Abstract: Voltage drop developed across a transformer primary winding coupled in series with a primary a.c. power circuit including an a.c. power source and an a.c. load is utilized to provide a secondary source of a.c. power having secondary voltage level stability which is substantially independent from otherwise influential changes in primary power circuit levels. Secondary power stabilization is mainly established by constant voltage limiting of the primary winding excitation by the forward voltage drop developed across an arrangement of semiconductor junctions coupled in parallel with the primary winding. The transformer may be used to change the source level of the secondary a.c. power which is produced, and to obtain electrical isolation between the primary power circuit and any ancillary circuits coupled with the secondary a.c. power source.

Abstract: A power controller is provided for controlling the average power provided from an AC voltage source power supply to an AC electrical load. Three shunt connected elements, comprising two electronic switches and a capacitor with rectifying diodes, are connected betwen the AC source and the load. A control circuit controls switching of the switches in timed relationship to the state of the voltage on the shunt capacitors so as to control the average power supply to the load. The control circuit switches one of the electrical switches to the conductive state thereof near the zero crossover of the AC wave of the source voltage and subsequently switches the second switch to the conducting state thereof at a variable time during each half wave in a manner that causes the first switch to return to the non-conducting state thereof.

Abstract: A system controls power to multiple a.c. lighting loads from both a central location and from individual controls that are located near the loads. The system includes individual wallbox dimmers that include enabling switches, a master control, and isolation means to accept input signals from the master control and to provide output signals to the dimmers. In a preferred embodiment, a dimmer also provides to the master control a signal that indicates the power being provided to the load that the dimmer controls. Preferably the individual controls provide linear slide dimming, in which the power provided to a load is determined by the slider position. The system permits simplified installation and replacement of system components.

Abstract: The proposed invention is an energy saving load control device primarily intended for inductive loads (i.e., fluorescent lighting, motors, etc.) operating from an alternating current (AC) source. The proposed device switches the load voltage off at arbitrary positions in the sine wave and simultaneously provides a commutating path for any inductive current. By switching the load voltage on and off and providing a commutating current path reduced energy consumption is realized.

Abstract: A circuit arrangement for providing in a fail-safe manner an alternating output signal to a load, e.g. in a railway signalling system. The load is connected across a first winding of a transformer, to opposite ends of a second winding of which transformer is connected a bi-directional current switching circuit. First and second modulated signal sources are connected to the bi-directional switching circuit. Each of the signal sources modulates a carrier signal with a modulation signal, the outputs of the signal sources being out of phase with respect to each other. The bi-directional switching circuit is operative to switch current through the second winding alternately in opposite directions at the frequency of the modulation signal. The circuit arrangement is such that if any of its components fails to operate correctly, the output appearing across the first winding is no greater than a threshold level.

Abstract: Power from an AC source is applied to a load under control of a power switching triac in response to signals from a feedback loop isolated from line voltage transients by means of a pair of opto-coupling devices respectively connecting the feedback loop to a load voltage sensor and the control electrode of the triac.

Abstract: A multiple location system is provided for controlling application of alternating-current power to a load. The system employs a dimming system in combination with one or more switches. In one embodiment, the system includes an override, so that a switch can provide power to the load even after the dimmer has turned the power off. In another embodiment, the dimming system includes an actuator, and the value of power to the load is determined substantially immediately upon setting of the actuator.

Abstract: A circuit for controlling power to a load from an AC voltage supply is disclosed. The circuit permits power input to begin at any point either the positive, negative or both halfwaves of an AC waveform and compensates for variations in the AC voltage supply to provide the same power level to the load.

Abstract: An off-line regulating power supply utilizes a regulating transistor which perates in a dissipative mode for only a portion of each half cycle of an input AC voltage in order to regulate an output voltage by truncating the input AC sinewave. This AC input signal is full wave rectified and coupled to a primary winding of a power transformer through the regulating transistor. One of a plurality of secondary windings is coupled to a voltage threshold detector which responds instantaneously to attainment of the threshold in each half cycle of operation to bias the regulating transistor from a saturated condition to an active dissipative impedance state which limits the output voltage to the threshold level. As the input AC sinewave peaks and declines in value, the regulating transistor is again biased into saturation when the voltage applied to the threshold detector drops below the threshold level.

Abstract: There is disclosed a phase-controlled switching circuit, comprising a controlled rectifier (e.g. bidirectional triode thyristor); an amplifier connected at its output terminal to the gate of the controlled rectifier; an ac Wheatstone bridge having at one of its arms a variable resistance (e.g. thermistor to CdS photoconductive cell), said ac Wheatstone bridge being connected at one branch to the input terminal of the amplifier and at its other branch between the cathode and anode of the controlled rectifier through a load; a time constant circuit connected with the variable resistance; a pair of mechanical contacts (e.g. relay) connected in parallel with the controlled rectifier and a dc source for electrifying the whole circuit.

Abstract: A method and apparatus to maintain the current-conducting state of a gate-turn-off thyristor by appropriate triggering. To maintain the thyristor's current-conducting state reliably and with little ignition energy consumed, a comparator signal is generated as soon as the voltage drop across the thyristor exceeds a preset limit value by a comparator stage. The comparator signal has a preset duration defined by a pulse duration limiting stage, and, if necessary, a subsequent pulse magnitude limiting stage can change the pulse magnitude as a function of the interval between two subsequent ignition current pulses. A controllable current source connected to the thyristor gate is controlled by these magnitude and duration limited pulses, but this controlled current source only triggers the thyristor when the limit value is exceeded.

