Electronic apparatus, and signal output method

Abstract

To provide an electronic apparatus and a signal output method that can reduce the power consumption of a circuit that removes noise mixed in a signal line.SOLUTION: An image forming apparatus comprises: a low-pass filter 31 that is connected to a signal line L1 used for transmission of a first control signal X1; and a non-inverting amplifier circuit 32 that includes a resistance switching unit 33 capable of switching the electric resistance between an inverting input terminal of an operational amplifier OP1 and the ground GN1 between a first value and a second value lower than the first value, and amplifies the first control signal X1 output from the low-pass filter 31. The electric resistance is switched from the first value to the second value before the first control signal X1 is input to the non-inverting amplifier circuit 32, and the electric resistance is switched from the second value to the first value after the first control signal X1 is input to the non-inverting amplifier circuit 32.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electronic device and a signal output method. [Background technology]

[0002] In electronic devices such as printers, noise can get mixed into the signal lines used to transmit control signals output from a control unit, causing malfunctions in the controlled device to which the control signal is input. In response to this, a circuit is known that removes noise mixed into the signal lines (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-50508 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, it is desirable that the power consumption of the circuit for removing noise that gets mixed into the signal line be as small as possible.

[0005] An object of the present invention is to provide an electronic device and a signal output method that can reduce the power consumption of a circuit that removes noise that gets mixed into a signal line. [Means for solving the problem]

[0006] According to one aspect of the present invention, an electronic device includes a signal line, a low-pass filter, a non-inverting amplifier circuit, a first switching processing unit, and a second switching processing unit. The signal line is used to transmit a control signal. The low-pass filter is connected to the signal line. The non-inverting amplifier circuit includes an operational amplifier and a resistance switching unit that can switch an electrical resistance between an inverting input terminal of the operational amplifier and ground between a first value and a second value lower than the first value, and amplifies the control signal output from the low-pass filter. The first switching processing unit switches the electrical resistance from the first value to the second value using the resistance switching unit before the control signal is input to the non-inverting amplifier circuit. The second switching processing unit switches the electrical resistance from the second value to the first value using the resistance switching unit after the control signal is input to the non-inverting amplifier circuit.

[0007] A signal output method according to another aspect of the present invention is executed by an electronic device including a signal line used to transmit a control signal, a low-pass filter connected to the signal line, an operational amplifier, and a non-inverting amplifier circuit including a resistance switching unit capable of switching an electrical resistance between an inverting input terminal of the operational amplifier and ground between a first value and a second value lower than the first value, and amplifying the control signal output from the low-pass filter, and includes a first switching step and a second switching step. In the first switching step, the resistance switching unit is used to switch the electrical resistance from the first value to the second value before the control signal is input to the non-inverting amplifier circuit. In the second switching step, the resistance switching unit is used to switch the electrical resistance from the second value to the first value after the control signal is input to the non-inverting amplifier circuit. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the power consumption of a circuit that removes noise that gets mixed into a signal line. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a block diagram showing the system configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the configuration of a signal circuit of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing the waveform of a first control signal output from a low-pass filter of the image forming apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the waveform of a first control signal output from a non-inverting amplifier circuit of the image forming apparatus according to the embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart showing an example of a signal output process executed by the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0011] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Fig. 1. In Fig. 1, the image forming apparatus 100 is indicated by a dashed line.

[0012] The image forming apparatus 100 is a multifunction peripheral that has multiple functions, such as a scanning function for reading an image from a document, a printing function for forming an image on a sheet based on image data, a fax function, and a copy function. The image forming apparatus 100 is an example of an electronic device of the present invention. The present invention may also be applied to electronic devices such as scanners, printers, fax machines, copy machines, personal computers, laptop computers, televisions, microwave ovens, and refrigerators.

[0013] As shown in FIG. 1, the image forming apparatus 100 includes an ADF (Auto Document Feeder) 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, an operation display unit 5, an attachment unit 6, a storage unit 7, and a main control unit 8.

