Power supply device, voltage application method, image forming device, and image forming method

Abstract

The present invention relates to a power supply device, a voltage application method, an image forming device, and an image forming method, in which a DC current is detected at a position where inflow of an AC voltage occurs, the increase in cost is minimized, and the detection error is reduced. A power supply device (α) that applies a voltage in which a DC voltage and an AC voltage are superimposed to a charging member (18) that charges an image carrier, includes an AC voltage generation section (810) that generates an AC voltage, a DC voltage generation section (820) that generates a DC voltage, a DC current detection section (840) that is provided on the output side of the DC voltage generation section (820) and detects an output DC current that flows into an image carrier (40), and an inflow alleviating unit (850) that alleviates inflow of an AC current to the DC current detection section.

Description

Technical Field

[0001] The present invention relates to a power supply device, a voltage application method, and an image forming apparatus and an image forming method having the power supply device and a charging component. Background Technology

[0002] In electrophotographic image forming apparatuses, there is a known AC charging method in which DC voltage and AC voltage are superimposed and applied to the charging component to charge the image carrier such as the photosensitive drum.

[0003] In addition, in image forming apparatus using AC charging, in order to determine the surface potential of the image carrier charged by the charging component, it is known to detect the output DC current of the power supply by means of a current detection circuit configured in the charging power supply that applies voltage to the charging component.

[0004] For example, in patent document 1, such as Figure 1 As shown, current detection is performed using an AC voltage generation unit 91, which serves as a high-voltage power supply 90 for charging. Since AC is superimposed on DC, the detection unit 93 extracts only the DC current and measures it using a high-voltage resistant component. This can be achieved by extracting the current through insulation or by lowering the high potential to a low potential. Therefore, when detection is performed using the high-voltage unit 91, the circuit for detecting the current becomes complex and costly in either case.

[0005] On the other hand, the configuration disclosed in Patent Document 2 is such that, in the configuration that superimposes the AC voltage onto the DC voltage, as... Figure 2 As shown, a current detection unit 98 for detecting the output DC current is provided in the output section of the DC voltage generating section 97, which serves as the charging power supply 95. In this configuration, since the detection unit is located in the low-voltage section, the current can be detected inexpensively and more easily.

[0006] However, Patent Document 2 does not consider the impact of AC voltage on the current flowing into the current detection unit 98. Therefore, depending on the number of samplings, errors may occur due to ripple voltage caused by the AC current flowing into the detection unit. Specifically, Figure 3 The waveform shown illustrates the reason for the difference in the average value due to different sampling rates in the detection of AC voltage input. For example... Figure 3 As shown in (a), relative to the ripple voltage frequency, with a sufficiently fast sampling rate and a large number of samples, the detected voltage, once averaged, will be the same as the original average voltage. However, as... Figure 3As shown in (b), when a sufficient sampling rate is not available and the number of samples is small, if a deviation point is detected and averaged, the result will be a value that deviates from the original average voltage. Therefore, when a sufficient sampling rate is not available, the maximum error value becomes the difference Vpp between the maximum and minimum values ​​of the ripple voltage.

[0007] On the other hand, if a sampling rate is sufficient relative to the ripple frequency in order to increase the number of samplings, the detection error caused by the ripple voltage can be suppressed. However, in order to achieve high-frequency sampling, the CPU utilization will increase, and a high-performance CPU will be required.

[0008] Therefore, in view of the above, the object of the present invention is to provide a power supply device that, when detecting DC current at a location where AC voltage is flowing in, can minimize the increase in cost and reduce detection error.

[0009] [Patent Document 1] Japanese Patent No. 5546269

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2021-096427 Summary of the Invention

[0011] To address the aforementioned issues, one aspect of the present invention provides a power supply device that applies a voltage consisting of overlapping DC and AC voltages to a charging component that charges an image carrier. The device is characterized by comprising: an AC voltage generating unit that generates the AC voltage; a DC voltage generating unit that generates the DC voltage; a DC current detection unit disposed at the output end of the DC voltage generating unit that detects the output DC current flowing into the image carrier; and an inflow mitigation unit that mitigates the inflow of AC current into the DC current detection unit.

[0012] According to one method, in a power supply device that detects DC current at the location where AC voltage flows in, the increase in cost can be minimized and the detection error reduced. Attached Figure Description

[0013] Figure 1 The diagram shows a configuration example of the charging power supply involved in Example 1.

[0014] Figure 2 The diagram shows a configuration example of the charging power supply involved in Example 2.

[0015] Figure 3 The diagram shown illustrates the reason for the difference in the average value due to different sampling rates in the detection of AC voltage input.

[0016] Figure 4The diagram shown is an example of the overall configuration of the image forming apparatus according to an embodiment of the present invention.

[0017] Figure 5 The diagram shown is an example of the configuration of the imaging device according to the embodiment.

[0018] Figure 6 The diagram shown is an explanatory diagram of the control of the high-voltage power supply for charging and the charging unit according to the first embodiment.

[0019] Figure 7 The diagram shown illustrates the configuration of the power supply device and the flow of current according to the first embodiment.

[0020] Figure 8 The diagram shows the ripple voltage on the output DC current with and without the AC current reduction section of the first embodiment.

[0021] Figure 9 The diagram shown illustrates the configuration of the power supply device and the flow of current according to the second embodiment.

[0022] Figure 10 The diagram shown is a functional block diagram of the CPU of the power control device according to the second embodiment.

[0023] Figure 11 The diagram shown illustrates the cancellation of ripple voltage.

[0024] Figure 12 The diagram shown details the ripple voltage generated upstream of the DC current sensing unit.

[0025] Figure 13 The diagram shown illustrates the configuration of the power supply device and the flow of current according to the third embodiment.

[0026] Figure 14 The diagram shown illustrates the configuration of the power supply device and the flow of current according to the fourth embodiment.

[0027] Figure 15 The diagram shown is an example of the first circuit of the phase detection mechanism.

[0028] Figure 16 What is shown is Figure 15 The diagram illustrates the waveform at point A, the generated rectangular wave, and the phase of the adjusted inverted waveform.

[0029] Figure 17 The diagram shown is an example of the second circuit of the phase detection mechanism.

[0030] Figure 18 What is shown is Figure 17The diagram illustrates the waveform at point A, the generated rectangular wave, and the phase of the adjusted inverted waveform.

[0031] Figure 19 The diagram shows examples of a normal sine wave and a distorted waveform during discharge.

[0032] Figure 20 The diagram shown illustrates the measurement range within the AC waveform.

[0033] Figure 21 The diagram shown illustrates the average crossover point (0 sec) within the AC waveform.

[0034] Figure 22 The diagram shown illustrates the timing of measurement at the measurement location within the AC waveform.

[0035] Figure 23 The image shown is a diagram of the sampling portion of the AC waveform.

[0036] Figure 24 The diagram shown illustrates the measurement deviation from the average of the waveform.

[0037] Figure 25 The figure shows a graph of the output voltage and the voltage value detected at the sampling time in the ripple voltage.

[0038] Figure 26 The table shown is related to the voltage of the output and ripple voltage measurement section.

[0039] Figure 27 The diagram shown illustrates the configuration of the power supply device and the flow of current according to the fifth embodiment.

[0040] Figure 28 The diagram shown is a functional block diagram of the storage unit and CPU of the power control device according to the fifth embodiment. Detailed Implementation

[0041] The following description, with reference to the accompanying drawings, illustrates the methods for carrying out the invention. In the drawings, the same symbols are used for the same structural parts, and sometimes repeated descriptions are omitted.

