JP2002095247A - Power supply and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise to a certain level as required in normal operation, and lower the noise level to a certain level as required and further sufficiently reduce the power consumption at a line filter for a second power supply unit 2 in power-saving mode in which only the second power supply unit 2 makes a noise source. SOLUTION: A power supply is provided with a first power supply unit 1 connected with an AC power supply through a power switch SW1; a second power supply unit 2 connected therewith bypassed with the switch, and a switch SW2 that separates a capacitor C1b, a component of a line filter for the second power supply, and the discharging resistor R1b thereof from a neutral line N in conjunction with the interrupt operation of the power switch SW1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a first power supply capable of cutting off an AC power input, and a second power supply constantly connected to the AC power input, and reduces noise generated in each power supply. The present invention relates to a power supply device reduced by a line filter provided on each input side. Further, an image forming apparatus (copying machine / printer / facsimile /
And the like in the following.

[0002]

2. Description of the Related Art A first power supply device having a large capacity and capable of cutting off an AC power input and having a line filter for noise reduction on the input side, and a small capacity and always connected to the AC power input so as to reduce noise on the input side. A power supply device having a second power supply device having a line filter for supplying DC power from both the first power supply device and the second power supply device during an image forming operation or during standby of the image forming operation. Accordingly, there is provided an image forming apparatus which receives a DC power supply from only the second power supply device in the power saving mode in which only the minimum necessary control functions are active.

[0003]

In the power supply device described above,
The line filter of each power supply device is designed such that the sum of noises generated from both the first power supply device and the second power supply device at the time of image forming operation or standby thereof satisfies a predetermined noise regulation standard. I have. This means that in the power saving mode in which only the second power supply supplies power (= is a noise source), the line filter of the second power supply has an excessive capacity. That is, in the power saving mode, the noise is suppressed to a level that is significantly lower than the noise regulation standard.

A line filter is a circuit element that reduces input feedback noise by increasing the internal impedance of a power supply device, and thus naturally consumes power. At the time of image forming operation and its standby, the power consumption of the line filter is accepted and the noise regulation standard is cleared as described above. Means that power is still being wasted while power becomes excessive.

According to the present invention, it is possible to reduce the sum of noises generated in the first and second power supply devices to a required level in a normal state,
A power supply capable of reducing noise generated in the second power supply in the power saving mode to a required level and sufficiently reducing power consumption generated in the line filter of the second power supply in the power saving mode; It is an object to provide an image forming apparatus using the power supply device.

[0006]

According to a first aspect of the present invention, a line filter for reducing noise is provided on the input side and connected to an AC power supply via a power switch to supply a DC power supply to a drive unit of a target device. A power supply device, a second power supply device having a line filter for noise reduction on an input side, connected to an AC power supply without a switch, and supplying DC power to a control unit of the target device; Switch means for switching a connection mode between the AC power supply and a line filter of the second power supply device in conjunction with a cutoff operation to suppress noise reduction capability of the line filter, thereby reducing power consumption. A power supply device characterized by the above-mentioned. Line filters are not limited to normal mode filters,
Also includes common mode filters. The line filter is described in detail in "Practical Power Supply Circuit Handbook, CQ Publishing Co., Ltd., written by Haruo Togawa, 17th edition, Chapter 9, pages 204 to 217, especially pages 208 and 213 to 217. AC
The power supply is, for example, a normal commercial power supply. The power switch is a main switch that is first turned on at the time of use. The target device is, for example, an image forming apparatus.
Each of the first and second power supply devices may be configured as a unit including a line filter, or may not be configured as a unit. The first power supply device may be configured to supply DC power also to a part of the control unit that is in the sleep state in the power saving mode. The interlocking between the power supply switch shutoff operation and the switching operation of the switch means can be realized by, for example, a relay circuit. Further, the power switch and the switch means are switched by a single-pole double-throw switch (a switch for exclusively switching between a power-on switch contact and a switch-on contact), or a double-pole single-throw switch (both switches are operated simultaneously). It can also be realized by configuring as a switch of the configuration). Also, the present invention can be realized by a configuration in which on / off of a power switch is detected, and an operation of a switch unit is instructed from a control unit in response to the detection.

