Power supply device and image forming apparatus

Abstract

To provide a power supply device capable of implementing a power supply circuit in which a voltage drop of a DC voltage in a DC voltage output circuit hardly occurs with a simple configuration without being affected by an AC voltage from an AC voltage output circuit, and to provide an image forming apparatus.SOLUTION: A DC voltage output circuit 42 of a developing power supply device 40 includes an output resistor R1, a first voltage dividing resistor R2, a second voltage dividing resistor R3, a capacitor C1, and an operational amplifier OP1. The capacitor C1 is provided in parallel with the second voltage dividing resistor R3. A cut-off frequency of a low-pass filter circuit 421 including the first voltage dividing resistor R2, the second voltage dividing resistor R3, and the capacitor C1 is set to a frequency lower than the frequency of an AC voltage output from an AC voltage output circuit 41.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a power supply device and an image forming apparatus. [Background technology]

[0002] In electrophotographic image forming devices such as copiers, printers, and facsimiles, a bias voltage consisting of a superimposed AC voltage and DC voltage is conventionally applied to a developing device that develops an electrostatic latent image formed on the surface of an image carrier with toner (see Patent Document 1).The AC voltage is applied to activate the movement of toner between a developing roller that holds the toner and the image carrier, and the density of toner that adheres to the image carrier by development is determined by the DC voltage.

[0003] In an image forming apparatus that forms an image using toner of multiple colors, such as a color image forming apparatus, it is necessary to supply a DC voltage corresponding to the toner to each developing device, and therefore the developing power supply device that generates the bias voltage is provided with multiple DC voltage output circuits provided according to the number of developing devices, and one AC voltage output circuit that supplies an AC voltage to each of these DC voltage output circuits. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-232450 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the bias voltage is generated by connecting an AC voltage branched from the output of an AC voltage output circuit to the output terminals of multiple DC voltage output circuits, the following problem can occur. For example, to prevent the AC voltage from affecting each DC voltage output circuit, it is necessary to provide an output resistor with a relatively large impedance in series with the output line of the DC voltage output circuit. However, if the output resistance is large, for example, when an image such as a solid image in which a large amount of toner moves to the image carrier is developed, the development current temporarily increases. This causes a voltage drop in the DC voltage, which results in insufficient development of lines near the solid image, resulting in a poor image quality in which the density of the lines after image formation is low.

[0006] An object of the present invention is to provide a power supply device and an image forming apparatus that can realize a power supply circuit with a simple configuration that is not affected by the AC voltage from the AC voltage output circuit and is less likely to cause a voltage drop in the DC voltage in the DC voltage output circuit. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a power supply device that generates a bias voltage in which an AC voltage and a DC voltage are superimposed, and applies the bias voltage to a voltage application target provided in an image forming apparatus, the power supply device including: an AC voltage output circuit that outputs the AC voltage; and a DC voltage output circuit that generates a DC voltage corresponding to the voltage application target, wherein each of the DC voltage output circuits has a first voltage dividing resistor provided between a power supply line of a voltage output unit and ground potential, a second voltage dividing resistor provided between the first voltage dividing resistor and the ground potential, a capacitor provided in parallel with the second voltage dividing resistor, and an operational amplifier that outputs a voltage amplified based on a resistive voltage divided by the first voltage dividing resistor to the power supply line, the output of the AC voltage output circuit being connected to the voltage output unit of the DC voltage output circuit, and the cutoff frequency of a low-pass filter circuit formed by the first voltage dividing resistor, the second voltage dividing resistor, and the capacitor is set to a frequency lower than the frequency of the AC voltage output from the AC voltage output circuit.

[0008] An image forming apparatus according to another aspect of the present invention includes the power supply device described above. [Effects of the Invention]

[0009] According to the present invention, it is possible to realize a power supply circuit with a simple configuration that is not affected by the AC voltage from the AC voltage output circuit and is less likely to cause a voltage drop in the DC voltage in the DC voltage output circuit. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the configuration of the image forming unit of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a circuit diagram showing an example of an AC voltage output circuit according to an embodiment of the present invention. [Figure 4] FIG. 4 is a circuit diagram showing an example of a DC voltage output circuit according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of the present invention, and does not limit the technical scope of the present invention.

