Abstract: A circuit arrangement for monitoring the current supply of an electric consumer has a voltage regulator connected to an operating voltage that is variable over time and has a voltage monitor for switching on a consumer exclusively during the constant phase of the supply voltage. The voltage monitor is defined by a comparator at one input of which a reference voltage proportional to the regulator output voltage is present and at the other input of which a difference voltage picked up at the regulator output and exceeding a threshold value is present. A switch-on and switch-off signal can be take off at the comparator output.

Abstract: A fail-safe system in a power regulation circuit for an automotive electronic circuit such as electronic anti-skid brake control system, which fail-safe system can perform fail-safe operation even when the power regulation circuit is damaged and thereby the supply voltage from the power regulation circuit varies significantly. The fail-safe system in a power regulation circuit includes a monitor power supply circuit independently of the power regulation circuit. The monitor power supply circuit is adapted to produce a reference signal to be compared with the output of the power regulation circuit in a fail-safe circuit. The fail-safe circuit produces an error signal when the output signal value drops below a given threshold defined by the reference signal value to activate an alarm signal generator and disconnect an actuator controlled by the control system in order to prevent the actuator from malfunctioning due to errors in the control system.

Abstract: A mains protection device for a.c. mains comprises a circuit for detecting whether or not the mains voltage is within an amplitude window. When the voltage goes above or below the window, the mains is disconnected from an appliance and when the voltage returns to within the window for a preset time, the mains is reconnected to the appliance.

Abstract: To protect electrical equipment against excessive applied input signals which, for example, may be analog signals, excessive with respect to positive or negative excess voltage in relation to an upper reference level (U.sub.Ref) and/or a lower reference level (GND), collector current control of the transistor (12) at the input (3) of the protective circuit by three transistors (11, 13, 14) holds the voltage level at the input (3) at the reference voltage level when a driving or signal supply circuit provides an excess voltage. The input transistors, and the further transistors, are connected in the form of a current mirror. The circuit can be constructed in dual form (11-14; 21-24) to provide for protection against negative over-voltage as well. Due to the symmetrical circuit structure, excellent temperature compensation is obtained. The circuit can easily be constructed in the form of an integrated circuit.

Abstract: A reserve power source, switchably connected to a network between a primary power supply and a load, provides an auxiliary power signal to the load when a power failure condition is detected in the signal from the primary power supply. The reserve power source includes a circuit for instantaneously detecting and switching upon the occurrence of a power outage. An overvoltage/noise detector circuit is included to detect when either a sustained overvoltage condition or a high, short duration overvoltage condition occurs. A low voltage detector circuit is included for detecting a low voltage, or brown-out, condition. When an overvoltage or low voltage condition is detected, a preferred embodiment of the invention switches the load to the auxiliary power signal within one-half cycle of, but in zero-crossing synchronization with, the primary power signal.

Abstract: This dynamic protection device is particularly intended for integrated circuits having input MOS stages and logic or analog inputs fed by voltages and/or currents whose value can increase above those bearable with traditional protection systems. The device is composed of a first section for protection against voltages above a first set threshold value and a second protection section against voltages below a set threshold value. The device is made in MOS technology and is disposed between the input of the circuit to be protected and the power supply.

Abstract: A circuit diagnosis and control device adapted to detect defects in a primary electrical circuit and temporarily discontinue power to the primary circuit in the event of a defect. A MOS transistor is connected in series with the power source and the primary circuit. A calculation device is connected with the MOS transistor and periodically tests a first voltage V.sub.GS, which may be different from zero, and a second voltage V.sub.DS, which must be higher than half of the voltage V.sub.BAT of the battery. In the event of a short circuit, the power is temporarily withheld from the primary circuit. An indication lamp may be controlled by the calculation device to inform the driver of the circuit condition. If V.sub.GS is not equal to zero and V.sub.DS is half of V.sub.BAT, a short circuit condition is indicated, for example, by a slow flashing of the indicator lamp. If V.sub.GS is equal to zero and V.sub.DS is less than half of V.sub.

