Power source device for electric apparatus and image processing device

Abstract

To provide a power supply device for an electric apparatus and an image processing device capable of easily simplifying a configuration and control.SOLUTION: A power supply device 3 includes an output capacitor 32, a switching power supply unit 31, a discharging unit 33, a switching unit 34 and an operation unit 35. The output capacitor 32 outputs an output voltage V1 relative to an electric load. The switching power supply unit 31 charges the output capacitor 32 to generate the output voltage V1. The discharging unit 33 is electrically connected to the output capacitor 32 to discharge the output capacitor 32. The switching unit 34 switches the output voltage V1 from a first voltage V11 to a second voltage V12 lower than the first voltage V11. The operation unit 35 operates the switching unit 34 and the discharging unit 33 in response to one control signal.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a power supply device for an electric device and an image processing device. [Background technology]

[0002] As a related art, an electrophotographic image processing apparatus (image forming apparatus) equipped with a power supply device that lowers a target voltage in response to switching from a normal mode to an energy saving mode (power saving mode) is known (see, for example, Patent Document 1). In the power supply device of the related art, a power supply circuit having a switching power supply charges an output capacitor (capacitor) and supplies an output voltage from the output capacitor to an electrical load. A discharge circuit is capable of discharging the voltage charged in the output capacitor. A CPU operates the discharge circuit in the process of lowering the output voltage from a first voltage to a second voltage in response to a transition from the normal mode to the energy saving mode (sleep mode). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-126001 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of the related art described above, the control for switching from the normal mode to the energy saving mode and the control for operating the discharge circuit are performed separately, making it difficult to simplify the configuration and control of the power supply device.

[0005] An object of the present invention is to provide a power supply device for electric equipment and an image processing device which can easily be simplified in configuration and control. [Means for solving the problem]

[0006] A power supply device for an electrical device according to one aspect of the present invention includes an output capacitor, a switching power supply unit, a discharge unit, a switching unit, and an operating unit. The output capacitor outputs an output voltage to an electrical load. The switching power supply unit generates the output voltage by charging the output capacitor. The discharge unit discharges the output capacitor by being electrically connected to the output capacitor. The switching unit switches the output voltage from a first voltage to a second voltage lower than the first voltage. The operating unit operates the switching unit and the discharge unit in response to a control signal.

[0007] According to another aspect of the present invention, there is provided an image processing apparatus including a power supply device for the electric device and a main body having an image processing function. The electric load includes the main body. Effect of the Invention

[0008] According to the present invention, it is possible to provide a power supply device for electric equipment and an image processing device that can easily be simplified in configuration and control. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic block diagram of an image processing device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing the appearance of the image processing device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic circuit diagram illustrating an example of a power supply device of the image processing apparatus according to the first embodiment. [Figure 4] FIG. 4 is a timing chart showing an example of the operation of the power supply device of the image processing apparatus according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example of the present invention, and is not intended to limit the technical scope of the present invention.

[0011] (Embodiment 1) [1] Overall configuration of image processing device First, the overall configuration of an image processing device 10 according to this embodiment will be described with reference to FIGS.

[0012] The image processing device 10 according to the present embodiment is, for example, a multifunction device having multiple functions such as a scanning function for acquiring image data from an original, a printing function for forming an image based on image data, a facsimile function, and a copy function. The image processing device 10 only needs to have an image processing function including at least one of a function for forming an image and a function for acquiring image data, and may be a printer, a scanner, a facsimile machine, a copy machine, or the like.

[0013] As shown in Fig. 1, the image processing device 10 includes an automatic document feeder 11, an image reading unit 12, an image forming unit 13, a paper feed unit 14, an operation display unit 15, a main body control unit 16, and a power supply unit 3. The automatic document feeder 11 is an ADF (Auto Document Feeder), and is therefore indicated as "ADF" in Fig. 1, and will also be referred to as "ADF 11" in the following description. In this embodiment, as shown in Fig. 2, the image processing device 10 includes a housing 101. The ADF 11, the image reading unit 12, the image forming unit 13, the paper feed unit 14, the operation display unit 15, the main body control unit 16, and the power supply unit 3 are provided in the housing 101.

[0014] The image processing device 10 includes a main body 1 having an image processing function. The ADF 11, an image reading unit 12, an image forming unit 13, a paper feed unit 14, an operation display unit 15, and a main body control unit 16 are provided in the main body 1. In other words, the image processing device 10 includes the main body 1 having an image processing function and a power supply device 3.

