Image processing device having voltage generating unit outputting control voltage

This application claims priority from Japanese Patent Application No. 2013-015277 filed Jan. 30, 2013. The entire content of the priority application is incorporated herein by reference.

The present invention relates to a technique for converting a DC voltage supplied from an external power source into a drive voltage and using the drive voltage to control processing pertaining to image processing.

There is a conventional integrated circuit having a power saving mode function. The integrated circuit includes a power-supplied circuit block and a power control circuit block. Power form a source is supplied to the power-supplied circuit block via a transistor. The power control circuit block controls the supply of power to the power-supplied circuit block. After detecting that conditions for shifting into a power saving mode have been satisfied, the power-supplied circuit block notifies the power control circuit block of that fact. After receiving the notification, the power control circuit block turns the transistor OFF (Closing operation) to cut off the supply of power from the power-source power to the power-supplied circuit block. Then, the power control circuit block monitors whether a cut-off cancellation signal is received from outside. If the power control circuit block determines that the cut-off cancellation signal has been received, the power control circuit block turns the transistor ON (Opening operation) to restart the supply of power from the power-source power to the power-supplied circuit block.

However, in conventional configuration, such as described above, different regulators are used to individually generate a control voltage that is used to control a voltage conversion unit which converts the power-source voltage into a voltage for the power-supplied circuit block, and another control voltage that is used to control a monitoring unit which monitors the cut-off cancellation signal. Therefore, it is difficult to reduce the size of the circuit configuration.

In view of the foregoing, it is an object of the present invention to provide a technique for reducing the size of a circuit configuration that applies control voltage to the voltage conversion unit and the monitoring unit.

In order to attain the above and other objects, the invention provides an image processing device. The image processing device includes an image processing unit, a power supply unit, a control unit, and a receiving unit. The image processing unit is configured to perform a process concerning an image. The power supply unit is configured to output a drive voltage. The power supply unit includes a monitoring unit, a voltage conversion unit, and a voltage generating unit. The control unit is configured to be driven by the drive voltage and control the image processing unit. The receiving unit is configured to receive an operation instruction. The monitoring unit performs a monitoring operation to determine whether the receiving unit receives the operation instruction. The monitoring unit outputs an activation instruction to the voltage conversion unit when the monitoring unit determines that the receiving unit receives the operation instruction. In response to the activation instruction from the monitoring unit, the voltage conversion unit performs a voltage conversion operation for converting a voltage applied by an external power source to the drive voltage. The voltage generating unit generates a control voltage based on a voltage applied by the external power source and applies the control voltage to both the monitoring unit and the voltage conversion unit.

The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective diagram of a printer according to an embodiment of the invention;

FIG. 2 is a block diagram illustrating an electrical configuration of the printer according to the embodiment; and

FIG. 3 is a timing chart illustrating operations of a printing control unit and a power supply unit in the printer.

A printer 1 according to embodiment of the invention will be described while referring to the accompanying drawings. The printer 1 has a function printing an image on a sheet such as printing paper. In the following description, the terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used throughout the description assuming that the printer 1 is disposed in an orientation in which it is intended to be used. In use, the printer 1 is disposed as shown in FIG. 1 . In FIG. 1 , the upper direction, the front direction, and the right direction are respectively shown by “U”, “F”, and “R”.

(Exterior Configuration of Printing Device)

As shown in FIG. 1 , the printer 1 includes a box-like casing 2 . The casing 2 includes a storage cassette 3 in a bottom section thereof The storage cassette 3 can accommodate a plurality of unprinted sheets. The storage cassette 3 can be drawn forward. The casing 2 further includes a discharge opening 2 A and a discharge tray 2 B on an upper side thereof. Printed sheets are discharged onto the discharge tray 2 B via the discharge opening 2 A.

The discharge tray 2 B includes an operation panel 4 at a front side thereof. A plurality of operation buttons 4 A and a liquid crystal display 4 B are provided on the operation panel 4 . A user operates the operation panel 4 to set various kinds of operation of the printer 1 and give execution instructions. When one of the operation buttons 4 A is pressed, the operation panel 4 outputs an operation signal SG 1 to the monitoring circuit 21 . In a lower portion of the right side of the casing 2 , a power switch 5 is provided. The power switch 5 is a mechanical switch (relay).

(Electrical Configuration of Printer)

As shown in FIG. 2 , the printer 1 is connected to, for example, a commercial power source 7 via a low-voltage power source 6 . The low-voltage power source 6 carries out AC/DC conversion of AC power (AC 100 V, for example) from the commercial power source 7 , and outputs a DC voltage (voltage of DC power) of a first drive voltage V 1 (24 V, for example). The first drive voltage V 1 is a voltage required to drive a printing unit 10 and other components, which will be described later.

