Abstract: An optical scanning device of the present invention includes at least one reflecting member intervening between a deflecting surface and a surface to be scanned. The device of the present invention effectively reduces the shading of the entire optics included therein by setting up unique conditions relating to the reflecting member.

Abstract: An improved electro-absorption semiconductor modulator using an external modulation, in which a multi-quantum well (MQW) structure for absorbing a light beam is provided to increase an optical absorption capability according to an electric field, thus increasing an optical power difference between ON and OFF states. Accordingly, the electro-absorption semiconductor modulator includes a semiconductor substrate; a lower cladding layer deposited over the semiconductor substrate; a multi-quantum well (MQW) layer comprised of barrier layers and undoped well layers stacked, in succession, predetermined times on the lower cladding layer, the barrier layers being doped with an impurity; an upper cladding layer deposited over the multi-quantum well layer; and, an ohmic contact layer deposited over the upper cladding layer. The impurity comprises an n-type dopant such as silicon and has a doping density of 1017/cm3.

Abstract: A novel optical-electrical MEMS device overlaid or covered with an optically transmissive substrate held spaced in inverted preferably flip-chip bonded fashion to the device, with transparent electrodes provided in the substrate for generating an upper mirror-actuating field to supplemental the customary lower mirror-well field, enabling complementary operation.

Abstract: A photonic crystal is formed on a semiconductor substrate using a semiconductor-based fabrication process by forming a number of alternating layers of material that have different dielectric constants. The layers of material are then etched to form a number of spaced-apart stacks of alternating layers of material. An interstack material is then formed between the stacks.

Abstract: A pyroelectric crystal, e.g. a LN crystal (1), is coated with conductive films (8). When polarization charges (4) are generated on the surface of the LN crystal (1) due to its pyroelectric effect upon accumulation of stress, the presence of the conductive films (8) induces on themselves reverse electric charges (9) matching the polarization charges (4) generated on the surface of the LN crystal (1). Therefore an electric field created by the polarization charges (4) is canceled by an electric field created by the reverse charges (9) induced on the conductive films (8). The conductive film (8b) formed on a face through which signal light is transmitted is formed from a medium transparent with respect to the signal light. Therefore the light path of the signal light is not blocked by the conductive film (8b), and the polarization charges (4) generated on the signal transmissive face can be neutralized.

Abstract: An optical amplifier includes an optical amplification medium, an excitation source to stimulate the amplification medium to output at least one wavelength gain peak, and a gain equalizer to equalize the output of the amplification medium such that gain is produced at wavelengths other than the wavelength gain peak. The gain equalizer may attenuate gain at the peak wavelength. The gain equalizer may equalize the output of the amplification medium such that gain is produced at wavelengths less than the wavelength gain peak. The optical amplifier may include both a gain equalizer and automatic level control circuitry to respectively maintain substantially uniform gain at wavelengths within an optical signal band and maintain constant output power.

Abstract: An optical amplifier for fiber-optic communications systems is provided. The optical amplifier may have variable optical attenuators for adjusting the power on each of multiple input channels. A multiplexer may be used to combine the input channels onto a single optical path. A gain stage may be used to provide optical gain for the optical signals on the optical path. A control unit may be used to control the variable optical attenuators and the gain stage to produce a desired spectrum.

Abstract: An optical system comprises, in succession from the object side, a first optical element of negative optical power, a second optical element of positive optical power, and a third optical element of negative optical power, at least one of the first to third optical elements being a refracting optical element having a reflecting curved surface.

Abstract: An optical device and microscope of simple construction are provided that are capable of readily attaining super resolution with good focusing performance. This comprises a light source means (2, 3, 4, 6, 8) that generates light of multiple different wavelengths, a light condensation means to focus lights of these multiple wavelengths on an object 1, and an emitted light detector means 17 for detection of light emitted from said object 1. Among said multiple lights of different wavelengths generated from said light source means, at least one light forms a condensed light pattern of multiple spatial modes. These multiple lights are condensed upon said object 1 such that part of the region of the condensed light pattern of said multiple spatial modes is made to spatially overlap with the condensed light pattern of the other light.

Abstract: A beam generator, or beam shaping system, for example for use in an optical scanner, creates a non-Gaussian beam which provides improved indicia-reading characteristics. In one embodiment, diffractive optical elements are used to create a Bessel-Gaussian scanning beam, which comprises a coherent combination of a Gaussian beam and a Bessel beam.