[0042] The following description uses an image forming apparatus of an electrophotographic type, which has a secondary transfer mechanism called a serial transfer mechanism, as an example to illustrate the implementation. Furthermore, the image forming apparatus is a multifunction printer (MFP) that integrates copying, printing, and faxing functions into a single unit.

[0043] <Example of the overall configuration of the image forming apparatus 100>

[0044] Figure 4 The diagram shown is an explanatory diagram of an example of the overall configuration of the image forming apparatus 100. The image forming apparatus 100 has an intermediate transfer unit at its center, and the intermediate transfer unit has an intermediate transfer belt 10 that is an annular belt. The intermediate transfer belt 10 is wound around a first support roller 14, a second support roller 15, and a third support roller 16, and is driven to rotate clockwise.

[0045] In addition, the image forming apparatus 100 has an intermediate transfer body cleaning unit 17 to the right of the second support roller 15 to remove residual toner on the intermediate transfer belt 10 after the toner image is transferred to the recording medium P.

[0046] Opposite to the intermediate transfer belt 10 disposed between the first support roller 14 and the second support roller 15, there is an imaging section 20 consisting of a yellow (Y) imaging section, a magenta (M) imaging section, a cyan (C) imaging section and a black (K) imaging section, with each color imaging section arranged side by side along the travel direction of the intermediate transfer belt 10.

[0047] Furthermore, the image forming units of each color are identical in configuration, except for the color of the toner used. Therefore, in the description and accompanying drawings, subscripts such as "Y", "M", "C", and "K" indicating the color of the toner used are appropriately omitted. Additionally, the image forming apparatus 100 may also have a white (W) image forming unit upstream of the yellow (Y) image forming unit in the traveling direction of the intermediate transfer belt 10. Figure 4 Its illustration is omitted.

[0048] The imaging unit 20 includes photosensitive elements 40 of various colors, a charging roller 18 as an example of a charging component, a developing unit, and a cleaning unit, and is mounted to the image forming apparatus 100 in a detachable manner. Here, the photosensitive element 40 is an example of an image carrier.

[0049] Furthermore, the image forming apparatus 100 has a beam scanning unit 21 above the image forming unit 20. The beam scanning unit 21 can form an electrostatic latent image (latent image) corresponding to the image data on the photoreceptors 40 of each color by irradiating the photoreceptors 40 of each color with a beam (laser) for image forming.

[0050] The electrostatic latent images of the photoreceptors 40 of various colors are developed by the developing unit, and the developed toner images of each color are overlapped and transferred once on the intermediate transfer belt 10. Thus, a colored toner image is formed on the intermediate transfer belt 10. The toner image is carried on the intermediate transfer belt 10 and moves (conveys) along the traveling direction of the intermediate transfer belt 10. Furthermore, the configuration of the imaging unit 20 is referenced... Figure 5 To be detailed elsewhere.

[0051] The image forming apparatus 100 includes a secondary transfer unit 22 below the intermediate transfer belt 10. The secondary transfer unit 22 is configured to support a secondary transfer belt 24, which is an annular belt, between two rollers 23, and to push the intermediate transfer belt 10 upwards to abut against the third support roller 16. The secondary transfer belt 24 is capable of transferring the toner image formed on the intermediate transfer belt 10 to the recording medium P.

[0052] Furthermore, the image forming apparatus 100 has a fixing unit 25 on the side of the secondary transfer unit 22. The fixing unit 25 fixes the toner image on the recording medium P, which is being transported in a secondary transfer state, onto the recording medium P. The fixing unit 25 includes a fixing roller 26 and a pressure roller 27, which are ring-shaped belts. Through the heat and pressure of the fixing roller 26 and the pressure roller 27, the toner image transferred to the surface of the recording medium P can be fixed onto the recording medium P.

[0053] Furthermore, in order to form an image on the back side of the recording medium P after the image has just been formed on the surface, the image forming apparatus 100 is provided with a sheet reversal unit 28 below the secondary transfer unit 22 and the fixing unit 25 to reverse the front and back of the recording medium P and send it out.

[0054] Next, a series of processes for forming an image on the recording medium P in the image forming apparatus 100 will be described.

[0055] When the "Copy" start button in the operation unit (not shown) of the image forming apparatus 100 is pressed, if the original document is placed on the document feed table 501 of the automatic document feeder (ADF) 400, which serves as an automatic document feeder, the ADF 400 will feed the original document onto the contact glass 502. On the other hand, if no original document is placed on the document feed table 501, the image reading unit 500, which has a first carriage 503 and a second carriage 504, will be activated in order to read the original document that is manually placed on the contact glass 502.

[0056] In the image reading unit 500, a light source contained in the first carriage 503 illuminates the contact glass 502. Reflected light from the original document surface is reflected towards the second carriage 504 by a first reflecting mirror contained in the first carriage 503, and then reflected by a reflecting mirror contained in the second carriage 504. The reflected light from the original document surface is then imaged on the imaging surface of the charge-coupled device (CCD) 506, which serves as a readout sensor, through the imaging lens 505. The CCD 506 captures an image of the original document surface and generates image data for each of the Y, M, C, and K colors based on the image signal captured by the CCD 506.

[0057] In addition, when the "print" start button is pressed, when there is an image formation instruction from an external device such as a personal computer (PC), or when there is an output instruction from a fax machine (FAX), the image forming apparatus 100 performs image preparation for each unit of the image forming section 20 at the same time as starting the rotation drive of the intermediate transfer belt 10.

[0058] Then, the image forming apparatus 100 begins the image formation process for each color. A laser modulated based on the image data of each color is irradiated onto the photoreceptor 40 for each color, forming an electrostatic latent image. Then, the toner images of each color, after being developed by the electrostatic latent image, are superimposed on the intermediate transfer belt 10 to form a single image.

[0059] Then, the recording medium P is fed into the secondary transfer unit 22 at the same time the leading edge of the toner image on the intermediate transfer belt 10 enters the secondary transfer unit 22. The toner image on the intermediate transfer belt 10 is then transferred a second time onto the recording medium P via the secondary transfer unit 22. The paper with the secondary transferred toner image is then fed into the fixing unit 25, where the toner image is fixed onto the recording medium P.

[0060] Here, the paper feeding of the recording medium P up to the secondary transfer position will be described. The recording medium P is successively fed from one of the multiple paper trays 44 arranged in the paper feeding unit 43 by the rotational drive of one of the paper feeding rollers 42 of the paper feeding table 200. Then, it is separated by the separating roller 45 and enters the transport roller unit 46, where it is transported by the transport roller 47. After that, it is guided to the transport roller unit 48 in the image forming apparatus 100, and after temporarily stopping upon contact with the alignment roller 49 of the transport roller unit 48, it is fed toward the secondary transfer unit 22 at the timing of the secondary transfer, as described above.

[0061] Alternatively, the user can insert the recording medium P into the manual paper feed tray 51 for paper feeding. When the user inserts the recording medium P into the manual paper feed tray 51, the image forming apparatus 100 rotates and drives the paper feed roller 50 to separate one sheet of the recording medium P from the manual paper feed tray 51 and pull it into the manual paper feed path 53. Then, similarly as described above, after temporarily stopping upon encountering the alignment roller 49, it is fed to the secondary transfer unit 22 at the timing of the secondary transfer.

[0062] The recording medium P, fixed and ejected in the fixing unit 25, is guided by the switching claw 55 to the ejection roller 56 and then stacked on the paper tray 57 after being ejected by the ejection roller 56. Alternatively, it is guided by the switching claw 55 to the sheet flipping unit 28, flipped by the sheet flipping unit 28, and then guided again to the secondary transfer position. Then, after an image is also formed on the back side of the recording medium P, it is ejected onto the paper tray 57 by the ejection roller 56.

