JP6204342B2 - Power supply apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a power supply apparatus and an image forming apparatus that supply power from an AC power source to a power supply target.

  In an image forming apparatus that prints image data on a transfer medium such as paper by an electrophotographic method, such as a printer, a copier, or a multi function peripheral (MFP), unfixed toner transferred to the transfer medium A fixing unit is provided that melts the image by heat and fixes the image on the transfer target. The fixing unit includes, for example, a fixing roller with a built-in heater and a pressure roller that is pressed against the fixing roller. When the transfer body to which the toner image is transferred passes between the fixing roller and the pressure roller, the toner image is fixed to the transfer body by heat and pressing force.

  A resistor, a halogen lamp, or the like is used for the heater of the fixing unit. This heater is connected to an AC power source (commercial power source) via a switching element such as a triac. In addition, a temperature sensor is disposed in the fixing unit, and the output of the heater is increased or decreased based on the output of the temperature sensor.

  Phase control is widely used for such heater output control. That is, the output of the heater is controlled by changing the phase angle of the AC waveform by switching the switching element from the OFF state to the ON state based on the zero cross signal output based on the zero cross of the AC waveform of the AC power supply. ing.

  In such a configuration, spike-like distortion occurs in the AC waveform of the AC power source due to the operation of switching the switching element from the OFF state to the ON state. This distortion is caused by a resonance phenomenon between the circuit impedance (particularly capacitive load) of the image forming apparatus and the impedance of the AC power supply (impedance of the indoor wiring network).

  When such a distortion occurs in the waveform of the AC power supply, the above-mentioned zero cross may occur at a position where it should not occur. In this case, the heater cannot be normally controlled. In addition, flickers that cause periodic brightness and darkness in devices (for example, lighting fixtures) connected to the same AC power source may occur due to such heater control abnormality.

  As a countermeasure against this type of problem, for example, Patent Document 1 discloses that between a diode bridge that rectifies an AC power supply and a rectifying capacitor in order to suppress flickering of LED lighting devices and fluorescent lamp inverter lighting devices that consume a large amount of power. Discloses a configuration in which a power control element (FET) is provided. In this configuration, at the same time as the triac is turned on, the conduction operation of the power control element is started, and the power control element is driven so that no oscillating current flows in the input current of the power supply device.

JP2013-012452A

  However, in the technique disclosed in Patent Document 1, each time the triac is turned on, the power control element that functions as a damping resistor is turned on. Therefore, when the triac is turned on, power loss is always generated in the power control element. That is, there is a disadvantage that power consumption is large.

  The present invention has been made in view of such conventional circumstances, and a power supply device capable of suppressing the occurrence of power supply abnormality with respect to a power supply target with a smaller power loss than in the past and An object is to provide an image forming apparatus.

  In order to achieve the above object, the present invention employs the following technical means. First, the present invention can provide a power supply device that supplies power from an AC power supply to a power supply target. That is, the power supply apparatus according to the present invention includes a switch unit, a zero cross detection unit, a supply power control unit, a distortion suppression circuit, a suppression circuit connection unit, and a circuit connection control unit. The switch unit is provided between the AC power supply and the power supply target, and switches between a power supply state and a power cut-off state. The zero cross detection unit detects the zero cross of the AC waveform by comparing the AC waveform of the AC power source with a predetermined threshold value, and outputs a zero cross signal. The supply power control unit controls the phase angle of the AC waveform that switches the switch unit from the power cut-off state to the power supply state based on the zero cross signal output from the zero cross detection unit, thereby determining the power supply ratio to the power supply target. Change. The distortion suppression circuit is connected to an electric circuit between the power supply target and the AC power source, and suppresses distortion generated in the AC waveform due to the switch unit switching from the power cutoff state to the power supply state. The suppression circuit connection unit switches between a state in which the distortion suppression circuit is electrically connected to the electric circuit and a state in which the distortion suppression circuit is electrically separated from the electric circuit. The circuit connection control unit sets the suppression circuit connection unit in a state in which the distortion suppression circuit and the electric circuit are electrically connected when the phase angle used by the supply power control unit belongs to a predetermined range. Further, when the phase angle used by the supply power control unit does not belong to the range specified in advance, the suppression circuit connecting unit is set in a state where the distortion suppression circuit and the electric circuit are electrically separated.

