefore the present invention includes the above-described load driving circuit. It can also be grasped as a liquid ejecting apparatus.

  In the liquid ejecting apparatus of the present invention, since the voltage waveform with high accuracy is generated by the load driving circuit described above, it is possible to control the operation of the actuator with high accuracy. It is possible to appropriately eject the liquid by accurately controlling the size, the ejection speed of the liquid, and the like.

  Further, since the above-described liquid ejecting apparatus of the present invention can be mounted on a printing apparatus, the present invention can also be grasped as a printing apparatus equipped with the above-described liquid ejecting apparatus.

  In such a printing apparatus of the present invention, the actuator provided in the ejection nozzle can be accurately driven by the load driving circuit described above, and as a result, liquid such as ink can be ejected with high precision. Therefore, it is possible to print a high quality image.

It is explanatory drawing which showed the rough structure of the inkjet printer carrying the voltage waveform generation circuit of a present Example. It is explanatory drawing which showed the mechanism inside an ejection head in detail. It is explanatory drawing which illustrated the voltage waveform (drive voltage waveform) applied to a piezo element. It is explanatory drawing which showed the drive voltage waveform generation circuit with which the inkjet printer of the present Example was equipped, and its peripheral circuit structure. It is explanatory drawing which showed the structure of the drive voltage waveform generation circuit of a present Example. It is explanatory drawing which showed a mode that a various voltage was output using the charge pump circuit of the drive voltage waveform generation circuit of a present Example. It is explanatory drawing which showed a mode that many types of voltage became possible by using the capacitor | condenser CC. It is explanatory drawing which showed notionally a mode that many types of voltages can be output by the drive voltage waveform generation circuit of a present Example. It is explanatory drawing which showed the drive voltage waveform generation circuit of the 1st modification which outputs the voltage of the capacitor | condenser CC directly to an output terminal. It is explanatory drawing which showed the drive voltage waveform generation circuit of the 2nd modification which enabled charge of the capacitor | condenser CC while outputting the voltage from the capacitor | condenser CC. It is explanatory drawing which showed the drive voltage waveform generation circuit of the 3rd modification which made it possible to connect the capacitor | condenser CC and a power supply in series. It is explanatory drawing which illustrated the drive voltage waveform generation circuit of the 4th modification which charges capacitor CC to the voltage different from the output voltage of a charge pump circuit. It is explanatory drawing which showed the drive voltage waveform generation circuit of the 5th modification which connects a charge pump circuit to the GND side, and connects the capacitor | condenser CC to the output terminal side.

Hereinafter, in order to clarify the contents of the present invention described above, an embodiment of an ink jet printer equipped with a voltage waveform generation circuit will be described in the following order.
A. Inkjet printer configuration:
B. Driving voltage waveform generation circuit of this embodiment:
C. Variation:
C-1. First modification:
C-2. Second modification:
C-3. Third modification:
C-4. Fourth modification:
C-5. Fifth modification:

A. Inkjet printer device configuration:
FIG. 1 is an explanatory diagram showing a rough configuration of an ink jet printer equipped with the voltage waveform generation circuit of this embodiment. As shown in the drawing, the inkjet printer 10 includes a carriage 20 that forms ink dots on the print medium 2 while reciprocating in the main scanning direction, a drive mechanism 30 that reciprocates the carriage 20, and paper of the print medium 2. The platen roller 40 is used for feeding. In the carriage 20, an ink cartridge 26 that contains ink, a carriage case 22 in which the ink cartridge 26 is mounted, and an ejection head that is mounted on the bottom surface side (side facing the print medium 2) of the carriage case 22 and ejects ink. 24 and the like are provided, and the ink in the ink cartridge 26 is guided to the ejection head 24 so that an accurate amount of ink can be ejected from the ejection head 24 toward the print medium 2.

  The drive mechanism 30 that reciprocates the carriage 20 includes a guide rail 38 that extends in the main scanning direction, a timing belt 32 that has a plurality of teeth formed therein, a drive pulley 34 that drives the timing belt 32, and a step motor. 36 or the like. A part of the timing belt 32 is fixed to the carriage case 22, and by driving the timing belt 32, the carriage case 22 can be accurately moved along the guide rail 38.

