JPH0993910A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which has enhanced a power efficiency and reducing a noise. SOLUTION: A power supply means is composed of a switching regulator 40 to supply DC power to a driver 44, a control means 42 for controlling this switching regulator 40, an operating means 46 and a sensor means 48. The control means 42 detects a voltage of the power induced on a secondary coil of the switching regulator 40 and controls selection of either one of the full-wave rectifying or voltage-doubler rectifying the AC power supply. With this control, when an output current of the switching regulator 40 is higher than the constant value, an active filter turns on and when an output current is lower than the constant value, the active filter turns off. Thereby, a harmonic current and an input current are lowered and higher efficiency and low noise can be realized.

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, for example, an image forming apparatus such as a copying machine or a laser printer.

[0002]

2. Description of the Related Art Conventionally, a switching regulator has been widely used as a DC power supply device for driving an image forming apparatus including an OA equipment if roughly classified, and a copying machine or a laser printer as a specific example. The reason is that a switching regulator including a DC-DC converter has characteristics such as small size, light weight, low cost, high efficiency, excellent constant voltage characteristic, and the like, and is excellent in compatibility with the above device. Further, the development of these OA devices is remarkable, and the consumption capacity of the DC power supply tends to increase remarkably as the device becomes multifunctional and faster.

Under such a tendency, a switching regulator as a rectifying / smoothing circuit for rectifying and smoothing an AC input power source from a commercial power source to supply DC power generally uses a capacitor input type smoothing circuit.

For this reason, the current waveform of the AC input power source is distorted in a pulse shape, and the harmonic current component remarkably increases. This harmonic is converted into power supply voltage distortion by the impedance of the commercial power supply line. If peripheral equipment or power distribution equipment is connected to the commercial power supply line of the same system including this power supply voltage distortion, it may cause abnormal noise or burnout in the connected peripheral equipment. Therefore, the improvement of the switching power supply that generates a lot of harmonic current is required by the International Electrotechnical Commission (I
EC) has become a major issue and its standardization is planned. As one method of reducing this harmonic current component,
Some use active filters.

The structure of a general switching regulator equipped with an active filter will be described with reference to FIG. The switching regulator of this conventional example is configured to include a two-converter switching power supply including an active filter circuit and a DC-DC converter.

The switching power supply with a built-in active filter of the two-converter type shown in FIG. 7 includes a step-up converter type active filter, a control circuit 31 for the active filter, a transformer T, and an FET 2 for switching the transformer T. , Its fet
It is composed of a control circuit 32 for controlling ON / OFF of 2, a diode D3 for rectifying the output on the secondary side, a smoothing capacitor C3 for smoothing the output on the secondary side, and the like. The step-up converter type active filter of this configuration unit has a rectifier circuit D1 for rectifying an AC input power source,
The configuration includes a choke coil L, a switching element FET1, a diode D2, and a smoothing capacitor C1.

In the conventional image forming apparatus having such a switching power supply, the active filter is turned on / off depending on the operation mode of the apparatus. A boost chopper method is generally used for this active filter. A switching power supply equipped with an active filter can significantly improve the power factor as compared with a capacitor input type switching power supply. Further, the problem of generation of harmonic current is solved.

[0008]

However, in the case of the conventional example of the image forming apparatus, the active filter is set to OF.
When F, the power supply voltage on the primary side of the DC-DC converter decreases. The occurrence of the power supply voltage drop causes various problems in the image forming apparatus. This mechanism will be described below.

In the 2-converter type regulator shown in FIG. 7, when the switching operation of the active filter is stopped, the choke coil L does not function as a choke coil, and a DC-type capacitor input method is used.
It is similar to a switching regulator using a DC converter circuit. However, when the operation of the active filter is stopped, the voltage on the primary side is not boosted and the voltage applied to the transformer T decreases. Therefore, the output voltage is reduced.

Since the power supply with the active filter of the two-converter system performs the switching operation at high speed even in the active filter portion, noise is generated more than the power supply without the active filter circuit. Further, there is a drawback that the efficiency as a power source is lowered due to the loss in the active filter circuit section.

