Abstract: A zero voltage, zero current switching boost converter is provided. The boost converter includes an input coupled to an input inductor, a main switch coupled to the input inductor that conducts currents through the input inductor to store energy in said input inductor, and a resonant circuit coupled to the main switch for conducting currents from the input to an output of the boost converter which includes a first series circuit of a first auxiliary switch and a second auxiliary switch coupled to the main switch, a second series circuit of a first output capacitor and a second output capacitor in parallel with the first series circuit, and a resonant inductor interposed between the first series circuit and the second series circuit that forms a first discharge loop and a second discharge loop to make the main switch turn on and off under a substantial zero voltage, wherein both the first auxiliary switch and the second auxiliary switch are turned on and off under a substantial zero current circumstance.

Abstract: An ignitor controller and method of providing the same triggers an ignitor switch of a gas appliance, such as a furnace, subsequent to the zero-crossing of the line voltage, but before the voltage exceeds +/−five volts. This effectively reduces EMI levels caused by the constant triggering of AC line voltage to the ignitor switch after +/−five volts, which constant triggering is needed to properly operate ignitors (e.g., silicon nitride ignitors) in electronic ignition systems. The controller includes a voltage detector circuit (i.e., a two transistor circuit), a series switch (i.e., a darlington array) and an energy storage device (i.e., a capacitor), which trigger the ignitor switch (e.g., a triac) sufficiently close to the line voltage zero-crossing to reduce line conducted interference.

Abstract: A zero voltage, zero current switching power factor correction converter comprises a boost unit including a first switch, a second switch and a resonant circuit at least comprising two energy storage elements, wherein the resonant unit is operatively configured to alternatively discharge electric energy from one of the energy storage elements to a load, a boost unit comprising a boost choke for receiving an AC voltage, a rectifying circuit coupled between the boost choke and the resonant unit, a third switch and a fourth switch respectively connected across one of the energy storage elements, and a power factor correction controller for respectively enabling the first switch and the second switch to turn on and off when a current flowing through the first switch is zero and a current flowing through the second switch is zero, and respectively enabling the third switch and the fourth switch to turn on and off when a voltage across the third switch is zero and a voltage across the fourth switch is zero.

Abstract: A water heater having a water tank and multiple electric resistance heating elements extending into the water tank for heating water in the tank. The water heater includes a proportional band temperature controller for conducting electric power to the electric resistance heating elements in bursts. Each burst of electric power is followed by a period during which the temperature controller does not conduct power to the electric resistance heating element. In one embodiment, each burst of electrical power lasts for about 95% or less of a cycle comprised of one burst of electric power followed by the period during which the temperature controller does not conduct electric power. Further, activation of the heating elements by the controller is carried out in a sequential or other timed or controlled fashion to permit uniform heating of the water in the tank.

Abstract: The present invention is directed to a circuit that is configured to detect a zero current condition at a certain point. The circuit includes a current mirror coupled to two transistors, where the first transistor is coupled to ground and the second transistor is coupled to the point being sensed. The outputs of both the first transistor and the second transistor are each coupled to an input of a comparator. The comparator is configured to determine when an equal voltage condition is present at the two inputs, which signifies a zero-current condition. Such a zero current detector can be used in a buck regulator to prevent a current flow from load to ground and attendant inefficiencies that result. An alternative embodiment involves the use of a controller to sense three different voltages to determine the state of the switches.

Abstract: An alternating-current electric power controlling apparatus including a switch and a controller. The switch is configured to be turned on or off to connect or disconnect an alternating-current electric power source and an electric load. The controller is configured to control the switch to turn on or off to adjust supply of electric power from the alternating-current electric power source to the electric load. The switch is configured to be turned on or off when an electric power amplitude is substantially equal to 0.

