Image formation device

Abstract

Provided is an image formation device capable of determining the failure of a DC / DC converter.　This image formation device comprises: an ASIC 111 that controls a main motor 160; an AC / DC converter 141; a first DC / DC converter V1; and a first switching element SW1. The AC / DC converter 141 can convert an AC voltage into DC voltages that are a first voltage and a second voltage lower than the first voltage. The first DC / DC converter V1 converts the first voltage into a third voltage. The first switching element SW1 is connected in parallel with the first DC / DC converter V1, and can be switched between an ON state and an OFF state on the basis of a control signal of the ASIC 111. When the first switching element SW1 is switched to the ON state, the second voltage is supplied to the ASIC 111, and when the first switching element is switched to the OFF state, the third voltage outputted from the first DC / DC converter V1 is supplied to the ASIC 111.

Description

Image forming device

[0001] The present invention relates to an image forming apparatus equipped with an AC / DC converter and a DC / DC converter.

[0002] Conventionally, an image forming apparatus equipped with an AC / DC converter and a DC / DC converter has been known (see Patent Document 1). This image forming apparatus includes an ASIC (main control circuit) that controls image formation. The ASIC receives power via an AC / DC converter that converts AC voltage supplied from a commercial power source into a first DC voltage, and a DC / DC converter that converts the first DC voltage into a second voltage that is lower than the first voltage.

[0003] Japanese Patent Application Laid-Open No. 2021-118666

[0004] However, in conventional image forming devices, if the DC / DC converter fails, power cannot be supplied to the ASIC, which has the problem that the ASIC cannot determine that the DC / DC converter has failed.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus that can determine whether a DC / DC converter has failed.

[0006] In order to achieve the above object, an image forming apparatus according to the present invention includes a photosensitive drum, a main motor, an ASIC, an AC / DC converter, a first DC / DC converter, and a first switching element. The main motor provides driving force to the photosensitive drum. The ASIC controls the main motor. The AC / DC converter is capable of converting AC voltage supplied from a commercial power source into DC voltages of a first voltage and a second voltage lower than the first voltage. The first DC / DC converter converts the first voltage into a third voltage lower than the first voltage. The ASIC is connected to a secondary side of the first DC / DC converter. The first switching element is connected in parallel with the first DC / DC converter. The first switching element is switchable between an ON state and an OFF state based on a control signal from the ASIC. When the first switching element is turned ON, the second voltage is supplied to the ASIC via the first switching element. When the first switching element is turned OFF, the third voltage output from the first DC / DC converter is supplied to the ASIC.

[0007] If the first switching element is turned on, voltage can be supplied to the ASIC without passing through the first DC / DC converter. Therefore, if the first switching element is turned on when the image forming apparatus is started up, the ASIC can be started up even if the first DC / DC converter has failed, and the ASIC can execute control to determine whether the first DC / DC converter has failed.

[0008] Furthermore, when the image forming apparatus is started up, the first switching element may be in an ON state, and the AC / DC converter may be configured to convert the AC voltage supplied from the commercial power source into the DC voltage of the second voltage.

[0009] When the image forming apparatus is started up, the switching element is in the ON state and the AC / DC converter converts the second voltage into a direct current voltage, so when the image forming apparatus is started up, the second voltage is supplied to the ASIC without passing through the first DC / DC converter, which allows the ASIC to start up even if the first DC / DC converter has failed.

[0010] In addition, the path for supplying voltage from the commercial power source to the ASIC may further include a second DC / DC converter arranged between the first DC / DC converter and the first switching element and the ASIC, and converting the second voltage or the third voltage into a fourth voltage lower than the second voltage and the third voltage.

[0011] Since the second DC / DC converter is further provided between the first DC / DC converter and the first switching element and the ASIC, the fourth voltage can be supplied to the ASIC.

[0012] The power supply may further include a third DC / DC converter that converts the first voltage output from the AC / DC converter into a fifth voltage that is smaller than the first voltage and larger than the third voltage, and a second switching element connected in parallel with the third DC / DC converter, the second switching element being switchable between an ON state and an OFF state based on a control signal from the ASIC.

[0013] The ASIC is equipped with a second switching element that is connected in parallel with the third DC / DC converter and can be switched between an ON state and an OFF state based on a control signal from the ASIC, so that the ASIC can perform control to determine whether there is a failure in the third DC / DC converter.

[0014] The fifth voltage may be the same as the second voltage.

[0015] Furthermore, when the image forming apparatus is started up, the second switching element may be in an ON state, and the AC / DC converter may be configured to convert the AC voltage supplied from the commercial power source into the DC voltage of the second voltage.

[0016] Furthermore, when the image forming apparatus is started up, the first switching element is in the ON state, and after the image forming apparatus is started up, the ASIC turns the second switching element to the OFF state, checks the response of the first device connected to the third DC / DC converter, and if there is a response from the first device, determines that the third DC / DC converter is normal.

[0017] The ASIC can determine that the third DC / DC converter is normal by checking the response of the first device when the second switching element is in the OFF state.

[0018] Furthermore, the ASIC may be configured to, after determining that the third DC / DC converter is normal, turn off the first switching element, check the response of the second device connected to the first DC / DC converter, and determine that the first DC / DC converter is normal if there is a response from the second device.

[0019] The ASIC can determine that the first DC / DC converter is normal by checking the response of the second device when the first switching element is in the OFF state.

[0020] Furthermore, the ASIC may be configured to, after determining that the third DC / DC converter is normal, turn off the first switching element while keeping the second switching element in the OFF state, and check the response of the second device connected to the first DC / DC converter.

[0021] Furthermore, the ASIC may be configured to, after determining that the third DC / DC converter is normal, turn the second switching element ON and the first switching element OFF, and check the response of the second device connected to the first DC / DC converter.

[0022] The ASIC may also be configured to switch the DC voltage output from the AC / DC converter from the second voltage to the first voltage when it determines that both the first DC / DC converter and the third DC / DC converter are normal.

[0023] Furthermore, the ASIC may be configured to turn the first switching element OFF after starting up the image forming apparatus, check the response of the second device connected to the first DC / DC converter, and determine that the first DC / DC converter is normal if there is a response from the second device.

[0024] The ASIC can determine that the first DC / DC converter is normal by checking the response of the second device even when the first switching element is in the OFF state.

[0025] The power supply may further include a main board on which the ASIC is mounted and a sub-board detachable from the main board, and the first DC / DC converter and the first switching element may be mounted on the sub-board.

[0026] By replacing the sub-board, the first DC / DC converter and the first switching element can be easily replaced.

[0027] The power supply may further include a main board on which the ASIC is mounted and a sub-board detachable from the main board, and the first DC / DC converter, the first switching element, the third DC / DC converter, and the second switching element may be mounted on the sub-board.

[0028] By replacing the sub-board, the first DC / DC converter, the first switching element, the third DC / DC converter, and the second switching element can be easily replaced.

[0029] The power supply may further include a main board on which the ASIC is mounted and a sub-board detachable from the main board, and the ASIC and the second DC / DC converter may be mounted on the main board.

[0030] The sub-board may also have a first connector to which the main board is directly connected without a harness.

[0031] The sub-board is directly connected to the main board without a harness, which reduces the number of harnesses required.