[0015] The ADF 11 transports an original document whose image is to be read by the image reading unit 12. The ADF 11 includes an original document setting unit, a plurality of transport rollers, an original document pressing unit, and a paper ejection unit.

[0016] The image reading unit 12 reads an image from a document and outputs image data corresponding to the read image. The image reading unit 12 includes a document table, a light source, a plurality of mirrors, an optical lens, a CCD (Charge Coupled Device), and the like.

[0017] The image forming unit 13 forms an image on a sheet by an electrophotographic method based on image data output from the image reading unit 12. The image forming unit 13 also forms an image on a sheet based on image data input from an information processing device external to the image processing device 10, such as a personal computer. The image forming unit 13 has four image forming units corresponding to four colors, C (cyan), M (magenta), Y (yellow), and K (black), an optical scanning device, an intermediate transfer belt, a secondary transfer roller, a fixing device, and the like. The image forming unit 13 may be configured to form an image on a sheet by an image forming method other than the electrophotographic method, such as an inkjet method, for example.

[0018] The image forming unit 13 forms an image on a sheet using toner as a developer. When the image forming unit 13 forms an image by an inkjet method, ink (another example of a developer) is supplied instead of toner. Examples of toner supplied to the image forming unit 13 include toner of multiple colors, such as C (cyan), M (magenta), Y (yellow), and K (black). After the image is formed in the image forming unit 13, the sheet is discharged (supplied) to an extension device or the like for post-processing.

[0019] The paper feed unit 14 supplies a sheet to the image forming unit 13. The paper feed unit 14 has a paper feed cassette, a manual feed tray, a sheet transport path, a plurality of transport rollers, etc. The image forming unit 13 forms an image on the sheet supplied from the paper feed unit 14. The sheet supplied to the image forming unit 13 is paper as an example, but is not limited to paper and may be, for example, a resin film, etc.

[0020] The operation display unit 15 is a user interface in the image processing device 10. The operation display unit 15 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit of the main body, and an operation unit such as a switch or a touch panel that inputs various information to the control unit of the main body in response to user operations. Furthermore, the image processing device 10 may be provided with, for example, a voice output unit and a voice input unit, in addition to or instead of the operation display unit 15, as a user interface.

[0021] The main body control unit 16 mainly comprises a computer system having one or more processors and one or more memories, and performs overall control of the image processing device 10. In the image processing device 10, the one or more processors execute programs to realize the functions of the main body control unit 16. In this embodiment, as an example, the main body control unit 16 includes a CPU (Central Processing Unit).

[0022] The power supply device 3 is a device that generates (outputs) power for the operation of the image processing device 10. The power supply device 3 is electrically connected to one or more electric loads and supplies power to the one or more electric loads. In this embodiment, the main body 1 of the image processing device 10 is the "electric load", and the power supply device 3 supplies power to each part of the main body 1 as the electric load. That is, the one or more electric loads to which power is supplied from the power supply device 3 include the ADF 11, the image reading unit 12, the image forming unit 13, the paper feeding unit 14, the operation display unit 15, and the main body control unit 16. In this way, the image processing device 10 includes the power supply device 3 for electric devices and the main body 1 having an image processing function. The electric load includes the main body 1.

[0023] In this embodiment, the power supply device 3 is electrically connected to an AC plug, and converts an AC voltage of 100V (or 200V) applied to the AC plug into, for example, a DC voltage of 24V and a DC voltage of 3.3V (or 5V). In other words, when the AC plug is connected to an outlet, AC power is applied to the power supply device 3 from an AC power source such as a system power source, and the power supply device 3 generates DC power from this AC power.

[0024] The power supply device 3 supplies a voltage of DC 24 V to a "first load" such as the ADF 11, the image reading unit 12, and the image forming unit 13. On the other hand, the power supply device 3 supplies a voltage of DC 3.3 V (or 5 V) to a "second load" such as the general control unit 7.

