Malfunction prevention device, image forming apparatus, and malfunction prevention method

Abstract

To prevent a malfunction of a protective circuit to continue the operation of a control unit even after a power switch is switched off.SOLUTION: A malfunction prevention device comprises: a power supply circuit 7 that is connected with an external power supply 100 and generates a first power supply output V1 and a second power supply output V2 from the external power supply 100; a control unit 8 that operates with the first power supply output V1 of the power supply circuit 7; a drive mechanism 70 that operates with the second power supply output V2 of the power supply circuit 7; a power supply switch 66 that switches off the second power supply output V2 in the power supply circuit 7; and a protection circuit (second output protection circuit 55) that protects the power supply circuit 7 while the second power supply output V2 is abnormal. When the second power supply output V2 is switched off by the power supply switch 66 in the operating state of the drive mechanism 70, the control unit 8 prevents a malfunction of the protection circuit.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a malfunction prevention device, an image forming apparatus, and a malfunction prevention method, and more particularly to a technique for preventing malfunction in an image forming apparatus. [Background technology]

[0002] Image forming devices such as MFPs (Multifunction Peripherals) installed in offices are devices shared by multiple users and execute various jobs such as copy jobs, scan jobs, print jobs, and fax jobs based on user instructions. In recent years, in order to accommodate teleworking and other needs, this type of image forming device is required to maintain its communication function via a network in an active state even when the power switch is turned off.

[0003] Conventionally, an image forming apparatus has been proposed in which a power switch that can be turned on and off by a user is connected to a control unit (for example, Patent Document 1). According to this conventional technology, when the power switch is turned off, a power control unit provided in the control unit can stop the power supply to each unit. Therefore, for example, when the power switch is turned off, the power supply to units other than the communication function is stopped, and the power supply to the unit that controls the communication function is continued, thereby maintaining the communication function in an active state. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-242680 Summary of the Invention [Problem to be solved by the invention]

[0005] 8 is a diagram showing an example of the configuration of a circuit in which a power switch 121 is connected to a control unit 120. This circuit includes a power supply circuit 110 connected to an external power supply 100, a control unit 120 driven by a first power output V1 generated in the power supply circuit 110, and a drive mechanism 130 driven by a second power output V2 generated in the power supply circuit 110. For example, the first power output V1 is a DC 5V power output, and the second power output V2 is a DC 24V power output.

[0006] The control unit 120 includes a CPU, a memory, and the like, and operates using the first power output V1 supplied from the power supply circuit 110 to control the operation of each unit. The control unit 120 is also capable of communicating via a network. A power switch 121 is connected to the control unit 120. Furthermore, the control unit 120 includes a power control unit 122 that operates when the power switch 121 is switched off.

[0007] The drive mechanism 130 includes various drive units mounted in the image forming apparatus. The drive mechanism 130 operates the various drive units using the second power output V2 supplied from the power supply circuit 110. For example, the drive mechanism 130 includes a polygon motor 131 that is driven when exposing an image carrier in the image forming apparatus.

[0008] The power supply circuit 110 includes a first converter 111 that generates a first power output V1 from AC power supplied from the external power supply 100, a second converter 112 that generates a second power output V2 from the AC power, a first output protection circuit 113 that is inserted on the output side of the first converter 111, and a second output protection circuit 114 that is inserted on the output side of the second converter 112. The first output protection circuit 113 monitors the current and voltage on its output side and, upon detecting an overcurrent or overvoltage, outputs a stop signal CNT1 to the first converter 111. This causes the first converter 111 to stop operating and stop the first power output V1. The second output protection circuit 114 also monitors the current and voltage on its output side and, upon detecting an overcurrent or overvoltage, outputs a stop signal CNT2 to the first converter 111. This causes the first converter 111 to stop operating and stop the first power output V1. Furthermore, upon receiving the stop signals CNT1 and CNT2, the first converter 111 outputs a stop signal CNT3 to the second converter 112. This causes the second converter 112 to stop operating and stop the second power supply output V2. In this way, the first output protection circuit 113 and the second output protection circuit 114 are configured to stop the function of the power supply circuit 110 when either one of them detects an overcurrent or an overvoltage.

[0009] Conventionally, in the above-described configuration, when the power switch 121 is switched off, the power supply control unit 122 outputs a stop signal CNT4 to the second converter 112. This causes the second converter 112 to stop operating and stop the second power output V2. On the other hand, the power supply control unit 122 does not output a stop signal to the first converter 111, so the first converter 111 does not stop operating and continues to output the first power output V1. Therefore, even when the power switch 121 is switched off, the control unit 120 can continue operating using the continuously supplied first power output V1, and can communicate via a network.

[0010] However, in the above configuration, for example, when the image forming apparatus is executing a print job and driving the polygon motor 131 of the drive mechanism 130, the power switch 121 may be turned off. At this time, when the power supply control unit 122 outputs a stop signal CNT4 to the second converter 112 to stop the operation of the second converter 112, the second power output V2 input to the second output protection circuit 114 is stopped. Accordingly, the second power output V2 output from the second output protection circuit 114 is also stopped.

[0011] On the other hand, because the polygon motor 131 has high inertia, it continues to rotate even after the second power output V2 has stopped. As a result, a back electromotive force or regenerative power is generated in the polygon motor 131 after the second power output V2 has stopped. When such a back electromotive force or regenerative power is generated, the second output protection circuit 114 erroneously detects that an overvoltage has occurred on the output side, causing a malfunction in which a stop signal CNT2 is output to the first converter 111. In this case, the first power output V1 supplied to the control unit 120 stops, causing a problem in that communication via the network becomes impossible.

[0012] The present invention has been made to solve the above problems, and aims to provide a malfunction prevention device, an image forming apparatus, and a malfunction prevention method that can prevent malfunctions caused by protection circuits. [Means for solving the problem]

[0013] In order to achieve the above object, the invention of claim 1 is a malfunction prevention device, comprising: a power supply circuit connected to an external power supply and generating a first power output and a second power output from the external power supply; a control unit operated by the first power output of the power supply circuit; a drive mechanism operated by the second power output of the power supply circuit; a power switch for switching on / off the second power output of the power supply circuit; By detecting an overcurrent or an overvoltage as an abnormality and stopping the power supply circuit when an abnormality is detected, a protection circuit for protecting the power supply circuit, the drive mechanism includes a movable member having a coil mounted thereon, and the movable member is driven by the second power output;When the second power output is switched off by the power switch while the drive mechanism is in an operating state, the control unit The protection circuit is controlled so that the protection circuit does not erroneously detect an abnormality due to a back electromotive force or a regenerative power generated in the coil, and the first power output is continuously output by the power supply circuit. The configuration is characterized by the above.

[0014] The invention according to claim 2 is the malfunction prevention device of claim 1, wherein the control unit stops operation of the protection circuit when the second power supply output is switched off by the power switch while the drive mechanism is in an operating state. The protection circuit may falsely detect an abnormality. This configuration is characterized by preventing this.

[0015] The invention according to claim 3 is the malfunction prevention device of claim 1, wherein the control unit changes a level at which the protection function of the protection circuit operates when the second power output is switched off by the power switch while the drive mechanism is in an operating state. The protection circuit may falsely detect an abnormality. This configuration is characterized by preventing this.

[0016] The invention of claim 4 is a malfunction prevention device of any of claims 1 to 3, characterized in that the power supply circuit generates the first power supply output and the second power supply output independently and separately from the external power supply.

