JP6394353B2 - Power supply device and image forming apparatus - Google Patents

Description

  The present invention relates to a power supply apparatus and an image forming apparatus, and more particularly to a technique for reducing power consumption in a power saving mode and shortening a return time from the power saving mode without using a storage battery.

  In recent years, awareness of energy conservation has increased, and environmental standards such as the ErP Directive (Energy-related Products Directive, 2009/125 / EC) and the International Energy Star Program have become stricter. For example, the ErP command requires that the power consumption in the off mode or the standby mode be 0.5 W or less, and in the field of the image forming apparatus, it is an urgent task to reduce the power consumption in the power saving mode. Yes.

  In response to such a problem, for example, the energy saving mode is the second predetermined time compared to the energy saving mode in which the power supply to the main components is cut off if there is no print start instruction from the host computer for the first predetermined time or longer. There has been proposed an image forming apparatus further provided with an off mode that cuts off power supply to an auxiliary component having a reception function with a host computer if it is not canceled (Patent Document 1). In this way, power consumption can be reduced as compared with the case where only the energy saving mode is provided.

JP 2002-067441 A JP 2007-047556 A JP 2012-047881 A JP 2012-196109 A

  However, in the above prior art, a loss occurs because the power converter is oscillated even in the off mode. As means for solving this, an image forming apparatus has been proposed in which a power converter is stopped after a predetermined time has elapsed in an image forming standby state to eliminate a loss associated with oscillation of the power converter (Patent Document 2). In this prior art, a power storage means is required to secure power for restarting the power converter when returning from the off mode.

  In addition, an image forming apparatus that shuts off AC power supplied to a power converter by a latching relay when shifting to a low power consumption mode has been proposed (Patent Document 3). In this way, since the AC power supply is cut off, there is no loss associated with the oscillation of the power converter, so the power consumption in the low power consumption mode can be reduced. However, when returning from the low power consumption mode, it is necessary to restart the power supply control IC (Integrated Circuit), and the recovery time becomes longer.

  Furthermore, there has been proposed a power supply control IC that stops oscillation while receiving power supply when the output voltage of the power converter falls below a threshold value (Patent Document 4). In this way, not only the loss due to the oscillation of the power converter can be eliminated, but also the power supply to the power control IC is maintained, so that the oscillation can be resumed without restarting the power control IC. it can. However, loss due to oscillation occurs.

  The present invention has been made in view of the above-described problems, and prevents loss due to oscillation of the power converter in the power saving mode and delays due to restart of the power control IC without requiring a capacitor. An object of the present invention is to provide a power supply apparatus and an image forming apparatus that can be prevented.

  In order to achieve the above object, a power supply apparatus according to the present invention receives power from an AC power supply and supplies power to a load mounted on a device having an operation mode and a power saving mode in which power consumption is lower than that of the operation mode. An AD converter circuit that rectifies an AC voltage from the AC power supply and supplies the DC voltage to the load; a PWM control circuit that adjusts an output voltage of the AD converter circuit by PWM control; and a latching relay contact A latching relay circuit that stops and restarts the PWM control by short-circuiting and opening the circuit, and the latching relay circuit operates by receiving the AC voltage directly or by rectifying the AC voltage, When the device shifts from the operation mode to the power saving mode, the voltage output of the AD converter circuit is reduced by stopping the PWM control. When the device shifts from the power saving mode to the operation mode, the PWM control is restarted to cause the AD converter circuit to output a voltage, and the PWM control circuit is in the power saving mode, By receiving the AC voltage directly or by rectifying the AC voltage, the minimum operating power capable of immediately restarting the PWM control is obtained.

  In this way, in the power saving mode, the PWM control of the AD conversion circuit is stopped, so that loss of power due to oscillation can be prevented. Moreover, since the PWM control circuit receives the minimum operating power from the AC power supply, the minimum operating state can be maintained during the power saving mode without requiring a capacitor. For this reason, when shifting from the power saving mode to the operation mode, the PWM control can be resumed without restarting the PWM control circuit.

  Therefore, power supply to the load can be resumed immediately when shifting from the power saving mode to the operation mode.