  In this power supply device, the distortion suppression circuit is selectively connected to an electric path between the power supply target and the AC power supply, thereby suppressing distortion generated in the AC waveform due to switching to the power supply state. be able to. That is, when the phase angle used by the supply power control unit belongs to the range specified in advance, the distortion suppression circuit is selectively connected to the electric circuit between the power supply target and the AC power supply. Therefore, since the distortion suppression circuit is selectively connected only when it is necessary to suppress the distortion generated in the AC waveform, the generation of the waveform distortion of the AC power supply is suppressed with a smaller power loss than in the past. be able to.

  In this power supply device, the above-described predesignated range can be set based on, for example, the peak value of the AC waveform, the magnitude of distortion generated in the AC waveform, and the threshold value used for detecting the zero cross. . Moreover, the distortion suppression circuit can employ a configuration including a damping resistor, for example.

  On the other hand, from another viewpoint, the present invention can provide an image forming apparatus. That is, an image forming apparatus according to the present invention includes the above-described power supply device, a transfer unit, and a fixing unit. The transfer unit transfers the toner image onto the transfer target. The fixing unit is the above-described power supply target, and heats and fixes the toner image transferred onto the transfer target to the transfer target.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the electric power supply abnormality with respect to electric power supply object can be suppressed with a smaller electric power loss compared with the past.

1 is a schematic configuration diagram illustrating an overall configuration of an image forming system according to an embodiment of the present invention. The figure which shows the hardware constitutions of the multifunctional device in one Embodiment of this invention. The figure which shows the structure of the electric power supply part with which the multifunctional device in one Embodiment of this invention is provided. 1 is a circuit diagram showing a zero-cross detection unit included in a multifunction machine according to an embodiment of the present invention. The figure which shows an example of the electric power supply by the electric power supply part with which the compound machine in one Embodiment of this invention is provided. The figure which shows an example of the electric power supply by the electric power supply part with which the compound machine in one Embodiment of this invention is provided. The figure which shows an example of the electric power supply by the electric power supply part with which the compound machine in one Embodiment of this invention is provided. The flowchart which shows an example of the electric power supply procedure which the electric power supply part with which the multifunctional machine with which one Embodiment of this invention is provided implements is shown. The figure which shows an example of the distortion suppression range set to the electric power supply part with which the multifunctional device in one Embodiment of this invention is provided.

  Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings. In the following, the present invention is embodied as a digital multifunction machine.

  FIG. 1 is a schematic configuration diagram illustrating an example of the overall configuration of a digital multifunction peripheral according to the present embodiment. As shown in FIG. 1, the multifunction peripheral 100 includes a main body 101 including an image reading unit 120 and an image forming unit 140, and a platen cover 102 attached above the main body 101. An operation panel 171 is provided on the front surface of the multi-function device 100 so that a user can give a copy start or other instruction to the multi-function device 100, and can check the status and settings of the multi-function device 100.

  An image reading unit 120 is provided on the upper portion of the main body 101. The image reading unit 120 reads an image of a document with the scanning optical system 121 and generates digital data (image data) of the image.

  The generated image data can be printed on a sheet as a transfer medium in the image forming unit 140. The generated image data can also be transmitted to other devices through a network (not shown).

  The image forming unit 140 prints the image data generated by the image reading unit 120 or the image data received from another device connected to the network on a sheet that is a transfer target. The image forming unit 140 feeds paper from the manual feed tray 151, the paper feed cassettes 152, 153, and 154 to the transfer unit 155 that transfers the toner image. The sheet on which the toner image is transferred in the transfer unit 155 is conveyed to the fixing device 156. The fixing device 156 has a fixing roller 157 and a pressure roller 158 with a built-in heater, and fixes the toner image on the sheet by heat and pressing force. The image forming unit 140 discharges the sheet that has passed through the fixing unit 156 to the discharge tray 149.

  FIG. 2 is a hardware configuration diagram of a control system in the multifunction machine. The MFP 100 according to the present embodiment includes a central processing unit (CPU) 201, a random access memory (RAM) 202, a read only memory (ROM) 203, a hard disk drive (HDD) 204, an image reading unit 120, and an image forming unit 140. A driver 205 corresponding to each drive unit is connected via an internal bus 206. The ROM 203, the HDD 204, and the like store programs, and the CPU 201 controls the multifunction peripheral 100 in accordance with instructions from the control program. For example, the CPU 201 uses the RAM 202 as a work area, and controls the operation of each driving unit by exchanging data and commands with the driver 205. The HDD 204 is also used to store image data obtained by the image reading unit 120 and image data received from other devices via a network.

