JP3466351B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, etc., which has a DC power supply device having an active filter and a regulator.

[0002]

2. Description of the Related Art FIG. 3 schematically shows an example of a conventional image forming apparatus.
Will be described. FIG. 3 is a schematic side view showing an example of a conventional image forming apparatus. In the image forming apparatus, when the original 2 is placed on the contact glass 1 provided above the original, the original size sensor 3 detects the presence or absence of the original 2 and the size of the original. When a copy start key (not shown) is pressed with the original 2 placed on the contact glass 1, the exposure lamp 4
The original is exposed by, and is read by the image sensor 9 composed of a CCD through the first mirror 5, the second mirror 6, the third mirror 7, and the lens assembly 8, and the image information is converted into an electric signal to form an image. It is processed. The laser diode 10 is controlled based on the image-processed data, and the laser beam writes an image on the photoconductor 15 through the cylinder lens 11, the polygon mirror 12 that rotates at a high speed and a constant speed, the lens 13, the writing mirror 14, and the like. .

Around the photosensitive member 15, a charging device 16, a developing device 17, a transfer belt 18, and a cleaning device 19 are provided. The photoconductor 15 has a cleaning device 19
Are uniformly charged to a predetermined high potential. When the charged photoconductor 15 is irradiated with the above laser light, the photoconductor 15
The upper surface potential changes according to the intensity of the irradiated light, and an electrostatic latent image is formed on the photoconductor 15. This electrostatic latent image becomes a toner image visualized by adsorbing toner by the developing device 17. On the other hand, the transfer paper 2 placed on the paper feed tray 20
1 is fed one by one, and the registration roller 22 transfers the transfer paper 2
1 is fed so as to overlap the toner image on the photoconductor 15. Further, the transfer paper 21 is conveyed by the transfer belt 18 to which a high voltage is applied, and the toner image is transferred at the contact portion between the transfer belt 18 and the photoconductor 15. The transfer paper 21 on which the toner image is transferred is further conveyed by the transfer belt 18,
The toner image is sent to the fixing device 23 and the toner image is fixed. The discharge of the transfer paper 21 that has been fixed to the outside of the image forming apparatus is detected by the paper discharge sensor 24.

In recent years, there has been a demand for power saving in such an image forming apparatus as well, especially in the case of an electrostatic image forming apparatus, since the heater in the fixing device 23 consumes a large amount of power.
The control has also been devised. However, the fixing device 23
Even when the heater of is not turned on, D
Due to the low efficiency of the C power supply, the supply of power to the control unit and the various sensors described above that are not needed during standby, and the leakage current, the image forming apparatus consumes more power than necessary. It may be possible to control the supply of power by using a relay or the like in order to reduce the useless power, but the low efficiency in the DC power supply cannot be eliminated.

Therefore, a power source required only for image formation and a power source required for non-image formation are independent in a DC power source,
There has also been proposed a power supply device which is composed of a regulator and which can stop the operation of the power supply necessary only during image formation in order to improve the efficiency of the power supply during non-image formation. Further, the image forming apparatus also tends to have an increased input current due to higher functionality and higher speed. Therefore, an active filter for reducing the harmonic current and improving the power factor is an effective means for a high-speed and high-performance image forming apparatus.

An example of a DC power supply device of an image forming apparatus equipped with an active filter as such a power factor correction circuit will be described with reference to FIG. FIG. 4 is a circuit diagram showing an example of a DC power supply device of a conventional image forming apparatus. The DC power source of the image forming apparatus is mainly required for driving the motors, clutches, solenoids, etc., and the power source V _AA for inputting a high-voltage power source, which is necessary for image formation of 24V or 38V, and is mainly required for non-image formation of 5V. Power supply V _CC for other control units and sensors, etc. +1
Other output power sources include 2V and -12V. Therefore, the power supply V _AA has a large output capacity and the power supply V _CC has a small output capacity. The drive system power supply V _AA has a large difference in output current between the standby state and the image forming state, and a large change in the output current even during the image forming state. Such a drive system power supply V
Compared to _AA , the output current of the other power supplies does not change so much, so when obtaining multiple outputs with one transformer, the output voltage of the drive system is often fed back for control. The other output is regulated to a constant voltage on the secondary side by another regulator such as a three-terminal regulator.

The active filter section is composed of an AC power supply 31.
Composed of a rectifying circuit 32 for rectifying the AC input from the device, a choke coil 33, a FET 34 which is a switching element, a diode 35, a smoothing capacitor 36 and a control circuit 37. The control circuit 37 causes the input current waveform to approach a sine wave. The duty of the pulse signal for turning on and off is controlled.