[0017] The invention of claim 5 is a malfunction prevention device of any one of claims 1 to 4, characterized in that the power supply circuit includes a first transformer that generates the first power supply output and a second transformer that generates the second power supply output.

[0018] The invention of claim 6 is a malfunction prevention device of any of claims 1 to 4, characterized in that the power supply circuit is configured such that a first secondary coil that generates the first power supply output and a second secondary coil that generates the second power supply output are wound around a core around which a primary coil to which the external power supply is connected is wound.

[0019] The invention according to claim 7 is the malfunction prevention device according to any one of claims 1 to 6, wherein the protection circuit is configured to detect an abnormality in the second power supply output. When it detectsThe configuration is characterized in that both the first power output and the second power output are stopped.

[0020] The invention of claim 8 is characterized in that, in the malfunction prevention device of any of claims 1 to 7, the control unit stops the second power output by the power supply circuit when the power switch is turned off.

[0021] The invention of claim 9 is a malfunction prevention device of any of claims 1 to 8, characterized in that the first power supply output is a DC power supply of a predetermined voltage, and the second power supply output is a DC power supply of a higher voltage than the first power supply output.

[0023] Claim 10 The invention according to claim Any of 1 to 9 In the malfunction prevention device, the movable member includes a motor or a solenoid.

[0024] Claim 11 The invention according to claim 1 to 10 In any one of the malfunction prevention devices, the drive mechanism drives a load when the second power output is supplied, and when the second power output is stopped, the drive mechanism drives the load by inertia. With the coil This configuration is characterized by generating a counter electromotive force.

[0025] Claim 12 The invention relates to: The malfunction prevention device according to any one of claims 1 to 11, The drive mechanism drives a plurality of loads by being supplied with the second power output, and the control unit, when the second power output is switched off by the power switch while the drive mechanism is in an operating state, controls the protection circuit in accordance with an operating state of a load among the plurality of loads whose inertial force is greater than a predetermined value. may falsely detect anomalies. This configuration is characterized by preventing this.

[0026] Claim 13 The invention relates to an image forming apparatus, comprising claims 1 to 12The configuration is characterized by including any one of the above malfunction prevention devices.

[0027] Claim 14 The invention according to claim 13 In the image forming apparatus, the drive mechanism is characterized by having a polygon motor.

[0028] Claim 15 The invention according to claim 13 or 14 In the image forming apparatus, the control unit is provided with a communication unit that communicates with an external device via a network.

[0029] Claim 16 The present invention relates to a power supply circuit connected to an external power supply and generating a first power output and a second power output from the external power supply, and a control unit operated by the first power output of the power supply circuit, A movable member having a coil mounted thereon is provided. a drive mechanism operated by the second power output of the power supply circuit; a power switch for switching off the second power output of the power supply circuit; By detecting an overcurrent or an overvoltage as an abnormality and stopping the power supply circuit when an abnormality is detected, a protection circuit for protecting the power supply circuit, when the second power output is switched off by the power switch while the drive mechanism is in an operating state, The protection circuit is controlled so that the protection circuit does not erroneously detect an abnormality due to a back electromotive force or a regenerative power generated in the coil, and the first power output from the power supply circuit is continuously output to the control unit. The configuration is characterized by the above.

[0030] Claim 17 The invention according to claim 16 a protection circuit for preventing a malfunction of the drive mechanism when the second power supply output is switched off by the power supply switch while the drive mechanism is in an operating state, the protection circuit being stopped from operating; may falsely detect anomalies This configuration is characterized by preventing the above.

[0031] Claim 18 The invention according to claim 16a level at which a protection function of the protection circuit is activated when the second power supply output is switched off by the power switch while the drive mechanism is in an operating state, may falsely detect anomalies This configuration is characterized by preventing the above. [Effects of the Invention]

[0032] According to the present invention, even if the power switch is operated and the second power output is switched off while the drive mechanism is in operation, the first power output can be continuously supplied to the control unit by preventing malfunction due to the protection circuit, so that the control unit can continue to operate even after the power switch is turned off. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 illustrates an example of the configuration of an image forming apparatus. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of an exposure unit. [Figure 3] FIG. 2 is a block diagram showing a detailed configuration example of a power supply circuit and a control unit of the image forming apparatus. [Figure 4] 10 is a flowchart showing a first processing procedure performed by a control unit. [Figure 5] 10 is a flowchart showing a second processing procedure performed by the control unit. [Figure 6] 10 is a flowchart showing a third processing procedure performed by the control unit. [Figure 7] FIG. 2 is a diagram illustrating a circuit configuration for separately generating a first power output and a second power output. [Figure 8] FIG. 1 is a diagram showing an example of the configuration of a conventional circuit in which a power switch is connected to a control unit. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Elements common to the embodiments described below are designated by the same reference numerals, and redundant description thereof will be omitted.

[0035] 1 is a diagram showing an example of the configuration of an image forming apparatus 1 according to one embodiment of the present invention. This image forming apparatus 1 is configured as an MFP (Multifunction Peripheral) equipped with multiple functions, such as copy, scan, print, and fax functions, and executes jobs designated by a user. This image forming apparatus 1 includes a printer unit 2, a scanner unit 3, an automatic document feeder (ADF) 4, an operation panel 5, a power supply circuit 7, and a control unit 8.

[0036] The scanner unit 3 is, for example, a flatbed image reading device that optically reads the image of a document set by a user and generates image data. The automatic document feeder 4 is located above the scanner unit 3 and automatically transports documents set on the document tray one by one to a position where the image is read by the scanner unit 3. The scanner unit 3 can not only read images from documents automatically transported by the automatic document feeder 4, but can also read images from a single document set on, for example, a platen glass. For example, the scanner unit 3 is provided with a drive mechanism such as a motor that moves the scanning optical system along the sub-scanning direction of the document when reading the image of the document set on the platen glass. The automatic document feeder 4 also is provided with a drive mechanism such as a motor that rotates a transport roller to automatically transport documents set on the document tray one by one.

[0037] The operation panel 5 serves as a user interface when the user uses the image forming apparatus 1. The operation panel 5 includes a display unit 6 that displays various setting screens and the like that can be operated by the user. For example, the display unit 6 includes a touch panel that can detect touch operations and the like by the user, and is configured as a display device that can display color images.

[0038] The printer unit 2 forms and outputs an image on a sheet 10 such as printing paper by, for example, electrophotography. The printer unit 2 includes a sheet transport mechanism 2a that transports the sheet 10, and an image forming mechanism 2b.

[0039] The sheet transport mechanism 2a picks up the top sheet 10 from a stack of sheets 10 stored in a paper feed tray 11 and transports the sheet 10 in the direction of arrow F1 along a transport path 14 indicated by a dashed line in the figure. For example, the image forming apparatus 1 is provided with multiple paper feed trays 11, and the sheet transport mechanism 2a feeds the sheet 10 from one of the multiple paper feed trays 11 designated by the user. The sheet transport mechanism 2a sends the single sheet 10 stored in the paper feed tray 11 to the transport path 14 using a pickup roller 12 and a paper feed roller 13. The transport path 14 is provided with a timing roller 15, a secondary transfer roller 16, a fixing unit 17, and a paper discharge roller 18. The sheet 10 transported along the transport path 14 stops temporarily at the position of the timing roller 15. Then, in the image forming mechanism 2b, timing roller 15 is driven to coincide with the time when the toner image that has been primarily transferred onto intermediate transfer belt 25 reaches the position of secondary transfer roller 16, and sheet 10 is fed toward secondary transfer roller 16. As a result, when sheet 10 passes the position of secondary transfer roller 16, the toner image that has been primarily transferred onto intermediate transfer belt 25 is secondarily transferred onto the surface of sheet 10. Sheet 10 with the transferred toner image is then subjected to heat and pressure treatments as it passes through fixing unit 17, and the toner image is fixed to its surface. Then, sheet 10 with the fixed toner image is discharged from discharge roller 18 onto discharge tray 19 on the top surface of printer unit 2.

