Fixing power supply, image forming apparatus, control method, and program

Abstract

To drive a halogen lamp in the same configuration by controlling power consumed by the halogen lamp irrespective of the power supply voltage of a destination.SOLUTION: An image forming apparatus 1 comprises a fixing power supply 5 that drives a fixing unit 4 comprising a halogen lamp 6 as a heat source. The fixing power supply 5 comprises an AC input section 30 to which AC voltage is connected, a PFC circuit 33 that outputs DC voltage from the AC voltage input to the AC input section 30, and a power control section 37 that controls power of the DC voltage output from the PFC circuit 33. The halogen lamp 6 is driven by the DC voltage in the power controlled by the power control section 37.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fixing power supply, an image forming apparatus, a control method, and a program, and more particularly to a power control technique in an image forming apparatus equipped with a halogen lamp. [Background technology]

[0002] Image forming devices such as MFPs (Multifunction Peripherals) have different power specifications depending on the destination. In Japan, where the input voltage is 100V, the rated current of the power plug is 15A. Therefore, image forming devices whose destination is Japan must consume 15A or less of current and 1500W or less of power per power cord. However, some image forming devices that are highly productive consume more than 1500W of power. Such image forming devices are equipped with two power cords, and each power plug must be plugged into a socket connected to a different breaker. Therefore, image forming devices equipped with two power cords have low market appeal.

[0003] An image forming apparatus includes a fixing unit for fixing an image formed on a sheet such as printing paper. The fixing unit includes a halogen lamp as a heat source. The image forming apparatus consumes a large amount of power to drive the halogen lamp and maintain the fixing roller at a predetermined temperature.

[0004] In the past, in the image forming apparatus as described above, a device has been proposed in which the input AC voltage is PWM-modulated at a modulation frequency higher than the frequency of the AC voltage and supplied to the halogen lamp (for example, Patent Document 1). In this conventional technology, when the voltage value of the AC voltage is higher than a reference voltage value, the modulation frequency is increased according to the voltage value of the AC voltage, and the duty ratio of the PWM modulation is decreased according to the voltage value of the AC voltage. In this way, the voltage supplied to the halogen lamp is controlled so as not to exceed the rated voltage of the halogen lamp.

[0005] Also, conventionally, an image forming apparatus has been proposed that can suppress deterioration of power supply efficiency even when the type of input power supply is changed (for example, Patent Document 2). This conventional image forming apparatus includes a power factor correction circuit that boosts the power supply voltage supplied from the power supply and outputs it to the heater side. This image forming apparatus uses the power supply voltage and the heater power of the heater to determine a switching frequency to be applied to the power factor correction circuit. Then, the image forming apparatus controls the power factor correction circuit to operate at the determined switching frequency. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-227737 A [Patent Document 2] JP 2017-102202 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the conventional technology of the above-mentioned Patent Document 1 drives the halogen lamp with AC voltage, but does not control the power consumed by the halogen lamp. Therefore, the power consumed by the fixing unit may exceed a predetermined power. Therefore, there are cases where the image forming apparatus must be equipped with two power cords. The conventional technology of Patent Document 2 is the same.

[0008] Furthermore, when a halogen lamp is used as a heat source, the filament resistance is small at room temperature before lighting, so when voltage is applied, a large inrush current flows instantaneously through the halogen lamp. This inrush current can cause the image forming device to consume a large amount of power instantaneously, sometimes exceeding 1500W.

[0009] The present invention has been made to solve the above-mentioned problems of the prior art. That is, the object of the present invention is to provide a fixing power supply, an image forming apparatus, a control method, and a program that can drive a halogen lamp with the same configuration regardless of the power supply voltage according to the destination by controlling the power consumed by the halogen lamp in order to realize high productivity with a single power cord. [Means for solving the problem]

[0010] In order to achieve the above object, the invention of claim 1 is a fixing power supply for driving a fixing unit equipped with a halogen lamp as a heat source, comprising: an AC input section to which an AC voltage is connected; a power factor correction circuit for outputting a DC voltage from the AC voltage input to the AC input section; and a power control section for power controlling the DC voltage output from the power factor correction circuit, wherein the halogen lamp is driven by the DC voltage power-controlled by the power control section.

[0011] The invention of claim 2 is the fixing power supply of claim 1, characterized in that the power control unit includes a switching circuit that switches the DC voltage supplied to the halogen lamp on and off, and a PWM control unit that PWM drives the switching circuit.

[0012] The invention of claim 3 is characterized in that, in the fixing power supply of claim 2, it further comprises a temperature detection sensor that detects the temperature in the vicinity of the halogen lamp, and the PWM control unit determines the duty ratio of the switching circuit based on the temperature detected by the temperature detection sensor.