Abstract: A protective circuit arrangement is provided for shutting down a power supply at the occurrence of a fault condition. The circuit arrangement allows current limiting in a switching transistor during a power on and/or power off cycle, but shuts down the power supply if current limiting occurs at any other time.

Abstract: A power supply system includes a main power unit for supplying power necessary for the operation of an electronic apparatus including a memory, an auxiliary power unit for supplying power necessary for retaining the memory contents, and a battery serving as a back-up of said main and auxiliary power units for supplying power necessary for retaining the memory contents. The memory is supplied with power from the main power unit when it is in the power-on state, from the auxiliary power unit when the main power unit is in the power-off state, and from the battery in the event of a.c. power failure.

Abstract: A battery back-up system providing a short term hold-up for a converter type switched power supply. The back-up system includes a regulated charger circuit for maintaining the battery in a charged condition and a direct current fan which cools the power supply in both the normal and battery back-up modes. Over-voltage protection for the system is provided during the battery back-up mode, and protection for the battery is provided against excessive battery charging voltages. The fan and regulator are automatically turned off when the battery reaches a deep discharge condition to protect the battery.

Abstract: Each digital module in a network is provided with a local power switching control subsystem wherein the local module uses a local power switching control logic card which controls main power and subordinate power units in a predetermined sequence. Power up/down conditions or incremental/decremental voltage conditions can be effected by a local operator or by an instruction from a remote master logic unit. The power subsystem can sense failure conditions and communicate this information to the remote master unit or to a local operator.

Abstract: A current limiting device that, with increases of input voltage, the current increases to a first value and, as the input voltage increases further, the current decreases to a second value so as to protect any of a plurality of loads that may be used therewith.

Abstract: A power distribution system includes a plurality of power sources and load transfer units including transistors and diodes connected in series and leading to a common power output, each of the transistors being controller switchable subject to voltage levels of the respective input and output sides of said transistors, and the voltage and current level of said common power output. The system is part of an interconnection scheme in which all but one of the power sources is connected to a single load transfer unit, enabling the survival of at least a single power source with the failure of one of the load transfer units.

Abstract: A DC power control circuit with status report and protection against overloads and short circuits is provided in which the output stage comprises at least one output amplifier whose input receives an external control logic signal and whose output is connected, through a current limiter, to the output of the circuit. The control circuit further comprises a voltage threshold detector which compares the residue voltage of the output stage with a threshold voltage corresponding to a maximum acceptable difference and which delivers a report signal representative of the sign of the difference between the residue voltage and the threshold voltage.

Abstract: Three possible types of "faults" may be detected in the ignition system of a vehicle, using simple combinational logic to provide an essentially error-free activation of an indicator when a true fault is present. "Fault" signals which mean non-rotation of the alternator, broken cables or short circuits and the like are distinguished from transient and less significant conditions. The latter conditions are prevented from activating the indicator. A single indicator lamp serves to alert the user to a serious fault requiring service.

Abstract: According to the present invention, an induction heating apparatus comprises a rectifying circuit for rectifying an AC voltage from an AC power source, an inverter circuit for converting a DC output from the rectifying circuit to a high frequency current and supplying it to a heating coil, a circuit for detecting a fluctuation in the AC power source through a low voltage converting section coupled to the AC power source, this detecting circuit having a detection characteristic which can hold the detecting state for at least a constant time, and a controlling circuit for controlling the inverter circuit in the stopped state or driving state in accordance with the presence or absence of a detection output from the circuit for detecting the fluctuation in the AC power source voltage.

Abstract: In an X-ray generator system having a pulse-width-modulated transistor inverter with associated flywheel diodes, method and apparatus is provided to sense when a diode associated with a non-pulse-width-modulated transistor is conducting and for inhibiting the turning on of that transistor during such period, to thereby avoid the transition from reverse conduction to direct conduction in an uncontrolled manner.

