JP2020068538A - Power supply device and image forming apparatus - Google Patents

Abstract

To suppress an abnormal noise caused in a transformer of a compact-sized, inexpensive, and versatilely-configured device.SOLUTION: A power supply device 15 comprises a transformer 21, a switching element 25, a switching control unit 26, and a current adjustment unit including a variable resistor 27 and a resistance control unit 28. The transformer 21 is configured by winding a primary coil 32 and a secondary coil 33 around a core part 30. The switching element 25, which is connected to the primary coil 32, switches on and off the power supply to the transformer 21 by switching on and off the current conduction of the element. The current adjustment unit is configured so as to be able to adjust an electric current flowing the primary coil 32 at the time of the current conduction of the switching element 25. The current adjustment unit controls an electric current so as to make the current having a prescribed first current value flow in the primary coil 32 in a normal mode, and controls an electric current so as to make the current having a second current value smaller than the first current value flow in the primary coil 32 in an energy-saving mode in which the electric current flows in the primary coil 32 intermittently.SELECTED DRAWING: Figure 2

Description

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

  The image forming apparatus includes a power supply device that supplies electric power to each unit. For example, a switching power supply circuit (power supply device) of Patent Document 1 includes a transformer having coils on a primary side and a secondary side, and a switch element connected to the coil on the primary side. The electric power generated on the primary side is transmitted to the secondary side via the transformer. The switching power supply circuit also includes an inductance switching unit that switches the inductance on the primary side of the transformer.

JP, 2005-50906, A

  In the power supply device described above, the inductance switching unit switches the connection destination of the switch element between a plurality of different positions in the coil on the primary side, and switches the inductance by switching the connection destination. In other words, the switching frequency of the switching operation is changed by switching the number of turns of the coil on the primary side. For example, when controlling the switching operation so that intermittent oscillation is performed in the standby mode (burst mode), the switching frequency is reduced to suppress abnormal noise such as noise of the transformer.

  However, if the connection destination of the switch element is switched between a plurality of positions in one transformer, the size of the transformer is increased and the cost is increased. If the number of turns is designed so that no abnormal noise is generated, the versatility of the transformer is reduced. When intermittent oscillation is performed in a burst mode such as a sleep mode, if the switching frequency is increased to be higher than the audible range, the efficiency of power supply to the secondary side will decrease.

  Therefore, in consideration of the above circumstances, an object of the present invention is to suppress an abnormal noise generated in a transformer with a configuration that is small, inexpensive, and highly versatile.

  A power supply device of the present invention includes a transformer configured by winding a coil around a core, and a switching element that is connected to the coil and switches between conduction and non-conduction to switch power supply and power supply stop to the transformer. A switching control unit that supplies a control signal to the switching element to control switching of the switching element; and a current adjusting unit that can adjust a current flowing through the coil when the switching element is in conduction, and In the normal mode, the current adjustment unit controls the coil so that a current having a predetermined first current value flows, while in the energy saving mode in which the current is intermittently supplied to the coil, the current adjustment unit causes the coil to have a first current value higher than the first current value. Is controlled so that a current having a smaller second current value flows.

  In the power supply device described above, the current adjustment unit is connected to the switching element, the variable resistor capable of changing the current flowing through the coil according to the resistance value of itself, and the resistance value of the variable resistor. And a resistance control unit for controlling the resistance control unit, wherein the resistance control unit sets the variable resistor to a predetermined first resistance value in the normal mode, while the resistance control unit sets the first variable resistor to the first resistance value in the energy saving mode. It is preferable to set the second resistance value larger than the resistance value.

  The power supply device further includes a vibration sensor that detects vibration of the transformer, and the resistance control unit, in the energy saving mode, the vibration width of the transformer detected by the vibration sensor is equal to or greater than a predetermined threshold value. At times, the variable resistor may be set to the second resistance value.

  An image forming apparatus of the present invention is equipped with the above-mentioned power supply device.

  According to the present invention, it is possible to suppress an abnormal noise generated in a transformer with a configuration that is small, inexpensive, and highly versatile.

