JP4882961B2 - Power supply device and image forming apparatus - Google Patents

Description

  The present invention relates to a power supply apparatus that can be controlled so that an output value falls within a predetermined range, and an image forming apparatus that forms an image on a recording medium using the output of the power supply apparatus.

  Conventionally, a power supply unit whose output value changes according to an input signal such as a PWM signal, a detection unit that detects the output value of the power supply unit as an analog signal, and an analog signal detected by the detection unit is converted into a digital signal Conversion means such as an A / D converter, and control means such as a CPU for controlling the input signal so that the output value falls within a predetermined range based on the digital signal converted into the conversion means. A power supply is considered. In this type of power supply device, when the detection means detects the output value of the power supply unit as an analog signal, the conversion means converts the analog signal into a digital signal. Then, the control means controls the input signal to the power supply unit based on the digital signal, so that the output value of the power supply unit (which may be any of current, voltage and power) is fed back so as to fall within a predetermined range. Can be controlled.

Further, in this type of power supply device, it has been proposed to perform feedback control by the control means, for example, every 10 ms based on a timer interrupt or the like (see, for example, Patent Document 1).
JP 2002-333785 A

  However, when feedback control is performed at regular intervals as in the above publication, if the interval is too wide, there is a possibility that sufficient responsiveness may not be obtained when the output value deviates from the predetermined range. If the output value is short, an excessive load may be applied to the CPU or the like when the output value is stable within the predetermined range. Therefore, the present invention provides a power supply apparatus that can be controlled so that an output value falls within a predetermined range, and an image forming apparatus that forms an image on a recording medium using the output of the power supply apparatus. Was made to be executable at intervals as needed.

The power supply device of the present invention made to achieve the above object includes a power supply unit whose output value changes according to an input signal, a detection unit that detects the output value of the power supply unit as an analog signal, and the detection unit detects Conversion means for converting the analog signal into a digital signal, control means for feedback- controlling the input signal so that the output value falls within a predetermined range based on the digital signal converted to the conversion means, and the conversion means Timing changing means for shortening the interval of at least one of the timing of performing the conversion or the timing of performing the feedback control by the control means as the degree of deviation of the output value from the predetermined range increases. It is characterized by that.

In the power supply device of the present invention configured as described above, when the detection means detects the output value of the power supply unit as an analog signal, the conversion means converts the analog signal into a digital signal. Then, the control means feedback-controls the input signal based on the digital signal so that the output value of the power supply unit falls within a predetermined range. In addition, the timing changing means may determine at least one of the timing at which the converting means performs the conversion or the timing at which the control means performs the feedback control so that the degree of deviation of the output value from the predetermined range is determined. The larger the size, the shorter . Therefore, in the present invention, at least one of the timing intervals, that is, the feedback control execution interval, is set to an appropriate interval according to the degree of deviation of the output value from the predetermined range (that is, the necessity). Can do.

In the present invention, the timing changing means shortens the interval as the degree of deviation of the output value from the predetermined range increases. Therefore, the larger the protruding degree from the predetermined range of the output value the distance is shortened, the responsiveness of the control when the output value is out of the predetermined range can be better improved.

  In addition, the timing changing unit may make the interval longer when the output value is within the predetermined range than when the output value is outside the predetermined range. In this case, when the output value is within the predetermined range, the interval is longer than when the output value is outside the predetermined range, and the processing load can be reduced when the output value is stable. it can.

  Furthermore, in any one of the power supply devices described above, the change width of the input signal that is changed by the control means by one control may be larger as the degree of deviation of the output value from the predetermined range is larger. In this case, the greater the degree of deviation of the output value from the predetermined range, the greater the change width of the input signal by one control, and the control responsiveness when the output value deviates from the predetermined range is further increased. It can be improved satisfactorily.

  Further, in any one of the power supply devices described above, an error acquisition unit that acquires an error width with respect to the actual output value of the digital signal converted by the conversion unit, and an error acquired by the error acquisition unit There may be provided a predetermined range setting means for setting a range obtained by adding a width to a desired control range of the output value as the predetermined range. In this case, the error acquisition unit acquires a width of an error with respect to the actual output value of the digital signal converted by the conversion unit. Then, the predetermined range setting means sets a range obtained by adding the error width to the desired control range of the output value as the predetermined range. For this reason, when the output value deviates from the desired control range within the error range, the output value is considered to be within the predetermined range, and therefore unnecessary input signal change due to the error is made. Therefore, more stable control can be executed.