[0063] On the other hand, the residual toner left on the intermediate transfer belt 10 after image transfer is removed by the intermediate transfer body cleaning unit 17 in preparation for the next image formation.

[0064] In this way, the image forming apparatus 100 can form a color image on the recording medium P.

[0065] <Composition of Imaging Unit 20>

[0066] Next, the image forming unit 20 of the image forming apparatus 100 will be described. Figure 5 The diagram shown is an explanatory diagram of an example of the structure of the imaging unit 20. Figure 5 The diagram shows an example of the configuration of the black-and-white imaging unit 20K. The other three-color imaging units 20Y, 20M, and 20C are configured identically to the black-and-white imaging unit 20K, except that the colors of the toners used in their respective imaging processes differ. Therefore, illustrations and explanations are omitted, and only the black-and-white imaging unit 20K will be described.

[0067] The imaging unit 20K includes a photosensitive element 40, a charging roller 18, a developer 29, a cleaning blade 13, and a collector 19.

[0068] The photoreceptor (photoreceptor drum) 40 is a negatively charged drum-shaped organic photoreceptor, with a photosensitive layer and the like disposed on a drum-shaped conductive support. The photoreceptor 40 is constructed by sequentially stacking a base layer (insulating layer), a charge-generating layer and a charge-transfer layer (photosensitive layer), and a protective layer, etc., on a conductive support serving as a base layer. A conductive material with a volume impedance of 10¹⁰ Ωcm or less can be used in the conductive support of the photoreceptor 40.

[0069] The charging roller 18 is a roller component formed by coating the outer periphery of a conductive core with an elastic layer of medium resistance. By applying a charging bias voltage, which is a DC voltage superimposed on an AC voltage, to the charging roller 18 from a high-voltage charging power supply 180, the surface of the photoreceptor 40 opposite the charging roller 18 becomes charged. Alternatively, a cleaning roller that removes dirt from the charging roller 18 may be configured to contact the charging roller 18.

[0070] The developer 29 has a developing roller 29a opposite to the photoreceptor 40. The developing roller 29a has a magnet fixedly disposed inside and forming magnetic poles on the outer circumferential surface of the roller, and a sleeve that rotates around the magnet. By forming multiple magnetic poles on the developing roller 29a by the magnet, the developer is carried on the developing roller 29a.

[0071] The cleaning blade 13 mechanically scrapes off any untransferable toner or other residues adhering to the surface of the photoreceptor 40. The cleaning blade 13 is a blade-shaped component made of a rubber material such as polyurethane rubber and is formed into a generally plate shape. It comes into contact with the surface of the photoreceptor 40 at a specified angle and with a specified pressure.

[0072] The collector 19 removes the charge from the surface of the photoreceptor 40 after the toner image has been transferred.

[0073] The photoreceptor 40, charged by the charging roller 18, is exposed by the beam scanning unit 21 according to image data. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 40. The developing unit 29 causes toner to adhere to the electrostatic latent image formed on the surface of the photoreceptor 40. Thus, the toner image is developed on the surface of the photoreceptor 40.

[0074] By applying a voltage generated by a high-voltage power supply 621 for transfer to the primary transfer roller 62, the toner image on the surface of the photoreceptor 40 is transferred onto the intermediate transfer belt 10 in a single pass. The toner image on the intermediate transfer belt 10 is transferred onto the recording medium P by the secondary transfer unit 22 and then fixed onto the recording medium P by the fixing unit 25. Residual toner and other contaminants on the surface of the photoreceptor 40 are removed by the cleaning blade 13. Charge on the surface of the photoreceptor 40 is removed by the collector 19.

[0075] In the case of color printing, four identical configurations are provided for each color, and each color transfers the toner image on the intermediate transfer belt 10, followed by a secondary transfer and fixing process.

[0076] In this embodiment, the charging roller 18 is positioned close to the photoreceptor 40 and in a non-contact manner relative to the photoreceptor 40. This charging method, which creates a small gap between the photoreceptor 40 and the charging roller 18, is called a non-contact charging method. According to this method, compared to contact charging methods that bring the photoreceptor 40 and the charging roller 18 into contact, foreign matter such as toner or lubricant remaining on the photoreceptor 40 is less likely to adhere to the charging roller 18, thus suppressing uneven charging caused by the adhesion of foreign matter. However, the embodiment is not limited to a non-contact charging method; a contact charging method may also be used.

[0077] <High-voltage power supply for charging according to the first embodiment>

[0078] Next, use Figure 6The process of supplying power to the charging roller 18 is explained. Figure 6 The diagram shown is an explanatory diagram of the control of the high-voltage power supply and the charging unit according to the first embodiment.

[0079] like Figure 6 As shown, a charging roller 18 is connected to a high-voltage power supply 180 for charging, and a power control device 70, which acts as a host controller to control the charging operation, is also connected to it. The high-voltage power supply 180 and the power control device 70 are combined to form a power supply device α.

[0080] The high-voltage power supply 180 for charging mainly includes an AC (alternating current) generation circuit 810 and a DC (direct current) generation circuit 820. The DC voltage output from the high-voltage power supply 180 is 100V~2000V, the AC voltage is AC_Vout: 500Vpp~3500Vpp, and the driving frequency is f: approximately 500~3000Hz.

[0081] First, AC control signals and DC control signals, which are instructions, are received from the CPU 71 of the power control device 70, respectively. The AC generation circuit 810 and DC voltage generation unit 820 of the charging high voltage power supply 180 then operate and generate high voltages respectively.

[0082] Then, the high-voltage power supply 180 for charging applies a voltage that is DC voltage superimposed on AC voltage to the charging roller 18, thereby charging the photosensitive element 40, which serves as an image carrier, through the charging roller 18.

[0083] Figure 7 The diagram shown illustrates the configuration and current flow in the power supply device α according to the first embodiment. Figure 6 , Figure 7 The details of the power supply device α will now be explained.

[0084] In addition to the AC generation circuit 810 and DC voltage generation unit 820 mentioned above, the high-voltage power supply 180 for charging also includes a coupling capacitor 830, a DC current detection unit 840, and an AC current reduction unit 850.

[0085] AC generation circuit 810 is an example of an AC voltage generation unit, which generates a specified AC voltage based on an AC control signal input from power control device 70. AC generation circuit 810 includes drive circuit 811, control circuit 812, and AC transformer 813.

[0086] The drive circuit 811 is the circuit that drives the AC transformer 813.

[0087] The AC transformer 813 generates AC voltage by being driven by the drive circuit 811. The primary side of the AC transformer 813 is composed of a multi-turn coil. In addition, one end of the secondary coil of the AC transformer 813 is connected to the charging roller 18, which serves as a load, while the other end is connected to the DC voltage generating unit 820 (one end of the secondary coil of the DC transformer 823) and the coupling capacitor 830, respectively.

[0088] The AC voltage generated by the AC transformer 813 is superimposed with the DC voltage generated by the DC voltage generating unit 820 and applied to the charging roller 18.

[0089] The control circuit 812 supplies a drive circuit control signal to the drive circuit 811 based on the current generated in the multi-turn coil of the AC transformer 813, thereby controlling the AC voltage generated by the AC transformer 813. Thus, the AC voltage generated by the AC transformer 813 becomes the target voltage represented by the AC control signal input from the upper-level power control device 70.

