A heating device heats a sheet to which a liquid discharge unit discharges a liquid. The heating device includes a first heater to heat the sheet that has passed through the liquid discharge unit, a vacuum conveyor to convey the sheet that has passed through the first heater while sucking the sheet, a second heater to heat the sheet being conveyed by the vacuum conveyor, and circuitry that cause the first heater to heat the sheet when sheet data regarding the sheet satisfies a predetermined condition.

A light irradiation unit includes a substrate having a longitudinal direction, the longitudinal direction being a first axis direction; multiple light sources arranged along the first axis direction on a first surface of the substrate; a heat dissipation member arranged on a second surface of the substrate opposite to the first surface; and a housing having a pair of first side surfaces holding the heat dissipation member therebetween in a second axis direction orthogonal to the first axis direction along the first surface. The substrate has, at an end portion in the first axis direction, an end surface intersecting the first axis direction. The location of the end surface in the first axis direction is near an edge of the first side surface along the first axis direction. The end surface is exposed from the housing or covered by a detachable protection member.

An image forming apparatus includes an AC input portion to which AC power is to be supplied from a commercial power source, an image forming unit configured to form an image on a recording material, a fixing device including a first fixing heater and a second fixing heater which are configured to generate heat, the fixing device being configured to heat the image on the recording material by using the first fixing heater and the second fixing heater to fix the image to the recording material, a first relay configured to be switched between a first state in which electric connection is established and a second state in which electric connection is not established, and a second relay configured to be switched between a third state in which electric connection is established and a fourth state in which electric connection is not established.

An image forming apparatus includes an AC input portion to which AC power is to be supplied from a commercial power source, an image forming unit configured to form an image on a recording material, a fixing device including a first fixing heater and a second fixing heater which are configured to generate heat, the fixing device being configured to heat the image on the recording material by using the first fixing heater and the second fixing heater to fix the image to the recording material, a first relay configured to be switched between a first state in which electric connection is established and a second state in which electric connection is not established, and a second relay configured to be switched between a third state in which electric connection is established and a fourth state in which electric connection is not established.

A light irradiation unit includes a substrate having a longitudinal direction, the longitudinal direction being a first axis direction; multiple light sources arranged along the first axis direction on a first surface of the substrate; a heat dissipation member arranged on a second surface of the substrate opposite to the first surface; and a housing having a pair of first side surfaces holding the heat dissipation member therebetween in a second axis direction orthogonal to the first axis direction along the first surface. The substrate has, at an end portion in the first axis direction, an end surface intersecting the first axis direction. The location of the end surface in the first axis direction is near an edge of the first side surface along the first axis direction. The end surface is exposed from the housing or covered by a detachable protection member.

A heating device heats a sheet to which a liquid discharge unit discharges a liquid. The heating device includes a first heater to heat the sheet that has passed through the liquid discharge unit, a vacuum conveyor to convey the sheet that has passed through the first heater while sucking the sheet, a second heater to heat the sheet being conveyed by the vacuum conveyor, and circuitry that cause the first heater to heat the sheet when sheet data regarding the sheet satisfies a predetermined condition.

A heating device includes a base, resistance heating elements, a power control circuit, a first temperature detector, a second temperature detector, a power interrupter, and control circuitry. The resistance heating elements are arranged in a longitudinal direction of the base and electrically connected in parallel. The first detector detects a temperature of a first resistance heating element. The second detector detects a temperature of a second resistance heating element. The power interrupter interrupts power supplied to the resistance heating elements when the temperature of the second resistance heating element becomes a predetermined temperature or more. The control circuitry controls the circuit such that a temperature of each resistance heating element becomes a predetermined temperature, based on a result of detection of the first detector, and interrupts the power supplied to the resistance heating elements when the second detector detects predetermined temperature information regarding the second resistance heating element.

The present subject matter describes a heating unit. The heating unit comprises a heating element and a controlling unit coupled to the heating element to determine a desired value of a direct current (DC) voltage based on heating element parameters. The desired value is a value of DC voltage desired for operation of the heating element. The controlling unit computes a value of a duty cycle parameter based on device input parameters and the desired value of the DC voltage. The heating unit further comprises a power factor correction (PFC) unit coupled to the controlling unit and the heating element to convert an input alternating current (AC) voltage, received by the PFC unit from an AC supply, to a direct current (DC) voltage of the desired value based on the duty cycle parameter. The PFC unit provides the DC voltage to the heating element.

A fixing unit includes a first heater, a first switch, a second heater, and a second switch. In an image forming mode, a controller controls the first switch and the second switch to keep a temperature of the fixing unit at a fixing temperature serving as a target temperature for fixing the image on the sheet. In a standby mode, the controller controls the first and second switches to keep the temperature of the fixing unit at a standby temperature, and controls the first and second switches such that a period in which a first current is supplied to the first heater and a period in which a second current is supplied to the second heater do not overlap.

In a caser where a first current is supplied to a first heater, a controller gradually increases the first current in a first period, supplies the first current based on a first duty cycle in a second period, and gradually reduces the first current to stop supplying the first current in a third period. In a case where a second current is supplied to a second heater, the controller gradually increases the second current in a fourth period, supply the second current based on a second duty cycle in a fifth period, and gradually reduces the second current to stop supplying the second current in a sixth period. The controller controls the supply of the second current such that part of the fourth period overlaps with the third period.