JP2003266878A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more reduce an electric power consumption at an energy saving mode in an imaging apparatus having a power supply device of a one converter system than that of a conventional power supply device of one converter system. <P>SOLUTION: The imaging apparatus has two operations modes of a normal imaging mode and a power saving mode having the electric power consumption reduced, and is provided with a power source unit having a 24 V output for converting a commercial AC to a DC via an AC/DC converter and outputting the current, and a 5 V output for voltage transforming the DC converted by the AC/DC converter via a DC/DC converter 12 and outputting the current. In the power saving mode, the output current of the 24 V output is shut at an output part of the power source unit, and a voltage of the current outputted by the 24 V output is changed with the use of a current detecting circuit 11 to a voltage which makes a converting efficiency of the AC/DC converter highest. <P>COPYRIGHT: (C)2003,JPO

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 using an electrophotographic system.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, a DC that drives a motor, a clutch, a solenoid and a high voltage power source.
Two systems of power sources are used: a high voltage power source (generally 12V or 24V) and a DC low voltage power source (generally 3.3V or 5V) that drives the CPU of the control board, various ICs, sensors and the like.

In the energy saving mode, the load of the DC high voltage power supply is turned off, so that the DC high voltage power supply is unnecessary. However, even if it is unnecessary, there is a unit that slightly consumes power when voltage is applied. Therefore, in order to reduce unnecessary power consumption during energy saving, D
C An energy-saving power supply technology is known that has an AC / DC converter for high-voltage power supply and an AC / DC converter for low-voltage power supply for DC, and turns off the AC / DC converter for DC high-voltage power supply in the energy-saving mode. ing. Figure 4
An outline of a conventional two-converter type energy-saving power supply device is shown in FIG. This energy-saving power supply device is provided with two AC / DC inverters for 24V output and 5V output, and by turning off the 24V output AC / DC converter in response to an external energy-saving control signal in the energy-saving mode. It is possible to reduce unnecessary power consumption. Also, A
The C / DC converter can always output a stable voltage by feeding back the voltage detected by the voltage detection circuit on the secondary side to the switching circuit on the primary side.

The energy-saving power source of the above-mentioned two converter system is
Since two transformers and control circuits are required, the size of the power supply is large and the cost is high. Therefore, it can be applied to medium-speed to high-speed image forming apparatuses,
In a low-speed layer image forming apparatus with a small power supply size, there may be a bottleneck in terms of size and cost. Therefore, in a low-speed layer image forming apparatus, a so-called 1-converter power supply system is generally used in which a DC high voltage power supply is made by an AC / DC converter and a DC high voltage power supply is made by a DC / DC converter. is there.

In the case of the power supply of 1 converter system, when the AC / DC converter of the DC high voltage power supply is turned off, DC / D
Since the input voltage of the C converter disappears and the DC low voltage power supply cannot be created, the AC / DC converter cannot be turned off. Therefore, there is a case where a switch is used to cut off the output of the DC high voltage power supply or the input of the control board.

FIG. 5 shows an outline of a conventional one-converter, two-output type energy-saving power supply device. The AC / DC converter produces 24V output, and the 24V DC / DC converter produces 5V output. DC / DC converter
Since there is no need to insulate by making 5V from 24V on the secondary side, there is no need for a transformer or the like, and the circuit size and cost are low. In the energy saving mode, the 24V output is cut off by the power output unit according to the energy saving control signal from the outside. As a result, the control board is not supplied with the voltage of 24 V, so that unnecessary power consumption is reduced.

The conversion efficiency of the DC / DC converter changes depending on the input voltage, the output voltage, and the output current. Figure 6
Table 1 shows an example of conversion efficiency of a commercially available DC / DC converter at an output power of 5V and a maximum output current of 3A.

[0008]

[Table 1]

[0009]

As described above, DC / DC
In the case of a converter, when the load is light, the lower the input voltage, the higher the conversion efficiency. 97.76 when input voltage is 6V when 5V current consumption in energy saving mode is 1A
It is converted in%, but when the input voltage is 12V, it is 9
4.26%, 91.4 when the input voltage is 16.5V
It becomes 4%, and the conversion efficiency decreases as the input voltage increases. Furthermore, the conversion efficiency when the input voltage is 24 V is less than 90%. Therefore,
In order to minimize the power loss in this DC / DC converter, it is necessary to lower the input voltage within the operation guarantee range.

