Abstract: An apparatus for and a method of controlling a high voltage in an image forming apparatus using the high voltage with a high alternating current voltage superimposed on a high direct current voltage. The apparatus includes: a high alternating current voltage output unit outputting the high alternating current voltage; a high direct current voltage output unit outputting the high direct current voltage; and a controlling unit controlling the high alternating current voltage output unit and the high direct current voltage output unit such that the high alternating current voltage is output before the high direct current voltage when the high voltage is required for printing.

Abstract: Disclosed is a device for measuring the density of an image in regard to a liquid test patch. The device has: a fan for drying a test patch by blowing air to the test patch disposed on at least one of a photosensitive medium, a photosensitive belt and printing paper; a sensor for projecting infrared light to the dried test patch and measuring the density of the test patch based on the reflected light of the infrared light reflected from the test patch; and an adjustment unit for adjusting the mixing ratio of a toner and a carrier in accordance with the measured density. The device measures the amount of light reflected from the dried liquid test patch, thus allowing the density of the image to be measured accurately.

Abstract: A duplex electro-photographic developing machine including a printing medium tray loading a printing medium, a tray open/closed detecting unit detecting whether the printing medium tray has been opened and closed, a transferring roller transferring a toner image onto the printing medium, a resistance measuring unit measuring a resistance value of the printing medium passing the transferring roller, and a concentration controlling unit controlling a concentration of the toner image according to the measured resistance value measured by the resistance measuring unit in response to the printing medium tray having changed from an open state to a close state.

Abstract: A consumable product unit, a consumable product replacement sensing apparatus and a method thereof are provided. First through third connection terminals of the consumable product unit are respectively and electrically connected to fourth through sixth connection terminals of the consumable product replacement sensing apparatus. A new product determining signal generating unit generates a signal corresponding to an effective resistance value of the consumable product unit connected to the consumable product replacement sensing apparatus through the fourth and fifth connection terminals. If the consumable product unit is new determined to be, an over-current supplying unit supplies an over-current to disconnect a fusible resistor of the consumable product unit and the new product determining signal generating unit generates the signal corresponding to an effective resistance value of one determining element of the consumable product unit.

Abstract: Disclosed is a printed circuit board comprising a contact terminal, which prevents a poor contact and reduces a manufacturing cost, and an image forming apparatus having the same. The printed circuit board comprises a circuit part for controlling and processing an operation of electronic appliance, and a large-area contact terminal formed by a group of small-area terminals for electric connection with external device. The small-area terminals can be formed in various types, respectively having regular size and shape and being distanced a predetermined interval. Accordingly, unevenness of the large-area contact terminal surface caused by soldering is prevented since a plurality of small-area terminals constitute a unit contact terminal of over a predetermined size. Therefore, quality of contact with external terminal improves. Further, manufacturing cost is reduced, and the manufacturing process becomes simple.

Abstract: A method of controlling a charging potential of an organic photoconductive cell (OPC) includes a first operation of applying two charging voltages Vc1 and Vc2 having respective duties D1 and D2 established in an engine controller unit (ECU) to a conductive roller via a high voltage power supply (HVPS) to charge the OPC, a second operation of measuring sensing voltages Vs1 and Vs2 through a sensing resistor Rs coupled to the conductive roller so that the ECU establishes a target charging current it and calculates a new charging voltage Vc3 and a new duty D3, a third operation of applying the new charging voltage Vc3 and the new duty D3 to the conductive roller via the HVPS to charge the OPC and measuring a charging current Ic3 of the conductive roller, and a fourth operation of comparing a difference between the charging current Ic3 of the conductive roller and the target charging current It with a tolerance value TOL to control the charging potential by using the target charging current when the difference is

Abstract: A toner reproduction curve (TRC) control method is provided.

Abstract: An apparatus for supplying a high voltage to a plurality of developer units has a high voltage source generating the high voltage, and a voltage switching unit including a plurality of switching elements provided between the plurality of developer units and the high voltage source to sequentially supply the voltage from the high voltage source to the plurality of developer units. The high voltage source supplies one voltage of a predetermined voltage level to the respective switching elements. The voltage switching unit has a plurality of high voltage distributing portions branching the voltage supplied to the switching elements into one or more voltages of differing voltage levels, and supplying the branch voltages and the initially supplied voltage to the respective developer units. A number of wiring harnesses or patterned connection lines, and contact-points and noise from the high voltage are reduced.

Abstract: A high developing voltage supply apparatus includes solenoid power switches, and a high developing voltage driver selectively outputting a solenoid driving signal to close one of the solenoid power switches to electrically close a corresponding mechanical contact, applying a high developing voltage to one of color development rollers corresponding to the mechanical contact closed and Kased on an image to be printed. A high developing voltage supply supplies the high developing voltage to developing roll shafts of the other color development rollers to stabilize potentials of the developing roll shafts, or, in the alternative, the high developing voltage supply apparatus may include a voltage supply supplying a self-biased voltage to the other color development rollers using the high developing voltage formed with a DC voltage VDC and an AC voltage VAC superimposed.