  An operation panel 171 and various sensors 207 are also connected to the internal bus 206. The operation panel 171 receives a user operation and supplies a signal based on the operation to the CPU 201. Further, the operation panel 171 displays an operation screen on a display provided in the operation panel 171 according to a control signal from the CPU 201. The sensor 207 includes various sensors such as an open / close detection sensor for the platen cover 102, a document detection sensor on the document table, a temperature sensor for the fixing device 156, and a detection sensor for the conveyed paper or document.

  FIG. 3 is a functional block diagram illustrating a power supply unit included in the multifunction peripheral according to the present embodiment. Here, only a portion for supplying AC power supplied from a commercial AC power source to the heater of the fixing roller 157, which is a power supply target, is shown. Note that the DC power used in each part of the MFP 100 including the CPU 201 described above is generated by an AC-DC converter (not shown) using AC power supplied from an AC power supply.

  In the example of FIG. 3, the power supply unit 300 of the multifunction device 100 is connected to the indoor wiring system 400 of the building where the multifunction device 100 is installed. In the indoor wiring system 400, the AC power supply 401 is connected to a power outlet by indoor wiring, and the power supply unit 300 and the AC power supply 401 are connected by inserting the outlet plug included in the power supply unit 300 into the power outlet. The

  As illustrated in FIG. 3, the power supply unit 300 includes a switch unit 301, a zero cross detection unit 302, a supply power control unit 303, a distortion suppression circuit 304, a suppression circuit connection unit 305, and a circuit connection control unit 306.

  The switch unit 301 is provided in a power supply line (electric circuit) between the AC power supply 401 and the heater 500, and switches between a power supply state and a power cut-off state. Although not particularly limited, in the present embodiment, the switch unit 301 includes a triac 311. By switching between the energized state and the cut-off state of the triac 311, the power supply state and the power cut-off state between the AC power supply 401 and the heater 500 are switched.

  The switch unit 301 includes a phototriac coupler 312. The phototriac coupler 312 includes a light emitting diode and a phototriac, and is connected to the triac 311 so that the triac 311 is energized when the light emitting diode is energized and light is incident on the phototriac. . As is well known, the triac 311 enters a cut-off state when a reverse voltage is applied or when a current flowing through the triac 311 becomes zero.

  The anode side of the light emitting diode of the phototriac coupler 312 is connected to a voltage source via a current limiting resistor 314, and the cathode side of the light emitting diode is grounded via a transistor 313. In this configuration, when the transistor 313 is turned on, the triac 311 is energized, and the AC power supply 401 and the heater 500 are in a power supply state. Note that a control signal for switching the on state and the off state of the transistor 313 is input from the supply power control unit 303 to the transistor 313.

  The zero cross detection unit 302 detects the zero cross of the AC waveform by comparing the AC waveform of the AC power supply 401 with a predetermined threshold value, and outputs a zero cross signal. FIG. 4 is a circuit diagram showing the zero-cross detection unit 302 in the present embodiment.

  As shown in FIG. 4, the zero-cross detection unit 302 includes a diode bridge circuit 321 that full-wave rectifies the AC waveform of the AC power supply 401. The anode of the light emitting diode of the photocoupler 323 is connected to the diode bridge circuit 321 via the current limiting resistor 322. The collector side of the phototransistor of the photocoupler 323 is connected to a voltage source via a resistor 324, and the emitter side is grounded. Further, an inverter circuit (NOT circuit) including a resistor 325, a capacitor 326, a transistor 327, and a resistor 328 is connected to the collector of the phototransistor. In this configuration, a negative logic of the logic level (High level or Low level) of the collector of the phototransistor of the photocoupler 323 is output from the output terminal 329.

  In the zero cross detection unit 302 illustrated in FIG. 4, for example, when the absolute value of the output voltage of the AC power supply 401 decreases, the light emission amount of the light emitting diode of the photocoupler 323 decreases. In this case, the resistance value of the phototransistor of the photocoupler 323 increases, and the potential input to the base of the transistor 327 increases. When the output voltage of the AC power supply 401 becomes smaller than the threshold voltage, the transistor 327 is turned on, and the potential of the output terminal 329 becomes a low level.

