JP2002354802A - Power saving control method of power supply, power supply device, and picture forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the power saving of a power supply device without the obstruction against an operation of a load, to realize the power saving of a power system power supply of an picture forming device, and to realize the power saving of all the power supplies of the picture forming device. SOLUTION: This picture forming device has an image forming device (100) having an image forming mechanism and an image formation control means, a switching power supply (4) which supplies a power to a transformer by a PWM switching method and detects a voltage (Vf11) supplied to a load on the secondary side of the transformer, a voltage control means (7) which controls a PWM duty to lead the voltage (Vf11) to a target voltage (VO11), a means (ISEN 0 and 7) which detects whether a current value (If0) varied according to a load exceeds a set value (Ireset) or not, and an output control means (7) which determines a rated voltage (24 V) as the target voltage (VO11) if the current value exceeds the set value (Ireset), and determines a lower value (22 V) within a tolerance range (24 V±10%) as the target voltage (VO11) if the current value is not higher than the set value (Ireset). In the other operation pattern, if the current value is not higher than the set value, a power system power supply (24 V) is turned off and a voltage of a control system power supply is reduced from 5 V to 4.6 V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power-saving control method for a power supply for supplying power to an electric load, and a power supply apparatus for implementing the method and an image forming apparatus using the same. Concerning the power saving of the period power supply. A typical image forming apparatus for performing such operations is a copying machine,
Printer or facsimile.

[0002]

2. Description of the Related Art For example, a commercial AC is input, and a DC voltage after rectification and smoothing is switched at a high frequency so that the transformer 1
2. Description of the Related Art A switching power supply circuit that applies a voltage to a secondary winding and rectifies a voltage induced in a secondary winding of a transformer to output a DC voltage is used in many electric appliances. The output voltage of this power supply circuit is stabilized at a constant voltage by detecting this and controlling the switching ratio (conduction period / switching cycle), that is, the duty of the PWM pulse. Recently, for example, digital signal processors (DSPs)
In some cases, digital control is used to perform this.

[0003] Japanese Patent Application Laid-Open No. 2000-333459 discloses that
2. Description of the Related Art An image recording apparatus is provided which includes a power supply of a power system for supplying power to a drive system and a logic system power supply for supplying power of a control system, and shuts off power supply to the power supply of the power system during standby.

Japanese Patent Application Laid-Open No. 11-126647 discloses an A
In an AC adapter that rectifies and smoothes the C voltage, performs high-frequency switching of the DC voltage with an inverter and a transformer, transforms the rectified voltage, and performs rectification and smoothing, the presence or absence of power supply from the AC adapter to the DC load is detected. A method for reducing power consumption, in which the high-frequency switching is performed intermittently, is disclosed.

[0005]

The above-mentioned Japanese Patent Application Laid-Open No. 2000-3
In an image forming apparatus such as the image recording apparatus disclosed in JP-A-33459, which has a so-called energy saving mode in which power supply to a power system power supply is cut off during standby, an image forming operation is immediately performed in response to a copy start or print start command. In the operation mode in which the power supply to the logic system and the power system is continued so that the power can be progressed to, the condition for switching to the energy saving mode is satisfied if the waiting state in which there is no command and no processing continues for the set time As a result, the power supply to the logic power supply for waiting for a command or another input is continued, but the power supply to the power supply is stopped. Therefore, in the waiting state during the set time,
The power consumption of the power supply is wasted as a result. If the setting time is set short, there is a possibility that the operability of the operator may be reduced, for example, switching to the energy saving mode while the operator is working on the copy preparation work and redoing the copy mode setting input to the copying machine from the beginning. There is. If the set time is set to be long, the power supply to the power source of the power system, which is wasted as a result, becomes long, and the power saving effect is reduced.

[0006] Japanese Patent Application Laid-Open No.
A power supply circuit, such as a C adapter, that detects the presence or absence of power supply from the power supply circuit to the load and interrupts high-frequency switching of the inverter when there is no power supply requires the addition of an intermittent signal generation circuit. It gets complicated. Not only that, high-frequency switching must be performed to recognize the presence or absence of power supply to the load, and if the intermittent cycle is long,
Since the presence or absence of power supply cannot be detected during the interruption period, there is a delay in detecting that the load is in the power supply required state.

A first object of the present invention is to save power of a power supply device, and a second object of the present invention is to realize this without causing a special delay in starting operation of a load, and to switch to an energy saving mode. A third object of the present invention is to further save power without impairing the judgment even during a set time for judging whether or not the condition is satisfied and without causing a special delay in starting the operation of the load. A fourth object is to realize the circuit without adding a circuit. A fifth object is to further enhance the energy saving effect of the power system power supply of the image forming apparatus, and a sixth object is to further enhance the energy saving effect of the entire power supply of the image forming apparatus.

[0008]

Means for Solving the Problems (1) PWM of input voltage
The power supply (4) that generates an output voltage corresponding to the PWM duty by switching detects whether the current value (If0) that fluctuates depending on whether power is supplied to the load exceeds the set value (Irest) or is equal to or less than the set value, When the set value is exceeded, the PWM duty is the value that outputs the rated voltage (24V). When the value is less than the set value, the PWM duty is set to the rated voltage (24V) tolerance range.
A power saving control method for a power supply that outputs a low voltage (22V) near the lower limit of (24V ± 10%).

[0009] In order to facilitate understanding, in the parentheses, the corresponding elements of the embodiment shown in the drawings and the symbols of the corresponding elements or the symbols of the corresponding items are added for reference. The same applies to the following.

According to this, when power is supplied to the load, the current value (If0) exceeds the set value (Irest), and accordingly, the PWM duty is set to a value for outputting the rated voltage (24V). Therefore, the rated voltage (24V) is applied to the load. When the power supply to the load is stopped, the current value (If0) becomes equal to or less than the set value (Irest), and accordingly, the PWM duty is set to the low voltage (22).
Since V) is a value to be output, standby power consumption of the power supply (4) is reduced.

Since this low voltage (22 V) is near the lower limit of the tolerance range (24 V ± 10%) of the rated voltage (24 V), power can be supplied to the load, and the minimum operation of the load can be guaranteed. . When the power supply to the load starts while the voltage is low (22V), the current value (If0) exceeds the set value (Irest), so the PWM duty value corresponding to this value outputs the rated voltage (24V). Therefore, the rated voltage (24 V) is applied to the load, and the optimal operation of the load is guaranteed.

[0012]

(2) The current value (If0) is a set value
When exceeding (Irest), set the rated voltage (24V) to the target value (VO11).
When the voltage is below the set value, the rated voltage tolerance range (24 V
A low voltage (22 V) near the lower limit of (± 10%) is set as the target value, and the output voltage (Vf11) of the power supply (4) is detected so that the detected value (Vf11) matches the target value (VO11). (1) The power saving control method for a power supply according to the above (1), wherein the PWM duty is changed.

According to this, the output voltage (Vf11) of the power supply (4)
Is set to the target value (VO11), the duty of the PWM switching of the input voltage is feedback-controlled.
Thereby, when the current value (If0) exceeds the set value (Irest), the power supply (4) generates the rated voltage (24V) and the set value (Ires
At the time below t), low voltage (22V) is generated. Target value (VO11)
The switching of the output voltage is automatically performed by the switching, and the switching of the output voltage is easy.

(3) The power supply (4) rectifies and smoothes commercial alternating current (AC), and supplies chopping current to the primary winding of the step-down transformer (TR11) via the switching element (FET1) to generate a secondary winding. A switching power supply (4) for rectifying the voltage to be applied;
As the current value (If0), an AC current value flowing into a circuit (3) for rectifying and smoothing commercial AC is detected;
Or (2) the power saving control method of the power supply.

The commercial alternating current (AC) has a high voltage of, for example, 100 V and uses a step-down transformer (TR11). For example, if the output voltage of the power supply (4) is 24 V, the input AC current of the power supply (4) The value is as low as 24/100 of the output current value. Therefore, for example, when converting a current level to a voltage level with a low resistor for detecting a current value, the power loss in the low resistor becomes Ri ² , so that the output current of the power supply (4) is more detected. Also, when the input AC current value is detected according to the present embodiment, the power loss in the low-resistance resistor for detection is smaller. Also,
A current transformer using an induction coil can be used as the current detecting means, and the current value can be easily detected.

Since the DC voltage at the stage where the commercial alternating current (AC) is rectified and smoothed is also a high voltage, even when the DC current value is detected at that stage, the current value is low. Since power is supplied, the power consumption of the low-resistance resistor for detection is greater than in the case of detecting an AC current value before the rectifying / smoothing circuit in a time series. Since the AC current value flows and is interrupted only during a period when the input AC voltage is higher than the voltage of the smoothing capacitor, the power loss in the low-resistance resistor for detection is small. Further, the direct current, which is the output of the rectifying and smoothing circuit, cannot be detected by the induction coil. Therefore, it is preferable to detect the input AC current value as in the present embodiment.

(4) A transformer (TR11), a primary side circuit (FET11) for switching and supplying power to a primary winding of the transformer in response to a PWM pulse, and a voltage generated in a secondary winding of the transformer is rectified and supplied to a load. Secondary side circuit (D11, D12, CH11) to supply power,
Means for detecting the voltage supplied to the load (VSEN11), and voltage control means (7) for controlling the duty of the PWM pulse so that the voltage detected by the load (Vf11) matches the target value (VO11), Current value (If0) that fluctuates depending on whether or not power is supplied to a load of the power supply device includes a set value.
Means to detect whether (Irest) is exceeded or below the set value (ISEN0,
7) When the current value exceeds the set value, the rated voltage (24V) is set to the target value (VO11). When the current value is less than the set value, the rated voltage within the tolerance range of the rated voltage (24V ± 10%) A power supply device comprising: output control means (7) for setting a lower value (22V) to the target value (VO11).