1 is a diagram illustrating a main configuration of an image forming apparatus according to a first embodiment of the present invention. 2 is a circuit diagram showing a main configuration of a power supply apparatus 100. FIG. 3 is a timing chart showing the operation of the power supply apparatus 100. It is a circuit diagram which shows the main structures of the power supply device 100 which concerns on the 2nd Embodiment of this invention. It is a circuit diagram which shows the main structures of the power supply device 100 which concerns on the 3rd Embodiment of this invention. 3 is a timing chart showing the operation of the power supply apparatus 100. It is a circuit diagram which shows the main structures of the power supply device 100 which concerns on the 4th Embodiment of this invention. It is a circuit diagram which shows the main structures of the power supply device 100 which concerns on the 5th Embodiment of this invention. 3 is a timing chart showing the operation of the power supply apparatus 100. It is a circuit diagram which shows the main structures of the power supply device 100 which concerns on the 6th Embodiment of this invention. 3 is a timing chart showing the operation of the power supply apparatus 100. It is a circuit diagram which shows the main structures of the power supply device 100 which concerns on the 7th Embodiment of this invention.

Embodiments of a power supply apparatus and an image forming apparatus according to the present invention will be described below with reference to the drawings.
[1] First Embodiment An image forming apparatus according to a first embodiment of the present invention will be described.
(1-1) Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described. As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment is a so-called monochrome printer, and includes a power supply device 100, an image forming unit 110, and a paper feeding unit 120. The power supply apparatus 100 receives supply of AC power from the commercial AC power supply 101 and supplies DC power to the image forming unit 110 and the paper feeding unit 120. The image forming unit 110 forms an image on the recording sheet supplied from the paper feeding unit 120 and discharges the image onto the paper discharge tray 130.

Hereinafter, the image forming unit 110 and the paper feeding unit 120 are collectively referred to as “load”. The image forming apparatus 1 has two operation modes, a power saving mode and an operation mode A. The power saving mode is an operation mode in which power consumption is lower than that in the operation mode A, and power supply to the load is stopped.
As shown in FIG. 2, the power supply device 100 includes a power converter 200, a latching relay circuit 210, and a power control unit 220.

(1-2) Power Conversion Next, power conversion by the power supply device 100 will be described.
The power converter 200 performs full-wave rectification on the AC voltage supplied from the AC power source 101 by the bridge rectifier circuit D1, smoothes it by the primary smoothing capacitor C1, and then transforms it by the transformer T1. In the AC power supply 101, an L (Live) line is connected to point a of the bridge rectifier circuit D1, and an N (Neutral) line is connected to point b. As a result, the AC voltage is full-wave rectified by the bridge rectifier circuit D1 to be a DC voltage.

The point d of the bridge rectifier circuit D1 is connected to the plus terminal of the primary smoothing capacitor C1, and the point c is connected to the minus terminal of the primary smoothing capacitor C1. As a result, the DC voltage output from the bridge rectifier circuit D1 is smoothed. As a result, a DC voltage about the peak voltage of the input voltage is generated.
The primary winding 201 of the transformer T1 is connected in parallel with the primary smoothing capacitor C1 via the switch SW1. An output voltage corresponding to the on-duty of the switch SW1 is supplied to the secondary winding 202 side and the auxiliary winding 203 side of the transformer T1.

The transformed voltage supplied from the secondary winding 202 is rectified and smoothed by the rectifier diode D3 and the smoothing capacitor C3, and is output to the load 230 (output voltage A).
(1-3) Control of output voltage A The output voltage A is controlled by the power supply control IC 204.
The secondary winding 202 is connected in parallel to the secondary smoothing capacitor C3 and the output voltage monitoring unit 205 via the rectifier diode D3. The output voltage monitoring unit 205 monitors the output voltage A of the transformer T1 and outputs a feedback signal indicating the magnitude of the output voltage A. The feedback signal is input to the feedback (FB) terminal of the power supply control IC 204 via the isolation circuit 206. The insulating circuit 206 is, for example, a photocoupler, and insulates the primary side and the secondary side of the transformer T1.

  The power supply control IC 204 controls the output voltage A of the transformer T1 by PWM (Pulse Width Modulation) by referring to the feedback signal input to the FB terminal and controlling the on-duty of the switch SW1. The power supply control IC 204 increases the on-duty of the switch SW1 if the output voltage is lower than the target voltage, and decreases the on-duty of the switch SW1 if it is higher.

(1-4) Power Supply to the Power Supply Control IC 204 The power supply control IC 204 operates by supplying two systems of power, that is, a startup power supply and a normal power supply.
The N line of the AC power supply 101 is also connected to the start-up power supply terminal of the power supply control IC 204 via the point b of the bridge rectifier circuit D1, the rectifier diode D4, and the start-up resistor R2. When the image forming apparatus 1 is turned on, a DC voltage obtained by half-wave rectifying the AC voltage by the current diode D4 is supplied as a starting power source for the power supply control IC 204.

The power supply control IC 204 starts the PWM control of the switch SW1 when supplied with the startup power, and supplies the DC voltage transformed by the secondary winding 202 and the auxiliary winding 203.
The auxiliary winding 203 is connected in parallel with the smoothing capacitor C2 via the rectifier diode D2. Further, both terminals of the smoothing capacitor C2 are connected to the power supply terminal of the power supply control IC 204. As a result, the transformed voltage supplied from the auxiliary winding 203 is rectified and smoothed by the rectifier diode D2 and the smoothing capacitor C2, and supplied to the power supply control IC 204 as a power supply voltage.

(1-5) Oscillation Control of Power Supply Converter 200 The power supply apparatus 100 stops and restarts the oscillation of the power converter 200 in order to control power supply according to the operation mode of the image forming apparatus 1. The latching relay circuit 210 is a circuit that stops or restarts the oscillation of the power converter 200.
In the power saving mode, the image forming apparatus 1 stops operation except for the transition / return instruction unit 240, the power supply control unit 220, and the latching relay circuit 210 that are necessary for returning to the operation mode A. The operation mode A is an operation mode that consumes more power than the power saving mode. In the operation mode A, for example, power is supplied to the load 230 so that the accepted job can be executed immediately.

The N line of the AC power supply 101 is connected to the plus terminal of the smoothing capacitor C4 via the rectifier diode D5. The rectifier diode D5 converts the AC voltage into a direct current by half-wave rectification. The DC voltage output from the rectifier diode D5 is smoothed by the smoothing capacitor C4.
The circuit in which the set coil 211 and the switch SW2 are connected in series is connected in parallel to the circuit in which the reset coil 212 and the switch SW3 are connected in series. A voltage dividing resistor R1 is connected in series to the parallel circuit. Further, the series circuit including the voltage dividing resistor R1 is connected in parallel with the smoothing capacitor C4. In this case, the voltage dividing resistor R1 is connected to the plus terminal side of the smoothing capacitor C4.

  The switches SW2 and SW3 are alternatively turned on. When the switch SW2 is turned on, a voltage obtained by dividing the voltage of the plus terminal of the smoothing capacitor C4 by the voltage dividing resistor R1 and the coil resistance of the set coil 211 is supplied to the set coil 211 as a coil voltage. When the switch SW3 is turned on, a voltage obtained by dividing the voltage of the plus terminal of the smoothing capacitor C4 by the voltage dividing resistor R1 and the coil resistance of the reset coil 212 is supplied to the reset coil 212 as a coil voltage.

Here, the coil voltage may be an AC voltage.
The power supply control unit 220 is connected to the latching relay circuit 210 and inputs a power saving mode transition signal to the switch SW2 via the on-time control unit 250, or the switch SW3 via the on-time control unit 250. An operation mode A return signal is input to
When the switch SW2 is turned on, the coil voltage of the set coil 211 rises and the contact 213 is connected. When the switch SW3 is turned on, the coil voltage of the reset coil 212 increases and the contact 213 is cut off.

The oscillation stop terminal of the power supply control IC 204 is connected to the negative terminal of the primary smoothing capacitor C1 through the contact 213. When the contact 213 is turned on, an oscillation stop signal is input to the power supply control IC 204. Thereby, the stop and restart of the oscillation of the power converter 200 are controlled.
When a power saving mode transition instruction is input from the transition / return instruction unit 240, the power supply control unit 220 inputs a power saving mode transition signal to the switch SW2 of the latching relay circuit 210 to turn on the switch SW2. Then, the voltage at the plus terminal of the smoothing capacitor C4 is supplied to the set coil 211 as a coil power supply, and the contact 213 is turned on, so that the oscillation stop signal is turned on and the oscillation of the power converter 200 is stopped.