Abstract: An alternator circuit comprises an alternator having an armature winding, a field winding, a voltage regulator, a fault detecting circuit, a lamp drive circuit having its input connected to the output of the fault detecting circuit, and a warning lamp driven by the drive circuit. The drive circuit includes a capacitor connected across its input, an input transistor, an output transistor, a current measuring resistor connected in series with the output transistor, and a transistor sensitive to both the voltage drop across the warning lamp and the voltage drop in the current measuring resistor. In the event of excessive current flow through the output transistor, the voltage sensitive transistor rapidly charges the capacitor thereby turning off the output transistor. The capacitor then discharges slowly and the cycle is repeated.

Abstract: Electronic circuitry senses over-voltage and under-voltage within narrow threshold limits, and voltage interruption, in the energization circuit of a sensitive load, such as a refrigeration compressor motor load, to protect against overheating damage and burn-out. Setting to a nominal operating line voltage is provided for to obviate readjustment to the threshold voltages of a window comparator utilized to sense over-voltage and under-voltage.

Abstract: Two different set voltages are respectively compared with a power source voltage. When the smaller set voltage which is close to a minimum operating voltage of an arithmetic circuit coincides with the power source voltage, a clock signal generator, and hence the arithmetic circuit are stopped. When the power source voltage increases to coincide with the larger set voltage after the clock signal generator is stopped, the clock signal generator and hence the arithmetic circuit are restarted.

Abstract: An apparatus for protecting machinery driven by electric motors from operating during over-load and light-load conditions, comprising: a current transformer operatively associated with an electrical supply line for the induction motor; a current-voltage transforming circuit for generating a control signal having a magnitude proportional to current flowing in the supply line; an upper limitation magnitude comparator for generating an over-load signal output whenever the magnitude of the control signal exceeds a predetermined upper safety value; a lower limitation magnitude comparator for generating a light-load signal output whenever the magnitude of the control signal is less than a predetermined lower safety level; an inhibitable protection timer for producing a fault persistence output signal whenever one of the over-load and light-load signal outputs is generated for a period of time longer than a predetermined protection time; a steady state timer for inhibiting an enable output signal for a predetermined

Abstract: A reset circuit which monitors the voltage of the power supplied to a microprocessor unit, and produces a low resistance to ground at the reset terminal of the microprocessor whenever the supply voltage changes from a low value to a high value, or from a high value to a low value. It is based upon the combination of two RC circuits of different time constants, such that when the supply voltage is constant, no current flows in these circuits. A transistor is connected to the RC network such that it carries current only when there is a changing voltage of the power supply. If the voltage increases or decreases, a second transistor acting as an electronic switch grounds the reset terminal, and when the voltage becomes constant again, either at a high value or a low value, the switch opens and the reset voltage goes high.

Abstract: Apparatus (10) is provided for controlling current through a motor (12), including a circuit (14) for generating motor speed command data, a circuit (26) for generating a control signal in response to a maximum value of current through the motor (12), a programmable data processor (72) for generating pulse trains in response to the command data, and a controllable supplying circuit (18) for coupling and decoupling power to the motor (12) in response to the pulse trains and for decoupling power to the motor (12) in response to the control signal independent of the pulse trains. By decoupling power from the motor (12) independent of the control produced by the data processor (72), the current limit is achieved even if the data processor (72) malfunctions, contrary to prior apparatus.

Abstract: A multi-phase undervoltage detection circuit is disclosed wherein a multi-phase input voltage is compared to a reference. If the peak level of the input voltage is above the reference, a capacitor is discharged. If the voltage of any one of the phases is below the reference, the capacitor charges above the level of the input to a flip-flop. At the same time the voltage of another of the phases clocks the flip-flop. Since the input of the flip-flop is "high" when it is clocked, it changes states and its output goes "low" which provides a circuit output indicative of an undervoltage condition. If no undervoltage condition exists, the flip-flop will not change states and the circuit output is indicative of a non-undervoltage condition.

Abstract: An electronic circuit for use in a vehicle equipped with an internal combustion engine. The electronic circuit comprises a constant-voltage regulated power-supply circuit, a control circuit having a central processing unit for controlling electrical apparatus installed in the vehicle, and a detecting circuit for detecting variations in supply voltage supplied from the power-supply circuit. The detecting circuit is adapted to generate an output signal when the supply voltage of the power-supply circuit is out of a predetermined range. The electronic circuit further includes circuitry responsive to the output signal of the detecting circuit to render the central processing unit inoperative and an alarm responsive to the same output signal to give warnings.