[0013] The invention according to claim 4 is the fixing power supply according to any one of claims 1 to 3, characterized in that the power factor correction circuit is capable of changing the DC voltage.

[0014] The invention according to claim 5 is the fixing power supply of claim 4, characterized in that the power factor correction circuit outputs the DC voltage as a voltage lower than that in a steady state when the halogen lamp starts to be driven, and outputs the DC voltage as a constant voltage in a steady state after a predetermined time has elapsed.

[0015] The invention of claim 6 is an image forming apparatus comprising: an AC input unit to which an AC voltage is connected; a power factor correction circuit that outputs a DC voltage from the AC voltage input to the AC input unit; a power control unit that performs power control of the DC voltage output from the power factor correction circuit; and a halogen lamp driven by the DC voltage that is power-controlled by the power control unit.

[0016] The invention according to claim 7 is characterized in that in the image forming apparatus according to claim 6, the halogen lamp is provided inside the fixing roller as a heat source for fixing an image onto a sheet.

[0017] The invention of claim 8 is characterized in that, in the image forming apparatus of claim 7, the power control unit includes a switching circuit that switches the DC voltage supplied to the halogen lamp on and off, and a PWM control unit that PWM drives the switching circuit.

[0018] The invention of claim 9 is characterized in that, in the image forming apparatus of claim 8, it further comprises a temperature detection sensor that detects the surface temperature of the fixing roller, and the PWM control unit determines the duty ratio of the switching circuit based on the temperature detected by the temperature detection sensor.

[0019] The invention of claim 10 is characterized in that, in the image forming apparatus of claim 9, it further comprises a current detection unit that detects the current flowing inside the apparatus other than the halogen lamp, and the PWM control unit further determines the duty ratio of the switching circuit based on the current detected by the current detection unit.

[0020] The invention of claim 11 is characterized in that, in the image forming apparatus of claim 10, the PWM control unit determines the duty ratio of the switching circuit so that the power consumed by the entire apparatus does not exceed a predetermined value.

[0021] The invention according to claim 12 is the image forming apparatus according to any one of claims 6 to 11, characterized in that the power factor correction circuit is capable of changing the DC voltage.

[0022] The invention of claim 13 is the image forming apparatus of claim 12, characterized in that the power factor correction circuit outputs the DC voltage as a voltage lower than that in a steady state when the halogen lamp starts to be driven, and outputs the DC voltage as a constant voltage in a steady state after a predetermined time has elapsed.

[0023] The invention of claim 14 is a method for controlling a halogen lamp performed in an image forming apparatus including an AC input unit to which an AC voltage is connected, a power factor correction circuit that outputs a DC voltage from the AC voltage input to the AC input unit, and a halogen lamp driven by the DC voltage output from the power factor correction circuit, the method including a determination step of determining a duty ratio when driving the halogen lamp with the DC voltage, and a drive step of driving the halogen lamp based on the duty ratio, wherein the determination step is configured to determine the duty ratio so that the power consumed by the image forming apparatus does not exceed a predetermined power.

[0024] The invention of claim 15 is a program executed in an image forming apparatus including an AC input unit to which an AC voltage is connected, a power factor correction circuit that outputs a DC voltage from the AC voltage input to the AC input unit, and a halogen lamp driven by the DC voltage output from the power factor correction circuit, the program causing the image forming apparatus to execute a determination step of determining a duty ratio when driving the halogen lamp with the DC voltage, and a drive step of driving the halogen lamp based on the duty ratio, the determination step being characterized in that the duty ratio is determined so that the power consumed by the image forming apparatus does not exceed a predetermined power. Effect of the Invention

[0025] According to the present invention, by controlling the power consumed by the halogen lamp, it is possible to drive the halogen lamp with the same configuration regardless of the power supply voltage according to the destination. Therefore, the image forming apparatus can achieve high productivity with a single power cord. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 illustrates an example of a configuration of an image forming apparatus. [Diagram 2] FIG. 2 is a circuit block diagram showing an example of the configuration of a fixing power supply; [Diagram 3] FIG. 2 is a diagram illustrating an example of a detailed circuit configuration of a PFC circuit. [Figure 4] FIG. 4 is a diagram showing a change in a DC voltage output from a PFC circuit. [Diagram 5] 10 is a flowchart illustrating an example of a processing procedure performed by a control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, elements common to each other are designated by the same reference numerals, and redundant description thereof will be omitted.