Abstract: A triac controller includes a triac driver that provides a triac control signal suitable for connection to a gate terminal of a triac, such that, when in a power-on condition, the control signal carries at least a first firing pulse during each half period of the alternating current power supply. A soft start subcircuit and a zero crossing detector directs the triac driver to produce the first firing pulse at a first firing pulse delay time after the zero crossing time. During a soft start operation the first firing pulse delay time varies monotonically with each successive half period from an initial delay time to a final delay time. An auto-retriggering subcircuit causes the triac driver to produce a second firing pulse at a predetermined retriggering delay time from an end of the first firing pulse if the triac is not in an on conduction state after the end of the first firing pulse during a same half period.

Abstract: An electric arc furnace includes a container for receiving metal, an electrode spaced apart from the container, and an electrical power source coupled to the electrode and the container for generating an electrical discharge between the electrode and the container for melting the metal in the container. The arc furnace includes a flicker controller for reducing flicker induced in the power source by the electric arc furnace. The flicker controller consists of a switch electrically connected between the power source and the electrode, and a control system coupled to the switch. The switch includes a gating input for controlling a conduction interval of the switch, and the control system applies gating signals to the gating input for maintaining a magnitude of reactive current flow through the arc furnace substantially constant.

Abstract: A fader wheel assembly for a lighting control console includes a fader wheel having a single hub mounted at an acute angle to the top wall of the console. The inclined orientation positions approximately half of smooth, rounded outer wall and rim surfaces above the console top wall in an arrangement that is comfortable for the user. A single bearing locates the wheel as well as a transducer that is supported essentially only by its attachment to the fader wheel. Resilient arms lightly hold the transducer in position.

Abstract: A heater controller uses measured power source voltage and either stored data that characterizes an electric resistance heater or current measurements to compute the fraction of time that the heater should be connected to the power source, thereby compensating the electric resistance heater against variations in the AC line voltage such that the heater power remains constant with line voltage variations, even for different nominal line voltages.

Abstract: A cycle-skipping power control algorithm provides control signal patterns based on generating a number of core patterns corresponding to main power levels and alternating between the core patterns to generate finer control levels. Advantageously, such a cycle-skipping control scheme provides fine power control resolution, and perceptible flicker due to pulsating AC line current is minimized, both in visibly radiant loads and in electric illumination devices in close proximity to the load.

Abstract: A boost converter topology is disclosed. The boost converter includes a resonant network comprising a saturable element, coupled to three series interconnected resonant diodes. In operation, the first of the three interconnected resonant diodes is a fast recovery type diode such that it stops conducting before the remaining resonant diodes. Due to the fast recovery of the first resonant diode and the configuration of the resonant network, the voltage across the auxiliary control switch of the boost converter does not drop before being turned on, thereby eliminating power losses associated with turning on the control switch.

Abstract: A cycle-skipping control system uses a pseudorandom number generator with a digital comparator to produce a random binary bit stream having a data rate equal to the frequency of the AC line. The bit stream is used to turn a power control switch coupled to the AC line source on and off such that the desired fraction of full load power is provided to the load. Fine power control resolution is achieved without requiring a long control period. In addition, perceptible flicker due to pulsating AC line current is reduced, both in visibly radiant loads and in electric illumination devices in close proximity to the load.

Abstract: An AC voltage reduction system and method providing highly efficient reduction of utility voltage with minimal electromagnetic interference is provided. The systems and methods may also be used to improve overall facility power factor. The AC voltage provided to a load, such as a group of lighting ballasts connected on a single circuit, is reduced by a controllable switch coupled in parallel with a capacitor between the AC source and the load. The switch is controlled to turn-on when the voltage across the capacitor is very close to zero and turn-off prior to the next zero-crossing of the line current. The turn-off time is selected in an open loop configuration independently of a measured characteristic of load voltage or watts. In order to provide proper operation of gas discharge lighting, the switch is initially turned off just in advance of the AC source current zero-crossing.

Abstract: Apparatus is described for controlling an electric heater incorporating at least one electric heating element (2A, 2B, 2C) and energized from a single voltage alternating current supply (8). The apparatus includes a control knob (15) for manually selecting any one of a predetermined number of power settings for the heater from the voltage supply (8), the power settings varying progressively between a minimum power setting and a maximum power setting. The apparatus further includes a controller (10) adapted and arranged to supply to the electric heater within a predetermined constant time interval in each power setting a first dissipated power level and a second dissipated power level. The first dissipated power level comprises a first selected proportion of half cycles in a predetermined number of half cycles of the voltage supply and the second dissipated power level comprises a second selected proportion of half cycles in a predetermined number of half cycles of the voltage supply.