[0025] The power supply device 3, for example, receives a control signal from the main body control unit 16 to determine the state of power supply to one or more electrical loads (ADF 11, image reading unit 12, image forming unit 13, paper feed unit 14, operation display unit 15, main body control unit 16, etc.). Specifically, the main body 1 has a plurality of operation modes including a normal mode and an energy saving (energy saving) mode. The energy saving mode is a mode in which the power consumption of the main body 1 can be reduced compared to the normal mode. When the main body 1 operates in the normal mode, the power supply device 3 supplies power to both the first load (ADF 11, etc.) and the second load (general control unit 7, etc.). On the other hand, when the main body 1 operates in the energy saving mode, the power supply device 3 supplies power only to the second load of the first load and the second load. Therefore, in the energy saving mode, the main body control unit 16 outputs a control signal (sleep signal) to the power supply device 3 to switch the state of power supply from the power supply device 3.

[0026] The image processing device 10 further includes a storage unit and a communication unit, etc. The storage unit includes one or more non-volatile memories, and stores information such as control programs for causing the main body control unit 16 to execute various processes in advance. The communication unit is an interface that executes data communication between the image processing device 10 and an external device connected via a communication network such as the Internet or a LAN (Local Area Network).

[0027] Incidentally, as a related art of this type of image processing device 10, there is known an electrophotographic image processing device (image forming device) equipped with a power supply device that reduces a target voltage in response to switching from a normal mode to an energy saving mode. In the power supply device of the related art, a power supply circuit having a switching power supply charges an output capacitor (capacitor) and supplies an output voltage from the output capacitor to an electrical load. A discharge circuit is capable of discharging the voltage charged in the output capacitor. A CPU operates the discharge circuit in the process of reducing the output voltage from a first voltage to a second voltage in response to a transition from the normal mode to the energy saving mode (sleep mode).

[0028] In the configuration of the related art described above, the control for switching from the normal mode to the energy saving mode and the control for operating the discharge circuit are performed separately, making it difficult to simplify the configuration and control of the power supply device.

[0029] In contrast to this, in this embodiment, a power supply device 3 for electrical equipment and an image processing device 10 that can easily be simplified in configuration and control are provided by the configuration described below.

[0030] [2] Power supply configuration Next, the configuration of a power supply device 3 for an electric device that supplies electric power (power source) to an electric load will be described in more detail with reference to Fig. 1. Fig. 1 is a block diagram showing a schematic configuration of the power supply device 3. In this embodiment, an image processing device 10 is an example of an electric device to which power is supplied from the power supply device 3.

[0031] As shown in FIG. 1, the power supply device 3 includes a switching power supply unit 31, an output capacitor 32, a discharge unit 33, a switching unit , and an operating unit .

[0032] The switching power supply unit 31 is a switching type power supply circuit that converts an AC voltage of 100V (or 200V) applied to an AC plug into a desired voltage, for example, a DC voltage of 24V, and outputs the voltage. An output capacitor 32 is electrically connected to the output terminal of the switching power supply unit 31, and the switching power supply unit 31 generates an output voltage V1 (see FIG. 3) by charging the output capacitor 32.

[0033] The output capacitor 32 outputs an output voltage V1 to an electrical load (main body 1). A pair of output terminals T1, T2 (see FIG. 3) are electrically connected to the output capacitor 32. As a result, the voltage across the output capacitor 32 is applied as the output voltage V1 between the pair of output terminals T1, T2. An electrical load is electrically connected to the pair of output terminals T1, T2, and the output voltage V1 generated across the output capacitor 32 is applied to the electrical load from the pair of output terminals T1, T2.

[0034] The discharge unit 33 is electrically connected to the output capacitor 32 to discharge the output capacitor 32. That is, the charge stored in the output capacitor 32 can be discharged by the discharge unit 33.

[0035] The switching unit 34 switches the output voltage V1 from a first voltage V11 to a second voltage V12. The second voltage V12 is a voltage lower than the first voltage V11 (V11>V12). Specifically, the switching unit 34 changes the output voltage V1 by controlling the switching power supply unit 31.

[0036] The operation unit 35 operates the discharge unit 33 and the switching unit 34. In this embodiment, the operation unit 35 operates both the switching unit 34 and the discharge unit 33 in response to one control signal (sleep signal). Specifically, the operation unit 35 electrically connects the discharge unit 33 to the output capacitor 32, thereby forcibly discharging the output capacitor 32 via the discharge unit 33. The operation unit 35 also operates the switching unit 34, which switches the output voltage V1 output by the switching power supply unit 31 from the first voltage V11 to the second voltage V12. In this embodiment, as an example, the control signal (sleep signal) can be input to the operation unit 35 from the main body control unit 16.