  On the other hand, when an operation mode A return instruction is input from the transition / return instruction unit 240, the power supply control unit 220 inputs an operation mode A return signal to the switch SW3 and turns on the switch SW3. Then, the voltage at the plus terminal of the smoothing capacitor C4 is supplied to the reset coil 212 as the coil power supply, and the contact 213 is turned off, so that the oscillation stop signal is turned off and the oscillation of the power converter 200 is resumed.

  The on-time control unit 250 blocks the signal so that it is turned off after a preset on-time after the power saving mode transition signal and the operation mode A return signal are turned on. In this way, the time for which power is supplied to the set coil 211 and the reset coil 212 can be limited, so that power consumption can be reduced and temperature rise of the power supply device 200 can be suppressed.

FIG. 3 is a timing chart showing the operation after returning from the operation mode A to the power saving mode until returning to the operation mode A.
First, an operation for shifting from the operation mode A to the power saving mode will be described.
When the transition / return instruction unit 240 outputs a power saving mode transition signal, the power supply control unit 220 turns on the power saving mode transition signal. Then, since the switch SW2 is turned on, power is supplied to the set coil 211, and the coil voltage increases.

  When the coil voltage of the set coil 211 becomes equal to or higher than the set voltage, the oscillation stop signal is turned on when the contact 213 is turned on, so that the oscillation of the power converter 200 is stopped and the voltage level of the output voltage A is lowered. However, the supply state of the starting power supply to the power supply control IC 204 is maintained, and the power supply voltage is maintained at the minimum operating voltage or higher. That is, power supply converter 200 is maintained in a state where oscillation (PWM control) can be resumed immediately.

  Note that the power saving mode transition signal input to the switch SW2 by the on-time control unit 250 is turned off after a predetermined time (10 milliseconds in this embodiment) after the power supply control unit 220 is turned on. However, even after the power saving mode transition signal is turned off, the contact 213 is mechanically maintained (latched) in the on state. Therefore, since it is not necessary to energize the set coil 211 in order to maintain the contact 213 in the on state, power consumption can be reduced and heat generation of the set coil 211 due to energization can be prevented.

Next, an operation for returning from the power saving mode to the operation mode A will be described.
When the transition / return instruction unit 240 outputs the operation mode A return signal, the power supply control unit 220 turns on the operation mode A return signal. Then, the switch SW3 is turned on, and when the coil voltage of the reset coil 212 rises above the reset voltage, the contact 213 is turned off and the oscillation stop signal is turned off.

Also in this case, the on-time control unit 250 controls the operation mode A return signal to be turned on for a predetermined time as in the case of the power saving mode transition signal. As a result, the energization time to the reset coil 212 can be shortened to the minimum necessary, so that power can be saved and heat generation can be prevented.
In the power supply control IC 204, since the power supply voltage is maintained at the minimum voltage or higher, the power converter 200 immediately resumes oscillation (PWM control), and the voltage level of the output voltage A rises to a preset value.

  Thus, in the power saving mode, the power converter 200 is stopped from oscillating, so that power consumption can be reduced. Even in the power saving mode, the power supply IC IC 204 is supplied with startup power from the AC power supply 101 and the power supply voltage is maintained at the minimum operating voltage or higher. Therefore, when returning to the operation mode A, the power control IC 204 The restart is unnecessary, and the oscillation of the power converter 200 can be resumed immediately. Accordingly, it is possible to shorten the time required for return.

[2] Second Embodiment Next, a second embodiment of the present invention will be described. The image forming apparatus according to the second embodiment has a configuration substantially similar to that of the image forming apparatus 1 according to the first embodiment, but is different in a power supply circuit of a latching relay circuit. Hereinafter, the description will be given mainly focusing on the differences.

In addition, the same code | symbol is attached | subjected about the component which is common in the image forming apparatus 1 which concerns on the said 1st Embodiment.
In the present embodiment, as shown in FIG. 4, the voltage dividing resistor R1 is connected to the point d of the bridge rectifier circuit D1 (in other words, the positive terminal of the primary smoothing capacitor). As a result, a voltage obtained by dividing the DC voltage output from the point d by the voltage dividing resistor R <b> 1 is supplied as the coil power supply for the set coil 211 and the reset coil 212.

