Abstract: An image forming apparatus: acquires, before start of current supply to electric elements including heater, information indicating rated power of the heater and total consumption power of the electric elements excluding the heater; subtracts the total consumption power from upper power limit of the apparatus, and calculates maximum power not exceeding the rated power and remaining power thus subtracted; obtains duty ratio based on assumption of current supply corresponding to the maximum power according to pulse modulation, and determines whether the duty ratio falls within predetermined range; and controls, when the duty ratio falls within the range, drive circuit to supply alternating current by pulse modulation method, and when the duty ratio falls outside the range, to supply the alternating current by phase control method that temporarily interrupts the supply of the alternating current to the heater in half cycles of the alternating current.

Abstract: A power supply control device including a chopper circuit generating a heater current for a halogen heater, a current feedback circuit generating a current feedback signal indicating a current amount based on an amount of the heater current, and a constant current circuit performing pulse-width modulation of the heater current amount according to a difference between a target heater current amount and the current amount indicated by the current feedback signal. The current feedback circuit switches between methods at least including a first method and a second method for generating the current feedback signal. The current feedback signal indicates a greater current amount with the first method than with the second method, and the current feedback circuit uses the first method during a period with a predetermined time length starting from when the halogen heater is turned on, and uses the second method after elapse of the period.

Abstract: An image forming apparatus: acquires, before start of current supply to electric elements including heater, information indicating rated power of the heater and total consumption power of the electric elements excluding the heater; subtracts the total consumption power from upper power limit of the apparatus, and calculates maximum power not exceeding the rated power and remaining power thus subtracted; obtains duty ratio based on assumption of current supply corresponding to the maximum power according to pulse modulation, and determines whether the duty ratio falls within predetermined range; and controls, when the duty ratio falls within the range, drive circuit to supply alternating current by pulse modulation method, and when the duty ratio falls outside the range, to supply the alternating current by phase control method that temporarily interrupts the supply of the alternating current to the heater in half cycles of the alternating current.

Abstract: An image forming apparatus includes: a fixing part including a heater, and a first temperature detection part configured to detect the temperature of the heater; a chopper circuit including a reactor, a freewheeling element, and a switching element, the chopper circuit being configured to switch an input direct current on and off in a specified duty cycle by using the switching element and to supply the current to the heater; and a control part configured to control the duty cycle based on a detection result obtained by the first temperature detection part, as well as to control a switching frequency of the switching element based on an operation mode of the image forming apparatus.

Abstract: A power supply control device including a chopper circuit generating a heater current for a halogen heater, a current feedback circuit generating a current feedback signal indicating a current amount based on an amount of the heater current, and a constant current circuit performing pulse-width modulation of the heater current amount according to a difference between a target heater current amount and the current amount indicated by the current feedback signal. The current feedback circuit switches between methods at least including a first method and a second method for generating the current feedback signal. The current feedback signal indicates a greater current amount with the first method than with the second method, and the current feedback circuit uses the first method during a period with a predetermined time length starting from when the halogen heater is turned on, and uses the second method after elapse of the period.

Abstract: A fuser control device includes: a fusing portion having a heater; a chopper portion including a reactor, a free-wheeling element, and a switching element; and a processor portion being configured to implement a first current control during an implementation period, the implementation period including a first time interval and a second time interval, the implementation period being longer than a commercial power period, the first current control for transferring a control signal having a predetermined duty ratio to the switching element during the first time interval and transferring a control signal having a 100% duty ratio to the switching element during the second time interval.

Abstract: An image forming apparatus includes a fixing unit that includes a roller and an electric heating wire heater, a current applying circuit that applies electrical current to the electric heater wire heater, a measuring unit electrically connected to the current applying circuit and that measures a value of electrical current that flows through the electric heating wire heater, and a controller that controls the electrical current that flows through the electric heating wire heater by controlling the current applying circuit based on the electrical current value measured by the measuring unit. The controller controls the electrical current to be less than or equal to an electrical current limit value. A magnitude of the electrical current limit value is linked to a magnitude of stable state electrical current.

