JP2009300959A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which copes with an input voltage of AC 100V and an input voltage of AC 200V with an inexpensive configuration by selecting and switching a voltage double rectifier and full wave rectification, depending on an AC input voltage, without directly detecting the AC input voltage and detecting the temperature of a load, to calculate a temperature change ratio and select an operation. <P>SOLUTION: The image forming apparatus has a constitution that includes a rectification switching means which switches the rectification of the AC input voltage to the full wave rectification or the voltage double rectifier, a zero-cross signal output means which detects and outputs the zero cross of the AC input voltage, a load temperature detecting means which detects the temperature state of the load after a power is supplied to the load, and a temperature change ratio calculating means which calculates a change ratio from the temperature change of the load for a predetermined period, and includes an operation selecting means which judges whether or not the temperature change ratio is higher than a predetermined change ratio and selects a normal operation or an abnormality processing operation from the duty ratio of a zero-cross signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a power supply corresponding to both an AC input voltage of 100 system and 200 V system, and forms a toner image on a print medium such as paper by a printer, a facsimile, a copying machine, etc. The present invention relates to an image forming apparatus having a fixing unit for fixing by heating and pressurizing with a heater for toner fixing.

  The image forming apparatus converts a voltage from an AC (alternating current) line of a commercial power source to generate a DC (direct current) voltage for use. In addition, an image forming operation is performed by supplying an AC voltage to a fixing (heating) heater as a load.

  Switching power supplies are widely used as power supply units that output AC input voltage to DC voltage, but the AC voltage value of commercial power supplies varies from country to country. Broadly divided into two types, 100V and 200V. The 100V system has an AC input of 100V to 120V and the 200V system has a nominal voltage of 200V to 240V. There are image forming apparatuses that incorporate the same power supply unit and are compatible with both 100V and 200V systems. In addition, there is an AC load such as a fixing heater that heats by applying an AC voltage in the image forming apparatus, and the fixing unit having the function of fixing the image on paper etc. is made the same unit without dividing the 100V system and the 200V system. is there.

  An image forming apparatus having a power supply compatible with both 100V system and 200V system and a fixing unit that is an AC load such as a fixing heater needs to be configured to switch a circuit that operates according to an AC input voltage.

  For example, as in Patent Document 1 and Patent Document 2, if the input AC voltage value is detected and the input voltage is 100 V, rectification to DC voltage is double voltage rectification, and if it is 200 V, full-wave rectification is performed. There is a configuration. For the fixing heater, there is a device that applies a full wave if it is a 100V AC input voltage, or applies a half wave by adjusting the application timing if it is a 200V AC input voltage.

  In general, such a fixing heater is supplied with electric power from an AC line via a switching element such as a triac. In a fixing unit using a halogen heater as a heat source, the temperature of the fixing unit is detected by a temperature detection element such as a thermistor temperature sensing element, and the switching element is turned on by a sequence controller included in the image forming apparatus based on the detected temperature. / Off controlled. That is, the power supply to the halogen heater is turned on / off, and the temperature is controlled so that the temperature of the fixing device becomes a target temperature.

On the other hand, in the fixing unit using the ceramic surface heater as the heat source, the temperature is detected by the sequence controller in the image forming apparatus based on the temperature difference between the temperature detected by the temperature detecting element and a preset target temperature. The phase angle or wave number corresponding to the power ratio supplied to the ceramic surface heater is determined, the switching element is turned on / off at the determined phase or wave number, and the temperature of the fixing unit is temperature controlled.
Japanese Unexamined Patent Publication No. 4-195180 JP-A-4-226480

  However, in the above conventional examples (Patent Document 1 and Patent Document 2), when the voltage is rectified to DC voltage, the AC input voltage is directly detected to switch between voltage doubler rectification or full wave rectification. It is necessary to connect parts for use. For this reason, it is necessary to configure a circuit by combining parts considering a withstand voltage of several hundred volts, and it is considered necessary to use expensive parts.

  As for the fixing unit, if the same heater is used for the 100V system and the 200V system, there is a problem that 4KW is consumed if the heater of 1KW at 100V is fully lit. For this reason, control that switches the current flow angle is required.

