JP2012039684A - Power supply device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device and an image forming apparatus capable of preventing the power supply device from malfunctioning even if a steep and excessive voltage fluctuation occurs in a power saving state with a light load.SOLUTION: The power supply device and the image forming apparatus, capable of shifting to a power saving state, increases a load of a secondary side when a voltage fluctuation of a primary side of a power supply is detected in a power saving state.

Description

  The present invention relates to a power supply device that supplies electric power to an electronic apparatus and an image forming apparatus including the power supply device.

  As an example of an electronic apparatus, FIG. 8 shows a configuration example of a laser beam printer 47 as an image forming apparatus that forms an image on a recording material. The laser beam printer of FIG. 8 has an image forming main body 30 (hereinafter referred to as the main body 30) that performs an image forming operation based on commands and data transmitted from an external device 43 such as a computer. In the main body 30 that performs the image forming operation, the surface of the photosensitive drum 31 that is an image carrier is uniformly charged by the charging roller 32, and then the exposure unit 33 applies laser light based on the image information to the surface of the photosensitive drum 31. To form an electrostatic latent image. Then, the developing device 34 develops the electrostatic latent image formed on the photosensitive drum 31 using a developer to form a developer image on the photosensitive drum 31. Then, the recording material 36 accommodated in the paper feeding cassette 35 is supplied into the main body 30 by the paper feeding roller 37, and the developer image on the photosensitive drum 31 is transferred to the recording material 36 by the transfer roller 38. Thereafter, the fixing device 39 fixes the developer image transferred to the recording material 36 to the recording material 36.

  The laser beam printer 47 has an engine controller 40 and a video controller 41 as control devices. These controllers 40 and 41 are connected by an interface 42 so as to be capable of two-way communication. The engine controller 40 controls the image forming operation of the main body 30. The video controller 41 is connected to the external device 43 through a general-purpose interface 44, expands image information transmitted from the external device 43 into bit data, and transmits the expanded bit data to the engine controller 40. Further, the main body 30 is provided with a power supply device 2, from which a high voltage generation unit 45 for an image forming operation, a driving force generation unit 46 including a motor, an exposure unit 33, an engine controller 40, and Power is supplied to the video controller 41. In recent years, a device such as the laser beam printer 47 has a function of transitioning to several power saving states (also referred to as energy saving states) for reducing power consumption in order to save power during standby when a printing operation is not performed. Is provided. As a method of shifting to this energy saving state, a method of reducing various loads in the apparatus as much as possible is adopted. For example, in an energy saving state, the engine controller 40 stops power supply from the power supply device 2 to the high voltage generation unit 45, the driving force generation unit 46, and the exposure unit 33 in order to reduce various loads in the apparatus. The control method is adopted. As another method, a method for improving the efficiency of the operation of the power supply device 2 itself is also employed. Below, the structure of the general power supply device 2 used for an image forming apparatus is demonstrated based on FIG. FIG. 9 shows an RCC power supply (self-excited ringing choke converter) as an example of the power supply device. In FIG. 9, the AC voltage supplied from the commercial AC power supply 1 is converted into a DC voltage by the primary filter 6, the diode bridge 7, and the primary electrolytic capacitor 8. The converted DC voltage is converted to a pulse voltage by the switching operation of the FET 10 and supplied to the primary winding of the transformer 9. The voltage induced in the secondary winding of the transformer 9 is rectified by the diode 12 and the electrolytic capacitor 13 to generate the DC voltage V1 and supply it to the load 3 on the secondary side. The load 3 corresponds to the high voltage generation unit 45, the driving force generation unit 46, the exposure unit 33, and the like in the above-described image forming apparatus. The control IC 11 that controls the switching operation drives the transformer 9 by controlling the switching operation of the FET 10 that outputs a desired DC voltage V1 by feedback of an output voltage (not shown). The drive voltage Vcc of the control IC 11 is a voltage obtained by rectifying the voltage induced in the auxiliary winding of the transformer 9 by the diode 14 and the electrolytic capacitor 15.

  Here, in the energy saving state described above, it is necessary to make the load 3 as small as possible and to make the operation of the power supply device 2 highly efficient. For example, Patent Document 1 proposes a technique for operating the power supply device 2 with high efficiency by causing the control IC 11 to intermittently drive the FET 10 (transformer 9) as a method for improving the operation efficiency of the power supply device.

