Abstract: A toner concentration sensor used in an electrophotographic recording apparatus using a 2-component developing method, includes a storage storing a developer including a toner and a carrier, a first oscillator including a first resonance circuit including a coil and a condenser, the coil of the first resonance circuit being disposed in a place where an inductance of the coil varies with a permeability of the developer stored in the storage, a second oscillator including a second resonance circuit including a coil and a condenser, the coil of the second resonance circuit being disposed in a place where an inductance of the coil is constant, and a detector for detecting outputted oscillator frequencies of the first and second oscillators to determine the permeability of the developer. Accordingly, the concentration of the toner is detected from the permeability of the developer.

Abstract: A high-voltage power source apparatus with a simple construction which outputs a voltage by overlapping a DC voltage with an AC voltage. An alternating current (AC) voltage generator generates an AC voltage and outputs the AC voltage to a secondary coil of a transformer. The AC voltage and the DC voltage are developed and simultaneously overlapped from a common secondary coil of the transformer. Thus, separate AC and DC voltage generators are not necessary to produce the overlapped voltage, simplifying construction. The DC portion of the overlapped voltage may be regulated by feeding back a sample of the output voltage to a control circuit which compares the feedback with a reference and regulates the DC portion accordingly. A plurality of the overlapped voltage circuits may be operated in parallel from a single secondary coil of the transformer.

Abstract: An electrophotographic printer maintains a surface potential of a photosensitive drum at a constant value even when a photosensitive layer corresponding to a surface of the photosensitive drum wears down. The electrophotographic printer includes a charging power supply 3, a charging roller 1, a photosensitive drum 2, a discharge unit 11, a charging current detection unit 4, a transfer power supply 9, a transfer roller 8, a transfer current detection unit 14, an arithmetic and control unit 12, and a memory unit 13.

Abstract: A power source including a transformer having a primary coil, a secondary coil, and a feedback coil; a resonance capacitor connected in parallel with the primary coil of the transformer in parallel, a switching unit having an input terminal which receives an input voltage input from the feedback coil of the transformer and which controls a current through the primary coil of the transformer according to the input voltage; and a current detection unit which detects the current in order to turn off the switching unit when the detected current is higher than a predetermined current. An output voltage stabilization circuit controls the input voltage at the input terminal of the switching unit, proportional to a voltage output by the secondary coil of the transformer.

Abstract: A high-voltage power source apparatus with a simple construction which outputs a voltage by overlapping a DC voltage with an AC voltage. An alternating current (AC) voltage generator generates an AC voltage and outputs the AC voltage to a secondary coil of a transformer. The AC voltage and the DC voltage are developed and simultaneously overlapped from a common secondary coil of the transformer. Thus, separate AC and DC voltage generators are not necessary to produce the overlapped voltage, simplifying construction. The DC portion of the overlapped voltage may be regulated by feeding back a sample of the output voltage to a control circuit which compares the feedback with a reference and regulates the DC portion accordingly. A plurality of the overlapped voltage circuits may be operated in parallel from a single secondary coil of the transformer.

Abstract: An electrophotographic printer maintains a surface potential of a photosensitive drum at a constant value even when a photosensitive layer corresponding to a surface of the photosensitive drum wears down. The electrophotographic printer includes a charging power supply 3, a charging roller 1, a photosensitive drum 2, a discharge unit 11, a charging current detection unit 4, a transfer power supply 9, a transfer roller 8, a transfer current detection unit 14, an arithmetic and control unit 12, and a memory unit 13.

Abstract: A power source including a transformer having a primary coil, a secondary coil, and a feedback coil; a resonance capacitor connected in parallel with the primary coil of the transformer in parallel, a switching unit having an input terminal which receives an input voltage input from the feedback coil of the transformer and which controls a current through the primary coil of the transformer according to the input voltage; and a current detection unit which detects the current in order to turn off the switching unit when the detected current is higher than a predetermined current. An output voltage stabilization circuit controls the input voltage at the input terminal of the switching unit, proportional to a voltage output by the secondary coil of the transformer.