  Further, the platen roller 40 is driven by a drive motor or a gear mechanism (not shown), and can feed the print medium 2 by a predetermined amount in the sub-scanning direction. Each of these mechanisms is controlled by a printer control circuit 50 mounted on the inkjet printer 10. Under the control of the printer control circuit 50, the platen roller 40 feeds the print medium 2 and the carriage case 22 An image is printed on the print medium 2 by ejecting ink from the ejection head 24 while moving in the main scanning direction.

  FIG. 2 is an explanatory view showing in detail the mechanism inside the ejection head. As shown in the drawing, the bottom surface of the ejection head 24 (the surface facing the print medium 2) is provided with a plurality of ejection ports 200, and ink droplets can be ejected from the respective ejection ports 200. It has become. Each ejection port 200 is connected to an ink chamber 202, and the ink chamber 202 is filled with ink supplied from the ink cartridge 26. A piezo element (piezoelectric element) 204 is provided on the ink chamber 202. When a voltage is applied to the piezo element 204, the piezo element is deformed to pressurize the ink chamber 202, thereby causing an ink droplet from the ejection port 200. Can be injected. Here, as is well known, the piezoelectric element 204 corresponds to a so-called capacitive load. Further, since the deformation amount of the piezo element 204 changes according to the applied voltage, if the voltage applied to the piezo element 204 is appropriately controlled, the force and timing of pressing the ink chamber 202 are adjusted and ejected. It is possible to change the size of the ink droplets. For this reason, the inkjet printer 10 applies the following voltage waveform to the piezo element 204.

  FIG. 3 is an explanatory diagram illustrating a voltage waveform (drive voltage waveform) applied to the piezo element. As shown in the figure, the drive voltage waveform has a trapezoidal waveform in which the voltage rises with time and then falls back to the original voltage. Further, the drawing shows how the piezo element 204 expands and contracts according to the drive voltage waveform. As shown in the figure, when the voltage of the drive voltage waveform increases, the piezo element 204 gradually contracts accordingly. At this time, since the ink chamber 202 is expanded by being pulled by the piezo element 204, ink can be supplied from the ink cartridge 26 into the ink chamber 202. As the voltage rises and reaches a peak and then drops, this time, the piezo element 204 expands to compress the ink chamber 202 and eject ink from the ejection port 200. At this time, the drive voltage waveform is lowered to a voltage lower than the original voltage (the voltage indicated as “initial voltage” in the figure), and the piezo element 204 is expanded from the initial state to sufficiently expand the ink. It can be extruded. Thereafter, the drive voltage waveform returns to the initial voltage, and correspondingly, the piezo element 204 also returns to the initial state.

  As described above, the inkjet printer 10 includes the piezo element 204 in the ink chamber 202, and can apply ink droplets from the ejection head 24 by applying an appropriate drive voltage waveform to the piezo element 204. It has become. For this reason, the ink jet printer 10 includes a drive voltage waveform generation circuit 100 that generates a drive voltage waveform in addition to the printer control circuit 50 that controls the operation of each mechanism.

  FIG. 4 is an explanatory diagram showing a drive voltage waveform generation circuit provided in the ink jet printer of the present embodiment and a peripheral circuit configuration. Although the detailed configuration of the drive voltage waveform generation circuit 100 will be described in detail later, the drive voltage waveform generation circuit 100 roughly generates a voltage waveform by changing the voltage from the power supply that generates the voltage and the power supply. And a waveform generation unit. The operation of the drive voltage waveform generation circuit 100 is controlled by the printer control circuit 50. The printer control circuit 50 controls the drive voltage waveform generation circuit 100 to generate a target drive voltage waveform. It is possible to do.

  The output of the drive voltage waveform generation circuit 100 is connected to the gate unit 300 as shown. The gate unit 300 includes a plurality of gate elements 302 connected in parallel, and a piezo element 204 is connected to the tip of each gate element 302. Each gate element 302 can be individually turned on or off, and if only the gate element 302 of the ejection port to which ink is to be ejected is turned on, only the corresponding piezoelectric element 204 can be turned on. An ink droplet can be ejected from the ejection port 200 by applying a drive voltage waveform.