FIG. 7 shows conversion efficiency characteristics of another commercially available DC / DC converter having an output voltage of 5V and a maximum output voltage of 1A. 5V current consumption in energy saving mode is 500mA
When the input voltage is 8V, the conversion efficiency is 88%, when the input voltage is 23V, the conversion efficiency is 80%, and when the input voltage is 38V, the conversion efficiency is 75%. The lower the voltage, the higher the conversion efficiency.

As described above, the conversion efficiency of the DC / DC converter generally changes according to the input voltage, and the input voltage with the highest efficiency exists in a certain load.

On the other hand, A for producing a DC voltage from a commercial AC power source
In the case of a C / DC converter, the conversion efficiency changes depending on the DC voltage to be created, but it does not change as much as the conversion efficiency of the DC / DC converter, and depending on the design, the conversion efficiency at the desired output voltage should be maximized. Is possible. Therefore, in the conventional one-converter energy-saving power supply device, there is a possibility that the power consumption in the energy-saving mode can be further reduced by improving the conversion efficiency of the DC / DC converter.

The present invention has been made in view of the above problems, and in an image forming apparatus having a 1-converter power supply device, the power consumption in the energy saving mode is
It is an object of the present invention to further reduce the power supply device of the converter type.

[0014]

In order to achieve the above object, the present invention has, as a first aspect, two types of operation modes: a normal image forming mode and a power saving mode with reduced power consumption. In the image forming apparatus, first direct current output means for converting commercial alternating current into direct current via an AC / DC converter and outputting the direct current, and direct current converted by the AC / DC converter via the DC / DC converter. A power source unit having a second direct current output means for transforming and outputting, and in the power saving mode, the output current from the first direct current output means is cut off at the output part of the power source unit, The image forming apparatus is characterized in that the voltage of the current output by the DC output means is changed to a voltage that maximizes the conversion efficiency of the AC / DC converter. According to the above configuration, the power consumption in the power saving mode can be reduced as compared with the conventional single converter power supply device.

In order to achieve the above object, the present invention provides, as a second aspect, an image forming apparatus having two kinds of operation modes, a normal image forming mode and a power saving mode in which power consumption is reduced. And a power supply unit equipped with a current output means for converting a commercial alternating current into a direct current through the AC / DC converter and outputting the converted direct current, and a switch for cutting off the output current from the DC / DC converter and the current output means. In a power saving mode, the control board is provided with the control board, and the output current from the current output means is shut off by the switch, and the output voltage from the power supply unit is changed by a control signal from the control means. An image forming apparatus characterized by the above. According to the above configuration, the power consumption in the power saving mode is 1
This can be reduced compared to the converter / 1 output power supply device.

In order to achieve the above object, the present invention provides, as a third aspect, an image forming apparatus having two kinds of operation modes, a normal image forming mode and a power saving mode in which power consumption is reduced. There is a first direct current output means for converting a commercial alternating current into a direct current through the AC / DC converter and outputting the direct current, and a direct current converted by the AC / DC converter is transformed through the DC / DC converter and output. A second power supply unit having a second DC output means for
In the power saving mode, the output current from the first DC output unit is shut off, and the voltage of the current output by the first DC output unit is set to the voltage at which the conversion efficiency of the AC / DC converter becomes the highest. The present invention provides an image forming apparatus characterized in that the conversion frequency is reduced and the switching frequency of the AC / DC converter is lowered. According to the above configuration, the power consumption in the power saving mode can be reduced as compared with the conventional single converter power supply device.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A preferred embodiment of an image forming apparatus according to the present invention will be described. FIG. 1 shows an energy-saving power supply device applied to the image forming apparatus according to the present embodiment. This image forming apparatus not only cuts off 24V in the energy saving mode, but also AC / D of 24V.
By using the energy-saving control signal, the detection voltage of the voltage detection circuit 11 of the C converter in the energy-saving mode in consideration of the conversion efficiency of the DC / DC inverter circuit 12 in the subsequent stage and the conversion efficiency of the AC / DC converter in the previous stage It is converted to a voltage that maximizes the efficiency seen from AC at a 5V output current.

