Abstract: A flexible reference voltage circuit includes a circuit for producing a first digital signal representative of a range of reference voltage levels; a circuit for producing a second digital signal representative of a selected reference voltage level within the range of reference voltage levels; an adder for adding the first and second digital signals to produce a third digital signal; and a digital to analog converter for providing an output voltage in response to the third digital signal. The method of producing a flexible reference voltage performed by the circuit is also claimed. The invention can be used with a differential protection circuit to provide a series of trip level ranges, with a series of selectable trip levels in each range. This is accomplished in a high accuracy circuit which is relatively simple to construct, thereby minimizing size and complexity of the current sensor module, in differential protection applications, or the circuitry, if used in a power system controller.

Abstract: A solid state circuit interruption arrangement monitors a current path to provide protection to both a load and a solid state switch. The arrangement includes an energy absorber for absorbing energy from the current path in response to the solid state switch interrupting the current path, and a control circuit for periodically generating the interrupt signal to interrupt the current path for prescribed intervals and to control the current supplied to the load between a maximum current level and a minimum current level.

Abstract: A controller associated with a dissipative electric load controls the level of average power applied to the load by an electric energy distribution network that supplies the dissipative load with a supply voltage. The controller comprises a detector for detecting a predetermined pulse duration modulation signal embedded in the level of the supply voltage provided by the distribution network, and a device for transmitting electric power originating from the distribution network to the load. The device for transmitting comprises a device for reducing the level of average power transmitted to the load, in response to a detection of said pulse duration modulation signal in the level of supply voltage. A decrease of the line voltage level for a given duration of power distribution voltage is initiated in order to control the average power consumption of the loads.

Abstract: A remotely controllable, full scale, AC or DC power attenuator, for attenuating power to a load as a function of an input control signal which represents a selected percentage of power to be applied to the load. Bidirectional series switch means are responsive to the input control signal for connecting and disconnecting power to the load.

Abstract: Electrosurgery apparatus includes an r.f. power amplifier with an output to a patient electrode. The amplifier is controlled by the voltage of input signals from a control unit which receives a sample of the voltage and current of the output signal. The voltage and current signals are supplied to A/D converters to provide two digital signals that are used to address a look-up table in an EPROM and provide a digital output representative of impedance. A switch is set by the user to the desired mode/power curve and this provides a digital signal which together with the impedance signal is used to address a second look-up table in an EPROM which contains digital representations of the required output voltage of the amplifier to produce the desired power level. An adder compares the required voltage with a feedback of the actual voltage to produce an error signal that is supplied to the amplifier to control its output.

Abstract: In a monitoring system for a bridge output stage which is connected in series with a controllable source of current, to the terminals of a source of operating voltage, the voltage over the bridge output stage and the voltage drop over a current-measurement resistor are fed to a subtraction circuit. The subtraction circuit is connected, via an analog-to-digital converter, to an input of a microcomputer, and a program is provided by which it is tested whether the voltage at the input of the microcomputer lies within a predetermined range. The operating voltage and the voltage over the controllable source of current are preferably fed to a further subtraction circuit the output of which is connected to an output of the subtraction circuit.

Abstract: A control device for switching a thyristor in a circuit including an a.c. voltage source, which comprises firing signal circuit having an input for receiving control signals, an output for providing firing signals for a thyristor and a detector for detecting zero-crossings of an a.c. voltage provided by the a.c. voltage source. The firing signal circuit further comprises an accumulating circuit for accumulating the control signals and for providing a firing signal when both the detector detects a zero-crossing of the a.c. voltage and the value of the accumulated signals is equal to or exceeds a first predetermined value, and subtracting circuit for subtracting a second predetermined value from the value of the accumulated signals when the firing signal is provided.

Abstract: A method of controlling the supply of power to electrical loads with a minimum of switching surges in which the loads are each electrically subdivided into at least two equal subloads. The subloads of each load can be connected each time arbitrarily in at least three main power stages to an A.C. mains. In order to obtain a minimum switching surge effect on the A.C. mains while providing finer power control six additional intermediate power stages are provided, in which starting from one of the three main power stages, the subloads are switched in a continuously repeated cycle of six A.C. half waves in the first intermediate power stages during the third and sixth half waves in each cycle and in the second intermediate power stages additionally during the second and fifth half waves each time to the next lower main power stage, which in the case of a series arrangement is that in which the power consumption is switched off.