  The printer control circuit 50 prints an image as follows using such a circuit configuration. First, based on the image data to be printed, the ejection port 200 for ejecting ink droplets and the size of the ejected ink droplet are determined, and the ink droplet of that size is ejected according to the size of the ejected ink droplet. A driving voltage waveform for determining the frequency is determined. Then, a command is sent to the gate unit 300 to make the gate element 302 corresponding to the injection port 200 conductive, and the drive voltage waveform generation circuit 100 is operated to generate a target drive voltage waveform. The drive voltage waveform thus generated is applied to the piezo element 204 of the target ejection port 200 via the gate element 302, and as a result, an ink droplet of the desired size is ejected from the target ejection port 200.

  Here, in order to reduce the size of the circuit that generates the drive voltage waveform, as described above, a circuit that changes the voltage by connecting or disconnecting a charged capacitor in series (a so-called charge pump circuit). ) Is preferably used to generate the drive voltage waveform. However, in a normal charge pump circuit, the number of types of voltage values that can be output is limited to the number of capacitors, so it is difficult to generate a drive voltage waveform with high accuracy. However, if a large number of capacitors are provided and an attempt is made to output a wide variety of voltages, the number of capacitors will increase this time, making it difficult to reduce the circuit configuration. Therefore, the drive voltage waveform generation circuit 100 according to the present embodiment employs the following circuit configuration to increase the number of voltages that can be output while suppressing the number of capacitors, thereby achieving a highly accurate drive voltage waveform. Can be generated.

B. Driving voltage waveform generation circuit of this embodiment:
FIG. 5 is an explanatory diagram showing the configuration of the drive voltage waveform generation circuit of this embodiment. As shown in the figure, the drive voltage waveform generation circuit 100 includes a power supply, capacitors C1 to C2 and a capacitor CC, and a switch for connecting them. Capacitor C1 and capacitor C2 can be connected to a power source via a switch indicated by “A” in the figure, and by connecting to power source, capacitor C1 and capacitor C2 have the same voltage as the power source. It is possible to charge (voltage indicated as “E” in the figure). These switches and power supply are operated by the printer control circuit 50, and the printer control circuit 50 can control the operation of the drive voltage waveform generation circuit 100 by operating them. Yes (see Figure 4).

  Further, the capacitors C1 to C2 and the power source constitute a so-called charge pump circuit, and can be connected to each other in series or disconnected by switching a switch. The drive voltage waveform generation circuit 100 according to the present embodiment uses the charge pump circuit to output a plurality of types of voltages as follows.

  FIG. 6 is an explanatory diagram showing how various voltages are output using the charge pump circuit of the drive voltage waveform generation circuit of this embodiment. FIG. 6A shows a state in which the same voltage as the voltage charged in the capacitor C1 (the voltage indicated as “E” in the figure) is output. As illustrated, when the switch SW1 is switched to the upper side of FIG. 6A, the switch SW2 is switched to the lower side of FIG. 6A, and the switch SW3 is switched to the upper side of FIG. Is connected to the output terminal, the same voltage as the voltage of the capacitor C1 (the voltage indicated by “E” in the figure) is output from the output terminal.

  Further, as shown in FIG. 6B, when the switch SW2 is switched from the state of FIG. 6A to the upper side of FIG. 6B, this time, the capacitor C1 and the capacitor C2 are connected in series. In this state, they can be connected to the output terminal. In this way, the voltage of the capacitor C2 is added to the voltage of the capacitor C1, so that the voltage “2E” can be output from the output terminal.

  Further, as shown in FIG. 6 (c), if the switch SW4 is switched from the state of FIG. 6 (b) to the upper side of FIG. 6 (c) so as to connect the power source, the capacitors C1 and C2 are switched. A power supply can be further connected in series to what is connected in series. In this way, since the voltage “E” of the power supply is further added to the total voltage “2E” of the capacitor C1 and the capacitor C2, a voltage “3E” can be output. As described above, the drive voltage waveform generation circuit 100 according to the present embodiment can output a plurality of types of voltages using the charge pump circuit including the capacitors C1 to C2 and the power source.

