Power supply control device, image forming apparatus, and power supply control method

Abstract

The objective is to provide a power control device that can enhance resistance to power supply noise. [Solution] A power control device according to one aspect of the present invention is a power control device that controls a power supply to a display device including a touch panel, and comprises: a plurality of noise filters connected between the power supply and the display device, each reducing power supply noise of different frequency components; a determination unit that determines the power supply noise based on a signal value detected using a scan signal which is a first scan frequency for detecting a touch position in the touch panel and a predetermined noise threshold; and a modification unit that changes the frequency of the scan signal based on the determination of the power supply noise and changes the connected noise filters according to the changed frequency of the scan signal.

Description

Technical Field

[0001] The present invention relates to a power control device, an image forming apparatus, and a power control method.

Background Art

[0002] Techniques for countermeasures against power noise of a capacitive touch panel are known. Patent Document 1 discloses a technique for changing a drive frequency or the like for specifying coordinates of a touch panel according to noise received by the capacitive touch panel. Further, Patent Document 2 discloses a technique for changing the frequency of a switching power supply when the frequency of the switching power supply overlaps with the drive frequency of the touch panel in order to suppress the influence of switching noise.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In an environment with power noise, a capacitive touch panel may cause large fluctuations in the signals generated by the touch panel, resulting in ghost touches that react even when not touched on the touch panel, and malfunction such as reaction at a location different from the touch position.

[0004] The techniques disclosed in Patent Document 1 and Patent Document 2 perform a process of changing the scan frequency according to noise as a countermeasure against noise to the capacitive touch panel. However, there are problems such as difficulty in dealing with the influence of noise having the same frequency as the changed scan frequency, and it is desired to further improve noise tolerance.

[0005] An object of the present invention is to provide a power control device capable of enhancing resistance to power noise in order to solve the above problems.

Means for Solving the Problems

[0006] A power control device according to one aspect of the present invention is a power control device that controls a power supply to a display device including a touch panel, and comprises: a plurality of noise filters connected between the power supply and the display device, each reducing power supply noise of different frequency components; a determination unit that determines the power supply noise based on a signal value detected using a scan signal which is a first scan frequency for detecting a touch position in the touch panel and a predetermined noise threshold; and a modification unit that changes the frequency of the scan signal based on the determination of the power supply noise and changes the connected noise filters according to the changed frequency of the scan signal. [Effects of the Invention]

[0007] The power control device according to the present invention can improve immunity to power supply noise. [Brief explanation of the drawing]

[0008] [Figure 1] This is a configuration diagram of a power supply control system according to the first embodiment of the present invention. [Figure 2] This is a circuit diagram showing the configuration of a noise filter according to the first embodiment of the present invention. [Figure 3] This figure shows the configuration of the touch sensor included in the touch panel according to the first embodiment of the present invention. [Figure 4] This is a block diagram showing the functional configuration of a power supply control device according to the first embodiment of the present invention. [Figure 5] This is a hardware configuration diagram of a power control device according to the first embodiment of the present invention. [Figure 6] This is a flowchart illustrating a power supply control method according to the first embodiment of the present invention. [Figure 7] This figure shows the configuration of an image forming apparatus equipped with a power control device according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the invention will be described below with reference to the drawings. In each drawing, the same reference numerals are used for identical components, and redundant explanations may be omitted.

[0010] [First Embodiment] <Overall configuration of power control system 1> Figure 1 is a diagram showing the configuration of a power supply control system 1 according to a first embodiment of the present invention. As shown in the figure, the power supply control system 1 comprises a power supply G, a power supply control device 10, a control unit 16, and a display device 70. The power supply G is, for example, a commercial power supply. The control unit 16 may be included in the display device 70, or it may be another device. Note that the configuration of the power supply control system 1 is not limited to the example shown.

[0011] The power control device 10 includes a plurality of noise filters 11, a switch 14, and a power conversion unit 15. In the illustrated example, there are four noise filters 11a to 11d, but the noise filters 11 are not limited to four. From the viewpoint of improving immunity to power supply noise supplied to the touch panel 71, it is preferable to include three or more noise filters 11. The power control device 10 controls the power supplied to the display device 70, including the touch panel 71.