[0037] According to the above-described configuration, when the operation mode of the main body 1 is switched from the normal mode to the energy saving mode, one control signal (sleep signal) is input to the operating unit 35, so that the operating unit 35 can operate both the discharge unit 33 and the switching unit 34. Therefore, when the switching unit 34 switches the output voltage V1 from the first voltage V11 to the second voltage V12, the discharge unit 33 forcibly discharges the output capacitor 32, and the output voltage V1 can be quickly reduced from the first voltage V11 to the second voltage V12 regardless of the electrical load. Moreover, since the control of switching from the normal mode to the energy saving mode (i.e., the control of switching the output voltage V1 from the first voltage V11 to the second voltage V12) and the control of operating the discharge unit 33 are performed by one control signal, there is an advantage that the configuration and control of the power supply device 3 can be easily simplified.

[0038] Furthermore, in this embodiment, the operating unit 35 is configured to operate the discharge unit 33 in response to the control signal, and then electrically disconnect the discharge unit 33 from the output capacitor 32. That is, when the operation mode of the main body 1 switches from the normal mode to the energy saving mode, the operating unit 35 electrically connects the discharge unit 33 to the output capacitor 32 to cause the discharge unit 33 to discharge the output capacitor 32, and then electrically disconnects the discharge unit 33 from the output capacitor 32, thereby ending the discharge of the output capacitor 32 by the discharge unit 33. This makes it possible to suppress power consumption in the discharge unit 33.

[0039] Particularly, in this embodiment, the operating unit 35 is configured to electrically disconnect the discharge unit 33 from the output capacitor 32 in conjunction with a drop in the output voltage V1 before the output voltage V1 reaches the second voltage V12. That is, after the discharge unit 33 starts discharging the output capacitor 32, in conjunction with a gradual drop in the output voltage V1, the discharge unit 33 is electrically disconnected from the output capacitor 32 at a timing before the output voltage V1 reaches the second voltage V12. As a result, after the output voltage V1 switches to the second voltage V12, the discharge unit 33 is disconnected from the output capacitor 32, so that power consumption in the discharge unit 33 can be suppressed.

[0040] [3] Examples of power supply devices Next, a specific example of the power supply device 3 will be described with reference to FIGS.

[0041] The power supply device 3 includes a pair of input terminals T3, T4 connected to an AC plug. The switching power supply unit 31 is electrically connected between the pair of input terminals T3, T4, and AC power is supplied to the switching power supply unit 31 by electrically connecting the AC plug to an external power supply AC1.

[0042] The switching power supply unit 31 includes a diode bridge DB1 and a capacitor C1 as a rectifying and smoothing circuit. A primary terminal of the diode bridge DB1 is connected to an external power supply AC1 via a fuse 301 and a filter circuit 302.

[0043] The switching power supply unit 31 includes a switching element Q1, a drive circuit 303, and a transformer 304. The switching element Q1 is a metal-oxide-semiconductor field effect transistor (MOSFET) that is turned on / off in response to a drive signal from the drive circuit 303 applied to a gate terminal.

[0044] The driving circuit 303 is a control IC (integrated circuit). The driving circuit 303 operates by receiving power from the charge stored in the capacitor C2, and causes the switching element Q1 to perform a switching operation. The driving circuit 303 is electrically connected to the primary terminal of the diode bridge DB1 via the diodes D1 and D2.

[0045] The switching element Q1, the primary winding Np1 of the transformer 304, and the resistor R1 are electrically connected in series between both ends of the capacitor C1. Therefore, a pulse current is supplied to the primary winding Np1 of the transformer 304 in response to the switching operation of the switching element Q1.

[0046] A capacitor C2 is electrically connected to the auxiliary winding Nb1 of the transformer 304 via a diode D3. Therefore, when the switching element Q1 performs a switching operation and a pulse current is supplied to the primary winding Np1 of the transformer 304, the capacitor C2 is charged by the AC voltage generated in the auxiliary winding Nb1. The voltage V2 across the capacitor C2 is applied to the drive circuit 303 as the power supply voltage for the drive circuit 303.

[0047] A parallel circuit of a resistor R2 and a capacitor C3 and a diode D4 are electrically connected in series between both ends of the primary winding Np1. A light receiving element PC2 of a photocoupler and a capacitor C4 are electrically connected in parallel to the drive circuit 303.