Abstract: A duplex electro-photographic developing machine including a printing medium tray loading a printing medium, a tray open/closed detecting unit detecting whether the printing medium tray has been opened and closed, a transferring roller transferring a toner image onto the printing medium, a resistance measuring unit measuring a resistance value of the printing medium passing the transferring roller, and a concentration controlling unit controlling a concentration of the toner image according to the measured resistance value measured by the resistance measuring unit in response to the printing medium tray having changed from an open state to a close state.

Abstract: A sheet feeding apparatus for an image forming device prevents a sheet jammed in a pickup roller from being damaged when a sheet feeding cassette is separated to remove the jammed sheet. The sheet feeding apparatus for the image forming device includes a sheet feeding cassette being removably installed in the image forming device and having a handle hole for adhesion and removal, a sheet pressure plate hinge-fixed in the sheet feeding cassette, to load and support sheets, an elastic member to elastically support the sheet pressure plate to be upwardly slanted, and a down lever installed at the lower portion of the sheet pressure plate to be moved forward or backward. When the down lever is pulled through the handle hole, the sheet pressure plate is downwardly rotated to compress the elastic member, and when the down lever is pushed, the sheet pressure plate returns to the original position by the elastic member.

Abstract: A consumable product unit, a consumable product replacement sensing apparatus and a method thereof are provided. First through third connection terminals of the consumable product unit are respectively and electrically connected to fourth through sixth connection terminals of the consumable product replacement sensing apparatus. A new product determining signal generating unit generates a signal corresponding to an effective resistance value of the consumable product unit connected to the consumable product replacement sensing apparatus through the fourth and fifth connection terminals. If the consumable product unit is new determined to be, an over-current supplying unit supplies an over-current to disconnect a fusible resistor of the consumable product unit and the new product determining signal generating unit generates the signal corresponding to an effective resistance value of one determining element of the consumable product unit.

Abstract: A method of controlling a charging potential of an organic photoconductive cell (OPC) includes a first operation of applying two charging voltages Vc1 and Vc2 having respective duties D1 and D2 established in an engine controller unit (ECU) to a conductive roller via a high voltage power supply (HVPS) to charge the OPC, a second operation of measuring sensing voltages Vs1 and Vs2 through a sensing resistor Rs coupled to the conductive roller so that the ECU establishes a target charging current It and calculates a new charging voltage Vc3 and a new duty D3, a third operation of applying the new charging voltage Vc3 and the new duty D3 to the conductive roller via the HVPS to charge the OPC and measuring a charging current Ic3 of the conductive roller, and a fourth operation of comparing a difference between the charging current Ic3 of the conductive roller and the target charging current It with a tolerance value TOL to control the charging potential by using the target charging current when the difference is

Abstract: A charging apparatus of a printer for charging a photoreceptor medium to a predetermined electric potential which includes a first electrode and a second electrode separated a predetermined distance from the first electrode and facing the photoreceptor medium, the charging apparatus includes a high voltage generating unit for generating a voltage set to the first electrode, a first varister connected to one end of the second electrode, a second varister having one end connected to the first varister in parallel and the other end connected to a ground terminal, a switching unit connected to the second varister in parallel and switched on/off, and an engine controller for controlling a duty of switching on/off of the switching unit to control a voltage maintained at the second electrode. Thus, the structure of a circuit is simplified and the size of the printer can be reduced.

Abstract: A toner reproduction curve (TRC) control method is provided.

Abstract: Disclosed is a device for measuring the density of an image in regard to a liquid test patch. The device has: a fan for drying a test patch by blowing air to the test patch disposed on at least one of a photosensitive medium, a photosensitive belt and printing paper; a sensor for projecting infrared light to the dried test patch and measuring the density of the test patch based on the reflected light of the infrared light reflected from the test patch; and an adjustment unit for adjusting the mixing ratio of a toner and a carrier in accordance with the measured density. The device measures the amount of light reflected from the dried liquid test patch, thus allowing the density of the image to be measured accurately.

Abstract: A printer including a power supply portion for converting power supplied from an external power source and supplying the same to the printer, a printer engine receiving power from the power supply portion through a power supply line, an auxiliary power storage portion for receiving power from the power supply portion to store auxiliary power, and supplying the auxiliary power necessary to drive the printer when the power supply from the external power source to the power supply portion is interrupted, a switching portion installed between the auxiliary power storage portion and the printer engine intermittently supplying power, and a printer controller for detecting a potential level of the power supply line and controlling the switching portion.

Abstract: A power supply controlling apparatus for a printer is provided which includes a switching unit connecting and disconnecting a discharge path of current rectified by a first rectifier receiving power from an external alternating current (AC) power supply, a switching controlling unit controlling the connection and disconnection of the switching unit, and a second rectifier rectifying electric energy induced in the second winding to generate a voltage for operating the printer.