With this power supply device, the power saving control methods (1) and (2) can be carried out, and the functions and effects described in (1) and (2) can be similarly obtained.

(4a) A transformer (TR11 / TR21), a primary-side circuit (FET11 / FET21) that supplies switching power to the primary winding of the transformer in response to a PWM pulse, and a voltage generated in a secondary winding of the transformer. The secondary side circuit (D
11, D12, CH11 / D21, D22, CH21), and means for detecting the voltage supplied to the load (VSE11 / VSEN21), respectively,
The first switching power supply circuit (4) having a high output voltage (24V) and the second switching power supply circuit (5) having a low output voltage, and the voltage detected by each voltage detecting means (VSE11 / VSEN21) is set at each target value (VO11). / VO21), a voltage control means (7) for controlling the duty of each PWM pulse, in a power supply device, the current value (If0) of the power supply device fluctuating depending on whether power is supplied to a load. Means (ISEN0, 7) for detecting whether the voltage is equal to or less than the set value (Irest), and an output for stopping the voltage output of the first switching power supply circuit (4) when the voltage is equal to or less than the set value, and starting the voltage output when exceeding the set value. Control means (7),
A power supply device comprising:

According to this, when the power supply to the load is stopped, the current value (If0) becomes equal to or less than the set value (Irest), and in response to this, the output control means (7) sets the first switching power supply circuit (4). , The standby power consumption of the power supply device is reduced.

When the control means connected to the second switching power supply circuit (5) operates to drive the load during the stop, the second switching power supply circuit (5) is thereby operated.
The output current of the power supply increases, and the current value (If0) of the power supply becomes the set value (Ir
est), the output control means (7) starts outputting the voltage of the first switching power supply circuit (4). This realizes driving of the load.

(4b) The output control means (7) is provided with a current value
When (If0) exceeds the set value (Irest), the rated voltage (5V) addressed to the second switching power supply circuit (5) is set to the target value (VO21) addressed to the circuit (5). A value lower than the rated voltage (4.6 V) within the rated voltage tolerance range (5 V ± 10%)
V) to the second switching power supply circuit (5).
The power supply according to (4a), as defined in 21).

According to this, the first switching power supply circuit
When the voltage output of (4) is stopped, the output voltage of the second switching power supply circuit (5) becomes a low value (4.6 V), so that the standby power consumption of the power supply device is further reduced.

Since this low value (4.6 V) is within the tolerance range (5 V ± 10%) of the rated voltage (5 V), the second switching power supply circuit
Power can be supplied to the control means connected to (5), and normal operation of the control means can be guaranteed. Second to drive the load
When the control means connected to the switching power supply circuit (5) operates, the output current of the second switching power supply circuit (5) increases, and the current value (If0) of the power supply device becomes the set value (Irest).
Is exceeded, the output control means (7) starts the voltage output of the first switching power supply circuit (4). This realizes driving of the load. Moreover, the second switching power supply circuit
The rated voltage (5V) addressed to (5) is set to the target value (V
O21), the optimal operation of the control means connected to the second switching power supply circuit (5) is guaranteed.

(4c) The transformer is a step-down transformer; the detecting means (ISEN0, 7) detects whether the input AC current (If0) of the power supply device exceeds a set value (Irest) or less than a set value. , The power supply of (4), (4a) or (4b).

According to this, the operation and effect described in the above (3) can be obtained similarly.

(5) a visual image forming apparatus (100) having an image forming mechanism (101-122) and visual image forming control means (51, 60), and forming a visual image corresponding to an image signal on paper; Transformer (TR11),
A primary circuit (FET11) for switching and supplying power to the primary winding of the transformer in response to a PWM pulse, and a secondary circuit for rectifying a voltage generated in a secondary winding of the transformer and supplying power to a load.
(D11, D12, CH11) and means for detecting the voltage supplied to the load
(VSEN11), including a switching power supply (4) for supplying power to the visual image forming device (100); so that the voltage (Vf11) detected by the voltage detection means (VSEN11) matches the target value (VO11), Voltage control means for controlling the duty of the PWM pulse
(7); means (ISEN0, 7) for detecting whether the current value (If0) of the switching power supply (4) fluctuating according to the presence or absence of power supply to the load exceeds or falls below a set value (Irest); When the current value (If0) exceeds the set value (Irest), the rated voltage (2
4V) is set to the target value (VO11), and when the value is equal to or less than the set value, output control to set the target value (VO11) to a value (22V) lower than the rated voltage within the tolerance range of the rated voltage (24V ± 10%). means
(7) An image forming apparatus comprising:

According to this, the current value (If0) exceeds the set value (Irest) when power is supplied to the visual image forming apparatus (100), and accordingly, the PWM duty is changed to the rated voltage (2).
Since the output value is 4 V), the rated voltage (24 V) is applied to the visual image forming apparatus (100). When the power supply to the visual image forming device (100) is stopped, the current value (If0) becomes equal to or less than the set value (Irest), and accordingly, the PWM duty is set to a value for outputting the low voltage (22V). The standby power consumption of the forming apparatus is reduced.

Since this low voltage (22 V) is within the tolerance range (24 V ± 10%) of the rated voltage (24 V), power can be supplied to the visual forming device (100), and the visual forming device (100) The minimum operation can be guaranteed. When the power supply to the visual forming device (100) starts while the voltage is low (22 V), the current value (If0) is changed to the set value (Ire
st), the PWM duty is set to a value that outputs the rated voltage (24 V) in response to this.
The rated voltage (24V) is applied to (100), and the image forming apparatus (100)
Optimal operation is guaranteed.

Since the duty of the PWM switching of the input voltage is feedback-controlled so that the output voltage (Vf11) of the switching power supply (4) matches the target value (VO11), the current value (If0) is set to the set value (Irest). When crossing power
(4) generates the rated voltage (24V), and generates a low voltage (22V) when the voltage is equal to or less than the set value (Irest). The output voltage is automatically switched by switching the target value (VO11), and the switching of the output voltage is easy.

(6) A visual image forming apparatus (100) having an image forming mechanism (101-122) and visual image forming control means (51, 60), and forming a visual image corresponding to an image signal on a sheet; Transformer (TR11 / TR2
1), a primary-side circuit (FET11 / FET21) that switches and supplies power to the primary winding of the transformer in response to a PWM pulse, and a secondary-side circuit that rectifies the voltage generated in the secondary winding of the transformer and supplies power to the load (D11, D12, CH11 / D21, D22, CH21), and means for detecting the voltage supplied to the load (VSEN11 / VSEN21), respectively, the output voltage is high and the image forming mechanism (101-122)
A first switching power supply (4) for supplying power to the electric equipment, a second switching power supply (5) for supplying low power to the visual formation control means (51, 60), and voltage detection means (VSEN11 / VSEN21). ) Detects each target value VO11 / VO2
A power supply (80) including voltage control means (7) for controlling the duty of each PWM pulse so as to conform to (1); a current value which varies depending on whether or not power is supplied to the load of the power supply (80) Means for detecting whether (If0) is equal to or less than the set value (Irest) (ISEN0,
7); and an output control means (7) for stopping the voltage output of the first switching power supply circuit (4) when the voltage is equal to or less than the set value.

According to this, when the power supply to the electric equipment of the image forming mechanism (101-122) is stopped, the current value (If0) becomes equal to or less than the set value (Irest), and the output control means (7 ) Stops the voltage output of the first switching power supply circuit (4), so that the standby power consumption of the image forming apparatus is reduced.

When stopped, the image forming mechanism (101-122)
Switching power supply circuit for powering electrical equipment
When the visual image formation control means (51, 60) connected to (5) operates, the output current of the second switching power supply circuit (5) increases, and the current value (If0) of the power supply device becomes the set value (Irest). ), The output control means (7) starts the voltage output of the first switching power supply circuit (4). This makes the imaging mechanism
(101-122) is realized.

(7) The output control means (7) outputs a current value (If
0) exceeds the set value (Irest), the rated voltage (5V) addressed to the second switching power supply circuit (5) is set to the target value (VO21) addressed to the circuit (5). A value lower than the rated voltage (4.6V) within the voltage tolerance range (5V ± 10%)
To the second switching power supply circuit (5).
The image forming apparatus according to (6), defined in (1).

According to this, the first switching power supply circuit
When the voltage output of (4) is stopped, the output voltage of the second switching power supply circuit (5) becomes a low value (4.6 V), so that the standby power consumption of the image forming apparatus is further reduced.

Since this low value (4.6 V) is within the tolerance range (5 V ± 10%) of the rated voltage (5 V), the second switching power supply circuit
Power can be supplied to the visual image formation control means (51, 60) connected to (5), and normal operation of the visual image formation control means (51, 60) can be guaranteed. When the visible image formation control means (51, 60) connected to the second switching power supply circuit (5) operates to drive the electric equipment of the image forming mechanism (101-122), the second switching power supply circuit (5 ) Output current increases and the power supply current
Output control means when (If0) exceeds the set value (Irest)
(7) starts the voltage output of the first switching power supply circuit (4). Thereby, the driving of the electric device of the image forming mechanism (101-122) is realized. Moreover, the rated voltage (5V) addressed to the second switching power supply circuit (5) is changed to the target value (VO21) addressed to the circuit (5).
Therefore, the optimal operation of the visual image formation control means (51, 60) connected to the second switching power supply circuit (5) is guaranteed.

(8) The transformer (TR11 / TR21) is a step-down transformer; the detecting means (ISEN0, 7) determines that the input AC current (If0) of the power supply device (80) exceeds a set value (Irest). The image forming apparatus according to the above (5), (6) or (7), which detects whether the value is equal to or less than a set value. According to this, the operation and effect described in the above (3) can be obtained similarly.