JP 2002-252773 A

  However, when the power supply device is driven to intermittently oscillate as in Patent Document 1 to shift to an energy saving state, the following problems occur. When the power supply device is transitioning to the energy saving state, a steep and excessive primary voltage fluctuation such as a lightning surge may occur, and then the power supply device may malfunction if the energy saving state is released. is there. The malfunction phenomenon will be described with reference to FIGS.

  FIG. 10 shows main part voltage waveforms of the power supply device 2 of FIG. In FIG. 10, Vgs is the gate voltage of the FET 10, Vds is the drain voltage of the FET 10, Vh is the voltage of the primary electrolytic capacitor 8, and Vcc is the drive voltage of the control IC 11. In the energy saving state, since the power supply device 2 is driven intermittently, Vgs becomes High and the time for which the FET 10 is turned on becomes very short. In this state, when a lightning surge occurs, Vh suddenly becomes a high voltage. That is, the voltage supplied to the primary winding of the transformer 9 increases rapidly. Immediately after the occurrence of the lightning surge, Vgs becomes High, and at the timing when the FET 10 is turned on, a voltage proportional to the voltage supplied to the primary winding of the transformer 9 is generated in the auxiliary winding of the transformer 9, and the control IC 11 The drive voltage Vcc increases. Here, since the time when Vgs becomes High is very short, Vcc does not reach a high voltage as the protection circuit of the control IC 11 (for example, a protection circuit such as a shutdown latch) operates. On the other hand, since the load 3 is extremely small, the energy emission to the secondary side of the transformer 9 is very small. Therefore, Vh holds a high voltage. During the period in which the high voltage state is maintained, for example, a command for instructing printing is sent from the external device 43 to the image forming apparatus, and a power switch (for example, a soft switch) (not shown) is displayed by the user. ) And the like, it is necessary to supply power to various loads in the image forming apparatus. That is, the energy emission to the secondary side of the transformer 9 is increased and power is supplied to the load 3. Therefore, the time when Vgs becomes High becomes long, the influence of Vh holding the high voltage appears in Vcc, and Vcc becomes a high voltage that reaches the threshold voltage (shutdown latch voltage) of the protection circuit of the control IC 11. As described above, when the method of reducing the load 3 as much as possible in the energy saving state or the method of intermittent oscillation driving for high efficiency is used, the malfunction of the power supply device occurs when Vh maintains a high voltage.

  This malfunction is caused, for example, by stopping the power supply to the video controller 41 as well as the high voltage generation unit 45, the driving force generation unit 46, and the exposure unit 33, thereby reducing the power consumption of the apparatus during standby from 0.5W to When the power is reduced to about 1.0 W, the more the load 3 is reduced, the more the energy saving state of the image forming apparatus becomes.

  As a countermeasure, a configuration in which Zener diodes are connected to both ends of the electrolytic capacitor 15 is conceivable so that Vcc does not reach the shutdown latch voltage of the control IC 11. In general, since the Zener voltage of the Zener diode varies from element to element, both the AC voltage fluctuation in the commercial AC power supply 1 and the steep and excessive primary side voltage fluctuation such as lightning surge are supported. It is difficult to respond appropriately. As another countermeasure, a configuration in which a lightning surge is absorbed by a primary circuit can be considered. For example, an element such as an arrester that operates only against an abnormal overvoltage such as a lightning surge and absorbs the overvoltage is used. However, providing an arrester increases the size and cost of the device.

  The present invention is for solving the above-described problems, and is a small and inexpensive power supply device that has a steep and excessive voltage fluctuation such as a lightning surge in a power saving state where the load on the secondary side is small. An object is to avoid a malfunction of the power supply device when the power saving state is canceled after the occurrence.

  The power source of the present invention for solving the above problems is a power source capable of generating a DC voltage from an input AC voltage and supplying it to a load and transitioning to a power saving state when waiting for operation. A primary voltage fluctuation detecting means for detecting a voltage fluctuation on the primary side of the power supply; and a secondary load increasing means for increasing a load on the secondary side of the power supply, and in the power saving state, the primary voltage fluctuation detecting means. When the voltage fluctuation detecting means detects the voltage fluctuation on the primary side, the load is increased by the secondary load increasing means.

  Further, another power source of the present invention is a power source that generates a DC voltage from an input AC voltage and supplies it to a load, and is capable of transitioning to a power saving state when waiting for operation. Secondary load increasing means for increasing the load on the secondary side of the power supply, and when the state is shifted to the power saving state, the load is increased by the secondary load increasing means.

