JP4568249B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device that supplies power to an electronic apparatus such as an image forming apparatus.

  In recent years, the number of image forming apparatuses that can operate in a power saving operation mode has increased. The power saving operation mode is an operation mode designed to reduce power consumption during standby. Normally, in the power saving operation mode, the image forming apparatus stops supplying power to a portion where power consumption is large while preparing to detect an external command input.

  The image forming apparatus shifts from the normal operation mode to the power saving operation mode when the time for waiting for a command becomes long. On the other hand, in order to return the image forming apparatus from the power saving operation mode to the normal operation mode, it is necessary to press a start key of the operation unit or input an image forming job from the outside.

  However, some users try to return the image forming apparatus to the normal operation mode by temporarily turning off the power switch of the image forming apparatus in the power saving operation mode and then turning on the power switch again. It was. At this time, if the period from when the power switch is turned off to when it is turned on again is short, the image forming apparatus may not detect that the power switch is turned off. The reason is that even after the power switch is turned off, power is continuously supplied into the image forming apparatus as long as the electric charge remaining in the smoothing capacitor is not lost. As a result, when the power switch is once turned off and then turned on, the operation mode of the image forming apparatus does not change at all, and the user may feel uncomfortable.

In view of this, in the prior art, there is a power supply circuit having a configuration in which the residual charge of the capacitor is discharged as thermal energy by a resistor in response to a power-off signal, thereby discharging the residual charge of the capacitor (for example, (See Patent Document 1).
Japanese Patent Laid-Open No. 10-322900

  However, when the method described in Patent Document 1 is used, it may take time to consume the residual charge of the capacitor. The reason is that the residual charge of the capacitor is only consumed by a single resistor.

  For this reason, if the interval until the power switch is turned on after the power switch is turned off is short, it is difficult to completely consume the charge of the smoothing capacitor during that time. As a result, as described above, when the power switch is once turned off and then turned on, the operation mode of the image forming apparatus may not change at all.

  An object of the present invention is to provide a power supply device capable of quickly consuming the charge of a smoothing capacitor in response to turning off of a main power supply.

  The power supply apparatus according to the present invention supplies power to the main apparatus. Examples of the main device include electronic devices such as an image forming apparatus.

  The power supply device includes a rectification unit, a power switch, a smoothing capacitor, a main power supply unit, a sub power supply unit, a switching unit, and a power failure detection unit. The rectification unit rectifies alternating current. The power switch is disposed between the rectifying unit and the commercial power source. The smoothing capacitor smoothes the direct current rectified in the rectifying unit. The main power supply unit has a first transformer whose primary side is connected to a smoothing capacitor. The sub power supply unit has a second transformer whose primary side is connected to a smoothing capacitor. The switching means switches on / off of the operation state of the main power supply unit according to the operation mode of the main device. Variations of the operation mode of the main apparatus include a normal operation mode and a power saving operation mode. The power failure detection unit detects that the power switch has been turned off by detecting an AC supply state from the commercial power source. An example of the power failure detection unit is a zero cross detection circuit.

  In the power supply apparatus having the above-described configuration, the switching unit switches the main power supply unit from off to on when the power failure detection unit detects the power switch off when the main power supply unit is off.

The switching means performs such switching in order to quickly discharge the electric charge stored in the smoothing capacitor. By turning on the main power supply unit while the power switch is off, the charge stored in the smoothing capacitor is quickly consumed by the main power supply unit.

  In consideration of energy loss in the transformer when supplying power to the power failure detection unit, the power failure detection unit is preferably connected to the primary side of the first transformer and the second transformer.

  It becomes possible to quickly consume the charge of the smoothing capacitor in response to turning off the main power supply.

  As shown in FIG. 1, the image forming apparatus 101 includes a document reading unit 102, a paper feeding unit 103, an image forming unit 104, and a paper discharge unit 140. The image forming apparatus 101 also includes a housing 2 that covers the document reading unit 102, the paper feeding unit 103, and the image forming unit 104. The housing 2 includes a front cover 1 that can be freely opened and closed.

  The configuration of the image forming apparatus 101 will be briefly described with reference to FIGS. 1 and 2. The document reading unit 102 is arranged on the upper part of the image forming apparatus 101. On the other hand, the sheet feeding unit 103 is disposed at the bottom of the image forming apparatus 101. The image forming unit 104 is disposed so as to be sandwiched between the document reading unit 102 and the paper feeding unit 103. The image forming unit 104 is configured to have a smaller horizontal cross section than the document reading unit 102 and the paper feeding unit 103. Therefore, a discharge space for discharging the sheet from the image forming unit 104 is generated so as to be surrounded by the document reading unit 102, the paper feeding unit 103, and the image forming unit 104. The paper discharge unit 140 is disposed in this discharge space.