[0028] FIG. 1 is a diagram showing an example of the configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 shown in FIG. 1 is an apparatus that executes a print job by forming an image by an electrophotographic method. The image forming apparatus 1 is also an apparatus that is capable of forming a color image by a tandem method. This image forming apparatus 1 includes a paper feed conveyance section 2, an image forming section 3, and a fixing unit 4 inside an apparatus main body 1a. The paper feed conveyance section 2 feeds and conveys sheets 11 such as printing paper one by one. The image forming section 3 forms an image on the sheet 11 conveyed by the paper feed conveyance section 2. The fixing unit 4 fixes the image formed on the sheet 11 by the image forming section 3 to the sheet 11.

[0029] The image forming apparatus 1 further includes, inside the apparatus body 1a, a job control unit 9 and a fixing power supply 5. The job control unit 9 controls the execution of a print job in the image forming apparatus 1. The fixing power supply 5 drives the fixing unit 4 when a print job is executed.

[0030] Furthermore, the image forming apparatus 1 includes a power cord 8a connected to an external power source 8 such as a commercial power source. The image forming apparatus 1 is supplied with power from the external power source 8 via this power cord 8a. The external power source 8 is an AC power source. The power supply voltage of the external power source 8 varies depending on the destination, and may be, for example, 100V, 110V, 120V, or 230V.

[0031] The paper feed conveying section 2 includes a paper feed tray 10 , a pickup roller 12 , a paper feed roller 13 , a conveying path 14 , a timing roller 15 , a secondary transfer roller 16 , and a paper discharge roller 17 .

[0032] The paper feed tray 10 is a container that stores a stack of sheets 11 such as printing paper. The paper feed tray 10 includes a lift plate 10a that can be raised and lowered with the sheets 11 stacked thereon, and a rear end regulating plate 10b that regulates the position of the rear end side of the sheets 11. The sheets 11 stored in the paper feed tray 10 are placed on the lift plate 10a, and are stored with the rear end of the sheet abutting against the rear end regulating plate 10b. For example, the lift plate 10a rises with the sheets 11 stacked thereon, thereby pressing the topmost sheet 11 of the stack of sheets 11 against the pickup roller 12.

[0033] The pickup roller 12 comes into contact with the uppermost sheet 11 among the multiple sheets 11 stored in the paper feed tray 10, and is driven to rotate in a predetermined direction (counterclockwise) to send at least one sheet 11 downstream.

[0034] The paper feed roller 13 is provided downstream of the pickup roller 12, and supplies the sheet 11 sent out from the pickup roller 12 to a transport path 14 further downstream. The paper feed roller 13 includes a drive roller 13a and a driven roller 13b. When multiple sheets 11 are sent out by the pickup roller 12, the multiple sheets 11 are separated at a nip portion between the drive roller 13a and the driven roller 13b. As a result, only the topmost first sheet 11 is supplied to the transport path 14.

[0035] The sheet 11, which is supplied to the transport path 14 by the paper feed roller 13, is transported along the transport path 14 in the direction of the arrow F2. A timing roller 15 is provided at a predetermined position along the transport path 14. The sheet 11 transported along the transport path 14 stops once its leading edge reaches the nip of the timing roller 15. The timing roller 15 is rotated in time with the image formed by the image forming unit 3 being transported to the position of the secondary transfer roller 16, and transports the sheet 11 towards the secondary transfer roller 16. When the sheet 11 passes the position of the secondary transfer roller 16, the image formed by the image forming unit 3 is secondarily transferred onto the surface of the sheet 11.

[0036] The sheet 11 onto which the image has been transferred at the position of the secondary transfer roller 16 then enters the fixing unit 4. The fixing unit 4 applies heat and pressure to the sheet 11 onto which the image has been transferred. This fixes the image transferred onto the sheet 11 onto the sheet 11. The sheet 11 onto which the image has been fixed is then discharged by the paper discharge rollers 17 from the discharge port 18 onto a paper discharge tray 19 provided at the top of the device main body 1a.

[0037] The image forming unit 3 forms toner images of four colors, Y (yellow), M (magenta), C (cyan), and K (black). The image forming unit 3 performs primary transfer of the toner images of each color in a superimposed state onto the intermediate transfer belt 23. As a result, a color image is formed on the intermediate transfer belt 23. Then, the image forming unit 3 performs secondary transfer of the color image onto the surface of the sheet 11 transported by the paper feed transport unit 2 when the color image formed on the intermediate transfer belt 23 passes a position facing the secondary transfer roller 16.

[0038] The image forming section 3 includes an intermediate transfer belt 23 formed of an endless belt. The intermediate transfer belt 23 is stretched around a driving roller 25 and a driven roller 24, and moves in a circular manner in the direction of an arrow F1. A plurality of exposure units 21Y, 21M, 21C, and 21K corresponding to the colors Y, M, C, and K are provided below the intermediate transfer belt 23. A plurality of image forming units 20Y, 20M, 20C, and 20K corresponding to the colors are provided so as to be joined to the lower surface side of the intermediate transfer belt 23. Primary transfer rollers 22Y, 22M, 22C, and 22K are provided inside the intermediate transfer belt 23, facing the image forming units 20Y, 20M, 20C, and 20K.