[0032] The power supply may further include a low-voltage power supply board on which an AC / DC converter is arranged, and the sub-board may have a second connector arranged thereon to which a terminal of a first harness that connects the low-voltage power supply board is connected.

[0033] The sub-board has a second connector to which the terminal of the first harness that connects the low-voltage power supply board is connected, so that the first DC / DC converter of the sub-board can receive DC voltage directly from the low-voltage power supply board without going through the main board.

[0034] The main board may further include a low-voltage power supply board on which an AC / DC converter is arranged, and a sub-connector may be arranged on the main board to which a terminal of a second harness that connects the low-voltage power supply board is connected.

[0035] Because the sub-board and the low-voltage power supply board are not connected by a harness, there is no need to disconnect the harness connecting the low-voltage power supply board when replacing the sub-board, making it easier to replace the sub-board.

[0036] According to the present invention, it is possible to provide an image forming apparatus that can determine whether a DC / DC converter has failed.

[0037] 1 is a cross-sectional view showing an image forming apparatus according to an embodiment; FIG. 2 is a perspective view showing a main board, a sub-board, a low-voltage power supply board, a main motor, etc.; FIG. 3 is a block diagram showing electrical connections and control signals for the main board, the sub-board, the low-voltage power supply board, the main motor, etc.; FIG. 4 is a top view of the image forming apparatus, showing the positional relationship between the main board, the sub-board, the metal plate, the low-voltage power supply board, and the main motor; FIG. 5 is a diagram showing a state in which the sub-board has been removed from the state of FIG. 4; FIG. 6 is a flowchart of a process for determining a failure of the third DC / DC converter and the first DC / DC converter; FIG. 7 is a time chart of a process for determining a failure of the third DC / DC converter and the first DC / DC converter; FIG. 8 is a time chart of a process for determining a failure of the third DC / DC converter and the first DC / DC converter in a modified example; FIG. 9 is a perspective view showing a main board, a sub-board, a low-voltage power supply board, a main motor, etc. in a modified example; FIG. 10 is a block diagram showing electrical connections and control signals for the main board, the sub-board, the low-voltage power supply board, the main motor, etc. in a modified example.

[0038] An embodiment of the present disclosure will be described in detail with reference to the accompanying drawings as appropriate. As shown in FIG. 1, an image forming apparatus 1 is a monochrome printer. In the following description, the front side (right side in FIG. 1) as viewed from a user using the image forming apparatus 1 will be referred to as the "front" and the rear side (left side in FIG. 1) as the "rear." The up-down direction is the vertical direction. The front-to-rear direction is perpendicular to the up-down direction. Furthermore, the left side (front side of the paper in FIG. 1) as viewed from the user will be referred to as the "left," and the right side (rear side of the paper in FIG. 1) will be referred to as the "left."

[0039] The image forming apparatus 1 includes a main body housing 10 , a front cover 20 , a sheet supply unit 30 , an image forming unit 40 , discharge rollers 81 , and an operation panel 180 .

[0040] The main body housing 10 is a housing that houses the sheet supply unit 30, the image forming unit 40, etc. The front cover 20 opens and closes a front opening 11 of the main body housing 10. The front opening 11 is formed in the front surface of the main body housing 10.

[0041] The operation panel 180 is disposed on the top surface 10A of the main body housing 10. The operation panel 180 can display various messages and can also be used to input commands to the image forming apparatus 1. The operation panel 180 is disposed on the front side of the main body housing 10.

[0042] The sheet supply unit 30 supplies sheets S to the image forming unit 40. The sheet supply unit 30 is located at the bottom inside the main body housing 10. The sheet supply unit 30 includes a sheet tray 31 and a sheet supply mechanism 32. The sheet tray 31 stores sheets S to be supplied to the image forming unit 40. The sheet tray 31 is detachable from the main body housing 10. The sheet tray 31 can be removed by pulling it forward from the main body housing 10. When attached to the main body housing 10, the sheet tray 31 is located below the image forming unit 40.

[0043] The sheet supply mechanism 32 includes a pickup roller 33, a separation roller 34, a separation pad 35, a first roller 36, and a registration roller 37. The pickup roller 33 feeds the sheets S stored in the sheet tray 31 toward the photosensitive drum 61. The separation roller 34 and the separation pad 35 separate the sheets S fed by the pickup roller 33 into single sheets. The first roller 36 and the registration roller 37 transport the sheets S toward the image forming unit 40.

[0044] The image forming section 40 forms an image on the sheet S. The image forming section 40 includes an exposure unit 50, a process unit 60, and a fixing unit 70.

[0045] The exposure unit 50 is located at the top of the main body housing 10. The exposure unit 50 has an optical device 51, a polygon mirror 52, and a polygon motor 53. The optical device 51 emits laser light. The polygon mirror 52 deflects the laser light emitted from the optical device 51. The polygon motor 53 rotates the polygon mirror 52. As shown by the imaginary lines, the exposure unit 50 emits a light beam from the optical device 51, which is deflected by the polygon mirror 52 and then exposes the surface of a photosensitive drum 61 of the image forming unit 40.

[0046] The process unit 60 is located between the exposure unit 50 and the sheet tray 31 inside the main body housing 10. When removing the process unit 60, the process unit 60 is pulled forward from the main body housing 10 with the front cover 20 open. The development unit 60B is detachable from the drum unit 60A when the process unit 60 is removed from the main body housing 10. The process unit 60 includes the drum unit 60A and the development unit 60B, which is detachable from the drum unit 60A.

[0047] The process unit 60 can be attached to and detached from the main body 10 through the front opening 11 when the front cover 20 is open. The drum unit 60A includes a photosensitive drum 61, a charger 62, and a transfer roller 63.

[0048] The photosensitive drum 61 is rotatable about a rotation axis 61X extending in a first direction. A toner image is formed on the surface of the photosensitive drum 61. The charger 62 uniformly and positively charges the photosensitive drum 61. The transfer roller 63 transfers the toner image onto the sheet S together with the photosensitive drum 61.

[0049] In the following description, the direction in which the rotation axis 61X of the photosensitive drum 61 extends is referred to as the "first direction." Furthermore, the direction perpendicular to the up-down direction and the first direction is referred to as the "second direction." Furthermore, the arrow directions in the drawings point to one side of each direction. Furthermore, the direction opposite to one side is referred to as the other side. In this embodiment, the first direction is the left-right direction, with one side of the first direction referring to the left side and the other side of the second direction referring to the right side. The second direction is the front-rear direction. In this embodiment, one side of the second direction is the rear side and the other side of the second direction is the front side.

[0050] The developing unit 60B has a developing roller 64, a supply roller 65, a layer thickness regulating blade 66, an agitator 67, and a toner storage section 68. The toner storage section 68 stores toner. The agitator 67 agitates the toner in the toner storage section 68. The agitator 67 also supplies toner to the supply roller 65. The supply roller 65 supplies toner to the developing roller 64. The layer thickness regulating blade 66 contacts the surface of the developing roller 64 and regulates the thickness of the toner on the developing roller 64 to a constant thickness.

