JP3833546B2 - Power supply device in image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to power saving of a power supply device in an image forming apparatus realized as a copying machine, and in particular, as the image forming apparatus, the apparatus main body, which is a basic configuration for image formation, is connected to a printer or receives a facsimile. The present invention relates to a configuration in which an optional device related to a network can be added in order to realize a function as a device.
[0002]
[Prior art]
Conventionally, the image forming apparatus is provided with a function of automatically shifting to a standby mode that minimizes power consumption when no operation is performed from the outside for a certain period of time. In such a device, when shifting from the operation mode to the standby mode, the CPU itself stops the operation according to the judgment of the CPU of the control unit, and only a part of predetermined circuits necessary for returning to the normal mode are included. Power consumption is suppressed by operating the.
[0003]
On the other hand, the power consumption of the power supply circuit is as large as that of the CPU. As a technique for suppressing the power consumption of the power supply circuit, for example, Japanese Patent Application Laid-Open No. 2001-282059 discloses two power supplies of a main power supply circuit and a sub power supply circuit. When the control unit that includes a circuit and is supplied with power from the main power supply circuit and controls the operation of the entire apparatus shifts to the standby mode, the main power supply circuit is turned on and off via the switching circuit. It is described that after the operation of the power supply circuit is stopped, the operation of the control unit itself is stopped and when the return operation is performed, the switching circuit restarts the main power supply circuit.
[0004]
Japanese Patent Laid-Open No. 2000-228873 proposes a switching power supply circuit that intermittently oscillates the main switching element in the standby state of the device.
[0005]
[Problems to be solved by the invention]
However, in any conventional technique, the power consumption of the power supply circuit is merely switched between the normal operation mode and the standby mode. On the other hand, image forming apparatuses have advanced functions and realize such network functions so that they can be used as printers linked to personal computers or workstations, or can be used as facsimile receivers. There are also configurations that can add optional devices.
[0006]
For such an optional device related to the network, the main body of the image forming apparatus may completely stop the operation, but it is necessary to always wait for transmission from the network and receive it. Since it is necessary to hold the data for a period from when the apparatus main body rises to when the image formation is completed, the power consumption is substantially equal to that during normal operation even during standby. Therefore, when the above-described conventional technology is applied to a configuration in which an optional device related to such a network can be added, it is configured to supply sufficient power to all the optional devices that may be added. There is a problem that a case where the effect of power saving is not sufficient occurs.
[0007]
An object of the present invention is to provide a power supply apparatus that can further reduce power consumption of a power supply during standby in an image forming apparatus in which an optional apparatus can be mounted.
[0008]
[Means for Solving the Problems]
The power supply apparatus in the image forming apparatus of the present invention is a power supply apparatus in an image forming apparatus in which an optional device related to a network can be added to the apparatus main body, the first power supply means for supplying power during operation of the apparatus main body, During standby of the apparatus main body, second power supply means for supplying power to a predetermined predetermined circuit in place of the first power supply means, and a mounting state of the optional apparatus are detected, and the optional apparatus is mounted. If not, the second power supply means includes power supply control means for reducing the output voltage as compared with the case where it is attached.
[0009]
According to the above configuration, in the image forming apparatus realized as a copying machine or the like, power is supplied from the first power supply means (main power supply) to the apparatus main body, which is a basic configuration for image formation, during normal operation. On the other hand, at the time of standby such as in the sleep mode, the apparatus main body may completely stop the operation. Therefore, in order to save power, the first power supply unit is stopped to enter the operation state. Instead of the first power supply means, power is supplied from the second power supply means (sub power supply) only to a predetermined part of the circuit required for recovery.
[0010]
At this time, in the case where an optional device related to the network is added to the device main body in order to realize a function as a printer or a facsimile receiving device, the optional device always waits for transmission from the network. In addition, since the received data must be held for a period from when the main body of the apparatus starts up until image formation is completed, the power supply control means sets the second power supply means to wait for the optional device. Output the required voltage. On the other hand, when the optional device is not mounted (no load), the power supply control means supplies the output voltage to the second power supply means as compared with the case where the optional device is mounted. Reduce.
