JP2002199729A - Power supply for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply for an image forming device which can further be reduced power in a waiting time and image forming time. SOLUTION: This image forming device power supply has a detection circuit (3) which detects an output voltage, a comparison circuit (4) which compares a detected voltage with a reference voltage, a PWM control circuit (5), which controls an output voltage to be constant according to the comparison result, and a transformer (1) which has a control output with a constant output voltage and a drive output outputted dependently. After a prescribed lapse of time, since the finish of an image forming operation, the reference voltage of the comparison circuit (4) is changed by a reference voltage changing signal outputted from a reference voltage changing means (8) according to a signal from a main control unit (7), and the control output voltage and the driving output voltage lower than the respective rated output voltages in the image forming operation are outputted. In a restoration state, the reference voltage of the comparison circuit (4) is changed, by the reference voltage changing signal outputted from the reference voltage changing means (8) according to a signal from the main control unit (7), so as to output the rated control output voltage and the rated drive output voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply used for an image forming apparatus such as a copying machine or a printer, and more particularly to a power supply for an image forming apparatus capable of reducing power consumption during standby.

[0002]

2. Description of the Related Art In recent years, prevention of global warming has been called for from the viewpoint of global environmental protection.
Energy saving, resource saving and recycling are essential. In particular, regarding energy conservation, the energy star proposed by the United States has now been introduced not only in the United States but also in Japan as an international energy star.
It is also reflected in European environmental regulations such as Swiss Energy 2000. In Japan, following the Global Warming Prevention Council, the Ministry of International Trade and Industry announced the criteria for copiers, home appliances, computers, etc. under the Energy Conservation Law, and set the energy consumption efficiency targets for fiscal 2006, including images for copiers and printers. In electronic devices such as forming apparatuses, home electric appliances, and personal computers, it is necessary to reduce not only the power during operation but also the power during standby. In recent years, switching-type power supplies with high conversion efficiency have become the mainstream as power supplies for electronic devices, so reducing the power consumption of image forming apparatuses and electronic devices equipped with switching-type power supplies is improving the efficiency of the system and reducing power consumption. It is an important issue to be realized by realizing it. In recent image forming apparatuses such as printers and copiers, the standby time is much longer than the operation time. In particular, it is said that a printer for personal computers is in a standby state for more than 90% of the time. It is said that energy stars have been specified to save energy during standby.

For this reason, in an image forming apparatus employing a switching type power supply, in order to reduce unnecessary power consumption during standby, power supply to parts not requiring standby power is stopped, and wasteful power during standby is wasted. Means for reducing power consumption have been proposed. For example, in an image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 5-333636, after an image forming operation, a power supply to a peripheral device or a motor control unit that does not require power supply is relayed based on an instruction from a main body control unit. Stop at. As a power switching means, a power relay has a large shape and lacks reliability. Therefore, it is general that the power switching means is constituted by a switching element FET.

FIG. 4 shows an example of the prior art which is basically the same as the prior art and in which the relay is replaced by a switching element FET. The circuit configuration is a one-switch forward type switching power supply having two outputs: a drive output 24V for driving a motor, a solenoid, and the like, and a control output 5V for a control circuit such as a CPU. The control output 5 V is fed back to perform PWM control (pulse width control), and the control output 5 V
Is stabilized, and the driving output 24V is a meta-stabilized output by dependent control. Further, a switching element FET11 is arranged in the drive output 24V circuit output section, and is configured to receive an energy saving signal from the image forming apparatus main body and turn on / off the switching element FET11.

[0005] With such a configuration, when the image forming operation is completed and a predetermined time has elapsed, the control circuit enters a sleep state and enters a standby state with a minimum necessary circuit, and the control circuit issues an energy saving signal to the power supply unit. In the power supply unit, the on / off control circuit 12 receives the energy saving signal, turns off the switching element FET11, and cuts off power supply to a circuit that does not require power during standby. Thereby, the power consumption during standby is reduced.

When returning from the energy saving mode,
The control circuit is changed from the sleep state to a steady state by a predetermined operation key or a print signal, an energy saving release signal is input to the power supply unit, the switching element FET11 is turned on, the driving output 24V is supplied to the main body, and the image forming operation is performed. It becomes possible. Note that the image forming operation requires a large current of at least 5 to 10 amperes for driving components such as a motor and a solenoid, which are necessary for the image forming operation, and for the unit. During the image forming operation, the switching element F
Since ET11 is always on, this switching element FE
The power loss at T11 is a considerable power loss. The drive output 24V as a dependent control increases in voltage when there is no output current when there is no load, and requires a dummy resistor R to suppress the voltage. The power loss here deteriorates the power supply efficiency especially during standby. Was.