Abstract: A controller for a load such as the heater elements of an actuator for drying the various zones or slices of a moving sheet of a papermaking machine includes silicon controlled rectifiers for each zone or slice of the moving sheet whose firing angle is controlled by an external power command signal. This power command signal is processed by a digital signal processor which strobes at a high rate the line voltage and load current to provide a closed loop feedback control technique for power being applied to the load and in addition, the processor, at the same time, has an open loop firing angle control routine which has a fast response time to protect against abnormal conditions within one-half cycle of load voltage.

Abstract: The combination of a heating element and a control unit therefor and methods of making and of operating the same are provided, the heating element normally being adapted to be operated by the continuous full-wave pulses of a certain high voltage alternating current source for a predetermined time period so as to provide a desired function thereof and the control unit being operatively interconnected to the heating element and having a first arrangement for operatively interconnecting the heating element to that certain high voltage alternating current source for the predetermined time period so as to provide a desired function thereof, the control unit having a second arrangement for operating the heating element with a certain repeating pattern of skipped complete half-wave pulses of another source of high voltage alternating current for the predetermined time period when that other source has a higher voltage than the certain source so that the heating element will not be adversely affected by the other sou

Abstract: An electric continuous-flow water heater generates a basic power with heating resistors in heating passages and a controllable power with three heating resistors in heating passages. The controllable power is controlled by a control system through a triac. At low flow rates two phases and a low controllable basic power is connected to the heating resistors. At high flow rates the heating resistors are star-connected and the controllable heating-resistors are delta-connected. An electric power output stage comprises a mains rectifier bridge, a Schmitt-trigger connected to the output thereof and a frequency divider with two outputs.The signals at the outputs are set by an edge of each third pulse and are reset by the corresponding edge of the following or next but one pulse. A semiconductor relay is optionally by the signals at the outputs through a selector switch or a logic circuit and is rendered conductive for one, two or three half waves.

Abstract: An economical astable multivibrator circuit provides a variable frequency, variable duty cycle digital signal for controlling a solid-state relay to provide power proportioning. An optical isolator receives analog input signals and converts those signals into a variable resistance signal for altering the RC time constant of the charge/discharge timing circuit. The controller is capable of driving several solid-state relays simultaneously and includes a powerstat adjustment for manually adjusting the range of power delivered to a load.

Abstract: Alternating current electric power fed to a load is controlled to a target value using phase control. During a half cycle of the alternating current waveform, sampling of voltage and square calculation of the sampled value are repeated. During the remaining half cycle, average value calculation based on the result of the above calculation, root calculation and proportional calculation are implemented. Thus, the power control cycle is completed within one cycle of the alternating current waveform. By utilizing a plurality of sampling data, dropped data locating in a non-sampling period therebetween is obtained by interpolation. Sampling starts in synchronism with the energizing start-up phase.

Abstract: The present invention pertains to a commutator containing a semiconductor operable with unidirectional current and bidirectional voltage and with controlled interruption and automatic ignition, and in which a semiconductor device with controlled commutation is utilized. In accordance with the invention, the commutator includes a logic gate (61) having an input which, when the anode-to-cathode voltage of the semiconductor device (2) is below a specific positive voltage close to zero, receives a logic signal from an adapting circuit (4) connected to the semiconductor anode. The other input of the logic gate receives a control logic signal, and the output of the gate is connected to another adapting circuit (5) which converts the logic signal output by the logic gate into a suitable control signal which is transmitted to a the control terminal of the semiconductor device (2).

Abstract: A multiple phase electricity switching apparatus having electrical components arranged and mounted on a heat sink structure which having the same external dimensions as a conventional electromagnetic relay. The switching apparatus controls the amount of electrical energy passing therethrough and into electrical resistance heating elements thereby controlling the temperature of the molten plastic raw materials. The switching apparatus includes a pair of inverse parallel connected SCR's (silicon control rectifier), a photo coupling, and a zero cross switching circuit. The SCRs are separately mounted on and separated by a structure having two parallel members. The electronic circuit components permit the electrical power supplied to the load to be switched more frequently thereby realizing improved temperature regulation.