[0012] Fig. 1 is a diagram showing the configuration of an image forming apparatus 10 according to this embodiment. In Fig. 1, for ease of explanation, the vertical direction when the image forming apparatus 10 is installed and ready for use is defined as the up-down direction D1. Furthermore, the left side of the image forming apparatus 10 as viewed in the drawing is defined as the front (front face), and the front-to-back direction D2 is defined. Furthermore, the left-to-right direction D3 is defined based on the front face of the image forming apparatus 10 in the installed state.

[0013] 1, image forming apparatus 10 is a multifunction peripheral having multiple functions, such as a scanning function for reading image data from an original, a printing function for forming an image based on the image data, a facsimile function, and a copy function. Image forming apparatus 10 may be a printer, a facsimile machine, a copy machine, or the like, as long as it has the function of forming an image.

[0014] The image forming apparatus 10 includes an automatic document feeder 1, an image reading unit 2, an image forming unit 3, a paper feeder 4, an operation display unit 6, and a control unit (not shown) that controls these units in an integrated manner. The automatic document feeder 1 is an ADF (Auto Document Feeder), and is therefore represented as "ADF" in FIG. 1 and will also be referred to as "ADF1" in the following description.

[0015] The ADF 1 transports an original document whose image is to be read by the image reading unit 2. The ADF 1 includes an original document setting unit, a plurality of transport rollers, an original document holder, and a paper discharge unit.

[0016] The image reading unit 2 reads an image from a document and outputs image data corresponding to the read image. The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, a CCD (Charge Coupled Device), and the like.

[0017] The image forming unit 3 realizes a printing function by forming a color or monochrome image on a sheet using an electrophotographic method. The image forming unit 3 forms an image on a sheet based on image data output from the image reading unit 2. The image forming unit 3 also forms an image on a sheet based on image data input from an information processing device such as a personal computer.

[0018] The paper feed unit 4 supplies sheets to the image forming unit 3. The paper feed unit 4 includes a paper feed cassette, a manual feed tray, a sheet transport path, and a plurality of transport rollers. The image forming unit 3 forms an image on the sheet supplied from the paper feed unit 4.

[0019] The control unit comprehensively controls the image forming apparatus 10. The control unit is mainly composed of a computer system having one or more processors and one or more memories. In the image forming apparatus 10, the one or more processors execute programs to realize the functions of the control unit.

[0020] The operation display unit 6 is a user interface in the image forming apparatus 10. The operation display unit 6 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit, and an operation unit such as a switch or a touch panel that inputs various information to the control unit in response to user operations.

[0021] Image forming section 3 performs a process of forming an image using four color toners. Image forming section 3 has four image forming units 31 to 34, an optical scanning device 35, an intermediate transfer device 36, a secondary transfer roller 37, a fixing device 38, a paper discharge tray 39, and a development power supply device 40 (an example of a power supply device of the present invention). In Figure 2, an enlarged view is shown in a speech bubble that schematically illustrates the configuration of image forming unit 34, one of the four image forming units 31 to 34.

[0022] Image forming unit 31 forms a Y (yellow) toner image. Image forming unit 32 forms a C (cyan) toner image. Image forming unit 33 forms an M (magenta) toner image. Image forming unit 34 forms a K (black) toner image.

[0023] The image forming units 31 to 34 each correspond to four colors: Y (yellow), C (cyan), M (magenta), and K (black), and have a common configuration except for the type of toner they use.

[0024] As shown in FIG. 2, each of the four image forming units 31 to 34 has a photosensitive drum 301 (an example of an image carrier), a charging roller 302, a developing device 303 including a developing roller 303A (an example of a voltage application object, a roller body, of the present invention), a primary transfer roller 304, a drum cleaning unit 305, and a toner container 306 (see FIG. 1).

[0025] The development power supply device 40 is a power supply device that generates a bias voltage (development bias) in which an AC voltage and a DC voltage are superimposed, and applies the bias voltage to the development roller 303A of each development device 303. The bias voltage is a voltage that is applied between the development roller 303A and the photosensitive drum 301, and toner moves from the development roller 303A to the photosensitive drum 301 due to a potential difference that occurs between the development roller 303A and the photosensitive drum 301 when the bias voltage is applied.

[0026] Furthermore, application of the bias voltage (development bias) causes a development current to flow between the development roller 303A and the photosensitive drum 301. The development current also includes a toner current that flows as the toner moves.

