Abstract: A method and circuit for reverse phase control of alternating current being delivered to a load are disclosed wherein voltage-controlled semiconductor switches, such as MOSFET's and IGBT's, are used as electronic switches to conduct voltage during the leading edge of the AC voltage cycle and conduction is terminated when the desired phase angle of the current flow has been reached. The disclosed method and circuit eliminate the need for zero crossing detection of the AC waveform and ensure that the voltage-controlled switches are always turned on before the zero crossing thereby minimizing radiated interference and incandescent lamp hum. The method used is primarily digital in nature making mechanical input or electronic input for the power control equally efficient to implement.

Abstract: A control circuit for heat fixing device for use in an image forming apparatus is disclosed. The control circuit comprises device for detecting a power source voltage, device for detecting zero-crossing points of the power source voltage, device for determining frequency of the source voltage from the detected zero-crossing points, device for determining a power supplying time based on the detected power supply voltage and the power source frequency, device for controlling the power supply to a load based on the determined power supply line, in such a manner that a given power is automatically applied to the load against the change or fluctuation of the power supply source.

Abstract: A method of controlling a-c power by means of thyristors for resistive electric furnace for achieving a temperature control thereof, comprises providing an output which varies between O and N cycles in response to an input analog signal which also varies between 0 and 100% by a burn-on and -off control at zero crossings of an a-c power source. According to the invention, the output is uniformly distributed throughout a control period comprising N cycle times. The output pattern is transit to another output pattern in response to a new analog input signal at the desired point in time.

Abstract: A relay control circuit which is capable of reliably controlling the transmission of electrical power in very small time increments. Specifically, the present invention features a proportional firing circuit which will create an SCR firing signal whose pulse timing is proportional to the magnitude of a variable input signal. The control circuit varies the conduction time for the SCRs by varying the time between firing signal pulses of fixed duration.

Abstract: A method and apparatus are disclosed for correcting the power factor of an input alternating current signal. The invention is adapted to generating an AC output signal connectable to one or more loads, such as capacitive loads. The circuit includes an energy storage inductor connected in series between the input and output terminals. A short circuit path is provided to connect output terminals during a portion of each half cycle of the AC input voltage waveform. The portion corresponds to the time necessary for the inductor to reach a level substantially corresponding to the peak level of current through the inductor when the short circuit path is disabled. In the preferred embodiment the enablement of the short circuit path between ouput terminals commences at the time the input voltage waveform crosses the zero reference value, and ends at a time at which the AC output voltage exceeds the input voltage.

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: 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: In a hybrid relay circuit for supplying current to a load with a AC power supply, an electromagnetic relay is provided and the contact thereof is connected in series to the load and the AC power. The electromagnetic relay is driven by a driving circuit in accordance with an input control signal, thereby switching the supply of current to the load.

Abstract: The invention concerns a drive interface (1) for an electronic static switch (3) such as a blocking thyristor or a transistorized blocking switch; this interface is inserted between said static switch and a control stage (2) designed to generate a logic control signal. Said interface comprises a circuit (5) for detecting the voltage across the two power electrodes of the static switch (3) and a drive circuit (6) receiving the signal emitted from the circuit (5) and the control signal; this drive circuit is designed to assure a polarity on the control electrode (3c) of the static switch such that:said polarity corresponds to blocking the switch when the control signal carries an OFF command, and/or the voltage across the power electrodes is different from 0,said polarity corresponds to the conduction state of the switch when the control signal corresponds to permission to conduct an the voltage across the power electrodes is near 0.

Abstract: An electric power control device is composed of plural resistor loads (1.sub.0 -1.sub.4) the heat-generating powers of which are different from one another, switch means (3.sub.0 -3.sub.4) connected in series to each of the resistor loads and adapted for the ON-OFF control of an ac power (2), and means (4.sub.0 -4.sub.4) for ON-OFF controlling the switch means so as to turn on or turn off the ac power and also for selectively controlling the individual resistor loads so as to adjust the heat-generating powers of all of the resistor loads in accordance with their corresponding desired heat-generating powers.