[0048] A diode D5 and an output capacitor 32 are electrically connected in series to the secondary winding Ns1 of the transformer 304. Therefore, when the switching element Q1 performs a switching operation and a pulse current is supplied to the primary winding Np1 of the transformer 304, the output capacitor 32 is charged by the AC voltage generated in the secondary winding Ns1.

[0049] A pair of output terminals T1, T2 are electrically connected to both ends of the output capacitor 32. A first load (ADF 11, image reading unit 12, image forming unit 13, etc.) is electrically connected to the pair of output terminals T1, T2. As a result, an output voltage V1 (for example, a voltage of DC 24 V) generated between the pair of output terminals T1, T2 is applied to the first load. In addition to the first load, a DC / DC converter is electrically connected to the pair of output terminals T1, T2. The DC / DC converter converts (steps down) the output voltage V1 generated between the pair of output terminals T1, T2 to a voltage of, for example, DC 3.3 V (or 5 V), and outputs it to a second load (general control unit 7, etc.).

[0050] Furthermore, a discharge unit 33 is electrically connected between both ends of the output capacitor 32. In this embodiment, a resistor R13 is an example of the discharge unit 33. The discharge unit 33 (resistor R13) is electrically connected in series with the switch element Q2 of the actuation unit 35 between both ends of the output capacitor 32.

[0051] In addition to the switch element Q2, the actuation section 35 includes resistors R3 to R12, a capacitor C5, transistors Tr1 and Tr2, a shunt regulator Z1, and a light-emitting element PC1 that is a photocoupler.

[0052] The resistor R3, the light emitting element PC1 of the photocoupler, and the shunt regulator Z1 are electrically connected in series across the output capacitor 32. The resistors R5 and R6 are electrically connected in series across the output capacitor 32. The transistor Tr2, the resistors R10, and the resistors R11 are electrically connected in series across the output capacitor 32. The connection point between the light emitting element PC1 and the shunt regulator Z1 is electrically connected to the connection point between the resistors R5 and R6 via a series circuit of the resistor R4 and the capacitor C5. The transistor Tr1 and the resistor R9 are electrically connected in series across the resistor R5.

[0053] Moreover, resistors R7 and R8 are electrically connected in series between the output terminal T1 and the control terminal T5. The base terminals of transistors Tr1 and Tr2 are electrically connected to the connection point between resistors R7 and R8. The gate terminal of switch element Q2 is electrically connected to the connection point between resistors R10 and R11 via resistor R12. Switch element Q2 is a MOSFET that turns on / off in response to a drive signal to the gate terminal.

[0054] The control terminal T5 is electrically connected to the main body control unit 16. A control signal (sleep signal) for switching the state of power supply from the power supply device 3 can be input to the control terminal T5 from the main body control unit 16. In other words, when switching from the normal mode to the energy saving mode, the main body control unit 16 outputs a control signal (sleep signal) to the control terminal T5 of the power supply device 3 and switches the state of power supply from the power supply device 3.

[0055] Next, the operation of the power supply device 3 having the above-mentioned configuration will be described with reference to Figures 3 and 4. Figure 4 shows an example in which the main body 1 operates in normal mode until time t1, and the operation mode is switched from the normal mode to the energy saving mode at time t1.

[0056] When the power supply device 3 starts up, it charges the capacitor C2 via the diodes D1 and D2, and when the voltage V2 across the capacitor C2 becomes equal to or higher than the operation start voltage V22 (see FIG. 4) of the drive circuit 303, the drive circuit 303 starts operating.

[0057] In the normal mode, the control signal input from the main body control unit 16 to the control terminal T5 is at H (High) level. In this state, the drive circuit 303 supplies a pulse current to the primary winding Np1 of the transformer 304 by switching the switching element Q1 as shown in Fig. 4. As a result, the output capacitor 32 is charged by the AC voltage generated in the secondary winding Ns1 of the transformer 304, and the output voltage V1 increases.