[0012] The noise filter 11 in the power control device 10 according to this embodiment reduces power supply noise supplied to the touch panel 71. The capacitive touch panel 71 may malfunction due to power supply noise of the same frequency as the scan frequency, which is the frequency of the scan signal used to detect the touch position. Therefore, the noise filter 11 has a frequency characteristic in which the impedance in the same frequency band as the scan frequency is high in order to reduce power supply noise. Each of the noise filters 11a to 11d has a frequency characteristic in which the impedance in the scan frequency band for each different scan signal is high.

[0013] Figure 2 is a circuit diagram showing the configuration of a noise filter 11 according to the first embodiment of the present invention. As shown in the figure, the noise filter 11 is a circuit in which, for example, a line-to-line capacitor 21, a common-mode coil 22, and ground-to-earth capacitors 23 and 24 are connected in either series or parallel. Note that the configuration of the noise filter 11 is not limited to the example shown. The line-to-line capacitor 21 is also called an X capacitor or across-the-line capacitor, and the ground-to-earth capacitors 23 and 24 are also called Y capacitors or line bypass capacitors.

[0014] Each noise filter 11 is equipped with a common-mode coil 22 that has a high impedance for the scan frequency of each different scan signal. By providing the noise filters 11, the power control device 10 can reduce power supply noise supplied to the touch panel 71. In addition, power fuses (not shown) may be provided between the power supply G and the noise filters 11, and between the noise filters 11 and the control unit 16 to suppress overcurrent.

[0015] The line-to-line capacitor 21 removes normal-mode noise. The ground-to-ground capacitors 23 and 24, along with the common-mode coil 22, remove common-mode noise. It is also possible to bypass at least one of the line-to-line capacitors 21, common-mode coils 22, and ground-to-ground capacitors 23 that constitute the noise filter 11, thereby optimizing the noise reduction effect released to the power supply G and the power factor and efficiency of the switching power supply.

[0016] In Figure 1, the switch 14 is connected between the power supply G and the display device 70 and switches the noise filter 11 connected to the power conversion unit 15. In the illustrated example, the switch 14 connects one of the four noise filters 11a to 11d based on instructions from the power control device 10, which will be described later.

[0017] For example, when it is determined by the power control device 10 that there is power noise in a state where the noise filter 11a is connected, the switch 14 may be switched to the noise filter 11b based on an instruction from the power control device 10. Note that the switching of the noise filter 11 is not limited to the order of the noise filters 11a to 11d, and may be according to the frequency of the power noise.

[0018] The power conversion unit 15 converts the AC (Alternating Current) voltage of the power supply G into a DC (Direct Current) voltage. The power conversion unit 15 may include a diode bridge that rectifies the AC input voltage after noise is removed by the noise filter 11. Further, the power conversion unit 15 performs smoothing processing of the power supply and converts the voltage into a DC voltage suitable for the operation of the touch panel 71. The power supply converted by the power conversion unit 15 is supplied to the control unit 16 and the touch panel 71.

[0019] The control unit 16 controls the operation of the touch panel 71 included in the display device 70. The control unit 16 is realized by an operable device such as a CPU (Central Processing Unit) and an ASIC (application specific integrated circuit). The control unit 16 may reduce the power supply voltage supplied to the touch panel 71 during a period when the touch panel 71 is not in use, and adjust the power supply voltage so as to supply the minimum power supply voltage within a range where no abnormality occurs in the operation of the touch panel 71. Note that the power supply voltage is always supplied to the touch panel 71 during a period when the entire power supply G of the system including the touch panel 71 is ON.

[0020] Further, the control unit 16 has a function as coordinate detection means. The control unit 16 acquires a signal value, which is a current value or a voltage value detected using a scan signal, from the touch panel 71. The control unit 16 calculates the coordinates touched on the touch panel 71 based on the acquired signal value.