Abstract: A speed-up circuit 10 is connected to a detection line 6 for feeding back the high voltage detection value of a high voltage detection circuit 5 to a high voltage stabilizing circuit 1. When a power supply switch is turned on, since a PNP transistor 12 of the speed-up circuit 10 is turned on, a resistor 11 is connected to the detection line 6, so that the high voltage detection value is reduced forcedly. Accordingly, the high voltage stabilizing circuit 1 increases the peak value of a flyback pulse generated by a resonance-type power supply circuit 2 to output higher high voltage thereby to shorten the rising time of the high voltage output supplied to the anode of a CRT. After the lapse of the predetermined time from the turning-on of the power supply switch, since the terminal voltage of a capacitor 13 having been charged through a resistor 14 exceeds almost the voltage at a point A, the PNP transistor 12 is turned off, so that the resistor 11 is separeted from the detection line.

Abstract: A flyback converter has a main switch coupling a primary winding of a transformer between supply terminals, a duty cycle of the main switch controlling an output of the converter derived from a secondary winding of the transformer. Soft (zero voltage) switching of the main switch is facilitated by a snubber capacitor in parallel with the main switch. An auxiliary circuit coupled in parallel with the snubber capacitor and main switch includes a series-connected auxiliary switch, capacitor, and inductor coupled via another inductor to a full wave rectifier arrangement for recovering energy from the snubber capacitor. Resonant circuits provided by the auxiliary circuit facilitate soft switching of the auxiliary switch for low power loss and high frequency operation. The switches can be MOSFETs with reverse-poled diodes in parallel with their drain-source paths.

Abstract: Disclosed is a device for controlling the operation of a machine comprising at least one measurement sensor, one circuit to control this operation as a function of a signal sent out by the sensor and one input for the supply of alternating electrical power to the machine. This control device includes a memory known as a program memory containing a set of membership functions, a set of decision rules and a fuzzy logic program, a fuzzy logic processor used to prepare a decision signal that depends on the signal sent out by the sensor, on these membership functions and on these rules all at the same time and that is used to activate the operation of this machine with this decision signal, and in the program memory, additional membership functions that take account, as variables, of the signals available at the electrical supply input and of the rules that take account of these membership functions. The disclosure can be applied to devices for the control of electrical machines.

Abstract: The control circuit includes: a series circuit of a first triac and a reactor; and a second triac in parallel with this series circuit so as to perform control of activation of a fixing heater. Since the fixing heater has a low resistance when the power switch is first turned on, the first triac is operated to perform phase angle control of current flow, and when the phase angle has become approximately equal to 180.degree., the first triac is stopped, at the same time the second triac starts to be operated. The switching from the first triac to the second triac is made quickly so that it is possible to reduce the power consumption from the reactor.

Abstract: A protection circuit for preventing non zero-voltage switching of a lamp resonant output circuit driven by upper and lower half-bridge switches. The protection circuit includes a sense resistor disposed between the lower half bridge switch and ground for developing a voltage corresponding to the current flowing through the lower switch. A comparator compares the voltage developed across the sense resistor against a fixed reference voltage and generates an output indicative of a non zero-voltage switching condition when the voltage across the sense resistor exceeds the fixed reference voltage. A latch is connected to the output of the comparator and generates a latch output signal which disables the generation of drive signals to the upper and lower switches in the event of a non zero-voltage switch condition.

Abstract: In a power control unit for controlling a power supply to a load connected to an AC power source by switching on half cycles, following three modes are carried out in the order of presented: a first control mode for continuously supplying a power which is composed of a plurality of half cycle switching waveforms of a first polarity to said load; a second control mode for continuously supplying a power which is composed of a plurality of half cycle switching waveforms of a second polarity to said load, said second polarity being different from said first polarity; and a third control mode for supplying a power of a half cycle of said first polarity and a power of a half cycle of said second polarity to said load in turn. This arrangement can attain an effect that both the harmonic noises and the flickers caused by a rush current are reduced.