(9) The visual image forming control means (51, 60)
In the operation mode in which visible image formation can be started, it is determined whether or not a condition for transition to the hibernation mode for stopping the voltage output of the first switching power supply circuit (4) for energy saving is satisfied. It is determined whether the condition is satisfied or not. When the condition for shifting to the sleep mode is satisfied, the voltage output of the first switching power supply circuit (4) is stopped. When the condition for shifting to the operation mode is satisfied, the first switching power supply circuit (4) is determined.
Instructing the output control means (7) to start the voltage output of
The image forming apparatus according to (6), (7) or (8), wherein the output control means (7) stops or starts the voltage output of the first switching power supply circuit (4) accordingly.

According to this, even in the operation mode, when the power supply to the electric device of the image forming mechanism (101-122) is stopped, the current value is reduced.
(If0) becomes equal to or less than the set value (Irest), and the output control means (7) correspondingly stops the voltage output of the first switching power supply circuit (4), so that the standby power consumption of the image forming apparatus is reduced. Therefore, the power saving effect of the image forming apparatus is high.

(10) In an image forming apparatus provided with a power supply device (4) having a switching element (FET11) for switching a current on the primary side and controlling a voltage on the secondary side, the primary side current (If0) Is detected, and the current on the primary side becomes equal to or less than a specified value (a value during which the image forming apparatus is on standby: Irest), and a predetermined time (Tuc ×
(DTh × 200 μsec) If the current value does not exceed the specified value, the switching element (FET11) is repeatedly turned on / off to supply current to the secondary side driving load (motor, etc.).
An image forming apparatus characterized in that the ON time of F is shortened to lower the output voltage (24 V or the like) to a low value (eg, “low value” within a tolerance range of 24 V ± 10%).

When the rated voltage is 24 V, the tolerance range is 24
V ± 10%, and the lower limit is 21.6V. In an embodiment described later, a rated value and a “low value” are selectively set as the target value VO11, and the output voltage of the power supply device (4) is adjusted to the target value VO11 by feedback control with the output voltage set to the target value VO11. Therefore, there may be a control error. Assuming that this error is less than 0.4 V, the “low value” is determined to be 22 V, and even if there is a feedback control error, the tolerance range 2
4 V ± 10%. When the image forming apparatus is on standby, the current (If0) on the primary side is less than 1A, and when the image formation is started, it greatly exceeds 1A.
st was set to 1A.

For the chopping cycle T, T1 in it
The switching voltage (FET11) is turned ON, and the output voltage is switched to the rated value (24V) or "low value" by changing the value of T1, that is, the energization duty of chopping (switching). During copying by the image forming apparatus,
The primary side current (If0) exceeds the specified value (1A). When the copy of the image forming apparatus is completed and the current (If0) on the primary side becomes equal to or less than the specified value (1A), it takes a predetermined time (Tuc × DTh × 2).
(00 μsec), the output voltage is decreased by switching T1 to a short ON time value (example: 24V → 22V).

As described above, by lowering the driving output voltage when the image forming apparatus is on standby, power consumption when the image forming apparatus is on standby is reduced. For example, if the rated voltage is changed from 24V to 22V slightly higher than the lower limit value 21.6V of the tolerance range, the load current when the driving output voltage of the image forming apparatus (standby) is 24V = I1, the image forming apparatus Load current when the drive output voltage during standby is 22 V =
Assuming I2, the power consumption reduction amount = 24 × I1−22 × I2.

(10) In an image forming apparatus provided with a power supply device (4) having a switching element (FET11) for switching a current on the primary side to control a voltage on the secondary side, a primary current (If0) Is detected, and the current on the primary side becomes equal to or less than a specified value (a value during which the image forming apparatus is on standby: Irest), and a predetermined time (Tuc ×
(DTh × 200 μsec) If the current value does not exceed the specified value, the switching operation of the switching element for supplying current to the secondary-side drive load (motor or the like) is stopped, and the output voltage (24 V or the like) is reduced to 0V. An image forming apparatus comprising:

According to this configuration, the output voltage for driving is stopped when the image forming apparatus is on standby, so that the consumption of the image forming apparatus during standby is reduced. For example, if the output voltage of 24V is 0V
In this case, the amount of reduction in power consumption = 24 V × current value during standby of the image forming apparatus.

(11) In addition to the above (10), the ON time of the switching element (FET 21) for supplying current to the control system (control board, etc.) on the secondary side is shortened, and the output voltage (5V) is set within the tolerance range. An image forming apparatus, wherein the value is set to a “low value” near the lower limit.

When the rated voltage is 5 V, the tolerance range is 5 V ±
10%, and the lower limit is 4.5V. In an embodiment described later, a rated value and a “low value” are selectively set as the target value VO21, and the output voltage is adjusted to the target value VO21 by feedback control that sets the output voltage to the target value VO21. obtain. Considering this error to be less than 0.1 V, the "low value" was determined to be 4.6 V, so that even if there was a feedback control error, the tolerance was within the tolerance range of 5 V ± 10%.

According to this, when the output voltage is changed from 5 V to 4.5 V, for example, the load current when the control output voltage is 5 V when the image forming apparatus is on standby is I1, and the control output is on when the image forming apparatus is on standby. Load current when the voltage is 4.6 V = I2
Then, the power consumption reduction amount becomes 5 × I1−4.6 × I2.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0050]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 shows an appearance of a multifunction copying machine according to one embodiment of the present invention. The multifunction copier generally includes an automatic document feeder [ADF] 30, an operation unit 20, a color scanner 10
A color printer 100; a relay unit 32; a finisher 34 with a shift tray capable of stacking a large amount of stapler and imaged paper;
3, a paper supply bank 35, and large-capacity paper supply trays 36 and 1
And a bin discharge tray 31.

FIG. 2 shows the configuration of the color printer 100. Reference numeral 101 denotes a flexible photosensitive belt serving as a belt-shaped image carrier.
3 and is conveyed in the direction of arrow A (clockwise) in the figure by the rotation of the rotating roller 102. In the figure 104
, A charging charger for uniformly charging the surface of the photoreceptor belt 101; and 105, a laser exposure device as an image writing unit. In the figure, reference numeral 106 denotes a color developing device, 106a denotes magenta, 106b denotes cyan,
c is yellow and 106d is a black developing unit.

Reference numeral 109 in the figure denotes an intermediate transfer belt which is an image carrier and an intermediate transfer medium.
Reference numeral 9 is mounted on the rotation rollers 110-112, and is driven by the rotation of the rotation roller 110 in the direction of arrow B (counterclockwise) in the figure.
Transported to The photoreceptor belt 101 and the intermediate transfer belt 109 are in contact with each other by a symbolless rotating roller of the photoreceptor belt 101. On the intermediate transfer belt 109 side of the contact portion, a bias roller 113 having conductivity is in contact with the back surface of the intermediate transfer belt 110 under predetermined conditions.

The photoreceptor belt 101 is connected to the charging charger 10.
After being uniformly charged by 4, exposure is performed by scanning of laser light modulated by an image recording signal by the laser exposure device 105. Thus, an electrostatic latent image is formed on the photosensitive belt 101. Here, the image recording signal for modulating the laser light is destined for each color (single color) obtained by decomposing a desired full-color image into magenta, cyan, yellow, and black (Bk) color information. The formation of the electrostatic latent image and the development with the color in the developing devices 106a to 106d are repeated for the number of colors (for example, magenta, cyan, yellow, and black, four times in total). The visualized images (toner images) appearing by the development are respectively superimposed and transferred on the intermediate transfer belt 9.

That is, each single-color image (toner image) formed on the photosensitive belt 1 rotating in the direction of arrow A in the figure is an intermediate transfer belt rotating in the direction of arrow B in synchronization with the photosensitive belt 101. A single transfer color of magenta, cyan, yellow, and black is sequentially transferred onto the transfer roller 109 by a predetermined transfer bias applied to the bias roller 113. The magenta, cyan, yellow, and black images superimposed on the intermediate transfer belt 109 are fed from the paper feed cassette 116a of the paper feed table 116 to the paper feed roller 117 and the transport roller pair 1.
18a, 118b, registration roller pair 119a, 119
The transfer is performed collectively on the transfer paper conveyed to the transfer roller 114 via b. After the transfer is completed, the toner image on the transfer paper is fixed (heat-pressed) on the transfer paper by the fixing device 120. As a result, the full-color image is completed, and the transfer paper is discharged to the discharge stack unit 122 via the discharge roller pairs 121a and 121b.

In the drawing, reference numeral 107 denotes a photosensitive belt 101.
, A cleaning blade for wiping off toner on the photoreceptor belt 101, and a cleaning device 115 for the intermediate transfer belt 109.
The fifteen cleaning brushes 115a are held at positions separated from the surface of the intermediate transfer belt 110 during the image forming operation, and are brought into contact with the surface of the intermediate transfer belt 110 after the formed image is transferred onto the above-described transfer paper.

The photosensitive belt 101, the charging charger 104, the intermediate transfer belt 109, and the cleaning device 1
Reference numerals 07 and 115 are integrated into a process cartridge to form a unit.

Reference numeral 108 denotes a toner adhesion amount sensor for detecting the amount of toner adhesion on the photosensitive belt 101. The toner adhesion amount sensor 108 used this time has a voltage V of a level corresponding to the amount of light received by the photodiode, with the light-emitting part being an infrared light emitting diode and the diffuse reflection light receiving part being a photodiode.
s, that is, a sensor that generates and outputs a detection signal, that is, a toner density sensor that measures the amount of diffuse reflected light.

Inside the fixing roller of the fixing device 120,
There is a fixing heater (halogen lamp) 123C, and the fixing energizing circuit 85 (FIG. 4) energizes the fixing heater 123C, whereby the fixing heater 123C generates heat and generates infrared rays to heat the fixing roller.