In the conventional image forming apparatus using the switching regulator equipped with the active filter described above, the primary side voltage drop of the switching regulator is likely to cause insufficient boosting of the secondary side output voltage. In addition, problems such as an increase in unnecessary noise and a reduction in power supply efficiency are also factors. It is known that such an adverse effect is likely to occur particularly in a multi-function peripheral that consumes a large amount of current in the standby state.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which has improved power consumption efficiency and reduced noise.

[0013]

In order to achieve the above object, an image forming apparatus of the present invention comprises a bridge rectifying means for full-wave rectifying an AC power supply, a voltage doubling rectifying means for doubling the voltage, a bridge rectifying means, and a voltage doubling. A switching means for selecting one of the voltage rectifying means, an active filter for boosting the voltage rectified by the selected rectifying means, a switching element for switching the rectified current, and a primary for the switched current. An image forming apparatus equipped with a switching regulator, which comprises a transformer that outputs electric power induced in a secondary winding by flowing in a winding.
The output voltage detection means detects the voltage of the electric power induced in the secondary winding, the switch control means that controls the switching of the switch means, and the filter control means that controls the operation of the active filter. The operation of the switch control means and the filter control means is controlled according to the magnitude of the voltage detected by the detection means.

Further, the above-mentioned image forming apparatus has a coupling means for feeding back the detection signal of the output voltage detecting means to the primary winding side of the transformer by means of an electrically insulated signal, and the fed back signal is provided. The operation may be controlled based on Further, a human body detection unit for detecting whether or not an operator approaches the image forming apparatus is provided, and an output signal of the human body detection unit is connected to the switch control unit, and the operation may be controlled by including the output signal.

The switch control means performs the image forming operation of the image forming apparatus after the output of the active filter is stabilized after turning on the active filter, and the image forming apparatus further operates the image forming apparatus. It is preferable to have operation means for inputting and control the operation including an operation signal from the operation means.

[0016]

Therefore, according to the image forming apparatus of the present invention,
Switching regulator Detects the voltage of the power induced in the secondary winding and controls the switching of the switching means for selecting one of the bridge rectifying means for full-wave rectifying the AC power supply and the double voltage rectifying means for double voltage rectification. Control the operation of the active filter. This control turns on the active filter when the output current of the switching regulator reaches a predetermined value due to the magnitude of the output voltage. Therefore, the harmonic current and the input current can be reduced.

[0017]

Embodiments of the image forming apparatus according to the present invention will now be described in detail with reference to the accompanying drawings. 1 to 6, there is shown an embodiment of the image forming apparatus of the present invention.
1 and 2 show the first embodiment, and FIGS. 3 to 6 show the second embodiment. 1 is a circuit configuration example of a switching regulator applied to the first embodiment, and FIG. 2 is an overall configuration sectional view of an image forming apparatus to which the power supply circuit of FIG. 1 is applied. FIG. 3 is a circuit diagram showing a configuration example of a switching regulator applied to the second embodiment. FIG.
FIG. 4 is a circuit configuration block diagram of a peripheral part including the switching regulator of FIG. 3. 5 and 6 are flowcharts showing an operation example of the second embodiment, respectively.

(First Embodiment) First, the structure and operation of a switching regulator applied to the image forming apparatus of the first embodiment will be described with reference to FIG. The main circuit configuration of the switching regulator 30 shown in FIG. 1 differs from that of FIG. 7 in that a circuit section for controlling the operation state of the regulation operation is added.

A switching regulator 30 applied to this embodiment detects a switch SW for switching a bridge rectification circuit and a voltage doubler rectification circuit in a rectification section of an input and an output current Io on a secondary side. To turn on / off the detection resistor Rs, the operation amplifier circuit 33 that receives the voltage across the detection resistor Rs as an input, the photocoupler PC for insulating the primary side and the secondary side, and the photocoupler PC. The transistor Tr1 and the transistor Tr2 for supplying power to the active filter circuit.

Each of the above-mentioned components is connected to a peripheral portion sandwiching a transformer T for coupling the primary and secondary. The other parts are compared with the switching regulator 60 of the conventional example in FIG. 7, and the connection of the terminals of the FET 2 and the acquisition source of the power supply to the control circuit 32 are changed.