  In this case, the error acquisition unit may acquire the width of the error based on a value of the digital signal when a predetermined input signal is input to the power supply unit. In this case, an accurate error width can be acquired based on the actual digital signal value.

  In addition, the image forming apparatus according to the present invention provides the power supply apparatus that shortens the interval as the degree of deviation of the output value from the predetermined range increases, or the output value when the output value is within the predetermined range. Including the power supply device that makes the interval longer than the case where it is outside the predetermined range, and image forming means that forms an image on a recording medium using the output of the power supply unit, and the control means includes: The image forming unit is also controlled in parallel.

  As described above, the power supply apparatus shortens the interval as the degree of deviation of the output value from the predetermined range increases, or the output value is out of the predetermined range when the output value is within the predetermined range. In the power supply apparatus in which the interval is longer than that in the case where the output value is within the predetermined range, the processing load is lighter than in the case where the output value is significantly out of the predetermined range. In the image forming apparatus of the present invention, since the control unit also executes control of the image forming unit in parallel, the processing load related to the power supply device is reduced when the output value is controlled within the predetermined range. Thus, the control of the image forming unit can be executed efficiently.

  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. Overall Configuration of Laser Printer 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 is usually used with the left front side of the paper as the front side.

  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.

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 direction of rotation of the second paper discharge roller 43, thereby discharging 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 the rotational force generated by a DC motor (not shown) to the second paper discharge roller 43 to perform the second paper discharge. This is a mechanism for switching the rotation direction of the roller 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 Between the fixing unit 90 and the duplex printing unit 60, a power supply unit 100 as an example of a power supply device that supplies power to each unit of the laser printer 1 is disposed. Next, the configuration of the power supply unit 100 will be described with reference to the circuit diagram of FIG.

  As illustrated in FIG. 3, the power supply unit 100 includes a control board 200 as an example of a control unit and a high-voltage board 110 as an example of a power supply unit. The control board 200 is provided with a CPU 210, a ROM 220, and a RAM 230, and the high voltage board 110 is provided with a high voltage power supply circuit 111. 3, in the configuration of the high voltage power supply circuit 111, the transfer bias current TR. Only the configuration for generating the CC is shown, and the illustration of the power supply system to other parts is omitted.

  The high-voltage power supply circuit 111 energizes the self-excited transformer 120 in which the energy stored in the primary winding 120A is transmitted to the secondary winding 120B by back electromotive force when energized from a 24V DC power supply and the primary winding 120A. A transistor 121 that switches a current to be generated, and a drive voltage control unit 130 that controls a base current of the transistor 121. An auxiliary winding 120C of the transformer 120 is provided between the base of the transistor 121 and the drive voltage control unit 130, and the voltage generated in the secondary winding 120B depends on the output voltage of the drive voltage control unit 130. Is controlled as follows.

  That is, when a voltage is output from the drive voltage control unit 130 and a base current flows to the transistor 121 via the auxiliary winding 120C, the transistor 121 is turned on, and the collector current from the 24V DC power source via the primary winding 120A is turned on. Flows, and the magnetic flux of the transformer 120 rises. Since this collector current does not exceed the upper limit current value obtained by amplifying the current value of the base current by the amplification factor of the transistor 121, the collector current of the transistor 121 is saturated. Then, the magnetic flux supplied from the primary winding 120A does not increase, the potential across the auxiliary winding 120C decreases, the base current of the transistor 121 decreases, and the transistor 121 turns off rapidly. At this time, the energy stored in the transformer 120 is transmitted to the secondary winding 120B by the back electromotive force of the transformer 120, the voltage is boosted, and a voltage is generated in the secondary winding 120B.