Therefore, the object of the first invention according to the present application is to select and switch between double voltage rectification and full wave rectification corresponding to the AC input voltage without directly detecting the AC input voltage, and to detect the temperature of the load. An object of the present invention is to provide an image forming apparatus that can cope with an input voltage of an AC 100V system and an AC 200V system with an inexpensive configuration by calculating a temperature change rate and selecting an operation.
Further, the object of the second invention is to select and switch between double voltage rectification and full wave rectification corresponding to the AC input voltage without directly detecting the AC input voltage, and to detect the current value with respect to the AC load. It is another object of the present invention to provide an image forming apparatus that can cope with an input voltage of an AC 100V system and an AC 200V system with an inexpensive configuration by detecting a current change rate and selecting an operation.

  In addition, an object of the third invention is to provide an image forming apparatus capable of supporting a wide AC input voltage range by selecting an AC 100V system or an AC 200V system process during an image forming operation corresponding to an AC input voltage. is there.

In order to achieve the above object, an image forming apparatus according to the first invention of the present application,
Rectification switching means for switching AC input voltage rectification to full-wave rectification or voltage doubler rectification, zero-cross signal output means for detecting and outputting a zero-cross of AC input voltage, and the temperature state of the load after power is applied to the load A load temperature detecting means for detecting and a temperature change rate calculating means for calculating a change rate from a load temperature change for a predetermined period, determining whether the temperature change rate is greater than the predetermined change rate, and duty ratio of the zero cross signal The operation selecting means for selecting the normal operation or the abnormal processing operation from the above.

  Further, the image forming apparatus according to the second invention of the present application includes a rectification switching means for switching the rectification of the AC input voltage to full wave rectification or double voltage rectification, and a zero cross signal output for detecting and outputting the zero cross of the AC input voltage. Current detecting means for detecting a supply current to a load using an AC input as a power supply source, and a current change rate calculating means for calculating a change rate of a current value to the load for a predetermined period. It is characterized by having operation selection means for determining whether the rate is larger than a predetermined change rate and selecting normal operation or abnormal processing operation from the duty ratio of the zero cross signal.

  According to a third aspect of the present invention, there is provided an image forming apparatus according to the first and second aspects, wherein the input voltage for selecting 100V or 200V AC input voltage processing during normal operation is selected. It has a selection means.

  As described above, according to the present invention, voltage doubler rectification and full-wave rectification are selected without directly detecting the voltage value of the AC line, and the input voltage of 100 V system and 200 V system can be obtained with an inexpensive component configuration. It is possible to provide an image forming apparatus that can be handled stably.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an image forming apparatus 1 according to an embodiment of the present invention, and shows an outline view and a cross-sectional view.

  2 shows a power supply unit (PS) 2 in the image forming apparatus 1 and a control unit (CON) 3 for performing processing in the image forming apparatus 1 and control during image formation. The power supply unit 2 is an optical unit for forming images with the motors 4 and 5, and supplies power to a scanner unit (SCN) 6 and a solenoid (SL) 7 incorporating a laser, a reflection mirror, and a motor.

  A plurality of sheets 8 are stacked in the image forming apparatus 1, and pass through a pickup roller 9 for kicking out the sheet 8 during image formation, a feed retard roller 10 for separating one sheet, and a conveying roller pair 11. 8 reaches the registration unit 12 that adjusts the posture of 8. The pickup timing of the sheet 8 is the suction timing of the solenoid 7, and the motors 4 and 5 and the scanner motor 6 are activated before that. The motors 4 and 5, the scanner unit 6, and the solenoid 7 are driven when the sheet 8 is conveyed and image formation is performed, and is not limited to the number in this embodiment. Further, it drives members necessary for driving a plurality of rollers in the image forming apparatus 1 and for forming an image on a sheet.

  The sheet 8 reaching the registration unit 12 is adjusted in posture and reaches the transfer unit 13, transferred with toner supplied from a toner storage unit 14 storing toner for image formation, and conveyed to the fixing unit 15 a.

