JP5640491B2 - Power supply device and image forming apparatus - Google Patents

Description

  The present invention relates to a power supply device that outputs DC power and an image forming apparatus including the same. The image forming apparatus includes a copying machine, a multifunction peripheral device (MFP) called a multifunction peripheral, and a printer.

  In various types of electrical equipment including an image forming apparatus, a DC power supply method is adopted that uses two main and sub DC / DC converters in order to save energy. The power efficiency of the main DC / DC converter is optimized for power supply during normal operation with relatively high power consumption, and the power efficiency of the sub DC / DC converter is a sleep mode in which power consumption is lower than that during normal operation. Optimized for small-load operation such as standby mode. Further, the main DC / DC converter is used only for power supply to a relatively heavy load such as a motor or a heater, and the sub DC / DC converter is used only for power supply to a relatively light load such as a control circuit. There is also a form.

  Regarding the proper use of the two DC / DC converters, Patent Document 1 describes a power supply device that operates both DC / DC converters when switching between a normal operation mode and a small load operation mode. In this power supply device, the main DC / DC converter is switched after the start-up time is predicted that the output of the sub DC / DC converter is expected to be steady after switching the sub DC / DC converter from OFF to ON at the time of shifting to the small load operation. Is switched from ON to OFF. Conversely, when switching to the normal operation, after switching the main DC / DC converter from OFF to ON, the sub DC / DC converter is switched from ON after the start-up time when the output of the main DC / DC converter is expected to be steady. Switch to OFF. The activation time of each DC / DC converter is stored in advance in the memory, and the activation time is counted by a counting circuit.

JP 2000-324820 A

  In the above-described prior art in which both the two DC / DC converters are operated only when the operation mode is switched, it is difficult to set a time period for a transient period in which both are operated. The starting time of each DC / DC converter is not constant because it depends on the state of the load. For this reason, if the transition period is short, the other converter is turned off before the start of the turned-on converter is completed, and there is a possibility that the power supply to the load is interrupted and the operation of the load is stopped. If the transition period is set longer, it is possible to prevent the power supply from being interrupted. However, switching from the small load operation mode to the normal operation mode is delayed, and the speed of operation of the electric device is impaired. Therefore, it is not preferable to set a long transition period.

  SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide a power supply apparatus having excellent controllability that does not require control of a DC / DC converter by predicting its startup time, and an image forming apparatus having the power supply apparatus.

A power supply device that achieves the above object is a power supply device that converts alternating current power into direct current power and outputs it, and is usually connected between an input terminal to which an alternating current power supply is connected and an output terminal to which a load is connected. The first converter for operation, the second converter for operation at a small load connected in parallel with the first converter at the input terminal and the output terminal, the first converter, and the second converter are controlled. A controller, and a voltage dividing resistor circuit that divides the voltage between the output terminals into three . In the power supply apparatus, the first converter may be configured to output a potential of an intermediate potential point on a low potential side of two intermediate potential points in the voltage dividing resistor circuit , and a first rectifying unit that rectifies the AC power. A first DC / DC converter that performs switching with respect to the output of the first rectifier so that the voltage between the terminals of the first rectifier is maintained at a potential when the voltage between the terminals is the first target voltage , and the second converter Is a second rectifier that rectifies the AC power, and the potential of the intermediate potential point on the high potential side of the two intermediate potential points in the voltage dividing resistor circuit is the voltage between the terminals of the output terminals . A second DC / DC converter that performs switching with respect to the output of the second rectifier so as to maintain the potential when the second target voltage is lower than one target voltage, and the controller From normal operation to small load operation It was switched the second converter in response to an instruction to stop the first converter without stopping the resumes the switching instruction receiving with power by the first converter output to the normal operation from a small load operation.

  According to the present invention, the two DC / DC converters can be selectively used according to the state of the load without depending on the control based on the prediction of the startup time of each DC / DC converter.

It is a block diagram which shows the structure of a power supply device. It is a timing chart which shows the relationship between the mode of load and operation | movement of a power supply device. It is a figure which shows the 1st example of the circuit structure of a power supply device. It is a figure which shows the 2nd example of the circuit structure of a power supply device. 1 is a diagram illustrating a configuration of a main part of an image forming apparatus including a power supply device.