[0051] The fixing unit 70 is located behind the process unit 60 inside the main body housing 10. The fixing unit 70 includes a heating unit 71 and a pressure roller 72. The heating unit 71 heats the sheet S. The pressure roller 72 is pressed against the heating unit 71.

[0052] In the image forming section 40, the exposure unit 50 emits a light beam onto the surface of the charged photosensitive drum 61. As a result, an electrostatic latent image based on image data is formed on the photosensitive drum 61. The development roller 64 supplies toner to the surface of the exposed photosensitive drum 61. As a result, a toner image is formed on the photosensitive drum 61.

[0053] The photosensitive drum 61 and the transfer roller 63 transport the sheet S supplied from the sheet supply unit 30. As a result, the toner image formed on the photosensitive drum 61 is transferred onto the sheet S. The heating unit 71 and the pressure roller 72 transport the sheet S onto which the toner image has been transferred. As a result, the toner image transferred onto the sheet S is fixed onto the sheet S.

[0054] The discharge rollers 81 are located above the fixing unit 70. The discharge rollers 81 discharge the sheet S, on which an image has been formed by the image forming section 40, onto the discharge tray 13. The discharge tray 13 is formed on the top surface 10A of the main body housing 10.

[0055] As shown in FIG. 2, the image forming apparatus 1 includes a main board 110 on which an ASIC 111 is arranged, a sub-board 120, a low-voltage power supply board 140, a high-voltage power supply board 150, a main motor 160, a sheet sensor SE1, and a temperature sensor SE2.

[0056] The main board 110 and the sub-board 120 are directly connected without a harness. The sub-board 120 and the low-voltage power supply board 140 are connected by a first harness H1. The sub-board 120 and the main motor 160 are connected by a second harness H2. The sub-board 120 and the polygon motor 53 are connected by a sixth harness H6. The main board 110 and the operation panel 180 are connected by a fourth harness H4. The main board 110 and the circuit board 50A of the exposure unit 50 are connected by a fifth harness H5.

[0057] The type of harness is arbitrary, and the harness may be an FFC (flexible flat cable).

[0058] The sheet sensor SE1 is a sensor that detects the sheet S. When the sheet sensor SE1 detects the sheet S, a detection signal is sent to the ASIC 111.

[0059] The temperature sensor SE2 is a sensor that detects the temperature. The temperature detected by the temperature sensor SE2 is sent to the ASIC 111.

[0060] The main board 110 includes an ASIC 111 , a main connector CM, a ROM 118 , and a RAM 119 .

[0061] The ROM 118 stores a control program, setting data, and the like for controlling the image forming apparatus 1. The RAM 119 is used as a working area from which the control program is read, and as a storage area for temporarily storing image data included in a print job.

[0062] The ASIC 111 is a semiconductor integrated circuit for executing print control of the image forming apparatus 1. The ASIC 111 is a control device that executes print control by performing arithmetic processing based on control programs and data stored in the ROM 118 and the RAM 119. In this embodiment, the ASIC 111 controls the operation panel 180, the exposure unit 50, and the main motor 160.

[0063] The main connector CM is a connector that is connected to the sub-board 120. The main connector CM is connected to the sub-board 120.

[0064] As shown in FIG. 2, the sub-board 120 has a first connector C1, a second connector C2, a third connector C3, a fourth connector C4, a fifth connector C5, a sixth connector C6, and a seventh connector C7.

[0065] The first connector C1 is a connector for connecting the sub-board 120 to the main board 110. The first connector C1 and the main connector CM are board-to-board connectors for connecting the boards together. At least one of the first connector C1 and the main connector CM may be a floating connector designed to absorb positional errors by moving relative to the main board 110 and the connector board 120.

[0066] The second connector C2 is a connector for connecting the low-voltage power supply board 140 to the sub-board 120. A terminal of the first harness H1 is connected to the second connector C2.

[0067] The third connector C3 is a connector for connecting the main motor 160 to the sub-board 120. A terminal of the second harness H2 is connected to the third connector C3.

[0068] The fifth connector C5 is a connector for connecting the operation panel 180 to the sub-board 120. A terminal of the fourth harness H4 is connected to the fifth connector C5.

[0069] The sixth connector C6 is a connector for connecting the circuit board 50A of the exposure unit 50 to the sub-board 120. A terminal of the fifth harness H5 is connected to the sixth connector C6.

[0070] The seventh connector C7 is a connector for connecting the polygon motor 53 to the sub-board 120. A terminal of the sixth harness H6 is connected to the seventh connector C7.

[0071] 3 , the low-voltage power supply board 140 has an AC / DC converter 141. The AC / DC converter 141 converts an AC voltage supplied from a commercial power source into a DC voltage of a first voltage and a second voltage lower than the first voltage. The AC / DC converter 141 outputs the DC voltage of the first voltage or the second voltage based on a control signal from the ASIC 111. In this embodiment, the first voltage is 24 V and the second voltage is 5 V.

[0072] The low-voltage power supply board 140 is covered by a box-shaped metal enclosure (not shown) and is housed in the main body housing 10 in a detachable manner.

[0073] The high-voltage power supply board 150 is detachably housed in the main body housing 10. The high-voltage power supply board 150 has a circuit that generates a high voltage by boosting the first voltage supplied from the low-voltage power supply board 140. The high-voltage power supply board 150 has a charging voltage application circuit 151, a developing voltage application circuit 152, and a transfer voltage application circuit 153.

[0074] The charging voltage application circuit 151 is a circuit that applies a positive charging voltage to the charger 62. The charging voltage is, for example, 5 kV to 8 kV. The developing voltage application circuit 152 is a circuit that applies a positive developing voltage to the developing roller 64. The developing voltage is, for example, 300 V to 500 V. The transfer voltage application circuit 153 is a circuit that applies a transfer voltage to the transfer roller 63. The transfer voltage application circuit 153 controls the transfer voltage so that the current flowing through the transfer roller 63 becomes a predetermined current value. The transfer voltage is, for example, about minus several thousand volts.

[0075] The sub-board 120 is a board electrically connected to the main board 110. The sub-board 120 does not have a control device such as an ASIC or a CPU or a main control circuit. The sub-board 120 has a first DC / DC converter V1, a first switching element SW1, a third DC / DC converter V3, a second switching element SW2, a main motor drive circuit 112, and a polygon motor drive circuit 113. Note that because FIG. 3 is a block diagram showing the electrical connections of each board, the positions of each connector differ in some respects from FIGS. 2 and 4.

[0076] The first DC / DC converter V1 is a converter that converts a first voltage into a third voltage, which is lower than the first voltage. In this embodiment, the third voltage is 3.3V.

[0077] The first DC / DC converter V1 has a primary side connected to the AC / DC converter 141. The first DC / DC converter V1 has a secondary side connected to the ASIC 111, the seat sensor SE1, and the temperature sensor SE2.