The switching regulator 30 of this embodiment
The other parts are a step-up converter type active filter, an active filter control circuit 31, a transformer T and a FET 2 for switching the transformer T, and an ON / OF of the FET 2.
The control circuit 32 controls F, the diode D3 that rectifies the output on the secondary side, the smoothing capacitor C3 that smoothes the output on the secondary side, and the like. The step-up converter type active filter of this configuration unit is configured to include a choke coil L, a switching element FET1, a diode D2, and a smoothing capacitor C1 after a rectifying circuit D1 that rectifies an AC input power source.

When the image forming apparatus is in a standby state or the like, the output current Io on the secondary side of the switching regulator 30 is small, and the harmonic current is also small, the switching regulator 30 having the above-described structure is applied. Is
The voltage across the detection resistor Rs is low. Therefore, no power is supplied to the control circuit 31 of the active filter, so that the active filter circuit is stopped.

When the output current Io is small, the harmonic current also becomes small, voltage distortion or the like does not substantially occur, the active circuit is stopped, and the efficiency of the power supply is improved. At this time, since the input voltage is not boosted, the changeover switch SW of the rectifier circuit is brought into the conducting state and the voltage doubler rectification is performed.

When the output current Io of the switching regulator 30 increases and exceeds a certain current value when the image forming apparatus is forming an image or the like, the voltage across the detection resistor Rs rises. Therefore, the diode of the photocoupler PC is turned on, power is supplied to the control circuit 31 of the active filter, and the active filter circuit operates.

An example of the structure of an image forming apparatus to which the above switching regulator 30 is applied will be described with reference to FIG. When the document 2 is placed on the contact glass 1, the document size sensor 3 can detect the presence or absence of the document 2 and the document size. When a copy start key (not shown) is pressed, the original 2 is exposed by the exposure lamp 4, and C is passed through the first mirror 5, the second mirror 6, the third mirror 7, and the lens 8.
It is read by the CD image sensor 9, converted into an electric signal, and subjected to image processing.

The laser diode 10 is controlled based on the image-processed data, and the laser light is emitted from the cylinder lens 1.
1. Polygon mirror 12, lens 1 that rotates at a constant speed at high speed
3. Write an image on the photoconductor 15 via 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
After being cleaned by, the charging device 16 is uniformly charged to a predetermined high potential. When the charged photoconductor 15 is irradiated with the above laser beam, the surface potential on the photoconductor 15 changes according to the intensity of the irradiated light, and an electrostatic latent image is formed on the photoconductor 15. This electrostatic latent image is developed by the developing device 17
Thus, the toner is adsorbed to form a visualized toner image.

On the other hand, the transfer papers 21 stacked on the paper feed tray 20 are fed one by one, and the registration rollers 22 feed the transfer papers 21 so as to overlap the toner images on the photoconductor 15. Further, the transfer paper is the transfer belt 18 to which a high voltage is applied.
The toner image is transferred at the contact portion between the transfer belt 18 and the photoconductor 15.

The transfer paper on which the toner image has been transferred is further conveyed by the transfer belt 18 and sent to the fixing device 23 to fix the toner image. The transfer paper 21 that has been fixed is detected by the paper discharge sensor 24 that the transfer paper 21 has been discharged to the outside of the image forming apparatus.

In the image copying apparatus constructed as above,
By operating the active filter circuit of the switching regulator 30, the harmonic current generated in the power supply can be reduced and the power factor is improved. Further, the input current of the image forming apparatus can be reduced. At this time,
Since the input voltage is boosted by the active circuit, the changeover switch SW of the rectifier circuit is turned off to perform the bridge rectification.

(Second Embodiment) FIGS. 3 to 6 show a second embodiment. In the switching regulator 40 applied to the present embodiment, as shown in FIG. 3, two signal terminals are newly provided as compared with the conventional switching regulator 60 shown in FIG. These signal terminals are
A control signal terminal for operating the active filter circuit and switching to the voltage doubler circuit, and a voltage feedback terminal for monitoring the primary side voltage of the transformer T.