FIG. 3 shows an outline of an electric system of the copying machine shown in FIG. One MPU 51 on the main control board 50 and one CPU 12 on the scanner control board 11 are used in the mechanical control section of the copying machine, that is, the main part of the image reading and image forming process control. The MPU 51 controls the image forming sequence, the fixing control, and the system-related control.
The PU 12 performs control related to the scanner. MPU
The 51 and the CPU 12 are connected by an image data interface and a serial interface.

In FIG. 3, reference numeral 20 denotes an operation unit;
Is an I / O control board on which an input / output electric circuit is mounted, 92 is an LD control board for controlling a laser beam for image exposure, 41 is a paper feed control board, 13 is a read control board on which a CCD is mounted, and 90 is a motherboard. is there.

Reference numeral 60 denotes a printer controller (board) for controlling a printer function for printing a document from a host such as a personal computer or a word processor, and a combined operation mode of copy, facsimile, and printer. Reference numeral 91 denotes an application extension unit for realizing a composite function, which is a facsimile control unit equipped with a facsimile function. 80 is a DC power supply / AC control board.

FIG. 4 shows a facsimile control unit 91, a fixing heater 123C, an I / O control board (input / output interface) 70, and a main control board (main controller) 50 from a DC power supply / AC control board 80 as a power supply device. ,
An outline of a power supply system to the motherboard 90 and the printer controller 60 and an outline of the printer controller 60 are shown.

Referring to FIG. 4, an MPU 51, a CPU peripheral ASIC (Application Specific IC) 54, an image processing A
There is an SIC 53 and an I / F (interface) 52 having an interface function with the printer controller 60 and a function of compressing and expanding image data.

The printer controller 60, which controls the system, includes a peripheral ASIC 64 having an interface between the MPU 61 and the main control board 50 for realizing the composite function, a communication function with the operation unit, and a memory control function, and others. is there.

Document scanner 10 for optically reading a document
In the reading unit, the reflected light of the lamp irradiation on the document is condensed on the light receiving element by the mirror and the lens in the reading unit.
The light receiving element (CCD) is provided in a sensor board unit (SBU) 13, and the image signal converted into an electric signal in the CCD is converted into a digital signal on the SBU 13, that is, read image data. , SBU13 to the image processing ASIC 53 on the main control board 50.

The image data read from the SBU 13 is transferred to the image processing ASIC 53, and the image processing ASIC 53
Corrects the signal deterioration due to the quantization into the optical system and the digital signal (the signal deterioration of the scanner system: distortion of the read image data due to the scanner characteristics), and transfers the image data to the printer controller 60. The data is written in the image memory MEM 65 or the hard disk device (HDD) 66. Or
A process for printer output is performed, and L of the printer 100 is
It is given to the D control board 92.

That is, the image processing ASIC 53 stores the read image data in the image memory MEM 65 or the HDD 66.
And the video data control (V) on the LD control board 92 without storing in the memory MEM65.
DC) and output the image with the laser printer function. As an example of storing data in the MEM 65, when copying a plurality of originals, the scanner 10 is operated only once, the read image data is stored in the MEM 65, and the stored data is read a plurality of times. As an example in which the MEM 65 is not used, there is a case where only one document is copied, and the read image data may be processed as it is for the printer output. Therefore, there is no need to write the MEM 65. In the case of document storage (storage), MEM
The data is stored in HDD 66 instead of 65.

First, the memory MEM 65 and the HDD 66
If none of the above is used, the image processing ASIC 53 performs image reading correction on the read image data, and then performs image quality processing for conversion to area gradation. The image data after the image quality processing is transferred to a VDC (video data controller) on the LD control board 92. For the signal changed to the area gradation, post-processing related to dot arrangement and pulse control for reproducing dots are performed by VDC (Video Data Control),
A reproduced image is formed on a transfer sheet by a laser printer function.

When additional processing, for example, rotation in the image direction, synthesis of images, and the like are performed when the data is stored in the memory MEM 65 and read out from the memory MEM 65, the image data subjected to the image reading correction is stored in the image memory of the printer controller 60. Sent to peripheral ASIC 64 with access control function. Here, under the control of the MPU 61 in accordance with the operation program stored in the flash EEPROM, the access control of the image data and the memory module MEM65 and the expansion of the print data of the external personal computer PC (character code / character bit conversion). Compress and decompress image data for effective use of memory. The data sent to the peripheral ASIC 64 is stored in the MEM 65 after data compression, and the stored data is read as needed. Read data is expanded,
The image data is returned to the original image data and is returned from the peripheral ASIC 64 to the image processing ASIC 53.

When the image processing is returned to the ASIC 53, image quality processing is performed, and pulse control is performed on the VDC on the LCD control board 92, and a visible image (toner image) is formed on transfer paper by a laser printer function. In the case of document storage, the description about MEM65
The description is read as D66.

The hard disk drive HDD 66 is provided for realizing the storage management of a large amount of documents. In this embodiment, the HDD 66 is connected to the memory controller of the peripheral ASIC 64, and the image data is stored in the HDD when the memory capacity of the MEM 65 is insufficient and when the accumulation is continued even if the power is turned off. When a plurality of standard documents (format documents) are read and held by a scanner, or when a standard document or a stored document is stored from a personal computer PC, image data is written into the HDD 66. Also, from the PC PC, CD-RO
Images on an information medium such as an M or DVD (Digital Video Device) can be read into the MEM 65 or the HDD 66.

The fax transmission function, which is one of the composite functions,
Image processing ASI for image data read by the original scanner 10
The image is read and corrected in C53 and transferred to the FAX control unit (FCU) 91. The FCU 91 performs data conversion to a public line communication network and transmits the data to the communication network as FAX data. For FAX reception, the line data from the communication network is converted into image data by the FCU 91, and the image processing ASI
Transferred to C53. In this case, no special image processing is performed, dot rearrangement and pulse control are performed in the VDC on the LCD control board 92, and a visible image is formed on the transfer paper by the laser printer function.

The MPU 51 of the main control board 50 controls the flow of image data,
U61 controls the entire system and manages activation of each resource. The function selection of the digital multifunction copying machine is selected and input by the operation unit 20, and the processing contents such as the copy function and the FAX function are set.

The power supply of the printer controller 60 is +5 VE which is in the energized state even in the sleep mode, and is the DC power supply / A
It is supplied from the second power supply circuit 5 on the C control board 80. The main control board 50 is supplied with +5 V, which is turned off by the switch 84 in the sleep mode, from the second power supply circuit 5. The I / O control board 70 is supplied with + 5V and + 24V, which are also turned off in the sleep mode, from the second power supply circuit 5 and the first power supply circuit 4, respectively.

A DC having a first power supply circuit 4, a second power supply circuit 5, a start-up power supply circuit 6, and a fixing energizing circuit 85
An external AC power supply 1, for example, commercial AC is supplied to the power supply / AC control board 80 via the main switch 2 which is turned on / off by a user and a noise filter. An external AC voltage is applied to the fixing energizing circuit 85. The noise filter blocks high-frequency noise of the 100 V commercial AC line from entering the electric circuit after the circuit 3 and also prevents high-frequency noise generated by the electric circuit from leaking to the commercial AC line.

DC conversion circuit 3 rectifies and smoothes an external AC voltage into a DC voltage. That is, the DC conversion circuit 3 is a rectifying and smoothing circuit, and includes a full-wave rectifying bridge and a smoothing capacitor. An output DC voltage of about 100 V of the circuit 3 is applied to the first power supply circuit 4 and the second power supply circuit 5. These circuits 4 and 5 are a DC / DC converter for outputting 5 V (control system voltage) and a 24 V
(Drive voltages for motors, solenoids, relays, etc.) Includes DC / DC converters for output. The DC power supply / AC control board 80 includes a digital controller 7 (hereinafter referred to as DSP 7), which is a DSP (Digital Signal Processor) for controlling the DC / DC converter circuits 4 and 5, and a start-up power supply circuit 6.

Each of the first power supply circuit 4 and the second power supply circuit 5 includes a switching regulator, a transformer receiving its output on a primary winding, a circuit for rectifying and smoothing the voltage of its secondary winding, and its output to a DSP 7. The input DC is a DC output from the DC conversion circuit 3 including an output circuit for feeding back.

A switch 84 is inserted in the + 5VE (+ 5V) output line of the second power supply circuit 5. A control signal for turning on / off the switch 84 is given from the printer controller 60 to the switch 84. When shifting to the sleep mode for energy saving, the printer controller 60 turns off the switch 84 by this control signal, gives an instruction to stop the output of the first power supply circuit 4 to the DSP 7, and stops the DC output operation of the circuit 4.

In response to a copy start or print command, the target temperature of heater energization of the fixing energizing circuit 85 is maintained at the fixing roller temperature as the fixing operation temperature determined for the fixing process of the transfer paper on which the toner image has been transferred. The standby mode (operation mode) in which image formation can be started with substantially no delay time, and the target temperature is set to 80% of the fixing operation temperature in order to reduce power consumption, and the other conditions are the same as those in the standby mode. In the low-power mode in which a return to the standby mode can be immediately performed when there is an operation input, the printer controller 60 turns on the switch 84 by the control signal and gives an output instruction of the first power supply circuit 4 to the DSP 7, 4 causes a DC output operation.

That is, in the sleep mode for energy saving, the switch 84 is turned off and the first power supply circuit 4 is turned off (output is stopped), and the printer controller 60 and the operation unit 2 are turned off.
0, + 5VE is continuously applied to the minimum number of electric elements or circuits to detect the action of the operator or the print command of the personal computer PC, which indicates the possibility of using the copying machine, for detecting the opening and closing of the pressure plate. In the printer controller 60,
+ 5VE is continuously applied to a circuit that waits for the detection and turns on the switch 84 in response to the detection and a memory that stores data that needs to be held in a non-volatile manner.