The transformer 38 has a primary winding 39 and a power source V.
_A secondary winding 40 for _AA and a secondary winding 41 for power supply V _CC are wound, and the output of the active filter is the transformer 38.
Will be input. The primary winding 39 of the transformer 38 is connected to a FET 42 which is a switching element, and a control circuit 43 which controls the duty of a drive pulse signal of the FET 42. The control circuit 43 keeps the level of the signal fed back from the output voltage of the power supply V _AA at a constant level.
The duty of the pulse signal for turning on / off the ET 42 is controlled, and thereby the output of the power supply V _AA is controlled to a constant voltage. At the output side of one secondary winding 40 of the transformer 38, a rectifying diode 44, a commutation diode 45,
An output terminal 48 for the power supply V _AA is connected through a forward converter including a choke coil 46 and a capacitor 47. On the output side of the other secondary winding 41 of the transformer 38, a rectifying diode 49, a smoothing capacitor 50, a regulator 51 and a capacitor 5
The output terminal 53 for the power supply V _CC is connected via the line 2. When the FET 42 is turned on and off, the regulator 50 also induces a voltage in the secondary winding 41 for the power supply V _CC , but since it does not reach a predetermined V _CC voltage value, it is for making this a constant voltage. Then, in this example, it is configured by a three-terminal regulator.

[0009]

However, in a power supply device equipped with a two-converter active filter as described above, the efficiency of the active filter is generally higher than that of a power supply not equipped with an active filter. The power supply becomes inefficient. Furthermore, the active filter is a very effective means for reducing the input current by improving the power factor and as a countermeasure for harmonic current, but the operation of the active filter is not stable at low output, noise is generated, There are problems such as a decrease in efficiency due to the active filter.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to output a power supply voltage in which a power factor is improved and a harmonic current is reduced during image formation. However, it is another object of the present invention to provide an image forming apparatus capable of obtaining a necessary minimum power supply voltage that does not deteriorate the efficiency during non-image formation.

[0011]

To achieve To achieve the object described above, the first means, in an image forming apparatus having a DC power supply device including an active filter and regulator, the DC power supply at the time of image formation Power supply voltage through the active filter and the regulator
Without the intervention of the output of said active filter, regulator
Perform the output of the power supply voltage through the chromatography data, in the standby state of the non-image-forming without passing through the active filter, is characterized by performing the output of the power supply voltage by a regulator.

The second means is characterized in that the active filter and the regulator in the first means can be on / off controlled by a control signal from the image forming apparatus.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the above-described conventional example and each embodiment, substantially the same components are given the same reference numerals, and the duplicate description will be omitted.

First, a first embodiment will be described with reference to FIG. FIG. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention.

In the first embodiment, the power source V
_AA and power supply V _CC are magnetically independent transformers 6
1 and 62, the transformer 61 has primary windings 63 and 2
The secondary winding 64 is wound, and the transformer 62 is wound with a primary winding 65 and a secondary winding 66. Like the above-mentioned conventional example, one terminal of the primary winding 63 of the transformer 61 for the power supply V _AA is composed of the choke coil 33, the FET 34 which is a switching element, the diode 35, the smoothing capacitor 36 and the control circuit 37. The active filter section is connected. Primary winding 6 of transformer 61
The other terminal of the FET 3 is connected to the FET 4 in the same manner as in the conventional example described above.
2 is connected to the drain terminal. Transformer 61 of 2
A rectifying diode 44, a commutation diode 45, and a choke coil 46 are provided on the side of the next winding 64 as in the above-described conventional example.
An output terminal 48 for the power supply V _AA is connected via a forward converter including a capacitor 47 and the like. Further, the control circuits 37 and 43 have ON / OFF control terminals 65 and 66, respectively, and control signals for instructing ON / OFF from a control unit (not shown) of the image forming apparatus are applied to these control terminals 65 and 66, This signal allows the control circuits 37 and 43 to be turned on and off.

On the other hand, one terminal of the primary winding 67 of the transformer 62 for the power supply V _CC is directly connected to the output side of the rectifier circuit 32 and rectified by the rectifier circuit 32 and the capacitor 68.
The smoothed voltage is used as the input voltage. The other terminal of the primary winding 67 of the transformer 62 is connected to the control circuit 71 via the drain terminal of the FET 69. This control circuit 71 is similar to the control circuit 43 described above in that the FET 69
It is for controlling the duty of the drive pulse signal. The secondary winding 72 of the transformer 62 is connected to the output terminal 53 for the power supply V _CC via a flyback converter including a rectifying diode 73 and a capacitor 74.