Abstract: An electrophotographic printer maintains a surface potential of a photosensitive drum at a constant value even when a photosensitive layer corresponding to a surface of the photosensitive drum wears down. The electrophotographic printer includes a charging power supply, a charging roller, a photosensitive drum, an erasing unit, a charging current observation unit, an arithmetic and control unit, and a memory unit. The arithmetic and control unit rotates the photosensitive drum a plurality of times while the erasing unit is turned off during an initial operation of the electrophotographic printer, controls the charging power supply to generate a charging voltage, adds values of the charging current while the photosensitive drum rotates a plurality of times, and stores a result of an addition of the values in the memory unit.

Abstract: A power supply supplies an a-c power as primary electric power and a d-c power as secondary electric power. A converter converts the primary electric power, for example, 100 VAC into the secondary electric power, for example, +5 VDC and +24 VDC. The primary electric power is used to heat, for example, a heat roller of a printer. An abnormal-temperature detector outputs a detection signal when the temperature of the heat roller heated by the primary electric power exceeds a predetermined temperature. A controller causes the converter to draw an additional current from the primary electric power in response to the detection signal so that a current drawn from the primary electric power exceeds a predetermined current. An abnormal current interrupter shuts down the current drawn from the primary electric power when the current drawn from the primary electric power exceeds the predetermined current. The power supply may have an abnormal current detector instead of the abnormal-temperature detector.

Abstract: An electrophotographic recording apparatus comprises a photosensitive drum, a transfer roller, a high voltage power supply circuit for applying a transfer voltage to the transfer roller and a CPU for controlling the entire apparatus. The high voltage power supply circuit supplies an output voltage corresponding to a control signal issued from the CPU as the transfer voltage to the transfer roller. At this time, the high voltage power supply circuit sends a current detection signal to the CPU to inform the same of an output current which flows to the transfer roller. On the other hand, the CPU outputs a control signal to the high voltage power supply circuit, the control signal corresponding to said current detection signal output from the high voltage power supply circuit. As a result, even if the output current is varied depending on the kind of the print medium and the resistance of the transfer roller, it is possible to generate the output voltage in accordance with the varied output current.

Abstract: There is provided a resonant circuit incorporating at least a coil L1 therein and a switching circuit for oscillation is connected to the resonant circuit and voltage doubler rectifier circuits 31 and 32 including capacitors C11, C12, C21 and C22 and diodes D11, D12, D21 and D22 are also connected to the resonant circuit. When the switching circuit for oscillation is turned on and off, the resonant voltage V.sub.L1 is generated in the resonant circuit and rectified with a voltage doubler amplitude by the voltage doubler rectifier circuits 31 and 32. A switching circuit for output changing over is connected to zero voltage terminals of the diodes D11 and D21 in the voltage doubler rectifier circuits 31 and 32. When the switching circuit for output changing over is turned on and off, an output voltage is selectively generated at output terminals OUT1 and OUT2.

Abstract: According to a method of adjusting a head gap, a wire dot head is set to a predetermined position of a reference head gap; a printing pattern for detecting printing time is printed by a plurality of pins; reference printing times of respective pins are detected. Next, a test printing is performed with test printing dots previously selected from printing data, and printing time of the test printing is detected. Then, the thickness of the printing media is calculated based on the reference printing time and the printing time of the test printing. At that time, a rule of thumb in which the difference of the printing time corresponds to the difference of the head gap, is used. Then, a shift amount of the wire dot head is calculated for setting the head gap to an optimum value according to the thickness of the printing media, and gap shifting mechanism shifts the wire dot head by the shift amount. This leads to highly accurate detection of the head gap and improves printing quality thereof.