  Further, when the absolute value of the output voltage of the AC power supply 401 increases, the light emission amount of the light emitting diode of the photocoupler 323 increases. In this case, the resistance value of the phototransistor of the photocoupler 323 decreases, and the potential input to the base of the transistor 327 decreases. When the output voltage of the AC power supply 401 becomes larger than the threshold voltage, the transistor 327 is turned off, and the potential of the output terminal 329 becomes High level.

  Therefore, as illustrated in FIG. 5A, the zero-cross detection unit 302 is at a low level while the AC waveform of the AC power supply 401 is in the range between the positive and negative thresholds Th, and is high when the AC waveform is outside the range. A zero-cross signal that is level is output. The zero cross signal is input to the supply power control unit 303.

  Based on the zero cross signal output from the zero cross detection unit 302, the supply power control unit 303 controls the phase angle of the AC waveform that switches the switch unit 301 from the power cut-off state to the power supply state. Change the supply rate. As described above, the supply power control unit 303 controls the amount of power supplied to the heater 500 by the heater control signal input to the base of the transistor 313. The supplied power control unit 303 inputs a heater control signal for controlling the transistor 313 to be turned on after a predetermined time has elapsed from a specific timing in the zero-cross signal (that is, at a specific phase angle). Although not particularly limited, in the present embodiment, the supply power control unit 303 controls a periodic control signal that switches from a low level to a high level after a predetermined time has elapsed from the falling edge of the zero-cross signal as a reference. Output as a signal. Note that the reference of the elapsed time may be a specific timing in the AC waveform, and not only the falling edge of the zero cross signal but also the rising edge of the zero cross signal can be used.

  FIGS. 5A, 6 </ b> A, and 7 </ b> A are diagrams illustrating power supply to the heater 500. FIG. 5A corresponds to a case where the power supplied to the heater 500 is 50% of the latter half of the half wave of the AC waveform (phase angle 90 degrees, power ratio 50%). FIG. 6A corresponds to a case where the electric power supplied to the heater 500 is 25% in the latter half of the half wave of the AC waveform (phase angle 135 degrees, power ratio about 9%). FIG. 7A corresponds to a case where the power supplied to the heater 500 is 75% of the latter half of the half wave of the AC waveform (phase angle 45 degrees, power ratio about 91%). 5A, 6A, and 7A, the horizontal axis corresponds to time. In each figure, an alternating current waveform, a waveform after full wave rectification, a zero cross signal, a heater control signal, and a heater supply waveform are shown in order from the top. Here, the AC waveform, the waveform after full-wave rectification, and the heater supply waveform are voltage waveforms. Further, the supply power control unit 303 starts heating control of the heater 500 from time Ts indicated in the heater control signal in each drawing.

  As shown in FIG. 5A, when the phase angle is 90 degrees, the supply power control unit 303 rises from the Low level to the High level when the time T1 elapses from the falling edge of the zero cross signal, and the zero cross A heater control signal that falls from a high level to a low level simultaneously with the fall of the signal is input to the transistor 313. Here, time T1 is a time interval from the falling edge of the zero-cross signal to the time when the phase angle reaches 90 degrees (the time when the AC waveform reaches the peak value).

  As shown in FIG. 6A, when the phase angle is 135 degrees, the supply power control unit 303 rises from the Low level to the High level when the time T2 has elapsed from the falling edge of the zero cross signal. The heater control signal that falls from the High level to the Low level simultaneously with the fall of the zero cross signal is input to the transistor 313. Here, the time T2 is a time interval from the falling edge of the zero-cross signal to the time point when the phase angle becomes 135 degrees.

  Further, as shown in FIG. 7A, when the phase angle is 45 degrees, the supply power control unit 303 rises from the Low level to the High level when the time T3 has elapsed from the falling edge of the zero cross signal. The heater control signal that falls from the High level to the Low level simultaneously with the fall of the zero cross signal is input to the transistor 313. Here, time T3 is a time interval from the falling edge of the zero-cross signal to the time point when the phase angle becomes 45 degrees.

  The distortion suppression circuit 304 is connected to an electric circuit between the heater 500 and the AC power supply 401, and suppresses distortion generated in the AC waveform due to the switch unit 301 switching from the power cutoff state to the power supply state. The distortion generated in the AC waveform includes a resistor 402 and an inductance 403 included in the indoor wiring of the indoor wiring system 400, and a bypass connected in parallel to the AC power supply 401 for the purpose of noise removal on the power input side of the power supply unit 300. This occurs due to the capacitor 307. As can be understood from FIG. 3, the resistor 402, the inductance 403, and the bypass capacitor 307 constitute a low-pass filter.