[0090] Additionally, a coupling capacitor 830, as an example of a coupling capacitor, is provided between the AC generation circuit 810 and the DC voltage generation unit 820. One end of the coupling capacitor 830 is connected to the other end of the secondary winding of the AC transformer 813, and the other end of the coupling capacitor 830 is grounded.

[0091] By configuring the coupling capacitor 830 in this way, the alternating current flowing between the AC generation circuit 810 and the charging roller 18 as a load flows primarily into the coupling capacitor 830, thereby preventing it from flowing into the DC voltage generation unit 820. Here, as Figure 7 As shown, the AC current Iac flowing outside the power supply indicated by the arrow, that is, outside the load 18, also flows into the coupling capacitor 830.

[0092] In addition, the coupling capacitor 830 also functions as a bypass capacitor through which only alternating current flows.

[0093] On the other hand, the DC voltage generating unit 820 is an example of a DC voltage generating unit, which is a circuit that generates a specified DC voltage based on a DC control signal input from the power control device 70. The DC voltage generating unit 820 includes a drive circuit 821, a control circuit 822, a DC transformer 823, a diode 824, a rectifier capacitor 825, and a resistor 826.

[0094] The drive circuit 821 drives the DC transformer 823. Driven by the drive circuit 821, the DC transformer 823 generates a DC voltage that is higher than the input voltage from the input voltage.

[0095] The DC voltage generated by the DC transformer 823 is superimposed on the AC voltage generated by the AC generation circuit 810 and applied to the load 18.

[0096] One end of the secondary winding of the DC transformer 823 is connected to the AC generation circuit 810 (the other end of the secondary winding of the AC transformer 813). The primary winding of the DC transformer 823 consists of a multi-turn coil.

[0097] The two ends of the DC transformer 823 are connected to the rectifier capacitor 825. As a result, the DC current flowing on the secondary side is separated into a DC current flowing outside the charging high-voltage power supply 180 and a DC current flowing inside the charging high-voltage power supply 180.

[0098] here, Figure 7 The arrow Idc_o represents the DC current flowing outside the high-voltage power supply 180 for charging, and the arrow Idc_i represents the DC current flowing inside the high-voltage power supply 180 for charging.

[0099] The control circuit 822 supplies a drive circuit control signal to the drive circuit 821 based on the current generated in the multi-turn coil of the DC transformer 823, thereby controlling the DC voltage generated by the DC transformer 823.

[0100] For example, if the current generated by the control circuit 822 in the multi-turn coil of the DC transformer 823 is smaller than the current corresponding to the target voltage indicated by the DC control signal input from the upper power control device 70, the control value of the drive circuit 821 is increased. Conversely, if the current generated by the control circuit 822 in the multi-turn coil of the DC transformer 823 is larger than the current corresponding to the target voltage indicated by the DC control signal input from the upper power control device 70, the control value of the drive circuit 821 is decreased.

[0101] Therefore, the control circuit 822 performs voltage stabilization control so that the output voltage of the DC voltage generator 820 becomes the target voltage indicated by the DC control signal. By using the current generated in the multi-turn coil of the DC transformer 823, voltage stabilization control can be performed with a simple circuit configuration.

[0102] Diode 824, rectifier capacitor 825, and resistor 826 form a half-wave rectifier circuit that rectifies and smooths the AC voltage for half a cycle to make it a DC voltage. The ripple in the output voltage has the same frequency as the AC power supply.

[0103] In the current output terminal of the half-wave rectifier circuit, a DC current detection unit 840 is provided via an AC current reduction unit 850. In the AC current reduction unit 850, the impedance is increased to suppress the AC component flowing into the current detection unit of the subsequent stage.

[0104] The DC current detection unit 840 is provided on the output side of the DC voltage generation unit 820. It is an output current detection unit that detects the output DC current and has a current detection element 841 and a detection AD inverter (hereinafter referred to as detection ADC) 842.

[0105] The current sensing element 841 is grounded by being connected between the DC voltage generation unit 820 and the reference potential unit. The function of the current sensing element 841 is to act as an impedance for detecting current using the ADC 842.

[0106] In this embodiment, the ADC842 detects the output DC current of the high-voltage power supply 180 for charging and outputs a current detection signal representing the output DC current to the upper control device 60.

[0107] Then, the potential information of the DC current detected by the detection ADC842 of the DC current detection unit 840 is input to the CPU (not shown) of the upper control device 60. Then, the upper control device 60 predicts the surface potential of the photoreceptor 40 based on the measured output DC current as the charging DC current detected by the DC current detection unit 840.

[0108] (Methods for calculating the surface potential of a photoreceptor)

[0109] Here, a method for calculating the surface potential of the photoreceptor 40 from the output DC current, which is the charging DC current, will be explained.

[0110] Since the photoreceptor 40 becomes charged by accumulating charge on its surface, charging the photoreceptor 40 is considered equivalent to charging the capacitor. Therefore, the charge (Q) accumulated in the photoreceptor 40 and the charging potential are...

[0111] Q=CV…Formula (1)

[0112] Between V, the following formula holds true. Additionally, in the following formula, C represents the electrostatic capacitance of photoreceptor 40.

[0113] Here, the charge Q accumulated in the photoreceptor 40 can be expressed and converted using the following formula.

[0114] Differentiate both sides

[0115] Q=∫Idc dt…Formula (2)

[0116] ∫ldc dt=CV…Equation (3)

[0117]

[0118] Here, the photoreceptor surface potential (Vd0) and the charging applied voltage (Vc) are constant before charging. In the charging process with AC voltage superimposed, since the charging applied voltage Vc = the current photoreceptor surface potential (Vd), the following equation (5) holds for the charging voltage V.

[0119] V = V c -Vd0=V d -V d0 ...Formula (5)

[0120] In addition, equation (6) also holds true.

[0121]

[0122] (ε: dielectric constant of the photoreceptor surface, S: photoreceptor surface area that contributes to charging, d: thickness of the photoreceptor surface, L: length of the photoreceptor that contributes to charging, λ: linear velocity)

[0123] By transforming this relation (6), the DC component (Idc) of the charging current can be derived using the following formula with respect to the photoreceptor surface potential (Vd).

[0124]

[0125] Here, it is known that in the non-contact charging method, the photoreceptor film thickness d hardly changes with time. Therefore, the film thickness d is constant, and the dielectric constant ε and the photoreceptor length L are also constant. It can be said that the DC component Idc of the charging current is proportional to the photoreceptor surface potential V (more accurately, Vd-Vd0).

[0126] Using this calculation method, the upper control device 60 can determine the inflow current of the photoreceptor 40, calculate the surface potential of the photoreceptor 40, and perform image control based on the measured output DC current detected by the DC current detection unit 840.

[0127] (AC current reduction section)

[0128] As described above, in this embodiment, an AC current mitigation unit 850 is provided in the stage before the DC current detection unit 840. The AC current mitigation unit 850 is an inflow mitigation unit that reduces the ripple voltage caused by the AC current flowing into the DC current detection unit 840 by being provided in the stage before the DC current detection unit 840.

[0129] In detail, the coupling capacitor 830 is originally intended to bypass the AC current, suppressing most of the AC current so that it does not flow to the DC current detection section 840. However, when the impedance of the first current detection line DL1 is low, AC current may sometimes flow through it.

[0130] Therefore, in this embodiment, an AC current mitigation unit 850 is provided immediately upstream of the DC current detection unit 840. As an example, the AC current mitigation unit 850 is a resistor. By setting a larger resistance value, the flow of AC current can be suppressed in the AC current mitigation unit 850.