  As shown in FIG. 1, the power supply device 1 includes a first converter 4 for normal operation connected between an input terminal 2 and an output terminal 3, and a first converter 4 in parallel with the input terminal 2 and the output terminal 3. Is connected to the second converter 5 for operation at the time of small load (for sleep), and the controller 6 for controlling the first converter 4 and the second converter. For example, a commercial AC power supply is connected to the input terminal 2 as an AC power supply 7, and a load 9 that receives DC power supplied from the power supply device 1 is connected to the output terminal 3. In this example, a power switch 8 is inserted between the AC power supply 7 and the input terminal 2.

  The first converter 4 includes a first rectifier 41 that rectifies AC power, and a first DC / DC that switches the output of the first rectifier 41 so that the output voltage approaches the first target voltage (Vm). And a DC converter 42. The second converter 5 outputs the second rectifier 51 that rectifies AC power and the output of the second rectifier 51 so that the output voltage value approaches the second target voltage (Vs) that is lower than the first target voltage (Vm). And a second DC / DC converter 52 that performs switching. The controller 6 receives the switching instruction from the normal operation to the light load operation issued by the control means for the load 9, stops the first converter 4 without stopping the second converter 5, and switches from the light load operation to the normal operation. In response to the switching instruction, power output by the first converter 4 is resumed.

  As shown in FIG. 2, the first converter 4 starts operating when the AC power supply 7 is turned on, and operates in the normal operation period T <b> 1 in which the power supply device 1 supplies power to the load 9 in the normal operation state. The first converter 4 stops in the sleep period T2 in which the power supply device 1 supplies power to the load 9 in the sleep state (small load state) that consumes less power than usual. On the other hand, even if AC power supply 7 is turned on, second converter 5 does not start operation immediately, and starts operation later than first converter 4 in response to an activation request from controller 6. Then, while the AC power supply 7 is turned on, the second converter 5 operates regardless of the normal operation period T1 and the sleep period T2. However, “operating” here means that the power output to the load 9 is possible, and does not mean the state of outputting power to the load 9. The period during which the second converter 5 outputs power to the load 9 is a sleep period T2 in which the first converter 4 stops.

  FIG. 3 shows a specific example of the circuit configuration of the power supply device 1.

  In the configuration of FIG. 3, the power supply device 1 supplies power to the control board 90 that executes the control program. The control board 90 is a load 9 for the power supply device 1. The power supply control unit 60 that is a functional element realized by executing a program on the control board 90 functions as the controller 6. That is, a part of the control board 90 is a component of the power supply device 1.

  The first converter 4 provided in the power supply device 1 as a main DC / DC converter has a rectifying diode bridge D11 and a smoothing capacitor C11 that constitute a rectifying unit 41. An AC power source 7 is connected to input points a and b of the rectifier diode bridge D11, and a switch SW4 is inserted between the input point a and the AC power source 7. The + terminal of the smoothing capacitor C11 is connected to the cathode of the rectifier diode bridge D11 and one end of the primary winding L11 of the transformer T11. The-terminal of the smoothing capacitor C11 is connected to the anode of the rectifier diode bridge D11 and is connected to the other end of the primary winding L11 via the semiconductor switch SW16. A switching signal S45 is input from the PWM controller 45 to the semiconductor switch SW16. The secondary winding L12 of the transformer T11 is connected in parallel to the series circuit of the rectifier diode D12 and the smoothing capacitor C12. The output voltage monitoring unit 46 connected in parallel with the smoothing capacitor C12 monitors the voltage obtained by dividing the output voltage (voltage between the output terminals) with the target voltage Vm selected to 3.4 volts by the voltage dividing resistors R11 and R12. Then, a feedback signal S46 indicating a deviation between the output voltage and the target voltage Vm is sent to the PWM control unit 45. An auxiliary winding L13 of a transformer T11 is connected to the PWM controller 45 as a driving power source. The PWM controller 45 receives the feedback signal S46 and controls the semiconductor switch SW16 so that the output voltage approaches the target voltage Vm.

