JP5225935B2 - Key matrix circuit and image forming apparatus having the circuit - Google Patents

Description

  The present invention relates to a circuit for detecting a user request input from a numeric keypad or the like arranged in a matrix, and particularly to a mode in which an image forming apparatus or the like operates with a low power consumption of about 1 W (power saving mode, low power mode). The present invention relates to a key matrix circuit that detects a return request from a sleep mode input from a numeric keypad arranged in a matrix in a power mode, an energy saving mode, a sleep mode, or the like. The present invention also relates to an image forming apparatus provided with such a key matrix circuit.

  In many cases, a printing apparatus such as a printer or a copy is connected to a network and these are used by a plurality of users. The printing apparatus used in this manner has a user's print request timing that varies from individual to individual, so that power is often turned on for a long time, and measures to reduce power consumption are required. In particular, a multifunction device (MFP: Multifunction Peripheral) having a copy function, a facsimile function, a network-compatible printer function, and a scanner function is not a simple printing device, and may not be turned off throughout the day, including at night. The need for power reduction is even higher. The image forming apparatus is an example of such a multifunction peripheral.

  For this reason, when the MFP is turned on but enters a standby state where there is no operation request, the power supply is automatically shifted to an energy saving mode such as an off state. This energy saving mode is normally canceled by a user operating a key operation for starting copying or scanning, or a print request via a network, and a printing operation is performed.

  As described above, an increasing number of image forming apparatuses operate by appropriately switching between the normal mode and the energy saving mode. In such an image forming apparatus, it is often controlled to return from the normal mode to the energy saving mode and to return to the normal mode when a predetermined key such as a return key is pressed in the energy saving mode. There are various energy saving modes, and there are a plurality of names for them. In the present invention, these energy saving modes are described as being representative of the sleep mode.

  In such an image forming apparatus, ten keys (numeric keys) are arranged in a matrix in order to designate the number of copies or an arbitrary magnification. In order to detect such an input from the numeric keypad, a drive circuit (scan circuit) is provided, and power is also consumed by this drive circuit between the key input and the key input. In the energy saving mode described above, it is also important to reduce power consumption by such a drive circuit. Based on such a viewpoint, Japanese Patent Laid-Open No. 2-13017 (Patent Document 1) discloses a keyboard with reduced power consumption. This keyboard is assumed to be a battery-powered portable input device.

  The keyboard disclosed in Patent Document 1 includes a key matrix in which key switches are connected in a matrix, a scanning circuit that sequentially outputs scan pulses to the key scanning lines of the key matrix and performs key scanning, and a key. When any key switch in the matrix is turned on, the scanning circuit is activated, and when the key switch turned on as a result of key scanning by this scanning circuit is identified, the scanning circuit operates. And a control unit for stopping.

  According to this keyboard, only when there is a key input, a scanning circuit that performs key scanning is operated until a key switch that is turned on in the key matrix is identified. Since the operation is stopped, energy consumption can be suppressed.

JP-A-2-13017

  As described above, many image forming apparatuses are controlled to return to the normal mode when a predetermined key such as a return key is pressed in the energy saving mode. However, Patent Document 1 is intended to save energy of the scanning circuit in the normal mode, and does not detect a key input for a return request from the energy saving mode to the normal mode in the energy saving mode. That is, an input from an arbitrary numeric keypad cannot be detected without operating the scanning circuit in the energy saving mode.

  For this reason, the conventional image forming apparatus includes a circuit for detecting a return activation signal, as shown in FIG. 5, even when a matrix-like key is provided. The diagram shown in FIG. 5A is a circuit diagram of the key matrix circuit, and the diagram shown in FIG. 5B is a circuit diagram of the activation signal circuit.

  The key matrix circuit shown in FIG. 5A operates with power supplied from the power supply VDD 101 that does not operate when the image forming apparatus is in the sleep mode. The activation signal circuit shown in FIG. 5B is operated by the power supplied from the power supply VDD 102 that always operates as long as the main power supply of the image forming apparatus is in the ON state, including when the image forming apparatus is in the sleep mode. To do.