  In such a low-pass filter, a resonance phenomenon occurs at the cutoff frequency. In the phase control in which the switch unit 301 is periodically switched from the power cutoff state to the power supply state as described above, harmonic components are included due to the switching of the switch unit 301. As a result, as shown in FIG. 5B, FIG. 6B, and FIG. 7B, when the switch unit 301 switches from the power cut-off state to the power supply state, Spike-like distortion (decrease in signal level) may occur in the AC waveform. Note that the magnitude of the distortion changes according to the impedance of the power supply unit 300 viewed from the AC power supply side and the magnitude of the current that flows when the switch unit 301 switches from the power cutoff state to the power supply state.

  Although not particularly limited, in the present embodiment, the distortion suppression circuit 304 is configured by a circuit in which a damping resistor 341 and a capacitor 342 are connected in series. Here, the damping resistor 341 has a function of reducing the resonance Q value, and the capacitor 342 has a function of shifting the resonance frequency. As shown in FIG. 3, the distortion suppression circuit 304 is connected in parallel to the heater 500.

  Here, a problem caused by the occurrence of spike-like distortion in the AC waveform will be described. As described in detail below, when a spike-like distortion occurs in the AC waveform, the zero-cross signal may be disturbed. When disturbance occurs in the zero-cross signal, depending on conditions, the heater control signal generated by the supply power control unit 303 based on the falling edge of the zero-cross signal is also different from a desired state. That is, a situation occurs in which the heater 500 is turned on at an unintended timing.

  FIGS. 5B, 6 </ b> B, and 7 </ b> B are diagrams for explaining a state in which distortion occurs in the AC waveform during power supply to the heater 500. FIG. 5B corresponds to a case where the intended phase angle is 90 degrees. FIG. 6B corresponds to a case where the intended phase angle is 135 degrees. FIG. 7B corresponds to a case where the intended phase angle is 45 degrees. In FIGS. 5B, 6B, and 7B, the horizontal axis corresponds to time. In each figure, an alternating current waveform, a waveform after full wave rectification, a zero cross signal, a heater control signal, and a heater supply waveform are shown in order from the top. Here, the AC waveform, the waveform after full-wave rectification, and the heater supply waveform are voltage waveforms. Further, the supply power control unit 303 starts heating control of the heater 500 from time Ts indicated in the heater control signal in each drawing.

  As shown in FIG. 5B, when the intended phase angle is 90 degrees, as in the case shown in FIG. 5A, the supply power control unit 303 sets the time T1 from the falling edge of the zero-cross signal. When the time elapses, a heater control signal that rises from the Low level to the High level and falls from the High level to the Low level simultaneously with the fall of the zero cross signal is input to the transistor 313.

  In this case, spike distortion (voltage drop) occurs in the AC waveform at the rising edge of the heater control signal. However, in this example, since the rising edge of the heater control signal is located in the vicinity of the peak value of the AC waveform, the signal level does not fall within the range between the positive and negative thresholds Th even when distortion occurs. Therefore, the zero cross signal is the same as the case shown in FIG. Therefore, the heater control signal is also the same as the case shown in FIG. As a result, the power supply to the heater 500 (the operation of the heater 500) is also the same as the example shown in FIG.

  On the other hand, as shown in FIG. 6B, when the intended phase angle is 135 degrees, the supply power control unit 303 starts from the falling edge of the zero-cross signal as in the case shown in FIG. When the time T2 elapses, a heater control signal that rises from the Low level to the High level and falls from the High level to the Low level simultaneously with the fall of the zero cross signal is input to the transistor 313.

  In this example, the rising edge of the heater control signal is far from the position where the AC waveform reaches the peak value, so if a spike-like distortion (voltage drop) occurs at the rising edge of the heater control signal, the signal level becomes a positive / negative threshold value. Enter the range between Th. Therefore, as shown in FIG. 6 (b), the zero-cross signal is set to the High level immediately after the time T2 has elapsed from the falling edge of the zero-cross signal at the time Ts and immediately after falling according to the occurrence of distortion. stand up.

  The heater control signal generated by the supply power control unit 303 to which such a zero cross signal is input rises from the Low level to the High level when the time T2 has elapsed from the falling edge of the zero cross signal at time Ts. However, since the zero cross signal is at a low level due to distortion at the time of rising, the heater control signal immediately becomes a low level. Further, since the supply power control unit 303 uses the falling edge of the zero cross signal due to distortion as a reference for the next rising position of the heater control signal, the heater control signal is the falling edge of the zero cross signal due to distortion. Rises from Low level to High level when time T2 elapses.