[0014] The ADF 1 transports documents to be scanned by the scanning function, and includes a document setting unit, a plurality of document transport rollers, a document holder, and a paper ejection unit.

[0015] The image reading unit 2 realizes the scanning function and includes a document table, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device).

[0016] The image forming unit 3 realizes the printing function and includes a photosensitive drum, a charging roller, an optical scanning device, a developing device, a toner container, a transfer roller, a cleaning device, a fixing device, and a paper discharge tray.

[0017] The paper feed unit 4 supplies sheets to the image forming unit 3. The paper feed unit 4 includes a paper feed cassette, a pickup roller, a paper feed roller, a plurality of sheet transport rollers, and a registration roller.

[0018] The operation display unit 5 is a user interface of the image forming apparatus 100. As shown in FIG. 1, the operation display unit 5 includes a display unit 11, an operation unit 12, and a sub-control unit 13. The display unit 11 is used to display information to the user. For example, the display unit 11 is a flat panel display such as a liquid crystal display. The operation unit 12 is used by the user to input information to the image forming apparatus 100. For example, the operation unit 12 includes operation keys and a touch panel. The sub-control unit 13 controls the operation display unit 5. The sub-control unit 13 is composed of electronic circuits such as integrated circuits (ASIC, DSP).

[0019] The mounting unit 6 has a USB connection terminal to which an external electronic device capable of inputting and outputting data in accordance with the USB standard is attached / detached. For example, a storage device 200 (see FIG. 1) that can write and read data in accordance with the USB standard is attached / detached to / from the mounting unit 6. For example, the storage device 200 is a USB memory.

[0020] The storage unit 7 is a nonvolatile storage device, such as a nonvolatile memory such as a flash memory, a solid state drive (SSD), or a hard disk drive (HDD).

[0021] The main control unit 8 performs overall control of the image forming apparatus 100. As shown in FIG. 1, the main control unit 8 includes a CPU 21, a ROM 22, and a RAM 23. The CPU 21 is a processor that executes various types of arithmetic processing. The ROM 22 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 21 to execute various types of processing. The RAM 23 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 21. The CPU 21 performs overall control of the image forming apparatus 100 by executing the various control programs that are stored in advance in the ROM 22.

[0022] The main control unit 8 can also switch the operation mode of the image forming apparatus 100 between a normal mode and a power saving mode in which power consumption is reduced compared to the normal mode. In the power saving mode, power supply to some of the components of the image forming apparatus 100 is stopped.

[0023] For example, when the operation mode of the image forming apparatus 100 is the normal mode, the main control unit 8 transitions the operation mode from the normal mode to the power saving mode if the image forming apparatus 100 remains in a non-operated state for a predetermined period of time or if a predetermined operation is performed on the operation unit 12. Furthermore, when the operation mode of the image forming apparatus 100 is the power saving mode, the main control unit 8 transitions the operation mode from the power saving mode to the normal mode if a user operation is received on the operation unit 12 or a print job is sent from an external information processing apparatus.

[0024] When the operation mode of the image forming apparatus 100 transitions from the power saving mode to the normal mode, the main control unit 8 inputs a first control signal X1 (see FIG. 2) (an example of a control signal of the present invention) to the sub-control unit 13. The first control signal X1 is output by switching the voltage of a signal line L1 (see FIG. 2) used to transmit the first control signal X1 from low to high. When the first control signal X1 is input, the sub-control unit 13 determines that the operation mode of the image forming apparatus 100 has transitioned from the power saving mode to the normal mode, and executes a predetermined return process. For example, the return process includes a process of starting power supply to the display unit 11 and a process of displaying an operation screen used to operate the image forming apparatus 100 on the display unit 11.

