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

Abstract

To appropriately drive to light a fixing lamp even when AC voltages supplied by a commercial power supply at a destination are different from each other, and prevent large rush current from flowing at the lighting of the fixing lamp.SOLUTION: A fixing power supply 5 driving a fixing unit 4 comprising a fixing lamp 6 as a heat source, comprises: an AC input unit 30 to which one AC power supply among a plurality of types of AC power supplies different in voltage from each other, is connected; a converter 33 that converts AC voltage of the one AC power supply connected to the AC input unit 30 into DC voltage; a booster circuit 34 that boosts the DC voltage to generate output voltage to be supplied to the fixing lamp 6; and a control unit 40 that changes the output voltage generated by the booster circuit 34 on the basis of a state of the fixing lamp 6 at the start of lighting of the fixing lamp 6.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 technique for controlling a fixing unit that includes a fixing lamp as a heat source. [Background technology]

[0002] Image forming apparatuses that form images on sheets using an electrophotographic method are equipped with a fixing unit. The fixing unit heats and melts the toner image transferred to the sheet, thereby fixing the image to the sheet. This type of fixing unit is equipped with a fixing lamp such as a halogen lamp as a heat source. The fixing power supply installed in the image forming apparatus drives and turns on the fixing lamp, thereby raising the temperature of fixing members such as a fixing roller to a predetermined temperature. Therefore, fixing units equipped with a fixing lamp consume a large amount of power.

[0003] In many countries, AC voltages supplied as commercial power sources vary, including 100V, 110V, 120V, and 230V. Therefore, it is common for image forming devices, such as multifunction peripherals (MFPs), to have different power specifications depending on the destination country. Conventional image forming devices are equipped with a fixing power supply that meets the power specifications of the destination country, and are shipped with a fixing power supply suitable for the destination country. However, in recent years, there has been a demand for devices that can use a common fixing power supply even when the AC voltage supplied by the commercial power source in the destination country is different.

[0004] In the past, in the image forming apparatus described above, it has been proposed to light and drive the fixing lamp with a constant DC voltage output from a power factor correction circuit regardless of the input AC voltage (for example, Patent Document 1). This conventional image forming apparatus converts the AC voltage to a DC voltage, and then boosts the DC voltage to generate the constant DC voltage for lighting and driving the fixing lamp. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-102202 Summary of the Invention [Problem to be solved by the invention]

[0006] When a fuser lamp such as a halogen lamp is used as the heat source for the fuser unit, the resistance of the filament is low if the fuser lamp cools down to room temperature before lighting. When a constant, boosted DC voltage is applied to the filament in this state, a large inrush current flows through the fuser lamp instantaneously. This inrush current causes the image forming device to consume a large amount of power instantaneously. This can cause the image forming device's power consumption to exceed the specified value for the destination country. In the worst case scenario, the breaker may trip, cutting off the power supplied to the image forming device.

[0007] The present invention has been made to solve the above-mentioned problems of the related art, and aims to provide a fixing power supply, an image forming apparatus, a control method, and a program that can reduce the inrush current when the fixing lamp is turned on, while being usable even when the AC voltage supplied by the commercial power source in the destination country is different. [Means for solving the problem]

[0008] In order to achieve the above object, the invention of claim 1 is a fixing power supply that drives a fixing unit equipped with a fixing lamp as a heat source, characterized in that it comprises: an AC input section to which one AC power supply among a plurality of types of AC power supplies with different voltages is connected; a converter that converts the AC voltage of the one AC power supply connected to the AC input section into a DC voltage; a boost circuit that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp; and a control section that changes the output voltage generated by the boost circuit based on the state of the fixing lamp when the fixing lamp starts to light up.

[0009] The invention of claim 2 is the fixing power supply of claim 1, wherein the control unit determines whether the state of the fixing lamp is a first state in which the temperature of the fixing lamp is equal to or higher than a predetermined temperature, or a second state in which the temperature of the fixing lamp is lower than a predetermined temperature, and if it determines that the fixing lamp is in the second state when the fixing lamp starts to light up, it sets the output voltage generated by the boost circuit to a voltage lower than a predetermined steady-state voltage and lights up the fixing lamp.

[0010] The invention of claim 3 is the fixing power supply of claim 2, wherein when the output voltage generated by the boost circuit is set to a voltage lower than a predetermined steady-state voltage when the fixing lamp starts to light, the control unit increases the output voltage to the steady-state voltage when a predetermined time has elapsed after the fixing lamp starts to light.

[0011] The invention of claim 4 is characterized in that in the fixing power supply of claim 3, when the control unit determines that the fixing lamp is in the first state when the lighting of the fixing lamp begins, the control unit sets the output voltage generated by the boost circuit to the steady-state voltage and lights up the fixing lamp.

[0012] The invention according to claim 5 is the fixing power supply of claim 1, further comprising a temperature detection unit that detects the temperature of the fixing lamp, and the control unit determines the state of the fixing lamp based on the temperature of the fixing lamp detected by the temperature detection unit.

[0013] The invention of claim 6 is characterized in that in the fixing power supply of claim 1, the control unit determines the state of the fixing lamp based on the elapsed time since the fixing lamp was turned off.

[0014] The invention of claim 7 is characterized in that, in the fixing power supply of claim 1, the boost circuit generates and outputs a constant steady voltage by performing a boost operation to boost the DC voltage.

[0015] An eighth aspect of the present invention provides the fixing power supply of the seventh aspect, characterized in that the steady voltage is higher than the voltages of the plurality of types of AC power supplies.

[0016] The invention of claim 9 is the fixing power supply of claim 7 or 8, characterized in that when the temperature of the fixing lamp is below a predetermined temperature, the control unit stops the boost operation by the boost circuit and outputs the DC voltage generated by the converter as the output voltage.

[0017] The invention of claim 10 is a fixing power supply according to claim 1, 2, 3, 5, 6, 7, or 8, further comprising a voltage detection unit that detects the voltage of the one AC power supply and a resistor connected in series to the fixing lamp, and the control unit supplies the output voltage output from the boost circuit to the fixing lamp via the resistor when the voltage detected by the voltage detection unit is equal to or higher than a predetermined voltage.