Abstract: An apparatus and method is provided for controlling electrical power from a power source to electrical loads in response to a decrease in power source voltage. A power source signal is compared to a predetermined signal voltage to determine whether and how much the voltage of the power source signal has decreased below that of a predetermined signal. A fraction of electrical power from the power source is transmitted to the loads as a function of how much the voltage of the power source signal has decreased below that of the predetermined signal.

Abstract: A family of DC-to-DC converters includes a multi-resonant snubber network connected in parallel with a power switching device. The multi-resonant snubber network includes an auxiliary switch that is connected to transfer the energy from a parasitic capacitance of the power switching device into a resonant inductor and to achieve zero-voltage turn-on of the power switching device. An additional resonant path is included in the snubber network to achieve zero-voltage turn-off of the auxiliary switch and the power switching device.

Abstract: A voltage-suppressed voltage source which uses switching devices to maintain a high performance, stable DC voltage by suppressing unstable DC voltages and providing a stable supply of power to a load. The voltage source has a partial resonance circuit for reducing power consumed while a switching device in the voltage source turns `on` and `off`.When a first switching device is off, unsuppressed DC voltages are stored in a resonance capacitor. When the first switching device is turned on, a resonance current flows from the resonance capacitor through a resonance coil and a second switching device just before the first switching device is turned on. This resonance current also induces a suppression effect to the output voltage, and allows the voltage suppressing portion to pass a current in the same direction as when the first switching device is on.

Abstract: A family of power converter is invented. Each of these converter accomplishes zero voltage switching to minimize switching losses. Also by the application of coupled inductor, conduction losses can also be minimized. The basic embodiment comprises of two switches connected across the input source. The switches are driven by asymmetrical driving pulses with variable duty cycle. A capacitor is connected to the node joining the two switches and an inductor is in turn connected to it. This inductor is connected to an output filter through a diode. The output filter comprises of an inductor and capacitor and diode combinations. This output filter inductor has two coupled windings which minimize conduction losses. The basic embodiment can be modified to provide converter with boost output or negative output. The embodiment can also be modified for isolated converter with transformer in both half bridge and full bridge circuit.

Abstract: A primary regulator having a zero-crossing detector and a voltage reference coupled to a processor is provided. The processor controls the on time of a primary transformer via a switching device isolated from the processor via a coupler A method of regulating a power supply to maintain a desired output voltage at a load including the steps of measuring an average output voltage at a load and controlling the on time of a switching device serially connected to a primary transformer input based on the measured output voltage and a zero-crossing signal.

Abstract: Apparatus and methods for AC power regulation for a wide range of complex capacitive and inductive loads which provide substantial reduction in power consumption while also providing a leading power factor. The system is self-adjusting for a wide range of loads and can reduce power consumption by 25 percent in lighting loads while producing minimal reduction in light output. The system utilizes a main switch consisting of back-to-back MOS Controlled Thyristor devices (MCTs) and a parallel capacitor bank in series with the load. The main switch is initially turned off slightly in advance of the load current zero crossing, and this in combination with the capacitor bank allows power to be reduced in a low noise fashion. The turn-off time is advanced gradually to regulate power at a target reduced level. At the target power level, load phase angle is measured and maintained to control the power savings ratio.

Abstract: Instabilities in the output voltage provided from an AC power supply system such as an uninterruptible power supply connected to a power factor correcting load are suppressed by a dynamic voltage regulation stabilizer system which is connected across the output lines from the power supply system to the load. The DVR stabilizer system includes a rectifier connected to the power supply system output lines. A capacitor is connected across the output nodes of the rectifier. Switching devices form a bridge that connects the capacitor to the output lines. Selected switching devices in the bridge are turned on for a selected duration encompassing the time of the peak of each half-cycle of the AC voltage waveform provided by the power supply system. During normal operation, where the peak AC voltage from the power supply system is substantially constant, the capacitor charges up through the rectifier to a voltage level near the peak value of the AC voltage waveform.