  However, only using such a charge pump circuit limits the number of voltages that can be output, so it is difficult to generate a drive voltage waveform with high accuracy. Therefore, as shown in FIG. 5 or FIG. 6, the drive voltage waveform generation circuit 100 of the present embodiment includes a capacitor CC in addition to the power supply and the capacitors C1 and C2. The capacitor CC is charged using a charge pump circuit composed of capacitors C1 to C2 and a power source, and the charged capacitor CC is used in combination with the capacitors C1 to C2 and the power source, thereby adding the above-described voltage. Thus, more types of voltages can be output. This point will be described with reference to FIG.

  FIG. 7 is an explanatory diagram showing how various types of voltages can be output by using the capacitor CC. FIG. 7A shows how the capacitor CC is charged. As shown in the figure, when charging the capacitor CC, the capacitors C1 to C2 constituting the charge pump circuit and the power source are connected in series, and the switch SW3 is operated to output the output of the charge pump circuit to the output terminal. Switch from side to capacitor CC side. Thereby, the output of the charge pump circuit is applied to the capacitor CC, and the capacitor CC is charged.

  Here, since the capacitor CC is charged with the voltage boosted by the charge pump circuit, the voltage of the capacitor CC after charging is different from the voltage of the power supply (or the voltages of the capacitors C1 to C2). For example, in the example of FIG. 7A, the capacitor CC is charged with the voltage “3E” boosted by the charge pump circuit, the voltage after charging becomes “3E”, and the voltage “ The voltage is different from “E”. From a different viewpoint, this means that the capacitor CC after charging becomes a new voltage source that generates a voltage different from that of the power source (or the capacitors C1 to C2).

  Therefore, if the capacitor CC is used in combination with the power source and the capacitors C1 to C2, it is possible to output a voltage different from the voltage (see FIG. 6) when only the capacitors C1 to C2 and the power source are used. That is, as shown in FIG. 7B, if the capacitor CC is connected in series to the capacitor C1, the capacitor CC is charged to “3E”, so that the voltage “4E” is output. It becomes possible. Further, as shown in FIG. 7C, if the capacitor C1 and the capacitor C2 are connected in series and connected in series to the capacitor CC, the capacitor CC is charged to the voltage “3E”. , “5E” can be output.

  As described above, in the drive voltage waveform generation circuit 100 of the present embodiment, the capacitor CC is charged by the charge pump circuit, and the capacitor CC is connected in series with the power source and the capacitors C1 to C2, thereby using the charge pump circuit. In addition to a voltage that can be output (see FIG. 6), a plurality of types of voltages can be output. This is possible because the capacitor CC is charged to a voltage different from that of the power source and the capacitors C1 and C2, as described above. This point will be supplementarily described with reference to FIG.

  FIG. 8 is an explanatory diagram conceptually showing how various types of voltages can be output by the drive voltage waveform generation circuit of this embodiment. On the left side of the graph in the figure, voltage values that can be output by the drive voltage waveform generation circuit 100 of this embodiment are shown. The white arrow in the figure represents the voltage value that can be output when the power supply and the capacitors C1 to C2 are used, and the hatched arrow is the voltage that can be newly output by using the capacitor CC. Represents a value.

  Generally, in a charge pump circuit, since a plurality of capacitors are charged to the same voltage, the value of the output voltage is determined by the number of capacitors connected in series. For this reason, as long as the number of capacitors connected in series is the same, the output voltage value is the same regardless of which capacitor is used, and even if the capacitor connected in series is replaced with another capacitor, a different voltage value is obtained. Cannot be output to increase the number of voltages that can be output. In view of these points, in the drive voltage waveform generation circuit 100 of the present embodiment, the capacitor CC is charged to a voltage different from the capacitors C1 to C2 and the power source. In this way, the voltage when the capacitor C1 and the capacitor C2 are connected in series (the voltage indicated as “2E” in the figure) and the voltage when the capacitor CC is used instead of the capacitor C2 (“4E in the figure). Therefore, by using the capacitor CC instead of the capacitor C2, it is possible to output a new voltage and increase the number of voltages that can be output.