  A rectifying diode 125 is connected in series to the secondary winding 120B, and a smoothing capacitor 126 and a discharging resistor are connected to both ends of the series circuit including the secondary winding 120B and the diode 125. 127 is connected in parallel. From the high voltage side of the secondary winding 120B, the transfer bias current TR. CC is energized. Further, the low voltage side of the secondary winding 120B is grounded via a resistor 128 as an example of detection means, and the voltage on the low voltage side is connected to the A / D port of the CPU 210 as a feedback voltage Vf. / D converter 211 (corresponding to conversion means). The feedback voltage Vf as an analog signal input to the A / D port is converted into a digital signal by the A / D converter 211 and processed inside the CPU 210. The A / D converter 211 has a digital output of 10 bits.

  On the other hand, the drive voltage control unit 130 is applied to the series circuit that grounds the output from the PWM port of the CPU 210 via the resistor 131 and the capacitor 132 in order, and the voltage between the resistor 131 and the capacitor 132 is applied to the base. And a transistor 133. The collector of the transistor 133 is connected to a 3.3 V DC power supply, and the emitter is grounded via the resistor 134 and the capacitor 135 in this order. Then, the voltage between the resistor 134 and the capacitor 135 is input to the auxiliary winding 120C described above.

  For this reason, when a PWM signal as an example of an input signal is output from the PWM port of the CPU 210, the voltage of the PWM signal is smoothed by the resistor 131 and the capacitor 132 and applied to the base of the transistor 133. Then, the base current of the transistor 121 similarly increases and decreases according to the increase and decrease of the duty ratio of the PWM signal (hereinafter simply referred to as PWM), and as a result, the transfer bias current TR. CC also increases or decreases in the same way.

  The transfer bias current TR. When CC is 0 μA, the feedback voltage Vf is also 0 V, and the transfer bias current TR. As the CC increases, the feedback voltage Vf input to the CPU 210 also increases. In addition to the ROM 220 and RAM 230 described above, the CPU 210 is connected to the image forming unit 10 including the various motors and laser light sources described above, and an interface 240 to which print data is input.

3. Control in Laser Printer of Embodiment Next, control executed by the CPU 210 in the present embodiment configured as described above will be described. FIG. 4 is a flowchart showing print processing executed when print data is input from an external device such as a personal computer via the interface 240.

  As shown in FIG. 4, in this process, first, ADC error detection control for detecting an A / D conversion error of the feedback voltage Vf input to the CPU 210 at S1 (S represents a step: the same applies hereinafter). (An example of error acquisition means) is executed. FIG. 5 is a flowchart showing details of the ADC error detection control.

  As shown in FIG. 5, in this process, first, the counter I is set to 0 in S11. In subsequent S12, the A / D conversion value of the feedback voltage Vf is read as D (I) without outputting a PWM signal from the PWM port, that is, in a state where a PWM signal of PWM = 0 is outputted. In subsequent S13, the counter I is incremented by one, and further in S14, it is determined whether or not I = 20.

  If I ≠ 20 (S14: N), the process proceeds to S12 described above, and D (I) corresponding to the incremented I is read. Then, if I = 20 (S14: Y) while the processes of S12 and S13 are repeated, the process proceeds to S15, and the read D (0) to D (19) are sorted in ascending order. . In S16, among the D (0) to D (19) sorted in ascending order, the first and second largest values are ignored as abnormal values, and the third largest value is stored in a predetermined area of the RAM 230 as an error ERR. Stored, and the process proceeds to S2 in FIG.

  Returning to FIG. 4, in S2, the high voltage interrupt timer is set to 2.0 ms, and in the subsequent S3, an upper limit value and a lower limit value (corresponding to a desired control range of the output value) of the feedback voltage Vf are set. Counters CNT1 and CNT2 and variable PCSM are reset to zero. In subsequent S4, interruption of a high pressure control routine described later is permitted, and MODE (mode) is set to DRV (operation). In the subsequent S5, the well-known print control for performing printing by the image forming unit 10 according to the print data is executed while executing the high-pressure control routine by interruption.

  In S6 following S5, it is determined whether or not printing is completed. If printing has not ended (S6: N), the process again proceeds to S5, and the printing control (S5) is continued while executing the high-pressure control routine by interruption. When printing is completed (S6: Y), interruption of the high-pressure control routine is prohibited in S7, MODE is set to STOP (stop), and the process ends.

