JP5796304B2 - Power supply device and image forming apparatus - Google Patents

Description

  The present invention relates to a power supply device and an image forming apparatus, and in particular, two power sources, a constant voltage output power source that uses externally supplied power as an input source, a power storage device, and a power source that uses the power of the power storage device as an input source. The present invention relates to a power supply device having a power supply, and an image forming apparatus such as a copier, a printer, a facsimile equipped with the power supply device, or a digital multifunction peripheral having a combination of these functions.

  In recent years, copiers, printers, facsimiles, and multi-function machines that combine these using an electrophotographic process have become multifunctional, and accordingly, the structure has become complicated and the maximum power consumption tends to increase. In order to reduce the factors of the image forming apparatus itself and the waiting time of the operator, such as the waiting time until the fixing device rises and the temporary interruption of the operation due to the fixing temperature drop during the printing or copying operation, the power supplied to the fixing heater is reduced. It tends to increase. On the other hand, since there is a limit to the power that can be supplied from a normal power supply line, this is a major limitation in designing the equipment.

  Accordingly, an invention provided with a power storage device has been proposed in order not to exceed the maximum suppliable power of the power supply line (for example, Patent Document 1 or 2). Among these, Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-236159) describes stabilization of a load applied voltage of a power supply device that supplies power to the load simultaneously with outputs of a first power supply and a second power supply, and a load when the load fluctuates. A first power source having a constant voltage output for supplying power to a load using externally supplied power as an input source in order to suppress fluctuations in applied voltage, and conversion means for converting a load current value flowing through the load into a current value signal And a signal generating means for generating a control signal for compensating for a shortage of the load current value represented by the current value signal exceeding the upper limit instruction value of the output current of the first power source, a power storage device, A second power source of constant current output that uses power as an input source and feeds power to the load in accordance with the control signal, and the first power source is connected to the power supply line on the load side from the current detection position of the conversion means. Set the voltage to the set value. Invention for controlling the power supply of the output voltage is disclosed.

  Patent Document 2 (Japanese Patent Laid-Open No. 3-203516) discloses a resistance protection circuit that is connected in series to a load and detects a current flowing through the load in order to prevent the resistance from generating heat and the resistance from generating heat. A switching means connected in parallel to the resistor, an overcurrent detecting means for detecting that a current has flowed to the resistor above a predetermined value, and an overcurrent flowing to the resistor by the overcurrent detecting means. And a holding means for holding the switching means in an ON state when it is detected.

  That is, in the invention described in Patent Document 1, a DC power source and a capacitor power source are connected in parallel, power is supplied to the secondary load from both power sources, and the stability of the voltage applied to the load is improved. The invention described in Patent Document 2 includes switching means connected in parallel with a resistor, overcurrent detection means, and means for turning on the switching means, and prevents heat generation of the resistor.

  However, the former requires a separate switching circuit for the output ON / OFF circuit of the capacitor system, and the circuit configuration is complicated. In the latter case, power is always supplied to the secondary load via the current detection resistor, and the power loss is large even when the power storage device is not used.

  Therefore, a problem to be solved by the present invention is to prevent power loss from becoming large when the power storage device is not used.

In order to solve the above-described problems, the present invention provides a first power source having a constant voltage output that uses externally supplied power as an input source, a power storage device that stores power supplied from the outside, and power of the power storage device A second power source used as a power source, connecting the output of the first power source and the output of the second power source in parallel, and simultaneously using the power from the first power source and the power from the second power source as a load A power supply device to supply, comprising a load current detection means for detecting a current flowing through the load before the load, and a switching means provided in parallel to the load current detection means, when the power storage device is not used Is characterized in that electric power is supplied to the load via the switching means, and the output of the second power source is turned on / off in conjunction with the ON / OFF of the switching means .

In the embodiment described later, the power supplied from the outside is the commercial AC power supply 27, the first power supply is the main power supply 29, the power storage device is the capacitor 37, the second power supply is the auxiliary power supply 32, and the load current detecting means. the load current detecting resistor 60 and the load current detector 33, switching means to the SW element 71, corresponding, respectively Re it.

  According to the present invention, it is possible to prevent the power loss from increasing when the power storage device is not used.

1 is a diagram illustrating a schematic configuration of an image forming system including a digital multifunction peripheral and a personal computer according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating a configuration of a printer of the digital multifunction peripheral of FIG. 1. It is a block diagram which shows the structure of a power supply device. It is a block diagram showing the structure of an input / output control part. It is a block diagram which shows the detailed structure of the constant voltage power supply, constant current power supply, load current detector, and current indicator which are shown in FIG. It is a block diagram which shows the modification of the principal part structure of FIG. 3 shown in FIG.

  According to the present invention, when the power storage device is not used, power is supplied to the 24V load via the switching means provided in parallel with the current detection resistor, and the ON / OFF of the switching means also serves as the output ON / OFF of the capacitor system. It is characterized by that.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an image forming system including a digital multi-function peripheral MF1 and a personal computer PC as an image forming apparatus according to an embodiment of the present invention.

  In the figure, a digital multi-function peripheral MF1 according to the present embodiment is a color digital multi-function peripheral that forms an image using four color toners. In general, an automatic document feeder (ADF) 120, an operation board 10, a scanner 100, and Each unit of the printer 200 is provided. The scanner 100 and the printer 200 are color scanners because they read color images and form color images, and are color printers. The operation board 10 and the scanner 100 with the ADF 120 are units that can be separated from the printer 200. The color scanner 100 includes a control board having a power device driver, a sensor input, and a controller, and the controller on the control board communicates directly or indirectly with the engine controller to perform timing control to read an original image.

  The digital multifunction peripheral MF1 functions as a printer of the personal computer PC, and performs communication via a network via a private network PN and a private branch exchange PBX (Private Branch eXchange).

FIG. 2 is a schematic configuration diagram showing the configuration of the printer 200 of the digital multifunction peripheral MF1 of FIG.
In the figure, the printer 200 includes four sets of toner image forming units a, b, and m for forming images of each color of magenta (M), cyan (C), yellow (Y), and black (black: K). c and d are arranged in this order along the moving direction of the first transfer belt (intermediate transfer belt) 208 (from left to right y in the figure). That is, it is a four-drum type (tandem type) full-color image forming apparatus. A static eliminating device, a cleaning device, a charging device 202, and a developing device 204 are arranged on the outer peripheral portion of the photosensitive member (drum) 201 that is rotatably supported and rotates in the direction of the arrow. A space for storing optical information emitted from the exposure device 203 is secured between the charging device 202 and the developing device 204. There are four (a, b, c, d) photoconductors 201, but the image forming component configuration provided around each is the same. The color of the color material (toner) handled by the developing device 204 is set to four colors such as M, C, Y, and K, and the only difference is that. A part of each photoconductor 201 of MCYK is in contact with the first transfer belt 208. As the photosensitive member, a belt-shaped photosensitive member can be used instead of the drum.

  The first transfer belt 208 is stretched between one drive roller and two support rollers, and rotates in the direction of arrow D1. On the back side of the first transfer belt 208 (inside the loop), a first transfer roller 211 is provided in the vicinity of the photoconductor 201. A cleaning device 213 for the first transfer belt 208 is disposed outside the belt loop and downstream of the second transfer roller 212. The cleaning device 213 wipes off unnecessary toner remaining on the surface after the toner image is transferred from the first transfer belt 208 to the transfer paper (paper) or the second transfer belt 215.

  The exposure apparatus 203 is an optical writing type exposure apparatus that performs laser writing using a known polygon mirror and imaging optical system, and optical information corresponding to full-color image formation is uniformly charged on the surface of each photoreceptor. Is irradiated as a latent image. An exposure apparatus using an LED array and an imaging optical system can be used instead of the polygon optical system.

  In FIG. 2, a secondary transfer device 220 is provided on the right side of the first transfer belt 208. The secondary transfer device 220 includes a second transfer belt 215 that is in contact with the first transfer belt 208, and a transfer nip is formed between the first transfer belt 208 and the second transfer belt 215, and the nip formation position is the secondary transfer belt. Position. The second transfer belt 215 is stretched between the driving roller and the support roller so as to be movable in the direction of the arrow D2, and the second transfer roller 212 is disposed on the back side (inside the loop). A cleaning device 216 for the second transfer belt, a charger 217, and the like are provided outside the belt loop. The cleaning device 216 wipes off the remaining unnecessary toner after transferring the toner to the paper.

  The sheets are stored in sheet feeding cassettes 209 and 210 in the lower part of the figure, and the uppermost sheet is conveyed one by one by the sheet feeding roller to the registration roller 233 through a plurality of sheet guides. Above the second transfer belt 215, a fixing device 214, a paper discharge guide 224, a paper discharge roller 225, and a paper discharge stack 226 are arranged. Above the first transfer belt 208 and below the paper discharge stack 226, a toner bottle storage portion 227 for storing supply toner is provided. The toner is stored in the form of a cartridge of four colors, magenta M, cyan C, yellow Y, and black K, and is appropriately supplied to the developing device 204 of the corresponding color by a powder pump or the like.

  Here, the operation of each unit during duplex printing is performed as follows. In double-sided printing, first, image formation is performed with the photoconductor 201. That is, by the operation of the exposure device 203, light from an LD light source (not shown) passes through an optical component (not shown), and among the photoconductors 201 uniformly charged by the charging device 202, the photoconductor of the image forming unit a. Then, a latent image corresponding to the writing information (information corresponding to the color) is formed. The latent image on the photoconductor 201 is developed by the developing device 204, and a visible image with toner is formed and held on the surface of the photoconductor 201. This toner image is transferred onto the surface of the first transfer belt 208 that moves in synchronization with the photoreceptor 201 by the first transfer means.

  The surface of the photoconductor 201 is cleaned by the cleaning device with the remaining toner, and is neutralized by the static eliminator to prepare for the next image forming cycle. The first transfer belt 208 carries the toner image transferred on the surface and moves in the direction of the arrow D1. A latent image corresponding to another color is written on the photoconductor 201 of the image forming unit b, and developed with a toner of the corresponding color to become a visible image. This image is overlaid on the visible image of the previous color already on the first transfer belt 208, and finally four colors are overlaid. In some cases, only monochrome black is formed.

  At this time, the second transfer belt 215 is moved in the direction of the arrow D2 in synchronization, and the image formed on the surface of the first transfer belt 208 is transferred to the surface of the second transfer belt 215 by the action of the second transfer roller 212. Is done.

  The first and second transfer belts 208 and 215 are moved while the images are formed on the respective photosensitive members 201 of the four image forming units a to d in the so-called tandem format. Can be shortened. When the first transfer belt 208 moves to a predetermined position, a toner image to be created on another side of the paper is formed again by the photoconductor 201 in the process described above, and paper feeding is started. The uppermost sheet in the sheet feeding cassette 209 or 210 is pulled out and conveyed to the nip of the registration roller 233. The sheet is fed from the registration roller 233 to the secondary transfer position in synchronism with the leading position of the image on which the four color images primarily transferred to the first transfer belt 208 are superimposed at the nip of the registration roller 233. At the secondary transfer position, the toner image on the surface of the first transfer belt 208 is transferred to one surface of the sheet fed between the first transfer belt 208 and the second transfer belt 215 by the action of the second transfer hand roller 212. Is done. Further, the sheet is conveyed upward, and the toner image already transferred onto the surface of the second transfer belt 215 as described above is transferred to the other surface of the sheet by the charger 217. At the time of transfer, the sheet is conveyed at a timing so that the positions of the images on both sides are normal.

  The paper having the toner images transferred on both sides in this way is sent to the fixing device 214, and the toner images (both sides) on the paper are melted and fixed at one time. Are discharged to a paper discharge tray (paper discharge stack) 226. As shown in FIG. 2, when the paper discharge units 224 to 226 are configured, the side (page) of the double-sided image that is later transferred to the paper, that is, the surface that is directly transferred from the first transfer belt 208 to the paper is the lower surface. Since the image is placed on the paper discharge stack 226, an image of the second page is created first and the toner image is held on the second transfer belt 215 in order to align the pages. The image is directly transferred from the first transfer belt 208 to the sheet. The image directly transferred from the first transfer belt 208 to the paper is a normal image on the surface of the photoconductor 201, and the toner image transferred from the second transfer belt 215 to the paper is a reverse image (mirror image) on the surface of the photoconductor 201. It is exposed to become. Such image forming order for page alignment and image processing for switching between normal and reverse images (mirror images) are also performed by image data read / write control on the memory on the controller. After transfer from the second transfer belt 215 to the paper, a cleaning device 216 including a brush roller, a collection roller, a blade, and the like removes unnecessary toner and paper dust remaining on the second transfer belt 215.

  In FIG. 2, the brush roller of the cleaning device for the second transfer belt 215 is in a state separated from the surface of the second transfer belt 215. The structure can swing around a fulcrum and can be brought into contact with and separated from the surface of the second transfer belt 215. Before the transfer onto the paper, the second transfer belt 215 is separated when carrying a toner image, and when cleaning is required, it is swung in the counterclockwise direction in FIG. The removed unnecessary toner is collected in a toner storage unit.

  The image forming process in the duplex printing mode in which the “duplex transfer mode” is set has been described above. In the case of duplex printing, printing is always performed by this image forming process.

  In the case of single-sided printing, there are two types of "single-sided transfer mode by the second transfer belt 215" and "single-sided transfer mode by the first transfer belt 208", and the single-sided transfer mode using the former second transfer belt 215 is set. In this case, a visible image formed in the first transfer belt 208 in three colors, four colors or monochromatic black is transferred to the second transfer belt 215, and then transferred to one side of the paper. There is no image transfer on the other side of the paper. In this case, a print screen exists on the upper surface of the printed paper discharged to the paper discharge tray 226. When the single-sided transfer mode using the latter first transfer belt 208 is set, a visible image formed in three colors, four colors, or single color black is transferred to the second transfer belt 215 on the first transfer belt 208. Instead, it is transferred to one side of the paper. There is no image transfer on the other side of the paper. In this case, a print screen exists on the lower surface of the printed paper discharged to the paper discharge stack 226.

FIG. 3 is a block diagram showing the configuration of the power supply apparatus.
In FIG. 3, the power supply includes a main power supply 29, a main power supply SW (switch) 28, a commercial AC power supply 27, an auxiliary power supply 32, an input / output control (unit) 20, a 24V system load 35, a 5V system load 34, and a current indicator. 64 and the fixing heating device 36 basically.

  In the power supply device, the commercial AC power supply 27 is supplied to the main power supply 29 and the auxiliary power supply 32 when the main power supply SW28 is turned on. A commercial AC voltage 27 is applied from the commercial AC power source 27 to a fixing power source 31 and a constant voltage power source (AC / DC converter) 30 which are AC control circuits of the main power source 29 and a capacitor charger 38 of the auxiliary power source 32. The fixing power source 31 feedback-controls the fixing device temperature using the fixing temperature signal given from the temperature detection 70 within the power range specified by the power instruction signal given from the input / output control 20.

  The constant voltage power supply 30 that is the first power supply of the main power supply 29 converts the commercial AC into DC by the bridge rectifier 80, the insulating switching circuit 81, and the rectifying / smoothing circuit 82, and sends it to the PWM controller 84 via the insulating error amplifier 83. Two DC constant voltages of 5V and 24V are generated by constant voltage feedback control using a given voltage detection signal, and are output to the 5V system load 34 and the 24V system load 35. In FIG. The isolated switching circuit 81, the rectifying / smoothing circuit 82, the isolated error amplifier 83, and the PWM controller 84 are distinguished by adding a subscript a to the 24V system load 35 and a subscript b to the 5V system load 34. .

  At this time, a 24V voltage detection signal (feedback signal) is output from the load current detector 33 to the current indicator 64. As will be described later, since the load current detector 33 has a resistance of several mΩ connected in series to the power supply line, when the load current detector 33 is provided after the voltage detection signal (feedback signal) capturing unit, The power supply voltage supplied to the system will fluctuate. For example, when a 10 mΩ resistor is connected to the current detection resistor of the load current detector 33 and the load changes from 5 A to 15 A, a fluctuation of 0.1 V (10 mΩ × (15A-5A)) occurs. Become. Further, when the current detection resistor of the load current detector 33 is added outside the main power supply 29, further fluctuations occur due to the influence of the wiring resistance. Therefore, in order to prevent the fluctuation of the DC load supply voltage due to the addition of the current detection resistor as described above, the voltage after the resistance is feedback controlled.

  The main power supply 29 has a configuration in which a SW element 71 is provided in parallel with the load current detector 33. When power is supplied to the 24V system load 35 via the load current detector 33, the power consumed by the load current detector 33 itself (for example, a 10 mΩ resistor is connected to the current detection resistor and the load is 10A). In this case, 1 W (10 mΩ × 10 A × 10 A)) is generated, and the power loss is larger than that of a normal system. In order to suppress this, during the period when power is not supplied from the auxiliary power source 32, the SW element 71 is turned on to supply power to the 24V system load 35 without going through the load current detector 33.

  In this embodiment, the auxiliary power source 32 is a capacitor charger 38, a capacitor 37 charged by the capacitor charger 38, and a constant current power source 26 that is a second power source that outputs constant current to the power supply line to the 24V system load 35. Composed. The reason why the auxiliary power supply 32 is fed to the 24V load 35 is that the auxiliary power supply must bear the increase in the amount of power supplied to the fixing heating device 36. This is because it is necessary to supply the auxiliary power supply 32 to a certain power supply line. For this reason, in the present embodiment, in consideration of an increase in the amount of power supplied to the fixing heating device 36 (for example, 300 W), the 24V system load 35 (for example, 500 W) that consumes more power than the 5V system load 34 (for example, 100 W) is assisted. The power supply 32 is supplied with power. When the increase in the amount of power supplied to the fixing heating device 36 is small or when the power consumption of the 5V system load 34 is large, the auxiliary power supply 32 can be fed to the 5V system load 34. .

  The load current detector 33 detects a 24V load current value, which is the sum of the current values simultaneously supplied from the constant voltage power supply 30 (first power supply) and the constant current power supply 26 (second power supply), and outputs a current detection signal as a current. This is given to the indicator 64. In addition, the input / output control (unit) 20 provides the current indicator 64 with the upper limit instruction data MCD that specifies the output current upper limit value of the constant voltage power supply 30. The current indicator 64 supplies the constant current power supply 26 with a current instruction signal indicating a value obtained by subtracting the upper limit instruction value from the 24V system load current value (= output current instruction value of the constant current power supply 26). The constant current power supply 26 supplies the electric power of the capacitor 37 to the 24V system load line with constant current by constant current control using the current value indicated by the current indication signal output from the current indicator 64 as a target value.

  The capacitor 37 of the auxiliary power source 32 is configured by a large capacity capacitor such as an electric double layer capacitor. Various selections other than the electric double layer capacitor are possible, but in this embodiment, an electric double layer capacitor that can be charged and discharged in a short time and has a long life is used. Since the terminal voltage (capacitor voltage) is lowered as the electric double layer capacitor is discharged, the constant current power supply 26 is arranged at the subsequent stage of the capacitor 37, so that a desired current value is obtained regardless of the fluctuation of the capacitor voltage. Is output.

FIG. 4 is a block diagram showing the configuration of an input / output control unit 20 (denoted as a control unit in FIG. 1 and denoted as input / output control in FIG. 4) 20.
In FIG. 4, the input / output control unit 20 includes a CPU 21, a ROM 22, a RAM 23, a nonvolatile RAM 24, and an I / O control unit 25. The CPU 21 controls the sensor 516, the 5V system load 34, and the 24V system load 35 in accordance with a control command from an engine control unit (not shown) that controls the printer 200, a program stored in the ROM 22, and a program and data stored in the nonvolatile RAM 24. Input / output control is performed on the power supply, and control of the power supply device is performed. The ROM 22 stores a program for operating the CPU 21, and the RAM 23 is used as a work memory for the CPU 21. The nonvolatile RAM 24 stores a power consumption table storing power consumption data in each load mode and each operation mode, a print processing time table storing time data required for print processing in each operation mode, and the like. The I / O control unit 25 controls input reading of each sensor 2516 of the full-color digital multi-function peripheral MF1, and controls individual driving of the 5V system load 34 and the 24V system load 35.

  The input / output control unit 20 performs input / output control and power supply control to the sensor 516 and the 5V system load 34 and 24V system load 35 in accordance with instructions associated with process control and sequence control such as image reading, printing, and copying of the engine control unit. Each load is operated sequentially according to each operation mode. The input / output control unit 20 also controls charging / discharging of the capacitor 37. The SW element 71 is turned off during the start-up of the device and the predetermined time after the start-up, and the load current detector The electric power stored in the capacitor 37 is supplied to the 24V system load 35 through 33. At this time, the amount of power supplied to the fixing heating device 36 is increased by a margin generated with respect to the power supplied from the commercial AC power supply 27.

  FIG. 5 is a block diagram showing detailed configurations of the constant voltage power supply 30, the constant current power supply 26, the load current detector 33, and the current indicator 64 shown in FIG.

  In FIG. 5, the constant voltage power supply 30 uses a shunt regulator 87 to generate a voltage detection signal obtained by dividing the voltage on the 24V system load 35 side of the load current detection resistor 60 included in the load current detector 33 by the voltage dividing resistors 85 and 86. The voltage is compared / amplified with the reference voltage, insulated by the photocoupler 88 and supplied to the PWM controller 83b as a constant voltage feedback signal, and the power supply voltage immediately before being supplied to the 24V system load 35 is controlled to a constant voltage.

  In this embodiment, the capacitor 37 is an electric double layer capacitor. The electric double layer capacitor has a low withstand voltage, and the charging upper limit voltage in use is 2.5V. Therefore, in order to obtain a high voltage, it is necessary to connect many in series. However, the same capacity can be obtained at a lower cost by using a small number of large capacitors rather than in series with many small capacitors. When power is supplied to the 24V system load 35 and the electric double layer capacitors are used in a series number of 9 or less, the charging upper limit voltage is 22.5 V or less, and therefore it is necessary to configure the constant current power supply 26 using a boost regulator. Therefore, in the present embodiment, the boost regulator 40 boosts the power of the capacitor 37 and outputs a constant current.

  The semiconductor switch 41 of the boost regulator 40 is conductive (ON) during the H period of the output PWM pulse of the PWM controller 42 and is nonconductive (OFF) during the L period. When the switch 41 is turned on, a current flows from the capacitor 37 to the reactor 43 and the switch 41, the reactor 43 stores power, and when the switch 41 is turned off, the stored power of the reactor 43 becomes high and the capacitor 45 is passed through the diode 44. Charge with high voltage. By repeating ON / OFF of the PWM pulse cycle of the switch 41, the voltage of the capacitor 45 rises, and power is supplied to the 24V system load 35 through the current detection resistor 47 and the current detection resistor 60 of the load current detector 33.

  The load current detector 33 amplifies the potential difference between both ends of the current detection resistor 60 with the differential amplifier 61, generates a load current signal proportional to the load current value, and outputs (applies) to the current indicator 64.

  The current indicator 64 analog-converts the current upper limit value instruction data MCD provided by the input / output control unit 20 into an upper limit instruction signal (voltage) by the D / A converter 65, and “differential load current detection value−upper limit” by the differential amplifier 66. "Indicated value" is calculated, and a differential voltage representing the calculation result is output to the constant current power supply 26 as a current instruction signal. That is, the current indicator 64 is a target value to be borne by the constant current power supply 26 by subtracting the output current upper limit value of the constant voltage power supply 30 indicated by the input / output control unit 20 from the 24V system load current detector. The constant current power supply 26 is instructed to output the current.

  The constant current power supply 26 amplifies the potential difference between both ends of the current detection resistor 47 with a differential amplifier 48, generates an output current signal proportional to the output current value, and supplies it to the differential amplifier 50. The differential amplifier 50 amplifies the difference between the target current values provided by the current indicator 64 from the output current signal, adds the voltage provided by the bias circuit, and instructs the PWM controller 42 to indicate the duty of the PWM pulse. Give as a signal.

  The PWM controller 42 determines the duty of the PWM pulse for driving the semiconductor switch 41 on / off to the duty specified as the duty instruction signal. That is, when the output signal of the current indicator 64 increases and the output voltage of the differential amplifier 50 increases, the duty of the PWM pulse is increased. As a result, the output current value of the boost regulator 40 increases. Accordingly, the voltage drop of the current detection resistor 47 increases, the level of the output current detection signal increases, and the output voltage of the differential amplifier 50 decreases, the PWM pulse duty decreases. As a result, the output current value of the boost regulator 40 decreases. By such feedback PWM control, the output current value of the boost regulator 40 subtracts the output current upper limit value MCD of the constant voltage power supply 30 instructed by the input / output control unit 20 from the 24V load current detection value given by the current indicator 64. It becomes a value corresponding to the difference.