  In addition, when outputting voltage with the charge pump circuit, it is possible to use a power source that charges the capacitor in addition to the capacitor. In such a case, the capacitor is charged by that power source. The voltage of the capacitor and the voltage of the capacitor are the same voltage. Therefore, the output voltage is the same regardless of whether the capacitor or the power supply is used, and the number of voltages that can be output cannot be increased even if the capacitor and the power supply are used separately. On the other hand, in the drive voltage waveform generation circuit 100 of the present embodiment, the voltage of the power supply and the voltage of the capacitor CC are different, so that the voltage when the capacitors C1 and C2 are connected to the power supply in series ( The voltage when the capacitor CC is used instead of the power supply (the voltage indicated as “5E” in the figure) is different from the voltage indicated as “3E”. Therefore, by using the capacitor CC instead of the power supply, it is possible to output a new voltage and increase the number of voltages that can be output.

  The right side of FIG. 8 illustrates a drive voltage waveform generated using the voltage that can be output in this way. Since the drive voltage waveform generation circuit 100 of the present embodiment can output various types of voltages, the voltage can be changed in small increments as shown in the figure, and the drive voltage waveform with high accuracy can be obtained. Can be generated. Thereby, in the inkjet printer 10 of the present embodiment, it is possible to apply a highly accurate driving voltage waveform to the piezoelectric element provided in the ejection port 200, and as a result, the piezoelectric element can be accurately controlled. Ink droplets can be ejected accurately.

  In the driving voltage waveform generation circuit 100 of this embodiment, the circuit configuration can be reduced by reducing the number of capacitors. That is, in the drive voltage waveform generation circuit according to the present embodiment, as described above, the output voltage differs between the case where the capacitor CC is used and the case where the capacitor CC is not used. Therefore, the number of capacitors connected in series is different. Even if they are the same, two voltages can be output. For this reason, by providing the capacitor CC, it is possible to output roughly twice as many types of voltages as the number of capacitors provided in the charge pump circuit. For this reason, it is not necessary to greatly increase the number of capacitors, and it is possible to reduce the circuit configuration by reducing the number of capacitors.

  Further, in the driving voltage waveform generation circuit 100 of the present embodiment, the capacitor CC can be charged to a voltage higher than that of other capacitors, so that the number of capacitors connected in series when outputting the voltage can be reduced. It is possible. That is, since the capacitor CC is charged to a higher voltage than other capacitors, the use of the capacitor CC can reduce the number of capacitors connected in series by that amount. For example, in the example shown in FIG. 7B, a voltage that is four times the voltage of the capacitor of the charge pump circuit is output, but in order to output a voltage that is four times, four capacitors are connected in series. There is no need, and two capacitors, a capacitor CC and a capacitor C1, may be connected in series.

  Generally, when capacitors are connected in series, the overall capacitance is lowered. Therefore, when many capacitors are connected in series, the capacitance of each capacitor needs to be increased in advance. In this respect, in the drive voltage waveform generation circuit of the present embodiment, the number of capacitors connected in series can be reduced, so that the capacitance of each capacitor can be kept small, and further, a smaller size can be achieved. It is also possible to further reduce the circuit configuration by using a capacitor. In addition, since the number of switches connected between the capacitors can be reduced, the circuit configuration can be further simplified, and the power consumption due to the internal resistance of the switches can be reduced. It is also possible to improve efficiency.

  In addition, when charging the capacitor CC (see FIG. 7A), the voltage of the capacitor C1 and the capacitor C2 may decrease, and the capacitor CC may not be charged sufficiently. In such a case, the capacitor C1 and the capacitor C2 may be recharged with the power source and then connected to the capacitor CC again. By repeating such an operation, the capacitor CC can be sufficiently charged.

