JP2012147548A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device that considers inrush current suppression and hit tolerance.SOLUTION: An inrush current resistance R1 is disposed in parallel with a relay switch RY1y. A comparator CP outputs an output signal to set on/off the operation of switching control sections CC1, CC3 on the basis of the comparison of voltage signals of a node Ng and a node Ni. The node Ni is set at a voltage level determined by resistive division of a voltage across a capacitor C8 disposed between a node Nh and a node Nd by a resistive element R6 and resistive elements R7, R8. The node Ng is set at a voltage level determined by resistive division of a voltage across a smoothing capacitor C1 disposed between a node Ne and a node Nf by resistive elements R2, R3.

Description

  The present invention relates to control of a power supply device.

  In order to save energy, equipment such as an image forming apparatus may be provided with a two-power-source power supply device having two converters, a main DC / DC converter and a sub DC / DC converter.

  Specifically, the main DC / DC converter optimizes power efficiency for power supply in the normal operation mode with large power consumption, and the sub DC / DC converter optimizes power efficiency for power supply with low power consumption. To do.

  On the other hand, in general, in a power supply device, a switch element is provided to supply power to the converter, and power is supplied to the converter by turning on the switch element.

  However, since an inrush current may flow into the converter when the switch element is turned on, for example, JP-A-60-156225 shows a case where an inrush current resistor is provided in parallel with the switch element. ing.

  Although the inrush current is suppressed by the configuration in which the inrush current resistor is provided, in the above publication, when the power supply is stopped, the switch element is turned off after a certain period of time, so the power supply is stopped. If the power supply is restarted immediately after that, that is, if the power supply is restarted before the switch element is turned off, the inrush current does not pass through the inrush current resistor via the switch element. The problem of flowing into the converter occurs.

  In this regard, Japanese Patent Application Laid-Open No. 7-163142 discloses a method in which the switch element is immediately turned off when the power supply is stopped, that is, when the voltage level of the power supply is lowered. By this method, the problem that the inrush current flows into the converter via the switch element without going through the inrush current resistor when the power supply is resumed immediately after the power supply is stopped is solved. That is, inrush current can be suppressed.

JP-A-60-156225 JP 7-163142 A

  However, since the switching control circuit for controlling the switch element in the above publication is configured to detect a drop in voltage level and immediately turn off the switch element, in the case of this configuration, it cannot cope with an instantaneous power supply interruption. That is, there is a possibility that the switch element may be turned off even when the power supply state is unstable and a momentary interruption occurs. In this case, the load on the inrush current resistor increases, and in the worst case, the inrush current resistor Alternatively, the switch element may be destroyed. In other words, there is a problem that the instantaneous interruption tolerance that cannot withstand the instantaneous interruption is small.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power supply device that takes into account the suppression of inrush current and the instantaneous interruption tolerance.

  A power supply device according to an aspect of the present invention is a power supply device connected to an AC power supply, connected to the AC power supply, connected to a rectifier circuit that rectifies the AC power supply, and an output terminal of the rectifier circuit, and is first connected to a load. A first power converter for supplying a direct current voltage, a second power converter connected to the output terminal of the rectifier circuit in parallel with the first power converter, and for supplying a second direct current voltage, and an alternating current A switch circuit for setting a power supply path between the power supply and the rectifier circuit to a conductive / non-conductive state, a switch control circuit for controlling the switch circuit in accordance with the second DC voltage, and a switch circuit connected in parallel The on / off of the first and second power converters is controlled according to the voltage of the first electric field capacitor included in the first power converter, using the inrush current preventing resistor and the AC power supply as a driving power supply. And a power control unit. The power supply control unit turns off the first and second power supply converters when the voltage of the drive power supply becomes equal to or lower than the voltage of the first electric field capacitor when the supply of the AC power supply is stopped. The power supply path is set to a non-conductive state by the switch circuit in accordance with the turn-off of the second power converter.

