Abstract: There is disclosed an electronic device which comprises means for detecting the occurrence of voltage fluctuation in the input or output voltage of a power source to produce an output signal, and means operative in response to the output signal for disabling a portion of the electronic device, such as a liquid crystal display element, thereby substantially elongating the lifetime of the particular portion of the electronic device.

Abstract: A circuit for monitoring conduction of a phase controlled, alternating current switch, e.g., a thyristor switch, looks at the voltage across the switch. This voltage has a high dv/dt whenever the switch stops and starts conducting current. The voltage detected from across the switch is processed as follows: it is differentiated to produce a train of voltage spikes of very short time duration and some lesser voltages; the lesser voltages are removed; the spikes are then amplified and extended in time duration; and finally the time extended spikes are integrated. The integrated voltage is a train of alternate positive and negative voltages averaging zero during normal switch operation. However, when the switch conducts one of the half cycles only, the integrated voltage rises in one polarity sense depending upon the half cycle conducted. A control circuit becomes operative upon the integrated voltage attaining a predetermined value to initiate a control function such as de-energize the switch.

Abstract: In a circuit of the type in which a command signal actuates a semiconductor switch which, in turn, actuates a load device and in which a clock signal is available, a protection circuit for protecting the semiconductor switch located in series with the load from excessive current in the event the load device is short circuited. The protection circuit includes a sensing circuit for sensing the voltage level at a point intermediate the semiconductor switch and the load. The protection circuit interfaces between the command signal and the clock signal in such a manner that the semiconductor switch is repeatedly momentarily energized if the load is shorted and a command signal is present.

Abstract: A circuit for protecting speakers connected to the output of an audio amplifier. The output of the amplifier is connected to a filter which blocks normal audio frequency signals but passes both high and low frequency signals outside the normal audio range. The positive and negative filter output signals are connected respectively to the inverting and non-inverting inputs of an operational amplifier whose output is connected via a turn-on delay circuit to a speaker relay, which, when closed, connects the speaker to the amplifier. The turn-on delay circuit prevents speaker relay closure until turn-on transients have ended. If a DC voltage or a high frequency signal is present at the amplifier output, the operational amplifier generates a signal to open the relay thereby disconnecting the speaker from the amplifier output. The speaker relay quickly opens when power is turned off so that amplifier turn-off transients are not connected to the speaker either.

Abstract: Converter circuit, in which a 50 or 60 cps a.c. voltage is converted into a d.c. voltage, the latter into an a.c. voltage of a higher frequency, e.g. 20-80 kilocycles, which is converted by way of one transformer into one or several separate d.c. voltages. The transformer comprises a divisible ferrite core; the primary winding and one or several secondary windings are placed on opposite core parts. Each secondary winding, together with a pertaining rectifying-, smoothing- and stabilizing -circuit and a limiting resistor is installed as an intrinsically safe power source on one print. Several prints of this kind may be placed on the secondary core part, one for each power source required. The electrical values of the circuit components are subject to certain specifications.

Abstract: A power supply protective circuit that responds to transient overloads, permanent overloads and excessive overloads to protect the power supply and the related switching transistor from damage. The circuit utilizes an astable multi-vibrator which is designed to be pulse modulated by transient overloads. In addition, the multi-vibrator is designed to be turned-off by permanent overloads and by an excessive overload condition. By this arrangement, the multi-vibrator remains in operation for normal transient overloads and does not require resetting manually when such an overload condition occurs.

Abstract: A conventional complementary symmetry push-pull type of current amplifier is modified by the inclusion of a diode which permits the predriver transistor, which otherwise would be turned off, to be turned on, when one of the fuses between the power supply and the amplifier blows, thereby maintaining the D.C. input to and hence the D.C. output of the amplifier at essentially zero volts and keep D.C. off the direct coupled loudspeaker.