[0039] The exposure units 21Y, 21M, 21C, and 21K are disposed below the image forming units 20Y, 20M, 20C, and 20K corresponding to each color. The exposure units 21Y, 21M, 21C, and 21K irradiate the surfaces of the image carriers (photosensitive drums) of the image forming units 20Y, 20M, 20C, and 20K corresponding to each color with scanning light based on image data, and form electrostatic latent images on the surfaces of the image carriers.

[0040] The image carrier of the image forming units 20Y, 20M, 20C, and 20K is composed of a photosensitive drum extending from the front side to the back side of the image forming apparatus, for example. A photosensitive layer is provided on the surface of the photosensitive drum. When an image is formed in each of the image forming units 20Y, 20M, 20C, and 20K, the image carrier is rotated in a predetermined direction (clockwise direction). The image forming units 20Y, 20M, 20C, and 20K are provided with a cleaner, a charging unit, and a developing unit around the image carrier. The charging unit charges the surface of the image carrier to a predetermined charge. When the surface of the image carrier is charged to a predetermined charge by the charging unit, an electrostatic latent image is formed on the surface of the image carrier by the scanning light emitted from the exposure units 21Y, 21M, 21C, and 21K. The developing unit applies a developer consisting of toner and carrier to the surface of the image carrier, thereby visualizing the electrostatic latent image with toner and forming a toner image on the image carrier. The toner image formed on the surface of the image carrier in this manner is primarily transferred to the intermediate transfer belt 23 by bias voltages applied from primary transfer rollers 22Y, 22M, 22C, and 22K when it comes into contact with the intermediate transfer belt 23, which moves in a circular motion in the direction of arrow F1.

[0041] Each of the image forming units 20Y, 20M, 20C, and 20K primarily transfers the toner images of each color onto the intermediate transfer belt 23 in a superimposed manner, thereby forming a color image on the surface of the intermediate transfer belt 23. This color image circulates in the direction of the arrow F1 together with the intermediate transfer belt 23. Then, when the intermediate transfer belt 23 passes between the secondary transfer roller 16 and the drive roller 25, it is joined to the surface of the sheet 11 sent out from the timing roller 15, and is secondarily transferred onto the surface of the sheet 11 by the bias voltage applied from the secondary transfer roller 16.

[0042] The fixing unit 4 includes a pair of fixing rollers, a heating roller 28 and a pressure roller 29. When the sheet 11 on which the image has been transferred passes through a nip between the heating roller 28 and the pressure roller 29, the sheet 11 is subjected to a heating process and a pressure process. This causes the image to be fixed to the sheet 11. A halogen lamp 6 serving as a heat source is provided inside the heating roller 28. The fixing power source 5 drives the halogen lamp 6 to raise the temperature of the heating roller 28. A temperature detection sensor 7 such as a thermistor is provided near the surface of the heating roller 28. The fixing power source 5 drives the halogen lamp 6 based on the surface temperature of the heating roller 28 detected by the temperature detection sensor 7.

[0043] 2 is a circuit block diagram showing an example of the configuration of the fixing power supply 5. The fixing power supply 5 includes an AC input unit 30, a noise filter circuit 31, a rectifier circuit 32, a PFC (Power Factor Correction) circuit (power factor improvement circuit) 33, a capacitor 34, a diode 35, a coil 36, and a power control unit 37.

[0044] The AC input unit 30 is connected to the external power supply 8 by the above-mentioned power cord 8a, and inputs the AC voltage supplied from the external power supply 8. The noise filter circuit 31 removes noise contained in the AC voltage. The rectifier circuit 32 is composed of a diode bridge or the like, and full-wave rectifies the AC voltage supplied from the external power supply 8. The voltage full-wave rectified by the rectifier circuit 32 is input to the PFC circuit 33.

[0045] The PFC circuit 33 converts the AC voltage input to the AC input unit 30 into a constant DC voltage and outputs it. That is, the PFC circuit 33 boosts the full-wave rectified voltage regardless of the AC voltage of the external power supply 8, and outputs a constant DC voltage in a steady state. For example, the steady-state DC voltage output from the PFC circuit 33 is 380 V. The DC voltage output from the PFC circuit 33 is held by the capacitor 34.

[0046] The power control unit 37 performs power control of the DC voltage output from the PFC circuit 33, and drives the halogen lamp 6. For example, the power control unit 37 operates in response to a command from the job control unit 9 when the job control unit 9 starts execution of a print job. The power control unit 37 includes a switching circuit 38 and a PWM control unit 39.