  In a power saving state where the load is small, it is possible to prevent the power supply device from malfunctioning even if a steep and excessive voltage fluctuation occurs.

It is a figure which shows the structural concept of the lightning surge countermeasure circuit in Example 1. FIG. It is a figure which shows the structure of the lightning surge countermeasure circuit in Example 1. FIG. It is a figure which shows the voltage waveform of the principal part of the lightning surge countermeasure circuit in Example 1. FIG. It is a figure which shows the structure of the lightning surge countermeasure circuit in Example 2. FIG. It is a figure which shows the control flowchart of the engine controller in Example 2. FIG. FIG. 6 is a diagram illustrating a configuration of a lightning surge countermeasure circuit according to a third embodiment. It is a figure which shows the structural concept of the lightning surge countermeasure circuit in Example 4. FIG. 1 is a diagram illustrating a configuration concept of an image forming apparatus. It is a figure which shows the conventional power supply device. It is a figure which shows the principal part voltage waveform of the conventional power supply device.

  Next, specific configurations of the present invention for solving the above-described problems will be described based on examples. In addition, the Example shown below is an example, Comprising: It is not the meaning which limits the technical scope of this invention only to them. Hereinafter, the configuration of the present invention will be described in detail with reference to examples.

  The configuration and operation of the first embodiment will be described below with reference to FIGS. 1, 2, and 3. In addition, about the structure and function same as said FIG. 9, FIG. 10, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  FIG. 1 shows a configuration of a power supply circuit in which measures are taken when an excessive voltage fluctuation such as a lightning surge occurs on the commercial AC power supply side (AC voltage input side) of the power supply. A feature of the circuit shown in FIG. 1 is that, when the device is in a predetermined power saving state (also referred to as an energy saving state), the occurrence of a voltage fluctuation on the primary side that is steep and excessive, such as a lightning surge, The change is detected by the fluctuation detection unit 5 and the secondary load increase unit 4 increases the load 3 for a predetermined time based on the detection result. The primary voltage fluctuation detection unit 5 indicates that the voltage Va generated in the secondary winding of the transformer 9 exceeds a predetermined value at the on-timing of the primary winding of the transformer 9 when the primary voltage Vh increases due to lightning surge. Detect and judge. As described above, in the method of reducing the load 3 as much as possible and the method of driving the power supply device 2 intermittently, the power supply device 2 may malfunction because the primary-side voltage Vh is maintained at a high voltage. Therefore, in this embodiment, the primary side voltage Vh is lowered. Note that the predetermined energy saving state in the present embodiment refers to, for example, not only the high voltage generation unit 45, the driving force generation unit 46, and the exposure unit 33 but also the video controller 41 in the image forming apparatus shown in FIG. In this state, the power supply is also turned off, and the apparatus is on standby with power saving. In this standby state, the power consumption of the image forming apparatus is in a state of being suppressed to about 0.5 W to 1.0 W, and the load 3 is reduced to the maximum in the image forming apparatus.

  Hereinafter, a detailed configuration of the present embodiment will be described with reference to FIG. The primary voltage fluctuation detection unit 5 in FIG. 1 includes resistors 16, 17, 18, 19, 20, 21, a capacitor 22, and a comparator 23. Further, the secondary load increasing unit 4 in FIG. 1 includes resistors 24, 25, 26 and a transistor 27. FIG. 3 shows voltage waveforms of main parts when the power supply device 2 (RCC power supply) of FIG. 1 is operating. In FIG. 3, Va is the voltage of the secondary winding of the transformer 9. The gate voltage Vgs (hereinafter referred to as Vgs) of the FET 10 as a switching element becomes High, and at the timing when the FET 10 is turned on, a negative potential corresponding to the winding number ratio of the transformer 9 with respect to the input voltage Vh on the primary side is Va. appear. By detecting the negative potential of Va by the primary voltage fluctuation detector 5, it is possible to detect the occurrence of an excessive voltage fluctuation such as a lightning surge. That is, immediately after the occurrence of a lightning surge, when Vgs becomes High and the voltage V− obtained by dividing Va by the resistors 16, 17, and 18 becomes lower than the preset reference voltage V + at the timing when the FET 10 is turned on. The output terminal of the comparator 23 is in an open collector state, and transmits a High signal to the secondary load increasing unit 4. Here, the reference voltage V + is set by dividing the DC voltage V1 by the resistors 19 and 20. In addition, the output terminal of the comparator 23 is a specification that becomes a high output in an open collector state when the reference voltage V +> V−, and a low output when the reference voltage V + <V−.

