JP2007014128A - Electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress fluctuations of a power source voltage, without using electrical equipment having a high rated voltage, in an electronic apparatus provided with a plurality of the electrical equipment that receives electric power from a power source. <P>SOLUTION: A voltage of 24 V rises during a reset process and a RAM checking process, but the voltage rise can be suppressed, by turning on transistors 516, 536 and by conducting a main fan 410 and a PS fan 430. Furthermore, because the voltage is supplied to the main fan 410 and the PS fan 430 via a Zener diode 515 or 535, only the voltage of 24 V at the maximum that is added. The voltage of 24 V rises, even in a transient period between a sleep mode and a stand-by mode, but the rise of the voltage of 24 V can be suppressed, since the transistors 516, 536 are turned ON by a current that flows via a Zener diode 521. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic device including a plurality of electrical components that receive power from a single power source, and more particularly to an electronic device that takes into account stabilization of the power supply voltage of the power source.

  Conventionally, as a DC power source for various electronic devices such as laser printers, for example, a relatively low voltage (eg, 3.3V) stabilized control system output for supplying power to a CPU or the like, a printer engine, a fan, etc. In some cases, a power supply having a drive system output with a relatively high voltage (for example, 24 V) for supplying power to a plurality of electrical components may be used. In addition, as this type of power supply, a switching power supply including a single transformer having the control system output and the drive system output on the secondary side may be used.

With this type of power supply, when the drive system output load is small and the control system output load is large, the drive system output voltage will increase if an attempt is made to stabilize the control system output voltage. There is. Therefore, in such a case, it has been proposed to increase the load of the drive system output by driving a load such as a fan to suppress the voltage increase of the drive system output (see, for example, Patent Document 1). ).
JP 11-196574 A

  However, in order to suppress the voltage rise of the drive system output by driving a fan or the like as in the above technique, a voltage having a rated voltage higher than the original voltage of the drive system output is not used. Fans are destroyed when climbing. For this reason, it becomes necessary to use an expensive fan having a high rated voltage, which increases the manufacturing cost of the apparatus. In addition to the power supply having two outputs for the control system and the drive system as described above, when a plurality of electrical components are supplied with power from one power supply, the original power supply is prepared in preparation for voltage fluctuation. It was necessary to use an electrical component having a rated voltage higher than the voltage. Therefore, the present invention is made for the purpose of suppressing fluctuations in the power supply voltage without using an electrical component having a high rated voltage in an electronic device having a plurality of electrical components that are supplied with power from a single power source. It was.

  The present invention made to achieve the above object is an electronic apparatus including a plurality of electrical components that are supplied with electric power from a single power source, and the output voltage of the power source increases or may increase. At a certain time, it is characterized in that an energization control means for applying the output voltage to a predetermined electrical component among the plurality of electrical components via a constant voltage element is provided.

  In the present invention configured as described above, when the output voltage of the power source increases or is likely to increase, the energization control means applies the output voltage to a predetermined electrical component among the plurality of electrical components. Apply. For this reason, the increase in the output voltage can be suppressed by increasing the power supply current flowing out from the power supply. Moreover, since the energization control means applies the output voltage to the predetermined electrical component via the constant voltage element, a high voltage is not applied to the predetermined electrical component. For this reason, even if the rated voltage of the predetermined electrical component is not so high, destruction of the predetermined electrical component can be avoided. Therefore, in the present invention, fluctuations in the power supply voltage can be suppressed without using an electrical component having a high rated voltage, and thus the manufacturing cost of the electronic device can be reduced.

  In the present invention, when the predetermined electrical component is further provided with a direct energization means for applying the output voltage without passing through the constant voltage element, the following further effects are produced. That is, in this case, the output voltage can be directly applied to the predetermined electrical component to drive the predetermined electrical component sufficiently.

  In addition, various modes are conceivable as a mode in which the energization control unit applies the output voltage to the predetermined electrical component via the constant voltage element, but the power source includes the stabilized output for the control system, A switching power supply including a transformer having a drive system output for supplying power to a plurality of electrical components; power is supplied from the control system output; and the predetermined electrical component is supplied by the drive system output. In the operation mode in which the electrical components other than the above are not driven, the energization control means may apply the output voltage via the constant voltage element.