Abstract: A line-frequency switching power supply for producing a regulated D.C. output voltage includes a pass element disposed between a rectifier circuit and an output terminal to which a filter is connected. The pass element is enabled when a zero-crossing of line voltage is detected, and switched on when the line voltage exceeds the voltage on the filter capacitor plus the operational drop across the pass element. The pass element is switched off when the output reaches a preselected D.C. output level, tripping a switch. Since the pass element is switched on for only a portion of a cycle of line voltage, power dissipation is minimized and efficiency is kept high. Regulators of type described herein suitably may be stacked on a single secondary winding to produce multiple output voltages, or may suitably function as preregulators for following linear regulators to produce very stable and constant D.C. output voltages with minimum power dissipation.

Abstract: A solid state relay is responsive to a control signal and is used with an impedance load and a source of alternating electrical power. The solid state relay is used to connect and disconnect the load from the source of alternating electrical power. The solid state relay turns on in response to a control signal and to a substantially zero voltage crossing of the alternating electrical power of the source. The solid state relay turns off in response to the control signal and to a substantially zero current crossing of the alternating electrical power of the source.

Abstract: What is proposed is an electronic circuit for controlling the amount of AC power delivered to an inductive or resistive load which continuously measures the actual phase lag between the load current and applied voltage and automatically adjusts the firing angle to provide the desired amount of AC power. The circuit includes an auxiliary on/off input with soft start and independently adjustable time delays for the on and off functions and also incorporates an input for remote power level control and features a half-wave rectified mode which delivers pulsating DC power to the load.

Abstract: A zero-current a.c. switching system is provided for controlling actuation of relay contacts between a power supply and a load. A primary switch selectively energizes the relay to maintain the relay contacts in the closed state. The load current flowing through the relay contacts to the load is sensed. A secondary switch responds to the sensed load current for normally conducting to energize the relay in parallel with the primary switch. The secondary switch ceases conducting each time the load current drops below a predetermined level to cease energizing the relay and open the relay contacts the next time the load current drops below the predetermined level following the opening of the primary switch.

Abstract: A series resonant converter is interposed between an unregulated voltage source and an output circuit. The converter employs a pair of power switches each, when on, completing a series resonant circuit from the source to a resonant tank circuit including the primary winding of a transformer coupled to the output circuit. The power switches are alternately turned on and off so that sinusoidal current pulses alternately flow in opposite directions in the primary winding at a frequency dependent on input and output conditions. The current flowing in the resonant circuit is monitored and the power switches are additionally controlled to prevent turn on of one switch and turn off of the other when current is still flowing in the resonant circuit.

Abstract: Zero crossing synchronous AC switching circuits are provided which employ piezoelectric ceramic bender-type switching devices for use in supplying loads of a resistive, inductive or capacitive nature. The circuits include zero crossing sensing sub-circuits for sensing the passage through zero value of a supply source of alternating current voltage and/or current and for deriving zero crossing timing signals representative of the occurrance of the zero crossings. The zero crossing timing signals are employed to control operation of a bender energizing potential control sub-circuit for selectively controlling application or removal of a bender energizing potential across the piezoelectric bender member of the bender-type switching devices.

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: An AC line voltage regulator having a voltage sensing circuit for sensing and producing signals representative of the difference between a predetermined voltage level and the line voltage level and a load current sensing circuit for sensing and producing a signal representative of the magnitude of a load current drawn from the regulator. An actuation circuit combines the signals produced by the voltage and current sensing circuits to control the timing of a selectively switchable dispensing circuit which dispenses energy into an oscillatory circuit oscillating at the line voltage frequency and connected between input and output ports of the regulator. The dispensing circuit permits a selectable amount of energy to be dispensed in the oscillatory tank to adjust the line voltage level by adding the energy to either buck or boost the line voltage as determined by the difference signal.

Abstract: A method and apparatus for regulating a microwave oven to a predetermined output power level. The anode current or a voltage corresponding to it is monitored to provide a signal indicative of the actual output power of the magnetron. Time is divided into a sequence of equal time intervals, each interval corresponding to fixed number of ac line cycles. In accordance with the signal, the number of ac cycles to be supplied to the power supply for each interval to regulate the output power towards the regulated level is determined. The determined number of cycles are supplied by switching at the zero current crossings between the line and the power supply. The switching is executed so that the supplied ac cycles are distributed substantially uniformly over the particular time interval.