Abstract: A phase imbalance logic module for a solid state motor protection system for a three-phase motor. Three-phase line currents are converted to corresponding voltages and rectified. The resultant output voltage is a poorly regulated DC voltage having a ripple of approximately 4% during normal operating conditions. In the event of a phase failure, even if not total, the corresponding ripple percentage increases. The phase imbalance logic network senses ripple and provides an output signal to trip a protective circuit breaker if the component of ripple becomes significantly large.

Abstract: To protect power transistors and similar electronic electronic control elements which have their main current paths serially connected to loads, one terminal of which is grounded, against short circuits within the loads and without substantial power loss in series sensing resistors, a resistor is connected in shunt with the main current path of the power electronic component, for example the emitter-collector path of a power resistor and a diode connected between this shunt-connected resistor, effectively at the junction of the load and the power semiconductor to the base of a driver transistor which controls the power semiconductor to apply the operating voltage at the junction to the base of the driver transistor so that the power transistor is controlled thereby to blocked condition if the voltage at the junction should drop from operating voltage, the diode, under normal operating condition, being blocked.

Abstract: A cyclical ON-OFF control signal is generated with a predetermined duty cycle to energize a load through a semi-conductor switch; a trouble signal is generated, for example by sensing voltage across the load, across the switch, temperature or the like, and, when the trouble signal exceeds a certain threshold (as determined, for example, by comparing the trouble signal with a reference in a differentially connected operational amplifier), the ON-signal to gate the switch ON is interrupted; and an OFF cycle of the cyclical generating means is started; if the trouble signal disappears, the normal cyclical repetition rate continues. A minimum interruption time is, however, provided determined by the OFF period of the cyclical generator and/or circuit components.

Abstract: An overload protection circuit for an amplifier is disclosed in which a signal supply means connected with the input of the amplifier is deactivated when the output of the amplifier exceeds a given value. Transducer means of the optoelectrical type are connected with the output terminals of the amplifier for operating a bistable device such as an operational amplifier to deactivate the signal supply means as long as the overload voltage occurs. Timing capacitor means maintain the signal supply means de-activated for a given period of time after the overload condition is terminated.

Abstract: A failsafe system for a skid control system for a multi-axle wheeled vehicle. The skid control system has a plurality of skid control modules, each of which is operatively associated with one of the axles of the vehicle and the skid control modules are operatively coupled by wiring on the vehicle. Each skid control module comprises a skid control circuit for skid controlling the wheels of the associated axle, which circuit is supplied from an electrical power source such as the vehicle battery, either regulated or unregulated. A failsafe circuit is provided in each skid control module and the failsafe circuits of the several modules are connected in cascade fashion to form a chain.

Abstract: In a gate input circuit for insulated gate field effect transistors, an insulated gate field effect transistor of depletion type is used, whose drain electrode (or source electrode) is connected to one terminal of a power source and whose source electrode (or drain electrode) is short-circuited with the gate electrode and connected to an input terminal of the gate input circuit through a resistor.

Abstract: A load protective circuit having a class B amplifying stage driven by a class A amplifier and a load DC coupled to the class B stage, in which means are provided for detecting an undesirable DC voltage at the output of the class B amplifying stage and for producing a control signal in response to the output of the detecting means. A first protective means shunts the input signal to the class B amplifier to ground in response to the control signal. A second protective means controls a switching means connected between the output point and ground so as to connect the output point of the class B amplifier to ground in response to the control signal to thereby remove any undesirable DC voltage from the output point of the amplifier and to protect the DC coupled load from being damaged.

Abstract: A solid state control system for controlling a high voltage primary power pplied to a plurality of power supplies by means of a TTL voltage level. Circuit means are provided to sense the power supply whose DC voltage goes to zero volts due to circuit anomalies, or other reasons. Upon sensing the anomaly the indicator means indicate via a storage device which power supply has failed, before interrupting the primary power.

Abstract: An electronic monitoring circuit to detect unbalanced voltage conditions on a three phase alternating current line employs the charging current to a condenser connected across a full wave rectifier bridge to trigger a multivibrator circuit that controls an output relay in accordance with the multivibrator cycles per cycle of the power line voltage.