  Preferably, the power supply control unit includes a comparator that compares the voltage of the first electric field capacitor included in the first power supply converter with the voltage of the drive power supply, and the comparator is driven when the supply of the AC power supply is stopped. When the voltage of the power supply becomes lower than the voltage of the first electric field capacitor, a signal for turning off the first and second power supply converters is output, and the power supply control unit is a load to which the first DC voltage is supplied. If the load is heavy, it further includes an adjustment circuit for adjusting the voltage of the drive power supply to be high.

  In particular, the power supply device is used in an image forming apparatus, and when the load is heavy, it corresponds to executing image formation in the image forming apparatus.

  Preferably, the switch circuit corresponds to any one of a relay circuit, a triac, and a thyristor.

  The power supply device according to the present invention is provided with a resistor for preventing inrush current, and a switch control circuit for controlling a switch circuit provided in parallel with the resistor compares the voltage of the drive power supply, and based on the comparison result, Since on-off control is performed, it is possible to achieve both suppression of inrush current and instantaneous interruption tolerance.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic block diagram of an image forming apparatus 100 according to an embodiment of the present invention. It is a figure explaining the operation panel 200 according to embodiment of this invention. It is a figure explaining the circuit structure of the power supply part 80 according to embodiment of this invention. It is a figure explaining the circuit structure of the power supply part 80 according to the modification of embodiment of this invention. It is a figure explaining the structure of the switch part according to the modification of embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.
Referring to FIG. 1, image forming apparatus 100 constitutes a copying machine and includes a plurality of operating units. Specifically, the image forming apparatus 100 includes a document conveying unit 20 that conveys a document, an image reading unit 26 that reads the conveyed document as image data, and an image forming unit that forms an image based on the read image data. 10, paper feeding units 15 and 16 for feeding recording paper, a fixing unit 40 for fixing an image transferred to the recording paper, and a post-processing unit 30 for performing post-processing on the recording paper. Including. Further, the image forming apparatus 100 is provided with a control unit that controls the whole, an input unit for inputting instructions, and the like. The image forming apparatus 100 is also provided with an in-machine fan 300 for cooling the in-machine temperature.

  The document placed on the document table 21 of the document conveyance unit (automatic document conveyance device) 20 is conveyed by the conveyance roller 22 or the like, read by the image reading unit 26, and discharged to the paper discharge tray 23.

  In addition, the CCD 24 of the image reading unit 26 acquires image data obtained by reading a document conveyed by the document conveying unit 20, for example. And it outputs to a control part.

  The image forming unit 10 includes a photoconductor as an image carrier, a charging unit, an exposure device, a developing device, a transfer roller, and the like, and forms an image on the recording paper P that is conveyed and the image surface is unfixed. The completed recording paper P is output to the fixing unit 40.

  In this example, although not shown, four developing devices are provided, and color printing is possible using each color of yellow, magenta, cyan, and black.

  The fixing unit 40 performs a fixing process on the recorded recording paper P that has not been fixed. The fixing unit 40 is provided with a fan 310, a fixing roller 312, and a heater 314 provided in the fixing roller 312.

  The sheet is discharged from the fixing unit 40 to the post-processing unit 30 as necessary, and the post-processing unit 30 performs post-processing such as punching and stapling.

The paper feeding units 15 and 16 feed the recording paper P to the image forming unit 10.
The paper feed unit 15 is provided with cassettes 132, 142, and 152 that store a plurality of recording papers having different sizes. Pickup rollers 131, 141, and 151 are provided corresponding to the cassettes 132, 142, and 152, respectively, and convey recording paper from the cassettes to the image forming unit 10. Further, the paper is fed from the paper feed unit 16 to the image forming unit 10 via the pickup roller 161. Note that recording sheets are conveyed one by one from the sheet feeding units 15 and 16 to the image forming unit 10.

FIG. 2 is a schematic block diagram of image forming apparatus 100 according to the embodiment of the present invention.
Referring to FIG. 2, here, a control unit 50 for controlling the entire image forming apparatus 100, a post-processing unit 30 for executing post-processing, and paper-feeding units 15 and 16 for feeding recording paper are provided. The input unit 60 including an operation panel, the image forming unit 10 for forming an image, the memory 70, the image reading unit 26, the document conveying unit 20, the fixing unit 40, and the power required for each unit. A power supply unit 80 for supply is provided.