[0018] The invention of claim 11 is a fixing power supply of claim 10, further comprising a switching circuit that switches between a first path that applies the output voltage output from the boost circuit directly to the fixing lamp without going through the resistor, and a second path that applies the output voltage to the fixing lamp via the resistor, and the control unit is configured to drive the switching circuit and switch the path that supplies the output voltage to the fixing lamp from the first path to the second path when the voltage detected by the voltage detection unit is equal to or higher than a predetermined voltage.

[0019] The invention according to claim 12 is the fixing power supply according to claim 1, characterized in that the fixing lamp is a halogen lamp.

[0020] The invention of claim 13 is an image forming apparatus having a fixing unit equipped with a fixing lamp as a heat source, characterized in that it comprises: an AC input unit to which one AC power source of multiple types of AC power sources with different voltages is connected; a converter that converts the AC voltage of the one AC power source connected to the AC input unit into a DC voltage; a boost circuit that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp; and a control unit that changes the output voltage generated by the boost circuit based on the state of the fixing lamp when the fixing lamp starts to light up.

[0021] The invention of claim 14 is a control method for an image forming apparatus including a fixing lamp, an AC input unit to which one AC power source out of multiple types of AC power sources with different voltages is connected, a converter that converts the AC voltage of the one AC power source connected to the AC input unit into a DC voltage, and a boost circuit that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp, characterized in that it has a step of determining a state of the fixing lamp when lighting of the fixing lamp begins, and a step of changing the output voltage output from the boost circuit based on the state of the fixing lamp.

[0022] The invention of claim 15 is a program executed in an image forming apparatus including a fixing lamp, an AC input unit to which one AC power source out of multiple types of AC power sources with different voltages is connected, a converter that converts the AC voltage of the one AC power source connected to the AC input unit into a DC voltage, and a boost circuit that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp, characterized in that the program causes the image forming apparatus to execute a step of determining a state of the fixing lamp when lighting of the fixing lamp begins, and a step of changing the output voltage output from the boost circuit based on the state of the fixing lamp. [Effects of the Invention]

[0023] According to the present invention, even if the AC voltage supplied by the commercial power source in the destination country is different, the fixing lamp can be driven and lit, and the inrush current that flows when the fixing lamp is lit can be reduced. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 illustrates an example of the configuration of an image forming apparatus. [Figure 2] 2 is a circuit block diagram showing an example of the configuration of a fixing power supply according to the first embodiment. FIG. [Figure 3] FIG. 2 is a diagram illustrating an example of a detailed circuit configuration of a booster circuit. [Figure 4] FIG. 2 is a block diagram showing the functional configuration of a control unit in the first embodiment. [Figure 5] 10 is a diagram showing a change in the output voltage of the boost circuit when the fixing lamp starts to light up and is in the second state. FIG. [Figure 6] 10 is a flowchart illustrating an example of a processing procedure performed by a control unit when the image forming apparatus is powered on. [Figure 7] 10 is a flowchart illustrating an example of a processing procedure performed by the control unit when a command to turn on the fixing lamp is received from the job control unit. [Figure 8] FIG. 10 is a circuit block diagram showing an example of the configuration of a fixing power supply in a second embodiment. [Figure 9] FIG. 10 is a block diagram showing the functional configuration of a control unit in a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Elements common to the embodiments described below are designated by the same reference numerals, and redundant description thereof will be omitted.

[0026] (First embodiment) 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 using an electrophotographic method. The image forming apparatus 1 is also an apparatus that is capable of forming color images using 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.

[0027] The image forming apparatus 1 also includes a job control unit 9 and a fixing power supply 5 inside the apparatus main body 1a. The job control unit 9 comprehensively 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.

[0028] The image forming apparatus 1 is connected to an external power source 8 such as a commercial power source, and operates on power supplied from the external power source 8. The fixing power source 5 also drives the fixing unit 4 on power supplied from the external power source 8. The power supply voltage of the external power source 8 varies depending on the destination, and is, for example, 100V, 110V, 120V, 230V, etc. In other words, the image forming apparatus 1 can be connected to one of multiple types of AC power sources with different voltages as the external power source 8.

[0029] The paper feed conveyance unit 2 includes a paper feed tray 10 , a pickup roller 12 , a paper feed roller 13 , a conveyance path 14 , a timing roller 15 , a secondary transfer roller 16 , and a paper discharge roller 17 .

[0030] 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 move up and down while the sheets 11 are stacked thereon, and a trailing edge restriction plate 10b that restricts the position of the trailing edge of the sheets 11. The sheets 11 stored in the paper feed tray 10 are placed on the lift plate 10a, with the trailing edge of the sheet abutting against the trailing edge restriction plate 10b. For example, the lift plate 10a moves up while the sheets 11 are stacked thereon, thereby pressing the topmost sheet 11 of the stack of sheets 11 against the pickup roller 12.

[0031] 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), thereby sending at least one sheet 11 downstream.

[0032] The paper feed roller 13 is provided downstream of the pickup roller 12 and supplies the sheet 11 sent out by 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 the nip between the drive roller 13a and the driven roller 13b. As a result, only the topmost sheet 11 is supplied to the transport path 14.

[0033] 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 arrow F2. A timing roller 15 is provided at a predetermined position along the transport path 14. The sheet 11, which is transported along the transport path 14, stops once its leading edge reaches the nip portion of the timing roller 15. The timing roller 15 is driven to rotate at the timing when the image formed by the image forming unit 3 is transported to the position of the secondary transfer roller 16, and transports the sheet 11 toward the secondary transfer roller 16. As 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.

[0034] 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 the paper discharge tray 19 provided at the top of the device main body 1a.

[0035] 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 a primary transfer of the toner images of each color in a superimposed state onto the intermediate transfer belt 23. This forms a color image on the intermediate transfer belt 23. When the color image formed on the intermediate transfer belt 23 passes a position facing the secondary transfer roller 16, the image forming unit 3 performs a secondary transfer of the color image onto the surface of the sheet 11 being transported by the paper feed transport unit 2.

[0036] The image forming unit 3 includes an intermediate transfer belt 23 configured as an endless belt. The intermediate transfer belt 23 is stretched over a drive roller 25 and a driven roller 24 and moves in a circular motion in the direction of 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 respective colors are provided adjacent to the underside 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.