  The configuration of the second converter 5 provided in the power supply device 1 as a sub DC / DC converter is basically the same as the configuration of the first converter 4 as follows, although there are differences in circuit constants and the presence or absence of the switch SW4. It is. The second converter 5 includes a rectifying diode bridge D21 and a smoothing capacitor C21 that constitute the rectifying unit 51. The AC power supply 7 is connected to the input points c and d of the rectifier diode bridge D21, and the + terminal of the smoothing capacitor C21 is connected to the cathode of the rectifier diode bridge D21 and one end of the primary winding L21 of the transformer T21. The-terminal of the smoothing capacitor C21 is connected to the anode of the rectifier diode bridge D21, and is connected to the other end of the primary winding L21 via the semiconductor switch SW26. A switching signal S55 is input from the PWM control unit 55 to the semiconductor switch SW26. The secondary winding L22 of the transformer T21 is connected in parallel to the series circuit of the rectifier diode D22 and the smoothing capacitor C22. The output voltage monitoring unit 56 connected in parallel with the smoothing capacitor C22 monitors the voltage obtained by dividing the output voltage (voltage between the output terminals) with the target voltage Vs selected to 3.3 volts by the voltage dividing resistors R21 and R22. Then, a feedback signal S56 indicating the difference between the output voltage and the target voltage Vs is sent to the PWM control unit 55. An auxiliary winding L23 of a transformer T21 is connected to the PWM controller 55 as a driving power source. The PWM controller 55 receives the feedback signal S56 and controls the semiconductor switch SW26 so that the output voltage approaches the target voltage Vs.

  The first converter 4 and the second converter 5 are connected in parallel to the control board 90 in the form of a diode OR. The control board 90 operates by receiving power from the first converter 4 or the second converter 5. The power supply control unit 60 realized by the operation of the control board 90 outputs the sleep signal S22, the start signal S23, and the stop signal S24 in a timely manner. The sleep signal S22 opens the switch SW4 of the first converter 4 in the sleep period T2, and cuts off the supply of AC power to the first converter 4. The start signal S23 causes the PWM control unit 55 of the second converter 5 to start switching control. The stop signal S24 causes the PWM control unit 45 of the first converter 4 to stop switching control. When the stop signal S24 is inactive, the PWM control unit 45 performs switching control.

  Next, the operation at the time of starting the power supply device 1 will be described.

  In FIG. 3, when AC power supply 7 is connected to power supply device 1 by turning on a power switch (not shown), AC power is supplied to first converter 4 and second converter 5. At this time, the start signal S23 is not output, and the PWM control unit 55 is stopped. Therefore, the semiconductor switch SW26 is in an OFF state, and no current flows through the transformer T21. Although rectification and smoothing are performed in the rectifier 51, the DC / DC converter 52 does not operate, and the second converter 5 is substantially stopped.

In the first converter 4, the switch SW4 is closed when the AC power supply 7 is connected, and the AC power supplied from the AC power supply 7 is rectified and smoothed by the rectifier 41.
A voltage V10 is generated on the secondary side due to the transformation by the transformer T11. The voltage V10 is rectified by the rectifier diode D12 and further smoothed by the smoothing capacitor C12. As a result, about 3.4 volts of DC power is supplied to the control board 90. This output is monitored by the output voltage monitoring unit 46, and switching control by the PWM control unit 45 is performed based on the feedback signal S46, and the output voltage is maintained at 3.4 volts.

  Power is supplied from the first converter 4 and the control board 90 is activated. After startup, the power supply control unit 60 sends a startup signal S23 to the PWM control unit 55 of the second converter 5. The PWM control unit 55 that has received the activation signal S23 is activated and starts outputting the switching signal S55. The semiconductor switch SW26 is turned on, and the power rectified and smoothed by the rectifying unit 51 is supplied to the transformer T21. A voltage V20 is generated on the secondary side due to the transformation by the transformer T21. The voltage V20 is rectified by the rectifier diode D22 and further smoothed by the smoothing capacitor C22. This produces a voltage of approximately 3.3 volts across the voltage divider resistor circuit. This voltage is monitored by the output voltage monitoring unit 56, and the switching control by the PWM control unit 45 is performed based on the feedback signal S56. The PWM controller 45 tries to maintain the output voltage at 3.3 volts.

