JP4341945B2 - Zero-cross detection method, power supply device, and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an AC voltage zero-cross detection method, a power supply device that implements the method, and an image forming apparatus using the same. The image forming apparatus is, for example, a copying machine, a printer, or a facsimile.
[0002]
[Prior art]
  The zero-cross signal indicates the switching point of the half-wave of the AC voltage waveform. For example, the half-wave base point is grasped for power control to the AC load by so-called phase control that switches the AC voltage with a semiconductor switching element and applies it to the load. Used to do.
[0003]
  A zero cross signal is used for phase control of the fixing heater of the image forming apparatus. The CPU that performs power control of the fixing heater is configured to generate a zero cross pulse interrupt when a zero cross signal is input. In the interruption process, the fixing heater is turned on / off every half cycle of the power supply frequency. Specifically, in one example, when an interruption occurs, a signal for turning off a triac, which is an ON / OFF device for the fixing heater, is generated, that is, a fixing heater OFF signal. That is, the triac control signal is set to the OFF instruction level. Next, a timer is started so that an internal timer interrupt is generated several ms after a certain point in the interrupt processing.
[0004]
  When a timer interrupt occurs after several ms, the CPU generates a signal for turning on the triac, that is, a fixing heater ON signal. That is, the triac control signal is set to the ON instruction level. In this way, the ON / OFF phase control of the fixing heater is performed by turning ON / OFF the triac using the zero cross pulse interruption.
[0005]
  In order to perform such phase control, a zero cross signal must be detected. The following are known methods for generating a zero-cross signal in a conventional image forming apparatus.
[0006]
  1. A zero-cross signal is generated by a zero-cross signal detection circuit that is a combination of a rectifier circuit and a photocoupler.
[0007]
  2. A zero cross signal is generated by a zero cross signal detection circuit combining a transformer and a photocoupler.
[0008]
  When the AC voltage waveform is a smooth sine wave as shown in FIG. 11 and there is no level fluctuation, in any of the above methods, the zero cross pulse is correctly generated at the zero cross point, and the pulse width of the zero cross pulse is constant. . However, when the AC voltage becomes close to the zero level due to noise outside the zero cross point, a zero cross pulse is generated there as shown in FIG. In FIG. 12, the upper waveform is the zero cross signal generated by the detection circuit, and the lower waveform is the alternating voltage in question.
[0009]
  In zero-crossing detection, zero-crossing was detected by a full-wave rectifier circuit and a photocoupler, or a combination of a transformer and a photocoupler. However, an environment using a power source for private power generation or an environment where many high-power devices were used. In the case of using the image forming apparatus, there is a problem that noise is applied to the AC power supply voltage and the zero cross is erroneously detected. If the zero cross is erroneously detected, the power supply frequency cannot be detected normally and an abnormal message is displayed, so that the image forming apparatus cannot be used.
[0010]
  When the image forming apparatus is used in such a noisy environment, the process of detecting the power supply frequency is stopped, the user is asked about the power supply frequency used in the image forming apparatus, and the ROM is set with the power supply frequency fixed. I was trying to install it on the device.
[0011]
  Japanese Patent Laid-Open No. 8-308215 discloses a detection device that starts a timer when a power supply voltage falls within a predetermined range of −Vth <V <Vth in order to prevent zero-crossing misdetection. Means for counting the time of staying at the terminal and detecting whether it is equal to or greater than a set value, and means for detecting that the polarity of the power supply voltage has been reversed before entering the predetermined range and after exiting, If the two means are satisfied, a zero cross signal is output.
[0012]
  The detection apparatus disclosed in Japanese Patent Laid-Open No. 11-318072 detects the power supply frequency by counting the number of zero cross signals detected from the zero cross detection circuit for an arbitrary time as an initial setting. Based on the detected frequency, an output signal synchronized with the zero cross point or counting is performed, and output control of the AC voltage is performed using the zero cross point as a trigger.
[0013]
  In general, in the initialization process immediately after the power of the image forming apparatus is turned on, a process is performed to detect whether a zero cross signal can be detected and whether the power frequency is 50 Hz or 60 Hz. In the zero cross detection process, if the CPU generates a zero cross interrupt, it is determined that the zero cross signal is generated. If there is no occurrence of a zero-cross interrupt, it is determined that a zero-cross signal has not been generated. In this case, the image forming apparatus displays no occurrence of the zero-cross signal on its operation unit. Next, whether the power supply frequency is 50 Hz or 60 Hz is based on how many zero cross interrupts are counted until the next timer interrupt is started, and the power supply frequency is 50 Hz, It is determined whether it is 60 Hz. In this determination, if the zero cross interrupt is counted 45 to 54 times, it is determined to be 50 Hz. Similarly, when the count is 55 to 64, it is determined as 60 Hz. When counting 0 to 44 times or 65 times or more, the image forming apparatus displays a zero cross detection abnormality on the operation unit.
[0014]
[Problems to be solved by the invention]
  The detection device disclosed in Japanese Patent Application Laid-Open No. 8-308215 has a problem that equipment is expensive because there are many additional circuits. The detection device disclosed in Japanese Patent Application Laid-Open No. 11-318072 may not be able to detect the correct power supply frequency when noise occurs frequently during power supply frequency detection.
[0015]
  In addition, in the detection of zero cross by conventional hardware, the voltage level for generating the zero cross signal is constant and does not change. Therefore, if the power supply frequency fluctuates, the zero cross signal width changes. When comparing 50 Hz and 60 Hz, the zero-cross width of 60 Hz is smaller than 50 Hz, and there is a problem that the time until the true zero-crossing is shortened after the CPU generates an interrupt due to a zero-cross signal. When the time until the true zero cross was shortened, the possibility that the OFF signal of the triac would not be in time for the rise of the AC voltage from the actual zero cross was considered.
[0016]
  The first object of the present invention is to correctly detect a zero cross by digital signal processing, and it is a second object to easily generate an accurate zero cross signal. A third object is to eliminate the occurrence or omission of a zero-cross signal even with a noisy AC power supply voltage. A fourth object is to always make the zero cross pulse width constant even when the AC power supply frequency changes.