[0040] The sheet conveying mechanism 2a also has a reversing path 20 that reverses the sheet 10. The reversing path 20 is provided with a path switching member 21 for switching the conveying path of the sheet 10 and a conveying roller 22 that conveys the sheet 10 in an inverted state through the reversing path 20. When forming images on both sides of the sheet 10, the path switching member 21 is driven to guide the sheet 10 with the image formed on the front side to the reversing path 20, and the conveying roller 22 is driven to turn the sheet 10 upside down in the reversing path 20 and supply it again to the timing roller 15. The path switching member 21 is driven by, for example, a solenoid and is configured to switch the conveying path of the sheet 10.

[0041] The image forming mechanism 2b includes a drive roller 23, a driven roller 24, an intermediate transfer belt 25, a secondary transfer roller 16, image forming units 30Y, 30M, 30C, and 30K that are individually provided corresponding to each of the colors Y (yellow), M (magenta), C (cyan), and K (black), and primary transfer rollers 26Y, 26M, 26C, and 26K that are arranged opposite each image forming unit 30Y, 30M, 30C, and 30K across the intermediate transfer belt 25.

[0042] The drive roller 23 is disposed opposite the secondary transfer roller 16 across the conveyance path 14 for the sheet 10, and is driven to rotate in a predetermined direction (counterclockwise) by a drive mechanism such as a motor (not shown). The driven roller 24 is disposed at a position spaced apart from the drive roller 23, at approximately the same height as the drive roller 23. The intermediate transfer belt 25 is an endless belt stretched over the drive roller 23 and the driven roller 24. The driven roller 24 is biased in a direction away from the drive roller 23 (to the left in FIG. 1) by a spring (not shown), thereby applying tension to the intermediate transfer belt 25. When the drive roller 23 is driven to rotate in a predetermined direction, the intermediate transfer belt 25 moves in a circular motion in the direction of arrow F2 in the figure, and the driven roller 24 is also rotated accordingly.

[0043] Image forming units 30Y, 30M, 30C, and 30K for the respective colors Y, M, C, and K are arranged at predetermined intervals below the intermediate transfer belt 25. The image forming units 30Y, 30M, 30C, and 30K only differ in the color of toner they handle, but have common specific configurations and operations. Hereinafter, when there is no need to distinguish between the image forming units 30Y, 30M, 30C, and 30K for the respective colors, they will be collectively referred to simply as "image forming unit 30."

[0044] The image forming unit 30 includes an image carrier 31 disposed opposite each of the primary transfer rollers 26Y, 26M, 26C, and 26K across the intermediate transfer belt 25. The image carrier 31 is formed, for example, as a photosensitive drum with a photosensitive layer formed on the surface of a cylindrical drum. Around the image carrier 31, a cleaner 35, a charging unit 32, an exposure unit 33, and a developing unit 34 are arranged. The cleaner 35 is used to remove toner remaining on the surface of the image carrier 31 without being primarily transferred to the intermediate transfer belt 25. The charging unit 32 charges the photosensitive layer on the surface of the image carrier 31 to a predetermined charge. The exposure unit 33 has a light source, such as a semiconductor laser or a light-emitting diode, and irradiates and exposes the surface of the image carrier 31 with light L4 from the light source based on image data to be drawn, thereby forming an electrostatic latent image on the photosensitive layer of the image carrier 31, which has been charged to a predetermined charge.

[0045] FIG. 2 is a diagram showing an example of the configuration of the exposure unit 33. The exposure unit 33 includes a light source 40, a polygon motor 41, an optical system 44, and a mirror 45. The light source 40 emits light (e.g., laser light) for exposing the image carrier 31. The polygon motor 41 deflects and scans the light from the light source 40, and includes a motor 42 and a polygon mirror 43. The polygon mirror 43 is a polyhedral mirror that is rotated by the motor 42. The motor 42 is a drive mechanism that rotates the polygon mirror 43 in a predetermined rotation direction (R direction). The optical system 44 includes, for example, an fθ lens. Light L1 emitted from the light source 40 is irradiated onto a predetermined position on the rotating polygon mirror 43 and converted into light L2 that is deflected and scanned by the rotation of the polygon mirror 43. The light L2 is converted by the optical system 44 into light L3 that scans at a constant speed in the main scanning direction (X direction). The light L3 is reflected by the mirror 45 to become light L4 that exposes the image carrier 31. An electrostatic latent image is formed on the surface of the image carrier 31 by this light L4.

[0046] The polygon motor 41 drives the polygon mirror 43, which has high inertia, to rotate at high speed. For example, even if the supply of power to drive the motor 42 is stopped while the polygon mirror 43 is rotating, the polygon mirror 43 continues to rotate due to inertia. Meanwhile, the motor 42 is equipped with a coil for rotating the rotation shaft to which the polygon mirror 43 is attached. Therefore, after the supply of power to drive the motor 42 is stopped, the polygon mirror 43 continues to rotate due to inertia, generating back electromotive force and regenerative power in the motor 42.

[0047] 1, the developing unit 34 is filled with a developer containing toner, and by applying the developer to the surface of the image carrier 31, the electrostatic latent image formed by the exposure unit 33 is visualized with toner. As a result, a toner image is formed on the surface of the image carrier 31.

[0048] The toner image formed on the surface of the image carrier 31 is primarily transferred to the intermediate transfer belt 25 when the intermediate transfer belt 25 passes between the image carrier 31 and the primary transfer rollers 26Y, 26M, 26C, and 26K. The primary transfer rollers 26Y, 26M, 26C, and 26K are driven to move toward and away from the image carrier 31 by, for example, a solenoid, and can bring the intermediate transfer belt 25 into contact with or separate from the surface of the image carrier 31. When the toner image formed on the image carrier 31 is primarily transferred to the intermediate transfer belt 25, each of the primary transfer rollers 26Y, 26M, 26C, and 26K brings the intermediate transfer belt 25 into contact with the image carrier 31 and applies a predetermined voltage to the roller surface, thereby primarily transferring the toner image from the image carrier 31 to the intermediate transfer belt 25.

[0049] This operation is performed sequentially in the image forming units 30Y, 30M, 30C, and 30K for each color, whereby Y, M, C, and K toner images are sequentially superimposed and primarily transferred onto the intermediate transfer belt 25, forming a color image. This color image is secondarily transferred onto the sheet 10 when the sheet 10 passes through the nip portion between the intermediate transfer belt 25 and the secondary transfer roller 16. Note that toner that is not secondarily transferred onto the sheet 10 and remains on the intermediate transfer belt 25 is collected by a cleaning means (not shown).

[0050] In addition to the polygon motor 41, the image forming mechanism 2b as described above is provided with a drive motor that rotates various rollers such as the pickup roller 12, and a drive mechanism that drives movable members such as solenoids that drive the path switching member 21 and primary transfer rollers 26Y, 26M, 26C, and 26K.