  When the power supply is configured as described above, in the operation mode as described above, there is little current flowing from the drive system output even though power is supplied from the control system output. It is known that the voltage of the current is likely to rise. Therefore, in such an operation mode, by applying a voltage via a constant voltage element to a predetermined electrical component supplied with power from the drive system output, it is possible to improve the voltage of the drive system output. Can be suppressed.

  In addition, various configurations are conceivable as the configuration of the energization control unit, but the energization control unit may be configured by a CPU and a switching element whose state is switched by the CPU. Also, when the operation of the energization control means is switched by the CPU in this way, the control of applying the output voltage to a predetermined electrical component via the constant voltage element when the output voltage actually increases is also performed by the output voltage. When there is a possibility of increasing (for example, the above-described operation mode and its transient state), the control for applying the output voltage to the predetermined electrical component via the constant voltage element can be satisfactorily performed.

  As another form of the energization control means, the power source includes a single transformer having a stabilized control system output and a drive system output for supplying power to the plurality of electrical components. The energization control means may be configured by a voltage detection element that detects a voltage rise of the drive system output and a switching element whose state is switched by the voltage detection element. In this case, when the voltage of the drive system output actually increases, this can be detected by the voltage detection element, and the output voltage can be applied to the predetermined electrical component via the constant voltage element.

  In addition, although various electrical components can be considered as the predetermined electrical component, the predetermined electrical component may be a cooling fan. The cooling fan does not affect the main operation of the electronic device even if the drive / stop is temporarily switched. Therefore, when the predetermined electrical component is a cooling fan, fluctuations in the power supply voltage can be suppressed without affecting the main operation of the electronic device.

  Further, in this case, the electronic device is an image forming apparatus provided with an image forming means for forming an image on a recording medium, and the cooling fan cools an interior product of the image forming apparatus. Also good.

  Next, embodiments of the present invention will be described with reference to the drawings. As described below, the present embodiment is an application of the present invention to a so-called laser printer as an image forming apparatus.

1. FIG. 1 is a perspective view showing the appearance of a laser printer 1 according to the present embodiment. The laser printer 1 is installed with the upper side of the paper as the upper side in the direction of gravity, and usually the left front side of the paper is the front side. Used as.

  The housing 3 of the laser printer 1 is formed in a substantially box shape (a rectangular parallelepiped shape), and a recording medium discharged from the housing 3 after printing is placed on the upper surface side of the housing 3. A paper discharge tray 5 is provided. In the present embodiment, paper such as paper or an OHP sheet is assumed as the recording medium.

  Further, the paper discharge tray 5 is configured with an inclined surface 5a that is inclined so as to descend from the upper surface of the housing 3 toward the rear side, and printing is finished on the rear end side of the inclined surface 5a. A discharge unit 7 for discharging the recording medium is provided.

  The upper cover 9 formed in a substantially U-shape so as to surround the paper discharge tray 5 (inclined surface 5a) in the casing 3 includes a case where the laser printer 1 is connected to the network and a case where the laser printer 1 is disconnected from the network. Are provided, a line switch 1a for switching, a job cancel switch 1b for forcibly ending (interrupting) printing, and the like.

2. Internal Configuration of Laser Printer FIG. 2 is a longitudinal sectional view showing the internal configuration of the laser printer 1. The image forming unit 10 accommodated in the laser printer 1 constitutes an image forming unit that forms an image on a recording medium, and the feeder unit 20 is a conveying unit that supplies the recording medium to the image forming unit 10. It constitutes a part of

  The first discharge chute 30 and the second discharge chute 40 are turned approximately 180 ° so as to make a U-turn in the transport direction of the recording medium on which image formation has been completed in the image forming unit 10, and the recording medium is fixed to the fixing unit. It constitutes a guide member that guides to a discharge portion 7 provided above 90 (details will be described later).

  The forward / reverse switching mechanism 50 reverses the transport direction of the recording medium ejected from the image forming unit 10 and simultaneously discharges the recording medium whose transport direction is reversed to the image forming unit 10 side. The double-sided printing unit 60 constitutes a conveyance path for a recording medium whose conveyance direction is reversed by the forward / reverse switching mechanism 50.