[0025] Incidentally, in the image forming apparatus 100, noise may be mixed into the signal line L1, causing malfunction in the sub-controller 13. For example, in the image forming apparatus 100, when the storage device 200 is attached to the attachment unit 6, electrostatic discharge may occur between the user's finger and the attachment unit 6. If the electrostatic discharge occurs while the image forming apparatus 100 is operating in the power saving mode, a high-frequency signal (noise) caused by the electrostatic discharge may be mixed into the signal line L1, causing the sub-controller 13 to erroneously determine that the operation mode of the image forming apparatus 100 has transitioned from the power saving mode to the normal mode.

[0026] In response to this, a circuit is known that removes noise that gets mixed into the signal line L1.

[0027] Here, it is desirable that the power consumption of the circuit that removes noise that gets mixed into the signal line L1 be as low as possible.

[0028] In contrast to this, in the image forming apparatus 100 according to the embodiment of the present invention, as will be described below, it is possible to reduce the power consumption of the circuit that removes noise that gets mixed into the signal line L1.

[0029] Specifically, the operation display unit 5 includes a signal circuit 14 shown in FIG.

[0030] [Configuration of signal circuit 14] Next, the configuration of the signal circuit 14 will be described with reference to Figures 2 to 4. In Figure 2, the low-pass filter 31, the non-inverting amplifier circuit 32, and the resistance switching unit 33 are indicated by dashed lines.

[0031] The signal circuit 14 is provided on a substrate 15 (see FIG. 2) on which the sub-controller 13 is mounted.

[0032] As shown in FIG. 2, the substrate 15 includes an input terminal 15A and an input terminal 15B.

[0033] A signal line L1 (see FIG. 2) is connected to the input terminal 15A. A signal line L2 (see FIG. 2) used to transmit a second control signal X2 (see FIG. 2) is connected to the input terminal 15B. The second control signal X2 is a signal for switching the gain of a non-inverting amplifier circuit 32 (described later), and is output by switching the voltage of the signal line L2 from low level to high level.

[0034] For example, the substrate 15 includes a first connector including input terminals 15A and 15B. The image forming apparatus 100 also includes a harness connected to the first connector. The signal lines L1 and L2 are included in the harness. The harness is connected to a second connector of a control substrate on which the components of the main control unit 8 are mounted.

[0035] As shown in FIG. 2, the signal circuit 14 includes a low-pass filter 31 and a non-inverting amplifier circuit 32.

[0036] The low-pass filter 31 is connected to the signal line L1. As shown in FIG. 2, the low-pass filter 31 includes a resistor R11 and a capacitor C1. One end of the resistor R11 is connected to the input terminal 15A. The other end of the resistor R11 is connected to the non-inverting input terminal of the operational amplifier OP1 of the non-inverting amplifier circuit 32. One end of the capacitor C1 is connected to the non-inverting input terminal of the operational amplifier OP1. The other end of the capacitor C1 is connected to the ground GN1.

[0037] When a high-frequency signal is mixed into the signal line L1, the low-pass filter 31 removes the high-frequency signal. This prevents the high-frequency signal from being input to the sub-controller 13. Therefore, malfunction of the sub-controller 13 caused by the input of a high-frequency signal to the sub-controller 13 is prevented.

[0038] Furthermore, when the first control signal X1 is output from the main control unit 8, the low-pass filter 31 removes high-frequency components from the first control signal X1 input via the signal line L1. As a result, the rise time t1 (see FIG. 3) of the first control signal X1 output from the low-pass filter 31 becomes longer than that before it was input to the low-pass filter 31.

[0039] The non-inverting amplifier circuit 32 amplifies the first control signal X1 output from the low-pass filter 31. As shown in FIG. 2, the non-inverting amplifier circuit 32 includes an operational amplifier OP1, a resistor R21, and a resistor switching unit 33. The non-inverting input terminal of the operational amplifier OP1 is connected to the output unit of the low-pass filter 31. The inverting input terminal of the operational amplifier OP1 is connected to the resistor switching unit 33. The inverting input terminal of the operational amplifier OP1 is connected to the output terminal of the operational amplifier OP1 via the resistor R21. The output terminal of the operational amplifier OP1 is connected to an input terminal (not shown) of the sub-control unit 13 to which the first control signal X1 is input.