  The control unit 50 is configured by, for example, a CPU (Central Processing Unit), reads various application programs stored in the memory 70, and controls each unit.

FIG. 3 is a diagram illustrating operation panel 200 according to the embodiment of the present invention.
Referring to FIG. 3, operation panel 200 includes display unit 212, power ON button 204 used to power on image forming apparatus 100, power OFF button 208 that shuts off power to image forming apparatus 100, and 10 key 202. And a start button 210.

  A touch panel is provided on the display unit 212, and a predetermined operation can be performed on the display unit 212.

  A 10 key 202 is a button for inputting the number of copies. The start button 210 is a button for instructing execution of processing such as copying / scanning.

  Also, various modes and other displays are performed on the display unit 212, and various settings can be performed in accordance with the display contents using the touch panel. For example, the display unit 212 is usually provided with buttons for basic / applied settings that are performed when a copy operation or a scan operation is executed. When each button is pressed, a hierarchical screen for performing detailed setting is displayed.

FIG. 4 is a diagram illustrating a circuit configuration of power supply unit 80 according to the embodiment of the present invention.
Referring to FIG. 4, power supply unit 80 according to the embodiment of the present invention includes a main power supply control unit CC2 for executing power supply to each unit in the normal operation mode (a heavy load state), and a main power supply Main DC / DC converter 82 for supplying power to controller CC2, sub power controller CC4 for supplying power in standby mode or sleep mode (light load), and sub power controller And a sub DC / DC converter 84 for supplying power to the CC 4.

  The power supply unit 80 includes a relay circuit RY1 provided to set a power supply path between the main DC / DC converter 82 and the AC power supply Vac to a conductive / non-conductive state, and a relay circuit RY1. An inrush current resistor R1 provided in parallel is provided.

  The relay circuit RY1 includes a relay switch RY1y and a relay coil RY1x, and the relay switch RY1y is turned on / off (conducting / non-conducting) according to the electromagnetic force according to the current flowing through the relay coil RY1x.

  The main DC / DC converter 82 and the sub DC / DC converter 84 share a rectifier circuit, a power factor correction circuit 88, and a smoothing capacitor C1.

First, the main DC / DC converter 82 will be described.
In main DC / DC converter 82, the positive power supply line of AC power supply Vac is electrically coupled to node Na via relay switch RY1y. The power supply line on the negative side of AC power supply Vac is electrically coupled to power supply node Nb.

  A rectifier circuit bridge-connected by four diodes D1 to D4 is provided between the node Na and the node Nb. Specifically, diode D1 has an anode side coupled to node Na and a cathode side coupled to node Nc. Diode D2 has an anode side coupled to node Nb and a cathode side coupled to node Nc. Diode D3 has an anode side coupled to node Nd and a cathode side coupled to node Na. Diode D4 has an anode side coupled to node Nd and a cathode side coupled to node Nb.

  The power factor of the rectified voltage output from the node Nc and the node Nd, which are output nodes of the rectifier circuit, is improved by the power factor improvement circuit 88 to be boosted, smoothed, and constant voltage.

  Then, the smoothing capacitor C1 and the primary winding L2 of the transformer T1 are connected in parallel via the switch Q2. As a secondary configuration, the secondary winding L3 of the transformer T1 is connected in parallel with the smoothing capacitor C2 between the power supply node Np and the power supply node Nq via the rectifier diode D6.

  As another secondary configuration, the secondary winding L4 of the transformer T1 is connected in parallel with the smoothing capacitor C3 between the power supply node Nr and the power supply node Ns via the rectifier diode D7.

  The switch Q2 is ON / OFF controlled (PWM control) by the switching controller CC1, and controls the switching of the transformer T1 by this operation to control the output voltage to be a predetermined voltage (24V, 5V). As an example, the predetermined voltage (5V) is used in the control unit 50, and the predetermined voltage (24V) is used in each part of the drive system having other motors and the like.

