JP5556165B2 - Power supply device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a power supply apparatus that supplies power to two systems from an AC original power supply. More specifically, the present invention relates to a power supply device that performs a first power supply via an active filter and a second power supply not via an active filter. Further, the present invention relates to an image forming apparatus equipped with the above power supply apparatus, wherein the heater of the fixing unit is heated by the second power supply and the other parts are driven by the first power supply. is there.

  2. Description of the Related Art Conventionally, a power supply device that supplies power to multiple systems from a single source power supply has been used. For example, in the image forming apparatus disclosed in Patent Document 1, power is supplied to an induction heating type fixing roller via an IH inverter or the like, and power is supplied to other portions via a DC / DC converter or the like. Like to do. Some image forming apparatuses that use, for example, a halogen heater as a heat source of the fixing roller other than the induction heating method also supply power separately to the halogen heater and other parts.

Japanese Patent Application Laid-Open No. 2004-77664

  However, the above-described conventional technique has a problem that noise generated between the two power supply units may be superimposed. For example, there is a case where alternating current is supplied as it is from an alternating current power source to a halogen heater, and direct current rectified to direct current and smoothed by an active filter is supplied to other portions. In this case, noise generated by switching on / off the power supply to the halogen heater and noise generated in the active filter are superimposed. For this reason, a large noise removal filter is required, which complicates the device configuration.

  The present invention has been made to solve the above-described problems of the prior art. That is, the problem is that the first power supply via the active filter and the second power supply not via the active filter are performed, and noise superposition between these power supply systems is prevented. It is in providing the power supply device. Another object of the present invention is to provide an image forming apparatus equipped with the power supply device.

  The power supply device of the present invention, which has been made for the purpose of solving this problem, supplies power from the main power source to the main load and the sub load, and includes a rectifier that rectifies AC power supplied from the main power source, An active filter unit that smoothes the power rectified by the rectifier unit and supplies power to the main load; and an auxiliary filter that supplies power to the sub load without passing through the active filter unit from the main power source and switches the power supply The control unit controls the supply switching element and the active filter unit and the sub supply switching element. The control unit stops the active filter unit when the sub supply switching element is switched from OFF to ON, and then determines in advance. When the length of time has elapsed, the stop of the active filter unit is released.

  By doing so, the active filter unit is stopped only within a predetermined period from the start of power supply to the subload while supplying power to the main load and the subload. . This is because this period is a time period during which noise is easily superimposed between the active filter unit and the sub load. This avoids noise superimposition.

Here, it switches to finally turn off the sub-supply switching element from ON, only when the elapsed predetermined time or longer, intends row to stop the active filter section. This is because if the sub load is energized until just before, no significant noise will be generated even if the power supply to the sub load is resumed.

  Here, the length of time from the stop of the active filter unit to its release may be equal to or less than the length of one cycle of the AC power of the original power source. This is because if the active filter unit is only stopped within such a short period of time, there is almost no hindrance to power supply to the main load.

  Moreover, it is desirable that the active filter unit has an active element, and the control unit stops the active filter unit by fixing the active element in an off state. This active element is responsible for the boosting function of the active filter section, etc., and by fixing this to the off state, the generation of noise from the active filter section can be stopped.

  The image forming apparatus of the present invention is equipped with the power supply apparatus of the present invention, and receives power from the active filter unit and applies a toner image to the medium. The image forming apparatus includes a fixing heater that thermally fixes the toner image to a medium that has been supplied and to which the toner image has been applied by the image forming unit. Since noise due to inrush current at the start of energization of the fixing heater is generated, noise superposition can be avoided by stopping the active filter at that timing.

  Here, a typical example of the fixing heater is a halogen heater, and the control unit preferably switches the sub-supply switching element by zero crossing. Zero-cross switching itself is a technique for reducing inrush current noise, but even in that case, noise cannot be completely prevented. Therefore, it is meaningful to apply the present invention.

  According to the present invention, the first power supply via the active filter and the second power supply not via the active filter, and the power supply configured to prevent noise from being superimposed between these power supply systems A device is provided. Further, an image forming apparatus equipped with the power supply device is provided.

1 is a configuration diagram of an image forming apparatus according to the present embodiment. It is a circuit diagram showing a configuration of a power supply device of the image forming apparatus of the present embodiment. It is a flowchart which shows the reference example of the stop control of the active filter part in the power supply device of this form. The stop control of the active filter section in the power supply device of the present embodiment is a flow chart showing.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to the image forming apparatus and its power supply apparatus shown in FIG.