[0078] The first switching element SW1 is connected in parallel with the first DC / DC converter V1. The first switching element SW1 can be switched between an ON state and an OFF state based on a control signal from the ASIC 111. The first switching element SW1 is, for example, a MOSFET. The first switching element SW1 is turned ON when the gate voltage exceeds a predetermined value by switching the output signal from the ASIC 111, and turned OFF when the gate voltage falls below the predetermined value. When the first switching element SW1 is turned ON, the voltage output from the AC / DC converter 141 is supplied to the second DC / DC converter V2, seat sensor SE1, temperature sensor SE2, etc. via the first switching element SW1 that is turned ON. In other words, the current from the AC / DC converter 141 bypasses the first DC / DC converter V1 and is supplied to the second DC / DC converter V2, seat sensor SE1, temperature sensor SE2, etc. On the other hand, when the first switching element SW1 is in the OFF state, the voltage output from the AC / DC converter 141 is supplied to the first DC / DC converter V1.

[0079] The third DC / DC converter V3 is a converter that converts the first voltage output from the AC / DC converter 141 into a voltage different from the third voltage, which is the voltage on the secondary side of the first DC / DC converter V1. The third DC / DC converter V3 is a converter that converts the first voltage output from the AC / DC converter 141 into a fifth voltage that is smaller than the first voltage and larger than the third voltage. In this embodiment, the fifth voltage is the same as the second voltage. That is, in this embodiment, the fifth voltage is 5 V.

[0080] The third DC / DC converter V3 has a primary side connected to the AC / DC converter 141. The third DC / DC converter V3 has a secondary side connected to the operation panel ASIC 181, the LAN I / F 114, and the USB I / F 116.

[0081] The second switching element SW2 is connected in parallel with the third DC / DC converter V3. The second switching element SW2 can be switched between an ON state and an OFF state based on a control signal from the ASIC 111. The second switching element SW2 is, for example, a MOSFET. The second switching element SW2 is turned ON when the gate voltage exceeds a predetermined value by switching the output signal from the ASIC 111, and turned OFF when the gate voltage falls below the predetermined value. When the second switching element SW2 is turned ON, the voltage output from the AC / DC converter 141 is supplied to the LAN I / F 114, the USB I / F 116, the fourth DC / DC converter V4, and the like via the second switching element SW2 that is turned ON. In other words, the current from the AC / DC converter 141 bypasses the third DC / DC converter V3 and is supplied to the LAN I / F 114, the USB I / F 116, the fourth DC / DC converter V4, and the like. On the other hand, when the second switching element SW2 is in the OFF state, the voltage output from the AC / DC converter 141 is supplied to the third DC / DC converter V3.

[0082] The main board 110 further has a main motor drive circuit 112, a polygon motor drive circuit 113, a second DC / DC converter V2, a fourth DC / DC converter V4, a LAN interface (I / F) 114, a LAN connector 115, a USB interface (I / F) 116, and a USB connector 117.

[0083] The main motor drive circuit 112 is a circuit that drives and controls the main motor 160. Specifically, the main motor drive circuit 112 is supplied with a first DC voltage from the low-voltage power supply board 140. The main motor drive circuit 112 outputs drive power to the main motor 160 based on a control signal sent from the ASIC 111. In this embodiment, the main motor drive circuit 112 is supplied with a 24 V voltage converted by the AC / DC converter 141.

[0084] The polygon motor drive circuit 113 is a circuit that drives and controls the polygon motor 53. Specifically, the polygon motor drive circuit 113 is supplied with a first DC voltage from the low-voltage power supply board 140. The polygon motor drive circuit 113 outputs drive power to the polygon motor 53 based on a control signal sent from the ASIC 111. In this embodiment, the polygon motor drive circuit 113 is supplied with a 24 V voltage converted by the AC / DC converter 141.

[0085] The second DC / DC converter V2 is disposed between the first DC / DC converter V1 and the first switching element SW1 and the ASIC 111 in a path that supplies voltage from the commercial power supply to the ASIC 111. The second DC / DC converter V2 converts the second voltage or the third voltage into a fourth voltage that is lower than the second voltage and the third voltage. In this embodiment, the fourth voltage is 1.1 V. That is, in this embodiment, the ASIC 111 is supplied with the 1.1 V voltage converted by the second DC / DC converter V2.

[0086] The fourth DC / DC converter V4 is disposed in a path for supplying voltage to the operation panel ASIC 181, between the third DC / DC converter V3 and second switching element SW2 and the operation panel ASIC 181. The fourth DC / DC converter V4 is a converter that converts the second voltage or the fifth voltage into a sixth voltage that is lower than the second voltage and the fifth voltage. In this embodiment, the sixth voltage is 1.2 V.

[0087] The LAN interface 114 is an interface for exchanging data with an external device connected to a LAN connector 115. In this embodiment, a voltage of 5 V converted by a third DC / DC converter V3 is supplied to the LAN interface 114. A LAN cable of the external device is connected to the LAN connector 115.

[0088] The USB interface 116 is an interface for exchanging data with an external device connected to a USB connector 117. In this embodiment, a voltage of 5 V converted by a third DC / DC converter V3 is supplied to the USB interface 116. The USB connector 117 is connected to a USB terminal of the external device.

[0089] The LAN connector 115 and the USB connector 117 are disposed at one end of the main board 110 in the second direction. The LAN connector 115 and the USB connector 117 are exposed to the outside of the main body housing 10 from one side (rear side) of the main body housing 10 in the second direction.

[0090] A LAN cable is connected to the LAN connector 115. When the LAN cable is connected to the LAN connector 115, the ASIC 111 can transmit and receive data to and from external devices.

[0091] The USB connector 117 is a connector to which a USB terminal of an external device such as a PC is connected. When the USB terminal of the external device is connected to the USB connector 117, the ASIC 111 can send and receive data to and from the external device.

[0092] The main motor 160 applies a driving force to the pickup roller 33, the separation roller 34, the first roller 36, the registration roller 37, the photosensitive drum 61, the developing roller 64, the supply roller 65, the agitator 67, the pressure roller 72, and the discharge roller 81 (see FIG. 1). The pickup roller 33, the separation roller 34, the first roller 36, the registration roller 37, the photosensitive drum 61, the pressure roller 72, and the discharge roller 81 receive the driving force from the main motor 160 and transport the sheet S (see FIG. 1).

[0093] The operation panel 180 has an operation panel ASIC 181 and an LCD 182. The operation panel ASIC 181 is a semiconductor integrated circuit for executing operations on the operation panel 180. The LCD 182 is a display into which commands can be input. Various messages are displayed on the LCD 182 in accordance with the operation panel ASIC 181. In this embodiment, a voltage of 1.2 V converted by the fourth DC / DC converter V4 is supplied to the operation panel ASIC 181.

[0094] As shown in Figure 4, the main board 110 is fixed to the main body housing 10. The mounting surface of the main board 110 faces a first direction. That is, the ASIC 111 is disposed on the board mounting surface facing the first direction. In this embodiment, the mounting surface of the main board 110 faces one side of the first direction, i.e., the left. The main connector CM faces one side of the first direction, i.e., the left. The main connector CM is connected to the first connector C1 of the sub-board 120.

[0095] The sub-board 120 is detachably fixed to the main housing 10. More specifically, the sub-board 120 is detachably fixed to the main board 110. At least a portion of the sub-board 120 faces the main board 110 in the first direction. The main board 110 is directly connected to the first connector C1 without a harness. In this embodiment, the first connector C1 faces the main connector CM in the first direction, and they face each other. That is, the first connector C1 is connected to the main board 110 in the first direction.