  An operation unit 23 is disposed above the image forming apparatus 101. The operation unit 23 includes a touch panel, displays an operation state of the image forming apparatus 101, and accepts an input operation from a user.

  As shown in FIG. 2, the document reading unit 102 includes document tables 105A and 105B made of transparent glass. An automatic document feeder 106 is disposed above the document tables 105A and 105B. The automatic document feeder 106 includes a document tray 107 and discharges documents placed on the document tray 107 one by one onto the sheet discharge tray 108 via the document table 105B.

  A first scanning body 110, a second scanning body 111, an imaging lens 112, and a CCD sensor 113 are disposed below the document tables 105A and 105B. The first scanning body 110 includes an exposure lamp 114 and a first reflection mirror 115. The second scanning body 111 includes a second reflection mirror 116 and a third reflection mirror 117. The exposure lamp 114 irradiates the original on the original table 105A or the original table 105B with light. First reflection mirror 115, second reflection mirror 116, and third reflection mirror 117 guide reflected light from the document to CCD sensor 113. The imaging lens 112 forms an image of the reflected light from the document on the CCD sensor 113. The CCD sensor 113 photoelectrically converts the imaged light to generate image data.

  At the time of reading a document, the first scanning body 110 moves at a speed V in the sub-scanning direction indicated by an arrow X parallel to the document tables 105A and 105B. Further, the second scanning body 111 moves in the sub-scanning direction at a speed V / 2 in conjunction with the first scanning body 110.

  The paper feed unit 103 includes a paper feed cassette 120. The paper feed cassette 120 stores paper to be subjected to image forming processing. The paper feed cassette 120 is configured to be drawable from the front surface of the image forming apparatus 101.

  The image forming unit 104 includes a paper conveyance path 191, a reverse conveyance path 192, a photosensitive drum 125, a charger 126, a laser scanning unit (hereinafter simply referred to as LSU) 130, a developing device 127, a transfer device 128, a cleaning unit 129, A registration roller 124 and a fixing device 131 are provided.

  The paper transport path 191 is formed between the paper feed cassette 120 and the paper discharge roller 135. The reverse conveyance path 192 is connected to the paper conveyance path 191 and is used when a double-sided image is formed. The photosensitive drum 125 is disposed so as to contact the paper transport path 191. The photosensitive drum 125 rotates counterclockwise as indicated by an arrow A. The charger 126 charges the outer peripheral surface of the photosensitive drum 125 to a predetermined potential. The LSU 130 forms an electrostatic latent image based on image data by irradiating the outer peripheral surface of the photosensitive drum 125 charged to a predetermined potential with laser light. The developing device 127 visualizes the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 125 to form a toner image. The transfer device 128 transfers the toner image formed on the outer peripheral surface of the photosensitive drum 125 onto a sheet. The cleaning unit 129 collects the toner remaining on the outer peripheral surface of the photosensitive drum 125. The registration roller 124 is disposed upstream of the photosensitive drum 125 in the paper conveyance path 191 and sends out the paper between the photosensitive drum 125 and the transfer device 128 at a predetermined timing. The fixing device 131 is disposed downstream of the photosensitive drum 125 in the paper conveyance path 191 and includes a heating roller 132 and a pressure roller 133. The fixing device 131 fixes the toner image attached to the paper by the heating roller 132 and the pressure roller 133 on the paper.

  A transport roller 134 and a paper discharge roller 135 are disposed downstream of the fixing device 131 in the paper transport path 191. A paper discharge unit 140 is disposed at a position for receiving the paper discharged to the outside by the paper discharge roller 135.

  The paper discharge unit 140 includes a fixed paper discharge tray 136 and a movable paper discharge tray 141. The movable paper discharge tray 141 is configured to reciprocate between an upper position and a lower position. When the movable paper discharge tray 141 is positioned at the upper position, the paper is discharged onto the fixed paper discharge tray 136. On the other hand, when the movable paper discharge tray 141 is located at the lower position, the paper is discharged onto the movable paper discharge tray 141.