  As shown in FIG. 5A, when power is supplied from the power supply VDD 101 to the key matrix circuit (normal mode), the output of the IC 101 is when the scan 101 signal (also referred to as a three-state control line) is at the low level. Becomes High level. When any one of SW101 to SW103 is pressed, the output of IC104 to IC106 (sense 101 signal to sense 103 signal) changes from the low level to the high level. By detecting this, any of SW101 to SW103 is detected. The pressed state is detected. Regarding three-state control, when one scan signal is set to Low, the other two scan signals are set to High, and the outputs of the other ICs are set to tri-state (high impedance state, floating state). By switching in this way, the states of SW104 to SW106 are detected by the sense 101 signal to the sense 103 signal when the scan 102 signal is at the low level, and the states of SW107 to SW109 are detected when the scan 103 signal is at the low level, respectively.

  As shown in FIG. 5B, when power is not supplied from the power supply VDD 101 to the key matrix circuit and power is supplied from the power supply VDD 102 to the activation signal circuit (sleep mode), the SW 110 is pressed. As a result, the output of the IC 108 changes from the Low level to the High level. By detecting this, the activation signal is generated and the activation request can be detected.

  As described above, conventionally, the keys arranged in a matrix require a scanning operation, and therefore, the key press cannot be detected unless the drive circuit for executing the scanning operation is operated. For this reason, a key for activation (corresponding to SW 110) is arranged separately from the keys arranged in a matrix, and a dedicated key used only for the activation request is required. This indicates that a dedicated button needs to be arranged on the operation panel.

  In addition, if an activation request is detected using a matrix-arranged key without providing a dedicated button, it is unnecessary to operate a drive circuit that executes a scan operation even in the sleep mode, which is wasteful. Consumes a lot of power. This is because even if the technique disclosed in Patent Document 1 is used, the technique disclosed in Patent Document 1 does not require a scanning operation in the sleep mode. The operation of the part is necessary. When the activation request is detected using the keys arranged in a matrix as described above, the scanning circuit and the control unit operate in the sleep mode, which causes a problem that the energy saving effect is low.

  Therefore, an object of the present invention is to provide keys arranged in a matrix, and capable of detecting an input from the keys arranged in the matrix in the sleep mode (power saving mode) and shifting to the normal mode. An object of the present invention is to provide a matrix circuit and an image forming apparatus including such a key matrix circuit.

  A key matrix circuit according to an aspect of the present invention detects a request to switch from a state operating in a power saving mode to a normal mode. This key matrix circuit is connected to a key matrix having a plurality of switches that are switched from an open state to a closed state in response to a key operation on a corresponding key, and a power source that operates in a normal mode. A scan-side circuit element that scans for each group, a sense-side circuit element that detects whether each switch is in an open state or a closed state corresponding to the scan in the normal mode, and a power source that operates in the power saving mode And a first circuit element for passing a current to all the switches constituting the key matrix from the sense side circuit element to the scan side circuit element, and responding to the operation of the first circuit element in the power saving mode Detecting the closed state of one of the switches and detecting the request for switching to the normal mode. And a second circuit element.

  According to this key matrix circuit, when operating in the normal mode, the scan side circuit element scans the key matrix for each switch group by the electric power supplied from the power source operating in the normal mode. The sense side circuit element detects whether each switch is in an open state or a closed state in response to the scan by the scan side circuit element. As a result, for example, nine switches arranged in a 3 × 3 matrix are scanned every three switches (divided into three groups), and which switch among the nine switches is opened. Whether it is switched to the closed state can be detected. Further, when operating in the power saving mode, the first circuit element forms a key matrix from the sense side circuit element to the scan side circuit element by the power supplied from the power source operating in the power saving mode. Pass current through all switches. In response to the operation of the first circuit element, the second circuit element detects the closed state of any one of the switches constituting the key matrix. Thereby, it is possible to detect whether any of the nine switches is switched from the open state to the closed state without scanning. When detected in this way, it is determined that switching from the power saving mode to the normal mode is requested. As a result, in the power saving mode, it can be detected that any one of the switches arranged in a matrix is pressed without scanning, and this is determined as a request for switching to the normal mode (startup request). be able to. For this reason, since the activation request is detected without scanning the key matrix in the power saving mode without using a dedicated key used only for the activation request, it is possible to suppress power consumption in the power saving mode.

  The first circuit element is an element that changes the direction of the current to the key matrix circuit between the normal mode and the power saving mode in response to a signal indicating the power saving mode state, and is driven by one driving circuit. Can be configured. The first circuit element is an element that changes the direction of the current to the key matrix circuit between the normal mode and the power saving mode in response to a signal indicating the power saving mode state. It can be configured to be driven.

  The first circuit element is driven by one drive circuit or a plurality of drive circuits provided on the basis of a necessary current value, and forms all of the key matrix from the sense side circuit element to the scan side circuit element. The necessary current can be passed through the switch.