[0051] Next, the functions of the power supply circuit 7 and the control unit 8 will be described. FIG. 3 is a block diagram showing an example of the configuration of the power supply circuit 7 and the control unit 8 of the image forming apparatus 1. The power supply circuit 7 is connected to an external power supply 100, generates a first power output V1 and a second power output V2 from AC power supplied from the external power supply 100, and supplies power to each unit of the image forming apparatus 1. The control unit 8 includes, for example, a CPU and memory (not shown), and operates using the first power output V1 output from the power supply circuit 7 to control the operation of each unit. The drive mechanism 70 includes movable members such as the various motors and solenoids provided in the image forming apparatus 1. For example, as shown in FIG. 3, the drive mechanism 70 includes a polygon motor 41, a drive motor 71, and a solenoid 72. The drive motor 71 may be a DC brushless motor, a stepping motor, a DC brush motor, or an AC motor. The drive mechanism 70 is configured to drive the polygon motor 41, drive motor 71, and solenoid 72 using the second power output V2 output from the power supply circuit 7. For example, the first power output V1 and the second power output V2 are both DC power supplies of a predetermined voltage, and the second power output V2 has a higher voltage than the first power output V1. Specifically, the power supply circuit 7 outputs the first power output V1 as DC 5V and the second power output V2 as DC 24V.

[0052] The power supply circuit 7 includes a noise filter 50, a PFC (Power Factor Correction) circuit 51, a first converter 52, a second converter 53, a first output protection circuit 54, and a second output protection circuit 55. The noise filter 50 is connected to an external power supply 100 and removes noise input from the external power supply 100. The PFC circuit 51 rectifies AC power to DC while correcting the power factor and outputs the DC power. The first converter 52 is configured, for example, by a DC / DC converter and converts the DC power output from the PFC circuit 51 into a first power output V1 of a first voltage (e.g., 5 V) and outputs the first power output V1. The second converter 53 is configured, for example, by a DC / DC converter different from the first converter 52 and converts the DC power output from the PFC circuit 51 into a second power output V2 of a second voltage (e.g., 24 V) and outputs the second power output V2.

[0053] The first output protection circuit 54 is interposed between the first converter 52 and the control unit 8. The first output protection circuit 54 monitors the current and voltage on its output side and detects an overcurrent or overvoltage as an abnormality. When the first output protection circuit 54 detects an overcurrent or overcurrent abnormality, it stops the function of the power supply circuit 7 to protect the power supply circuit 7 and the image forming apparatus 1. For example, when the first output protection circuit 54 detects an overcurrent or overvoltage on the output side, it outputs a stop signal CNT1 to the first converter 52. This causes the first converter 52 to stop operating and stop outputting the first power output V1. Furthermore, when the first converter 52 stops operating in response to the stop signal CNT1, it outputs a stop signal CNT3 to the second converter 53. This also causes the second converter 53 to stop operating and stop outputting the second power output V2. Therefore, when the first output protection circuit 54 detects an overcurrent or an overvoltage, the power supply circuit 7 stops functioning, and neither the first power output V1 nor the second power output V2 is supplied.

[0054] The second output protection circuit 55 is interposed between the second converter 53 and the drive mechanism 70. The second output protection circuit 55 monitors the current and voltage on its output side and detects an overcurrent or overvoltage as an abnormality. When the second output protection circuit 55 detects an overcurrent or overvoltage abnormality, it stops the function of the power supply circuit 7 to protect the power supply circuit 7 and the image forming apparatus 1. For example, when the second output protection circuit 55 detects an overcurrent or overvoltage on the output side, it outputs a stop signal CNT2 to the first converter 52. This causes the first converter 52 to stop operating and stop outputting the first power output V1. Furthermore, when the first converter 52 stops operating in response to the stop signal CNT2, it outputs a stop signal CNT3 to the second converter 53. This also causes the second converter 53 to stop operating and stop outputting the second power output V2. Therefore, when the second output protection circuit 55 detects an overcurrent or an overvoltage, the power supply circuit 7 stops functioning, and neither the first power output V1 nor the second power output V2 is supplied.

[0055] In this way, the power supply circuit 7 is configured to stop functioning of the power supply circuit 7 and stop output of both the first power output V1 and the second power output V2 when an abnormality such as an overcurrent or an overvoltage is detected in either the first output protection circuit 54 or the second output protection circuit 55.

[0056] The control unit 8 includes a panel control unit 61, a communication control unit 62, a job control unit 63, a determination unit 64, and a power control unit 65. Each of the panel control unit 61, the communication control unit 62, the job control unit 63, the determination unit 64, and the power control unit 65 is a function realized in the control unit 8, for example, by the CPU of the control unit 8 reading and executing a predetermined program stored in advance in memory.

[0057] The panel control unit 61 controls the operation panel 5. For example, the panel control unit 61 displays a job setting screen on the display unit 6 of the operation panel 5 and accepts job setting operations by the user. The panel control unit 61 can also detect a job execution instruction from the user via the operation panel 5.

[0058] The communication control unit 62 is connected to the communication unit 9. The communication unit 9 communicates with external devices via a network such as a LAN (Local Area Network) and is configured, for example, by a NIC (Network Interface Card). The communication control unit 62 communicates with external devices via the communication unit 9. For example, the communication control unit 62 can receive print jobs, FAX jobs, etc. to be executed in the image forming apparatus 1 via the communication unit 9.

[0059] The job control unit 63 functions when the panel control unit 61 detects an instruction to execute a job from the user, or when the communication control unit 62 receives a job, and controls the execution of the job specified by the user.

[0060] For example, when an instruction to execute a copy job is given, the job control unit 63 operates the scanner unit 3, the automatic document feeder 4, and the printer unit 2, and executes the scan job and the print job in cooperation with each other. In other words, the job control unit 63 comprehensively controls the operations of reading the image of the document set by the user and forming and outputting the image on the sheet 10. At this time, the job control unit 63 drives the drive mechanisms 70 provided in the scanner unit 3, the automatic document feeder 4, and the printer unit 2, respectively.

[0061] Furthermore, when execution of a print job is specified, the job control unit 63 operates the printer unit 2 to execute the specified print job. That is, the job control unit 63 controls the operation of forming and outputting an image specified by the user on a sheet 10. At this time, the job control unit 63 drives the drive mechanism 70 provided in the printer unit 2. For example, the job control unit 63 drives the polygon motor 41, drive motor 71, and solenoid 72 provided in the drive mechanism 70. Therefore, during execution of the print job, the polygon mirror 43, which is a load with high inertia, is driven to rotate at high speed by the polygon motor 41.

[0062] The job control unit 63 can also send and receive fax data via a public telephone line (not shown). Therefore, when a user specifies a fax transmission job, the job control unit 63 generates fax data based on image data to be transmitted by fax and transmits the fax data to the specified destination. The image data to be transmitted by fax may be image data generated by the scanner unit 3, or may be image data received from an external device via the communication unit 9.

[0063] Furthermore, a storage unit 69 is connected to the job control unit 63. For example, the storage unit 69 is a non-volatile storage device configured by a hard disk drive (HDD) or a solid state drive (SSD). The storage unit 69 can store image data generated by the scanner unit 3, image data received via the communication unit 9, and the like. When a user specifies that image data be stored in the storage unit 69, the job control unit 63 stores the specified image data in the storage unit 69. When a print job or a FAX transmission job is specified based on the image data stored in the storage unit 69, the job control unit 63 reads the image data specified by the user from the storage unit 69 and executes the job specified by the user. The job control unit 63 can also transmit the image data stored in the storage unit 69 to an external device via the communication unit 9.