[0007]

As described above, in the prior art, it was not sufficient to reduce the power consumption during standby and image formation. SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply for an image forming apparatus that can solve the above-described problems of the related art and can further reduce power during standby and during image formation.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a detection circuit for detecting an output voltage, a comparison circuit for comparing the detected output voltage with a reference voltage, A PWM control circuit that performs PWM control so that the output voltage is constant based on the comparison result by the comparison circuit; and a transformer driven by an output of the PWM control circuit, and a secondary side of the transformer includes: In a power supply for an image forming apparatus configured to have a plurality of outputs of a control output that is a constant voltage output and a drive output that is dependently output, when a predetermined time has elapsed after the end of the image forming operation, On the basis of the energy saving signal from the control unit, the reference voltage of the control output voltage of the comparison circuit is changed by the reference voltage change signal output from the reference voltage change means, and the control output voltage is changed. Output voltage for driving is lower than the rated output voltage during the image forming operation, and at the time of recovery, based on the energy saving signal from the control unit of the image forming apparatus, based on the reference voltage change signal output from the reference voltage changing means. The reference voltage of the comparison circuit is changed, and a rated output voltage during an image forming operation is output as the control output voltage.

Further, according to the invention described in claim 2, according to claim 1,
In the invention described above, the predetermined time can be changed by operating a key provided in the image forming apparatus. According to a third aspect of the present invention, in the first aspect of the invention, the control output voltage at the time of low output is set to a lower limit value of a control circuit element operable range in the energy saving mode. According to a fourth aspect of the present invention, in the first aspect of the invention, the control output voltage at the time of low output is set to a predetermined ratio or more of the rated voltage of the control circuit element rated voltage in the energy saving mode and equal to or less than the rated voltage. The voltage was used.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. Since the control circuit voltage of the image forming apparatus is supplied to a CPU, an integrated circuit, and the like,
A relatively low voltage of about V is used, and constant voltage accuracy suitable for these elements is required. Specifically, 3-5% accuracy is often required. For example, 24 V is supplied as a drive output as a drive voltage for a motor, a solenoid, or the like, and the constant voltage regulation is often 10% or around 10%.

FIG. 1 is a configuration diagram of a power supply circuit showing a first embodiment of the present invention. As shown, the power supply circuit of this embodiment includes a transformer 1, smoothing circuits 2a and 2b for smoothing the secondary output voltage, a detection circuit 3 for detecting a control output voltage, and a detected control output. A comparison circuit 4 for comparing the voltage with the reference voltage, a PWM control circuit 5 for performing PWM control so that the control output voltage is constant based on the comparison result, an FET 6, and the like are provided. The output of the PWM control circuit 5 The transformer 1 is driven via the FET 6 and the transformer 1 is driven.
And outputs a control output at a constant voltage to the secondary side of the control signal, and outputs a meta-stabilized drive output in a dependent manner. In addition, a reference voltage changing unit 8 that changes a reference voltage based on an energy saving signal (hereinafter, abbreviated as an energy saving signal) from the main body control unit 7 and outputs the reference voltage to the comparison circuit 4 is provided.

With this configuration, the control output 5V is output with a constant voltage accuracy of about 1% to 2%. At all times (during standby, during image forming operation, from the end of the image forming operation to a predetermined time), the voltage level of the control output 5V detected by the detection circuit 3 is input to the comparator of the comparison circuit 4, and the reference voltage (control output Is set to, for example, 5 V)
Then, the result is driven via the PWM control circuit 5 to drive the FET 6, and the feedback control is performed from the secondary side of the transformer 1 so that the control output 5V becomes constant. Also, 24V of the driving output is dependent on the 5V feedback circuit, and is affected by the load current of the control output 5V, but is not affected by the AC input voltage.
Although the output becomes a meta-stabilized output, it is output within a constant voltage accuracy range of about 10% which has no problem in image forming operation.