[0017]
[Means for Solving the Problems]
  (1) The amplitude of the full-wave rectified waveform of the monitoring target AC voltage is half-wave by repetitive reading of the short period by A / D conversion and collation with the amplitude data of the AC voltage held in the memory. Whether the start point = end point (sin0 °)Judgment andJudgment of timing when it is the peak of half wave (sin90 °)When,Is repeated (Figs. 8 and 9), and timing is started at the timing when the half-wave start point = end point (sin0 °) (27 in Fig. 8), and the timing when the half-wave apex (sin90 °) is reached The start timing (A = Tc-10) and end timing (B = Tc + 10) of the zero cross pulse are determined from the value (Tc) (FIGS. 9 and 10), and the zero cross is expressed only between the start timing and the end timing. Zero-cross detection method for generating level zero-cross pulses (45-47 in FIG. 10).
[0018]
  In addition, in order to make an understanding easy, the code | symbol of the corresponding element of the Example which is shown in drawing and it mentions later, or an equivalent element, or a corresponding matter was added for reference. The same applies to the following.
[0019]
  According to this, since the zero cross timing is detected in accordance with the waveform of the monitoring target AC voltage and the zero cross signal is generated, accurate zero cross detection can be performed even for a power supply in which noise is present. Since the next zero cross point is predicted in advance and the next zero cross signal is generated according to the prediction, a highly reliable zero cross signal that is not affected by noise is generated. Since the zero cross signal width is always constant, for example, in the triac conduction phase control by the CPU (or MPU), the period from when the CPU is interrupted by the zero cross signal until reaching the true zero cross is always constant, and the zero cross In the interrupt processing by the signal, the reliability that the triac can be turned off before the true zero cross always reaches is improved.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
  (2) The specific constant frequency in which the amplitude of the full-wave rectified waveform of the monitored AC voltage is repeatedly read in a short period by A / D conversion over a period exceeding 1 period / 4, and the obtained amplitude data group is held in the memory The frequency of the monitoring target AC voltage is determined by collating with the amplitude data group of the AC voltage (FIGS. 6 and 7),
  The starting point of the half-wave of the monitored AC voltage by repetitively reading the amplitude of the full-wave rectified waveform of the monitored AC voltage in a short cycle by A / D conversion and the amplitude data of the AC voltage held in the memory = Is it the end point (sin0 °)?Judgment andJudgment of timing when it is the peak of half wave (sin90 °)When,Is repeated (Figs. 8 and 9), and timing is started at the timing when the half-wave start point = end point (sin0 °) (27 in Fig. 8), and the timing when the half-wave apex (sin90 °) is reached The start timing (A = Tc-10) and end timing (B = Tc + 10) of the zero cross pulse are determined from the value (Tc) (FIGS. 9 and 10), and the zero cross is expressed only between the start timing and the end timing. Zero-cross detection method for generating level zero-cross pulses (45-47 in FIG. 10).
[0021]
  According to this, even when there is an AC power supply frequency of 50 Hz and 60 Hz as in Japan, for example, it is automatically determined which one is present. The operational effects described in (4) above are obtained in the same way.
[0022]
  (3) Rectifier circuit to convert AC voltage to DC voltage (82);
  Transformer (TR1), switching element (FET1) that switches the DC voltage output from the rectifier circuit (82) and supplies power to the primary winding of the transformer, and turns on / off the switching element (FET1) in response to PWM pulses A plurality of switching power supply circuits (PC1-PC4) including diodes (D1, D2) for rectifying the voltage generated in the secondary winding of the switching driver (DRIV1) and the transformer (TR1); and
  A PWM pulse is given to each of the switching power supply circuits (PC1-PC4) to control the generation of individual DC voltages, and the amplitude of the full-wave rectified waveform of the AC voltage is repeatedly read in a short cycle by A / D conversion. Is the timing when the monitored AC voltage becomes the half-wave start point = end point (sin0 °) based on the comparison with the AC voltage amplitude data stored in the memory?Judgment andJudgment of timing when it is the peak of half wave (sin90 °)When,Is repeated (Figs. 8 and 9), and timing is started at the timing when the half-wave start point = end point (sin0 °) (27 in Fig. 8), and the timing when the half-wave apex (sin90 °) is reached The start timing (A = Tc-10) and end timing (B = Tc + 10) of the zero cross pulse are determined from the value (Tc) (FIGS. 9 and 10), and the zero cross is expressed only between the start timing and the end timing. Generating a level zero cross pulse (45-47 in FIG. 10), power output controller (85);
A power supply device comprising:
[0023]
  Since this power supply device detects the zero-cross timing according to the waveform of the monitored AC voltage and generates a zero-cross signal, the zero-cross detection is performed accurately even for a power supply in which noise is present. Since the next zero cross point is predicted in advance and the next zero cross signal is generated according to the prediction, a highly reliable zero cross signal that is not affected by noise is generated. Since the zero-cross signal width is always constant, the reliability and stability of control performed based on the width becomes high.
[0024]
  (4)A period between the start timing and the end timing is constant; the power supply device according to (3).
[0025]
  (5)The start timing is a timing shorter by half of the zero cross pulse width than the timing value (Tc) of the timing at which the peak of the half wave is reached, and the end timing is zero crossing from the timing value (Tc) of the timing at which the peak of the half wave is reached The power supply device according to claim 3 or 4, wherein the timing is longer by half the pulse width..
[0026]
  (6) The photoconductor (114), a charger (119) for charging the photoconductor, an exposure device (161-146) for exposing image light to the charged surface of the photoconductor, and the electrostatic latent image generated by the exposure to a visible image Developing device (120), means for transferring the visible image onto transfer paper (115-117),and,An image forming apparatus including a fixing device (123) for fixing a visible image of the transfer paper to the transfer paper,
  Furthermore, the power supply device according to any one of the above (3) to (5) is provided;
  The power supply further includes:A fixing energization circuit (80ac) having a triac for applying the AC voltage to the heater (123C) of the fixing device (123);
  The image forming apparatus further includes an on-phase control means (51) for generating a triac control signal having an on instruction level at a timing when the triac based on the zero cross pulse is to be turned on and supplying the triac control signal to the triac;
An image forming apparatus comprising:
[0027]
  According to this, in the triac conduction phase control of the fixing energization circuit (80ac) by the on phase control means (51), the on phase control means (51) is interrupted by the zero cross signal and then reaches the true zero cross. The period until the time is always constant, and the reliability of being able to turn off the triac until the true zero cross always arrives in the interrupt processing by the zero cross signal is improved. That is, the stability and reliability of the power control of the fixing heater is improved.