  As described above, in the drive voltage waveform generation circuit 100 according to the present embodiment, the capacitor CC is charged to a voltage different from that of the power source and the capacitors C1 and C2, so that the number of capacitors is not significantly increased. It is possible to generate a high-precision drive voltage waveform by outputting various types of voltages. As a result, the circuit configuration can be reduced in size, and further, power consumption can be suppressed by suppressing power consumption at a switch or the like for connecting capacitors to each other.

C. Modified example:
Hereinafter, a modification of the above-described embodiment will be described. Note that, in the modification described below, the same components as those in the above-described embodiment are denoted by the same reference numerals as those in the embodiment, and detailed description thereof is omitted.
C-1. First modification:
In the drive voltage waveform generation circuit of the embodiment described above, the output voltage of the capacitor CC is described as being output from the output terminal in combination with the output voltages of the capacitor C1 and the capacitor C2 (FIGS. 7B and 7C). )). However, the output voltage of the capacitor CC may be output as it is from the output terminal without being combined with the capacitor C1 or the capacitor C2.

  FIG. 9 is an explanatory diagram showing a drive voltage waveform generation circuit of a first modification that directly outputs the voltage of the capacitor CC to the output terminal. As shown in the figure, the capacitor CC can be connected to the output terminal via a switch indicated by “B” in the figure, and the voltage of the capacitor CC is not passed through the capacitor C1 or the capacitor C2. It is possible to output directly from the output terminal. In this way, while the capacitor CC is outputting a voltage to the output terminal, the capacitor C1 and the capacitor C2 do not need to output a voltage. During that time, the switch indicated by “A” in the figure is operated, Capacitor C1 and capacitor C2 can be charged. In this way, even if the voltage of the capacitor C1 and the capacitor C2 decreases while outputting the drive voltage waveform, it is possible to recharge the capacitor C1 and the capacitor C2 while using the capacitor CC. The drive voltage waveform can be output more quickly by omitting the time for recharging the capacitor C1 and the capacitor C2.

  Note that, as described above with reference to FIG. 3, in the inkjet printer 10, a predetermined voltage (a voltage indicated as “initial voltage” in FIG. 3) is applied to the piezo element 204 in advance. Therefore, if the capacitor CC is charged to the initial voltage, the initial voltage can be applied to the piezo element 204 using the capacitor CC. This is more preferable because the capacitor C1 and the capacitor C2 can be charged while the initial voltage is applied to prepare for the output of the drive voltage waveform. In addition, since it is not necessary to separately prepare a power source for applying the initial voltage, the apparatus configuration can be further reduced in size.

C-2. Second modification:
In addition, while the voltage is output from the capacitor CC to the output terminal, not only the capacitor C1 and the capacitor C2 but also the capacitor CC can be charged.

  FIG. 10 is an explanatory diagram showing a drive voltage waveform generation circuit of a second modified example in which the capacitor CC can be charged while the voltage is output from the capacitor CC. As shown in the figure, in the drive voltage waveform generation circuit of the second modification, the capacitor CC is connected to the output terminal, and the output of the charge pump circuit including the power source and the capacitors C1 to C2 is connected to the capacitor via the diode. The CC is supplied to the CC (see the portion indicated by “B” in the figure). In this way, when the voltage is output from the capacitor CC and the voltage of the capacitor CC decreases, the power is supplied from the charge pump circuit to the capacitor CC via the diode. The CC can be charged.

C-3. Third modification:
In the drive voltage waveform generation circuit 100 of the above-described embodiment, it is possible to selectively use the power source and the capacitor CC by switching the switch SW0 (see FIG. 6C and FIG. 7C). However, it is possible not only to use the capacitor CC and the power supply properly, but also to connect both in series and use them simultaneously.

  FIG. 11 is an explanatory diagram showing a drive voltage waveform generation circuit of a third modified example in which a capacitor CC and a power source can be connected in series. As shown in the figure, in the drive voltage waveform generation circuit of the third modified example, it is possible to connect the capacitor CC and the power supply in series by switching the switch indicated by “C” in the drawing. Yes. If the drive voltage waveform generation circuit has such a configuration, it is possible to output a voltage obtained by adding the voltages of the power supply and all the capacitors (in the example of FIG. 11, the voltage indicated as “6E” in the figure). Therefore, the number of voltages that can be output can be further increased.