2.1. Feeder unit The feeder unit 20 includes a paper feed tray 21 housed in the lowermost part of the housing 3, a paper feed roller 22 that is provided above the front end of the paper feed tray 21 and transports a recording medium to the image forming unit 10, In addition, the image forming apparatus includes a separation roller 23 and a separation pad 24 that separate the recording medium conveyed by the paper feeding roller 22 one by one. Then, the recording medium placed on the paper feed tray 21 is conveyed to the image forming unit 10 disposed substantially at the center in the housing 3 so as to make a U-turn on the front side in the housing 3. Is done.

  In addition, in the conveyance path of the recording medium from the paper feed tray 21 to the image forming unit 10, the image forming surface (printing surface) of the recording medium is attached to the outside of the top portion of the portion that turns in a substantially U shape. A paper dust removing roller 25 that removes paper dust and the like is disposed, and a counter roller 26 that presses the recording medium to be conveyed against the paper dust removing roller 25 is disposed inside the top portion.

  Further, at the entrance of the image forming unit 10 in the transport path from the paper feed tray 21 to the image forming unit 10, a resist composed of a pair of rollers that applies a transport resistance to the recording medium and adjusts the transport state of the recording medium. A roller 27 is provided.

2.2. Image Forming Unit The image forming unit 10 includes a scanner unit 70, a process cartridge 80, a fixing unit 90, and the like.

2.2.1. Scanner Unit The scanner unit 70 is provided on the upper portion of the housing 3 and forms an electrostatic latent image on the surface of a photosensitive drum 81 described later. A polygon driven by a laser light source (not shown) and a polygon motor 450. A mirror 72, an fθ lens 73, a reflecting mirror 74, a lens 75, and a reflecting mirror 76 are included.

  Then, the laser beam based on the image data emitted from the laser light source is deflected by the polygon mirror 72, passes through the fθ lens 73, the optical path is turned back by the reflecting mirror 74, and further passes through the lens 75, and then reflected. When the optical path is bent downward by the mirror 76, the surface of the photosensitive drum 81 is irradiated and an electrostatic latent image is formed.

2.2.2. Process Cartridge The process cartridge 80 is detachably disposed in the housing 3 below the scanner unit 70. The process cartridge 80 includes a photosensitive drum 81, a charger 82, a transfer roller 83, and a development roller. It is composed of a cartridge 84 and the like.

  The photoconductive drum 81 extends along the longitudinal direction of the drum main body 81a at a cylindrical drum main body 81a formed by a positively chargeable photosensitive layer whose outermost layer is made of polycarbonate or the like, and the axis of the drum main body 81a. And a drum shaft 81b that rotatably supports the drum body 81a.

  The charger 82 charges the surface of the photosensitive drum 81 prior to the formation of the electrostatic latent image by the laser beam. The charger 82 is predetermined so as not to come into contact with the photosensitive drum 81 at the upper rear side of the photosensitive drum 81. The photosensitive drum 81 is disposed opposite to the photosensitive drum 81 with a gap. The charger 82 according to the present embodiment employs a scorotron charger that charges the surface of the photosensitive drum 81 substantially uniformly with positive charges using corona discharge.

  The transfer roller 83 is disposed so as to face the photosensitive drum 81 and rotates in conjunction with the rotation of the photosensitive drum 81, and when the recording medium passes near the photosensitive drum 81, the transfer roller 83 is attached to the photosensitive drum 81. By applying a charge opposite to the charged charge (in this embodiment, a negative charge) to the recording medium from the side opposite to the printing surface, the toner attached to the surface of the photosensitive drum 81 is printed on the recording medium. It constitutes a transfer means for transferring to the surface.

  The developing cartridge 84 includes a toner storage chamber 84a that stores toner, a toner supply roller 84b that supplies the toner to the photosensitive drum 81, a developing roller 84c, and the like.

  The toner stored in the toner storage chamber 84a is supplied to the developing roller 84c side by the rotation of the toner supply roller 84b. Further, the toner supplied to the developing roller 84c is carried on the surface of the developing roller 84c, adjusted to have a predetermined thickness by the layer thickness regulating blade 84d and frictionally charged, and then in the scanner unit 70. The exposed surface of the photosensitive drum 81 is supplied.