[0021] The control unit 16 converts the signal input from the touch panel 71 into a digital signal using a built-in A / D converter, and performs FFT (Fast Fourier Transform) or the like on this digital signal to analyze the frequency of the noise signal. Further, the control unit 16 includes an A / D converter that converts the analog signal input from the touch panel 71 into a digital signal.

[0022] The display device 70 includes a touch panel 71. The touch panel 71 is a means for receiving an input from a user by a touch operation using an input means such as a finger or a touch pen on the touch panel 71. For example, a capacitance-type touch panel is used as the touch panel 71, and a detection signal of a sensor caused by the contacting input means is output. The touch panel 71 has, for example, 31 sensors arranged vertically and 54 sensors arranged horizontally, and may detect an input means that contacts or approaches the touch panel 71 based on the detection signal generated by the sensors.

[0023] FIG. 3 is a diagram showing the configuration of a touch sensor 72 included in the touch panel 71 according to the first embodiment of the present invention. As shown in the figure, the touch sensor 72 includes a plurality of drive electrodes 721 arranged at regular intervals, and a plurality of detection electrodes 722 that intersect the drive electrodes 721 in a grid pattern and are arranged at regular intervals. Each drive electrode 721 and each detection electrode 722 are arranged so as to be insulated. Note that the configuration of the touch sensor 72 is not limited to the illustrated example.

[0024] A scan signal having a rectangular AC voltage formed by high and low voltage levels and having a scan frequency for detecting a touch position is input from the control unit 16 to each drive electrode 721. The control unit 16 inputs the scan signal to each drive electrode 721. The scan frequency is the frequency of the scan signal.

[0025] When a scan signal is input to each drive electrode 721, capacitance is generated between the drive electrode 721 and the detection electrode 722 near the intersection of the drive electrode 721 and the detection electrode 722. In the following description, the capacitance between the drive electrode 721 and the detection electrode 722 will also be referred to as the inter-electrode capacitance.

[0026] Each detection electrode 722 outputs a current to the control unit 16 that indicates the detected change in inter-electrode capacitance. However, the touch panel 71 having a capacitive touch sensor 72 is susceptible to false detection of contact operations due to the influence of power supply noise from the power supply G. False detection of contact operations here refers to the detection of a change in inter-electrode capacitance as a change caused by a contact operation, even though the user has not made any contact with the touch panel 71. The reason why there is a concern about false detection of contact operations due to the influence of noise is that the electric field between the electrodes changes due to the noise, and the inter-electrode capacitance changes along with that change.

[0027] <Configuration of power control device 10> Figure 4 is a block diagram showing the functional configuration of a power control device 10 according to the first embodiment of the present invention. The power control device 10 includes a plurality of noise filters 11, a determination unit 12, and a modification unit 13.

[0028] From the viewpoint of being able to withstand power supply noise including broadband frequency noise, it is preferable that there are three or more noise filters 11. One of the noise filters 11 is connected between the power supply G and the display device 70, and each reduces power supply noise of different frequency components. Each noise filter 11 also has a common mode coil 22 with a high impedance at a different scan frequency. For example, when the touch coordinates of the touch panel 71 are determined by a scan signal at a first scan frequency, the noise filter 11 reduces power supply noise of the frequency component at the first scan frequency.

[0029] The determination unit 12 determines power supply noise based on the signal value detected using a scan signal of a first scan frequency for detecting the touch position on the touch panel 71 and a predetermined noise threshold. More specifically, the determination unit 12 determines that power supply noise is present when the signal value, or the difference between the maximum and minimum values ​​of the signal value, is greater than or equal to a predetermined noise threshold when using a scan signal of a first scan frequency.

[0030] If, for example, three noise filters 11 are provided, the determination unit 12 sets three predetermined noise thresholds for determining power supply noise. The three noise thresholds may be the same or different.

[0031] The modification unit 13 changes the frequency of the scan signal used to detect signal values ​​in the touch panel 71 based on the power supply noise determination by the determination unit 12, and changes the noise filter 11 connected between the power supply G and the display device 70 according to the changed scan signal frequency. When changing the noise filter 11, the modification unit 13 outputs an instruction to the switch 14 regarding the change of the noise filter 11 to be connected.