[0028]
  (7) Further, the image scanner (10) for reading the image of the document is provided,6) Image forming apparatus. According to this, the above (6A copier capable of obtaining the effects described in (1) is realized.
[0029]
  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.
[0030]
【Example】
  FIG. 1 shows the appearance of a digital copying machine which is an embodiment of the present invention. This digital copying machine is roughly an automatic document feeder [ADF] 30, an operation unit 20, a color scanner 10, a color printer 100, a relay unit 32, a stapler and a large amount of imaged paper. The unit includes a finisher 34 with a shift tray, a duplex reversing unit 33, a paper feed bank 35, a large-capacity paper feed tray 36, and a 1-bin paper discharge tray 31.
[0031]
  FIG. 2 shows the configuration of the color printer 100. The writing optical unit as the exposure unit converts the color image data from the scanner 10 into an optical signal, performs optical writing corresponding to the original image, and forms an electrostatic latent image on the photosensitive drum 114. The optical writing optical unit includes a laser light emitter 141, a light emission drive control unit (not shown) that drives and emits the light, a polygon mirror 143, a rotation motor 144 that rotationally drives this, an fθ lens 142, a reflection mirror 146, and the like. ing. The photosensitive drum 114 rotates counterclockwise as indicated by an arrow. Around the photosensitive drum 114, a photosensitive member cleaning unit 121, a charge eliminating lamp 114M, a charger 119, and a latent image potential on the photosensitive drum are detected. A potential sensor 114D, a selected developer of the revolver developing device 120, a development density pattern detector 114P, an intermediate transfer belt 115, and the like are arranged.
[0032]
  The revolver developing device 120 includes a BK developing device 120K, a C developing device 120C, an M developing device 120M, a Y developing device 120Y, and a revolver rotation driving unit (not shown) that rotates each developing device in a counterclockwise direction as indicated by an arrow. (Omitted). Each of these developing devices pumps up the developing sleeves 120KS, 120CS, 120MS, 120YS, which rotate by bringing the ears of the developer into contact with the surface of the photosensitive drum 114, in order to visualize the electrostatic latent image. It consists of a developing paddle that rotates for stirring. In the standby state, the revolver developing device 120 is set at a position where development is performed by the BK developing device 120. When the copying operation is started, the scanner 10 starts reading BK image data at a predetermined timing. Based on the data, laser writing and latent image formation are started. Hereinafter, an electrostatic latent image based on Bk image data is referred to as a Bk latent image. The same applies to C, M, and Y image data. In order to enable development from the leading edge of the Bk latent image, before the leading edge of the latent image reaches the developing position of the Bk developing device 120K, the developing sleeve 120KS starts to rotate, and the Bk latent image is developed with Bk toner. . Thereafter, the developing operation of the Bk latent image area is continued. When the trailing edge of the latent image has passed the Bk latent image position, the developing operation is immediately performed from the developing position by the Bk developing device 120K by the developing device for the next color. The revolver developing device 120 is driven and rotated to the position. This rotation operation is completed at least before the leading edge of the latent image by the next image data arrives.
[0033]
  When the image forming cycle is started, the photosensitive drum 114 rotates counterclockwise as indicated by an arrow, and the intermediate transfer belt 115 rotates clockwise by a drive motor (not shown). As the intermediate transfer belt 115 rotates, BK toner image formation, C toner image formation, M toner image formation, and Y toner image formation are sequentially performed. Finally, intermediate transfer is performed in the order of BK, C, M, and Y. A toner image is formed over the belt 115. The BK image is formed as follows. That is, the charger 119 uniformly charges the photosensitive drum 114 to about −700 V with a negative charge by corona discharge. Subsequently, the laser diode 141 performs raster exposure based on the Bk signal. When the raster image is exposed in this manner, the charge proportional to the exposure light amount disappears in the exposed portion of the uniformly charged photosensitive drum 114, and an electrostatic latent image is formed. The toner in the revolver developing device 120 is negatively charged by stirring with the ferrite carrier, and the BK developing sleeve 120KS of the developing device is connected to the metal base layer of the photosensitive drum 114 by a power supply circuit (not shown). It is biased to a potential in which a negative DC potential and an AC are superimposed. As a result, the toner does not adhere to the remaining portion of the photosensitive drum 114, and Bk toner is adsorbed to the uncharged portion, that is, the exposed portion, so that Bk visible similar to the latent image. An image is formed. The intermediate transfer belt 115 is stretched around a driving roller 115D, a transfer counter roller 115T, a cleaning counter roller 115C, and a driven roller group, and is rotated by a driving motor (not shown). A Bk toner image formed on the photosensitive drum 114 is applied to a belt transfer corona discharger (hereinafter referred to as a belt transfer unit) 116 on the surface of an intermediate transfer belt 115 that is driven at a constant speed in contact with the photosensitive member. Is transcribed by. Hereinafter, the toner image transfer from the photosensitive drum 114 to the intermediate transfer belt 115 is referred to as belt transfer. Some untransferred residual toner on the photosensitive drum 114 is cleaned by the photosensitive member cleaning unit 121 in preparation for reuse of the photosensitive drum 114. The toner collected here is stored in a waste toner tank (not shown) via a collection pipe.
[0034]
  In addition, on the intermediate transfer belt 115, Bk, C, M, and Y toner images that are sequentially formed on the photosensitive drum 114 are sequentially aligned on the same surface to form a four-color superimposed belt transfer image. Thereafter, batch transfer is performed on the transfer paper with a corona discharge transfer device. By the way, on the photosensitive drum 114 side, the process proceeds to the C image forming process after the BK image forming process. At a predetermined timing, reading of C image data by the scanner 10 is started, and laser light writing by the image data is performed. Then, a C latent image is formed. The C developing device 120C rotates the revolver developing device after the rear end of the previous Bk latent image has passed with respect to the developing position and before the front end of the C latent image has arrived. Develop the image with C toner. Thereafter, the development of the C latent image area is continued. When the trailing edge of the latent image passes, the revolver developing device 120 is driven and the C developing device 120C is sent out in the same manner as in the previous Bk developing device. The M developing device 120M is positioned at the developing position. This operation is also performed before the leading edge of the next M latent image reaches the developing unit. It should be noted that the image forming process for each of the M and Y images will not be described because the image data reading, latent image forming, and developing operations are in accordance with the Bk image and C image processes described above.