[0040] The resistance switching unit 33 is capable of switching the electrical resistance between the inverting input terminal of the operational amplifier OP1 and the ground GN1 between a first value and a second value lower than the first value.

[0041] 2, the resistor switching unit 33 includes a resistor R22 (an example of a first resistor of the present invention), a resistor R23 (an example of a second resistor of the present invention), and a transistor Q1 (an example of a switch of the present invention). The resistors R22 and R23 are connected in series between the inverting input terminal of the operational amplifier OP1 and ground GN1. The transistor Q1 is an NPN transistor. The base terminal of the transistor Q1 is connected to the input terminal 15B. The collector terminal of the transistor Q1 is connected to the current path between the resistors R22 and R23. The emitter terminal of the transistor Q1 is connected to ground GN1.

[0042] The transistor Q1 switches between conductive and cut-off states of a short-circuit path that shorts both ends of the resistor R23 depending on whether or not the second control signal X2 is input. Specifically, the transistor Q1 cuts off the short-circuit path when the second control signal X2 is not input from the main control unit 8. This sets the electrical resistance between the inverting input terminal of the operational amplifier OP1 and ground GN1 to the first value. On the other hand, the transistor Q1 turns on the short-circuit path when the second control signal X2 is input from the main control unit 8. This sets the electrical resistance between the inverting input terminal of the operational amplifier OP1 and ground GN1 to the second value.

[0043] In the non-inverting amplifier circuit 32, the resistance between the inverting input terminal of the operational amplifier OP1 and ground GN1 is switched between the first value and the second value by the resistance switching unit 33, thereby switching the gain of the non-inverting amplifier circuit 32 between a third value and a fourth value. For example, the third value is approximately 1x. Also, the fourth value is 5x.

[0044] For example, in the non-inverting amplifier circuit 32, the electrical resistance value of the resistor R22 is set to one-fourth the electrical resistance value of the resistor R21. As a result, when the electrical resistance between the inverting input terminal of the operational amplifier OP1 and ground GN1 is set to the second value, the gain of the non-inverting amplifier circuit 32 is 5 times. Also, in the non-inverting amplifier circuit 32, the electrical resistance value of the resistor R23 is set to 1000 times the electrical resistance value of the resistor R21. As a result, when the electrical resistance between the inverting input terminal of the operational amplifier OP1 and ground GN1 is set to the first value, the gain of the non-inverting amplifier circuit 32 is approximately 1 time.

[0045] In the image forming apparatus 100, when the first control signal X1 is input from the main control unit 8, the gain of the non-inverting amplifier circuit 32 is set to the fourth value. This makes it possible to make the rise time t2 (see FIG. 4) of the first control signal X1 output from the non-inverting amplifier circuit 32 shorter than the rise time t2 before being input to the non-inverting amplifier circuit 32 (see FIG. 3). Therefore, it is possible to improve the transmission speed of the first control signal X1, which was reduced by providing the low-pass filter 31.

[0046] The resistor switching unit 33 may include a digital potentiometer instead of the resistor R23 and the transistor Q1.

[0047] [Configuration of main control unit 8] Next, the configuration of the main control unit 8 will be described with reference to FIG.

[0048] As shown in FIG. 1, the main control unit 8 includes a first switching processing unit 24 and a second switching processing unit 25.

[0049] Specifically, a signal output program for causing the CPU 21 to function as each processing unit shown in Fig. 1 is stored in advance in the ROM 22 of the main control unit 8. The CPU 21 executes the signal output program to function as each processing unit shown in Fig. 1.

[0050] Note that some or all of the processing units included in the main control unit 8 may be configured with electronic circuits. The signal output program may also be a program for causing a plurality of processors to function as the processing units shown in FIG.