[0027] The development power supply device 40 includes an AC voltage output circuit 41 (see FIG. 3) that outputs the AC voltage, and a plurality of DC voltage output circuits 42 that generate DC voltages corresponding to the respective development rollers 303A of the plurality of development devices 303. The configurations of the AC voltage output circuit 41 and the DC voltage output circuit 42 will be described later.

[0028] An electrostatic latent image is formed on photosensitive drum 301. Photosensitive drum 301 is rotatably supported about a rotation axis extending in left-right direction D3 by a unit housing that houses photosensitive drum 301, charging roller 302, and drum cleaning unit 305. Photosensitive drum 301 receives a driving force supplied from a motor, for example, and rotates in rotation direction D5 shown in FIG.

[0029] The charging roller 302 charges the surface (outer peripheral surface) of the photosensitive drum 301 to a positive polarity. Specifically, the charging roller 302 charges the surface of the photosensitive drum 301 by receiving a high voltage from a charging power supply device (not shown). However, the charging roller 302 is not limited to a configuration that charges the surface of the photosensitive drum 301 to a positive polarity, and may also charge the surface to a negative polarity.

[0030] The surface of the photosensitive drum 301, which has been charged by the charging roller 302, is irradiated with light based on image data from the optical scanning device 35. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 301. In other words, the portion of the surface of the photosensitive drum 301 that is irradiated with light from the optical scanning device 35 becomes the "image portion."

[0031] The developing device 303 performs a developing process to develop the electrostatic latent image formed on the surface of the photosensitive drum 301. In this embodiment, the developing device 303 performs development using a two-component developer containing toner and carrier. The developing device 303 includes a case, a pair of stirring members, a magnet roller, and a developing roller 303A. The case rotatably supports the pair of stirring members, the magnet roller, and the developing roller 303A around a rotation axis extending in the left-right direction D3. The case also contains toner and carrier of the color used in the developing device 303. The pair of stirring members stir the toner and carrier contained in the case to charge the toner. In this embodiment, the toner is positively charged. However, the charged polarity of the toner is not limited to positive and may be negative. The magnet roller picks up the toner and carrier stirred by the pair of stirring members and supplies the toner to the surface (outer circumferential surface) of the developing roller 303A.

[0032] Developing roller 303A uses charged toner to develop the electrostatic latent image formed on photosensitive drum 301. Specifically, developing roller 303A is electrically connected to developing power supply 40, and a bias voltage (developing bias) is applied to developing roller 303A, which is a superposition of an AC voltage and a DC voltage generated by developing power supply 40. This generates a potential difference between developing roller 303A and photosensitive drum 301, and this potential difference causes the toner on developing roller 303A to be supplied to the surface of photosensitive drum 301. In other words, a developing electric field is formed by applying a high-voltage bias voltage between developing roller 303A and photosensitive drum 301 by developing power supply 40, and the charged toner moves from developing roller 303A to photosensitive drum 301. As a result, a toner image corresponding to the electrostatic latent image is formed on the surface of photosensitive drum 301.

[0033] The primary transfer roller 304 transfers the toner image formed on the surface of the photosensitive drum 301 by the developing device 303 onto the outer circumferential surface of the intermediate transfer belt 361 (see FIG. 2). Specifically, the primary transfer roller 304 receives a high voltage from a transfer power supply (not shown), thereby transferring the toner image formed on the surface of the photosensitive drum 301 onto the outer circumferential surface of the intermediate transfer belt 361. In other words, a transfer electric field is formed between the photosensitive drum 301 and the primary transfer roller 304 by applying a high-voltage transfer bias from the transfer power supply, and the charged toner moves from the photosensitive drum 301 to the intermediate transfer belt 361. As a result, the toner image is formed (transferred) onto the outer circumferential surface of the intermediate transfer belt 361.

[0034] Drum cleaning unit 305 cleans the surface of photosensitive drum 301 after the toner image has been transferred by primary transfer roller 304. For example, drum cleaning unit 305 has a blade-shaped cleaning member and a transport member. The cleaning member comes into contact with the surface of photosensitive drum 301 to remove toner adhering to the surface. The transport member transports the toner removed by the cleaning member to a toner storage container.

[0035] The toner container 306 supplies toner to the case of the developing device 303 corresponding to the color of the toner contained therein.