[0037] Exposure units 21Y, 21M, 21C, and 21K are disposed below image forming units 20Y, 20M, 20C, and 20K corresponding to each color. These exposure units 21Y, 21M, 21C, and 21K irradiate the surfaces of the image carriers (photosensitive drums) of 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.

[0038] The image carriers of the image forming units 20Y, 20M, 20C, and 20K are composed of photosensitive drums extending from the front to the back of the image forming apparatus. A photosensitive layer is provided on the surface of the photosensitive drum. When an image is formed in each image forming unit 20Y, 20M, 20C, or 20K, the image carriers are rotated in a predetermined direction (clockwise). Each image forming unit 20Y, 20M, 20C, or 20K includes 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. Once 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 scanning light irradiated from the exposure units 21Y, 21M, 21C, or 21K. The developing unit applies a developer consisting of toner and carrier to the surface of the image carrier, developing 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 way comes into contact with the intermediate transfer belt 23, which circulates in the direction of arrow F1 as the image carrier rotates. At this time, the toner image is primarily transferred onto the intermediate transfer belt 23 by bias voltages applied from primary transfer rollers 22Y, 22M, 22C, and 22K.

[0039] Each image forming unit 20Y, 20M, 20C, and 20K forms a color image on the surface of the intermediate transfer belt 23 by primarily transferring a toner image of each color onto the intermediate transfer belt 23 in a superimposed manner. This color image circulates integrally with the intermediate transfer belt 23 in the direction of arrow F1. When the intermediate transfer belt 23 passes between the secondary transfer roller 16 and the drive roller 25, the color image is joined to the surface of the sheet 11 being fed out from the timing roller 15. At this time, the color image is secondarily transferred to the surface of the sheet 11 by a bias voltage applied from the secondary transfer roller 16.

[0040] The fixing unit 4 includes a pair of fixing members: a heating roller 28 and a pressure roller 29. The sheet 11, onto which an image has been transferred, is subjected to heat and pressure treatments as it passes through the nip between the heating roller 28 and the pressure roller 29. At this time, the toner image transferred to the sheet 11 melts, thereby fixing the image to the sheet 11. A fixing lamp 6, which serves as a heat source, is provided inside the heating roller 28. The fixing lamp 6 is, for example, a halogen lamp. The fixing power supply 5 turns on and drives the fixing lamp 6 to raise the temperature of the heating roller 28. A temperature detection unit 7, which is configured as a temperature detection sensor, is provided near the surface of the heating roller 28. The temperature detection unit 7 is, for example, configured as a thermistor. The fixing power supply 5 drives the fixing lamp 6 based on the surface temperature of the heating roller 28 detected by the temperature detection unit 7.

[0041] 2 is a circuit block diagram showing an example of the configuration of the fixing power supply 5 in the first embodiment. The fixing power supply 5 includes an AC input unit 30, a noise filter circuit 31, a rectifier circuit 32, a converter 33, a capacitor 35, a diode 36, a coil 37, and a switching circuit 38. The fixing power supply 5 also includes a voltage detection unit 39 and a control unit 40.

[0042] The AC input unit 30 is connected to an external power source 8 and inputs an AC voltage supplied from the external power source 8. As described above, various external power sources 8 are connected to the image forming apparatus 1 depending on the destination. Therefore, the AC input unit 30 connects one of a plurality of types of AC power sources with different voltages as the external power source 8. Therefore, the AC voltage input to the AC input unit 30 is various voltages such as 100V, 110V, 120V, and 230V. The AC input unit 30 outputs the AC voltage input from the external power source 8 to the noise filter circuit 31.

[0043] The noise filter circuit 31 removes noise contained in the AC voltage. The rectifier circuit 32 is configured with 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 becomes a voltage corresponding to the AC voltage of the external power supply 8. The rectifier circuit 32 outputs the full-wave rectified voltage to the converter 33.

[0044] Converter 33 is configured, for example, by an AC / DC converter, and converts the full-wave rectified voltage output from rectifier circuit 32 into a DC voltage. Converter 33 includes a boost circuit 34. Boost circuit 34 converts the full-wave rectified voltage into a DC voltage and then boosts the DC voltage to generate a constant DC voltage. Once the full-wave rectified voltage is converted into a DC voltage, the DC voltage becomes a voltage corresponding to the AC voltage of external power supply 8. For example, if the AC voltage of external power supply 8 is 100 V, a DC voltage of approximately 100 V is generated when the full-wave rectified voltage is converted into a DC voltage. Furthermore, if the AC voltage of external power supply 8 is 230 V, a DC voltage of approximately 230 V is generated when the full-wave rectified voltage is converted into a DC voltage. Boost circuit 34 receives this DC voltage as an input voltage and generates a constant DC voltage (e.g., 380 V) as an output voltage by boosting the input voltage. That is, the boost circuit 34 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. The output voltage from the boost circuit 34 is maintained by the capacitor 35.

[0045] The voltage detection unit 39 detects the voltage of the external power supply 8 connected to the AC input unit 30. For example, the voltage detection unit 39 is connected to the output terminal of the noise filter circuit 31 and detects the AC voltage that appears at that output terminal. However, this is not limiting, and the voltage detection unit 39 may be connected to the AC input unit 30 or the output terminal of the rectifier circuit 32. Furthermore, the voltage detection unit 39 may detect the voltage of the external power supply 8 based on the DC voltage obtained after the voltage that has been full-wave rectified in the converter 33 is converted to DC. When the voltage detection unit 39 detects the voltage of the external power supply 8, it outputs the detection result to the control unit 40.

[0046] The control unit 40 drives the fixing lamp 6 with the DC voltage output from the boost circuit 34 of the converter 33. The control unit 40 includes a CPU 41 and a ROM 42. The ROM 42 is a non-volatile memory that stores computer-readable programs and the like. The CPU 41 is a hardware processor that reads and executes the programs stored in the ROM 42. When the CPU 41 executes the programs, the control unit 40 drives the fixing lamp 6 and operates the fixing unit 4.

[0047] For example, when the image forming apparatus 1 is powered on, the control unit 40 determines the boost amount in the boost circuit 34 based on the voltage detected by the voltage detection unit 39, and drives the boost circuit 34 based on that boost amount. For example, the control unit 40 generates a control signal CNT specifying the boost amount and outputs the control signal CNT to the boost circuit 34, thereby driving the boost circuit 34. As a result, the boost circuit 34 generates a DC voltage of a constant voltage (e.g., 380 V) regardless of which of multiple types of AC power supplies is connected as the external power supply 8, and enters a steady state in which it outputs that constant voltage. Therefore, the converter 33 outputs the constant voltage (e.g., 380 V) as the steady voltage.