Therefore, at the time of image formation, the control terminal 6
A control signal for turning on the control circuits 37 and 43 is applied from 5, 66. When the control circuits 37 and 43 are turned on, the choke coil 33, the FET 34, and the diode 3 are turned on.
5, the active filter composed of the smoothing capacitor 36 and the control circuit 37 operates, and the regulator composed of the FET 42 and the control circuit 43 which control the output of the power supply V _{AA at} a constant voltage also operates. In this way, the active filter operates to eliminate the harmonic current problem and to supply the power supply voltage for the drive system with improved power factor to the output terminal 48.
Can be obtained from Further, the voltage from the rectifier circuit 32 is also directly applied to the primary winding 67 of the transformer 62 as a voltage smoothed by the capacitor 68, and the FET 69 and the control circuit 71 also operate to determine the output of the power supply V _CC. The voltage is controlled and a predetermined voltage is output from the secondary winding 72 to the output terminal 53.

On the other hand, during non-image formation such as during standby,
A control signal for turning off the control circuits 37 and 43 is applied from the control terminals 65 and 66. As a result, the control circuits 37 and 43 do not operate and the transformer 61 cannot operate, so that no output appears at the output terminal 48. However, on the transformer 62 side, as in the case of image formation, A
The AC input from the C power supply 31 is applied to the rectifier circuit 32 and the capacitor 68. As a result, the rectified and smoothed voltage is applied to the primary winding 67, and this voltage causes the FET
69 and the control circuit 71 also operate to supply a predetermined voltage to the secondary winding 7
2 to the output terminal 53 as the power supply V _CC . Power supply V
_Since the output current of _CC is small, the input current value and harmonic current are at a level that does not cause a problem without using an active filter.

Next, a second embodiment shown in FIG. 2 will be described. FIG. 2 is a circuit diagram of the power supply device according to the second embodiment.

In the second embodiment, the power source V
_CC is stepped down by a transformer 81 and an output is obtained by a three-terminal regulator. That is, the transformer 81 of the power source V _CC is provided with the transformer 81 in which the primary winding 82 is connected to the AC power source 31. The output side of the secondary winding 83 of the transformer 81 has a rectifying circuit 84 and a smoothing capacitor 8
5, it is connected to the output terminal 53 for the power supply V _CC through the three-terminal regulator 86 and the capacitor 87. As described above, the power supply V _CC may directly _lower the AC input voltage by the transformer 81 and obtain the output by the three-terminal regulator 86.

[0021]

[Effect of the Invention] As apparent from the above description, according to the invention 請 Motomeko 1, wherein the active filter and regulator can be operated to the minimum necessary in accordance with the operation of the image forming apparatus, When outputting the voltage required for image formation that requires measures against harmonic current, the active filter operates, so the power factor is improved, and measures against harmonic current can be eliminated. In addition, since the voltage is output without passing through an active filter during standby of non-image forming operation, instability of operation can be improved and a power supply voltage with less noise can be efficiently output, and image forming with low power consumption can be achieved. A device can be provided.

According to a second aspect of the present invention, the active filter and the regulator perform on / off control according to a control signal from an image forming apparatus, and the active filter is automatically activated during standby after image formation is completed. The power consumption during standby can be suppressed to the minimum necessary.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a power supply device according to a second embodiment of the present invention.

FIG. 3 is a schematic side view showing an example of a conventional image forming apparatus.

FIG. 4 is a circuit diagram showing an example of a power supply device in a conventional image forming apparatus.

[Explanation of symbols]

31 AC power supply 32 Rectifier circuit 33,46 Choke coil 34,42 FET 35,44,45,73 Diode 36,47,68,74,85,87 Capacitor 37,43,71 Control circuit 61,62,82 Transformer 63, 67,82 Primary winding 64,72,83 Secondary winding 65,66 ON / OFF control terminal 86 Regulator 53 Output terminal for power supply V _CC

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H02M 7/217 H02M 7/217 (72) Inventor Hiroto Oishi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-6-339268 (JP, A) JP-A-5-341692 (JP, A) JP-A-6-121523 (JP, A) JP-A-4-178171 (JP, A) Fukui Hira 2-333052 (JP, U) Furukai Hira 4-52213 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 21/00 370-540 G03G 21/14 B41J 29/00-29/70 H02J 3/00 H02M 3/00-3/44 H02M 7/00-7/40

Claims (2)

(57) [Claims] 1. A image forming apparatus having a DC power supply device including an active filter and regulator, the DC power supply, the active and the output of the power supply voltage through the active filter and the regulator during image formation ・
Output of the power supply voltage through the regulator without passing through the filter
The image forming apparatus is characterized in that a power source voltage is output by a regulator without performing the active filter during standby during non-image formation. 2. The image forming apparatus according to claim 1, wherein the active filter and the regulator can be on / off controlled by a control signal from the image forming apparatus.