[0096] The main connector CM and the first connector C1 are board-to-board connectors for connecting the boards together. At least one of the main connector CM and the first connector C1 may be a floating connector designed to absorb positional errors by moving relative to the main board 110 and the sub-board 120.

[0097] In the second direction, the connection portion between the second harness H2 and the low-voltage power supply board 140 is located closer to the sub-board 120 than to the main board 110.

[0098] The image forming apparatus 1 further includes a metal plate 130 , an electric clutch 170 , and a gear train 190 .

[0099] The metal plate 130 is fixed to the main body housing 10. The metal plate 130 is a metal plate and extends in a direction perpendicular to the first direction. The metal plate 130 supports the main motor 160. The sub-board 120 is detachably supported by the metal plate 130.

[0100] In the first direction, the metal plate 130 is located between the main board 110 and the sub-board 120. The main board 110 and the metal plate 130 are located at different positions in the second direction. Specifically, the metal plate 130 is located in front of the main board 110.

[0101] The metal plate 130 has a convex portion 131 that protrudes toward the sub-substrate 120. The sub-substrate 120 is fixed to the convex portion 131 with a screw N. The convex portion 131 protrudes to one side in the first direction when the sub-substrate 120 is fixed to the metal plate 130. The convex portion 131 serves as a spacer that ensures a distance between the sub-substrate 120 and the portion of the metal plate 130 other than the convex portion 131 when the sub-substrate 120 is fixed to the metal plate 130.

[0102] The electric clutch 170 is switchable between a transmission state in which the driving force from the main motor 160 is transmitted to the pickup roller 33 and a disconnection state in which the driving force from the main motor 160 is not transmitted to the pickup roller 33 .

[0103] The gear train 190 is made up of a plurality of gears and is in mesh with a motor gear MG provided on the output shaft of the main motor 160 and the electric clutch 170. The gear train 190 receives driving force from the main motor 160 and transmits the driving force to the pickup roller 33 via the electric clutch 170.

[0104] The electric clutch 170 and the gear train 190 are located on the other side in the second direction from the main motor 160. In the second direction, the main board 110, the sub-board 120, the main motor 160, and the pickup roller 33 are arranged in this order. Therefore, in the second direction, the sub-board 120 is disposed between the main motor 160 and the main board 110.

[0105] Here, the main body housing 10 has a first region RE1 and a second region RE2. The first region RE1 is located outside the photosensitive drum 61 in the first direction and is a region on one side of the photosensitive drum 61 in the first direction. The second region RE2 is located outside the photosensitive drum 61 in the first direction and is a region on the other side of the photosensitive drum 61 in the first direction.

[0106] The main board 110, the sub-board 120, the metal plate 130, the main motor 160, the electric clutch 170, and the gear train 190 are all arranged in the first region RE1. The low-voltage power supply board 140 is arranged in the second region RE2.

[0107] The main body housing 10 has a first end 1E and a second end 2E. The first end 1E is the left end of the main body housing 10, i.e., the end of the main body housing 10 closest to the first region RE1 in the first direction. The second end 2E is the right end of the main body housing 10, i.e., the end of the main body housing 10 farther from the first region RE1 than the first end 1E in the first direction.

[0108] The distance D1 between the sub-substrate 120 and the first end 1E is smaller than the distance D2 between the main substrate 110 and the first end 1E (D1<D2). Furthermore, the distance D1 between the sub-substrate 120 and the first end 1E is smaller than the distance D3 between the metal plate 130 and the first end 1E (D1<D3). In this embodiment, the distance D3 between the metal plate 130 and the first end 1E is smaller than the distance D2 between the main substrate 110 and the first end 1E (D3<D2). Thus, in this embodiment, of the main substrate 110, the sub-substrate 120, and the metal plate 130, the sub-substrate 120 is located on the outermost side of the first region RE1, and the main substrate 110 is located on the innermost side.

[0109] The mounting surfaces of the main board 110 and the sub-board 120 face in a first direction. In this embodiment, the mounting surface of the main board 110 faces one side in the first direction, i.e., toward the left. The ASIC 111 is disposed on the surface of the main board 110 facing the first end 1E. The mounting surface of the sub-board 120 faces the other side in the first direction, i.e., toward the right. That is, the first DC / DC converter V1 is disposed on the surface of the sub-board 120 facing the second end 2E.

[0110] The second harness H2 extends from the first region RE1 to the second region RE2 along the first direction. Specifically, the second harness H2 extends from the first region RE1 to the second region RE2, passing through a region on one side of the rotation axis 61X of the photosensitive drum 61 in the second direction.

[0111] The main board 110 and the sub-board 120 are located in an area on one side of the rotation axis 61X of the photosensitive drum 61 in the second direction.

[0112] As shown in Figures 4 and 5, the sub-board 120 can be attached to and detached from one side in the first direction relative to the main board 110. Therefore, the main body housing 10 has a second opening 12 and a side cover 12A on one side in the first direction. The second opening 12 is an opening formed in the first region RE1. The second opening 12 is an opening for attaching and detaching the sub-board 120. The side cover 12A is detachable from the main body housing 10, and covers the second opening 12 when attached. Furthermore, when the side cover 12A is removed, the second opening 12 is opened, and the sub-board 120 can be attached and detached through the second opening 12.

[0113] When removing the sub-board 120 from the main body housing 10, the side cover 12A is removed from the state shown in FIG. 4 to the state shown in FIG. 5. When the side cover 12A is removed, the second opening 12 is opened. With the second opening 12 open, the user removes the corresponding harness terminals from the second connector C2, the third connector C3, the fourth connector C4, the fifth connector C5, and the sixth connector C6. Then, the user removes the two screws N (see FIG. 2) located at the front of the sub-board 120.

[0114] After removing each connector and screw N, the user pulls the sub-board 120 to one side in the first direction, for example, to the left. Pulling the sub-board 120 to one side in the first direction disconnects the first connector C1 of the sub-board 120 from the main connector CM of the main board 110, and the sub-board 120 can be pulled out to one side in the first direction, for example, to the left.

[0115] When attaching the sub-board 120 to the main housing 10, the side cover 12A is removed and the sub-board 120 is inserted into the second opening 12. Then, the first connector C1 of the sub-board 120 is faced to the main connector CM of the main board 110 and pushed in. This connects the first connector C1 to the main connector CM, allowing the rear of the sub-board 120 to be attached to the main board 110. In this state, the front of the sub-board 120 is fixed to the metal plate 130 with screws N. This fixes the front and rear of the sub-board 120 to the main housing 10.

[0116] Once the sub-board 120 is fixed to the main body housing 10, the corresponding harness terminals are connected to the second connector C2, the third connector C3, the fourth connector C4, the fifth connector C5, and the sixth connector C6. After connecting each connector, the side cover 12A is attached to the main body housing 10. In this way, the sub-board 120 can be easily attached to and detached from the main board 110 from one side in the first direction.

[0117] Here, the transmission path of the power supplied from the low-voltage power supply board 140 and the transmission path of the control signal sent from the ASIC 111 will be described.