  Next, the secondary load increasing unit 4 turns on the transistor 27 in accordance with the High signal, thereby energizing the resistor 26 and increasing the load 3. Then, energy is released and Vh is lowered as much as Vh increases to the secondary side of the transformer 9. The time for Vh to drop is set by the time constant T determined by the resistors 16, 17, 18 and the capacitor 22, and the Vh corresponding to the increase caused by the lightning surge drops due to the FET 10 being repeatedly turned on several times. To go. When Vh drops, the reference voltage V + <V− is established, and a Low signal is sent to the secondary load increasing unit 4. The secondary load increasing unit 4 turns off the transistor 27 and increases the load 3. Stop operation. As described above, Vh can be lowered at the timing when Vgs immediately after the occurrence of excessive primary voltage fluctuation such as a lightning surge and the FET 10 is turned on. Thereby, after that, when the energy saving state is canceled, the malfunction of the power supply device 2 can be avoided. The value of the resistor 26 may be set to a value that sufficiently lowers Vh. Specifically, since the increased voltage generated by the lightning surge is about 100 V, the resistance value of the resistor 26 is set according to the increased voltage value, the winding number ratio of the transformer 9 (for example, 7: 2), etc. Set to about 100-300Ω. Further, the energization time of the resistor 26 for sufficiently lowering Vh may be set by appropriately selecting the time constant T determined by the resistors 16, 17, 18 and the capacitor 22. In this embodiment, the time constant T is set so that the energization time is several hundred μsec. Further, the operation of this embodiment performs an operation of temporarily increasing the load 3 when a lightning surge occurs, so that the energy saving state can be maintained in the low power consumption state.

  As described above, in this embodiment, in an energy saving state where the load is extremely small, a configuration in which a steep and excessive primary side voltage fluctuation such as a lightning surge is detected to increase the load is adopted. Thereby, even if the energy saving state is canceled after the occurrence of excessive voltage fluctuation on the primary side in the energy saving state, it is possible to avoid the malfunction of the power supply device, and further to maintain the energy saving state in the low power consumption state. .

  Next, the configuration and operation of the second embodiment will be described with reference to FIGS. 4, 5, and 6. In addition, about the structure and function same as said Example 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the present embodiment, the configuration of the secondary load increasing section 4 in the first embodiment is different. The configuration details of the power supply circuit of the present embodiment will be described with reference to FIG. In the present embodiment, the secondary load increasing section 4 of the first embodiment (FIG. 1) is a microcontroller 28 (hereinafter referred to as a CPU 28) that controls the operation of the image forming apparatus, which is a main part of the engine controller 40. ing. That is, the present embodiment is characterized in that a circuit for changing the clock oscillation frequency of the CPU 28 is provided to form the secondary load increasing unit 4. It is premised on a method of reducing the power consumption of the CPU 28 by lowering the oscillation frequency of the CPU 28 than in the standby state of the image forming operation or stopping the clock oscillation itself in the energy saving state. Hereinafter, control for executing both the secondary load increasing unit 4 and the increased load 3 by switching the operation of the CPU 28 using this method will be described based on the control flowchart of FIG. 5 is executed by the engine controller 40.

  First, the engine controller 40 controls the CPU 28 to turn off the power supply to each load of the image forming apparatus and lower the clock oscillation frequency of the CPU 28, thereby causing the image forming apparatus to transition to the energy saving state (S1). In this state, when a lightning surge occurs, the engine controller 40 determines whether or not the primary voltage fluctuation detection unit 5 has detected an excessive voltage fluctuation on the primary side (S2). When the primary voltage fluctuation detection unit 5 determines that an excessive voltage fluctuation on the primary side has been detected, a high signal is input to the input port PI of the CPU 28. Then, the CPU 28 recognizes the occurrence of excessive voltage fluctuation, determines that it is necessary to temporarily increase the load, and raises its own clock oscillation frequency. That is, the CPU 28 functions as the secondary load increasing unit 4 and the load 3 in the first embodiment (S3). Then, after the input voltage Vh on the primary side sufficiently drops and the time for absorbing the influence of the voltage fluctuation has elapsed, the image forming apparatus is again shifted to the energy saving state (S1). On the other hand, if the primary voltage fluctuation detection unit 5 does not detect an excessive voltage fluctuation on the primary side, the energy saving state is maintained unless a command to cancel the energy saving state is received (S4, S5). When the energy saving state cancel command is received, the image forming apparatus is shifted to the normal operation state (S6).