Next, the sub DC / DC converter 84 will be described.
As described above, the sub DC / DC converter 84 shares the rectifier circuit, the power factor correction circuit 88, and the smoothing capacitor C1 with the main DC / DC converter 82. The sub DC / DC converter 84 is switched in parallel with the smoothing capacitor C1. The primary winding L5 of the transformer T2 is connected to one node Ne of the smoothing capacitor C1 through Q3. Further, the switch Q3 is connected to the node Nd.

  As a secondary configuration, the secondary winding L6 of the transformer T2 is connected in parallel with the smoothing capacitor C5 between the power supply node Nt and the power supply node Nu via the rectifier diode D12.

  Relay coil RY1x is connected in parallel with smoothing capacitor C5 between power supply node Nt and power supply node Nu.

  The switch Q3 is on / off controlled (PWM control) by the switching control unit CC3, and controls the transformer T2 by this operation to control the output voltage to be a predetermined voltage (5V). As an example, the predetermined voltage (5 V) is used by the control unit 50.

  Next, a power supply control circuit that controls the driving (on / off) of the switching controllers CC1 and CC3 will be described.

  The power supply control circuit has a startup circuit. The start-up circuit includes a diode D16 and a resistance element R9, and is connected in series between the power supply line on the positive electrode side of the AC power supply Vac and the node Nh.

  The power supply control circuit supplies power to the switching controllers CC1 and CC3 using the auxiliary winding L7 of the transformer T2.

  Specifically, capacitor C8 is connected between power supply node Nh and node Nd. The rectifier diode D15 and the auxiliary winding L7 are connected in series so as to be in parallel with the capacitor C8.

  Bipolar transistor Q6 is provided, the collector side is connected to node Nh, and the emitter side is connected to node Nj. A resistance element R4 is connected between the emitter and the base. The base side of bipolar transistor Q6 is connected to the output terminal of comparator CP via resistance element R5.

  The positive pole side of the comparator CP is connected to a connection node Ng between resistance elements R2 and R3 provided in series between both end nodes Ne and Nf of the smoothing capacitor C1. The negative pole side of the comparator CP is connected to a connection node Ni between the resistance element R6 and the resistance element R7 with respect to the resistance elements R6 to R8 connected in series between the node Nh and the node Nd.

  Bipolar transistor Q7 has a collector side connected to a connection node between resistance elements R7 and R8, and an emitter side connected to ground voltage GND. A control signal / PRINT is input to the base. The control signal / PRINT is output from the control unit 50.

  Although not shown here, a switch element is provided between the AC power supply Vac and the power supply unit 80, and is linked to the power ON button 204 and the power OFF button 208 described above. It is assumed that the switch element is turned on by pressing. In addition, it is assumed that the switch element becomes non-conductive when the power OFF button 208 is pressed. When the switch element becomes conductive, the AC power supply Vac and the power supply unit 80 are electrically connected.

First, the operation when the power supply unit 80 is activated in the normal operation mode will be described.
First, when a power ON button 204 is pressed, a switch element (not shown) is turned on. Thereby, AC power supply Vac and power supply unit 80 are electrically coupled.

  When AC power supply Vac and power supply unit 80 are electrically coupled, a startup operation is executed via a startup circuit.

  Specifically, power is supplied to the switching controllers CC1 and CC3 via the diode D16 and the resistor element R9, which constitute the starting circuit, and the bipolar transistor Q6. The bipolar transistor Q6 is conductive when the base is at the “L” level. In this example, the output of the comparator CP is at the “L” level when the output is in the normal operation mode. That is, the comparator CP compares the voltage levels of the node Ni and the node Ng, and outputs the “L” level when the voltage level of the node Ni is higher than the voltage level of the node Ng. Thereby, operation | movement of switching control part CC1, CC3 is started.

  On the other hand, as will be described later, when the supply of the AC power supply Vac is stopped, the output of the comparator CP becomes the “H” level when the voltage level of the node Ni becomes lower than the voltage level of the node Ng. In this case, the operations of the switching control units CC1 and CC3 are stopped.