[0035]
  The belt cleaning device 115U includes an inlet seal, a rubber blade, a discharge coil, and a contact / separation mechanism for the inlet seal and the rubber blade. After transferring the first color Bk image to the belt, while transferring the second, third, and fourth color images to the belt, the blade seal mechanism separates the inlet seal, rubber blade, etc. from the intermediate transfer belt surface. deep.
[0036]
  A paper transfer corona discharger (hereinafter referred to as a paper transfer unit) 117 transfers AC + DC or DC components to the transfer paper and the intermediate in a corona discharge system in order to transfer the superimposed toner image on the intermediate transfer belt 115 onto the transfer paper. This is applied to the transfer belt.
[0037]
  Various sizes of transfer paper are stored in the transfer paper cassette 182E and the paper supply bank 35, and the paper stored in the designated size is fed in the direction of the registration roller pair 118R by the paper supply roller 183E or the like. Paper / conveyed. Reference numeral 112B2 denotes a paper feed tray for manually feeding OHP paper, cardboard, or the like. At the time when the image formation is started, the transfer paper is fed from one of the paper feed trays and stands by at the nip portion of the registration roller pair 418R. When the leading edge of the toner image on the intermediate transfer belt 115 approaches the paper transfer unit 117, the registration roller pair 118R is driven so that the leading edge of the transfer paper coincides with the leading edge of the image, and the paper and the image are transferred. Matching is done. In this way, the transfer paper is superimposed on the color superposition image on the intermediate transfer belt and passes over the paper transfer device 117 connected to a positive potential. At this time, the transfer paper is charged with a positive charge by the corona discharge current, and most of the toner image is transferred onto the transfer paper. Subsequently, when the paper passes through a separation static eliminator (not shown) disposed on the left side of the paper transfer unit 117, the transfer paper is neutralized, peeled off from the intermediate transfer belt 115, and transferred to the paper conveyance belt 122. The transfer paper onto which the four-color superimposed toner images are collectively transferred from the surface of the intermediate transfer belt is conveyed to the fixing device 123 by the paper conveyance belt 122, and the toner is transferred to the nip portion between the fixing roller 123A and the pressure roller 123B controlled to a predetermined temperature. The image is fused and fixed, sent out of the main body by a pair of discharge rollers 124, and stacked face up on a copy tray (not shown).
[0038]
  Inside the fixing roller 123A, there is a fixing heater (halogen lamp) 123C. The fixing heater 123C is energized by a fixing energizing circuit 85 (FIG. 4), whereby the fixing heater 123C generates heat and generates infrared rays. Then, the fixing roller 123C is heated.
[0039]
  The surface of the photosensitive drum 114 after the belt transfer is cleaned by a photosensitive member cleaning unit 121 including a brush roller, a rubber blade, and the like, and is uniformly discharged by a discharging lamp 114M. Further, the intermediate transfer belt 115 after the toner image is transferred to the transfer paper is again cleaned by pressing the blade with the blade contact / separation mechanism of the cleaning unit 115U. In the case of repeat copying, the operation of the scanner and the image formation on the photosensitive member are continued to the fourth color image process for the first sheet, and then proceed to the first color image process for the second sheet at a predetermined timing. In the intermediate transfer belt 115, the second Bk toner image is belt-transferred to the area where the surface is cleaned by the belt cleaning device following the batch transfer process of the first four-color superimposed image onto the transfer paper. So that After that, the operation is the same as the first sheet.
[0040]
  FIG. 3 shows an outline of the electric system of the copying machine shown in FIG. One MPU 51 on the main control plate 50 and one CPU 12 on the scanner control plate 11 are used as a copier mechanical control unit, that is, a main part of image reading and image forming process control. The MPU 51 performs image-related sequence and fixing control and system-related control, and the CPU 12 performs scanner-related control. The MPU 51 and the CPU 12 are connected by an image data interface and a serial interface.
[0041]
  In FIG. 3, 20 is an operation unit, 70 is an I / O control board, 92 is an LD control board for controlling laser light for image exposure, 41 is a paper feed control board, and 13 is a reading control board on which a CCD is mounted. , 90 is a motherboard, 60 and 91 are application expansion units for realizing a composite function, 91 is a facsimile control unit equipped with a FAX function, 60 is a printer function for printing a document of a host such as a personal computer or word processor, and the like. A printer controller (board) for controlling a composite operation mode of copying, facsimile, and printer. Reference numeral 80 denotes a power supply device.
[0042]
  On the DC power supply / AC control board 80, there is a switching power supply unit 80dc that generates direct current voltages of several kinds of voltage values, and heater dosing power according to the conduction phase of the TRIAC that controls the fixing temperature by supplying commercial alternating current to the fixing heater. There is a fixing heater energization circuit (AC output) 80ac that can control the above.
[0043]
  FIG. 4 shows an outline of the switching power supply unit 80dc on the DC power supply / AC control board 80 and an outline of the electric load fed by it. The switching power supply unit 80dc includes a filter 81 for removing AC AC noise fed by closing (on) an unillustrated original power switch (AC input switch), a rectifying / smoothing circuit 82 for rectifying and smoothing the AC voltage, and a DC voltage Each DC voltage generator PC1 to PC4 that performs generation, a digital controller (using a digital signal processor DSP) 85 that controls voltage generation (generation / stop and output power) of each DC voltage generator, and an original power switch are opened A switch circuit (SW) 83 that is turned on when the AC power supply AC is applied to the switching power supply unit 80 dc and a DC voltage appears in the rectifying and smoothing circuit 82 and the battery 84 is applied to the DSP 85. When this switch circuit 83 is turned on, the battery that supplies the necessary power supply voltage to the DSP 85 Consisting of 4.
[0044]
  Each of the DC voltage generators PC1 to PC4 is connected to a load such as a scanner motor or an ADF (automatic document feeder), and supplies a necessary voltage to each load. The DSP 85 of the switching power supply unit 80 dc communicates with the printer controller 60 mounted on the motherboard 90 by UART (Universal Asynchronous Receiver Transmitter: Serial communication). Although not shown, the printer controller 90 is a computer system including a CPU, a nonvolatile memory, a ROM, a RAM, and an image memory.