In this way, the rectifier diode D5 and the smoothing capacitor C4 dedicated to the coil power source described in the first embodiment are not necessary, and the circuit configuration can be simplified. In addition, since a DC voltage is supplied as a coil power supply, a more stable power supply is possible than a configuration using an AC voltage.
[3] Third Embodiment Next, a third embodiment of the present invention will be described. The image forming apparatus according to the third embodiment has substantially the same configuration as that of the image forming apparatus 1 according to the first embodiment, but has a different terminal for inputting an oscillation stop signal to the power supply control IC 204. Yes. Hereinafter, the description will be given mainly focusing on the differences.

In addition, the same code | symbol was attached | subjected about the component common to the image forming apparatus 1 which concerns on the said 1st Embodiment.
In the present embodiment, as shown in FIG. 5, the oscillation stop signal is input to the FB terminal of the power supply control IC 204.
When shifting from the operation mode A to the power saving mode, as shown in FIG. 6, when the shift / return instruction unit 240 outputs a power saving mode shift signal, the power supply control unit 220 turns on the power saving mode shift signal. Then, the switch SW2 is turned on. As a result, power is supplied to the set coil 211, and the contact 213 is turned on when the coil voltage rises above the set voltage. Then, the oscillation stop signal is turned on, and the voltage at the FB terminal of the power supply control IC 204 drops.

When the voltage at the FB terminal drops below the threshold voltage, the power converter 200 stops oscillating. Then, although the voltage level of the output voltage A decreases, the power supply for starting is supplied from the AC power supply 101 to the power supply control IC 204, so that the power supply voltage is maintained at the minimum operating voltage or higher.
When returning from the power saving mode to the operation mode A, when the transition / return instruction unit 240 outputs the operation mode A return signal, the power supply control unit 220 turns on the operation mode A return signal and the switch SW3 is turned on. As a result, when the coil voltage of the reset coil 212 rises above the reset voltage, the contact 213 is turned off and the oscillation stop signal is turned off.

When the voltage at the FB terminal of the power supply control IC 204 rises and exceeds the threshold voltage, the power supply control IC 204 is maintained at the minimum voltage or higher, so that the power converter 200 immediately resumes oscillation and the output voltage A The voltage level rises to a preset value.
[4] Fourth Embodiment A fourth embodiment of the present invention will be described. Since the image forming apparatus according to the fourth embodiment operates in the operation mode B that consumes more power than the operation mode A, in addition to the configuration of the image forming apparatus 1 according to the first embodiment, It is characterized by having a configuration for supplying an output voltage B higher than the output voltage A. Hereinafter, the description will be given focusing on this feature.

Also in the present embodiment, the same reference numerals are given to components common to the image forming apparatus 1 according to the first embodiment.
As shown in FIG. 7, in the present embodiment, a power converter 700 is added, and an output voltage B higher than the output voltage A is supplied to the load 730. For this reason, a switch SW5 for connecting and shutting off power supply to the power supply control IC 704 provided in the power converter 700 is provided, and the switch SW5 is turned on and off by a power converter 700 stop signal output from the load 230.

For example, in a job execution state such as a printing operation, since a high output voltage B is required (operation mode B), the load 230 outputs a power converter 700 stop signal and the switch SW5 is turned on.
(4-1) Power Supply Conversion The power supply converter 700 transforms the DC voltage, which is full-wave rectified by the bridge rectifier circuit D1 and smoothed by the primary smoothing capacitor C1, with the transformer T2.

  The primary winding 701 of the transformer T2 is connected in parallel with the primary smoothing capacitor C1 through the switch SW4 between the negative terminal of the primary smoothing capacitor C1. An output voltage corresponding to the on-duty of the switch SW4 is supplied to the secondary winding 702 side of the transformer T2. The transformed voltage supplied from the secondary winding 702 is rectified and smoothed by the rectifier diode D7 and the smoothing capacitor C5, and output to the load 730 (output voltage B).

(4-2) Control of output voltage A The output voltage B is controlled by the power supply control IC 704.
The secondary winding 702 is connected in parallel to the output voltage monitoring unit 705 and the load 730 via the rectifier diode D7 and the positive terminal of the secondary smoothing capacitor C5. The output voltage monitoring unit 705 monitors the output voltage B and outputs a feedback signal B indicating the magnitude of the output voltage B. The feedback signal B is input to the FB terminal of the power supply control IC 704 via the insulation circuit 706.

The power supply control IC 704 performs PWM control on the output voltage A with reference to the feedback signal B. The insulating circuit 706 insulates the primary side and the secondary side of the transformer T2.
Note that the voltage level of the output voltage B is not only PWM controlled by the power supply control IC 704 but also higher than the output voltage A by adjusting the winding ratio between the primary winding 701 and the secondary winding 702 of the transformer T2. May be.