In the low power mode, power is supplied to all the power supply units, and only the set temperature of the fixing heater 123C is lowered. In this embodiment, the fixing energizing circuit 85 is an AC circuit that energizes the fixing heater 123C by phase control using a triac. In addition, triac and A
During the C input, there is a heater power relay that is turned on by the + 24V output of the first power circuit 4, and when the first power circuit 4 generates + 24V, the heater power relay is turned on and the triac is connected to the AC input Is done. When the first power supply circuit 4 stops outputting +24 V, the heater power supply relay is turned off, and the triac is cut off from the AC input. The MPU 51 of the main control plate 50 controls the conduction phase of the triac so that the temperature of the fixing roller (fixing temperature) becomes the target temperature.

The analysis and display of the key-in data from the operation unit 20 are controlled by the MPU 61 of the printer controller 60.
Performs control, and an interface with the operation unit 20 is provided by the peripheral ASIC 64. In this embodiment, the peripheral ASIC 64 and the operation unit 20 are connected via the motherboard 90, the main control board 50, and the scanner control board 11. The printer controller 60 is connected to a pressure plate open / close detection (not shown) via the motherboard 90, the main control plate 50, and the scanner control plate 11, similarly to the operation unit 20.

The pressure plate open / close detection is a detection switch for detecting the opening / closing of the ADF 30 when the ADF 30 is connected to the scanner, and is a detection switch for detecting the opening / closing of the pressure plate for document pressing when the ADF 30 is not mounted. . In any case, the pressure plate open / close detection generates a signal indicating whether the ADF or the document pressing platen is open,
This is the case when the scanner control board 10 and the main control board 5 are in any of the image processing operation state (operation mode), the standby mode (operation mode), the low power mode and the sleep mode.
0 and the motherboard 90 to the peripheral ASIC 64 of the printer controller 60, and the MPU 61 reads this signal. A power supply (+ 5V) for representing a signal indicating whether or not it is in an open state, and a power supply (+ 5V) for detecting the ON of an input key of the operation unit 20 and generating a detection signal
E) is given from the process controller 60 to the open / close detection switch and the operation unit 20 via the motherboard 90, the main control board 50, and the scanner control board 10.

When the ADF 30 is provided, it is connected to the scanner control board 11. A detection signal of a document sensor for detecting whether or not a document is present on the platen of the ADF 30 is also
The peripheral AS of the printer controller 60 is transmitted via the scanner control board 11, the main control board 50, and the motherboard 90.
The signal is given to the IC 64, and the MPU 61 reads this signal. A power supply (+ 5VE) for the document sensor to generate a detection signal indicating the presence or absence of a document is also supplied from the process controller 60 to the document sensor via the motherboard 90, the main control board 50, and the scanner control board 10.

The facsimile control unit FCU 91
The FCU 91 performs data conversion to the public line communication network PN and transmits it to the PN as FAX data. FAX reception is performed when the line data from the PN is converted into image data by the FCU 91, and is directly stored in the ASIC 53 via the ASIC 64 or temporarily stored in the MEM 65. Is transferred to the ASIC 53 via the ASIC 64. In this case, no special image quality processing is performed, and dot rearrangement and pulse control are performed in the printer 100, and a visible image is formed on transfer paper in the image forming unit of the printer 100.

Referring to FIG. 4, an alternating current detection circuit ISEN
0 detects an AC current value flowing into the DC conversion circuit 3 and generates a voltage representing the value, that is, an analog detection signal,
It is applied to the analog signal input terminal of the A / D converter of the DSP 7. In the AC current detection circuit ISEN0 of this embodiment, a low-resistance resistor generates an AC voltage proportional to the AC current value flowing into the DC conversion circuit 3, and the full-wave rectification bridge rectifies the AC voltage and smoothes the AC voltage. The circuit converts to a DC voltage without AC ripple. This DC voltage is applied to the light emitting diode of the photocoupler, and the light receiving element of the photocoupler generates the analog detection signal at a level corresponding to the light intensity of the light emitting diode. "Standby detection" for determining whether the load of the first power supply circuit 4 is in a standby state (an "inactive" state that is not an operating state for image formation), which will be described later (FIG.
0), the standby state is determined when the AC current value flowing into the DC conversion circuit 3 is equal to or smaller than a threshold value Irest (for example, an effective value of 1 A), but the AC current detection circuit ISEN0 determines the AC input current for this determination. It is provided to detect the value.

FIG. 5 shows an outline of the DC conversion circuit 3, the first power supply circuit 4, the second power supply circuit 5, and the starting power supply circuit 6. 100V commercial AC voltage is applied to AC input terminals IN1, IN
2 to the DC conversion circuit 3. The DC conversion circuit 3 includes a rectification / smoothing circuit including a full-wave rectification diode bridge DB1 and a smoothing capacitor C1. The DC conversion circuit 3 also has a starter circuit including a resistor R1 and a relay RA1, and an AC voltage is also applied thereto. When an AC voltage is applied, a voltage input terminal Vcc of the DSP 7 of the relay RA1 is applied.
And the diode D32 connected to the battery B1 closes the relay contact RA1, whereby the battery voltage is applied to the voltage input terminal Vcc of the DSP 7 and the DSP 7 is started, and the first power supply circuit 5 and the second power supply circuit And outputs a first PWM pulse PWM1 and a second PWM pulse PWM2 to the drivers DRIVE11 and DRIVE21.
As a result, the first power supply circuit 4 generates a voltage (power system voltage) of about 24 V, the second power supply circuit 5 generates a voltage of about 5 V (control system voltage), and the voltage of about 5 V is applied to each part of the control circuit. Is applied to Each control circuit is activated by this voltage.

The DC voltage converted by DC conversion circuit 3 is applied to transformer TR 11 of first power supply circuit 4 and second power supply circuit 5.
And to the primary winding of TR21. When the switching elements FET11 and FET21 are turned on, a current flows from the DC conversion circuit 3 to the primary side ground via each primary winding and each switching element.

Drive circuit DRIV1 of first power supply circuit 4
Reference numeral 1 is connected to a PWM output port PWM1 for outputting a first PWM pulse PWM1, which is a switching ON / OFF signal of the DSP 7. With DRIV11, transformer TR11 and switching element FET11,
A primary side switch circuit is configured, and the output voltage of the DC conversion circuit 3 is chopped by switching in response to the PWM pulse, and a pulse is supplied to the primary winding of the transformer TR11.

On the secondary side of the transformer TR11, there is an output circuit for converting the pulse voltage induced in the secondary winding into a direct current and outputting the direct current. The output circuit includes diodes D11 and D12,
Choke coil CH11, secondary current overcurrent detection 2
Secondary side overcurrent detection circuit ISEN12, output voltage detection circuit V
It is composed of SEN11 and smoothing capacitor C11.

The secondary overcurrent detection circuit ISEN12 is configured to convert the current flowing through the output circuit of the first power supply circuit 4 into a voltage (secondary current detection signal) corresponding to the magnitude of the current and output the converted voltage. (Secondary current detection signal) output from the A / D conversion input port If1 of the DSP 7
Apply to 1.

The output voltage detection circuit VSEN11 outputs a voltage proportional to the output voltage Vout11 (24V) of the first power supply circuit 4 to the A / D conversion input port Vf11 of the DSP 7.
Is applied.

The transformer TR21 of the second power supply circuit 5
The output circuit on the secondary side has the same configuration as that of the first power supply circuit 4, but further has a startup power supply circuit 6 for supplying power to the DSP 7. This circuit 6 includes a transformer TR2
It comprises a diode D31 connected to the third tertiary winding, a capacitor C31, a constant voltage circuit CV31, and a diode D33 for preventing backflow. Power supply terminal V of DSP7
Between the cc and GND, the battery B1 and the diode D3
2. Further, the relay RA1 of the starting circuit in the DC conversion circuit 3
A series circuit of a contact that is opened and closed by a relay piece RA1 that is closed and driven by the relay contact is connected.

FIG. 6 shows the configuration of the DSP 7. In this example, the event manager is used for the PWM pulse generator 7e. This includes a plurality of PWM pulse output ports, and the CPU 7a loads data for defining a PWM pulse and a pulse duty addressed to each output port into a pulse generation control register in the PWM pulse generator 7e. With this load, the PWM pulse generator 7e
Generates a PWM pulse specified by the register data and outputs the PWM pulse from the PWM pulse output port. In this embodiment, two PWM pulses are output from the two PWM pulse output ports PWM1 and PWM2 to the switching drivers DRIVE11 and DRIVE21. Data defining the cycle and duty of each PWM pulse is set by the CPU 7a in the pulse generator 7e.

The A / D converter 7h in the DSP 7 has the first
The output current (If11) and output voltage (Vf1) of the power supply circuit 4
1) and a feedback signal indicating the circuit temperature (TEM), a feedback signal indicating the output current (If21) and the output voltage (Vf21) of the second power supply circuit 5, and an AC current value output from the AC current detection circuit ISEN0. An analog detection signal is applied. The A / D converter 7h converts the feedback signal applied to the designated input channel into digital data under the control (instruction) of the CPU 7a via the interface 7g, and latches it in its own output register. Then, a conversion completion signal is generated.

In response to the conversion completion signal, the CPU 7a reads the feedback digital data (A / D conversion data) and changes the output voltage of the power supply circuit to the set voltage (2
4V, 5V) and calculation of the PWM pulse duty and writing of the data defining the duty to the pulse generator 7e, or detection of an abnormality in the output current of the power supply circuit or detection of an overheating abnormality in the first power supply circuit 4. I do. Of the CPU 7a,
The program that performs the above operations or processes is EEPRO
It is written in M7b. The RAM 7c is used for temporarily storing or storing data.