[0036] The optical scanning device 35 forms an electrostatic latent image on each of the photosensitive drums 301 of the four image forming units 31 to 34. In this embodiment, the optical scanning device 35 includes two optical scanning units 351 and 352.

[0037] The toner images of each color formed by each of the multiple image forming units 31 to 34 are transferred in a superimposed manner onto the outer circumferential surface of the intermediate transfer belt 361. As a result, a color image (toner image) is formed on the outer circumferential surface of the intermediate transfer belt 361.

[0038] 2, the intermediate transfer device 36 includes an intermediate transfer belt 361, a drive roller 362, a tension roller 363, and a belt cleaning unit 364. The intermediate transfer device 36 uses the intermediate transfer belt 361 to transport the toner images formed by the image forming units 31 to 34 to a transfer position P1 (see FIG. 2) where the toner images are transferred by the secondary transfer roller 37.

[0039] The intermediate transfer belt 361 is an endless belt onto which the toner images of each color are transferred from each photosensitive drum 301. The intermediate transfer belt 361 is looped around a drive roller 362 and a tension roller 363, which are spaced apart in the front-to-rear direction D2 of the image forming apparatus 10. The drive roller 362 rotates by receiving a driving force supplied from a motor. This causes the intermediate transfer belt 361 to rotate in a rotation direction D4 shown in FIG. 2. The toner images transferred onto the outer surface of the intermediate transfer belt 361 are transported to a transfer position P1 by a secondary transfer roller 37 as the intermediate transfer belt 361 rotates. A belt cleaning unit 364 cleans the outer surface of the intermediate transfer belt 361 after the toner images have been transferred at the transfer position P1.

[0040] The secondary transfer roller 37 transfers the toner image formed on the outer peripheral surface of the intermediate transfer belt 361 onto a sheet supplied by the paper feed unit 4. As shown in FIG. 2, the secondary transfer roller 37 is disposed opposite the tension roller 363 across the intermediate transfer belt 361, so as to be in contact with the outer peripheral surface of the intermediate transfer belt 361. The secondary transfer roller 37 is pressed toward the tension roller 363 by a biasing member. The secondary transfer roller 37 is electrically connected to a power supply circuit (not shown), and when a high voltage is applied from the power supply circuit, the secondary transfer roller 37 transfers the toner image formed on the outer peripheral surface of the intermediate transfer belt 361 onto a sheet passing through a transfer position P1 (see FIG. 3) where the secondary transfer roller 37 and the intermediate transfer belt 361 come into contact.

[0041] The fixing device 38 fuses and fixes the toner image transferred to the sheet by the secondary transfer roller 37 to the sheet. For example, the fixing device 38 includes a fixing roller and a pressure roller. The fixing roller is arranged to be in contact with the pressure roller, and heats the toner image transferred to the sheet to fix it to the sheet. The pressure roller applies pressure to the sheet passing through the contact area formed between the fixing roller and the pressure roller.

[0042] The sheet on which the image has been formed is discharged to the discharge tray 39.

[0043] However, when the bias voltage is generated by connecting an AC voltage branched from the output of AC voltage output circuit 41 of development power supply 40 to the output sections of multiple DC voltage output circuits 42, the following problem can occur. For example, to prevent the AC voltage from AC voltage output circuit 41 from affecting each of DC voltage output circuits 42, it is necessary to provide an output resistor with a relatively large impedance in series with the output line of DC voltage output circuit 42. However, when the output resistance is large, for example, when an image such as a solid image in which a large amount of toner moves to photosensitive drum 301 is developed, the development current temporarily increases, and the resulting DC voltage drop can cause insufficient development of lines near the solid image, resulting in a defective image in which the density of the lines after image formation is low.

[0044] In contrast, the developing power supply device 40 of the image forming apparatus 10 according to this embodiment has the configuration described below, and is therefore not affected by the AC voltage from the AC voltage output circuit 41 (see FIG. 3), making it difficult for a voltage drop in the DC voltage in the DC voltage output circuit 42 to occur. This makes it possible to supply a stable bias voltage at all times.

[0045] As described above, the developing power supply 40 according to this embodiment includes an AC voltage output circuit 41 (see FIG. 3) and a plurality of DC voltage output circuits 42. The developing power supply 40 includes one AC voltage output circuit 41 and a number of DC voltage output circuits 42 corresponding to the number of developing devices 303 (four in this embodiment). In the developing power supply 40, the output of the AC voltage output circuit 41 is branched into a plurality of branches, which are connected to the voltage output units Vout2 (see FIG. 4) of the plurality of DC voltage output circuits 42. As a result, a bias voltage in which an AC voltage is superimposed on a DC voltage is output from the voltage output unit.