It is a sectional view showing a printer concerning one embodiment of the present invention. It is a circuit diagram showing a power supply device of a printer according to an embodiment of the present invention. FIG. 3 is a perspective view showing a transformer in the power supply device of the printer according to the embodiment of the present invention. FIG. 3 is a perspective view showing a transformer in which a core part is disassembled in the power supply device of the printer according to the embodiment of the present invention. FIG. 3 is a perspective view showing a core portion of a transformer in the power supply device of the printer according to the embodiment of the present invention. FIG. 3 is a perspective view showing a primary coil and a secondary coil of a transformer in the power supply device of the printer according to the embodiment of the present invention. 6 is a graph showing a primary side current of a transformer, a control signal of a switching element, and a resistance value of a variable resistor in a power supply device for a printer according to an embodiment of the present invention.

  First, the overall configuration of the printer 1 (image forming apparatus) according to the embodiment of the present invention will be described with reference to FIG. Hereinafter, for convenience of explanation, the front side of the paper in FIG. 1 is referred to as the front side of the printer 1. Arrows L, R, U, and Lo that are appropriately attached to the respective drawings indicate the left side, the right side, the upper side, and the lower side of the printer 1, respectively.

  The printer 1 includes a printer body 2 having a substantially box shape, a paper feed cassette 3 for storing sheets is provided at the bottom of the printer body 2, and a paper discharge tray 4 is provided at the top of the printer body 2.

  An exposure device 5 composed of a laser scanning unit (LSU) is arranged below the paper discharge tray 4 in the upper part of the printer body 2. An image forming unit 6 is provided below the exposure device 5 in the printer body 2. The image forming unit 6 is rotatably provided with a photosensitive drum 7, which is an image carrier. Around the photosensitive drum 7, a charging device, a developing device connected to a toner container, a transfer roller, A cleaning device is arranged along the rotation direction of the photosensitive drum 7.

  Further, inside the printer body 2, a paper transport path 10 is provided. A sheet feeding unit 11 is provided in the vicinity of the sheet feeding cassette 3 at the upstream end of the transport path 10, and a transfer unit 12 including a photosensitive drum 7 and a transfer roller is provided in the middle stream portion of the transport path 10. A fixing device 13 is provided in the downstream portion of the transport path 10, and a paper discharge unit 14 is provided in the vicinity of the paper discharge tray 4 at the downstream end of the transport path 10.

  Further, inside the printer body 2, a power supply device 15 that supplies electric power to each unit of the printer 1 and a control device 16 that integrally controls each unit of the printer 1 are provided. The control device 16 includes a CPU and the like, and is connected to a storage device 17 such as a ROM and a RAM. The control device 16 is connected to each part of the printer 1, and controls each part connected to the control device 16 based on a control program and control data stored in the storage device 17.

  When the printer 1 operates during printing (image forming operation) or ready (preparation for image forming operation), the control device 16 sets the operation mode of the power supply device 15 to supply sufficient electric power to each part of the printer 1. Set to normal mode. On the other hand, when the printer 1 does not print, the control device 16 sets the operation mode of the power supply device 15 to an energy saving mode such as sleep for reducing power consumption.

  Next, the image forming operation of the printer 1 will be described. The printer 1 starts an image forming operation when image data is input from an external computer or the like and a print start instruction is given. In the image forming operation, first, the surface of the photoconductor drum 7 is charged by the charging device of the image forming unit 6, and then the laser beam from the exposure device 5 exposes the photoconductor drum 7 corresponding to the image data. Then, an electrostatic latent image is formed on the surface of the photosensitive drum 7. Next, the developing device of the image forming unit 6 develops this electrostatic latent image into a toner image using toner.

  On the other hand, among the papers stored in the paper feed cassette 3, the paper of the designated size and type is taken out by the paper feed unit 11 and is transported on the transport path 10. The sheet on the conveyance path 10 is conveyed to the transfer unit 12 at a predetermined timing, and the transfer unit 12 transfers the toner image on the photosensitive drum 7 to the sheet. The sheet on which the toner image is transferred is conveyed to the fixing device 13, and the fixing device 13 fixes the toner image on the sheet. The sheet on which the toner image is fixed is ejected from the sheet ejection unit 14 to the sheet ejection tray 4.

  Next, the configuration of the power supply device 15 will be described with reference to FIG. As shown in FIG. 2, the power supply device 15 is connected to the AC power supply 20, and includes a transformer 21, a primary rectifying circuit 22, an output terminal 23, a smoothing circuit 24, a switching element 25, and a switching control unit 26. A variable resistor 27, a resistance control unit 28, and a vibration sensor 29. The variable resistor 27 and the resistance control unit 28 function as a current adjustment unit that adjusts the current flowing through the primary coil 32 of the transformer 21.