2.2.3. Fixing Unit The fixing unit 90 is disposed downstream of the photosensitive drum 81 in the recording medium conveyance direction, and heats and melts the toner transferred to the recording medium for fixing. Specifically, the fixing unit 90 is disposed on the printing surface side of the recording medium to heat the toner, and is disposed on the opposite side of the heating roller 91 across the recording medium. A pressure roller 92 that presses the recording medium toward the heating roller 91 is provided.

  Incidentally, the heating roller 91 according to the present embodiment is composed of a metal tube whose surface is coated with a fluororesin, and a halogen lamp for heating in the metal tube. The metal roller shaft is covered with a roller made of a rubber material.

In the image forming unit 10 described above, an image is formed on a recording medium as follows.
In other words, the surface of the photosensitive drum 81 is uniformly positively charged by the charger 82 as it rotates, and then exposed by high-speed scanning of the laser beam emitted from the scanner unit 70. As a result, an electrostatic latent image corresponding to the image to be formed on the recording medium is formed on the surface of the photosensitive drum 81.

  Next, when the developing roller 84c rotates, the positively charged toner carried on the developing roller 84c is formed on the surface of the photosensitive drum 81 when it contacts the photosensitive drum 81. Of the electrostatic latent image, that is, the surface of the uniformly positively charged photosensitive drum 81, is supplied to the exposed portion where the potential is lowered by the laser beam. As a result, the electrostatic latent image on the photosensitive drum 81 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 81.

  Thereafter, the toner image carried on the surface of the photosensitive drum 81 is transferred to a recording medium by a transfer bias applied to the transfer roller 83. The recording medium to which the toner image has been transferred is conveyed to the fixing unit 90 and heated, and the toner transferred as the toner image is fixed to the recording medium, thereby completing the image formation.

2.3. First Discharge Chute In the laser printer 1 according to the present embodiment, the first discharge chute 30 is disposed on the rear end side in the housing 3 as shown in FIG. On the side, that is, in the vicinity of the first discharge chute 30, a rear cover 3b that opens and closes an opening 3a formed in the housing 3 is rotatably assembled.

  The first discharge chute 30 is disposed downstream of the fixing unit 90 in the transport direction in the transport direction of the recording medium, and the transport direction of the recording medium in which image formation has been completed in the image forming unit 10. Is rotated approximately 90 ° to guide the recording medium to the second discharge chute 40.

  The first discharge chute 30 is disposed on the downstream side in the recording medium conveyance direction from the front chute 31 disposed at a portion where the recording medium discharged from the fixing unit 90 first contacts, and the front chute 31. The outer chute 32 is provided. Each of the front chute 31 and the outer chute 32 is formed with a plurality of protruding front chute ribs 31a and outer chute ribs 32a extending along the recording medium conveyance direction. The ribs 31a and 32a are guided toward the second discharge chute 40 while being in contact with the leading ends of the ribs 31a and 32a. Further, the first discharge chute 30 is provided with a first paper discharge roller 34a, and a first pinch roller 34b is provided at a position facing the first paper discharge roller 34a on the fixing unit 90 side.

  The first paper discharge roller 34a is a transport roller that applies a transport force to the recording medium by rotating while contacting the recording medium, and the first pinch roller 34b is a first paper discharge sandwiching the recording medium. The recording medium is pressed toward the first paper discharge roller 34a from the side opposite to the roller 34a. For this reason, the recording medium discharged from the fixing unit 90 is conveyed to the second discharge chute 40 side so as to be sandwiched between the first discharge roller 34a and the first pinch roller 34b.

2.4. Second discharge chute The second discharge chute 40 is provided on the upper cover 9 with a predetermined gap 40a with respect to the first discharge chute 30, and the conveying direction is turned by approximately 90 ° by the first discharge chute 30. The recording medium is further turned by approximately 90 ° and guided to the discharge unit 7.

  Further, a gap 40a between the first discharge chute 30 and the second discharge chute 40 is a recording medium conveyance path (conveyance path indicated by a thick two-dot chain line) whose conveyance direction is reversed by the forward / reverse switching mechanism 50. Part of. Incidentally, in FIG. 2, a transport path indicated by a thick one-dot chain line indicates a transport path of a recording medium transported by the feeder unit 20.