  The fixing unit 15 a presses and heat-fixes an image on the sheet 8. Heating is performed by applying an AC voltage to the fixing heater 15b. The sheet 8 passes through the paper discharge roller pair 16. The 17 conveyance path switching flapper switches the conveyance path so that the sheet 8 is discharged and stacked in the image forming apparatus 1 with the image forming surface facing down, so that the sheet 8 is discharged and stacked on the sheet discharge tray 18. The 17 conveyance path switching flapper also switches the conveyance path when conveying the sheet 8 to the upper part of the image forming apparatus for conveyance to a post-processing apparatus (not shown).

  FIG. 2 is a diagram illustrating a connection configuration of a power supply unit, a load control unit, and a load in the image forming apparatus according to the embodiment of the present invention.

  FIG. 2 shows an entire electric circuit configuration in the image forming apparatus, and 2 is a block showing a power supply unit (PS). This is a switching power supply that converts an alternating current (AC) supply source such as a commercial power supply into direct current (DC) within the power supply unit 2. Reference numeral 100 denotes a switch, and reference numeral 101 denotes a bridge rectifier circuit.

The 102 triac is arranged to switch the method of applying the DC voltage after rectification to the 104 smoothing capacitor and the 105 smoothing capacitor to full wave rectification or voltage doubler rectification. The 102 triac is switched on / off depending on the presence or absence of an output pulse from the 103 full-wave rectification / double voltage rectification switching unit. In the on state, voltage doubler rectification is performed, and in the off state, full wave rectification is performed. A pulsed voltage is generated between SELH and SELL, and the 103a capacitor smoothes the voltage applied to the circuit composed of the 103b resistor, the 103c Zener diode, and the 103d switching element (for example, MOSFET). When a voltage which is equal to or higher than the zener voltage of 103c and can turn on the switching element of 103d is applied to 103d, the pulsed voltage between SELH and SELL is bypassed by 103d without being applied to 102 triac. If the pulse voltage between SELH and SELL is not applied to 102 triacs, a full-wave rectification state is established. If the voltage at which the switching element 103d cannot be turned on, the pulse voltage between SELH and SELL is applied to the 102 triac, and the 102 triac is turned on, resulting in voltage doubler rectification.
The higher the potential of the AC input voltage, the larger the voltage amplitude of the pulse between SELH and SELL, and the higher the voltage after smoothing at 103a.

  The driving of the 102 triac can be controlled by switching the switching element 103d off / on depending on the difference between the AC input voltage 100V system and the 200V system. That is, the 103c Zener diode is set so that the 103d switching element is turned off when the AC 100V system is input, and the 103d switching element is turned on when the AC 200V system is input.

  The 106a and 106b diodes are connected to both electrodes of the 104 and 105 smoothing capacitors, and stabilize the potential of the 104 and 105 smoothing capacitors. In the 106a and 106b diodes, when the capacitor potential becomes unbalanced due to the residual charge of the capacitor during the discharging of the 104 and 105 smoothing capacitors, the potentials of the 104 and 105 smoothing capacitors are in an equilibrium state around the midpoint potential DCM. In this way, the reverse potential is prevented from being applied to the capacitor.

  The 107a and 107b resistors are connected to stabilize the midpoint potential DCM of the 104 and 105 smoothing capacitors. Further, the switch 104 is connected to discharge the electric charge remaining in the smoothing capacitors 104 and 105 when the switch 100 is turned off.

  Reference numeral 109 denotes a diode for half-wave rectifying the input from the AC line. A transistor 113 is a combination of a 115 photocoupler and resistors 110, 111, and 112, and switches the output of a zero cross (ZEROX) signal pulled up by a resistor 114.

  The light emitting element in the 115 photocoupler is connected to the DCH side on the positive potential side of the above-described 104 and 105 smoothing capacitors via the 112 resistor, and is also connected to the midpoint potential DCM which is a potential lower than DCH. When the 113 transistor is turned on with the voltage half-wave rectified from the 109 diode, the light emitting element in the 115 photocoupler is turned off and the ZEROX signal becomes a high output. If the 113 transistor is off, the light emitting element in the 115 photocoupler is lit and the ZEROX signal becomes a low output signal. This ZEROX signal switching timing is the timing at which the AC line voltage is switched between positive and negative.