  In the example of FIG. 6B, the AC waveform is located near the peak value at the rising edge of the heater control signal when the time T2 has elapsed from the falling edge of the zero-cross signal due to distortion. Therefore, even if spike-like distortion occurs at the rising edge of the heater control signal, the signal level does not fall within the range between the positive and negative threshold values Th. Therefore, the zero cross signal falls when the AC waveform subsequently enters a range between the positive and negative threshold values Th.

  Thereafter, since such an operation is repeated, the zero-cross signal rises at a phase angle of 135 degrees, as shown in FIG. 6B, and a pulse with a relatively short on-time and an AC waveform has a peak value. The waveform rises in the vicinity of the position and appears alternately with pulses having a relatively long on-time.

  As described above, the triac 311 is energized when the transistor 313 is turned on, and is then turned off when a reverse voltage is applied or when the current flowing through the transistor 313 becomes zero. Therefore, when the heater control signal as described above is input to the transistor 313, the heater supply waveform has a power supply portion of the energization time Ta corresponding to the rising at the position of the phase angle of 135 degrees, and the AC waveform has a peak value. A waveform appears alternately with the power supply portion of the energization time Tb corresponding to the rise in the vicinity of the position.

  As is clear from comparison with FIG. 6A, the power supply portion at time Ta is originally intended time, but the power supply portion at time Tb is longer than originally intended time Ta. Therefore, the ON time of the heater 500 is periodically disturbed, and normal heater control cannot be performed. Further, since the period of the disturbance does not coincide with the period of the AC waveform, such a periodic heater control abnormality can cause flicker.

  Further, as shown in FIG. 7B, when the intended phase angle is 45 degrees, the supply power control unit 303 starts from the falling edge of the zero-cross signal as in the case shown in FIG. When the time T3 has elapsed, a heater control signal that rises from the Low level to the High level and falls from the High level to the Low level simultaneously with the fall of the zero cross signal is input to the transistor 313.

  In this example, the rising edge of the heater control signal is away from the position where the AC waveform has a peak value. Therefore, when spike-like distortion occurs at the rising edge of the heater control signal, the signal level is between the positive and negative threshold values Th. Enter the range. For this reason, as shown in FIG. 7B, the zero-cross signal, when time T3 has elapsed from the falling edge of the zero-cross signal at time Ts, immediately goes to the High level immediately after falling according to the occurrence of distortion. stand up.

  The heater control signal generated by the supply power control unit 303 to which such a zero cross signal is input rises from the Low level to the High level when the time T3 has elapsed from the falling edge of the zero cross signal at time Ts. However, since the zero cross signal is at a low level due to distortion at the time of rising, the heater control signal immediately becomes a low level. Further, since the supply power control unit 303 uses the falling edge of the zero cross signal due to distortion as a reference for the next rising position of the heater control signal, the heater control signal is the falling edge of the zero cross signal due to distortion. Rises from the Low level to the High level when the time T3 has elapsed.

  In the example of FIG. 7B, the rising edge of the heater control signal when the time T3 has elapsed from the falling edge of the zero-cross signal due to distortion is the same energization period of the triac 311 caused by the immediately preceding rising edge. include. That is, the triac 311 is not switched from the shut-off state to the energized state by the rising edge of the heater control signal. Therefore, no spike-like distortion occurs at the rising edge of the heater control signal. The zero cross signal falls thereafter when the AC waveform enters a range between the positive and negative threshold values Th. Thereafter, since such an operation is repeated, the zero cross signal is a pulse with a relatively short on-time that rises at a position where the phase angle is 45 degrees as shown in FIG. 7B, and then the same in the triac 311. The waveform rises within the energization period, and the pulses appear alternately with pulses having a relatively long on-time.

  When the heater control signal as described above is input to the transistor 313, disturbance of the heater control signal within the same energization period in the triac 311 does not affect the state of the triac 311 at all. Therefore, although periodic disturbance occurs in the heater control signal, the power supply to the heater 500 (operation of the heater 500) is the same as the case shown in FIG.