  The transformer 21 is a transformer that receives AC current power from the AC power supply 20, converts the voltage of this power using electromagnetic induction, and outputs the converted power. The transformer 21, for example, as shown in FIGS. 3 to 6, includes a core portion 30, a bobbin portion 31, a primary coil 32, and a secondary coil 33.

  As shown in FIGS. 3 to 5, for example, the core portion 30 is configured by combining a pair of EER type cores 30 a formed in an E shape in plan view. Each EER type core 30a has a middle leg 30b (core) and outer legs 30c on both sides of the middle leg 30b. The core portion 30 is formed in a rectangular frame shape that is long in the axial direction (for example, the horizontal direction) with the middle leg 30b around which the primary coil 32 and the secondary coil 33 are wound as an axis.

  The bobbin portion 31 is formed into a cylindrical shape by combining, for example, a cylindrical primary side bobbin 31a and a cylindrical secondary side bobbin 31b, and is fitted to the middle leg 30b of the core portion 30 as shown in FIG. (Inserted). Flange 31c is formed at both ends of the bobbin portion 31 in the axial direction, and the flange 31c is fitted between the middle leg 30b and the outer leg 30c of the core portion 30 so that the bobbin portion 31 is attached to the core portion 30. Be locked.

  The primary coil 32 is wound along the outer peripheral surface of the primary side bobbin 31a, and the secondary coil 33 is wound along the outer peripheral surface of the secondary side bobbin 31b. That is, the primary coil 32 and the secondary coil 33 are wound around the core portion 30 (middle leg 30b) via the bobbin portion 31. A tape, a sheet, or the like may be wound around the outer peripheral surfaces of the wound primary coil 32 and secondary coil 33 for protection and insulation. The primary side bobbin 31a and the secondary side bobbin 31b may include input terminals and output terminals that electrically connect the primary coil 32 and the secondary coil 33, respectively. In another embodiment, the primary coil 32 and the secondary coil 33 may be directly wound around the core portion 30 (middle leg 30b).

  The primary rectifier circuit 22 is provided between the AC power supply 20 and the transformer 21 on the primary side of the transformer 21, and rectifies the AC current of the power output from the AC power supply 20 to the transformer 21. The primary rectifier circuit 22 is configured by, for example, a bridge type rectifier circuit in which four diodes are combined, and is connected to the primary coil 32 of the transformer 21.

  The output terminal 23 is provided on the secondary side of the transformer 21, is connected to each unit of the printer 1, and outputs the electric power transformed by the transformer 21 to each unit of the printer 1. The output terminal 23 is connected to the output end of the secondary coil 33. The end of the secondary coil 33 on the input side may be grounded.

  The smoothing circuit 24 is provided on the secondary side of the transformer 21 between the transformer 21 and the output terminal 23, and smoothes the current of the power output from the transformer 21 and outputs the smoothed current to the output terminal 23. The smoothing circuit 24 is composed of, for example, a smoothing capacitor, and is connected between the output side end of the secondary coil 33 and the input side end of the secondary coil 33.

  The switching element 25 is provided on the primary side of the transformer 21, and switches between conduction and cancellation of conduction in accordance with a control signal from the switching control unit 26, thereby switching between power supply and power supply stoppage from the AC power supply 20 to the transformer 21. . The switching element 25 is provided, for example, between the primary rectifier circuit 22 and the primary coil 32 of the transformer 21, and when the control signal is on, the primary rectifier circuit 22 and the primary coil 32 are electrically connected to each other to supply power. Become. On the other hand, when the control signal is off, the switching element 25 releases the electrical connection between the primary rectifier circuit 22 and the primary coil 32 and is in the state of stopping the power supply.

  The switching control unit 26 includes a CPU, an IC, and the like, and operates by receiving power supply from another DC power supply. The switching control unit 26 outputs an ON or OFF control signal to the switching element 25 to control the power supply and the power supply stop of the transformer 21. The switching control unit 26 controls the switching element 25 by feedback control based on the secondary voltage so that the voltage of the power output from the output terminal 23 (secondary voltage) is maintained constant on the secondary side. Determine the signal.