[0045]
  The power supply waveform detection circuit 86 generates a pulsating flow (continuous half-wave shown in FIG. 11) obtained by full-wave rectification of the AC power supply AC and applies it to the A / D conversion input port of the DSP 85. The power supply waveform detection circuit 86 sets the AC power supply AC to 3/100, adjusts 144 V to be exactly 4.32 V, and inputs it to the DSP 85.
[0046]
  As will be described in detail later, the DSP 85 reads the amplitude of the pulsating current by A / D conversion at a period of 100 μs, and stores the amplitude data group of the AC half wave period in the 50 Hz AC half wave stored in the memory. It is checked against the amplitude data group whether the AC power supply AC is 50 Hz (60 Hz) (FIGS. 6 and 7). Thereafter, the amplitude of the pulsating flow is A / D converted at a cycle of 100 μs and the reading is repeated, and the read amplitude data is collated with the amplitude data group of AC half-waves stored in the memory at the determined frequency. Estimate the phase of the time point, start timing when the phase is AC half-wave start point = end point, that is, sin 0 ° (= sin 180 °), and when the phase is sin 90 ° (half-wave apex), save the time value Tc at that time Then, the start timing A = Tc-10 (1 unit is 100 μs) and the end timing B = Tc + 10 are set. When the zero cross pulse start timing is reached, the zero cross signal level of the zero cross pulse output port is The level is switched to the level indicated, and when the end timing is reached, the level is returned to the level not indicating the zero cross pulse (FIG. 8-10). This process is repeated. The zero cross pulse generated in this way is applied to the zero cross pulse interrupt input terminal of the MPU 51 (FIG. 3) of the main control plate 50 via the I / O control plate 70.
[0047]
  The fixing energization circuit 80ac (FIG. 4) for energizing the fixing heater 123C includes a series circuit of a triac and an electric relay interposed between the AC power source AC and the fixing heater 123C. A DC 24V generated by the switching power supply circuit PC3 is applied to an electric coil of the electric relay via a door switch (interlock switch) (not shown). While the DC voltage is applied, the electric relay is connected to the AC power supply AC. It is energized between the triacs. When the switching power supply circuit PC3 does not generate DC 24V or when the door switch is opened by opening the door, the application of DC 24V is lost, so that the electric relay cuts off the electric path between the AC power supply AC and the triac.
[0048]
  The MPU 51 of the main control plate 50 calculates a triac conduction phase corresponding to the deviation between the fixing temperature (detected value) and the target value during a period in which the fixing temperature is necessary. When a zero cross pulse arrives from the DSP 85, a zero cross pulse interrupt occurs. By processing, the triac control signal applied to the gate of the triac of the fixing energization circuit 80ac is switched to the level indicating non-conduction through the I / O control board 70, and the timer of the calculated triac conduction phase value is started to interrupt the internal timer. Allow. When the timer expires, the triac control signal applied to the triac gate is switched to a level instructing conduction by internal timer interrupt processing. By such interrupt processing, the MPU 50 controls the conduction phase of the triac. As a result, the fixing temperature of the fixing device 123 is controlled to the target value.
[0049]
  FIG. 5 shows a configuration of the switching circuit 83 and the 5V generation unit PC1 of the switching power supply unit 80dc. A 100 V commercial AC voltage is applied from the AC input terminals IN1 and IN2 to the rectifying and smoothing circuit 82 through the noise filter 81 when a main power switch (not shown) is turned on. The noise filter 81 has an input filter that blocks high-frequency noise of the 100V commercial AC line from entering the switching power supply unit 80dc and prevents high-frequency noise generated by the switching power supply unit 80dc from leaking to the commercial AC line. . The AC voltage is applied through this input filter to a rectifying / smoothing circuit 82 including a full-wave rectifying diode bridge and a smoothing capacitor.
[0050]
  Further, the AC voltage is also applied to a starting circuit composed of a resistor R1 and a relay RA1. When AC voltage is applied, the relay contact RA1 closes the relay contact inserted between the diode D4 of the switch circuit (SW) 83 and the operating voltage input terminal Vcc of the DSP 85 of the relay RA1. Since the diode D4 is connected to the battery 84, the battery voltage is applied to the DSP 85, whereby the DSP 85 is activated and outputs the first to fourth PWM pulses to the 5V generator PC1 to 38V generator PC4, respectively. .
[0051]
  As a result, all of the 5V generators PC1 to 38V generator PC4 are in an operating state, and generate the DC voltages shown in FIG. Hereinafter, the 5V generation unit PC1 will be described as an example.
[0052]
  The output DC voltage of the rectifying / smoothing circuit 82 is applied to the primary winding of the transformer TR1 in the 5V generator PC1. When the switching element FET1 is turned on, a current flows from the rectifying / smoothing circuit 82 to the primary side ground via the primary winding, the switching element FET1 and the current value detection circuit ISEN1.
[0053]
  In the current value detection circuit ISEN1, the current flowing through the FET 1 flows through the current detection resistor, and the voltage of the resistor is proportional to the primary current. This voltage is a primary current detection signal, and the current value detection circuit ISEN1 generates a signal indicating an overcurrent and gives it to the DSP 85 when the detection signal exceeds a set level. In response to this, the DSP 85 turns off the FET1. When the next PWM pulse output period is reached, the FET 1 is turned on. That is, output of a new PWM pulse is started.
[0054]
  The drive circuit DRIV1 is connected to a PWM output port that outputs a first PWM pulse that is a switching ON / OFF signal of the DSP 85. The primary side switching circuit is constituted by DRIV1, transformer TR1 and switching element FET1, and the output voltage of rectifying and smoothing circuit 82 is chopped by switching in response to the PWM pulse, and the primary winding of transformer TR1 is pulse-energized.
[0055]
  On the secondary side of the transformer TR1, there is an output circuit that converts a pulse voltage induced in the secondary winding into a direct current and outputs it. The output circuit includes diodes D1 and D2, choke coil CH1, secondary side overcurrent detection circuit ISEN2 that detects secondary side overcurrent, output voltage detection circuit VSEN1, and a smoothing capacitor.