[0064] The determination unit 64 determines the operating state of the image forming apparatus 1. For example, the determination unit 64 is configured to determine whether the drive mechanism 70 provided in the image forming apparatus 1 is in an operating state where it is operating, or whether the drive mechanism 70 is in an inactive state where it is not operating. As described above, when a job is being executed by the job control unit 63, the drive mechanism 70 is in an operating state. Therefore, the determination unit 64 determines that the drive mechanism 70 is in an operating state when a job is being executed in the image forming apparatus 1. Note that when the drive mechanism 70 is in an operating state, the determination unit 64 can further determine whether a load with high inertia is being driven by the drive mechanism 70.

[0065] The power supply control unit 65 controls the state of power supply in the image forming apparatus 1. A power switch 66 that can be turned on and off by the user is connected to the power supply control unit 65. When the power switch 66 is turned off by the user, the power supply control unit 65 turns off the second power output V2 output from the power supply circuit 7. That is, when the power supply control unit 65 detects that the power switch 66 has been turned off, it outputs a stop signal CNT4 to the second converter 53. This causes the second converter 53 to stop operating and stop outputting the second power output V2. Therefore, when the power switch 66 is turned off, the supply of the second power output V2 from the power supply circuit 7 to the drive mechanism 70 stops.

[0066] On the other hand, even when the power switch 66 is turned off, the power supply control unit 65 does not output a stop signal to the first converter 52. Therefore, even when the power switch 66 is turned off, the supply of the first power output V1 from the power supply circuit 7 to the control unit 8 is not stopped. Therefore, even after the power switch 66 is turned off, the control unit 8 can continue to operate using the first power output V1 and can communicate with an external device via the communication unit 9, for example.

[0067] Furthermore, when the power switch 66 is switched from off to on, the power supply control unit 65 starts the operation of the second converter 53. This causes the second converter 53 to resume operation and output the second power output V2. Therefore, when the power switch 66 is switched from off to on, the supply of the second power output V2 from the power supply circuit 7 to the drive mechanism 70 is resumed, and the image forming apparatus 1 becomes ready to execute a job.

[0068] Furthermore, when the power switch 66 is off, even if the power switch 66 is not operated, for example, if the panel control unit 61 detects a user operation on the operation panel 5, or if the communication control unit 62 receives a job via the communication unit 9, the power control unit 65 can start the operation of the second converter 53. Therefore, a telework user who uses the image forming apparatus 1 from outside the office can use the image forming apparatus 1 even if the power switch 66 is switched off.

[0069] Incidentally, when a job such as a print job is being executed by the job control unit 63, the user may accidentally turn off the power switch 66. This type of turn-off operation may be performed by mistake, or it may be performed intentionally by the user. An example of an intentional turn-off operation may be when the user issues a command to start execution of a job, then realizes that they have instructed the wrong job, and turns off the power switch 66 in an attempt to interrupt the execution of the job midway.

[0070] If the power switch 66 is turned off during job execution and the power supply control unit 65 stops the second converter 53, a malfunction of the second output protection circuit 55 occurs. Therefore, the control unit 8 of this embodiment has a function to prevent the malfunction of the second output protection circuit 55. In other words, the control unit 8 functions as a malfunction prevention device. In the control unit 8, the determination unit 64 constantly determines whether the drive mechanism 70 in the image forming apparatus 1 is in an operating state. Therefore, the power supply control unit 65 is configured to stop the operation of the second converter 53 while preventing the malfunction of the second output protection circuit 55 based on the determination result of the determination unit 64 when the power switch 66 is turned off.

[0071] For example, when a job is being executed in the image forming apparatus 1, the determination unit 64 determines that the drive mechanism 70 is in an operating state. When the power switch 66 is turned off by the user in this state, the power control unit 65 outputs a stop signal CNT4 to the second converter 53 and also outputs a control signal CNT5 to the second output protection circuit 55. This control signal CNT5 may be a signal that stops the operation of the second output protection circuit 55, or may be a signal that changes the level at which the second output protection circuit 55 detects an overvoltage.

[0072] When the control signal CNT5 is a signal for stopping the operation of the second output protection circuit 55, the power supply control unit 65 outputs the control signal CNT5 to the second output protection circuit 55, causing the second output protection circuit 55 to stop operating. This stops the protection function of the second output protection circuit 55. Therefore, even if the movable members such as the polygon motor 41, drive motor 71, and solenoid 72 continue to operate due to inertia after the second power supply output V2 has stopped, causing back electromotive force or regenerative power, it is possible to prevent the second output protection circuit 55 from erroneously detecting the occurrence of an overvoltage.

[0073] Furthermore, when the control signal CNT5 is a signal that changes the overvoltage detection level in the second output protection circuit 55, the power supply control unit 65 outputs the control signal CNT5 to the second output protection circuit 55, causing the second output protection circuit 55 to change the level (voltage level) at which overvoltage is detected to a level higher than the normal level. For example, if the normal level is 24 V, upon receiving the control signal CNT5, the second output protection circuit 55 changes the level at which overvoltage is detected to a voltage of approximately 30 V, which is higher than 24 V. This prevents the second output protection circuit 55 from erroneously detecting the occurrence of an overvoltage, even if the movable members such as the polygon motor 41, drive motor 71, and solenoid 72 continue to operate due to inertia after the second power supply output V2 has stopped, generating back electromotive force or regenerative power.

[0074] Preventing the second output protection circuit 55 from erroneously detecting an overvoltage can prevent the second output protection circuit 55 from outputting a stop signal CNT2 to the first converter 52. As a result, even after the power switch 66 is turned off, it is possible to continue operating the first converter 52, and the first power output V1 continuously supplied from the power supply circuit 7 can enable the control unit 8 to operate normally.

[0075] Therefore, even if the power switch 66 is turned off by the user while a job is being executed, the image forming apparatus 1 of this embodiment can continue to operate the control unit 8 normally and can continuously communicate with external devices via the communication unit 9. Therefore, a telework user can continue to use the image forming apparatus 1 even from outside the office.

[0076] Next, the operation of the control unit 8 to prevent malfunction of the second output protection circuit 55 will be described with some examples.

[0077] Fig. 4 is a flowchart showing a first processing procedure by the control unit 8. For example, the processing based on the flowchart in Fig. 4 is processing that is repeatedly performed by the control unit 8 when the first power output V1 is normally supplied to the control unit 8.

[0078] 4, the control unit 8 first determines whether or not a job execution instruction from the user has been detected (step S10). If a job execution instruction has been detected (YES in step S10), the control unit 8 starts executing the job specified by the user (step S11). For example, if the job is a copy job, a scan job, or a print job, the control unit 8 drives the drive mechanism 70 to operate the scanner unit 3, the automatic document feeder 4, or the printer unit 2, thereby executing the job specified by the user.

[0079] After starting the execution of the job, the control unit 8 determines whether the execution of the job has ended (step S12). If the execution of the job has not ended (NO in step S12), the control unit 8 determines whether the power switch 66 has been turned off by the user (step S13). If the power switch 66 has not been turned off (NO in step S13), the processing by the control unit 8 returns to step S12. Therefore, if the execution of the job ends without the power switch 66 being turned off (YES in step S12), the processing by the control unit 8 ends.