  For example, the switching control unit 26 outputs a control signal of ON to the switching element 25 when the secondary side voltage becomes lower than a predetermined lower limit voltage. When outputting the ON control signal to the switching element 25, the switching control unit 26 performs continuous oscillation to output a control signal that is continuously turned on and off when the power supply device 15 operates in the normal mode. . On the other hand, when the power supply device 15 operates in the energy saving mode, the switching control unit 26 performs burst oscillation that intermittently outputs a control signal that is turned on every predetermined period, and intermittently supplies a current to the primary coil 32. The switching control unit 26 may input a signal indicating the operation mode of the power supply device 15 from the control device 16.

  The variable resistor 27 has one end connected to the switching element 25 via the switching control unit 26, and changes the resistance value of the variable resistor 27 with respect to the current (primary-side current) flowing through the primary coil 32 when the switching element 25 is conducting. Fluctuate according to. The other end of the variable resistor 27 may be grounded. The variable resistor 27 is composed of, for example, a digital potentiometer or the like, and changes its own resistance value to be the resistance value of the input signal in accordance with the input signal indicating the resistance value. For example, as shown in FIG. 7, the primary side current increases as the resistance value of the variable resistor 27 decreases, while the primary side current decreases as the resistance value of the variable resistor 27 increases. By reducing the primary-side current, the amount of current flowing through the secondary coil 33 decreases in one switching operation. Even if the primary side current is reduced, it does not affect the control signal of the switching element 25.

  The resistance control unit 28 is composed of a CPU, an IC and the like, and operates by receiving power supply from another DC power supply. The resistance control unit 28 is connected to the variable resistor 27, determines a resistance value set in the variable resistor 27, and outputs an input signal indicating the resistance value to the variable resistor 27.

  For example, the resistance control unit 28 sets the variable resistor 27 to a predetermined first resistance value (for example, 160 KΩ) in the normal mode, while setting the variable resistor 27 to be larger than the first resistance value in the energy saving mode. 2 resistance value (for example, 220 KΩ) is set. This reduces the primary-side current on the order of tens of mA (for example, from 50 mA to 20 mA). The difference between the first resistance value and the second resistance value may be several tens of kΩ, and the reduction of the primary side current due to this may be several tens mA. If the primary-side current decreases too much, the secondary-side voltage may drop when the power (current) output from the output terminal 23 is consumed on the secondary side. Therefore, the resistance control unit 28 The decrease of the primary side current is adjusted so that such a drop of the secondary side voltage does not occur. The resistance control unit 28 may input a signal indicating the operation mode of the power supply device 15 from the control device 16.

  Further, the resistance control unit 28 is connected to the vibration sensor 29, inputs a detection signal indicating the vibration width (amplitude) of the transformer 21 from the vibration sensor 29, and sets the variable resistor 27 in accordance with the detection signal. Determine the resistance value. For example, in the energy saving mode, the resistance control unit 28 sets the variable resistor 27 to the second resistance value when the amplitude of the transformer 21 exceeds a predetermined threshold value (for example, 100V to 220V).

  The vibration sensor 29 is a sensor that detects a physical vibration of the transformer 21, and is configured of, for example, a piezoelectric element that can detect a minute amplitude, and is attached to the transformer 21. The vibration sensor 29 is arranged, for example, in the center of the transformer 21 in the axial direction and in the center of the height direction (for example, the vertical direction).

  According to the present embodiment, as described above, the power supply device 15 of the printer 1 (image forming apparatus) includes the transformer 21, the switching element 25, the switching control unit 26, the variable resistor 27, and the resistance control unit 28 ( Current adjusting unit). The transformer 21 is configured by winding the primary coil 32 (coil) and the secondary coil 33 around the middle leg 30b (core) of the core portion 30. The switching element 25 is connected to the primary coil 32 and switches between conduction and cancellation of conduction to switch between power supply and power supply stoppage to the transformer 21. The switching control unit 26 supplies a control signal to the switching element 25 to control switching of the switching element 25. The current adjusting unit is configured to adjust the current flowing through the primary coil 32 when the switching element 25 is conducting. In the normal mode, the current adjustment unit controls the primary coil 32 so that a current having a predetermined first current value flows, while in the energy-saving mode in which the current is intermittently passed through the primary coil 32, the first current flows through the primary coil 32. The control is performed so that a current having a second current value smaller than the value flows.