Abstract: Heating apparatus particularly for flameless atomization in spectrophotometers includes a variable electrical power source and a resistive heating element. A desired final temperature and the rate of change of the element temperature (ramp rate) is input to a control circuit. A storage means is provided for storing data relating the heating element temperature to the energy input (voltage) to the heating element required to maintain the heating element at a constant temperature. Processing means calculates from the various data the voltage required to be supplied to the element by the power source to change the temperature thereof at the selected ramp rate until it reaches the final temperature. In spectrophotometers the apparatus accurately controls the carbon rod temperature through drying, ashing and atomizing stages.

Abstract: A circuit for generating control signals used in detecting a power failure in an uninterruptible power supply in which the A.C. signals of the power supply are examined to output a first signal representing the zero crossing of the A.C. signals. This first signal is used to reset an oscillator whose output clock signals are synchronized with the frequency of the A.C. signals by a phase lock loop circuit. The clock output of the phase lock loop circuit operates a counter whose output count is used to address a programmable read-only memory which outputs binary bits to a digital-to-analog converter which in turn outputs a full wave rectified sine wave operating at the system frequency which is used as a reference to detect the occurrence of a power failure in the main source of A.C. power signals. A second control signal is generated indicating a power failure condition which is used in switching an inverter into the power supply for supplying A.C. signals to a load.

Abstract: Methods for operating a control circuit, having a programmable signal characteristic, in a manner so as to gradually vary a D.C. analog output level from an initial value to a final value, as well as for abrupt changes therein, when an isolation-and-rectification network is used to recover a D.C. voltage of programmably controlled amplitude. The methods also provide for a pulsed output condition in a circuit for providing a periodic signal of programmably controlled amplitude. In such a circuit, the output signal amplitude may be controlled by external data signals to values less than, equal to and greater than, the substantially constant amplitude of an oscillator waveform. Both programmable (computer-controlled) and hard-wired circuitry are disclosed for controlling the output signal by the methods of this invention.

Abstract: A solid state electronic power switch selectively controls power delivered to a load such as a fan. A momentary contact control switch is provided which is connected to a switching logic circuit whose output state changes when the control switch is activated. A plurality of power control circuits are connected in parallel with one another and in series with a load across a power source. Each of the power control circuits includes either an SCR or a triac element. A turn-on control circuit is provided connected to the SCR or triac for initial turn-on only when a voltage across the element is small compared to a peak-to-peak voltage across it prior to application of gate voltage. With the system of the invention, the load such as a fan can be operated at various discrete power levels without the associated mechanical and electrical noise problems of previous systems.

Abstract: In a lighting installation comprising light sources each connected to an A.C. supply system, a control device including: power variation circuits connected to the different sources and each comprising means for varying the electrical power supplied to the respective source, in response to magnitude variations of an electrical quantity, and control circuits associated to the different sources and each comprising a clock circuit, an illuminating programme circuit in which is recorded a programme representing desired timed variations of the illuminating power for a given period, a selection circuit receiving clock pulses from the clock circuit and connected to the programme circuit for selecting an illuminating power dependent on the elapsed time from the beginning of said period, and an output circuit for converting said selected power to a particular magnitude of said electrical quantity.

Abstract: A variable voltage power supply includes a switching device through which line AC current is passed in response to the time during which a level setting voltage is applied to a control circuit for the switching device. During the duration of the level setting signal, periodic electrical signals are applied to a counter which is cyclicly incremented and decremented between predetermined lower and upper count limits until the level setting signal is terminated. The count is used as a measure of time into each half cycle of the line AC voltage at which the switch device is closed, the switch device being opened in response to the zero voltage crossing at the end of each half cycle of the AC voltage.

Abstract: The invention relates to an arrangement for digital brightness control of lamps or groups of lamps in control channels particularly for use in planetarium illumination comprising in each control channel a programmable counter, a bistable flip-flop, and a power control stage. Each control channel is connected to a mains synchronizing stage and to a pulse generator. The control channel produces a mains synchronous pulse sequence frequency the pulse width repitition ratio of which depends on the selected division ratio of the programmable counter. The inventional solution offers a simple digital and controllable circuit arrangement for control of thyristors or triacs or transistors which, in turn, control the brightness of lamps or lamp groups.

Abstract: An electric power source device for electrolytical production or coloring of alumilite, wherein pulses are generated at a predetermined phase of A.C. source, the pulses are frequency-divided by a non-contact circuit and, depending on the results of the frequency division, analogue switches respectively comprising a non-contact circuit are driven to actuate rectifier units for rectifying the A.C. source. Outputs of alternately reversed polarities with distinctly sharp rising and falling are provided.