In this embodiment, when the image forming operation of the image forming apparatus has been completed and a predetermined time has elapsed, the main body control unit 7 of the image forming apparatus enters a sleep state in which it operates with a minimum necessary circuit, and further consumes more power. In order to reduce power, an energy-saving ON signal is output from the main body control unit 7 to the reference voltage changing unit 8 of the power supply circuit unit. In response to the energy-saving ON signal, the reference voltage changing means 8 outputs a reference voltage level change signal for lowering the output voltage to the comparison circuit 4.

FIG. 2 shows a configuration example of the comparison circuit 4. The comparison circuit 4 changes the resistance value of the variable resistor R to change the reference voltage, and operates so that the control output 5V is output lower than during image formation. Driving output 2 which is also dependent control
4V also drops. As a result, in the so-called energy-saving mode, which requires the most energy saving after a lapse of a predetermined time from the image forming operation, the entire image forming apparatus is in a further sleep state, and energy saving can be achieved.

In addition, for returning to the image forming operation,
User operations such as document setting and key operation of the image forming apparatus,
An energy saving off signal is output from the main body control unit 7 to the reference voltage changing unit 8 of the power supply circuit unit by a print signal or the like. The reference voltage changing means 8 outputs a reference voltage level change signal for increasing the output voltage to the comparison circuit 4 in response to the energy saving off signal. In the comparison circuit 4, as a result of changing the reference voltage, the control output 5V
It operates to output. At the same time, the output voltage of the drive for the slave control is also increased to 24V.
Thereafter, after performing various initial settings and the like, various loads and the like are controlled, and the image forming operation is performed without any problem.

Thus, according to this embodiment, in the energy saving mode, it is possible to reduce the power consumption of driving parts and units such as motors and solenoids necessary for image forming operations, and to cut off the current for this purpose. Therefore, no power loss occurs in the FET at the time of image formation, and the power consumption in the main body control unit 7 can be reduced by lowering the control output voltage. Dummy resistor R
Becomes unnecessary, and it is possible to eliminate the power of several watts which has been constantly consumed here, and a great effect can be expected in reducing the power consumption.

Next, a second embodiment will be described with reference to FIG. In this embodiment, a predetermined time setting until the image forming operation of the image forming apparatus ends and the sleep state in which the main body control unit 7 operates with the minimum necessary circuit is set in advance in the factory shipping state of the image forming apparatus. The setting time can be changed by key input of the operation unit 9 of the image forming apparatus, so that the set time can be changed by a key input of the operation unit 9 of the image forming apparatus. To enable both energy saving and user convenience.

In the third embodiment of the present invention, when the image forming operation of the image forming apparatus is completed and a predetermined time has elapsed, the main body control unit 7 of the image forming apparatus operates in a sleep mode which operates with a minimum necessary circuit. To reduce the power consumption, the main body control unit 7 supplies the reference voltage changing means 8 of the power supply circuit unit.
, An energy-saving ON signal is output. Thereby, the reference voltage changing means 8 responds to the energy saving ON signal to the comparison circuit 4 to set the control output voltage to the lower limit value of the control circuit element operable range in the energy saving mode. Output the change signal.

Thus, in the comparison circuit 4, as a result of the change of the reference voltage, the control output is lower than 5V in the normal state.
It operates to output as low as 3.5V to 4V. At the same time, the driving output 24V which is the dependent control is similarly reduced to 70 to 80% of the steady state. As a result, in the so-called energy saving mode in which the most energy saving is required after the elapse of a predetermined time from the image forming operation, the entire image forming apparatus is in a further sleep state, and the greatest energy saving can be achieved.

Next, a fourth embodiment will be described. When the image forming operation of the image forming apparatus has been completed and a predetermined time has elapsed, the main body control unit 7 of the image forming apparatus enters a sleep state in which it operates with a minimum necessary circuit, and further reduces the power consumption of the image forming apparatus. An energy-saving ON signal is output from the main body control unit 7 to the reference voltage changing unit 8 of the power supply circuit unit. Thereby, the reference voltage changing means 8 sets the control output voltage to the comparison circuit 4 between the control circuit element rated voltage in the energy saving mode and, for example, 90% of the rated voltage in response to the energy saving ON signal. For changing the reference voltage level.