  The resistance value of the resistor connected to the second circuit element can be configured to be larger than the resistance value of the connected resistor connected to the first circuit element.

  By doing so, it is possible to prevent the current on the scan side from wrapping around and generate a request for switching to the normal mode (start-up request) signal in the second circuit element. Furthermore, since the resistance value connected to the second circuit element is large, the activation request signal can be created while suppressing current consumption.

  The second circuit element can be configured to detect the switching request in response to a signal indicating the power saving mode state.

  In this way, the activation signal can be generated only in the power saving mode. In this way, it is possible to avoid a problem that may be caused by the start signal generated in the normal mode by preventing the start signal from being output in the normal mode.

  An image forming apparatus according to another aspect of the present invention includes any one of the key matrix circuits described above.

  In an image forming apparatus that is required to reduce power consumption in the power saving mode, the activation request is detected without scanning the key matrix in the power saving mode. For this reason, power consumption in the power saving mode can be suppressed in the image forming apparatus. Further, since the activation request is detected using the keys arranged in a matrix, a dedicated key used only for the activation request is not required for the image forming apparatus.

  According to the key matrix circuit and the image forming apparatus according to the present invention, since the activation request is detected without scanning the key matrix in the power saving mode, power consumption in the power saving mode can be suppressed. Further, in the image forming apparatus, there is no need to arrange a dedicated button for activation request for switching from the power saving mode to the normal mode.

1 is a cross-sectional view showing an internal structure of an image forming apparatus including a key matrix circuit according to an embodiment of the present invention. 1 is a circuit diagram of a key matrix circuit according to a first embodiment of the present invention. It is a circuit diagram of the key matrix circuit based on the 2nd Embodiment of this invention. It is a circuit diagram of the key matrix circuit based on the 3rd Embodiment of this invention. FIG. 6 is a circuit diagram of a conventional key matrix circuit and a circuit diagram of a start signal circuit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same parts are denoted by the same reference numerals. Their functions and names are also the same. Therefore, detailed description thereof will not be repeated. In the following description, the image forming apparatus according to the embodiment of the present invention is described as a tandem full color type, but may be a full color type of another format (for example, four cycles) or a monochrome type. Further, the image forming apparatus is provided with a circuit (key matrix circuit) that is a key arranged in a matrix such as a numeric keypad and detects a key input by a scanning operation, and has more power than the normal mode when there is no operation request. Any device can be used as long as it can shift to an energy saving mode (sleep mode) in which the consumption of energy is suppressed.

<First Embodiment>
FIG. 1 is a sectional view showing an internal structure of an image forming apparatus 100 including a key matrix circuit according to the first embodiment of the present invention. As will be described later, the image forming apparatus 100 also includes a key matrix circuit according to another embodiment of the present invention.

  The image forming apparatus 100 forms a multicolor image or a single color image on a predetermined sheet (recording paper) in accordance with image data transmitted from the outside. In general, the image forming apparatus 100 is an image forming apparatus. 100 main body units 110 and an automatic document processing apparatus 120. The main body 110 includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit 6, a fixing unit 7, a paper feed cassette 81, a paper discharge tray 91, and the like. It is configured.

  A document placing table 92 made of transparent glass on which a document is placed is provided on the upper part of the main body 110, and an automatic document processing device 120 is attached to the upper side of the document placing table 92. The automatic document processing device 120 automatically conveys the document on the document placing table 92. Further, the automatic document processing device 120 is configured to be rotatable in the direction of arrow M, and the document can be placed manually by opening the document table 92.

  Image data handled in the image forming apparatus 100 is data corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, four developing devices 2, photosensitive drums 3, chargers 5, and cleaner units 4 are provided so as to form four types of latent images corresponding to the respective colors, and four of black, cyan, magenta, and yellow are provided. One image station is configured.

  The charger 5 functions to uniformly charge the surface of the photosensitive drum 3 to a predetermined potential. The exposure unit 1 is configured as a laser scanning unit (LSU) provided with a laser emitting portion, a reflection mirror, and the like. The exposure unit 1 includes a polygon mirror that scans a laser beam and optical elements such as a lens and a mirror for guiding the laser beam reflected by the polygon mirror to the photosensitive drum 3.