[0011]
Therefore, the power consumption of the power supply itself can be reduced during the standby, and further power saving can be realized.
[0012]
In the power supply apparatus in the image forming apparatus according to the present invention, the power supply control unit lowers the output voltage by causing the second power supply unit to oscillate intermittently.
[0013]
According to said structure, by making it oscillate intermittently, the efficiency of a 2nd power supply means is further improved, and further power saving can be implement | achieved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS.
[0015]
FIG. 1 is a block diagram showing an electrical configuration of a power supply device 1 in an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is realized as a copying machine including a scanner and a printer. The image forming unit is supplied with power from the main power supply circuit 2 in the normal operation mode, and is not supplied with power in the standby mode. , Has stopped working. The power supply apparatus 1 is generally configured to include the main power supply circuit 2, the sub power supply circuit 3, and a CPU 4 that controls the entire apparatus.
[0016]
When the CPU 4 detects that no image formation or user operation is performed for a certain period of time, the CPU 4 outputs a start signal to the switching control IC 10 of the sub power circuit 3 to start the operation of the sub power circuit 3. Further, after outputting a sleep signal to the main power supply circuit 2 to stop the operation of the main power supply circuit 2, the operation of the main power supply circuit 2 is stopped, and the standby mode is entered. When the main power supply circuit 2 is restarted as will be described later, the CPU 4 is also restarted by supplying power from the main power supply circuit 2 to prepare for image formation.
[0017]
The sub power supply circuit 3 is a switching type power supply circuit in this example, and commercial alternating current from the commercial power supply 11 is input to the diode bridge 12 and the smoothing capacitor C1 and rectified and smoothed. A series circuit of the primary winding N1 of the transformer N and the main switching element Q is connected in parallel to the smoothing capacitor C1 serving as a DC power source. The main switching element Q is realized by, for example, a bipolar transistor or a field effect transistor, and is shown as a field effect transistor in the example of FIG. The main switching element Q is ON / OFF controlled by the switching control IC 10.
[0018]
When the main switching element Q is turned on and an exciting current flows through the primary winding N1, a voltage is induced in the secondary winding N2 of the transformer N, and the voltage is smoothed by the diode D1 and the smoothing capacitor C2. After that, it is output as the power supply voltage Vcc. The power supply voltage Vcc is supplied to the main power supply start circuit 13 required for the restart, and is additionally mounted as necessary via the diode D2 as one or a plurality of option boards (in FIG. 1). Reference numerals B1 and B2).
[0019]
In FIG. 1, the option board B1 is a board for realizing a function as a facsimile receiving apparatus, and the option board B2 is a board for realizing interlocking as a printer. Therefore, these option boards B1 and B2 are related to the network, and need to always wait for transmission from the network, and receive the received data until the apparatus main body rises and image formation is completed. Therefore, it is necessary to normally operate even in the standby mode. In the normal operation mode, power is supplied from the main power supply circuit 2 to the option boards B1 and B2 via the diode D3.
[0020]
A series circuit of a light emitting diode D4 of the photocoupler PC, a transistor TR1 and a Zener diode ZD and a series circuit of voltage dividing resistors R1 and R2 are connected between the power supply lines of the power supply voltage Vcc. . A starting resistor R3 is interposed between the collector and base of the transistor TR1. The feedback value Vref of the power supply voltage Vcc divided by the voltage dividing resistors R1 and R2 is input to the base of the transistor TR1. Therefore, when the power supply voltage Vcc rises, the transistor TR1 is turned on by the starting resistor R3 and the light-emitting diode D4 of the photocoupler PC is turned on. Thereafter, the light-emitting diode has a brightness corresponding to the feedback value Vref and therefore the level of the power supply voltage Vcc D4 lights up.