According to a second aspect of the present invention, in the first aspect, the switch means is inserted between a hot line connecting the AC power supply and the second power supply device and a neutral line. A power supply device, wherein a capacitor forming a part of a line filter and a discharge resistor of the capacitor are disconnected from any one of the lines in conjunction with a shutoff operation of the power switch. According to a third aspect of the present invention, in the first aspect, the switch means comprises the AC
A coil inserted into a hot line connecting a power supply and the second power supply to form a part of the line filter, and / or inserted into a neutral line connecting the AC power supply and the second power supply. The power supply device is characterized in that the coil forming a part of the line filter is short-circuited in conjunction with the shut-off operation of the power switch. According to a fourth aspect of the present invention, there is provided an image forming apparatus including the power supply device according to any one of the first to third aspects.

[0008]

Embodiments of the present invention will be described below. [1] Common configuration: First, the configuration common to the conventional power supply device and the power supply device of the present invention will be described with reference to FIGS. 1, 5, and 6, and the problems of the conventional power supply device will be specifically described. Will be explained. FIG. 1 shows a circuit configuration of the printer main body. The printer body 5 includes a power switch SW1, a first power unit 1, a second power unit 2, a drive unit 3, and a controller unit 4. The printer body 5 is connected to a commercial power supply (AC power supply) through two lines, a hot line H and a neutral line N, and receives power supply through this line. Hereinafter, the hot line H and the neutral line N are referred to as “commercial power supply line (hot line / neutral line)”.

A commercial power supply line (hot line / neutral line) is connected to the second power supply unit 2 and also to the first power supply unit 1 via the power switch SW1. The first power supply unit 1 converts the supplied AC power into DC power (5 V and 24 V), supplies 5 V to the controller unit 4, and supplies 24 V to the drive unit 3. The second power supply unit 2
The supplied AC power is converted into DC power (5 V) and supplied to the controller unit 4. Although not shown in FIG. 1, the controller unit 4 uses 5 V supplied from the first power supply unit 1 for driving electric components such as a control IC necessary for executing a printing operation. Further, 5 V supplied from the second power supply unit 2 is necessary for returning from the power saving mode such as the ON / OFF operation of the power switch SW1 and the setting conditions of the printer to the image forming operation and the standby state of the image forming operation. Used to drive minimal electrical components.
By the above-described power supply, the printer main body 5 operates.

The state of the printer main body 5 includes a print state (image forming operation execution state), an image forming operation standby state,
And a power saving mode. In the printing state, the power switch SW1 is in an ON (energized) state. In this state, both the first power supply unit 1 and the second power supply unit 2 receive the supply of AC power. This AC
The power input is converted to a DC power and supplied to the drive unit 3 and the controller unit 4. Thereby, the controller unit 4 controls the drive unit 3 to perform a printing operation.

In the standby state, similarly, the power switch SW
Reference numeral 1 denotes an ON (energized) state. Therefore, both the first power supply unit 1 and the second power supply unit 2 receive the supply of AC power. The AC power input is converted to a DC power and supplied to the drive unit 3 and the controller unit 4. This allows the controller unit 4 to control the drive unit 3 to perform a printing operation, and waits for a printing operation command.

In the power saving mode, the power switch S
W1 is off (cut off). In this state, only the second power supply unit 2 receives the supply of AC power. This A
The C power input is converted to a DC power and supplied to the controller unit 4. Thereby, the power switch SW
The minimum number of electric components in the controller unit 4 necessary for returning from the power saving mode to the standby / printing state, such as ON / OFF operation of the printer 1 and printer setting conditions, are driven. Therefore, it is possible to return to the standby / printing state as needed. In the power saving mode, the first power supply unit 1 does not consume power because it is cut off from the commercial power supply. Of course, it is not a noise source.