  An abnormal noise such as the sound of the transformer 21 occurs due to the resonance (magnetostriction) between the switching operation frequency and the core portion 30 of the transformer 21, and the distortion is also affected by the amount of current flowing through the transformer 21. According to the present embodiment, in the energy saving mode, a small current is caused to flow through the primary coil 32 to reduce the amount of current flowing through the secondary coil 33, thereby suppressing abnormal noise such as noise generated in the transformer 21. it can. At this time, since it is not necessary to change the number of windings of the transformer 21, it is not necessary to increase the size of the transformer 21, and the cost of the transformer 21 can be suppressed. Further, it is not necessary to design the number of windings of the transformer 21 so that no abnormal noise is generated, and the transformer 21 having high versatility can be applied. In the energy saving mode, since the electric power used in each part of the printer 1 is small, when the magnitude of the current flowing through the secondary coil 33 is reduced, the number of times the current is passed through the secondary coil 33 is increased, that is, By increasing the frequency, the value of the output voltage is maintained so that the voltage drop of the output voltage does not occur.

  For example, the current adjustment unit is connected to the switching element 25 and is capable of changing the current flowing through the primary coil 32 according to the resistance value of the variable resistor 27, and a resistor for controlling the resistance value of the variable resistor 27. And a control unit 28. The resistance control unit 28 sets the variable resistor 27 to a predetermined first resistance value in the normal mode, while setting the variable resistor 27 to a second resistance value larger than the first resistance value in the energy saving mode.

  With this, the current flowing through the primary coil 32 can be adjusted by a simple configuration in which the resistance value of the variable resistor 27 is controlled, and abnormal noise such as noise of the transformer 21 can be suppressed.

  Further, the power supply device 15 further includes a vibration sensor 29 that detects the vibration of the transformer 21. In the energy saving mode, the resistance control unit 28 sets the variable resistor 27 to the second resistance value when the vibration width of the transformer 21 detected by the vibration sensor 29 becomes equal to or larger than a predetermined threshold value.

  As a result, the resistance value of the variable resistor 27 is changed according to the vibration width of the transformer 21, which is related to abnormal noise such as the noise of the transformer 21, so that the current amount of the transformer 21 can be controlled more accurately. You can

  In the present embodiment, the case where the configuration of the present invention is applied to the monochrome printer 1 has been described. However, in another different embodiment, the present invention is applied to another image forming apparatus such as a color printer, a copying machine, a facsimile, and a multifunction peripheral. It is also possible to apply the configuration of.

1 Printer (image forming device)
6 image forming unit 15 power supply device 16 control device 20 AC power supply 21 transformer 22 primary rectifying circuit 23 output terminal 24 smoothing circuit 25 switching element 26 switching control unit 27 variable resistor (current adjusting unit)
28 Resistance control section (current adjusting section)
29 Vibration sensor 30 Core part 32 Primary coil 33 Secondary coil

Claims (4)

A transformer constructed by winding a coil around a core,
A switching element that is connected to the coil and that switches between conduction and cancellation of conduction to switch power supply and stop of power supply to the transformer,
A switching control unit that supplies a control signal to the switching element to control switching of the switching element,
A current adjusting unit capable of adjusting the current flowing through the coil when the switching element is conducting,
In the normal mode, the current adjusting unit controls the coil so that a current having a predetermined first current value flows, while in the energy saving mode in which the current is intermittently applied to the coil, the first current value is applied to the coil. A power supply device characterized by controlling so that a current having a second current value smaller than that of the current flows. The current adjusting unit is connected to the switching element, a variable resistor capable of changing the current flowing through the coil according to its resistance value,
A resistance control unit for controlling the resistance value of the variable resistor,
The resistance control unit sets the variable resistor to a predetermined first resistance value in the normal mode, and sets the variable resistor to a second resistance value larger than the first resistance value in the energy saving mode. The power supply device according to claim 1, wherein the power supply device is set. Further comprising a vibration sensor for detecting the vibration of the transformer,
The resistance control unit sets the variable resistor to the second resistance value when the vibration width of the transformer detected by the vibration sensor becomes equal to or larger than a predetermined threshold in the energy saving mode. The power supply device according to claim 2.   An image forming apparatus comprising the power supply device according to claim 1.

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