[0118] 3 , when the first switching element SW1 is in the OFF state, the first DC / DC converter V1 is supplied with a DC voltage of 24 V or 5 V from the AC / DC converter 141. The first DC / DC converter V1 converts the DC voltage of 24 V or 5 V to 3.3 V and supplies it to the second DC / DC converter V2, the seat sensor SE1, and the temperature sensor SE2. In this way, when the first switching element SW1 is turned OFF, the DC voltage of 3.3 V output from the first DC / DC converter V1 is supplied to the ASIC 111.

[0119] When the first switching element SW1 is turned on, the 5V DC voltage supplied from the AC / DC converter 141 is supplied to the second DC / DC converter V2, the seat sensor SE1, and the temperature sensor SE2 via the first switching element SW1, not to the first DC / DC converter V1. In this way, when the first switching element SW1 is turned on, the 5V DC voltage is supplied to the ASIC 111 via the first switching element SW1, without passing through the first DC / DC converter V1.

[0120] When the second switching element SW2 is turned OFF, the third DC / DC converter V3 is supplied with a DC voltage of 24 V or 5 V from the AC / DC converter 141. The third DC / DC converter V3 converts the DC voltage of 24 V or 5 V to 5 V and supplies it to the fourth DC / DC converter V4, the LAN interface 114, and the USB interface 116.

[0121] When the second switching element SW2 is in the ON state, the 5V DC voltage supplied from the AC / DC converter 141 is supplied to the fourth DC / DC converter V4, LAN interface 114 and USB interface 116 via the second switching element SW2, rather than to the third DC / DC converter V3.

[0122] The ASIC 111 is supplied with a DC voltage of 1.1 V from the second DC / DC converter V2.

[0123] The main motor drive circuit 112 is supplied with a 24 V DC voltage from the AC / DC converter 141. When the main motor drive circuit 112 is supplied with a 24 V DC voltage, the main motor drive circuit 112 converts the 24 V DC voltage into a drive voltage for the main motor 160 based on a control signal sent from the ASIC 111, and outputs the drive voltage to the main motor 160.

[0124] Polygon motor drive circuit 113 is supplied with a DC voltage of 24 V or 5 V from AC / DC converter 141. When a DC voltage of 24 V is supplied, polygon motor drive circuit 113 converts the DC voltage of 24 V into a drive voltage for polygon motor 53 based on a control signal sent from ASIC 111, and outputs the drive voltage to polygon motor 53.

[0125] The operation panel ASIC 181 is supplied with a DC voltage of 1.2 V from the fourth DC / DC converter V4.

[0126] The ASIC 111 transmits control signals to the main motor drive circuit 112, the polygon motor drive circuit 113, the sheet sensor SE1, the temperature sensor SE2, the LAN interface 114, and the USB interface 116. The ASIC 111 also receives data from the charging voltage application circuit 151, the developing voltage application circuit 152, the transfer voltage application circuit 153, the main motor 160, the polygon motor 53, the sheet sensor SE1, the temperature sensor SE2, the LAN interface 114, and the USB interface 116.

[0127] The ASIC 111 receives commands input to the LCD 182 via the operation panel ASIC 181. The ASIC 111 can also display messages on the LCD 182 via the operation panel ASIC 181.

[0128] Here, a failure determination process for determining whether or not the first DC / DC converter V1 and the third DC / DC converter V3 have failed when the image forming apparatus 1 is started will be described.

[0129] The first switching element SW1 and the second switching element SW2 are in the ON state when the image forming apparatus 1 is started up. Also, when the image forming apparatus 1 is started up, the AC / DC converter 141 converts the AC voltage supplied from the commercial power supply into a DC voltage of 5 V.

[0130] Although not shown in the figure, the sub-board 120 has a circuit that uses the 5V DC voltage output by the AC / DC converter 141 when the image forming apparatus 1 is started up to turn on the first switching element SW1 and the second switching element SW2.

[0131] Furthermore, when the image forming apparatus 1 is started up, the first switching element SW1 is in the ON state, and therefore the 5 V DC voltage supplied from the AC / DC converter 141 is supplied to the second DC / DC converter V2 via the first switching element SW1. When the 5 V DC voltage is supplied to the second DC / DC converter V2, the 1.1 V DC voltage is supplied from the second DC / DC converter V2 to the ASIC 111. When the 1.1 V DC voltage is supplied to the ASIC 111, the ASIC 111 starts up.

[0132] After the ASIC 111 starts up, the ASIC 111 turns off the second switching element SW2, checks for responses from the LAN interface 114 and the USB interface 116 connected to the third DC / DC converter V3, and determines that the third DC / DC converter V3 is normal when there are responses from the LAN interface 114 and the USB interface 116. The LAN interface 114 and the USB interface 116 are examples of a first device.

[0133] After determining that the third DC / DC converter V3 is normal, the ASIC 111 turns the first switching element SW1 OFF, checks the responses of the seat sensor SE1 and the temperature sensor SE2 connected to the first DC / DC converter V1, and determines that the first DC / DC converter V1 is normal if responses are received from the seat sensor SE1 and the temperature sensor SE2. The seat sensor SE1 and the temperature sensor SE2 are examples of a second device. In this embodiment, after determining that the third DC / DC converter V3 is normal, the ASIC 111 turns the first switching element SW1 OFF while keeping the second switching element SW2 OFF, and checks the responses of the seat sensor SE1 and the temperature sensor SE2 connected to the first DC / DC converter V1.

[0134] If the ASIC 111 determines that both the first DC / DC converter V1 and the third DC / DC converter V3 are normal, it switches the DC voltage output from the AC / DC converter 141 from 5 V to 24 V. This causes the image forming apparatus 1 to end the failure determination process and start up properly.

[0135] When the DC voltage output from the AC / DC converter 141 is switched to 24V, a DC voltage of 24V is supplied to the polygon motor drive circuit 113, and the polygon motor 53 becomes drivable.

[0136] Furthermore, when the DC voltage output from the AC / DC converter 141 is switched to 24V, a DC voltage of 24V is supplied to the first DC / DC converter V1.

[0137] Furthermore, when the DC voltage output from the AC / DC converter 141 is switched to 24V, the DC voltage of 24V is supplied to the third DC / DC converter V3.

[0138] An example of a process for determining whether the third DC / DC converter V3 and the first DC / DC converter V1 have failed in the image forming apparatus 1 configured as above will be described with reference to the flowchart of FIG. 6 and the time chart of FIG.

[0139] 6 and 7 , when the image forming apparatus 1 is started up, the AC / DC converter 141 converts the AC voltage supplied from the commercial power source into a DC voltage of 5 V. Furthermore, when the image forming apparatus 1 is started up, the first switching element SW1 and the second switching element SW2 are in the ON state. Therefore, when the image forming apparatus 1 is turned ON (S1, Yes: time t1), a DC voltage of 1.1 V is supplied to the ASIC 111 via the first switching element SW1 and the second DC / DC converter V2, and the ASIC 111 is started up.

[0140] After the ASIC 111 is started up, the ASIC 111 turns off the second switching element SW2 (S2: time t2), and determines whether there is a response from the LAN interface 114 and the USB interface 116 (S3: time t2 to t3).

