Abstract: A switched-mode power supply includes a transformer, a switching element, a switching controller, a voltage generator circuit, an overvoltage protection circuit, and a load increase circuit. The overvoltage protection circuit is configured to, when a first DC voltage outputted from the voltage generator circuit is below a predetermined voltage, apply a first drive voltage to an input terminal of the switching controller, and to, when the first DC voltage exceeds the predetermined voltage, apply a second drive voltage, which is different from the first drive voltage, to the input terminal, whereby the switching controller stops controlling switching operation. The load increase circuit is configured to, when the output voltage exceeds a threshold voltage, flow a current from the secondary side, thereby increasing a load applied to the secondary side. The threshold voltage is less than a rated voltage of the transformer and greater than the target voltage.

Abstract: An AC voltage detection device has a rectifying circuit configured to rectify an AC voltage output from an AC power source, a voltage-pulse conversion circuit configured to convert a rectified voltage rectified in the rectifying circuit to a first pulse signal having a period shorter than a half of a period of the AC voltage, a pulse transmission circuit configured to perform signal transmission with electrical insulation by converting the first pulse signal to a physical signal other than an electrical signal and converting the physical signal to a second pulse signal being an electrical signal, and a controller to which the second pulse signal is input. The controller calculates the voltage value of the AC voltage from a characteristic value of the second pulse signal.

Abstract: A switched-mode power supply includes a transformer, a switching element, a switching controller, a voltage generator circuit, an overvoltage protection circuit, and a load increase circuit. The overvoltage protection circuit is configured to, when a first DC voltage outputted from the voltage generator circuit is below a predetermined voltage, apply a first drive voltage to an input terminal of the switching controller, and to, when the first DC voltage exceeds the predetermined voltage, apply a second drive voltage, which is different from the first drive voltage, to the input terminal, whereby the switching controller stops controlling switching operation. The load increase circuit is configured to, when the output voltage exceeds a threshold voltage, flow a current from the secondary side, thereby increasing a load applied to the secondary side. The threshold voltage is less than a rated voltage of the transformer and greater than the target voltage.

Abstract: An image forming apparatus, including: a photoconductor configured to be rotatable; a charger configured to charge the photoconductor; an overcurrent detector configured to output an overcurrent detection signal in response to detection of an overcurrent in the charger; and a controller, wherein the controller is configured to execute: an obtaining process of obtaining the overcurrent detection signal output from the overcurrent detector; a first counting process of counting a first number of detections based on the overcurrent detection signal obtained in the obtaining process, the first number of detections being the number of the overcurrent detection signals synchronized with a first cycle corresponding to one rotation of the photoconductor; and a first determining process of determining whether the first number of detections is not smaller than a first threshold which is not smaller than 2.

Abstract: An AC voltage detection device has a rectifying circuit configured to rectify an AC voltage output from an AC power source, a voltage-pulse conversion circuit configured to convert a rectified voltage rectified in the rectifying circuit to a first pulse signal having a period shorter than a half of a period of the AC voltage, a pulse transmission circuit configured to perform signal transmission with electrical insulation by converting the first pulse signal to a physical signal other than an electrical signal and converting the physical signal to a second pulse signal being an electrical signal, and a controller to which the second pulse signal is input. The controller calculates the voltage value of the AC voltage from a characteristic value of the second pulse signal.

Abstract: An image forming apparatus, including: a photoconductor configured to be rotatable; a charger configured to charge the photoconductor; an overcurrent detector configured to output an overcurrent detection signal in response to detection of an overcurrent in the charger; and a controller, wherein the controller is configured to execute: an obtaining process of obtaining the overcurrent detection signal output from the overcurrent detector; a first counting process of counting a first number of detections based on the overcurrent detection signal obtained in the obtaining process, the first number of detections being the number of the overcurrent detection signals synchronized with a first cycle corresponding to one rotation of the photoconductor; and a first determining process of determining whether the first number of detections is not smaller than a first threshold which is not smaller than 2.