The printing unit 10 , a printing control unit 11 , and a power supply unit 12 are provided in the casing 2 . For example, the printing unit 10 is a printing mechanism of an electrophotographic type or ink jettype to print an image on unprinted sheets. The printing unit 10 includes a driving source 10 A. The drive source 10 A include a drive motor of a conveyance mechanism that carries a sheet, and a polygon motor that an optical scanning device includes.

The printing control unit 11 includes, for example, a central processing unit (referred to as CPU, hereinafter) 11 A, a memory 11 B, and an image processing unit 11 C. The memory 11 B includes, for example, a RAM and a ROM. The memory 11 B stores programs for performing various kinds of operation of the printer 1 , and image data. The CPU 11 A controls each section of the printer 1 in accordance with a program that is read from the memory 11 B. The media in which the various programs are stored include not only the memory 11 B, but also nonvolatile memories such as CD-ROMs, hard disk devices, and flash memories.

The power supply unit 12 is a composite circuit on which a plurality of circuits that perform different functions are provided. More specifically, the power supply unit 12 includes a DC/DC converter 20 , a monitoring circuit 21 , a register 22 , an oscillation circuit 23 , a regulator 24 , and a motor control circuit 25 .

The regulator 24 generates an internal voltage V 3 (e.g., 5 V) by regulating the first drive voltage V 1 , and applies the internal voltage V 3 to the DC/DC converter 20 , the monitoring circuit 21 , the register 22 , the oscillation circuit 23 , and the motor control circuit 25 . The internal voltage V 3 is used to operate (drive) the circuits 20 to 25 , or is a voltage that is required to carry out control of each of the functions. Incidentally, the regulator 24 may be a linear regulator or a switching regulator.

The oscillation circuit 23 outputs a clock signal CL of a predetermined frequency, and supplies the clock signal CL to the DC/DC converter 20 , the monitoring circuit 21 , the register 22 , and the motor control circuit 25 . Incidentally, the oscillation circuit 23 can employ publicly-known various structures.

The DC/DC converter 20 carries out a voltage conversion operation in which the first drive voltage V 1 output from the low-voltage power source 6 is converted into a second drive voltage V 2 (e.g., 3.3 V). The second drive voltage V 2 is a voltage (operation voltage) required to drive the printing control unit 11 . More specifically, the DC/DC converter 20 includes a control logic circuit 20 A and a conversion circuit 20 B. The internal voltage V 3 is applied to the control logic circuit 20 A. In the voltage conversion operation, the conversion circuit 20 B is applied by the first drive voltage V 1 and converts the first drive voltage V 1 to the second drive voltage V 2 . The control logic circuit 20 A is able to control the voltage conversion operation of the DC/DC converter 20 , such as switching operation, in synchronization with a clock cycle of the clock signal CL. In other words, the control logic circuit 20 A controls the conversion circuit 20 B when the voltage conversion operation is performed.

The monitoring circuit 21 can operate by the applied internal voltage V 3 . The monitoring circuit 21 determines whether or not one of the operation buttons 4 A of the operation panel 4 is pressed. After the monitoring circuit 21 determines, based on the operation signal SG 1 from the operation panel 4 , that the operation button 4 A is pressed, the monitoring circuit 21 outputs an ON-instruction signal SG 2 to the register 22 .

The monitoring circuit 21 includes a frequency division circuit 21 A and a noise cancel circuit 21 B. The frequency division circuit 21 A outputs frequency-divide clock that is obtained by dividing the frequency of the clock signal CL from the oscillation circuit 23 . The noise cancel circuit 21 B is a circuit that removes a noise signal generated by chattering or electromagnetism of peripheral devices from a signal input into the monitoring circuit 21 , at timing that is in synchronization with the clock cycle obtained by frequency-division of the frequency division circuit 21 A. The noise cancel circuit 21 B allows the monitoring circuit 21 to accurately monitor a signal generated by pushing of the operation button 4 A. Moreover, the noise cancel circuit 21 B uses the clock cycle obtained by the frequency-division circuit 21 A. Compared with a structure in which the clock cycle that is not yet frequency-divided is used, the monitoring circuit 21 can reduce power consumed by the noise cancel operation, while appropriately determining whether the signals are noise.

The register 22 can perform a writing operation in synchronization with the clock cycle of the clock signal CL when the internal voltage V 3 is applied to the register 22 . The printing control unit 11 registers OFF-instruction information on the register 22 . The monitoring circuit registers ON-instruction information on the register 22 by outputting the signal SG 2 . Here, the OFF-instruction information and the ON-instruction information are selectively registered on the register 22 . The motor control circuit 25 can control to drive the drive source 10 A included in the printing unit 10 , at timing in synchronization with the clock cycle of the clock signal CL, when the internal voltage V 3 is applied to the motor control circuit 25 .

