Abstract: An optical switch for switching an optical path by changing the refractive index of the circumference of a light coupling region of a directional coupler is disclosed. Such a change is accomplished by a photochromic compound in the circumferential medium of the light coupling region. Such a photochromic compound when beamed with light of a specific wavelength undergoes a photochromic reaction which changes the refractive index of the circumferential medium of the light coupling region. Such a reaction is reversible when beamed with light of another specific wavelength.

Abstract: In order to provide miniaturization and increased-frequency operation of a DC-DC converter used with a computer, etc., a capacitor is connected in parallel with a switching element when the switching element is turned off to reduce turn-off loss. When the switching element is turned on, the capacitor and a DC power source are connected in series to supply the energy stored in the capacitor to a load circuit to result in a high initial voltage being applied across the load circuit.

Abstract: There is provided a drawing process for producing an optical fiber which comprises drawing the optical fiber from a preform therefor under tension to form the optical fiber while heating and melting the preform, wherein an outer diameter of the optical fiber on which no coating has been provided is measured at a position at which shrinkage of the outer diameter of the optical fiber, while stretched, is not larger than 0.5% and drawing conditions are controlled based on the deviation of the measured diameter from a preselected outer diameter.

Abstract: The switching of the positive (or pullup power) and negative (or pulldown power) semiconductor elements, are controlled by driving circuits which are in turn controlled by level shift circuits which have a first current control circuit and a second current control circuit coupled in parallel and this parallel connection is coupled in series with the control N-channel MOSFET of a current mirror circuit in a circuit loop arrangement with a control power supply. The first and second current control circuits are responsive to first and second control pulses of pulse widths t.sub.1 and t.sub.1 +t.sub.2, in accordance with a driving signal such that the first current control circuit supplies a first current level to the control N-channel MOSFET during the first time period t.sub.1 and the second current control circuit supplies a second current level, smaller than that of the first current level, thereto for a predetermined time period t.sub.1 +t.sub.

Abstract: A polymer clad optical fiber comprising a core made of glass selected from the group consisting of quartz glass and optical glass, a cladding made of a cured material of a polymer composition comprising a ladder type polymethylsiloxane, a linear polymethylsiloxane having hydroxyl groups and optionally a solvent, and optionally a protecting layer made of a polymer material comprising a ladder type polysiloxane having phenyl side groups, which has low light transmission loss and increased mechanical strength.

Abstract: A current sensing circuit for sensing a main current flowing through a power semiconductor element or elements, by utilizing a second current which is small in magnitude compared to the main current and varies depending on the main current, and sensing the second current through a current mirror circuit as a bias current of a differential circuit, and a function of sensing the temperature of the semiconductor element being afforded to the current sensing circuit through selection of a bias voltage.

Abstract: A key assembly which is composed of a flat key and a credit card-like key holder members. This assembly does not make the pocket bulky and can conveniently be used as a spare key for a car door lock, a building door lock, etc.

Abstract: A switching power supply using a step-up transformer whose impedance viewed from its primary side is different from the impedance viewed from its secondary side whereby the inductance of its primary and secondary windings are settable independently of each other.

Abstract: A reactive power compensator for an electric power system includes a voltage control circuit which amplifies a differential voltage between the potential command value and a potential signal corresponding to the voltage of the electric power system detected by a potential detector. The voltage control circuit outputs a reactive power compensation control signal. The control signal is fed to a reactive power output circuit which controls the voltage of the power system in order to compensate for reactive power in the power system. A gain calculation circuit is provided for setting the gain of the voltage control circuit to a value proportional to the level of short-circuit capacity of the system power on the system power supply side of the reactive power output circuit.

Abstract: A monolithic integrated circuit device comprises first and second output terminals, a power switching circuit which is connected across the first and second output terminals and through which electric current is supplied to an external load from an external power source, a driving a circuit for generating a first drive signal to be supplied to the power switching circuit, and a third output terminal in electrical connection with the driving circuit for derivation of electric energy from the driving circuit as a second drive signal to be spplied to an external circuit via the third output terminal. The monolithic integrated circuit device is capable of not only controlling power supply to an external load but also driving an external circuit which may be another power switching cirtcuit cooperative with the power switching circuit in the present monolithic integrated circuit device for the purpose of controlled power supply to the external load or which may be other types of electronic circuits.

Abstract: In a power conversion system, a DC voltage of a DC power supply is converted into a predetermined high-frequency voltage by an inverter, and a high-frequency low voltage generated from the inverter is converted into a high-frequency high voltage by a transformer. A high-frequency high voltage generated from a secondary winding of the transformer is converted into a predetermined low-frequency voltage by a frequency changing circuit. The commutating operation of the frequency changing circuit is performed by a control circuit in response to the output current of the frequency changing circuit and in synchronism with the starting time of the short-circuiting prevention period of the inverter. As a result, the converted output of the power conversion system is prevented from decreasing.