Abstract: A control for the heating section of a blow-molding machine is provided. The control permits independent selection of periods for high and low power energization of each radiant heating element of the heating section heater assembly. Power is provided by an alternating current source and switching of the power to the heating elements is accomplished at the zero crossing points of the supply voltage. To regulate the power in the heating elements against variations of supply voltage from a nominal value, a duty cycle control scheme is provided for selectively applying and withholding full cycles of the supply voltage to the heating elements. The determination of whether a cycle is to be applied or withheld is made by computing a duty cycle ratio comparing the power available from a minimum voltage expected to the power available from the actual supply voltage. Supply cycle switching is accomplished to distribute the application of cycles in two during the periods.

Abstract: A switching circuit in a power supply for switching between a main power source and a standby power source includes gating device operated at the time failure of the main power source occurs to disable the operation of a plurality of MOSFETs which are switched by high frequency clock signals to couple the main power source to a load. When the main power source returns, the gating device switches the MOSFETs in synchronization with the power signals supplied by the main power source. The circuit includes a transformer operated by the high frequency clock signals to switch the MOSFETs, enabling the transfer of the power signals from the main source to the standby source to occur at the time the main power source fails.

Abstract: An induction heating system (40) is provided and includes a plurality of induction heating coils (118). Touch control pads (50, 52, 70, 72) are provided together with circuitry (80) for generating energization control signals. Circuitry (112, 116) is provided for electrically energizing the induction heating coils (118). An electronic digital processor (82) is responsive to the energization control signals for generating energization signals for actuating and controlling the energization circuitry (112, 116) to thereby vary the energization of the plurality of induction heating coils (118).

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: A power circuit for a precipitator utilizes a pair of silicon controlled rectifiers (SCR's) which are triggered by detecting the zero crossover of a power signal. The power transmitted through the SCR's is determined by the time period from the detection of the zero crossover to the generation of the trigger signal. Power signals are typically subject to noise which interferes with the detection of the zero crossover. Filters are provided for reducing the noise interference but function without altering the phase relation of the zero crossover of the filtered signal in respect to the unfiltered power signal. A pulse train of higher frequency than the power signal is generated to provide a plurality of triggering pulses for the SCR. Further, phase control signals are generated for each SCR to prevent the generation of trigger pulses when the SCR's are reverse biased.

Abstract: A switching system for sequential connection of a plurality of loads to an alternating current supply comprises a computer for generating switch selection data in the form of serial bits along a single line to a distributor arrangement which decodes the selection data and provides control signals to switch devices which connect the loads to the supply. The distributor arrangement includes a circuit for inhibiting supply of the control signals to the respective switch devices unless the voltage of the supply phase connected by the device is substantially zero. Additionally the control signals are time-advanced with respect to the zero voltage conditions so that the switch devices can be placed in states in which they can connect a load before disconnection of a preceding load.

Abstract: A control system for applying operating power to an analytical furnace includes a first circuit providing output signals consisting of a series of binary bits in a predetermined pattern with each bit corresponding to a unit of power to be applied to an analytical furnace according to the pattern of bits and a control circuit coupled to the first circuit and including output terminals for coupling the control circuit to an analytical furnace. The control circuit responds to the binary bits to provide pulses of operating power to the output terminals in a sequence corresponding to and controlled by the binary bits. The pattern of bits provides stepwise increasing temperature levels for the analytical furnace in a very predictable and controlled fashion such that samples combusted by the furnace will emit specimen gases associated with different compounds containing the specimen gas at different temperature levels.

Abstract: A thyristor control circuit arrangement which overcomes the problem of radio frequency interference comprises two parallel-connected oppositely-poled thyristors (TH1 and TH2) arranged to conduct alternatively for supplying power to a load (L) from an a.c. supply and thyristor control means (GA1-GA6 and LA1 and LA2) for detecting the polarity of the voltage across the parallel-connected thyristors (TH1 and TH2) and in response to the operation of ON/OFF control means consequently to condition one of the thyristors which has a negative voltage across it in readiness for immediate firing thereof as the voltage changes from a negative to a positive voltage.

Abstract: A circuit arrangement contains an oscillator for producing high frequency pulses, a gate circuit, a pulse transformer and a triac. The high frequency pulses can be connected to the primary winding of the transformer by way of the gate circuit. The secondary winding of the transformer is connected in the control circuit of the triac. The line voltage load is connected in the output circuit of the triac. A switch is arranged at the output of the gate circuit and is connected to the primary winding of the transformer. The switch is closed only during the presence of one polarity of the pulses so that a current can only flow through the primary winding of the transformer during a corresponding interval.