  The 200 load control unit controls 208 load 1 (fixing heater), 209 load 2 and 210 load N in the image forming apparatus. Also, the ZEROX signal line is input to the 200 load control unit, and the 200 load control unit calculates a duty ratio which is a high ratio or a low ratio of the ZEROX waveform.

  207 is a sensor that detects the temperature of 208 load 1 (fixing heater), and is installed in contact, indirect contact, or non-contact with 208 load 1 (fixing heater). Input to the load controller. In the present embodiment, 208 load 1 (fixing heater) is an AC load ceramic surface heater. The 209 loads 2 and 210 loads N are DC loads connected to the GND, and are loads of DC motors and other actuators.

  FIG. 3 is a diagram illustrating the configuration of the 108 switching unit in the power supply unit in the image forming apparatus according to the embodiment of the present invention.

  Reference numeral 116 denotes a switching transformer. Reference numeral 116a denotes a primary main winding. The voltage between DCH and DCL after rectification is applied by 118 switching elements controlled by a 117 power supply IC. Reference numeral 116b denotes an auxiliary winding for supplying operating power to the 117 power supply IC. Reference numeral 116c denotes a secondary output Vcc1 output winding, and reference numeral 116d denotes a secondary output Vcc2 output winding.

  Reference numeral 116e denotes a rectification switching winding on the primary side, which is a winding that outputs a voltage determined by a winding ratio between the winding and the main winding. A voltage between DCH and DCL is applied to the main winding 116a in a pulsed manner by a 117 power supply IC and 118 switching elements. A pulsed voltage is generated between SELH and SELL. The pulse voltage generated between SELH and SELL is input to the 103 full-wave rectification / double voltage rectification switching unit in FIG. When securing the voltage between DCH and DCL so that the AC input voltage is almost the same for both the AC100V system and AC200V system, the 103 full-wave rectification / double voltage rectification switching unit, when the 100V system voltage is input, Control is performed so that a potential equal to or lower than a predetermined voltage is generated between SELH and SELL to turn on 102 triac. When the 102 triac is turned on, voltage doubler rectification occurs.

  When an AC200V system voltage is input, a potential higher than the predetermined voltage is generated between SELH and SELL. In this case, the 103 full-wave rectification / double voltage rectification switching unit controls to turn off the 102 triac. Full-wave rectification occurs when the 102 triac is off.

  The 119 diode in FIG. 3 is a rectifier diode that rectifies the output from the 116c winding, and 120 is a smoothing capacitor. The smoothed voltage becomes Vcc1.

  A 121 diode is a rectifier diode that rectifies the output from the 116d winding, and 122 is a smoothing capacitor. The smoothed voltage becomes Vcc2.

  However, in this embodiment, Vcc1 <Vcc2, and the 123 photocoupler and the 124 feedback unit are circuits for stabilizing the potential of Vcc1, and Vcc2 varies according to the output of Vcc1.

  Regarding the voltage control feedback of Vcc1 and Vcc2, the method and configuration are not particularly limited.

  FIG. 4 is a diagram illustrating a configuration of a 200 load control unit in the image forming apparatus according to the embodiment of the present invention.

  Reference numeral 201 denotes a CPU (Central Processing Unit) which is a central processing unit, and 201a contains a ROM (Read Only Memory) which is a nonvolatile memory. However, 201a may be a rewritable memory, and the stored contents are held even when the power output is stopped. Reference numeral 201b denotes a RAM (Random Access Memory) which is a volatile memory, which holds results and data calculated in the 201 CPU, and inputs / outputs information from the 201c I / O (Input / Output) and A / D (Analog / Digital) This memory stores input values from the converter. The 201 c I / O and A / D converters are connected to an external circuit of the 201 CPU. For example, a signal of a predetermined voltage level is input / output from the outside of the 201 CPU, or a voltage that is an analog value from the outside is A A process of obtaining a digital value by / D conversion is performed.