[0131] Furthermore, in the DC current sensing section 840, it is more preferable to increase the resistance value of the resistor constituting the current sensing element 841 for current sensing.

[0132] Specifically, when the AC output is as follows,

[0133] Frequency: 1290Hz, Voltage: 2200Vpp, Current: 2.7mA

[0134] When the combined resistance of the AC current reduction unit 850 and the current detection element 841 is 20kΩ, the ripple voltage detected by the detection ADC 842 is about 50mVpp.

[0135] When the combined resistance of the AC current reduction unit 850 and the current detection element 841 is 56kΩ, the ripple voltage detected by the detection ADC 842 is reduced to about 20mVpp.

[0136] Therefore, when the resistance is 20kΩ, the detected value must take into account the variation of ±50mV. However, when the resistance is 56kΩ, compared to ±20mV, the tolerance of less than half needs to be considered.

[0137] Figure 8 The diagram shows the ripple voltage flowing into the detection ADC842. Figure 8 In the example, (a) shows an example of detecting ripple voltage in ADC842 without mitigation unit, and (b) shows an example of detecting ripple voltage in ADC842 with mitigation unit 850.

[0138] like Figure 8 As shown in (b), by adding the AC current mitigation unit 850, the inflow of AC current is suppressed, and the ripple voltage of the potential of the ADC842 is reduced (suppressed). Thus, because the ripple width is reduced, even if it is not possible to perform... Figure 3 (b) shows the high-speed readout (sampling) and detection ADC842 is also able to detect the output DC current with high accuracy.

[0139] However, by adding an AC current reduction section 850 as in the first embodiment, such as Figure 8As shown, although it has some effect, it is difficult to make the impedance infinite even with the addition of the AC current reduction unit 850, so it is impossible to make the ripple voltage caused by the AC current flowing through the DC current detection unit 840 zero. In addition, for various reasons, it is sometimes difficult to install the AC current reduction unit.

[0140] Therefore, other methods for reducing the error caused by the ripple voltage of the output DC current detected by the DC current detection unit 840 will be described below.

[0141] <Second Implementation>

[0142] Figure 9 The diagram shown illustrates the configuration of the power supply device β according to the second embodiment and the flow of current. Figure 10 The diagram shown is a functional block diagram of the CPU 71A of the power control device 70A.

[0143] In the second embodiment, an anti-waveform application unit is provided as a unit to suppress ripple voltage in the output DC current detected by the DC current detection unit 840. The anti-waveform application unit is implemented by a power control device 70A, which serves as a host controller.

[0144] The inverse waveform application unit applies the inverse waveform (inverse waveform) of the ripple voltage envisioned by the DC current detection unit 840 to the second DC current detection line DL2 of the detection ADC73, which connects the current detection element 841 and the power control device 70A.

[0145] In this embodiment, the host control device 60 calculates the surface potential of the photoreceptor 40 and performs image control based on the output DC current detected by the detection ADC 73 included in the power control device 70A (measuring the output DC current). In order to suppress the ripple voltage superimposed on the output DC current detected by the detection ADC 73, the power control device 70A in this embodiment has the function of applying an inverted waveform of the envisioned ripple voltage.

[0146] The power control device 70A includes a CPU 71A, a memory 72, an AD converter 73 for detecting ADC, and a DA converter 74 for applying DAC. Among them, the CPU 71A, the memory 72, and the DAC 74 function as an inverse waveform application unit.

[0147] The memory 72 stores the relationship between the control signal, which is the AC output value, and the ripple voltage. Specifically, it stores the expected ripple waveform, i.e., the ripple waveform caused by the AC output, based on the voltage of the generated AC current. Furthermore, for the stored ripple waveform, the degree of ripple generated is pre-measured for each condition based on the applied voltage and current, and stored in the memory 72.

[0148] The detection ADC73 detects the DC current flowing through the second DC detection line DL2. The detection ADC73 is located inside the power control device 70A. Because it is connected to the output side of the DC voltage generation unit 820, it also functions as a DC current detection unit to detect the output DC current flowing from the charging high voltage device 180A into the photosensitive element 40.

[0149] here, Figure 10 The diagram shows the functional module of CPU 71A in the power control device 70A. (Refer to...) Figure 10 The CPU 71A, which is a calculation unit, includes a DC current calculation unit 711, a control signal instruction unit 712, a current ripple calculation unit 713, and an inverse waveform calculation unit 714.

[0150] The DC current calculation unit 711 calculates the DC current based on the feedback voltage detected by the detection ADC 73.

[0151] The control signal command unit 712 issues commands to control signals (DC control signals and AC control signals). Specifically, it issues commands to the CLK signal, which corresponds to the frequency of the AC current flowing through the coupling capacitor 830, i.e., the high / low signal with the same frequency as the AC current, and the output voltage signal of the AC current.

[0152] Furthermore, the ripple calculation unit 713 calculates the ripple voltage based on the current control signal (AC control signal) and the information stored in the memory 72. The calculated ripple voltage is the AC switching ripple; the influence of DC ripple is small and therefore ignored (see reference). Figure 12 ).

[0153] Then, the inverse waveform calculation unit 714 calculates the inverse waveform (inverse waveform) of the envisioned ripple voltage and outputs the command to the application DAC 74.

[0154] Then, the inverted waveform of the ripple waveform calculated by the CPU71A is generated by the DAC74 and applied to the DC current detection line DL2.

[0155] In addition, as an output unit that applies a rippled inverted waveform, if the DAC74 has insufficient capacity or requires impedance conversion, an operational amplifier can be further set up to amplify the output.

[0156] here, Figure 11 The diagram shown illustrates the principle of ripple voltage cancellation. The inverse waveform application unit in this embodiment applies voltage to... Figure 11 (a) shows a current sensing line that generates ripple voltage, applying an input calculated based on current control information and stored memory information. Figure 11(b) shows the inverted waveform of the ripple voltage. Thus, the ripple voltage is canceled out, as shown... Figure 11 As shown in (c), the error caused by ripple voltage is reduced in the output DC current detected by the detection ADC73.

[0157] Figure 12 The diagram shown is an illustration of the ripple voltage generated upstream of the current sensing element 841.

[0158] The ripple voltage generated in the first DC current sensing line DL1 before the current sensing element 841 is typically a voltage waveform that combines the DC switching ripple and the AC output ripple.

[0159] exist Figure 12 In the diagram, (a) represents the ripple generated by the AC current flowing in, (b) represents the ripple generated by the DC switch, and (c) represents the ripple appearing in the DC current detection unit 840. Additionally, Figure 12 (c) For illustration, the voltage waveform is shown when the AC current reduction section 850 is not provided.

[0160] As an example, when the AC output frequency is 1280Hz and the DC switching frequency is 50kHz, such as Figure 12 As shown in (c), the ripple waveform that appears in the second DC detection line DL2 is a waveform that overlaps with the waveform of 1280Hz and the waveform of 50kHz.

[0161] Here, the current flowing from the AC current does not change regardless of whether the DC voltage output is ON or OFF. Therefore, when the DC output is OFF, the ripple caused by the AC current inflow is measured in advance and stored in the memory 72.

[0162] Regarding the switching ripple of DC circuits, although it cannot be eliminated, it is relatively... Figure 12 (a) and Figure 12 (b) It is known that the ripple caused by the AC output is much larger than that caused by the DC switch. Therefore, by applying an inverted waveform of the ripple voltage caused by the AC output to cancel the ripple caused by the AC output as described above, the ripple in the output DC current detected by the detection ADC73 is reduced, which can significantly reduce the detection error caused by the ripple.