FIG. 5 is a block diagram of a conventional power supply unit (a portion surrounded by a broken line 6 in FIG. 1). First,
The operation of the switching power supply and the mounted components will be described with reference to the first power supply unit 1 in FIG. Commercial power supply (AC power supply)
The input passes through a bridge diode BD1a through a commercial power supply line (hot line / neutral line) and a power supply switch SW1, is full-wave rectified, and is charged into a primary smoothing capacitor C2a. The energy charged in the primary smoothing capacitor C2a is transmitted from the primary side to the secondary side via the transformer T1a by the on / off operation of the switching element S1a.

The electric power transmitted to the secondary side is converted into 5 V and 24 V via a rectifying / smoothing circuit 7 a and supplied to the drive unit 3 and the controller unit 4. Since the switching element S1a is switched at a high frequency (approximately 100 KHz), high frequency noise is generated. In order to prevent this high-frequency noise from flowing out through a commercial power supply line (hot line / neutral line), a filter (line filter) for removing noise is provided. In the illustrated circuit, a coil L1a and a coil L2
a and the capacitor C1a. Note that the resistor R1
a is a discharging resistor of the capacitor C1a. Coil L
1a and the coil L2a are called a normal mode coil,
Between lines (between hot line H and neutral line N)
High-frequency noise (normal mode noise) generated in The capacitor C1a is called an across-the-line capacitor, which also reduces normal mode noise.

In addition to the above, the noise includes a noise called a common mode noise generated between the line and GND (between the hot line and the neutral line and the ground line (the ground line is omitted in the figure)). As a filter for removing the common mode noise, an element called a common mode coil or a line bypass capacitor is sometimes mounted, but is omitted in the figure. It should be noted that the present invention can be similarly applied to these.

The second power supply unit 2 operates in substantially the same manner as the first power supply unit 1. The difference between the second power supply unit 2 and the first power supply unit 1 is that the power switch SW1
This is connected to a commercial power supply line (hot line / neutral line) without using a power line, and the power transmitted to the secondary side is converted to 5 V and supplied only to the controller unit 4. Regarding each element of the first power supply unit 1 and each element of the second power supply unit 2, “a” is used in the first power supply unit 1 as a symbol to be added last for the same element, In the power supply unit 2, the correspondence between the two is shown by using “b”.

Next, problems of the circuit configuration of FIG. 5 will be described with reference to FIG. FIG. 6A shows the first power supply unit 1.
(B) schematically shows the level of noise generated by the second power supply unit 2 (same as above). Shown in The line filter of each power supply unit is designed so that the sum of them is equal to or lower than a predetermined noise regulation standard. That is, as shown in FIG. 3 (c), each power supply unit is set so that the above sum (shown by a solid line in the figure) is equal to or lower than a predetermined noise regulation standard level (shown by a dashed line in the figure). A line filter is designed.

As a result of this design, in the power saving mode in which only the second power supply unit 2 is active (= becomes a noise source), as shown in FIG. It will be far below the level of the noise regulation standard. As far as the noise regulation is concerned, there is no problem with the characteristic of FIG. 6D, but on the other hand, in order to greatly reduce the noise level, a disadvantage that the power consumption by the line filter must be accepted. is there. For this reason, in the present invention, power consumption in the line filter for the second power supply unit 2 in the power saving mode is suppressed as follows (= the noise reduction capability of the line filter is reduced). ). Hereinafter, this suppression method will be described below with reference to FIGS.

First, a description will be given with reference to FIG. 2 showing the first embodiment. The circuit of FIG. 2 is substantially similar to the circuit of FIG. The circuit of FIG. 2 is different from the circuit of FIG. 5 in that in the circuit of FIG. 2, an across-the-line capacitor C1b and a discharge resistor R1b for the capacitor C1b are connected to a neutral line N via a switch SW2. That is the point. The switch SW2 is connected to the power switch SW1.
It is configured to be shut off in conjunction with the shutoff operation and to be closed in conjunction with the closing operation.

