JP5965351B2 - Power shut-off device and image processing device - Google Patents

Description

  The present invention relates to a power cut-off device and an image processing device including a power switch having an electromagnetic reset function.

  In recent years, MFPs (Multi Function Peripherals) having a plurality of functions are used in offices and the like. A multifunction machine is often used in a situation where it is connected to an information processing terminal such as a personal computer through a network such as a LAN (Local Area Network). It functions as a printer device that prints image data input from the information processing terminal on paper, functions as a facsimile device that transmits image data input from the information processing terminal by facsimile, and is used in the information processing terminal. Function as an image reading device that acquires image data to be acquired, or function as a document management device that stores document image data in a searchable manner.

  Multifunction devices connected by such a network are often installed at a location away from the information processing terminal. For example, when an abnormality occurs, the operator of the information processing terminal can switch the power switch of the multifunction device. In many cases, it is difficult to immediately turn off the switch. For this reason, some multifunction peripherals include a power switch having an electromagnetic reset function (see, for example, Patent Documents 1 and 2). The electromagnetic reset function is a function of switching a switch from an on state to an off state by electromagnetic force. Such a power switch can be configured by, for example, a contact switch and an electromagnet that drives the contact switch. . In this multifunction device, for example, when an abnormality is detected, or when an instruction is input from the operator via the network, the electromagnet is energized, so that the operator is not at the location of the multifunction device. The power switch of the multifunction device can be switched to the off state.

  For example, in Patent Document 1, as a technology related to a printing apparatus including a power switch with an electromagnetic reset function, a power switch with an electromagnetic reset function is turned on in response to a power-off signal output by a CPU (Central Processing Unit) of the printing apparatus. A configuration is disclosed in which the driving of a fixing unit or the like that operates at a high voltage is stopped when it is not switched to the off state. In addition, even when there is no power off command from the host computer, the CPU of the printing device outputs a power off signal when the standby state of the printing device continues for a predetermined time in a specific time zone, and an electromagnetic reset function is provided. A configuration for switching a power switch from an on state to an off state is disclosed.

  Patent Document 2 discloses a color image forming apparatus including a power switch with an electromagnetic reset function, which has a frequency of use of a monochrome print mode and a color print mode when the power switch with an electromagnetic reset function is switched from an on state to an off state. A configuration for changing to a high print mode is disclosed. As a result, when the power switch is turned on, it can be immediately driven in the frequently used print mode, and the time-efficient print processing can be performed. Patent Document 2 also discloses a configuration that suppresses the deterioration of the power switch by prohibiting the supply of power to the large current load when the power switch with an electromagnetic reset function is switched from the on state to the off state.

  On the other hand, as described above, the power switch having the electromagnetic reset function is switched from the on state to the off state by driving the electromagnetic circuit in accordance with a power off signal (for example, a high level signal or a low level signal) output from the CPU. . Various techniques for preventing an abnormal operation or the like of a driving target have been proposed for such a CPU signal output (see Patent Documents 3 and 4).

  For example, Patent Document 3 discloses a configuration in which a control output line of a CPU and an output line of a system reset IC that inputs a reset signal to a reset terminal of the CPU when a power supply voltage drops are connected by a Schottky barrier diode. With this configuration, even when the potential of the control output line of the CPU is fixed to a signal level at which a load such as an LED (Laser Emitted Diode) is driven when the power supply voltage drops, the destruction of the load can be prevented.

  Further, Patent Document 4 is reversed even when the signal level of the chip select terminal of the CPU is fixed while the external storage element connected to the CPU is in an active state when the CPU shifts to the standby mode. A configuration is disclosed in which a signal level is input to a chip enable terminal of an external storage element. With this configuration, the power consumption of the external storage element when the CPU is in the standby mode is reduced.

JP-A-9-128177 Japanese Patent Laid-Open No. 9-258614 Japanese Patent Laid-Open No. 9-065568 JP 2001-222473 A

  As described above, the power switch having the electromagnetic reset function is switched from the on state to the off state in accordance with the signal level output from the CPU. For example, in a configuration in which a high level signal (high potential state) or a low level signal (low potential state) is output to an output terminal of a CPU that outputs a signal for driving a reset function of a power switch, a high level signal is used as a power off signal. When a high level signal is output to the output terminal of the CPU, the reset function of the power switch operates to switch from the on state to the off state.