Abstract: The invention relates to modification of a laser beam produced, for purposes of aiming at a target, by instruments for measuring, controlling and treatment, such as pyrometers. The invention further provides methods, for aiming of such an instrument at a target by use of a single beam, and splitting the aiming beam into fractional beams for defining a selected area of the target, and particularly as an automatically repeated action, the fractional beams being directed, for example, to indicate points on the target bounding a selected area thereof, or again being directed at successive shifted points bounding the selected area of the target, or yet again with the fractional beams being merged to define a closed loop area of the target.

Abstract: The illumination optical system includes a lens array having a plurality of lenses for splitting the light emitted from a light source into a plurality of sub-beams, at least some lenses of the lens array being decentered. The thickness of each of the lenses constituting the lens array is adjusted such that the step difference at the boundaries between the lenses falls within a predetermined step difference.

Abstract: A projection lens of the following structure was invented for the purpose of providing a bright projection optical system with the F-number of approximately 2 or lower while maintaining good optical characteristics, in an image display apparatus. The projection lens is constructed of six lens units, a first lens unit L1 of a negative optical power, a second lens unit L2 of a positive optical power, a third lens unit L3 of a positive optical power, a fourth lens unit L4 of a negative optical power, a fifth lens unit L5, and a sixth lens unit L6 of a positive optical power, in the order named from the enlargement conjugate side, and four lens units (L2 to L5) out of the lens units move toward the enlargement conjugate side during zooming from the wideangle extreme to the telephoto extreme.

Abstract: A zoom lens has the following lens components in the order named from the object side: a front lens component of a negative optical power, which has a first lens unit of a positive optical power and a second lens unit of a negative optical power in the order named from the object side; and a rear lens component of a positive optical power, which has a third lens unit of a positive optical power and a fourth lens unit of a positive optical power in the order named from the object side. The zoom lens varies a spacing between principal points of the front lens component and rear lens component by varying a spacing between the first lens unit and the second lens unit and a spacing between the third lens unit and the fourth lens unit, in order to effect zooming. The first lens unit and the fourth lens unit change their moving direction midway through zooming from the wide-angle end to the telephoto end.

Abstract: The invention relates to a magnetic drive focusing device with at least one lens within a chamber and an adjuster with magnets outside the chamber. Positioned between the lens and the chamber is a second sleeve with helical guide paths. As the adjuster is moved outside the chamber, the magnetic field within the chamber causes the lens within the chamber to move. As the lens rotates, non-magnetic guides which ride in the helical guide paths force the lens to move axially within the device.

Abstract: The present invention provides an improved optical reading and recording system utilizing optical system employing an aspherical solid immersion lens (SIL). The improved optical system has an aspherical SIL between an objective lens and the recording media. The aspherical SIL reduces the focused electromagnetic radiation beam spot size by providing an increased numeric aperture (NA) of the optical system. The aspherical surface of the SIL provide greater manufacturing and operating tolerances between the objective lens and the aspherical SIL. Greater manufacturing tolerances provide an easier to manufacture optical system. Increased ease of manufacture reduces the cost of optical systems.

Abstract: A control apparatus for a recording medium traveling speed relative to a reproduction apparatus comprises a control apparatus (1B) for designing a recording medium traveling speed characteristic relative to a recording medium position of a recording medium in a reproduction apparatus (2), generating a recording medium traveling speed control signal (S2) based on the designed recording medium traveling speed characteristic and supplying the control signal to the reproduction apparatus (2) and controlling the reproduction apparatus (2), and a display apparatus (1A) for displaying the recording medium traveling speed characteristic diagram designed by the control apparatus (1B) and an input apparatus (1C), (1D) for designing the recording medium traveling speed characteristic of the control apparatus (1B), whereby the control apparatus for a recording medium traveling speed relative to a reproduction apparatus capable of designing an arbitrary and desired recording medium traveling speed characteristic relative

Abstract: A circuit for measuring signal output of a transducer includes an amplifier having a differential input and a single ended output referenced to a fixed potential. One transducer terminal is coupled through a source follower to an input terminal of the differential input and the other transducer terminal is coupled through a source follower and a resistive element to the other input terminal of the differential input whereby the transducer terminals are isolated from the fixed potential. A voltage to current converter converts the voltage at the single ended output to an output current that is applied to an input branch of a current mirror. A first output branch of the current mirror supplies a current equal to the converter output current to one terminal of the differential input. A second output branch of the current mirror supplies a current equal to the converter output current to the other terminal of the differential input.