  An image forming apparatus 501 of this embodiment shown in FIG. 1 includes a paper feed tray 502 at the lower part of the apparatus. The paper feed tray 502 stores recording media such as printing paper. The image forming apparatus 501 is an apparatus that takes out recording media one by one from the paper feed tray 502, forms an image on the recording medium, and discharges the recording medium. Therefore, the image forming apparatus 501 is provided with a paper feed roller 510a that takes out recording media from the paper feed tray 502 one by one, and conveyance rollers 510b and 510c that convey the taken out recording medium to the image forming unit.

  The image forming unit in the image forming apparatus 501 includes a laser unit 503, four-color photoconductors 505a, 505b, 505c, 505d, four-color developing units 504a, 504b, 504c, 505d, an intermediate transfer belt 506, transfer rollers 510d, 4 Color toner bottles 507a, 507b, 507c, 507d and other known elements are included.

  As a result, an image is formed as follows. That is, the laser unit 503 exposes the four color photoconductors 505a, 505b, 505c, and 505d according to the image data to form a latent image. Then, the latent images are developed by the four color developing units 504a, 504b, 504c, and 504d to form toner images. These toner images are superimposed on the intermediate transfer belt 506 and transferred onto a recording medium by a transfer roller 510d. As a result, a toner image is applied to the recording medium. When the toner in the developing units 504a, 504b, 504c, and 505d decreases, the toners of the respective colors are replenished from the four color toner bottles 507a, 507b, 507c, and 507d.

  In addition to these, the image forming apparatus 501 has a fixing device 508 and a paper discharge roller 510e. The fixing device 508 melts the toner image applied on the recording medium by heating and pressing and fixes the toner image on the recording medium. As the heat source, a halogen heater described later is used. The paper discharge roller 510e discharges the recording medium on which the toner image has been fixed to the outside of the apparatus.

  The image forming apparatus 501 further includes a main motor 509a, a fixing motor 509b, a black developing motor 509c, a color developing motor 509d, and a color photoconductor motor 509e. The main motor 509a is in charge of driving the paper feed roller 510a, the transport rollers 510b and 510c, the intermediate transfer belt 506, and the black photosensitive member 505d. A fixing motor 509b drives a roller of the fixing device 508. The black developing motor 509c drives the rotating part of the black developing unit 504d. The color developing motor 509d drives the rotating portions of the yellow, magenta, and cyan developing units 504a, 504b, and 504c. A color photoconductor motor 509e drives yellow, magenta, and cyan photoconductors 505a, 505b, and 505c.

  The configuration of the power supply device of the image forming apparatus 501 is shown in FIG. The power supply apparatus of FIG. 2 operates by receiving 50 Hz AC power from an external power supply Vac outside the apparatus. The main components of the power supply device of FIG. 2 are an active filter unit AF, a triac TRIAC, and a control unit CPU.

  The active filter portion AF is a part for supplying DC power to the main motor 509a, the fixing motor 509b, the black developing motor 509c, the color developing motor 509d, and the color photosensitive motor 509e of the image forming apparatus 501. For this reason, diodes D1 to D4 are provided on the front side of the active filter portion AF. The diodes D1 to D4 constitute a rectification unit, and full-wave rectifies the AC power of the external power supply Vac and inputs it to the active filter unit AF.

  In order to smooth the pulsating flow with a high power factor, the active filter AF performs smoothing while increasing the pressure once. Details thereof will be described later. A transformer T1, a MOS transistor Q2, a diode D6, and a capacitor C2 are arranged behind the active filter unit AF in order to step down the DC boosted by the active filter unit AF and supply it to the motors. These element groups behind the active filter portion AF constitute a DC-DC converter.

  A reactor L1 and a diode D5 are arranged in series in this order from the input side on the high line (line on the cathode side of the diodes D1 and D2) in the active filter portion AF. On the other hand, a resistor R3 is arranged in the low line (the anode side line of the diodes D3 and D4). The resistor R3 is for detecting the output current of the active filter portion AF. The resistors R1 and R2 are connected in series between the position on the upstream side of the reactor L1 on the high line and the position on the upstream side of the resistor R3 on the low line. The resistors R1 and R2 output an alternating current phase signal Vacph that is a voltage obtained by dividing the input voltage in the active filter portion AF.