  In the control flowchart of FIG. 5, the method of reducing the clock oscillation frequency of the CPU 28 in the energy saving state has been described as an example. However, the same control can be performed even in an energy saving state in which the clock oscillation of the CPU 28 is stopped. Further, the example in which the primary voltage fluctuation detection unit 5 illustrated in FIG. 4 binarizes and outputs the detection result by the comparator 23 (output of High / Low) has been described. For example, as illustrated in FIG. In addition, the resistors 19 and 20 and the comparator 23 may be deleted from the primary voltage fluctuation detection unit 5 and the analog voltage itself may be input to the A / D port of the CPU 28 for processing.

  When the signal sent from the primary voltage fluctuation detection unit 5 is input to the input port PI of the CPU 28, the clock frequency of the CPU 28 is increased. When the clock oscillation is stopped, the clock oscillation operation is started. This increases the load. Further, the CPU 28 can finely variably set the time for increasing the load by changing the clock oscillation frequency only for the time corresponding to sufficiently lowering the primary side input voltage Vh.

  In the present embodiment, since the control is performed using the CPU 28, it is possible to perform the process of transitioning to the energy saving state again after the time when the input voltage Vh sufficiently drops has elapsed. Further, in the configuration using the A / D port of the CPU 28, not only the occurrence of an excessive voltage fluctuation such as a lightning surge can be detected, but also the degree of fluctuation can be detected as an analog level. Thus, according to the degree of voltage fluctuation, the CPU 28 can appropriately set the time for increasing the load by switching the clock frequency finely and variably. Thereby, the input voltage Vh resulting from the occurrence of voltage fluctuation can be reduced in a short time. Therefore, in addition to obtaining the same effect as the configuration described in the first embodiment, it is possible to optimize the time for increasing the load.

  As described above, according to this embodiment, when the energy saving state is canceled after an excessive voltage fluctuation such as a lightning surge occurs in the energy saving state where the load on the secondary side is extremely small, the power supply device Can be avoided and maintained in a power saving state.

  Next, the configuration and operation of the third embodiment will be described with reference to FIG. In addition, about the structure and function same as said Example 2, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  A detailed configuration of the power supply circuit of this embodiment will be described with reference to FIG. The feature of this embodiment is that resistors 24, 25, and 26 and a transistor 27 are further added to the CPU 28 as the secondary load increasing section 4 in FIG. 4 described in the second embodiment. This embodiment is effective when, for example, the load amount when the clock oscillation frequency of the CPU 28 is increased and the load is increased is not sufficient to decrease the fluctuation voltage Vh on the primary side in a short time. Specifically, resistors 24, 25, and 26 and a transistor 27 are connected to the output port PO of the CPU 28 to operate the circuit. That is, in addition to using itself as the secondary load increasing unit 4 and the load 3 described in the first embodiment, the CPU 28 transmits a high signal from the output port PO, turns on the transistor 27, and turns on the resistor 26. Increase the load. Thereby, in addition to obtaining the same effect as the configuration described in the first and second embodiments, the load amount and the time for increasing the load when increasing the load are set more appropriately, and the primary The voltage fluctuation Vh resulting from the excessive voltage fluctuation on the side can be reduced in a short time. The primary voltage fluctuation detection unit 5 shown in FIG. 6A is configured to perform processing by binarizing the detection result by the comparator 23. For example, as shown in FIG. The resistors 19, 20 and the comparator 23 may be deleted from the fluctuation detection unit 5, and the detection result of the analog voltage may be input to the A / D port of the CPU 28 for processing.

  As described above, according to this embodiment, when the energy saving state is canceled after an excessive voltage fluctuation such as a lightning surge occurs in the energy saving state where the load on the secondary side is extremely small, the power supply device Can be avoided, and the energy saving state can be maintained in the low power consumption state.

  Next, Example 4 will be described with reference to FIG. In addition, about the structure and function same as said Example 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The present embodiment has a simple configuration in which only the secondary load increasing section 4 is provided without providing the primary voltage fluctuation detecting section 5 in the first to third embodiments. The characteristic point of the present embodiment is that the secondary load increasing unit 4 constantly increases the load 3 in a predetermined energy saving state of the apparatus.