(Operation of Printing Control Unit and Power Supply Unit)

After a user connects the low-voltage power source 6 to the commercial power source 7 and turns the power switch 5 ON, as shown in FIG. 3 , the low-voltage power source 6 outputs power of the first drive voltage V 1 . Then, the regulator 24 outputs the internal voltage V 3 generated from the first drive voltage V 1 . The oscillation circuit 23 outputs the clock signal CL when the internal voltage V 3 is applied to the oscillation circuit 23 .

When the internal voltage V 3 is applied to the control logic circuit 20 A, the control logic circuit 20 A controls the conversion circuit 20 B to perform the voltage conversion operation in synchronization with the clock cycle of the clock signal CL. The conversion circuit 20 B begins to apply the second drive voltage V 2 to the printing control unit 11 . The control logic circuit 20 A regularly and repeatedly carries out an ON/OFF monitoring process to check if either the OFF-instruction information or the ON-instruction signal has been written in the register 22 . In a normal mode described below, the ON-instruction information is written in the register 22 .

The printing control unit 11 can switch between the normal mode and an OFF mode. The normal mode is an operation mode in which the printing control unit 11 can control a printing operation of the printing unit 10 as the second drive voltage V 2 is applied to the printing control unit 11 . The OFF mode is a power saving mode in which the second drive voltage V 2 is not applied to the printing control unit 11 and the printing control unit 11 cannot control the printing operation of the printing unit 10 . The printing control unit 11 may be configured shift into not only the OFF mode, but also into another power saving mode in which power consumption is less than in the normal mode. Or, the printing control unit 11 may switch between the normal mode and another power saving mode in which power consumption is less than in the normal mode. As the second drive voltage V 2 is applied from the conversion circuit 20 B, the printing control unit 11 shifts into the normal mode, and, for example, the printing control unit 11 monitors, through the monitoring circuit 21 , whether or not one of the operation buttons 4 A is pressed. If the printing control unit 11 determines, based on the monitoring results, that printing instruction is received, then, the printing control unit 11 starts the printing operation of the printing unit 10 .

In the normal mode, the printing control unit 11 regularly and repeatedly performs a transition determination process to determine whether predetermined transition conditions are satisfied. For example, the transition conditions include whether a standby state in which the operation panel 4 does not accept the user's input operations such as printing instructions continues for a reference period of time. If the printing control unit 11 determines that the transition conditions have been satisfied, then the printing control unit 11 performs a writing process. In the writing process, the printing control unit 11 writes the OFF-instruction information in the register 22 .

After confirming, through the ON/OFF monitoring process, that the OFF-instruction information has been written in the register 22 , the control logic circuit 20 A stops the ON/OFF monitoring process, and also stops the voltage conversion operation of the DC/DC converter 20 , that is, the control logic circuit 20 A prevents the conversion circuit 20 B from applying the second drive voltage V 2 to the printing control unit 11 . In this manner, the printing control unit 11 shifts into the OFF mode. The internal voltage V 3 is applied to the motor control circuit 25 . The motor control circuit 25 can perform an operation for controlling the drive source 10 A. Moreover, the motor control circuit 25 regularly and repeatedly carries out an ON/OFF monitoring process to check if either the OFF-instruction information or the ON-instruction signal has been written in the register 22 .

The internal voltage V 3 is applied to the monitoring circuit 21 . The monitoring circuit 21 therefore performs an operation monitoring process to determine whether or not one of the operation buttons 4 A of the operation panel 4 is pressed, regardless of whether the printing control unit 11 is in the normal mode or the OFF mode. The monitoring circuit 21 may monitor, in the OFF mode, only a specific operation button 4 A that functions as a soft power switch, out of a plurality of operation buttons 4 A. More specifically, for example, the monitoring circuit 21 repeatedly reads operation signals SG 1 in accordance with the clock cycle obtained by frequency-division of the frequency division circuit 21 A.

The noise cancel circuit 21 B compares a signal level of each of the inputted operation signals SG 1 with an operation determination threshold value for each of the clock cycles obtained by frequency-division of the frequency-division circuit 21 A. If an event in which the signal level is greater than or equal to the operation determination threshold value happens a reference number of times (e.g., three times) or more sequentially, then the noise cancel circuit 21 B determines that one of the operation buttons 4 A is pressed. If the number of the events in which the signal level is greater than or equal to the operation determination threshold value is less than the reference number, then the noise cancel circuit 21 B determines that the signal is noise, and that none of the operation buttons 4 A is pressed.

In the normal mode, the monitoring circuit 21 sequentially write the results of monitoring by the operation monitoring process in the register 22 . The printing control unit 11 sequentially checks the information written in the register 22 , and controls the printing unit 10 based on the checked information. In the OFF mode, if the monitoring circuit 21 determines, through the operation monitoring process, that one of the operation buttons 4 A is pressed, then the monitoring circuit 21 gives a startup signal SG 3 to the control logic circuit 20 A, and performs a writing process to write the ON-instruction information in the register 22 .