  The suppression circuit connection unit 305 switches between a state in which the distortion suppression circuit 304 is electrically connected to the electric circuit between the heater 500 and the AC power supply 401 and a state in which the distortion suppression circuit 304 is electrically separated from the electric circuit. In the present embodiment, the suppression circuit connection unit 305 includes a transistor switch connected in series to the distortion suppression circuit 304. By turning on the transistor switch, the distortion suppression circuit 304 is electrically connected to the electric circuit between the heater 500 and the AC power supply 401. Further, by turning off the transistor switch, the distortion suppression circuit 304 is electrically separated from the electric circuit between the heater 500 and the AC power supply 401.

  The circuit connection control unit 306 is configured to electrically connect the suppression circuit connection unit 305 to the distortion suppression circuit 304 and the above-described electric circuit when the phase angle used by the supply power control unit 303 belongs to the range specified in advance. And In addition, when the phase angle used by the supply power control unit 303 does not belong to the range specified in advance, the circuit connection control unit 306 makes the suppression circuit connection unit 305 electrically connected to the distortion suppression circuit 304 and the above-described electric circuit. Let it be in a state of separation.

  As described above, in the present embodiment, the suppression circuit connection unit 305 is configured by a transistor switch. Therefore, in the present embodiment, the circuit connection control unit 306 is configured to input a control signal for switching between the ON state and the OFF state of the suppression circuit connection unit 305 to the control terminal of the transistor switch.

  In the above configuration, the power supply control unit 303 and the circuit connection control unit 306 can be realized by the CPU 201 executing, for example, a program stored in the ROM or HDD using the RAM as a work area.

  FIG. 8 is a flowchart illustrating an example of a power supply procedure performed by the power supply unit included in the multifunction peripheral. The procedure starts with, for example, a power supply instruction to the heater 500 being input to the supply power control unit 303 as a trigger. At this time, the supply power control unit 303 determines the phase angle based on the input power supply instruction and the temperature of the heater 500.

  When this procedure starts, the circuit connection control unit 306 acquires the phase angle from the supply power control unit 303 (step S801). Then, the circuit connection control unit 306 compares the acquired phase angle with a predesignated angle range (step S802). The angle range can be set based on, for example, the peak value of the AC waveform, the magnitude of distortion generated in the AC waveform, and the threshold Th used for detecting the zero cross. More specifically, as the angle range, the angle range in which the heater control signal may be disturbed as described above, that is, the angle range in the vicinity of the peak value and the angle range in which the zero-cross detection unit 302 outputs a low level. A range excluding can be set.

  FIG. 9 is a diagram illustrating an example of the distortion suppression angle range specified by the circuit connection control unit 306 in the waveform after full-wave rectification. FIG. 9 shows that the phase angle range in which the zero-cross signal is at the low level is 0 degree to 20 degrees, 160 degrees to 200 degrees, 340 degrees to 360 degrees, and the angle range of the phase angle near the above-described peak value. Is a case where the phase angle is in the range of 70 to 110 degrees and 250 to 290 degrees. In this example, each range of 20 degrees to 70 degrees, 110 degrees to 160 degrees, 200 degrees to 250 degrees, 290 degrees to 340 degrees may cause disturbance in the heater control signal. The circuit connection control unit 306 designates a certain angle range. Here, the range in which the heater control signal may be disturbed is set as the above-mentioned angle range, but the heater control signal is disturbed as in the case of the above-described phase angle of 135 degrees. However, the configuration may be such that the angle range is set except for the phase angle range in which no disturbance occurs in the control of the heater itself.

  When the acquired phase angle belongs to the specified angle range, the circuit connection control unit 306 inputs the control signal for turning on the suppression circuit connection unit 305 to the suppression circuit connection unit 305, thereby causing the distortion suppression circuit 304 to Then, it is electrically connected to the electric path between the heater 500 and the AC power supply 401 (steps S802 Yes, S803). On the other hand, when the acquired phase angle does not belong to the specified angle range, the circuit connection control unit 306 inputs a control signal for turning off the suppression circuit connection unit 305 to the suppression circuit connection unit 305, thereby suppressing distortion. The circuit 304 is electrically separated from the electric circuit between the heater 500 and the AC power supply 401 (steps S802 No, S806).

  The above process is continued until the heater control end instruction is input to the supply power control unit 303 (No in steps S804 and S805). In addition, when the phase angle used for heater control is changed, the supplied power control unit 303 notifies the circuit connection control unit 306 to that effect. In response to the notification, the circuit connection control unit 306 acquires the phase angle from the supply power control unit 303 and performs the above procedure again based on the acquired phase angle (steps S804 Yes and S801). When an instruction to end heater control is input to the supply power control unit 303, the procedure ends (Yes in step S805).