[0047] The switching circuit 38 is configured with, for example, an IGBT (Insulated Gate Bipolar Transistor), etc. The switching circuit 38 drives the halogen lamp 6 by PWM modulating the DC voltage output from the PFC circuit 33.

[0048] The PWM control unit 39 determines a duty ratio for turning on and off the switching circuit 38, and controls the switching circuit 38 on and off based on the duty ratio. The PWM control unit 39 drives the halogen lamp 6 with a DC voltage output from the PFC circuit 33. Therefore, the power consumed by the fixing unit 4 depends on the duty ratio at which the switching circuit 38 is turned on and off. The PWM control unit 39 can easily control the power consumed by the fixing unit 4 by changing the duty ratio. The PWM control unit 39 includes a control unit 40 and a drive circuit 41.

[0049] The control unit 40 determines a duty ratio for turning on and off the switching circuit 38. The drive circuit 41 drives the switching circuit 38 based on the duty ratio determined by the control unit 40.

[0050] The control unit 40 acquires the surface temperature of the heating roller 28 detected by the temperature detection sensor 7, and determines the duty ratio so that the surface temperature of the heating roller 28 becomes a predetermined temperature. At this time, the control unit 40 determines the duty ratio so that the power consumed by the fixing unit 4 does not exceed a predetermined power. Since the halogen lamp 6, which is a heat source, has a small filament resistance at room temperature, a large inrush current flows instantaneously when a voltage is applied at the start of driving. Therefore, the control unit 40 limits the duty ratio at the start of driving the halogen lamp 6 to a relatively small value so that the power consumed by the fixing unit 4 does not exceed a predetermined power. When the halogen lamp 6 rises in temperature, the resistance of the filament increases, so that the current flowing through the halogen lamp 6 gradually stabilizes. Therefore, the control unit 40 relaxes the restriction on the duty ratio as the halogen lamp 6 rises in temperature, and determines the duty ratio so that the surface temperature of the heating roller 28 becomes a predetermined temperature. In this way, the control unit 40 performs power control of the DC voltage output from the PFC circuit 33 when determining the duty ratio, so that the power consumed by the fixing unit 4 does not exceed a predetermined power.

[0051] The control unit 40 can also change the duty ratio of the switching circuit 38 so that the power consumed by the entire image forming apparatus 1 does not exceed a predetermined value. In this case, the control unit 40 is connected to a current detection unit 27 that detects the current flowing inside the apparatus other than the halogen lamp 6. The control unit 40 determines the duty ratio so that the sum of the current detected by the current detection unit 27 and the current flowing through the halogen lamp 6 does not exceed a predetermined value. This allows the control unit 40 to limit the power consumed by the entire apparatus so that it does not exceed a predetermined value (for example, 1500 W).

[0052] The drive circuit 41 drives the switching circuit 38 to turn on and off based on the duty ratio determined by the control unit 40. When the switching circuit 38 is turned on, a direct current output from the PFC circuit 33 flows to the halogen lamp 6 via the coil 36 and the switching circuit 38. On the other hand, when the switching circuit 38 is turned off by a drive signal from the drive circuit 41, the magnetic energy stored in the coil 36 is released as a current. This current flows through the halogen lamp 6 and is returned to the coil 36 again via the diode 35.

[0053] Furthermore, the PFC circuit 33 can change the DC voltage that is output. Therefore, the PFC circuit 33 can change the DC voltage when driving the halogen lamp 6. For example, the control unit 40 outputs a control signal CNT to the PFC circuit 33. This control signal CNT is a signal that specifies the DC voltage that is the output of the PFC circuit 33. The PFC circuit 33 outputs a DC voltage according to the control signal CNT.

[0054] Fig. 3 is a diagram showing an example of a detailed circuit configuration of the PFC circuit 33. Fig. 3 illustrates an example in which the PFC circuit 33 has a two-phase configuration of phases A and B. However, the PFC circuit 33 is not limited to a two-phase configuration, and may have a three or more phase configuration or a single phase configuration.

[0055] The PFC circuit 33 shown in FIG. 3 includes a PFC control circuit 50, an A-phase power device 51, an A-phase coil 52, an A-phase resistor 53, an A-phase diode 54, a B-phase power device 55, a B-phase coil 56, a B-phase resistor 57, a B-phase diode 58, and an output electrolytic capacitor 59.

[0056] The PFC control circuit 50 controls the on / off of the A-phase power device 51 and the B-phase power device 55. A control signal CNT output from the control unit 40 is input to the PFC control circuit 50. The PFC control circuit 50 determines the duty ratio of the A-phase power device 51 and the B-phase power device 55 based on the control signal CNT, and drives the A-phase power device 51 and the B-phase power device 55.