2.5. Forward / reverse switching mechanism and double-sided printing unit The forward / reverse switching mechanism 50 switches the rotation direction of the second paper discharge roller 43 to discharge the recording medium conveyed from the first discharge chute 30 to the discharge unit 7 (paper discharge). The case of transporting to the tray 5) side and the case of transporting to the gap 40a side are switched. For example, the forward / reverse switching mechanism 50 uses a solenoid (not shown) to switch the number of gears that transmit a rotational force generated by a DC motor (see FIG. 4), which will be described later, to the second paper discharge roller 43. 43 is a mechanism for switching the rotation direction of 43. The second pinch roller 43b disposed opposite to the second paper discharge roller 43 rotates in a manner to sandwich the recording medium in cooperation with the second paper discharge roller 43, so that the second recording roller and the second recording roller 43b are rotated. The contact surface pressure with the paper discharge roller 43 is increased.

  The duplex printing unit 60 has a plurality of guide ribs (not shown) formed in a protruding shape so as to extend in the conveyance direction (front-rear direction) of the recording medium, and contacts the recording medium while rotating. A plurality of rollers (not shown) for applying a conveyance force to the recording medium are provided, and the recording medium conveyed from the second paper discharge roller 43 through the gap 40a is conveyed to the image forming unit 10. .

2.6. Power Supply Unit A power supply unit 100 that supplies power to each unit of the laser printer 1 is disposed between the fixing unit 90 and the duplex printing unit 60. Next, the configuration of the power supply unit 100 will be described with reference to the circuit diagram of FIG. In addition, the power supply unit 100 is configured to simultaneously supply a voltage (24V in the present embodiment) supplied to various motors and the like and a voltage (3.3V in the present embodiment) supplied to a logic circuit that controls each unit. Output.

  As shown in FIG. 3, the power supply unit 100 includes, on the primary side of the transformer 200, a rectifier circuit 120 that rectifies current supplied from a commercial power supply 110 (AC100V), a smoothing capacitor 130, and a transformer 200. A switching element 140 that switches energization to the primary coil and an oscillation control circuit 150 that controls ON / OFF of the switching element 140 are provided.

  The oscillation control circuit 150 constitutes a photocoupler together with a secondary side photodiode 161 described later, and internally includes a phototransistor 160 that is turned on / off by receiving light emitted from the photodiode 161. In the present embodiment, the oscillation control circuit 150 assumes a self-excited configuration in which the switching element 140 oscillates at an oscillation frequency defined by ON / OFF of the phototransistor 160. A separately-excited configuration that controls the energization time to the primary side of the transformer 200 may be used. In the present embodiment, a flyback in which energy is accumulated in the transformer 200 when the switching element 140 is turned on and an electromotive force is generated on the secondary side when the switching element 140 on the primary side is turned off. The configuration of the method was adopted.

  On the secondary side of the transformer 200, a first output line 311 that outputs a voltage of 24V via a rectifier element 310 and a second output line 313 that outputs a voltage of 3.3V via a rectifier element 312 are provided. It has been. Since the voltage of 3.3V output to the second output line 313 is supplied to the logic circuit or the like as described above, it needs to be stabilized. Therefore, in the power supply unit 100, a photodiode 161 is connected between the second output line 313 and the ground line 314, and the output voltage of the second output line 313 is obtained by the photodiode 161 and the phototransistor 160 that constitutes the photocoupler. Feedback to the primary side.

  The photodiode 161 is turned on when the output of the second output line 313 becomes higher than a predetermined value and the shunt regulator 321 becomes conductive from the second output line 313 to the ground line 314. Note that the voltage of the second output line 313 at which the shunt regulator 321 becomes conductive can be finely adjusted by the variable resistor 330. In the self-excited type as in the present embodiment, when the photodiode 161 is lit, the oscillation frequency of the switching element 140 is increased, the amount of energization on the primary side of the transformer 200 is decreased, and the voltage on the secondary side is decreased. Feedback controlled. On the other hand, when the voltage of the second output line 313 decreases, the photodiode 161 is turned off and the energization amount on the primary side increases.

2.7. As shown in FIGS. 1 and 2, the laser printer 1 further includes a main fan 410 that cools the entire image forming unit 10 around the fixing unit 90 as a cooling fan. A PS fan 430 for cooling the power supply unit 100 is provided. Then, as shown in FIG. 4, these main fan 410 and PS fan 430 are connected to an ASIC (application specific integrated circuit) 500 incorporating a CPU via a main fan drive circuit 510 and a PS fan drive circuit 530, respectively. Has been.