[0141] In step S3, if the ASIC 111 determines that there is no response from the LAN interface 114 and the USB interface 116 (S3, No), it determines that the third DC / DC converter V3 is faulty because power is not being supplied from the third DC / DC converter V3 to the LAN interface 114 and the USB interface 116 (S4).

[0142] In step S3, if the ASIC 111 determines that there is a response from the LAN interface 114 and the USB interface 116 (S3, Yes), it determines that the third DC / DC converter V3 is not faulty because power is being supplied from the third DC / DC converter V3 to the LAN interface 114 and the USB interface 116, and turns on the first switching element SW1 (S5: time t3).

[0143] After step S5, the ASIC 111 determines whether there is a response from the seat sensor SE1 and the temperature sensor SE2 (S6: time t3 to t4).

[0144] In step S6, if the ASIC 111 does not determine that there is a response from the seat sensor SE1 and the temperature sensor SE2 (S6, No), it determines that the first DC / DC converter V1 is faulty because power is not being supplied from the first DC / DC converter V1 to the seat sensor SE1 and the temperature sensor SE2 (S7).

[0145] In step S6, if the ASIC 111 determines that there is a response from the seat sensor SE1 and the temperature sensor SE2 (S6, Yes), it determines that the first DC / DC converter V1 is not faulty because power is being supplied from the first DC / DC converter V1 to the seat sensor SE1 and the temperature sensor SE2, and switches the DC voltage output from the AC / DC converter 141 from 5V to 24V (S8: time t4).

[0146] As described above, the present embodiment provides the following advantages. The image forming apparatus 1 includes the ASIC 111, the AC / DC converter 141, the first DC / DC converter V1, and the first switching element SW1. By turning the first switching element SW1 ON, the image forming apparatus 1 can supply voltage to the ASIC 111 without passing through the first DC / DC converter V1. Therefore, if the first switching element SW1 is turned ON when the image forming apparatus 1 is started, the ASIC 111 can be started even if the first DC / DC converter V1 is faulty, and the ASIC 111 can execute control to determine whether the first DC / DC converter V1 is faulty.

[0147] Furthermore, when the image forming apparatus 1 is started up, the first switching element SW1 is in the ON state and the AC / DC converter 141 converts the AC voltage to the second voltage (5 V), so when the image forming apparatus 1 is started up, the second voltage (5 V) is supplied to the ASIC 111 without passing through the first DC / DC converter V1. Therefore, the ASIC 111 can be started up even if the first DC / DC converter V1 has failed.

[0148] Furthermore, since the second DC / DC converter V2 is further provided between the first DC / DC converter V1 and the first switching element SW1 and the ASIC 111, a fourth voltage (1.1 V) can be supplied to the ASIC 111. By supplying an appropriate voltage to the ASIC 111, it is possible to suppress breakdowns and malfunctions of the ASIC 111.

[0149] The image forming apparatus 1 also includes a second switching element SW2 that is connected in parallel with the third DC / DC converter V3 and is switchable between an ON state and an OFF state based on a control signal from the ASIC 111. This allows the ASIC 111 to execute control for determining whether or not the third DC / DC converter V3 has failed.

[0150] Furthermore, the ASIC 111 can determine that the third DC / DC converter V3 is normal by checking the responses of the LAN interface 114 and the USB interface 116 when the second switching element SW2 is in the OFF state.

[0151] Furthermore, the ASIC 111 can determine that the first DC / DC converter V1 is normal by checking the responses of the seat sensor SE1 and the temperature sensor SE2 when the first switching element SW1 is in the OFF state.

[0152] Furthermore, the image forming apparatus 1 allows for easy replacement of the sub-board 120. By replacing the sub-board 120, the first DC / DC converter V1, the first switching element SW1, the third DC / DC converter V3, and the second switching element SW2 can be easily replaced.

[0153] Furthermore, the sub-board 120 is directly connected to the main board 110 without a harness, which reduces the number of harnesses required.

[0154] The sub-board 120 also has a second connector C2 to which a terminal of a first harness H1 that connects to the low-voltage power supply board 140 is connected. Therefore, the first DC / DC converter V1 of the sub-board 120 can receive DC voltage directly from the low-voltage power supply board 140 without going through the main board 110.

[0155] Although the embodiment has been described above, the image forming apparatus 1 can be modified as appropriate as exemplified below.

[0156] In the above-described embodiment, the first voltage is 24 V, the second voltage is 5 V, the third voltage is 3.3 V, the fourth voltage is 1.1 V, the fifth voltage is 5 V, and the sixth voltage is 1.2 V, but each voltage can be set arbitrarily.

[0157] In the above-described embodiment, the fifth voltage is the same as the second voltage, but they do not have to be the same voltage.

[0158] In the above-described embodiment, after determining that the third DC / DC converter V3 is normal, the ASIC 111 turns the first switching element SW1 to the OFF state while keeping the second switching element SW2 in the OFF state, and checks the responses of the seat sensor SE1 and temperature sensor SE2 connected to the first DC / DC converter V1 (see Figure 7). However, as shown in Figure 8, the ASIC 111 may be configured to turn the second switching element SW2 to the ON state and the first switching element SW1 to the OFF state, and check the responses of the seat sensor SE1 and temperature sensor SE2 connected to the first DC / DC converter V1, after determining that the third DC / DC converter V3 is normal.

[0159] In the above-described embodiment, the sub-board 120 has two DC / DC converters, the first DC / DC converter V1 and the third DC / DC converter V3, but the sub-board 120 may have only one DC / DC converter, the first DC / DC converter V1. In this case, after starting up the image forming apparatus 1, the ASIC 111 turns off the first switching element SW1, checks the responses of the sheet sensor SE1 and the temperature sensor SE2 connected to the first DC / DC converter V1, and determines that the first DC / DC converter V1 is normal if there are responses from the sheet sensor SE1 and the temperature sensor SE2.

[0160] Even in this case, the ASIC 111 can determine that the first DC / DC converter V1 is normal by checking the responses of the seat sensor SE1 and the temperature sensor SE2 when the first switching element SW1 is in the OFF state.

[0161] In the embodiment described above, the sub-board 120 was provided with the second connector C2 to which the terminal of the first harness H1 that connects the low-voltage power supply board 140 is connected. However, as shown in Figures 9 and 10 , the main board 110 may be provided with a sub-connector CS to which the terminal of the second harness H2 that connects the low-voltage power supply board 140 is connected. In the embodiment shown in Figures 9 and 10 , the main board 110 and the low-voltage power supply board 140 are connected by a harness, and the sub-board 120 and the low-voltage power supply board 140 are not connected by a harness. Therefore, when replacing the sub-board 120, it is not necessary to disconnect the harness that connects the low-voltage power supply board 140. As a result, the effort required when replacing the sub-board 120 can be reduced.

[0162] In the above-described embodiment, the low-voltage power supply board 140 and the high-voltage power supply board 150 are not directly connected, but the low-voltage power supply board 140 and the high-voltage power supply board 150 may be directly connected without going through the main board 110, the sub-board 120, etc. In this case, the high-voltage board 150 is supplied with a direct current of the first voltage output from the AC / DC converter 141 without going through the main board 110 or the sub-board 120. According to this embodiment, the low-voltage power supply board 140 and the high-voltage power supply board 150 are both arranged in the second region RE2, and therefore the power lines can be shortened.