  However, a signal of a desired signal level corresponding to the operation state of the multifunction device is output to the output terminal of the CPU that outputs a signal for driving the reset function of the power switch when the CPU is operating normally. Limited. Since the CPU is a digital circuit, the signal level output to the output terminal does not operate normally when the power supply voltage applied to the CPU does not reach the operating lower limit voltage of the CPU, for example, when the power is turned on. May be in an uncontrollable state (indeterminate state). In this state, a low level signal may be output to the output terminal of the CPU, or a high level signal may be output. Such an undefined state occurs when the I / O power supply reaches the operation lower limit voltage at the time of power-on, for example, before the CPU core power supply. Here, the core power source is a power source supplied to a core portion (register or built-in memory) that decodes or executes an instruction input in the CPU. The I / O power source is a power source supplied to an interface circuit portion other than the core portion of the CPU.

  In the above-described configuration, when a high level signal is output in this situation, the power switch is switched to an off state. That is, although the multifunction device is started with the power switch turned on, a malfunction occurs in which the reset function of the power switch operates to switch to the off state.

  Such a malfunction of the reset function can be avoided, for example, by sequence control of power supply. That is, first, the core power is supplied, and after reaching the operating lower limit voltage of the core, the I / O power is supplied. In this configuration, since the I / O power is not supplied until the core part of the CPU starts operating normally, a signal may be output to the output terminal in a situation where the core part does not operate normally (undefined state). Absent.

  However, in order to realize such sequence control, it is necessary to install a regulator for sequence control and a DC-DC converter, so that a space for installing these components is required and the cost is increased. .

  On the other hand, as disclosed in Patent Documents 3 and 4, it is conceivable to input a reset signal to the reset terminal of the CPU. In this case, when the reset signal is input, the CPU outputs a low level signal to the output terminal of the signal that drives the reset function of the power switch. However, the above-mentioned indefinite state occurs in a situation where the core unit is not operating normally, and even if a reset signal is input to the reset terminal in a situation where the core unit is not operating normally, the above output There is no guarantee that a low level signal will be output to the pin.

  The present invention has been made in view of the above-described problems of the prior art, and is a power supply having an electromagnetic reset function that can prevent malfunction of the reset function at low cost without employing a complicated structure. It is an object of the present invention to provide a power shut-off device and an image processing device including a switch.

  In order to achieve the above object, the present invention employs the following technical means. That is, the power shutoff device according to the present invention includes a contact switch, a power shutoff means, and a potential maintaining circuit. The contact switch is interposed in a power line connected to the power source, and switches between an on state and an off state. The power shut-off means switches the contact switch from the on state to the off state by electromagnetic force according to the potential of the signal output terminal to be monitored of the specific circuit. The specific circuit includes, for example, a control circuit that outputs a power-off signal that is an instruction to switch the contact switch from an on state to an off state. The potential maintaining circuit is connected to the signal output terminal, and after the power supply to the specific circuit is started based on the power supplied from the power source through the contact switch in the ON state, at least the specific circuit outputs a signal. During the period until the potential output to the terminal is stabilized, the potential of the signal output terminal is maintained at a potential at which the power shut-off means does not perform the switching operation. For example, in a configuration in which the power shut-off means performs the switching operation when the signal output terminal is higher than the reference potential, the potential maintaining circuit maintains the potential of the signal output terminal below the reference potential.

  In this configuration, the potential of the signal output terminal to be monitored is output to at least the signal output terminal after the potential maintenance circuit starts supplying power based on the power supplied from the power source through the contact switch in the on state. The voltage is maintained at a specific potential until the potential is stabilized. Therefore, for example, after the power is turned on, a power off signal may appear at the signal output terminal within a period in which the output of the control circuit that outputs the power off signal, which is an instruction to switch the contact switch from the on state to the off state, is indefinite. Absent. Therefore, it is possible to reliably prevent the malfunction of the power shut-off device when the power is turned on.

  In the above power shut-off device, when application of a DC potential is started simultaneously to the power line of the specific circuit and the power line of the potential maintaining circuit based on the power supplied from the power source through the contact switch in the ON state. In the potential maintaining circuit, the power shut-off means does not perform the switching operation for the signal output terminal for a predetermined time from when the DC potential applied to its own power supply line reaches the potential at which it can operate. A configuration including a reset IC (Integrated Circuit) that outputs a potential and then enters an open state can be employed. Alternatively, in the potential maintaining circuit, the direct current potential applied to its own power supply line reaches a predetermined potential that is equal to or higher than the potential at which the specific circuit can operate until it reaches the potential at which the specific circuit can operate. It is possible to employ a configuration including a reset IC that outputs a potential at which the power shut-off means does not perform a switching operation to the signal output terminal and then enters an open state.