Abstract: Electronic switching circuit is provided for controlling transfer of electrical power from an alternating polarity electrical power supply to a load means through use of a field-effect transistor device as the controlling element. A circuit arrangement is provided for switching into the "on" condition primary power control field-effect transistor device only when the voltage thereacross is at a relatively low value and for switching into the "off" condition this device in a gradual manner, relatively slowly reducing currents flowing therethrough. A circuit arrangement for a command source directing operation of the primary power transfer control field-effect transistor device provides command source isolation.

Abstract: A method and circuit as disclosed herein for varying the current to N electrical loads by the use of SCR's, the arrangement being such that the total current is sinusoidal and of uniform amplitude at a particular setting. The technique involves the steps of generating a load sequence waveform, the period of which is nN full cycles of the ac source where n is any positive integer, and, during each period of the waveform, generating a load firing pattern for initiating the flow of a current I in each load, the load pattern being such that (a) the currents in each of the loads are initiated at instants which are n full cycles of the ac source apart, and (b) maintaining the current in each load for d full cycles of the ac source, where d is a duty factor and is any positive integer equal to or greater than n, but less than or equal to nN, whereby the total current drawn from the ac source is uniform and equal to dI/n.

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 power control system is disclosed which controls the power output of one or more resistive heating elements in response to operator selected power level settings. Control of power to the elements is accomplished by generating a multi-bit binary word representing a selected power level, each bit being operative to control the application of power to the element during a different control interval. A control word is generated for each element and is updated once during every associated control period, a period comprising a number of intervals equal to the number of heating elements. The heating elements are of a type which draw a relatively high current during a transient heat-up period. The application of power to other elements is inhibited when one of the elements is having power applied thereto during its transient period. Power control for each element is staggered by testing a bit of different positional value in each word during any given interval.

Abstract: A control circuit for a power switch like a triac to be connected in series with a load device, at a situs where only one AC power conductor and a conductor extending to the load device is available, is energized from a DC power supply energized from these conductors. The power supply includes at least one rectifier connected in series with a capacitor, the terminals of which capacitor constitute the DC output terminal of the DC power supply, an impedance of much greater resistance than that of the load device and through which the capacitor is charged when the triac is in its non-conductive mode, and a normally non-conductive triggerable low impedance threshold device shunting the high impedance and triggered momentarily into conduction as the applied AC voltage goes through zero when the triac is to be in its conductive mode. Current flow through this threshold device triggers the power switch into conduction a short interval after passage of this voltage through zero.

Abstract: In the disclosed circuit, a bilateral breakdown switch such as a triac includes two terminals for connecting an AC source to a load. A variable input arrangement, such as one which includes an LED and a photoresistor, operates a control electrode on the switch to turn the switch on and off in response to an input signal. The switch is disabled when the momentary AC voltage exceeds a predetermined value. This is done by a sensor that senses voltage and a bilateral switching arrangement that responds to the sensor and turns off the switch in response to a voltage higher than a predetermined value. According to one embodiment, the bilateral switching arrangement is composed of two complementarily poled transistors connected in parallel with respective bases connected to the sensor. Series diodes provide unidirectionality for the transistors. Back-to-back parallel diodes connected to the control electrode compensate for the voltage drop caused by the series diodes.

Abstract: A power control system is disclosed for controlling the power output of a resistive heater element in response to operator selected power level settings by varying the rate at which a power pulse of constant duration is applied to the element. The system includes circuitry for generating a control signal representing a selected power output for the element, circuitry for identifying recurring patterns of a binary counter, the patterns recurring at different rates, and a logic arrangement for uniquely associating each of the patterns with a selected power setting. The binary counter and the power pulse control are synchronized with the power supply to trigger a power switching device at or near zero crossovers of the supply.

Abstract: What is proposed is an electronic circuit for controlling the amount of AC power delivered to an inductive or resistive load which continuously measures the actual phase lag between the load current and applied voltage and automatically adjusts the firing angle to provide the desired amount of AC power. The circuit includes an auxiliary on/off input with soft start and independently adjustable time delays for the on and off functions and also incorporates an input for remote power level control and features a half-wave rectified mode which delivers pulsating DC power to the load.