With this configuration, the noise level generated by each of the power supply units 1 and 2 in FIG.
It becomes as shown in. FIG. 3 is substantially the same as FIG. FIG. 3 differs from FIG. 6 in that the noise level in the power saving mode in FIG. 6 is much lower than the noise regulation standard (= large wasteful power consumption) as shown in FIG. On the other hand, FIG. 3 shows that the noise level in the power saving mode is slightly lower than the noise regulation standard level as shown in FIG. Although the noise level is thus increased, in the circuit of FIG. 2, wasteful power consumption (power consumption by the discharge resistor R1b) in the line filter for the second power supply unit is suppressed. I have.

Next, a description will be given with reference to FIG. 4 showing a second embodiment. The circuit of FIG. 4 is substantially similar to the circuit of FIG. The circuit of FIG. 4 differs from the circuit of FIG. 5 in that both ends of the normal mode coil L1b can be short-circuited by the switch SW3 in the circuit of FIG. The switch SW3 is configured to be turned on in conjunction with the shut-off operation of the power switch SW1, and to be shut off in conjunction with the turn-on operation. That is, in the power saving mode, both ends of the normal mode coil L1b are set to the same potential so that they do not function as a line filter (= do not consume power).

Therefore, also in the case of the circuit of FIG. 4, the noise level generated by each of the power supply units 1 and 2 in FIG. 4 is as shown in FIG. 3, as in the case of the circuit of FIG. That is, the same effect as the circuit of FIG. 2 can be obtained.

[0023]

According to the first aspect of the present invention, there is provided a first power supply connected to an AC power supply via a power switch, a second power supply connected to the AC power supply without a switch, and a power supply switch. Switch means for switching the connection mode between the AC power supply and the line filter of the second power supply device in conjunction with the cutoff operation of the second power supply device to suppress its noise reduction ability, thereby reducing power consumption. And the total amount of noise generated in the second power supply device can be reduced to a required level, and the noise generated in the second power supply device in the power saving mode can be reduced to a required level. The power consumption generated by the line filter of the second power supply device can be sufficiently reduced. According to the second and third aspects of the present invention, it is possible to specifically provide a component of the line filter that is switched by the switch means. According to the fourth aspect of the present invention, it is possible to provide an image forming apparatus having a power supply device having the above functions.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a power supply unit of a printer according to an embodiment (and a related art) and units supplied with the power supply unit.

FIG. 2 is a circuit diagram showing a power supply unit according to the first embodiment.

FIG. 3 is an explanatory diagram showing a comparison between noise levels in the power supply unit of FIG. 2;

FIG. 4 is a circuit diagram showing a power supply unit according to a second embodiment.

FIG. 5 is a circuit diagram showing a conventional power supply unit.

FIG. 6 is an explanatory diagram showing a comparison between noise levels in the power supply unit of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st power supply unit 2 2nd power supply unit 3 Drive unit 4 Controller unit H Hot line N Neutral line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 EF16 JA20 ZA01 5G065 AA00 AA01 DA06 DA07 EA06 EA07 FA02 GA04 GA06 GA07 JA07 KA02 KA05 LA07 MA03 MA10 NA01 NA02 NA03 5H730 AA01 AA14 AS00 AS01 BB23 BB81 CC01 EE01

Claims (4)

[Claims] 1. A first power supply device having a line filter for noise reduction on an input side, connected to an AC power supply via a power switch, and supplying a DC power supply to a drive unit of a target device; A second power supply device having a line filter for noise reduction, connected to an AC power supply without a switch, and supplying a DC power supply to a control unit of the target device; and A power supply device comprising: switch means for switching a connection mode between an AC power supply and a line filter of the second power supply device to suppress noise reduction capability of the line filter, thereby reducing power consumption. 2. The line filter according to claim 1, wherein the switch is inserted between a hot line connecting the AC power supply and the second power supply device and a neutral line. A power supply device, comprising: disconnecting a capacitor and a discharge resistor of the capacitor from any one of the lines in conjunction with a shutoff operation of the power switch. 3. The coil according to claim 1, wherein the switch is inserted into a hot line connecting the AC power supply and the second power supply device and forms a part of the line filter. A coil inserted into a neutral line connecting the AC power supply and the second power supply device and forming a part of the line filter is short-circuited in conjunction with a shut-off operation of the power switch. Power supply. 4. An image forming apparatus comprising the power supply device according to claim 1.