Abstract: AC-DC boost switching power conversion apparatus delivers power from a bipolar input voltage source to a load at a unipolar load voltage without including rectifiers directly in the path of the current which is delivered from the input source. By this means the converter exhibits lower power loss in semiconductor diodes and switches than is exhibited by prior art converters which interpose a rectifier between a bipolar source and a DC-DC boost converter. Power processing is performed by circuitry of the kind which includes an inductive element in series with the bipolar input source, shunt paths which include switching elements for recirculating a bipolar shunt current back toward the input source, a controller for turning the switching elements on and off during each of a series of converter operating cycles and rectification elements which are arranged to deliver a unipolar current to the load.

Abstract: A controller for performing a zero voltage switching using a resonance mode converter, and an electronic ballast adopting the same, includes a power controller, a shutdown protection circuit and a brownout circuit, and performs a switching when voltage of a switching element is zero, thereby preventing excessive power consumption, enhancing efficiency and decreasing noise.

Abstract: A pulse width modulated controller controls a zero-voltage switching resonant power converter or inverter. The on time of the power switch (110) of the converter or inverter is varied by an error amplifier (280) such that the output voltage of the converter or inverter maintains proportionality to a reference voltage (290). The off time is terminated by a switch-voltage detector (320) when the voltage across the power switch (110) drops below a threshold voltage (330) due to the natural resonance of the external resonating capacitor (120) and inductors (130 and 150). In the first two embodiments of the invention, a single timing capacitor (260) is employed both for determining the on time and the off time. In two other embodiments, two timing capacitors (262 and 264) are employed for separately determining the maximum allowed off time and the variable on time.

Abstract: Lamp dimmers are disclosed in which, in the course of varying average power supplied to the lamp load, the semiconductor power control devices transition between one and the other of substantially conductive and non-conductive power conditions, the duration of the transition by the power control devices themselves is increased beyond the minimum possible duration to reduce generated EMI. The dimmers disclosed provide for varying the direction, duration, shape, and phase angle of transitions.

Abstract: A triac-based electronic control system (20) for an electrical appliance which alternately applies and disrupts power in full cycles or full half cycles. Each zero crossing in a wave cycle is detected and this information is input into a microprocessor (U1) along with a user selected power level. The microprocessor outputs a triac control signal (36) to alternately turn ON and turn OFF power to a heater element (22) to produce a duty cycle used to achieve the desired heating level.

Abstract: In order to equalize voltage shares of DC-side voltage dividing capacitors of a three-level power converting apparatus for converting a DC voltage to a three-level AC phase voltage, there is provided an arrangement for compensating for rising and falling instances of a three-level AC voltage pulse depending on a difference voltage between the two voltage dividing capacitors and the polarity of the AC current, thereby adjusting a zero-voltage period of the AC voltage.

Abstract: AC-DC boost switching power conversion apparatus delivers power from a bipolar input voltage source to a load at a unipolar load voltage without including rectifiers directly in the path of the current which is delivered from the input source. By this means the converter exhibits lower power loss in semiconductor diodes and switches than is exhibited by prior art converters which interpose a rectifier between a bipolar source and a DC-DC boost converter. Power processing is performed by circuitry of the kind which includes an inductive element in series with the bipolar input source, shunt paths which include switching elements for recirculating a bipolar shunt current back toward the input source, a controller for turning the switching elements on and off during each of a series of converter operating cycles and rectification elements which are arranged to deliver a unipolar current to the load.

Abstract: A power converter circuit provides low conversion losses, low generated noise and output power controllability. The circuit includes a controller, at least two transistors and an output network that provides impedance matching and operating point stabilization functions. The output network also enables zero voltage switching of the transistors, thus reducing radiated noise and minimizing (and possibly eliminating almost completely) switching losses. The controller circuitry includes an oscillator which is capable of self synchronizing to the resonant frequency of the components of the output network. Power modulation (e.g., for dimming of a lamp) is accomplished simply by desynchronizing and increasing the oscillator frequency. Thus, the control architecture allows the use of external parts of lower precision and cost while providing dimming capability in a single stage.