  6 and 7 are flowcharts showing the high-pressure control routine. This process is repeatedly executed every time the high voltage interrupt timer counts up. As shown in FIG. 6, in this process, first, in S51, the A / D conversion value of the feedback voltage Vf is read as ADD. In subsequent S52, the ADD is determined from the lower limit set in S3. It is determined whether or not the value is equal to or greater than the value obtained by subtracting the error ERR (lower limit −ERR). If ADD is less than the lower limit −ERR (S52: N), it is determined in S53 whether MODE is UP (increase). When this process is first executed, MODE = DRV (see S4) (S53: N), the process proceeds to S54, and the PWM at that time (the initial value may be 0) is PCSM. At the same time, MODE is set to UP, and the process proceeds to S55. If it is determined in S53 that MODE = DRV has already been established (S53: N), the process directly proceeds from S53 to S55.

  In S55, it is determined whether or not the ADD read in S51 is smaller than a value obtained by subtracting a numerical value 20 (20> ERR) from the lower limit value (lower limit −20). If ADD is smaller than the lower limit −20 (S55: Y), the PWM is increased by a predetermined value ΔPWM2 in S56, and the process proceeds to S57. In S57, the high voltage interrupt timer is set to 0.5 ms, the counter CNT2 is incremented by 1, and this high voltage control routine is once terminated. Then, until the high voltage interrupt timer counts up and the next high voltage control routine is executed (about 0.5 ms), the CPU 210 executes well-known print control for performing printing by the image forming unit 10. .

  Here, the numerical value 20 will be described. In this embodiment, since the A / D converter 211 having a digital output of 10 bits is used, the output thereof takes a value of 0 to 1023 (decimal value). Assuming that 511 (decimal value) close to the center is set as the control target value, a value corresponding to 4% of the target value (511 * 0.04≈20) is used as the switching timing of the interrupt time of the high-voltage interrupt timer. I use it. Note that the switching timing of the interrupt time of the high-voltage interrupt timer can be set as appropriate within a range of 2% to 10% (≈10 to 50) of the target value. The error ERR of the A / D converter 211 is normally expected to be about 1% of the maximum output value.

  On the other hand, if ADD is equal to or lower than the lower limit −20 (S55: N), PWM is increased by a predetermined value ΔPWM1 (ΔPWM2> ΔPWM1> 0) in S58, and the process proceeds to S59. In S59, the high voltage interrupt timer is set to 1 ms, the counter CNT1 is incremented by 1, and this high voltage control routine is once terminated. Then, the well-known print control for performing printing by the image forming unit 10 is executed in the CPU 210 until the high-voltage interrupt timer counts up and the next high-pressure control routine is executed (about 1 ms).

  If it is determined in S52 that the ADD is equal to or higher than the upper limit −ERR (S52: Y), in S62, the ADD is set to the upper limit set in S3, and the error ERR is set. It is determined whether or not the value is equal to or less than the value obtained by adding (upper limit + ERR). When ADD is larger than the upper limit + ERR (S62: N), it is determined in S63 whether MODE is DOWN (down). If MODE = DOWN (S63: Y), the process proceeds to S65 as it is. If MODE ≠ DOWN (S63: N), the PWM at that time is set to PCSM and MODE is set to DOWN in S64. After that, the process proceeds to S65.

  In S65, it is determined whether or not the ADD read in S61 is larger than a value obtained by adding the numerical value 20 to the upper limit (upper limit +20). If ADD is larger than the upper limit +20 (S65: Y), the PWM is decreased by ΔPWM2 in S66, and the process proceeds to S57 described above. On the other hand, if ADD is not more than the upper limit +20 (S65: N), the PWM is decreased by ΔPWM1 in S68, and the process proceeds to S59 described above.

  If it is determined in S62 described above that ADD is equal to or lower than the upper limit + ERR (S62: Y), that is, if the lower limit −ERR ≦ ADD ≦ upper limit + ERR, the process proceeds to S71. In S71, the value obtained by multiplying the value of the counter CNT1 at that time by the above ΔPWM1 is set as PCAM1, and P1 is calculated by the following equation using the PCAM1.