Abstract: A printed chip-on-board substrate is for mounting a high-power semiconductor chip. As a construction for efficiently releasing or dissipating heat to be generated in the semiconductor chip, the printed substrate has a printed interconnected substrate and a metal plate bonded on a back side of the substrate. The printed interconnected substrate is constructed by forming an interconnected layer on a surface of the substrate. At a mount area where the semiconductor chip is to be mounted, an opening is formed reaching the metal plate. The metal plate covers the opening on the side of the back side and is formed with a thickness capable of providing rigidity sufficient to support thereon at least the semiconductor chip to be mounted.

Abstract: A drive system for a wire dot head is provided with sensors for detecting displacements of corresponding print wires. Each sensor outputs a movement initiation timing signal and an impact timing signal for the corresponding print wire. An electric current to be fed to an associated coil is normally controlled by these timing signals. It is detected whether these timing signals are obtained in a predetermined time period. If not, electric power is continuously fed to the coil or is forcedly cut off so that the timing signals are obtained within the predetermine time period.

Abstract: Printing control includes determining printing dot density of print data to be supplied to a printing head, averaging the printing dot density during a predetermined period of time based on the printing dot density determined, selecting a printing speed in response to the average value of printing dot density, and controlling printing to print at the selected printing speed.

Abstract: A printed chip-on-board substrate is for mounting a high-power semiconductor chip. As a construction for efficiently releasing or dissipating heat to be generated in the semiconductor chip, the printed substrate has a printed interconnected substrate and a metal plate bonded on a back side of the substrate. The printed interconnected substrate is constructed by forming an interconnected layer on a surface of the substrate. At a mount area where the semiconductor chip is to be mounted, an opening is formed reaching the metal plate. The metal plate covers the opening on the side of the back side and is formed with a thickness capable of providing rigidity sufficient to support thereon at least the semiconductor chip to be mounted.

Abstract: In a wire-dot impact printer having a capacitance detector for detecting a displacement of each armature by a sensor electrode arranged opposite the armature, a space is formed between each sensor electrode and its associated armature, and a shield pattern is formed with a small space left around each sensor electrode. The shield pattern is fed with a potential at least equal to the potential of each sensor electrode. This makes it possible to reduce the influence of noise upon detection of a capacitance by the capacitance detector. A noise canceling electrode is also disposed around each sensor electrode and is connected to the sensor electrode, whereby a noise canceling circuit is further provided to eliminate noise voltage. The noise canceling circuit can eliminate a noise voltage picked up by the sensor electrode and the noise canceling electrode.

Abstract: In a printer in which a print head and a print medium are moved relative to each other in a spacing direction and in a line-feed direction, the position of the print head in the spacing direction is detected, and the stoppage of the print head during a spacing operation is detected, and the stop position in the spacing direction is stored. When the print head stops, reverse line-feed is performed by a first amount. The spacing operation is then performed in the same direction as before the carriage stopped. A forward line-feed is then performed by the first amount, and then the spacing operation is performed in the opposite direction. If the print head stops again at the same stop positon, an error indication is made. If the print head does not so stop, the spacing operation is continued.

Abstract: In a driving apparatus for a wire-dot print head having electromagnets for driving print wires, each electromagnet comprising a core and a coil, sensing coils are provided in association with the respective electromagnets and provided to interlink the magnetic flux passing through the core of the associated electromagnet, a magnetic flux detecting circuit is connected to the sensing coils for detecting the magnetic flux passing through the core, and a control and drive circuit is responsive to the detected magnetic flux for deciding the termination of the energization of the drive coil.

Abstract: A wire dot printer has a thermistor that detects the temperature of a print head and a counter that starts counting when the detection temperature exceeds an alarm temperature. The printer can be controlled by switching over between normal-printing and reduced-character-printing in which a reduced number of print wires is used. When the detection temperature exceeds the alarm temperature, the printer will first stop and then control the print head in such a way as to reduce the temperature. Once the temperature drops back down below the alarm temperature, the printer will perform reduced-character-printing for a definite period of time based on the length of time from when the temperature exceeded the alarm temperature to when the temperature dropped back down below the alarm temperature. By increasing the length of time in which reduced-character-printing is carried out, the amount of heat given off by the print head decreases.