[0046] Fig. 3 is a circuit diagram that schematically shows the configuration of AC voltage output circuit 41, and Fig. 4 is a circuit diagram that schematically shows the configuration of DC voltage output circuit 42. Both the circuit diagrams of Fig. 3 and Fig. 4 are simplified diagrams that omit illustration of electronic elements and wiring other than the essential parts of the present invention.

[0047] 3, AC voltage output circuit 41 has a transformer 411 that transforms an AC voltage (primary AC voltage) input from outside at a predetermined transformation ratio, and four branch circuits 412 that branch the output of the AC voltage (secondary AC voltage) transformed by transformer 411 into four. The output of each of the four branch circuits 412 is connected to a power supply line L2 that leads to a voltage output section Vout2 of the corresponding DC voltage output circuit 42, and the branched secondary AC voltages are superimposed on the DC voltage output from DC voltage output circuit 42.

[0048] Each branch circuit 412 has an internal resistor 4121 and a capacitor 4122 connected in series to the branch line L1. A voltage output section Vout1 of each branch circuit 412 is connected to the power supply line L2 of the DC voltage output circuit .

[0049] 4, the DC voltage output circuit 42 outputs an input DC voltage from a voltage output unit Vout1 through a power supply line L2. The DC voltage output circuit 42 has an output resistor R1, a first voltage dividing resistor R2, a second voltage dividing resistor R3, internal resistors R4 to R7, a capacitor C1, an operational amplifier OP1 (an example of an operational amplifier of the present invention), and transistors TR1 and TR2.

[0050] The output resistor R1 is connected in series to the power supply line L2 leading to the voltage output section Vout1.

[0051] The first voltage dividing resistor R2 is provided between the power supply line L2 and the ground potential. The second voltage dividing resistor R3 is provided between the first voltage dividing resistor R2 and the ground potential. The first voltage dividing resistor R2 and the second voltage dividing resistor R3 are provided in series on a line connecting the power supply line L2 and the ground potential.

[0052] The capacitor C1 is connected in parallel to the second voltage-dividing resistor R3, and one end of the capacitor C1 is connected to the ground potential, and the other end is connected to the midpoint between the first voltage-dividing resistor R2 and the second voltage-dividing resistor R3. The first voltage-dividing resistor R2, the second voltage-dividing resistor R3, and the capacitor C1 form a low-pass filter circuit 421.

[0053] Input terminal V of operational amplifier OP1 IN+ The non-inverting input terminal is connected to the midpoint between the first voltage divider resistor R2 and the second voltage divider resistor R3. IN- For example, an analog voltage of a predetermined voltage generated by the control unit is input to the inverting input terminal of the control unit. The analog voltage may be supplied from an analog voltage output terminal of a CPU mounted on the control unit, or may be supplied from a DC / AC converter connected to the CPU.

[0054] The operational amplifier OP1 has an input terminal V IN+ and input terminal V IN- Compare the voltage at the input terminal VIN+ When the voltage at the output terminal Vout2 is high, the output voltage at the output terminal Vout of the operational amplifier OP1 gradually increases. The output terminal Vout is connected to the base terminal of the transistor TR1. When the base voltage of the transistor TR1 increases, the collector current of the transistors TR1 and TR2 increases, and the voltage drop across the internal resistor R4 increases. This causes the DC voltage at the voltage output terminal Vout2 to decrease.

[0055] In addition, the operational amplifier OP1 has an input terminal V IN+ and input terminal V IN- Compare the voltage at the input terminal V IN+ When the voltage at the output terminal Vout of the operational amplifier OP1 is low, the output voltage at the output terminal Vout of the operational amplifier OP1 gradually decreases. When the base voltage of the transistor TR1 decreases, the collector current of the transistor TR1 decreases, and the voltage drop across the internal resistor R4 becomes smaller. As a result, the DC voltage at the voltage output section Vout2 increases.