Abstract: A fuser control device includes: a fusing portion having a heater; a chopper portion including a reactor, a free-wheeling element, and a switching element; and a processor portion being configured to implement a first current control during an implementation period, the implementation period including a first time interval and a second time interval, the implementation period being longer than a commercial power period, the first current control for transferring a control signal having a predetermined duty ratio to the switching element during the first time interval and transferring a control signal having a 100% duty ratio to the switching element during the second time interval.

Abstract: An image forming apparatus includes an induced voltage detection portion configured to detect an induced voltage Vk in a motor; and an engagement/disengagement completion time detection portion configured to detect an engagement completion time and a disengagement completion time based on the induced voltage Vk detected by the induced voltage detection portion. The engagement completion time is a time at which engagement of a clutch is actually completed. The disengagement completion time is a time at which disengagement of the clutch is actually completed. A control portion determines a command timing based on any one of the engagement completion time and the disengagement completion time detected by the engagement/disengagement completion time detection portion, the command timing being a time at which a command is given to the clutch to perform an engaging operation or a disengaging operation.

Abstract: An induction heating device includes: a resonant circuit provided with a coil heating a workpiece inductively and a capacitor, the coil and the capacitor being coupled in parallel with each other; a switching element coupled in series with the resonant circuit; a power supply which applies to the resonant circuit, a direct-current input voltage whose instantaneous value can be changed with the lapse of time; and a power controller which controls power to the workpiece by turning the switching element ON at a certain time and changing an ON period of the switching element, and the power controller is characterized by turning the switching element ON with a delay of an integral multiple of a resonant period of the resonant circuit if a value of power to the workpiece is equal to or lower than a first threshold which is predetermined.

Abstract: An image forming apparatus includes an induced voltage detection portion configured to detect an induced voltage Vk in a motor; and an engagement/disengagement completion time detection portion configured to detect an engagement completion time and a disengagement completion time based on the induced voltage Vk detected by the induced voltage detection portion. The engagement completion time is a time at which engagement of a clutch is actually completed. The disengagement completion time is a time at which disengagement of the clutch is actually completed. A control portion determines a command timing based on any one of the engagement completion time and the disengagement completion time detected by the engagement/disengagement completion time detection portion, the command timing being a time at which a command is given to the clutch to perform an engaging operation or a disengaging operation.

Abstract: An electromagnetic induction heating apparatus comprises: a resonance circuit that includes a inductor and a capacitor; a direct-current electric power supply; and a switching element performing ON and OFF switching of electric power supplied to the resonance circuit by the direct-current electric power supply; performs intermittent control of the electric power supply by controlling the ON and OFF switching at regular intervals, and by performing control to stop the electric power supply when not controlling the ON and OFF switching, wherein during the intermittent control, the switching control unit performs gradual control such that, upon beginning the control of the ON and OFF switching, the electric power supply gradually increases to reach a target value, and upon stopping the control of the ON and OFF switching, the electric power supply gradually decreases from the target value until stopping, such that the gradual decrease involves fewer steps than the gradual increase.

Abstract: An image forming apparatus having: a power source applying alternating current voltage to the magnetizing coil; a demagnetizing coil switchable between a conductive state and a cutoff state, and when in the conductive state, cancelling out a portion of a magnetic flux produced by the magnetizing coil; a contact switch and a semiconductor switch electrically connected in parallel, and, in combination, bringing the demagnetizing coil into the conductive state or the cutoff state; and a control unit opening or closing the switches separately. The control unit: opens or closes the semiconductor switch in synchronization with a zero-crossing of the alternating current voltage at least when the contact switch is open; opens or closes the contact switch only when the semiconductor switch is closed; and opens the semiconductor switch when the demagnetizing coil brought into the conductive state by the contact switch needs to be maintained in the conductive state.