[0163] Thus, in this embodiment, by generating an inverted waveform of the ripple caused by the AC output, and applying an inverted waveform of the ripple voltage to the second DC detection line DL2 to be detected, the ripple voltage is eliminated, the error caused by the ripple is reduced, and the output DC current is detected with high precision by detecting the ADC73, thereby enabling the output of a high-precision measured output DC current.

[0164] Furthermore, in illustrating the configuration of the second embodiment and the third to fifth embodiments described below... Figure 9 , Figure 13 , Figure 14 , Figure 27 Although the description focuses on a configuration where the control of the inverted waveform of the applied ripple voltage is performed in addition to the AC current reduction section 850, the AC current reduction section may not be provided in the configuration where the inverted waveform of the applied ripple voltage is applied.

[0165] <Third Implementation Method>

[0166] In the second embodiment described above, in order for the detection ADC73 to detect the voltage that has canceled the ripple component, an inverted waveform output from the application DAC74 of the power control device 70A is applied to the current detection line DL2. However, it is also possible to omit the application DAC74 and instead have the power control device itself detect the DC current of the output without canceling the ripple voltage, apply the inverted waveform, and output the measured DC current.

[0167] Figure 13 The diagram shown illustrates the configuration of the power supply device γ according to the third embodiment and the flow of current.

[0168] In this embodiment, in the power control device 70B, the current detected by the detection ADC 73B is input to the CPU 71B and corrected before being output as a measured output DC current. At this time, within the CPU 71B of the power control device 70B, for the current detected by the detection ADC 73B, a calculation assuming an inverted waveform is performed based on control information and memory information to calculate a detection current that cancels out ripple, and this calculation result is used as the measured output DC current. Therefore, the measured output DC current output from the CPU 71B reduces the error caused by ripple by using the detected current.

[0169] In detail, the power control device 70B of this embodiment generates the above-mentioned power supply based on the AC control signal and the ripple voltage of each condition stored in the memory 72. Figure 11 (b) The inverted waveform of the ripple voltage caused by the AC output. Then, inside the power control device 70B, the inverted waveform of the ripple voltage caused by the calculated AC output is added to the output DC current contained in the ripple voltage detected by the detection ADC73B to calculate... Figure 11 (c) The output DC current that cancels out the ripple is output as the measured output DC current. Then, the host control device 60 calculates the surface potential of the photoreceptor 40 based on the calculated measured output DC current, and can perform image control, etc.

[0170] Thus, in this embodiment, the DC voltage is calculated by eliminating the ripple in the CPU 71B while the detection waveform containing the ripple voltage detected by the detection ADC 73B is processed inside the power control device 70B. Compared with the configuration of the second embodiment, this allows for the calculation of the output DC current (measurement of the output DC current) with high accuracy while reducing the number of DA inverters (applying DAC) inside the power control device 70B.

[0171] Here, in order to cancel out the ripple voltage contained in the detected output DC current, phase alignment is required. The power control device 70A (70B) described above controls the output AC voltage and DC voltage respectively by outputting DC control signals and AC control signals, so there is no problem as long as the phase is aligned according to the control signals.

[0172] However, depending on the circuit configuration following the control signal, sometimes the detected ripple voltage and the generated inverted ripple waveform are not in phase. In this case, since the phase cannot be aligned based on the control signal, a phase detection mechanism is needed.

[0173] <Fourth Implementation>

[0174] Therefore, in this embodiment, except Figure 9 In addition to the configuration shown in the second embodiment, a phase detection mechanism is also provided.

[0175] Figure 14 The diagram shown illustrates the configuration of the power supply device δ according to the fourth embodiment and the flow of current. In this embodiment, a phase detection mechanism 860 is provided in the high-voltage power supply 180C for charging, connecting the second DC current detection line DL2 and the power control device 70C.

[0176] As an example of a phase detection unit, the phase detection mechanism 860 detects the phase of the ripple voltage at point A of the second DC current detection line DL2, which is located before the DC current detection unit 840. As a result, the power control device 70C of this embodiment applies an inverted waveform to point B, which is downstream of point A, by aligning the phase of the detected ripple voltage, thereby canceling the ripple in the output DC current detected by the detection ADC 73. In the power control device 70C of this embodiment, the CPU 71C, the memory 72, and the application DAC 74C are used as inverted waveform application units.

[0177] (Example of the first circuit of the phase detection unit)

[0178] Figure 15 The diagram shown is a first circuit example of the phase detection mechanism 860. Figure 16 What is shown is Figure 15A diagram illustrating point A, the generated rectangular wave, and the phase of the adjusted inverted waveform.

[0179] Figure 15 The phase detection mechanism 860 has a capacitor 861 and a comparator 862 connected to a ground terminal.

[0180] In this configuration, the potential at point A is coupled using capacitor 861 and compared with GND (0V) via comparator 862. Figure 16 As shown in (b), a rectangular wave with only the + portion being HIGH is generated. Then, by aligning the start of the inverted waveform of the generated ripple voltage with the start of the HIGH portion of the rectangular wave, as shown... Figure 16 As shown in (c), it is possible to make the same as Figure 16 (a) is the phase-aligned inverse waveform of the ripple voltage. Thus, the envisioned inverse waveform of the ripple created by phase adjustment can cancel out the phase alignment with the ripple voltage.

[0181] Furthermore, in situations where coupling is difficult in comparator 862, it is equipped with phase detection capabilities. In comparator 862, the DC component is kept as close to zero as possible by having the DC voltage output be OFF and the AC voltage output be ON. Therefore, phase detection is achieved by comparing a small voltage (below the zero peak of the ripple) at the terminal connected to GND.

[0182] (Example of the second circuit of the phase detection unit)

[0183] Figure 17 The diagram shown is an example of the second circuit of the phase detection mechanism 860C. Figure 18 What is shown is Figure 17 The diagram illustrates the waveform at point A, the rectangular wave generated by the circuit, and the phase of the inverted waveform.

[0184] Figure 17 The phase detection mechanism 860C has a comparator 863 connected to a constant voltage source 864.

[0185] In this example, such as Figure 18 As shown in (a), the waveform at point A is not centered at 0, but rather shifted towards the + side. At this point, as... Figure 18 As shown in (b), the duty cycle of the rectangular wave output from the comparator 863 of the phase detection mechanism 860C is not 50%.

[0186] Confirm via CPU71C of power control unit 70C Figure 18(b) The rising and falling edges of the rectangular wave are used, and the timing of the center between these edges is taken as the timing of the detected ripple waveform's peaks (maximum and minimum values). Thus, by controlling the phase, the timing of the minimum and maximum values ​​in the generated inverted ripple waveform is made consistent with the timing of the detected maximum and minimum values, respectively. Figure 18 As shown in (c), it is possible to create and output the same as Figure 18 (a) is the inverted waveform of the phase-aligned ripple voltage.

[0187] Thus, in this embodiment, when a ripple-inverted waveform is generated in the power control device 70C, the controlled voltage and phase are calculated, and a ripple-inverted waveform aligned with the detected ripple voltage and phase is generated. Then, the phase-aligned ripple-inverted waveform is applied to point B, which is closer to the detection ADC 73 than point A (the DC current detection line DL2 is downstream of the location connecting the phase detection mechanism 860). This cancels out the ripple voltage generated by the AC current inflow, allowing the detection ADC 73 to detect the ripple-suppressed output DC current.

[0188] Therefore, in this embodiment, by calculating the phase of the ripple voltage, the ripple voltage can be eliminated with higher accuracy, and the output current of the DC can be detected with higher accuracy.