続くＳ７２では、その時点のカウンタＣＮＴ２の値に上記ΔＰＷＭ２をかけた値がＰＣＡＭ２とされ、更に、そのＰＣＡＭ２を用いて次式によってＰ２が計算される。

In subsequent S72, the value obtained by multiplying the value of the counter CNT2 at that time by the above ΔPWM2 is set as PCAM2, and P2 is calculated by the following equation using the PCAM2.

更に、続くＳ７３では、ＭＯＤＥ＝ＵＰであるか否かが判断される。ＭＯＤＥ＝ＵＰの場合は（Ｓ７３：Ｙ）、処理はＳ７４へ移行し、ＰＷＭの値がＰＣＳＭ＋Ｐ１＋Ｐ２に変更され、続くＳ７５にて、ＭＯＤＥがＤＲＶに変更される。更に続くＳ７６では、高圧割り込みタイマが２ｍｓにセットされ、カウンタＣＮＴ１，ＣＮＴ２が０にリセットされて、この高圧制御ルーチンが一旦終了する。すると、高圧割り込みタイマがカウントアップして次にこの高圧制御ルーチンが実行されるまでの間（約２ｍｓ）に、ＣＰＵ２１０では、画像形成部１０による印刷を行う周知の印刷制御が実行される。

Further, in subsequent S73, it is determined whether or not MODE = UP. When MODE = UP (S73: Y), the process proceeds to S74, the PWM value is changed to PCSM + P1 + P2, and in S75, MODE is changed to DRV. In the subsequent S76, the high voltage interrupt timer is set to 2 ms, the counters CNT1 and CNT2 are reset to 0, and this high voltage control routine is temporarily terminated. Then, until the high voltage interrupt timer counts up and the next high voltage control routine is executed (about 2 ms), the CPU 210 executes well-known print control for performing printing by the image forming unit 10.

  If it is determined that MODE ≠ UP in S73 (S73: N), it is determined in S77 whether MODE = DOWN. If MODE = DOWN (S77: Y), after the PWM value is changed to PCSM-P1-P2 in S78, the process proceeds to S75 described above. If MODE ≠ DOWN (S77: N) The process proceeds to S76 as it is (that is, without changing the PWM).

  In this embodiment, the processing of S56, S58, S66, S68, S74, and S78 is the control means, the high-voltage interrupt timer setting processing in S57, S59, and S76 is the timing changing means, and the lower limit in S52 and S62 is − The calculation process of ERR or upper limit + ERR is a process corresponding to the predetermined range setting unit. Further, the equations used in S71, S72, S74, and S78 are direct search methods that the value of ADD at time T changes along the exponential function curve expressed by the following equation based on the time constant τ of the system. Is an approximate expression. However, in the following equation, A and B are predetermined coefficients.

４．本実施の形態の効果
このように、本実施の形態では、ＡＤＤが上限＋ＥＲＲと下限−ＥＲＲとの間に入って安定しているときは高圧割り込みタイマを２ｍｓと長く設定しているので（Ｓ７６）、処理負荷を軽減して印刷制御を効率的に実行することができる。また、ＡＤＤが上記範囲に入っていないときは高圧割り込みタイマを１ｍｓに設定し（Ｓ５９）、ＡＤＤが上限＋２０と下限−２０との間になく所望の制御範囲から大きく外れているときは高圧割り込みタイマを０．５ｍｓと更に短く設定しているので（Ｓ５７）、制御の応答性を良好に確保することができる。

4). As described above, in this embodiment, when the ADD is between the upper limit + ERR and the lower limit -ERR and is stable, the high voltage interrupt timer is set to be as long as 2 ms (S76). ), The processing load can be reduced and print control can be executed efficiently. Further, when the ADD is not within the above range, the high voltage interrupt timer is set to 1 ms (S59), and when the ADD is not between the upper limit +20 and the lower limit -20 and greatly deviates from the desired control range, the high voltage interrupt is set. Since the timer is set to be as short as 0.5 ms (S57), good control responsiveness can be ensured.