  Further, the smoothing capacitor C1 is charged through the resistance element R1 by electrically connecting the AC power supply Vac and the power supply unit 80.

  First, the sub DC / DC converter 84 is activated and the transformer T2 oscillates. As a result, the relay switch RY1y is turned on according to the electromagnetic force flowing through the relay coil RY1x.

  Then, the relay switch RY1y is turned on, the main DC / DC converter 82 is activated, and the transformer T1 oscillates.

  Then, the voltage transformed by the transformer T1 is supplied to the secondary side. The voltage generated on the secondary side is rectified by rectifier diodes D6 and D7 and smoothed by smoothing capacitors C2 and C3. Then, a predetermined voltage (24V, 5V) is supplied to the main power supply controller CC2.

  As a result, the main power supply control unit CC2 is activated, and a voltage necessary for the normal operation mode is supplied to each unit of the image forming apparatus.

  Next, a case where there is no input of a job such as a print job in the image forming apparatus 100 for a certain time will be described.

  When there is no input of a job such as a print job for a certain time, the normal operation mode is shifted to the standby mode. The control unit 50 instructs the main power supply control unit CC2 of the power supply unit 80 to shift to the standby mode. Accordingly, the main power supply control unit CC2 stops supplying to each unit.

  Further, the control unit 50 instructs the sub power supply control unit CC4 of the power supply unit 80 to shift to the standby mode, and a voltage necessary for the standby mode is supplied from the sub power supply control unit CC4 to each unit.

Next, an operation when the power supply of the power supply unit 80 is cut off will be described.
As described above, when the power OFF button 208 is pressed, a switch element (not shown) is turned off. Thereby, AC power supply Vac and power supply unit 80 are electrically connected and separated.

  When the AC power supply Vac and the power supply unit 80 are electrically connected and separated, the output signal of the comparator CP changes.

  Comparator CP receives voltage signals at nodes Ni and Ng, but the voltage level at node Ni decreases as AC power supply Vac is connected or disconnected.

  When the voltage at the node Ni becomes equal to or lower than the voltage at the node Ng, the comparator CP supplies an “H” level output signal to the base of the bipolar transistor Q6.

  Thereby, the bipolar transistor Q6 is turned off. That is, power supply to the switching control units CC1 and CC3 is interrupted.

  As the power supply to the switching control units CC1 and CC3 is cut off, the current supply to the relay coil RY1y is stopped, so that the relay switch RY1y is turned off.

  In the configuration according to the embodiment of the present invention, comparator CP outputs an output signal that sets on / off of the operation of switching control units CC1 and CC3 based on a comparison between the voltage signals at nodes Ng and Ni. Node Ni is set to a voltage level obtained by resistively dividing the voltage across capacitor C8 provided between nodes Nh and Nd by resistance element R6 and resistance elements R7 and R8. The node Ng is set to a voltage level obtained by resistance-dividing the voltage across the smoothing capacitor C1 provided between the node Ne and the node Nf with the resistance elements R2 and R3. That is, the output signal is set based on the comparison of the voltage across the smoothing capacitor C1 and the capacitor C8.

  Here, transistor Q7 is turned on / off in accordance with control signal / PRINT, and when control signal / PRINT is at "H" level, transistor Q7 is turned on, and the connection node between ground voltage GND and resistance elements R7, R8 and Are electrically connected. By this operation, the voltage level of the node Ni is lowered by resistance division with the resistance elements R6 and R7.

  In the standby mode (light load state), control signal / PRINT is set to “H” level. Thereby, the transistor Q7 is turned on.

  In this case, even if a momentary interruption occurs temporarily, the load is light, so that it is unlikely that the voltage level of the node Ni is excessively lowered and malfunctions.

  On the other hand, in the normal operation mode (a heavy load state), control signal / PRINT is set to “L” level. Thereby, the transistor Q7 is turned off. By this operation, the voltage level of the node Ni becomes resistance division between the resistance element R6 and the resistance elements R7 and R8, and the voltage level of the node Ni is higher than when the control signal / PRINT is at “H” level.