Abstract: A fixed frequency, variable duty cycle voltage regulator having a precision reference voltage source is provided. The reference voltage source has a variable temperature coefficient. The output of the precision reference voltage source is combined by a digitally switched attenuator to provide a staircase waveform to a comparator. This variable staircase waveform is compared against the output of an alternator. The comparator sets the output of a flip-flop to an off state when the staircase waveform goes below the output from the alternator. This removes the drive from a current switch which switches off the current flow through the field coil of the alternator.

Abstract: A fixed frequency, variable duty cycle voltage regulator having a precision reference voltage source is provided. The reference voltage source is a bandgap reference circuit including a plurality of series-connected diodes and having a variable temperature coefficient. The output of the precision reference voltage source is combined by a digitally switched attenuator to provide a staircase waveform to a comparator. This variable staircase waveform is compared against the output of an alternator. The comparator sets the output of a flip-flop to an off state when the staircase waveform goes below the output from the alternator. This removes the drive from a current switch which switches off the current flow through the field coil of the alternator. Current limiting protection is provided to the regulator output.

Abstract: An improved control circuit for accurately regulating the power from a supply of unregulated AC voltage to a load, such as a fan motor, via a signal responsive conduction-control switch. The circuit employs first and second comparators. One input to the first comparator is a DC signal representative of desired power level. The other input of the first comparator is a signal having a DC component and a ripple component. The output of the first comparator is a rectangular waveform having a duty factor which is a function of the desired power level relative to the reference load power level. The first comparator output is integrated and then supplied as an input to the second comparator. A sawtooth signal of constant DC level provides the other input to the second comparator. The sawtooth is a submultiple, or preferably a multiple of the AC supply frequency.

Abstract: Disclosed is a method and circuit for automatically adjusting the firing angle of a switching element, such as a thyristor or triac, to minimize surge currents produced in reactive loads in AC power applications. A typical application would be in a microwave oven controller when the circuit would be used as an interface between the microwave oven control circuitry and the thyristor driving a magnetron. The circuit is comprised of a digital-control, phase-locked loop oscillator which produces a series of triggering pulses which are synchronized with the AC line voltage; the oscillator oscillates at a known frequency and clocks a counter during one half-cycle of the line voltage, resetting the counter during the opposite half-cycle. A peak fire detection circuit is coupled to the oscillator. An enable signal is generated by the microwave oven control circuitry. Since the oscillator frequency is known, the AC line voltage peak occurs at a known state of the counter.

Abstract: A phase control device for use in a phase control circuit, which forms a comparison signal synchronous with an a.c. power source, then compares this comparison signal directly with a preset phase control angle signal, and controls a phase control element provided in the a.c. phase control circuit by the compared output.

Abstract: There is disclosed herein a method and apparatus for controlling the power dissipation in a load particularly suitable for use as a dimmer control for lighting circuits. Selected half cycles are applied to a load, such as an incandescent lamp. The number and sequence of the half cycles applied to the load are selected by logic circuitry which, according to the setting of a dimmer control, determines how many complete half cycles out of the total available to apply to the load. Zero crossing switching is used.

Abstract: A universal power supplying module for controlling the application of power to a plurality of loads is disclosed. The universal power module receives a Pulse-Width Modulated (PWM) data signal which includes a plurality of PWM pulses. Each of the PWM pulses is associated with a respective one of the loads and has a width which is indicative of whether or not power is to be applied to its associated load. The universal power module stores binary information in accordance with the pulse width of the PWM pulses and controls the application of power to the loads as a function of the stored information.

Abstract: This relates to a phase control circuit for regulating the amount of power applied to an a.c. device by triggering on a thyristor at some time during each half cycle of an a.c. signal applied thereto. The thyristor turns off at the next zero crossover of the a.c. signal. When a first counter reaches a predetermined state, a trigger pulse is generated. The length of time it takes the first counter to reach the predetermined state can be varied by periodically loading the first counter with the contents of an up/down counter. The contents of the up/down counter may be varied by an operator or by associated circuitry.

Abstract: An apparatus for applying AC power to a load while maintaining a minimum charge across a capacitor for use as a DC power supply, that may be connected in series with the power supply and load, and does not require a parallel connection to the power supply, including power control means responsive to the phase of the power supply signal such that the voltage across said power control means is allowed to rise to a given voltage each cycle, before power is applied to the load, and charging means operable to charge said capacitor to said given voltage.