  The 202 current detection unit detects a current when power from the AC line is consumed, and is connected to the 203 drive circuit 1 and incorporates a 202a current transformer and a 202b current detection circuit. The 202b current detection circuit is configured to be capable of detecting a current value and integrating the current value for a predetermined period, and is connected to the 201 CPU via an I / O and A / D converter of 201c. In addition, in the integration of the current value for a predetermined period, the output voltage from the 202 current detection unit may be calculated by 201 CPU via the A / D conversion of 201c.

  The 203 drive circuit 1 is connected to AC lines ACH and ACN, and the 204 drive circuit 2 and 205 drive circuit N are connected to the outputs of Vcc1 and Vcc2.

  Further, each drive circuit is connected to 201 CPU via 201c I / O.

  The 201 CPU performs processing necessary for the image forming process according to the processing procedure stored in the ROM 201 a. At that time, the 201 CPU controls each drive circuit via the I / O port 201 c while saving the data being processed in the RAM 201 b and controls each load.

  The 201 CPU also calculates a time change rate (di / dt) of the current value within a predetermined period. For example, the time change rate (di / dt) of the current value is used as information for a criterion for switching processing according to the time change rate of the current value of the AC load connected to the 203 drive circuit 1. And

  A sensor input circuit 206 adjusts the voltage level before inputting the output from the 207 temperature sensor to the 201 CPU. Further, the 201 CPU performs a process of calculating the temperature value from the 206 sensor input circuit as dT / dt which is the temperature change rate during the predetermined period Δt.

  The temperature detected by the 207 temperature sensor is A / D input to the 201 CPU via the 206 sensor input circuit. The temperature of 208 load 1 (fixing heater) is monitored by the 200 load control unit, and the power ratio to be supplied is calculated by comparing with the set temperature of 208 load 1 (fixing heater) set by the 200 load control unit. Then, the supplied power ratio is converted into a phase angle (phase control) or a wave number (wave number control), and the 201 CPU controls the 203 drive circuit 1 according to the control condition.

  When calculating the power ratio supplied to the 208 load 1 (fixing heater), for example, in the case of phase control, the following control table is provided in the ROM 201a, and control is performed based on this control table. Do.

  If the resistance component of 208 load 1 (fixing heater) is common to the AC100V system and 200V system, for example, the phase angle or wave number that sets the power ratio at the time of AC100V system input and the phase that sets the power ratio at the time of AC200V system input There is a method of setting the angle or wave number differently, and it is assumed that processing between AC100V system and AC200V system is switched.

  FIG. 5 is a flowchart showing processing in the image forming apparatus, and the operation will be described with reference to the AC input waveform, the DC waveform after rectification, and the zero cross (ZEROX) waveform in FIGS. To do.

  6 and 7, the DC voltage smoothed after rectification is represented by solid lines as DCH and DCL, the midpoint potential DCM of 104 and 105 smoothing capacitors in FIG. 2 is a dotted line, and the AC input voltage waveform is a single point. It is represented by a chain line.

  Further, the difference between the cathode side voltage (Di_K) of the 109 diode of FIG. 2 and the midpoint potential DCM is represented by a solid line as Di_K-DCM.

  In step 300, processing for detecting the temperature of 208 load 1 (fixing heater) at the time of image formation is performed.

  Step 301 is a process of calculating dT / dt, which is the temperature change rate during the predetermined period Δt. The calculation process is performed within the 201 CPU. However, the temperature change rate calculation method may be, for example, the temperature change ΔT obtained by a calculation method in which temperature information after a plurality of temperature detection processes is integrated for a predetermined period Δt and an average value and temperature variation are taken into account. The method is not particularly limited. Further, it may be calculated as a change rate in each temperature range of the heater. For example, up to the allowable temperature limit is divided by a predetermined temperature range, and the temperature change rate within each range is set to be stored in the 201b RAM, and compared with the corresponding data in the 201a ROM stored in advance. It is also possible to do.