C-4. Fourth modification:
In the drive voltage waveform generation circuit of the above-described embodiment, the capacitor CC is described as being charged to the same voltage as the output voltage of the charge pump circuit. However, the capacitor CC may be charged to a voltage different from that of the power source and the capacitors C1 to C2, and is not necessarily charged to the same voltage as the output voltage of the charge pump.

  FIG. 12 is an explanatory diagram illustrating a drive voltage waveform generation circuit of a fourth modification that charges the capacitor CC to a voltage different from the output voltage of the charge pump circuit. As shown in FIG. 12A, in the drive voltage waveform generation circuit of the fourth modified example, it is possible to connect two capacitors, a capacitor CC1 and a capacitor CC2, in series (in the figure). (Refer to the part indicated by “D”) With two capacitors connected in series, these capacitors can be charged by a charge pump circuit. For this reason, each of the two capacitors is charged to a voltage half the output voltage of the charge pump circuit (a voltage indicated as “1.5E” in the figure). Then, since the voltage of the capacitor CC1 (or the capacitor CC2) is different from the voltage of the power supply and the capacitors C1 and C2, various types of capacitors C1 and C2 can be used by combining the power supply and the capacitor CC1 (or the capacitor CC2). A voltage can be output.

  Further, when the voltage is output using the capacitor CC1 and the capacitor CC2, as shown in FIG. 12B, the capacitor CC1 and the capacitor CC2 may be used in a state of being connected in parallel. In this way, the overall capacitance of the capacitor CC1 and the capacitor CC2 can be increased, so that more power can be supplied, and the frequency of charging the capacitor CC1 and the capacitor CC2 is reduced to reduce the driving voltage. Waveforms can be generated more quickly.

C-5. Fifth modification:
In the embodiment and the modification described above, when the charge pump circuit and the capacitor CC are connected in series with the output terminal, the charge pump circuit is connected to the output terminal side, and the capacitor CC is connected to the GND side. It has been described that it is connected (see FIG. 7C). However, conversely, a charge pump circuit may be connected to the GND side and a capacitor CC may be connected to the output terminal side.

  FIG. 13 is an explanatory diagram showing a drive voltage waveform generation circuit of a fifth modified example in which a charge pump is connected to the GND side and a capacitor CC is connected to the output terminal side. As shown in the figure, in the drive voltage waveform generation circuit 100 of the fifth modification, it is possible to connect the capacitor CC to the output terminal via a switch indicated by “F” in the drawing. In addition, the charge pump circuit can be connected to GND through the switch SW4. Therefore, in a state where the charge pump circuit and the capacitor CC are connected in series, the capacitor CC is connected to the output terminal side, and the charge pump circuit is connected to the GND side.

  In this case, since the charge pump circuit is connected to the GND, even when the charge pump circuit and the capacitor CC are connected in series and a high voltage is output, the voltage applied to each switch of the charge pump circuit is reduced. It can be kept low. For example, in the example of FIG. 13, it is possible to output a voltage value of “5E” by connecting the charge pump circuit and the capacitor CC in series, but the charge pump circuit is connected to GND. Therefore, the voltage applied to the switch SW1 is suppressed to “E”, which is the voltage of one capacitor. Similarly, the voltage applied to the switch SW2 is suppressed to “2E”, which is the voltage of two capacitors. In this way, if the charge pump circuit is connected to the GND side, the voltage applied to each switch of the charge pump circuit can be kept low. Therefore, each switch of the charge pump circuit has resistance to voltage (withstand voltage). However, it is possible to use a small switch. As a result, it is possible to further simplify the circuit configuration of the drive voltage waveform generation circuit 100 using a switch with a low withstand voltage, and further simplify the circuit for controlling the switch by using a switch with a low withstand voltage. Accordingly, the circuit configuration of the printer control circuit 50 (see FIG. 4) that controls the switch can be simplified.