Abstract: A power supply system includes: a switching power supply; and a control device, wherein the switching power supply includes: a transformer; a semiconductor switching element; a switch control unit; and a rectifying/smoothing circuit, the switch control unit is supplied with power from the main power supply, starts to control the switching of the semiconductor switching element, and oscillates a primary side of the transformer to induce a voltage on the secondary side of the transformer, the control device outputs a control pulse signal to the switch control unit to stop the oscillation of the transformer, thereby changing the mode of the switching power supply to an output stop mode, in an output mode in which the switching power supply smoothes the voltage induced on the secondary side and outputs the smoothed voltage.

Abstract: A power supply system includes: a switching power supply configured to rectify and smooth an AC voltage of an AC power supply to generate a predetermined DC voltage; a low-capacity power supply circuit that generates a zero-cross detection signal corresponding to zero-cross points of the AC power supply based on a rectified current flowing in a smoothing capacitor; and a controller configured to receive the zero-cross detection signal from the signal generating circuit and perform a determining process of determining whether it is possible to perform detection process of the zero-cross points based on a voltage value of the zero-cross detection signal. If the control unit determines that it is possible to perform the detection process of the zero-cross points, the control unit performs a zero-cross point detecting process of detecting the zero-cross points based on the zero-cross detection signal.

Abstract: A power supply system includes: a switching power supply for converting an AC voltage from an AC power supply into a DC voltage; a latching relay provided on an AC input line for switching a connection state of the switching power supply with the AC power supply in response to a relay drive signal; a control device for generating a relay control signal; a relay drive circuit for generating the relay drive signal in response to an input of the relay control signal and driving the latching relay by the relay drive signal; a battery for supplying electric power to the control device and the relay drive circuit when they are connected; and a switch for switching the connection state of the battery with respect to the control device and the relay drive circuit.

Abstract: A power supply system comprises: a switching power supply for generating a DC voltage by rectifying and smoothing an AC voltage of an AC power supply; a control device switching the switching power supply between the normal mode and a power saving mode; and a low-capacity power supply circuit supplying electric power to the control device in the power saving mode. The low-capacity power supply circuit includes: two capacitors, each including one end connected to the AC power supply; a rectifier circuit that is electrically connected between the other ends of the capacitors, and rectifies the AC voltage applied between the first and second capacitors; and a zero-crossing detecting circuit that is connected to a current path at the rear stage of the rectifier circuit, and detects zero-crossing points of the AC power supply.

Abstract: A power supply system includes: a switching power supply configured to convert an AC voltage from an AC power supply into predetermined DC voltages, and outputs the DC voltages; a switch circuit provided on an AC input line, the switch circuit being configured to be switched on and off and supply AC power to the power supply when the switch circuit is turned on; a low-capacity power supply circuit connected. to the AC input line at a front stage of the switch circuit, the low-capacity power supply circuit being configured to supply electric power to the switch circuit if the power supply is active and supply predetermined electric power if the power supply is not used; and a control device configured to receive the predetermined electric power from the low-capacity power supply circuit. When the power supply is not used, the control device turns off the switch circuit.

Abstract: In a heating device, a detector detects AC voltage of the AC power source. A control device detects a zero-cross timing of the AC voltage by using the detector and generate a signal having a high level period of time, a low level period of time, a rising transition changing from a low level to a high level, and a falling transition changing from the high level to the low level. The signal is such a form that at least one of the rising transition and the falling transition is in incoincidence with the zero-cross timing. The control device controls the heating switch to perform a switching action in which the heating switch is rendered on when the zero-cross timing is detected during the high level period of time and rendered off when the zero-cross timing is detected during the low level period of time.

Abstract: A power supply system includes a switching power supply for outputting a predetermined DC voltage by converting an AC voltage from an AC power supply, a latching relay provided on an AC input line for switching a connection state of the switching power supply and the AC power supply in response to a relay drive signal, a storage circuit storing electricity from the switching power supply, a control device for receiving electric power from the storage circuit in a disconnection state, and a relay drive circuit for generating the relay drive signal and outputting it to the latching relay. The control device determines whether an amount of charge of the storage circuit has decreased to a predetermined amount of charge in the disconnection state, and generates and outputs the relay control signal to the relay drive circuit.