  Thereby, the above-described effects can be obtained with a very simple configuration and space saving.

  On the other hand, in another aspect, the present invention can also provide an image processing apparatus including the above-described power shut-off device.

  According to the present invention, it is possible to prevent malfunction of the reset function at power-on without adopting a complicated configuration.

1 is a schematic configuration diagram showing the overall configuration of a multifunction machine according to an embodiment of the present invention. The figure which shows the hardware constitutions of the multifunctional device in one Embodiment of this invention. 1 is a functional block diagram showing a power shut-off device provided in a multifunction machine according to an embodiment of the present invention. The block diagram which shows an example of the structure which implement | achieves the power-supply-cutoff apparatus in one Embodiment of this invention The figure explaining the power-supply-cutoff operation in one Embodiment of this invention The figure which shows an example of the power-supply-cutoff operation in one Embodiment of this invention

  Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings. In the following, the present invention is embodied as a power cutoff device for a digital multifunction machine.

  FIG. 1 is a schematic configuration diagram illustrating an example of the overall configuration of a digital multifunction peripheral according to the present embodiment. As shown in FIG. 1, the multifunction peripheral 100 includes a main body 101 including an image reading unit 120 and an image forming unit 140, and a platen cover 102 attached above the main body 101. A document table 103 is provided on the upper surface of the main body 101, and the document table 103 is opened and closed by a platen cover 102. Further, the platen cover 102 includes a document conveying device 110. An operation panel 171 is provided on the front surface of the multi-function device 100 so that the user can give a copy start or other instruction to the multi-function device 100, and can check the status and settings of the multi-function device 100.

  An image reading unit 120 is provided below the document table 103. The image reading unit 120 reads an image of a document with the scanning optical system 121 and generates digital data (image data) of the image. The document can be placed on the document table 103 or the document transport device 110. The scanning optical system 121 includes a first carriage 122, a second carriage 123, and a condenser lens 124. The first carriage 122 is provided with a linear light source 131 and a mirror 132, and the second carriage 123 is provided with mirrors 133 and 134. The light source 131 illuminates the document. The mirrors 132, 133, and 134 guide reflected light from the document to the condenser lens 124, and the condenser lens 124 forms an optical image on the light receiving surface of the line image sensor 125. In the scanning optical system 121, the first carriage 122 and the second carriage 123 are provided so as to be able to reciprocate in the sub-scanning direction 135. By moving the first carriage 122 and the second carriage 123 in the sub-scanning direction 135, the image of the document placed on the document table 103 can be read by the image sensor 125. When reading an image of a document set on the document conveying device 110, the image reading unit 120 temporarily fixes the first carriage 122 and the second carriage 123 according to the image reading position, and passes the image reading position. Are read by the image sensor 125. The image sensor 125 generates image data of a document corresponding to, for example, each color of R (red), G (green), and B (blue) from the light image incident on the light receiving surface. The generated image data can be printed on paper in the image forming unit 140. Further, the data can be transmitted to another device (not shown) through the network 162 by the network adapter 161.

  The image forming unit 140 prints image data obtained by the image reading unit 120 or image data received from another device connected to the network 162 on a sheet. The image forming unit 140 includes a photosensitive drum 141. The photosensitive drum 141 rotates in one direction at a constant speed. Around the photosensitive drum 141, a charger 142, an exposure unit 143, a developing unit 144, and an intermediate transfer belt 145 are arranged in this order from the upstream side in the rotation direction. The charger 142 uniformly charges the surface of the photosensitive drum 141. The exposure device 143 irradiates the surface of the uniformly charged photoconductor drum 141 with light according to the image data, and forms an electrostatic latent image on the photoconductor drum 141. The developing device 144 attaches toner to the electrostatic latent image and forms a toner image on the photosensitive drum 141. The intermediate transfer belt 145 transfers the toner image on the photosensitive drum 141 onto a sheet. When the image data is a color image, the intermediate transfer belt 145 transfers each color toner image onto the same sheet. The RGB color image is converted into C (cyan), M (magenta), Y (yellow), and K (black) format image data, and the image data of each color is input to the exposure unit 143.