  Next, the detailed configuration of the secondary load increasing unit 4 in FIG. 7A will be described with reference to FIG. The secondary load increasing unit 4 includes a CPU 28, resistors 24, 25 and 26, and a transistor 27. The CPU 28 transmits a High signal from the output port PO to turn on the transistor 27 before performing the process of transitioning to a predetermined energy saving state. Thereby, the resistor 26 is energized and the load 3 is increased. When this configuration is used, the power consumption in a predetermined energy saving state is always increased, and although the effect of reducing the power consumption is small as compared with the first to third embodiments, an excessive voltage fluctuation such as a lightning surge is caused. It is possible to easily prevent malfunction of the power supply device 2 due to the occurrence of.

  As described above, according to this embodiment, when the energy saving state is canceled after an excessive voltage fluctuation such as a lightning surge occurs in the energy saving state where the load on the secondary side is extremely small, the power supply device Can be avoided.

DESCRIPTION OF SYMBOLS 1 Commercial AC power supply 2 Power supply device 3 Load 4 Secondary load increase part 5 Primary voltage fluctuation detection part 6 Primary filter 7 Diode bridge 8 Primary electrolytic capacitor 9 Transformer 10 FET
11 Control IC
12, 14 Diode 13, 15 Electrolytic capacitor

Claims (13)

A power supply that generates a DC voltage from an input AC voltage, supplies it to a load, and is capable of transitioning to a power saving state when waiting for operation,
Primary voltage fluctuation detecting means for detecting voltage fluctuation on the primary side of the power source;
A secondary load increasing means for increasing the load on the secondary side of the power source,
In the power saving state, when the primary voltage fluctuation detecting unit detects the voltage fluctuation on the primary side, the load is increased by the secondary load increasing unit. A power supply that generates a DC voltage from an input AC voltage, supplies it to a load, and is capable of transitioning to a power saving state when waiting for operation,
A secondary load increasing means for increasing the load on the secondary side of the power source,
When the power saving state is entered, the load is increased by the secondary load increasing means.   A transformer and control means for controlling the drive of the power source, and by driving a switching element on the primary side of the transformer by a signal from the control means, the voltage generated on the secondary side of the transformer The power supply according to claim 1, wherein the DC voltage is generated.   The power supply according to claim 3, wherein the control unit drives the switching element to intermittently oscillate in the power saving state.   The power source according to claim 3 or 4, wherein the primary voltage fluctuation detecting means detects a voltage fluctuation on a primary side of the power source based on a voltage generated on a secondary side of the transformer.   The image forming apparatus according to claim 1, wherein the secondary load increasing unit is a circuit that increases the load by controlling a connection state of a resistor.   2. The power supply according to claim 1, wherein the amount by which the secondary load increasing means increases the load is set to a value corresponding to a voltage fluctuation on a primary side of the power supply.   2. The power supply according to claim 1, wherein the time during which the secondary load increasing unit increases the load is set based on a detection result of voltage fluctuation on the primary side detected by the primary voltage fluctuation detecting unit. . An image forming apparatus including a power source that generates a DC voltage from an input AC voltage and supplies the DC voltage to a load, and is capable of transitioning to a power saving state when waiting for an image forming operation,
Primary voltage fluctuation detecting means for detecting voltage fluctuation on the primary side of the power source;
A secondary load increasing means for increasing the load on the secondary side of the power source,
When the image forming apparatus detects the voltage fluctuation on the primary side by the primary voltage fluctuation detecting unit in the power saving state, the image forming apparatus increases the load by the secondary load increasing unit. An image forming apparatus including a power source that generates a DC voltage from an input AC voltage and supplies the DC voltage to a load, and is capable of transitioning to a power saving state when waiting for an image forming operation,
Primary voltage fluctuation detecting means for detecting voltage fluctuation on the primary side of the power source;
A secondary load increasing means for increasing the load on the secondary side of the power source,
When the image forming apparatus transitions to the power saving state, the load is increased by the secondary load increasing means. A controller for controlling the operation of the image forming apparatus;
The image forming apparatus according to claim 9, wherein in the power saving state, an oscillation frequency of a clock for driving the controller is lower than that in a standby state of an image forming operation.   The image forming apparatus according to claim 11, wherein clock oscillation of the controller is stopped in the power saving state.   The image forming apparatus according to claim 11, wherein the secondary load increasing unit increases the load by increasing a clock oscillation frequency for driving the controller.

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