Since the 24V output is cut off, even if the voltage changes, it does not affect the control board. Therefore,
It is possible to set a desired voltage considering only the 5V output. Here, it is possible to reduce the loss of the DC / DC converter 12 in the energy saving mode by changing the voltage to 24 V in the normal mode and 6 V in the energy saving mode, and improve the efficiency as a total power source. I am trying.

The output voltage of the AC / DC converter in the energy saving mode depends on the characteristics of the AC / DC converter and DC / DC.
Depending on the characteristics of the converter 12, it is converted into the most efficient one in total.

[Second Embodiment] A second embodiment in which the present invention is preferably implemented will be described. FIG. 2 shows an energy-saving power supply device applied to the image forming apparatus according to the present embodiment. In this embodiment, the power supply is a single output power supply,
The output voltage is changed by the control signal from the control board.
On the control board, 24V cutoff switch 21 and DC / D
By having the C converter 22 and shutting off the 24V cutoff switch 21 on the control board in the energy-saving mode, and changing the output by the control signal to the power supply unit, the same effect as the first embodiment can be obtained. To be

[Third Embodiment] A third embodiment in which the present invention is preferably implemented will be described. FIG. 3 shows an energy-saving power supply circuit applied to the image forming apparatus according to the present embodiment. The image forming apparatus according to the present embodiment controls the switching circuit 31 on the primary side to reduce the switching frequency, in addition to the same operation as in the first embodiment,
It is possible to further improve the total power supply efficiency.

[0022]

As is apparent from the above description, according to the present invention, in the image forming apparatus having the one-converter type power supply device, the power consumption in the energy saving mode is lower than that of the conventional one-converter type power supply device. Can be further reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an energy-saving power supply device applied to an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an energy-saving power supply device applied to an image forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an energy-saving power supply device applied to an image forming apparatus according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a conventional 2-converter energy-saving power supply device.

FIG. 5 is a diagram showing a conventional one-converter, two-output type energy-saving power supply device.

FIG. 6 is a diagram showing conversion efficiency characteristics of a commercially available DC / DC converter.

FIG. 7 is a diagram showing conversion efficiency characteristics of another DC / DC converter.

[Explanation of symbols]

11 Voltage detection circuit 12, 22 DC / DC converter 21 switch 31 switching circuit

Claims (3)

[Claims] 1. An image forming apparatus having two kinds of operation modes, a normal image forming mode and a power saving mode in which power consumption is reduced, wherein commercial AC current is converted into DC through an AC / DC converter. First direct current output means for outputting the converted direct current and the direct current converted by the AC / DC converter
A power supply unit having a second direct current output means for transforming and outputting through a C / DC converter, and in the power saving mode, output current from the first direct current output means is output from the power supply unit. The image forming apparatus is characterized in that the voltage of the current output by the first DC output means is changed to a voltage that maximizes the conversion efficiency of the AC / DC converter. 2. An image forming apparatus having two kinds of operation modes, a normal image forming mode and a power saving mode in which power consumption is reduced, wherein commercial alternating current is converted into direct current through an AC / DC converter. A power supply unit having a current output means for converting and outputting, and a control board having a DC / DC converter and a switch for interrupting an output current from the current output means, and in the power saving mode, An image forming apparatus, wherein an output current from the current output unit is shut off by a switch, and an output voltage from the power supply unit is changed by a control signal from the control unit. 3. An image forming apparatus having two types of operation modes, a normal image forming mode and a power saving mode in which power consumption is reduced, wherein commercial AC current is converted into DC through an AC / DC converter. First direct current output means for outputting the converted direct current and the direct current converted by the AC / DC converter
A power supply unit having a second direct current output means for transforming and outputting through a C / DC converter, and cutting off the output current from the first direct current output means in the power saving mode, An image forming apparatus, wherein the voltage of the current output by the first DC output means is converted into a voltage that maximizes the conversion efficiency of the AC / DC converter, and the switching frequency of the AC / DC converter is lowered.