[0058] Then, when the output voltage V1, which is the voltage across the output capacitor 32, reaches the first voltage V11, the divided voltage between resistors R5 and R6 becomes equal to or higher than the threshold voltage of the shunt regulator Z1, and the light-emitting element PC1 of the photocoupler emits light. When the light-emitting element PC1 of the photocoupler emits light, the light-receiving element PC2 of the photocoupler on the primary side of the transformer 304 turns on, and the capacitor C4 is short-circuited. The drive circuit 303 detects that the output voltage V1 is equal to or higher than the first voltage V11 when the capacitor C4 is short-circuited and the terminal voltage becomes an L (Low) level.

[0059] This allows the drive circuit 303 to change the switching operation of the switching element Q1 depending on whether the output voltage V1 is equal to or greater than the first voltage V11, thereby enabling the output voltage V1 to be maintained at the first voltage V11. For example, if the output voltage V1 is equal to or greater than the first voltage V11, the drive circuit 303 reduces the duty ratio of the switching operation to reduce the power generated in the secondary winding Ns1 of the transformer 304. In this way, the drive circuit 303 is able to maintain the output voltage V1 at the first voltage V11 by feeding back the output voltage V1 divided by the resistors R5 and R6 via a photocoupler.

[0060] While the operation mode of the main body 1 is the normal mode, the power supply device 3 maintains the output voltage V1, which is the voltage across the output capacitor 32, at the first voltage V11 through the operations described above.

[0061] On the other hand, in the energy saving mode, the control signal input from the main body control unit 16 to the control terminal T5 is at L (Low) level. In this state, the power supply device 3 switches the output voltage V1, which is the voltage across the output capacitor 32, to a second voltage V12 lower than the first voltage V11. In this embodiment, the drive circuit 303 is an example of a switching unit 34.

[0062] Specifically, in the normal mode, the power supply device 3 sets the target voltage of the output voltage V1 to the first voltage V11 by turning off the transistor Tr1 of the operation unit 35. In contrast, in the energy saving mode, the power supply device 3 sets the target voltage of the output voltage V1 to the second voltage V12 by turning on the transistor Tr1 of the operation unit 35.

[0063] That is, when the control signal input to the control terminal T5 switches from H level to L level, the transistor Tr1 is turned on by the voltage division of the output voltage V1 between the resistors R7 and R8. As a result, the resistor R9 is electrically connected in parallel to the resistor R5, and when the voltage division between the resistors R5, R9, and R6 becomes equal to or higher than the threshold voltage of the shunt regulator Z1, the light-emitting element PC1 of the photocoupler emits light, and the light-receiving element PC2 of the photocoupler is turned on. That is, in the energy saving mode, when the output voltage V1 becomes equal to or higher than a voltage (second voltage V12) lower than the first voltage V11 in the normal mode, the capacitor C4 is short-circuited and the terminal voltage becomes L (Low) level, thereby detecting that the output voltage V1 is equal to or higher than the second voltage V12.

[0064] This allows the drive circuit 303 to change the switching operation of the switching element Q1 depending on whether the output voltage V1 is equal to or greater than the second voltage V12, thereby enabling the output voltage V1 to be maintained at the second voltage V12. For example, if the output voltage V1 is equal to or greater than the second voltage V12, the drive circuit 303 reduces the duty ratio of the switching operation to reduce the power generated in the secondary winding Ns1 of the transformer 304. In this way, the drive circuit 303 is able to maintain the output voltage V1 at the second voltage V12 by feeding back the output voltage V1 divided by the resistors R5, R9, and R6 via a photocoupler.

[0065] In this embodiment, when switching from the normal mode to the energy saving mode, it is necessary to significantly reduce the output voltage V1, so the drive circuit 303 temporarily stops the switching operation of the switching element Q1. When the switching operation of the switching element Q1 stops, power is no longer generated in the secondary winding Ns1 of the transformer 304, and therefore the output voltage V1 gradually decreases from the first voltage V11 as the output capacitor 32 discharges.

[0066] However, when discharging only by the electric load connected to the pair of output terminals T1 and T2, the discharge time required to reduce the output voltage V1 to the second voltage V12 may be long. While the switching operation of the switching element Q1 is stopped, power is not generated in the auxiliary winding Nb1 of the transformer 304, so that the voltage V2 across the capacitor C2 that generates the power supply voltage of the drive circuit 303 also gradually decreases from the voltage V21. At this time, the voltage V2 across the capacitor C2 needs to be maintained at or above the operation start voltage V22 of the drive circuit 303. For this purpose, it is conceivable to increase the capacity of the capacitor C2, but in that case, there is a concern about adverse effects such as a delay in start-up time. Therefore, when switching from the normal mode to the energy saving mode, it is desirable to reduce the output voltage V1 to the second voltage V12 in a relatively short time.