5. Other Embodiments of the Invention The present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the gist of the present invention. For example, in the above embodiment, ADD is controlled to fall between a value obtained by adding error ERR to the upper limit value and a value obtained by subtracting error ERR from the lower limit value. You may control so that it may enter between the said lower limits. However, in the above embodiment, when the ADD is out of the error ERR from the desired control range (between the upper limit value and the lower limit value), the ADD is regarded as being within the predetermined range. Therefore, unnecessary PWM change due to the error ERR is suppressed (S77: N), and more stable control can be executed. In addition, in the above embodiment, since the error ERR is actually measured by the ADC error detection control shown in FIG. 5, a more accurate error ERR can be acquired. That is, the error ERR may be written in the ROM 203 at the time of shipment or the like and read as appropriate. In this case, the process of reading the error ERR from the ROM 230 corresponds to the error acquisition means.

  In the above embodiment, the transfer bias current TR. Although the present invention is applied to a system that performs constant current control of CC, the present invention can be similarly applied to a system that performs constant voltage control or constant power control. Further, in the above embodiment, the execution interval of the high voltage control routine is changed according to the value of ADD, but it is also possible to change only the interval at which the feedback voltage Vf is A / D converted to ADD. Furthermore, in the above embodiment, the values of P1 and P2 are calculated as described above (S71, S72), but these values are tabulated and read from the ROM 230 according to the values of CNT1, CNT2, etc. But you can.

  The values of ΔPWM1 and ΔPWM2 may be the same value (referred to as ΔPWM). Also in this case, ΔPWM is increased or decreased at a short interval as the value of ADD deviates from the desired control range, so that control responsiveness can be ensured. However, in the above embodiment, as the ADD value deviates from between the upper and lower limits, the width of change in PWM by one control increases, and the control response when ADD deviates from between the upper and lower limits is further improved. Can be improved.

  In the above embodiment, the control system in which the output value increases when the PWM increases is taken as an example. However, the control system in which the output value increases when the PWM decreases or the constant voltage with the negative output value. The present invention can be similarly applied to a control system in which the feedback value decreases when the output value is large, such as during control.

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 a flowchart showing the printing process performed by the control system of the power supply unit. It is a flowchart showing ADC error detection control in the printing process. It is a flowchart showing the high voltage | pressure control routine in the printing process. It is a flowchart showing the continuation of the high voltage | pressure control routine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer 10 ... Image forming part 20 ... Feeder part 70 ... Scanner part 80 ... Process cartridge 81 ... Photoconductor drum 82 ... Charger 83 ... Transfer roller 84 ... Developing cartridge 90 ... Fixing unit 100 ... Power supply unit 120 ... Transformer 130 ... Driving voltage control unit 200 ... Control board 210 ... CPU
220 ... ROM 230 ... RAM 240 ... interface

Claims (6)

A power supply unit whose output value changes according to an input signal;
Detecting means for detecting an output value of the power supply unit as an analog signal;
Conversion means for converting the analog signal detected by the detection means into a digital signal;
Control means for feedback- controlling the input signal so that the output value falls within a predetermined range based on the digital signal converted by the conversion means;
Timing changing means for shortening the interval of at least one of the timing at which the converting means performs the conversion or the timing at which the control means performs the feedback control as the degree of deviation of the output value from the predetermined range increases. When,
A power supply device comprising:   2. The power supply device according to claim 1, wherein the timing changing unit makes the interval longer when the output value is within the predetermined range than when the output value is outside the predetermined range. 3. The power supply device according to claim 1, wherein a change width of the input signal changed by the control unit by one control is larger as a degree of deviation of the output value from the predetermined range is larger. Error acquisition means for acquiring a width of an error with respect to the actual output value of the digital signal converted by the conversion means;
Predetermined range setting means for setting, as the predetermined range, a range obtained by adding the error range acquired by the error acquisition means to a desired control range of the output value;
The power supply device according to any one of claims 1 to 3, characterized in that with a. 5. The power supply apparatus according to claim 4 , wherein the error acquisition unit acquires the error width based on a value of the digital signal when the predetermined input signal is input to the power supply unit. The power supply device according to claim 1 or 2 ,
Image forming means for forming an image on a recording medium using the output of the power supply unit;
With
The image forming apparatus characterized in that the control means also executes control of the image forming means in parallel.

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