Abstract: A method sets bit densities and track densities for a plurality of heads in a data storage device. The method includes determining an initial bit density and an initial track density for each head. An initial total capacity for the storage device is determined based on the initial track densities and the initial bit densities. A desired capacity for the storage device is selected and the initial total capacity and the desired capacity are compared. One of either a bit density or a track density is then adjusted so that the data storage device has an adjusted capacity that provides some excess capacity over the desired capacity where the excess capacity is less than any excess capacity that was present between the initial capacity and the desired capacity. A data storage device formed through this method is also provided.

Abstract: A peak detection circuit receives a playback signal from a magnetic storage medium and generates a peak detection signal. A shift register transmits the peak detection signal, and a pattern detection circuit is responsive to signals from the shift register to detect a first predetermined temporal pattern of peaks in the peak detection signal. A pattern correction circuit adjusts the relative timing of peaks in the peak detection signal so that the first predetermined temporal pattern of peaks in the peak detection signal is converted to a second predetermined temporal pattern of peaks in a corrected peak detection signal.

Abstract: An information storage apparatus for carrying out a signal processing for a partial response system through a recording medium. A recording unit converts an RZ input code into an NRZI code and records the NRZI code in the recording medium through a write head, thereby giving a (1−D) waveform processing to the RZ input code. An equalizing unit carries out Nyquist equalization for a reproduction code reproduced from the recording medium through a read head based on an equalizing transmission characteristic obtained by dividing a cosine roll-off characteristic setting ¼ of a maximum frequency determined by the RZ input code to be a Nyquist frequency by a transmission characteristic of a magnetic recording and reproducing system. A maximum likelihood detecting section carries out maximum likelihood detection for the code string which is Nyquist equalized by the equalizing section.

Abstract: An information storage device (10, 510, 610, 710) includes a cradle (12, 512, 612, 712) which can removably receive a cartridge (11, 411, 511, 611, 711). The cartridge contains a rotatably supported disk (91, 326-327), and a pivotal actuator arm (101) which supports a read/write head (107, 331-334) for movement adjacent the disk. A coil (117) on the arm interacts with an external magnetic field to effect pivotal movement of the arm. The cartridge may contain a spin motor (92) for effecting rotation of a disk. A preamplifier (111) and an electrostatic discharge buffer (112) are provided for the head. A read-only memory (186) contains characteristic information about the cartridge, and an hour meter (191) contains information about the cumulative amount of time that the cartridge has been used. A connector (71) is provided to electrically couple external circuitry to electrical components within the cartridge.

Abstract: A reproducing circuit for a MR head is proposed, wherein a MR head is interposed between a pair of current source circuits and a feedback amplifier is provided for controlling the current of the pair of the current source circuits so that a terminal voltage of the MR head becomes a predetermined value. Reproduced output from the MR head is derived from an amplifier having balanced input terminals for canceling noises and ripple components included in a power source.

Abstract: A method and apparatus for removing second order distortion is disclosed. The method couples a differential load between two source followers of a gain stage. The apparatus includes a differential load having two MOS transistors of unequal channel width/length ratios. The differential load implements a square and summing function in a single circuit eliminating the need to split the signal path.

Abstract: A disk and spindle motor assembly of a rotating disk drive is constrained from freely rotating when not in use to reduce fretting of the spindle assembly bearings in the presence of vibration. Preferably, a small electric current is driven through at least one of the spindle motor drive coils to hold the spindle assembly in a fixed angular position while the disk drive is not in use. The spindle motor is preferably a brushless DC motor comprising a multi-phase electrically driven stator and a permanent magnet rotor. Drive transistors normally drive the different phases under control of a processor. To constrain the drive, at least one of the drive transistors for a phase is activated. The rotor is preferably rotated periodically to a different angular position by driving a different phase of the stator. The rotor is alternatively constrained by mechanical means. The exemplary environment is an on-board motor vehicle application.

Abstract: Methods and apparatus for a magnetic tape drive, which allow a magnetic tape to be positioned with respect to a tape head. The invention includes actively controlling the position of a tape guide used to support the tape as it passes over the tape head. By controlling the position of the tape guide, the tape can be caused to move a direction perpendicular to the primary direction of travel of the tape. One method of the invention includes providing a first tape guide aligned along a primary axis and disposed proximate a first side of the tape head. The tape is moved across the first tape guide and the tape head in a primary direction while the first tape guide is pivoted, to thereby cause the tape to move in a secondary direction essentially perpendicular to the primary direction.