[0189] <Fifth Implementation>

[0190] In the fourth embodiment described above, although the phase is calculated, it is more preferable to also determine the timing of sampling in the output DC current, which includes the ripple voltage.

[0191] Here, Figure 19 The image shows a normal sine wave and a deformed waveform during discharge. Figure 19 In the diagram, (a) represents a normal sine wave, and (b) represents a deformed waveform during discharge.

[0192] During contact charging, such as Figure 19 As shown in (a), almost no distortion occurs in the AC waveform. However, in contactless charging, when there is a gap between the photoreceptor 40 and the charging roller 18, and the voltage reaches a certain value, discharge will occur from the charging roller 18 to the photoreceptor 40, charging the photoreceptor. Because more current flows during this discharge than usual, in contactless charging, as... Figure 19 As shown in (b), the AC waveform may sometimes be distorted.

[0193] Furthermore, in any one of the first, second, and fourth embodiments, in the detection of the DC current flowing through point C before detecting the ADC73, even if a ripple voltage is generated due to the influence of the AC current, as long as sampling can be performed at a certain part of the ripple waveform and the degree of difference between that part and the average voltage can be predicted, the current detection can be performed without being affected by the ripple.

[0194] However, certain portions of the measured waveform, near 0V, can sometimes be distorted depending on the control circuit. Furthermore, because this portion is the most skewed, it is more likely to have larger errors compared to other portions, and therefore, this should be avoided.

[0195] Since the degree of deformation varies due to factors such as gap or load, the preferred measurement location is the area before deformation. Furthermore, since the discharge through the charging roller 18, which acts as a load, can cause uneven deformation, it is desirable to avoid measurements at locations after discharge. Therefore, it is preferable to perform measurements (sampling) at a specific location above 0V and before the start of discharge.

[0196] Therefore, in this embodiment, the timing for measuring the output DC current that includes the ripple voltage caused by the AC voltage is set in such a way that the preferred measurement range is within the waveform of the AC voltage.

[0197] Figure 20 The diagram illustrates the measurement range within the AC waveform. The preferred measurement location is the portion above 0V and below the discharge section indicated by the circle.

[0198] Therefore, in this embodiment, similar to the fourth embodiment, the phase detection of the ripple voltage at point A of the second DC current detection line DL2 is performed by the phase detection mechanism 860 (860C). Then, the power control device 70D outputs a point 1 of the waveform and determines the timing of the average value crossover point (0sec) that becomes the center of the waveform.

[0199] In this specification, the average crossover point 0sec refers to the portion of the ripple waveform that rises towards the positive side from the average point. For example, the above... Figure 16 (a) or Figure 20 The waveform at point A shifts evenly relative to point 0, so the zero-crossing point from the - side to the + side becomes the average value crossing point 0sec. On the other hand, the above... Figure 18 (a) The waveform at point A moves evenly around the average value which is higher than 0, so the average value intersection point (0sec) is the position indicated by the arrow that crosses the average value which is higher than 0 from the - side to the + side.

[0200] Figure 21The diagram illustrates the measurement range relative to the average crossover point (0 sec) within the AC waveform. As mentioned above, as the sampling timing in the output current waveform that includes ripple voltage, it is necessary to determine how much time has elapsed since the average crossover point (0 sec) before measurement.

[0201] As an example, when the AC frequency is 1700Hz (1 cycle ≈ 0.588ms), the discharge starts at a point 0.125ms after 0 seconds when the gap between the charging roller 18 and the photosensitive element 40 is 0.005mm, which is approximately 620V.

[0202] Here, when sampling the ripple voltage, since it is desirable to perform the measurement below the start of discharge, the measurement (sampling) is preferably performed within 0 sec to 0.125 ms from the average value crossover point.

[0203] Therefore, it is necessary to pre-store in memory the point in which the distance has advanced from the average value crossover point 0 seconds for measurement. At this time, with different frequencies or outputs, since the time to reach the discharge potential from 0 seconds varies with each frequency, it is necessary to determine it for each frequency.

[0204] By measuring within the range of such a waveform, the output current, including the ripple voltage, can be measured above the average crossover point (0 sec) and before the start of discharge before waveform distortion.

[0205] Figure 22 The diagram illustrates the sampling timing corresponding to the sampling portion within one cycle of the AC waveform. The result is that measurements can be performed at the same location on the waveform as long as only the portion where the sampling has elapsed at least 0.1 ms since 0 sec is measured.

[0206] In this embodiment, the CPU occupancy will not be increased by measuring all waveforms or increasing the number of samples, such as... Figure 22 As shown, by performing the waveform distortion within one cycle in the CPU71D (reference) Figure 27 By measuring a single point within the permissible range, a stable voltage can be measured.

[0207] Figure 23 The image shows a sampling portion of the AC waveform. Figure 24 The diagram shown illustrates the deviation of the measured average value from the average value of the waveform.

[0208] In this embodiment, as described above, since the sampling time is intentionally set after a predetermined interval has elapsed from the crossover point of the average value, therefore... Figure 24As shown, the measured average value is detected as deviating from the average value of the waveform. Subsequently, when calculating the surface potential of the photoreceptor 40 based on the sampled output DC current, this measurement deviation needs to be corrected in order to correctly use the average value of the waveform.

[0209] The correction value used to correct for the measurement deviation is determined in advance according to each AC voltage specified by the control signal, confirming how much the voltage at the measured point deviates from the average, and stored in memory 72D (reference). Figure 27 )middle.

[0210] Figure 25 The diagram shown is an example of the voltage values ​​for the AC output and the ripple voltage of the subsequent stage.

[0211] like Figure 25 When the maximum AC voltage output shown in (a) is 700V, the voltage at the sampling time after a specified interval of 0.1ms from the crossover point of the average value in the corresponding ripple voltage is as follows: Figure 25 (b) shows 10mV.

[0212] like Figure 25 (c) When the maximum value of the output AC voltage is 1400V, the voltage at the sampling time after a specified interval of 0.1ms from the crossover point of the average value in the corresponding ripple voltage is as follows: Figure 25 (d) shows 20mV.

[0213] Figure 25 (b) shows 10mV, Figure 25 The 20mV shown in (d) is equivalent to Figure 24 The measurement deviation (amount of deviation) between the average value of the measurements shown and the average value of the waveform.

[0214] Thus, since the measurement deviation is determined by the amplitude of the AC voltage, each AC voltage is stored. Alternatively, if the AC frequencies are the same and the measurements are taken at the same time, the deviation, being proportional to the voltage, can also be measured at multiple points and tabulated using its slope.

[0215] Figure 26 The table shown is an example of a correlation table representing the relationship between the AC drive frequency, AC output value, sampling timing (measurement point), and measurement deviation.

[0216] like Figure 25 Relationship Figure 26 As shown in the relevant table, the measurement deviation (deviation amount) at the sampling time (measurement point) also varies according to the AC voltage. Therefore, the correlation of measurement deviation for each AC frequency is tabulated or graphed for each AC frequency and stored in memory.

[0217] At this point, the voltage at the measurement point in the output value set at this frequency does not exceed the discharge start voltage. Therefore, the detected measurement value minus the average deviation equals the average value.

[0218] Then, after measurement, by adding (subtracting) the deviation from the averaged value, it is assumed that the error in the ripple voltage disappears. After that, an inverted waveform with the deviation adjusted can be generated, and by canceling the more precise ripple in the output DC current, a high-precision measurement value (measured output DC current) can be obtained.