  The image forming unit 140 feeds paper from the manual feed tray 151, the paper feed cassettes 152, 153, and 154 to the transfer unit between the intermediate transfer belt 145 and the transfer roller 146. Various sizes of paper can be placed or stored in the manual feed tray 151 and the paper feed cassettes 152, 153, and 154. The image forming unit 140 selects a sheet specified by the user or a sheet corresponding to the automatically detected document size, and feeds the selected sheet from the manual feed tray 151 or the cassettes 152, 153, and 154 by the feeding roller 155. . The fed paper is transported to the transfer section by transport rollers 156 and registration rollers 157. The sheet on which the toner image is transferred is conveyed to the fixing device 148 by the conveyance belt 147. The fixing device 148 has a fixing roller 158 and a pressure roller 159 with a built-in heater, and fixes the toner image on the sheet by heat and pressing force. The image forming unit 140 discharges the sheet that has passed through the fixing device 148 to the discharge tray 149.

  Electric power for driving each unit of the multifunction peripheral 100 is supplied from a commercial AC power source 191. The AC power supplied from the commercial AC power supply 191 is rectified in the power supply circuit 182, and the rectified DC power is supplied to each part of the multifunction peripheral 100. The multi-function device 100 includes a power shut-off device 181 interposed between a power supply circuit 182 and a commercial AC power supply 191. As will be described in detail below, the power shut-off device 181 includes a power switch having an electromagnetic reset function, and switches the power switch from the on state to the off state as necessary, thereby switching from the commercial AC power source 191 to the power circuit 182. Shut off the AC power supply.

  FIG. 2 is a hardware configuration diagram of a control system in the multifunction machine. The multifunction peripheral 100 according to the present embodiment includes a CPU (Central Processing Unit) 201, a RAM (Random Access Memory) 202, a ROM (Read Only Memory) 203, an HDD (Hard Disk Drive) 204, an original transport device 110, and an image reading unit 120. A driver 205 corresponding to each drive unit in the image forming unit 140 is connected via an internal bus 206. The ROM 203, the HDD 204, and the like store programs, and the CPU 201 controls the multifunction peripheral 100 in accordance with instructions from the control program. For example, the CPU 201 uses the RAM 202 as a work area, and controls the operation of each driving unit by exchanging data and commands with the driver 205. The HDD 204 is also used to store image data obtained by the image reading unit 120 and image data received from other devices through the network adapter 161.

  An operation panel 171 and various sensors 207 are also connected to the internal bus 206. The operation panel 171 receives a user operation and supplies a signal based on the operation to the CPU 201. Further, the operation panel 171 displays an operation screen on a display provided in the operation panel 171 according to a control signal from the CPU 201. The sensor 207 includes various sensors such as an open / close detection sensor for the platen cover 102, a document detection sensor on the document table 103, a temperature sensor for the fixing device 148, and a detection sensor for the conveyed paper or document.

  FIG. 3 is a functional block diagram of the power shut-off device provided in the multifunction machine according to the present embodiment. As shown in FIG. 3, the power cutoff device 181 of the multifunction peripheral 100 according to the present embodiment includes a contact switch 301, a power cutoff unit 302, and a potential maintaining circuit 303.

  The contact switch 301 is interposed between power supply lines 311 and 312 that connect the commercial AC power supply 191 and the power supply circuit 182 and switches between an on state and an off state. The power supply circuit 182 removes power noise from the AC power supplied from the commercial AC power supply 191 and rectifies it, and converts it into DC power supplied to each part of the multifunction peripheral 100. In the present embodiment, the power supply circuit 182 includes a circuit that generates at least 3.3 V and 5 V DC sources. 3 shows a state in which the power supply circuit 182 supplies DC power to the power supply cutoff unit 302, the potential maintaining circuit 303, and the cutoff control circuit 331 through the power supply lines 313, 314, and 315, respectively.

  Although not particularly limited, the contact switch 301 is inserted into one of a pair of power supply lines 311 and 312 that connect the commercial AC power supply 191 and the power supply circuit 182, and the one power supply line is turned on (conductive state) and turned off. 1-circuit 1-contact switch for switching between (interrupt state) and 2-circuit 1-contact for switching between the on-state (conductive state) and off-state (cut-off state) of each power line inserted into both power lines 311 and 312 It can be configured by a switch. As shown in FIG. 4, in the present embodiment, the contact switch 301 is constituted by a two-circuit one-contact switch.