  The main fan drive circuit 510 includes a transistor 511 connected in series to the main fan 410, and the output voltage of the port P1 of the ASIC 500 is divided by resistors 512 and 513 and applied to the base of the transistor 511. . The port P1 is grounded via a resistor 514. The main fan drive circuit 510 further includes a transistor 516 connected to the collector of the transistor 511 via a Zener diode 515. The output voltage of the port P2 of the ASIC 500 is connected to resistors 517 and 518 at the base of the transistor 516. A partial pressure is applied. The port P2 is connected to a 3.3V power source (second output line 313 in FIG. 3) via a resistor 519.

  Here, the voltage drop due to the Zener diode 515 is 12V. Therefore, when the transistor 511 is turned on, the main fan 410 can be driven at full speed by applying the full voltage of 24V. When the transistor 516 is turned on, the voltage drop of the Zener diode 515 causes a voltage of 12V to the main fan 410. Can be applied and driven at half speed. Further, the voltage of the 24V power supply (the voltage of the first output line 311) is applied to the base of the transistor 516 via the Zener diode 521 and the resistor 522. The Zener voltage of the Zener diode 521 is 30V, and when the voltage of the 24V power supply rises to 30V or more due to voltage fluctuation, current flows through the Zener diode 521, the resistors 522, 518, the transistor 516 is turned on, and the main fan 410 Is driven at half speed.

  Similarly, the PS fan drive circuit 530 includes a transistor 531 connected in series with the PS fan 430. The output voltage of the port P3 of the ASIC 500 is divided by resistors 532 and 533 and applied to the base of the transistor 531. Is done. The port P3 is grounded via a resistor 534. A transistor 536 is connected to the collector of the transistor 531 via a Zener diode 535, and the output voltage of the port P4 of the ASIC 500 is divided by resistors 537 and 538 and applied to its base. The port P4 is connected to a 3.3V power source via a resistor 539.

  When the transistor 531 is turned on, the PS fan 430 can be driven at full speed. When the transistor 536 is turned on, the voltage drop of the Zener diode 535 causes the PS fan 430 to be driven at half speed. Can be driven. Further, the base of the transistor 536 is also connected to the anode of the Zener diode 521 through the resistor 542. For this reason, when the voltage of the 24V power supply rises to 30V or higher, the transistor 536 is turned on and the PS fan 430 is driven at half speed. Further, the ASIC 500 is connected with a DC motor drive circuit 441 that drives the DC motor 440 with electric power supplied from a 24V power supply.

3. Control in Laser Printer of Embodiment Next, the control executed by the ASIC 500 in this embodiment configured as described above will be described with reference to the flowchart of FIG. When the power of the laser printer 1 is turned on, the ASIC 500 starts the process of FIG.

  When the process is started, first, the CPU of the ASIC 500 is reset in S1 (S represents a step: the same applies below), and in the subsequent S2, a RAM check process including a program check process is performed. Until these steps S1 and S2 are completed, the ASIC 500 cannot execute various controls by software. Therefore, during this time, the DC motor 440 is turned off, and the main fan 410 and the PS fan 430 are driven by the main fan driving circuit 510 and the PS fan driving because the ports P1 to P4 of the ASIC 500 are input ports (high impedance state). The following control 1 is performed by the circuit 530.

  That is, the transistor 511 is turned off via the resistors 514 and 512, and the transistor 516 is turned on via the resistors 519 and 517. As a result, a voltage obtained by subtracting the voltage drop (12 V) due to the Zener diode 515 from the voltage of the 24 V power supply (hereinafter referred to as 24 V voltage) is applied to the main fan 410. Similarly, when the transistor 531 is turned off and the transistor 536 is turned on, a voltage obtained by subtracting the voltage drop (12 V) due to the Zener diode 535 from the 24 V voltage is also applied to the PS fan 430.

  In subsequent S3, the ports P1 to P4 are once controlled to L in response to the fact that the ASIC 500 can be controlled, whereby the main fan 410 and the PS fan 430 are also temporarily turned off. At this time, a current of 0.15 A is supplied to the DC motor 440. However, since the amount of current is small, the DC motor 440 does not rotate and remains stationary.