  Further, the MOS transistor Q1 is disposed between the position between the reactor L1 and the diode D5 on the high line and the position downstream of the resistor R3 on the low line. Further, a capacitor C1, resistors R4 and R5 are arranged between a position downstream of the diode D5 in the high line and a position downstream of the resistor R3 in the low line. Of these, resistors R4 and R5 are connected in series, and a capacitor C1 is arranged in parallel to these series bodies. The resistors R4 and R5 output a feedback voltage signal Vdcfb that is a voltage obtained by dividing the output voltage Vdc in the active filter portion AF.

The active filter unit AF is further provided with an amplifier A1, a multiplier MUL, an amplifier A2, a triangular wave oscillator OSC1, a comparator CMP1, and an AND operator AND. The amplifier A1 performs proportional-integral control of the feedback voltage signal Vdcfb with the boost voltage command Vdc *. The boost voltage command Vdc * is a fixed voltage set in advance. The output Vdcao of the amplifier A1 is input to the multiplier MUL together with the alternating current phase signal Vacph. Thereby, the output Vdcao and the alternating current phase signal Vacph are multiplied. The output current signal Idc * is proportionally integrated and controlled by the amplifier A2 with the detection current Idcf b detected by the resistor R3.

  The output Idcao of the amplifier A2 is compared with the carrier signal output from the triangular wave oscillator OSC1 by the comparator CMP1. Based on the comparison result, the comparator CMP1 generates an output Q1on * which is a PWM duty signal for turning on and off the MOS transistor Q1. The output Q1on * is input to the AND calculator AND together with the active filter on / off signal PFCC output from the control unit CPU. The AND signal of the AND operation unit AND, that is, the logical product of the output Q1on * and the active filter on / off signal PFCC is the gate input signal of the MOS transistor Q1. Since the active filter on / off signal PFCC is on except in special cases as will be described later, the MOS transistor Q1 is substantially turned on / off by the output Q1on *.

  When MOS transistor Q1 is on, a current flows through reactor L1. When MOS transistor Q1 is off, reactor L1 tries to maintain the current, and charge is accumulated in capacitor C1. By repeating this, an output voltage Vdc (a voltage across the capacitor C1) boosted to a constant value of about 400V is obtained. This voltage Vdc is the output voltage of the active filter portion AF. And the power factor at that time is a high value almost close to 1.

  That is, the reactor L1 is an element that retains energy when a current is passed. The capacitor C1 is an element having a function of storing energy. The MOS transistor Q1 is an active element that accumulates the energy of the reactor L1 in the capacitor C1 by repeating ON / OFF. By repeating ON / OFF of the MOS transistor Q1, energy is stored in the capacitor C1, and the voltage is boosted.

  The output voltage Vdc is stepped down to 24V by a DC-DC converter constituted by the transformer T1 and the like, and is supplied to the motors. That is, the primary coil of the transformer T1 and the MOS transistor Q2 are arranged in series between the output terminals of the active filter portion AF. A diode D6 is disposed on the high line (24V) of the secondary coil of the transformer T1. Further, a capacitor C2 is disposed between the downstream side of the diode D6 and the low line (GND) of the secondary coil of the transformer T1. Here, by turning on / off the MOS transistor Q2, the output voltage Vdc of about 400V is stepped down and transmitted to the secondary side of the transformer T1. Of course, the primary side and the secondary side of the transformer T1 are insulated. Thus, a constant voltage of 24V is obtained.

  On the other hand, the triac TRIAC is a switching element that turns on / off the power supply to the halogen heater H1 of the fixing device 508 of the image forming apparatus 501. That is, the AC power of the external power source Vac is supplied to the halogen heater H1 without the active filter portion AF and the rectifying portion on the front side thereof. Here, the triac TRIAC is arranged in the power supply path to the halogen heater H1. The halogen heater H1 is not a part of the power supply device but one of the components of the fixing device 508.

  The control unit CPU outputs an operation signal Tron * to the triac TRIAC and an active filter on / off signal PFCC. The control of the triac TRIAC by the control unit CPU is a control for keeping the fixing device 508 at a fixed fixing temperature. Here, the on / off switching of the triac TRIAC is performed at the time of zero crossing. This is to reduce noise generated by turning on / off current application to the halogen heater H1. On the other hand, the control of the active filter unit AF by the control unit CPU is to allow the operation in a normal state and to temporarily stop the operation only in a special case described later.