[0051] Before the first control signal X1 (see FIG. 2) is input to the non-inverting amplifier circuit 32, the first switching processing unit 24 uses the resistance switching unit 33 to switch the electrical resistance between the inverting input terminal of the operational amplifier OP1 and the ground GN1 from the first value to the second value.

[0052] Specifically, when the main control unit 8 outputs the first control signal X1, the first switching processing unit 24 outputs the second control signal X2 a predetermined first time before the output timing of the first control signal X1.

[0053] After the first control signal X1 (see FIG. 2) is input to the non-inverting amplifier circuit 32, the second switching processing unit 25 uses the resistance switching unit 33 to switch the electrical resistance between the inverting input terminal of the operational amplifier OP1 and the ground GN1 from the second value to the first value.

[0054] Specifically, when the first control signal X1 is output from the main control unit 8, the first switching processing unit 24 stops outputting the second control signal X2 a predetermined second time after the output timing of the first control signal X1.

[0055] [Signal output processing] 5, the signal output method of the present invention will be described below along with an example of the procedure of the signal output process executed by the main control unit 8 in the image forming apparatus 100. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the main control unit 8. The signal output process is executed when the operation mode of the image forming apparatus 100 transitions from the power saving mode to the normal mode.

[0056] <Step S11> First, in step S11, the main control unit 8 executes a first switching process to switch the electrical resistance between the inverting input terminal of the operational amplifier OP1 and the ground GN1 from the first value to the second value using the resistance switching unit 33. The process of step S11 is an example of a first switching step of the present invention, and is executed by the first switching processing unit 24 of the main control unit 8.

[0057] Specifically, the main control unit 8 outputs the second control signal X2, which sets the gain of the non-inverting amplifier circuit 32 to the fourth value (for example, 5 times).

[0058] <Step S12> In step S12, the main control unit 8 determines whether or not the first time has elapsed since the first switching process was executed.

[0059] Here, when the main control unit 8 determines that the first time has elapsed since the first switching process was executed (Yes in S12), it shifts the process to step S13. On the other hand, when the first time has not elapsed since the first switching process was executed (No in S12), the main control unit 8 waits for the first time to elapse since the first switching process was executed in step S12.

[0060] <Step S13> In step S13, the main control unit 8 outputs the first control signal X1.

[0061] <Step S14> In step S14, the main control unit 8 determines whether or not the second time has elapsed since the output of the first control signal X1.

[0062] Here, if the main control unit 8 determines that the second time has elapsed since the output of the first control signal X1 (Yes in S14), it shifts the process to step S15. On the other hand, if the second time has not elapsed since the output of the first control signal X1 (No in S14), the main control unit 8 waits for the elapse of the second time since the output of the first control signal X1 in step S14.

[0063] <Step S15> In step S15, the main control unit 8 executes a second switching process to switch the electrical resistance between the inverting input terminal of the operational amplifier OP1 and the ground GN1 from the second value to the first value using the resistance switching unit 33. The process of step S15 is an example of a second switching step of the present invention, and is executed by the second switching processing unit 25 of the main control unit 8.

[0064] Specifically, the main control unit 8 stops outputting the second control signal X2, thereby setting the gain of the non-inverting amplifier circuit 32 to the third value (for example, approximately 1).

[0065] In this way, in the image forming apparatus 100, the gain of the non-inverting amplifier circuit 32 is set to the fourth value (for example, 5 times) before the first control signal X1 is input to the non-inverting amplifier circuit 32. This makes it possible to improve the transmission speed of the first control signal X1, which is reduced by providing the low-pass filter 31.

[0066] Furthermore, in the image forming apparatus 100, after the first control signal X1 is input to the non-inverting amplifier circuit 32, the gain of the non-inverting amplifier circuit 32 is set to the third value (for example, approximately 1x). This makes it possible to reduce the current flowing from the output terminal of the operational amplifier OP1 in the non-inverting amplifier circuit 32 to ground GN1 via resistors R21 and R22 during the output period of the first control signal X1, compared to a configuration in which the gain of the non-inverting amplifier circuit 32 cannot be switched. In other words, it is possible to reduce the power consumption of the non-inverting amplifier circuit 32 during the output period of the first control signal X1.