[0056] Therefore, the DC voltage of the voltage output section Vout2 is the input terminal V of the operational amplifier OP1 IN- Specifically, it is calculated using the following formula (1):

[0057] Vout2=[(R2+R3) / R3]×V IN- ···(1)

[0058] In this embodiment, the cutoff frequency of the low-pass filter circuit 421 is set to a frequency lower than the frequency of the AC voltage output from the AC voltage output circuit 41. In other words, the resistance values ​​of the first voltage dividing resistor R2 and the second voltage dividing resistor R3 and the capacitance of the capacitor C1 are determined so that the cutoff frequency is lower than the frequency of the AC voltage output from the AC voltage output circuit 41.

[0059] Since the cutoff frequency is set in this manner, when an AC voltage is input from the AC voltage output circuit 41 to the DC voltage output circuit 42, even if the AC voltage is transmitted to the low-pass filter circuit 421, the low-pass filter circuit 421 prevents the AC voltage from being input to the input terminal V IN+ Therefore, the output of the operational amplifier OP1 does not fluctuate, and the output voltage of the DC voltage output circuit 42 is stable. In other words, in such a DC voltage output circuit 42, it is possible to supply a stable bias voltage without being affected by the AC voltage from the AC voltage output circuit 41.

[0060] On the other hand, it is desirable that the cutoff frequency be set to a frequency higher than the frequency of the development current that flows from the development roller 303A to the photosensitive drum 301 when the bias voltage is applied to the development roller 303A during development of the photosensitive drum 301. In other words, the resistance values ​​of the first and second voltage dividing resistors R2 and R3 and the capacitance of the capacitor C1 are determined so that the cutoff frequency is higher than the frequency of the development current. This is because it is desirable that the low-pass filter circuit 421 be able to follow changes in current that correspond to image data that is the subject of image formation processing.

[0061] For example, if the peripheral speed (linear speed) of photosensitive drum 301 during development is 200 mm / sec, an electrostatic latent image of multiple line images (striped pattern) extending in the axial direction is formed on the surface of photosensitive drum 301, the line width is 1 mm, and the circumferential line spacing is 1 mm, the period in which the line images repeatedly face the point opposite developing roller 303A is 1 / 100 seconds, and the development current that flows during development contains a frequency of 100 Hz.

[0062] If the low-pass filter circuit 421 cannot keep up with the frequency, the development current causes a voltage drop across the output resistor R1, causing the voltage of the voltage output unit Vout2 to drop in the black horizontal lines (the black parts that make up the striped pattern) where the current increases, and then the voltage returns to normal in the white horizontal lines (the white parts that make up the striped pattern). This can cause a decrease in density in the black horizontal lines. To prevent this decrease in density, it is desirable to set the cutoff frequency to a frequency (e.g., 150 Hz) higher than the frequency of the development current.

[0063] In the above embodiment, the power supply device for development 40 that outputs a bias voltage to be applied to development roller 303A has been exemplified as the power supply device of the present invention, but the present invention is not limited to this configuration. The power supply device of the present invention can also be applied to a power supply device for transfer that applies the transfer bias to primary transfer roller 304. In this case, the voltage application target of the present invention is primary transfer roller 304, and the image carrier of the present invention is intermediate transfer belt 361.

[0064] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0065] <Appendix 1> A power supply device that generates a bias voltage in which an AC voltage and a DC voltage are superimposed, and applies the bias voltage to a voltage application target provided in an image forming apparatus, an AC voltage output circuit that outputs the AC voltage; a DC voltage output circuit that generates a DC voltage corresponding to the voltage application object, Each of the DC voltage output circuits comprises: a first voltage dividing resistor provided between the power supply line of the voltage output unit and the ground potential; a second voltage dividing resistor provided between the first voltage dividing resistor and the ground potential; a capacitor connected in parallel to the second voltage dividing resistor; an operational amplifier that outputs a voltage amplified based on a resistance voltage divided by the first voltage dividing resistor to the power supply line; an output of the AC voltage output circuit is connected to the voltage output section of the DC voltage output circuit, a cutoff frequency of a low-pass filter circuit formed by the first voltage dividing resistor, the second voltage dividing resistor, and the capacitor is set to a frequency lower than the frequency of the AC voltage output from the AC voltage output circuit.

[0066] <Appendix 2> 2. The power supply device according to claim 1, wherein the voltage application target is a roller that adheres toner to an image carrier included in the image forming apparatus.