[0032] More specifically, the modification unit 13 modifies the system to detect the signal value using a scan signal with a second scan frequency different from the first scan frequency when the determination unit 12 determines that power supply noise is present. The modification unit 13 then modifies the noise filter 11 connected between the power supply G and the display device 70 to a noise filter 11 that reduces power supply noise of the frequency component of the second scan frequency.

[0033] Figure 5 is a hardware configuration diagram of a power control device 10 according to a first embodiment of the present invention. The power control device 10 has the function of an information processing device (computer). The power control device 10 includes a CPU (Central Processing Unit) 101, RAM 102, ROM (Read Only Memory) 103, and I / O (Input / Output) 104 which are interconnected by a bus.

[0034] The CPU 101 controls the entire power control device 10 by executing the program 110 using the RAM 102 as work memory. The ROM 103 is a non-volatile memory such as flash memory and stores the program 110. The CPU 101 provides the functions according to this embodiment by executing the program 110. The I / O 104 is an input / output interface.

[0035] <Power control method> Figure 6 is a flowchart illustrating a power supply control method according to the first embodiment of the present invention. The power supply control method is performed by a power supply control device 10 that controls the power supplied to a display device 70 including a touch panel 71.

[0036] The flowchart shown illustrates the processing in the configuration of the power control system 1 shown in Figure 1, assuming that noise filter 11a is connected. Noise filters 11a to 11d reduce power supply noise at frequencies A, B, C, and D, respectively. The noise filters 11 are switched in the order of noise filters 11a to 11d by switch 14.

[0037] First, the determination unit 12 acquires a signal value detected on the touch panel 71 using a scan signal with a scan frequency of A to detect the touch position (S101). Then, the determination unit 12 compares the detected signal value with a predetermined noise threshold (S102).

[0038] If the detected signal value, or the difference between the maximum and minimum values ​​of the signal value, is smaller than a predetermined noise threshold (Yes in S102), the control unit 16 determines the touch coordinates from the acquired signal value (S103).

[0039] If the detected signal value, or the difference between the maximum and minimum values ​​of the signal value, is greater than or equal to a predetermined noise threshold, the determination unit 12 determines that there is power supply noise with frequency A (No. in S102). At this time, the modification unit 13 changes the detection of the signal value using a scan signal with a scan frequency B that is different from scan frequency A (S104).

[0040] Then, the modification unit 13 changes the noise filter 11 connected between the power supply G and the display device 70 to a noise filter 11 that reduces power supply noise of the frequency component of scan frequency B, and the switch 14 switches the noise filter 11 (S105).

[0041] Next, the determination unit 12 acquires a signal value detected on the touch panel 71 using a scan signal with a scan frequency of B for detecting the touch position (S106). Then, the determination unit 12 compares the detected signal value with a predetermined noise threshold (S107).

[0042] If the detected signal value, or the difference between the maximum and minimum values ​​of the signal value, is smaller than a predetermined noise threshold (Yes in S107), the control unit 16 determines the touch coordinates from the acquired signal value (S103).

[0043] If the detected signal value, or the difference between the maximum and minimum values ​​of the signal value, is greater than or equal to a predetermined noise threshold, the determination unit 12 determines that there is power supply noise with frequency B (No. in S107). At this time, the modification unit 13 changes the detection of the signal value using a scan signal with a scan frequency C that is different from scan frequency B (S108).

[0044] Then, the modification unit 13 changes the noise filter 11 connected between the power supply G and the display device 70 to a noise filter 11 that reduces power supply noise of the frequency component at scan frequency C, and the switch 14 switches the noise filter 11 (S109).

[0045] Next, the determination unit 12 acquires a signal value detected on the touch panel 71 using a scan signal with a scan frequency of C for detecting the touch position (S110). Then, the determination unit 12 compares the detected signal value with a predetermined noise threshold (S111).

[0046] If the detected signal value, or the difference between the maximum and minimum values ​​of the signal value, is smaller than a predetermined noise threshold (Yes in S111), the control unit 16 determines the touch coordinates from the acquired signal value (S103).