Abstract: A dimmer circuit uses a triac for controlling application of power to a hot terminal where a load will be connected. A DC power supply develops DC power for powering a control circuit which includes a zero crossing detector circuit connected to an integrated circuit chip which develops a timer pulse at the appropriate time to dim the light. The timer pulse is output to a pulse stretching circuit which actually drives the triac. The pulse stretching circuit stretches the pulse to a maximum of one-half of a cycle. This ensures that the triac will be turned on even if the inductive current delays the establishment of adequate latching current. This creates a more symmetrical waveform and results in a reduced DC offset.

Abstract: An on-board electric vehicle battery charger includes a surge limiter circuit, a power factor control circuit, and a resonant inverter circuit. The power factor control circuit includes a boost regulator circuit providing a fixed voltage on an output capacitor. The resonant inverter circuit uses a resonance capacitor and the leakage inductance of an output transformer to establish a resonance frequency at least 500 times the AC input power frequency.

Abstract: A circuit is provided for obtaining precise lamp voltage control and for compensating for varying or fluctuating input from an AC voltage source. The lamp is switched on by a switching device such as a triac. When the triac is powered, a simultaneous powering occurs of a second switching device such as an SCR. The SCR produces a scaled down RMS voltage output which closely matches the actual RMS lamp voltage. This second simulated voltage is precisely controlled in a feedback circuit which includes an RMS to DC converter and a feedback controller. The controller compares a converted DC voltage with a reference voltage and generates a firing pulse to the triac which is advanced or delayed so as to compensate for variations in the AC source as manifested by variations in the converted DC signal relative to the reference signal.

Abstract: AC-DC boost switching power conversion apparatus delivers power from a bipolar input voltage source to a load at a unipolar load voltage without including rectifiers directly in the path of the current which is delivered from the input source. By this means the converter exhibits lower power loss in semiconductor diodes and switches than is exhibited by prior art converters which interpose a rectifier between a bipolar source and a DC-DC boost converter. Power processing is performed by circuitry of the kind which includes an inductive element in series with the bipolar input source, shunt paths which include switching elements for recirculating a bipolar shunt current back toward the input source, a controller for turning the switching elements on and off during each of a series of converter operating cycles and rectification elements which are arranged to deliver a unipolar current to the load.

Abstract: A contactor for selectively connecting at least one alternating current (AC) power line to a load and sourcing an AC current having periodic zero crossings includes a fixed contact; a movable contact mechanism; an operating mechanism for engaging and moving the movable contact to an open position in the absence of a closing signal; and a synchronized opening mechanism for disabling the closing signal in synchronization with a zero crossing of the AC current. The operating mechanism is disengaged from the movable contact, in a closed position, by a gap having a predetermined length in order that the contacts are separated at the AC current zero crossing. The contactor may further include a vacuum bottle for enclosing the fixed and movable contact therein. The movable contact may be carried within the vacuum bottle by a bottle stem which protrudes from the bottle and has a surface for engagement by the operating mechanism.

Abstract: There is disclosed a two wire AC power supply for proximity switch integrated circuits. A problem has existed with previous power supplies in that such have been implemented using discrete devices, which take up valuable room on any printed wiring assembly. This invention therefore provides a two wire AC power supply for a proximity switch integrated circuit, wherein at least some circuitry associated with the power supply is provided within the integrated circuit. The power supply preferably comprises a bridge rectifier (BR1), a voltage regulator (Z1, R1, M1), a thyristor (SCR), a diode (D1), a storage capacitor (CVS), a comparator, and an AND gate, wherein at least the comparator and the AND gate are provided within the integrated circuit.

Abstract: The present invention discloses a method and system for controlling a power supply by delivering stable output voltage independent of load. The control system includes a sensor for sensing a state variable, a fuzzy logic controller for generating a control action, and an actuator for regulating the power supply in accordance with the control action. The fuzzy logic controller generates a fuzzy logic knowledge base using low-level fuzzy logic controllers and a mode selector in one embodiment and a fuzzy logic proportional integral controller in another embodiment. The generated fuzzy logic knowledge base is compiled in a look-up table and is used to quickly and efficiently control a power supply device such as a resonant converter.