As a result, the comparison circuit 4 operates so that the control output is lower than 5 V at the steady state, for example, 4.5 V as a result of the change of the reference voltage. At the same time, the driving output 24V which is the dependent control is similarly reduced to, for example, about 90% of the steady state. As a result, what is called the most energy-saving after a predetermined time has passed since the image forming operation,
In the energy saving mode, the entire image forming apparatus is in a sleep state, and further energy saving can be achieved while ensuring reliability. As described above, in this embodiment, a two-output circuit having a control output of 5 V and a drive output of 24 V has been described for convenience of explanation. However, the present invention can be implemented regardless of the output voltage and the number of output systems. .

[0022]

As described above, according to the present invention,
According to the first aspect of the present invention, when a predetermined time has elapsed from the end of the image forming operation, the reference voltage of the control output voltage of the comparison circuit is changed by the reference voltage change signal based on the energy saving signal from the control unit of the image forming apparatus. The output voltage for control and the output voltage for driving are output lower than the rated output voltage during the image forming operation. At the time of recovery, the output voltage is compared with the reference voltage change signal based on the energy saving signal from the control unit of the image forming apparatus. The reference voltage of the circuit is changed, and the rated output voltage during the image forming operation is output as the control output voltage and the driving output voltage. The power consumption of components and units can be reduced, and there is no need to provide a current-blocking FET for that purpose. Te, to the power loss in the FET during the image formation does not occur, by decreasing the control output voltage, to be reduced the power consumption in the main control unit,
The need for a dummy resistor, which is conventionally required in a rectifier circuit, is eliminated, and the power consumption of several watts, which is always consumed here, can be eliminated, and a great effect can be expected in reducing power consumption.

According to the second aspect of the present invention, there is provided the first aspect.
In the invention described above, the user can change the predetermined time after the end of the image forming operation by operating the keys provided on the image forming apparatus, so that both the reduction in power of the image forming apparatus and the usability of the user can be achieved. According to the third aspect of the present invention, in the first aspect of the present invention, the control output voltage at the time of low output is the lower limit value of the operable range of the control circuit element in the energy saving mode. The entire image forming apparatus is in a further sleep state, and more effective power reduction can be achieved.

Further, according to the invention described in claim 4, according to claim 1,
In the described invention, the output voltage for control at the time of low output is a voltage that is equal to or higher than a predetermined ratio of the rated voltage of the control circuit element rated voltage and equal to or lower than the rated voltage in the energy saving mode. The entire forming apparatus is in a further sleep state, and more effective power reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a power supply circuit showing a first embodiment of the present invention.

FIG. 2 is a detailed view of a main part of a power supply circuit according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a power supply circuit according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a power supply circuit showing an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transformer 2 Smoothing circuit 3 Detection circuit 4 Comparison circuit 5 PWM control circuit 6 FET 7 Main body control part 8 Reference voltage change means 9 Operation part

Claims (4)

[Claims] 1. A detection circuit for detecting an output voltage, a comparison circuit for comparing the detected output voltage with a reference voltage, and a PWM control for maintaining the output voltage constant based on a comparison result by the comparison circuit. PWM control circuit to perform and its P
An image forming apparatus comprising: a transformer driven by an output of a WM control circuit; and a secondary side of the transformer having a plurality of outputs of a control output of a constant voltage and a drive output of a dependent output. In the power supply, when a predetermined time has elapsed after the end of the image forming operation, the control output of the comparison circuit is controlled by the reference voltage change signal output from the reference voltage change unit based on the energy saving signal from the control unit of the image forming apparatus. The reference voltage of the voltage is changed to output the control output voltage and the drive output voltage lower than the rated output voltage at the time of the image forming operation, and upon return, based on the energy saving signal from the control unit of the image forming apparatus, The reference voltage of the comparison circuit is changed by the reference voltage change signal output from the reference voltage changing means, and the control circuit outputs the control output voltage and the drive output voltage. Power image forming apparatus being characterized in that the arrangement for outputting the rated output voltage at the time of image forming operation. 2. The power supply for an image forming apparatus according to claim 1, wherein the predetermined time is changeable by operating a key provided on the image forming apparatus. . 3. The power supply for an image forming apparatus according to claim 1, wherein the control output voltage at the time of low output is set to a lower limit value of a control circuit element operable range in the energy saving mode. Power supply for the image forming apparatus. 4. The power supply for an image forming apparatus according to claim 1, wherein the control output voltage at the time of low output is a voltage which is equal to or higher than a predetermined ratio of the rated voltage of the control circuit element rated voltage in the energy saving mode and equal to or lower than the rated voltage. A power supply for an image forming apparatus, characterized in that: