JP2012039801A - Power supply device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device and image formation device, which efficiently use an auxiliary power supply part in addition to a main power supply part.SOLUTION: In an image formation device 1, a main power supply part 3 generates electric power from a commercial AC power source PW and supplies it to a load. A load current value that flows a 24V system load 10 is detected with a load current detector 36. A current indicator 6 compares the detected load current value with an output current upper-limit value MCD, and it outputs a current value instruction signal representing a current value which is a shortfall corresponding to an excessive value of the load current over the output current upper-limit value MCD, to an auxiliary power supply part 4. At an input/output control part 5, the main power supply part 3 generates an applicable power from the commercial AC power supply PW, and if a residual electric power available by subtracting the electric power required by a load other than the 24V system load 10 from the applicable electric power is insufficient for the electric power required for the 24V system load 10, the output current upper-limit value MCD which is outputted to the current indicator 6 is controlled so that the auxiliary power supply part 4 generates the electric power corresponding to the insufficient amount from the accumulated electric power in a capacitor 42, which is supplied to the 24V system load 10.

Description

  The present invention relates to a power supply device and an image forming apparatus, and more particularly to a power supply device and an image forming apparatus that use an auxiliary power supply unit in addition to a main power supply unit.

  An image forming apparatus using an electrophotographic process is represented by a composite apparatus combining a copy function, a printer function, a scanner function, a facsimile function, and the like. In addition, an image forming apparatus using an electrophotographic process has an image forming apparatus itself such as a waiting time until the fixing unit rises and a temporary interruption of operation due to a decrease in fixing temperature during the image forming operation. In order to reduce this factor and the waiting time for the operator, the power supplied to the fixing heater tends to increase. As a result, not only the normal power consumption required for the image forming apparatus during normal operation is increasing, but also the maximum required power consumption is increasing.

  In this way, while the power consumption increases, the upper limit of the suppliable power amount is determined in the commercial AC power source. Therefore, in the image forming apparatus, only the power amount supplied to the main power supply unit by the commercial AC power source is determined. Then, there arises a situation in which the maximum required power consumption cannot be met. Conventionally, a power storage device (capacitor) is mounted, the power storage device is used as an auxiliary power source, and power from the auxiliary power source is secondary-sided. A technique for supplying more electric power to the fixing heater by supplying it to the load is already known. In other words, a fixing heater used in an electrophotographic image forming apparatus is a fixing heater that warms up (when the fixing heater is raised from a cooled state to a temperature at which toner can be fixed) to increase the temperature in a short time. You need to give as much power as possible. However, the power that can be supplied from the commercial power supply is limited, and the power that is supplied from the maximum power that can be supplied from the commercial power supply is reduced by subtracting the power supplied to the secondary load such as the motor and clutch used in the image forming apparatus. Is the maximum power that can be supplied to the fixing heater. Therefore, not only power supply from a commercial power supply but also more power can be supplied by supplying power from an auxiliary power supply unit such as a chargeable power storage device (for example, a capacitor of an electric double layer capacitor) to a secondary load. A technique for supplying the toner to the fixing heater is already known.

  Conventionally, a DC power supply unit (constant voltage power supply unit) that generates a direct current (DC) power supply from a commercial power supply of the image forming apparatus and supplies it to a load, and a constant current power supply unit that uses a power storage device that stores the commercial power supply In order to increase the stability of the voltage applied to the load when power is supplied from both power supply units to the secondary load when connected in parallel, the upper limit indication value (MCD) of the output current is supplied to the constant voltage power supply unit. The constant voltage power supply unit is configured to prevent the current exceeding the upper limit instruction value from being output, and the constant current power supply unit supplements the current exceeding the upper limit instruction value of the constant voltage power supply unit to supply the load to the load. It is disclosed (see Patent Document 1).

  However, in the prior art described in the above publication, there is a need for improvement in order to reduce power consumption by performing more efficient power consumption.

  In other words, the power storage device mainly generates power loss when charging a commercial AC power supply to a capacitor, and the constant voltage power supply unit mainly generates power loss when converting from alternating current (AC) to direct current (DC). To do. Then, comparing the power loss in this power storage device with the power loss in the constant voltage power supply unit, it is known that the power loss in the power storage device is much larger than the power loss in the constant voltage power supply unit. Yes.

  However, in the prior art described in the publication, the constant voltage power supply unit is provided with an upper limit instruction value of the output current, and the constant voltage power supply unit uses a power storage device connected in parallel with the constant voltage power supply unit. Power supply is used even when the load does not require more power than the maximum power that can be supplied from the commercial power supply. Since power is supplied from the constant current power supply unit, the power loss of the entire image forming apparatus may be increased, and improvement is required.

  Therefore, the present invention improves the power utilization efficiency by supplying only the power exceeding the maximum power that can be supplied by the main power supply means that generates internal power directly from the external power supply from the auxiliary power supply means using the power storage means. An object of the present invention is to provide a power supply device and an image forming apparatus that can be used.

  In order to achieve the above object, according to the present invention, the main power supply means generates a predetermined constant voltage power from the power supplied from the outside and supplies it to the load, and the load current flowing through the predetermined constant voltage load among the loads The current detection means detects the value, and the current instruction means compares the detected load current value with a predetermined upper limit current value to determine a shortage current value that the load current exceeds the upper limit current value. The load current value indicated by the current value indicating signal output from the current indicating means from the stored power stored in the power storing means for storing the electric power supplied from the outside by the auxiliary power supply means The constant current power is generated and supplied to the predetermined constant voltage load, and the control means generates the power other than the predetermined constant voltage load from the power generated by the main power supply means from the power supplied from the outside. Subtract the power required for other loads required by other loads When the remaining power is insufficient with respect to the power required by the predetermined constant voltage load, the upper limit current value is varied, and the power for the shortage is supplied to the auxiliary power supply means. .

  Further, according to the present invention, the control means generates power other than the predetermined constant voltage load from power that can be generated from the power supplied from the outside and can be supplied to all loads including a variable load whose power consumption varies greatly depending on an operating state. When the power obtained by subtracting the necessary power required by the load is insufficient for the power required by the predetermined constant voltage load, the upper limit current value is controlled to supply the insufficient power to the auxiliary power supply means. It is good also as making it supply.

  Furthermore, the present invention is characterized in that the main power supply means and the auxiliary power supply means are connected in parallel, and power can be supplied to the predetermined constant voltage load from both the main power supply means and the auxiliary power supply means. Also good.

  According to the present invention, only the power exceeding the maximum power that can be supplied by the main power supply means that directly generates internal power from the external power supply is supplied from the auxiliary power supply means using the power storage means, thereby improving the power utilization efficiency. it can.

1 is a schematic block configuration diagram of a power supply system of an image forming apparatus to which an embodiment of the present invention is applied. The circuit block diagram of the principal part of a main power supply part and an auxiliary power supply part. FIG. 6 is a transition diagram of currents to the fixing heating unit and the 24∨ system load from the startup immediately after the power is turned on.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 3 are diagrams showing an embodiment of a power supply apparatus and an image forming apparatus according to the present invention. FIG. 1 is an image forming apparatus 1 to which an embodiment of the power supply apparatus and the image forming apparatus according to the present invention is applied. It is a schematic block block diagram of the power supply system.

  1, the image forming apparatus 1 has a power supply system configured as shown in FIG. 1, and includes a main power switch (SW) 2, a main power supply unit 3, an auxiliary power supply unit 4, and an input / output control unit 5. A current indicator 6, a fixing heating unit 7, a temperature detection unit 8, a 5V system load 9, a 24V system load 10, and the like.

  The main power switch 2 is supplied with 100V commercial AC power (commercial AC power) PW, which is an external power supply, via a power cord, and the main power switch 2 is turned on so that the main power switch 2 is turned on. External power is supplied to the power supply unit 3 and the auxiliary power supply unit 4.

  Although not shown, the image forming apparatus 1 includes a paper feeding unit, a printer unit, a scanner unit, an ADF (Auto Document Feeder), an operation display unit, a control unit, and the like. An external device is connected via a network such as an area network. The image forming apparatus 1 uses the above-described units according to the operation of the operation display unit, etc., to perform various functions such as an image reading function, a printing function (printer function), a copying function (copying function), and a facsimile communication function. Execute. In addition, the image forming apparatus 1 communicates with an external device via a network to transmit and receive image data.

  The paper feed unit includes a plurality of paper feed trays, a transport unit, and the like, and various sizes of paper (recording paper) are stored in each paper feed tray in an arbitrary paper feed direction. The transport unit includes a registration roller, and selectively feeds the paper stored in each paper feed tray to the registration roller, adjusts the timing with the registration roller, and then transports the paper to the printer unit.

  For example, a four-drum (tandem) full-color printer unit is used as the printer unit, and includes a laser exposure unit, an image forming unit, a fixing unit, a storage unit, and the like. In the image forming unit, C (cyan), M (magenta), Y (yellow), and B (black) image forming units are arranged side by side on the transfer belt, and according to the image data of each color from the laser exposure unit. An electrostatic latent image formed on the image forming unit is formed, and the electrostatic latent image on each color image forming unit is developed with each color toner to form a toner image. The printer unit forms a color image on the paper by directly superimposing the toner image on the image forming unit of each color directly on the paper or via an intermediate transfer belt, and finally transferring it onto the paper. The sheet on which the color image is formed is conveyed to the fixing unit, and the toner image is fixed by heating and pressurizing the sheet on which the toner image is transferred by the fixing heating unit 7 of the fixing unit. Send the paper to the paper output tray. Note that the image forming unit may form only a monochrome black image using only a black image forming unit, and the exposure unit is not limited to the one using a laser. The exposure part provided with the image formation part may be sufficient.

  The main power supply unit (main power supply means) 3 includes a fixing power supply unit 21 and a constant voltage power supply unit 22. The constant voltage power supply unit 22 is an AC / DC converter and includes a bridge rectifier 31 and a 24V system. Insulated switching circuit 32a for load 10, rectifying / smoothing circuit 33a, insulating error amplifier 34a, PWM (Pulse Wide Mosulation) controller 35a, insulating switching circuit 32b for 5V system load 9, rectifying / smoothing circuit 33b, an insulation type error amplifier 34b, a PWM controller 35b, and a load current detection unit 36 for detecting the load current of the 24V system load 10.

  The fixing power supply unit 21 is an AC control circuit, and uses the detected temperature signal detected by the temperature detecting unit 8 within the power range specified by the power instruction signal supplied from the input / output control unit 5. The power supplied to the fixing heating unit 7 is feedback controlled so as to control the temperature to the fixing temperature.

  The constant voltage power supply unit 22 converts the commercial AC power supply PW into a DC (direct current) constant voltage by the bridge rectifier 31 and the insulating switching circuit 32b and the rectifying / smoothing circuit 33b for the 5V system load 9, and supplies them to the 5V system load 9. At the same time, the DC voltage from the rectifying / smoothing circuit 33b to the 5V system load 9 is returned as an FB (feedback) signal to the PWM controller 35b via the isolated error amplifier 34b, and the PWM controller 35b performs the isolated switching based on the FB signal. Switching control of the circuit 32b is performed.

  Similarly, the constant voltage power supply 102 converts the commercial AC power supply PW into a DC (direct current) constant voltage by the bridge type rectifier 31 and the insulation type switching circuit 32a and the rectifying / smoothing circuit 33a of the 24V system load 10, and supplies the 24V system load 10 to the 24V system load 10. At the same time, the DC voltage from the rectifying / smoothing circuit 33a to the 24V system load 10 is returned as an FB (feedback) signal to the PWM controller 35a via the insulation type error amplifier 34a, and the PWM controller 35a is insulated based on the FB signal. Switching control of the type switching circuit 32a is performed.

  The auxiliary power supply unit (auxiliary power supply means) 4 includes a capacitor charger 41, a capacitor 42, a voltage detection circuit 43, a constant current power supply unit 44, and the like, and is based on a current value instruction signal from a current indicator 6 described later. The constant current power to the 24V system load 10 is supplied. The capacitor charger 41 and the capacitor 42 function as power storage means as a whole.

  That is, the commercial AC power supply PW is supplied to the capacitor charger 41 of the auxiliary power supply unit 4 via the main power switch 2, and the capacitor charger 41 charges the capacitor 42 so that the voltage detection circuit 43 is constant. The voltage to the current power supply unit 44 is detected. The constant current power supply unit 44 generates auxiliary power of constant current corresponding to the current value instruction signal from the current indicator 6 by using the charge charged in the capacitor 42, and the load current detector 36 is generated. To the 24V system load 10. As the capacitor 42 of the auxiliary power supply unit 4, various types of capacitors can be used as long as they have a predetermined large capacity. However, in this embodiment, charging and discharging can be performed in a short time and the life is long. An electric double layer capacitor is used. Moreover, since the auxiliary power supply unit 4 of the present embodiment uses an electric double layer capacitor as the capacitor 42, as a characteristic of the electric double layer capacitor, the terminal voltage (capacitor voltage) becomes lower as it is discharged. The constant current power supply unit 44 is arranged on the downstream side of the capacitor 42 so that a required current value can be output even if the capacitor voltage fluctuates. Since the load current detector 36 uses a resistor R1 (see FIG. 2) of several mΩ for current detection, a current sensor of the load current detector 36 is provided behind the voltage detection signal (feedback signal) capturing unit. When the resistor R1 is provided, the load applied voltage fluctuates due to the increase or decrease in voltage drop in the current detection resistor R1 due to the increase or decrease in the load current value. For example, when a 10 mΩ resistor is connected as the current detection resistor R1 of the load current detector 36 and the load changes from 5 A to 15 A, the load applied voltage of 0.1 V (10 mΩ × (15A-5A)) fluctuates. Will do. Furthermore, if the current detection resistor R1 of the load current detector 36 is added to the outside of the main power supply unit 3, a load applied voltage fluctuation more than the above will occur due to the influence of the wiring resistance.

  Therefore, in order to prevent the fluctuation of the DC load applied voltage due to the addition of the current detection resistor, the image forming apparatus 1 of this embodiment uses the voltage after passing through the resistor R1 of the load current detector 36 as the insulation type error amplifier 34a and Feedback is performed by the PWM controller 35a, and constant voltage control, that is, feedback control is performed so that the feedback voltage matches the target value.

  Then, the auxiliary power supply unit 4 reduces the increase in the amount of power supplied to the fixing heating unit 7 from the amount of power supplied from the constant voltage power supply unit 22 that consumes the commercial AC power supply PW to the 24V system load 10. The reduced power is supplemented by power supply from the auxiliary power supply unit 4 to the 24∨ load 10.

  In view of this, the image forming apparatus 1 according to the present exemplary embodiment consumes more power than the 5V load 9 (for example, 100 W) in consideration of an increase in the amount of power supplied to the fixing heating unit 7 (for example, 300 W). Power is supplied from the auxiliary power supply unit 4 to the 24V system load 10 (for example, 500 W). When the increase in the amount of power supplied to the fixing heating unit 7 is small or when the power consumption of the 5V system load 9 is large, the 5V system load 9 may be supplied with power from the auxiliary power supply unit 4.

  Although not shown, the input / output control unit (control means) 5 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a nonvolatile RAM, an I / O control unit, and the like. Each unit is connected to a data bus and a control bus (address bus).

  The I / O control unit is connected to a current indicator 6, an auxiliary power supply unit 4, a main power supply unit 3, various sensor units, loads 9, 10, and the like. The I / O control unit is connected to the image forming apparatus 1. The detection signal reading by each sensor and the individual driving of the 24V system load 10 are controlled.

  The ROM stores various programs such as an engine control program and the power control program of the present invention, and necessary data. The CPU stores control commands from the engine control, programs stored in the ROM, and non-volatile RAM. In accordance with the stored program and data, the RAM is used as a work memory, and input / output control for the loads 9 and 10 and control of the power supply units 3 and 4 are performed. The nonvolatile RAM includes an operation state of each load 9, 10; a power consumption table storing power consumption data in each operation mode; a print processing time table in which time data required for print processing in each operation mode is registered; A table or the like for determining the current upper limit value MCD is stored.

  The input / output control unit 5 performs input / output control and power supply control to the sensors and loads 9 and 10 according to instructions accompanying process control and sequence control such as engine control image reading, printing, copying, etc., according to each operation mode. Then, the loads 9 and 10 are operated sequentially.

  The input / output control unit 5 also controls charging / discharging of the capacitor 42, and the 24 V system load is calculated from the electric power stored in the capacitor 42 during the start-up of the image forming apparatus 1 and a predetermined time after the start-up. 10 is powered.

  In FIG. 1, the portion surrounded by a broken line, that is, the constant voltage power supply unit 22 and the auxiliary power supply unit 4 of the main power supply unit 3 are configured as shown in FIG.

  In FIG. 2, for the main power supply unit 3, the load current detector (current detection means) 36 of the constant voltage power supply unit 22 connected to the 24V system load 10 has a load current detection resistor R <b> 1 as the main power supply unit 3. Is mounted on the same substrate as the main power supply unit 3 and the voltage across the load current detection resistor R1 is different from that of the constant voltage power supply unit 22 (main power supply unit 3). As an interface signal between the board and the load current detector 36 provided on the board, the differential amplifier OP1 of the load current detector 36 and a resistor (not shown) attached to the differential amplifier OP1 are connected by a connector and a harness. Yes. If comprised in this way, it can suppress that the output accuracy of the power supply of the constant voltage power supply part 22 by extension (elongation) of the constant voltage feedback loop of the constant voltage power supply part 22 can be suppressed, and remote control the constant voltage power supply part 22 Without being compatible with sensing, it is possible to maintain the output accuracy of the power supply and suppress an increase in the cost of the constant voltage power supply unit 22. Further, when the mechanism on the auxiliary power supply unit 4 side, that is, the combination of the auxiliary power supply unit 4, the current indicator 6, and the load current detector 36 is made optional, the main power supply unit 3 is changed when the auxiliary power supply mechanism is not installed. Without being necessary, the auxiliary power supply unit 4, the current indicator 6, the differential amplifier OP1 of the load current detector 36 and the associated resistor can be easily removed from the main power supply unit 3, and the cost of the main power supply unit 3 can be reduced. The main power supply unit 3 that can be connected to the auxiliary power supply mechanism such as the auxiliary power supply unit 4 can be constructed at low cost only by adding the load current detection resistor R1.

  The constant voltage power supply unit 22 of the main power supply unit 3 includes voltage dividing resistors R2 and R3, a shunt regulator SR, a photocoupler PC, and the like, and is subsequent to the load current detection resistor R1 of the load current detector 36 (DC 24V system load 10 side). Is divided by voltage dividing resistors R2 and R3 and input to the shunt regulator SR as a voltage detection signal. The isolated error amplifier 34a compares / amplifies the voltage detection signal with the reference voltage by the shunt regulator SR, insulates it by the photocoupler PC, and sends it to the PWM controller 35a as a feedback signal (FB) for constant voltage control. Output. The PWM controller 35a PWM-controls the primary side current of the insulating switching circuit 32a and supplies the voltage of the power supply line between the current detection resistor R1 and the 24V system load 10 immediately before being supplied to the 24V system load 10, that is, the load The applied voltage is controlled at a constant voltage.

  The constant current power supply unit 44 of the auxiliary power supply unit 4 includes a boost regulator 50 and an output current controller 60. The boost regulator 50 includes a PWM controller 51, a semiconductor switch Ts, a reactor Rt, a diode D, a capacitor C, and the like. An output current controller 60 includes a current detection resistor R4, a differential amplifier OP2, a differential amplifier OP3, and a bias circuit. K1, K2, etc. are provided.

  As described above, the auxiliary power supply unit 4 of the present embodiment uses an electric double layer capacitor as the capacitor 42. However, the electric double layer capacitor has a low withstand voltage and a charging upper limit voltage in use is 2.5V. Therefore, in order to obtain a high voltage, it is necessary to connect a large number of capacitors in series. However, the same capacity can be obtained at a lower cost by using a small number of large-capacity capacitors than by connecting a large number of small-capacitance capacitors in series. Therefore, the auxiliary power supply unit 4 of the present embodiment uses a capacitor 42 in which nine or less electric double layer capacitors are connected in series, and a shortage with respect to 24 kg is added to the constant current power supply unit 44. It supplements by providing. That is, when nine electric double layer capacitors are used, the charging upper limit voltage is 22.5 V or less, so that the boost regulator 50 boosts the voltage by 1.5∨ to supply 24∨ to the 24∨ system load 10 at a constant current. To do.

  The step-up regulator 50 performs on / off control of the semiconductor switch Ts by the output PWM pulse of the PWM controller 51, boosts the stored power of the reactor Rt, and charges the capacitor C with high voltage via the diode D. That is, when the semiconductor switch Ts is turned on (conductive), a current flows from the capacitor 42 to the reactor Rt and the semiconductor switch Ts, the reactor Rt stores electricity, and the semiconductor switch Ts is turned off (non-conductive). Is stored in a high voltage, and the capacitor C is charged with a high voltage through the diode D. The step-up regulator 50 increases the voltage of the capacitor C by repeating ON / OFF of the PWM pulse period of the semiconductor switch Ts, and passes through the current detection resistor R4 and the current detection resistor R1 of the load current detector 36, thereby causing a 24V system load. 10 is fed.

  The load current detector (current detection means) 36 amplifies the potential difference between both ends of the current detection resistor R1 with the differential amplifier OP1, and is a load current signal (analog voltage) proportional to the load current value to the 24V system load 10. Is output to the current indicator 6 as a load current detection value.

  The current indicator (current indicator means) 6 includes a D / A converter CT, an operational amplifier OP4, and the like. The current indicator 6 analog-converts the output current upper limit value (upper limit current value) MCD input from the input / output control unit 5 into an upper limit instruction signal (voltage) by the D / A converter CT. “Load current detection value−output current upper limit value MCD” is calculated, and a differential voltage representing the calculation result is output to the constant current power supply unit 44 as a current value instruction signal (current instruction value).

  That is, the current indicator 6 subtracts the output current upper limit value MCD of the constant voltage power supply unit 22 input from the input / output control unit 5 from the load current detection value input from the load current detector 36 for the 24V system load 10. The difference value is used as the target current value to be borne by the constant current power supply unit 44 of the auxiliary power supply unit 4, and the current output of the target current value is instructed to the constant current power supply unit 44 as a current instruction value (target current value).

  In the constant current power supply unit 44, the differential amplifier OP2 amplifies the potential difference between both ends of the current detection resistor R4, generates an output current signal proportional to the output current value, and outputs the output current signal to the differential amplifier OP3. The differential amplifier OP3 amplifies the difference between the output current value indicated by the output current signal input from the differential amplifier OP2 and the target current value (current instruction value) input from the current indicator 6, and further, a bias circuit The voltage given by K2 is added and output to the PWM controller 51 as a PWM pulse duty instruction signal.

  The PWM controller 51 determines the duty of the PWM pulse to the duty specified by the duty instruction signal input from the differential amplifier OP3, and drives the semiconductor switch Ts on / off with the PWM pulse duty. That is, when the target current value (current instruction value) output from the current indicator 6 increases and the output voltage of the differential amplifier OP3 increases, the constant current power supply unit 44 increases the duty of the PWM pulse and increases the boost regulator 50. Increase the output current value. When the output current value of the boost regulator 50 increases, the constant current power supply unit 44 increases the voltage drop of the current detection resistor R4, and the current detection resistor R4 detects the output current detection signal output from the differential amplifier OP2. Control is repeatedly performed such that the output current value increases, the output voltage of the differential amplifier OP3 decreases, the duty of the PWM pulse decreases, and the output current value of the boost regulator 50 decreases. That is, the constant current power supply unit 44 uses the feedback PWM control as described above to determine the output current value of the boost regulator 50 from the detection value of the load current detector 36 to the 24∨ load 10 provided by the current indicator 6. This is a value corresponding to the difference obtained by subtracting the output current upper limit value MCD of the constant voltage power supply unit 22 instructed by the input / output control unit 5.

  Next, the operation of this embodiment will be described. The image forming apparatus 1 according to the present exemplary embodiment uses a power that exceeds the maximum power that can be supplied from the main power supply unit 3 that directly generates internal power from the commercial AC power supply PW, from the auxiliary power supply unit 4 that uses the capacitor 42 to the 24∨ system load. 10 to improve the power utilization efficiency.

  That is, the image forming apparatus 1 includes loads 9, 10, and a load from a main power supply unit 3 that outputs power supplied from an external commercial AC power supply PW as an input source and an auxiliary power supply unit 4 that uses a capacitor 42. Electric power is supplied to the fixing heating unit 7, but electric power from the auxiliary power supply unit 4 is supplied only when the load 10 needs electric power exceeding the output current upper limit value MCD by the constant voltage power supply unit 22.

  In the image forming apparatus 1, the input / output control unit 5 switches the main power switch 2 from open to closed (ON), or the image forming apparatus 1 returns from the energy saving mode (power saving mode) to the standby mode. The constant voltage power supply unit 22 of the main power supply unit 3 starts +5 V output, +5 V (operation voltage) is applied to the input / output control unit 5, and the input / output control unit 5 performs input / output control in response to the power-on reset pulse. When the initialization of the unit 5 is completed, the input / output control unit 5 executes the power feeding control shown in FIG.

  That is, the transition of the supply current to the fixing heating unit 7 and the load current to the 24V system load 10 from the startup immediately after the operating voltage is applied to each part of the image forming apparatus 1 can be shown as in FIG. it can.

  In FIG. 3A, in the fixing reload period T1 in which the fixing temperature immediately after the main power switch 2 is turned on is raised to the target temperature, in order to satisfy the starting time required by the image forming apparatus 1, the normal time is exceeded. Also, a large amount of electric power (for example, 1300 W) is supplied to the fixing heating unit 7, and the fixing heating unit 7 is started up as quickly as possible to a temperature at which printing can be performed. Raising the fixing temperature of the fixing unit to a temperature at which printing is possible in this way is called fixing reload.

  Once the fixing heating unit 7 rises to a temperature at which printing can be performed, as shown in FIG. 3A as a print start T2, in order to maintain the temperature, the supply current to the fixing heating unit 7 is higher than that at the time of fixing reload. However, at the start of printing T2 after the completion of fixing reloading, the drop in the fixing temperature due to the paper passing is large, so the power to the fixing heating unit 7 is increased during the period until the temperature stabilizes than during normal printing. There is a need to.

  After the start of printing, when the temperature of the fixing heating unit 7 becomes stable, the required power of the fixing heating unit 7 decreases and stabilizes as shown as T3 in the printing operation in FIG.

  In addition, during the printing operation T3, the supply current to the fixing heating unit 7 is equal to or less than the current that can be supplied from the commercial AC power supply PW. However, as shown in FIG. As shown in FIG. 3 (c), the total current value including the supply current to the fixing heating unit 7 is the current that can be supplied from the commercial AC power supply PW. The value may be exceeded.

  However, the power supply from the capacitor 42 of the auxiliary power supply unit 4 to the 24∨ load 10 is inferior in the charging efficiency of the capacitor 42, and the power supply compared to the power supply from the constant voltage power supply unit 22 of the main power supply unit 3. The loss is great.

  Therefore, in the image forming apparatus 1 according to the present embodiment, the current exceeding the current that can be supplied by the commercial AC power supply PW in order to reduce the power loss caused by the power supply from the capacitor 42 in the power supply to the 24 へ system load 10. The output current upper limit value MCD output from the input / output control unit 5 to the current indicator 6 is set so that only the power is supplied from the capacitor 42 to the 24∨ load 10.

  The input / output control unit 5 calculates the current required by the fixing heating unit 7 from the fixing temperature signal output from the temperature detection unit 8 of the fixing heating unit 7, and detects the load current included in the load current detector 36. The required current of the 24∨ load 10 is calculated by the resistor R1.

  Now, the input / output control unit 5 assumes that the current value required by the fixing heating unit 10 is A, the required current of the 24∨ load 10 is B, and the current value that can be supplied from the commercial AC power supply PW is X, A + B If it is ≦ X, the required current B of the 24∨ load 10 is set as the power upper limit current set value MCD. On the other hand, if A + B> X, the input / output control unit 5 sets B− (A + B−X) = X−A as the power upper limit current set value MCD. In this way, the upper limit current set value MCD can be set so that only the current exceeding the current that can be supplied by the commercial AC power supply PW is supplied from the capacitor 42 of the auxiliary power supply unit 4 to the 24∨ load 10. .

  As described above, in the image forming apparatus 1 according to the present embodiment, the main power supply unit (main power supply unit) 3 generates predetermined constant voltage power from the power supplied from the commercial AC power supply (external) PW, and the loads 7 and 9. 10, and a load current detector (current detection means) 36 detects the load current value flowing through the 24 ∨ system load 10, which is a predetermined constant voltage load among the loads 7, 9, 10. The current indicator (current indicating means) 6 compares the load current value with the output current upper limit value MCD which is a predetermined upper limit current value, and the load current exceeds the output current upper limit value MCD. A current value instruction signal indicating a current value is output to the auxiliary power supply unit (auxiliary power supply unit) 4, and the auxiliary power supply unit 4 stores power in a capacitor (power storage unit) 42 that stores electric power supplied from the commercial AC power supply PW. The current value indicator output by the current indicator 6 from the stored power The constant current power of the load current value indicated by the signal is generated and supplied to the 24∨ system load 10, and the input / output control unit (control unit) 5 is the power supplied from the main power source unit 3 from the commercial AC power source PW. The remaining power obtained by subtracting the other load required power required by the load other than the 24∨-system load 10 from the power that can be generated and supplied to the entire load is insufficient with respect to the power required by the 24∨-system load 10 If so, the output current upper limit value MCD output to the current indicator 6 is controlled to supply the insufficient power to the auxiliary power supply unit 4.

  Therefore, compared with the power supply from the constant voltage power supply unit 22 of the main power supply unit 3, the power supply using the capacitor 42 having a large power loss is directly supplied from the commercial AC power supply PW which is an external power supply. The power use efficiency can be improved by limiting only to the power exceeding the maximum power that can be supplied by the main power supply unit 3 that generates the internal power to be supplied to each load.

  Further, in the image forming apparatus 1 of this embodiment, the input / output control unit 5 generates from the power supplied from the commercial AC power source PW, and the fixing heating unit 7 is a fluctuating load whose power consumption varies greatly depending on the operation state. If the power required for loads other than the 24∨ load 10 is subtracted from the power required for the load other than the 24∨ load 10 from the power that can be supplied to all loads including The MCD is controlled to supply the insufficient power to the auxiliary power supply unit 4.

  Therefore, even when there is a load with large fluctuations such as the fixing heating unit 7 as the load, only the power exceeding the power that can be generated from the commercial AC power supply PW is generated by the auxiliary power supply unit 4 and supplied to the 24V system load 10. can do.

  Further, in the image forming apparatus 1 of the present embodiment, the constant voltage power supply unit 22 and the auxiliary power supply unit 4 of the main power supply unit 3 are connected in parallel, and the constant voltage power supply unit 22 and the auxiliary power supply unit 4 of the main power supply unit 3 are connected. It is possible to supply power to the 24∨ system load 10 from both sides.

  Therefore, it is possible to appropriately supply from the auxiliary power supply unit 4 power that is insufficient with only the power from the main power supply unit 3.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

  The present invention can be used for a power supply device using an auxiliary power supply unit in addition to a main power supply unit, and an image forming apparatus such as a copying apparatus, a printer device, and a composite apparatus including the power supply device.

1 Image forming apparatus 2 Main power switch (SW)
3 Main Power Supply Unit 4 Auxiliary Power Supply Unit 5 Input / Output Control Unit 6 Current Indicator 7 Fixing Heating Unit 8 Temperature Detection Unit 9 5V System Load 10 24V System Load PW Commercial AC Power Supply 21 Fixing Power Supply Unit 22 Constant Voltage Power Supply Unit 31 Bridge Rectifier 32a Isolated switching circuit 33a Rectification smoothing circuit 34a Isolated error amplifier 35a PWM controller 32b Isolated switching circuit 33b Rectification smoothing circuit 34b Isolated error amplifier 35b PWM controller 36 Load current detection unit 41 Capacitor charger 42 Capacitor 43 Voltage detection circuit 44 Constant Current power supply R1 Load current detection resistor OP1 Differential amplifier R2, R3 Voltage dividing resistor SR Shunt regulator PC Photocoupler 50 Boost regulator 51 PWM controller Ts Semiconductor switch Rt Reactor D Diode C Sita 60 Output current controller R4 current detection resistor OP2 differential amplifier OP3 differential amplifier K1, K2 bias circuit

JP 2007-236159 A

Claims (4)

Main power supply means for generating a predetermined constant voltage power from the power supplied from the outside and supplying it to the load;
Current detection means for detecting a load current value flowing in a predetermined constant voltage load among the loads;
Current indicating means for comparing the load current value with a predetermined upper limit current value and outputting a current value indicating signal indicating a shortage current value where the load current exceeds the upper limit current value;
Power storage means for storing power supplied from outside;
Auxiliary power supply means for generating the constant current power of the shortage current value indicated by the current value instruction signal from the stored power stored in the power storage means and supplying the predetermined constant voltage load;
The remaining power obtained by subtracting the other load required power required by the load other than the predetermined constant voltage load from the power that the main power supply means generates from the power supplied from the outside and can be supplied to the entire load is the predetermined constant voltage. Control means for varying the upper limit current value and supplying the auxiliary power means to the auxiliary power means when the power required by the load is insufficient;
A power supply device comprising: The power supply device also supplies power to a variable load whose power consumption varies greatly depending on the operating state,
The control means includes
The power required for the predetermined constant voltage load is the power obtained by subtracting the necessary power required by a load other than the predetermined constant voltage load from the electric power generated from the externally supplied power and supplied to all loads including the variable load. 2. The power supply device according to claim 1, wherein when the electric power is insufficient, the upper limit current value is controlled to supply the shortage of electric power to the auxiliary power supply unit.   The power supply device is characterized in that the main power supply means and the auxiliary power supply means are connected in parallel, and power can be supplied to the predetermined constant voltage load from both the main power supply means and the auxiliary power supply means. The power supply device according to claim 1 or 2.   An image forming apparatus for forming an image by operating each part including the image forming part as a load by power supplied from the power supply part, comprising the power supply device according to any one of claims 1 to 3. Image forming apparatus.

Images