The above is the operation when the auxiliary power supply 32 is used. Hereinafter, the operation when the auxiliary power supply 32 is not used will be described.
When the auxiliary power supply 32 is not used, the SW element 71 provided in parallel with the load current detection resistor 60 is turned on. Since the current passes through a path having a small resistance value, power is supplied to the load through the SW element 71 having a resistance value smaller than that of the load current detection resistor 60, and power loss consumed in the power supply line is reduced when the auxiliary power supply is used. It is possible to suppress the comparison. Here, the power loss consumed in the power supply line can be made equal to that of the normal system. For this reason, the SW element 71 should be switched from OFF to ON when the 24V system load 35 is lightly loaded (such as in the standby mode of the system). Inrush current can be suppressed, and problems such as relay welding can be prevented.

  In order to reduce power loss, it is preferable to use a SW element 71 having a resistance value as small as possible. Therefore, in this embodiment, a relay is used.

  Further, when the power storage device is not used, a normally closed relay is used in order to suppress power consumption for ON driving of the SW element (relay) 71 itself.

6 is a block diagram showing a modification of the main configuration of FIG. 3 shown in FIG.
As can be seen from the block diagram showing the detailed configuration of the constant voltage power supply 30, the constant current power supply 26, the load current detector 33, and the current indicator 64 according to FIG. 6, the modification of FIG. The output ON / OFF signal supplied to the PWM controller 42 of the auxiliary power supply is deleted, and the configuration other than this is the same as the configuration shown in FIG. With this configuration, the contact resistance of the SW element (relay) 71 is less than or equal to the resistance value of the current detection resistor 33. When the relay is on (on), the load current detector 33 has a low load even when the load is high. Judge and operate. That is, the power supply from the auxiliary power supply 32 is stopped when the relay is conductive (ON). This configuration utilizes such a characteristic operation, and is configured to simultaneously control ON / OFF of the output of the auxiliary power supply device by ON / OFF of the SW element (relay) 71.

  In the configuration shown in FIG. 5, the output ON / OFF of the power storage device is controlled by using an ON / OFF terminal (switch 41) provided in the PWM controller 42 of the constant current power supply 30. As a result, according to the present modification, power loss can be suppressed without incurring system complexity due to the addition of a power consumption reduction function (the SW element 71 and the ON / OFF control circuit for the SW element 71).

As described above, according to the present embodiment,
1) When the capacitor 37 is not used, power is supplied to the 24V system load 35 via the SW element (relay) 71 provided in parallel with the current detection resistor 60, so that power loss can be suppressed.

2) Further, since the output of the auxiliary power source 32 using the capacitor 37 as a power source is also turned on / off by the ON / OFF of the SW element 71, the ON / OFF circuit configuration in the auxiliary power source of the capacitor output may be complicated. Absent.
There are effects such as.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention, and all technical matters included in the technical idea described in the claims are included. The subject of the present invention. The above embodiment shows a preferable example, but those skilled in the art can realize various alternatives, modifications, variations, and improvements from the contents disclosed in this specification, These are included within the scope defined by the appended claims.

27 Commercial AC power supply 29 Main power supply 32 Auxiliary power supply 33 Load current detector 37 Capacitor 60 Load current detection resistor 71 SW element MF1 Image forming apparatus

JP 2007-236159 A Japanese Patent Laid-Open No. 3-203516

Claims (5)

A first power source with a constant voltage output using an externally supplied power as an input source;
A power storage device that stores power supplied from outside, and a second power source that uses the power of the power storage device as an input source;
Have
A power supply device for connecting the output of the first power supply and the output of the second power supply in parallel, and simultaneously supplying power from the first power supply and power from the second power supply to a load;
A load current detecting means for detecting a current flowing through the load at a preceding stage of the load and a switching means provided in parallel to the load current detecting means;
When the power storage device is not used, electric power is supplied to the load via the switching means, and the output of the second power source is turned on / off in conjunction with the ON / OFF of the switching means. A power supply device characterized by that. The power supply device according to claim 1,
The power supply apparatus according to claim 1, wherein the ON timing of the switching means is set at a light load . The power supply device according to claim 1 or 2,
The power supply apparatus, wherein the switching means includes a relay . The power supply device according to claim 3 ,
The power supply apparatus, wherein the relay is normally closed . An image forming apparatus comprising the power supply device according to any one of claims 1 to 4 .