Abstract: A multiple location system is provided for controlling application of alternating-current power to a load. The system employs a triac as a power carrying device, the gate control circuit for which has been modified to include auxiliary switching. Potentiometers are disposed at various different locations for determining, responsively to the setting or positioning of an actuator, such as the slide control of a linear potentiometer, the magnitude of respective control signals substantially immediately upon setting of the actuator. The signals are mutually exclusively applied to control the triac in accordance with which of the actuators is being set. Alternatively, the control signals can be applied in accordance with which one of a series of take-command switches (one for each location) was last operated. In either case, only two wires are necessary to connect the different locations to one another. In one embodiment, the actuator controls a pair of momentary-close switches associated therewith (e.g.

Abstract: A power converter for converting 60 Hertz line power to 20 kilohertz power for driving a low voltage incandescent lamp (42). A field effect transistor power switch section (12) is connected through bridge rectifiers (10, 32) for charging a capacitor filter (34) with the AC input power. A 20 kHz oscillator (38) drives a half-bridge inverter (36) for coupling the capactitor voltage to the lamp (42) as high frequency power. The conduction of the FET power switch (12) is controlled by a phase locked loop (16) for synchronizing the conduction with the zero crossing points of the AC cycle. A ramp generator (18) and a summing network (20) are responsive to a lamp intensity control (22) for changing the conduction duty cycle of the FET power switch (12) such that a desired lamp intensity is maintained.

Abstract: A power control system for electrical apparatus, in which a unidirectional rectifying device is connected to one of a plurality of loads connected mutually in parallel, an ignition circuit comprising a plurality of resistors is connected between the loads and a switching element whose conduction phase is controllable, and at least one of the resistors in the ignition circuit is connected through the unidirectional rectifying device to the said load, whereby the power supply to each of the plurality of loads can be controlled in an individual manner by means of the single switching element.

Abstract: A control circuit for selecting different modes of operation for an outside building light which is operated by interrupting the current to the control circuit from a standard wall switch.The First mode of operation is continuous light for normal use. The second mode produces a flashing light which can be used for alert conditions.The initial application of power from the wall switch always produces the continuous light mode. The second mode can then be selected by switching the power off and then rapidly back on. The control circuit is installed at the light in an adaptor between the bulb and the bulb's socket and can therefore be used without requiring any changes to the switches or existing wiring of the building.

Abstract: With a triac placed in series with a load, a threshold detector feeds a modulator supplying a pulse with a given delay with respect to a change of condition of the threshold detector. The output of the modulator is fed through a gate and a monostable flip-flop to the gate electrode of the triac. After the first gate pulse, if the threshold detector detects another voltage rise at the terminals of the triac during a period of time determined by a second monostable flip-flop, this change of condition causes, through an AND gate, the OR gate and the first monostable flip-flop, another pulse to be supplied to the gate electrode of the triac. The result is an increase in the reliability of triggering a triac and reduction in the consumption of the control circuit.

Abstract: This apparatus can limit the power by limiting the duty cycle of current carried by a pair of lines. These lines intermittently conduct electrical power. A clock can provide a periodic timing signal. This clock is resettable to change the phasing of the timing signal. A switch serially coupled to at least one of the lines can periodically interrupt current of the lines with a period proportional to the period of the periodic timing signal. A resetter coupled to at least one of the lines can reset the clock in response to the average magnitude of voltage across the lines increasing by a predetermined extent.

Abstract: This apparatus can apply electrical power to a supply terminal from a pair of lines having a variable current and voltage. The apparatus has a voltage tapper and a series device. The voltage tapper is coupled to the lines and to the terminal for applying to the latter power drawn from the lines when their voltage difference exceeds a predetermined value. The series device is serially coupled into a given one of the lines for producing a voltage drop. The series device is coupled to the supply terminal for supplying power thereto as a predetermined function of the voltage drop of the series device.

Abstract: Apparatus can limit power by limiting the duty cycle of current carried by a pair of lines. The lines intermittently conduct electrical power. The apparatus has a clock, a converter and a switch system. The clock can provide a timing signal. The converter is driven by the lines and can convert its intermittent electrical signals to uninterrupted power and can supply this uninterrupted power to the clock. The switch system responds to the timing signal and can periodically interrupt at least one of the lines.

Abstract: A load and the main conductions paths of first and second TRIACs are connected in series between first and second power terminals across which an alternating voltage is applied. The first TRIAC is for controlling the power dissipated in the load and the second TRIAC is for unconditionally removing power to the load a predetermined time after the first and second TRIACs are turned-on. The first and second TRIACs are interconnected so that the main terminal 1 (MT1) of one is connected to the main terminal 1 (MT1) of the other at a common point. A control circuit for turning-on and turning-off each TRIAC is connected between the gate electrode of each TRIAC and the common point.

Abstract: Power supply and method in which the primary current to a transformer is switched on and off to maintain the output of the supply at a desired level. When the energizing current is off, an additional current is applied to the transformer to maintain the core at a level of magnetization such that the full hysteresis characteristic of the transformer is utilized during the next half cycle of operation.