Referring back to FIG. When the commercial AC voltage is turned on, that is, when the main switch 2 is closed and the commercial AC voltage is applied to IN1 and IN2, the DC voltage rectified by the diode bridge DB1 causes a current to flow through the resistor R1 to the relay RA1 of the starting circuit. The contact RA1 for applying the voltage of the battery B1 to the power supply voltage input terminal Vcc of the DSP 7 closes. As a result, the operating voltage is supplied to the DSP 7, the DSP 7 is activated, and the CPU 7a
The control operation shown in FIG. 7A is performed according to the program in the ROM 7b.

That is, referring to FIG.
When the operating voltage is applied thereto, U7a initializes each register and each data, puts the input / output port in a standby state (initialization: step 1), and (the period and duty of the PWM pulse) applied to the pulse generator 7e. The PWM register, which is an output register for storing data defining the following, stores an initial value (a PWM pulse period, a first reference value defining a duty for 24V output, and a second reference defining a duty for 5V output). Value) (step 2). These data are stored in the EEPROM 7b.
It is written on the CPU operation program. In the following description, when writing a step number or symbol in parentheses, the word “step” is omitted, and only the step number or symbol is written.

Next, the CPU 7a resets the interrupt register of the pulse generator 7e, and resets the PW of the pulse generator 7e.
The data of the PWM register is written to the M pulse generation control register (3). The pulse generator 7e generates (outputs) a PWM pulse based on the written data.
To start. Next, the CPU 7a starts a program timer for a time period of 200 μsec (4), and permits a timer interrupt responding to the time over (5).

Then, it waits for an interrupt to occur, during which MP
Waiting for an instruction to turn off the first power supply circuit 4 for transition to the sleep mode or an instruction to turn on the first power supply circuit 4 for return to the operation mode from U51 (UART connector 7k) (6, 8) Also, it is checked whether the “TUc clocking” (40) repeated in a 200 μsec cycle in the “A / D conversion end interrupt” ADI shown in FIG. 8 has been repeated a set number of times TUc (TOF = 1). (10).

When the off instruction (pause mode instruction) of the first power supply circuit 4 arrives, the CPU 7a writes "1" indicating this to the register FR24V (7), and the on instruction (operation mode instruction) of the first power supply circuit 4 is issued. Upon arrival, the CPU 7a writes "0" representing this to the register FR24V (9). "A / D conversion end interrupt" ADI is set number of times T
When Uc is repeated, "1" is written in the register TOF by the "A / D conversion end interrupt" ADI. At this time, "standby detection" (11) is executed to clear the register TOF (10- 11-12), and wait for a new “time measurement of TUc” (40) to be repeated a set number of times TUc.
The details of the “standby detection” (11) will be described later with reference to FIG.

When the condition for shifting from the operation mode to the sleep mode is satisfied, the MPU 6 of the printer controller 60
1 gives an instruction to turn off the first power supply circuit 4 to the MPU 51 on the main control board 50, and the MPU 51
After the transfer to the PU 7a, the switch 84 is turned off.
When the condition for shifting from the halt mode to the operation mode is satisfied, the MPU 61 of the printer controller 60 turns on the switch 84, whereby the MPU on the main control board 50 is turned on.
After the activation of the first power supply circuit 51, an instruction to turn on the first power supply circuit 4 is given thereto, and the MPU 51 transfers the instruction to the CPU 7a of the DSP 7.

Next, reference will be made to FIG. After the CPU 7c permits the interrupt (5, 6) as described above,
When the μsec timer times out, the CPU 7a proceeds to a timer interrupt (TII) shown in FIG.
Restart 200 μsec timer (21), A / D
The input voltage channel of the converter 7h is No. Set to 0 to instruct the A / D converter 7h to perform A / D conversion (22),
Enable the interrupt that responds to the completion of A / D conversion (2
3). The A / D converter 7h has an input port No. The digital conversion of the analog signal of 0, that is, the feedback signal (Vf21) representing the output voltage of the second power supply circuit 5 is started, and when this is completed, an end signal (converted data read ready) is generated. In response to the end signal, the CPU 7a proceeds to an A / D conversion end interrupt (ADI) shown in FIG.

The CPU 7a receives an interrupt (AD1) shown in FIG.
Is the input port (channel) for the A / D conversion just completed
(31-34) corresponding to No. If it is 0, “5V voltage control” (35) is If it is “1”, “24V voltage control” (36) is If it is 2, "5V secondary current abnormality control" (37)
No. In the case of No. 3, “24V secondary current abnormality control” (38) If it is 4, "temperature abnormal control" (38) is executed.

FIG. 9 shows the contents of "5 V voltage control" (35). When proceeding to this, the CPU 7a sets the A / D converter 7h
(Data output voltage of the second power supply circuit 5)
Is read into the register Vf21 (41), and it is checked whether it is not less than the set value Rf5VU (abnormal overvoltage) or not more than the set value Rf5VL (abnormal low voltage) (42a, 42b). If the set value is less than Rf5VU and more than Rf5VL, an error amount of the output voltage data read this time with respect to a fixed target voltage value VO21 = 5V is calculated, and the error amount is converted into a PWM pulse duty correction amount. This correction amount is the PWM set at that time.
PWM21 data that defines the output pulse duty in addition to the pulse duty is calculated (43), and is calculated as C
The PWM 21 register is updated and written in the PU 7a or in the PWM 21 register defined in the RAM 7c, and the data of the PWM 21 register is written into the PWM 21 pulse generation control register of the pulse generator 7e (44). Thereby, the pulse generator 7
The PWM pulse e outputs to the pulse output port PWM21 changes to a duty for setting the error amount of the output voltage to zero. This is feedback control of the output voltage of the second power supply circuit 5.

The output voltage of the second power supply circuit 5 is equal to the set value Rf5
If VU or more or Rf5VL or less, CPU
7a writes data with a PWM duty of 0% to the PWM11 register and the PWM21 register (47). Thereby, the pulse output of the pulse generator 7e (PWM1
1, PWM21) stops, and FET11 and F
ET21 turns off. Next, the CPU 7a prohibits all interrupts permitted to itself (48). As a result, the DSP 7 stops operating until the AC voltage is cut off once and turned on again, and both the first power supply circuit 4 and the second power supply circuit 5 stop operating and output is stopped.

When the duty of the PWM pulse (PWM 21) is updated as described above, regardless of the abnormality of either the above-mentioned overvoltage or low voltage, the CPU 7a sets the No. of the A / D conversion input channel. A / D converter 7 specifying 1
h is instructed to perform A / D conversion (45), and an interrupt responding to completion of A / D conversion is permitted (46). A / D converter 7h
Is the input port No. 1, the feedback signal (V) representing the output voltage of the first power supply circuit 4.
The digital conversion of f11) is started, and when the digital conversion is completed, an end signal (conversion data read ready) is generated. CPU
7a responds to this end signal to proceed to the A / D conversion end interrupt (ADI) shown in FIG. 8, and then to "24V voltage control" (36) from step 32 in FIG.

FIG. 10 shows the contents of "24 V voltage control" (36). This content is described in “5V Voltage Control” (3
5) is similar to the output voltage V of the first power supply circuit 4.
The PWM pulse (PWM11) given to the driver FET11 of the first power supply circuit 4 is set so that f11 is set to a target voltage value VO11 (= 24V / 22V) in which a different value is set depending on whether the apparatus is in the standby state. The duty is similarly feedback-controlled (51, 52a, 52b, 52
d, 53, 54). However, this is the case where the operation mode is designated and FR24V = 0 (data in the register FR24V is 0).

When the sleep mode is set for energy saving and FR24V = 1, the CPU 7a sets the PWM duty 0% that restricts the FET 11 of the first power supply circuit 4 to OFF to the PWM data ( 52b, 52c),
This is written to the PWM register (54). This allows
The 24V output operation of the first power supply circuit 4 stops. That is, the first power supply circuit 4 is turned off.

If the output voltage VF11 of the first power supply circuit 4 is an overvoltage abnormality (the output voltage is equal to or higher than Rf24VU) or a low voltage abnormality (less than Rf24VL), the VPU of the DSP 7
7a stops the driving of the first power supply circuit 4 and sets the register FR
"1" (prohibition of driving of the first power supply circuit 4) is written to 24V (57), and the PWM11 data is set to 0 (power supply duty 0: power supply stop) (58).

When the output voltage Vf11 of the first power supply circuit 4 is in the normal range and the duty of the PWM pulse (PWM11) is updated, the CPU 7a sets the No. of the A / D conversion input channel. A / D conversion is instructed to the A / D converter 7h by designating 2 (55), and an interrupt responding to completion of the A / D conversion is permitted (56). The A / D converter 7h has an input port No. The digital conversion of the analog signal of No. 2, that is, the feedback signal (If21) representing the output current of the second power supply circuit 5, is started, and when this is completed, an end signal (converted data read ready) is generated. In response to this end signal, the CPU 7a proceeds to an A / D conversion end interrupt (ADI) shown in FIG.
V Secondary Current Abnormality Control ”(37).

When the process proceeds to “5V secondary current abnormality control” (37), the CPU 7a stores the A / D converter 7 in the register If21.
The converted data (output current data of the first power supply circuit 4) is read, and it is checked whether the converted data is not less than the set value Rf5ViU (abnormal overcurrent) or not more than Rf5ViL (abnormal low current). If so, the CPU 7a stops driving the first power supply circuit 4 and the second power supply circuit 5, and
Stop the control operation.