[0048] Fig. 3 is a diagram showing an example of a detailed circuit configuration of the boost circuit 34. Note that Fig. 3 illustrates an example in which the boost circuit 34 has a two-phase configuration of phases A and B. However, the boost circuit 34 is not limited to a two-phase configuration, and may have a three- or more-phase configuration or a single-phase configuration.

[0049] The boost circuit 34 shown in FIG. 3 includes a boost 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.

[0050] The boost control circuit 50 controls the on / off of the A-phase power devices 51 and the B-phase power devices 55. A control signal CNT output from the control unit 40 is input to the boost control circuit 50. Based on the control signal CNT, the boost control circuit 50 determines the duty ratios of the A-phase power devices 51 and the B-phase power devices 55 and drives the A-phase power devices 51 and the B-phase power devices 55.

[0051] When A-phase power device 51 is turned on, magnetic energy accumulates in A-phase coil 52. When A-phase power device 51 is turned off, this magnetic energy is released as a voltage to the output side. The released voltage is added to the input voltage. As a result, a voltage higher than the input voltage is output to output electrolytic capacitor 59.

[0052] Similarly, when the B-phase power device 55 is turned on, magnetic energy accumulates in the B-phase coil 56. When the B-phase power device 55 is turned off, this magnetic energy is released as a voltage to the output side. The released voltage is added to the input voltage. As a result, a voltage higher than the input voltage is output to the output electrolytic capacitor 59.

[0053] The boost control circuit 50 changes the duty ratio of the A-phase power device 51 and the B-phase power device 55 based on the control signal CNT. That is, the boost control circuit 50 changes the duty ratio of the A-phase power device 51 and the B-phase power device 55 based on the boost amount determined by the control unit 40. This changes the magnetic energy stored in the A-phase coil 52 and the B-phase coil 56, changing the voltage (boost amount) added to the input voltage. Therefore, the boost control circuit 50 boosts the DC voltage generated by the DC conversion by the converter 33 according to the boost amount determined by the control unit 40, generating an output voltage that is a steady voltage (e.g., 380 V). In this case, the steady voltage is generated to be higher than the voltages of the multiple types of AC power supplies connectable to the image forming apparatus 1. In this way, the boost control circuit 50 controls the output voltage output from the boost circuit 34 by changing the duty ratio according to the control signal CNT.

[0054] However, if the control signal CNT specifies the boost width as 0, the boost control circuit 50 does not turn on the A-phase power device 51 and the B-phase power device 55. In this case, the boost operation by the boost circuit 34 stops, and the output voltage of the boost circuit 34 becomes equal to the input voltage.

[0055] 2, when the job control unit 9 starts execution of a print job, the control unit 40 drives the fixing lamp 6 in response to a command from the job control unit 9. Upon receiving a lamp lighting command from the job control unit 9, the control unit 40 drives the switching circuit 38 via the drive circuit 43 to light up the fixing lamp 6.

[0056] The switching circuit 38 is configured by, for example, an IGBT (Insulated Gate Bipolar Transistor), etc. The switching circuit 38 drives the fixing lamp 6 by modulating the DC voltage output from the boost circuit 34 of the converter 33 using PWM (Pulse Width Modulation).

[0057] The control unit 40 determines the duty ratio for turning the switching circuit 38 on and off and outputs the duty ratio to the drive circuit 43. The drive circuit 43 drives the switching circuit 38 on and off based on the duty ratio determined by the control unit 40. When the switching circuit 38 is turned on, a DC voltage output from the boost circuit 34 is applied to the fixing lamp 6 via the coil 37 and the switching circuit 38, causing a current to flow through the fixing lamp 6 and light up. On the other hand, when the switching circuit 38 is turned off by a drive signal from the drive circuit 43, the magnetic energy stored in the coil 37 is released as a current. This current flows through the fixing lamp 6 and is returned to the coil 37 via the diode 36. When the fixing lamp 6 lights up in this way, the heating roller 28 is heated from the inside.

[0058] The control unit 40 acquires the surface temperature of the heating roller 28 detected by the temperature detection unit 7, and determines the duty ratio so that the surface temperature of the heating roller 28 becomes a predetermined temperature. Therefore, the control unit 40 can maintain the surface temperature of the heating roller 28 at a predetermined temperature when a print job is executed in the image forming apparatus 1.

[0059] Incidentally, the resistance of the filament of the fixing lamp 6 decreases as the temperature drops. For example, when the filament of the fixing lamp 6 has cooled to room temperature, if a DC voltage boosted to a steady voltage (e.g., 380 V) by the boost circuit 34 is applied to the fixing lamp 6 to light the fixing lamp 6, a large inrush current will flow through the fixing lamp 6. To reduce this inrush current, the control unit 40 of this embodiment is configured to determine the lamp state of the fixing lamp 6 when the fixing lamp 6 starts to light up, and to change the output voltage generated by the boost circuit 34 according to the lamp state.

[0060] Fig. 4 is a block diagram showing the functional configuration of the control unit 40. When the CPU 41 executes a program stored in the ROM 42, the control unit 40 functions as a boost width determination unit 60, a control signal output unit 61, a timer count unit 62, a lamp state determination unit 63, and a lamp drive unit 64, as shown in Fig. 4.

[0061] The boost width determination unit 60 functions, for example, immediately after the image forming apparatus 1 is powered on, and determines the boost width in the boost circuit 34 based on the voltage detected by the voltage detection unit 39. The control signal output unit 61 generates a control signal CNT based on the boost width determined by the boost width determination unit 60, and outputs it to the boost control circuit 50. As a result, the boost circuit 34 boosts the DC voltage generated by converting the AC voltage, to generate and output a steady voltage (for example, 380 V).

[0062] Furthermore, when the control signal output unit 61 receives a command from the lamp state determination unit 63 to reduce the output voltage from the boost circuit 34, it sets the boost amount specified in the control signal CNT to 0. In this case, the boost operation by the boost circuit 34 stops, and the output voltage output from the boost circuit 34 becomes a voltage lower than the steady-state voltage (for example, 380 V).

[0063] The timer counting unit 62 counts the time that has elapsed since the fixing lamp 6 was turned off. When the fixing lamp 6 is turned off from a lit state, the temperature of the filament starts to drop from that timing. The temperature of the filament gradually drops as time passes since the lamp was turned off. By counting the time that has passed, the timer counting unit 62 provides the lamp status determining unit 63 with a reference value for determining the lamp status of the fixing lamp 6.

[0064] The lamp state determination unit 63 functions when it receives a command to turn on the fixing lamp 6 from the job control unit 9. The lamp state determination unit 63 determines the lamp state of the fixing lamp 6 when the fixing lamp 6 starts to light up. For example, the lamp state determination unit 63 determines whether the lamp state of the fixing lamp 6 is a first state in which the temperature of the filament of the fixing lamp 6 is equal to or higher than a predetermined temperature, or a second state in which the temperature of the filament of the fixing lamp 6 is lower than the predetermined temperature. Here, the first state is a state in which the inrush current is not very large even when a steady voltage (e.g., 380 V) is applied to the fixing lamp 6 when the fixing lamp 6 starts to light up. The second state is a state in which an excessive inrush current flows when a steady voltage (e.g., 380 V) is applied to the fixing lamp 6 when the fixing lamp 6 starts to light up.

[0065] However, the lamp state determination unit 63 cannot directly detect the temperature of the filament of the fixing lamp 6. Therefore, the lamp state determination unit 63 determines the lamp state by one or both of the following two methods.

[0066] The first method is a method of determining the lamp state of the fixing lamp 6 based on the elapsed time counted by the timer counting unit 62. The lamp state determining unit 63 acquires the elapsed time counted by the timer counting unit 62. If the acquired elapsed time is less than a predetermined time, the lamp state determining unit 63 determines that the fixing lamp 6 is in the first state. If the acquired elapsed time is equal to or greater than the predetermined time, the lamp state determining unit 63 determines that the fixing lamp 6 is in the second state.

[0067] The second method is a method of determining the lamp state of the fixing lamp 6 based on the temperature detected by the temperature detection unit 7. The surface temperature of the heating roller 28 detected by the temperature detection unit 7 correlates with the temperature of the filament of the fixing lamp 6. Therefore, the lamp state determination unit 63 determines the lamp state based on the temperature detected by the temperature detection unit 7. For example, if the temperature detected by the temperature detection unit 7 is equal to or higher than a predetermined temperature, the lamp state determination unit 63 determines that the fixing lamp 6 is in the first state. On the other hand, if the temperature detected by the temperature detection unit 7 is lower than the predetermined temperature, the lamp state determination unit 63 determines that the fixing lamp 6 is in the second state.

[0068] If the lamp state determination unit 63 determines that the fixing lamp 6 is in the first state when the fixing lamp 6 starts to light up, it does not send a command to the control signal output unit 61 to reduce the output voltage from the boost circuit 34. Because the temperature of the filament of the fixing lamp 6 is above a predetermined temperature, even if a steady voltage (e.g., 380 V) is applied when the fixing lamp 6 starts to light up, a large inrush current does not flow through the fixing lamp 6. Therefore, the lamp state determination unit 63 allows the fixing lamp 6 to light up at the steady voltage (e.g., 380 V).

[0069] On the other hand, if it is determined that the fixing lamp 6 is in the second state when the lighting of the fixing lamp 6 starts, the lamp state determination unit 63 sends a command to the control signal output unit 61 to reduce the output voltage from the boost circuit 34. As a result, the boost amount is specified as 0 in the control signal CNT output from the control signal output unit 61, and the boost operation by the boost circuit 34 stops.

[0070] After the lamp state determination unit 63 makes a determination, the lamp drive unit 64 drives the switching circuit 38 via the drive circuit 43 to turn on the fixing lamp 6. At this time, if the lamp state determination unit 63 determines that the state is the first state, the fixing lamp 6 is driven to turn on with a steady voltage. On the other hand, if the lamp state determination unit 63 determines that the state is the second state, the fixing lamp 6 is driven to turn on with a voltage lower than the steady voltage. By driving the fixing lamp 6 to turn on with a voltage lower than the steady voltage, it is possible to prevent an excessive inrush current from flowing through the fixing lamp 6 when the fixing lamp 6 starts to turn on.

[0071] The lamp state determination unit 63 sends a command to the control signal output unit 61 to reduce the output voltage from the boost circuit 34, and then sends a command to restore the output voltage to a steady voltage when the fixing lamp 6 starts to light. For example, the lamp state determination unit 63 outputs a command to the control signal output unit 61 to restore the output voltage to a steady voltage when a predetermined time has elapsed since the fixing lamp 6 started to light. Based on this command, the control signal output unit 61 outputs a control signal CNT specifying the boost amount determined by the boost amount determination unit 60 to the boost control circuit 50. As a result, the output voltage from the boost circuit 34 returns to a steady voltage (for example, 380 V).

[0072] FIG. 5 is a diagram showing changes in the output voltage of the boost circuit 34 when the fixing lamp 6 is in the second state when it starts to light up. When the fixing lamp 6 is in the second state, as shown in FIG. 5(a), for example, the boost circuit 34 outputs an output voltage V1 that is lower than the steady voltage V2 at the lighting start timing T0. This prevents an excessive inrush current from flowing through the fixing lamp 6. Thereafter, the boost circuit 34 increases the output voltage at timing T1, when a predetermined time Ts has elapsed since the lighting start timing T0, and returns the output voltage to the steady voltage V2. This predetermined time Ts is set in advance as the time required for the resistance of the filament of the fixing lamp 6 to reach a predetermined value or higher. For example, the predetermined time Ts is about 500 ms to 1 s.

[0073] 5(b) shows an example in which the output voltage of the boost circuit 34 is gradually increased from the lighting start timing T0 and returns to the steady voltage V2 at timing T1 after a predetermined time Ts has elapsed. In this case as well, when lighting of the fixing lamp 6 starts, the fixing lamp 6 is driven at voltage V1, which is lower than the steady voltage V2, so that the inrush current can be kept small.

[0074] The lamp state determination unit 63 may employ either the control shown in FIG. 5(a) or FIG. 5(b) as the control for restoring the output voltage of the boost circuit 34 to the steady voltage V2.

[0075] Next, a processing procedure performed by the control unit 40 will be described. FIG. 6 is a flowchart showing an example of a processing procedure performed by the control unit 40 when the image forming apparatus 1 is powered on. That is, the processing procedure shown in FIG. 6 is performed when the image forming apparatus 1 is started up. When the image forming apparatus 1 is powered on, the control unit 40 detects the voltage of the external power supply 8 (step S1). Next, the control unit 40 determines the boost amount in the boost circuit 34 based on the voltage of the external power supply 8 (step S2). The control unit 40 generates a control signal CNT based on the determined boost amount (step S3). After generating the control signal CNT, the control unit 40 starts outputting the control signal CNT to the boost circuit 34. As a result, the boost circuit 34 boosts the DC voltage generated by the external power supply 8 and enters a steady state in which it outputs a constant DC voltage (e.g., 380 V).

[0076] 7 is a flowchart showing an example of a processing procedure performed by the control unit 40 when a command to turn on the fixing lamp 6 is received from the job control unit 9. When the control unit 40 receives the command to turn on the fixing lamp 6, it first determines the lamp status of the fixing lamp 6 (step S10). At this time, the control unit 40 may determine the lamp status using the first method described above, or may determine the lamp status using the second method. Based on the result of determining the lamp status, the control unit 40 determines whether the temperature of the filament of the fixing lamp 6 is below a predetermined temperature (step S11).

[0077] If the temperature of the fixing lamp 6 is lower than the predetermined temperature (YES in step S11), the fixing lamp 6 is in the second state. In this case, the control unit 40 performs a process to reduce the output voltage output from the boost circuit 34 (step S14). That is, the control unit 40 changes the control signal CNT output to the boost circuit 34 from the steady state. More specifically, the control unit 40 changes the boost amount in the boost circuit 34 to 0. This stops the boost operation in the boost circuit 34, and the output voltage output from the boost circuit 34 switches to a voltage lower than the steady voltage (e.g., 380 V). That is, the output voltage from the boost circuit 34 decreases to a voltage that is approximately equal to the voltage of the external power supply 8.

[0078] When the control unit 40 reduces the output voltage of the boost circuit 34, it starts lighting the fixing lamp 6 (step S15). At this time, the control unit 40 changes the setting of the DC voltage supplied to the fixing lamp 6 to a voltage lower than the steady voltage. Therefore, the control unit 40 can prevent an excessive inrush current from flowing to the fixing lamp 6.

[0079] When the lighting of the fixing lamp 6 starts, the control unit 40 determines whether a predetermined time Ts has elapsed (step S16). If the predetermined time Ts has elapsed (YES in step S16), the temperature of the filament of the fixing lamp 6 has risen to or above the predetermined temperature. Therefore, the control unit 40 increases the output voltage from the boost circuit 34 and returns it to a steady voltage (e.g., 380 V) (step S17). That is, the control unit 40 outputs a control signal CNT specifying the boost amount determined in step S2 to the boost circuit 34, thereby causing the boost circuit 34 to perform a boost operation. As a result, the fixing lamp 6 is driven to light at a steady voltage (e.g., 380 V).

[0080] On the other hand, if the temperature of the fixing lamp 6 is equal to or higher than the predetermined temperature (NO in step S11), the fixing lamp 6 is in the first state. In this case, the control unit 40 sets the output voltage from the boost circuit 34 to a steady voltage (e.g., 380 V) (step S12). That is, the control unit 40 continues to output the control signal CNT generated in step S3 to the boost circuit 34. Then, the control unit 40 starts lighting the fixing lamp 6 at the steady voltage (step S13). At this time, because the temperature of the fixing lamp 6 is equal to or higher than the predetermined temperature, no large inrush current flows through the fixing lamp 6.

[0081] Thereafter, the control unit 40 determines whether the execution of the print job by the job control unit 9 has ended (step S18). For example, when the last sheet 11 fed by the paper feed conveyance unit 2 during the execution of the print job passes through the fixing unit 4, the control unit 40 determines that the execution of the print job has ended. When the execution of the print job has ended (YES in step S18), the control unit 40 stops the lighting of the fixing lamp 6 (step S19). Then, the control unit 40 starts a timer counting operation (step S20). This timer counting operation counts the elapsed time since the fixing lamp 6 was turned off. When the execution of the next print job starts, the control unit 40 can determine the lamp state of the fixing lamp 6 based on the elapsed time counted by the timer counting operation.

[0082] As described above, the fixing power supply 5 of this embodiment drives the fixing unit 4 equipped with the fixing lamp 6 as a heat source. As described above, the fixing power supply 5 includes an AC input unit 30 to which one of multiple AC power supplies with different voltages is connected. The fixing power supply 5 also includes a converter 33 that converts the AC voltage of the AC power supply connected to the AC input unit 30 into a DC voltage, and a boost circuit 34 that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp 6. The fixing power supply 5 further includes a control unit 40 that changes the output voltage generated by the boost circuit 34 based on the lamp state of the fixing lamp 6 when the fixing lamp 6 starts to light. The fixing power supply 5 having this configuration can reduce the output voltage output from the boost circuit 34 and supplied to the fixing lamp 6 if the lamp state of the fixing lamp 6 is below a predetermined temperature when the fixing lamp 6 starts to light. Therefore, the fixing power supply 5 of this embodiment can properly light the fixing unit 4 even when a different AC voltage is supplied from a commercial power source in the destination country, and can also minimize the inrush current when the fixing lamp 6 lights up.

[0083] (Second embodiment) Next, a second embodiment of the present invention will be described. In the first embodiment, if the temperature of the fixing lamp 6 is below a predetermined temperature when the fixing lamp 6 starts to light, the boosting operation of the boost circuit 34 is stopped, thereby lowering the DC voltage supplied to the fixing lamp 6 to a voltage lower than the steady-state voltage. Therefore, in the first embodiment, if the AC voltage input to the AC input unit 30 is 100 V, the DC voltage supplied to the fixing lamp 6 can be lowered to approximately 100 V. However, if the AC voltage input to the AC input unit 30 is 230 V, the DC voltage supplied to the fixing lamp 6 can only be lowered to approximately 230 V, which is a smaller voltage drop than when the AC voltage is 100 V. Therefore, in this embodiment, a configuration example will be described in which the DC voltage applied to the fixing lamp 6 can be made uniform even when different AC voltages are input to the AC input unit 30.