Abstract: An image forming apparatus includes: a fixing part including a heater, and a first temperature detection part configured to detect the temperature of the heater; a chopper circuit including a reactor, a freewheeling element, and a switching element, the chopper circuit being configured to switch an input direct current on and off in a specified duty cycle by using the switching element and to supply the current to the heater; and a control part configured to control the duty cycle based on a detection result obtained by the first temperature detection part, as well as to control a switching frequency of the switching element based on an operation mode of the image forming apparatus.

Abstract: An image forming apparatus includes a timing roller for conveying paper in the image forming apparatus, a first motor receiving supply of electric power from a power source for driving the timing roller, a second motor receiving supply of electric power from the power source, a sensor for detecting whether a jam occurs at the conveyance roller, a drive relay for cutting off supply of electric power from the power source to the first and second motors, if occurrence of a jam is detected, and a control circuit for controlling an operating state of the second motor such that regenerative power produced at the first motor due to rotation of the conveyance roller is supplied to the second motor, if occurrence of a jam is detected.

Abstract: An induction heating device including a coil which inductively heats a workpiece of a fuser with an input voltage obtained from an alternating current voltage by rectification; a switching element coupled in series with the coil; a peak voltage detector which detects a peak value of the input voltage; an effective voltage detector which detects an effective value of the input voltage; a crest factor calculator which calculates an actual crest factor of the input voltage based on the peak value of the input voltage and the effective value of the input voltage; and a power controller which achieves control of power to the fuser by controlling the duty ratio of ON and OFF periods of the switching element.

Abstract: An image forming apparatus having: a power source applying alternating current voltage to the magnetizing coil; a demagnetizing coil switchable between a conductive state and a cutoff state, and when in the conductive state, cancelling out a portion of a magnetic flux produced by the magnetizing coil; a contact switch and a semiconductor switch electrically connected in parallel, and, in combination, bringing the demagnetizing coil into the conductive state or the cutoff state; and a control unit opening or closing the switches separately. The control unit: opens or closes the semiconductor switch in synchronization with a zero-crossing of the alternating current voltage at least when the contact switch is open; opens or closes the contact switch only when the semiconductor switch is closed; and opens the semiconductor switch when the demagnetizing coil brought into the conductive state by the contact switch needs to be maintained in the conductive state.

Abstract: An image forming apparatus includes a timing roller for conveying paper in the image forming apparatus, a first motor receiving supply of electric power from a power source for driving the timing roller, a second motor receiving supply of electric power from the power source, a sensor for detecting whether a jam occurs at the conveyance roller, a drive relay for cutting off supply of electric power from the power source to the first and second motors, if occurrence of a jam is detected, and a control circuit for controlling an operating state of the second motor such that regenerative power produced at the first motor due to rotation of the conveyance roller is supplied to the second motor, if occurrence of a jam is detected.

Abstract: An electromagnetic induction heating apparatus comprises: a resonance circuit that includes a inductor and a capacitor; a direct-current electric power supply; and a switching element performing ON and OFF switching of electric power supplied to the resonance circuit by the direct-current electric power supply; performs intermittent control of the electric power supply by controlling the ON and OFF switching at regular intervals, and by performing control to stop the electric power supply when not controlling the ON and OFF switching, wherein during the intermittent control, the switching control unit performs gradual control such that, upon beginning the control of the ON and OFF switching, the electric power supply gradually increases to reach a target value, and upon stopping the control of the ON and OFF switching, the electric power supply gradually decreases from the target value until stopping, such that the gradual decrease involves fewer steps than the gradual increase.

Abstract: While a recording sheet is passing through a fixing nip formed between a heating roller 41 having a heating layer and a pressing roller 42 pressed against the roller 41, a coil 43 is exited by high-frequency power from a power source and causes the layer to generate heat. An unfixed image on the recording sheet is fixed by the heat. The power source detects a zero cross timing of a rectified alternating current, detects an instantaneous value at a point a predetermined period after the zero cross timing, calculates an effective power of the alternating current based on the instantaneous value, and controls the output power to be a desired value determined based on the effective power and the surface temperature of the roller 41. Thus power input to the power source can be quickly detected and power output to the coil can be quickly and stably controlled.