When the output current value is within the normal range,
The CPU 7a determines the number of the A / D conversion input channel. 3 and instructs the A / D converter 7h to perform A / D conversion.
Enable the interrupt that responds to the completion of the D conversion. The A / D converter 7h has an input port No. The digital conversion of the analog signal of No. 3, that is, the feedback signal (If11) representing the output current of the first power supply circuit 4, is started, and when this is completed, an end signal (converted data read ready) is generated.
In response to the end signal, the CPU 7a responds to A shown in FIG.
Proceeds to the / D conversion end interrupt (ADI), and proceeds from step 34 of FIG. 8 to "24V secondary current abnormality control" (38).
Proceed to.

The contents of the "24V secondary current abnormality control" (38) are roughly the same as the "5V secondary current abnormality control" (37) described above. This “24V secondary current abnormality control”
In (38), if the output current (If11) of the first power supply circuit 4 is an overcurrent abnormality (the output current is Rf24iU or more) or a low current abnormality (Rf24iL or less), the VP of the DSP 7
U7a stops driving of the first power supply circuit 4 and
"1" (drive prohibition of the first power supply circuit 4) is written to R24V, and the PWM11 data is set to 0 (power supply duty 0: power supply stop).

If the output current (If11) of the first power supply circuit 4 is within the normal range, the CPU 7a determines the A / D conversion input channel No. 4 and the A / D converter 7h outputs A / D
D conversion is instructed, and an interrupt responding to completion of A / D conversion is permitted. The A / D converter 7h has an input port No. The digital conversion of the analog signal of No. 4, that is, the temperature detection signal (THM) of the thermistor TH provided in the first power supply circuit 4 is started, and when this is completed, an end signal (reading of conversion data read) is generated. In response to the end signal, the CPU 7a proceeds to an A / D conversion end interrupt (ADI) shown in FIG. 8, and proceeds from step 34 in FIG.
Proceed to (39).

When the process proceeds to the "temperature abnormality control" (39), the CPU
7a reads the data (the temperature detection data of the thermistor TH) converted by the A / D converter 7h into the register TEM, and determines whether the data is equal to or more than the set value RfTEMU (overheating abnormality) or Rf
Check if it is less than TEML (sensor error). If the value is equal to or more than the set value RfTEMU or equal to or less than RfTEML, the CPU 7a stops driving the first power supply circuit 4 and stores “1” in the register FR24V (prohibits driving of the first power supply circuit 4).
Is written, and the PWM11 data is set to 0 (power supply duty 0: power supply stop).

When the detected temperature is within the normal range, and
As described above, the PWM11 data is set to 0 in response to the temperature abnormality.
Then, the CPU 7a ends the "temperature abnormality control" (39) and proceeds to "time measurement of TUc" (40).

In the "time measurement of TUc" (40), the value of the time counter (register) TCR is incremented by 1 (40a), and it is checked whether or not it has reached the set value TUc (for example, 5) (40b). . When TUc is reached, "1" is written to the register TOF (40c), and the time counter TCR is initialized (40d). Then, returning to the main routine ((a) of FIG. 7), since the data TOF of the register TOF is "1", "standby detection" (11) is executed, and the data TOF of the register TOF is initialized to "0". Become After that, "Time measurement of TUc" (40)
Is repeated TUc times, "1" is written to the register TOF (40c), so "standby detection" (11) is TUc × 2
The cycle is repeated at a cycle of 00 μsec and 1 msec when TUc = 5.

As described above, "A / D conversion end interrupt" A
Reading of the feedback signal (A / D
Conversion), updating of the PWM pulse duty, detection of output abnormality, and detection of temperature abnormality are repeated in a predetermined order. These series, that is, steps 22 and 23 in FIG.
And "A / D conversion end interrupt" shown in FIG. 8 (AD1)
The time required to perform steps 31-40 of
Since the time is less than 0 μsec, this series of processing is performed for 200
Completes before the μsec timer times out. When the 200 μsec timer expires, CP
U7a is a timer interrupt (TI) shown in FIG.
Execute I) again. Thus, the control cycle of the CPU 7a is substantially 200 μsec. The PWM pulse has a frequency of about 100 KHz.

By the above control operation of the CPU 7a, DS
P7 is an output voltage circuit VSE input to the port Vf21.
Turn on / off the switching element FET21 so that the output voltage value of N21 becomes a predetermined voltage (VO21 = 5V).
Drive pulse DRIV21
Output to The switching element FET21 is driven ON / OFF via the drive circuit DRIV21 to excite the transformer TR21. Then, the AC voltages induced in the secondary coil and the tertiary coil are rectified and smoothed, respectively.
DC voltages (5V, 5VE, Vcc) are output. DS
P7 always has an output voltage value (Vf21) of a predetermined voltage value 5
The ON duty calculation of the switching ON / OFF and the pulse output of the duty are continued so as to be V.

Similarly, the DSP 7 calculates a switching signal for turning on / off the switching element FET11 so that the output voltage value of the output voltage circuit VSEN11 input to the port Vf11 becomes a predetermined voltage (VO11 = 24V / 22V). Then, the data is output to the drive circuit DRIV11. The switching element FET11 is turned on / off via the drive circuit DRIV11, and the transformer TR1
1 is excited. The DSP 7 always outputs the output voltage value (Vf1
The ON duty calculation of switching ON / OFF and the pulse output of the duty are continued so that 1) becomes a predetermined voltage value (VO11 = 24V / 22V).

Note that the input AC current value If0 of the DC conversion circuit 3 is set to the set value I by the "standby detection" (11) described later.
When the voltage exceeds the rest, the predetermined voltage value VO11 is set to 24V, but when If0 is equal to or less than the set value Irest, the predetermined voltage value VO11 is set to 22V. When VO11 is set to 24V, the duty of PWM1 is high, and the output voltage of the first power supply circuit 4 is as high as 24V. And the output voltage of the first power supply circuit 4 is as low as 22V.

A state in which the input AC current If0 exceeds the set value Irest is regarded as a high load state in which there is a high possibility that power is being supplied to the load for image formation.
This is regarded as a standby state in which no image forming operation is performed.

As already mentioned, the sleep mode in which the output of the first power supply circuit 4 is stopped and the switch 84 is opened to stop the power supply to the control circuit which is not related to the command reading in order to save energy. An operation mode in which the output of the first power supply circuit 4 is started and the switch 84 is closed to provide an operable voltage to all circuits, and an operable voltage is applied to all circuits in the same manner as the operation mode, There are three types of system control modes: a low power mode in which the target temperature is set to 80% of the fixing temperature value (fixed value). The low power mode is included in the operation mode.

Incidentally, the operation mode includes an instruction waiting state in which an image forming operation can be immediately started when an image forming instruction is issued, and is not necessarily during the image forming operation. Even in the operation mode, when the image forming operation is not performed and the image forming instruction is awaited, the input AC current value of the DC conversion circuit 3 is set to the set value I.
It is a "standby state" below rest.

FIG. 11 shows the contents of "standby detection" (11). At this point, the CPU 7a of the DSP 7 sends the analog input channel No. to the A / D converter 7i. Instruct the digital conversion of the signal No. 5 and write the A / D converted digital data, that is, the current detection value data of the AC current detection circuit ISEN0, to the register If0 (61). Next, it is checked whether or not the current detection value data If0 is equal to or smaller than a set value Irest (for example, an effective value of 1 A) which is a threshold for determining whether or not the apparatus is in a standby state (standby state) (62).

If the value is not less than the set value Irest, there is a high possibility that the image forming operation is being performed. Therefore, the target value VO11 of the output voltage of the first power supply circuit 4 is set to 24 V (62-63), and the state determination register is set. REF, IRF and counter CC
Initialize the data of R (also a register) (64-6
6). This target value VO11 = 24V is the same as the aforementioned “24V
In step 53 of “Voltage control” (36: FIG. 10), the output voltage reaches the target value.
Is controlled.

When the current detection value data If0 of the current detection circuit ISEN0 switches to the set value Irest or less, "1" indicating that the switch to the set value Irest or less is written to the register IRF (62-67). -68), the counter CCR is incremented by one (69). Thereafter, the current detection value data If0 of the current detection circuit ISEN0 is continued.
Is less than or equal to the set value Irest, the “standby detection” (11) is TUc × 200 μsec (for example, 1
msec), the counter CCR is incremented by one in this cycle (62-67-71-6).
9). The count value CCR of the counter CCR is equal to the set value DT.
h (for example, 2000), the CPU 7a
The target value VO11 of the output voltage of the power supply circuit 4 is set to 22 V (70, 72), and "1" indicating that the low voltage output (standby state) is being performed is written to the register REF (73).
Since this target value VO11 = 22V becomes the output voltage target value in step 53 of the above-mentioned “24V voltage control” (36: FIG. 10), the output voltage of the first power supply circuit 4 is controlled to 22V. When the low-voltage output (standby state) is performed, the current detection value data I of the current detection circuit ISEN0 is output.
As soon as f0 exceeds the set value Irest, the first power supply circuit 4
The output voltage target value VO11 is set to 24 V (6
2, 63).

That is, from the state where the current detection value data If0 of the current detection circuit ISEN0 is equal to or lower than the set value Irest, Ire
Since the target value VO11 of the output voltage of the first power supply circuit 4 is set to 24 V immediately after switching to the state exceeding st, the delay in switching this target value is TUc × 200 μ (for example, 1
msec). On the other hand, when the current detection value data If0 is switched to the set value Irest or less, the set value Irest or less becomes TUc × 200 μ × DTh (for example, 2 s).
ec), the target value VO11 of the output voltage of the first power supply circuit 4 is set to 22 V. Therefore, after the power consumption of the load has decreased to the low value in the standby state, the first power supply circuit has a delay of 2 sec. The target value VO11 of the output voltage of the circuit 4 is 2
Reduced to 2V.