  The power shut-off means 302 switches the contact switch 301 from the on state to the off state by electromagnetic force in accordance with the potential (signal level) of the signal output terminal to be monitored of a specific circuit. In the example of FIG. 3, the power shut-off means 302 monitors the signal level of the signal output terminal 332 that outputs the power-off signal of the shut-off control circuit 331 that generates the power-off signal. Here, the power shut-off means 302 switches the contact switch 301 from the on state to the off state if the signal level of the signal output terminal 332 is at a high level (high potential state) higher than the reference potential.

  The mechanism for switching the contact switch 301 from the on state to the off state is not particularly limited, but in the present embodiment, the power shut-off means 302 includes a solenoid. By driving the solenoid in accordance with the signal level of the signal output terminal to be monitored, the conductor that electrically connects the contacts of the contact switch 301 is moved, and the contact switch 301 is switched from the on state to the off state. .

  Note that the shutdown control circuit 331 is a circuit that generates a power-off signal in accordance with the state of the multifunction peripheral 100, and includes, for example, a CPU that determines whether or not to perform power shutdown. The CPU may be the CPU 201 described above, or a CPU provided separately in the power shut-off device 181.

  The potential maintaining circuit 303 is connected to the signal output terminal 332. Then, after the power supply to the interruption control circuit 331 is started based on the power supplied from the commercial AC power supply 191 through the contact switch 301 in the ON state (that is, after the power supply is started from the power supply circuit 182), At least during the period until the signal level output to the signal output terminal 332 by the cutoff control circuit 331 is stabilized, the signal level of the signal output terminal 332 is maintained at a signal level at which the power cutoff unit 302 does not perform the switching operation. As described above, in the present embodiment, the power shut-off unit 302 performs the switching operation of the contact switch 301 if the signal level of the signal output terminal 332 is high. Therefore, the potential maintaining circuit 303 maintains the signal level of the signal output terminal 332 at a low level (low potential state) equal to or lower than the reference potential during the period.

  FIG. 4 is a diagram showing a specific example of the power shut-off means 302 and the potential maintaining circuit 303 described above. As shown in FIG. 4, the power shut-off means 302 includes a switch Q1, a switch Q2, and a diode D1 that are constituted by transistors.

  The switch Q1 has a configuration in which a base and a collector of an NPN transistor with a collector grounded are connected via a resistor R3. A resistor R2 is connected to the base that is a signal input terminal. Similarly, the switch Q2 has a configuration in which the base and emitter of the PNP transistor are connected via a resistor R5. A resistor R4 is connected to the base which is a signal input terminal. The emitter is connected to a DC power supply of 5 V in the power supply circuit 182 described above via a power supply line 313. The collector is connected to the cathode of a diode D1 whose anode is grounded. When the voltage applied to both ends (between the anode and cathode) of the diode D1 becomes 5V, the electromagnetic driving means 401 including the solenoid is driven, and the contact switch 301 is switched from the on state to the off state.

  The other end of the resistor R4 of the switch Q2 is connected to the emitter of the NPN transistor that constitutes the switch Q1. The other end of the resistor R2 of the switch Q1 is connected to the signal output terminal 332 of the shutoff control circuit 331 via the resistor R1.

  As described above, the cutoff control circuit 331 includes a CPU, and includes the core unit 333 and the I / O unit 334 as its components. The core unit 333 is a core part (register, built-in memory, etc.) that decodes and executes instructions input in the CPU, and the I / O unit 334 is an interface circuit part other than the core part of the CPU. The core unit 333 and the I / O unit 334 are connected to a 3.3 V DC power source in the power circuit 182 described above via a power line 315.

  In the power shut-off means 302 having the above configuration, the potential (signal level) of the signal output terminal 332 is input to the switch Q1 via the resistor R1. For example, when the signal level of the signal output terminal 332 is a high level higher than a reference potential (for example, 0.9 V), the switch Q1 is turned on, and the emitter and collector of the PNP transistor are turned on. . At this time, the switch Q2 is also turned on, and the emitter and collector of the NPN transistor are brought into conduction. As a result, the DC potential of 5 V supplied through the power supply line 313 is applied to the cathode of the diode D1. In this case, since a voltage is applied to the diode D1 in the reverse direction, a potential difference of 5 V is generated between the cathode and the anode of the diode D1. The solenoid 401 is driven by the potential difference.

  On the other hand, when the signal level of the signal output terminal 332 is a low level that is a low potential equal to or lower than the reference potential, the switch Q1 is turned off, and the emitter and collector of the PNP transistor are cut off. At this time, the switch Q2 is also turned off, and the emitter and collector of the NPN transistor are also cut off. As a result, there is no potential difference of 5V between the cathode and anode of the diode D1, and the solenoid is not driven 401. Therefore, the contact switch 301 does not switch from the on state to the off state.

  In the present embodiment, the potential maintaining circuit 303 is connected between the resistor R1 and the resistor R2. As shown in FIG. 4, in the present embodiment, the potential maintaining circuit 303 uses a reset IC that is widely used as an element that generates a reset signal to be input to the reset terminal of the CPU. Generally, a reset IC has a fixed potential (for example, a voltage applied to its output terminal) when the DC potential applied to its own power supply line is between the time when it reaches its operable potential and the time when it reaches a predetermined potential. The grounding potential is output, and when the potential is equal to or higher than a predetermined potential (operation upper limit potential), the output terminal is opened. In addition, in a reset IC that can adjust the delay time of the operation start timing and the operation end timing by an external capacitor, the DC potential applied to its own power supply line is changed by combining the above-described operation and the delay time. The output terminal potential can be maintained at a predetermined potential or lower for a predetermined time after reaching the operable potential. Although not particularly limited, in this embodiment, a reset IC whose delay time can be adjusted by an external capacitor is used.

  As shown in FIG. 4, the reset IC 3031 includes a power supply terminal 3032, an output terminal 3033, and a capacitor connection terminal 3034 for adjusting a delay time. The power supply terminal 3032 is connected to a 5V DC power supply of the power supply circuit 182 through a power supply line 314. The output terminal 3033 is connected between the resistor R1 and the resistor R2 as described above. The capacitor connection terminal 3034 is grounded through the capacitor C1. The reset IC 3031 outputs a ground potential to the output terminal 3033 during operation, and the output terminal 3033 is opened above the operation upper limit potential.

  For example, when the contact switch 301 is switched from the OFF state to the ON state and the commercial AC power supply 191 is turned on to the power supply circuit 182, the power supply circuit 182 outputs a predetermined potential such as 3.3V or 5V at the moment of turning on the power. I can't do it. That is, the DC potential output from the power supply circuit 182 gradually rises from 0 V to several tens of msec, for example, and reaches a predetermined potential.

  The reset IC 3031 to which such a DC potential is applied to the power supply terminal 3032 starts its operation when the potential of the power supply terminal 3032 reaches an operation lower limit voltage (for example, 0.7 V). Although depending on the circuit configuration of the reset IC 3031, in this embodiment, the reset IC 3031 outputs a potential equivalent to that of the power supply terminal 3032 to the output terminal 3033 below the operation lower limit voltage, and if the output IC 3031 exceeds the operation lower limit voltage, the output terminal The ground potential is output to 3033. Then, when the potential of the power supply terminal 3032 further rises and exceeds a predetermined voltage defined as the operation upper limit voltage, the reset IC 3031 opens the output terminal 3033.

  Next, the operation of the power shut-off device 181 having the above configuration will be described. FIG. 5 is a diagram illustrating an example of the power shutoff operation of the power shutoff device 181. In FIG. 5, the horizontal axis corresponds to time, and the vertical axis corresponds to the signal level (potential). In FIG. 5, the potential of the 5V DC power supply (the potential of the power supply lines 313 and 314) output from the power supply circuit 182 and the potential of the 3.3V DC power supply (the potential of the power supply line 315) and the potential maintaining circuit 303 exist. In addition, the potential of the signal output terminal 332 of the cutoff control circuit 331, the potential of the output terminal 3033 of the reset IC 3031, and the potential of the signal output terminal 332 of the cutoff control circuit 331 when the potential maintaining circuit 303 is connected are shown together. ing. Here, it is assumed that the operation lower limit voltage of the reset IC 3031 is 0.7V, and the operation lower limit voltage of the core unit 333 of the cutoff control circuit 331 is 2.85V.

  As shown in FIG. 5, when the contact switch 301 is switched from the OFF state to the ON state and the commercial AC power supply 191 is connected to the power supply circuit 182, the 5V DC power supply potential and the 3.3V DC power supply potential output from the power supply circuit 182. Gradually rises from 0V, and finally the 5V DC power supply potential reaches 5V and becomes a steady state, and the 3.3V DC power supply potential reaches 3.3V and becomes a steady state.