Abstract: A power supply system includes: a switching power supply; a switching unit for switching a connection state between an AC power supply and the switching power supply; an electricity storage unit; an auxiliary power supply circuit for feeding charging current to the electricity storage unit; a driving circuit for driving the switching unit; a voltage detection circuit for detecting a voltage of the AC power supply; and a control device configured to perform: an overvoltage detection process of determining whether the AC power supply is an overvoltage based on a detection value of the voltage detection circuit; and a process of, in a case where an overvoltage is detected, keeping the switching unit at a cutoff state where the alternating current power supply and the switching power supply are disconnected.

Abstract: In a heating device, a heater has first and second terminals. The first terminal is connectable to an alternating current source. The adjustment portion selectively establishes and disconnects a first connection between the second terminal and the alternating current source. The switching portion selectively establishes and disconnects a second connection between the heater and the alternating current source. The generating circuit has a third terminal connected to the alternating current source and a fourth terminal connected between the second terminal and the adjustment portion. The generating circuit generates a zero-cross signal of the alternating current source.

Abstract: An AC voltage detecting circuit comprises: a first capacitor including a first electrode configured to connect to one end of an AC power supply, and a second electrode; a second capacitor including a first electrode configured to connect to the other end of the AC power supply, and a second electrode; a current-to-voltage converting circuit, which is connected in series between the second electrode of the first capacitor and the second electrode of the second capacitor, and which is connected to a reference potential, wherein the current-to-voltage converting circuit causes the AC current to pass through the current-to-voltage converting circuit when the AC current returns to the AC power supply, and converts an AC current output from the AC power supply into an detection AC voltage; and a voltage detecting unit, which detects an AC input voltage of the AC power supply, based on the detection AC voltage.

Abstract: In a heating device, a heater has first and second terminals. The first terminal is connectable to an alternating current source. The adjustment portion selectively establishes and disconnects a first connection between the second terminal and the alternating current source. The switching portion selectively establishes and disconnects a second connection between the heater and the alternating current source. The generating circuit has a third terminal connected to the alternating current source and a fourth terminal connected between the second terminal and the adjustment portion. The generating circuit generates a zero-cross signal of the alternating current source.

Abstract: A power supply system includes: a switching power supply, which rectifies and smoothes an AC voltage of an AC power supply to generate a first DC voltage in a normal mode; a control unit, which controls the switching power supply to switch between the normal mode and a power saving mode; and a low-capacity power supply circuit, which supplies power to the control unit in the power saving mode, and which includes: a first capacitor, which includes a first electrode connected to one end of the AC power supply, and a second electrode; a second capacitor, which includes a first electrode connected to the other end of the AC power supply, and a second electrode; a rectifying circuit, which rectify an AC voltage applied to both capacitors; and a smoothing circuit, which smoothes the rectified AC voltage to generate a smooth voltage.

Abstract: A switching power source includes: a transformer; a semiconductor switching element that is provided at a primary side of the transformer; a rectifying-and-smoothing circuit that is provided at a secondary side of the transformer; a switching controller configured to perform a switching control to turn on-and-off the semiconductor switching element, wherein the switching controller comprises: a stoppage circuit configured to perform a stoppage process to stop the switching control when a first-level control signal is input, a restart circuit configured to restart the switching control when a second-level control signal different in its level from the first-level control signal, and a limiting circuit configured to limit, at the time of a start-up of the switching power source, a performance of the stoppage process performed by the stoppage circuit until an output voltage of the switching power source increases to a target voltage.

Abstract: A power supply system includes: a switching power supply; and a control device, wherein the switching power supply includes: a transformer; a semiconductor switching element; a switch control unit; and a rectifying/smoothing circuit, the switch control unit is supplied with power from the main power supply, starts to control the switching of the semiconductor switching element, and oscillates a primary side of the transformer to induce a voltage on the secondary side of the transformer, the control device outputs a control pulse signal to the switch control unit to stop the oscillation of the transformer, thereby changing the mode of the switching power supply to an output stop mode, in an output mode in which the switching power supply smoothes the voltage induced on the secondary side and outputs the smoothed voltage.