[0057] When the A-phase power device 51 is turned on, magnetic energy is stored in the A-phase coil 52. When the A-phase power device 51 is turned off, this magnetic energy is released as a voltage to the output side. The voltage released at this time is added to the input voltage. Therefore, a voltage higher than the input voltage is output to the output electrolytic capacitor 59. The same applies to the operation of the B-phase power device 55.

[0058] The PFC control circuit 50 can change the magnetic energy stored in the A-phase coil 52 and the B-phase coil 56 by changing the duty ratio of the A-phase power device 51 and the B-phase power device 55. Therefore, the PFC control circuit 50 can change the DC voltage output from the PFC circuit 33. The PFC control circuit 50 outputs a DC voltage according to an instruction from the control unit 40 by changing the duty ratio according to the control signal CNT.

[0059] For example, when the halogen lamp 6 starts to operate at room temperature, the control unit 40 outputs a control signal CNT to the PFC circuit 33 to lower the DC voltage output therefrom below the steady state. After the halogen lamp 6 starts to operate, the control unit 40 instructs the PFC circuit 33 to gradually increase the DC voltage and output it as a constant steady state voltage after a predetermined time has elapsed.

[0060] As a result, the DC voltage output from the PFC circuit 33 changes as shown in FIG. 4. That is, the PFC circuit 33 outputs a DC voltage V1 lower than the DC voltage V2 in the steady state when the halogen lamp 6 starts to be driven (timing T0). By driving the halogen lamp 6 with a DC voltage V1 lower than the DC voltage V2 in the steady state when the halogen lamp 6 starts to be driven, the inrush current of the halogen lamp 6 can be suppressed to a small value. The halogen lamp 6 increases in temperature as time passes from the start of driving, and the resistance of the filament increases. Accordingly, the PFC circuit 33 gradually increases the DC voltage V1 to the DC voltage V2. Then, the PFC circuit 33 outputs the DC voltage V2 in the steady state (for example, 380 V) at timing T1 when a predetermined time Ts has elapsed from the start of driving, according to a control signal CNT from the control unit 40. The predetermined time Ts is, for example, about 500 ms.

[0061] For example, the control unit 40 includes a hardware processor such as a CPU (Central Processing Unit) and a non-volatile memory. A computer-readable program to be executed by the hardware processor is recorded in advance in the non-volatile memory. The hardware processor reads and executes the program to perform the above-mentioned control processing.

[0062] FIG. 5 is a flowchart showing an example of a processing procedure performed by the control unit 40. When this processing is started, the control unit 40 waits until the job control unit 9 starts executing a print job (step S10). When the print job starts, the control unit 40 reduces the DC voltage output from the PFC circuit 33 (step S11). This prevents an excessive inrush current from flowing when the halogen lamp 6 starts to be driven. Then, the control unit 40 determines the duty ratio at the start of driving the halogen lamp 6 (step S12). At this time, the control unit 40 determines the duty ratio of the switching circuit 38 based on the temperature detected by the temperature detection sensor 7 and the current detected by the current detection unit 27. Then, the control unit 40 outputs the determined duty ratio to the drive circuit 41 and starts driving the halogen lamp 6 (step S13).

[0063] When the driving of the halogen lamp 6 starts, the temperature of the halogen lamp 6 rises, and the resistance of the halogen lamp 6 also increases. Therefore, when the driving of the halogen lamp 6 starts, the control unit 40 increases the DC voltage output from the PFC circuit 33 (step S14).

[0064] The control unit 40 judges whether or not a predetermined time Ts has elapsed since the start of driving the halogen lamp 6 (step S15). If the predetermined time Ts has elapsed (YES in step S15), the control unit 40 maintains the DC voltage output from the PFC circuit 33 at a constant steady voltage (step S16). If the predetermined time Ts has not elapsed (NO in step S15), the DC current output from the PFC circuit 33 has not reached the steady output voltage. In this case, the process of step S16 by the control unit 40 is skipped.

[0065] Next, the control unit 40 acquires the temperature detected by the temperature detection sensor 7 (step S17). As a result, the control unit 40 detects the surface temperature of the heating roller 28. The control unit 40 also acquires the current detected by the current detection unit 27 (step S18). As a result, the control unit 40 detects the current flowing inside the device other than the halogen lamp 6. Then, the control unit 40 determines the duty ratio of the switching circuit 38 based on the temperature detected in step S17 and the current detected in step S18 (step S19). For example, the control unit 40 determines a duty ratio that can maintain the surface temperature of the heating roller 28 at a predetermined temperature while limiting the power consumed by the entire image forming device 1 so as not to exceed a predetermined value. Then, the control unit 40 performs PWM control of the switching circuit 38 with the duty ratio determined in step S19 (step S20).