  As shown in FIG. 4, in this embodiment, the core unit 333 and the I / O unit 334 of the interruption control circuit 331 have a 3.3V DC power supply when the contact switch 301 is switched from the off state to the on state. A potential is applied simultaneously. In this configuration, the core unit 333 does not operate normally after the power supply by the 3.3V DC power supply is started until the 3.3V DC power supply potential reaches the operation lower limit voltage of 2.85V. Therefore, as shown in FIG. 5 as the potential of the signal output terminal 332 when there is no potential maintaining circuit, until the 3.3V DC power supply potential reaches 2.85V after the contact switch 301 is switched from the off state to the on state. The output of the signal output terminal 332 of the interruption control circuit 331 is in an indefinite state (signal output terminal potential indefinite period P1). When the 3.3V DC power supply potential exceeds the operation lower limit voltage of 2.85V, the core unit 333 operates normally. Therefore, if there is no circumstance (for example, failure) that outputs a power-off signal for switching the contact switch 301 from the on state to the off state, the potential of the signal output terminal 332 is switched to the off state by the power shut-off means 302. It becomes a low level (in this case, 0V) without being performed.

  On the other hand, in the reset IC 3031 in which the 5V DC power source is connected to the power supply terminal 3032, the potential of the 5V DC power source is applied when the contact switch 301 is switched from the off state to the on state. The application of the 5V DC power supply potential occurs simultaneously with the application of the 3.3V DC power supply potential to the cutoff control circuit 331. In this configuration, as shown in FIG. 5, the reset IC 3031 is connected to the output terminal 3033 from the start of power supply by the 5V DC power supply until the 5V DC power supply potential reaches the operating lower limit voltage of 0.7V. A potential equivalent to 3032 is output. When the 5V DC power supply potential exceeds the operation lower limit voltage, the reset IC 3031 operates, and the potential of the output terminal 3033 of the reset IC 3031 becomes 0V without the power shut-off means 302 switching to the off state. Thereafter, when the 5V DC power supply potential exceeds the operation upper limit voltage of the reset IC 3031, the output terminal 3033 of the reset IC 3031 is opened. In this embodiment, the reset IC 3031 having an operation upper limit voltage exceeding 2.85 V is used, or even if the operation upper limit voltage is 2.85 V or less, the signal output terminal potential indefinite period is adjusted by adjusting the delay time using the capacitor C1. From the end point of P1, the potential of the output terminal 3033 of the reset IC 3031 is set to be maintained at 0 V from the end of the period P2 (signal output terminal potential maintaining period P0).

  As a result, in the configuration of the present embodiment shown in FIG. 4, the potential of the signal output terminal 332 is the signal output terminal potential when the potential maintaining circuit is connected, as shown in FIG. Until the 5V DC power supply potential reaches 0.7V after switching to, the potential is equivalent to the power supply terminal 3032 of the reset IC 3031 (that is, 0.7V or less). When the 5V DC power supply potential exceeds 0.7V, the potential of the signal output terminal 332 is maintained at 0V until the signal output terminal potential maintaining period P0 ends. When the signal output terminal potential maintaining period P0 ends, the output terminal 3033 of the reset IC 3031 is opened. At this time, as described above, the 3.3V DC power supply potential exceeds 2.85V, The potential of the output terminal 332 is maintained at 0 V by the output of the cutoff control circuit 331 itself.

  Therefore, according to the configuration of the present embodiment, in the configuration in which power is simultaneously supplied to the core unit 333 and the I / O unit 334 of the cutoff control circuit 331 that outputs the power-off signal, the contact switch 301 is switched from the off state to the on state. Even when the power supply potential lower than the operation lower limit voltage is supplied and the signal level of the signal output terminal 332 is in an indefinite state when the power is switched on, the power shut-off device 181 turns the contact switch 301 off due to a malfunction. Switching can be prevented.