[0080] On the other hand, the user may turn off the power switch 66 before the job execution is completed. In this case, when the power supply control unit 65 detects that the user has turned off the power switch 66, it detects that the power supply switch 66 has been turned off before the job execution is completed, based on the determination result of the determination unit 64 (YES in step S13). Then, the control unit 8 outputs a control signal CNT5 to the second output protection circuit 55 to stop the protection function of the second output protection circuit 55 (step S14). This causes the second output protection circuit 55 to stop operating. Next, the control unit 8 outputs a stop signal CNT4 to the second converter 53 (step S15). This causes the second converter 53 to stop operating, and the second power output V2 supplied from the power supply circuit 7 is stopped. When the second converter 53 stops operating, the protection function of the second output protection circuit 55 has already stopped. Therefore, even if back electromotive force or regenerative power is generated in the drive mechanism 70 after the supply of the second power output V2 is stopped, the entire power supply circuit 7 will not stop. Therefore, even after the power switch 66 is turned off, the control unit 8 can continue to operate using the first power output V1 that is continuously supplied from the power supply circuit 7.

[0081] On the other hand, if a job execution instruction is not detected in step S10 (NO in step S10), the control unit 8 determines whether the power switch 66 has been turned off by the user (step S16). As a result, if the power switch 66 has not been turned off (NO in step S16), the processing by the control unit 8 ends. On the other hand, if the power switch 66 has been turned off (YES in step S16), the control unit 8 outputs a stop signal CNT4 to the second converter 53 (step S15). This causes the second converter 53 to stop operating, and the second power output V2 supplied from the power supply circuit 7 is stopped. In this case, because the drive mechanism 70 is not operating, the second output protection circuit 55 will not malfunction even if the supply of the second power output V2 is stopped. Therefore, the control unit 8 can continue to operate using the first power output V1 continuously supplied from the power supply circuit 7 even after outputting the stop signal CNT4 to the second converter 53.

[0082] Next, Fig. 5 is a flowchart showing a second processing procedure by the control unit 8. Similar to Fig. 4, the processing based on the flowchart in Fig. 5 is processing that is repeatedly performed by the control unit 8 when, for example, the first power output V1 is normally supplied to the control unit 8.

[0083] The flowchart in FIG. 5 differs from the flowchart in FIG. 4 in step S17. That is, if the user turns off the power switch 66 while the job execution is not yet completed, the power supply control unit 65 detects that the power switch 66 was turned off while the job execution is not yet completed based on the determination result of the determination unit 64 (YES in step S13). Then, the control unit 8 outputs a control signal CNT5 to the second output protection circuit 55, changing the level at which the second output protection circuit 55 detects an overvoltage (step S17). As a result, the second output protection circuit 55 changes the voltage at which it detects an overvoltage to a higher voltage than before. Therefore, even if a back electromotive force or regenerative power is generated as a result of the drive mechanism 70 continuing to operate due to inertia after the second power output V2 stops, the second output protection circuit 55 will no longer detect the back electromotive force or regenerative power as an overvoltage. Next, the control unit 8 outputs a stop signal CNT4 to the second converter 53 (step S15). As a result, the second converter 53 stops operating, and the second power output V2 supplied from the power supply circuit 7 stops. When the second converter 53 stops operating, the level at which the second output protection circuit 55 detects an overvoltage has already changed, making it possible to prevent malfunction of the second output protection circuit 55. Therefore, even after the power switch 66 is turned off, the control unit 8 can continue to operate using the first power output V1 that is continuously supplied from the power supply circuit 7. Note that steps other than those described above are the same as the processing described in the flowchart of FIG. 4.

[0084] Incidentally, when the second power supply output V2 stops during job execution, the second output protection circuit 55 malfunctions because the drive mechanism 70 includes movable parts equipped with coils, such as the polygon motor 41, drive motor 71, and solenoid 72, and these movable parts drive a load with high inertia. In other words, if the load with high inertia continues to operate after the second power supply output V2 stops, the operation of the load generates back electromotive force and regenerative power in the coil, causing the second output protection circuit 55 to erroneously detect an overvoltage. In particular, when a load with high inertia, i.e., a load with inertia greater than a predetermined value, is driven, the back electromotive force and regenerative power generated by the coil are large, making it more likely that the second output protection circuit 55 will erroneously detect an overvoltage. However, when a load with low inertia, i.e., a load with inertia equal to or less than a predetermined value, is driven, the back electromotive force and regenerative power generated by the coil are small, so the second output protection circuit 55 will not erroneously detect an overvoltage.

[0085] Therefore, when determining whether the drive mechanism 70 is in an operating state, the determination unit 64 may determine whether a load with an inertial force greater than a predetermined value is being driven in the drive mechanism 70, and determine whether the drive mechanism 70 is in an operating state that will cause the second output protection circuit 55 to malfunction. For example, the polygon motor 41 drives and rotates the polygon mirror 43, which is a load with an inertial force greater than a predetermined value. Therefore, the determination unit 64 determines that the drive mechanism 70 is in an operating state that will cause the second output protection circuit 55 to malfunction if the drive mechanism 70 is in an operating state in which the polygon motor 41 is operating. Alternatively, the determination unit 64 may determine that the drive mechanism 70 is in an operating state that will cause the second output protection circuit 55 to malfunction if the drive mechanism 70 is driving a load with an inertial force greater than a predetermined value.

[0086] Fig. 6 is a flowchart showing a third processing procedure by control unit 8. Similar to Fig. 4, the processing based on the flowchart in Fig. 6 is processing that is repeatedly performed by control unit 8, for example, when first power output V1 is normally supplied to control unit 8. The flowchart in Fig. 6 also shows a processing procedure for preventing malfunction of second output protection circuit 55 when the second output protection circuit 55 is in an operating state that causes it to malfunction.

[0087] 6, the control unit 8 first determines whether or not a job execution instruction from the user has been detected (step S20). If a job execution instruction has been detected (YES in step S20), the control unit 8 starts executing the job specified by the user (step S21). For example, if the job is a copy job, a scan job, or a print job, the control unit 8 drives the drive mechanism 70 to operate the scanner unit 3, the automatic document feeder 4, or the printer unit 2, thereby executing the job specified by the user.

[0088] When the execution of a job is started, the control unit 8 activates the determination unit 64. The determination unit 64 then detects the current operating state of the drive mechanism 70 (step S22) and determines whether the second output protection circuit 55 is in an operating state that would cause a malfunction (step S23). If the second output protection circuit 55 is in an operating state that would cause a malfunction (YES in step S23), the determination unit 64 sets the malfunction prevention flag to ON (step S24). For example, if the polygon motor 41 is operating during the execution of the job, the determination unit 64 determines that the second output protection circuit 55 is in an operating state that would cause a malfunction, and sets the malfunction prevention flag to ON. On the other hand, if the second output protection circuit 55 is not in an operating state that would cause a malfunction (NO in step S23), the determination unit 64 resets the malfunction prevention flag to OFF (step S25). For example, if the polygon motor 41 is not operating during execution of a job, the determining unit 64 determines that the second output protection circuit 55 is not in an operating state that would cause a malfunction, and resets the malfunction prevention flag to off.