(4-3) Power Supply to the Power Supply Control IC 704 The power supply control IC 704 is connected to the auxiliary winding 203 via the rectifier diode D6, the plus terminal of the smoothing capacitor C2, and the switch SW5. Operates by feeding.
(4-4) Oscillation Control of Power Converter 700 First, the case where the power is turned on or the operation mode A is restored from the power saving mode will be described.

  In this case, when the power converter 200 starts supplying the output voltage A to the load 230, the power converter 700 stop signal is canceled (turned on), and power is supplied to the power control IC 704. Then, the power supply control IC 704 starts PWM control of the transformer T2, and a DC voltage is supplied to the secondary winding 702. The DC voltage is rectified by the diode D7 and the smoothing capacitor C5 is smoothed, whereby the output voltage B is output.

The output voltage monitoring unit 705 monitors the voltage level of the output voltage B, and inputs the feedback signal B to the FB terminal of the power supply control IC 704 via the insulation circuit 706. The power supply control IC 704 performs PWM control with reference to the feedback signal B so that the voltage level of the output voltage B becomes a preset value. The output voltage B is supplied to the load 730.
Next, the case of shifting to the power saving mode will be described.

When the load 230 outputs (turns off) the power converter 700 stop signal, the switch SW5 is cut off, and the power supply from the auxiliary winding 303 to the power supply control IC 704 is cut off. Then, the PWM control by the power supply control IC 704 stops, so that the oscillation of the power converter 700 stops and the supply of the output voltage B to the load 730 stops.
Circuit operations other than the power converter 700 are the same as those in the first embodiment.

[5] Fifth Embodiment Next, a fifth embodiment of the present invention will be described. The image forming apparatus according to the present embodiment has substantially the same configuration as that of the image forming apparatus 1 according to the first embodiment, but controls the latching relay circuit 210 by monitoring the AC power supply 101. It is different. Hereinafter, the description will be given focusing on the differences.

  In power supply device 100 according to the present embodiment, as shown in FIG. 8, AC power supply monitoring unit 800 is connected to the N line of AC power supply 101 via rectifier diode D8. Further, the AC power supply monitoring unit 800 inputs an AC power supply off signal to the power supply control unit 220. Accordingly, since the latching relay circuit is controlled according to the AC power supply off signal, the oscillation of the power converter 200 is stopped and restarted according to the on / off state of the AC power supply 101.

FIG. 9 is a timing chart showing the operation of the power supply apparatus 100 when the AC power supply 101 transitions from the on state to the off state.
As shown in FIG. 9, the AC power supply monitoring unit 800 monitors the effective value of the AC voltage supplied from the AC power supply 101, and when the state where the effective value drops below a predetermined value continues for a predetermined time, the AC power supply Turn off signal.

When the AC power supply off signal is turned on, the power supply controller 220 turns on the switch SW3 by turning on the operation mode A return signal. When the coil voltage of the reset coil 212 rises above the reset voltage, the contact 213 is turned on, the oscillation stop signal is turned off, and the oscillation of the power converter 200 is restarted.
In this way, since the contact 213 is always turned off after the AC power supply 101 is turned off, the FB terminal voltage of the power supply control IC 204 is kept below the off mode threshold voltage when the AC power supply 101 is turned on thereafter. Therefore, it is possible to prevent a start-up failure of the power supply control IC 204.

[6] Sixth Embodiment Next, a sixth embodiment of the present invention will be described. The image forming apparatus according to the present embodiment has substantially the same configuration as that of the image forming apparatus 1 according to the fifth embodiment, but differs in the configuration for turning off the contact 403. Hereinafter, the description will be given focusing on the differences.

  In the fifth embodiment, as shown in FIG. 10, the AC power supply monitoring unit 800 starts the AC power supply 101 and outputs an AC power supply off signal, whereas in the present embodiment, The output voltage monitoring unit 1000 is provided to monitor the output voltage A, and when the state where the output voltage A drops below a predetermined value continues for a predetermined time, the output voltage A off signal is input to the power supply control unit 220, The contact 403 is turned off.