  As described above, in the multi-function device 100, the distortion suppression circuit 304 is selectively connected to the electric circuit between the heater 500 and the AC power supply 401 that are power supply targets, so that the power supply state is changed from the power cut-off state. It is possible to suppress the distortion that occurs in the AC waveform due to the switching. That is, when the phase angle used by the power supply control unit 303 belongs to the range specified in advance, the distortion suppression circuit 304 is selectively connected to the electric circuit between the heater 500 and the AC power supply 401. Therefore, since the distortion suppression circuit 304 is selectively connected only when it is necessary to suppress the distortion generated in the AC waveform, the waveform distortion of the AC power supply 401 can be generated with a smaller power loss than in the prior art. Can be suppressed.

  Moreover, since it is possible to prevent the heater 500 from being abnormally driven at a period different from the period of the AC waveform, it is possible to suppress the occurrence of flicker due to the abnormal driving.

  The above-described embodiments do not limit the technical scope of the present invention, and various modifications and applications other than those already described are possible within the scope of the present invention. For example, the circuit configurations of the switch unit 301, the zero-cross detection unit 302, and the distortion suppression circuit 304 shown in the above embodiment are merely examples, and any circuit configuration that exhibits the same effect can be adopted. The distortion suppression circuit 304 preferably includes a damping resistor 341. However, if the distortion generated in the AC waveform due to the switch unit 301 switching from the power cutoff state to the power supply state can be suppressed, the damping resistor 341 The structure which does not contain may be sufficient.

  In addition, in the above-described embodiment, the present invention is embodied as a digital multi-function peripheral having a power supply unit. However, the present invention is not limited to a digital multi-function peripheral, and is not limited to a digital multi-function peripheral. The present invention can also be applied to any power supply apparatus that supplies power.

  According to the present invention, it is possible to suppress the occurrence of power supply abnormality with respect to a power supply target with a smaller power loss than in the prior art, which is useful as a power supply apparatus and an image forming apparatus.

100 MFP (image forming device)
140 Image forming section 155 Transfer section 156 Fixing device (fixing section)
300 Power supply unit (power supply device)
DESCRIPTION OF SYMBOLS 301 Switch part 302 Zero cross detection part 303 Supply power control part 304 Distortion suppression circuit 305 Suppression circuit connection part 306 Circuit connection control part 341 Damping resistance 401 AC power supply 500 Heater (electric power supply object)

Claims (4)

A power supply device that supplies power from an AC power source to a power supply target,
A switch unit that is provided between the AC power source and the power supply target, and switches between a power supply state and a power cut-off state;
Detecting a zero cross of the alternating current waveform by comparing the alternating current waveform of the alternating current power supply with a predetermined threshold, and outputting a zero cross signal;
Based on the zero-cross signal output from the zero-cross detection unit, the power supply ratio to the power supply target is changed by controlling the phase angle of the AC waveform that switches the switch unit from the power cutoff state to the power supply state. A power supply control unit;
A distortion suppression circuit that is connected to an electric circuit between the power supply target and the AC power supply, and that suppresses distortion generated in the AC waveform due to the switch unit switching from a power cut-off state to a power supply state;
A suppression circuit connection unit that switches between a state of electrically connecting the distortion suppression circuit to the electrical circuit and a state of electrical isolation from the electrical circuit;
When the phase angle used by the supply power control unit belongs to a predetermined range, the suppression circuit connection unit is set in a state in which the distortion suppression circuit and the electric circuit are electrically connected, and the supply power control unit When the phase angle used by does not belong to a predesignated range, the suppression circuit connection unit, the circuit connection control unit for bringing the distortion suppression circuit and the electrical circuit into a state of being electrically separated,
A power supply device comprising:   2. The power supply according to claim 1, wherein the predetermined range is set based on a peak value of the AC waveform, a magnitude of the distortion generated in the AC waveform, and a threshold used for detection of the zero crossing. apparatus.   The power supply device according to claim 1, wherein the distortion suppression circuit includes a damping resistor. The power supply device according to any one of claims 1 to 3,
A transfer portion for transferring a toner image onto a transfer target;
A fixing unit that is the power supply target and heats and fixes the toner image transferred onto the transfer target member to the transfer target member;
An image forming apparatus comprising:

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