The image forming apparatus according to the present embodiment is configured so that the switching regulator 40 shown in FIG. 3 has a power supply section connected to the peripheral circuit section shown in FIG. In FIG.
The power supply unit applied to this embodiment is a switching regulator 40, a CPU, a memory, an I / O port, a control unit 42 having a driver and a voltage detection unit, a drive unit 44 having a motor, a clutch, a solenoid, and the like, and an operation unit 46. ,
It is provided with a human body detection sensor which is turned on when an operator approaches the front of the apparatus, and a sensor unit 48 having a document set sensor for detecting the presence or absence of a document set. In this configuration, the voltage feedback (abbreviated as voltage FD) and control signal (abbreviated as SW control) terminals of the switching regulator 40 and the output signal of the output DC power supply are connected to the control unit 42.

In the circuit configuration of this embodiment, when the image forming apparatus consumes a small amount of current in the standby mode or the like, the active filter circuit is turned off and the rectifier circuit is a voltage doubler circuit (SW).
On). When the drive unit 44 having a load such as a motor operates at the time of image formation and the current consumption is large, the active filter circuit is turned on, and the rectifier circuit is a bridge circuit (S).
W off).

When the mode of the switching regulator 40 is switched, the input voltage on the primary side of the transformer T is detected by the detection resistor R2, and the operation of the load such as the motor is started after the voltage is stabilized.

According to this embodiment, the on / off control of the rectifying circuit changeover switch SW and the active filter circuit is controlled by a signal from the control unit of the image forming apparatus, and the switching regulator 40 is switched according to the mode of the image forming apparatus. It can be executed more reliably at any timing.

FIG. 5 is a flow chart showing an operation example 1 of the second embodiment. In this flowchart, when the image forming apparatus is in the standby state, it is first determined in step S11 whether the operation panel or the operation key of the operation unit 46 has been operated. When operated, a signal from the control unit 42 turns on the active filter circuit of the switching regulator 40 and switches the rectifier circuit to a bridge circuit (S1).
2). Next, in step S13, it is determined whether or not a start key (not shown) on the operation panel is pressed,
When pressed, the primary side voltage of the transformer T shown in FIG. 3 is detected by the detection resistor R2, and when the voltage reaches a predetermined value, the image forming operation is started. If the voltage is below the predetermined value, the image forming operation is started after the voltage reaches the predetermined value (S14, S15).
After the job of image forming operation is completed, after a certain period of time,
Turn off the active filter circuit and switch to the voltage doubler rectifier circuit. Further, in an image forming apparatus having a plurality of functions such as a copying function and a printer function, the same control as above is performed when a print command or the like is issued from an external device.

FIG. 6 is a flow chart showing an operation example 2 of the second embodiment. In this flowchart, when the image forming apparatus is in the standby state, it is first determined in step S21 whether the human body detection sensor (48) is turned on. When it is detected that the human body detection sensor is turned on, the active filter circuit of the switching regulator is turned on by a signal from the control unit 42, and the rectifier circuit is switched to the bridge circuit (S22). Next, in step S23, it is determined whether or not the start key on the operation panel is pressed, and when it is pressed, the image forming operation is started. Next, the voltage on the primary side of the transformer may be detected as in S14 of FIG.

In step S25, it is determined whether the image forming operation has been completed. When the job is completed, it is determined again whether or not the human body detection sensor is on, and if it is on, the process returns to step S23. If it is off, turn off the active filter circuit of the switching regulator and switch to the voltage doubler rectifier circuit.

In the image copying apparatus of the second embodiment having the above construction, the switching regulator 4 is also used as in the first embodiment.
By operating the active filter circuit of 0, the harmonic current generated in the power supply is reduced and the power factor is improved.
Further, since the on / off of the active filter circuit and the switching of the rectifying circuit are performed by the signal from the control unit of the image forming apparatus, the switching of the switching regulator depending on the mode of the apparatus can be performed more reliably. Further, after turning on the active filter circuit, the operation of the image forming apparatus is started after detecting that the output voltage of the active circuit has reached a predetermined value. As a result, it is possible to prevent a decrease in output voltage due to an increase in output current when the active filter circuit is switched on and off, and prevent malfunction of the device and occurrence of an abnormal image. Further, when the operation panel of the image forming apparatus is operated and it is detected that there is a person near the apparatus, the active filter circuit is turned on and the rectifying circuit is switched to shorten the waiting time until the output is stabilized when the mode is switched. .