Abstract: In a voltage resonance type switching power source apparatus, which has a step-up transformer, a resonance capacitor connected in series with a primary winding of the transformer, and a transistor connected in parallel with the capacitor to cause a resonant oscillation current by the on-off operation thereof, an on signal of the transistor is produced in synchronism with a second signal, which is obtained by delaying a first signal depending on a voltage induced in a detecting winding provided in the transformer by a predetermined delay time.

Abstract: An impedance for short-circuit prevention is connected with a secondary winding side of a transformer of a resonant converter comprising a resonant circuit, a D.C. input source, and a switching devices. The short-circuit prevention impedance is driven by the driving current generated in a driving winding in accordance with a resonance current at the primary winding side of the transformer, thereby obviating the stop of an oscillation. The oscillation can be stopped at a timing of not generating a surge voltage in the switching devices by detecting a current returning to the D.C. input power source.

Abstract: A power conversion apparatus comprises an inverter for converting a voltage of a DC power source into AC power having a frequency higher than the commercial frequency, a transformer, fed by the inverter, for outputting AC power, which is adjusted at a desired voltage, a frequency converter, formed by two pairs of two gate turn-off thyristors (GTOs) connected in reverse-parallel, for converting the frequency of the AC power supplied from the transformer into the commercial frequency, and an energy regenerating device having capacitors for absorbing the energy of a spike voltage occurring due to a circuit inductance upon interruption of a current of each GTO of the frequency converter and a bridge circuit, formed by GTOs and diodes connected in reverse-paralel therewith, for switching over the direction of connecting the capacitors with a secondary winding of the transformer in accordance with the polarity of a voltage of the secondary winding in such a manner that the energy stored in the capacitors is regener

Abstract: A power supply circuit comprises first charge storing means, second and third charge storing means supplying their charged voltages so as to be used as sources of predetermined voltages applied to associated loads respectively, switch means capable of selectively establishing at least a first mode and a second mode so that, in the first mode, the first and second charge storing means are connected in series with a d.c. power source to be charged by a power supply voltage, while, in the second mode, the first charge storing means is electrically isolated from the d.c. power source and the second charge storing means, and the third charge storing means is connected to the first charge storing means in a closed circuit to be charged by the charges stored in the first charge storing means, and a drive circuit driving the switch means so that the switch means repeats an operation cycle including at least the first mode and the second mode executed in that order.

Abstract: An apparatus for molding of plastic products in which a softened plastic material is extruded from an extruder in the shape of belts or rods, the extruded material is introduced onto a main molding roll having an outer surface with a contour of the piece to be molded and the plastic material is formed into a shape corresponding to the outer surface of the main molding roll by utilizing the fluidity of the plastic material, followed by rapid cooling, to produce a plastic product having a curved shape.

Abstract: An optical fiber comprising core glass having therearound a cladding comprising fluorine-containing quartz glass and a process for producing the same are disclosed. Said cladding is composed of an inner portion having a prescribed thickness and a constant fluorine content through its thickness and an outer portion having its fluorine content being gradually decreased in a radial direction so that its outermost surface has a fluorine content of about 0.7% by weight or less relative to SiO.sub.2.

Abstract: An AC motor such as an induction motor or a synchronous motor is driven by a PWM inverter. Turn-on of the PWM inverter is controlled by PWM pulse signals obtained as a result of comparison between voltage command signals (a modulation signal) and a carrier wave signal. The voltage command signals are obtained as a function of errors between current command signals and detected current signals. Ripples included in the voltage command signals are so suppressed as to be decreased as the rotation speed of the AC motor becomes lower. By so suppressing the ripples, the level of noise generated from the motor can be reduced especially when the motor operates in a low-speed rotation range.

Abstract: Disclosed is a control circuit for a power converter apparatus using self-extinction devices as switching devices, in which turn on and turn off operations of the self-extinction devices are controlled by gate pulses which have been subject to pulse width modulation with a pulse train having a pulse width which is sinusoidally varied, and, at the same time, the self-extinction devices in same phase are made conductive in a predetermined period corresponding to an output voltage reference value to make an output of the power converter apparatus be in a shorted state in the sense of DC current to thereby control the output of the power converter apparatus.

Abstract: An apparatus for controlling a current type inverter including a bridge circuit of bridge-connected self-extinguish elements triggered by pulse width modulation signals. A current is provided for applying a single or plural triggering pulses having a desired pulse width to those self-extinguish elements connected in series with the other self-extinguish elements forming the pairs in the bridge circuit and which other self-extinguish elements are turned on by the pulse width modulation signals. By the above manner of control, the current type inverter can generate output currents of sinusoidal waveform, and the value of the output currents can be controlled over a very wide range.