[0089] Next, the control unit 8 determines whether the job execution has ended (step S26). If the job execution has not ended (NO in step S26), the control unit 8 determines whether the user has turned off the power switch 66 (step S27). If the power switch 66 has not been turned off (NO in step S27), the process by the control unit 8 returns to step S22. Therefore, if the user does not turn off the power switch 66, the control unit 8 repeatedly executes the process of turning on or off the malfunction prevention flag depending on the operating state of the drive mechanism 70 until the job execution ends. Therefore, even if the malfunction prevention flag is off immediately after the job execution starts, if, for example, the polygon motor 41 is driven and it is determined that the second output protection circuit 55 is in an operating state that will cause a malfunction, the malfunction prevention flag is set to on after a predetermined time has elapsed since the job execution started. Conversely, even if the malfunction prevention flag is set to ON immediately after the execution of a job starts, if, for example, the driving of the polygon motor 41 is stopped before the execution of the job ends and it is determined that the second output protection circuit 55 is not in an operating state that would cause a malfunction, the malfunction prevention flag is reset to OFF. Then, if the execution of the job ends without the power switch 66 being turned OFF (YES in step S26), the control unit 8 resets the malfunction prevention flag to OFF (step S31) and ends the process.

[0090] On the other hand, if the user turns off the power switch 66 before the job execution is completed (YES in step S27), the power supply control unit 65 of the control unit 8 determines whether the malfunction prevention flag is set to ON (step S28). If the malfunction prevention flag is ON (YES in step S28), the power supply control unit 65 executes a malfunction prevention process for the second output protection circuit 55 (step S29). That is, the power supply control unit 65 outputs a control signal CNT5 to the second output protection circuit 55 to stop the protection function of the second output protection circuit 55 or change the level at which the second output protection circuit 55 detects an overvoltage. Next, the power supply control unit 65 outputs a stop signal CNT4 to the second converter 53 (step S30). This stops the operation of the second converter 53, and the second power output V2 supplied from the power supply circuit 7 is stopped. When the second converter 53 stops operating, the second output protection circuit 55 has already been prevented from malfunctioning. Therefore, even if back electromotive force or regenerative power is generated in the drive mechanism 70 after the supply of the second power output V2 is stopped, the entire power supply circuit 7 will not stop. Therefore, even after the power switch 66 is turned off, the control unit 8 can continue to operate using the first power output V1 that is continuously supplied from the power supply circuit 7.

[0091] Furthermore, when the power switch 66 is turned off during job execution, if the malfunction prevention flag is off (NO in step S28), the power supply control unit 65 skips the process of step S29 and executes the process of step S30. That is, the power supply control unit 65 outputs a stop signal CNT4 to the second converter 53 without outputting a control signal CNT5 to the second output protection circuit 55, thereby stopping the second power output V2 supplied from the power supply circuit 7. In this case, the operating state of the image forming apparatus 1 is not an operating state that would cause the second output protection circuit 55 to malfunction, so even if the supply of the second power output V2 from the power supply circuit 7 is stopped, the supply of the first power output V1 is not stopped. Therefore, even after the power switch 66 is turned off, the control unit 8 can continue to operate using the first power output V1 continuously supplied from the power supply circuit 7.

[0092] On the other hand, if an instruction to execute a job is not detected in step S20 (NO in step S20), the processing by the control unit 8 ends. In this case, however, as shown in Fig. 4 or 5, it may be possible to determine whether the power switch 66 has been turned off by the user, and if the power switch 66 has been turned off, to output a stop signal CNT4 to the second converter 53 to stop the operation of the second converter 53.

[0093] As described above, the image forming apparatus 1 of this embodiment includes a malfunction prevention device that prevents malfunction of the second output protection circuit 55. That is, the malfunction prevention device includes the power supply circuit 7 that is connected to the external power supply 100 and generates the first power output V1 and the second power output V2 from the external power supply 100, the control unit 8 that operates using the first power output V1 of the power supply circuit 7, the drive mechanism 70 that operates using the second power output V2 of the power supply circuit 7, the power switch 66 that switches off the second power output V2 of the power supply circuit 7, and the second output protection circuit 55 that protects the power supply circuit 7 in the event of an abnormality in the second power output V2. The malfunction prevention device is configured so that when the second power output V2 is switched off by the power switch 66 while the drive mechanism 70 is operating, the control unit 8 prevents malfunction of the second output protection circuit 55.

[0094] In the malfunction prevention device having such a configuration, when the power switch 66 is turned off while the drive mechanism 70 is operating, the control unit 8 can turn off the second power output V2 while preventing malfunction of the second output protection circuit 55. Therefore, the power supply circuit 7 can turn off only the second power output V2 and continue to supply the first power output V1 to the control unit 8. Therefore, the control unit 8 can continue to operate even after the second power output V2 is turned off, and can continue to communicate with external devices via the network.

[0095] In particular, the drive mechanism 70, which is operated by the second power output V2, includes movable parts such as the polygon motor 41 equipped with a coil, the drive motor 71, and the solenoid 72. These movable parts generate back electromotive force and regenerative power when high-inertia loads such as the polygon mirror 43 continue to operate even after the second power output V2 has stopped, causing the second output protection circuit 55 to malfunction. For this reason, the malfunction prevention device determines whether or not a factor that would cause the second output protection circuit 55 to malfunction has occurred based on the operating state of the drive mechanism 70, and is configured to appropriately prevent the second output protection circuit 55 from malfunctioning.

[0096] Furthermore, the timing at which the control unit 8 prevents the second output protection circuit 55 from malfunctioning may be the same as the timing at which the second power output V2 supplied from the power supply circuit 7 is switched off, or may be a timing before the timing at which the second power output V2 supplied from the power supply circuit 7 is switched off. In other words, it is preferable to configure the timing at which the control unit 8 prevents the second output protection circuit 55 from malfunctioning so that it is not later than the timing at which the second power output V2 supplied from the power supply circuit 7 is switched off.

[0097] Furthermore, the above-described control unit 8 may be configured to prevent malfunction by stopping the operation of the second output protection circuit 55 when the second power output V2 is switched off by the power switch 66 while the drive mechanism 70 is in operation. By having the control unit 8 stop the operation of the second output protection circuit 55, it is possible to reliably prevent malfunction of the second output protection circuit 55.

[0098] Furthermore, the above-described control unit 8 may be configured to prevent malfunction by changing the level at which the protection function of second output protection circuit 55 operates when second power output V2 is switched off by power switch 66 while drive mechanism 70 is in operation. In this case, control unit 8 can reliably prevent malfunction of second output protection circuit 55 while allowing second output protection circuit 55 to continue operating.

[0099] As described above, the power supply circuit 7 has the first converter 52 and the second converter 53, with the first converter 52 generating the first power output V1 from the external power supply 100 and the second converter 53 generating the second power output V2 from the external power supply 100. In other words, the power supply circuit 7 is configured to generate the first power output V1 and the second power output V2 independently and separately from the external power supply 100. Therefore, even if the supply of the second power output V2 is stopped by turning off the power switch 66, the power supply circuit 7 can continue to generate the first power output V1 and can stably supply the first power output V1 to the control unit 8.

[0100] Furthermore, the configuration in the power supply circuit 7 for independently generating the first power output V1 and the second power output V2 may be a configuration different from the configuration in which the first converter 52 and the second converter 53 are provided.

[0101] 7A and 7B are diagrams illustrating circuit configurations for separately generating a first power output V1 and a second power output V2. As shown in FIG. 7A, the power supply circuit 7 may include a first transformer 81 that generates the first power output V1 from an external power supply 100 and a second transformer 82 that generates the second power output V2 from the external power supply 100. For example, in the configuration shown in FIG. 7A, even if the switch connected to the second transformer 82 is opened by a stop signal CNT4, the first transformer 81 can continue to generate the first power output V1 from the external power supply 100.