[0040]

As is apparent from the above description, the image forming apparatus of the present invention detects the voltage of the electric power induced in the secondary winding of the switching regulator and performs full-wave rectification and double voltage rectification of the AC power supply. Any one is selected to control the operation of the active filter on and off. Therefore, when the output current of the switching regulator is a certain value or more, the active filter is turned on to reduce the harmonic current and the input current and prevent the damage of peripheral devices and the like. Further, when the output current is a predetermined value or less, the harmonic current is small, and the influence on peripheral devices and the like is small, the active filter can be turned off to improve efficiency and reduce noise.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a switching regulator applied to a first embodiment of an image forming apparatus of the present invention.

FIG. 2 is a sectional view of the overall configuration of an image forming apparatus to which the power supply circuit of FIG. 1 is applied.

FIG. 3 is a circuit diagram of a switching regulator applied to a second embodiment.

4 is a circuit configuration block diagram of a peripheral portion including the switching regulator of FIG.

FIG. 5 is a flowchart showing an operation example 1 of the second embodiment.

FIG. 6 is a flowchart showing an operation example 2 of the second embodiment.

[Explanation of symbols]

 30, 40 Switching regulator 31 Control circuit for active filter 32 Control circuit for controlling ON / OFF of FET2 33 Operation amplification circuit 42 Control section 44 Drive section 46 Operation section 48 Sensor section

[Procedure amendment]

[Submission date] June 12, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of drawings]

FIG. 1 is a circuit diagram of a switching regulator applied to a first embodiment of an image forming apparatus of the present invention.

FIG. 2 is a sectional view of the overall configuration of an image forming apparatus to which the power supply circuit of FIG. 1 is applied.

FIG. 3 is a circuit diagram of a switching regulator applied to a second embodiment.

4 is a circuit configuration block diagram of a peripheral portion including the switching regulator of FIG.

FIG. 5 is a flowchart showing an operation example 1 of the second embodiment.

FIG. 6 is a flowchart showing an operation example 2 of the second embodiment.

FIG. 7 is a circuit diagram of a switching regulator applied to a conventional image forming apparatus.

[Explanation of Codes] 30, 40 Switching Regulator 31 Control Circuit for Active Filter 32 Control Circuit for Controlling ON / OFF of FET2 33 Operational Amplifier Circuit 42 Control Section 44 Drive Section 46 Operation Section 48 Sensor Section

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroto Oishi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (5)

[Claims] 1. A bridge rectifying means for full-wave rectifying an AC power source and a double voltage rectifying means for double voltage rectifying, a switch means for selecting one of the bridge rectifying means and the double voltage rectifying means, and the selected one. And an active filter for boosting the voltage rectified by the rectifying means, a switching element for switching the rectified current, and a transformer for outputting the electric power induced in the secondary winding by passing the switched current through the primary winding. An image forming apparatus including a switching regulator, including: an output voltage detecting unit that detects a voltage of electric power induced in the secondary winding; a switch control unit that controls switching of the switch unit; A filter control means for controlling on / off of the operation of the filter, and the voltage detected by the output voltage detection means. Image forming apparatus and controls the operation of the filter control means and said switch control means by the size of the. 2. The image forming apparatus further comprises a coupling means for feeding back the detection signal of the output voltage detecting means to the primary winding side of the transformer by an electrically insulated signal, and the feedback means is provided. The image forming apparatus according to claim 1, wherein the operation is controlled based on the signal. 3. The image forming apparatus further comprises a human body detecting means for detecting whether or not an operator approaches the image forming apparatus, and an output signal of the human body detecting means is connected to the switch control means, The image forming apparatus according to claim 1, wherein the operation is controlled by including the output signal. 4. The switch control means performs the image forming operation of the image forming apparatus after the output of the active filter is stabilized after the active filter is turned on. The image forming apparatus according to any one of items. 5. The image forming apparatus further comprises operation means for inputting an operation of the image forming apparatus, and the operation is controlled by including an operation signal from the operation means. 5. The image forming apparatus according to any one of items 4 to 4.