Abstract: A method and an apparatus for controlling a disk drive are contrived to reduce consumed electric power of a spindle motor of the disk drive while an operation continues. The disk drive has a disk storage medium, the spindle motor for rotating the disk storage medium, and a head for reading data on the disk storage medium. This control method comprises a first step of detecting a load of the spindle motor or a load capacity of a power source of the disk drive, and a second step of selecting any one of a first mode of revolving the spindle motor at a comparatively high speed and reading the data on the disk storage medium by the head, and a second mode of revolving the spindle motor at a comparatively low speed and reading the data on the disk storage medium by the head in accordance with a detected result of the first step.

Abstract: A method is provided for writing a servo-pattern on a storage medium. According to the method, first timing marks are written at a first radial position of the storage medium, and the head is moved to a second radial position. Time intervals between selected pairs of the first timing marks are measured, and other timing marks are written at the second radial position of the storage medium. The measuring step is performed after the moving step. In one preferred method, the steps of moving, measuring, and writing other timing marks are repeated until the servo-pattern is written on an entire surface of the storage medium. A method is also provided for generating an initial aligned pattern of timing marks for self-servo-writing on a storage medium.

Abstract: A hard disk drive apparatus is capable of reducing a noise effectively during operation and capable of enhancing the reliability of the drive. The hard disk drive has first and second ribs that are formed near a pivot for an actuator so that a tilt of the pivot is prevented when the actuator is operated. Also, vibration absorbing members are interposed between the first and second ribs on the side of a base and a cover so that the vibration absorbing members are brought into contact with the cover. These vibration absorbing members are located in an intermediate portion between fixing places for fixing the cover to the base and a fixing place for fixing the cover to the pivot.

Abstract: In a T-head design, it is desirable to reduce the side-writing that occurs during the write operation. The side-writing causes the track width to increase and therefore reduces the track density that can be achieved. The side-writing is caused by certain corners of the T-head producing extraneous fluxes over the magnetic disk. The extraneous fluxes write to the magnetic disk, causing the track width to be increased. The present invention recesses part of the T-head from the air bearing surface by a focused ion beam milling, an ion milling, or an etching process. The extraneous fluxes are therefore recessed from the magnetic disk by a shallow distance sufficient to prevent writing to the magnetic disk, but not so great a distance to inhibit the flux carrying capacity of the structure to the actively writing pole tip.

Abstract: A data storage device has a shock sense indicator disposed within its housing. The shock sense indicator may provide visible, audible, and/or machine-detectable indication of whether the data storage device has been subjected to a physical shock over some threshold. Machine detection of the shock state can be accomplished optically, mechanically, or electrically. A data storage drive has a detection switch that interfaces with a shock detector of a data storage device to ensure that no harmful operation is performed on a data storage device that has been subjected to a physical shock, thereby avoiding potential loss or corruption of data.

Abstract: A head element is made into contact with the surface of a recording medium so as to realize a float-up degree of 5 nm. Accordingly, a slider incorporating the head element for recording and reproducing data to and from the recording medium is provided thereon with a plurality of pads having step parts, and one of the plurality of pads, on which the head element is mounted, has a height which is less than that of the other pads. Thus, the pads other than the pad on which the head element is mounted are floated up while the pad on which the head element is mounted is stably made into contact with the surface of the recoding medium by means of a meniscus suction force and a damping action of lubricant applied on the surface of the recording medium.

Abstract: In order to provide a suspension, a head suspension assembly, and a disk drive apparatus that can contribute to an increase of record and playback reliability, holes 3c in ribs 3b of the head suspension assembly 3 are provided. This design decreases the displacement of a head slider 2 that is caused by Karman vortex streets occurring near the ribs 3b in company with the rotation of the magnetic disk 1.

Abstract: An actuator assembly for positioning read/write heads above a data storage media comprises a pivotally mounted carriage arm assembly with a voice coil and a magnetic device having a plurality of poles for generating a magnetic field. The voice coil is positioned with its effective portions crossing through the magnetic field to generate at least one pair of driving forces in a direction substantially orthogonal to a seeking direction of the read/write heads. The carriage arm driven by said pair of forces has substantially no reacting force generated onto the pivot so that the servo bandwidth of the head positioning assembly can be improved and achieves a high degree of head positioning accuracy.

Abstract: The invention relates to a microactuator comprising a movable structure having a symmetric axis about which the movable structure are divided into two parts which can produce the same movement but in opposite directions; two active arms built with piezoelectric material; two stationary structures to connect the two active arms at their two ends, respectively. The invention also relates to a disk drive suspension which is incorporated with the microactuator.