[0047] If the detected signal value, or the difference between the maximum and minimum values ​​of the signal value, is greater than or equal to a predetermined noise threshold, the determination unit 12 determines that there is power supply noise with frequency C (No. in S111). At this time, the modification unit 13 modifies the detection of the signal value using a scan signal which is a pulse with a scan frequency D different from the scan frequency C (S112).

[0048] Then, the modification unit 13 changes the noise filter 11 connected between the power supply G and the display device 70 to a noise filter 11 that reduces power supply noise of the frequency component at scan frequency D, and the switch 14 switches the noise filter 11 (S113).

[0049] Furthermore, the determination unit 12 acquires a signal value detected on the touch panel 71 using a scan signal with a scan frequency of D for detecting the touch position (S114). Then, the control unit 16 determines the touch coordinates from the acquired signal value (S103).

[0050] These steps execute the power control method according to one embodiment of the present invention. However, the power control method according to one embodiment of the present invention may include other steps as appropriate, depending on the measurement conditions, measurement environment, etc.

[0051] <Effects of the power control device 10 according to the first embodiment> In this embodiment, the power control device 10 determines the presence or absence of power supply noise based on the signal value detected using a scan signal for detecting the touch position in the touch panel 71 and a predetermined noise threshold. If power supply noise is present, the scan frequency of the scan signal is changed, and the noise filter 11 is changed to one that reduces the power supply noise of the frequency component of the changed scan frequency.

[0052] Then, if there is still power supply noise after changing the scan signal frequency and the noise filter 11, the power control device 10 further changes the scan frequency of the scan signal and changes the noise filter 11 to one that reduces the power supply noise of the frequency component of the changed scan frequency.

[0053] Thus, the power control device 10 implements both hardware-based countermeasures against power supply noise, such as providing multiple noise filters 11 with different frequency characteristics, and software-based countermeasures, such as changing the noise filters 11 according to the power supply noise. Therefore, according to the power control device 10 of this embodiment, resistance to power supply noise can be increased, and the operability of the touch panel 71 that supplies power can be maintained.

[0054] [Second Embodiment] <Overall configuration of the image forming apparatus 100> Figure 7 shows the configuration of an image forming apparatus 100 equipped with a power control device 10 according to a second embodiment of the present invention. The image forming apparatus 100 is an MFP (Multifunction Peripheral / Printer / Product) that incorporates functions such as scanning, copying, printing, and facsimile into a single housing. The image forming apparatus 100 has an output function that records full-color images and monochrome images on a recording sheet P based on input image data. The sheet P is a printable sheet, such as printing paper of various sizes and thicknesses.

[0055] The image forming apparatus 100 may be an electrophotographic copier. The main body 1M of the image forming apparatus 100 includes a paper feed unit 2, an image forming unit 3, and a power control device 10. An automatic document transport unit 5 (hereinafter referred to as ADF 5) is also arranged on the main body 1M. The power control device 10 may be built into the image forming apparatus 100 as shown in the figure, or it may be a separate device that is connected to the image forming apparatus 100 in a manner that enables communication.

[0056] The paper feeding unit 2 transports the supplied sheet P to the image forming unit 3. The image forming unit 3 can, for example, form electrostatic latent images of each color based on the image read by the ADF 5. Then, toner is transferred onto the electrostatic latent images, and the toner images developed on the multiple photoreceptor drums 31 are primary transferred to the primary transfer unit 32, and the toner images are secondary transferred to the sheet P in the secondary transfer unit 33 adjacent to the primary transfer unit 32.

[0057] The sheet P, transported to the fixing unit 34, has a full-color image fixed by pressurization and heating within the fixing unit 34. After this, it is sent from the fixing unit 34 to the paper discharge roller pair and discharged onto the discharge tray 35 outside the machine.

[0058] The sheets P discharged into the discharge tray 35 are detected by the detection means 38. The detection means 38 includes a detection filler 36 and an optical sensor 37 that detects the detection filler 36. The detection filler 36 contacts the sheet P and rotates each time a sheet P is discharged into the discharge tray 35, and a signal is transmitted from the optical sensor 37 to the power control device 10 as it rotates. Therefore, by using the detection means 38, the number of sheets P discharged into the discharge tray 35 can be detected.