[0021]
On the other hand, on the primary side, the voltage induced in the auxiliary winding N3 of the transformer N is smoothed by the diode D5 and the smoothing capacitor C3 to be a control power supply, and the output voltage is the switching power supply. The capacitor C4 is supplied to the control IC 10 and charged through the current limiting resistor R4 and the phototransistor TR2 of the photocoupler PC. The charging voltage of the capacitor C4 is input to the switching control IC 10 via the resistor R5.
[0022]
Therefore, when the light emitting diode D4 is lit with the luminance corresponding to the level of the power supply voltage Vcc, the charging current ICA of the capacitor C4 also corresponds to the level of the power supply voltage Vcc. A constant voltage operation is performed in which the duty is controlled so that the secondary side voltage is constant.
[0023]
In the power supply device 1 configured as described above, it should be noted that in the present invention, in the standby mode, the power supply voltage Vcc varies depending on whether or not the option boards B1 and B2 are installed. Is to be done. For this reason, the option boards B1 and B2 are provided with detection resistors OP1 and OP2, respectively, which are power supply control means. These detection resistors OP1 and OP2 are installed in the specified slots of the apparatus main body. Then, the voltage dividing resistor R2 is connected in parallel.
[0024]
Therefore, when the option boards B1 and B2 are installed, the feedback value Vref decreases, the luminance of the light emitting diode D4 decreases, and the charging current ICA of the capacitor C4 also tends to decrease. In contrast, the switching control IC 10 increases the duty of the main switching element Q by the above-described constant voltage operation, and tries to maintain the feedback value Vref at a specified voltage. As a result, the power supply voltage Vcc is stabilized at a relatively high voltage required for operating the option boards B1 and B2, for example, 5V.
[0025]
On the other hand, when the option boards B1 and B2 are not installed, the feedback value Vref is relatively high, the luminance of the light emitting diode D4 is high, and the charging current ICA of the capacitor C4 tends to increase. On the other hand, the switching control IC 10 intermittently oscillates the main switching element Q by the constant voltage operation described above, whereby the power supply voltage Vcc is the minimum voltage necessary for the main power supply starting circuit 13 to operate, for example, Stabilized to 3V.
[0026]
When the option boards B1 and B2 receive data from the network, start signals are output from the option boards B1 and B2, and the start signals are given to the main power supply start circuit 13 via the OR circuit 14. . Further, the main power supply starting circuit 13 is supplied with the power supply voltage Vcc via a switch SW and a pull-up resistor R6, and the user can operate the switch SW realized by a print switch or the like by a user operation. When the switch SW is turned on, the power supply voltage Vcc is given as a start signal.
[0027]
FIG. 2 is a graph showing the relationship between the charging current ICA and the switching state of the main switching element Q. As described above, the duty of the main switching element Q increases as the option boards B1 and B2 are mounted, the load is heavy, the luminance of the light emitting diode D4 decreases, and the charging current ICA decreases. Below 2 mA, the maximum duty is fixed at 80%, and maximum power is supplied to the secondary side at a specified frequency. On the other hand, as the load is lighter and the luminance of the light emitting diode D4 is increased and the charging current ICA is increased, the duty is reduced, and the minimum value is 20% when the charging current ICA is 10 mA.
[0028]
When the charging current ICA is 10 mA or more, which is a level that can be reliably determined that the option boards B1 and B2 are not installed, voltage control cannot be performed at the specified frequency, for example, 100 kHz. The intermittent oscillation state is reached at 20 kHz. Whether or not the option boards B1 and B2 are installed can be determined from the feedback value of the power supply voltage Vcc by increasing or decreasing the load. However, in the present invention, switching between the normal oscillation and the intermittent oscillation is performed reliably. Therefore, the detection resistors OP1 and OP2 are provided on the option boards B1 and B2.