[0056]
  The secondary-side overcurrent detection circuit ISEN2 is configured to convert the current flowing through the output circuit of the 5V generation unit PC1 into a voltage (secondary current detection signal) corresponding to the magnitude of the current, and output it from ISEN2. The voltage (secondary current detection signal) is applied to the A / D conversion input port of the DSP 85. When the secondary overcurrent detection circuit ISEN2 detects an overcurrent or the output voltage detection circuit VSEN1 detects an overvoltage, the DSP 85 turns off the FET1 and stops the PWM pulse output.
[0057]
  The same applies to the configurations and operations of the circuits PC2 to PC4 that generate the other voltage values, and the control operation of the DSP 85 for them. However, the generation circuit having a large power capacity of the generation circuit is such that a plurality of switching element FETs are used in parallel connection, or a thermistor for protecting the temperature of the circuit is added and the voltage (temperature) is given to the DSP 85. For example, temperature abnormalities are monitored.
[0058]
  The CPU and MPU that monitor input even in the energy saving standby mode and the circuit that generates an external input signal in the energy saving standby mode of the printer controller 60, the I / O control board 70, and the main control board 50 are fed by the 5V generator PC1. To do.
[0059]
  When the original power switch of the copier is turned on, the AC power AC is input to the switching power supply unit 80dc. The AC power supply passes through the filter with noise 81 and is full-wave rectified by the rectifying / smoothing circuit 82. When the output voltage exceeds the set value, the current flowing through the electric relay coil RA1 causes the relay contact RA1 of the switch circuit 83 to close.
[0060]
  As a result, the voltage accumulated in the battery 84 is supplied to the DSP 85, and the DSP 85 is activated. The DSP 85 first starts outputting a PWM pulse to the 5V generation unit PC1, whereby the 5V generation unit PC1 generates a 5V voltage. The generated 5V voltage is applied to the CPU and MPU that monitor input even in the energy saving standby mode and the circuit that generates an external input signal in the energy saving standby mode of the printer controller 60, the I / O control board 70, and the main control board 50. Is done. The primary winding of the transformer TR1 is excited by turning on / off the FET 1 in response to the PWM pulse. As a result, the tertiary winding connected to the switch circuit 83 induces a voltage, which is rectified by the diode D3 and smoothed by the capacitor C2. The voltage is made constant by the constant voltage circuit CV1, and the driving voltage for the DSP 85 is supplemented through the diode D5.
[0061]
  In response to the output of the 5V generation unit PC1 rising from 0V to 5V, the CPU of the printer controller 60 is activated, and the CPU of the printer controller 60 generates all DC voltages to the DSP 85 through UART communication (PC1 to PC1). Command PC4) to turn on. Upon receiving the command, the DSP 85 turns on all the DC voltage generation units (PC1 to PC4). That is, the PWM pulse is output to each of PC1 to PC4. Here, the ON of the first generation unit PC1 means the start of the power output control of the DSP 85 according to the command (control) of the CPU of the printer controller 60 from the start operation of the ON response of the original power switch.
[0062]
  When all the generation units PC1 to PC4 are started up, that is, when each output voltage is equal to or higher than each set value, the DSP 85 notifies the CPU of the printer controller 60 that the DC voltage has risen (ready) by UART communication.
[0063]
  Next, generation of a zero cross pulse by the DSP 85 will be described.
[0064]
  Please refer to FIG. The DSP 85 performs AD conversion on the pulsating voltage output from the power supply waveform detection circuit 86 every time 100 μs has elapsed, and first saves 100 AD conversion data, that is, an amplitude data group (step 1-6). In the following, the word “step” is omitted in parentheses, and step no. Enter only numbers.
[0065]
  Reference is now made to FIG. The saved amplitude data of 100 times is compared with the amplitude data (100 pieces) of the waveform curve of the power frequency of 50 Hz previously stored in the memory. From the comparison, it is determined whether the power frequency is 50 Hz or not (60 Hz) (11), and the current angle (phase value) of the power waveform at the time when 100 data reading is completed (current time) is confirmed and saved. (12, 13).
[0066]
  Please refer to FIG. At the next AD conversion interruption after 100 μs, the obtained AD conversion value is converted into a voltage conversion value, and the amplitude data of the waveform curve of the data table addressed to 50 Hz or 60 Hz determined by the above determination from the saved current angle. Compare the current angle and check the current angle, and update the saved value. Thereafter, the phase angle is 0 ° (sin 0) while repeating the process of checking the current angle and updating the saved value to the latest value while sequentially tracing the obtained voltage conversion value of the AD conversion and the amplitude data of the waveform curve of the data table. (° = sin 180 ° point) is checked (21-26).
[0067]
  Here, there is no problem if the voltage conversion value of AD conversion at the point of sin 0 ° is approximated with the data in the data table, but if it is not approximated with the table data and is an abnormal value, sin 0 If there is no problem in the comparison result up to °, the abnormal value at sin 0 ° is determined as noise, and the point at sin 0 ° is determined as a trace sin 0 °. When sin 0 ° is detected, a counting operation is started to count the number of subsequent 100 μs interruptions (27).
[0068]
  Please refer to FIG. The count of the number of executions of the 100 μs interrupt continues until a sin 90 ° point is detected (31-37). At the time when sin 90 ° is detected or traced, the count value Tc (the elapsed time from sin 0 ° to sin 90 °) of the number of times 100 μs interrupt has been executed is saved (38).
[0069]
  When the end of the flow of FIG. 9 is reached, the processing of FIG. 10 is started simultaneously with returning to the processing of FIG. The process of FIG. 10 will be described next.
[0070]
  Here, since the time length from the next quarter period sin 90 ° to sin 180 ° is considered to be equal to the time length from sin 0 ° to sin 90 °, the time length corresponding to the saved count value Tc, that is, The time length from sin 0 ° to sin 90 ° is determined as the time length from sin 90 ° to the next zero cross point sin 180 °. As a result, the timing of the next zero cross point sin 180 ° can be predicted and calculated.
[0071]
  Please refer to FIG. When the count value Tc is saved, the timing setting for generating the zero cross signal and the output of the zero cross signal are performed here. A process of creating a zero-cross pulse with a pulse width of 2 ms wide centered on the zero-cross point predicted above (after Tc from the current time) is performed. That is, at the time when 1 ms (100 μs × 10) is subtracted from the length Tc (100 μs × Tc) from the sin 90 ° time point to the zero cross point at the sin 180 ° time point, the output of the zero cross signal is set to the low level representing the zero crossing. Specifically, the calculation is made based on the count value Tc saved above. In order to set the start timing of the zero cross pulse after “Tc-1 ms”,
            Timer value A = Tc-10
(41). Next, the timing for returning the zero cross signal from the low level to the high level, that is, the end timing of the zero cross pulse is calculated. At the time when 1 ms is added from the time of sin 180 °, the output of the zero cross signal is set to the high level. Specifically, the calculation is made based on the count value Tc saved above. In order to set the end timing of the zero cross pulse to “Tc + 1 ms”,
            Timer value B = Tc + 10
(42).