  However, the secondary rectifier circuit outputs of the first converter 4 and the second converter 5 are diode-or connected, and the output voltage (3.4 volts) of the first converter 4 is the output voltage (3.3) of the second converter 5. Therefore, DC power is supplied from the first converter 4 to the control board 90 in the normal operation after the power supply device 1 is activated. At this time, the second converter 5 performs a switching operation in which the ON width of pulse width modulation (PWM) is set to the lower limit (minimum) of the variable range.

  Next, the operation of the power supply device 1 when shifting to sleep will be described.

  After the control board 90 shifts to the sleep mode, the power control unit 60 outputs a sleep signal S22 so as to turn off the switch SW4. The switch SW4 that has received the sleep signal S22 is turned off, and the supply of AC power to the first converter 4 is cut off. The first converter 4 stops and power is supplied from the second converter 5 to the control board 90. At this time, a stop signal S24 may be sent from the power supply controller 60 of the control board 90 to the PWM controller 45 to stop the PWM controller 45 and the semiconductor switch SW16.

  If the first converter 4 is stopped, the power is immediately supplied from the second converter 5 to the control board 90, so that the power supply to the control board 90 is not interrupted at the time of sleep transition.

  Next, the operation of the power supply device 1 when returning from the sleep operation mode to the normal operation mode will be described.

  The power supply control unit 90 of the control board 90 sends a sleep signal 22 to the switch SW4 so that the switch SW4 is turned on before returning. The switch SW4 that has received the sleep signal S22 is turned on, and AC power is supplied to the first converter 4. The first converter 4 is activated in the same manner as at startup (when power is turned on), and power of 3.4 volts is supplied to the control board 90.

  Since the second converter 5 supplies power to the control board 90 until the power supply by the first converter 4 starts, the power supply to the control board 90 is not interrupted when returning from sleep.

  With the above operation, it is possible to switch the converter that supplies power in accordance with the switching of the operation mode in the control board 90 without interrupting the supply of power to the control board 90.

  The output voltage of the power supply device 1 changes between 3.4 volts and 3.3 volts in the normal operation period T1 and the sleep operation period T2, but the drop voltage from the output end of the power supply device 1 to the input end of the control board 90 Is larger during a normal operation with a heavy load and smaller during a sleep operation with a light load, so that almost the same voltage can be obtained at the input end of the control board 90. In this example, the difference between the target voltages Vm and Vs is set to 0.1 volts, but the target voltages Vm and Vs can be appropriately set in consideration of the drop voltage. However, it is necessary to make the target voltage Vs lower than the target voltage Vm.

FIG. 4 shows a second example of the circuit configuration of the power supply device. In the power supply device 1b of FIG. 4, the output voltage monitoring unit 46 of the first converter 4b and the output voltage monitoring unit 56 of the second converter 5b are one voltage dividing resistor. Monitor the voltage divided by the circuit. Other configurations are the same as those in FIG. 3 described above.

  The voltage dividing resistor circuit includes three resistors R13, R14, and R15 connected in series, and divides the voltage between the output terminals into three. The output voltage monitoring unit 46 of the first converter 4b monitors the potential of the intermediate potential point on the low potential side of the two intermediate potential points in the voltage dividing resistor circuit, and sets this potential to the set potential corresponding to the target voltage Vm. The first converter 4b operates to keep it. The output voltage monitoring unit 56 of the second converter 5b monitors the potential of the intermediate potential point on the higher potential side of the two intermediate potential points in the voltage dividing resistor circuit, and sets this potential to the set potential corresponding to the target voltage Vs. The second converter 5b operates to keep it.

  Since the potential monitored by the output voltage monitoring unit 56 is necessarily higher than the potential monitored by the output voltage monitoring unit 46, the second converter 5b outputs the output voltage when the first converter 4b attempts to increase the output voltage. As a result, the output voltage of the second converter 5b can be more reliably lowered than the output voltage of the first converter 4b.

  FIG. 5 illustrates a configuration of a main part of the image forming apparatus 100 including the power supply device 1. An image forming apparatus 100 illustrated in FIG. 5 is a tandem color printer that prints a color image or a monochrome image by electrophotography. Since four color toner images of yellow (Y), magenta (M), cyan (C), and black (K) are formed in parallel during color image formation, the image forming apparatus 100 includes the intermediate transfer belt 20 and the intermediate transfer belt. There are four process units UY, UM, UC, UK arranged along the belt 20. The process unit UK for forming a black (K) image includes a photosensitive drum 11, a charging device 12, a print head 13, a developing device 14, a primary transfer device 15, and a cleaning device 16, and other process units. UY, UM, and UC also have similar components except for the difference in toner colors.