  In subsequent S4, the ASIC 500 shifts to the standby mode. At this time, the ports P1, P2, P3, and P4 are controlled to L, H, L, and H, respectively, so that the voltage drop of the Zener diode 515 or 513 from the 24V voltage to the main fan 410 and the PS fan 430, respectively. A voltage minus the minute is applied. Also at this time, a current of 0.15 A is applied to the DC motor 440.

  After shifting to the standby mode in S4, it is determined in S5 whether or not an image formation command has been issued. If there is no image formation command (S5: N), whether or not a predetermined sleep condition has been established is determined in S6. Is judged. If the sleep condition is not satisfied (S6: N), the process proceeds to S4 described above. Thus, the standby mode is maintained until either the image formation command or the sleep condition is satisfied by the loop processing of S4 to S6. That is, during this time, a voltage obtained by subtracting the voltage drop of the Zener diode 515 or 513 from the 24 V voltage is applied to the main fan 410 and the PS fan 430, respectively, and a current of 0.15 A is applied to the DC motor 440.

  If there is an image formation command due to data being input from the outside during the standby by the loop processing of S4 to S6 (S5: Y), a known image formation processing is executed in S7. During the image forming process, the ports P1, P2, P3, and P4 are controlled to H, L, H, and L, respectively, so that the main fan 410 and the PS fan 430 are driven at full speed, and the DC motor 440 is driven. Rotates with a current of 1A. Various rollers and the like are driven by the rotation of the DC motor 440, and image formation by the image forming unit 10 can be executed as described above. When the image forming process is completed, the process shifts again to S4 and shifts to the standby mode described above.

  On the other hand, when a predetermined sleep condition such as no data input or operation being performed for a predetermined time or longer is established during standby by the loop processing of S4 to S6 (S6: Y), the main fan 410, PS fan 430, and DC motor 440 are satisfied. Is turned off (S10), and the ASIC 500 shifts to the sleep mode (S11). During the sleep mode, the port setting in the immediately preceding process, that is, the port setting for turning off the main fan 410, the PS fan 430, and the DC motor 440 is maintained.

  As described above, when the ASIC 500 shifts from the standby mode to the sleep mode, the main fan 410, the PS fan 430, and the DC motor 440 are turned off, so that the 24V voltage may temporarily rise to 30V or more. is there. In the present embodiment, at this time, the following control 2 is executed by the main fan drive circuit 510 and the PS fan drive circuit 530. That is, in this case, the Zener diode 521 becomes conductive from the 24V power source toward the resistors 522 and 542. Then, the transistors 516 and 536 are turned on, and a voltage is applied to the main fan 410 and the PS fan 430 via the Zener diode 515 or 535.

  In subsequent S12, it is determined whether or not there is any trigger input. If not (S12: N), the process proceeds to the above-described S11 and continues the sleep mode. When a trigger is input during the sleep mode (S12: Y), the process proceeds to S4, and the above-described standby mode is performed. Even when shifting from the sleep mode to the standby mode, the output current from the 3.3V power supply increases while the current output from the 24V power supply is small, so the 24V voltage rises and the above-described control 2 is executed. There is a case.

4). Next, the effect produced by the above-described control will be described with reference to FIG. As shown in FIG. 6, at the time of reset processing (Reset) and RAM check processing (RAMCheck), the 3.3V average current is 0.8 A even though the average output current (24 V average current) from the 24 V power supply is small. Alternatively, since the voltage is 1.4 A, the 24V voltage increases. However, the control 1 suppresses the increase in the 24V voltage by energizing the main fan 410 and the PS fan 430. However, even in this case, although the 24V voltage rises to 30V or 34 to 36V, the main fan 410 and the PS fan 430 are applied with a voltage obtained by subtracting the voltage drop of the Zener diode 515 or 535. And the PS fan 430 is only applied with a voltage of 24V at the maximum.

  In addition, since the current of 0.15 A is supplied to the DC motor from the completion of the RAM check to the standby (Stand by) (S3, S4), the 24V voltage is stabilized. In addition, since the voltage is applied to the main fan 410 and the PS fan 430 through the Zener diode 515 or 535 even in the standby mode (S4), even if the 24V voltage rises, the main fan 410 and the PS fan 430 A large voltage is not applied.