[0072]
  Thereafter, the timer value A of the timer for setting the zero cross signal to Low from the timing of sin 90 ° and the timer value B for returning the zero cross signal to the High level are started (43), and the level of the zero cross signal is switched by timer interrupt processing. I do. That is, when the timer of timer value A expires, the zero cross signal is switched to the low level (44, 45), and when the timer of timer value B expires, the zero cross signal is returned to the high level (46, 47). Thereby, the pulse width of the zero cross pulse is always 2 ms (100 μs × 20).
[0073]
  Subsequent calculation of the next zero cross point and signal generation repeat the above process.
[0074]
  There are 50 Hz frequency bands and 60 Hz frequency bands in Japan. The determination of which power source frequency is may be performed by the MPU 51 that receives a zero cross signal.
[0075]
  Even if the power supply frequency is 50 Hz or 60 Hz, the zero cross pulse width is constant at 2 ms, so the time required from the zero cross pulse interrupt to the true zero cross is constant regardless of the power supply frequency. ON / OFF processing can be performed.
[0076]
  As described above, when the main power switch is turned on, the DSP instructs all of the 5V generators PC1 to 38V generator PC4 to generate DC voltages, and when all of them generate respective DC voltages, the printer The CPU of the controller 60 instructs each part of the copying machine to execute a homing operation for adjusting a homing position such as a scanner position and a FIN (finisher) tray position.
[0077]
  When the homing operation is finished, the CPU of the printer controller 60 checks whether or not the power saving function is set. If the power saving function is set, the 12V generation unit PC2 and the 24V generation unit PC3 that are DC voltages that are not required to be generated are set. Commands the DSP 85 to stop the DC voltage generation of the 38V generator PC4. In response to this, the DSP 85 stops the voltage generation control of the generation units PC2 to PC4. This is done by opening the PWM pulse output ports to these generators PC2 to PC4 to the FET off instruction level and stopping the PWM pulse output to them. Thereby, the power consumption inside the generation units PC2 to PC4 is substantially eliminated.
[0078]
  Thereafter, normal processing of the copying machine is performed. Normal copying machine operations are well known and will not be described. As is well known in this normal processing, the CPU of the printer controller 60 sets the power saving mode when there is no copy or print instruction and there is no operation on the operation unit 20 and the set time has elapsed. In this embodiment, the DSP 85 is instructed to stop the DC voltage generation of the generators PC2 to PC4. In response to this, the DSP 85 stops the voltage generation control of the generation units PC2 to PC4.
[0079]
  When the copying machine is warmed up and scanning is set in a copy-ready state, for example, when an original is placed on the contact glass and the copy start key is pressed, the CPU of the printer controller 60 sets the scanning setting. It is determined that it has been made, and the DSP 85 is instructed to turn on DC voltage generation of the 38V generator PC4. In response to this, the DSP 85 starts PWM pulse output to the 38V generation unit PC4, and the 38V generation unit PC4 supplies a 38V voltage to the motor driver of the scanner motor. The CPU of the printer controller 60 issues an ON command to the 38V generator PC4 after issuing the ON command of the 38V generator PC4 based on the delay time data until the 38V voltage of the 38V generator PC4 rises in the nonvolatile memory inside the printer controller 60. The clock pulses are counted until the time corresponding to the delay time data has passed. That is, time is measured. If the delay time has passed, a command to start the scanner is sent to the motor control unit on the scanner control board 11.
[0080]
  When the scanning of the original is completed and the scanner operation is no longer necessary, the CPU of the printer controller 60 instructs the DSP 85 to stop the 38V voltage generation of the 38V generation unit PC4 when it becomes unnecessary. The DSP 85 stops the 38V voltage generation control of the 38V generator PC4. Thereafter, the CPU of the printer controller 60 performs normal processing of the copying machine.
[0081]
  Similarly, if a document is set on the ADF (automatic document feeder) 30 and the copy start key is pressed, it is determined that the ADF has been set, and the CPU of the printer controller 60 determines that the 38V generator PC4 and the 24V voltage generator. Command to generate voltage for PC3. In response to this, the DSP 85 generates and controls 38V voltage and 24V voltage. As a result, 38V voltage and 24V voltage are supplied to the ADF 30.
[0082]
  The CPU of the printer controller 60 determines the ON command based on the delay time data until both the 38V voltage of the 38V generator PC4 and the 24V voltage of the 24V generator PC3 are stored in the nonvolatile memory in the controller 60. The time is measured until the time for the delay time data has passed since the issue. If it passes, an ADF operation enable command is given to the ADF 30.
[0083]
  When an original is set in the ADF 30 and the copy start key is pressed, the scanner also moves at the same time, so scan setting is also performed at the same time. Since the operation at the time of scan setting is as described above, a description thereof is omitted here.
[0084]
  When all the documents set in the ADF have been sent, the ADF is not set, and the CPU of the printer controller 60 instructs the DSP 85 to stop the voltage generation of the 38V generator PC4 and the 24V voltage generator PC3. In response to this, the DSP 85 stops the generation control of the 38V voltage and the 24V voltage. That is, power supply to the ADF 30 is stopped.
[0085]
  The same applies to the use of FIN (finisher). When the peripheral machine FIN is connected to the copying machine main body and the paper is discharged, the CPU of the printer controller 60 determines the FIN setting. The subsequent processing is the same as that for scan setting and ADF setting.
[0086]
  The copier of this embodiment has a power saving mode. This means that when the copier is not used for a long time, only the 5V voltage of the 5V generator PC1 is left, the other DC voltages are turned off, and although not shown, the AC power supply to the fixing heater is turned off, In this mode, a low power consumption state is realized. This power saving mode automatically shifts when the copying machine is not operated for a preset time. Alternatively, when the power subkey on the operation unit 20 is pressed for a few seconds, the process proceeds. To cancel the power saving mode, press the power subkey for a few seconds.