  When 208 load 1 (fixing heater) has the same resistance value and energization with the same wave number, the current per cycle to be energized is larger in the AC200V system and the temperature change rate is larger than in the AC100V system. Also, in the case of phase control, when the power ratio in the AC100V system is used as a reference, for example, when power is turned on at a phase angle of 90 °, which is 50% duty, the temperature change of the AC200V system increases and the rate of temperature change also increases. Become.

  In step 302, it is determined whether the calculation of the temperature change rate is completed. In step 303, it is determined whether the temperature change rate is greater than a predetermined value. For example, when the predetermined value that is the criterion in step 303 is the temperature change rate dT / dt_100 at the time of AC100V system input, compared with the temperature change rate dT / dt_200 at the time of AC200V system input, dT / dt_100 <dT / dt_200 It becomes the relationship.

  If the temperature change rate is equal to or less than the predetermined value in step 303, the process proceeds to step 304.

  The power supply unit 2 performs voltage doubler rectification when the AC input voltage is 100 V, and operates as represented by the AC and DC waveforms shown in FIG. The duty ratio of the ZEROX waveform is 50%. This is because the difference between the cathode side voltage (Di_K) of the 109 diode in FIG. 2 and the midpoint potential DCM of the smoothing capacitors 104 and 105 (Di_K-DCM) is the same as the period higher than the DCL voltage and the DCL potential. It is shown that. In step 304, it is determined whether the duty ratio of the ZEROX waveform is 50%. In the case of almost 50%, in step 305, the normal AC100V processing is performed. If it greatly deviates from 50%, there is a possibility that the ZEROX circuit failure or the rectifier circuit failure is abnormal, so proceed to Step 306 and cut off energization to 208 load 1 (fixing heater) as a failure process for ensuring safety. Process.

  If it is determined in step 303 that the temperature change rate is greater than dT / dt_100 at the time of AC100V input, it is determined in step 307 whether the duty ratio of the ZEROX waveform is 50%. In the case of almost 50%, it is determined that an abnormal temperature rise of 208 load 1 (fixing heater) has occurred, and the process proceeds to step 306, and processing for cutting off energization to 208 load 1 (fixing heater) is performed as a failure process for ensuring safety.

  If the duty ratio of the ZEROX waveform greatly deviates from 50% as shown in FIG. 7 in step 307, it is determined that the input is AC200V system, and the process proceeds to step 308 to perform normal processing of AC200V system.

  These processes shown in the flowchart of FIG. 5 are repeatedly executed while the image forming apparatus is powered on.

  As described above, full-wave rectification or voltage doubler rectification is switched without directly detecting the voltage value of the AC line, and the temperature change rate of the load due to the duty ratio of the zero cross signal and the input of AC power to the load is calculated and processed. By switching the, the processing of the image forming apparatus can be switched according to the input voltage depending on whether the AC input is 100V or 200V.

  A second embodiment of the present invention will be described.

  FIG. 8 is a flowchart showing processing in the image forming apparatus. Steps 304 to 308 are the same as the processing in the flowchart of FIG.

  In step 400, processing for detecting a current value to 208 load 1 (fixing heater) at the time of image formation is performed.

  Step 401 is a process of calculating a time change rate (di / dt) of a current value within a predetermined period by the 200 load control unit shown in FIG.

  In step 402, it is determined whether the calculation of the current change rate has been completed. In step 403, it is determined whether the current change rate is greater than a predetermined value. When 208 load 1 (fixing heater) has the same resistance value and energization with the same wave number, the current per cycle to be energized is larger in the AC200V system and the current change rate is larger than in the AC100V system. In the case of phase control, when the power ratio in the AC100V system is used as a reference, for example, when power is turned on at a phase angle of 90 °, which is 50% duty, the current change in the AC200V system increases and the current change rate also increases. Become.

  For example, if the judgment criterion in step 403 is the current change rate di / dt_100 at the time of AC 100V system input, compared with the current change rate di / dt_200 at the time of AC 200V system input, the relationship of di / dt_100 <di / dt_200 Become.

  When the AC input voltage is 100V, the 10 power supplies are double voltage rectified, and the duty ratio of the ZEROX waveform is 50%.