[0059] The image reading unit 4 includes a first carriage 41 equipped with a light source and a mirror member, a second carriage 42 equipped with a mirror member, an imaging lens 43, an imaging unit 44 equipped with a light receiving unit, a slit glass 45, a platen glass 46, and a stopper member 47.

[0060] The first carriage 41 illuminates the original document S as it passes over the slit glass 45 with illumination light from a light source. The reflected light that passes through the slit glass 45 and is reflected off the surface (first surface) of the original document S is then imaged by the imaging lens 43 onto the imaging unit 44 via the mirror members mounted on the first carriage 41 and the second carriage 42, and read as a surface reading image. At the first reading position R, the surface image of the original document S may be conjugate with respect to the imaging unit 44 with respect to the imaging lens 43.

[0061] The stopper member 47 is provided between the slit glass 45 and the platen glass 46, and is positioned by abutting the document S placed on the platen glass 46 against it. When scanning a document placed on the platen glass 46 while it is abutting against the stopper member 47, the first carriage 41 and the second carriage 42 move in the sub-scanning direction (left-right direction in the figure).

[0062] The first carriage 41 and the second carriage 42 move in the sub-scanning direction at a speed ratio of, for example, 2:1. Even with the movement of the first carriage 41 and the second carriage 42 at such a speed ratio, the optical path length from the surface of the document S to the imaging lens 43 does not change.

[0063] Then, as the first carriage 41 and the second carriage 42 are moved, light is shone from the light source onto the original document S, and the reflected light from the original document S is reflected back by the mirror members mounted on the first carriage 41 and the second carriage 42. The reflected light is then imaged by the imaging lens 43 and read by the imaging unit 44.

[0064] The ADF5 is configured as a sheet-through automatic document transport device. The ADF5 comprises a document table 51 which is a document placement platform, a document transport unit 52 consisting of various rollers and guide members, and a document output tray 53 for collecting document sheets S after image scanning. The document table 51 can place a single cut-sheet document sheet S or a stack of multiple document sheets S.

[0065] Regardless of the width of the original document sheet S, it is positioned and placed on the document table 51 by ensuring that one of its rear edges always abuts against the same point. Therefore, when the original document sheet S is fed onto the slit glass 45 by the ADF 5, its left edge always passes towards the rear during transport.

[0066] The display device 70 includes a touch panel 71. The touch panel 71 has display functions for the current settings and selection screen of the image forming apparatus 100, and accepts input from the user. The touch panel 71 also includes a numeric keypad for accepting setting values ​​for image forming conditions such as density settings, and a start key for accepting a copy start command.

[0067] <Effects of the power control device 10 according to the second embodiment> According to the power control device 10 of this embodiment, immunity to power supply noise can be increased, and the operability of the touch panel 71 included in the image forming apparatus 100 that supplies power can be maintained.

[0068] Although embodiments have been described above, the present invention is not limited to the embodiments described above, and various modifications and improvements are possible within the scope of the present invention.

[0069] Each of the functions of the embodiments described above can be realized by one or more processing circuits. Hereinafter, "processing circuit" as used herein includes processors programmed to execute each function by software, such as processors implemented by electronic circuits, as well as devices such as ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), FPGAs (Field Programmable Ggate Arrays), and conventional circuit modules designed to execute each of the functions described above.