The control of the active filter unit AF by the control unit CPU will be described in detail. First, that describes a control intends follow the flow chart of the reference example shown in FIG. This control is started when the main switch of the image forming apparatus 501 is turned on. Thereafter, this control is continued until the main switch is turned off or disconnected from the external power source Vac.

  As soon as this control is started, the control unit CPU turns on the active filter on / off signal PFCC (S1). That is, the operation of the active filter unit AF is started. As a result, the motors of the image forming apparatus 501 can be driven. At the same time, temperature control of the fixing device 508 by the operation signal Tron * is also started. The fixing device 508 is heated up to a predetermined fixing temperature, and on / off of current application to the halogen heater H1 is switched as appropriate so that the temperature is maintained within a good range. As a result, the image forming apparatus 501 is ready to form an image in accordance with the print command.

  Next, the control unit CPU determines whether or not the operation signal Tron * is switched from off to on (S2). If switching from OFF to ON has not been performed (S2: No), the determination of S2 is repeated again without proceeding to S4 and thereafter. That is, the status of the operation signal Tron * is monitored. In this state, the operation of the active filter unit AF is continued.

  When the operation signal Tron * is switched from OFF to ON (S2: Yes), the control unit CPU switches the active filter ON / OFF signal PFCC to OFF (S4). Then, in the active filter unit AF, the signal PFCON is fixed to be off regardless of the value of the output Q1on *. For this reason, the ON / OFF repetition of the MOS transistor Q1 is stopped and fixed to OFF. As a result, the operation of the active filter unit AF is stopped. Note that S2 is judged Yes only when the operation signal Tron * is switched from OFF to ON. The determination in S2 is No, whether it is kept on, switched from on to off, or kept off.

  In this state, the system waits for 20 milliseconds (S5). Thereafter, the active filter on / off signal PFCC is switched on (S6). Thereby, the operation of the active filter unit AF is resumed. And it returns to S2 again and will be in the state which monitors the condition of the operation signal Tron *.

  Here, the operation of the active filter section AF is stopped for 20 milliseconds of S5, but the influence hardly appears on the output voltage of the DC-DC converter. This is because even if the on / off repetition of the MOS transistor Q1 is stopped, the charge accumulated in the capacitor C1 does not immediately disappear. For this reason, in about 20 milliseconds, neither the output voltage Vdc of the active filter portion AF nor the secondary side voltage (24 V) is lowered. Therefore, there is no problem in the image forming operation of the image forming apparatus 501.

  Here, 20 milliseconds is one cycle of the external power supply Vac (50 Hz). This is because there is no problem in power supply to each part of the image forming apparatus 501 unless the time during which the operation of the active filter part AF stops exceeds this one period.

  The reason for stopping the active filter portion AF in this way is a measure against noise. In the active filter portion AF, a loop is formed by the MOS transistor Q1 and a diode D5 nearby. For this reason, during the operation of the active filter portion AF, noise is inevitably generated due to the ON / OFF repetition of the MOS transistor Q1. On the other hand, when the energization of the halogen heater H1 is started, noise is generated from the inrush current. As described above, this on / off switching is zero-cross switching, and noise is reduced. However, some noise is unavoidable.

  For this reason, if the operation of the active filter portion AF is continued even when the energization of the halogen heater H1 is started, both noises are superimposed. In order to avoid this noise superimposition, in the present embodiment, the above-described control of S4 is performed. For this reason, in the image forming apparatus 501 of the present embodiment, the noise removal filter does not have to be so large. Note that the noise of the halogen heater H1 is reduced after about 20 milliseconds from the start of energization of the halogen heater H1. Therefore, thereafter, the operation of the active filter unit AF may be resumed.

Pause control of the active filter section AF, row Uno is the invention according to the flowchart of FIG. 4 in place of the flowchart of FIG. The only difference between the flowchart of FIG. 4 and the flowchart of FIG. 3 is that the determination of S3 is inserted between S2: Yes and S4. The rest is the same. Therefore, this difference will be described.

  In the flowchart of FIG. 4, even if the determination of S2: Yes is made, the process does not immediately proceed to S4, but the determination of S3 is performed before that. In S3, it is determined whether or not 10 seconds or more have elapsed since the previous switching of the operation signal Tron * from on to off. If the determination in S3 is No, the determination in S2 is repeated again without proceeding to S4 and subsequent steps, as in the case of S2: No. Only when the determination in S3 is Yes, stop control of the active filter AF after S4 is performed.