  In step 304, it is determined whether the duty ratio of the ZEROX waveform is 50%. In the case of almost 50%, in step 305, the normal AC100V processing is performed. If it greatly deviates from 50%, there is a possibility that the ZEROX circuit failure or the rectifier circuit failure is abnormal, so proceed to Step 306 and cut off energization to 208 load 1 (fixing heater) as a failure process for ensuring safety. Process.

  If it is determined in step 403 that the current change rate is greater than di / dt_100 at the time of 100V input, it is determined in step 307 whether the duty ratio of the ZEROX waveform is 50%. In the case of almost 50%, the process proceeds to step 306 as an abnormal current change of 208 load 1 (fixing heater), and a process of cutting off energization to 208 load 1 (fixing heater) is performed as a failure process for ensuring safety.

  If the duty ratio of the ZEROX waveform greatly deviates from 50% in step 307, the process proceeds to step 308 and the normal processing of AC200V system is performed. In this way, the input voltage is selected.

  These processes shown in the flowchart of FIG. 8 are repeatedly executed while the power of the image forming apparatus is turned on.

  As described above, full-wave rectification or voltage doubler rectification is switched without directly detecting the voltage value of the AC line, and the duty ratio of the zero cross signal and the rate of change in the load current due to the input of AC power to the load are calculated and processed. By switching the, the processing of the image forming apparatus can be switched according to the input voltage depending on whether the AC input is 100V or 200V.

1 is a diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. 1 is a diagram illustrating a connection configuration of a power supply unit, a load control unit, and a load in an image forming apparatus according to Embodiment 1 of the present invention. 1 is a diagram illustrating a configuration of a switching unit in a power supply unit in an image forming apparatus according to Embodiment 1 of the present invention. 1 is a diagram illustrating a configuration of a load control unit in an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a flowchart illustrating processing in the image forming apparatus according to the first exemplary embodiment of the present invention. The figure which showed the voltage waveform in the power supply part which concerns on Example 1 of this invention. The figure which showed the voltage waveform in the power supply part which concerns on Example 1 of this invention. FIG. 6 is a flowchart illustrating processing in an image forming apparatus according to Embodiment 2 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Power supply part 15a Fixing part 15b Fixing heater (load 1)
DESCRIPTION OF SYMBOLS 101 Bridge rectifier circuit 102 Triac 103 Full wave rectification / double voltage rectification switching part 104,105 Primary side smoothing capacitor 108 Switching part 116 Switching transformer 117 Power supply control IC
118 Primary-side switching element 200 Load control unit 201 CPU
202 current detection circuit 202a current transformer 202b current value integration circuit 203, 204, 205 drive circuit 1, 2, 3
207 Temperature sensor 208, 209, 210 Load 1 (fixing heater), 2, N

Claims (3)

Rectification switching means for switching the rectification of the AC input voltage to full-wave rectification or voltage doubler rectification,
Zero cross signal output means to detect and output zero cross of AC input voltage,
Load temperature detecting means for detecting the temperature state of the load after power is applied to the load;
Temperature change rate calculating means for calculating the change rate from the temperature change of the load during a predetermined period,
Determine if the temperature change rate is greater than the predetermined change rate,
An image forming apparatus comprising operation selection means for selecting a normal operation or an abnormal processing operation from a duty ratio of a zero cross signal. Rectification switching means for switching the rectification of the AC input voltage to full-wave rectification or voltage doubler rectification,
Zero cross signal output means to detect and output zero cross of AC input voltage,
Current detection means for detecting a supply current to a load using an AC input as a power supply source;
Current rate of change calculation means for calculating the rate of change of the current value to the load for a predetermined period;
Determine whether the current change rate is greater than the predetermined change rate,
An image forming apparatus comprising operation selection means for selecting a normal operation or an abnormal processing operation from a duty ratio of a zero cross signal. The image forming apparatus according to claim 1, wherein:
An image forming apparatus comprising input voltage selection means for selecting 100V or 200V AC input voltage processing during normal operation.

Images