  In the above, the ink jet printer equipped with the drive voltage waveform generation circuit of the present embodiment has been described. However, the present invention is not limited to all the above embodiments, and may be implemented in various modes without departing from the gist thereof. Is possible. For example, the drive voltage waveform generation circuit of this embodiment may be mounted on a printing apparatus (so-called line head printer or the like) having a larger ejection head. In the case of such a printing apparatus, since a large number of drive elements are mounted as the ejection head increases in size, the circuit configuration that generates the drive voltage waveform tends to increase in size. In this regard, if the drive voltage waveform generation circuit of this embodiment is used, the circuit configuration can be reduced in size.

  Further, in the above-described embodiment, the case where the drive voltage waveform generation circuit of the present embodiment is applied to the drive circuit of the piezo element of the ink jet printer has been described as an example. It is possible to apply to various devices that are driven according to the above. For example, the present invention can be applied to a display device that can operate with a voltage such as a liquid crystal panel or an organic EL panel. Further, in a fluid ejecting apparatus as a surgical tool for incising or excising a living tissue by ejecting a liquid such as water or saline in a pulse shape, the volume of the liquid chamber is changed by driving a piezo element to It is also possible to apply to a pulsating flow generation device that converts to a pulsating pulsating flow. Even when driving such a device, since various types of voltages can be output, various elements such as a liquid crystal element and an organic EL can be accurately operated. In addition, since various types of voltages can be output, the number of gradation values of the display device can be increased. Needless to say, not only the display device but also any device that can be driven by a voltage can output a wide variety of voltages, so that the device can be driven accurately.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet printer, 20 ... Carriage, 22 ... Carriage case, 24 ... Ejection head, 26 ... Ink cartridge, 30 ... Drive mechanism, 32 ... Timing belt, 34 ... Drive pulley, 36 ... Step motor, 38 ... Guide rail, 40 DESCRIPTION OF SYMBOLS ... Platen roller, 50 ... Printer control circuit, 100 ... Drive voltage waveform generation circuit, 200 ... Ejection port, 202 ... Ink chamber, 204 ... Piezo element, 300 ... Gate unit, 302 ... Gate element.

Claims (5)

A load driving circuit for driving the load by applying a voltage to the load,
A plurality of first power storage elements that are charged by receiving a supply of voltage from a power source;
A series power storage element group configuring unit that configures a series power storage element group in which the first power storage elements are connected in series by switching a connection state between the plurality of first power storage elements;
A second storage element charging means for charging a second storage element different from the first storage element using the series storage element group;
A first connection state in which the second storage element and the series storage element group are connected to a load in a state where the charged second storage element and the series storage element group are connected in series; and the second storage element, A load comprising: voltage applying means for switching a second connection state in which the series storage element group is connected to the load in a state in which the series connection with the series storage element group is disconnected, and applying a voltage to the load Driving circuit. The load driving circuit according to claim 1,
A second power storage element connecting means for connecting the second power storage element to the load in a state in which the series power storage element group is disconnected from the load;
The first power storage element is a load drive circuit that receives supply of voltage from the power source in a state where the second power storage element is connected to the load. A load driving circuit for driving the load by applying a voltage to the load,
A first power storage element that is charged by receiving a voltage from a power source;
A second power storage element that is charged by receiving a voltage from the power source;
A series power storage element group constituting means constituting a series power storage element group in which the first power storage element and the second power storage element are connected in series;
A third storage element charging means for charging a third storage element different from the first storage element and the second storage element by using the series storage element group;
In a state where the charged third storage element and the series storage element group are connected in series, a first connection state in which the third storage element and the series storage element group are connected to a load, and the third storage element A load comprising: voltage applying means for switching a second connection state in which the series storage element group is connected to the load in a state in which the series connection with the series storage element group is disconnected, and applying a voltage to the load Driving circuit. A load driving circuit according to any one of claims 1 to 3,
An injection nozzle for injecting liquid;
An actuator connected to the load drive circuit as the load and driven by the load drive circuit to eject the liquid from the ejection nozzle.   A printing apparatus comprising the liquid ejecting apparatus according to claim 4.

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