  The outline of the image forming operation is as follows. For example, when a color print job is given from an external device (not shown) (for example, a personal computer), the charging device 12 uniformly charges the surface of the photosensitive drum 11 in the process units UY, UM, UC, UK. A light beam emitted from the print head 13 is controlled on and off in accordance with image data from an external device, and a latent image is formed on the surface of the photosensitive drum 11. The latent image is developed into a toner image by the developing device 14 and is primarily transferred to the intermediate transfer belt 20 by the primary transfer device 15. The toner images of the four colors are superimposed on the intermediate transfer belt 20 by primary transfer synchronized with the movement of the intermediate transfer belt 20. In parallel with the formation of the four-color toner images, the paper P of the type and size specified by the job is taken out from the paper storage unit 24, and the intermediate transfer belt 20 and the secondary transfer roller 27 are opposed to each other by the conveying roller 26. It is conveyed to the next transfer position. The paper P onto which the toner image has been secondarily transferred from the intermediate transfer belt 20 passes through the fixing device 80 and is then discharged to the paper discharge tray 29 by the paper discharge roller pair 28. When the paper P passes through the fixing device 80, the toner is melted and the image is fixed on the recording paper.

  This series of operations is controlled by a control circuit including a central processing unit (CPU) as a computer provided in the control board 90. The CPU operates by receiving DC power from the power supply device 1.

  In the above embodiment, the AC power source 7 is not limited to a commercial AC power source. In a device having a configuration using a DC power supply system, AC converted from DC by an inverter can be supplied to the power supply device 1.

1 Power supply device 7 AC power supply (AC power supply)
2 Input terminal 9 Load 90 Control board (load)
3 Output terminal 4, 4b 1st converter 5, 5b 2nd converter 6 Controller 60 Power supply control part (controller)
41 First rectifier 42 First DC / DC converter 51 Second rectifier 52 Second DC / DC converter T1 Normal operation period T2 Sleep operation period 100 Image forming apparatus

Claims (4)

A power supply device that converts AC power into DC power and outputs the power,
A first converter for normal operation connected between an input terminal to which an AC power supply is connected and an output terminal to which a load is connected;
A second converter for small load operation connected in parallel with the first converter to the input terminal and the output terminal;
A controller for controlling the first converter and the second converter ;
A voltage dividing resistor circuit that divides the voltage between the output terminals into three ,
The first converter includes a first rectifier that rectifies the AC power, and a voltage at a low-potential-side intermediate potential point of two intermediate potential points in the voltage dividing resistor circuit. A first DC / DC converter that performs switching with respect to the output of the first rectifier so as to maintain the potential at the first target voltage.
A second rectifier configured to rectify the AC power; and a potential at a middle potential point on a higher potential side of the two middle potential points in the voltage dividing resistor circuit between the output terminals. A second DC / DC converter that performs switching on the output of the second rectifier so as to maintain a potential when the voltage is a second target voltage lower than the first target voltage. ,
The controller receives the switching instruction from the normal operation to the operation at a small load, stops the first converter without stopping the second converter, and receives the switching instruction from the operation at the small load to the normal operation. A power supply apparatus that restarts output of power by the first converter. The first DC / DC converter performs switching when the potential of the intermediate potential point on the low potential side in the voltage dividing resistor circuit is lower than a set potential,
The second DC / DC converter unit, the power supply device according to claim 1, wherein the potential of the intermediate electric potential point of the high potential side performs switching when less than the set potential. The first converter is in an operating state capable of outputting electric power to the load in response to the connection of the AC power supply at the time of starting the power supply to which the AC power supply that was in a disconnected state is connected.
2. The second converter is in an operation state in which power can be output to the load in response to an activation request given from the controller after the first converter is in an operation state when the power source is activated. Or the power supply device of 2 . A power supply device according to any one of claims 1 to 3 ,
A control circuit that operates by receiving power from the power supply device;
An image forming apparatus comprising: a mechanism controlled by the control circuit to print an image on a sheet.

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