[0029]
FIG. 3 is a graph showing the relationship between the output power of the sub power supply circuit 3 and the power conversion efficiency. In the example of FIG. 3, the total power supplied to the option boards B1 and B2 is 5W. When the option boards B1 and B2 are installed and 5 W of power is supplied to them, 70% efficiency can be secured, whereas the power consumption when the option boards B1 and B2 are not installed. Is about 1 W, and it is understood that the power conversion efficiency is reduced to 40%. The reduction of the power conversion efficiency indicates that the ratio of wasted power such as heat loss of the main switching element Q is large with respect to the power to be converted.
[0030]
Therefore, when the option boards B1 and B2 are not installed, the output voltage Vcc of the sub power supply circuit 3 is reduced, thereby reducing the power consumption of the power supply itself during standby and realizing further power saving. Can do.
[0031]
Further, the output voltage Vcc is lowered by intermittent oscillation, so that the efficiency of the sub power supply circuit 3 can be further improved and further power saving can be realized.
[0032]
【The invention's effect】
In the image forming apparatus according to the present invention, as described above, in the image forming apparatus realized as a copying machine or the like, power is supplied from the first power supply unit (main power supply) during normal operation, and during standby, When power is supplied from the second power supply means (sub power supply) instead of the first power supply means, and an optional device related to the network is not added to the apparatus main body, it is compared with the case where it is added. Thus, the output voltage of the second power supply means is lowered.
[0033]
Therefore, it is possible to reduce the power consumption of the power supply itself during the standby time and realize further power saving.
[0034]
Further, as described above, the power supply device in the image forming apparatus of the present invention reduces the output voltage by causing the second power supply means to oscillate intermittently.
[0035]
Therefore, the efficiency of the second power supply means is further improved, and further power saving can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electrical configuration of a power supply device in an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing a relationship between a primary feedback current and a switching state of a main switching element in a switching power supply.
FIG. 3 is a graph showing a relationship between output power of a sub power supply circuit and power conversion efficiency.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Power supply device 2 Main power supply circuit (1st power supply means)
3 Sub power supply circuit (second power supply means)
4 CPU810 switching control IC
DESCRIPTION OF SYMBOLS 11 Commercial power supply 12 Diode bridge 13 Main power supply starting circuit 14 OR circuit B1, B2 Option board (option apparatus)
C1 to C3 Smoothing capacitor C4 Capacitors D1 to D3 and D5 Diode D4 Light emitting diode N Transformer OP1 and OP2 Detection resistor (power control means)
PC photocoupler Q main switching element R1, R2 voltage dividing resistor R3 starting resistor R4 current limiting resistor R5 resistor R6 pull-up resistor SW switch TR1 transistor TR2 phototransistor ZD zener diode

Claims (5)

In a power supply device in an image forming apparatus in which an optional device related to a network can be added to the device main body,
A first power supply means for supplying power during operation of the apparatus main body; and a second power supply means for supplying power instead of the first power supply means to some predetermined circuits during standby of the apparatus main body. And detecting the mounting state of the optional device during standby of the device main body. When the optional device is not mounted, the output is output to the second power supply unit compared to when the optional device is mounted. And a power supply control means for reducing the voltage.   2. The power supply apparatus for an image forming apparatus according to claim 1, wherein the power supply control means lowers an output voltage by causing the second power supply means to oscillate intermittently. The predetermined part of the circuit is an activation circuit for activating the first power supply means,
The power supply control means detects a mounting state of the option device during standby of the apparatus main body, and the starter circuit operates the output voltage of the second power supply means when the option device is not mounted. The power supply device according to claim 1, wherein the power supply device is lowered to a minimum voltage required for the operation. 2. A voltage dividing resistor for reducing a resistance value of a circuit by connecting resistors provided in the option device in parallel when the option device is mounted on the device main body. The power supply device described in 1. When the optional device is mounted on the device main body, a resistor provided in the optional device is connected in parallel to provide a voltage dividing resistor that reduces the resistance value of the circuit,
The power supply control means causes the second power supply means to oscillate intermittently and reduce an output voltage based on a relatively high resistance value of the circuit without the optional device being mounted. The power supply device in the image forming apparatus according to claim 2.

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