[0163] In the above-described embodiment, the ASIC 111 determines that the third DC / DC converter V3 is normal by checking the responses of both the LAN interface 114 and the USB interface 116 when the second switching element SW2 is in the OFF state. However, the determination may be made based on either the LAN interface 114 or the USB interface 116 alone, or by checking the responses of other devices, etc., or by the presence or absence of a load.

[0164] In the above-described embodiment, the ASIC 111 determines that the first DC / DC converter V1 is normal by checking the responses of both the seat sensor SE1 and the temperature sensor SE2 when the first switching element SW1 is in the OFF state, but the determination may be made by checking either the seat sensor SE1 or the temperature sensor SE2 alone, or by checking the responses of other devices, etc., or by the presence or absence of a load.

[0165] In the above-described embodiment, the main board 110 and the sub-board 120 are connected directly to each other using a board-to-board connector without a harness, but they may be connected to each other via a harness. If the main board 110 and the sub-board 120 are connected to each other via a harness, the main board 110 can be removed by first disconnecting the harness terminals.

[0166] In the above-described embodiment, the main connector CM of the main board 110 and the first connector C1 of the sub-board 120 face each other in the first direction, but they may face each other in a direction different from the first direction. For example, when the main connector CM and the first connector C1 face each other in the first direction, the main board 110 is pulled out from the first direction.

[0167] In the above-described embodiment, the main motor drive circuit 112 and the polygon motor drive circuit 113 are arranged on the main board 110, but at least one of the main motor drive circuit 112 and the polygon motor drive circuit 113 may be arranged on the sub-board 120.

[0168] In the above-described embodiment, the image forming apparatus 1 is a monochrome printer, but the image forming apparatus may be, for example, a color printer. The image forming apparatus may also be a copier, a multifunction peripheral, or the like. In the embodiment, an electrophotographic image forming apparatus is exemplified, but the image forming apparatus may also be, for example, an inkjet image forming apparatus, a dot impact image forming apparatus, or the like.

[0169] The elements described in the embodiments and modifications may be implemented in any combination.

[0170] 1 Image forming apparatus 53 Polygon motor 110 Main board 111 ASIC 112 Main motor drive circuit 113 Polygon motor drive circuit 120 Sub-board 140 Low voltage power supply board 141 AC / DC converter 160 Main motor SW1 First switching element SW2 Second switching element V1 First DC / DC converter V2 Second DC / DC converter V3 Third DC / DC converter V4 Fourth DC / DC converter

Claims

1. An image forming apparatus comprising: a photosensitive drum; a main motor that provides driving force to the photosensitive drum; an ASIC that controls the main motor; an AC / DC converter that can convert AC voltage supplied from a commercial power source into DC voltages of a first voltage and a second voltage lower than the first voltage; a first DC / DC converter that converts the first voltage into a third voltage lower than the first voltage, the first DC / DC converter having the ASIC connected to its secondary side; and a first switching element connected in parallel to the first DC / DC converter, the first switching element being switchable between an ON state and an OFF state based on a control signal from the ASIC, wherein when the first switching element is turned ON, the second voltage is supplied to the ASIC via the first switching element, and when the first switching element is turned OFF, the third voltage output from the first DC / DC converter is supplied to the ASIC.

2. The image forming apparatus according to claim 1, characterized in that, when the image forming apparatus is started up, the first switching element is in an ON state, and the AC / DC converter converts the AC voltage supplied from a commercial power source into the DC voltage of the second voltage.

3. The image forming apparatus according to claim 1, further comprising a second DC / DC converter arranged between the first DC / DC converter and the first switching element and the ASIC in the path that supplies voltage from a commercial power source to the ASIC, and that converts the second voltage or the third voltage into a fourth voltage that is lower than the second voltage and the third voltage.

4. The image forming apparatus according to claim 1, further comprising: a third DC / DC converter that converts the first voltage output from the AC / DC converter into a fifth voltage that is smaller than the first voltage and larger than the third voltage; and a second switching element connected in parallel with the third DC / DC converter, the second switching element being switchable between an ON state and an OFF state based on a control signal from the ASIC.

5. An image forming apparatus according to claim 4, wherein the fifth voltage is the same as the second voltage.

6. The image forming apparatus according to claim 4, characterized in that, when the image forming apparatus is started up, the second switching element is in an ON state, and the AC / DC converter converts the AC voltage supplied from a commercial power source into the DC voltage of the second voltage.

7. The image forming apparatus according to claim 6, wherein the first switching element is in the ON state when the image forming apparatus is started up, and the ASIC, after starting up the image forming apparatus, turns the second switching element to the OFF state, checks for a response from a first device connected to the third DC / DC converter, and determines that the third DC / DC converter is normal when there is a response from the first device.

8. The image forming apparatus according to claim 7, wherein the ASIC, after determining that the third DC / DC converter is normal, turns off the first switching element, checks for a response from a second device connected to the first DC / DC converter, and determines that the first DC / DC converter is normal if there is a response from the second device.

9. The image forming apparatus of claim 8, wherein the ASIC, after determining that the third DC / DC converter is normal, turns the first switching element OFF while keeping the second switching element OFF, and checks the response of the second device connected to the first DC / DC converter.

10. The image forming apparatus of claim 8, wherein the ASIC, after determining that the third DC / DC converter is normal, turns the second switching element ON and the first switching element OFF, and checks the response of the second device connected to the first DC / DC converter.

11. An image forming apparatus as described in any one of claims 8 to 10, characterized in that the ASIC switches the DC voltage output from the AC / DC converter from the second voltage to the first voltage when it determines that both the first DC / DC converter and the third DC / DC converter are normal.

12. The image forming apparatus according to claim 2, characterized in that, after the image forming apparatus is started, the ASIC turns off the first switching element, checks for a response from a second device connected to the first DC / DC converter, and determines that the first DC / DC converter is normal if there is a response from the second device.

13. The image forming apparatus according to claim 1, further comprising: a main board on which the ASIC is arranged; and a sub-board detachable from the main board, wherein the first DC / DC converter and the first switching element are arranged on the sub-board.

14. An image forming apparatus as described in claim 6, further comprising: a main board on which the ASIC is arranged; and a sub-board detachable from the main board, wherein the first DC / DC converter, the first switching element, the third DC / DC converter, and the second switching element are arranged on the sub-board.

15. An image forming apparatus as described in claim 3, further comprising: a main board on which the ASIC is arranged; and a sub-board detachable from the main board, wherein the ASIC and the second DC / DC converter are arranged on the main board.

16. An image forming apparatus according to any one of claims 13 to 15, wherein the sub-board has a first connector to which the main board is directly connected without using a harness.

17. An image forming apparatus as described in any one of claims 13 to 15, further comprising a low-voltage power supply board on which the AC / DC converter is arranged, and wherein the sub-board is arranged with a second connector to which a terminal of a first harness that connects the low-voltage power supply board is connected.

18. An image forming apparatus as described in any one of claims 13 to 15, further comprising a low-voltage power supply board on which the AC / DC converter is arranged, and wherein the main board is arranged with a sub-connector to which a terminal of a second harness that connects the low-voltage power supply board is connected.

Images