Abstract: The invention is a magnetoresistive recording head including the reader portion that has a top and bottom shield, a first auxiliary electrical connection, a second auxiliary electrical connection, a first auxiliary electrical contact, and a second auxiliary electrical contact, where the first auxiliary electrical connection electrically connects the first auxiliary electrical contact to the top shield, and where the second auxiliary electrical connection electrically connects the second auxiliary electrical contact to the bottom shield.

Abstract: A magnetic head is provided that has a smaller amount of change in asymmetry with respect to the MR height, and has an improved resolution for a reproduction signal. In a magnetic head including a magnetoresistive device as a read device for reading magnetic recording information recorded on a magnetic recording medium, the magnetostriction constant of a soft magnetic substance forming the magnetoresistive device is 0 or below. Since the magnetostriction constant of the magnetoresistive device is 0 or below, the amount of change in asymmetry with respect to the MR height is reduced. Therefore, even when the MR height is slightly changed, the asymmetry does not vary significantly.

Abstract: A dual tunnel junction sensor operates without the requirement of first and second shield layers. This is accomplished by making first and second free layer structures antiparallel (AP) coupled structures. The first free layer structure has first and second AP coupled layers and the second free layer structure has third and fourth AP coupled layers. The thicknesses of the first and third AP coupled layers, which are preferably equal, are different from the thicknesses of the second and fourth AP coupled layers, which are also preferably equal. Field signals from perpendicular or longitudinally recorded magnetic disks rotate the magnetic moments of the first and second free layer structures so that resistances on each side of a pinning layer are additive. Extraneous field signals, other than signal fields from the rotating magnetic disk, are cancelled by common mode rejection.

Abstract: A magnetoresistive angular sensor (1) is provided which determines a magnetic field direction. A high angular accuracy over a wide range of magnetic field strengths is obtained. The magnetoresistive angular sensor comprises a main sensing element (2) which is electrically connected to a first correction sensing element (6) with a first reference magnetization axis (9) and a second correction sensing element (8) with a second reference magnetization axis (10), the first (9) and the second (10) reference magnetization axes making correction angles &THgr; between 5° and 85° of opposite sign with the main reference axis (3).

Abstract: At least a part of the insulation layers is made of an insulation material which increases electric conductivity thereof when an ultraviolet radiation is irradiated. Thus, improved resistance properties against ESD can be obtained during fabrication.

Abstract: A magnetoresistive (MR) device includes a synthetic antiferromagnetic (AFM) layer having an Fe/FeSi/Fe construction. A first Fe layer of the synthetic AFM layer has a magnetization substantially in a first direction, while a second Fe layer of the synthetic AFM layer has a magnetization substantially in a second direction that is substantially antiparallel to the first direction. The magnetoresistive device can be a spin valve in which a first surface of the synthetic AFM layer is adjacent to a pinning layer, and a second surface of the synthetic AFM layer is adjacent to a spacer layer. Further, the spin valve includes a free layer that overlies the spacer, thereby being separated from the synthetic AFM layer by the spacer. The pinning layer, synthetic AFM layer, spacer, and free layer can be bounded by a first shield and a second shield to provide magnetic shielding of the spin valve sensor.

Abstract: A magnetoresistive element includes a first antiferromagnetic film, a first magnetic film having a magnetization direction fixed by magnetic coupling with the first antiferromagnetic film, a second antiferromagnetic film, a second magnetic film having a magnetization direction fixed by magnetic coupling with the second antiferromagnetic film, a third magnetic film having a magnetization direction able to rotate in response to an applied magnetic field, a first nonmagnetic film disposed between the first magnetic film and the third magnetic film, and a second nonmagnetic film disposed between the second magnetic film and the third magnetic film. The third magnetic film is disposed between the first nonmagnetic film and the second nonmagnetic film, the first magnetic film is disposed between the first antiferromagnetic film and the first nonmagnetic film, and the second magnetic film is disposed between the second antiferromagnetic film and the second nonmagnetic film.

Abstract: A thin film head includes a GMR element formed of an antiferromagnetic layer, a pinning layer, a nonmagnetic conductive layer, a free magnetic layer, and a pair of the right and the left laminated longitudinal biasing layers. Each of the biasing layers contains a high coercivity ferromagnetic layer, a nonmagnetic layer and a low coercivity ferromagnetic layer provided on the free magnetic layer of the GMR element. The high coercivity ferromagnetic layer and low coercivity ferromagnetic layer are antiferromagnetically exchange-coupled via the nonmagnetic layer, and the high coercivity ferromagnetic layer and free magnetic layer located next to the high coercivity ferromagnetic layer are ferromagnetically coupled.