  The exposure unit 1 has a function of forming an electrostatic latent image corresponding to the image data on the surface thereof by exposing the charged photosensitive drum 3 according to the input image data. The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toners of four colors (Y, M, C, K). The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt unit 6 disposed above the photosensitive drum 3 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and an intermediate transfer belt cleaning unit 65. I have. Four intermediate transfer rollers 64 are provided corresponding to the respective colors Y, M, C, and K. The intermediate transfer belt driving roller 62, the intermediate transfer belt driven roller 63, and the intermediate transfer roller 64 are driven to rotate while the intermediate transfer belt 61 is stretched. The intermediate transfer roller 64 provides a transfer bias for transferring the toner image on the photosensitive drum 3 onto the intermediate transfer belt 61.

  The intermediate transfer belt 61 is provided so as to be in contact with the four photosensitive drums 3, and each color toner image formed on the photosensitive drum 3 is sequentially superimposed and transferred onto the intermediate transfer belt 61. Thus, a color toner image (multicolor toner image) is formed on the intermediate transfer belt 61. The intermediate transfer belt 61 is formed in an endless shape using, for example, a film having a thickness of about 100 μm to 150 μm.

  The toner image is transferred from the photosensitive drum 3 to the intermediate transfer belt 61 by an intermediate transfer roller 64 that is in contact with the back side of the intermediate transfer belt 61. A high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 64 in order to transfer the toner image. The intermediate transfer roller 64 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 mm to 10 mm and whose surface is covered with a conductive elastic material (for example, ethylene-propylene-diene rubber, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt 61. In this embodiment, a roller-shaped electrode is used as the transfer electrode, but a brush-shaped electrode or the like can be used in addition to that.

  As described above, the electrostatic latent images visualized according to the respective colors on the respective photosensitive drums 3 are stacked on the intermediate transfer belt 61. In this way, the laminated image information is transferred onto the recording sheet by the transfer roller 10 disposed at the contact position between the recording sheet and the intermediate transfer belt 61 described later by the rotation of the intermediate transfer belt 61.

  At this time, the intermediate transfer belt 61 and the transfer roller 10 are pressed against each other at a predetermined nip, and a voltage for transferring the toner to the recording paper is applied to the transfer roller 10 (opposite to the toner charging polarity (−)). Polarity (+) high voltage). Further, in order to obtain the above nip constantly, the transfer roller 10 uses either the transfer roller 10 or the intermediate transfer belt driving roller 62 as a hard material (metal or the like) and the other as a soft material such as an elastic roller (elastic rubber roller). Or a foamed resin roller or the like).

  Further, as described above, the toner adhering to the intermediate transfer belt 61 by contacting the photosensitive drum 3 or the toner remaining on the intermediate transfer belt 61 without being transferred onto the recording paper by the transfer roller 10 is used in the next step. Therefore, the intermediate transfer belt cleaning unit 65 is configured to remove and collect the toner. The intermediate transfer belt cleaning unit 65 is provided with a cleaning blade that contacts the intermediate transfer belt 61, for example, as a cleaning member. The intermediate transfer belt 61 that contacts the cleaning blade is driven by an intermediate transfer belt driven roller 63 from the back side. It is supported.

  The paper feed cassette 81 is a tray for storing sheets (recording paper) used for image formation, and is provided below the exposure unit 1 of the main body 110. A sheet used for image formation can also be placed on the manual paper feed cassette 82. A paper discharge tray 91 provided above the main body 110 is a tray for collecting printed sheets face down.

  The main body 110 is provided with a substantially vertical sheet conveyance path S for sending the sheets of the sheet feeding cassette 81 and the manual sheet feeding cassette 82 to the sheet discharge tray 91 via the transfer roller 10 and the fixing unit 7. It has been. In the vicinity of the paper transport path S from the paper feed cassette 81 or the manual paper feed cassette 82 to the paper discharge tray 91, there are a pickup roller 11a, a pickup roller 11b, a plurality of transport rollers 12a to 12d, a registration roller 13, and a transfer roller. 10, a fixing unit 7 and the like are arranged.

  The conveyance rollers 12a to 12d are small rollers for promoting and assisting conveyance of the sheet, and a plurality of the conveyance rollers 12a to 12d are provided along the sheet conveyance path S. The pickup roller 11 a is provided near the end of the paper feed cassette 81, picks up sheets one by one from the paper feed cassette 81, and supplies them to the paper transport path S. Similarly, the pickup roller 11b is provided near the end of the manual paper feed cassette 82, picks up one sheet at a time from the manual paper feed cassette 82, and supplies it to the paper transport path S.

  The registration roller 13 temporarily holds the sheet being conveyed on the sheet conveyance path S. The sheet has a function of conveying the sheet to the transfer roller 10 at the timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the sheet are aligned.

  The fixing unit 7 includes a heat roller 71 and a pressure roller 72, and the heat roller 71 and the pressure roller 72 rotate with the sheet interposed therebetween. The heat roller 71 is set to have a predetermined fixing temperature by a control unit based on a signal from a temperature detector (not shown), and the pressure roller 72 and the toner are thermocompression-bonded to the sheet. The multicolor toner image transferred onto the sheet is melted, mixed and pressed, and thermally fixed to the sheet. An external heating belt 73 for heating the heat roller 71 from the outside is provided.

  Next, the sheet conveyance path will be described in detail. As described above, the image forming apparatus 100 is provided with the paper feed cassette 81 and the manual paper feed cassette 82 for storing sheets in advance. In order to feed sheets from these sheet feeding cassettes 81 or manual sheet feeding cassettes 82, pickup rollers 11a or pickup rollers 11b are arranged to guide the sheets one by one to the sheet conveyance path S.

  The sheet conveyed from the sheet feeding cassette 81 or the manual sheet feeding cassette 82 is conveyed to the registration roller 13 by the conveying roller 12a in the sheet conveying path S, and aligns the leading edge of the sheet with the leading edge of the image information on the intermediate transfer belt 61. It is conveyed to the transfer roller 10 at a timing, and image information is written on the sheet. Thereafter, the sheet passes through the fixing unit 7 so that the unfixed toner on the sheet is melted and fixed by heat, and is discharged onto the sheet discharge tray 91 through the conveyance roller 12b disposed thereafter.

  The above-mentioned conveyance path is for a single-sided printing request for a sheet. On the other hand, when a double-sided printing request is made, the trailing edge of the sheet that has finished single-sided printing and has passed through the fixing unit 7 as described above. When the sheet is held by the final conveying roller 12b, the conveying roller 12b rotates backward to guide the sheet to the conveying rollers 12c and 12d. Thereafter, after printing is performed on the back surface of the sheet through the registration roller 13, the sheet is discharged to the discharge tray 91.

  In the image forming apparatus 100, hardware keys that are operation buttons (operation keys) for inputting a request for image formation by a user are provided on the plate-like operation panel 90. The ten keys are arranged in a matrix, and a pressed key is detected by a key matrix circuit. The operation panel 90 is provided with a display panel for displaying the state of the image forming apparatus 100 or the job processing status. When keys arranged in a matrix are pressed, numbers corresponding to the keys detected by the key matrix circuit are displayed on this display panel.

  The image forming apparatus 100 according to the present embodiment includes a key matrix circuit 1000 shown in FIG. The key matrix circuit 1000 will be described below.

  2 includes a power supply 1001 (VDD1) that does not supply power to the key matrix circuit 1000 when the image forming apparatus 100 is in the sleep mode, and an image forming apparatus including when the image forming apparatus 100 is in the sleep mode. As long as the main power supply 100 is in an ON state, a power supply 1002 (VDD2) that always supplies power to the key matrix circuit 1000, switches 1031 to 1039 (SW1 to SW9) arranged in a matrix, and a circuit on the scan side The element 1011 (IC1) to the circuit element 1013 (IC3), the sensing side circuit element 1014 (IC4) to the circuit element 1016 (IC6), and the conventional ground side are provided, and the sleep state signal (sleep low level) is provided. The power supply 1002 (V The power supplied from D2) comprising circuit elements 1017 to flow a current to the switch 1,031 to 1,039 (SW1 to SW9) and (IC 7), the circuit element 1020 which outputs a start signal and (IC 10). The state of the switches 1031 to 1039 (SW1 to SW9) is either an open state or a closed state that changes according to a user's key operation.

  Further, the key matrix circuit 1000 includes a diode 1051 (D1) provided between the switch 1033 (SW3) and the circuit element 1020 (IC10), and a switch 1036 (SW6) and the circuit element 1020 (IC10). And a diode 1053 (D3) provided between the switch 1039 (SW9) and the circuit element 1020 (IC10). Further, the key matrix circuit 1000 includes a resistor 1041 (R1) provided between the input side of the circuit element 1020 (IC10) and GND, a switch 1037 (SW7), and a circuit element 1017 (IC7). , A resistor 1043 (R3) provided between the switch 1038 (SW8) and the circuit element 1017 (IC7), a switch 1039 (SW9), and a circuit element 1017 (IC7). ) And a resistor 1044 (R4) provided therebetween.