  FIG. 6 is a diagram showing measured values of the potential of the 3.3V DC power supply of the power supply circuit 182 and the potential of the signal output terminal 332 of the cutoff control circuit 331. In FIG. 6, the horizontal axis corresponds to time, and the vertical axis corresponds to potential. In this example, for the sake of explanation, the shutoff control circuit 331 outputs a power-off signal after the signal output terminal potential maintaining period P0 ends. From FIG. 6 to FIG. 5, the period from when the contact switch 301 is switched from the OFF state to the ON state until the operation lower limit voltage of the interruption control circuit 331 is exceeded (signal output terminal potential maintaining period P0), the signal It can be understood that the potential of the output terminal 332 is maintained at a potential (0.9 V or less) at which the power shut-off means 302 does not drive the solenoid 401.

  As described above, in the multi-function device 100, at least after the potential of the signal output terminal 332 that outputs the power-off signal is started from the power supply circuit 182 by switching the contact switch 301 from the off state to the on state, The potential maintaining circuit 303 maintains the specific potential for a period until the potential output from the cutoff control circuit 331 to the signal output terminal 332 is stabilized. For this reason, the power-off signal does not appear at the signal output terminal 332 within a period in which the output of the cutoff control circuit 331 is indefinite after the power is turned on. Therefore, it is possible to reliably prevent the malfunction of the power shut-off device 181 when the power is turned on. In the multifunction device 100, since the power shut-off device 181 is configured by the reset IC 3031, it is possible to obtain a malfunction prevention effect with a very simple configuration and space saving.

  In the above embodiment, the power cutoff unit 302 performs the switching operation when the signal output terminal 332 is at a higher potential than the reference potential. However, the power cutoff unit 302 has the signal output terminal 332 at the reference potential. Alternatively, the switching operation may be performed when the potential is lower than that. In this case, the potential maintaining circuit 303 can be a reset IC that outputs a potential higher than the reference potential during operation.

  As described above, according to the present invention, it is possible to prevent malfunction of the reset function at power-on without adopting a complicated configuration.

  The above-described embodiments do not limit the technical scope of the present invention, and various modifications and applications other than those already described are possible within the scope of the present invention. For example, in the MFP 100, the configuration in which the potential maintaining circuit 303 includes the reset IC 3101 has been described as a particularly preferable form. However, by using a circuit having a function equivalent to that of the reset IC, at least the reset function at the time of power-on is provided. It is possible to obtain the effect of preventing malfunction.

  In the above-described embodiment, the present invention is embodied as a power shut-off device for a digital multi-function peripheral. However, the present invention is not limited to a digital multi-function peripheral, and an arbitrary image processing apparatus such as a printer, a copier, and an electromagnetic reset function. It is also possible to apply the present invention to any power shut-off device having a power switch.

  According to the present invention, it is possible to prevent malfunction of the reset function at the time of power-on without adopting a complicated configuration, which is useful as a power shut-off device and an image processing device.

100 MFP (image processing device)
181 Power supply interruption device 182 Power supply circuit 191 Commercial AC power supply (power supply)
301 Contact switch 302 Power shut-off means 303 Potential maintaining circuit 3031 Reset IC
311 to 315 Power line 331 Shutdown control circuit 332 Signal output terminal 401 Electromagnetic drive means (solenoid)

Claims (3)

A contact switch interposed between the power line connected to the power source and switching between the on state and the off state;
In accordance with the potential of the signal output terminal to be monitored of a specific circuit, a power cutoff means for switching the contact switch from an on state to an off state by electromagnetic force;
After power supply to the circuit is started based on the power supplied from the power source through the contact switch that is connected to the signal output terminal and in the ON state, at least the potential that the circuit outputs to the signal output terminal is A potential maintaining circuit for maintaining the potential of the signal output terminal at a potential at which the power shut-off means does not perform a switching operation during a period until stabilization;
In a power shut-off device comprising :
Based on the power supplied from the power source through the contact switch in the ON state, application of a DC potential is simultaneously started to the power line of the specific circuit and the power line of the potential maintaining circuit,
The potential maintaining circuit has a DC potential applied to its own power supply line for a predetermined time from when the DC potential applied to its own power supply line reaches a potential at which it can operate, or The potential that the power shut-off means does not perform the switching operation is output to the signal output terminal from when the operable potential is reached until the predetermined potential that is equal to or higher than the potential at which the specific circuit can operate is output. A power shut-off device comprising a reset IC that is subsequently opened . The power shut-off means performs a switching operation when the signal output terminal of the specific circuit is higher than a reference potential, and the potential maintaining circuit maintains the potential of the signal output terminal below the reference potential. The power shut-off device according to claim 1. An image processing apparatus comprising the power shut-off device according to claim 1.

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