Abstract: A simplified power on/off protect circuit is provided to enable logic above a predetermined power supply voltage level and disable the logic below such predetermined voltage level. The circuit comprises a zener diode in combination with a transistor such that the zener controls the voltage level at which the transistor turns on. The transistor enables the logic.

Abstract: A reclosing system for d-c feeder circuit breakers used on transit systems is disclosed. Circuit breaker closure is prevented when the feeder circuit voltage is in a predetermined voltage range and when the feeder circuit impedance is less than a given value, which is less than the impedance which would be presented by a parked train in a deenergized portion of the transit rails. A Wheatstone bridge is inserted into the circuit during the load impedance measurement. The Wheatstone bridge circuit is compensated for positive or negative rail return voltage. The automatic reclosing scheme is locked out after two closures of the circuit breaker followed by automatic tripping within six minutes, or by twelve load impedance measurements, which are performed within three minutes and which all fail to lead to a circuit breaker closure.

Abstract: A fault detection and inhibit circuit for a power control unit in an electric traction motor propelled vehicle of the type wherein the power control unit includes a chopper circuit and a bypass contactor for shunting the chopper circuit when its percent conduction exceeds a relatively high value and a main contactor for connecting the chopper circuit and motor to a power source. The circuit assures that neither the main contactor, the bypass contactor nor the chopper circuit are in a shorted condition before permitting the application of power to the system. In the event of a running failure, the circuit prevents restarting until the failed condition has recovered.

Abstract: A computer power/temperature protector is provided. A control and disconnect circuit is responsive to a power interruption to disconnect power from a computer to which the protector unit is connected in-line, and thereafter responsive to a reset signal to connect power to the computer. A power interruption is obtained automatically when a voltage failure occurs on the power cable to the computer. A thermostatic switch also automatically interrupts power when the ambient temperature of the room in which the computer or other load is located exceeds an adjustable pre-set level. A power emergency disconnect switch is provided for manually interrupting power. Furthermore, the present invention provides at least one varistor for shunting transient voltages. The varistors are automatically connected to the power lines of the cable when the apparatus is manually reset to supply power to the computer.

Abstract: Power supply sensing circuitry comprises a first comparator for determining whether the power supply potential voltage exceeds by a predetermined amount the voltage required to operate a data processing system connected to the power supply potential, and a second comparator for determining whether the power supply potential is at least the voltage required to operate the connected data processing system.

Abstract: A digital data processing system for protecting and controlling an electric system, wherein plural data values indicative of system limits are generated and supplied to a processing unit for processing thereof. The data values are converted to digital signals and stored in a digital memory at addresses selected by an address designation unit. Each memory address has associated therewith a predetermined decimal point position. Addresses from the address designation unit are converted to decimal point display signals which can be stored in the memory and used by the processing unit to determine the decimal point position during processing of the data signals stored in the memory.

Abstract: A protective circuit for a class B OTL circuit such as a vertical deflection circuit and a sound output circuit of a television set. The protective circuit comprises a first voltage comparator circuit having one input terminal applied with a detection signal in the form of an average voltage of an output signal of the OTL circuit and the other input terminal applied with a first reference voltage, and a second voltage comparator circuit having one input terminal applied with the detection signal and the other input terminal applied with a second reference voltage which is different from the first reference voltage. Either one of the voltage comparator circuits is operated when the output terminal of the OTL circuit is short-circuited to either the power supply voltage line or earth.

Abstract: A failure detector is provided for detecting unidirectional failures in triacs, particularly as used in power factor controllers for induction motors. In a first embodiment, the triac voltage waveform is sensed and upon detection of an unbalanced signal, corresponding to failure of the triac in either the positive or negative direction, the triac is turned full on in both directions. In a second embodiment, a pair of pulsed signals are derived, the pulse durations of which are proportional to the phase difference between the load current and voltage for each half cycle, and the triac is turned full on responsive to a difference in pulse duration between the half cycle signals. An unidirectional open circuit detector is adapted to use a signal from either of the first and second embodiments to turn the triac off in response to an open circuit failure in either direction.