  The circuit element 1011 (IC1) is supplied with power from the power supply 1001 (VDD1) and connected to a three-state control line to receive a scan signal (scan 1 signal). When the scan 1 signal is at the low level, the output of the circuit element 1011 (IC1) is at the high level. The circuit element 1012 (IC2) and the circuit element 1013 (IC3) also have the same configuration and configuration as the circuit element 1011 (IC1).

  When the switch 1031 (SW1) is pressed while the scan 1 signal is at the low level, the sense 1 signal that is the output of the circuit element 1016 (IC6) changes from the low level to the high level, and the switch 1032 (SW2) is pressed. Then, the sense 2 signal that is the output of the circuit element 1015 (IC5) changes from the low level to the high level, and when the switch 1033 (SW3) is pressed, the sense 3 signal that is the output of the circuit element 1014 (IC4) is low. The level changes from the high level to the high level. By detecting these, it is detected whether any of the switch 1031 (SW1) to the switch 1033 (SW3) is pressed.

  With regard to the three-state control, when one scan signal is set to the low level, the other two scan signals are set to High, and the outputs of the other ICs are set to tristate (high impedance state, floating state).

  After the scan 1 signal is set to the low level (both the scan 2 signal and the scan 3 signal are both at the high level) and the state of the sense 1 signal to the sense 3 signal is detected, the scan 1 signal is set to the high level and the scan 2 signal is Whether the switch 1034 (SW4) to the switch 1036 (SW6) is pressed by detecting the state of the sense 1 signal to the sense 3 signal by setting it to the low level (the scan 3 signal is at the high level at this time). Is detected.

  After the scan 2 signal is set to the low level (both the scan 1 signal and the scan 3 signal are at the high level) and the state of the sense 1 signal to the sense 3 signal is detected, the scan 2 signal is set to the high level in the same manner. Then, the scan 3 signal is set to the low level (the scan 1 signal is at the high level at this time), and any one of the switch 1037 (SW7) to the switch 1039 (SW9) is pressed by detecting the state of the sense 1 signal to the sense 3 signal. It is detected whether it is done.

  Note that the circuit element 1011 (IC1) to the circuit element 1016 (IC6) are not supplied with power from the power supply 1001 (VDD1) in the sleep state. For this reason, in order to protect from the latch-up in which an electric current flows into the off side, elements with a latch-up protection circuit are used for the circuit elements 1011 (IC1) to 1016 (IC6).

  Thus, in the normal mode, the key matrix circuit 1000 according to the present embodiment is pressed when any one of the switches 1031 (SW1) to 1039 (SW9) arranged in a matrix is pressed. When one of the switches 1031 (SW1) to 1039 (SW9) arranged in a matrix is pressed in the sleep mode, the pressed switch is the switch 1031 (SW1) to A function of detecting that any one of the nine switches of the switch 1039 (SW9) is pressed (without specifying which switch among the nine switches) is provided. Hereinafter, this function will be described.

  In order to realize such a function, the key matrix circuit 1000 includes a circuit element 1017 (IC7) and a circuit element 1020 (IC10).

  The circuit element 1017 (IC7) is supplied with power from the power supply 1002 (VDD2) (whether in the normal mode or in the sleep mode) and also receives a sleep state signal (low level during sleep). The circuit element 1017 (IC7) is connected to the switch 1031 (SW1), the switch 1034 (SW4), and the switch 1037 (SW7) through the resistor 1042 (R2), and the switch 1032 (R3) through the switch 1032 (R3). SW2), a switch 1035 (SW5) and a switch 1038 (SW8), and connected to a switch 1033 (SW3), a switch 1036 (SW6) and a switch 1039 (SW9) via a resistor 1044 (R4).

  When the sleep state signal input to the circuit element 1017 (IC7) is switched from a high level (normal mode) to a low level (during sleep) (at this time, power is supplied from the power supply 1001 (VDD1) to the key matrix circuit 1000. The output from the circuit element 1017 (IC7) changes from Low level to High level.

  The switches 1031 (SW1) to 1039 (SW9) arranged in a matrix are connected to the circuit elements 1014 (IC4) to 1016 (IC6) that function in the normal mode as described above, and also in the sleep mode. It is connected to a functioning circuit element 1020 (IC10). A diode 1051 (D1) to a diode 1053 (D3) are provided between the switch 1031 (SW1) to the switch 1039 (SW9) and the circuit element 1020 (IC10) to limit the direction of current. . Further, the output sides of the diodes 1051 (D1) to 1053 (D3) are connected to each other, and a resistor 1041 (R1) is provided between the connection point and GND, and the potential at the connection point is input. A circuit element 1020 (IC10) is provided.