  The case where it is determined No in S3 is a case where it is turned on again 10 seconds after the halogen heater H1 is turned off. In such a case, the halogen heater H1 has not yet cooled down, and the temperature is relatively high. For this reason, the electrical resistance of the halogen heater H1 is high, and the inrush current is mitigated by this high resistance. Therefore, there is no need to deliberately perform stop control of the active filter portion AF.

  The case where it is determined Yes in S3 is a case where it is turned on only after 10 seconds or more have passed since the halogen heater H1 was turned off. In such a case, the halogen heater H1 is considerably cooled and is close to room temperature. For this reason, the electrical resistance of the halogen heater H1 is lowered, and an inrush current flows remarkably. Therefore, it is necessary to perform stop control of the active filter portion AF. Of course, 10 seconds here is an example, and an appropriate value may be determined in advance according to the type of the halogen heater H1 to be used.

  As described above in detail, in the present embodiment, power is supplied to each motor of the image forming apparatus 501 through the active filter unit AF by receiving AC power from the external power supply Vac. Separately from this, power is supplied to the halogen heater H1 of the fixing device 508 without passing through the active filter portion AF. Here, when the supply of power to the halogen heater H1 is started, the active filter portion AF is stopped for a time within one cycle of the AC of the external power supply Vac. Thereby, the superimposition of the switching noise of the active filter portion AF and the inrush current noise of the halogen heater H1 is avoided. Thus, a power supply device that does not require a large noise countermeasure and an image forming apparatus using the power supply device are realized.

  Further, the active filter unit AF is stopped only when the halogen heater H1 is turned on after 10 seconds or more after the halogen heater H1 is turned off. I can finish it.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.

  For example, the image forming apparatus may be anything as long as it has a fixing unit, and may be a monochrome machine or a 4-cycle machine. The type of toner used is not limited. Further, the heat source of the fixing device is not limited to the halogen heater, and any other heat source may be used as long as it involves a resistance heating phenomenon. Further, other types of active elements may be used instead of the MOS transistors Q1 and Q2. The configuration of the active filter portion AF itself may be different from that in the circuit diagram of FIG. The rectifying unit may be a half-wave rectifier. Further, the output Vdc of the active filter unit AF may be directly supplied to the load without going through the DC-DC converter.

501 Image forming apparatuses 504a to 504d Developing units 505a to 505d Photoconductor 506 Intermediate transfer belt 508 Fixing devices 509a to 509e Motors AF Active filter unit CPU Control unit D1 to D4 Diode (rectifying unit)
H1 Halogen heater Q1 MOS transistor TRIAC Triac

Claims (5)

In a power supply that supplies power from the main power source to the main load and sub load,
A rectifying unit for rectifying AC power supplied from a main power source;
An active filter for smoothing the power rectified by the rectifier and supplying power to the main load;
A sub-supply switching element for supplying power from the main power source to the sub-load without going through the active filter unit and switching the power supply;
A control unit for controlling the active filter unit and the sub-supply switching element;
The controller is
When the sub-supply switching element is switched from OFF to ON, the active state is limited only when a predetermined first length of time has elapsed since the last switching of the sub-supply switching element from ON to OFF. While stopping the filter part,
Thereafter, when the predetermined second length of time has elapsed, the active filter section is released from being stopped. The power supply device according to claim 1,
The power supply apparatus according to claim 1, wherein the second length in the control unit is equal to or less than one cycle of AC power of the original power supply. In the power supply device of Claim 1 or Claim 2 ,
The active filter section has an active element;
The power supply apparatus according to claim 1, wherein the control unit stops the active filter unit by fixing the active element in an off state. In the image forming apparatus equipped with any one power supply of claims 1 to 3 receives power supply from the active filter section, and an image forming unit for imparting a toner image on the medium,
An image forming apparatus comprising: a fixing heater configured to thermally fix a toner image to a medium that is supplied with electric power through the sub-supply switching element and receives a toner image applied thereto by the image forming unit. The image forming apparatus according to claim 4 ,
The fixing heater is a halogen heater;
The image forming apparatus, wherein the control unit switches the sub-supply switching element by zero crossing.

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