FIG. 11 is a timing chart showing the operation of the power supply apparatus 100 in the present embodiment.
As shown in FIG. 11, when the AC power supply 101 is turned off, the output voltage A drops. The output voltage monitoring unit 207 turns on the output voltage A off signal when the state where the output voltage A is equal to or lower than the predetermined value continues for a predetermined time. Then, the power supply control unit 220 turns on the operation mode A return signal, turns on the switch SW3, and turns off the contact 213. As a result, when the oscillation stop signal is turned off, the power control IC 204 resumes the oscillation of the power converter 200.

In this way, the contact 213 is always turned off after the AC power supply 101 is turned off, as in the fifth embodiment, so that the FB terminal voltage of the power supply control IC 204 is turned off when the AC power supply 101 is turned on thereafter. It is held below the threshold voltage. Accordingly, it is possible to prevent a start-up failure of the power supply control IC 204.
[7] Seventh Embodiment Next, a seventh embodiment of the present invention will be described. The image forming apparatus according to the present embodiment has substantially the same configuration as the image forming apparatus 1 according to the first embodiment, but the primary side and the secondary side of the transformer T1 are insulated. It is different. Hereinafter, the description will be given focusing on the differences.

  In the present embodiment, as shown in FIG. 12, insulating circuits 1201 and 1202 are provided on circuits that connect the power supply control unit 220 to the switches SW2 and SW3, respectively. As the insulating circuits 1201 and 1202, for example, photocouplers can be used. The power supply control unit 220 outputs a power saving mode transition signal and an operation mode A return signal via the isolation circuits 1201 and 1202, respectively.

By adopting such a configuration, the primary side circuit and the secondary side circuit are insulated, and thus the safety of the power supply apparatus 200 can be improved.
[8] Modifications As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .

(8-1) In the above-described embodiment, the case where the power supply apparatus 100 is mounted inside the image forming apparatus 1 has been described as an example. However, it is needless to say that the present invention is not limited to this. It may be installed outside the image forming apparatus 1 and connected to the image forming apparatus 1 for use.
(8-2) In the above embodiment, the case where the oscillation stop signal is input to the oscillation stop terminal or the FB terminal has been described as an example. However, it is needless to say that the present invention is not limited to this and is replaced with these terminals. May be input to the power-off terminal.

The power-off terminal is a terminal for stopping and restarting the power reception from the auxiliary winding 203. When the power reception is stopped, the power control IC 204 stops the PWM control and the oscillation of the power converter 200 is stopped. .
(8-3) Although not specifically described in the above embodiment, the transfer / return instruction unit 240 has received a new job from the time when the image forming apparatus 1 ends the job until a predetermined time elapses. When not input, when the user instructs the shift to the power saving mode, or when the weekly timer is instructed, the shift to the power saving mode may be instructed.

Further, the transition / return instruction unit 240 sets a weekly timer when a predetermined time has elapsed since the transition to the power saving mode, when a new job is input to the image forming apparatus 1, or when any user is accepted. When instructed, a return to the operation mode A may be instructed.
Further, when the image forming apparatus 1 is a reading device that reads an image from a document and includes a reading device having an automatic document feeder (ADF) that automatically conveys the document one by one, automatic The operation may be returned from the power saving mode to the operation mode A when the original is set on the original conveying apparatus.

The weekly timer is a device or program that controls the operation of the image forming apparatus 1 in a weekly cycle. For example, a routine operation is automatically performed on the image forming apparatus 1 such as turning on the power at the beginning of the week or turning off the power at the weekend. To run.
(8-4) Although the case where the image forming apparatus is a monochrome printer has been described in the above embodiment, the present invention is not limited to this, and may be a color printer or provided with a scanner. It may be a copying machine. Furthermore, the present invention can be applied to obtain a similar effect even in a facsimile machine having a communication function or a multi-function peripheral (MFP) having these functions. it can.

  (8-5) In the above embodiment, the case where the power supply apparatus 100 is built in the image forming apparatus 1 has been described as an example. However, it is needless to say that the present invention is not limited thereto. The forming apparatus 1 may be externally attached. Further, the power supply apparatus 100 may supply power to devices other than the image forming apparatus 1, and in this case, the effect of the present invention is the same regardless of whether the power supply device 100 is incorporated in the device or externally attached.

  The image forming apparatus according to the present invention is useful as an apparatus that reduces power consumption in the power saving mode and shortens the return time from the power saving mode without using a storage battery.

