Abstract: A parallel resonant induction cooking surface unit comprises a voltage fed inverter which drives a load circuit, comprised of a main induction drive coil, a tuning capacitor coupled in parallel with the main induction drive coil, and an inductor coupled in series with the main induction drive coil, with a square wave voltage, causing the main induction drive coil to generate a time variant magnetic field resulting in eddy currents being induced in the surface of a metallic, food-containing utensil positioned adjacent to the main induction drive coil, and hence, utensil heating. By tuning the load circuit to resonance at or near the square wave frequency, reactive currents therein are minimized, resulting in improved power factor. Moreover, resultant main induction drive coil voltage and current are nearly sinusoidal, thereby achieving reduced electromagnetic interference radiation at frequencies greater than the square wave frequency.

Abstract: Method and apparatus for evenly distributing the switching duty among power transistors in a full bridge inverter controlled by current band PWM, by switching first the top half of the bridge and then the lower half of the bridge to shape the output current waveform.

Abstract: An analog and a digital control is provided which causes a dc to ac inverter operated in the constant power mode to supply sinusoidal current to a utility while drawing maximum power from a solar array. The current drawn from the array is forced to be proportional to the array voltage by a variable gain amplifier so that the inverter presents a resistive load to the array which remains statically stable under rapid changes of insolation while using a perturb-and-observe method of maximum power tracking. The perturb-and-observe method adjusts the gain of the variable gain amplifier to achieve maximum power output from the solar array.

Abstract: An improved induction heating apparatus comprises a full bridge inverter with each inverter leg fabricated of first and second serially coupled field effect transistors. A control apparatus coupled to the gate of each field effect transistor of each leg alternately renders the first and second field effect transistors of each inverter leg conductive. By varying the phase delay between initiation of alternate conduction of the field effect transistors of one inverter leg and subsequent initiation of alternate conduction of the field effect transistors of the other inverter legs in response to operator commands, smooth induction heating apparatus power control is achieved.

Abstract: A single phase AC to DC power converter is provided which accepts a single AC line input voltage and provides a DC output voltage. Input current feedback is used to control the converter and to provide high quality sinusoidal line currents in phase with the applied line voltage. In another embodiment, a three phase AC to DC converter is realized as a delta connection of three isolated single phase AC to DC converters. Reduction in peak transistor currents of the switching transistor in each single phase converter is accomplished by the introduction of third harmonics to each of the single phase AC to DC power converters. Each of the three single phase AC to DC converters are synchronized so that the current pulses at the outputs of the three AC to DC converters are staggered in time reducing the amount of filtering required at the load.

Abstract: A single transistor DC--DC battery charger provides ohmic isolation with a multiple winding high frequency transformer. The transistor's duty cycle is determined from an isolated voltage proportional to battery voltage obtained from a signal winding of the transformer when the transistor is off.

Abstract: A multipole permanent magnet rotor is positioned on a shaft and rotatably mounted in a multiphase stator having two windings per stator phase. A distributor comprising a pattern of conducting and non-conducting material is mounted to turn with the rotor shaft. Pickup "fingers" in contact with the distributor, gate appropriate FET's of the pairs of FET's associated with each stator phase in sequence, with timing dependent on the instantaneous shaft position, to generate a rotating flux field. A voltage across the windings provides the current for flux generation, and can be supplied by a full wave rectified single phase AC source. The speed of rotation of the motor can be controlled by varying the voltage supplied.

Abstract: A field controlled thyristor or a field terminated diode is used in a gate assisted turn off mode in a resonant circuit commutated switching dc/dc converter to convert power from one voltage level to another voltage level. A diode allows energy trapped in stray inductances to be delivered directly to the load rather than be dissipated in snubber resistors.

Abstract: An improved proportional base drive circuit for rapidly and efficiently switching a high current bipolar load transistor comprises a transformer having first and second serially coupled primary windings, and first and second secondary windings coupled to the collector and to the base, respectively, of a high current load transistor for supplying the transistor with collector current and base current proportional to the collector current, respectively. A diverter circuit is coupled to the second secondary transformer winding and to the base and emitter of the load transistor. During intervals when the second transformer primary winding is effectively short circuited to initiate load transistor turn-off, the diverter circuit diverts current in the second secondary winding away from the load transistor base and also removes load transistor stored charge to effect rapid load transistor turn-off, thereby assuring reliable transistor switching.

Abstract: A half-wave and a full-wave rectifier using transistors as rectifying elements have independently controlled multiple output voltages obtained from a single power supply. The transistor used as a rectifying element has its turn-on controlled thus allowing voltage control by phase control action.

Abstract: A high gain latching Darlington transistor comprises a gate turn-off thyristor and a load transistor coupled in Darlington configuration. Circuit means including a diode are coupled to the gate turn-off thyristor and the transistor to provide a low loss path for load transistor current which reverse biases the gate-cathode junction of the thyristor at thyristor turn-off to prevent premature device conduction. The latching Darlington transistor configured in this manner thus operates as a conventional gate turn-off thyristor, capable of being pulsed into and out of conduction, but yet exhibits improved dv/dt capability and increased turn-off gain, typically between 10 and 100 times the turn-off gain of the individual gate turn-off thyristor.