Abstract: A circuit apparatus including a circuit interrupter connected between an AC supply and electrical equipment to be protected and operational in a first condition to transmit power therebetween and operational in a second condition to interrupt power transmission therebetween, a control circuit for producing the first condition in response to normal supply voltage and for producing said second condition in response to abnormal supply voltage, a delay circuit connected to the control circuit and adapted to produce a minimum time delay between successive occurrences of the first condition, an overvoltage circuit adapted to produce the second condition in response to a voltage from the supply that exceeds a predetermined maximum level, and an undervoltage circuit adapted to produce the second condition in response to a voltage from the supply that is below a given threshold level.

Abstract: A detector for high-voltage, polyphase gear, having a fuse-switch combination in each phase and a switch operator, includes voltage sensors which provide first time-varying signals indicative of the magnitude and phase orientation of the phase-to-ground voltages on each phase within the gear at the load side of the fuses. The first signals are vectorially added to provide a second time-varying signal, the peak value of which varies as the magnitude and phase orientation of the phase-to-ground voltages of the phases. The second signal is compared to a reference; an error signal is generated when and as long as the phase-to-ground voltages vary beyond set limits. A timer responds to the error signal and provides a third signal a predetermined time after initiation of the error signal, but only if the error signal persists for such time. The third signal is used to cause the operator to open the switches.

Abstract: Electrical apparatus to monitor electrical three-phase power includes circuitry to protect three-phase equipment from excessive variations in line voltage, phase to phase unbalance, and reverse phase sequencing; to protect personnel against automatic restart of equipment at return of line power; and protect power sources against overload at return of line power, after power interruptions.

Abstract: A monitor for a polyphase power line continuously compares the voltage on each phase of the power line with reference voltages that are selected percentages above and below the average of the power line voltages to detect voltage unbalance and with fixed voltages to detect high or low voltage conditions. The monitor is also responsive to phase sequence.

Abstract: A computer power/temperature protector is provided. A control and disconnect circuit is responsive to a power interruption to disconnect power from a computer to which the protector unit is connected in-line, and thereafter responsive to a reset signal to connect power to the computer. A power interruption is obtained automatically when a voltage failure occurs on the power cable to the computer. A thermostatic switch also automatically interrupts power when the ambient temperature of the room in which the computer or other load is located exceeds an adjustable pre-set level. A power emergency disconnect switch is provided for manually interrupting power. Furthermore, the present invention provides at least one varistor for shunting transient voltages. The varistors are automatically connected to the power lines of the cable when the apparatus is manually reset to supply power to the computer.

Abstract: A high gain voltage responsive current source supplies emitter current to a lateral input PNP transistor in a monolithic integrated circuit voltage responsive switch and, in conjunction with an impedance between the voltage signal input terminal and base region of the input PNP transistor, protects the voltage responsive switch from negative voltage transients at the signal input terminal.

Abstract: An electrical system monitor is shown as employing a quad-chip C-MOS integrated circuit for sensing when the voltage of a monitored circuit, monitored sub-circuit, monitored branch circuit or monitored circuit portion deviates, by a preselected magnitude, from a selected magnitude of voltage; upon such deviation occurring, a related switch is actuated causing energization of sensory warning apparatus and, in another aspect of the invention, a switching device is actuated to open a related load circuit.In a further embodiment the quad-chip C-MOS integrated circuit is, in the same general manner, responsive to sensing preselected deviations from a selected magnitude of current and, upon the occurrence thereof causing actuation of related switch means.

Abstract: A power supply sequencing apparatus utilizing a pair of MOS-FET devices to simultaneously apply or remove the positive and negative power supply sources to an electronic unit.

Abstract: A circuit is described for protecting a semiconductor junction device such as a transistor against damage from high voltage transients that can be produced by kinescope arcing in a television receiver. The protected device is coupled to a circuit point at which the transients can appear. The protection circuit comprises a normally nonconductive protection transistor with a collector coupled to a source of operating potential, a base coupled to a source of threshold conduction bias reference voltage, and an emitter connected to the circuit point at which high voltage transients are likely to appear. The base bias of the protection transistor is determinable independent of the bias of the protected device, and the protection circuit is connected to the protected device with substantially zero voltage offset between the circuit point and the protected device.