[0067] In this embodiment, the operation unit 35 operates the switching unit 34 (drive circuit 303) and the discharge unit 33 (resistor R13), thereby making it possible to reduce the output voltage V1 to the second voltage V12 in a relatively short time. That is, in the power supply device 3 according to this embodiment, a control signal (sleep signal) input to the control terminal T5 operates the switching unit 34 (drive circuit 303) and the discharge unit 33 (resistor R13). Specifically, when the control signal input to the control terminal T5 switches from H level to L level, the transistor Tr1 is turned on by the voltage division of the output voltage V1 between resistors R7 and R8, and the transistor Tr2 is also turned on.

[0068] When the transistor Tr2 is turned on, the switch element Q2 is turned on by the voltage division of the output voltage V1 between the resistors R10 and R11. As a result, the resistor R13 as the discharge unit 33 is electrically connected between both ends of the output capacitor 32, and the electrical energy stored in the output capacitor 32 is discharged through the resistor R13. Therefore, the power supply device 3 according to this embodiment can reduce the output voltage V1 to the second voltage V12 in a relatively short time and switch from the normal mode to the energy saving mode.

[0069] Furthermore, when the discharge unit 33 (resistor R13) is operated and the output voltage V1 drops from the first voltage V11 to reach a third voltage V13 higher than the second voltage V12, the operation unit 35 electrically disconnects the discharge unit 33 (resistor R13) from the output capacitor 32. Specifically, when the output voltage V1 is the third voltage V13, the divided voltage of the resistors R10 and R11 matches the threshold voltage of the switch element Q2. Therefore, when the output voltage V1 falls below the third voltage V13, the divided voltage of the resistors R10 and R11 falls below the threshold voltage of the switch element Q2, and the switch element Q2 turns off. As a result, the resistor R13 as the discharge unit 33 is opened, and discharging at the resistor R13 stops.

[0070] 4, the period from time t1 to time t2 is the period during which the discharge unit 33 operates, that is, the period during which the discharge unit 33 is electrically connected to the output capacitor 32. As a result, the discharge unit 33 is electrically disconnected from the output capacitor 32 at the timing (time t2) before the output voltage V1 reaches the second voltage V12, and therefore, power consumption in the discharge unit 33 can be avoided after the output voltage V1 switches to the second voltage V12 (switches to the energy saving mode).

[0071] As an example, when the first voltage V11 is 24V and the second voltage V12 is 8V, the third voltage V13 that opens the discharge unit 33 is set to 10V.

[0072] [4] Variations The multiple components included in the power supply device 3 may be distributed across multiple housings. For example, at least one of the switching power supply unit 31, the output capacitor 32, the discharge unit 33, the switching unit 34, and the operation unit 35 may be provided separately.

[0073] 3, the specific configuration of the power supply device 3 can be changed as appropriate as long as the same function can be realized. For example, the discharge unit 33 is not limited to the resistor R13, but may be a capacitor, a light-emitting element, or another electric load. [Explanation of symbols]

[0074] 1 Main unit (electrical load) 3. Power supply (for electrical equipment) 10 Image processing device (electrical equipment) 31 Switching power supply section 32 Output Capacitor 33 Discharge section 34 Switching section 35 Operating part V1 Output voltage V11 First voltage V12 Second voltage

Claims

1. an output capacitor that outputs an output voltage to an electrical load; a switching power supply unit that generates the output voltage by charging the output capacitor; a discharge unit electrically connected to the output capacitor to discharge the output capacitor; a switching unit that switches the output voltage from a first voltage to a second voltage that is lower than the first voltage; and an operation unit that operates the switching unit and the discharge unit in response to a control signal. Power supply for electrical equipment.

2. The operation unit operates the discharge unit in response to the control signal, and then electrically disconnects the discharge unit from the output capacitor. A power supply device for an electrical device according to claim 1.

3. The operation unit electrically disconnects the discharge unit from the output capacitor before the output voltage reaches the second voltage in response to a decrease in the output voltage. A power supply device for an electrical device according to claim 2.

4. A power supply device for an electrical device according to any one of claims 1 to 3; A main body having an image processing function, The electrical load includes the main body. Image processing device.

Images