[0102] 7(b), the power supply circuit 7 may be configured with a transformer 83 that separately generates a first power output V1 and a second power output V2. This transformer 83 has a primary coil 85 wound around the primary side of a core 84, and a first secondary coil 86 and a second secondary coil 87 wound around the secondary side. The first secondary coil 86 generates the first power output V1 from the external power supply 100, and the second secondary coil 87 generates the second power output V2 from the external power supply 100. In this configuration, even if the switch connected to the second secondary coil 87 is opened by the stop signal CNT4, the first secondary coil 86 can continue to generate the first power output V1 from the external power supply 100.

[0103] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the contents described in the above embodiments, and various modifications are applicable.

[0104] For example, in the above embodiment, an example has been given in which, when the first output protection circuit 54 detects an abnormality, it outputs a stop signal CNT1 to the first converter 52, and the first converter 52 outputs a stop signal CNT3 to the second converter 53. However, this is not limiting. For example, the first output protection circuit 54 may be configured to output the stop signal CNT1 to both the first converter 52 and the second converter 53 when it detects an abnormality, thereby simultaneously stopping the operations of the first converter 52 and the second converter 53. The same applies to the second output protection circuit 55. For example, the second output protection circuit 55 may be configured to output the stop signal CNT2 to both the first converter 52 and the second converter 53 when it detects an abnormality, thereby simultaneously stopping the operations of the first converter 52 and the second converter 53.

[0105] In the above embodiment, the power supply circuit 7 is provided with the first output protection circuit 54 that stops the function of the power supply circuit 7 when an abnormality in the first power output V1 is detected. However, the power supply circuit 7 may be configured without the first output protection circuit 54.

[0106] Furthermore, in the above embodiment, the image forming apparatus 1 is configured as an MFP with multiple functions. However, the image forming apparatus 1 is not limited to an MFP. For example, the image forming apparatus 1 may be a printer or a facsimile machine. Furthermore, in the above embodiment, the image forming apparatus 1 is a color machine capable of forming color images, but is not limited to this. The image forming apparatus 1 may also be a monochrome machine that forms only monochrome images on the sheet 10.

[0107] Furthermore, in the above embodiment, an example has been given in which the malfunction prevention device that prevents malfunction of the second output protection circuit 55 is mounted on the image forming apparatus 1. However, the device to which the above-described malfunction prevention device can be applied is not limited to the image forming apparatus 1. In other words, the above-described malfunction prevention device can be applied to any device that includes a movable member equipped with a coil such as a motor, and is configured so that a control unit controls the operation of the movable member. [Explanation of symbols]

[0108] 1. Image forming device 7 Power circuit 8 Control Unit 9. Communications Department 41 Polygon motor (moving part) 54 1st output protection circuit 55 2nd output protection circuit (protection circuit) 63 Job control section 64 Judgment section 65 Power supply control unit 66 Power switch 70 Drive mechanism 71 Drive motor (moving parts) 72 Solenoid (moving part) 100 External power supply V1 First power output V2 2nd power output

Claims

1. a power supply circuit connected to an external power supply and configured to generate a first power output and a second power output from the external power supply; a control unit that operates using the first power output of the power supply circuit; a drive mechanism operated by the second power output of the power supply circuit; a power switch that switches off the second power output of the power supply circuit; a protection circuit that detects an overcurrent or an overvoltage of the second power supply output as an abnormality and protects the power supply circuit by stopping the power supply circuit when an abnormality is detected; Equipped with the drive mechanism includes a movable member having a coil mounted thereon, and drives the movable member with the second power output; The control unit controls the protection circuit so that when the second power supply output is switched off by the power switch while the drive mechanism is in an operating state, the protection circuit does not erroneously detect an abnormality due to back electromotive force or regenerative power generated in the coil, and causes the power supply circuit to continue outputting the first power supply output.

2. The malfunction prevention device described in claim 1, characterized in that when the second power output is switched off by the power switch while the drive mechanism is in an operating state, the control unit stops operation of the protection circuit to prevent the protection circuit from falsely detecting an abnormality.

3. The malfunction prevention device described in claim 1, characterized in that when the second power supply output is switched off by the power switch while the drive mechanism is in an operating state, the control unit prevents the protection circuit from falsely detecting an abnormality by changing the level at which the protection function of the protection circuit operates.

4. 4. The malfunction prevention device according to claim 1, wherein the power supply circuit generates the first power output and the second power output independently and separately from the external power supply.

5. 5. The malfunction prevention device according to claim 1, wherein the power supply circuit comprises a first transformer that generates the first power supply output and a second transformer that generates the second power supply output.

6. A malfunction prevention device as described in any one of claims 1 to 4, characterized in that the power supply circuit has a core around which a primary coil to which the external power supply is connected is wound, and a first secondary coil that generates the first power supply output and a second secondary coil that generates the second power supply output are wound around the core.

7. 7. The malfunction prevention device according to claim 1, wherein the protection circuit stops both the first power supply output and the second power supply output when it detects an abnormality in the second power supply output.

8. 8. The malfunction prevention device according to claim 1, wherein the control unit stops the second power output from the power supply circuit when the power switch is turned off.

9. the first power output is a DC power supply of a predetermined voltage; 9. The malfunction prevention device according to claim 1, wherein the second power output is a DC power supply having a voltage higher than that of the first power output.

10. 10. The malfunction prevention device according to claim 1, wherein the movable member includes a motor or a solenoid.

11. A malfunction prevention device as described in any one of claims 1 to 10, characterized in that the driving mechanism drives a load when the second power supply output is supplied, and when the second power supply output stops, the inertia of the load generates a back electromotive force in the coil.

12. the drive mechanism drives a plurality of loads when the second power supply output is supplied thereto; The malfunction prevention device described in any one of claims 1 to 11, characterized in that when the second power output is switched off by the power switch while the drive mechanism is in an operating state, the control unit prevents the protection circuit from falsely detecting an abnormality in accordance with the operating state of a load among the plurality of loads whose inertial force is greater than a predetermined value.

13. An image forming apparatus comprising the malfunction prevention device according to any one of claims 1 to 12.

14. 14. The image forming apparatus according to claim 13, wherein the drive mechanism includes a polygon motor.

15. 15. The image forming apparatus according to claim 13, wherein the control unit includes a communication unit that communicates with an external device via a network.

16. a power supply circuit connected to an external power supply and configured to generate a first power output and a second power output from the external power supply; a control unit that operates using the first power output of the power supply circuit; a drive mechanism having a movable member mounted with a coil, the drive mechanism driving the movable member using the second power output of the power supply circuit; a power switch that switches off the second power output of the power supply circuit; a protection circuit that detects an overcurrent or an overvoltage of the second power supply output as an abnormality and protects the power supply circuit by stopping the power supply circuit when an abnormality is detected; A method for preventing malfunction of an image forming apparatus, comprising: A malfunction prevention method characterized by controlling the protection circuit so that when the second power supply output is switched off by the power switch while the drive mechanism is in an operating state, the protection circuit does not erroneously detect an abnormality due to back electromotive force or regenerative power generated in the coil, and allowing the power supply circuit to continue outputting the first power supply output to the control unit.

17. The malfunction prevention method according to claim 16, characterized in that when the second power supply output is switched off by the power switch while the drive mechanism is in an operating state, the operation of the protection circuit is stopped to prevent the protection circuit from falsely detecting an abnormality.

18. The malfunction prevention method according to claim 16, characterized in that when the second power supply output is switched off by the power switch while the drive mechanism is in an operating state, the level at which the protection function of the protection circuit operates is changed to prevent the protection circuit from falsely detecting an abnormality.

Images