Abstract: A power transistor used in a chopper circuit to control field excitation of a vehicle motor when in a power mode is also used to control charging current from an a-c to d-c rectifier to the vehicle battery when in a battery charging mode. Two isolating diodes and a small high frequency filter inductor are the only elements required in the chopper circuit to reconfigure the circuit for power or charging modes of operation.

Abstract: In an inverter-synchronous machine drive system wherein a synchronous machine is excited by an inverter from a source of direct current, a pair of controlled bidirectional conduction means are serially coupled across the source of direct current potential, and are coupled at their junction through a commutating capacitor to the machine neutral terminal. Each controlled bidirectional conduction means, together with corresponding phase connected thyristor within the inverter, is correspondingly gated in a predetermined sequence so as to cause alternating voltage to be applied across each corresponding machine phase for initial machine excitation.

Abstract: An improved battery charger circuit for rapidly charing a battery by increasing the rate of battery charge acceptance through periodic battery discharge during the charging process includes a pair of first and second controlled rectifier circuits coupled to an AC source and adapted for coupling to a battery. The first controlled rectifier circuit is rendered conductive during the charging intervals to supply the battery with charge current from the AC source. The second controlled rectifier circuit is rendered conductive during battery discharge intervals to discharge the battery in a substantially lossless manner by conducting battery discharge current through the AC source, thus realizing a highly efficient battery charger.

Abstract: Three pairs of series-connected inverter main thyristors are coupled in parallel across a unidirectional current source with the junction between thyristors of each pair being adapted for coupling to a respective phase of a three phase wye-connected inductive load. A first and second pair of serially-connected auxiliary thyristors are coupled in parallel across the current source, with the junction between thyristors of the first and second auxiliary pairs coupled by a first and second commutating capacitance, respectively, to the load neutral. Control means, responsive to conduction of a main thyristor, render a respective one of the thyristors of the first and second auxiliary thyristor pairs conductive in accordance with inverter load current to commutate a conductive main thyristor by coupling a respective one of the first and second commutating capacitances in series with a respective load phase across the conductive main thyristor.

Abstract: An induction cooking system comprises at least one induction surface unit which includes an induction coil operatively positioned adjacent to a metallic, food-containing utensil. A switching means is coupled in series with the coil across a source of rectified AC and is rendered conductive at a prescribed rate to energize the coil, causing the coil to generate magnetic flux which, in turn, causes eddy currents to be circulated in the utensil surface. The circulating eddy currents in the utensil surface result in joule losses causing food heating. Reactive energy present in the induction coil during intervals when the switching means is non-conductive is stored in a reactive power converter for subsequent discharge across the source of rectified AC. Selectively discharging the reactive power converter during the valleys of the AC input wave to the induction coil allows the coil to be energized during the entire 360.degree. of the AC input wave, thus realizing an efficient induction cooking system.

Abstract: A high current switching transistor controlling a load in its collector circuit receives from a drive circuit sufficient base current necessary to render the transistor conductive. A low loss inductor and switching means are connected to the base of the transistor such that when switching means are rendered nonconductive, current from the inductor flows into the base of the transistor to render it conductive, thus energizing the load.Regulating means coupled between a source of relatively high DC potential and the inductor together with unidirectional feedback path means provide a continuous current into the inductor such that when regulating means are substantially nonconductive, current is diverted away from the base of the high current transistor and circulates through the unidirectional feedback path and low loss inductor.

Abstract: An improved battery charger circuit for rapidly charging batteries by increasing the rate of battery charge acceptance through periodic battery discharge pulses during the charging process includes first and second chopper circuits coupled in parallel through an inductor across the DC source for coupling to a battery.The first chopper circuit controls the amplitude of battery charge current while the second chopper circuit controls the amplitude of battery discharge current and provides a low impedance conduction path for discharge current to be returned to the DC source, thus realizing an efficient battery charger circuit.

Abstract: A ferrite magnetic core includes a one-piece rectangular outer member with aligned circular apertures in which the ends of a cylindrical center member are retained to thus establish a radial air gap. Radial magnetic forces acting on the core members are summed to zero to theoretically eliminate movement and result in low acoustic noise in high operating frequency power inductors and transformers. A magnetic bridge is added to reduce air gap fringing flux outside the core. Other modifications and a "C" core configuration are described.

Abstract: A single phase, high frequency chopper ballast without large magnetic and capacitive components for gaseous discharge lamps such as the Lucalox.sup.R lamp is operated on full wave rectified line voltage. A small auxiliary capacitor stores energy during the peaks of the rectified line voltage when the voltage is high enough to maintain lamp discharge. During the low voltage valley regions the auxiliary capacitor is discharged to supply augmented chopper input voltage or load circuit voltage and provide energy to maintain lamp ionization during the valley regions until the rectified line voltage rises to a usable level.