  As illustrated in FIG. 3, the image forming apparatus 101 includes a control unit 60. The control unit 60 is connected to the power supply unit 70. The power supply unit 70 corresponds to the power supply device of the present invention, and the configuration thereof will be described later.

  The control unit 60 includes a ROM 62, a RAM 63, a CPU 61, a LAN board 81, a FAX boat 82, and drivers 64-68. The ROM 62 stores a program necessary for the operation of the image forming apparatus 101. The RAM 63 is a volatile memory that temporarily stores image data of a read document. The CPU 61 controls the overall operation of the image forming apparatus 101 based on a program stored in the ROM 62. The LAN board 81 has a function for communicating with an external device such as a personal computer connected via the network 83. The FAX boat 82 has a function for communicating with an external device such as a facsimile machine connected via the public line 84.

  The driver 64 drives the document reading unit 102 based on a signal from the CPU 61. The driver 65 drives the paper feed unit 103 based on a signal from the CPU 61. The driver 66 drives the image forming unit 104 based on a signal from the CPU 61. The driver 67 operates the motor 142 based on a signal from the CPU 61 to raise or lower the movable paper discharge tray 141. The driver 68 notifies the CPU 61 of the contents of the input operation performed on the operation unit 23. Further, the driver 68 controls the display operation of the operation unit 23 based on a signal from the CPU 61.

  The image forming apparatus 101 operates in either the normal operation mode or the power saving operation mode. The image forming apparatus 101 exhibits a copier function, a printer function, and a FAX function in the normal operation mode. On the other hand, in the power saving operation mode, the image forming apparatus 101 waits until a copy job, a printer job, or a FAX job is input while minimizing power consumption.

  A schematic configuration of the power supply unit 70 will be described with reference to FIG. The power supply unit 70 includes a power switch 10 connected to a commercial power supply 80. The power switch 10 is connected to the rectifier circuit 12A. The rectifier circuit 12A rectifies the alternating current from the commercial power supply 80 to make it a direct current. The rectifier circuit 12A is connected to the smoothing capacitor 26. The smoothing capacitor 26 smoothes the direct current rectified in the rectifier circuit 12A.

  Further, the rectifier circuit 12 </ b> A is connected to the main power supply unit 14. The main power supply unit 14 is connected to the control unit 60 of the image forming apparatus 101. In the present embodiment, the control unit 60 corresponds to the main control unit of the present invention. A connection point 25 </ b> B connected to the sub power supply unit 16 is provided between the smoothing capacitor 26 and the main power supply unit 14. The sub power supply unit 16 is connected to the switching unit 20.

  On the other hand, a connection point 25A connected to the zero-cross detection circuit 18 is provided between the power switch 10 and the rectifier circuit 12A via the rectifier circuit 12B. The zero-cross detection circuit 18 detects that the power switch 10 is turned off by detecting the supply state of alternating current from the commercial power source 80. In the present embodiment, the zero cross detection circuit 18 corresponds to the power failure detection unit of the present invention.

  Next, each component of the power supply unit 70 will be described with reference to FIG. The main power supply unit 14 includes a transformer 27, an FET 29, a transistor 40, a phototransistor 30B, a light emitting diode 30A, and a control IC 24. The transformer 27 has a primary side connected to the smoothing capacitor 26 and a secondary side connected to the control unit 60. The FET 29 has its gate connected to the control IC 24 and is used to control the oscillation of the transformer 27. The transistor 40 has a collector connected to the control IC 24 and a base connected to the zero-cross detection circuit 18. The phototransistor 30B is configured to conduct by receiving light from the light emitting diode 30A. The light emitting diode 30A is connected to the power supply line and grounded via a Zener diode, and is configured to emit light when the potential at the connection point 25C exceeds a predetermined value. The control IC 24 controls the operation of the main power supply unit 14.

  The sub power supply unit 16 includes a transformer 33, an FET 31, a phototransistor 34B, and a control IC 28. The primary side of the transformer 33 is connected to the smoothing capacitor 26. The FET 31 has a gate connected to the control IC 28 and is used to control the oscillation of the transformer 33. The phototransistor 34B is configured to receive light from the light emitting diode 34A of the switching unit 20 and to conduct.