[0067] Therefore, in the image forming apparatus 100, it is possible to reduce the power consumption of the signal circuit 14 that removes noise that gets mixed into the signal line L1.

[0068] [Notes on the Invention] The following will provide an outline of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0069] <Appendix 1> an operational amplifier and a non-inverting amplifier circuit including a resistance switching unit that can switch an electrical resistance between an inverting input terminal of the operational amplifier and ground between a first value and a second value lower than the first value, the non-inverting amplifier circuit amplifying the control signal output from the low-pass filter; a first switching processing unit that uses the resistance switching unit to switch the electrical resistance from the first value to the second value before the control signal is input to the non-inverting amplifier circuit; and a second switching processing unit that uses the resistance switching unit to switch the electrical resistance from the second value to the first value after the control signal is input to the non-inverting amplifier circuit.

[0070] <Appendix 2> The electronic device described in Appendix 1, wherein the resistance switching unit includes a first resistor and a second resistor arranged in series between the inverting input terminal and a ground, and a switch that switches between conduction and cut-off of a short-circuit path that short-circuits both ends of the second resistor.

[0071] <Appendix 3> a signal output method executed by an electronic device comprising: a signal line used to transmit a control signal; a low-pass filter connected to the signal line; an operational amplifier; and a non-inverting amplifier circuit including a resistance switching unit capable of switching an electrical resistance between an inverting input terminal of the operational amplifier and ground between a first value and a second value lower than the first value, the non-inverting amplifier circuit amplifying the control signal output from the low-pass filter, the signal output method comprising: a first switching step of switching the electrical resistance from the first value to the second value using the resistance switching unit before the control signal is input to the non-inverting amplifier circuit; and a second switching step of switching the electrical resistance from the second value to the first value using the resistance switching unit after the control signal is input to the non-inverting amplifier circuit. [Explanation of symbols]

[0072] 1 ADF 2 Image reading unit 3 Image forming unit 4 Paper feed section 5 Operation display section 6 Mounting part 7 Memory section 8 Main control section 11 Display section 12 Control section 13 Sub-control section 14 Signal circuit 15 PCB 24 First switching processing section 25 Second switching processing section 31 Low-pass filter 32 Non-inverting amplifier circuit 33 Resistor switching section 100 Image forming device

Claims

1. a signal line used for transmitting a control signal; a low-pass filter connected to the signal line; a non-inverting amplifier circuit including an operational amplifier and a resistance switching unit that can switch an electrical resistance between an inverting input terminal of the operational amplifier and ground between a first value and a second value lower than the first value, and that amplifies the control signal output from the low-pass filter; a first switching processing unit that switches the electrical resistance from the first value to the second value using the resistance switching unit before the control signal is input to the non-inverting amplifier circuit; a second switching processing unit that switches the electrical resistance from the second value to the first value using the resistance switching unit after the control signal is input to the non-inverting amplifier circuit; An electronic device comprising:

2. The resistance switching unit is a first resistor and a second resistor connected in series between the inverting input terminal and a ground; a switch that switches between conduction and interruption of a short-circuit path that short-circuits both ends of the second resistor; The electronic device according to claim 1 , comprising:

3. A signal output method executed by an electronic device including: a signal line used to transmit a control signal; a low-pass filter connected to the signal line; an operational amplifier; and a non-inverting amplifier circuit including a resistance switching unit that can switch an electrical resistance between an inverting input terminal of the operational amplifier and ground between a first value and a second value lower than the first value, and that amplifies the control signal output from the low-pass filter, a first switching step of switching the electrical resistance from the first value to the second value using the resistance switching unit before the control signal is input to the non-inverting amplifier circuit; a second switching step of switching the electrical resistance from the second value to the first value using the resistance switching unit after the control signal is input to the non-inverting amplifier circuit; A signal output method including:

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