[0066] The control unit 40 determines whether the execution of the print job has been completed (step S21). If the execution of the print job has not been completed (NO in step S21), the process by the control unit 40 returns to step S15. The control unit 40 then repeatedly executes the process from step S15 onwards. Even when the process from step S15 onwards is repeatedly executed, the control unit 40 drives the halogen lamp 6 while restricting the power consumed by the entire image forming apparatus 1 so as not to exceed a predetermined value. Therefore, the power consumption of the image forming apparatus 1 does not exceed the predetermined value. On the other hand, when the execution of the print job has been completed (YES in step S21), the control unit 40 stops driving the halogen lamp 6 (step S22).

[0067] As described above, the fixing power supply 5 of the image forming apparatus 1 drives the halogen lamp 6 of the fixing unit 4 with the DC voltage output from the PFC circuit 33. This fixing power supply 5 includes a power control unit 37. The power control unit 37 is configured to perform power control of the DC voltage output from the PFC circuit 33, and drives the halogen lamp 6 with the power-controlled DC voltage. Therefore, the fixing power supply 5 can control the power consumed by the fixing unit 4 so that it does not exceed a predetermined value. The part in the image forming apparatus 1 that consumes the most power is the fixing unit 4. The fixing power supply 5 controls the power consumed by the fixing unit 4, so that it is also possible to control the power consumed by the image forming apparatus 1.

[0068] Moreover, the PFC circuit 33 of the fixing power supply 5 boosts the full-wave rectified voltage and outputs a constant DC voltage in a steady state, regardless of the AC voltage of the external power supply 8. For example, when the AC voltage of the external power supply 8 changes, the voltage value of the voltage full-wave rectified by the rectifier circuit 32 changes. On the other hand, the above-mentioned control unit 40 can specify the DC voltage output from the PFC circuit 33 with the control signal CNT. That is, the control unit 40 can cause the PFC circuit 33 to output a constant DC voltage by detecting the AC voltage of the external power supply 8. Therefore, it is more preferable that the control unit 40 detects the AC voltage of the external power supply 8 and outputs the control signal CNT based on the AC voltage. Since the PFC circuit 33 outputs a constant DC voltage in a steady state regardless of the AC voltage of the external power supply 8, the fixing power supply 5 can control the power consumed by the fixing unit 4 by adjusting the duty ratio of the switching circuit 38. Therefore, the fixing power supply 5 can control the power consumption by simple control.

[0069] By including the fixing power supply 5 as described above, the image forming apparatus 1 can achieve high productivity with a single power cord 8a. In other words, the image forming apparatus 1 can drive the halogen lamp 6 with the same configuration no matter where it is used.

[0070] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the contents described in the above embodiments. In other words, various modifications can be applied to the present invention.

[0071] For example, in the above embodiment, the power control when driving the halogen lamp 6 provided as a heat source in the fixing unit 4 has been described. However, the power control described in the above embodiment is not limited to being applicable to the halogen lamp 6 of the fixing unit 4. For example, when the image forming apparatus 1 is equipped with a scanner that reads an image of a document, a halogen lamp may be installed as a light source that illuminates the image of the document. In such a case, the above-mentioned power control can also be applied to the halogen lamp that illuminates the image of the document.

[0072] In the above embodiment, an example has been described in which the control unit 40 determines the duty ratio so that the sum of the current detected by the current detection unit 27 and the current flowing through the halogen lamp 6 does not exceed a predetermined value. However, if a separate power control unit is provided to control the power consumed by units other than the fixing unit 4, the control unit 40 does not need to perform control taking into account the power consumed by units other than the fixing unit 4. In that case, the control unit 40 only needs to control so that the power consumed by the fixing unit 4 does not exceed a predetermined value. Therefore, the control unit 40 does not need to determine the duty ratio based on the current detected by the current detection unit 27, and only needs to determine the duty ratio based on the temperature detected by the temperature detection sensor 7.

[0073] In the above embodiment, an example has been described in which the DC voltage output from the PFC circuit 33 is reduced when the drive of the halogen lamp 6 starts. However, when print jobs are executed continuously in the image forming apparatus 1, the temperature of the halogen lamp 6 may already be rising when the execution of a print job starts. Therefore, when the temperature of the halogen lamp 6 has already risen to or above a predetermined temperature, the control unit 40 may perform control so as not to reduce the DC current output from the PFC circuit 33 when the drive of the halogen lamp 6 starts.