  The switching unit 20 switches on / off of the operation state of the main power supply unit according to the operation mode of the image forming apparatus. Specifically, the switching unit 20 turns on the operation state of the main power supply unit 14 when the image forming apparatus 101 is in the normal operation mode, and turns off the operation state of the main power supply unit 14 when in the power saving operation mode. The switching unit 20 includes a light emitting diode 32A, a light emitting diode 34A, a transistor 44, and a control IC 21. The light emitting diode 32A is connected to the power supply line and grounded via the transistor 44. The light emitting diode 34A is connected to a power supply line and grounded via a Zener diode, and is configured to emit light when the potential at the connection point 25D exceeds a predetermined value. The base of the transistor 44 is connected to the control IC 21 and is switched on / off in accordance with a signal from the control IC 21. In the present embodiment, the switching unit 20 and the control IC 24 constitute the switching means of the present invention.

  The control IC 21 switches on / off the transistor 44 based on a signal from the control unit 60. Specifically, the control IC 21 turns off the transistor 44 in the normal operation mode. When the transistor 44 is off, the operating state of the main power supply unit 14 is on. On the other hand, the control IC 21 turns on the transistor 44 in the power saving operation mode. When the transistor 44 is on, the light emitting diode 32A emits light and the phototransistor 32B becomes conductive. As a result, the operating state of the main power supply unit 14 is turned off, and the oscillation of the transformer 27 is stopped.

  The control IC 21 is connected to the sub power supply unit 16 and volatilely stores the operation state of the image forming apparatus 101. That is, the control IC 21 is configured to automatically reset when the power supply from the sub power supply unit 16 is lost. In the present embodiment, the control IC 21 corresponds to the operation state management unit of the present invention.

  The zero cross detection circuit 18 is connected to the primary side of the first transformer and the second transformer. The zero cross detection circuit 18 includes a capacitor 36 and a comparator 38. The capacitor 36 is configured so that the accumulated charge is discharged when a zero cross signal is received. The comparator 38 is arranged so that the potential of the capacitor 36 is input. The output of the comparator 38 is connected to the base of the transistor 40 via the signal line 42. The comparator 38 is configured to output a low level signal while detecting a zero cross signal, and to output a high level signal when no zero cross signal is detected.

  In the above configuration, when the zero cross signal is not detected in the power saving operation mode, a high level signal is output from the comparator 38 to the base of the transistor 40, and the transistor 40 is turned on. When the control IC 24 detects the conduction of the transistor 40, the control IC 24 restarts the oscillation of the transformer 27.

  As a result, the residual charge of the smoothing capacitor 26 is discharged in a short period. When the smoothing capacitor 26 runs out of charge, both the main power supply unit 14 and the sub power supply unit 16 stop operating. When power from the sub power supply unit 16 is not supplied, the control IC 21 of the switching unit 20 is reset.

  When the control IC 21 is reset, the operation mode setting contents of the image forming apparatus 101 stored in the control IC 21 disappear. That is, since the control IC 21 forgets that the image forming apparatus 101 is in the power saving operation mode, when the image forming apparatus 101 is activated next time, the setting of the operation mode of the image forming apparatus 101 returns to the normal operation mode. .

  Therefore, it is possible to reliably return the image forming apparatus 101 from the power saving operation mode to the normal operation mode also by a method of turning off the power switch 10 once and then turning it on.

  Finally, the description of the above-described embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1 is a perspective view showing an external appearance of an image forming apparatus. 1 is a diagram illustrating a schematic configuration inside an image forming apparatus. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus. It is a figure which shows schematic structure of a power supply part. It is a figure which shows the structure of a power supply part.

Explanation of symbols

10-Power switch 12A, 12B-Rectifier circuit 14-Main power supply unit 16-Sub power supply unit 70-Power supply unit 80-Commercial power supply

Claims (2)

A power supply device applied to a main device operable in a normal operation mode or a power saving operation mode,
A rectifier that rectifies alternating current;
A power switch disposed between the rectifying unit and a commercial power source;
A smoothing capacitor for smoothing the direct current rectified in the rectifying unit;
A main power supply unit having a first transformer having a primary side connected to the smoothing capacitor;
A sub power supply unit having a second transformer having a primary side connected to the smoothing capacitor;
Switching means for switching on / off the operation state of the main power supply unit according to the operation mode of the main device;
A power failure detection unit that detects that the power switch is turned off by detecting an AC supply state from the commercial power source;
With
The switching means switches the main power supply unit from off to on when the power failure detection unit detects the power switch off when the main power supply unit is off , and
The power supply apparatus according to claim 1, wherein the switching unit includes an operation state management unit that volatilely stores an operation state of the main apparatus.   The power supply device according to claim 1, wherein the power failure detection unit is connected to a primary side of the first transformer and the second transformer.

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