[0084] 8 is a circuit block diagram showing an example of the configuration of the fixing power supply 5 in the second embodiment. This fixing power supply 5 includes resistors 71, 72, and 73 and a switching circuit 74 in addition to the configuration described in the first embodiment.

[0085] Resistors 71, 72, and 73 are all connected in series to the fixing lamp 6. These resistors 71, 72, and 73 have different resistance values. For example, when the DC voltage output from the boost circuit 34 of the converter 33 is about 230 V, resistor 71 has a resistance value that allows a voltage of about 100 V to be applied to the fixing lamp 6 by dividing the voltage with the filament whose resistance is low. Furthermore, when the DC voltage output from the boost circuit 34 of the converter 33 is about 120 V, resistor 72 has a resistance value that allows a voltage of about 100 V to be applied to the fixing lamp 6 by dividing the voltage with the filament whose resistance is low. Furthermore, resistor 73 has a resistance value that allows a voltage of about 100 V to be applied to the fixing lamp 6 by dividing the voltage with the filament whose resistance is low when the DC voltage output from the boost circuit 34 of the converter 33 is about 110 V.

[0086] The switching circuit 74 has multiple switch circuits 75, 76, 77, and 78. The switch circuit 75 is connected to one end of a resistor 71 and opens and closes a second path 82 through which the output voltage from the boost circuit 34 is applied to the fixing lamp 6 via the resistor 71. The switch circuit 76 is connected to one end of a resistor 72 and opens and closes the second path 82 through which the output voltage from the boost circuit 34 is applied to the fixing lamp 6 via the resistor 72. The switch circuit 77 is connected to one end of a resistor 73 and opens and closes the second path 82 through which the output voltage from the boost circuit 34 is applied to the fixing lamp 6 via the resistor 73. The switch circuit 78 is connected to one end of the fixing lamp 6 and opens and closes a first path 81 through which the output voltage from the boost circuit 34 is applied to the fixing lamp 6 without passing through the resistors 71, 72, and 73. The opening and closing operations of these switch circuits 75, 76, 77, and 78 are controlled by the control unit 40.

[0087] If the control unit 40 determines that the fixing lamp 6 is in the second state when the lighting of the fixing lamp 6 starts, it stops the boosting operation of the boost circuit 34, as in the first embodiment. At this time, the control unit 40 drives the switching circuit 74 based on the voltage detected by the voltage detection unit 39, and switches the path for supplying the output voltage of the boost circuit 34 to the fixing lamp 6 from the first path 81 to the second path 82.

[0088] 9 is a block diagram showing the functional configuration of the control unit 40 in the second embodiment. The control unit 40 has a function as a switching control unit 65 in addition to the functions described in the first embodiment.

[0089] The switching control unit 65 individually drives and controls the switch circuits 75, 76, 77, and 78 included in the switching circuit 74. For example, when the image forming apparatus 1 is powered on, the switching control unit 65 closes the switch circuit 78 and opens the other switch circuits 75, 76, and 77. The switching circuit 74 then maintains the state in which the switch circuit 78 is closed and the other switch circuits 75, 76, and 77 are open as a steady state.

[0090] When the lamp state determination unit 63 determines that the fixing lamp 6 is in the second state when the fixing lamp 6 starts to light up, the switching control unit 65 drives the switching circuit 74 as necessary to switch each of the switch circuits 75, 76, 77, and 78 from the steady state. The switching control unit 65 determines whether or not it is necessary to drive the switching circuit 74 to switch the switch circuits 75, 76, 77, and 78 based on the voltage detected by the voltage detection unit 39. For example, if the voltage detected by the voltage detection unit 39 is a predetermined voltage (e.g., 100 V), the switching control unit 65 determines that it is not necessary to drive the switching circuit 74. On the other hand, if the voltage detected by the voltage detection unit 39 is a voltage (e.g., 110 V, 120 V, or 230 V) higher than the predetermined voltage (e.g., 100 V), the switching control unit 65 determines that it is not necessary to drive the switching circuit 74.

[0091] When the switching control unit 65 determines that it is necessary to drive the switching circuit 74, it drives the switching circuit 74 and switches the path for supplying the output voltage from the boost circuit 34 to the fixing lamp 6 from the first path 81 to the second path 82. At this time, the switching control unit 65 selects one of the three switch circuits 75, 76, and 77 to be closed, based on the voltage detected by the voltage detection unit 39.

[0092] For example, when the voltage detected by the voltage detection unit 39 is 230V, the switch circuit 75 is selected and closed, and the switch circuit 78 is switched to the open state. As a result, the DC voltage of 230V output from the boost circuit 34 is supplied to the fixing lamp 6 via the resistor 71. Therefore, the switching control unit 65 can set the voltage applied to the fixing lamp 6 to about 100V.

[0093] Furthermore, for example, when the voltage detected by the voltage detection unit 39 is 120V, the switch circuit 76 is selected and closed, and the switch circuit 78 is switched to the open state. As a result, the DC voltage of 120V output from the boost circuit 34 is supplied to the fixing lamp 6 via the resistor 72. In this case as well, the switching control unit 65 can set the voltage applied to the fixing lamp 6 to about 100V.

[0094] Furthermore, for example, when the voltage detected by the voltage detection unit 39 is 110V, the switch circuit 77 is selected and closed, and the switch circuit 78 is switched to the open state. As a result, the DC voltage of 110V output from the boost circuit 34 is supplied to the fixing lamp 6 via the resistor 73. In this case as well, the switching control unit 65 can set the voltage applied to the fixing lamp 6 to about 100V.

[0095] Therefore, the fixing power supply 5 of this embodiment can equalize the DC voltage applied to the fixing lamp 6 when the fixing lamp 6 is in the second state, even if different AC voltages are input to the AC input unit 30. In particular, the fixing power supply 5 equalizes the DC voltage to match the smallest voltage among the multiple AC voltages input to the AC input unit 30, and therefore can appropriately prevent a large inrush current from flowing through the fixing lamp 6.

[0096] Other configurations and operations in this embodiment are the same as those described in the first embodiment.

[0097] (Variation) 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 above embodiments.

[0098] For example, in the above-described embodiments, the AC voltage input to the AC input unit 30 is 100V, 110V, 120V, 230V, etc. However, in some foreign countries, AC voltages other than those exemplified above are used as commercial power supply AC voltages. The configurations of the above-described embodiments can also be applied to AC voltages other than 100V, 110V, 120V, and 230V.

[0099] In the above embodiment, an example has been described in which the control unit 40 that drives the fixing unit 4 is provided in the fixing power supply 5. However, the control unit 40 does not have to be provided in the fixing power supply 5. In other words, the above-mentioned control unit 40 may be implemented in the image forming apparatus 1.

[0100] In the above embodiment, an example has been described in which the program executed by the CPU 41 of the control unit 40 is pre-recorded in the ROM 42. However, the program is not limited to being pre-recorded in the ROM 42. For example, the image forming apparatus 1 may acquire a program from an external source and store it in the control unit 40. In this case, the program may be provided in a downloadable form via a network such as the Internet. Alternatively, the program may be provided in a form recorded on a computer-readable recording medium such as a CD-ROM or a USB memory. [Explanation of symbols]

[0101] 1. Image forming device 4 Fuser unit 5 Fixing power supply 6 Fixing lamp 7 Temperature detection section 8 External power supply 9 Job control section 28 Heating roller (fixing roller) 30 AC input section 33 Converter 34 Boost circuit 39 Voltage detection unit 40 Control Unit 43 Drive circuit 60 Boost width determination unit 61 Control signal output section 62 Timer count section 63 Lamp status determination unit 64 Lamp driver 65 Switching control section 71, 72, 73 Resistance 74 Switching circuit 75, 76, 77, 78 Switch circuit

Claims

1. A fixing power supply that drives a fixing unit having a fixing lamp as a heat source, an AC input unit to which one AC power supply out of a plurality of types of AC power supplies with different voltages is connected; a converter that converts an AC voltage of the one AC power supply connected to the AC input unit into a DC voltage; a booster circuit that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp; a control unit that changes the output voltage generated by the boost circuit based on the state of the fixing lamp when the lighting of the fixing lamp starts; A fixing power supply comprising:

2. 2. The fixing power supply according to claim 1, wherein the control unit determines whether the state of the fixing lamp is a first state in which the temperature of the fixing lamp is equal to or higher than a predetermined temperature, or a second state in which the temperature of the fixing lamp is lower than the predetermined temperature, and if the control unit determines that the state is the second state when the fixing lamp starts to light up, sets the output voltage generated by the boost circuit to a voltage lower than a predetermined steady-state voltage and lights up the fixing lamp.

3. 3. The fixing power supply according to claim 2, wherein, when the output voltage generated by the boost circuit is set to a voltage lower than a predetermined steady-state voltage at the time when the lighting of the fixing lamp starts, the control unit increases the output voltage to the steady-state voltage when a predetermined time has elapsed after the lighting of the fixing lamp starts.

4. 4. The fixing power supply according to claim 2, wherein when the control unit determines that the fixing lamp is in the first state at the start of lighting of the fixing lamp, the control unit sets the output voltage generated by the boost circuit to the steady voltage and lights up the fixing lamp.

5. a temperature detection unit that detects the temperature of the fixing lamp; Further provided with 2. The fixing power supply according to claim 1, wherein the control unit determines the state of the fixing lamp based on the temperature of the fixing lamp detected by the temperature detection unit.

6. 2. The fixing power supply according to claim 1, wherein the control unit determines the state of the fixing lamp based on the time that has elapsed since the fixing lamp was turned off.

7. 2. The fixing power supply according to claim 1, wherein the boost circuit performs a boosting operation to boost the DC voltage, thereby generating and outputting a constant steady voltage.

8. 8. The fixing power supply according to claim 7, wherein the steady voltage is higher than the voltages of the plurality of types of AC power supplies.

9. 9. The fixing power supply according to claim 7, wherein the control unit stops the boosting operation of the boost circuit and causes the converter to output the DC voltage as the output voltage when the temperature of the fixing lamp is lower than a predetermined temperature.

10. a voltage detection unit that detects a voltage of the one AC power supply; a resistor connected in series to the fixing lamp; Further provided with 9. The fixing power supply according to claim 1, wherein the control unit supplies the output voltage output from the boost circuit to the fixing lamp via the resistor when the voltage detected by the voltage detection unit is equal to or higher than a predetermined voltage.

11. a switching circuit that switches between a first path that applies the output voltage output from the boost circuit directly to the fixing lamp without passing through the resistor and a second path that applies the output voltage to the fixing lamp via the resistor; Further provided with 11. The fixing power supply according to claim 10, wherein the control unit drives the switching circuit to switch the path for supplying the output voltage to the fixing lamp from the first path to the second path when the voltage detected by the voltage detection unit is equal to or higher than a predetermined voltage.

12. 2. The fixing power supply according to claim 1, wherein the fixing lamp is a halogen lamp.

13. An image forming apparatus having a fixing unit equipped with a fixing lamp as a heat source, an AC input unit to which one AC power supply out of a plurality of types of AC power supplies with different voltages is connected; a converter that converts an AC voltage of the one AC power supply connected to the AC input unit into a DC voltage; a boosting circuit that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp; a control unit that changes the output voltage generated by the boost circuit based on the state of the fixing lamp when the lighting of the fixing lamp starts; An image forming apparatus comprising:

14. A fixing lamp; an AC input unit to which one AC power supply out of a plurality of types of AC power supplies with different voltages is connected; a converter that converts an AC voltage of the one AC power supply connected to the AC input unit into a DC voltage; a booster circuit that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp; A control method for an image forming apparatus comprising: a step of determining a state of the fixing lamp at the time when the lighting of the fixing lamp starts; changing the output voltage output from the boost circuit based on the state of the fixing lamp; A control method comprising:

15. A fixing lamp; an AC input unit to which one AC power supply out of a plurality of types of AC power supplies with different voltages is connected; a converter that converts an AC voltage of the one AC power supply connected to the AC input unit into a DC voltage; a booster circuit that boosts the DC voltage to generate an output voltage to be supplied to the fixing lamp; A program executed in an image forming apparatus comprising: a step of determining a state of the fixing lamp at the time when the lighting of the fixing lamp starts; changing the output voltage output from the boost circuit based on the state of the fixing lamp; A program characterized by executing the following.

Images