[0074] In the above embodiment, an example has been described in which the program executed by the hardware processor of the control unit 40 is recorded in a non-volatile memory in advance. However, the program is not limited to being recorded in a non-volatile memory in advance. For example, the image forming apparatus 1 may adopt a configuration in which the program is acquired from an external source and stored in the control unit 40. In this case, the program may be provided in a form that allows downloading via a network such as the Internet. Also, the program may be provided in a form that is recorded in a computer-readable recording medium such as a CD-ROM or a USB memory. [Explanation of symbols]

[0075] 1. Image forming device 4 Fuser unit 5 Fixing power supply 6 Halogen lamps 7 Temperature detection sensor 8 External power supply 27 Current detection section 28 Heating roller (fixing roller) 30 AC input section 32 Rectifier circuit 33 PFC circuit (power factor correction circuit) 37 Power Control Unit 38 Switching Circuits 39 PWM control unit 40 Control section 41 Drive circuit

Claims

1. A fixing power supply for driving a fixing unit having a halogen lamp as a heat source, an AC input section to which an AC voltage is connected; a power factor correction circuit that outputs a DC voltage from an AC voltage input to the AC input unit; a power control unit that controls the power of a DC voltage output from the power factor correction circuit; and driving the halogen lamp by the DC voltage that is power-controlled by the power control unit.

2. The power control unit is a switching circuit for switching on and off the DC voltage supplied to the halogen lamp; A PWM control unit that PWM drives the switching circuit; The fixing power supply according to claim 1 , further comprising:

3. a temperature detection sensor for detecting a temperature in the vicinity of the halogen lamp; Further comprising: The fixing power supply according to claim 2 , wherein the PWM control section determines a duty ratio of the switching circuit based on the temperature detected by the temperature detection sensor.

4. 4. The fixing power supply according to claim 1, wherein the power factor correction circuit is capable of changing the DC voltage.

5. 5. The fixing power supply according to claim 4, wherein the power factor correction circuit outputs the DC voltage as a voltage lower than that in a steady state when the halogen lamp starts to be driven, and outputs the DC voltage as a constant voltage in the steady state after a predetermined time has elapsed.

6. an AC input section to which an AC voltage is connected; a power factor correction circuit that outputs a DC voltage from an AC voltage input to the AC input unit; a power control unit that controls the power of a DC voltage output from the power factor correction circuit; a halogen lamp driven by the DC voltage, the power of which is controlled by the power control unit; An image forming apparatus comprising:

7. 7. The image forming apparatus according to claim 6, wherein the halogen lamp is provided inside a fixing roller as a heat source for fixing an image onto a sheet.

8. The power control unit is a switching circuit for switching on and off the DC voltage supplied to the halogen lamp; A PWM control unit that PWM drives the switching circuit; The image forming apparatus according to claim 7 , further comprising:

9. a temperature detection sensor for detecting a surface temperature of the fixing roller; Further comprising:

9. The image forming apparatus according to claim 8, wherein the PWM control unit determines a duty ratio of the switching circuit based on the temperature detected by the temperature detection sensor.

10. a current detection unit that detects a current flowing inside the device other than the halogen lamp; Further comprising:

10. The image forming apparatus according to claim 9, wherein the PWM control unit further determines a duty ratio of the switching circuit based on the current detected by the current detection unit.

11. 11. The image forming apparatus according to claim 10, wherein the PWM control unit determines a duty ratio of the switching circuit so that power consumed by the entire apparatus does not exceed a predetermined value.

12. 12. The image forming apparatus according to claim 6, wherein the power factor correction circuit is capable of changing the DC voltage.

13. 13. The image forming apparatus according to claim 12, wherein the power factor correction circuit outputs the DC voltage as a voltage lower than that in a steady state when the halogen lamp starts to be driven, and outputs the DC voltage as a constant voltage in the steady state after a predetermined time has elapsed.

14. an AC input section to which an AC voltage is connected; a power factor correction circuit that outputs a DC voltage from an AC voltage input to the AC input unit; a halogen lamp driven by a DC voltage output from the power factor correction circuit; A method for controlling the halogen lamp in an image forming apparatus comprising: a determining step of determining a duty ratio when driving the halogen lamp with the DC voltage; a driving step of driving the halogen lamp based on the duty ratio; having The control method according to claim 1, wherein the determining step determines the duty ratio so that power consumed by the image forming apparatus does not exceed a predetermined power.

15. an AC input section to which an AC voltage is connected; a power factor correction circuit that outputs a DC voltage from an AC voltage input to the AC input unit; a halogen lamp driven by a DC voltage output from the power factor correction circuit; A program executed in an image forming apparatus comprising: a determining step of determining a duty ratio when driving the halogen lamp with the DC voltage; a driving step of driving the halogen lamp based on the duty ratio; Run the command, The program, wherein the determining step determines the duty ratio so that power consumed by the image forming apparatus does not exceed a predetermined power.

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