  In the transition period between the sleep mode and the standby mode, the 24V voltage may increase as described above. In this case, however, the increase in the 24V voltage is suppressed by the control 2. In this case, although shown as “Note 1” in FIG. 6, only the voltage of 22 to 24 V is applied to the main fan 410 or the PS fan 430 and the transistor 516 or 536 in total. For this reason, a rated 24V fan can be used for the main fan 410 and the PS fan 430, and an increase in the 24V voltage can be suppressed satisfactorily.

  In the above-described embodiment, the ASIC 500, the Zener diode 521, and the transistors 516 and 536 serve as energization control means, the Zener diodes 515 and 535 serve as constant voltage elements, the ASIC 500 and the transistors 511, 531 serve as direct energization means, 100 is a switching power supply, the first output line 311 is a drive system output, the second output line 313 is a control system output, the transistors 511 and 531 are switching elements, the Zener diode 521 is a voltage detection element, the main fan 410 and PS fan 430 correspond to a predetermined electrical component and a cooling fan, respectively.

  The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist of the present invention. For example, a detection unit that detects a 24V voltage at three or more voltage levels is provided and connected to the ASIC 500, and the ASIC 500 switches ON / OFF of the transistors 516 and 536 based on the voltage detected by the detection unit. Then, the fluctuation of the 24V voltage can be suppressed more satisfactorily.

  The predetermined electrical component may be an electrical component other than the cooling fan. However, the cooling fan does not affect the main operation of the laser printer 1 even if the drive / stop is temporarily switched. Therefore, when the predetermined electrical component is a cooling fan, fluctuations in the power supply voltage can be suppressed without affecting the main operation of the laser printer 1. Furthermore, the present invention can be applied to electronic devices other than the image forming apparatus.

1 is a perspective view illustrating an appearance of a laser printer to which the present invention is applied. It is a longitudinal cross-sectional view showing the internal structure of the laser printer. It is a circuit diagram showing the structure of the power supply unit of the laser printer. It is explanatory drawing showing the structure of the control system of the laser printer. It is a flowchart showing the process performed by ASIC of the control system. It is explanatory drawing showing the effect produced by the process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer 10 ... Image formation part 20 ... Feeder part 22 ... Feed roller 70 ... Scanner part 72 ... Polygon mirror 80 ... Process cartridge 81 ... Photoconductor drum 90 ... Fixing unit 100 ... Power supply unit 140 ... Switching element 150 ... Oscillation control circuit 160 ... phototransistor 161 ... photodiode 200 ... transformer 311 ... first output line 313 ... second output line 410 ... main fan 430 ... PS fan 440 ... DC motor 441 ... DC motor drive circuit 450 ... polygon motor 510 ... Main fan drive circuit 511, 516, 531, 536 ... Transistors 515, 521, 535 ... Zener diode 530 ... PS fan drive circuit

Claims (7)

An electronic device comprising a plurality of electrical components that receive power from a single power source,
When the output voltage of the power source rises or is likely to rise, energization control means for applying the output voltage to a predetermined electrical component of the plurality of electrical components via a constant voltage element,
Electronic equipment characterized by comprising. Direct energization means for applying the output voltage to the predetermined electrical component without going through the constant voltage element,
The electronic device according to claim 1, further comprising: The power source is composed of a switching power source including one transformer having a stabilized output for a control system and an output for a drive system that supplies power to the plurality of electrical components.
In an operation mode in which power is supplied from the control system output and the electrical components other than the predetermined electrical components are not driven by the drive system output, the energization control means outputs the output via the constant voltage element. The electronic device according to claim 1, wherein a voltage is applied. The electronic device according to claim 1, wherein the energization control unit includes a CPU and a switching element whose state is switched by the CPU. The power source is composed of a switching power source including one transformer having a stabilized output for a control system and an output for a drive system that supplies power to the plurality of electrical components.
3. The energization control means comprises a voltage detection element that detects an increase in voltage of the drive system output, and a switching element whose state is switched by the voltage detection element. Electronics. The electronic apparatus according to claim 1, wherein the predetermined electrical component is a cooling fan. The electronic apparatus is an image forming apparatus including an image forming unit that forms an image on a recording medium,
7. The electronic apparatus according to claim 6, wherein the cooling fan cools an interior part of the image forming apparatus.

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