Second Embodiment In the second embodiment, in the standby state (If0 ≦ Irest), the driving of the first power supply circuit 4 is stopped to change its output voltage from 24 V to 0 V, and the second power supply circuit 5 The output voltage is reduced from 5V to 4.6V. When the output voltage of the first power supply circuit 4 is set to 0 V, the fixing energizing circuit 85
The power relay that opens and closes the commercial AC voltage inside is turned off, and the fixing heater cannot be energized. However, even in the standby state where the image forming operation is not performed,
Electricity is required for warming up or for maintaining a preheating temperature at which the fixing temperature can be raised immediately.

Therefore, as shown in FIG. 12, in the second embodiment, in the first embodiment, two
The power relay of 4V drive is omitted, an AC relay RA2 is inserted in front of the input terminal of the fixing energizing circuit 85, and the AC relay RA2 is energized (driven) by a third relay RA3 that can be driven at 4.6V. I did it. The DSP 7 opens and closes the third relay RA3 via a relay driver RD3. Other hardware of the second embodiment includes:
This is the same as the first embodiment.

FIG. 13 shows the CPU of the DSP 7 in the second embodiment.
7A shows the content of “standby detection” (11) executed by the control unit 7a. In the second embodiment, the CPU 7a determines the current detection value data If0
Is a set value Ire which is a threshold value for determining whether the apparatus is in a standby state.
If not st (waiting state), the target value VO11 of the output voltage of the first power supply circuit 4 is set to 24V, and the target value VO21 of the output voltage of the second power supply circuit 5 is set to 5V (63). . Since this target value VO11 = 24V becomes the output voltage target value in step 53 of "24V voltage control" (36: FIG. 10) having the same contents as in the first embodiment, the output voltage of the first power supply circuit 4 becomes 24V. Controlled. Target value VO21 =
Since the 5V becomes the output voltage target value in step 43 of “5V voltage control” (35) shown in FIG.
Is controlled to 5V.

The current detection value data If0 of the current detection circuit ISEN0 is switched to the set value Irest or less, and the current detection value data If0 of the current detection circuit ISEN0 continues thereafter.
Is less than or equal to the set value Irest and the count value CC of the counter CCR
When R reaches the set value DTh (for example, 2000), the second
The CPU 7a of the embodiment sets the target value VO11 of the output voltage of the first power supply circuit 4 to 0V and sets the target value VO21 of the output voltage of the second power supply circuit 5 to 4.6V. This target value VO11 = 0V is the same as “2” in the first embodiment.
Since the output voltage target value is obtained in step 53 of “4V voltage control” (36: FIG. 10), the driving of the first power supply circuit 4 is stopped, and the output voltage becomes 0V. Target value VO21 = 4.6V
Is the output voltage target value in step 43 of “5V voltage control” (35) shown in FIG. 14, so that the output voltage of the second power supply circuit 5 is controlled to 4.6V.

If the data in the register FR24V is "0" (operation mode designation), the CPU 7a energizes the third relay RA3 via the relay driver RD3 (74, 75). As a result, the relay contact is closed, the AC relay RA2 is energized and turned on, and the AC energizing circuit 8 is turned on.
5 is supplied with a commercial AC voltage. If the data in the register FR24V is "1" (pause mode designation), the CPU 7a
Stops the energization of the third relay RA3 (74, 7
6). This opens the relay contact to open the AC relay R
The energization of A2 is stopped, and the commercial AC voltage to the AC energizing circuit 85 is cut off.

Other control operations of the CPU 7a of the DSP 7 of the second embodiment are the same as those of the first embodiment.

[0136]

As described above, when the power supply to the load is stopped, the current value falls below the set value, and accordingly, the PWM duty is set to a value for outputting a low voltage, or the voltage output of the power supply is stopped. Therefore, standby power consumption of the power supply is reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a multifunction color copier equipped with a power supply according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an outline of an image forming mechanism of the color printer 100 shown in FIG.

FIG. 3 is a block diagram showing a system configuration of an electric system of the copying machine shown in FIG.

FIG. 4 shows a power supply device according to the first embodiment shown in FIG.
FIG. 3 is a block diagram showing an electric circuit division on a power supply / AC control board 80 and an outline of an electric control system supplied with power.

FIG. 5 shows a first power supply circuit 4 and a second power supply circuit 5 shown in FIG.
FIG. 4 is an electric circuit diagram of a start-up power supply circuit 6.

FIG. 6 is a block diagram showing a configuration of a digital control unit DSP7 shown in FIG.

7A is a flowchart showing a control operation of a CPU 7a shown in FIG. 6, and FIG. 7B is a flowchart showing an outline of a timer interrupt process.

8 is an A / D converter 7i of the CPU 7a shown in FIG.
7 is a flowchart showing the contents of an interrupt process executed in response to the completion of A / D conversion of FIG.

9 is a flowchart showing the contents of “5V voltage control” (35) shown in FIG.

FIG. 10 is a flowchart showing the contents of “24V voltage control” (36) shown in FIG.

FIG. 11A shows “standby detection” (11) shown in FIG.
6 is a flowchart showing the contents of the above.

FIG. 12 shows a DC power supply device according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing divisions of electric circuits on a power supply / AC control board 80.

FIG. 13 shows a digital controller D of the power supply device according to the second embodiment.
"Standby detection" of CPU 7a (not shown) inside SP7
It is a flowchart which shows the content of (11).

FIG. 14 is a digital control unit D of the power supply device according to the second embodiment.
It is a flowchart which shows the content of "5V voltage control" (35) of CPU7a (not shown) inside SP7.

[Explanation of symbols]

1: AC power supply 2: Main switch 20: Operation unit 100: Printer 101: Photoreceptor belt 102, 103: Rotating roller 104: Charging charger 105: Laser exposure device 106: Color developing device 107: Cleaning blade 109: Intermediate transfer belt 110-112: Rotating roller 113: Bias roller 114: Transfer roller 115: Cleaning device 116: Paper feed table 117: Paper feed roller 118a, 118b: Transport roller pair 119a, 119b: Registration roller pair 120: Fixing device 121a, 121b : Paper discharge roller pair 122: paper discharge stack section

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C061 AP03 AP04 AQ06 AR01 HH11 HK19 HT01 HT06 HT07 2H027 DA01 EF16 EJ17 ZA01 5H730 AA14 AS05 BB23 BB57 BB82 BB88 CC01 DD04 EE02 EE08 EE10 EE59 FD51V05 F05 FD51 V05

Claims (6)

[Claims] An input voltage is switched by PWM switching.
Detects whether the current value of the power supply that generates the output voltage corresponding to the M duty exceeds or falls below the set value depending on whether or not power is supplied to the load. A power saving control method for a power supply, wherein a PWM duty is set to a value to output a low voltage near a lower limit value of a tolerance range of a rated voltage when the value is equal to or less than a set value. 2. When the current value exceeds a set value, a rated voltage is set to a target value. When the current value is less than the set value, a low voltage near a lower limit value of a tolerance range of the rated voltage is set to a target value. 2. The power saving control method for a power supply according to claim 1, wherein the PWM duty is changed so that the detected value matches the target value. 3. The power supply is a switching power supply that rectifies and smoothes a commercial alternating current and supplies a chopping current to a primary winding of a step-down transformer via a switching element to rectify a voltage generated in a secondary winding. Detecting an AC current value flowing into a circuit for rectifying and smoothing commercial AC;
The power saving control method for a power supply according to claim 1. 4. A transformer, wherein a primary winding of the transformer has a PWM
A primary-side circuit for switching power supply in response to a pulse, a secondary-side circuit for rectifying a voltage generated in a secondary winding of the transformer and supplying power to a load, a unit for detecting a voltage for supplying power to the load,
And so that the voltage it detects matches the target value,
A voltage control unit for controlling a duty of the PWM pulse; a unit for detecting whether a current value of the power supply device that fluctuates depending on whether power is supplied to a load exceeds a set value or less than a set value; Output control means for setting the rated voltage to the target value when the current value exceeds the set value, and setting the target voltage to a value lower than the rated voltage within a tolerance range of the rated voltage when the current value is equal to or less than the set value. A power supply device characterized by the above-mentioned. 5. An image forming apparatus comprising: an image forming mechanism;
A visual image forming apparatus for forming a visual image corresponding to an image signal on paper; a transformer, a primary circuit for switching and supplying power to a primary winding of the transformer in response to a PWM pulse, and a secondary winding of the transformer. A switching power supply for supplying power to the image forming apparatus, comprising: a secondary side circuit for rectifying voltage and supplying power to the load; and a means for detecting voltage supplied to the load; the voltage detected by the voltage detection means matches a target value. Voltage control means for controlling the duty of the PWM pulse; means for detecting whether a current value of the switching power supply fluctuating depending on whether power is supplied to a load exceeds a set value or less than a set value; and When the value exceeds the set value, the rated voltage is set to the target value, and when the value is equal to or less than the set value, an output value within a tolerance range of the rated voltage and a value lower than the rated voltage is set to the target value. An image forming apparatus comprising: a control unit; 6. An image forming apparatus comprising: an image forming mechanism;
A visual image forming apparatus for forming a visual image corresponding to an image signal on paper; a transformer; a primary circuit for switching and supplying power to a primary winding of the transformer in response to a PWM pulse; and a secondary winding of the transformer. A first switching power supply having a high output voltage and supplying power to the electric device of the image forming mechanism, the first switching power supply comprising: a secondary side circuit for rectifying a voltage and supplying a voltage to the load; and a unit for detecting a voltage supplied to the load. A second switching power supply that supplies a low voltage to the visual image formation control unit, and a voltage control unit that controls the duty of each PWM pulse so that the voltage detected by each voltage detection unit matches each target value. Means for detecting whether a current value of the power supply device that fluctuates depending on whether or not power is supplied to a load is equal to or less than a set value; and An output control means for stopping the voltage output of the source circuit.