  Since such a circuit is provided, in the key matrix circuit 1000, when the output from the circuit element 1017 (IC7) is at a high level (during sleep), the switches 1031 (SW1) to 1039 (SW9) are all open. Then, the input of the circuit element 1020 (IC10) is set to the low level by the resistor 1041 (R1), and the output of the circuit element 1020 (IC10) is at the low level. This state is detected as a state where there is no activation request.

  On the other hand, when any one of the switch 1031 (SW1) to the switch 1039 (SW9) is pressed, the resistor 1042 (R2) to the resistor 1041 (R1) is output from the output of the circuit element 1017 (IC7). Current flows through the capacitor 1044 (R4), the switch 1031 (SW1) to the switch 1039 (SW9), and the diode 1051 (D1) to the diode 1053 (D3). For example, when the switch 1031 (SW1) is pressed, the circuit element 1017 (IC7) → resistor 1042 (R2) → switch 1031 (SW1) → diode 1051 (D1) → resistor 1041 (R1) → GND closed circuit Is configured. In this case, the resistance value of the resistor 1041 (R1) needs to be sufficiently larger than the resistance value of the resistor 1042 (R2). This is because the circuit element 1020 (IC10) generates an activation signal by preventing the current on the scan line side from wrapping around. Furthermore, by increasing the resistance value of the resistor 1041 (R1), it is possible to create a start signal while suppressing current consumption in the closed circuit.

  By this closed circuit and the power source 1002 (VDD2), the input of the circuit element 1020 (IC10) is switched from the Low level to the High level. As a result, the output (activation signal) of the circuit element 1020 (IC10) changes from the Low level (no activation request state) to the High level (activation request state).

  As described above, in the key matrix circuit 1000 according to the present embodiment and the image forming apparatus 100 including the key matrix circuit 1000, the keys are arranged in a matrix in order to efficiently input a large number (for example, nine) of keys. And a resistor is provided on the sense line side, and a current is passed from the resistor side in the sleep mode to detect the depression of an arbitrary key on the scan line side to generate an activation signal. For this reason, in the normal mode, it is possible to detect which of the matrix keys is pressed by supplying a current from the scan side to the sense side in the key matrix circuit. In sleep mode, by changing the current to flow from the resistor side of the sense line to the scan side (in normal mode, current flows from the scan side of the key matrix to the sense line side, but in sleep mode, the current is passed from the sense line side to the scan side) By driving only one line instead of a large number of lines, it is possible to pass a current through all the keys on the matrix. This eliminates the need for a key scan operation, can reduce power consumption, and can detect a return request from the sleep mode to the normal mode using keys arranged in a matrix.

<Second Embodiment>
The key matrix circuit 2000 according to the second embodiment of the present invention will be described below. Note that the key matrix circuit 2000 according to the present embodiment is also mounted on the same image forming apparatus 100 as in the first embodiment. As described above, image forming apparatus 100 (FIG. 1) is the same as that of the first embodiment described above, and thus detailed description thereof will not be repeated.

  In the key matrix circuit 1000 according to the first embodiment described above, the circuit element 1017 (IC7) receives a signal indicating the sleep mode state, and the direction of the current is changed to be different from that in the normal mode. In this case, the key matrix circuit 1000 is driven by one drive circuit (circuit element 1017 (IC7)).

  In the key matrix circuit 2000 according to the present embodiment, a plurality of driving circuits (circuit element 1017 (IC7), circuit element 1018 (IC8), and circuit element 1019 ( The key matrix circuit 2000 is driven by IC9)).

  FIG. 3 shows a key matrix circuit 2000 according to the present embodiment. Hereinafter, the difference between the key matrix circuit 2000 and the key matrix circuit 1000 according to the first embodiment will be described.

  As shown in FIG. 3, the key matrix circuit 2000 is different from the key matrix circuit 1000 in the configuration of the drive circuit during sleep. The key matrix circuit 2000 is a circuit having the same function in addition to the circuit element 1017 (IC7) provided for the resistor 1042 (R2), the resistor 1043 (R3), and the resistor 1044 (R4). An element 1018 (IC8) and a circuit element 1019 (IC9) are provided. A circuit element 1017 (IC7) is connected to the resistor 1044 (R4), a circuit element 1018 (IC8) is connected to the resistor 1043 (R3), and a circuit element 1019 (IC9) is connected to the resistor 1042 (R2). Is connected.