[0087]
  When the set time elapses without the copying machine being used, or when there is an instruction to shift to the power saving mode by the power sub key, the CPU of the printer controller 60 sets the power saving mode and the DSP 85 other than the 5V generator PC1 is set. The DC voltage generation (PC2 to PC4) is instructed to stop. When the power saving mode is set, if the power sub key is pressed for a few seconds, or if there is an operator operation on the copying machine or a print command from the host (personal computer), the CPU of the printer controller 60 switches the power saving mode. It cancels and instructs the DSP 85 to generate DC voltages of the generation units PC2 to PC4.
[0088]
【The invention's effect】
  Accurate detection of AC voltage zero crossing. Accurate zero-cross detection can be performed even with an AC power supply with noise.
[Brief description of the drawings]
FIG. 1 is a front view showing an appearance of a color copying machine according to an embodiment of the present invention.
2 is a longitudinal sectional view showing an outline of an internal mechanism of the color printer 100 shown in FIG. 1. FIG.
3 is a block diagram showing a system configuration of an electric system of the copying machine shown in FIG.
4 is a block diagram showing an outline of a switching power supply unit 80dc on the DC power / AC control board 80 shown in FIG. 3. FIG.
5 is a block diagram showing an outline of an electric circuit of a 5V generator PC1 and a switch circuit 83 shown in FIG.
6 is a flowchart showing sampling of AC amplitude for AC power frequency determination by the digital signal processor DSP 85 shown in FIGS. 4 and 5. FIG.
FIG. 7 is a flowchart showing an AC power supply frequency determination based on sampling data in the DSP 85;
FIG. 8 is a flowchart showing a first part of processing of DSP 85 for detecting zero-crossing of AC power supply voltage and generating zero-crossing pulses.
FIG. 9 is a flowchart showing a second part of processing of DSP 85 for detecting zero-crossing of AC power supply voltage and generating zero-crossing pulses.
FIG. 10 is a flowchart showing a third part of processing of DSP 85 for detecting zero-crossing of AC power supply voltage and generating zero-crossing pulses.
11 is a graph showing a detection output of an ideal AC power supply voltage half wave of the power supply waveform detection circuit 86 shown in FIG. 4. FIG.
FIG. 12 is a waveform diagram showing an AC voltage carrying noise and a zero cross pulse generated by a conventional zero cross detection circuit.
[Explanation of symbols]
35: Paper feed bank 36: Mass feed tray
114: Photoconductor 115: Intermediate transfer belt
116, 117: Transcription charger
119: Charger charger
120: Developer 123: Fixing device
143: Polygon mirror
RA1: Electric coil and relay piece of electric relay
DRIV1: Switching driver
ISEN1, 2: Current detection circuit
VSEN1: Voltage detection circuit
CV1: Constant voltage circuit

Claims (6)

The starting point of the half-wave of the monitored AC voltage by repetitively reading the amplitude of the full-wave rectified waveform of the monitored AC voltage in a short cycle by A / D conversion and the amplitude data of the AC voltage held in the memory = repetition timing of the determination that a timing of determination and half-wave apex of which was the end point, and starts counting at the timing when a half-wave start = end point was the apex of the half-wave timing A zero-cross detection method for determining a zero-cross pulse having a level representing a zero-cross only between the start-end timing and the end-timing, by determining the start-end timing and end-end timing of the zero-cross pulse from the measured time value. The amplitude of the full-wave rectified waveform of the monitored AC voltage is repeatedly read in a short cycle by A / D conversion over a period exceeding 1 cycle / 4, and the obtained amplitude data group has a specific constant frequency held in the memory. Check the frequency of the AC voltage to be monitored against the amplitude data group of the AC voltage,
Monitored AC by comparing the amplitude of the full-wave rectified waveform of the monitored AC voltage in a short cycle by A / D conversion with the amplitude data of the determined AC voltage held in the memory. Repeat the determination voltage is either timing became apex of the judgment and a half-wave or the timing of a start point = end point of the half-wave, and starts counting at the timing when a half-wave start = end point, a half-wave A zero-cross detection method for generating a zero-cross pulse having a level representing a zero-cross only between the start-end timing and the end-timing, by determining a start-end timing and an end-timing of the zero-cross pulse from a measured time value of the timing at which the zero-cross is reached. A rectifier circuit that converts AC voltage to DC voltage;
Generated in the transformer, the switching element that switches the DC voltage output from the rectifier circuit and supplies power to the primary winding of the transformer, the switching driver that drives the switching element on / off in response to the PWM pulse, and the secondary winding of the transformer A plurality of switching power supply circuits including a diode for rectifying the voltage to be applied; and
A PWM pulse is applied to each of the switching power supply circuits to control the generation of individual DC voltages, and the amplitude of the full-wave rectified waveform of the AC voltage is repeatedly read in a short cycle by A / D conversion and held in a memory. by matching the amplitude data of the AC voltage is, the monitored AC voltage and determining whether timing has become vertices of the determination and a half-wave or the timing of a start point = end point of the half-wave, repeatedly, the half-wave Level that starts timing at the timing when the start point = end point, determines the start and end timings of the zero cross pulse from the timing value of the timing at which the half wave peaked, and represents the zero cross only between the start and end timings Power output controller that generates zero-crossing pulses;
A power supply device comprising: The power supply device according to claim 3, wherein a period between the start timing and the end timing is constant . The start timing is a timing shorter by half of the zero cross pulse width than the timing value of the half-wave apex, and the end timing is half the zero cross pulse width of the timing of the half-wave apex. It is timing; The power supply device of Claim 3 or 4 . Photoconductor, charger for charging the same, exposure device for exposing image light to the charged surface of the photoconductor, developer for developing an electrostatic latent image generated by exposure, and means for transferring the developed image to transfer paper And an image forming apparatus including a fixing device that fixes a visible image of the transfer paper to the transfer paper,
Furthermore, the power supply device according to any one of claims 3 to 5 is provided;
The power supply device further includes a fixing energization circuit having a triac for applying the AC voltage to a heater of the fixing device;
The image forming apparatus further generates an on-phase control unit that generates a triac control signal having an on instruction level at a timing when the triac based on the zero cross pulse is to be turned on and supplies the triac control signal to the triac;
An image forming apparatus comprising:

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