[0219] Figure 27 The diagram shows the configuration and current flow of the power supply device ε according to the fifth embodiment. In this embodiment, the power control device 70D differs from the fourth embodiment in that the current detected by the detection ADC 73D is input to the CPU 71D and output as a measured output DC current. In the power control device 70D of this embodiment, the CPU 71D, memory 72D, and application DAC 74D function as an inverse waveform application unit RD, while the CPU 71D and memory 72D also function as a measurement waveform selection and correction unit S.

[0220] Figure 28 The diagram shows the functional modules within the memory 72D and CPU 71D of the power control device 70D according to the embodiment.

[0221] The memory 72D has a ripple voltage storage unit 721 and a deviation amount storage unit 722. The ripple voltage storage unit 721 stores the ripple voltage of each specified AC voltage in the control signal. The deviation amount storage unit 722 stores... Figure 26 Such tabular or graphical representations show the correlation of measurement deviations for each AC frequency.

[0222] In addition to the aforementioned DC current calculation unit 711, control signal command unit 712, current ripple calculation unit 713, and reverse waveform calculation unit 714, the CPU71D may also execute a ripple phase confirmation unit 715, an output current average value calculation unit 716, a measurement position determination unit 717, a deviation addition calculation unit 718, a voltage value output unit 719, and a reverse waveform phase adjustment unit 710.

[0223] In this embodiment, firstly, as a preliminary preparation, the AC frequency, AC voltage, time from the average value crossover point 0 sec, and the relationship between the deviation from the average value are measured and stored in advance in the deviation storage unit 722 of the memory 72D.

[0224] The ripple phase confirmation unit 715 confirms the phase of the measured ripple waveform and confirms the position of the average value crossover point 0sec.

[0225] The measurement location determination unit 717 determines, based on the AC frequency, how many seconds have passed since the average value crossover point 0 seconds ago, to perform the measurement, i.e., to determine the sampling timing (measurement point).

[0226] The DC current calculation unit 711 and the output current average value calculation unit 716 perform measurements and calculate average values.

[0227] The deviation calculation unit 718 adds (subtracts) the deviation voltage that aligns with the output voltage to the average voltage. That is, the average value of the measured values ​​is calculated by "measured value - deviation of average value = average value".

[0228] The voltage output unit 719 sends the average value of the measured value (the DC current value at the measurement point minus the average deviation) detected by the ADC 73D as the measured output DC current to the upper control device 60 for predicting the surface potential of the photoreceptor 40.

[0229] Similar to the fourth embodiment, the inverse waveform phase adjustment unit 710 generates and outputs an inverse waveform of the ripple voltage in alignment with the detected phase.

[0230] In this embodiment, as described above, even if the waveform is distorted due to non-contact charging, the deviation can be measured and corrected by specifying a measurement point, thus suppressing ripple error. Even with a distorted waveform, the DC output current can be detected with high precision.

[0231] The preferred embodiments have been described in detail above, but the embodiments are not limited to those described above. Various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

Claims

1. A power supply device that applies a voltage superimposed on DC and AC voltages to a charging component that charges an image carrier, characterized in that it comprises: An AC voltage generating unit generates the AC voltage; A DC voltage generation unit generates the DC voltage; A DC current detection unit is disposed at the output terminal of the DC voltage generation unit to detect the output DC current flowing into the image carrier, and The inverse waveform application unit applies an inverse waveform of the ripple voltage conceived by the DC current detection unit to the DC current detection unit.

2. The power supply device according to claim 1, characterized in that: The DC current detection unit includes a detection AD converter for detecting the output DC current flowing into the image carrier, and a current detection element that forms the impedance of the detection AD converter. The inverse waveform application section applies the inverse waveform of the ripple voltage to the DC current detection line between the detection AD inverter and the current detection element.

3. The power supply device according to claim 2, characterized in that: The inverse waveform application unit outputs a control signal to cause the AC voltage generation unit to generate a specified AC voltage, and The inverse waveform application part has: The ripple voltage storage unit pre-stores the generated ripple waveform for each specified AC voltage of the control signal; The calculation unit, based on the current control signal, envisions the resulting ripple waveform and calculates the inverse waveform of the envisioned ripple waveform, and The DA inverter generates the inverse waveform of the calculated ripple waveform and outputs it to the DC current detection line.

4. The power supply device according to claim 3, characterized in that: A phase detection unit is provided to detect the phase of the output DC ripple voltage in the DC current detection line. The inverse waveform application unit aligns the phase of the calculated inverse waveform with the phase of the detected ripple voltage and outputs it to the downstream side of the DC current detection line where the phase detection unit is connected.

5. The power supply device according to claim 4, characterized in that: The inverse waveform application unit also has a deviation storage unit to pre-store the relationship between the deviation between the detected value and the actual detected value at each specified AC frequency measurement point of the generated ripple voltage. The calculation unit, based on the control signal and the deviation amount in the stored measurement points, imagines a ripple waveform that takes into account the deviation amount, and calculates the inverse waveform of the imagined ripple waveform that takes into account the deviation amount.

6. A power supply device that applies a voltage superimposed with DC and AC voltages to a charging component that charges an image carrier, characterized in that... include: An AC voltage generating unit generates the AC voltage; A DC voltage generation unit generates the DC voltage; as well as The control device outputs a control signal to cause the AC voltage generating unit to generate the specified AC voltage, and is also connected to the output terminal of the DC voltage generating unit to calculate the output DC current flowing into the image carrier. The control device has: The AD inverter is connected to the output side of the DC voltage generator and detects the DC current. The ripple voltage storage unit pre-stores the generated ripple waveform for each specified AC voltage of the control signal, and The calculation unit, based on the current control signal, imagines the generated ripple waveform, calculates the inverse waveform of the imagined ripple waveform, and adds the calculated inverse waveform to the detected DC current containing the ripple as the output DC current.

7. An image forming apparatus, characterized in that... include: The power supply device according to any one of claims 1 to 6; Image carrier; The charging component that energizes the image carrier, and A control device that calculates the surface potential of the image carrier based on the output DC current.

8. A method for applying a voltage, consisting of overlapping DC and AC voltages, to a charging component that charges an image carrier, characterized by comprising: The AC voltage generation step for generating the AC voltage; The DC voltage generation step for generating the DC voltage; A DC current detection step, which detects the output DC current flowing into the image carrier, is provided at the output end of the DC voltage generation unit. The inverted waveform of the ripple voltage conceived by the DC current detection unit is applied to the inverted waveform application step of the DC current detection unit.

9. A method for applying a voltage, consisting of overlapping DC and AC voltages, to a charging component that charges an image carrier, characterized by comprising: The AC voltage generation step for generating the AC voltage; The DC voltage generation step for generating the DC voltage, and The system outputs a control signal to cause the AC voltage generation unit to generate the specified AC voltage, and also connects to the output terminal of the DC voltage generation unit to calculate the output DC current flowing into the image carrier. The control steps include: An AD conversion process that connects to the output side of the DC voltage generation unit and detects the DC current. For each specified AC voltage of the control signal, a ripple voltage storage process is performed to pre-store the generated ripple waveform, and Based on the current control signal, imagine the generated ripple waveform, calculate the inverse waveform of the imagined ripple waveform, and add the calculated inverse waveform to the detected DC current containing the ripple as the calculation process for the output DC current.

10. An image forming method for an image forming apparatus, characterized in that... The image forming apparatus includes: The power supply device according to any one of claims 1 to 6; Image carrier; The charging component that energizes the image carrier, and A control device that calculates the surface potential of the image carrier based on the output DC current.

Images