Abstract: A soldering system is disclosed having a stored program microcontroller by which one or more temperatures can be selected for a soldering iron tip. The system then automatically maintains such tip temperature during the soldering operation. The programmed microcontroller is coupled through input/output and interface circuits to a heating control that in turn is connected to the iron heater element for switching AC power in units of full waveform cycles across the element while the temperature of the tip is measured by a resistor sensor and an associated bridge measurement circuit so as to produce a signal that is applied to an input of the microcontroller forming a feedback loop. This causes the resistor sensor and hence the iron tip to reach the desired temperature.

Abstract: An A.C. power supply controller for a capacitive load such as an array of electroluminescent panels (1) having circuit elements (10 to 15) for producing a pulsed switching waveform (p) centered on the zero-crossing points (z) of an applied alternating voltage waveform, powerswitch (17) for connecting the applied voltage waveform or another voltage waveform to the load in response to the pulsed switching waveform (p), and control elements (5) for widening the pulse width of the switching waveform (p) symmetrically about the zero-crossing points (z) to vary the power applied to the load. The circuit elements (10 to 15) includes a rectifier (10) that rectifies the applied alternating voltage waveform, and a comparator (13) that compares the rectified waveform with a control D.C. input level (15) to produce an output level between adjacent crossing points of the two signals about the zero-crossing points (z). A linear potentiometer varies the D.C. input level (15).

Abstract: This present invention takes advantage of the understanding that the voltage rating associated with resistive heating element can be ignored over the common line voltage range, provided the power dissipation is controlled. This is accomplished by applying a fractional amount of power to a heating element from the power source. The method consists basically of determining, or estimating, a ratio of the amount to be applied to the amount of power available. A control signal is generated with a duty cycle approximately equal to that ratio. A zero crossing switch, under control of the control signal switches half cycles to the heating element. Thus, by applying a portion of the available half cycles to the heating element, the average power dissipation by the heating element can be controlled.

Abstract: Disclosed is a heater control device which controls a heater used in an image forming apparatus such as a laser printer, a copying machine, or a facsimile machine. The heater control device includes a switch for connecting and disconnecting an application of an alternating current voltage to the heater used in the image forming apparatus, and a switch control unit for varying a period of time for the application of the alternating current voltage to the heater per unit period of time by controlling the switch in accordance with a value of the alternating current voltage applied to the heater. The heater control device can be used regardless of the differing voltage levels of available commercial power provided in various geographic regions of the world respect to voltage.

Abstract: A high-efficiency analog power amplifier is disclosed. The amplifier utilizes pulse-width-modulation ("PWM") signals to operate electrical switching devices coupled in series across a d.c. power source. A resonant circuit coupled to the transistors periodically places zero and non-zero voltage levels across each transistor. The frequency and width of the PWM signals are relative to the components of the resonant circuit--enabling each transistor to switch off and on only when zero volts appears across the transistor.

Abstract: A lighting control system distributes both the alternating current supply and control signals representing desired adjustments to fixture parameters, such as intensity, via connections including power contacts and, for control signals, an electrically isolating coupling comprising an effective source and detector.

Abstract: Power saving circuitry is provided for use with fluorescent lights, inductive loads and resistive loads. The circuitry comprises a power circuit connectable to an alternating circuit power supply and a control circuit. The power circuit includes a bilateral switch, and the control circuit includes means for timing the operation of the bilateral switch so that the switch conducts current for a predetermined time during each half-cycle of the power supply which terminates at a predetermined interval before the end of each half cycle. A preferred embodiment of the power saving circuitry, adapted for use with fluorescent lights or inductive loads such as electrical motors, also comprises a Back-EMF suppressor circuit. The bilateral switches are preferably made up of one or more unilateral switch devices such as field effect transistors. The subject circuitry reduces power consumption while at the same time providing for a power factor correction.