After receiving the startup signal SG 3 , the control logic circuit 20 A restarts an ON/OFF monitoring process. Then, the control logic circuit 20 A confirms that the ON-instruction information has been written in the register 22 , and instructs the conversion circuit 20 B to start the voltage conversion operation again, and begins to apply the second drive voltage V 2 to the printing control unit 11 . As a result, the printing control unit 11 goes back to the normal mode from the OFF mode.

(Advantageous Effects of the Embodiment)

According to the embodiment, the DC/DC converter 20 and the monitoring circuit 21 can operate by the applied internal voltage V 3 generated by the common regulator 24 . Compared with a structure in which different voltage generation units apply control voltages to the DC/DC converter 20 and the monitoring circuit 21 such as regulators, the size of the circuit configuration used to apply control voltage to the DC/DC converter 20 and the monitoring circuit 21 can be reduced. Moreover, the register 22 , the oscillation circuit 23 , and the motor control circuit 25 , too, can operate by the internal voltage V 3 generated by the common regulator 24 . Therefore, the size of the circuit configuration of the entire power supply unit 12 can be further reduced, and power consumption can be reduced.

The DC/DC converter 20 , the monitoring circuit 21 , the register 22 , and the motor control circuit 25 perform various kinds of operation by using the clock signal CL from the common oscillation circuit 23 . Compared with a structure in which a plurality of oscillation units respectively dedicated for the monitoring circuit 21 , the register 22 , and the motor control circuit 25 are provided, the size of the circuit configuration used to output the clock signal can be reduced, and power consumption can be reduced.

The noise cancel circuit 21 B reads an operation signal level in accordance with the clock cycle obtained by frequency-division of the frequency division circuit 21 A, and compares the operation signal level with the operation determination threshold value to remove noise. Therefore, the DC/DC converter 20 and the noise cancel circuit 21 B can use the clock signal CL of the common oscillation circuit 23 , while the DC/DC converter 20 and the noise cancel circuit 21 B operate in accordance with different cycles.

While the invention has been described in detail with reference to the embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention.

The present invention can be applied not only to the printer 1 , but also to a facsimile machine, a copy machine, or a multifunction machine that include other functions such as a scanning function along with a printing function. Or, the present invention can be applied to an image display device that displays an image on a display medium such as a display screen not shown in figures, an image scanning device that scans an image on a document sheet, or an image data processing device that makes modifications, such as conversion or editing, to image data.

Instead of the operation panel 4 , as a mechanism for accepting operation instructions input by a user, a signal reception unit may be provided to accept, as operation instructions, external signals from external devices, such as the cut-off cancel signal that instructs to cancel stopping the voltage conversion operation of the DC/DC converter 20 . The operation buttons 4 A may be of a mechanical-button type such as push button, or be of a soft-button type such as touch panel.

Instead of the printing unit 10 , a mechanism that performs processing pertaining to images may be provided, such as a display unit that displays an image on a display medium, an image scanning unit, or an image data conversion unit.

In the embodiment, the CPU 11 A or the image processing unit 11 C controls operations of the printing control unit 11 . However, a plurality of CPUs controls the operation s of the image processing unit 11 C together. Or, only hardware such as ASIC (Application Specific Integrated Circuit) controls the operations of the image processing unit 11 C.

Instead of logic circuits such as the register 22 , RAMs or flash memories may be provided.

Instead of the regulator 24 , other publicly-known constant-voltage circuits may be provided.

Instead of hardware circuits such as the monitoring circuit 21 , a CPU and a memory are provided and the CPU controls a monitoring operation. Or, a CPU and a hardware circuit control are provided, and the CPU together with the hardware circuit performs a monitoring operation together. The monitoring circuit 21 may not include a noise cancel circuit.

When the printing unit 10 include an applying circuit that applies a printing bias voltage to a photo conducting member, a voltage control circuit instead of the motor control circuit 25 may be provided to control whether or not to apply the bias voltage to the photo conducting member.

If the control logic circuit 20 A confirms that the OFF-instruction information has been written in the register 22 , the control logic circuit 20 A may stop the voltage conversion operation of the DC/DC converter 20 while continuing the ON/OFF monitoring process.

The power supply unit 12 may have different regulator from the regulator 24 . At least one of the register 22 , the oscillation circuit 23 , and the motor control circuit 25 may run on an internal voltage generated by that different regulator.

The power supply unit 12 may have a different oscillation circuit from the oscillation circuit 23 . At least one of the register 22 and the motor control circuit 25 may be operated by a clock signal supplied from that different oscillation circuit.