  The sleep state signal (sleep low level) is input to any of the circuit elements 1017 (IC7), 1018 (IC8), and 1019 (IC9), and power is supplied from the power supply 1002 (VDD2). The

  By using a plurality of drive circuits in this way, it becomes possible to avoid a shortage of drive current that could occur in one drive circuit.

<Third Embodiment>
The key matrix circuit 3000 according to the third embodiment of the present invention will be described below. Note that the key matrix circuit 3000 according to the present embodiment is also mounted on the same image forming apparatus 100 as in the first and second embodiments. As described above, image forming apparatus 100 (FIG. 1) is the same as that of the first embodiment described above, and thus detailed description thereof will not be repeated.

  In the key matrix circuit 1000 according to the first embodiment described above, since the power supply 1002 (VDD2) supplies power to the key matrix circuit 1000 even in the normal mode that is not in the sleep mode, the switch 1031 (SW1) in the normal mode. ) To 1039 (SW9), the circuit is configured so that an activation signal is generated when one of the switches is pressed.

  In the key matrix circuit 3000 according to the present embodiment, the activation signal is generated only in the sleep mode in response to the case where the activation signal is not preferably generated in the normal mode.

  FIG. 4 shows a key matrix circuit 3000 according to this embodiment. Hereinafter, the difference between the key matrix circuit 3000 and the key matrix circuit 1000 according to the first embodiment will be described.

  As shown in FIG. 4, the key matrix circuit 3000 is different from the key matrix circuit 1000 in the configuration of the circuit elements that output the activation signal. The key matrix circuit 3000 includes a circuit element 1021 (IC11) and a resistor 1045 (R5) instead of the circuit element 1020 (IC10) (instead of the buffer IC).

  Electric power is supplied to the circuit element 1021 (IC11) from the power supply 1002 (VDD2) (whether in the normal mode or the sleep mode), and a sleep state signal is input to the circuit element 1021 (IC11). The circuit element 1021 (IC11) generates and outputs an activation signal only in the case of the sleep state signal (sleep low level).

  In this way, by generating the activation signal only at the time of sleep, it is possible to prevent the activation signal from being output in the normal mode. For this reason, it is possible to avoid a problem that may have been caused by the activation signal generated in the normal mode.

<Modification>
The key matrix circuit may be configured by appropriately combining the above-described embodiments. For example, according to the key matrix circuit 2000 according to the second embodiment and the third embodiment. A combination with the key matrix circuit 3000 is conceivable.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the embodiment described above. The scope of the present invention is indicated by each claim in the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are intended. Including.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 1000, 2000, 3000 Key matrix circuit 1001, 1002 Power supply 1011-1021 Circuit element 1031-1039 Switch 1041-1045 Resistor 1051-1053 Diode

Claims (5)

A key matrix circuit for detecting a request to switch from a state operating in a power saving mode to a normal mode,
A key matrix having a plurality of switches that are switched from an open state to a closed state in response to a key operation on a corresponding key;
A scan-side circuit element that is connected to a power source that operates in a normal mode and scans the key matrix for each switch group;
In a normal mode, in response to the scan, a sense side circuit element that detects whether each of the switches is in an open state or a closed state;
A first circuit element that is connected to a power source that operates in a power saving mode, and that allows a current to flow from the sense side circuit element to the scan side circuit element to all the switches constituting the key matrix;
A second circuit element for detecting a request for switching to a normal mode by detecting a closed state of any of the plurality of switches in response to an operation of the first circuit element in a power saving mode; viewing including the door,
The key circuit circuit, wherein the second circuit element detects the switching request in response to a signal indicating a power saving mode state .   The first circuit element is an element that changes a current direction to the key matrix circuit between a normal mode and a power saving mode in response to a signal indicating a power saving mode state. The key matrix circuit according to claim 1, which is driven.   The first circuit element is an element that changes a direction of current to the key matrix circuit between a normal mode and a power saving mode in response to a signal indicating a power saving mode state, and includes a plurality of driving circuits. The key matrix circuit according to claim 1, which is driven.   The resistance value of the resistor connected to the second circuit element is larger than the resistance value of the connected resistor connected to the first circuit element. The key matrix circuit described. With a key matrix circuit according to any one of claims 1 to 4, the image forming apparatus.

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