Abstract: A fail safe control circuit in which an input signal for initiating control of a potentially dangerous system is amplified only if it lies between given limits and also only if electrical power is being supplied to the system. The outputs of the amplifiers are monitored to check their correct operation, and two independent optical output signals obtained therefrom. The optical signals are arranged independently to operate switches in the system, such that both switches have to operate before the system can be actuated.

Abstract: An unbalanced DC voltage detecting circuit which includes first and second switching transistors with one connected to the output terminal of a power amplifier through a low pass filter and the other connected to the output terminal through a DC level shifting device and the low pass filter with the outputs of the first and second transistors connected to a third switching transistor which controls current to a relay such that when said third transistor is turned off, the relay is deenergized to open a circuit to a load. The first and second transistors are controlled by unbalanced DC voltage which exceeds predetermined levels.A second embodiment includes temperature control to prevent overheating.

Abstract: A utility monitor for detecting and storing power line disturbances is provided which includes peak-voltage sensing means for over-voltages which provides an interrupt signal at the time of a strobe pulse indicative of a voltage rise above a preset threshold and which removes the interrupt signal when said peak voltage drops a preselected amount below the preset threshold value. A peak-voltage sensing means for under-voltages is also included for obtaining an interrupt output at the time of said strobe pulse indicative of a voltage drop below a preset threshold and for removing the interrupt output when said peak-voltage rises a preset amount above the preselected threshold value. A preselected number of cycles of said input sinewave voltage are stored before and after said interrupt.

Abstract: In some circumstances it is important to maintain a d.c. potential within a specific range of a critical value. The circuit shown will provide a fail-safe signal if the potential deviates from the allowed range. Two zener diodes and two optically coupled isolators are used. If the d.c. potential remains within the critical range, an a.c. test signal back biases one optically coupled isolator and forward biases the other on the positive half cycle; and on the negative half cycle back biases the other and forward biases the one. Thus the two optically coupled isolators conduct on alternate half cycles of the a.c. test signal. If the d.c. potential strays from the required range, the optically coupled isolators stop alternate conduction and a fail signal is given. If either zener diode should fail in a mode which alters its characteristics so that the circuit would fail to detect a voltage excursion outside the allowed range, a fail signal is given.

Abstract: A protection circuit for protecting the thyristors of a series circuit of several thyristors, each of which has a corresponding firing circuit to which its anode-cathode voltage is applied.

Abstract: A display and power supply system in which the power supply uses a switching frequency which is higher than the highest linear deflection rate used in a cathode ray tube display device supplied by the power supply and in which the frequency of the power supply and the information repetitively displayed on the display are synchronized to eliminate interference of the power supply frequency with the display characteristics.

Abstract: A control circuit for limiting the output voltage of a voltage regulator or the like to a safe level for consumers connected close to the voltage regulator. The output voltage of the regulator is measured and compared to a reference. If the voltage exceeds the preset level then the circuit is energized to prevent further tap change that would increase the voltage output. A time delay is provided to prevent immediate de-energization of the circuit when the voltage drops below the preset level. Should line fluctuations cause further voltage increase, then the circuit will cause a tap change so as to reduce the output voltage. If the output voltage drops below a preset level then the circuit will prevent further tap changing which would cause any further lowering of the output voltage.

Abstract: Apparatus for on-site testing of wrist straps or shoe straps of the type d to prevent the buildup of electrostatic charges on the body and clothing of a worker engaged in handling charge-sensitive electronic devices. The worker wearing a grounding strap connects the grounding strap to a terminal on the tester and touches a touch pad on the apparatus. The tester incorporates the resistance of the grounding strap and the worker wearing the strap into a voltage divider. If the incorporated resistance is within acceptable limits, an indicating lamp is lighted to show that the grounding strap is working properly. An indicating signal may also be coupled to a computer for automatic recordkeeping.