[0070] Examples of the present invention are as follows: <1> A power control device that controls the power supplied to a display device including a touch panel, Multiple noise filters connected between the power supply and the display device, each reducing power supply noise of different frequency components, The touch panel includes a determination unit that determines the power supply noise based on a signal value detected using a scan signal which is a first scan frequency for detecting the touch position and a predetermined noise threshold, A modification unit that changes the frequency of the scan signal based on the determination of the power supply noise, and changes the connected noise filter according to the changed frequency of the scan signal, A power control device equipped with the following features. <2> The determination unit determines that power supply noise exists when the difference between the maximum and minimum values ​​of the signal value when using the scan signal which is the first scan frequency is greater than or equal to the predetermined noise threshold. The aforementioned <1> The power control device described above. <3> The noise filter reduces the power supply noise having the same frequency components as the first scan frequency. The aforementioned <1> or the above <2> The power control device described above. <4> The modified unit, when it is determined that power supply noise is present, is modified to detect the signal value using the scan signal of a second scan frequency different from the first scan frequency, and the connected noise filter is changed to a noise filter that reduces the power supply noise of the frequency component of the second scan frequency. The aforementioned <1> From the above <3> A power control device as described in any one of the following. <5> Each of the noise filters is equipped with a common mode coil that has a high impedance in the scan frequency band for each of the scan signals. The aforementioned <1> From the above <4> A power control device as described in any one of the following. <6> The noise filter comprises three or more of the above-mentioned noise filters, The predetermined noise threshold for determining the power supply noise is set to 3 or more. The aforementioned <1> From the above <5> A power control device as described in any one of the following. <7> The aforementioned <1> From the above <6> A power control device as described in any one of the following: Image forming apparatus. <8> A power control method performed by a power control device that controls the power supply to a display device including a touch panel, and which is connected between the power supply and the display device and includes a plurality of noise filters that reduce power supply noise of different frequency components, wherein In the touch panel, the steps include determining the power supply noise based on a signal value detected using a scan signal which is a first scan frequency for detecting the touch position and a predetermined noise threshold, The steps include: changing the frequency of the scan signal based on the determination of the power supply noise, and changing the connected noise filter according to the changed frequency of the scan signal; A power control method including [Explanation of symbols]

[0071] 1. Power control system 10 Power supply control device 11,11a~11d Noise filter 12 Judgment section 13 Changes 14 switches 15 Power Conversion Unit 16 Control Unit 22 Common Mode Coils 70 Display device 71 Touch panel 100 Image forming apparatus G power supply [Prior art documents] [Patent Documents]

[0072] [Patent Document 1] Japanese Patent Publication No. 2021-86538 [Patent Document 2] Japanese Patent Publication No. 2016-123246

Claims

1. A power control device that controls the power supplied to a display device including a touch panel, Multiple noise filters connected between the power supply and the display device, each reducing power supply noise of different frequency components, The touch panel includes a determination unit that determines the power supply noise based on a signal value detected using a scan signal which is a first scan frequency for detecting the touch position and a predetermined noise threshold, A modification unit that changes the frequency of the scan signal based on the determination of the power supply noise, and changes the connected noise filter according to the changed frequency of the scan signal, A power control device equipped with the following features.

2. The determination unit determines that power supply noise exists when the difference between the maximum and minimum values ​​of the signal when using the scan signal which is the first scan frequency is greater than or equal to the predetermined noise threshold. The power control device according to claim 1.

3. The noise filter reduces the power supply noise having the same frequency component as the first scan frequency. The power control device according to claim 1.

4. The modified unit, when it is determined that power supply noise is present, is modified to detect the signal value using the scan signal of a second scan frequency different from the first scan frequency, and the connected noise filter is changed to a noise filter that reduces the power supply noise of the frequency component of the second scan frequency. The power control device according to claim 1.

5. Each of the noise filters is equipped with a common mode coil that has a high impedance in the scan frequency band for each of the scan signals. The power control device according to claim 1.

6. The noise filter comprises three or more of the above-mentioned noise filters, The predetermined noise threshold for determining the power supply noise is set to 3 or more. The power control device according to claim 1.

7. A power control device according to any one of claims 1 to 6, Image forming apparatus.

8. A power control method performed by a power control device that controls the power supply to a display device including a touch panel, and which is connected between the power supply and the display device and includes a plurality of noise filters that reduce power supply noise of different frequency components, wherein In the touch panel, the steps include determining the power supply noise based on a signal value detected using a scan signal which is a first scan frequency for detecting the touch position and a predetermined noise threshold, The steps include: changing the frequency of the scan signal based on the determination of the power supply noise, and changing the connected noise filter according to the changed frequency of the scan signal; A power control method including

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