[0067] <Appendix 3> the voltage application target is a plurality of rollers that adhere toner to an image carrier included in the image forming apparatus, 2. The power supply device according to claim 1, wherein a plurality of the DC voltage output circuits are provided corresponding to the plurality of roller bodies, respectively.

[0068] <Appendix 4> 4. The power supply device according to claim 3, wherein the output of the AC voltage output circuit is branched into a plurality of parts and connected to the voltage output sections of the plurality of DC voltage output circuits.

[0069] <Appendix 5> the AC voltage output circuit has a transformer that transforms an input primary AC voltage at a predetermined transformation ratio to generate a secondary AC voltage; 5. The power supply device according to claim 4, wherein a secondary output of the transformer is branched into a plurality of parts and connected to the voltage output sections of the plurality of DC voltage output circuits.

[0070] Appendix 6 4. The power supply device according to claim 2, wherein the cutoff frequency is set to a frequency higher than the frequency of a current flowing from the roller body to the image carrier due to application of the bias voltage.

[0071] Appendix 7 the image carrier is a photosensitive drum on the surface of which an electrostatic latent image is formed, 4. The power supply device according to claim 2, wherein the roller body is a developing roller that supplies toner to the electrostatic latent image to develop it.

[0072] Appendix 8 An image forming apparatus comprising the power supply device according to any one of appendixes 1 to 7. [Explanation of symbols]

[0073] 3: Image forming unit 10: Image forming device 31-34: Image forming unit 40:Development power supply device 41: AC voltage output circuit 42: DC voltage output circuit 301: Photosensitive drum 303: Developing device 303A: Developing roller 304: Primary transfer roller 305: Drum Cleaning Department 306: Toner container 361: Intermediate transfer belt 411: Transformer 412: Branch circuit 421: Low-pass filter circuit 4121: Internal resistance 4122: Capacitor C1: Capacitor L1: Branch line L2: Power line OP1: operational amplifier R1: Output resistor R2: 1st voltage dividing resistor R3: Second voltage dividing resistor Vout1: Voltage output section Vout2: Voltage output section

Claims

1. A power supply device that generates a bias voltage in which an AC voltage and a DC voltage are superimposed, and applies the bias voltage to a voltage application target provided in an image forming apparatus, an AC voltage output circuit that outputs the AC voltage; a DC voltage output circuit that generates a DC voltage corresponding to the voltage application object, The DC voltage output circuit a first voltage dividing resistor provided between a power supply line of the voltage output unit and a ground potential; a second voltage dividing resistor provided between the first voltage dividing resistor and the ground potential; a capacitor connected in parallel to the second voltage dividing resistor; an operational amplifier that outputs a voltage amplified based on a resistance voltage divided by the first voltage dividing resistor to the power supply line, an output of the AC voltage output circuit is connected to the voltage output section of the DC voltage output circuit, a cutoff frequency of a low-pass filter circuit formed by the first voltage dividing resistor, the second voltage dividing resistor, and the capacitor is set to a frequency lower than the frequency of the AC voltage output from the AC voltage output circuit.

2. 2. The power supply device according to claim 1, wherein the voltage application target is a roller that adheres toner to an image carrier included in the image forming apparatus.

3. the voltage application target is a plurality of rollers that adhere toner to an image carrier included in the image forming apparatus, The power supply device according to claim 1 , wherein a plurality of the DC voltage output circuits are provided corresponding to the plurality of roller bodies, respectively.

4. 4. The power supply device according to claim 3, wherein the output of said AC voltage output circuit is branched into a plurality of parts and connected to the voltage output sections of said plurality of DC voltage output circuits, respectively.

5. the AC voltage output circuit has a transformer that transforms an input primary AC voltage at a predetermined transformation ratio to generate a secondary AC voltage; 5. The power supply device according to claim 4, wherein the output of the secondary side of the transformer is branched into a plurality of parts and connected to the voltage output sections of the plurality of DC voltage output circuits, respectively.

6. 4. The power supply device according to claim 2, wherein the cutoff frequency is set to a frequency higher than a frequency of a current flowing from the roller body to the image carrier due to application of the bias voltage.

7. the image carrier is a photosensitive drum on the surface of which an electrostatic latent image is formed, 4. The power supply device according to claim 2, wherein the roller body is a developing roller that supplies toner to the electrostatic latent image to develop it.

8. An image forming apparatus comprising the power supply device according to claim 1 or 2.

Images