Abstract: An arc fault causes the line voltage across the line terminals of an arc fault circuit interrupter (AFCI) to change its characteristic voltage pulse shape as the line voltage is momentarily removed from the AFCI terminals after the arc extinguishes and before it re-strikes by introducing a flat voltage portion to the pulse shape. This flat voltage portion changes the voltage pulse width. An arc detector/processor detects this change in pulse width to produce a signal indicative of upstream (line side) arcing. The flat voltage portion can also be detected using clamping diodes and charging capacitors.

Abstract: A structure is designed with an external terminal (100) and a reference terminal (130). A first transistor (106) has a current path coupled to the external terminal and has a first control terminal (114). A second transistor (110) has a current path coupled between the current path of the first transistor and the reference terminal and has a second control terminal (126). A bias circuit comprises a third transistor (116) having a first conductivity type and a fourth transistor (124) having a second conductivity type. The third and fourth transistors have respective current paths coupled in series to the reference terminal. The bias circuit is arranged to produce a first voltage at the first control terminal and a second voltage different from the first voltage at the second control terminal.

Abstract: A power semiconductor circuit drives a load connected an output terminal. An output switch switches the output terminal to either one of an on-state and an off state. An internal state signal terminal produces an internal state of the circuit as a signal. An internal state signal switch switches the internal state signal terminal to either one of an on-state and an off-state. An internal state sensor detects the internal state of the circuit. A logic circuit is given with a control signal from an external control circuit, a detecting signal of the internal state sensor, and the signal from the internal state signal terminal, and switches the output switch and the internal state signal switch to either one of the on-state and the off-state on the basis of the given signals.

Abstract: A clamping MOS transistor-based overvoltage protection circuit is provided for a bidirectional transmission gate FET coupled between input and output ports. When the voltage applied to the input port exceeds the supply voltage by a MOS gate threshold, the clamping MOS transistor is turned on, pulling the voltage applied to the gate of the transmission gate FET very close to the applied overvoltage level by a voltage differential less than a diode drop. This reduction in Vgs of the transmission gate FET reduces its source-to-drain current, as the device operates deeper in a sub-threshold region, increasing the overvoltage rating for the same leakage current specification. In a second embodiment, a clamping MOS device is coupled on either side of the source-drain path of the transmission gate's FET device.

Abstract: An overcurrent/leakage protection circuit installed in an electric socket or the like for over current/electric leakage protection, which includes a relay, a SCR (silicon controlled rectifier) which controls the relay, a trigger circuit which triggers the SCR, a constant current detector, and a micro current detection amplifier, wherein the relay has a common contact connected to a first power line, a normal close contact for power output of the first power line, and a normal open contact bridged to a second power line through an alarm lamp; the trigger circuit is driven to trigger the SCR upon detection of an overcurrent or short-circuit detected by the constant current detector or an electric leakage by the micro current detection amplifier, causing the normal close contact to be opened to cut off power supply from the load.

Abstract: A remote control and power protection circuit installed in an electric outlet and adapted to control the operation of each electric socket of the electric outlet by means of a remote controller and to automatically trip off the circuit upon an overcurrent or overvoltage. The remote control and power protection circuit includes a CPU having voltage/current detector and amplifier circuit means and voltage/current judging circuit means adapted to detect the voltage/current value of inputted power supply, and to drive a red LCD to flash and a buzzer to buzz when inputted current value approaches the rated value, and to drive an overload switch element to trip off power supply upon an overcurrent or overvoltage.

Abstract: The present invention relates to a technique of limiting an overcurrent of a power semiconductor element (1) such as an IGBT. In a background art overcurrent protection circuit (10P), when an emitter current (i) and a current sense current (is) do not show the same behavior even in a transient state, the current sense current tends to momentarily increase at a turnoff, and in such a case, the energizing capability of a MOSFET (2P) in the overcurrent protection circuit increases and the turnoff speed of an IGBT (1P) becomes much faster than necessary and as a result, a surge voltage disadvantageously increases. Then, in the present invention, a diode (5) having a forward voltage set not lower than a threshold voltage of the MOSFET (2) is so provided as a voltage clamping circuit (4) between a gate electrode (2G) and a source electrode (2S) as to be biased in the forward direction in an overcurrent protection circuit (10) of an IGBT (1).