  Therefore, when a momentary interruption occurs temporarily, even if the voltage level of the node Ni decreases because the load is heavy, the voltage level of the node Ni is set to be high in advance (the node Ng and the node Ni). Therefore, it is difficult to be lower than the voltage level of the node Ng, and it is possible to cope with instantaneous interruption.

  As an example, as the instantaneous interruption tolerance, the voltage of the node Ni can be set so that the maximum power can be maintained for one AC cycle in the case of a load during printing.

  That is, an inrush current resistor is provided to prevent an inrush current, and the switch element is controlled based on the voltage comparison of the comparator CP. Comparator CP can suppress a state (malfunction) in which the output signal of the comparator is inverted due to a momentary interruption or the like by setting a large potential difference for voltage comparison in advance when the load is heavy. It becomes.

  FIG. 5 is a diagram illustrating a circuit configuration of power supply unit 80 according to the modification of the embodiment of the present invention.

  Referring to FIG. 5, the difference from the configuration of FIG. 4 is that relay switch RY <b> 1 y is changed to switch unit 86. Since the other points are the same, detailed description thereof will not be repeated.

  In the configuration of FIG. 4, the configuration in which the relay switch is provided has been described. However, the configuration is not limited thereto, and other configurations can be applied. The switch control unit 85 controls the on / off of the switch unit 86.

FIG. 6 is a diagram illustrating a configuration of a switch unit according to a modification of the embodiment of the present invention.
Referring to FIGS. 6A and 6B, a thyristor and a triac are shown, respectively. The switch control unit 85 generates and outputs a thyristor or triac gate signal.

Even in this configuration, the same operation as in FIG. 4 can be realized.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 10 Image formation part, 15, 16 Paper feed part, 20 Original conveyance part, 21 Original stand, 22 Conveyance roller, 23 Paper discharge tray, 26 Image reading part, 30 Post-processing part, 40 Fixing part, 50 Control part, 60 input Section, 70 memory, 80 power supply section, 82, 84 DC / DC converter, 86 drive circuit, 88 power factor correction circuit, 100 image forming apparatus.

Claims (4)

A power supply device connected to an AC power source,
A rectifier circuit connected to the AC power source and rectifying the AC power source;
A first power converter connected to the output terminal of the rectifier circuit for supplying a first DC voltage to a load;
A second power converter connected to the output terminal of the rectifier circuit in parallel with the first power converter and for supplying a second DC voltage;
A switch circuit for setting a power supply path between the AC power supply and the rectifier circuit to a conductive / non-conductive state;
A switch control circuit for controlling the switch circuit according to the second DC voltage;
An inrush current preventing resistor connected in parallel with the switch circuit;
A power control unit that controls on / off of the first and second power converters according to a voltage of a first electric field capacitor included in the first power converter, using the AC power as a driving power;
The power supply control unit turns off the first and second power converters when the voltage of the driving power supply becomes equal to or lower than the voltage of the first electric field capacitor when the supply of the AC power supply is stopped,
The switch control circuit is a power supply device in which the switch circuit sets the power supply path to a non-conductive state by the switch circuit in accordance with turning off of the second power converter. The power supply control unit includes a comparator that compares the voltage of the first electric field capacitor included in the first power supply converter with the voltage of the drive power supply,
The comparator outputs a signal for turning off the first and second power converters when the voltage of the drive power supply becomes lower than the voltage of the first electric field capacitor when the supply of the AC power supply is stopped. Output,
The power supply apparatus according to claim 1, wherein the power supply control unit further includes an adjustment circuit for adjusting a voltage of the drive power supply high when the load supplied with the first DC voltage is heavy. The power supply device is used in an image forming apparatus,
The power supply apparatus according to claim 2, wherein the heavy load corresponds to executing image formation in the image forming apparatus.   The power supply device according to claim 1, wherein the switch circuit corresponds to any one of a relay circuit, a triac, and a thyristor.

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