1 ……………… Image forming apparatus 100 ………… Power supply device 101 ………… AC power supply 200, 700… Power supply converter 204 ………… Power supply control IC
210 ......... Latching relay circuit 220 .......... Power supply control unit 230, 730 ... Load 240 ............... Transition / return instruction unit

Claims (12)

A power supply device that receives power from an AC power source and supplies power to a load mounted on a device having an operation mode and a power saving mode in which power consumption is smaller than the operation mode,
An AD conversion circuit that rectifies an AC voltage from the AC power source and supplies the DC voltage to the load;
A PWM control circuit for adjusting the output voltage of the AD converter circuit by PWM control;
A latching relay circuit that stops and restarts the PWM control by short-circuiting and opening the latching relay contact;
The latching relay circuit is
Operates by receiving the AC voltage directly or by rectifying the AC voltage,
When the device shifts from the operation mode to the power saving mode, the voltage output of the AD converter circuit is stopped by stopping the PWM control,
When the device shifts from the power saving mode to the operation mode, the AD converter circuit outputs a voltage by resuming the PWM control,
The PWM control circuit is
In the power saving mode, a power supply device that obtains minimum operating power that can immediately resume the PWM control by receiving the AC voltage directly or by rectifying the AC voltage. The PWM control circuit has a feedback terminal for receiving a feedback signal indicating the output voltage,
2. The latching relay circuit stops and restarts the PWM control by short-circuiting and opening a circuit that inputs a signal for stopping the PWM control to the feedback terminal by a latching relay contact. The power supply described. The PWM control circuit has a power-off terminal for stopping power reception required for continuing PWM control,
The latching relay circuit stops and restarts the PWM control by short-circuiting and opening a circuit that inputs a signal for stopping power reception required for continuing the PWM control to the power-off terminal by a latching relay contact. The power supply device according to claim 1. The device further has a high voltage mode that consumes more power than the operation mode,
A high-voltage converter circuit that transforms a DC voltage obtained by rectifying and smoothing the AC voltage by the AD converter circuit and outputs a DC voltage higher than the output voltage of the AD converter circuit;
4. The power supply device according to claim 1, further comprising: a high voltage control circuit that performs PWM control so that an output voltage of the high voltage conversion circuit becomes a target high voltage. 5. The effective value of the AC voltage from the AC power source, the DC voltage obtained by rectifying and smoothing the AC voltage from the AC power source by the AD converter circuit, and the output voltage of the AD converter circuit are lower than a predetermined voltage. 5. The power supply device according to claim 1, further comprising a return preparation circuit that causes the latching relay circuit to resume the PWM control after continuing for a predetermined time or more. An instruction circuit that operates by receiving the output voltage of the AD conversion circuit, and outputs an instruction signal that instructs the latching relay circuit to stop and restart the PWM control;
A relay circuit that receives the instruction signal from the instruction circuit and instructs the latching relay circuit to stop and restart the PWM control;
6. The power supply device according to claim 1, wherein the relay circuit electrically insulates the instruction circuit side and the latching relay circuit side. 2. A regulation circuit that regulates an energization time for energizing a coil that short-circuits and opens the latching relay contact so that the latching relay circuit stops and restarts the PWM control to a predetermined time or less. The power supply apparatus in any one of 6. The power supply device according to claim 1, wherein the device is an image forming apparatus. The latching relay circuit is
When there is no new job input until a predetermined time or more has elapsed after the image forming apparatus completes the job, or when the user of the image forming apparatus gives an instruction to shift from the operation mode to the power saving mode, or the image forming apparatus 9. The power supply device according to claim 8, wherein the PWM control is stopped when the weekly timer of the instruction instructs a shift from the operation mode to the power saving mode. The latching relay circuit is
When a predetermined time has elapsed since the image forming apparatus transitioned from the operation mode to the power saving mode, when the image forming apparatus accepts any user operation, or when the weekly timer of the image forming apparatus is in the operation mode from the power saving mode. The power supply apparatus according to claim 8 or 9, wherein the PWM control is resumed when an instruction to shift to is issued. When the image forming apparatus includes a reading unit that reads an image from a document, and a supply unit that supplies a document set by a user to the reading unit.
The power supply apparatus according to claim 8 or 10, wherein the latching relay circuit restarts the PWM control when a document is set on the supply unit. An image forming apparatus comprising the power supply device according to claim 1.

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